Prediction of Acid Mine Drainage Generation from Mine Waste at an Abandoned Mining Site in a Semi-arid Environment

Mine tailing deposits may result in environmental issues when abandoned and exposed to environmental conditions. This case study focuses on the “El Lavadero” tailing deposit, an abandoned mining environmental liability located in San Felipe de Jesús, Sonora, Mexico. To forecast its acid mine drainage (AMD) generation potential, the modified acid–base accounting (ABA) test was performed. The results in tailings fluctuated within the following ranges: Eh (257–583 mV), pH (1.7–6.4), E.C. (4425–51,065 µS cm−1), Stotal (2.75–13.23%), SO42− (4.72–20.77%), and CaCO3 (< DL–12.71%); and PTE (mg kg−1): Cd (12–407), Cr (16–29), Cu (149–685), Fe (95,760–186762), Mn (2432–23,759), Pb (11,258–27,146) and Zn (2212–69,417). These tailings had higher PTE levels than their surrounding agricultural soil, with the following behavior: Fe > Zn > Pb > Mn > Cu > Cd > Cr. PTE levels were significantly higher than those established by both international standards and Mexican environmental regulations. X-ray diffraction and scanning electron microscopic studies conducted in mine tailings and agricultural soil identified primary (i.e., pyrite) and secondary minerals (i.e., gypsum and jarosite). The mobility test showed low mobility rates for Cr and Pb; Cu, Fe, Mn, Zn, and Cd showed higher mobility rates. The modified ABA test indicated that “El Lavadero” deposit tailings were AMD potential generators; therefore, they were classified as hazardous (SEMARNAT, 2003 & 2009). Acidic leachates with high PTE levels can affect the water supply sources of San Felipe de Jesús and effluents discharged into the Sonora River, including the surrounding crops meant for human and animal consumption. Hence, rehabilitation of the "El Lavadero” tailing deposit is recommended to alleviate the environmental impact. Alternatives include the construction of a low-permeability barrier downstream.