Estimating long-term leaching of As, Pb, and Zn in old mine wastes from center of Mexico

The mining industry in Mexico has generated a large amount of waste containing potentially toxic elements that have been dumped directly on the ground for many years. Therefore, additional studies are needed to evaluate the environmental impact of these metals. This work performed dynamic leaching tests of potentially toxic elements from historical mining wastes from Monte de San Nicolás and Mineral de Peregrina in the Mining District of Guanajuato, Mexico. The EN 14405:2017 Standard was used L/S ratios at 0.1, 0.2, 0.5, 1, 2, 5, 10, and extended at L/S ratios, 13, 16 and 20. The studied elements were As, Pb, and Zn; the calculated mobility, or release, was determined using the equation proposed by the Dutch Building Materials Decree at liquid-to-solid ratios of 10 and 20. The pH of the tailings and the high percentages of carbonates indicate a low possibility of generating acid drainage. The As, Pb, and Zn cumulative release were greater at the Peregrina site with values of 0.904, 0.016, and 0.210 mg/kg respectively. The 100-year arsenic release estimate at the Peregrina site was 2186 mg/m² at a liquid/solid ratio of 10 and 3408 mg/m² at a liquid/solid ratio of 20, thus exceeding the Dutch decree limit in 15 and 10 years respectively.