SOIL, WATER, AND ENVIRONMENTAL PHYSICS ACROSS SCALES

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1004173
• Multistate No.: W-3188
• Project Start Date: Oct 1, 2014
• Project End Date: Sep 30, 2019
• Program Code: [(N/A)]- (N/A)

Recipient Organization
WASHINGTON STATE UNIVERSITY
240 FRENCH ADMINISTRATION BLDG
PULLMAN,WA 99164-0001

Performing Department
Crop & Soil Sciences

Non Technical Summary
We will investigate the role of particulates for fate and transport of contaminants in soils and sediments. Particulates are ubiquitous in the environment, and include nanoparticle, clay minerals, iron oxides, bacteria, viruses, and radionuclides. We will clarify how these particles can move through soils and potentially contaminate groundwater resources. We particularly focus on interactions of particulates with the air-water interface. Air-water interfaces are always present in soils and unsaturated sediments, and present a potential attachment site for particulates; however, air-water interfaces are usually not stable and move with drainage and imbibition of water in soils. Movement of air-water interfaces can mobilize and transport contaminants.

Animal Health Component

50%

Research Effort Categories

Basic

50%

Applied

50%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
102	0110	2050	100%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
0110 - Soil;

Field Of Science
2050 - Hydrology;

Keywords

contaminant transport

colloid fate and transport

Goals / Objectives
To improve our fundamental understanding of soil physical properties and processes, and how they interact with other environmental and biogeochemical processes across various spatial and temporal scales. To extend our knowledge of scale-appropriate methodologies to improve stakeholder-management of soil and water resources that benefit agricultural, natural resource and environmental sustainability. To develop and evaluate new instruments and analytical methods to connect our understanding of mass and energy transport in soil at different scales to environmental transformations.

Project Methods
We will investigate interactions of colloids with interfaces, and fate and transport of potential agricultural and emerging contaminants by conducting a combination of laboratory column experiments, numerical modeling, greenhouse studies, and field scale research. Colloids in porous media interact with the solid-liquid and liquid-gas interfaces. We will use microscopic (electron and confocal microscopy, tensiometry) and macroscopic (goniometry, light scattering, column experiments) techniques to investigate and quantify the interactive processes. We will also use theoretical calculations to quantify interaction forces. Identifying and quantifying the mechanisms controlling colloid fate and transport in the vadose zone will be incorporated into mathematical models (HYDRUS). We will also use laboratory methods, primarily column breakthrough curves, batch sorption experiments, soil microcosm batch studies to examine the processes which control bioactive chemical fate and transport. Controlled experiments and observations from the field using soil extracts, lysimetry, and wells will be used to identify field fate and transport mechanisms.

Progress 10/01/14 to 09/30/19

Outputs
Target Audience:Scientific peers, Department of Energy, Environmental Engineering and Consulting Companies, Farmers, Industry Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Training for graduate students. How have the results been disseminated to communities of interest?Journal articles have been published, research results have been presented at invited seminars and volunteered presentations at professional meetings. What do you plan to do during the next reporting period to accomplish the goals?We will continue the work on the biodegradable plastic mulches, colloid transport, life in the dry limit of earth, and WEPP development and application.

Impacts
What was accomplished under these goals? We developed a new theory that allows us to predict and quantify fate and transport of hollow nanoparticles in soils. Many emerging nanoparticles are hollow, such a carbon nanotubes, and our theory paved the way for a better understanding of such nanoparticles in the environment. We also showed that our current methods to extract and quantify nano- and microplastics in soils are insufficient. Our research on biodegradable plastic mulch films showed that biodegradable plastics hold promise, but the release of micro- and nanoparticles from biodegradable plastic upon degradation warrants additional investigation and calls for longer field testing to ensure that either complete biodegradation occurs or that no long-term harm to the environment is caused. Goal (1): To improve our fundamental understanding of soil physical properties and processes, and how they interact with other environmental and biogeochemical processes across various spatial and temporal scales. Nanoparticles play an important role our daily lives: health care products, cleaning agents, foods, clothing, and sporting goods all contain nanoparticles. Theory exists to predict environmental fate of solid nanoparticles; however, many nanoparticles are hollow, so existing theory cannot be applied. We developed a theoretical framework to quantify interactions of hollow nanoparticles with solid-water and solid-air interfaces. This theory now allows us to predict fate and transport of hollow nanoparticles in soil and groundwater. We evaluated the effects of freezing-thawing and wetting-drying on heavy metals leaching from biosolids. Biosolids samples were irrigated with water at two flow rates and three flow-stop events in 24 h intervals. During the period of flow-stop, biosolids were subjected to different temperatures, water contents, or freezing-thawing. We found that intermittent irrigation or rainfall will enhance the risk of metals leaching from biosolids after land application. However, freezing of biosolids during winter will not cause an enhanced leaching of metals in spring when biosolids and soils thaw. Application of biosolids in fall will therefore not cause enhanced leaching of metals out of land-applied biosolids. Goal (2): To extend our knowledge of scale-appropriate methodologies to improve stakeholder-management of soil and water resources that benefit agricultural, natural resource and environmental sustainability. Extraction and quantification of nano- and microplastics from sediments and soils is challenging. Although no standard method has been established so far, flotation is commonly used to separate plastic from mineral material. We tested the efficiency of flotation for the extraction of nano- and microplastics from biosolids and soil. Our results indicate that while flotation generally works to separate plastic nano- and microbeads in a solution, the challenge is to quantitatively extract nano- and microbeads from a biosolids or soil matrix. Samples high in organic matter content require removal of the organic matter, but the common method of oxidation leads to poor extraction efficiencies for nano- and microbeads. We also evaluated the degradation of biodegradable plastics during 18-week, full-scale composting, and determined whether additives from the plastics are released upon degradation. Two biodegradable plastic films were placed into meshbags and buried in the compost. The results showed >99% macroscopic degradation of PLA/PHA and 97% for PBAT film. Polymers in the biodegradable films degraded; however, micro- and nanoparticles, most likely carbon black, were observed on meshbags. We applied the Water Erosion Prediction Project (WEPP) model to seven paired, nested watersheds within the Mica Creek Experimental Watershed in northern Idaho, USA. The goal was to evaluate the ability of WEPP to simulate the direct and cumulative effects of clear-cutting and partial-cutting on water and sediment yield. We modified WEPP to better represent changes in the Leaf Area Index during post-harvest forest vegetative recovery. Good agreements were achieved between (i) simulated and observed streamflow with no calibration and (ii) predicted and observed suspended sediment yield by calibrating a single channel critical shear stress parameter, for a 16-year (1992-2007) period. The variability in the critical shear parameter for different stream channels in the study watersheds was directly related to the observed mean particle size on the stream bed and suggests that applications of the WEPP model in ungauged basins could potentially set the critical shear parameter based on particle size. Overall, the simulated results demonstrate the potential of WEPP as a modeling tool for forestland watershed management, particularly for estimating the effects of hydrograph modification on stream sediment transport. This is the first time WEPP stream sediment transport algorithms are evaluated on large watersheds. Goal (3): To develop and evaluate new instruments and analytical methods to connect our understanding of mass and energy transport in soil at different scales to environmental transformations. We developed a new method to determine the plant available water in soil-biochar mixtures. Current methods to determine the plant available water are time consuming and require specialist equipment. Our new method is based on a centrifuge method first described in the 1920s. New centrifuge technology today allows to resurrect this method. We developed calibration equations and tested the method with soils of different textures. The new method is fast and accurate, and allows rapid screening of many different soil-biochar mixtures. We are currently refining the method and calibration equations.

Publications

• Type: Journal Articles Status: Published Year Published: 2018 Citation: Wang, Z., S. E. Taylor, P. Sharma, and M. Flury, Poor extraction efficiencies of polystyrene nano- and microplastics from biosolids and soil, PLoS ONE, 13, e0208009, doi.org/10.1371/journal.pone.0208009, 2018.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Yang, W., J. Shang, P. Sharma, B. Li, K. Liu, and M. Flury, Colloidal stability and aggregation kinetics of biochar colloids: Effects of pyrolysis temperature, cation type, and humic acid concentrations, Sci. Total Environ., 658, 13061315, 2019.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Wang, Z., and M. Flury, Effects of freezing-thawing and wetting-drying on heavy metal leaching from biosolids, Water Environ. Res., 91, 465-474, 2019.
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Shen, C., S. A. Bradford, M. Flury, Y. Huang, Z. Wang, and B. Li, DLVO interaction energies for hollow particles: The filling matters, Langmuir, 34, 1276412775, 2018.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Sintim, H. Y., S. Bandopadhyay, M. E. English, A. I. Bary, J. M. DeBruyn, S. M. Schaeffer, C. A. Miles, J. P. Reganold, and M. Flury, Impacts of biodegradable plastic mulches on soil health, Agric. Ecosystems Environ., 273, 3649, 2019.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Sintim, H. Y., A. I. Bary, D. G. Hayes, M. E. English, S. M. Schaeffer, C. A. Miles, A. Zelenyuk, K. Suski, and M. Flury, Release of micro- and nanoparticles from biodegradable plastic during in situ composting, Sci. Total Environ., 675, 686693, 2019.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Srivastava, A., E. S. Brooks, M. Dobre, W. J. Elliot, J. Q. Wu, D. C. Flanagan, J. A. Gravelle, and T. E. Link, Modeling forest management effects on water and sediment yield from nested, paired watersheds in the interior Pacific Northwest, USA using WEPP, Sci. Total Environ., 2019. (in press).

Progress 10/01/17 to 09/30/18

Outputs
Target Audience:Scientific peers, Department of Energy, Environmental Engineering and Consulting Companies, Farmers, Industry Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Training for graduate students. How have the results been disseminated to communities of interest?Journal articles have been published, research results have been presented at invited seminars and volunteered presentations at professional meetings. What do you plan to do during the next reporting period to accomplish the goals?We will continue the work on the biodegradable plastic mulches, colloid transport, life in the dry limit of earth, and WEPP development and application.

Impacts
What was accomplished under these goals? We have demonstrated that in the driest places on earth, there lives a metabolically active, microbial community. The finding, that even under the most extreme conditions on earth there are active microorganisms, suggests that we likely also will find microbial life on Mars, where at some locations, conditions are similar to the driest locations on earth. From our studies on biodegradable plastic mulch, we demonstrated that within 2 years, the biodegradable plastics had only minimal impact on soil health. This makes biodegradable plastic potentially a viable alternative to conventional polyethylene plastic. We have carried out a simulation study evaluating fuel reduction treatment effects in a national forest, US Pacific Northwest. We have shown that fuel reduction treatments, such as thinning and prescribed burns to treated hillslopes, may lead to an increase in water yield and significant alterations in hydrological processes. Goal (1): To improve our fundamental understanding of soil physical properties and processes, and how they interact with other environmental and biogeochemical processes across various spatial and temporal scales. We have analyzed moisture conditions along a west-east transect in the Atacama desert and related the moisture conditions to signals of microbial life. Even in the most extreme locations in the Atacama desert, moisture conditions episodically are favorable for microbial live, such that an active microbial community can develop which becomes dormant during extended dry periods, but which becomes active during episodic rainfall. The resilience of this microbial community to extreme conditions shows that life on earth is nearly ubiquitous. We have continued to work on evaluating the interactions of colloids with air-water and solid-water interfaces. We have done theoretical calculations to quantify interactions of biochar colloids with the solid-water interface and biochar colloids with themselves. Experiments were conducted to determine the colloidal stability of biochars of different origin and different processing methods. We have determined critical coagulation concentrations for these different biochars. Our findings show that the aggregation of biochar colloids is highly dependent on pyrolysis temperature, natural organic matter, and cation type of the aqueous solution. Goal (2): To extend our knowledge of scale-appropriate methodologies to improve stakeholder-management of soil and water resources that benefit agricultural, natural resource and environmental sustainability. We continued our work with biodegradable plastic mulches; particularly, we studied the effect of biodegradable plastic mulches on soil health. Field experiments have been setup with corn as the vegetable crop. We measured soil quality parameters in spring and in fall to quantify changes that may have occurred due to the use of biodegradable plastic mulch. So far, only minimal changes in soil health were observed. In laboratory experiments with mesocosms, we have studied whether and to what degree earthworms (nighcrawler) would pull plastic fragments into their burrows and ingest plastic pieces. We found that earthworms indeed pull plastic fragments into their burrows, but that ingestion depended on the age and weathering of the plastic pieces. Only heavily weathered plastic was ingested by earthworms. We continued to make made substantial improvements to the Water Erosion Prediction Project (WEPP) model, which led to improved handling of forest thinnings on soil erosion. Suitable fuel reduction treatments are needed in the Colville National Forest, Washington, to reduce the risk of severe wildfire. We conducted a simulation study for the East Deer Creek Watershed, a subwatershed of the Colville National Forest. We applied the WEPP (Water Erosion Prediction Project) in combination with FlamMap, a fire behavior model, to identify high-risk erosion hillslopes following wildfire to aid in forest fuel reduction planning and to evaluate the effects of fuel treatments on the watershed hydrological response. Goal (3): To develop and evaluate new instruments and analytical methods to connect our understanding of mass and energy transport in soil at different scales to environmental transformations. Nothing to report under this goal.

Publications

• Type: Journal Articles Status: Published Year Published: 2018 Citation: Schulze-Makuch, D., et al. A transitory microbial habitat in the hyperarid Atacama Desert, Proc. Natl. Acad. Sci. USA, 115, 26702675, 2018.
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Zhang, L., H. Y. Sintim, A. I. Bary, D. G. Hayes, L. C. Wadsworth, M. B. Anunciado, and M. Flury, Ingestion and transport of polyethylene and biodegradable plastic mulch by Lumbricus terrestris, Sci. Total Environ., 16001608, 2018.
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Srivastava, A., J. Q. Wu, W. J. Elliot, E. S. Brooks, D. C. Flanagan, A simulation study to estimate effects of wildfire and forest management on hydrology and sediment in a forested watershed, Northwestern U.S., Trans. ASABE 61, 15791601, 2018.

Progress 10/01/16 to 09/30/17

Outputs
Target Audience:Scientific peers, Department of Energy, Environmental Engineering and Consulting Companies, Farmers, Industry Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Graduate, undergraduate, and visiting scientist training opportunities. How have the results been disseminated to communities of interest?Journal articles have been published, research results have been presented at invited seminars and volunteered presentations at professional meetings. What do you plan to do during the next reporting period to accomplish the goals?Al activities reported are still ongoing and will be continued.

Impacts
What was accomplished under these goals? We have published a comprehensive review article on the role of air-water interfaces on colloid fate and transport in unsaturated porous media. This article summarizes and synthesizes the current state of knowledge on this topic. Knowledge of transport mechanisms of polycyclic aromatic hydrocarbons (PAHs) in soils and sediments is of utmost importance in areas affected by oil spills, storm water and road runoff, industrial wastewater, and landfill leachate. In soils and sediments, PAH tend to partition to the solid phase, rendering them immobile. The presence of suspended colloids, however, can mobilize PAH and allow them to leach to groundwater. Our work with biodegradable plastic mulches has demonstrated that field investigations are needed to assess whether and how mulches degrade, laboratory experiments cannot mimic field conditions. Goal (1): To improve our fundamental understanding of soil physical properties and processes, and how they interact with other environmental and biogeochemical processes across various spatial and temporal scales. Knowledge of transport mechanisms of polycyclic aromatic hydrocarbons (PAHs) in soils and sediments is of utmost importance in areas affected by oil spills, storm water and road runoff, industrial wastewater, and landfill leachate. In soils and sediments, PAH tend to partition to the solid phase, rendering them immobile. The presence of suspended colloids, however, can mobilize PAH and allow them to leach to groundwater. The movement of air-water interfaces can perform a similar role in mobilizing PAH. The efforts on analyzing soil modeling processes have led to the publication of a major review and synthesis article on the challenges and directions of modeling of soil processes. With a team of microbiologists, geologists, geochemists, geneticists, and astrobiologists, I continued the research on the dry limits of life on Earth and Mars. We analyzed samples from a moisture-gradient in the Atacama desert in Chile, one of the driest places on Earth. Our portion of the work focuses on analyzing water contents and water activities in soil samples from the Atacama desert. Goal (2): To extend our knowledge of scale-appropriate methodologies to improve stakeholder-management of soil and water resources that benefit agricultural, natural resource and environmental sustainability. Biodegradable plastic mulches are a promising alternative to polyethylene mulches. We studied the effect of simulated and agricultural weathering on the physicochemical properties of biodegradable plastic mulch films. The tensile strength and thermostability of PLA/PHA increased by weathering, suggesting the formation of cross-links between the polyesters and inorganic filler. This study demonstrated that weathering of biodegradable plastic mulches very much depends on the mulch type and the local climatic and weather conditions. In recent years we have made substantial improvements to the Water Erosion Prediction Project (WEPP) model, which led to enhanced computations for deep percolation, subsurface lateral flow, and frozen soil. Additionally, the incorporation of channel routing has made the WEPP model well suited for large watersheds with perennial flows. Nonetheless, WEPP is limited in modeling forested watersheds where groundwater baseflow is substantial. To overcome this limitation and further increase its applicability, we incorporated nonlinear algorithms into WEPP (v2012.8) for estimating baseflow, and applied the model to a subwatershed of the Upper Cedar River Watershed in western Washington State. We auto-calibrated the model using a model-independent parameter estimation tool, and compared the performance of the current version of WEPP without baseflow and the modified WEPP model with baseflow. Compared to the current WEPP, the modified version yielded more agreeable streamflow to the observed data and better reproduced hydrograph recessions during the low-flow periods and the general trend of the hydrographs. The incorporation of a baseflow component into WEPP will help forest managers to assess the alterations in hydrological processes and water yield for their forest management practices.

Publications

• Type: Journal Articles Status: Published Year Published: 2017 Citation: Hayes, D. G., L. C. Wadsworth, H. Y. Sintim, M. Flury, M. English, S. Schaeffer, and A. M. Saxton, Effect of diverse weathering conditions on the physicochemical properties of biodegradable plastic mulches, Polymer Testing, 62, 454467, 2017. (dx.doi.org/10.1016/j.polymertesting.2017.07.027)
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Yang, W., Y. Wang, P. Sharma, B. Li, K. Liu, J. Liu, M. Flury, and J. Shang, Effect of naphthalene on transport and retention of biochar colloids through saturated porous media, Colloids Surf. Physicochem. Eng. Aspects, 530, 146154, 2017. (dx.doi.org/10.1016/j.colsurfa.2017.07.010)
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Flury, M., and S. Aramrak, Role of air-water interfaces in colloid transport in porous media: A review, Water Resour. Res., 53, 52475275, 2017. (dx.doi.org/10.1002/2017WR020597)
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Sintim, H. Y., and M. Flury, Is biodegradable plastic mulch the solution to agricultures plastic problem?, Environ. Sci. Technol., 51, 10681069, 2017. (dx.doi.org/10.1021/acs.est.6b06042)
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Srivastava, A., J. Q. Wu, W. J. Elliot, E. S. Brooks, and D. C. Flanagan, Modeling streamflow in a snow-dominated forest watershed using the Water Erosion Prediction Project (WEPP) model, Trans. ASABE, 60, 1171-1187, 2017.
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Zhang, X., H. Lei, L. Zhu, M. Qian, G. Yadavalli, J. Wu, and S. Chen, From plastics to jet fuel range alkanes via combined catalytic conversions, Fuel, 188, 28-38, 2017.

Progress 10/01/15 to 09/30/16

Outputs
Target Audience:Scientific peers, Department of Energy, Environmental Engineering and Consulting Companies Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Graduate Student Training How have the results been disseminated to communities of interest?Journal articles have been published, research results have been presented at invited seminars and volunteered presentations at professional meetings. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? We investigated transport of polycyclic aromatic hydrocarbons (PAH) in porous media. In soils and sediments, PAH tend to partition to organic matter and mineral phases, and are, therefore, relatively immobile. However, moving air-water interfaces may scour PAH from solid phases and translocate PAH. We studied the effect of moving air-water interfaces on the transport of fluoranthene, a four-ring PAH, in unsaturated porous media. We used fluorescent confocal microscopy to visualize and quantify fluoranthene in a glass channel filled with glass beads. Results showed that fluoranthene did not move with moving water under saturated flow, but capillary fringe fluctuations were effective in translocating fluoranthene. Fluoranthene partitioned to the air-water interface and moved along with moving air-water interfaces. The complexity of soil and its importance to a wide range of ecosystem services presents major challenges to the modeling of soil processes. I have collaborated with some of my colleagues on analyzing recent advances in modeling soil processes. The soil community needs to develop a new generation of soil models based on a systemic approach with relevant physical, chemical, and biological processes to address critical knowledge gaps in our understanding of soil processes. We reviewed the role of modeling soil processes in quantifying key soil processes that control ecosystem services, with a focus on provisioning and regulating services. We identified key challenges in modeling soil processes, including the systematic incorporation of heterogeneity and uncertainty, the integration of data and models, and strategies for effective integration of knowledge on physical, chemical, and biological soil processes. Knowledge of transport mechanisms of PAH in soils and sediments is of utmost importance in areas affected by oil spills, storm water and road runoff, industrial wastewater, and landfill leachate. In soils and sediments, PAH tend to partition to the solid phase, rendering them immobile. The presence of suspended colloids, however, can mobilize PAH and allow them to leach to groundwater. The movement of air-water interfaces can perform a similar role in mobilizing PAH. The efforts on analyzing soil modeling processes have led to the publication of a major review and synthesis article on the challenges and directions of modeling of soil processes. With a team of microbiologists, geochemists, geneticists, and astrobiologists, I am collaborating on investigating the dry limits of life on Mars. We are using the Atacama desert in Chile as analog site for Martian soils. I am working on evaluating water contents and water activities as they relate to microbial life.

Publications

• Type: Journal Articles Status: Published Year Published: 2016 Citation: Chahal, M. K., J. B. Harsh, and M. Flury, Translocation of fluoranthene in porous media by advancing and receding air-water interfaces, Colloids Surf. Physicochem. Eng. Aspects, 492, 6270, 2016.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Vereecken, H., A. Schnepf, J. W. Hopmans, M. Javaux, D. Or, T. Roose, J. Vanderborght, M. Young, W. Amelung, M. Aitkenhead, S. D. Allisson, S. Assouline, P. Baveye, M. Berli, N. Bruggemann, P. Finke, M. Flury, et al., Modeling soil processes: Key challenges and new perspectives, Vadose Zone J., 15, doi:10.2136/vzj2015.09.0131, 2016.
• Type: Journal Articles Status: Accepted Year Published: 2016 Citation: Sintim, H. Y. Is Biodegradable Plastic Mulch the Solution to Agriculture's Plastic Problem? Environ. Sci. Technol. (in press).

Progress 10/01/14 to 09/30/15

Outputs
Target Audience:Scientific peers, Department of Energy, Engineering Companies responsible for Hanford cleanup Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Training of one PhD student How have the results been disseminated to communities of interest?Journal articles have been published, research results have been presented at invited seminars and volunteered presentations at professional meetings What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Colloids and nanoparticles are emerging contaminants. While most studies on colloid and nanoparticle transport are done with spherical model colloids, many colloids and nanoparticles have a different than spherical shape. We investigated the effect of particle shape on colloid transport in unsaturated porous media. We created particles of different shapes by modifying the shape of spherical polystyrene microspheres. We created oblong and barrel-shaped, angular particles and studied their transport through sand media under unsaturated flow conditions. Particle transport was strongly affected by water saturation: more transport occurred under high water saturation than under low water saturation. Colloids were retained and released from a secondary energy minimum with more angular-shaped colloids being retained and released. This shows that particle shape is important for colloid transport, i.e., colloids with angular shape are preferentially retained in unsaturated porous media. We also investigated the transport of polycyclic aromatic hydrocarbons (PAHs). PAHs tend to partition to organic matter and mineral phases, and are, therefore, relatively immobile. However, moving air-water interfaces may scour PAH from solid phases and translocate PAHs. We investigated the effect of moving air-water interfaces on the transport of fluoranthene, a four-ring PAH, in unsaturated porous media. We mainly focused on the fate of PAHs during capillary fringe fluctuations. Results showed that capillary fluctuations caused translocation of PAHs. PAHs were removed from the capillary fringe during imbibition and successive drainage. Many emerging contaminants associate with colloids or are colloids themselves, e.g., nanoparticles and microspheres. We have shown that shape is an important parameter controlling fate and transport of colloids in porous media, particularly if the media are variably water saturated. Angular-shaped colloids are preferentially retained and do not transport as readily as do spherical colloids. PAHs tend to partition to the air-water interface in variably water saturated soils and sediments, and moving air-water interfaces are capable of translocating otherwise immobile PAHs.

Publications

• Type: Journal Articles Status: Published Year Published: 2015 Citation: Knappenberger, T., S. Aramrak, and M. Flury, Transport of barrel and spherical shaped colloids in unsaturated porous media, J. Contam. Hydrol., 180, 6979, 2015.
• Type: Journal Articles Status: Accepted Year Published: 2016 Citation: Dickson, J. O., J. B. Harsh, M. Flury, and E. M. Pierce, Immobilization and exchange of perrhenate in sodalite and cancrinite, Micropor. Mesopor. Mater., 214, 115120, 2015.
• Type: Journal Articles Status: Accepted Year Published: 2016 Citation: Chahal, M. K., J. B. Harsh, and M. Flury, Translocation of fluoranthene in porous media by advancing and receding air-water interfaces, Colloids Surf. Physicochem. Eng. Aspects, (in press), 2016.