Evaluación del impacto de la acidificación en la calidad del agua de la quebrada Quilcayhuanca, Ancash, Perú

Glacial retreat exposes sulfide rocks and drives in situ weathering; consequently, acidic pH conditions and high concentrations of metals can occur in water, sediment, and soil. The objective of this study was to evaluate the impact of acidification due to glacial retreat on the water quality of Quebrada Quilcayhuanca in Áncash, Perú, using the plant Lemna minor and the cladoceran Daphnia magna in ecotoxicity tests. The physical-chemical parameters and the surface water (SA) toxicity and sediment elutriate (SE) were determined at seven sampling points through bioassays with L. minor and D. magna. In the physical-chemical analyses, the pH was ≤4, the electrical conductivity (EC) was 380 µS/cm, and the turbidity was 113 UNT. Cd, Pb, Ni, and Zn concentrations exceeded the Environmental Quality Standard (EQS) for water in Perú. In contrast, those of As, Cd, Cu, Pb, and Zn exceeded the Canadian sediment regulations, and those of Cd and As, the ECA for soil in Perú. The concentration values at which no effect from exposure to the pollutant (NOEC) was observed in SA and SE were ≤6.25% and 12.5% for chlorosis; we registered the formation of new leaves and the total number of L. minor fronds for the seven points, and its dry weight only in one of the points. In the test with D. magna, the mean effective concentration for immobility (EC₅₀-48h) fluctuated between 43.55% and 51.14%, and the mean lethal concentration (LC₅₀-48h) between 50% and 57.66% in the trials for SE and SA. The ecotoxicity of SA and SE due to Quebrada Quilcayhuanca's glacier retreat was associated with the pH and the presence of heavy metals.