Metal concentrations and metal mobility in unsaturated mine wastes in mining areas of Goa, India

To aid in evaluating the environmental impacts of mining activities in the State of Goa, India, this paper examines water–soil interactions occurring in the mining area. Using flame atomic absorption spectroscopy, mine and mineral processing wastes (tailings) from the Codli mining area were examined for their metal concentrations. And it was found that these wastes contain several metals such as Cr, Zn, Pb, Cd, Ni, Mn, Fe and Cu. Among the various metals present, iron and manganese were found to be very high in concentration. Groundwater samples collected from five dug-wells in the study area were tested for their metal concentrations during the pre-monsoon and monsoon periods. It was found that some metal concentrations in the pre-monsoon water samples were high compared to those in the post-monsoon water samples. Experiments were performed to ascertain the acid producing potential (APP) of the mine wastes and their potential influence on metal leaching into the surface and groundwater of the area. The APP of the wastes from Codli area was estimated to be of the order of 0.005 mole of H+/g. In addition, the metal leachability associated with these metal bearing wastes under the influence of acidic rainwater was examined through the synthetic precipitation leaching procedure tests and the results are discussed in detail. Thus, in general, it was found that ground and surface water in the mining area is highly vulnerable to heavy metal contamination.