Pesticide distribution and ecotoxicological risk in the Ayuquila-Armería river

Pesticides make an important contribution to increased global agricultural production; however, their intensive use represents a risk to biota in both the short and long terms. The physical and chemical characteristics of these compounds, as well as their versatility in agricultural, domestic, and public health use, have led them to become widely present in the environment. The objectives of this study were to evaluate the spatiotemporal distribution of pesticides in the surface water of the Ayuquila-Armería river and to conduct an ecotoxicological risk assessment in algae, macroinvertebrates, and fish. The presence of 11 analytes was determined, being λ-cyhalothrin, ametrine, and malathion the pesticides with highest concentrations, and carbendazim, malathion, and glyphosate those with the highest frequency of detection (> 70 %). The number of pesticides detected per sample presented no significant temporal differences, and there was no significant effect of the crops or vegetation adjacent to the study sites on the number of pesticides detected per sample. The sampling conducted in November 2019 (wet season) presented the greatest difference in concentrations of most pesticides, compared to the other samplings. The ecotoxicological risk assessment showed that the macroinvertebrates (Daphnia magna) are the most vulnerable to the concentrations of pesticides in surface water, followed by fish and algae. Regulation of the importation, trade, and management of malathion and λ-cyhalothrin is crucial in order to reduce the presence of their residues and the risks associated with them.