| Agricultural soil is the most important and basic production data of agricultural production,and it is an important natural resource for human survival.However,in recent years,with the rapid development of urbanization,industrialization and agricultural intensification,more and more pollutants containing heavy metals have been spread to the soil of agricultural land by various ways.This paper takes Qingyang County in the south of Anhui Province as the research area,through the analysis of the survey results of heavy metal pollution in the soil of agricultural production areas in Anhui Province,using descriptive statistical analysis,single factor pollution index method,Nemero comprehensive pollution index method and ground accumulation index evaluation method to analyze and evaluate the degree of heavy metal pollution in the soil of the study area,and through correlation analysis,principal component analysis and cluster analysis,combined with PMF model,the sources of heavy metals in the soil of the study area were analyzed,and the spatial characteristics of heavy metals were determined by geostatistical knowledge.The purpose of this paper is to reveal the present situation of heavy metal pollution in agricultural soil in the study area,and to provide theoretical basis for the investigation,treatment and remediation of heavy metal pollution in agricultural land.The results show that:1.The average value of Cd,Hg,As,Pb,Cr content in agricultural soil of the study area is0.32,0.1,14.38,49.44,87.42 mg·kg-1,respectively;The p H range is between 4.6 and 8.7,with an average of 5.88;The average Cd content in the study area is higher than soil environmental quality secondary standard,and the accumulation degree is relatively high;The contents of five heavy metals in most sites exceed the chemical background values of soil elements in Anhui Province;The variation degree of the five heavy metals was above the medium level,and the heavy metal content was affected by human factors;Except for Cr,the total distance of Cd,Hg,As,Pb is more than three times of soil environmental quality standard,and the dispersion of Cd,Hg,As,Pb content in the study area is relatively high,so human factors are more likely to influence them.2.The results of single factor pollution index show that,the pollution rates of Cd,Hg,As,Pb and Cr in the soil of agricultural land were 26.93%,3.81%,23.47%,3.35%and 2.23%respectively,and Cd and As pollution are serious,indicating that they have been seriously affected by human factors,and need to take timely measures to repair;There is also a small amount of pollution in Hg,Pb and Cr.3.The results of the internal Nemero composite pollution index show that,in the study area,the proportion of point of clean,alert,mildly polluted,moderately polluted,and severely polluted was 50.64%,24.52%,19.74%,2.87%and 2.23%,respectively.Research areas have pollution level of 24.84%,mainly light pollution,a higher percentage of pollution,human activities have obvious influence to the research of farmland soil in the area of ecological environment,but it is still manageable,there are a lot of points close to the line,the risk of a breakthrough at any time,and local governments need to be taken seriously.4.The accumulation and pollution of soil heavy metals in agricultural land were analyzed by accumulation index method.Pollution point ratio of Cd,Hg,As,Pb and Cr were 85.35%,66.24%,36.62%,33.12%and 28.34%respectively;The mean values of all the five heavy metals accumulation indexes were 0.84,0.531,-0.336,-0.041 and-0.308 respectively,and the accumulation index of Cd and Hg is higher on average.As,Pb and Cr accumulation index is low on average,but there is a danger of pollution,and measures should be taken in time to deal with it,and soil pollution repair and other management work should be carried out in low pollution level.5.The soil heavy metal content of soil in the study area was characterized as,Cr and Hg in diluvium soil parent material of the upper quartile,mean,median and lower quartile different from those of the other three,showed a higher level,and the Cd,As and Pb in four kinds of soil parent material of the upper quartile,mean,median and lower quartile has no obvious difference,therefore,it is speculated that Hg and Cr are affected by natural factors,and the content of Cd,As and Pb mainly comes from human factors.The soil heavy metal content of different altitudes in the study area was characterized by,in the range of 6～90 m above sea level,the content of 5 heavy metals increased with altitude,and when the altitude was greater than 90 m,the content of 5 heavy metals did not decrease,so presumably at 6～90maltitude,the main source of heavy metal pollution are atmospheric precipitation,and when altitude above 90 m,the main source are densely populated areas of the solid waste garbage and human activities such as automobile exhaust.6.The results of multivariate statistical analysis show that,in correlation analysis,Cd,As,Pb was significantly positive correlation between each other（P≤0.01）or less,the source of three kinds of elements are likely same,content of spatial distribution of possible space consistency,Hg and Cr were significantly positive correlation（P≤0.01）or less,two elements source could be the same,content of spatial distribution of possible space consistency.In principal component analysis,Cd,As and Pb content have high loading in PC1,which is the first principal component;Hg and Cr content have high loading in PC2,which is the second principal component.In cluster analysis,icicles are consistent with the results of tree graphs.When the clustering number is small and the clustering distance is far away,Cd,As and Pb are grouped together,and Hg and Cr are grouped together.7.The analysis results of PMF receptor model show that,Cd has a high concentration in factor 1,and the contribution rate is 39.6%,which is explained as the source of industrial and mineral pollution;As and Pb have a high concentration in factor 2,and the contribution rate is 42.3%,which is explained As the comprehensive pollution source of traffic pollution sources and atmospheric deposition;Hg and Cr have a high concentration in factor 3,and the contribution rate is 18.1%,which is explained soil parent material.Based on the quantitative analysis,the accumulation of heavy metals in agricultural land in the research area is mainly affected by the pollution sources of industrial and mining sources,the pollution sources of traffic sources and the comprehensive pollution sources of atmospheric sedimentation and the source of the soil.8.The spatial structure and spatial distribution results show that,the content of Cd in the northern part of the study area is generally high,among which,there are obviously high value areas in the local areas of Dingqiao town,Muzhen town,Xinhe town,Rongcheng town,and temple area;In addition to the high value area of Hg in Xinhe town,the Hg content in the study area is generally low;In the northern part of the research area,As content is generally high,there are high value areas in Xinhe town,Muzhen town,and Qiaomu town;In the northern part of the research area,there are five local regions with high Pb content,among them,Xinhe town,Muzhen town and Yangtian town have a small scope,and there is a large area of Pb content in Rongcheng town in Qingyang county;The overall Cr content of the study area was basically below 250 mg·kg-1 standard,and only slightly higher in the local area of Zhubei town and Miaoqian town.As a whole,the spatial distribution of the content of Cd,Hg,As,Pb,Cr in the study area has no obvious trend of increasing and decreasing,and there are obvious high value areas.According to the distribution of land use status such as mining area and heavy industry,the content of Cd,As,and Pb is mainly determined by industrial and mining activities,atmospheric pollution,sewage irrigation,traffic pollution and other human factors,and Hg and Cr mainly come from natural factors such as soil parent material. |
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