ROLES OF MICROPLASTICS IN RECLAIMED WATER - ALTERING PERSISTENCE AND BIOAVAILABILITY OF ANTIMICROBIALS IN AGRICULTURAL SOILS

Due to an increasing demand for freshwater supply, recycled or treated municipal wastewater has been considered analternative water sourcefor agricultural irrigation, especially in highly populated regions and/or semi-arid regions. However, significant levels of microplastics and antimicrobials often found in municipal wastewaters have raised a health concern if these reclaimed waters are used for agricultural food production. A number of studies have already observed that crops and plants could take up micropollutants including antimicrobials from reclaimed waters while a recent study has demonstrated that microplastics in soils can affect crop yield and plant performances . Despite the co-existence of microplastics and antimicrobials in reclaimed water, there has been no study examining their interactions and influences in agroecosystems. Importantly, many of these microplastics canabsorb hydrophobic micropollutants and increase their chemical persistence in the environment for a long time. We thus hypothesize that existing microplastics in reclaimed water can enhance the persistence and bioavailability of hydrophobic antimicrobials in soils and their uptake in plants and food crops.Hypothesis I: Roles of Microplastics on Antimicrobials- Microplastics, which serve as a vector, effectively absorb and concentrate hydrophobic antimicrobials from treated municipal wastewater, protecting these pollutants from photo- and bio-degradation during water conveyance, and eventually allowing long-distance transport and extended residence time in agroecosystems.HypothesisII: Uptake of Antimicrobials in the Presence of Microplastics- Microplastics enriched with antimicrobials from recycled municipal wastewater could become a source of antimicrobials in agricultural soils for an extended period, enhancing its bioavailability in soils and uptake into plants in agroecosystems.Hypothesis III: Risk Reduction Strategies- Bioavailability of antimicrobials from microplastics in agroecosystems depends on both soil organic matter and microplastics contents in the rhizosphere; therefore, uptake of antimicrobials by food crops can be reduced through increasing soil organic amendments or filtering reclaimed water within-situfiltration.