Rural Energy Consumption And Exposure Risk Of People With Harmful Metals In Water And Soil Environment In The Northern And Southern Foothills Of Qinling Mountains

Qinling is an important ecological environment protection area in China.In recent years,with the rapid development of economy and urbanization,the development scale of industry,agriculture and tourism in the northern and southern foothills of Qinling Mountains are becoming larger and larger.The changes of blind exploitation,steep slope cultivation,mining,energy consumption of residents and the resulting environmental pollution problems are gradually emerging.Harmful metals are persistent pollutants which are difficult to degrade and have strong migration.They widely exist in water,soil,dust,plants and other different media in nature,and accumulates in animals through the food chain,thus causing harm to human body and ecosystem.Qinling is an important ecological barrier and ecological space in China.Therefore,to systematically explore the changes of energy consumption structure of rural residents in the southern and northern foothills of Qinling and the pollution and risk of human activities to the soil and water ecological environment will provide the basic data basis for the protection of the "great Qinling",the realization of the "beautiful countryside" and the realization of the construction plan of rural environmental continuous improvement in Shaanxi Province.In this study,the rural villages and towns in the southern and northern foothills of Qinling Mountains were selected as the study area(Lantian County,Zhouzhi County,Mian County,Chenggu County,Xunyang County,Ankang City,and Luonan County,Shangluo City,totally 4 cities,6 counties and 14 villages).174 drinking water samples,191 surface dust samples,151 fuel samples and 940 household energy consumption questionnaires were collected.Based on the analysis of the energy structure and change characteristics of rural households,this paper explores the content distribution,accumulation characteristics and population exposure risk of harmful metals in rural water and soil environment,and expounds the relationship between the change of energy consumption structure and the change of rural water and soil environment quality.The main conclusions are as follows:(1)The concentration of NO3-in drinking water of 14 villages in the northern and southern foot of Qinling Mountains,except for three villages in Xunyang County,Ankang,exceeded the upper limit of the standard of drinking water hygiene standard(GB57492006)by 10 mg/L.Co?Cd?Cr?Cu?Ni?Pb?Sb and Zn all exceeded the standard to some extent.The pollution degree of harmful metals in water body shows the characteristics of Ankang>Shangluo>Hanzhong>Xi'an.Non carcinogens Cu,Ni,Pb,Sb,Zn have less non carcinogenic risk to human body,and the risk index is in the range of 1.0E-09 to 5.0E-08,which is acceptable for human body.The carcinogenic risk index of Cd and Cr caused by drinking water has exceeded the acceptable level recommended by the five international health organizations,which has posed a certain threat to human health.(2)Eleven metals of As,Ba,Co,Cr,Cu,Fe,Mn,Ni,Pb,Sr,Zn in surface dust all exceeded the soil background value of Shaanxi Province in different degrees in 13 villages and towns,among which the exceeding degree of Co,Pb,Zn was the highest among 11 harmful metals,and the exceeding degree of three villages in Xunyang County of Ankang was the most serious.The pollution load index of 11 kinds of harmful metals is in the range of 1-2,which belongs to light pollution,showing XY-MW>XY-CY>LNJC>MX-FC>MX-XBP>XY-XH>LT-XZ>ZZ-XFT>LT-XZ>CG-XJM>ZZ-QH>LN-LK>CG-EL.The non-carcinogenic risk caused by elements As,Co,Cr,Cu,Mn,Ni,Pb,Sr,Zn is tolerable for human body,and the risk index for adults is less than 1.However,the non-carcinogenic risk index for children is greater than 1,which is more than acceptable for human body and threatens the health of children.For adults,the carcinogenic risk index of As,Co,Cr,Ni of Xunyang county has exceeded 10-4.For children,12 villages except Erli village in Chenggu County are all over 10-4.Therefore,it is important to pay attention to the health risks of harmful metals.(3)Based on the investigation of the energy consumption structure of 14 villages in the north and south foot of Qinling Mountain,it is concluded that most of the rural residents in the north and south foot of Qinling Mountain burn coal and firewood indoors for cooking and heating.According to the annual coal consumption of 14 villages and the emission factors of civil coal combustion in Shaanxi Province,Zn,Pb and Mn in the harmful metals released from coal combustion of 14 villages are estimated to be the main elements,which corresponds to the serious over standard of Zn and Pb in the dust at the North and south foot of Qinling Mountains.The release amount of Cr and Ni is next toZn,Pb and Mn in the harmful elements,which is closely related to the over standard of Pb and Ni in some water samples of Lantian and Zhouzhi counties,slightly over standard of Ni in villages and towns of Mian and Chenggu counties in Hanzhong,and over standard of Cr and Ni in drinking water samples of Xunyang and Ankang.It shows that one of the sources of harmful metals in dust and water in the northern and southern foot of Qinling Mountains is the harmful element released by coal combustion.Relevant researches also showed that coal combustion,burning trees,straw,etc.were produce harmful metals attached to soot particles and bottom ash,thus entering the atmosphere,water,soil dust environment.