Geochemical Distribution Of Multi-media Potentially Harmful Elements And Exposure Risk To Children In Energy-based City Yulin

Energy city is one of the most important types of cities in China.In the process of energy exploitation and processing,toxic metals in energy are released into the surrounding environment due to human factors.After toxic metals enter the surrounding environment,they accumulate in large quantities and cannot be decomposed in the natural process,causing pollution to the soil,water,air and plants,and posing certain health risks to animals and humans.Therefore,it is very important to analyze the geochemical distribution characteristics of toxic metals in the multi-media environment of energy cities and explore the health risks of population,which can provide theoretical support for the macroscopical governance of urban environment and the prevention and control of health safety.Yulin city,an energy city,is taken as research area in this study,the spatial distribution characteristics,pollution degree,source and migration patterns of heavy metals in dust,water,soil and plants were systematically studied and the comprehensive exposure risks of multi-media environment for children aged 0-6 was evaluated,and the blood lead level of children aged 0-6 was predicted,in order to establish the basic geochemical data of harmful metals in multi-media environment of Yulin City,and provide science basics for the treatment of toxic metals and epidemic prevention and control of children,The main conclusions of this study are as follows:（1）The concentrations of Ba,Cd,Co,Pb,Sr,Zr,Al₂O₃,CaO,K2O,MgO and Na₂O in urban dust and urban soil were higher than the soil background value in Shaanxi province,and the concentrations of toxic metals As,Cr,Mn,Sr and Zn in plant leaves were lower than those in urban dust and soil.The content of harmful metals Cd,Cr,Cu,Pb,Zn in urban water meets the national class Ⅱ water quality standard,and the concentration of CO,Mn,Sb does not exceed the limit value.The spatial distribution of toxic metals in urban dust、soil、water and plants is greatly affected by human activities.The pollution sources are traffic sources、coal mining and processing sources、coal combustion sources.The evaluation results of the index of geoaccumulation show that Cd,Co,Cu,Pb,Zn and Zr in urban dust are above the moderate pollution level,while other elements are at non pollution or low pollution level.In urban soil,Cd,Co,Sr and Zn are above the moderate pollution level while other elements are at the non-pollution or low pollution level.The results of potential ecological risk index evaluation show that the comprehensive pollution of hazardous metals in dust and soil is at the level of moderate pollution and above in Yulin city.（2）The results of the migration characteristics of toxic metals in soil/dust-plant system showed that the average migration coefficient of each harmful metal element was less than 1 and the plant enrichment was poor.The correlation analysis results of As,Cr,Mn,Pb,Sr and Zn in urban dust and soil showed that Pb in dust had significant correlation with that in soil,while other toxic metals had no significant correlation.Correlation analysis results of toxic metals As,Cr,Mn,Sr and Zn in urban dust-soil-plants show that As in dust is significantly correlated with As and Zn in plant leaves,and toxic metals Sr and Zn are more dispersed than other elements.（3）The EPA model was used to evaluate the comprehensive health risks of hazardous metals in the multi-media environment of Yulin city through the hand-mouth,respiratory and skin exposure pathways.Results show that the comprehensive non carcinogenic exposure risk of as,Cd,Cr,Co,Cu,Mn,Ni,Pb,Sr,V,Zn to children aged 0-1 is less than 1,while the comprehensive non carcinogenic exposure risk of as and Cr to children aged 1-6（excluding 1 year old）is greater than 1 and The comprehensive non carcinogenic exposure risk value of Pb to children aged 3-6 years（excluding 3 years old）is greater than 1.In soil and dust environmental media,the comprehensive carcinogenic exposure risk of As,Cr and Ni to children are within the tolerable range of human body,while Cd and Co have no comprehensive carcinogenic exposure risk to children.The comprehensive non-carcinogenic exposure risk of Mn,Cd,Ni and Zn to children aged 0-6 years is less than 1,while the comprehensive non-carcinogenic exposure risk of Pb to children aged 4-6 years（excluding 4 years）is greater than 1.The combined carcinogenic exposure risk of Cd and Cr to children aged 0-6 years is within the acceptable range for children.The prediction results of IEUBK model show that the blood lead level of children aged 0-6 in Yulin city is lower than the limit of 100μg·L^-1 in China.However,the blood lead level of children aged 1-4 years（excluding 1 year old）is greater than 50 μg·L^-1,which should be paid special attention.