MICROPLASTICS FATE AND TRANSPORT IN AGRICULTURAL SOIL: INTERRELATION OF HYDRODYNAMICS, CHEMISTRY, AND MATERIAL SCIENCES

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: ACTIVE
• Funding Source: AFRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 1022155
• Grant No.: 2020-67019-31166
• Cumulative Award Amt.: $482,080.00
• Proposal No.: 2019-06559
• Project Start Date: May 1, 2020
• Project End Date: Apr 29, 2025
• Grant Year: 2020
• Program Code: [A1401]- Foundational Program: Soil Health

Recipient Organization
UNIVERSITY OF MEMPHIS, THE
315 ADMINISTRATION BLDG
MEMPHIS,TN 381523302

Performing Department
Civil Engineering

Non Technical Summary
The application of agricultural plastic products is increasing due to their economic benefits in providing an early and better-quality harvests. Despite the short-term benefits provided by plastic products, their long-term sustainability issues and negative impacts on soil health are not well understood. Although several studies investigated the microplastics (MPs) biodegradation and transport by terrestrial organisms, little is known regarding the influence of photo and mechanical degradations on MPs surface characteristics, attachment to the soil particles, and eventual transport through the soil. In line with Bioenergy, Natural Resources, and Environment program priorities to understand soil health processes to ensure sustainable agricultural production, we propose an innovative project to better understand the plastic residual fate and transport within agricultural soil. We will examine the MPs degradation and fragmentation through bench-scale and field studies. Furthermore, we will model the long-term migration of plastic residuals to the deep soil by applying analytical chemistry, polymer science, engineering, and hydrodynamic techniques. The proposed project investigates the influence of combined photo and mechanical degradations on MPs fragmentation, surface chemistry, and morphology alteration (1), elucidates the interrelation between MPs, soil particles and water pore flow to identify MPs vertical transport through the soil (2), and develops the numerical models to simulate the MPs transport and deposition processes (3). This study will provide the foundation for continued exploration of agricultural soil pollution. Framing this problem more accurately by revealing the MPs degradation and transport within the soil alert the decision-makers regarding the plastics long-term threats associated to the soil sustainability.

Animal Health Component

100%

Research Effort Categories

Basic

(N/A)

Applied

100%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
101	0110	2020	100%

Knowledge Area
101 - Appraisal of Soil Resources;

Subject Of Investigation
0110 - Soil;

Field Of Science
2020 - Engineering;

Keywords

degradation

fate

microplastics

soil pollution

transport

Goals / Objectives
The primary scientific goal of this effort is to investigate the microplastics (MPs) fate and transport processes through agricultural soil systems. We will examine the MPs degradation and fragmentation through bench-scale and field studies. Furthermore, we will model and predict the long-term migration of plastic residuals to the deep soil by applying analytical chemistry, polymer science, engineering, and hydrodynamic techniques. The proposed effort includes three specific objectives: (Objective 1) investigate the influence of combined photo and mechanical degradations on MPs fragmentation, surface chemistry, and morphology alteration, (Objective 2) elucidate the interrelation between MPs, soil particles and water pore flow to identify MPs vertical transport through the soil, and (Objective 3) develop the numerical models to simulate the MPs transport and deposition process.

Project Methods
Task 1: Investigate the combined effect of UV exposure and mechanical abrasion on MPs alteration and fragmentation A-Evaluate the MPs Surface Alteration and Fragmentation: LDPE in the form of particles and mulch are selected for this study. A sandy loam soil/sandy soil will be used to conduct the degradation experiments. A floatation approach will be applied for extracting MPs from the soil samples using the NaCl solution. The floating substances will be separated using a paper filter. Residuals will be sonicated and then floatation will be conducted again. But to exclude the role of sonication on MPs further degradation, a set of control samples will be sonicated to identify the optimum sonication intensity and time durations. The substances separated through this practice will be visually inspected using optical microscope purchased with this grant. The number and size distribution of MPs will be evaluated using the recorded microscopy images. The surface chemistry will be characterized using ATR-FTIR and XPS. The MPs' surface morphology alteration will be evaluated using Field Emission Scanning Electron Microscopy (FE-SEM).B-Accelerated Photo Degradation: New LDPE particles and mulch will be exposed to UV light to simulate the photodegradation in agricultural farmlands. The QUV accelerated weathering tester located in the PI's lab, will be used to conduct the photodegradation at a variety of UV intensities and time durations. After each exposure period, MPs will be characterized for surface chemistry and morphology changes using the methods described earlier.C: Simulated Mechanical Abrasion: After applying accelerated photodegradation, the MPs will be mixed with loamy sand and will be placed in amber glass bottles to be shaken for 30 days using an orbital shaker, to simulate the abrasion of MPs with the soil particles. Then MPs will be separated from soil particles, their size distribution, surface chemistry and morphology will be examined using the methods described earlier.D: Field Study: Several soil samples will be collected from a hops field following the 1st year implementation of the LDPE plastic mulch. This field is located at the Agricenter International. After removing the plastic mulch and tilling the farm at the end of the harvesting cycle, the soil samples will be collected. The surface morphology and chemistry will be evaluated for extracted MPs using microscopy imaging and ATR-FTIR spectroscopy. The extracted MPs will be subjected to the mechanical abrasion process for 30 days, and their fragmentation will be evaluated by analyzing the plastic particles' size distributions. The results will be compared with the simulated laboratory experiments, where UVA degraded LDPE plastic mulch of the same size was exposed to the mechanical abrasion process.Task 2: Investigate the factors influence MPs vertical transport through the soil systemsNew LDPE particles with distinct size distributions of dp <100 mm, and 300 mm < dp <500 mm and similarly, sized particles that were aged through the process described in Task 1, will be used for the column experiments. The MPs will be added to ultrapure water at different concentrations. Different soil columns will be packed to investigate the role of soil particle size, grain distribution, hydraulic conductivity, and pore spaces on the MPs transport and attachment. Different hydraulic conditions will be applied to generate various pore water velocity. Bromide tracer will be used as a conservative tracer to accurately estimate the pore water velocity and resident time. A-Column Transport Experiments: The column transport experiments will be conducted to examine MPs' mobility within the soil profile. For this purpose, 3 cm diameter plexi-glass columns with different (sample space) lengths of 5, 10, 15, and 20 cm will be wet packed with pre-processes soil. A peristaltic pump will be used to inject MPs solutions with constant rates into the vertically oriented soil columns. To create a uniform and evenly distributed flow, two layers of clean gravel will be set above and bottom of the sandy soil. The soil sample and gravel layers will be separated using stainless-steel screens.To examine the influence of soil characteristics on MPs transport and attachment within the soil system, different homogenized soils representing sand, sandy loam, and loamy sand will be produced. The peristaltic pump will first induce bromide tracer for 3 pore volume. Sonicated MPs suspension is then injected for more than 10 pore volumes. The effluent samples will be collected and analyzed for tracer using the spectrophotometer located in PI's lab to determine the tracer breakthrough curves. These curves will be analyzed to estimate the accurate pore water velocity and flow hydraulic conditions. The MPs will be separated from the collected samples using the floatation and filtration approaches. In addition to the breakthrough curves, the spatial distribution of MPs attached to the soil particles will be determined in two steps. First, as an initial estimation, pore spaces that are visible through the transparent plexi-glass column will be examined by an optical microscope purchased with this grant. This will allow us to estimate the MPs' infiltration depth through the intact soil column.B- MPs Separation and Quantification: Following the completion of each experiment, the spatial distribution of MPs in the soil column will be evaluated. For this purpose, the sand column will be carefully excavated from the bottom end at 1 cm intervals. The samples will be dried for 48 h. The process described in Task 1 will be performed to separate the MPs from the soil samples. To count the number of MPs, the MPs particles will be homogenized in 20 mL glass vials, then 20 µL subsamples will be removed and spread onto the glass fiber filter and counted under an optical microscope. Finally, the total number of MPs in each sample will be calculated. Using the number of MPs and their specific volume, the mass will be estimated and used for modeling purposes later (Task 3). To evaluate the precision of MPs separation and counting approach a series of control samples will be prepared using the clean sand and MPs at different fractions, and analyzed following the described method, then recovery percentage will be evaluated. At the end of each experiment, a mass balance analysis will be conducted using effluent concentration data and final spatial distribution of retained MPs in the soils.Task-3: Prediction of MPs transport through the soil column with numerical modelingNumerical models will be developed to simulate the MPs transport and their attachment to soil particles. Proper boundary conditions representing each laboratory experiments will be introduced, and finally, the partial differential equation will be solved using appropriate mathematical approaches like finite difference and finite volume models. The developed numerical models will be calibrated by real breakthrough and soil sample data collected in Task-2. During the calibration procedure, several unknown parameters, which control the attachment process will be evaluated. The calibrated numerical models which can adequately simulate experimental data generated in Task-2 will be used to identify the most and least influential factors through a series of numerical sensitivity analysis. Such valuable information will shed light on a better understanding of the MPs transport mechanisms, which is indeed vital to maintain healthy soil and enhance agriculture sustainability.

Progress 05/01/24 to 04/30/25

Outputs
Target Audience:The target audience for this project includes undergraduate and graduate students, academic researchers, industry professionals, policymakers, and community stakeholders. At the university level, the project engages undergraduate and graduate students in civil and environmental engineering, hydrology, and geosciences through coursework, research, and mentorship, including those participating in the NSF-funded Vertically Integrated Projects (VIP) program. High school students and K-12 educators are also important components of the audience, particularly through dual enrollment courses such as Engineering 1009/1010: Introduction to Engineering Problem Solving, which introduce foundational concepts in environmental science, pollution, and systems thinking. Beyond academia, the project reaches scientists, engineers, and policymakers through invited talks at international conferences, research institutes, and professional forums, where findings on microplastic pollution--especially in stormwater and agricultural contexts--are shared. Public audiences, including environmentally conscious community members, are engaged through events such as the Science Café at Overton Park Conservancy in Memphis, TN, where complex research is presented in an accessible and engaging manner. This multi-tiered approach ensures that the project informs and inspires a wide range of stakeholders, from K-12 students and teachers to researchers, public officials, and the general public. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Courses:The project has created diverse training and professional development opportunities through academic coursework spanning undergraduate, graduate, and high school levels in the two states of Tennessee (University of Memphis) and Missouri (University of Missouri). Undergraduate students enrolled in Hydraulics and Hydrology Lab (CIVL 3182), along with graduate students in Aquatic Chemistry (CEE 8225), and Computational Methods in Hydraulics and Hydrology (CIVL 8901), received targeted instruction on microplastic (MP) pollution. High school students in dual enrollment courses (ENGR 1009 and 1010: Engineering Problem Solving) at White Station High School in Memphis, TN, were also introduced to these emerging environmental challenges. A key emphasis was placed on MP contamination in agricultural fields. Students were trained to understand the environmental significance of MPs, identify their sources--particularly from plastic mulch, biosolids, and irrigation runoff--examine transport and degradation mechanisms in soil and water systems, and apply methods for quantification and numerical modeling. This integrated approach equipped students with interdisciplinary knowledge and practical skills to address the growing concern of MP pollution in agroecosystems. Invited Speakers:Project findings were disseminated through several invited talks and keynote presentations at national and international venues, offering critical insights into MPpollution in various environmental contexts. These presentations covered topics such as the fate and transport of MPs in stormwater systems (Environmentally Responsible Transportation Center, University of Missouri at Kansas City - April 2024), the weathering of plastic materials and their role in contaminant transport (Plastics Challenges and Biotechnological Solutions Conference, European Federation of Biotechnology - March 2024), and the influence of MPs' intrinsic and extrinsic characteristics on environmental degradation and heavy metal mobility (Indian Institute of Science Education and Research, Kolkata - September 2024, and Karlsruhe Institute of Technology - June 2024). Additionally, a public engagement talk was delivered at Science Café, Overton Park Conservancy in Memphis, TN (2024), focusing on the broader implications of MP pollution and sustainability. Students involved in the project supported these engagements by contributing to data analysis, visualization, and the development of communication materials. These experiences provided practical training in science communication, exposed students to international research platforms, and helped them understand how to present complex environmental topics to both technical and general audiences. These opportunities significantly enriched students' professional development by strengthening their research dissemination skills, interdisciplinary awareness, and confidence in engaging with global environmental challenges. Training Graduate Students: This research project has provided an opportunity to train three Ph.D. students about plastics degradation processes and transport within the environment during this reporting period. Furthermore, thesestudents have learned multiple advanced methodologies to simulate the environmental degradation process, characterize the plastics' surface chemistry and morphology characteristics, and MP quantification processes. The graduate students were trained to use advanced technologies essential for investigating MP pollution. These technologies included Accelerated Weathering units, Micro-FTIR, fluorescent microscopy, and microplastic separation and quantification techniques, which will be valuable tools for them to use in their future careers. Undergraduate Student Research:The project also leveraged the NSF-funded Vertically Integrated Projects (VIP) program to expand undergraduate involvement. One undergraduate student, participating through the VIP program,independently developed and ran a research project investigating the impact of microplastics on plant growth and health--aligning closely with the project's focus on agricultural systems. This hands-on opportunity allows the student to gain experience in experimental design, data analysis, and scientific communication. PhD students involved in the project have also benefited from mentoring VIP undergraduates, enhancing their leadership, teaching, and project management skills. Through this structure, undergraduates gain foundational knowledge of environmental pollution and scientific inquiry, while graduate students build essential mentoring and professional development experience. These activities, combined with international research dissemination, provide a rich environment for learning, collaboration, and capacity building in emerging environmental science challenges. How have the results been disseminated to communities of interest?The results have been demonstrated through peer-reviewed publications, dissertation, conference presentations, and invited seminars to researchers, graduate and undergraduate students, industry practitioners, and policymakers. Peer-Reviewed Publications 1. L. Bhattacharjee, A. Gopakumar Nair, A. Beheshtimaal, F. Jazaei, A. Ccanccapa-Cartagena, M. Salehi, mechanisms of microplastic generation from polymer-coated controlled-release fertilizers (PC-CRFs),Journal of Hazardous Materials(2025), 486, 137082,doi.org/10.1016/j.jhazmat.2024.137082 2. A. Ccanccapa-Cartagena, A. N. Gopakumar, and M. Salehi, A straightforward Py-GC/MS methodology for quantification of microplastics in tap water.MethodX(2025), 14, 103173,doi.org/10.1016/j.mex.2025.103173 3. G. Bonyadinejad, M. Salehi, A simple methodology for in situ study of microplastics' aggregation. Journal of Clean Soil Air Water (2024), 52(6), 2300378, doi.org/10.1002/clen.202300378 4.Bakhshaee, A., Babakhani, P., Ashiq, M.M., Bell, K., Salehi, M., Jazaei., F.Potential impacts of microplastic pollution on soil-water-plant dynamics.Scintific Reports- Nature15, 9784 (2025). https://doi.org/10.1038/s41598-025-93668-0 Conference Presentations 1. A. Ccanccapa, A. Nair Gopakumar, M. Salehi, Development of a Py-GC/MS Methodology for Quantification of Microplastics in Water Samples, AWWA/MO Conference, March 2024 (Poster) [2ndplace poster presentation award] 2. Alireza Bakhshaee, Farhad Jazaei, Muhammad Masood Ashiq, Sohail Ahmed Tufail. Microplastic Quantification Using Combined Fluorescence Microscopy and Hotplate Techniques, AGU Fall Meeting 2024 3. Mohammad Hamza Sohail Ahmed Tufail, Farhad Jazaei, Alireza Bakhshaee, Muhammad Masood Ashiq. Assessment of Microplastic Contamination in Biosolids from Wastewater Treatment Plants and Its Implications for Terrestrial Environments, AGU Fall Meeting 2024 4.A Bakhshaee, F Jazaei, MM Ashiq, SA Tufail, AS Ali. Microplastic Identification and Quantification Using Combined Fluorescence Microscopy and Hotplate Techniques, AGU Fall Meeting 2024 Invited Talks 1. Maryam Salehi, "Microplastics in stormwater runoff: investigating fate, transport, and contaminant uptake", Environmentally Responsible Transportation Center, University of Missouri at Kansas City, April 2024 (Virtual) 2. Maryam Salehi, "Plastic Weathering and Contaminant Transport within the Environment, Plastics Challenges and Biotechnological Solutions Conference" Keynote Speaker,European Federation of Biotechnology, March 2024 (Virtual) 3. Maryam Salehi, "Investigating the impacts of microplastics' intrinsic and extrinsic characteristics on their environmental degradation and heavy metal transport",Department of Earth Sciences, Indian Institute of Science Education and Research, Sep 2024, Kolkata, India (Virtual) 4. Maryam Salehi, "Investigating the impacts of microplastics' intrinsic and extrinsic characteristics on their environmental degradation and heavy metal transport",Institute of Nuclear Disposal, Karlsruhe Institute of Technology(KIT), June 2024, Karlsruhe, Germany 5. Farhad Jazaei, "Microplastic Pollution: What We Know--and What We Still Don't!" Science Café at Overton Park Conservancy, Memphis, TN (2024) PhD dissertation: 1. Linkon Bhattacharjee. Mechanical Degradation of Plastics: An Implication for Agricultural Soil Health, PhD Dissertation, University of Memphis (2024). 2. Muhammad Masood Ashiq. Integrated field, laboratory, and modeling approach to investigate microplastic transport in the soil systems. PhD Dissertation. University of Memphis (2024). What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Objective (1): Investigate the influence of combined photo and mechanical degradations on MPs fragmentation, surface chemistry, and morphology alteration. Investigate the influence of combined photo and mechanical degradations on Microplastics(MPs) fragmentation, surface chemistry, and morphology alteration. In response to growing concerns about the inefficiencies of conventional fertilizers and the environmental risks associated with plastic pollution, this study focused on evaluating the performance and degradation behavior of polymer-coated controlled-release fertilizers (PC-CRFs). While these advanced fertilizers offer improved nutrient delivery and crop productivity, their polymer coatings raise important questions about their long-term environmental footprint, particularly regarding MPrelease under field-relevant conditions. This project aimed to address these concerns through a comprehensive investigation of the chemical, environmental, and mechanical dynamics of two commercially available PC-CRFs. The study successfully fulfilled its three primary objectives through a series of targeted experimental tasks. First, the physicochemical properties and nutrient release behaviors of two commercially available PC-CRFs, referred to as Type A and Type B, were thoroughly characterized. Using pyrolysis-GC/MS, the coatings were found to consist of polyethylene (PE) in Type A and alkyd resin in Type B, each exhibiting distinct thermal and mechanical behaviors. Nutrient release trials conducted in both ultrapure water and microplastic-free soil over 25 days revealed that Type A released TN and TP at a 3:1 ratio in water and 50:1 in soil, while Type B showed a 1.8:1 ratio in water and 32:1 in soil, with reduced phosphorus release in soil attributed to strong binding interactions. Structural analysis post-release using FE-SEM showed that Type A prills were largely emptied with moderate porosity, whereas Type B prills retained nutrients but exhibited substantial surface damage, including cracks and MPs, indicative of fragmentation. Second, MP release from Type A PC-CRFs was quantified in both aqueous and soil systems. A total of 28 ± 8 MPs (6 ± 1.6 MP/g) were released in water, while 107 ± 35 MPs (72 ± 8 MP/g) were detected in soil columns, with additional depth-wise MP migration confirmed down to 2 inches. This indicated clear leaching and dispersion behavior of MPs under field-like conditions. Third, mechanical degradation of Type A microcapsules was simulated to represent surface wear and shear stress typically encountered in agricultural environments. Surface wear tests under 2.0 N and 4.0 N forces for 10 and 60 seconds demonstrated a time-dependent fragmentation behavior, with up to 337 ± 72 MPs (67 ± 14 MP/g) generated under 2.0 N for 60 seconds, and a shift toward smaller particle sizes with increased abrasion time. Compression tests simulating axle loads (298 N and 422 N) produced 345 ± 38 and 452 ± 104 MPs/g, respectively, without a statistically significant difference. The emergence of transverse cracks, voids, and surface fatigue features across all degradation conditions highlighted the mechanical vulnerability of the polymer coatings and their contribution to MP generation. These integrated chemical, environmental, and mechanical assessments collectively validated the hypothesis that both nutrient efficiency and MP pollution are directly influenced by PC-CRF formulation and external mechanical stressors. Objective (2): Elucidate the interrelation between MPs, soil particles, and water pore flow to identify MPs' vertical transport through the soil.This objective was successfully completed prior to the current reporting period, providing a critical foundation for advancing Objective (3) during this phase of the project (see below). Objective (3): Develop the numerical models to simulate the MPs transport and deposition process. This objective was successfully achieved by developing and validating a novel experimental and modeling framework to assess the transport behavior under realistic environmental conditions. Recognizing the limitations of conventional packed column experiments, where MPs are introduced via suspension,we designed a new column system that simulates actual field conditions (Objective 2), where buoyant MPs are deposited on the soil surface and are subsequently driven downward by storm or irrigation water. This setup allowed us to track the vertical transport of low-density polyethylene MPs (10 ± 2 µm), comparing pristine versus UV-photodegraded forms, under different environmental variables, including natural organic matter (NOM) and contrasting soil types (silt loam vs. silt). Experimental results revealed that buoyant MPs can penetrate significantly below the soil surface when present in the topsoil layer--contrary to traditional assumptions. Silt soils exhibited higher MP transport compared to silt loam soils due to lower clay content and larger pore spaces. The presence of humic acid (a form of NOM) enhanced MP mobility by increasing surface repulsion and reducing attachment. Furthermore, UV-photodegraded MPs, due to increased surface functional groups and charge, showed higher mobility than their pristine counterparts. These trends underscore the critical influence of natural variables such as soil texture, organic matter, and photochemical aging on MP behavior in the subsurface. To simulate and understand these transport phenomena, an advection-dispersion-reaction model was developed using the finite difference approach, incorporating key processes known to govern particle movement in porous media--namely attachment, detachment, blocking, and straining. Unlike prior studies, where MPs were assumed to be uniformly dispersed in the inflow, our modeling approach accounted for surface-spiked MPs and applied a Cauchy-type boundary condition at the top of the soil column (z = 0 cm). This hybrid boundary allowed simultaneous representation of both dispersive and advective dynamics, providing a realistic framework for MP entry from the soil surface. At the outlet (z = 10 cm), a finite column boundary condition enabled accurate simulation of natural MP outflow. The model was calibrated using experimental data from breakthrough curves and retention profiles. Parameter optimization was achieved using the interior point method, improving model precision and objectivity over traditional manual fitting. Goodness-of-fit was assessed using Root Mean Square Error (RMSE) and Nash-Sutcliffe Efficiency (NSE), both confirming strong agreement between the model and observed data. Collectively, the experimental and numerical findings confirm that even buoyant, hydrophobic MPs can travel through soil layers under natural hydrological drivers and that factors such as photodegradation and NOM presence significantly increase this mobility. These insights not only validate our new methodology but also emphasize the need to integrate realistic environmental scenarios in future risk assessments and predictive modeling of MP contamination in agricultural systems.

Publications

• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2025 Citation: L. Bhattacharjee, A. Gopakumar Nair, A. Beheshtimaal, F. Jazaei, A. Ccanccapa-Cartagena, M. Salehi, mechanisms of microplastic generation from polymer-coated controlled-release fertilizers (PC-CRFs), Journal of Hazardous Materials (2025), 486, 137082, doi.org/10.1016/j.jhazmat.2024.137082
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2025 Citation: A. Ccanccapa-Cartagena, A. N. Gopakumar, and M. Salehi, A straightforward Py-GC/MS methodology for quantification of microplastics in tap water. MethodX (2025), 14, 103173
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2025 Citation: G. Bonyadinejad, M. Salehi, A simple methodology for in situ study of microplastics aggregation. Journal of Clean Soil Air Water (2024), 52(6), 2300378, doi.org/10.1002/clen.202300378
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2025 Citation: Bakhshaee, A., Babakhani, P., Ashiq, M.M., Bell, K., Salehi, M., Jazaei., F. Potential impacts of microplastic pollution on soilwaterplant dynamics. Scintific Reports- Nature 15, 9784 (2025).
• Type: Other Journal Articles Status: Under Review Year Published: 2025 Citation: M.M. Ashiq, P. Babakhani, B. Waldron, M. Salehi, K. Bell, and F. Jazaei. Penetration of buoyant microplastic in soils during infiltration events under realistic contamination conditions. Science of the Total Environment
• Type: Theses/Dissertations Status: Published Year Published: 2024 Citation: Linkon Bhattacharjee. Mechanical Degradation of Plastics: An Implication for Agricultural Soil Health, PhD Dissertation, University of Memphis.
• Type: Theses/Dissertations Status: Published Year Published: 2024 Citation: Muhammad Masood Ashiq. Integrated field, laboratory, and modeling approach to investigate microplastic transport in the soil systems. PhD Dissertation. University of Memphis.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2024 Citation: A. Ccanccapa, A. Nair Gopakumar, M. Salehi, Development of a Py-GC/MS Methodology for Quantification of Microplastics in Water Samples. , AWWA/MO Conference, March 2024 (Poster)
• Type: Other Status: Accepted Year Published: 2024 Citation: Maryam Salehi, Microplastics in stormwater runoff: investigating fate, transport, and contaminant uptake, Environmentally Responsible Transportation Center, University of Missouri at Kansas City, April 2024 (Virtual)
• Type: Other Status: Accepted Year Published: 2024 Citation: Maryam Salehi, Plastic Weathering and Contaminant Transport within the Environment, Plastics Challenges and Biotechnological Solutions Conference Keynote Speaker, European Federation of Biotechnology, March 2024 (Virtual)
• Type: Other Status: Accepted Year Published: 2024 Citation: Maryam Salehi, Investigating the impacts of microplastics' intrinsic and extrinsic characteristics on their environmental degradation and heavy metal transport, Department of Earth Sciences, Indian Institute of Science Education and Research, Sep 2024, Kolkata, India (Virtual)
• Type: Other Status: Accepted Year Published: 2024 Citation: Maryam Salehi, Investigating the impacts of microplastics' intrinsic and extrinsic characteristics on their environmental degradation and heavy metal transport, Institute of Nuclear Disposal, Karlsruhe Institute of Technology (KIT), June 2024, Karlsruhe, Germany
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2024 Citation: Alireza Bakhshaee, Farhad Jazaei, Muhammad Masood Ashiq, Sohail Ahmed Tufail. Microplastic Quantification Using Combined Fluorescence Microscopy and Hotplate Techniques, AGU Fall Meeting 2024
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2024 Citation: Mohammad Hamza Sohail Ahmed Tufail, Farhad Jazaei, Alireza Bakhshaee, Muhammad Masood Ashiq. Assessment of Microplastic Contamination in Biosolids from Wastewater Treatment Plants and Its Implications for Terrestrial Environments, AGU Fall Meeting 2024
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2024 Citation: A Bakhshaee, F Jazaei, MM Ashiq, SA Tufail, AS Ali. Microplastic Identification and Quantification Using Combined Fluorescence Microscopy and Hotplate Techniques, AGU Fall Meeting 2024

Progress 05/01/20 to 04/29/25

Outputs
Target Audience:Through a coordinated, multi-sector outreach strategy, this project informed and inspired audiences across academia, industry, policy, and the broader community, supporting the advancement of soil health, environmental sustainability, and responsible agricultural practices. The project experienced challenges during its early stages due tothe COVID-19 pandemic, which created logistical challenges; however, the project successfully adapted, and its outcomes were not affected. Throughout the project, significant efforts were made to reach a wide range of target audiences, including scientists and research scholars, undergraduate and graduate students, K-12 students and educators, industry practitioners, policymakers, and community stakeholders. Scientists and research scholars were informed through many published peer-reviewed journal publications (11 published and one under review) and more than 19 oral and poster presentationsat major national and international conferencessuch as the AGU Fall Meeting and the ACS Midwest Conference. In addition, more than five invited talks were delivered at venues such as the University of Missouri and the University of Alabama. Details of allinvited talks, conference presentations, and publication activities are detailed in other sections of the final report. Undergraduate and graduate students were actively engaged through coursework and research training activities. Project findings were integrated into several courses, including Environmental Systems Engineering (CIVL3140), Physical/Chemical Treatment (CIVL6134/4143), Water Chemistry (CIVL7903/8903), Hydrology (CIVL3181), and Computational Methods in Hydraulics and Hydrology (CIVL8901) in multiple years. Students also participated in experimental training involving advanced technologies such as accelerated weathering units, micro-FTIR, and fluorescent microscopy. Moreover, participation in the NSF-funded Vertically Integrated Projects (VIP) program further expanded undergraduate involvement, encouraging students to develop independent research projects related to MPs and soil health. K-12 students, teachers, and parents were engaged through outreach activities, including the Girl Experiencing Engineering Summer Program at the University of Memphis and the Science Café event hosted by the Overton Park Conservancy in Memphis, TN. Dual-enrollment courses, such as Engineering 1009/1010: Introduction to Engineering Problem Solving (White Station High School, Memphis, TN). These initiatives helped raise awareness of microplastic pollution and soil sustainability among younger audiences and the broader community. Industry practitioners and policymakers were informed through public science communication events and invited presentations at academic and professional forums. Research findings were presented in formats accessible to technical and non-technical audiences, aiming to inform future policies, improve agricultural plastic management practices, and promote sustainable land use strategies. Through a comprehensive and adaptive outreach strategy targeting scientists and research scholars, undergraduate and graduate students, K-12 students and educators, industry practitioners, policymakers, and community stakeholders, the project successfully disseminated knowledge, advanced scientific understanding, trained future environmental scientists and engineers, and promoted actions toward mitigating microplastic pollution impacts on agricultural soil systems. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Throughout the duration of the project, extensive training and professional development opportunities were created for undergraduate students, graduate students, K-12 students and educators, as well as for early-career researchers and community participants. These efforts were central to the project's broader impacts, ensuring the development of future leaders in environmental science, engineering, and sustainable agriculture. A particular focus was placed on addressing emerging environmental challenges, especially the growing problem of plastic pollution in soil and water systems. Undergraduate and graduate students benefited from a range of academic coursework directly informed by project findings. Project-related content was integrated into multiple classes at the University of Memphis, Memphis, TN, including Environmental Systems Engineering (CIVL3140), Physical/Chemical Treatment (CIVL6134/4143), Computational Methods in Hydraulics and Hydrology (CIVL8901), Water Chemistry (CIVL7903/8903), and Hydrology (CIVL3181). Additionally, at the University of Missouri, Columbia, MO, graduate students enrolled in Aquatic Chemistry (CEE8225) received targeted instruction related to MPs pollution and transport. High school students participated through dual-enrollment courses such as Engineering 1009/1010: Introduction to Engineering Problem Solving, gaining early exposure to environmental science and sustainability concepts. These educational efforts provided students with interdisciplinary knowledge and practical problem-solving skills necessary for tackling complex environmental issues, particularly the environmental threats posed by microplastics. The project also created robust research training experiences for graduate students at both institutions. Several Ph.D. students were intensively trained in advanced laboratory methodologies essential for microplastic investigations, including the use of Accelerated Weathering units for simulating environmental degradation, Micro-FTIR spectroscopy for polymer identification, fluorescent microscopy for particle visualization, and microplastic separation and quantification from complex environmental matrices, specifically soil and water. Graduate students also contributed to the development and calibration of numerical models predicting MPs transport in soil, building strong competencies in environmental simulation, analytical modeling, and predictive assessment. Additionally, graduate students gained mentorship experience by supervising undergraduate researchers, further enhancing their leadership, teaching, and project management skills. Undergraduate students were actively involved through research assistantships and participation in the NSF-funded Vertically Integrated Projects (VIP) program at the University of Memphis. These students contributed significantly to the research effort by assisting with running experiments, collecting field and laboratory data, and analyzing experimental results. They independently developed and executed research projects investigating the effects of MPs on plant health, soil sustainability, and nutrient cycling. Through these research experiences, undergraduates built strong technical competencies, gained early exposure to the scientific method, and developed communication skills critical for graduate study and professional careers. Professional development opportunities were further expanded through a variety of workshops and outreach programs. A major example was the two-day workshop, "Agricultural Plastic Pollution and Its Impacts," jointly hosted by the University of Memphis, Memphis, TN, and the University of Missouri, Columbia, MO. This workshop blended virtual and in-person participation formats, exposing undergraduate students to a combination of lectures, field soil sampling, MPs separation techniques, and basic fluorescent microscopy. Additionally, a two-day virtual workshop was organized specifically for high school students, introducing them to fundamental concepts of MP pollution, methods of MPs detection, and the environmental impacts of MPs accumulation in agricultural soils. A virtual summer workshop was also conducted for minority and underrepresented K-12 students as part of the Girl Experiencing Engineering (GEE) Summer Program at the University of Memphis, helping to raise early awareness of plastic pollution in agricultural environments. ASTEM professional development workshop was organized for K-12 teachers, providing hands-on training in MPs separation techniques, fluorescent microscopy, and instructional strategies to integrate plastic pollution topics into their classroom curricula. Beyond laboratory and classroom experiences, students and early-career researchers also gained valuable exposure to professional science communication. Project results were presented at major national and international conferences, including the ACS Midwest Conference, the AGU Fall Meeting, and the Water Professionals Conference (WPC), where students actively contributed to the preparation of posters, oral presentations, and peer-reviewed manuscripts. Public outreach efforts, such as the Science Café hosted at Overton Park Conservancy in Memphis, TN, allowed students to practice translating complex scientific findings into accessible knowledge for broader community audiences, further strengthening their communication skills. Overall, the project established a rich, multi-layered training environment across both the University of Memphis and the University of Missouri. It empowered a new generation of scientists and engineers with interdisciplinary expertise, technical skills, and professional readiness necessary to address the complex challenges of environmental pollution, particularly the critical and growing issue of microplastic contamination in agricultural systems. How have the results been disseminated to communities of interest?Peer-Reviewed Journal Articles (11 Published, 1 Under Review) L. Bhattacharjee, A. Gopakumar Nair, A. Beheshtimaal, F. Jazaei, A. Ccanccapa-Cartagena, M. Salehi. Mechanisms of microplastic generation from polymer-coated controlled-release fertilizers (PC-CRFs). Journal of Hazardous Materials, 486 (2025): 137082. https://doi.org/10.1016/j.jhazmat.2024.137082 A. Ccanccapa-Cartagena, A. N. Gopakumar, M. Salehi. A straightforward Py-GC/MS methodology for quantification of microplastics in tap water. MethodX, 14 (2025): 103173. https://doi.org/10.1016/j.mex.2025.103173 A. Bakhshaee, P. Babakhani, M.M. Ashiq, K. Bell, M. Salehi, F. Jazaei. Potential impacts of microplastic pollution on soil-water-plant dynamics. Scientific Reports - Nature, 15 (2025): 9784. https://doi.org/10.1038/s41598-025-93668-0 M.M. Ashiq, P. Babakhani, B. Waldron, M. Salehi, K. Bell, F. Jazaei. Penetration of buoyant microplastic in soils during infiltration events under realistic contamination conditions. Science of the Total Environment (Under Review). G. Bonyadinejad, M. Salehi. A simple methodology for in situ study of microplastics' aggregation. CLEAN - Soil, Air, Water, 52(6) (2024): 2300378. https://doi.org/10.1002/clen.202300378 L. Bhattacharjee, F. Jazaei, M. Salehi. Insights into the mechanism of plastics' fragmentation under abrasive mechanical forces: an implication for agricultural soil health. CLEAN - Soil, Air, Water, 51(8) (2023): 2200395. https://doi.org/10.1002/clen.202200395 M.M. Ashiq, F. Jazaei, K. Bell, A.S. Ali, A. Bakhshaee. Abundance, spatial distribution, and physical characteristics of microplastics in stormwater detention ponds. Frontiers of Environmental Science & Engineering, 17(10) (2023): 124. https://doi.org/10.1007/s11783-023-1724-y A. Herath, et al. Partitioning of heavy metals in sediments and microplastics from stormwater runoff. Chemosphere, 332 (2023): 138844. https://doi.org/10.1016/j.chemosphere.2023.138844 F. Jazaei, T. Jamal Chy, M. Salehi. Can microplastic pollution change soil-water dynamics? Results from controlled laboratory experiments. Water, 14(21) (2022): 3430. https://doi.org/10.3390/w14213430 A. Herath, M. Salehi. Studying the intrinsic and extrinsic factors influencing microplastics photodegradation behavior and heavy metals uptake in urban stormwater. Environmental Pollution, 308 (2022): 119629. https://doi.org/10.1016/j.envpol.2022.119629 G. Bonyadinejad, M. Salehi, A. Herath. Investigating the sustainability of agricultural plastic products: Combined influence of polymer characteristics and environmental conditions on microplastics aging. Science of the Total Environment, 839 (2022): 156385. https://doi.org/10.1016/j.scitotenv.2022.156385 K. Aghilinasrollahabadi, M. Salehi, T. Fujiwara. Investigate the influence of microplastics weathering on their heavy metals uptake in stormwater. Journal of Hazardous Materials, 408 (2021): 124439. https://doi.org/10.1016/j.jhazmat.2020.124439 Conference Papers, Presentations, and Invited Talks (Total 24) A. Bakhshaee, F. Jazaei, M.M. Ashiq, S.A. Tufail, A.S. Ali. Microplastic Identification and Quantification Using Combined Fluorescence Microscopy and Hotplate Techniques. AGU Fall Meeting, 2024. Mohammad Hamza Sohail Ahmed Tufail, F. Jazaei, A. Bakhshaee, M.M. Ashiq. Assessment of Microplastic Contamination in Biosolids from Wastewater Treatment Plants and Its Implications for Terrestrial Environments. AGU Fall Meeting, 2024. Alireza Bakhshaee, F. Jazaei, M.M. Ashiq, S.A. Tufail. Microplastic Quantification Using Combined Fluorescence Microscopy and Hotplate Techniques. AGU Fall Meeting, 2024. Maryam Salehi. Investigating the impacts of microplastics' intrinsic and extrinsic characteristics on their environmental degradation and heavy metal transport. Institute of Nuclear Disposal, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany, June 2024. Maryam Salehi. Investigating the impacts of microplastics' intrinsic and extrinsic characteristics on their environmental degradation and heavy metal transport. Department of Earth Sciences, Indian Institute of Science Education and Research (IISER), Kolkata, India, September 2024 (Virtual). Maryam Salehi. Plastic Weathering and Contaminant Transport within the Environment. Plastics Challenges and Biotechnological Solutions Conference, European Federation of Biotechnology, March 2024 (Virtual). Maryam Salehi. Microplastics in stormwater runoff: investigating fate, transport, and contaminant uptake. Environmentally Responsible Transportation Center, University of Missouri at Kansas City, April 2024 (Virtual). A. Ccanccapa, A. Nair Gopakumar, M. Salehi. Development of a Py-GC/MS Methodology for Quantification of Microplastics in Water Samples. AWWA/MO Conference, March 2024 (Poster). M.M. Ashiq, F. Jazaei, A. Bakhshaee. Unraveling Spatial Variability of Microplastics Distribution in Stormwater Ponds. AGU Fall Meeting, San Francisco, December 2023. M.M. Ashiq, F. Jazaei. Investigating the spatial patterns of microplastics in the soil of stormwater ponds. Student Research Forum, University of Memphis, April 2023. A. Herath, D.K. Datta, G. Bonyadinejad, M. Salehi. Studying the heavy metals uptake by microplastics and sediments in stormwater. MOAWWA/MWEA Joint Conference, Ozark, MO, March 2023. G. Bonyadinejad, M. Salehi. Studying the microplastics' aggregation in water: An implication for water resources protection. TN/KN WPC Conference, Memphis, TN, August 2023. L. Bhattacharjee, F. Jazaei, M. Salehi. Studying the plastic release by slow-release fertilizers: implications for stormwater pollution. TN/KN WPC Conference, Memphis, TN, August 2023. M. Salehi, G. Bonyadinejad. Studying the effect of plastic mulch photodegradation on its biodegradation process. ACS Midwest Conference, St. Louis, MO, October 2023 (Oral). Herath, M. Salehi. Studying the intrinsic and extrinsic factors influencing microplastics photodegradation behavior and heavy metals uptake in urban stormwater. AEESP Conference, Saint Louis, MO, June 2022 (Poster). M. Salehi. A systematic investigation of microplastics' weathering, fragmentation, and heavy metals transport within urban storm runoff. AEESP Conference, Saint Louis, MO, June 2022 (Oral). L. Bhattacharjee, M. Salehi. Studying the plastics' fragmentation under abrasive wear forces: an implication for agricultural plastics' degradation through the soil. AEESP Conference, Saint Louis, MO, June 2022 (Poster). R. Bonyadinejad, M. Salehi. Investigating the plastics aging within farmlands: an implication for sustainable agriculture. AEESP Conference, Saint Louis, MO, June 2022 (Poster). G. Bonyadinejad, M. Salehi. Mechanistic understanding of microplastics' photodegradation within the terrestrial environment: an implication for water resources protection. AGU Fall Meeting, Chicago, December 2022 (Oral). Mahammad Masood Ashiq, F. Jazaei, A. Bakhshaee. Investigation and Identification of the Microplastics Presence in the Soil. AGU Fall Meeting, 2022. L. Bhattacharjee, M. Salehi. An investigation of factors influencing plastics fragmentation under abrasive mechanical forces: an implication for agricultural soil health. Graduate Students Research Forum, University of Memphis, March 2022. G. Bonyadinejad, M. Salehi, A. Herath. Investigating the sustainability of agricultural plastic products: combined influence of polymer characteristics and environmental conditions on microplastics aging. Graduate Students Research Forum, University of Memphis, March 2022. R. Bonyadinejad, M. Salehi, F. Jazaei. Microplastics photodegradation: An implication for water resources protection. Water Professional Conference (WPC21), Chattanooga, TN, August 2021 (Oral). ? What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? The project successfully addressed all its primary objectives over the grant period, despite initial logistical challenges due to the COVID-19 pandemic. A comprehensive body of work was developed, combining experimental, analytical, and numerical approaches to better understand the fate and transport of microplastics (MPs) in agricultural soils. The accomplishments are organized by major objectives across all years, providing an integrated view of progress and outcomes. For Objective 1: Investigate the Influence of Combined Photo and Mechanical Degradations on MPs Fragmentation, Surface Chemistry, and Morphology Alteration, significant advances were made in understanding the influence of combined photo and mechanical degradation processes on MPs fragmentation, surface chemistry, and morphology alteration. Bench-scale experiments using UVA irradiation chambers simulated photodegradation, while mechanical abrasion tests at different normal loadssimulated wear effects. Analysis using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy, Differential Scanning Calorimetry (DSC), Gel Permeation Chromatography (GPC), and Field Emission Scanning Electron Microscopy (FE-SEM) revealed that photodegraded plastics exhibited greater surface oxidation, higher fragmentation rates, and reduced mechanical stability compared to new plastics. Biodegradation experiments under thermophilic conditions (55°C) further demonstrated enhanced breakdown of photodegraded plastic mulch materials. Moreover, the surface charge of MPs was found to become more negative after photodegradation, as confirmed by zeta potential measurements. Additional experiments evaluated the aggregation behavior of new and photodegraded MPs in varying water chemistries, showing that natural organic matter (NOM) reduced the aggregation of new MPs, while photodegraded MPs exhibited increased aggregation. The study also extended to polymer-coated controlled-release fertilizers (PC-CRFs), which were found to release MPs during nutrient delivery, with MP release rates significantly higher in soil compared to water. These integrated findings provide critical insights into how environmental weathering processes alter MPs' physicochemical properties, ultimately affecting their fragmentation, degradation, and environmental behavior. Under Objective 2: Elucidate the Interrelation Between MPs, Soil Particles, and Water Pore Flow to Identify MPs' Vertical Transport Through Soil, extensive experimental efforts were directed toward elucidating the vertical transport of MPs through soil systems under simulated rainfall and irrigation conditions. Column studies using different soil types (sand, sandy loam, and loamy sand) were performed with MPs ranging in size from 10 µm to 300 µm. Initial experiments demonstrated that larger MPs (100-300 µm) were retained near the surface in fine sand columns, prompting a shift to smaller particle sizes for subsequent studies (~20µm). Soil purification techniques, including heating at 550°C, were developed to eliminate background organic matter and MPs, improving experimental precision. Breakthrough curves (BTCs) and retention profiles were generated to characterize MPs movement, with key findings indicating that MPs mobility depends strongly on soil texture, pore structure, and particle size. Experiments incorporating natural organic matter, simulated through humic acid solutions, showed enhanced MP mobility by reducing particle-soil attachment. Photodegraded MPs were found to migrate more readily than pristine MPs, highlighting the influence of surface chemistry changes on transport behavior. Comparative tests using glass beads and natural soils revealed clear differences in transport dynamics, with real soils showing greater retention and extended tailing effects. Overall, the results demonstrated that MPs' vertical movement in soil is controlled by a combination of soil properties, water chemistry, and MPs' surface characteristics, providing a foundation for realistic risk assessments of MPs in agricultural environments. For Objective 3:Develop the Numerical Models to Simulate MPs Transport and Deposition Processes, the project focused on the development, refinement, and validation of numerical models to simulate MPs transport and deposition processes. An advection-dispersion-reaction model using the finite difference method was created to simulate key transport mechanisms, including attachment, detachment, straining, and blocking within porous media. Early modeling efforts reproduced benchmark results from published studies (e.g., Bradford et al., 2003) to ensure model accuracy. As experimental data accumulated, the model was progressively refined, incorporating Cauchy-type boundary conditions to better simulate real-world conditions where MPs are deposited onto the soil surface rather than introduced in suspension. Calibration efforts aligned model predictions with experimental BTCs and retention profiles, using optimization techniques such as the Interior Point Method to minimize fitting errors. Key findings from both experiments and simulations indicated that buoyant MPs, even with low densities, can migrate significantly below the soil surface, especially in soils with lower clay content and in the presence of humic substances. Photodegraded MPs exhibited greater mobility than pristine MPs, further validating the model's predictive capability. These advances provided a novel framework for understanding and predicting MPs transport behavior under realistic agricultural conditions.

Publications

• Type: Conference Papers and Presentations Status: Accepted Year Published: 2024 Citation: A. Ccanccapa, A. Nair Gopakumar, M. Salehi. Development of a Py-GC/MS Methodology for Quantification of Microplastics in Water Samples. AWWA/MO Conference, March 2024 (Poster).
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2023 Citation: M.M. Ashiq, F. Jazaei, A. Bakhshaee. Unraveling Spatial Variability of Microplastics Distribution in Stormwater Ponds. AGU Fall Meeting, San Francisco, December 2023.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2023 Citation: M.M. Ashiq, F. Jazaei. Investigating the spatial patterns of microplastics in the soil of stormwater ponds. Student Research Forum, University of Memphis, April 2023.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2023 Citation: A. Herath, D.K. Datta, G. Bonyadinejad, M. Salehi. Studying the heavy metals uptake by microplastics and sediments in stormwater. MOAWWA/MWEA Joint Conference, Ozark, MO, March 2023.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2023 Citation: G. Bonyadinejad, M. Salehi. Studying the microplastics aggregation in water: An implication for water resources protection. TN/KN WPC Conference, Memphis, TN, August 2023.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2023 Citation: L. Bhattacharjee, F. Jazaei, M. Salehi. Studying the plastic release by slow-release fertilizers: implications for stormwater pollution. TN/KN WPC Conference, Memphis, TN, August 2023.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2023 Citation: M. Salehi, G. Bonyadinejad. Studying the effect of plastic mulch photodegradation on its biodegradation process. ACS Midwest Conference, St. Louis, MO, October 2023 (Oral).
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2022 Citation: Herath, M. Salehi. Studying the intrinsic and extrinsic factors influencing microplastics photodegradation behavior and heavy metals uptake in urban stormwater. AEESP Conference, Saint Louis, MO, June 2022 (Poster).
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2022 Citation: M. Salehi. A systematic investigation of microplastics weathering, fragmentation, and heavy metals transport within urban storm runoff. AEESP Conference, Saint Louis, MO, June 2022 (Oral).
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2022 Citation: L. Bhattacharjee, M. Salehi. Studying the plastics fragmentation under abrasive wear forces: an implication for agricultural plastics degradation through the soil. AEESP Conference, Saint Louis, MO, June 2022 (Poster).
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2022 Citation: R. Bonyadinejad, M. Salehi. Investigating the plastics aging within farmlands: an implication for sustainable agriculture. AEESP Conference, Saint Louis, MO, June 2022 (Poster).
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2022 Citation: G. Bonyadinejad, M. Salehi. Mechanistic understanding of microplastics photodegradation within the terrestrial environment: an implication for water resources protection. AGU Fall Meeting, Chicago, December 2022 (Oral).
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2022 Citation: Mahammad Masood Ashiq, F. Jazaei, A. Bakhshaee. Investigation and Identification of the Microplastics Presence in the Soil. AGU Fall Meeting, 2022.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2022 Citation: L. Bhattacharjee, M. Salehi. An investigation of factors influencing plastics fragmentation under abrasive mechanical forces: an implication for agricultural soil health. Graduate Students Research Forum, University of Memphis, March 2022.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2022 Citation: G. Bonyadinejad, M. Salehi, A. Herath. Investigating the sustainability of agricultural plastic products: combined influence of polymer characteristics and environmental conditions on microplastics aging. Graduate Students Research Forum, University of Memphis, March 2022.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2021 Citation: R. Bonyadinejad, M. Salehi, F. Jazaei. Microplastics photodegradation: An implication for water resources protection. Water Professional Conference (WPC21), Chattanooga, TN, August 2021 (Oral).
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2025 Citation: L. Bhattacharjee, A. Gopakumar Nair, A. Beheshtimaal, F. Jazaei, A. Ccanccapa-Cartagena, M. Salehi. Mechanisms of microplastic generation from polymer-coated controlled-release fertilizers (PC-CRFs). Journal of Hazardous Materials, 486 (2025): 137082.
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2025 Citation: A. Ccanccapa-Cartagena, A. N. Gopakumar, M. Salehi. A straightforward Py-GC/MS methodology for quantification of microplastics in tap water. MethodX, 14 (2025): 103173.
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2025 Citation: A. Bakhshaee, P. Babakhani, M.M. Ashiq, K. Bell, M. Salehi, F. Jazaei. Potential impacts of microplastic pollution on soilwaterplant dynamics. Scientific Reports - Nature, 15 (2025): 9784.
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2022 Citation: A. Herath, M. Salehi. Studying the intrinsic and extrinsic factors influencing microplastics photodegradation behavior and heavy metals uptake in urban stormwater. Environmental Pollution, 308 (2022): 119629.
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2022 Citation: G. Bonyadinejad, M. Salehi, A. Herath. Investigating the sustainability of agricultural plastic products: Combined influence of polymer characteristics and environmental conditions on microplastics aging. Science of the Total Environment, 839 (2022): 156385.
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2021 Citation: K. Aghilinasrollahabadi, M. Salehi, T. Fujiwara. Investigate the influence of microplastics weathering on their heavy metals uptake in stormwater. Journal of Hazardous Materials, 408 (2021): 124439.
• Type: Other Journal Articles Status: Under Review Year Published: 2025 Citation: M.M. Ashiq, P. Babakhani, B. Waldron, M. Salehi, K. Bell, F. Jazaei. Penetration of buoyant microplastic in soils during infiltration events under realistic contamination conditions. Science of the Total Environment
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2024 Citation: G. Bonyadinejad, M. Salehi. A simple methodology for in situ study of microplastics aggregation. CLEAN  Soil, Air, Water, 52(6) (2024): 2300378.
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2024 Citation: L. Bhattacharjee, F. Jazaei, M. Salehi. Insights into the mechanism of plastics fragmentation under abrasive mechanical forces: an implication for agricultural soil health. CLEAN  Soil, Air, Water, 51(8) (2023): 2200395.
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2023 Citation: M.M. Ashiq, F. Jazaei, K. Bell, A.S. Ali, A. Bakhshaee. Abundance, spatial distribution, and physical characteristics of microplastics in stormwater detention ponds. Frontiers of Environmental Science & Engineering, 17(10) (2023): 124.
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2023 Citation: A. Herath, et al. Partitioning of heavy metals in sediments and microplastics from stormwater runoff. Chemosphere, 332 (2023): 138844.
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2022 Citation: F. Jazaei, T. Jamal Chy, M. Salehi. Can microplastic pollution change soilwater dynamics? Results from controlled laboratory experiments. Water, 14(21) (2022): 3430.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2024 Citation: A. Bakhshaee, F. Jazaei, M.M. Ashiq, S.A. Tufail, A.S. Ali. Microplastic Identification and Quantification Using Combined Fluorescence Microscopy and Hotplate Techniques. AGU Fall Meeting, 2024.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2024 Citation: Mohammad Hamza Sohail Ahmed Tufail, F. Jazaei, A. Bakhshaee, M.M. Ashiq. Assessment of Microplastic Contamination in Biosolids from Wastewater Treatment Plants and Its Implications for Terrestrial Environments. AGU Fall Meeting, 2024.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2024 Citation: Alireza Bakhshaee, F. Jazaei, M.M. Ashiq, S.A. Tufail. Microplastic Quantification Using Combined Fluorescence Microscopy and Hotplate Techniques. AGU Fall Meeting, 2024.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2024 Citation: Maryam Salehi. Investigating the impacts of microplastics' intrinsic and extrinsic characteristics on their environmental degradation and heavy metal transport. Institute of Nuclear Disposal, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany, June 2024.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2024 Citation: Maryam Salehi. Investigating the impacts of microplastics' intrinsic and extrinsic characteristics on their environmental degradation and heavy metal transport. Department of Earth Sciences, Indian Institute of Science Education and Research (IISER), Kolkata, India, September 2024 (Virtual).
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2024 Citation: Maryam Salehi. Plastic Weathering and Contaminant Transport within the Environment. Plastics Challenges and Biotechnological Solutions Conference, European Federation of Biotechnology, March 2024 (Virtual).
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2024 Citation: Maryam Salehi. Microplastics in stormwater runoff: investigating fate, transport, and contaminant uptake. Environmentally Responsible Transportation Center, University of Missouri at Kansas City, April 2024 (Virtual).

Progress 05/01/23 to 04/30/24

Outputs
Target Audience:Scientists and Research Scholars: The results of our project were shared with scientists and research scholars via multiple research seminars, conferences (oral and poster presentations), and peer-reviewed publications. This information will enhance their knowledge of plastic pollutants and provide valuable insights into the fate of microplastics in the soil system. Our research sheds light on the surface chemistry and morphology changes that occur during the photo and mechanical degradations of microplastics and the transport of microplastics through soil systems, which are crucial for understanding their potential interactions with other pollutants in the environment and their impact on environmental biodiversity, ecosystem sustainability, and food safety. Undergraduate and Graduate Students: In our Environmental System Engineering (CIVL3140) class, as well as our physical/chemical treatment (CIVL6134/4143) classes, we provided training on pollution in the agricultural soil system to both undergraduate and graduate students. In addition, we covered advanced transport processes related to the movement of microplastics in the topsoil and conducted numerical simulations of these processes in graduate-level courses such as Computational Method in Hydraulics and Hydrology (CIVL 8901) and Groundwater Hydraulics (CIVL7195). Two undergraduate students were hired as hourly research assistants and were also given exposure to the project. By sharing our project results with undergraduate and graduate students, we aimed to encourage critical thinking about the extent of plastic pollution in agricultural soil and motivate students to consider careers in the agriculture industry that promote sustainability. K-12 students, teachers, and parents:K-12 students, parents, and teachers were briefed on research significance and approaches at departmental, college, and university events, as well as through PIs' in-person visits and outreach efforts. Changes/Problems:A one-year, no-cost extension was requested and subsequently approved by the USDA in response to the challenges and disruptions caused by the COVID-19 pandemic throughout the duration of this project. What opportunities for training and professional development has the project provided?Courses: Undergraduate students in courses like Environmental System Engineering (CIVL3140)and Hydrology (CIVL3181), along with graduate students taking Aquatic Chemistry (CEE8225), Computational Methods in Hydraulics and Hydrology (CIVL 8901), received comprehensive training on various aspects of microplastic (MP) pollution. This included understanding its significance, identifying sources, exploring transportation and degradation processes, and learning approaches for quantification and modeling. Through these courses, students gained valuable insights into the complexities of MP pollution and its environmental implications, equipping them with the knowledge and skills necessary to address this pressing issue effectively. Invited Seminars: The knowledge of plastic's weathering within the environment and its influence on contaminant transport has been disseminated to scientists, graduate students, and undergraduate students through invited seminars at theUniversity of Missouri, Kansas City (UMKC), Environmentally Responsible Transportation Center andPlastics Challenges and Biotechnological Solutions Conference by European Federation of Biotechnology. Training Graduate Students: This research project has provided an opportunity to train four Ph.D. students about plastics degradation processes and transport within the environment. Furthermore, these four students have learned multiple advanced methodologies to simulate the environmental degradation process, characterize the plastics' surface chemistry and morphology characteristics, and MP quantification processes. The graduate students were trained to use advanced technologies essential for investigating microplastic pollution. These technologies included Accelerated Weathering units, Micro-FTIR, fluorescent microscopy, and microplastic separation and quantification techniques, which will be valuable tools for them to use in their future careers. Workshops:A collaborative two-day workshop convened at both the University of Memphis and the University of Missouri, blending virtual and in-person participation formats. The workshop, entitled " Agricultural Plastic Pollution and Its Impacts," could draw numerous undergraduate attendees eager to delve into the complexities of MP pollution, exploring its nuances through a series of engaging lectures, discussions, and interactive sessions. Through lectures, discussions, and hands-on activities--including soil filtration, field soil sampling at the Memphis Agricenter, MP separation from soil samples, and basic fluorescent microscopy--students gained practical insights into the complexities of studying this emerging contaminant. Through this comprehensive workshop, participants not only encountered the challenges inherent in studying emerging pollutants like MP but also gained valuable skills crucial for future research and environmental stewardship. How have the results been disseminated to communities of interest?The results have been demonstrated through peer-reviewed publications, conference presentations, and invited seminars to researchers, graduate, and undergraduate students, industry practitioners, and policymakers. Peer-Reviewed Publications Bhattacharjee, Linkon, Farhad Jazaei, and Maryam Salehi. "Insights into the mechanism of plastics' fragmentation under abrasive mechanical forces: An implication for agricultural soil health."CLEAN-Soil, Air, Water51.8 (2023): 2200395. Ashiq, Muhammad Masood, et al. "Abundance, spatial distribution, and physical characteristics of microplastics in stormwater detention ponds."Frontiers of Environmental Science & Engineering17.10 (2023): 124. Bonyadinejad, Gholamreza, and Maryam Salehi. "A simple methodology for in situ study of microplastics' aggregation."CLEAN-Soil, Air, Water(2024): 2300378. Herath, Amali, et al. "Partitioning of heavy metals in sediments and microplastics from stormwater runoff."Chemosphere332 (2023): 138844. Conference and presentations M. Salehi, G. Bonyadinejad, Studying the effect of plastic mulch photodegradation on its biodegradation process, ACS Midwest Conference, St. Louis, MO, Oct 2023 (Oral) L. Bhattacharjee, F. Jazaei, M. Salehi, Studying the plastic release by slow-release fertilizers, implications for stormwater pollution, 2023 TN/KN WPC Conference, Memphis, TN, Aug 2023 (Poster) G. Bonyadinejad, M. Salehi, Studying the microplastics' aggregation in water: An implication for water resources protection, 2023 TN/KN WPC Conference, Memphis, TN, Aug 2023 (Poster) A. Herath*, D. K. Datta, G. Bonyadinejad, M. Salehi, Studying the heavy metals uptake by microplastics and sediments in stormwater, 2023 MOAWWA/MWEA Joint Conference, Ozark MO, March 2023 (Poster) M. M. Ashiq, F. Jazaei, Investigating the spatial patterns of microplastics in the soil of stormwater ponds, Student Research Forum, University of Memphis, April 2023 (Poster) M. M. Ashiq, F. Jazaei, A. Bakhshaee, Unraveling Spatial Variability of Microplastics Distribution in Stormwater Ponds, AGU Fall Meeting, San Francisco, Dec 2023 (Poster) ?Ph.D. Dissertation Gholamreza Bonyadinejad, Investigating the Environmental Weathering of Plastics Used within the Agricultural Fields, Department of Civil Engineering, The University of Memphis, 2023 What do you plan to do during the next reporting period to accomplish the goals?Objective 1)During the upcoming reporting period, our focus will be on completing the data analysis for our study on the release of microplastics (MPs) from polymer-coated controlled-release fertilizers (PCFs). This analysis aims to enhance our understanding of plastic pollution resulting from PCF application in agricultural settings. The coatings of PCFs typically consist of non-biodegradable polymers such as polyethylene, polyolefin, and polyurethane. When these microcapsules remain in agricultural lands, they are subject to various external mechanical forces, including abrasion, compression, and fatigue. These forces can induce localized stress on the polymer coatings, potentially leading to fragmentation. Thus, we will investigate the impact of soil particle abrasion and compression from agricultural machinery on further fragmentation of PCF prills within farmlands. To achieve these objectives, we will conduct experimental studies to simulate the effects of abrasion, compression, and other mechanical forces on PCFs in agricultural environments. We will also continue data collection and analysis related to MP release from PCFs to gain insights into their behavior and environmental impact. Objective 2) This objective is accomplished. Objective 3)For the upcoming reporting period, we will focus on improving our MP transport simulation modeling techniques in order to accurately capture the physical processes affecting the transport of microplastics in soil environments. By improving simulations of physical processes, such as the attachment and detachment of MP from soil particle surfaces and their blocking and straining through soil pores, we can better understand how MP are transported and retained in soil. For the upcoming reporting period, we will focus on the study of appropriate mathematical boundary conditions for MP-spiked soil layers used in laboratory experiments in an attempt to replicate lab results of MP transport. Furthermore, we will use rigorous optimization methods to refine our numerical model predictions and calibrate them to the results of the laboratory experiments in order to minimize subjectivity during the calibration process. To enhance our model's accuracy and reliability, we will identify the best optimizing technique that aligns lab results with predicted outcomes. Using different boundary conditions and optimization techniques, we expect to gain a deeper understanding of and better capability to predict MP transport in farmland soils. We will also focus on finalizing the findings and submitting them in peer-reviewed journals.

Impacts
What was accomplished under these goals? (Objective 1) Investigate the influence of combined photo and mechanical degradations on MPs fragmentation, surface chemistry, and morphology alteration. In light of the critical importance of surface chemistry alterations in residual microplastics (MPs) resulting from photodegradation, affecting their aggregation behavior and mobility, we conducted a bench-scale study. Using a simplified methodology, we examined the aggregation of new and photodegraded MPs under different water chemistry conditions. For this, we conducted a six-week accelerated photodegradation experiment. Then, we characterize the surface chemistry and surface charge alteration of MPs due to the photodegradation through Fourier transform infrared (FTIR) spectroscopy and zeta potential measurements. The water chemistry variables in this study were water pH and concentration of humic acid (HA) as a representative natural organic matter (NOM) in water. The aggregation of the MPs was evaluated by monitoring the number of clusters forming over time following their intense dispersion in water. The surface chemistry analysis revealed the formation of oxidized surface functional groups on low density polyethylene (LDPE) MPs, and zeta potential measurements demonstrated the creation of more negative surface charge due to the photodegradation of these MPs. Additionally, the results showed that NOM presence reduced the aggregation tendency of new LDPE MPs due to enhanced electrostatic repulsion. However, pH fluctuations and the use of synthetic stormwater versus ultrapure water did not influence the aggregation kinetics of new MPs. Notably, the aggregation behavior of photodegraded MPs differed significantly from that of new MPs, exhibiting less aggregation compared to the new MPs. Additionally, photodegraded MPs showed a greater tendency for aggregation in stormwater compared to ultrapure water. This research enhances our understanding of MP transport and fate in aquatic environments and the associated environmental risks. Moreover, we investigated the mechanisms of plastic release from polymer-coated control release (PCF) fertilizers as there has been increased interest in PCFs recently. While PCFs efficiently release nutrients, their plastic coatings raise concerns about potential long-term impacts on soil health and ecosystems. Thus, this study was conducted to examine PCFs' physiochemical characteristics and their alterations during the nutrient release process, along with their nutrient release kinetics, and MP release pattern. For this purpose, two commercially available PCFs were utilized. The accelerated nutrient release experiments were conducted at 45 °C for 25 d in two media of ultrapure water and soil. PCFs' chemical composition, surface chemistry, and morphology characteristics were examined through pyrolysis gas chromatography-mass spectrometry (Py-GC-MS), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and field emission scanning electron microscopy (FE-SEM). Polyethylene was identified as the major plastic present in both PCFs. The release of total phosphorous (TP) and total nitrogen (TN) from the target PCFs into the contact water was examined over the release period. The nutrient release process induced osmotic pressure, resulting in the swelling of the coating, which led to the formation of microscopic pores and cracks on the PCF coatings, consequently generating MPs. The MP release from these PCFs into the contacting water and soil media was studied through µ-FTIR spectroscopy. The findings showed that the TP and TN concentrations in the effluent from the soil column were significantly lower than the ultrapure water for both examined PCFs. On the other hand, the release of MPs from PCFs type A and B into the soil column was approximately nine and seven times greater than in water. The study underlines the need for further investigation of the long-term environmental impacts of using PCFs in farming. Objective (2) Elucidate the interrelation between MPs, soil particles, and water pore flow to identify MPs' vertical transport through the soil. We conducted an experiment using vertical soil columns to study the movement of MPs (MP) in soil. The soil column was spiked with LDPE plastics as a layer of plastic. A methodology for MP extraction and quantification was developed for analyzing the MP concentration in water samples. MPs retention profile and breakthrough curve provided valuable insights into MPs transport. We estimated pore velocity under rainfall or irrigation conditions by injecting deionized water-dissolved NaCl solutions (1 g/L) into the vertical soil and analyzing the concentration of salt at the breakthrough curve. Previously, we conducted a trial experiment with farmland soil, i.e., sandy loam. Separate experiments were conducted to examine the impact of deionized water and dissolved organic matter on LDPE MPs transport in two different farmland soils, i.e., sandy loam and loamy sand. The influent for these experiments comprised deionized water and a humic acid (HA) solution. The HA powder, obtained from ThermoScientific, was fully dissolved in deionized water at a concentration of 50 mg/L and continuously injected into the columns, to replicate natural soils with organic matter. Additionally, we investigated the transport capability of degraded MP compared to new MP. We have therefore developed a mechanism to degrade MP using accelerated weathering systems, QUV, which was available in our laboratory. In a QUV weathering tester, LDPE particles were evenly distributed in 1 mm thick glass Petri dishes. A UV-AB meter was used to measure UVA bulb irradiation intensity in real-time, and plastic particles were moved every 24 hours. Fourier-transform infrared spectroscopy was used to verify degradation. Duplicate columns were used for each experimental condition to assess the influence of soil types, new and degraded LDPE particles, as well as influential and non-influential soil types. This multifaceted approach provided an understanding of the complex interactions between soil characteristics, water composition, and MP transport dynamics in agricultural soils. Our initial findings indicate that LDPE MP retention decreases with increasing sand volume in the soil matrix. HA solution, as well as UV-photodegradation on MP, could also contribute to this decrease in retention. In order to gain a comprehensive understanding of these impacts, we're still investigating them in greater detail. Objective (3) develop the numerical models to simulate the MPs transport and deposition process. Considerable advancements have been made in developing numerical models to simulate the transportation and deposition of MP. Our primary focus has been on the refinement of the existing model and calibration efforts based on experimental data.The model has been refined to account for blocking phenomena and several physical processes affecting MP transport through soil pores such as attachment, detachment, and straining. Using reported relevant benchmark tests and analytical solutions, we rigorously validated the numerical model. A number of mathematical boundary conditions were investigated that could better reflect the transport of MP in soil columns. To calibrate the developed model, experimental data were analyzed, aligning predictions with observed outcomes; however, further improvements are needed to better understand MP transport. Various optimization methods were carefully evaluated to identify the best combination of accuracy and computational efficiency. Our systematic approach ensures that our calibrated model accurately captures the intricate dynamics of MP transport in agricultural soils. As a result of this approach, not only will breakthrough curves and retention profiles be predicted, but also a better understanding of how MPs interact with soil will be gained.?

Publications

• Type: Conference Papers and Presentations Status: Other Year Published: 2023 Citation: M. M. Ashiq, F. Jazaei, Investigating the spatial patterns of microplastics in the soil of stormwater ponds, Student Research Forum, University of Memphis, April 2023
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2023 Citation: M. M. Ashiq, F. Jazaei, A. Bakhshaee, Unraveling Spatial Variability of Microplastics Distribution in Stormwater Ponds, AGU Fall Meeting, San Francisco, Dec 2023
• Type: Conference Papers and Presentations Status: Other Year Published: 2023 Citation: L. Bhattacharjee, F. Jazaei, M. Salehi, Studying the plastic release by slow-release fertilizers, implications for stormwater pollution, 2023 TN/KN WPC Conference, Memphis, TN, Aug 2023
• Type: Conference Papers and Presentations Status: Other Year Published: 2023 Citation: G. Bonyadinejad, M. Salehi, Studying the microplastics aggregation in water: An implication for water resources protection, 2023 TN/KN WPC Conference, Memphis, TN, Aug 2023
• Type: Conference Papers and Presentations Status: Other Year Published: 2023 Citation: A. Herath, D. K. Datta, G. Bonyadinejad, M. Salehi, Studying the heavy metals uptake by microplastics and sediments in stormwater, 2023 MOAWWA/MWEA Joint Conference, Ozark MO, March 2023
• Type: Journal Articles Status: Published Year Published: 2024 Citation: Bonyadinejad, Gholamreza, and Maryam Salehi. "A simple methodology for in situ study of microplastics aggregation." CLEANSoil, Air, Water (2024): 2300378.
• Type: Journal Articles Status: Published Year Published: 2023 Citation: L. Battacharjee, F. Jazaei, M. Salehi, (2023) Insights into the mechanism of plastics fragmentation under abrasive mechanical forces: an implication for agricultural soil health. Journal of Clear Air Water and Soil. 2200395, doi.org/10.1002/clen.202200395
• Type: Journal Articles Status: Published Year Published: 2023 Citation: Ashiq, Muhammad Masood, et al. "Abundance, spatial distribution, and physical characteristics of microplastics in stormwater detention ponds." Frontiers of Environmental Science & Engineering 17.10 (2023): 124.
• Type: Journal Articles Status: Published Year Published: 2023 Citation: Herath, Amali, et al. "Partitioning of heavy metals in sediments and microplastics from stormwater runoff." Chemosphere 332 (2023): 138844.
• Type: Conference Papers and Presentations Status: Other Year Published: 2023 Citation: M. Salehi, G. Bonyadinejad, Studying the effect of plastic mulch photodegradation on its biodegradation process, ACS Midwest Conference, St. Louis, MO, Oct 2023 (Oral)

Progress 05/01/22 to 04/30/23

Outputs
Target Audience:Scientists and Research Scholars: The results of our project were shared with scientists and research scholars via multiple research seminars, conferences (oral and poster presentations), and peer-reviewed publications. This information will enhance their knowledge of plastic pollutants and provide valuable insights into the fate of microplastics in the soil system. Our research sheds light on the surface chemistry and morphology changes that occur during the photo and mechanical degradations of microplastics and the transport of microplastics through soil systems which are crucial for understanding their potential interactions with other pollutants in the environment and their impact on environmental biodiversity, ecosystem sustainability, and food safety. Undergraduate and Graduate Students: In our Environmental System Engineering (CIVL3140) class, as well as our physical/chemical treatment (CIVL6134/4143) classes, we provided training on pollution in the agricultural soil system to both undergraduate and graduate students. In addition, we covered advanced transport processes related to the movement of microplastics in the topsoil and conducted numerical simulations of these processes in graduate-level courses such as Computational Method in Hydraulics and Hydrology (CIVL 8901) and Groundwater Hydraulics (CIVL7195). By sharing our project results with undergraduate and graduate students, we aimed to encourage critical thinking about the extent of plastic pollution in agricultural soil and motivate students to consider careers in the agriculture industry that promote sustainable agricultural products and help resolve this problem. Graduate students were also trained to utilize advanced technologies vital in microplastic pollution investigations, including Accelerated Weathering units, Micro-FTIR, fluorescent microscopy, and microplastic separation and quantification techniques, to be used in their future careers. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Courses:The undergraduate students enrolled in Environmental System Engineering (CIVL3140) and Hydrology (CIVL3181) classes and graduate students enrolled in Water Chemistry (CIVL7903/8903) classes have been trained on plastic pollutant fate within agriculture fields. Moreover, advanced transport processes that control the microplastics transport in topsoil and their numerical simulation were discussed in the graduate course titled Computational Method in Hydraulics and Hydrology (CIVL 8901). Invited Seminars: The knowledge of plastic's weathering within the environment and its influence on contaminant transport has been disseminated to scientists, graduate, and undergraduate students through invited seminars at the University of Missouri in Columbia, University of Missouri, Science and Technology in Rolla, and City of Columbia, and the Lakes of Missouri Volunteer program. University of Missouri, Science and Technology, Department of Civil, Architectural, and Environmental Engineering, "A systematic investigation of microplastics' weathering, fragmentation, and heavy metals transport in urban storm runoff", Rolla MO, Dec 2022 University of Missouri, School of Natural Resources, "Life in plastics not so fantastic", Columbia MO, Nov 2021 The City of Columbia, Office of Sustainability, "Unwrapping the Plastics: An investigation of plastics' fate and contaminant transport within the environment", Columbia MO, Sep 2022 The Lakes of Missouri Volunteer Program, 30th Anniversary, "Life in plastics not so fantastic", Columbia, Columbia MO, Oct 2022 Training K-12 students and their teachers on plastic pollution: A week-long summer workshop called Girl Experiencing Environmental Engineering (GEEE) was conducted to educate middle and high school students on environmental pollution and particularly plastic pollution A half-day workshop is conducted for K-12 teachers and educators on environmental pollution and particularly plastic pollution. At the Herff College of Engineering Eday at the University of Memphis, a research presentation and awareness-raising event were held for a half-day. The event was attended by K12 students, teachers, and members of the general public, all of whom were interested in learning more about STEM research and its applications. Training Graduate Students: This research project has provided an opportunity to train four Ph.D. students about plastics degradation processes and transport within the environment. Furthermore, these four students have learned multiple advanced methodologies to simulate the environmental degradation process, characterize the plastics' surface chemistry and morphology characteristics, and MP quantification processes. The graduate students were trained to use advanced technologies essential for investigating microplastic pollution. These technologies included Accelerated Weathering units, Micro-FTIR, fluorescent microscopy, and microplastic separation and quantification techniques, which will be valuable tools for them to use in their future careers. How have the results been disseminated to communities of interest?The results have been demonstrated through peer-reviewed publications, conference presentations, workshops, and invited seminars to researchers, graduate, and undergraduate students, industry practitioners, and policymakers. Moreover, the undergraduate and graduate students have been informed about plastic pollution within the farmlands, their transport within the soil, and their impacts through the following courses taught by PIs,Environmental System Engineering (CIVL3140),Hydrology (CIVL3181),Computational Methods in Hydraulics and Hydrology (CIVL7198), and Aquatic Chemistry (CEE8225). What do you plan to do during the next reporting period to accomplish the goals?During the next period, we will complete an analysis of the data we collected regarding the combined impacts of photo and mechanical degradation of biodegradation of plastic mulch. The results obtained by accelerated mechanical degradation of new and photodegraded plastic film and pellet will be compared to the data collected by the field investigation. Moreover, the photodegradation behavior of plastic mulch under real field conditions will be compared to the accelerated experiments over varied exposure periods. Moreover, the photodegraded and mechanically abraded MPs of different sizes will be prepared and characterized for the column experiments. The column experiments will be conducted to evaluate the influence of surface chemistry and morphology variations of aged MPs on the extent of their vertical transport through the soil column. The planned column experiments will be carried out using various soils, and the numerical models will be calibrated accordingly. The resulting data will then be interpreted in order to gain a deeper understanding of the mechanisms involved in the transport of MP. Following the data interpretation, the results will be disseminated to the community of interest by publishing the peer-reviewed paper and conference presentation. The outreach program will be conducted to disseminate the project outcome to the framers and stakeholders. A series of online presentations will be prepared to be posted on the website of the International Agricenter and Extension office at Mizzou. Two training workshops will be conducted to enhance the undergraduate students understanding the agricultural soil pollution with a specific focus on plastic residuals at the University of Memphis and the University of Missouri. These two-day workshops will be conducted through in-class lectures, hands-on activities in the field, and laboratory analyses.

Impacts
What was accomplished under these goals? (Objective 1) Investigate the influence of combined photo and mechanical degradations on MPs fragmentation, surface chemistry, and morphology alteration We completed our investigation of the fragmentation of plastics under different normal loadings. Studying the plastics' surface morphology variations due to the abrasion process revealed the microcutting as the dominant process at low normal loads (4 N). However, a combination of microploughing and microcutting occurred by increasing the normal force to 8 N. Despite the significant surface morphology variations of the new LDPE film due to the abrasion process; the water contact angle did not alter. Furthermore, the fragmentation behavior of photodegraded LDPE pellets and films was compared to the new plastics. The extent of the microplastics generation due to the fragmentation process was quantified using fluorescence microscopy imaging. The localized stress and strains at the contact sites of plastic and sand particles resulted in abrasion of the plastic surface. According to the results, the normal loadings and duration of abrasion play a significant role in the degree of fragmentation of plastics. The results demonstrated a significant difference between the fragmentation behavior of new and photodegraded plastics. Despite the new LDPE films, the photodegraded LDPE films were completely disintegrated due to the abrasion process. Following our research on agricultural plastics' photodegradation and fragmentation within the farmland, we have investigated the impacts of plastic mulch photo and mechanical degradation on their biodegradation within the soil system. For this purpose, regular nonbiodegradable low-density polyethylene (LDPE) mulch and biodegradable plastic mulch were irradiated with UVA for 3, 6, and 9 weeks in a QUV chamber. The plastic mulches' surface chemistry alterations were analyzed using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) Spectroscopy. The variations of their crystalline percentage were analyzed using Differential Scanning Calorimetry (DSC). The mechanical degradation of plastic mulches was conducted via our newly developed method of abrasion with sandpaper. The mechanically degraded plastic mulches were generated by applying a normal force of 2.0 N on the new plastic mulch for 5 min abrasion duration. As the main biodegradation media, the soil was collected from Agricenter International and sieved with a 5 mm opening size sieve. The active compost inoculum was sieved and mixed with the soil. Nutrients were added to this mixture to promote microorganisms' growth. The biodegradation experiments were conducted at the thermophilic phase (55 ?C) for 45 days. The biodegradation media was maintained under aerobic conditions during all experiments. A pipe connected to a pump was used to introduce air throughout the mixture media from the bottom of the beaker to maintain aerobic conditions. After that, samples were collected, washed, air-dried, and weighed for further analysis. The extent of biodegradation was determined using ATR-FTIR spectroscopy, Differential Scanning Calorimetry (DSC), Gel Permeation Chromatography (GPC), and Field Emission Scanning Electron Microscopy (FE-SEM). The GPC was used to study the changes in molecular weight of the polymeric structure of the mulches, and FE-SEM imaging was conducted to identify the surface morphology variations due to the biodegradation process. Objective (2) Elucidate the interrelation between MPs, soil particles, and water pore flow to identify MPs' vertical transport through the soil A series of transport experiments were performed using varied column lengths and soil types, including sand and sandy loam, to estimate the time scale of the process and experiments. With this data, a practical and efficient setup was devised that enables multiple experiments with replicates to be executed in the lab without oversimplifying the process. As a result, the optimum length of 5 inches was selected. Fine sand was utilized in subsequent experiments, which passed through sieve #25 and was retained on sieve #40. It was decided to preprocess the sand to remove the plastic and organic matter (OM) impurities, as simply washing of sand with deionized water did not suffice. We heated the fine sand to ignite background MP and OM after establishing a suitable range of heating times and temperatures. It was found that heating the natural organic matter and MPs at 550°C for 3 hours was effective in burning and removing the impurities, which was significantly below quartz and clay melting point. Multiple experiments were performed to examine the movement of LDPE MPs that varied in size from 106 to 300 μm. The flow rate was estimated assuming a fully saturated condition with a thin (<2 mm) water ponding layer to mimic the infiltration flow after rainfall or irrigation. Effluent samples were collected over multiple intervals for a duration of the experiment ranging from 6 to 12 hours. The MPs were analyzed and quantified using a fluorescence microscope and Nile Red dye. Results show that MPs sized between 106 μm to 300 μm did not move through the fine sand. As a result, the idea of using MPs of 10 μm for fine sand was adopted. We also opted to conduct a series of experiments utilizing glass beads of the same size to establish a benchmark for the transport process of MPs that could be used as a basis for comparison. Glass beads have uniform pore structure and a smoother surface than sand, which creates less surface area for MP to attach to. The peak of the BTC was observed after 3 PVs, and the rise and fall of the BTC peak were relatively abrupt within 6 PVs. However, the BTC continued to tail from 6 PVs to 20 PVs. MP retention profiles inside sand and glass beads decreased exponentially with depth. As a follow-up to our experiments with fine porous media, we tested the transport of MPs through real agricultural field soil. The type of soil was identified using sieve and hydrometer analysis with the PARIO Particle Size Analyzer, which revealed that it was sandy loam. The soil was purified by heating it to 550°C for three hours to remove any impurities. A spiked layer of MPs was placed on top of the soil within the columns. Compared to the BTC for glass beads, the rise of the sandy loam BTC was less steep, as it took 2.5 PVs of water to reach the BTC peak. Additionally, the falling limb of the BTC for the sandy loam soil was much different than that of the glass beads. It had a steadier decline, which transitioned to a tailing effect after 8 PVs, in contrast to the glass beads, which only required 6 PVs. These results highlight the varying behavior of MPs in different types of soils. During the research, an efficient and time-saving MP separation method was developed for better MP quantification of soil samples with high silt and clay contents. Objective (3)develop the numerical models to simulate the MPs transport and deposition process A numerical model has been developed to investigate the transport of microplastics in saturated soil. The model utilizes the advection-dispersion-reaction partial differential equation, which is solved using the finite difference method. The reaction component of the model accounts for several physical processes that impact the transport of MP through soil pores, including attachment, detachment, and straining. To assess the reliability of the developed model, we validated it using input parameters from a prior study conducted by Bradford et al. (2003) and reproduced their results. We compared the simulated data produced by our model with their experimental data and modeling results, including the breakthrough curve (BTC) and retention profile (RP). This process helped us ensure the developed model's accuracy and reliability. The developed model will be calibrated by the experimental data to investigate the MP transport processes.

Publications

• Type: Journal Articles Status: Published Year Published: 2021 Citation: K. Aghilinasrollahabadi, M. Salehi, T. Fujiwara, (2021) "Investigate the Influence of Microplastics Weathering on Their Heavy Metals Uptake in Stormwater", Journal of Hazardous Materials, 408, 124439
• Type: Journal Articles Status: Published Year Published: 2022 Citation: F. Jazaei, T. Jamal Chy, M. Salehi, (2022) Can microplastic pollution change soilwater dynamics? results from controlled laboratory experiments, Water, 14(21), 3430. doi.org/10.3390/w14213430
• Type: Journal Articles Status: Published Year Published: 2022 Citation: A. Herath, M. Salehi, (2022) Studying the intrinsic and extrinsic factors influence microplastics photodegradation behavior and heavy metals uptake in urban stormwater, Environmental Pollution, 308, 119629. doi.org/10.1016/j.envpol.2022.119628
• Type: Journal Articles Status: Published Year Published: 2022 Citation: G. Bonyadinejad, M. Salehi, A. Herath, (2022) Investigating the sustainability of agricultural plastic products, combined influence of polymer characteristics and environmental conditions on microplastics aging, Science of Total Environment, 839, 156385. doi.org/10.1016/j.scitotenv.2022.156385
• Type: Journal Articles Status: Accepted Year Published: 2022 Citation: L. Battacharjee, F. Jazaei, M. Salehi, Insights into the mechanism of plastics fragmentation under abrasive mechanical forces: an implication for agricultural soil health. Submitted to the Journal of Clear Air Water and Soil. Fall 2022
• Type: Journal Articles Status: Accepted Year Published: 2023 Citation: Ashiq Muhammad Masood, Jazaei Farhad, Bell Kati, Ali Ahmed Shakir Ali, Bakhshaee Alireza, Babakhani Peyman. Abundance, spatial distribution, and physical characteristics of microplastics in stormwater detention ponds soil. Frontiers of Environmental Science & Engineering. 2023
• Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: Mahammad Masood Ashiq, Farhad Jazaei, Alireza Bakhsaee. Investigation and Identification of the Microplastics Presence in the Soil. AGU Fall Meeting 2022
• Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: G. Bonyadinejad, M. Salehi, Mechanistic understanding of microplastics photodegradation within the terrestrial environment: An implication for water resources protection, AGU Fall Meeting, Chicago, Dec 2022 (Oral)
• Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: R. Bonyadinejad, M. Salehi, Investigating the plastics aging within farmlands, an implication for sustainable agriculture, AEESP 2022, Saint Louis MO, June 2022 (Poster)
• Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: L. Battacharjee, M. Salehi, Studying the plastics fragmentation under abrasive wear forces, an implication for agricultural plastics degradation through the soil, AEESP 2022, Saint Louis MO, June 2022 (Poster)
• Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: M. Salehi, A systematic investigation of microplastics weathering, fragmentation, and heavy metals transport within the urban storm runoff, AEESP 2022, Saint Louis MO, June 2022 (Oral)
• Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: Herath, M. Salehi, Studying the intrinsic and extrinsic factors influence the microplastics photodegradation behavior and heavy metal uptake in urban stormwater, AEESP 2022, Saint Louis MO, June 2022 (Poster)

Progress 05/01/21 to 04/30/22

Outputs
Target Audience:Scientists and Research Scholars: The scientists and research scholars were informed about our results through the research seminar and peer-reviewed publication. The results generated within this project will promote their understanding of plastic pollutants and offer them important insights regarding the eventual fate of microplastics within the soil system. Understanding the microplastics' surface chemistry and morphology variations due to the photo and mechanical degradation processes provides a critical piece of information regarding their possible interaction with other pollutants present within the environment and their relevant impacts on environmental biodiversity, ecosystem sustainability, and food safety. Undergraduate and Graduate Students: Several undergraduate and graduate students who were enrolled in Environmental System Engineering (CIVL3140) class and physical/chemical treatment (CIVL6134/4143) classes were trained on the pollution within the agricultural soil system. Moreover, advanced transport processes controlling the transport of microplastics on topsoil and numerical simulation of them were discussed in a graduate-level course, Computational Method in Hydraulics and Hydrology (CIVL 8901) and Groundwater Hydraulics (CIVL7195). Demonstration of the project results to undergraduate and graduate students could promote their critical thinking regarding the extent of the plastic pollution problem within the agricultural soil and motivate them to consider careers within the agriculture industry to better resolve this problem and promote sustainable agricultural products. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Courses: The undergraduate students enrolled in Environmental System Engineering (CIVL3140) class and graduate students enrolled in the Physical/chemical treatment (CIVL6134/4143) class have been trained on plastic pollutants' fate within agriculture fields. Moreover, advanced transport processes that control the microplastic transport in topsoil and their numerical simulation were discussed in the graduate course titled Computational Method in Hydraulics and Hydrology (CIVL8901) andGroundwater Hydraulics (CIVL 7195). Invited Seminars: The knowledge of plastic's weathering within the environment and its influence on contaminant transport has been disseminated to scientists, graduate, and undergraduate students through invited seminars at the University of Memphis and the University of Notre Dame. The University of Memphis, Physics and Material Science Department, "Investigate the influence of microplastics weathering on their heavy metal uptake in stormwater", Nov 2021 The University of Notre Dame, Department of Civil & Environmental Engineering & Earth Sciences, "Investigate the influence of microplastics weathering on their heavy metal uptake in stormwater", April 2021 Workshop for High School Students: A plastic pollution workshop has been conducted for students who participated in the Environmental Alliance Clubat the White Station high school in the Shelby County school district in Memphis (October 2021). The information regarding plastic pollution within the environment and agricultural fields has been provided to the students. Training Graduate Students: This research project has been provided an opportunity for training four Ph.D. about plastics degradation processes and transport within the environment. Furthermore, these four students have learned multiple advanced methodologies to simulate the environmental degradation process and characterize the plastics' surface chemistry and morphology characteristic. How have the results been disseminated to communities of interest?The results have been demonstrated through peer-reviewed publications, conference presentations, andinvited seminars to the researchers, graduate, and undergraduate students, industry practitioners, and policymakers. Moreover, the undergraduate and graduate students have beeninformed about plastic pollution within the farmlands, their transport within the soil, and their impacts through the courses taught by PIs. Peer-Reviewed Publication Md Hadiuzzaman, M. Salehi, T. Fujiwara, Examine the Role of Microplastics' Photodegradation on their Fragmentation and Heavy Metal Transport in Stormwater, Environmental Research, (2022), In-Press Under Review Publication 1) G. Bonyadinejad, M. Salehi, A. Herath, Investigating the sustainability of agricultural plastic products, the combined influence of polymer characteristics and environmental conditions on microplastics aging, Science of Total Environment, Spring 2022 2) F. Jazaei, T. J. Chy; C. Meier, M. Salehi, Can Microplastic Pollution Change Soil-Water Characteristics and Potentially Cause Hydrological Impacts? -- Statistical Analyses of Controlled Laboratory Experiments, Submitted to the Journal of Science of Total Environment, Spring 2022 Conference Presentation R. Bonyadinejad, M. Salehi, F. Jazaie, Microplastics photodegradation: An implication for water resources protection, Water Professional Conference (WPC21), Chattanooga TN, Aug 2021 (oral) G. Bonyadinejad, M. Salehi, A. Herath, Investigating the sustainability of agricultural plastic products, the combined influence of polymer characteristics and environmental conditions on microplastics aging, The University of Memphis, Graduate Students Research Forum, March 2022 L. Bhattacharjee, M. Salehi, An investigation of factors influence the plastics fragmentation under abrasive mechanical forces: an implication for the agricultural soil health, The University of Memphis, Graduate Students Research Forum, March 2022 Invited Seminars The University of Memphis, Physics and Material Science Department, "Investigate the influence of microplastics weathering on their heavy metal uptake in stormwater," Nov 2021 The University of Notre Dame, Department of Civil & Environmental Engineering & Earth Sciences, "Investigate the influence of microplastics weathering on their heavy metal uptake in stormwater," April 2021 Courses: The undergraduate students enrolled in Environmental System Engineering (CIVL3140) class and graduate students enrolled in the physical/chemical treatment (CIVL6134/3134) class have been trained on plastic pollutants fate within agriculture fields. Moreover, advanced transport processes that control the microplastic transport in topsoil and their numerical simulation were discussed in the graduate course titled Computational Method in Hydraulics and Hydrology (CIVL8901) and Groundwater Hydraulics (CIVL7195). What do you plan to do during the next reporting period to accomplish the goals?During the next reporting period, the following tasks will be completed under research objectives 1, 2, and 3. (Objective 1)Investigate the influence of combined photo and mechanical degradations on MPs fragmentation, surface chemistry, and morphology alteration The results generated forthe comparison of accelerated microplastics' degradation experiments to the field study will be interpreted, and further laboratory investigation will be conducted in case needed. The accelerated photodegradation and mechanical abrasion experiments will be optimized to better simulate the real environmental weathering conditions. Then, the microplastics of different size distributions will be weathered to undergo the transport study in objective 2. (Objective 2) Elucidate the interrelation between microplastics (MPs), soil particles, and water pore flow to identify microplastics' vertical transport through the soil The column experiments will be conducted toexamine the influence of soil characteristics on microplastic transport and attachment within the soil system, more than 12 homogenized soils representing sand, sandy loam, and loamy sand will be produced. Before wet packing the soils, their physical properties, including grain size distribution, median size, porosity, and hydraulic conductivity, will be evaluated. Before initiating the experiments, the soil columns will be flushed with several cycles of ultrapure water. The peristaltic pump will first induce bromide (conservative) tracer for 3 pore volume. Sonicated MPs suspension is then injected for more than 10 pore volumes. A total of 20 effluent samples will be collected and analyzed for tracer using Hach UV-VIS DR6000 spectrophotometer located in PI's lab to determine the tracer breakthrough curves. These curves will be analyzed to estimate the accurate pore water velocity and flow hydraulic conditions. During the test, a total of 50 MPs effluent samples will be collected. The MPs will be separated from the collected samples using the floatation and filtration approaches. In addition to the breakthrough curves, the spatial distribution of microplastics attached to the soil particles will be determined in two steps. First, as an initial estimation, pore spaces that are visible through the transparent plexi-glass column will be examined by the microscope purchased with this grant. This will allow us to estimate the microplasticinfiltration depth through the intact soil column. Finally, the MPs attached to the soil particles will be carefully separated and evaluated. This column test will be repeated with different pore velocities and MP suspension concentrations. Following the completion of each experiment, the spatial distribution of MPs in the soil column will be evaluated. For this purpose, the sand column will be carefully excavated from the bottom end at 1 cm intervals. Using the number of MPs and their specific volume, the mass will be estimated and used for modeling purposes later. To evaluate the precision of the microplastics separation and counting approach a series of control samples will be prepared using the clean sand and MPs, and analyzed following the described method, then recovery percentage will be evaluated. At the end of each experiment, a mass balance analysis will be conducted using effluent concentration data and final spatial distribution of retained MPs in the soils. Objective (3): Prediction of MPs transport through the soil column with numerical modeling Numerical models will be developed to simulate the MPs' transport and their attachment to the soil. Proper boundary conditions representing each laboratory experiments will be introduced, and finally, the partial differential equation will be solved using appropriate mathematical approaches like finite difference and finite volume models. The developed numerical models will be calibrated by real breakthrough and soil sample data collected in Task-2. During the calibration procedure, several unknown parameters, which control the attachment process will be evaluated. The calibrated numerical models which can adequately simulate experimental data generated in Objective 2 will be used to identify the most and least influential factors through a series of numerical sensitivity analysis.

Impacts
What was accomplished under these goals? Objective (1)Investigate the influence of combined photo and mechanical degradations on MPs fragmentation, surface chemistry, and morphology alteration. Task 1:Combined Influence of Polymer Characteristics and Environmental Conditions on Microplastics Photodegradation This research task is focused on better understanding the combined influence of polymer characteristics and environmental conditionson microplastics' (MPs) photodegradation within the agricultural soil system. For this purpose, the photodegradation behavior of low density polyethylene (LDPE) MPs was studied through accelerated UVA radiation experiments under two different relative humidity (RH10and RH70) and soil deposition conditions. Metallic sieves were used to separate the LDPE particles of <106 µmand 300 µm
Publications

• Type: Journal Articles Status: Accepted Year Published: 2022 Citation: Md Hadiuzzaman, M. Salehi, T. Fujiwara, Examine the Role of Microplastics Photodegradation on their Fragmentation and Heavy Metal Transport in Stormwater, Environmental Research, (2022), Accepted
• Type: Journal Articles Status: Submitted Year Published: 2022 Citation: G. Bonyadinejad, M. Salehi, A. Herath, Investigating the sustainability of agricultural plastic products, the combined influence of polymer characteristics and environmental conditions on microplastics aging, Science of Total Environment, Spring 2022
• Type: Journal Articles Status: Submitted Year Published: 2022 Citation: F. Jazaei, T. J. Chy; C. Meier, M. Salehi, Can Microplastic Pollution Change Soil-Water Characteristics and Potentially Cause Hydrological Impacts?  Statistical Analyses of Controlled Laboratory Experiments, Submitted to the Journal of Science of Total Environment
• Type: Conference Papers and Presentations Status: Published Year Published: 2021 Citation: R. Bonyadinejad, M. Salehi, F. Jazaie, Microplastics photodegradation: An implication for water resources protection, Water Professional Conference (WPC21), Chattanooga TN, Aug 2021 (oral)
• Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: G. Bonyadinejad, M. Salehi, A. Herath, Investigating the sustainability of agricultural plastic products, the combined influence of polymer characteristics and environmental conditions on microplastics aging, The University of Memphis, Graduate Students Research Forum, March 2022
• Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: L. Battacharjee, M. Salehi, An investigation of factors influence the plastics fragmentation under abrasive mechanical forces: an implication for the agricultural soil health, The University of Memphis, Graduate Students Research Forum, March 2022
• Type: Theses/Dissertations Status: Accepted Year Published: 2021 Citation: T. J. Chy, Can microplastic pollution change the water dynamics of our soil resources? Department of Civil Engineering, The University of Memphis, 2021

Progress 05/01/20 to 04/30/21

Outputs
Target Audience:Scientists and Research Scholars:The scientists and research scholars were informed about our results through the research seminar and peer-reviewed publication. The results generated within this project will promote their understanding of plastic pollutants and offer them important insights regarding the eventual fate of microplastics within the soil system. Understanding the microplastics' surface chemistry and morphology variations due to the photo and mechanical degradation processes provides a critical piece of information regarding their possible interaction with other pollutants present within the environment and their relevant impacts on environmental biodiversity, ecosystem sustainability, and food safety. Industry Practitioners: The local industry practitioners in Memphis were informed about the project results through a seminar conducted in the Engineers Club of Memphis. Raising the industry practitioners' awareness of plastic residuals' long-term accumulation within the soil system may encourage them to develop more sustainable agricultural practices and devise more effective technologies to remove the plastic mulch residuals from agricultural fields after harvesting, more effectively. Minority and Underrepresented K-12 Students: The minority and underrepresented K-12 students were educated on plastic pollution within the agricultural soil system through a virtual workshop conducted in the Girl Experiencing Engineering summer program at the University of Memphis. They have learned the importance of sustainable agricultural practices to maintain soil health and ensure food safety. This training could promotetheir understanding of the critical impacts caused by plastic pollutants. Undergraduate and Graduate Students: A demonstration has been conducted in Herff Scholar day to encourage prospective undergraduate and graduate students to pursue a future career in Environmental Engineering to tackle the plastic pollution problem within the agricultural field. Several undergraduate and graduate students who were enrolled in Environmental System Engineering (CIVL3140) class and Water Chemistry (CIVL7903/8903) classes were trained on the pollution within the agricultural soil system. Moreover, advanced transport processes controlling the transport of microplastics on topsoil and numerical simulation of them were discussed in a graduate-level course, Computational Method in Hydraulics and Hydrology (CIVL 8901). Demonstration of the project results to undergraduate and graduate students could promote their critical thinking regarding the extent of the plastic pollution problem within the agricultural soil and motivate them to consider future careers within the agriculture industry to better resolve this problem and promote sustainable agricultural products. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Courses: The undergraduate students enrolled in Environmental System Engineering (CIVL3140) class and graduate students enrolled in Water Chemistry (CIVL7903/8903) class have been trained on plastic pollutant fate within agriculture fields.Moreover, advanced transport processes that controlthe microplastics transport intopsoil and their numerical simulation were discussed in the graduate course titledComputational Method in Hydraulics and Hydrology (CIVL 8901). Summer Workshop: A short workshop was conducted about plastic pollution for minority and underrepresented students who participated in the Girl Experiencing Engineering (GEE) summer program conducted by South West STEM HUB at the University of Memphis. Demonstration: A demonstration about plastic mulch degradation and distribution within the agricultural soil system was presented in Herff Scholar day for prospective undergraduate and graduate students. Training Graduate Students: This research project has been provided an opportunity for training three Ph.D. and two MSc students about plastics degradation processes and transport within the environment. Furthermore, these fivestudents have learned multiple advanced methodologies to simulate the environmental degradation process and characterize the plastics surface chemistry and morphology characteristics. How have the results been disseminated to communities of interest?Peer-Reviewed Publication K. Aghilinasrollahabadi, M. Salehi, T. Fujiwara, (2021) "Investigate the Influence of Microplastics Weathering on Their Heavy Metals Uptake in Stormwater", Journal of Hazardous Materials, 408, 124439 Other Products: Courses: The undergraduate students enrolled in Environmental System Engineering (CIVL3140) class and graduate students enrolled in Water Chemistry (CIVL7903/8903) class have been trained on plastic pollutant fate within agriculture fields.Moreover, advanced transport processes that controlthe microplastics transport intopsoil and their numerical simulation were discussed in the graduate course titledComputational Method in Hydraulics and Hydrology (CIVL 8901). Events: Summer Workshop: A short workshop was conducted about plastic pollution for minority and underrepresented students who participated in the Girl Experiencing Engineering (GEE) summer program conducted by South West STEM HUB at the University of Memphis. Demonstration: A demonstration about plastic mulch degradation and distribution within the agricultural soil system was presented in Herff Scholar day for prospective undergraduate and graduate students. Mentoring: Three Ph.D. and two MSc students have been mentored by PI's to conduct the simulated environmental degradation experiments, characterize the surface chemistry and morphology of samples, and quantify the extent of plastics fragmentation. What do you plan to do during the next reporting period to accomplish the goals?During the next reporting period, the following tasks will be conducted to complete our first objective aiming to evaluate the microplastics' degradation and fragmentation under simulated environmental conditions. For this purpose, the data collected through accelerated photo and mechanical degradation experiments will be analyzed and interpreted completely. We already started our field study by deploying the regular low density polyethylene (LDPE) mulch and biodegradable LDPE mulch in an agricultural field. We will continue collecting the plastic samples from the field and analyze their surface chemistry to identify how our accelerated photodegradation experiments deviate from the real environmental conditions. Furthermore, at the end of the harvesting cycle, the plastic mulch will be removed, and the field will be tilled. After that, the soil samples will be collected, and the microplastics number and size distribution will be quantified within the soil samples. The microplastics extracted from the soil samples will be subjected to the mechanical abrasion process, and their fragmentation will be evaluated. The results will be compared to the data collected from simulated laboratory experiments. We will develop our column transport experiments pursuing our second objective to investigate the factors that influence microplastics vertical transport through the soil systems. The new and degraded microplastics with two different size distributions will be fed through the transport columns under a variety of flow conditions and soil types to examine the influence of microplastics characteristics on their vertical transport and attachment within the soil system. Before wet packing, the soil columns, the soil physical properties, including the grain size distribution, median size, porosity, and hydraulic conductivity, will be evaluated. The tracer breakthrough curves will be determined to estimate the accurate pore water velocity and flow hydraulic conditions for the transport columns. The microplastics penetration through the columns and attachment to the soil particles will be examined through their extraction from effluent and soil samples, respectively.

Impacts
What was accomplished under these goals? The Application of agricultural plastic products such as mulch, greenhouse covers, and silage films is increasing due to their economic benefits in providing an early and better quality harvest. Despite the short-term benefits provided by plastic products, their long-term sustainability issues and negative impacts on soil health and ecology are not well understood. For instance, after the removal of plastic mulch from the field, some plastic residuals remain in the soil. As plastic residuals expose to solar radiation and mechanical forces, they might be fragmented into small particles called microplastics (d<5mm). Microplastics (MPs) are considered an emerging threat to soil health as they may influence soil biophysics, geochemistry, and ecology. Recent studies have revealed overwhelming evidence of direct and indirect deleterious impacts caused by MPs' pollution in the soil system. Thus, it is critical to better understand the fate and transport of MPs within the agricultural soil system to better estimate their negative impacts and develop effective management strategies. The primary scientific goal of this research is to investigate the MPs' fate and transport processes through agricultural soil systems. During the first year of this project, we have conducted the following major tasks pursuing our first objective to investigate the influence of combined photo and mechanical degradations on MPs' fragmentation, surface chemistry, and morphology alteration. A literature review regarding the usage of agricultural plastic products and their exposure to the physical and mechanical forces while present in the agricultural fields has been conducted. The studies that examined the influences of plastics' characteristics and environmental conditions on photodegradation kinetics have been reviewed. The accelerated UV-A photodegradation experiments have been conducted for low density polyethylene (LDPE) particles, regular LDPE mulch, and biodegradable LDPE mulch. The degree of plastic oxidation due to the photodegradation under different relative humidity and for varied durations of time was estimated. Furthermore, the accelerated UV-B photodegradation experiments have been conducted for LDPE and polyethylene terephthalate (PET) films for varied durations of time. In this research, two different protocols have been developed to simulate the degradation and fragmentation of MPs through exposure to mechanical forces during abrasion with the soil particles. In the first method, mechanical weathering of MPs was conducted by abrasion of LDPE and PET MPs with sand particles. Thus, the bottles containing these MPs and silt/sand were shaken for different durations of time (30, 45, 60, and 90 days). To study the influence of combined photo and mechanical degradations on MPs fragmentation, the photodegraded LDPE and PET MPs were subjected to mechanical weathering. Then, the number and size distribution of the generated plastic fragments were quantified. For this quantification, a protocol was developed to separate the MPs from a mixture of sand based on floatation, filtration, and fluorescence microscopy. The second mechanical degradation protocol has been developed to identify the extent of plastics fragmentation under an accelerated abrasive process. In this method, the plastic samples have been abraded with sandpaper. The influence of vertical loading, abrasive ratio, and abrasion duration on the number and size distribution of generated plastic fragments has been investigated. The surface morphology variations of plastic samples due to the photodegradation and mechanical weathering experiments were analyzed using the Field Emission Scanning Electron Microscopy (FE-SEM) and Atomic Force Microscopy (AFM). The surface wettability was examined through water contact angle measurements. The surface chemistry was investigated through Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-Ray Photoelectron spectrophotometry (XPS). The accelerated photodegradation experiments revealed the creation of several oxidized functional groups onto the surface of all examined plastic samples after exposure to UV-A and UV-B irradiations. Furthermore, the Carbonyl Index, an indicator of MPs surface oxidation, has been raised by increasing the duration of the photodegradation process. A greater level of relative humidity (70%) present within the environment reduced the photodegradation intensity for LDPE MPs and LDPE mulch compared to the condition where a lower relative humidity was present (10%). The larger LDPE particles (300µm
Publications

• Type: Journal Articles Status: Published Year Published: 2021 Citation: Khashayar Aghilinasrollahabadi, Maryam Salehi, Tomoko Fujiwara, Investigate the influence of microplastics weathering on their heavy metals uptake in stormwater, Journal of Hazardous Materials, Volume 408, 2021, 124439,ISSN 0304-3894, https://doi.org/10.1016/j.jhazmat.2020.124439.