Natural attenuation along subsurface flow paths based on modeling and monitoring of a pesticide metabolite from three case studies

Abstract Background Groundwater—especially for the use as drinking water—is a strictly protected resource in existing guidelines pesticide registration and water protection EU. One aspect that has hardly played role this context so far is attenuation of concentrations along flow path from regulatory leaching concentration at depth 1 m below applied field to raw abstraction systems. The soil metabolite N,N-dimethylsulfamide (DMS) formed two fungicidal substances: tolylfluanid dichlofluanid. According EU guidance document on relevant metabolites groundwater, DMS “non-relevant” metabolite. However, long-term application active substances permanent crops resulted elevated quantifiable amounts groundwater catchment areas supplying plants. Therefore, case DMS, substantial monitoring data available. This enables combination with modeling, quantitative analysis natural over time distance. To end, extensive real-world three studies Germany were analyzed. Results environmental fate was evaluated according respective determined study sites. Analyses using combined modeling approaches well, performed obtain comparable results. These merged outcomes show total factors 12–93 leachate down wells—close collection. If further downwards collected considered, overall factor even higher (40–246). Conclusions conditions are very diverse, thus providing wide range attenuating conditions. When following its formation treated field, into aquifer, within aquifer collection site, continuously consistently decreasing. results represent conservative estimations due non-sorptive, quick transport processes. Extended other sorptive solutes, it represents lower end expected attenuation. processes suggested consideration risk assessments more realistic yet still protective evaluation water.