Environmental Risk Assessment Of Heavy Metals And Soil Microbial Characteristics In A Tailings Reservoir In Inner Mongolia

This article taken a non-ferrous metal tailings pond in Baotou city,Inner Mongolia as the research object,to analyze the content characteristics and sources of heavy metals in the soil of the study area,and the cumulative index method,Nemerow pollution index method and potential ecological hazard index method were used to evaluate the heavy metal pollution in the soil.In addition,health assessment of soil heavy metal content in the study area was conducted based on the Guidelines for Risk Assessment of Contaminated Sites and the USEPA Health Risk Assessment.Meanwhile,according to the actual situation of the study area,the influence of heavy metals on the microbial community under different land use types was also been explored.The main conclusions are as follows:（1）The heavy metal content of Cr and Cu in the soil of the study area did not exceed the screening value of agricultural land pollution risk,while the content of Pb（11.36%）,Zn（4.55%）and Cd（13.64%）samples exceeded the screening value of risk.The high value regions of Pb,Zn and Cd were mainly concentrated in the areas that near the tailing slag.（2）Mn,Pb,Zn and Cd were the main pollutants in the soil in the study area,and the source analysis results indicated that the source was the tailings pond.The content of Cu and Cr in the soil of the study area was lower than the screening value of agricultural land pollution risk.It was judged that the content of them was mainly affected by the soil parent material,followed by the traffic.（3）There was a significant accumulation trend of heavy metals in the soil of the study area,with six heavy metals exceeding the background value and the accumulation rate above 50%.The result of Nemero comprehensive pollution index shown that the clean area accounts for 81.82%.The potential ecological damage index of soil heavy metals indicated that 81.82%of the sampling points in the study area were in the level of slight damage.（4）Based on the Guidelines for The Risk Assessment of Contaminated Sites and the USEPA Health Risk Assessment model,the results of carcinogenic risk assessment of heavy metal Cr⁶⁺and Cd by the two evaluation methods were consistent,and neither of them would cause carcinogenic risk to residents in the research area.While there were differences in the non-carcinogenic risk assessment.The assessment result of guideline indicated that only Mn shown a non-carcinogenic risk under three exposure pathways,while the assessment result of USEPA shown that all heavy metals were no carcinogenic risk.（5）There were differences in basic physical-chemical properties,microbial community composition,and microbial community function of soil under different land use types.In addition,Proteobacteria,Actinobacteria,and Acidobacteria were resistant to heavy metal pollution.The annotated Nitrate reduction,Aerobic chemoheterotrophy,Nitrification,and Aerobic ammonia oxidation have relatively high abundance of ecological functional groups,but the functional proportion of each region was different.