| Southern Jiangxi is rich in tungsten resources and has a long history of mining,which is known as "the tungsten capital of the world".Long-term exploitation of tungsten mines has led to serious heavy metal pollution,posing potential risks to local ecological environment and residents’ health.In this paper,188 soil samples and 20 rice samples were collected from a tungsten mine area in Dayu-Chongyi area,Ganzhou,Jiangxi Province.The contents of 7 kinds of heavy metals(Cd,Hg,Pb,As,Cr,Cu and Zn)in the soil and rice seeds were measured,the pollution characteristics of heavy metals in the study area were analyzed and the possible pollution risks and health risks caused by heavy metals were evaluated.The results are as follows:Soil samples in the study area showed an obvious acidification trend,with an average soil p H of 5.22.The average contents of heavy metal elements Cd,Hg,Pb,As,Cr,Cu and Zn in soil were 0.86,0.16,79.95,35.29,71.53,39.84 and 118.12mg/kg,respectively,which showed the result that the pollution of soil Cd and As was serious.Geostatistical analysis toolbox of Arc GIS was used to analyze spatial distribution of heavy metals.CA and PCA by SPSS showed that soil pollution may mainly come from industrial and mining activities,agriculture and atmospheric deposition,among which industrial and mining activities may be the main source of Cd,Pb and Zn,agricultural production activities may be the main source of As and Cu,and Hg pollution mainly comes from atmospheric deposition.The single-factor soil pollution index and the geo-accumulation index were used to evaluate the risk of heavy metal pollution in soil.The results showed that the Cd and As pollution in the study area was the most widely distributed and the pollution degree was the most serious.The results of Nemerow comprehensive pollution index showed that the average PI of soil heavy metal was 1.94,and the comprehensive pollution rate was 71.28%,showing a moderate pollution degree overall.The analysis results of soil potential ecological risk index showed that the average values of potential ecological risk indexes of Cd,Hg,Pb,As,Cr,Cu and Zn were 70.19,13.02,4.34,11.84,0.57,3.92 and 0.58,respectively,and the average values of potential ecological risk indexe of Cd was far higher than those of other heavy metals.The average value of comprehensive ecological risk index of soil was104.46,which mainly had a low ecological risk.The contribution rate of Cd to comprehensive potential ecological risk of soil was 67.19%,followed by Hg and As,with 12.46% and 11.33% respectively.In the soil-rice system,the comprehensive pollution rate of root soil was 50%,which was mainly in moderate degree of pollution,and the main pollution was contributed by Cd and As.The comprehensive pollution rate of rice seeds reached75%,among which Cd pollution was serious,with 65% samples exceeding the standard,and 15% samples were slightly polluted by Hg,meanwhile,the contents of other heavy metals reached the food safety standards.The average BCF of rice were1.144,0.152,0.001,0.006,0.001,0.137 and 0.222,respectively,in which the BCF of Cd is much higher than that of other heavy metals,indicating that rice had a strong bioconcentration ability for Cd,which might be related to the migration and transformation mechanism of Cd in the soil-rice system and the soil p H.The results of health risk assessment show that the comprehensive non-carcinogenic risk in the study area is much greater than 1,and there is a significant non-carcinogenic risk.The main risk factors are Cd and As,with contribution rates of 49.15% and 29.32%,respectively;the comprehensive carcinogenic risk is much greater than 1×10-4.There is a significant risk of cancer,and the main risk factor is Cd,with a contribution rate of 94.6%.To sum up,heavy metals Cd and As in the study area were seriously polluted the soil and the rice,which had potential threats to local soil environment and human health,and deserved to be paid attention to. |
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