The spatial distribution and accumulation characteristics of heavy metals in steppe soils around three mining areas in Xilinhot in Inner Mongolia, China

Abstract

Metal deposition has become a major environmental problem in China due to its adverse effects on human and ecosystem health, particularly in Inner Mongolia, where frequent dust storms (due to steppe degradation and desertification) and soil pollution (associated with the increasing mining activities) have occurred in recent decades. To assess spatial distribution of heavy metals and the influences of mining activities on geochemical behavior of heavy metals in soils, soil samples with depth of 0-10, 10-20, and 20-30cm at each site were collected from different directions in the vicinity of three mines (coal mine, gold mine, and fluorite mine) in a typical steppe zone of Inner Mongolia, China. Six elements (Cd, Pb, Zn, Cr, Cu, and Ni) in the soils were analyzed using inductively coupled plasma emission spectrometer (ICP-OES). The results indicated that the average concentrations of Cd, Pb, Zn, Cr, Cu, and Ni in the soil of the study area around three mines were lower than the second class level of the National Soil Environment Safety Standard, but mostly were higher than the background value of soil in the Inner Mongolia. Northwest, southwest, and northeast wind directions have a great influence on the distribution of metals in coal, gold, and fluorite mine area, respectively. The concentration of heavy metals in coal, gold, and fluorite increased with the distance from the center of the mine, then reached a peak, then decreased gradually. The vertical mobility of metals in soil profiles was slightly significant for Cd>Cr>Zn>Ni in coal mine area and was not significant in gold and fluorite mines. Multivariate statistical methods such as principal component analysis and cluster analysis, coupled with correlation coefficient analysis, showed that Cd, Cu, Cr, and Ni in the mining area came from the same source, while Zn and Pb came from the other source. That the sources of heavy metals in the mining area were discussed would not only enhance our knowledge regarding the soil pollution status in the study area but would also provide us information to manage the sources of these elements in the study area.