| Soil is an important natural resource for human survival,which provides basic environmental conditions for human production and life.At the same time,many pollutants will be transported and accumulated through the soil.Among them,the harm of heavy metals is particularly prominent,which will seriously damage the health of human nerves and pHysical functions.In recent years,the problem of soil heavy metal pollution in China has become more and more prominent,constantly threatening human health and the safety of agricultural products,which has caused the whole society to pay more and more attention to the problem of soil heavy metal pollution.The research contents of soil heavy metals mainly include spatial modeling and prediction,pollution assessment and source analysis.At present,most of the soil source analysis is in the qualitative stage,so it is difficult to accurately evaluate the contribution of each pollution source to pollution,which brings some difficulties to the prevention and control of pollution.In addition,the current research is lack of research on the mechanism of the source distribution of heavy metals in soil,especially the differentiation of landscape.Therefore,a typical mining and smelting city was selected as the study area,the contents of Cd,Co,Cr,Cu,Mn,Ni,Pb and Zn in surface soil were investigated,and the spatial distribution characteristics of heavy metals in soil were analyzed by geostatistics.The single factor pollution evaluation method was used to evaluate the local heavy metal pollution,and the principal component-multiple linear regression method was selected to identify the types of pollution sources and quantitatively analyze the pollution contribution rate of each pollution source.Finally,the geograpHical detector is used to find out the landscape factors which have influence on the distribution of heavy metals in soil and the influence range or type of main landscape factors,so as to provide scientific basis for the protection and treatment of heavy metals in soil.To achieve sustainable ecological development.The main conclusions of this study are as follows:1.The results of basic statistical analysis of heavy metal content showed that the average values of Cd,Cu,Pb and Zn were 1.14 mg / kg,175.45 mg / kg,102.77 mg / kg and 256.73 mg / kg,respectively,which were 6.71,5.71,3.85,3.07 times of the background value,respectively.The results showed that these four elements were obviously enriched in soil.Among them,Cd,Cu and Pb reached the degree of serious pollution.The average values of Co,Cr,Mn and Ni were 14.65,34.93,672.265 and 28.14 mg/kg,respectively.The maximum values of the samples exceeded the background values,indicating that the four elements were enriched in some areas.From the point of view of the coefficient of variation,Cd,Cu and Pb belong to high variation,and the regional variation is obvious;the coefficient of variation of Zn and Mn is 0.91 and 0.53 respectively,which belongs to medium variation,while Cr,Co and Ni belong to weak variation,and the regional difference is relatively small.In addition,there was a significant correlation between Cd,Mn,Pb and Zn,and the correlation coefficient was between 0.424 and 0.901.The correlation coefficient between Co and Cu reached 0.631 / Cr and Ni,which may be affected by the same pollution source.2.The spatial distribution of heavy metal content was predicted by geostatistics method.The results showed that Cd,Cu and Zn were seriously polluted in the study area,Cr and Ni were relatively clean in the study area,and only a small number of areas were polluted.In particular,the enrichment areas of Cd,Mn,Pb and Zn in the southeast are near mining and smelting areas,so it is inferred that the pollution of these elements comes from mining and smelting activities,and the contents of Co and Cu are relatively high near the site of Tonglushan ancient copper deposit.It shows that Co and Cu are more likely to be affected by copper mining pollution,and the relatively high value area of Cr also appears near industrial land,and its content distribution may be affected by human activities.The evaluation results of interpolation accuracy show that the interpolation results meet the accuracy requirements.3.The results of single factor pollution assessment showed that Ni was in a clean state in the study area,and pollution occurred in a small part of Pb,while the overall pollution degree of Co,Mn and Zn was relatively light,but most of the areas were in a critical state of cleanliness.The risk of pollution is high.The pollution degree of Cd,Cr and Cu is high,and there are highly polluted areas,which have a great risk to the soil ecological environment.It is worth noting that the evaluation results of some elements are highly similar to those of industrial activities,indicating that long-term industrial activities have resulted in a significant accumulation of heavy metals.Therefore,the relevant departments need to carry out long-term soil ecological risk supervision of industrial land and nearby areas to ensure the basic environment for human survival.4.Three main pollution sources in the study area were analyzed by PCA-MLR source analysis method,and 80.51% of the total variance was explained.Factor 1,Cd,Mn,Pb and Zn are high load factors,which represent the comprehensive mining source.The heavy metal elements with high load of factor 2 are Co and Cu,which represent the source of copper mining and smelting.Factor 3 is a natural source,and Cr and Ni are the recognition elements of this component.Comprehensive mineral mining and smelting contribute 45% of the total pollution,copper mining and smelting contribute 28.3% of the total pollution,and the contribution rate of natural factors is 26.7%.Therefore,73.3% of the pollution in the study area is man-made,and all of them are related to mining activities,indicating that long-term mineral mining and smelting have caused great pollution to the regional soil.5.The distance from the road,the distance and elevation from the industrial and mining land are the main landscape impact factors of comprehensive mining pollution sources,copper mining-smelting pollution sources and natural sources,respectively,with Q values of 0.208,0.126 and 0.129,respectively.The results of interaction detector show that the pairwise combination of landscape factors selected in this study will produce nonlinear enhanced interaction,and the explanatory power to the contribution rate of pollution sources is greater than that of single environmental factor.The results of ecological detector show that there are significant differences in the influence of the distance from the road,the distance from the industrial and mining land and the land use type factors on the comprehensive mining pollution sources. |
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