Glyphosate, aminomethylphosphonic acid, and glufosinate ammonium in agricultural groundwater and surface water in China from 2017 to 2018: Occurrence, main drivers, and environmental risk assessment

Abstract

Glyphosate and glufosinate ammonium are the main herbicides used to control weeds in no-tillage agricultural fields in China. However, their leaching risk to groundwater and ecological risk to aquatic organisms remain unclear. From the agricultural basins among 10 provinces of China, glyphosate, its main metabolite aminomethylphosphonic acid (AMPA), and glufosinate ammonium were detected in 1.01%, 0.86%, 0% of 694 groundwater samples with the maximum concentrations of 2.09, 5.13, and <0.05 μg/L, and were detected in 14.3%, 15.8%, and 2.6% of 196 surface water samples with the maximum levels of 32.49, 10.31 and 13.15 μg/L. Furthermore, to evaluate the main drivers of exposure to the targets in water bodies, the fate models were used. The model simulation indicated that spray drift and overflow runoff were the key factors affecting the exposure to targets in surface water adjacent to rice field, whereas the spray drift deposition, runoff, and erosion induced the exposure to the targets in pond water close to dry land crop fields under different meteorological conditions and soil characteristics. The targets in groundwater posed a low risk to water consumption, while fish embryos might be at unacceptable risk due to glufosinate ammonium exposure in surface water with median risk quotient (RQ) equal to 55.6. The results highlight the spatial and seasonal distribution of glyphosate, AMPA, and glufosinate ammonium in groundwater and surface water in agricultural basins of China, providing the first evidence to the environmental risk of the targets to drinking water consumption and aquatic organism safety in China agriculture system.