Enrichment Condition and Security Risk Assessment of Heavy Metals in Soil-Crops System around the Gangue Dumps

Abstract

This paper aims to make a study of the distribution patterns, the enrichment characteristics and the corresponding contamination conditions caused by the heavy metal contents in the soil-crops (soybean, corn and rice) around the coal gangue dump. Samples of soils and food crops were collected around Xinji coal gangue dump by the intercept method. The concentrations of Zn, Cu, Pb, Cd, and Cr in the soils and food crops were analyzed by inductively coupled plasma optical emission spectrometer (ICP-OES). With a contrastive analysis done with the enrichment features of the root and the transfer ability of the seeds among the different food crops. In order to evaluate the pollution condition of the three corps, the single factor pollution index and the Nemerow comprehensive index. The results showed that the soil is alkaline, and the max concentrations of Zn, Cu, Pb, Cd, Cr in the soils at the depth of 20∼60 cm, which are below the background values of Huainan soil. In the top soil (0∼20 cm), Zn, Cu, Pb, Cd, Cr each their peak values at a distance away from the coal gangue dump, and then, with increasing distance from the coal gangue dump gradually decreased; the remnant concentrations of Zn, Cu, Pb, Cd and Cr in the different plant organs are also in the degrading order of root > stem > seed, but that of Pb in the leaves turns to be significantly higher; The absorptive ability of the corn roots for the heavy metals proves to be higher than soybean and rice whereas the seed transferring ability turns to be reversed, for such differences account for the different root features and the stem transferring ability of the three food crops. The Nemerow comprehensive index of the three food crops has been found and illustrated also in the degrading order of corn > rice > soybean, with corn being affected by the light pollution, rice and soybean affected at the warning level.