Environmental quality and ecological risk assessment in three water reserves of the Pampas region (Argentina).

Agricultural intensification in Argentina's Pampas region threatens aquatic ecosystems, including natural water reserves. We assessed environmental quality and ecological risk in three reserves in two headwater systems using physicochemical parameters, regional indices (ICAP, ICRP), and ecotoxicological metrics (Risk Quotients, Toxic Units, Potential Ecological Risk). Eight sites were sampled during a La Niña period with low flow, analyzing water, sediments, and riparian zones. Waters were slightly alkaline (pH 7.5-8.9) with high conductivity (> 1000 μS cm⁻¹). ICAP ranged from 2.6 (high pollution) to 8.2 (light pollution), while ICRP indicated mostly good riparian conditions except at one urban site (70). In water, glyphosate and AMPA ranged from 0.3 to 0.6 μg L⁻¹ and 0.7 to 2.2 μg L⁻¹, respectively. In sediments, cypermethrin reached 380 μg kg⁻¹. Copper was the most abundant metal in sediments (28-65 mg kg⁻¹), with moderate cadmium contamination (Igeo = 0.4) at one site. Risk analysis showed RQs > 1 in five sites and TUs > 1 in one site, indicating significant ecological concern. Multivariate analysis revealed distinct impacts at headwater and urban sites. Results highlight cumulative pressures even within protected reserves and the need for integrated monitoring, agrochemical regulation, and riparian buffers to safeguard aquatic biodiversity.