[Health Risk Assessment of Heavy Metals in Agricultural Soils Around the Gangue Heap of Coal Mine Based on Monte Carlo Simulation].

To analyze the pollution characteristics of heavy metals in the soil of farmland surrounding the gangue heap of a coal mine in Chongqing, the Nemerow, Muller, and Hakanson indices were used. Meanwhile, to investigate the health risks of heavy metals in soil, a health risk assessment model was employed using Monte Carlo simulation. The results revealed that the average contents of Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn were higher than their soil background values, and the Muller index (Igeo) from high to low was as follows:Cd>Hg>Cu>As>Ni>Zn>Cr>Pb. The Nemerow index (PN) demonstrated that the results of the assessment indicated mainly light pollution (1Cu>Ni>Cr>Zn>As>Pb>Hg. The Hakanson index (RI) demonstrated that the results of the assessment indicated mainly moderate ecological risk (150 ≤ RI<300). The single ecological risk index (Eri) from high to low was as follows:Cd>Hg>As>Cu>Ni>Pb>Cr>Zn. The health risk assessment of heavy metals revealed that the non-carcinogenic health risks of children and adults could be ignored, but carcinogenic health risks existed, with an average total carcinogenic risk index (TCR) of 1.04E-5 and 3.94E-6, respectively. The major carcinogenic factors were As and Cd. Sensitivity analysis of non-carcinogenic health risks revealed that the ingestion rate of soil (Ringest) was the most sensitive, followed by the contents of As. Meanwhile, sensitivity analysis of carcinogenic health risks indicated that the content of As was the most sensitive, followed by the ingestion rate of soil (Ringest). In general, the health risks of children, including non-carcinogenic and carcinogenic risks, were higher than those of adults.

[Health Risk Assessment and Environmental Benchmark of Cadmium in Farmland Soils around the Gangue Heap of Coal Mine, Chongqing].

To analyze the health risk assessment and environmental benchmark of cadmium in farmland soils surrounding the gangue heap of a coal mine in Chongqing, Hakanson, the ecological risk index and health risk assessment were used. Meanwhile, the soil environmental reference value of the regional cultivated land was inverted based on the species sensitive distribution model (SSD). The results showed that the dryland soil was polluted by Cd, with an over-standard rate of 55.8%, and the paddy field soil was polluted by Cd, with an over-standard rate of 31.6%. The corn was polluted by Cd, with an over-standard rate of 4.4%, and the rice was not polluted by Cd. The Hakanson ecological risk index showed that Cd was mainly characterized in soils by high ecological risk and considerable ecological risk. The health risk assessment indicated that Cd presented low non-carcinogenic risk by corn and rice; however, it showed acceptable carcinogenic risk by corn and unacceptable carcinogenic risk by rice in this study. The sensitivity analysis of health risks showed that the content of Cd was the most sensitive. The SSD inversion showed that the reference values for Cd in dryland soil of pH ≤ 5.5, 5.57.5 had HC5 values of 0.491, 0.382, 0.376, and 0.588 mg·kg-1, respectively, and that for Cd in paddy soil had an HC5 value of 0.807 mg·kg-1. The reverse analysis showed that the HC5 of Cd in dryland soil (pH ≤ 7.5) and paddy soil was relatively relaxed and was higher than the soil risk screening values, which showed that the current standard was relatively loose. However, the HC5 of Cd in dryland soil (pH>7.5) was lower than the soil risk screening values, which showed that the current standard was relatively strict. It is suggested that the current soil standard could be adjusted in this area.