Identification of mining waste using remote sensing technique: A case study in El Triunfo town, BCS, México

Mining in México is directly responsible for serious environmental impacts due to the lack of control in the management of mining shafts with high concentrations of potential toxic elements (PTE). These residues are subject to erosion and weathering processes, becoming high risk pollution sources for the health of the inhabitants. In the study area, El Triunfo, Baja California Sur, it is necessary to determine the location and composition of the mining shafts to carry out soil remediation in the near future. High resolution multispectral images of Pleiades satellite are appropriate tools for monitoring and classification of environmental risks, especially useful for the study of sediment distribution. For identify and georeferenced mining tailings within a semi-desert environment, we used remote sensing technique, by using the supervised classification tool and Maximum Likelihood algorithm. The results revealed 32 potential zones with mining residues which were visited to validate the technique, confirming that 87.5% had mining residues. Mining tailings in the area are collected in hills up to 20 m in height with scarce to nil vegetation and are composed of uncompacted reddish material. Laser diffraction analysis showed that the mean grain size is medium silt (25 μm). The maximum concentrations of PTE were determined by instrumental neutron activation analysis and inductively coupled plasma mass spectrometry and validated with certified reference material giving the next results: As: 15000 mg/kg; Cd: 327 mg/kg; Cu: 1920 mg/kg; Pb: 88900 mg/kg; and Sb: 20200 mg/kg. We classified the mining wastes as extremely enriched in PTE using the normalized enrichment factor and extremely contaminated using the geoaccumulation index. We concluded that the remote sensing technique is a very useful tool for identifying local mining waste, the composition of which puts the health of inhabitants at risk; it is advisable that remediation work should be carried out in the short term.