Polluting potential from mining wastes: proposal for application a global contamination index

Indices of contamination (IC) are usually employed to assess the hazardousness associated with potentially toxic elements (PTE) from mining wastes (MW). For such, it is necessary to know the total concentrations of the PTE and local, regional, or global background or reference levels which are tolerable or acceptable threshold values for total content in soils. Although scientific literature is vast regarding the application of IC to MW, there is scarce research on the reference levels that must be employed in locations with no established comparison values. This study proposes basic reference levels for the global application of PTE contents in MW, leading to a global index of contamination (ICG). To this end, it was determined that the PTE to be assessed in MW should be As, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Sb, Se, V, and Zn. From the analysis of background and baseline values for soils, reference values for the PTE compiled from worldwide standards or studies on soil and sediment evaluation, and PTE content in MW, a classification is proposed for ICG that considers MW as very low, low, moderate, high, and very high contamination potential. The findings presented herein can be helpful in the comparison of multiple types of MW, representing the contamination hazard by particle emission due to erosion processes that reach the soils or sediments of the surrounding environment. This evaluation can aid in the decision-making process regarding the reutilization of some types of MW that receive a low classification.