Characteristics and Ecological Risk Assessment of Heavy Metal Pollution of Triassic osmotic Paddy Soil in the Southwest of Guizhou Province

To investigate the pollution status and spatial distribution of heavy metals in paddy soil of the southwest Guizhou Province, the arable layer of paddy soil samples were collected and the concentrations of Cd, Hg, As, Pb, Cr and soil pH were measured and analyzed by multivariate statistical techniques. The variety of spatial distribution for 5 heavy metals were studied using geographic information system (GIS). Single factor pollution index, Nemero comprehensive pollution index and potential ecological risk index were applied to evaluate the heavy metal contamination degree. The results show that the mean concentrations of heavy metals in the surface of paddy soil were in the order of w(Cr)(201.68 mg·kg^-1) > w(Pb)(38.25 mg·kg^-1) > w(As)(30.70 mg·kg^-1) > w(Cd)(0.68 mg·kg^-1) > w(Hg)(0.22 mg ·kg^-1). The contents of Cd and As in some soil samples were higher than risk screening values for soil contamination of agricultural land in the Soil Environmental Quality Standard (GB 15618-2018), whereas the Hg, Pb and Cr contents were lower than the screening values. Anthropogenic influence caused an enrichment of Cd and As in paddy soils. The accumulation of Cd, Hg, As and Cr in soil was mostly affected by gold smelting, coal combustion and agricultural strategies, and the main sources of Pb were exhaust emission. Current study confirm that heavy metal pollution and industrial activities in smelters posed a serious threat to environmental quality. According to the single-factor pollution index, the pollution degree was in the order of Cd > As > Cr > Hg > Pb, and the Nmeiro comprehensive pollution index showed 39.64% points in the study area exceed 1. As for the ecological risk assessment, the risk index (RI) value of the 5 kinds of heavy metals was 63.78, which was lower than the lowest value of RI (150), and indicated the degree of ecological risk belonged to slight scale.