Environmental Implications and Risk Assessment of Pesticide Residues in Soils and Water in One of the Most Important Agricultural Regions in Niger

In sub-Saharan Africa, intensive pesticide use in irrigated agriculture is threatening the quality of soil, water bodies and ecosystem services, yet integrated risk assessments remain limited. This study evaluated the environmental implications and risks of pesticide residues in soils (0–20 cm; n = 15) and irrigation water (n = 15) from off-season irrigation area of the Goulbi Maradi Valley, Niger. Twelve commonly used pesticides in Djiratawa, Maradi 3 and Tibiri, were quantified by High-Performance Liquid Chromatography with Variable Wavelength Detector (HPLC-VWD), revealing Tibiri as a contamination hotspot, where the total pesticide residues in soil and irrigation water reached 6.4 and 19.7 times the respective European Union soil and drinking water benchmarks, dominated by Cypermethrin, Emamectin benzoate and Chlorpyrifos ethyl in soils, and Emamectin benzoate and Dichlorvos in water. Multivariate analysis showed that soil particle size, particularly higher clay content, controlled the retention of strongly sorbing compounds, while pH and salinity governed the occurrence of more soluble residues in irrigation water. While non-carcinogenic risks for Adults and Children via soil and water exposure were acceptable (Hazard Quotient and Hazard Index < 1), ecological risks were unacceptable, with Folsomia candida and Daphnia magna the most affected organisms, driven by Emamectin benzoate (Toxicity Exposure Ratio < 2). Priority actions include phasing out Dichlorvos and Paraquat dichloride, tightening controls on Emamectin benzoate and expanding food-chain monitoring, particularly in vegetables and fish, to support multi-trophic risk assessment and safer irrigation management.