Environmental exposure and risk assessment of pesticide mixtures in aquatic organisms from the Tagus River Basin

Abstract

The widespread use of pesticides impacts human, animal and ecosystem health. Pesticide pollution causes significant freshwater biodiversity decline in Europe. In the present work, the occurrence of a large number of currently used pesticides (199) and mixtures was investigated in 90 samples from the fluvial environment, collected from a European emblematic watershed characterized by different land use, livestock farm and population density influences. Multiple pesticides were detected in high concentrations in all matrices (8097 ng/L, 3223 ng/g dry weight, 252 ng/g d.w., max. in water, sediment and fish, respectively). Herbicides exhibited a ubiquitous presence in water and sediment, while insecticides predominated in fish. Glyphosate and its transformation product aminomethylphosphonic acid (AMPA) reached the highest median concentrations in water and sediment, while pyrimethanil M605F002 and p,p’-DDE highlighted in fish. In addition to agricultural inputs, other anthropogenic sources (e.g., urban runoff, wastewater inputs) were found to influence pollution in rivers. The sum of all individual pesticides, metabolites and degradation products surpassed the threshold value (500 ng/L) established in the European Water Framework Directive for surface water in 11 out of 13 locations, and at least one exceedance for individual compounds was observed in all sites studied. Although only 7 % of the single pesticides were designated high risk, pesticide mixture ratios evinced potential ecological risk for aquatic and sediment-dwelling organisms. Furthermore, a total of 27 different hazardous pesticides were identified in the aquatic ecosystems.