Granulometric and Geochemical Distribution of Arsenic in a Mining Environmental Liability in a Semi-arid Area

Abstract

The present study refers to the "El Lavadero" tailings deposit, considered a mining environmental liability (MEL), located near San Felipe de Jesús town, Sonora, in northwest Mexico; the objective was to determine the total arsenic (As) content, its granulometric and geochemical distribution, and its mobilization capacity and bioavailability. The results in the oxidized and unoxidized tailings indicated low pH (potential of hydrogen) values (2.4–5.7) and elevated concentrations of total arsenic (8235–36,004 mg kg^− 1), which predominated in the finer granulometric fractions (< 0.05 mm). Arsenic also prevails in agricultural soil's finest fraction (> 2 mm). The above may represent adverse environmental effects because these particles can be transported and suspended in water media. Regarding the effluent sediments, arsenic prevails in the coarsest fraction (> 2 mm). A significant percentage of As (5–40%) was observed in the tailings (oxidized and unoxidized) distributed in the non-residual geochemical fraction (fraction I + fraction II + fraction III) (1106–7675 mg kg-1), indicating a potential for mobilization and bioavailability. Depending on the environmental conditions (redox potential (Eh) and pH), As can redissolve and present high mobility in abiotic media, potentially having a final impact on the environment and possible effects on human health. Based on the above, it is essential to rehabilitate the "El Lavadero" MEL to avoid a more significant environmental impact. Additionally, the quality of the water from the supply sources surrounding the "El Lavadero" MEL is recommended to be periodically monitored.