Dr. Martin Tsz-Ki Tsui (Biology) received new funding from Clemson University for the project “Roles of Microplastics in Reclaimed Water – Enhancing Persistence and Bioavailability of Antimicrobials in Agricultural Soils.” Dr. Ayalew Osena is co-principal investigator on the project.
Recycled municipal wastewater has been considered an important alternative source water to mitigate water shortage problem in geographic areas with high populations and/or semi-arid climate, including southwestern United States. However, using these waters related to any human consumption including agricultural and food production raises serious health concerns. In particular, the elevated levels of diverse hydrophobic contaminants such as antimicrobials are often found in recycled wastewater, which may compromise the food crop productivity and human health consuming these agricultural products.
One class of emerging pollutants, microplastics, have potential to interact with these hydrophobic antimicrobial compounds, but have not been fully examined regarding their consequences in crop-soil system receiving recycled wastewater. To elucidate the interactive effects between microplastics and antimicrobials in agroecosystems, the researchers propose a four-year project involving field surveys, controlled laboratory studies, and greenhouse pot experiments to evaluate the environmental fate and bioavailability of antimicrobials as altered by microplastics in water, soil, and plants.
Antimicrobials are selected for this study because these hydrophobic chemicals can be absorbed onto microplastics and desorbed slowly for biological uptake, and can pose inhibitory effects to beneficial microbial communities (bacteria and fungi) in agricultural soils supporting productive growth of major crops, or directly taken up by food crops.
There will be three major objectives in this project: 1) distributions and partitioning of microplastics in the field receiving recycled wastewater; 2) interactions of antimicrobials-microplastics in soil-plant system; and 3) risk reduction strategies. Through collaboration with USDA-ARS scientists, we will conduct surveys from diverse field sites, which have been irrigated with recycled municipal wastewaters for over a decade, to determine distributions of both microplastics and antimicrobials in soil profiles.
Controlled laboratory studies will be carried out to determine the kinetics of degradation and adsorption-desorption isotherms of antimicrobials with microplastics in both wastewater and soil water. Mesocosm experiments with major crops will be set up to examine the effects of microplastics of different polymer, quantity, and sizes on their interaction with antimicrobials on soil microbes and their gaining of antimicrobial resistance, water and soil dynamics, plant growth and performance.
The researchers will also evaluate different soil amendment approaches through greenhouse experiments to mitigate the impacts of microplastics and antimicrobials on soil quality and plant growth. With the results from the controlled studies and field investigations, we will develop a box model describing the distribution, bioavailability, and uptake of antimicrobials under the influences of microplastics in agroecosystems irrigated with recycled wastewater.