Pollution Characteristics And Health Risk Assessment Of Heavy Metals In Farmland Soils In The East Of Shuozhou

With the continuous development of social economy and the continuous advancement of urbanization,the heavy metal pollution of farmland soil caused by various industries,transportation industries,and agricultural activities has become more and more serious.It will cause harm to the local environment and endanger human health.This study collected 131 farmland soil surface samples from three counties in the eastern part of Shuozhou City to determine eight heavy metals in the soil: cadmium,chromium,arsenic,mercury,lead,copper,zinc,and nickel Content.The single factor index method,Nemerow comprehensive pollution index method,geo-accumulation index method,potential ecological hazard index method,and the human health risk assessment method recommended by the US EPA were used to evaluate the heavy metal pollution status and health risks of farmland soil in the study area.The main results are as follows:1)The pH range of farmland soil in the study area is 7.58-9.02,which belongs to alkaline soil.The contents of the eight heavy metals of Cd,Cr,As,Hg,Pb,Cu,Zn,and Ni are 0.05-0.12、37.82-126.10、0.34-12.36、0.01-1.36、11.69-34.86、13.21-43.73、34.78-177.70 和 9.41-40.11 mg/kg.The skewness,kurtosis,and coefficient of variation of Hg in farmland soils in the study area are the highest among the eight heavy metals.It shows that Hg is greatly disturbed by man-made,and its maximum and minimum values are nearly ten times different.2)Ni and Cr in farmland soils in the study area are mainly derived from parent materials and are also related to industrial activities such as coal burning and smelting;Hg and As mainly come from the burning of fossil fuels,and some As may be related to emissions from aquaculture;Cu,Pb and Zn may be contributed by mining,processing and transportation in mining areas;Cd mainly comes from the application of agricultural chemical fertilizer.In this paper,the spatial distribution of heavy metal content was studied and analyzed by inverse distance weighting method.The results showed that the contents of Hg,Cr,Ni and As were higher in the west and southwest of the study area,which may be related to the local coal industry.The content of Cd,Pb and Zn in the east and southeast of the study area is relatively high,which is related to convenient transportation and good agricultural development.3)Based on the background value of heavy metals in Shanxi soil as the standard,the results of single factor index method show that Hg pollution in farmland soil in the study area is the most serious,13% of soil samples being slightly polluted,22.1% of soil samples being slightly polluted,22.9% of soil samples being moderately polluted and 33.6% of soil samples being heavily polluted;The evaluation results of Nemerow comprehensive index method show that the farmland soil in the west,south and southeast of the study area is heavily polluted,while the northern area is mostly lightly and moderately polluted,and a small part is heavily polluted.The evaluation results of geoaccumulation index method show that the study area is slightly polluted;The evaluation results of the potential ecological hazard index method show that Hg in farmland soil has a strong ecological hazard,and other heavy metals belong to mild ecological hazards.According to the statistics of sampling sites,33.6% of the sites with mild ecological hazards;42% of the sites with moderate ecological hazards;12.2% of the sites with strong ecological hazards;10.7 of the sites with strong ecological hazards %;The samples with extremely strong ecological hazards account for 1.5%.4)The results of the health risk assessment show that the heavy metal non-carcinogenic health risk index HQ and comprehensive non-carcinogenic health risk index HI are both less than 1,the exposure risk of children is greater than that of adults;The comprehensive carcinogenic health risk index DMN is between 10^-4and 10^-6,which is in an acceptable range.After the correction of bioavailability,the values of HI and DMN in the soil in the study area decreased,and remained within the acceptable range.