Progress 05/01/20 to 03/13/25
Outputs
Target Audience:Target audiences: Scientific peers, Students, State and Federal Environmental Regulatory Agencies, Farmers, General public, Biosolids Producers, Waste Waste Treatment Plant Operators, Government Policy Makers. Efforts: We have presented our research at both local and international conferences. Presentations were made at the annual meeting of the Soil Science Society of America, the European Geoscience Union and the American Geophysical Union. A podcast was recorded with the "WSU Wheat Beat Podcast" on "Potential Impacts of Microplastics in Agricultural Soils", in which we highlighted our research project and the general issue of microplastics in farmland. Invited presentations were given at Northwest Biosolids, the University of Tennessee, the Swiss Federal Institute of Technology in Zurich, Northwest Agricultural and Forestry University in Yangling, Shenyang Agricultural University in Shenyang, and China Agricultural University in Beijing. We used the research to highlight the importance of biosolids in our university classes. Results of the project were also presented to growers and public stakeholders as a Webinar within a Plastic-Soil Health Webinar organized by WSU Extension. We have also presented our work to a congressional delegation in Washington DC through the Soil Science Society of America's Congressional Soils Caucus. We also presented our work to the Michigan Biosolids Conference. In March 2023 we had discussions with the congressional staff of US congresswoman Ms. Perez about microplastics in agricultural and food systems, and we helped draft a bill to the US House of Representatives to propose an amendment to the Food, Agriculture, Conservation, and Trade Act of 1990 to include as a high-priority research and extension area research on microplastics in land-applied biosolids. This bill will be introduced in the 1st Session of the 118th Congress. Changes/Problems:The Covid-19 pandemic has caused delays at the start of the project with student recruiting, field activities, and laboratory work. We have been able to recruit a graduate student, but another student from China could not travel to the US. We used the time where we had restricted access to the laboratory by shifting from laboratory to more theoretical work (doing theoretical work on sampling and numerical simulations) and working on review articles. Access to important laboratory facilities and instruments has been limited in 2020 and 2021. Since then, the project has proceeded as planned, and, with the no-cost extension, all planned activities could be successfully completed. What opportunities for training and professional development has the project provided?The project has supported two graduate students working on plastic extractions, quantifications, and data analysis. These two graduate students successfully graduated with a PhD from WSU. We also supported two visiting PhD students from the Czech Republic, who helped with the sampling of the atmospheric deposition collectors. The graduate students presented their results at the annual meetings of the Soil Science Society of America in every year of the project. We have disseminated our results at the annual meeting of the European Geoscience Union in Vienna, the Soil Science Society Annual Meeting, and the Annual Meeting of the American Association of the Advancement of Sciences, where we have convened symposia and sessions. One of the students has presented his research at the Congressional Soil Caucus. One of the graduate students received an Encompass Fellowship, sponsored by the ASA-CSSA-SSSA and Bayer Crop Science. How have the results been disseminated to communities of interest?We have presented a seminar at the Environmental Molecular Science Laboratory in Richland, in support of our proposal submitted to the MONet program. We have also been actively engaged with Northwest Biosolids and the King County Department of Natural Resources, two stakeholder entities involved in managing of biosolids in the Pacific Northwest, informing them about our research progress. We also have communicated our research results to the congressional staff of US congresswoman Ms. Perez about microplastics in agricultural and food systems, and we helped draft a bill to the US House of Representatives to propose an amendment to the Food, Agriculture, Conservation, and Trade Act of 1990 to include as a high-priority research and extension area research on microplastics in land-applied biosolids. Ms. Perez has passed this amendment through the House of Representatives and this amendment was introduced to the Senate by Senators Mr. Merkely, Mr. Booker, Mr. Van Hollen, Mr. Whitehouse, and Mr. Wyden. The bill was read and introduced in the Senate on January 18, 2024, and will be as the "Research for Healthy Soils Act". Through this bill, if approved, the Section 1672(d) of the Food, Agriculture, Conservation, and Trade Act of 1990 (7 U.S.C. 5925(d)) would be amended by: "MICROPLASTICS IN LAND-APPLIED BIOSOLIDS ON FARMLAND. Research and extension grants may be made under this section for the purposes of carrying out or enhancing research on the agricultural impacts of plastic or plastic-coated particles that are less than 5 millimeters in any dimension (referred to in this paragraph as 'microplastics') in land-applied biosolids on farmland, including: (A) by conducting surveys and collecting data on microplastic concentration, particle size, and chemical composition in land-applied biosolids on farmland; (B) through the development or analysis of wastewater treatment techniques to filter out or biodegrade microplastics from biosolids intended to be used for agricultural purposes; (C) by conducting an analysis of the impact on agricultural crops and soil health of microplastics in land-applied biosolids on farmland; (D) by conducting research to better understand how wastewater processing impacts microplastics; and (E) by conducting research to better understand the fate, residence time, and transport of microplastics on farmland." We collaborated with the Wilson Center (https://www.wilsoncenter.org) on writing an article about microplastic pollution in agricultural soils. The Wilson Center is a non-partisan think tank chartered by Congress in 1968 as the official memorial to President Woodrow Wilson, and is the nation's key non-partisan policy forum for tackling global issues through independent research and open dialogue to inform actionable ideas for the policy community. The article we wrote discusses plastic pollution of farmland and potential solutions to the ever increasing amount of plastic accumulating therein. 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): Quantify and characterize micro- and macroplastics in biosolids of a waste water treatment plant. We have obtained historic samples of biosolids from the South Waste Water Treatment Plant in Seattle from 1997 and 2017. Two more recent biosolids samples from 2019 and 2020 were collected and have been used to extract microplastics. We tested two different extraction methods based on two recent scientific articles where biosolids samples have been analyzed for microplastics. The optimal method included removal of organic matter with Fenton's reagent, followed by a fractionation of plastics with density separation using a ZnCl2 solution. The fractionated samples were filtered and analyzed for particle number and particle identification. The amount of microplastics identified from biosolids samples was 12,000 particles/kg dry biosolids. Objective (2): Determine whether long-term application of biosolids to agricultural soils has led to accumulation of micro- and macroplastics. We have obtained historic soil samples from a site where biosolids from the South Waste Water Treatment Plant (see Objective 1) have been applied since 1997. This site is a dryland wheat field, where different rates of biosolids are tested for agronomic performance. We have taken samples in 2019, right after a fresh application of biosolids has been made. Soil samples were taken following the standard protocol from the previous sampling that has been conducted at the site to assess nutrient status and soil quality. The sampling consisted of taking 12 consolidated soil cores with a 4-cm soil auger from three depths (0-4, 4-8, 8-12 inches or 0-10, 10-20, 20-30 cm). To test the sampling protocol and to verify the methodology, we tested the biosolids and the soil by analyzing for silver. Silver is much easier to measure than plastics, as it can be quantified with ICP-MS with a low detection limit and with high accuracy. Natural silver contents on soils is very low, so silver is a good tracer for biosolids. We analyzed all our historic samples for silver concentrations and determined a time-series of silver concentrations in soils and biosolids. The data show a clear trend of decreasing silver concentrations in biosolids over time, likely because of the declining use of silver in dentistry. In 2019, we took a series of new soil samples from the field site, following the same protocol as for the historic samples. Based on observations of biosolids in the field, we determined that biosolids, and therefore also the plastic particles, occurred in clusters on the field. This clustering likely will affect how effective small soil cores are in taking representative samples, and we hypothesized that taking small soil cores will not be an effective method to sample for microplastics. Restrictions of extensive field work due to Covid-19 prevented us from doing more field sampling. So, we decided to test the sampling with numerical simulations. We simulated an agricultural field that has been polluted with microplastic particles and then took soil samples with different sampling methods, and quantified plastic concentrations by numerically counting the plastic particles in the soil samples. The numerical sampling simulations also allowed us to quantify the error of the sampling methods. The simulation results showed that a box sampling method, with taking soil samples from a large 1 m by 1 m block, and then reducing the sample volume by the quartering method will provide the most accurate measure of the plastic concentrations. We used this method for future sampling at the field site. We completed the analyses of the microplastic contents in the different experimental treatments of our long-term field trial (0, 4.8, 6.9, and 9.0 tons dry biosolids/ha). We quantified the number of plastic particles present, and based on the shape and size of the observed plastic particles, we have calculated also the mass concentrations of the plastics in the soil. The results showed that biosolids applications indeed led to a significantly higher plastic concentration in the soil compared to the no-biosolids control treatment, but we could not detect a significant difference among the different rates of biosolids applications. We also could not detect significant differences between sampling depths (0-5 cm and 5-10 cm). The amounts of plastics detected in the pooled 0-10 cm depth interval were 383, 500, and 361 particles/kg dry soil in the 0--10 cm depth for low, medium, and high biosolids application rates, respectively. We also identified the color and shape of the plastic particles. The color of the plastics differed by shape. Plastic films were glossy, fragments were mostly blue with angular shape, and some white microbeads (pellets) with circular shape were also observed, fibers had various different colors. Among all the microplastics identified, generally >50 percent were fibers, with the remainder mostly fragments. Using laser-directed infrared spectroscopy, we identified the plastic polymers as polyamide, polyethylene, PVC, polyurethane, PET, polyvinyl alcohol, polyehtylmethacrylate, and rubber. Objective (3): Evaluate interactions of microplastics with plant roots. The experiments to evaluate interactions and uptake of microplastics with plant roots were conducted in growth chambers. We used two plant types with different root systems: Arabidopsis thaliana, which as a tap root, and Triticum aestivum (wheat), which has a fibrous root system. The plants were exposed to micro- and nanoplastics in different growth media: hydroponics, agar, and soil. We used three different types of nanoplastics: 40 nm and 200 nm carboxylate-modified polystyrene beads (negatively charged) and 200 nm amine-modified polystyrene beads (positively charged). We analyzed the plant roots with confocal microscopy for the presence of plastic particles and found that nanoplastics mainly accumulate at the outside of the roots, but the negatively charged nanoplastics can penetrate the root tissue, mostly by the apoplastic pathway, i.e., by motion in between the cells, without active uptake into the interior of the cells. To further corroborate these findings, we have also been doing scanning and transmission electron microscopy on root thin sections. We have found the 40 nm beads inside plant roots, but not the 200 nm beads, suggesting a size-dependent uptake. Objective (4): Collect and characterize atmospheric deposition of microplastics. We installed four rainfall samplers (260-2510 NWS Type Rain Gauge) in late spring 2021 at the Douglas County field site. Two samplers were installed upwind and two samplers were installed downwind of the biosolids plots to determine whether plastics can be transported off the field plots by wind. First atmospheric samples were taken in fall 2021, but were contaminated with insects who were attracted and fell into the water collected by the rainfall samplers. We then installed a screen to prevent insects to enter the sampler and collection area. Analysis for microplastics was done by visual counting by microscopy and Laser-directed infrared spectroscopy. The atmospheric samples showed the presence of alkyd varnish, likely originating from paint of houses, rubber, possibly from tire rub off, and also natural materials, such as cellulose and chitin. Atmospheric deposition contributed a considerable input of microplastics: we estimated that the 2-year of atmospheric plastic depositions contributed to about 1 to 4 percent of the mass of microplastics found in the soil, and 2 to 12 percent of number of plastics.
Publications
- Type:
Peer Reviewed Journal Articles
Status:
Published
Year Published:
2025
Citation:
Adhikari, K., K. A. Sanguinet, C. I. Pearce, and M. Flury, Uptake of polystyrene nanospheres by wheat and Arabidopsis roots in agar, hydroponics, and soil, Environ. Sci.: Nano, 12, 16851696, 2025. (doi.org/10.1039/d4en01182a)
- Type:
Peer Reviewed Journal Articles
Status:
Published
Year Published:
2025
Citation:
Shokri, N., M. Aminzadeh, M. Flury, Y. Jin, M. A. Matin, P. Panagos, B. S. Razavi, D. A. Robinson, P. Smith, K. Todd-Brown, G. Toth, A. Zarei, and K. Madani, Sustainability Nexus AID: Soil Health, Sustainability Nexus Forum, 33, 3, doi.org/10.1007/s00550025005606, 2025.
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Progress 05/01/23 to 04/30/24
Outputs
Target Audience:Target audiences: Scientific peers, Students, State and Federal Environmental Regulatory Agencies, Farmers, General public, Biosolids Producers, Waste Waste Treatment Plant Operators. Efforts: We have presented our research at both local and international conferences. Presentations were made at the annual meeting of the European Geoscience Union and the annual meeting of the Soil Science Society of America in Salt Lake City. We used the research to highlight the importance of biosolids in our university classes. We have presented our research at an invited seminar at the Environmental Molecular Science Laboratory in Richland and at the China Agricultural University in Beijing, China. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project has supported two graduate students working on plastic extractions, quantifications, and data analysis. We also supported a visiting PhD student from the Czech Republic, who has helped with the sampling of the atmospheric deposition collectors. One of the graduate students has presented the results at the annual meeting of the Soil Science Society of America in St. Louis. A second visiting PhD student from the Czech Republic will join our lab in spring 2024, and we are currently working on also inviting a Chinese visiting PhD student to join our lab in fall 2024. We have disseminated our results at the annual meeting of the European Geoscience Union in Vienna, where we have convened a symposium on fate and transport of nanoparticles and biocolloids in the subsurface. How have the results been disseminated to communities of interest?We have presented a seminar at the Environmental Molecular Science Laboratory in Richland, in support of our proposal submitted to the MONet program. We have also been actively engaged with Northwest Biosolids and the King County Department of Natural Resources, two stakeholders involved in managing of biosolids in the Pacific Northwest, informing them about our research progress. We also have communicated our research results to the congressional staff of US congresswoman Ms. Perez about microplastics in agricultural and food systems, and we helped draft a bill to the US House of Representatives to propose an amendment to the Food, Agriculture, Conservation, and Trade Act of 1990 to include as a high-priority research and extension area research on microplastics in land-applied biosolids. Ms. Perez has passed this amendment through the House of Representatives and this amendment was introduced to the Senate by Senators Mr. Merkely, Mr. Booker, Mr. Van Hollen, Mr. Whitehouse, and Mr. Wyden. The bill was read and introduced in the Senate on January 18, 2024, and will be as the "Research for Healthy Soils Act". Through this bill, if approved, the Section 1672(d) of the Food, Agriculture, Conservation, and Trade Act of 1990 (7 U.S.C. 5925(d)) would be amended by: "MICROPLASTICS IN LAND-APPLIED BIOSOLIDS ON FARMLAND. Research and extension grants may be made under this section for the purposes of carrying out or enhancing research on the agricultural impacts of plastic or plastic-coated particles that are less than 5 millimeters in any dimension (referred to in this paragraph as 'microplastics') in land-applied biosolids on farmland, including: (A) by conducting surveys and collecting data on microplastic concentration, particle size, and chemical composition in land-applied biosolids on farmland; (B) through the development or analysis of wastewater treatment techniques to filter out or biodegrade microplastics from biosolids intended to be used for agricultural purposes; (C) by conducting an analysis of the impact on agricultural crops and soil health of microplastics in land-applied biosolids on farmland; (D) by conducting research to better understand how wastewater processing impacts microplastics; and (E) by conducting research to better understand the fate, residence time, and transport of microplastics on farmland." What do you plan to do during the next reporting period to accomplish the goals?We have applied for a 1-year no-cost extension of the project, which was approved in January 2024. This will allows us to continue and complete the plant uptake experiments, with the additional experiments on plant biomass and reactive oxygen species. We will continue the experiments of plant uptake in soil systems and complete the confocal visualization experiments. We will also continue with transmission electron imaging of root cross-sections. We have submitted an NSF Equipment proposal to obtain a Laser Direct Fourier-transformed Infrared Imaging System (Agilent Technologies), which will allow us to do more plastic quantification and identification in our own laboratory, rather than sending samples out to the University of Massachusetts for analysis. Scientific articles will on these experiments will be completed and written up. We have also started to write a perspective article on plastics in agriculture in general, which we plan to complete in spring 2024. We have submitted a MONet proposal (Molecular Observation Network) to take soil samples from our field site, so we can correlate soil health parameters to microplastic concentrations, and thereby evaluate the impacts of microplastics deposited by biosolids on soil health. The MONet proposal was approved and we will take the first soil samples in April/May 2024. This work related to soil health, although not part of our original proposal, is highly relevant because we need to know how plastics affect overall soil health, so we can judge the impacts of biosolids on agricultural lands and ultimately prescribe regulations on microplastic contents of biosolids. This aspect of the work also has been included in the new "Research for Healthy Soils Act" (see discussion about this in the previous section). We anticipate that the graduate student Kaushik Adhikari will graduate in the fall semester 2024 or spring semester 2025.
Impacts
What was accomplished under these goals?
Objective (1): Quantify and characterize micro- and macroplastics in biosolids of a waste water treatment plant. We have further quantified the number of plastic particles and identified the polymer types by using an LDIR instrument (Laser-directed infrared spectroscopy). This instrument allowed us to scan a large area of a filter for the presence of microplastics and identify the plastic polymers by comparison with a standard spectral library. The amount of microplastics identified from biosolids samples was 12,000 particles/kg dry biosolids. We have made use of the LDIR instrument at the University of Massachussetts, Stockbridge School of Agriculture. The data obtained have been incorporated into a technical manuscript that was published in early 2024 (Adhikari et al., 2024). We have also written and submitted an NSF Instrument proposal to acquire an LDIR instrument for our laboratory. This proposal is currently under review and we should hear about the results of the proposal review in early 2024. Objective (2): Determine whether long-term application of biosolids to agricultural soils has led to accumulation of micro- and macroplastics. In this reporting period, we have completed the analyses of the microplastic contents in the different experimental treatments of our long-term field trial (0, 4.8, 6.9, and 9.0 tons dry biosolids/ha). We have quantified the number of plastic particles present, and based on the shape and size of the observed plastic particles, we have calculated also the mass concentrations of the plastics in the soil. The results showed that biosolids applications indeed led to a significantly higher plastic concentration in the soil compared to the no-biosolids control treatment, but we could not detect a significant difference among the different rates of biosolids applications. We also could not detect significant differences between sampling depths (0-5 cm and 5-10 cm). The amounts of plastics detected in the pooled 0-10 cm depth interval were 383, 500, and 361 particles/kg dry soil in the 0--10 cm depth for low, medium, and high biosolids application rates, respectively. This compares to a plastic concentration of 117 particles/kg dry soil observed in the control soil. We also identified the color and shape of the plastic particles. The color of the plastics differed by shape. Plastic films were glossy, fragments were mostly blue with angular shape, and some white microbeads (pellets) with circular shape were also observed, fibers had various different colors. Among all the microplastics identified, generally >50 percent were fibers, with the remainder mostly fragments. In the soil with low biosolids application, a plastic piece was found likely to be fragmented from a birthday balloon. We also found two birthday balloons, entangled by the plant stubbles remaining from the previous crop in the no-till field. Using laser-directed infrared spectroscopy, we identified the plastic polymers as polyamide, polyethylene, PVC, polyurethane, PET, polyvinyl alcohol, polyehtylmethacrylate, and rubber. The plastic polymer signature in the biosolids-amended soils matched that of the biosolids, supporting that the plastics in the soil indeed originated from biosolids applications. The results so far have indicated that biosolids indeed lead to an accumulation of microplastics, but the question now is whether the amounts of plastics are substantial enough to impact soil health and plant growth. To address these questions, we will assess soil health parameters in the different plots. We have written a MONet proposal, which would allow us to quantify detailed biogeochemical and soil physical parameters, which we then can use to correlate with the plastic concentrations measured. We have written up these results of the current studies in form of a technical journal article, which was published in Science of the Total Environment (Adhikari et al., 2024). Objective (3): Evaluate interactions of microplastics with plant roots. The experiments to evaluate interactions and uptake of microplastics with plant roots have been continued. We have been using using two plant types with different root systems: Arabidopsis thaliana, which as a tap root, and Triticum aestivum (wheat), which has a fibrous root system. The plants were exposed to micro- and nanoplastics in different growth media: hydroponics, agar, and soil. We are using three different types of nanoplastics: 40 nm and 200 nm carboxylate-modified polystyrene beads (negatively charged) and 200 nm amine-modified polystyrene beads (positively charged). The experiments with hydroponics and agar media have been completed, and we are currently working on the soil medium experiments. These have been proven to be more challenging because soil particles tend to adhere to the root surface and impact the quality of the confocal imaging we are using to visualize the plastic particles. Different soil media have been tested and we are currently using a greenhouse soil mix. We have analyzed the plant roots with confocal microscopy for the presence of plastic particles and found that nanoplastics mainly accumulate at the outside of the roots, but the negatively charged nanoplastics can penetrate the root tissue, mostly by the apoplastic pathway, i.e., by motion in between the cells, without active uptake into the interior of the cells. To further corroborate these findings, we have also been doing scanning and transmission electron microscopy on root thin sections. We have found the 40 nm beads inside plant roots, but not the 200 nm beads, suggesting a size-dependent uptake. We have also been working on determining the effects of the plastic particles on plant growth parameters (wet and dry biomass of roots and shoots) and plant stress indicators (ROS: reactive oxygen species). The initial results indicate that plant growth is not impacted by plastic particles in agar media, but some differences in plant growth are observed in hydroponic systems. We are currently confirming these results. We are preparing a scientific journal article on these experiments. This article will be another chapter in the student's (Kaushik Adhikari) dissertation. We have written up the results presently available. Objective (4): Collect and characterize atmospheric deposition of microplastics. We have continued to monitor atmospheric deposition of plastics at the field site. We have taken atmospheric samples in Spring and Summer 2023, and analyzed these samples for microplastics. Analysis was done by visual counting by microscopy and Laser-directed infrared spectroscopy. These data were incorporated into the journal article to complete an 2 year of sampling period (Adhikari et al., 2024). The atmospheric samples showed the presence of alkyd varnish, likely originating from paint of houses, rubber, possibly from tire rub off, and also natural materials, such as cellulose and chitin. Atmospheric deposition contributed a considerable input of microplastics: we estimated that the 2-year of atmospheric plastic depositions contributed to about 1 to 4 percent of the mass of microplastics found in the soil, and 2 to 12 percent of number of plastics. The two birthday balloons found in the field contributed 11.4 g of plastic, which corresponds to a mass concentration of 3.6 mg/m2 if we assume the mass of the balloons distributed over the entire research plot (15 m × 213 m). This single plastic input makes up 29 percent of the total amount of plastics found in the control treatment or 1.9 percent of the plastic in the high biosolids treatment. Compared to the atmospheric deposition, the balloons contributed to 180 percent of the natural yearly plastic deposition.
Publications
- Type:
Other
Status:
Published
Year Published:
2023
Citation:
Flury, M., 2023. Microplastics in Biosolids and Biosolids-Amended Soils. Northwest Biosolids, Newsletter Short Stories, https://nwbiosolids.org/microplastics-in-biosolids-and-biosolids-amended-soils.
- Type:
Other
Status:
Published
Year Published:
2022
Citation:
Flury, M., D. G. Hayes, and K. Mancl, 2022, Biodegradable Plastics-A Potential Solution for Agricultural Mulch? InsightOut, 8, 6269. www.wilsoncenter.org/publication/insightout-issue-8-closing- loop-plastic-waste-us-and-china?collection=46001
- Type:
Journal Articles
Status:
Published
Year Published:
2023
Citation:
Astner, A. F., A. B. Gillmore, Y. Yu, M. Flury, J. M. DeBruyn, S. M. Schaeffer, and D. G. Hayes, Formation, behavior, properties and impact of micro- and nanoplastics on agricultural soil ecosystems (a review), NanoImpact, 31, 100474, doi:10.1016/j.impact.2023.100474, 2023.
- Type:
Journal Articles
Status:
Published
Year Published:
2024
Citation:
Yu, Y., M. Velandia, D. G. Hayes, L. W. DeVetter, C. A. Miles, and M. Flury, Biodegradable plastics as alternatives for polyethylene mulch films, Adv. Agron., 183, 121192, 2024.
- Type:
Journal Articles
Status:
Published
Year Published:
2024
Citation:
Adhikari, K., C. I. Pearce, K. A. Sanguinet, A. I. Bary, I. Chowdhury, I. Eggleston, B. Xing, and M. Flury, Accumulation of microplastics in soil after long-term application of biosolids and atmospheric deposition, Sci. Total Environ., 912, 168883, doi.org/10.1016/j.scitotenv.2023.168883, 2024.
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2025
Citation:
Adhikari, K., C. I. Pearce, K. A. Sanguinet, and M. Flury, Uptake of Polystyrene Nanospheres by Wheat and Arabidopsis Roots in Agar, Hydroponics, and Soil, (in preparation).
|
Progress 05/01/22 to 04/30/23
Outputs
Target Audience:Target audiences: Scientific peers, Students, State and Federal Environmental Regulatory Agencies, Farmers, General public, Biosolids Producers, Waste Waste Treatment Plants. Efforts: We have presented our research at both local and international conferences. Presentations were made at the annual meeting of the European Geoscience Union (in person) and the annual meeting of the Soil Science Society of America in Salt Lake City. We also have been invited to talk abut our research on micro- and nanoplastics at the press conference of the European Geoscience Union annual meeting. A podcast was recorded with the "WSU Wheat Beat Podcast" on "Potential Impacts of Microplastics in Agricultural Soils", in which we highlighted our research project and the general issue of microplastics in farmland. In March 2023 we had discussions with the congressional staff of US congresswoman Ms. Perez about microplastics in agricultural and food systems, and we helped draft a bill to the US House of Representatives to propose an amendment to the Food, Agriculture, Conservation, and Trade Act of 1990 to include as a high-priority research and extension area research on microplastics in land-applied biosolids. This bill will be introduced in the 1st Session of the 118th Congress. We also prepared an outreach article "Microplastics in Biosolids and Biosolids-Amended Soils" for the Northwest Biosolids short story newsletter (https://nwbiosolids.org/microplastics-in-biosolids-and-biosolids-amended-soils). Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project has supported two graduate students working on plastic extractions and quantifications. The two graduate students have presented their results at the annual meeting of the Soil Science Society of America in Salt Lake City. One of the graduate student also has disseminated her results "WSU Wheat Beat Podcast" and press conference. One of the graduate students also has received an Encompass Fellowship, sponsored by the ASA-CSSA-SSSA & Bayer Crop Science. This Fellowship provided leadership training at the annual meeting of the Soil Science Society of America and the student will work with a mentor from Bayer Crop Science throughout the year to obtain professional training. We have also been working on inviting and hosting two graduate students from the Czech Republic to join our group as international visiting students. How have the results been disseminated to communities of interest?Two journal articles have been prepared, and research results have been presented at invited seminars and volunteered presentations at professional meetings. A podcast has been recorded for the "WSU Wheat Beat Podcast" on "Potential Impacts of Microplastics in Agricultural Soils". A feature article was published in CSA News in microplastic pollution in agricultural soils based on some of our research we had presented at the Annual Meeting of Soil Science Society of America. At that meeting, we also presented a workshop to the undergraduate student organization of SSSA. We have collaborated with the Wilson Center (https://www.wilsoncenter.org) on writing an article about microplastic pollution in agricultural soils. The Wilson Center is a non-partisan think tank chartered by Congress in 1968 as the official memorial to President Woodrow Wilson, and is the nation's key non-partisan policy forum for tackling global issues through independent research and open dialogue to inform actionable ideas for the policy community. The article we wrote discusses plastic pollution of farmland and potential solutions to the ever increasing amount of plastic accumulating therein. What do you plan to do during the next reporting period to accomplish the goals?We will continue to refine our quantification and identification of the soil and biosolids samples, complete the experiments of the plant-plastic particle interactions and plant uptake of plastics, and we will continue to sample atmospheric deposition of microplastics with our atmospheric deposition samplers. We are currently sending our samples out for quantification and identification on a LDIR System (Laser Direct Fourier-transformed Infrared Imaging System). For the plant-plastic interaction experiments we are using confocal and scanning electron microscopy at the WSU Francheschi Microscopy and Imaging Center. We submitted NIFA Equipment proposal to obtain a Laser Direct Fourier-transformed Infrared Imaging System (Agilent Technologies), which was not funded. We plan to resubmit this proposal after revisions. We will continue the plant-nanoplastics uptake experiments with hydroponic solutions and soil media. Scientific articles will on these experiments will be completed and written up.
Impacts
What was accomplished under these goals?
Objective (1): Quantify and characterize micro- and macroplastics in biosolids of a waste water treatment plant. Most of work for this objective have been completed during the last reporting period. We have further refined our analytical identification and quantification of microplastics extracted from biosolids samples to obtain more reliable data. We have calculated annual loads of microplastics to farmland due to biosolids applications, and have also worked on converting measured number concentrations to mass concentrations. This will allow us to compare the input of microplastics from biosolids with the input by atmospheric deposition. Objective (2): Determine whether long-term application of biosolids to agricultural soils has led to accumulation of micro- and macroplastics. We have completed the extractions of the soil samples from the different experimental treatments biosolids applications of 0, 4.8, 6.9, and 9.0 Mg/ha) for isolating microplastics. The microplastics were extracted from soil with a protocol involving organic matter removal by Fenton's reaction and a density separation with zinc chloride. Microplastics were then visualized and counted with a microscope, and plastic identification was done by Fourier-transformed infrared spectroscopy. We observed an increasing amount of microplastics in the soil with higher biosolids applications, but the differences were not statistically significant. However, the biosolids-amended treatments had a significantly higher content of microplastics than the non-amended control treatment, indicating the biosolids contribute significantly to the microplastic load in soils. We observed about the same amount of microplastics in 0-5 cm and 5-10 cm depth. The majority of the plastics observed were fibers, followed by fragments, pellets, and films. We identified the plastic polymers as polyamide, polyethylene, PVC, polyurethane, PET, polyvinyl alcohol, polyehtylmethacrylate, and rubber. The plastic polymer signature in the biosolids-amended soils matched that of the biosolids, supporting that the plastics in the soil indeed originate from biosolids applications. We are currently analyzing the experimental data by calculating mass concentrations of plastics and comparing with atmospheric inputs. We are also writing up the results in form of scientific manuscript and have prepared a draft of this manuscript. We also have prepared a comprehensive review article on biodegradable plastics used in agriculture. Biodegradable plastics can be used as an alternative to conventional plastics and would help to minimize plastic pollution of farmland when single-use plastics would be replaced with biodegradable plastics. Objective (3): Evaluate interactions of microplastics with plant roots. We continued the experiments to evaluate interactions of microplastics with plant roots. Arabidopsis and wheat seeds have been germinated on agar media and propidium iodide staining is used to stain the root cells and make them better visible under the confocal microscope. We are using three different types of nanoplastics: 40 nm and 200 nm carboxylate-modified polystyrene beads (negatively charged) and 200 nm amine-modified polystyrene beads (positively charged). We have completed the experiments where plants are grown in agar medium, and we are continuing with the experiments where plants will be grown in hydroponic solution and soil media. The experiments with agar media have shown that nanoplastics mainly accumulate at the outside of the roots, but the negatively charged nanoplastics can penetrate the root tissue, mostly by the apoplastic pathway, i.e., by motion in between the cells, without active uptake into the interior of the cells. The graduate student working on these experiments has spent the fall semester 2022 and spring semester 2023 at the Pullman main campus to use the confocal microscopy facility at the university's microscopy center. The student will likely remain at the main campus and continue with these experiments in the fall semester 2023. Objective (4): Collect and characterize atmospheric deposition of microplastics. Atmospheric samples from the installed atmospheric samplers were taken in April 2022, July 2022, and October 2022. The next samplings are scheduled in April (after the snow has receded from the field site), July, and October 2023. The samples taken from April 2022, July 2022, and October 2022 have been analyzed for microplastic contents and polymer identification has been completed. The atmospheric samples showed the presence of alkyd varnish, likely originating from paint of houses, rubber, possibly from tire rub off, and also natural materials, such as cellulose and chitin. We continue to analyze the atmospheric samples.
Publications
- Type:
Other
Status:
Published
Year Published:
2022
Citation:
Flury, M., D. G. Hayes, and K. Mancl, Biodegradable Plastics-A Potential Solution for Agricultural Mulch? InsightOut, 8, 6269, 2022. www.wilsoncenter.org/publication/insightout-issue-8-closing- loop-plastic-waste-us-and-china?collection=46001
- Type:
Other
Status:
Published
Year Published:
2023
Citation:
Flury, M., 2023. Microplastics in Biosolids and Biosolids-Amended Soils. Northwest Biosolids, Newsletter Short Stories, https://nwbiosolids.org/microplastics-in-biosolids-and-biosolids-amended-soils.
- Type:
Journal Articles
Status:
Submitted
Year Published:
2023
Citation:
Yu, Y., Velandia, M., Hayes, D.G., DeVetter, L.W., Miles, C.A., and Flury, 2023. Biodegradable plastics as alternatives for polyethylene mulch films. Advances in Agronomy, in review.
- Type:
Journal Articles
Status:
Other
Year Published:
2023
Citation:
Adhikari, K., Pearce, C.I., Sanguinet, K.A., Bary, A.I., and Flury, M., 2023. Accumulation of microplastics in soil after long-term application of biosolids, to be submitted to Science of The Total Environment, in preparation.
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Progress 05/01/21 to 04/30/22
Outputs
Target Audience:Target audiences: Scientific peers, Students, State and Federal Environmental Regulatory Agencies, Farmers, General public, Biosolids Producers, Waste Waste Treatment Plants. Efforts: We have presented our research at both local and international conferences. Presentations were made at the annual meeting of the European Geoscience Union (virtual) and the annual meeting of the Soil Science Society of America in Salt Lake City. An update article and a podcast were completed and recorded on the current state of knowledge about fate and transport of microplastics in terrestrial systems. Results of the project were also presented to growers and public stakeholders as a Webinar within a Plastic-Soil Health Webinar organized by WSU Extension. Changes/Problems:Covid-19 restrictions still caused some delays in field sampling in early 2021, but the sampling campaign did take place in May/June 2021. Access to laboratory equipment at the Environmental Molecular Science Laboratory was also restricted, but we have been able to do measurements facilitated by the staff of the Environmental Molecular Science Laboratory itself. In the future, no further restrictions due to Covid-19 are expected. What opportunities for training and professional development has the project provided?The project has supported two graduate students working on plastic extractions and quantifications and numerical simulations of plastic sampling in terrestrial systems. A Postdoc has worked on thermo-gravimetric analysis and mass spectroscopy. The two graduate students have presented their results at the annual meeting of the Soil Science Society of America in Salt Lake City. One of the graduate student also has disseminated her results in the Field, Lab, Earth Podcast Series of the American Society of Agronomy. One of the graduate students also has received an Encompass Fellowship, sponsored by the ASA-CSSA-SSSA & Bayer Crop Science. This Fellowship provided leadership training at the annual meeting of the Soil Science Society of America and the student will work with a mentor from Bayer Crop Science throughout the year to obtain professional training. The Fellowship will also include a meeting with the Soil Caucus and congressional delegations in Washington DC, if Covid restrictions allow. How have the results been disseminated to communities of interest?Three journal articles have been published, and research results have been presented at invited seminars and volunteered presentations at professional meetings. A podcast has been recorded for the Field, Lab, Earth Podcast Series of the American Society of Agronomy. What do you plan to do during the next reporting period to accomplish the goals?For the next reporting year, we will continue with the plastic extractions of the soil and biosolids samples and complete the experiments of the plant-plastic particle interactions and plant uptake of plastics. For the plant-plastic interaction experiments we are using confocal and scanning electron microscopy at the WSU Francheschi Microscopy and Imaging Center. We are also planning to write and submit a NIFA Equipment proposal to obtain a Laser Direct Fourier-transformed Infrared Imaging System (Agilent Technologies), which would allow us to better quantify the extracted microplastic particles and at the same time would provide particle size and shape information of the plastic particles. We will further start with the sampling and quantification of the atmospheric deposition samplers.
Impacts
What was accomplished under these goals?
Objective (1): Quantify and characterize micro- and macroplastics in biosolids of a waste water treatment plant. We have further refined and optimized our protocol to extract microplastics from biosolids and soil samples. The optimal extraction protocol was tested and verified with spiked samples where a known amount of plastic microplastics of different shapes were added to uncontaminated soil samples and the extraction efficiency was quantified. Extraction efficiencies for Nylon fibers, polyester wool fibers, and polypropylene granules were 60 +-0, 70 +- 12, and 85 +- 19% respectively. We further continued and refined the development of thermogravimetric analysis and mass spectrometry (TGA-MS) to quantify and identify microplastics in biosolids and soil samples. We improved our calibration equations to predict plastic concentrations. Previous samples were then reanalyzed. We determined the limits of detection of plastic concentrations as 0.078 wt% (99% confidence interval) and 0.050 wt% (95% confidence interval). The limits of quantification were determined as 14 wt% (99% confidence interval) and 2.70 wt% (95% confidence interval). Objective (2): Determine whether long-term application of biosolids to agricultural soils has led to accumulation of micro- and macroplastics. Due to Covid restrictions on field work, our sampling campaign to take a new set of soil samples was delayed. Instead, we conducted theoretical studies on how to best sample soil for plastic analysis. We simulated different sampling strategies with computer modeling. In these simulations, we distributed plastic particles at different concentrations in an agricultural field, and the took soil samples, again with a simulation, and finally quantified the amounts of plastics in these soil samples. Plastic particles were randomly distributed or in spatial clusters. The results of these numerical simulations showed that the best sampling method to quantify microplastics in soils is to take a large block rather than multiple small core samples. We recommend to sample a 1 m by 1 m large area of soil, homogenize this large sample in the field and then reduce the sampling volume with the quartering method. The sample size will depend on the initial plastic concentration in the soil but because this initial concentration is not known a priori, a large are of 1 m by 1 m is sufficiently large for most environmentally relevant plastic concentrations. We implemented this sampling method at our Douglas County field site in late spring 2021 and we took soil samples with the method we have developed based on the numerical simulations described above. Soil samples were taken from 0-5 cm and 5-10 cm depth. Samples were taken from three biosolids treatments (4.8, 6.9, and 9.0 Mg/ha) and from a no biosolids-amended control plot. We have started to extract these soil samples to quantify plastic concentrations. These extractions are ongoing. We also studied the formation of micro- and nanoplastics from plastic mulch films when composted. We found that plastic films degrade into micro- and nanoplastics and, in addition, additives, such as TiO2 nanoparticles, are released when the plastic polymers degrade. Objective (3): Evaluate interactions of microplastics with plant roots. We started the experiments to evaluate interactions of microplastics with plant roots have been conducted. Arabidopsis and wheat seeds have been germinated on agar media and several different dye staining techniques have been tested. Experiments with different sized and differently charged plastic micro- and nanobeads are currently ongoing. We are using three different types of nanoplastics: 40 nm and 200 nm carboxylate-modified polystyrene beads (negatively charged) and 200 nm amine-modified polystyrene beads (positively charged). The graduate student working on these experiments is spending the spring semester 2022 at the Pullman main campus to use the confocal microscopy facility at the university's microscopy center. Objective (4): Collect and characterize atmospheric deposition of microplastics. We installed four rainfall samplers (260-2510 NWS Type Rain Gauge) in late spring 2021 at the Douglas County field site. Two samplers were installed upwind and two samplers were installed downwind of the biosolids plots to determine wether plastics can be transported off the field plots by wind. First atmospheric samples were taken in fall 2021, but were contaminated with insects who were attracted and fell into the water collected by the rainfall samplers. We then installed a screen to prevent insects to enter the sampler and collection area. First atmospheric samples are planned to be taken in April 2022 and May 2022.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2021
Citation:
Yu, Y., and M. Flury, How to take representative samples to quantify microplastic particles in soil?, Sci. Total Environ., 748, 147166, doi.org/10.1016/j.scitotenv.2021.147166, 2021. (doi.org/10.1016/j.scitotenv.2021.147166)
- Type:
Journal Articles
Status:
Published
Year Published:
2021
Citation:
Flury, M., and R. Narayan, Biodegradable plastic as integral part of the solution to plastic waste pollution of the environment, Current Opinion Green Sustainable Chem., 30, 100490, doi.org/10.1016/j.cogsc.2021.100490, 2021. (doi.org/10.1016/j.cogsc.2021.100490)
- Type:
Journal Articles
Status:
Published
Year Published:
2022
Citation:
Yu, Y., H. Y. Sintim, A. F. Astner, D. G. Hayes, A. I. Bary, A. Zelenyuk, O. Qafoku, L. Kovarik, and M. Flury, Enhanced transport of TiO2 in unsaturated sand and soil after release from biodegradable plastic during composting, Environ. Sci. Technol., 56, 23982406, 2022. (doi.org/10.1021/acs.est.1c07169)
- Type:
Other
Status:
Other
Year Published:
2021
Citation:
We have also given several interviews to newspapers on the topic of plastic pollution in the environment.
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Progress 05/01/20 to 04/30/21
Outputs
Target Audience:Target audiences: Scientific peers, Students, State and Federal Environmental Regulatory Agencies, Farmers, General public, Biosolids Producers, Waste Waste Treatment Plants. Efforts: We have reached out to target audience through a variety of means. Our project was presented at regional biosolids conferences. We have been featured in the WSU Wheat Beat Podcast, a podcast mainly targeted to wheat farmers in the Pacific Northwest. We have also presented our work to a congressional delegation in Washington DC through the Soil Science Society of America's Congressional Soils Caucus. We also presented our work to the Michigan Biosolids Conference. All these activities were done over Zoom. Changes/Problems:The Covid-19 pandemic has caused delays with student recruiting, field activities, and laboratory work. We have been able to recruit a graduate student, but another student from China could not travel to the US. We hope to recruit this student later this year when travel restrictions are lifted. We have used the time where we had restricted access to the laboratory by shifting from laboratory to more theoretical work (doing theoretical work on sampling and numerical simulations) and working on review articles. Access to important laboratory facilities and instruments has been limited in 2020 and 2021, but the laboratory work will become more intense again after the Covid-19 restrictions will be fully lifted. What opportunities for training and professional development has the project provided?We have recruited a new graduate student to work on this project. The graduate student has started his program in Fall 2020 and has taken courses for his graduate program. This student has started with his literature review and with the chemical extractions of plastics from biosolids. Another graduate student has worked on the TGA-MS analysis, and has graduated in Fall 2020. A postdoc has taken over some of the work on the TGA-MS analysis. Another graduate student has worked on the numerical simulations of plastic sampling. Students have presented their work at the Annual Meeting of the Soil Science Society of America, and at Departmental Seminars. One of the students, Stephen Taylor, has presented at the Congressional Soil Caucus. All these activities did take place on Zoom. How have the results been disseminated to communities of interest?Two journal articles have been published, and 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?For the next reporting year, we will conduct soil sampling at the field site following the new sampling protocol that we have developed based on the numerical simulations described above. This sampling will take place at the end of April. At the same time, we will also install the rainfall gauges to sample for atmospheric plastic deposition at the field site. We started to write up the revised sampling protocol in form of a scientific article and will complete this article in the next few weeks. We will further start with the chemical extractions of biosolids and soil samples taken with the new sampling protocol.
Impacts
What was accomplished under these goals?
Up to 80% of biosolids are land-applied in the United States. Biosolids provide valuable nutrients and organic matter to soils and therefore generally help to improve soil health. However, biosolids also contain heavy metals and other pollutants. To prevent contamination of soils, certain pollutants in biosolids are regulated, and biosolids can only be land-applied if regulated pollutants are less then a certain concentration. Biosolids also contain microplastics, and these microplastics are transferred to soils along with the land-applied biosolids. While it has been shown that microplastics can cause harm to soil organisms and impact soil health, it is not known how much plastics is present in biosolids and how much plastic will accumulate in soils when biosolids are repeatedly applied as fertilizers to soils. In this project, we will quantify microplastics in biosolids and in a soil that has received biosolids as fertilizer for the past 22 years. We will provide data on whether biosolids are a significant source of microplastics in soils and whether microplastics should be regulated in biosolids as a pollutant. Objective (1): Quantify and characterize micro- and macroplastics in biosolids of a waste water treatment plant. We have obtained historic samples of biosolids from the South Waste Water Treatment Plant in Seattle from 1997 and 2017. Two more recent biosolids samples from 2019 and 2020 were collected and have been used to extract microplastics. We tested two different extraction methods based on two recent scientific articles where biosolids samples have been analyzed for microplastics. The optimal method included removal of organic matter with Fenton's reagent, followed by a fractionation of plastics with density separation using a ZnCl2 solution. The fractionated samples were filtered and are now being analyzed for particle number and particle identification. We have also developed an analysis method based on a combination of thermogravimetric analysis and mass spectrometry (TGA-MS) to quantify and identify microplastics in biosolids and soil samples. This method is based on recent scientific paper where soil samples have been extracted for plastics particles. We have tested the TGA-MS method with plastic standards (polyethylene, polypropylene, polystyrene, polyamide, polyethylene teraphthalate), and also with selected biosolids and soil samples. In contrast to the density separation method described above, the TGA-MS method is destructive, that is, the extracted plastics can not be visualized with microscopy, so no size and shape information can be obtained. However, the advantage is that we can analyze for nanoplastics with TGA-MS, which is difficult with density separation methods. We plan to use both methods in parallel. Objective (2): Determine whether long-term application of biosolids to agricultural soils has led to accumulation of micro- and macroplastics. We have obtained historic soil samples from a site where biosolids from the South South Waste Water Treatment Plant have been applied since 1997. This site is a dryland wheat field, where different rates of biosolids are tested for agronomic performance. We also have taken new samples in 2019, right after a fresh application of biosolids has been made. Soil samples were taken following the standard protocol from the previous sampling that has been conducted at the site to assess nutrient status and soil quality. The sampling consisted of taking 12 consolidated soil cores with a 4-cm soil auger from three depths (0-4, 4-8, 8-12 inches or 0-10, 10-20, 20-30 cm). To test the sampling protocol and to verify the methodology, we tested the biosolids and the soil by analyzing for silver. Silver is much easier to measure than plastics, as it can be quantified with ICP-MS with a low detection limit and with high accuracy. Natural silver contents on soils is very low, so silver is a good tracer for biosolids. We analyzed all our historic samples for silver concentrations and determined a time-series of silver concentrations in soils and biosolids. The data show a clear trend of decreasing silver concentrations in biosolids over time, likely because of the declining use of silver in dentistry. In the soil samples, silver concentrations started to increase when biosolids were applied, and we were able to obtain a good mass balance for silver over a time period from 1997 to 2017. We also determined that most of the silver is present in biosolids and soil as silver sulfide nanoparticles. The good mass balances obtained for silver suggest that we also should be able to obtain good mass balances with plastics. In 2019, we were able to take a series of new soil samples from the field site, following the same protocol as for the historic samples. Based on observations of biosolids in the field, we determined that biosolids, and therefore also the plastic particles, occurred in clusters on the field. This clustering likely will affect how effective small soil cores are in taking representative samples, and we hypothesized that taking small soil cores will not be an effective method to sample for microplastics. Restrictions of extensive field work due to Covid-19 prevented us from doing more field sampling. So, we decided to test the sampling with numerical simulations. We simulated an agricultural field that has been polluted with microplastic particles and then took soil samples with different sampling methods, and quantified plastic concentrations by numerically counting the plastic particles in the soil samples. We used to the concept of the representative elementary volume to determine how much soil needs to be sampled to obtained a representative measurement. The numerical sampling simulations also allowed us to quantify the error of the sampling methods. The simulation results showed that a box sampling method, with taking soil samples from a large 1 m by 1 m block, and then reducing the sample volume by the quartering method will provide the most accurate measure of the plastic concentrations. We will therefore use this new method in our future sampling at the field site. Given the restrictions during the Covid-19 pandemic to access laboratory facilities, we have shifted some experimental activities to more theoretical work that could be done without having to be in the laboratory physically. We have worked on a review article on fate and transport of micro- and nanoplastics in soils, and have successfully published this review in 2021. Objective (3): Evaluate interactions of microplastics with plant roots. Work on this objective has not yet commenced. It is scheduled in years 3 and 4 of the project. Objective (4): Collect and characterize atmospheric deposition of microplastics. We have purchased four rainfall samplers (260-2510 NWS Type Rain Gauge) to be installed at the field site in spring 2021. We will install two samplers upwind and two samplers downwind of the biosolids plots. Analysis of the long-term wind patters at the field site have shown that the predominant wind direction is west to east, so will install two samplers in the west and two samplers in the east of the biosolids plots.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Taylor, S. E., C. I. Pearce, I. Chowdhury, L. Kovarik, S. Baum, A. I. Bary, and M. Flury, Long-term accumulation, vertical distribution, and speciation of silver nanoparticles in biosolids-amended soils, J. Environ. Qual., 49, 16791689, 2020.
- Type:
Journal Articles
Status:
Published
Year Published:
2021
Citation:
Yu, Y., and M. Flury, Current understanding of subsurface transport of micro- and nanoplastics in soil, Vadose Zone J., 20, e20108, doi.org/10.1002/vzj2.20108, 2021.
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