Integrative assessment of heavy metal risks in mining polluted sediments and soils of Aguascalientes, Mexico

Residual metals from mining activities pose significant risks to both the environment and human health, especially when they exist in bioavailable and mobile forms. In areas where complex physicochemical characteristics make it difficult to estimate metal mobility, assessing these risks requires an integrated approach. In this case study environmental risk was assessed by integrating the following indicators: ratio between total metal concentration and reference values, geoaccumulation index (Igeo), risk characterization ratio (RCR) and mobility factor (MF). The highest concentrations of Cd, Pb, Cu and Zn in sediments were 45.95, 743.01, 220.24 and 2992.84 mg/Kg, respectively while the concentrations in soils were 26.23, 953, 553.46, and 11948.80 mg/Kg, respectively. The Igeo confirmed moderate to heavily contaminated soils and sediments. Additionally, the RCR exceeded the quotient 1 for all metals, suggesting a significant ecological risk. High MF (up to 70 %) was observed for Cd in both sediments and soils. However, for Pb, Cu and Zn an average of 15 % was observed only in sediments. This study reveals that physicochemical characteristics, pH, Eh, texture, organic matter and CEC influence metal mobility and indicate anthropogenic metal contamination in readily available forms, highlighting the importance of comprehensive physicochemical evaluations and integrative use of different pollution indicators when assessing contamination levels and evaluating associated risks of polluted environments to both human health and the environment.