Analysis on the Distribution Characteristics and Influence Mechanism of Migration and Transformation of Heavy Metals in Mining Wasteland

Abstract

In order to explore the distribution characteristics and the influence mechanism of migration and transformation of heavy metals in mining wasteland, soil and tailings samples were collected from the mining wasteland in the Dabaoshan Mining area, Guangdong Province, and the morphological characteristics of heavy metals were analyzed. At the same time, the pollution sources of the mining area were analyzed using Pb stable isotope analysis, and the characteristics and influencing factors of heavy metal migration and transformation in the mining area were expounded by combining X-ray diffraction analysis, transmission electron microscope-energy spectrum analysis (TEM-EDS), and Raman analysis of typical minerals in the mining area, as well as laboratory-simulated leaching experiments. Morphological analysis showed that the forms of Cd, Pb, and As in the soil and tailings samples in the mining area were mainly the residual phase, accounting for 85%-95% of the total, followed by the iron and manganese oxide-bound form (1%-15%). The main mineral types in the soil and tailings in the Dabaoshan Mining area were pyrite (FeS2), chalcopyrite (CuFeS2), and metal oxides, as well as a small amount of sphalerite (ZnS) and galena (PbS). Acidic conditions (pH=3.0) were beneficial to the release and migration of Cd and Pb from soil, tailings, and minerals (pyrite, chalcopyrite) and from the residual phase to the non-residual phase. Lead isotope analysis showed that the lead in the soil and tailings mainly came from the release of metal minerals in the mining area, and the contribution of diesel in the mining area was less than 30%. Multivariate statistical analysis showed that Pyrite, Chalcopyrite, Sphalerite, and Metal oxide were the main sources of heavy metals in the soil and tailings in the mining area, in which Cd, As, and Pb were mainly contributed by sphalerite and metal oxide. The form change in heavy metals in the mining wasteland was easily affected by environmental factors. The form characteristics and migration and transformation factors of heavy metals should be considered in the source control of heavy metal pollution in mining wasteland.