| Heavy metal pollution destroys the soil environment quality, directly or indirectly influences the human health. Daqing is an important oil exploitation region in China. In recent years, due to the oil exploration and the development of chemical industry,falling oil produced, leakage of oil wells and gathering pipeline leading to oil leakage,resulting in increased pollution of heavy metal in farmland soil around. In order to better understand the heavy metal pollution and whether the soil could bring harm to human health, this study selected 70 samples in our villages in Datong for sampling and testing analysis, the contents of Cu, Pb, Hg, Zn, Cr, As, Ni, Cd were determined by experiments, described the characteristics of heavy metal content. In order to understand the pollution situation of study area, this paper evaluated soil pollution by using single factor pollution index method, Nemerow integrated pollution index method,geo-accumulation index method and potential ecological risk assessment method.Health risk assessment by using "four steps" metal evaluated soil carcinogenic factor risk and non-carcinogenic factor risk, for understanding the harm of pollution soil brought to human health, and put forward corresponding suggestions. It could provide theoretical basis for protecting the Datong area soil environment and human health, at the same time to promote the sustainable development of green agriculture. The results were as follows:(1) The content of eight kinds of heavy metal was difference, and all the samples were more than two kinds of heavy metals, which were combined pollution. Cu, Cd, Ni are not exceeded, Pb, Hg had been a large area of accumulation, which were heavy pollution. Analysis of variation coefficient showed that: Cu was weak variation; Cr, As and Cd were strong variation.(2) From single factor pollution index, Cu, Cd and Ni were not contaminated, Cr,As and Zn were slight pollution, Pb, Hg were heavy pollution and its wide range.The pollution contribution rate of Hg was 55.66%, and according to the contribution rate of pollution in descending order of: Hg > Pb > Cu > Ni > Zn > Cr > Cd > As.(3) Nemerow pollution index showed that, all samples were contaminated, which84.29% belonged to the heavy pollution. According to the overall pollution situation analysis of the four villages, the pollution levels of four villages were reached fifth level,the pollution was very serious. Its pollution index: Laoshantou village > Bajingzi village > Taiyangsheng village > Shuangyushu village.(4) From geo-accumulation index, Cu, Cd, Cr, As, Zn, Ni were not contaminated,the majority of samples produced Pb pollution. And all samples produced Hg pollution,which 32.85% was at the moderate to heavy level of pollution. The geo-accumulation index of the four villages was only different from the pollution of Pb. Pb in Laoshantou village was no pollution, in the other three villages were in no pollution to medium pollution.(5) From single-element potential ecological risk index, Cu, Pb, Cd, Cr, As, Zn, Ni were low potential ecological risk. The potential ecological risk of Hg was relative high,which 77.14% were the weight of potential ecological risk. From the comprehensive potential hazard, 70% samples were in medium ecological harm, 22.86% samples were in strong ecological harm, which Hg pollution contribution rate was the highest its reached 90.67%. The potential ecological risk level of four villages was in the medium ecological risk.(6) From human health risk assessment, the risk of intake through the mouth was the major route of exposure; it was greater than the risk of intake through the skin.Non-carcinogenic risk was ranked for four villages: Taiyangsheng village > Laoshantou village > Shuangyushu village > Bajingzi village. Carcinogenic risk was ranked for four villages: Laoshantou village > Bajingzi village > Shuangyushu village > Taiyangsheng village. Carcinogenic risk of Laoshantou village reached 9.90E-07, it had been close to the risk limits. It was close to the risk limits, need to be paid attention. |
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