| Yunnan Province is located in the Yunnan-Guizhou Plateau,and its topography is complex and diverse so that forming multi-type soils and land uses,and diversified mineral resources.However,with the development of social production and economy,the problems in the existing mining development model and a large number of agricultural production activities would aggravate the pollution of soil heavy metals in Yunnan Province.Previous studies mostly interpolated regional soil heavy metals content by geostatistical methods but ignored the difference of heavy metal content caused by the soil properties.In this study,Yunnan Province was taken as the research area.Soil samples from typical profiles in Yunnan Province were collected according to soil types and land use patterns based on the data of the second national soil survey,and the soil heavy metals database in Yunnan Province was constructed.The spatial distribution and sources of soil heavy metals in Yunnan Province was analyzed by statistical method,and the pollution and risk of soil heavy metals were assessed.The main results were as follows:1.There are great differences in heavy metal content between sampling points.The contents of Cr in soil of Yunnan Province ranged from 8.72 to 1564.35 mg/kg,Cu from 2.76 to 371.19 mg/kg,As from 0.81 to 117.26 mg/kg,Cd from 0.03 to 9.79 mg/kg,Hg from 0.003 to 5.94 mg/kg,and Pb from 4.30 to 318.38 mg/kg.Except for As,the contents of other soil heavy metals in Yunnan exceed the background values of heavy metals in Yunnan soil,but don’t exceed the risk screening or control values of heavy metals in agricultural soil of China.The data of soil heavy metal content in Yunnan Province obtained in this study are close to the relevant research data.The data of soil heavy metal content assigned by the new method based on soil type and land use pattern is reliable2.Through the spatial distribution map of soil heavy metals of Yunnan Province,it was found that the contents of Cr,As,Cd and Hg are high in northeastern Yunnan;the soil of southeastern Yunnan has high contents of As,Cd and Hg;the soil of western Yunnan has high contents of Cr,As and Cd;the soil of northwestern Yunnan has high contents of Cr,As and Hg;and the soil of southwestern Yunnan has high contents of As and Pb;the soil of central Yunnan has low contents of Cr,Cu,As.Cd,Hg and Pb.3.Among the soil types in Yunnan Province,the highest contents of four heavy metals,Cr,Cu.Cd and Pb,are found in swampy soil,yellow soil,red soil and volcanic ash soil respectively;the highest contents of Hg and As are found in lime soil;the content characteristics of six heavy metals are dififerent under three land use patterns,among which the highest contents of Cr.Cu and Cd are found in grassland.The highest contents of As and Pb appear in agricultural land,while the contents of Hg has slight difference under three land use patterns;the highest content of Cr and Cu appear in northwestern Yunnan and western Yunnan respectively;the highest content of As,Cd,Hg and Pb appear in southeastern Yunnan;the lowest content of Cr,Hg and Pb appear in the southeast.central and northwest of Yunnan,respectively.The lowest contents of Cu,As and Cd are found in the southwestern Yunnan;the variation of heavy metal contents with altitude and slope is inconsistent in the six geographical regions of Yunnan Province;among the boroughs of Yunnan Province,there are high contents of heavy metals in Nujiang,Diqing,Qujing,Lijiang,Xishuangbanna,Baoshan,Kunming,Wenshan and Honghe.4.There is a weak-low-medium correlation among the soil heavy metals in Yunnan Province.There are very significant correlations among Pb-As,Cd-Cu-Cr and Pb-Cd-Hg heavy metals in six geographic regions.These heavy metals may have the same source.The contents of soil heavy metals of six geographical regions in Yunnan Province are mainly affected by parent materials,industrial and mineral activities and agricultural activities.5.On the whole,there is slight pollution of Hg in the soil of Yunnan Province,while the pollution of other heavy metals such as Cr,Cu,As,Cd and Pb can be neglected.Several elements show low potential ecological risk,Cr,Cu.As and Pb,for instance;Cd shows medium potential ecological risk,Hg shows medium and high potential ecological risk,and the compound ecological risk of several heavy metals is medium.There is no non-carcinogenic health risk but carcinogenic risk of soil heavy metals in Yunnan Province.The theoretical carcinogenic rate caused by soil heavy metals in six geographical regions is 15-33 per million people,and As contributes the most to the non-carcinogenic risk and carcinogenic risk in Yunnan Province.The comprehensive ecological risk of soil heavy metals deserves our attention.The relevant departments should strengthen the prevention and control of soil heavy metals which have prominent impact on the regional ecological environment.Based on the classification of soil types and land use patterns,a database of soil heavy metals in Yunnan Province was established.The spatial distribution and sources of Cr,Cu,As,Cd,Hg and Pb in surface soil of Yunnan Province were analyzed,and the pollution and influence degree of soil heavy metals of Yunnan Province were evaluated.The method provides a new basis of the spatial assignment of soil heavy metals and the data supports for soil heavy metals management in Yunnan Province.It is of great significance to update and share information of soil heavy metals resources in China. |
