Heavy Metals Pollution Evaluation And Sources Analysis In The Surrounding Farmland Soil Of Guobei Coal Mine

Coal dust,gangue and wastewater from mining activities such as coal mining,washing and processing and transportation enter the surrounding environment,causing heavy metal pollution in the soil of agricultural land around coal mines,thus endangering agricultural ecosystems and human health.The Guobei coal mine is one of the larger well fields in the region,and its large-scale mining and coal washing and processing have a long life.The area around this coal mine mainly produces grain and cash crops such as cotton,fruits and herbs,so it is especially important to ensure good soil environmental quality.However,so far there is no systematic study on the assessment of the current situation of heavy metals pollution and source analysis of the surrounding farmland soil of Guobei coal mine in Bozhou City.Therefore,how to systematically and comprehensively assess the current situation of heavy metals contamination of farmland soils in the region and identify the possible sources of contamination is not only related to the protection,restoration and economic and social development of the local farmland soil environment,but also provides guidance for the evaluation and remediation of the pollution of farmland soil environment in similar areas.In this study,152 surface soil samples and 20 soil profile samples were collected from the surrounding farmland soil of Guobei coal mine in Bozhou City,and the contents of 7 heavy metals,Ni,As,Cr,Zn,Cu,Cd and Pb,were determined.Firstly,SPSS software was used to conduct basic statistical analysis on the level of 7 heavy metals in farmland soils and the characteristics of vertical distribution and leaching of heavy metals,and the interpolation function of Arc GIS was used to analyze the spatial distribution characteristics of heavy metals.then the pollution load index evaluation method,potential ecological risk assessment method and human health risk assessment method were used to comprehensively evaluate the heavy metal pollution of farmland soils,and the Monte Carlo method was used to simulate the potential ecological risk of heavy metals in farmland soils.Monte Carlo method was used to probabilistically simulate the potential ecological risk of heavy metals in farmland soils.finally,correlation analysis and PCA analysis were used to determine the sources of heavy metal pollution in farmland soils around the Guobei coal mine,and then APCS-MLR was used to quantitatively assign the pollution sources.The specific conclusions are as follows:(1)There is a trend of enrichment of heavy metals in the surrounding farmland soil of Guobei coal mine,which is influenced by human activities.As can be seen from the statistics of heavy metal content of farmland soils around the Guobei coal mine,the average values of heavy metals Ni,As,Cr,Zn,Cu,Cd and Pb content all exceed the background values of surface soil in Huaibei-Bozhou,but the average values are all lower than the screening values of soil heavy metals pollution risk.The coefficients of variation of heavy metals Zn and Cd were large,indicating that Zn and Cd in farmland soils in the study area were influenced by human activities.(2)The accumulation of heavy metals in the surrounding farmland soil of Guobei coal mine is related to the distance from the coal mine,and the spatial distribution of heavy metals is related to human activities such as coal mining.The seven heavy metals showed an overall decreasing trend with increasing distance from the coal mine in all three directions: east,west and north.The high values of Zn and Cd were mainly distributed in the farmland within 1 km from the Guobei coal mine.(3)The soil heavy metal content in the surrounding farmland soil of Guobei coal mine has a trend of decreasing from near surface to underground,and the enrichment of heavy metals in the near surface soil is influenced by human activities.The variation pattern of heavy metals in the two soil profiles showed a high degree of similarity,heavy metals content decreases vertically with increasing soil depth,it further indicates that the local soil environment is significantly influenced by anthropogenic activities.The sources of heavy metals in the two soil profiles were similar and most of them exceeded the background values,suggesting that some heavy metals generated by anthropogenic activities migrate to deeper layers of the soil by leaching.(4)The pollution level,ecological risk and human health risk of heavy metals in the surrounding farmland soil of Guobei coal mine are low.Heavy metal pollution evaluation and risk assessment shows that the overall level of soil heavy metals pollution in the surrounding farmland soil of Guobei coal mine is at a low level,Cd pollution is more serious,the subsequent need to strengthen the focus on Cd monitoring.The human health risk index shows that heavy metals are more likely to accumulate in children living in the study area and cause some noncarcinogenic health risks,and there is no risk of cancer in the study area for the time being.(5)The accumulation of heavy metals in the surrounding farmland soil of Guobei coal mine is influenced by multiple factors.From the APCS-MLR analysis,it can be concluded that heavy metals Ni,Cr,Cu and Pb were mainly influenced by natural factors with contributions of 67.68%,59.56%,85.16% and 100.00%,respectively.Heavy metals As and Zn are influenced by agricultural activities such as agricultural fertilization and mining activities such as coal mine wastewater discharge and coal gangue accumulation,with contribution rates of 84.30%and 79.77%,respectively.The contribution of heavy metal Cd by natural and anthropogenic factors was relatively similar.