Pesticide residue patterns along edaphic and climatic gradients in Peruvian coastal and andean agroecosystems

Abstract

The intensive use of pesticides in commercial agriculture in developing countries poses risks to human and environmental health. In Peru, information on pesticide residue distributions and their relationships with environmental factors remains limited. This study quantified pesticide residues in crop leaves, soil, and water across contrasting agroecosystems in the coastal valleys of Chancay-Huaral and Pativilca and the high-Andean valleys of Mantaro and Tarma. A total of 86 samples were analyzed for 92 pesticide compounds using validated LC-MS/MS and GC–MS/MS methods. Associations with edaphoclimatic variables were assessed using multivariate and predictive approaches. Pesticide residues were detected predominantly in crop foliage, whereas soil and water showed lower detection frequencies (16% of sampling points). Coastal valleys exhibited higher detection frequency (528 vs. 72 detections) and a greater percentage of contaminated samples (100% vs 68%) than high-Andean systems. Among samples with detectable hazardous pesticides, 70% exceeded Codex Alimentarius maximum residue limits (MRLs). Banned compounds, including methamidophos and chlorpyrifos, were also detected, indicating gaps in regulatory compliance. Pesticide variables were filtered based on detection frequency (≥ 5%) and WHO toxicological classification and grouped by chemical class to identify representative compounds. Occurrence patterns were significantly associated with clay, total organic carbon, available potassium, and precipitation according to ordination and predictive models. These results show that pesticide occurrence and magnitude are structured by environmental conditions and agricultural intensity, highlighting the need for geographically targeted monitoring and risk management strategies in Peru.