Tracing analysis of heavy metals in farmland soils of Yu County, Yangquan

Soil heavy metal in coal mine area and its surrounding farmland exceeding the standard has attracted the attention of all circles of society.There are two different views on the reasons for this.Tracing the source of heavy metals in mining area and its surrounding farmland is not only important to farmland ecology and environmental protection, but also has great value to ensure the development and utilization of mineral, mining enterprises development and green mine construction.Therefore, for two different views, this research selected the farmland soil with coal mine area and its surrounding in Yu County as object.The research methods include mass's test, classical statistics and statistical methods.Through the comparison of heavy metal content and spatial variation characteristics between farmland soil and coal, gangue and mining waste water, the soil heavy metal in the study area was traceability analyzed.The results of heavy metal content in different samples showed that except Hg, pulverized coal is 1.05-1.99 times larger than lump coal.The fully weathered gangue is 1.16-6.57 times of fresh gangue.The spontaneous combustion gangue is 1.19-9.20 times of the non-spontaneous combustion gangue.In addition to Cd and Pb, the mud gangue is 1.34-4.78 times higher than the sandy gangue.The heavy metals in mining wastewater, except Pb, were not detected.The heavy metal content of soil is lower than that of pulverized coal, fully weathered gangue and self-burning coal, but higher than that of lump coal and fresh gangue, and much higher than that of mining waste water.The results of spatial distribution of heavy metal content in farmland soil showed that the variation law of heavy metal content in soil with different distance was basically the same.The heavy metal content value of farmland soil at different distances around coal heap (well) and coal gangue mountain (heap) mainly conforms to the index model.The Nugget C₀ of eight kinds of soil heavy metal content are all positive, but it varied greatly under the influence of positive basement effect.Farther away, the smaller the sill C₀+C is, and Zn>Pb>Cu>Cr>Ni>As>Cd>Hg, the spatial variability is weakening.The structural factors of heavy metal content decreased with the increase of distance, and the random data was strongly spatial autocor-relation when the distance was more than 50 m, that is, the content of heavy metals in soil was greatly influenced by natural factors.When the distance is less than 50 m, the stochastic data has medium spatial correlation, that is, the content of heavy metals in soil is affected by natural factors and is also affected by human activities.The decision coefficient R² of heavy metal content in farmland soil at different distances in 0.50-1.00,|ME|and|MSE|are close to 0,|ASE|is close to|RMSE|, the|RMSSE|is close to 1, which shows that the semi-variation function theory model has good fitting effect to the test data, the accuracy is high and the predicted value is close to the measured value, which accurately reflects the spatial distribution characteristics of heavy metal in soil under each case, thus ensures the spatial interpolation accuracy of heavy metal content in farmland soil at different distances.The results show that the heavy metals in the soil of the coal mine area and its surrounding farmland are mainly derived from the parent rock weathering, and coal mining will not lead to the increase of heavy metal content in the large areas of farmland and exceed the standard.At the same time, the conclusions obtained are scientifically demonstrated by using the principles of mineralogy and crystallization.