The transboundary Meric Delta along the Turkish-Greek border is a significant ecological site protected under the international RAMSAR convention. The wetlands in the basin receive agricultural drainage during the irrigation season. Pesticides from adjacent farmland that enter into these wetlands pose a big threat to the aquatic life and species in the wetland system. Furthermore, these pollutants have potential to reach downstream water bodies including Meric River, negatively impacting water quality. Four organophosphate pesticides (chlorpyrifos, diazinon, fenthion, dichlorvos) commonly used in the basin were selected for inclusion in this study.  Stream sediments from wetlands and agricultural drains were collected during irrigation season, transported to the laboratory on ice, spiked with the organophosphate pesticides and rates of pesticide loss were measured with a standardized biodegradation assay. In addition to the biotransformation experiments, adsorption of pesticides to sediment and plant samples was measured and linear partitioning coefficients (K<sub>d</sub>) were determined. In general, organophosphate pesticides exhibited faster biotransformation rates in the agricultural drain sites compared to the wetland sites. The average half-lives of pesticides ranged from 1.8 to 35 days with chlorpyrifos exhibiting the slowest biotransformation rate and dichlorvos having the fastest biotransformation rate. To confirm the applicability of the obtained kinetic results on larger scale, a pilot scale laboratory mesocosm reactor was constructed with sediments and plants collected from one wetland site. The wetland mesocosm reactor was spiked with the organophosphate pesticides and the fate of pesticides in the reactor was determined. The results of these experiments are part of an effort to understand factors controlling the fate of organophosphate pesticides in riparian wetlands and to determine the effectiveness of constructed wetlands as Best Management Practices (BMPs) for pesticide mitigation in agricultural watersheds.<br/>

Fate of organophosphate pesticides in wetlands receiving agricultural drainage

254th National Meeting (2017)

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