| With the rapid development of urbanization and industrialization,industrial activities and human life have made great contributions to heavy metal pollutants in soil through various pathways.Soil heavy metal pollution has attracted increasing attention.The accumulation of heavy metals in soil is difficult to be removed and recovered due to their ubiquity,toxicity,and persistence.Therefore,it is necessary for soil environmental protection and pollution control to understand the pollution status,health risks,and explore pollution sources accurately.In this study,heavy metals in farmland soil around an industrial park in Baoji City were selected as the research object.62 pairs of soil and wheat grain samples were collected in the summer of 2018 to determine the concentration of 7 heavy metals?Cd,Cr,Cu,Hg,Ni,Pb,and Zn?.The enrichment coefficient and pollution index were used to analyze the enrichment status and pollution status of heavy metals in soil,and the human health risks were comprehensively evaluated.The effects of various environmental factors were studied with the help of geographical detectors.Based on the analysis above,the Finite Mixing Distribution Function?FMDM?and Positive Matrix factorization?PMF?were combined to allocate and quantify the contribution source.The mian results are as follows:?1?Soil heavy metals in study area showed cumulative effects,of which the accumulation of Cd,Pb and Hg was the most obvious.In about 50%of the samples,the Cd content exceeded the soil pollution screening value,resulting in pollution.In general,soil heavy metals in the study area showed a slight pollution level.?2?The health risk assessment results showed that,the non-carcinogenic hazard index of single metal was all less than 1,among which Zn,Cu and Cr contributed the most.The carcinogenic risk index of single metal was also lower than 1×10-4,among which Cd and Ni were the largest contributors.The comprehensive health risks of multiple heavy metals were all higher than the corresponding thresholds.The non-carcinogenic hazard index of children was higher than that for adults,but the carcinogenic risk index of adults was three times higher than that for children.Therefore,the health risk of a single metal was low,but its comprehensive effect could not be ignored.The non-carcinogenic and carcinogenic risk of dietary intake pathway was 2-4 orders of magnitude higher than that of three non-dietary exposure pathways.The consumption of self-grown crops in this study area was the major pathway to heavy metal exposure.?3?The health risks of local residents were influenced by both human activities and natural factors,among which the most importment environmental contributors were:distance from Pb-Zn smelter,distance from thermal power plant,distance from coal chemical enterprise,elevation,soil p H,etc.The interaction between them was more important than the single factor.?4?The sources analysis results of soil heavy metals showed that Cr,Cu and Ni were mainly derived from natural inputs.Industrial activities of Pb-Zn smelters were the main sources of soil Cd,Pb and Zn.Meanwhile,the emissions from coal-fired power plants dominated the distribution of soil Hg.In this study,the pollution probability of soil Cr,Cu and Ni was relatively low,and there was no obvious high-risk hot spot area;the risk of Hg contamination was moderate;and its high-risk area was close to coal-fired power plants and Pb-Zn smelters;Cd,Pb and Zn pollution risks were generally higher,with high-risk hotspots mainly located around various enterprises,villages and traffic roads.The results of this study revealed the current status of soil heavy metal pollution in the study area,the associated human health risks and their main pollution sources.These heavy metals will pose a potential threat to the health of local residents.Therefore,active measures should be taken to prevent and control for soil heavy metal pollution in the area. |
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