| As an important industrial and agricultural base and commodity food base in China,the quality of land in the Yangtze River Delta region is directly related to the production of local agricultural products and related agricultural income,which has important agricultural and ecological economic values.The unreasonable human development activities will cause the accumulation of heavy metals in the soils of the region,which will affect the quality of soil environment and the production safety of agricultural products,and finally,will further threaten the health of the surrounding population through the food chain.In this paper,we selected Jinhua City,a Jinqu Basin city in the Yangtze River Delta,as the study area,and collected 209 surface cropland soil samples in the study area according to the grid sampling method to determine the contents of eight heavy metals,As,Cd,Cr,Cu,Hg,Ni,Pb and Zn,respectively.The spatial distribution characteristics of soil heavy metal pollution in the area were analyzed by fitting semi-variance functions with GS+9.0 and spatial interpolation with ordinary kriging;comparing the two commonly used source analysis models,absolute principal component/multiple linear regression model（APCS-MLR）and positive definite matrix factor analysis model（PMF）,to determine the main sources of soil heavy metal pollution in the area and their contribution rates,and also based on the source analysis results,a health risk assessment model was constructed to quantify the health risk of soil heavy metals to humans in the region.The relevant results showed that:（1）The mean values of As,Cd,Cr,Cu,Hg,Ni,Pb and Zn in arable soils in Jinhua were 6.37,0.18,36.73,18.60,0.11,11.95,32.48 and 26.15 mg?kg-1,respectively,among which the mean contents of Hg,Cu,Zn,Pb and Cd elements exceeded the background values of Zhejiang Province and Chinese soil background values;the strong coefficients of variation for Hg,Ni and Cr indicate the existence of strong spatial distribution discontinuities;compared with the risk screening values for soil contamination of agricultural land in China,the average content of heavy metals in each arable land in Jinhua is less than its corresponding critical value,indicating that although a certain degree of contamination exists in the arable soil in this area,it still meets the criteria for agricultural activities.（2）The spatial distribution characteristics of eight soil heavy metals in the study area were analyzed by using kriging spatial interpolation,and the results showed that the high value areas of element As were mainly concentrated in the central,northern and western areas of Jinhua City,and the distribution of Hg was more uniform,and the high value areas were sporadically distributed in the central and western parts of Jinhua City;the spatial distribution of Cr,Cu and Ni elements had similarity,and the high value areas were concentrated in the central and western parts of Jinhua City,including Lanxi City,Wucheng District and Jindong District;Ni,Cu and Zn elements were also significantly enriched in the southern part of Wuyi County.（3）The source analysis results show that Ni,Cr,Cu and Zn are mainly"natural sources"influenced by soil-forming parent material,with a contribution rate of 24.29%;Cd,Cu and As are mainly"agricultural pollution sources"caused by excessive fertilizer and pesticide use,with a contribution rate of 30.06%;As is mainly"industrial pollution sources"caused by industrial activities,with a contribution rate of 13.42%;Hg is mainly"atmospheric deposition"caused by coal combustion activities,with a contribution rate of 13.27%;Zn and Pb elements are mainly"traffic pollution sources"caused by traffic emissions,with a contribution rate of 18.9%.（4）The results of human health risk assessment show that the health risks（including carcinogenic and non-carcinogenic risks）caused by non-dietary intake in the three exposure routes are much greater than those caused by skin contact and inhalation.Among them,the non-carcinogenic risk of 8 heavy metals to adults and children is less than 1,which is within the acceptable range,and the total carcinogenic risk of adults is1.69E-05,which is within the acceptable range,but the total carcinogenic risk of children is 1.30E-04,has exceeded the carcinogenic risk threshold of 1.00E-04,especially the carcinogenic risk caused by the As element（1.16E-04）,and the relevant departments need to pay attention.（5）The results of the human health risk assessment based on the PMF model showed similarities in the probability of carcinogenic and non-carcinogenic risks for adults and children for each source of pollution.In terms of non-carcinogenic risk,industrial sources had the highest non-carcinogenic risk for adults（32.92%）and children（30.47%）,followed by agricultural sources（21.34%and 29.31%）,natural sources（26.26%and 18.56%）,traffic sources（15.47%and 17.04%）,and atmospheric fallout sources（4.02%and 4.62%）;in terms of carcinogenic risk,the industrial sources had the highest carcinogenic risk for adults（60.74%）and children（61.50%）,followed by agricultural sources（32.94%and 33.19%）,traffic sources（3.3%and 3.09%）,natural sources（1.35%and 0.27%）,and atmospheric fallout sources（1.67%and 1.65%）.Therefore,control of Cd,Cu,and As from industrial and agricultural sources is key to prevent health risks in adults and children.（6）The geographic detector results show that the spatial differentiation q of different soil heavy metal health risks in the study area ranges from 0.035 to 0.119,and the q values of different soil heavy metal health risks are in the order As>Pb>Cd>Cr>Cu>Hg>Ni>Zn,the spatial distribution of soil heavy metal health risks caused by Hg,Ni and Zn in Jinhua City was relatively balanced,while the spatial distribution of soil heavy metal health risks caused by As,Pb Cd Cr and Cu was more discrete.In the study area,it is necessary to implement regional control for the treatment of heavy metals As,Pb Cd,Cr and Cu in cultivated soil,while the soil pollution caused by Hg,Ni and Zn requires coordinated treatment of various districts and counties to reduce their health risk level. |
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