Pollution Characteristics And Health Risk Assessment Of Soil Heavy Metals In East Junggar Region

With the rapid growth of socio-economic development and increasing needs of industrial manufacturing,the coal mine activities in Zhundong area has intensified gradually.At the same time,these mining activities brought negative effects to soil environment that deterioration of the soil.The accumulation of heavy metals in the soil by surface runoff and wind enter the food chain in a direct or indirect ways bring serious threat to human health and life safety.Therefore,this study takes Zhundong area as the research site,the content of heavy metals including Zn?Cu?Cr?Hg?As and Pb had measured on 168 sampling points.The cross validation selection used to select optimum method from four Interpolation methods including Ordinary Kriging?OK?,Inverse Distance Weighted?IDW?,Local Polynomial Interpolation?LPI?and Radial Basis Functions?RBF?and analyzed the characteristics of soil heavy metal enrichment,spatial variability and pollution distribution,the main pollution sources identified by different indexes as single factor pollution index?P_i?,Nemerow pollution index?P_N?,geo-accumulation index(I_geo),pollution load index?PLI?and potential ecological risk index?HRI?.Based on the health risk assessment model,we calculated the carcinogenic and non-carcinogenic risk index in three exposure ways,including direct intake,respiratory intake and skin contact,and further evaluated the risk level of heavy metals to human health.The main conclusions are as follows:?1?The average values of 6 elements in Zn,Cu,Cr,Hg,As and Pb were43.25⁴9.18,20.62²2.20,43.23⁸5.86,14.90³2.41,0.02⁰.06 and 23⁸5.86respectively.The amount ranking is Cr>Zn>As>Cu>Pb>Hg;The amounts of Pb?Hg and As are More than 1.5³ times the background value and showing that these three elements main pollution heavy metals;?2?The nugget value of elements are positive;the nugget coefficient of Cu?Cr?Pb and As are between 25.0%⁷4.1%,all belong to medium spatial correlation.It indicate that this is the effects both natural and human factors.Precision comparison of different interpolation methods shows that IDW and RBF are the most effective interpolation methods.On the whole,the MRE and RMSE of all elements are low,but the accuracy of AC is higher;?3?Comparing the distribution features of heavy metal pollution,in A region,pollution distribution of all elements except Hg are decreasing from the northwest to the southeast.High concentration of Pb and As be seen around the Wucaiwan coal mine area;the lowest value were the northern margin of the Desert Grassland Nature Reserve;there is no significant difference on distribution features of Zn?Cu and Cr in B and C region.But high values of As?Hg and Pb are presented in the area of frequent human activities.It is indicated that pollution is not only related to natural factors,but also closely related to the human activities;?4?Based on different pollution indexes,overall pollution degree are As>Hg>Pb>Cr>Cu>Zn;four elements?As?Hg?Cr and Pb?are basically in moderate or severe pollution levels in different pollution assessment and high contribution rate to pollution.The PLI value in three different parts are respectively 1.69?1.15 and 1.08and belong to moderate level pollution;HRI values are 166.16?83.80 and 91.79,shows that the total potential ecological risk in the study area belong to strong or moderate level;?5?Significant correlation be seen between Zn,Cu,As,and Cr in the three regions;The principle component load of Cr and Hg is 0.63 and 0.88 in the A area,exceeded the background value of Xinjiang,the source of pollution may come from solid waste from coal mine areas.There is no correlation between Pb and other elements,indicating that it has an independent source of pollution such as Waste gas from fly ash and transportation;the Zn,Cu and Cr elements in the B region are highly correlated and belong to the same principal component,which are mainly influenced by natural factors such as the parent material of the soil,but the pollution source of the As may be industrial waste water;the sources of As and Hg contamination in the C region may come from the chemical fertilizers and pesticides needed for agricultural production,by contrast,the main source of Pb pollution is from the wear of large agricultural machinery tires and the feces of livestock and poultry;?6?By the assessment of human health risk in soil heavy metals in the study area,all elements have a certain non-carcinogenic risk,meanwhile,Cr,Pb and As have carcinogenic risk;direct intake is the main way of exposure to health risks;the rank of the non-carcinogenic risk index of each element is HQ_As>HQ_Pb>HQ_Cr>HQ_Cu>HQ_Hg>HQ_Znn and HI values in three region are 0.25?0.31 and 0.30 and these elements have less or acceptable risk to human health.But carcinogenic risk index rank of Cr?Pb and As is CRAs>CRCr>CRPb and TCR values in three regions are2.85E-03?3.27E-05 and 2.98E-05.It shows that there is a high risk of carcinogenesis around the open-pit coal mine,and the relevant departments should be paid attention to prevention and make control measures.