Pollution Characteristics And Health Risk Assessment Of Heavy Metals In Foliar Dust Of Huainan City

Foliar dust reflects a certain area and time of near-surface atmospheric particulate matter pollution,its smaller size particles ware easier for human breathing inhalation or attached to the skin,hair and clothing surface.Therefore,this study selected Huainan common green tree species heather as the research object,and the leaf dust at the height of 0.7~1.5m was collected,this height was close to the height of children's daily breathing and activity,in order to simulate children in a particular area of dust exposure.In this study,Huainan City was divided into six functional zones,and the spatial distribution and sources of heavy metals in foliar dust of different functional areas of Huainan City was discussed and the carcinogenicity and non-carcinogenic risks of heavy metals to children was evaluated by the American EPA exposure risk assessment model.It was found that the heavy metals contents in the foliar dust of the residential area ware higher,and the threat to the health of the children was bigger.Considering that the residential area was an important place for people to live,therefore,this study re-divided Huainan City into three regions,and collected foliar dust samples from the residential areas of the three regions in four seasons.The temporal and spatial distribution of heavy metals in foliar dust in residential areas was studied,and the health risk assessment was carried out for children.The main conclusions of this study were as follows:(1)The average amount of foliar dust in the six functional areas of Huainan City was between 1.43 and 62.86 mg·g-1,and the order was: coal transportation district>commercial traffic district > residential district > economic development district >cultural and educational district>parks and greenery district.The average amount of foliar dust in the residential areas of Huainan City was between 0.88 and 16.32 mg·g-1,and the seasonal distribution was: winter > autumn > spring > summer,spatial distribution was: mining area> central city> Shannan New District.(2)The contents of heavy metals in foliar dust in different functional areas of Huainan City were higher than those of soil background values,among which Zn,Pb and Cu reached 5.60 times,5.06 times and 4.68 times of background value.The spatial distribution of heavy metal contents was: cultural and educational district>parks and greenery district>residential district>economic development district>commercial traffic district>coal transportation district.The contents of heavy metals in foliar dust of residential areas were also higher than those of soil background values and the highest contents of heavy metals was in winter of four seasons,in center city and Shannan New District of three regions.(3)The sources of heavy metals in different functional areas in Huainan were differences,Transport emissions ware the main sources in commercial traffic district,economic development district and coal transportation district.The sources in cultural and educational district,parks and greenery district and residential district became more complex,in addition to emissions from traffic,but also it may come from industrial emissions,coal burning,cooking activities and wear of public facilities.The sources of heavy metals varied in different functional districts and different seasons of residential in Huainan,traffic emission was the common source of heavy metals in the four seasons.In addition to transportation factors,winter,spring also from coal combustion,summer,autumn also affected by power plants,industrial emissions and wear of public facilities.Heavy metal mainly from coal ash itself and truck emission in mining district,in center city mainly from traffic emission,in Shannan New District mainly due to construction dust impact.(4)The carcinogenic risk indexes of Ni,As,Cr in foliar dust in the six functional areas of Huainan City were less than the safety threshold.The total non-carcinogenic risk in Huainan reached 1.36,exceeds the safety threshold of 1.0,already have constituted a hazard to the health of children.Non-carcinogenic risk was higher in cultural and educational district,parks and greenery district and residential district.The carcinogenic risk of Cr,Ni,As in foliar dust of residential areas in different areas and seasonal ware also lower than the safety threshold.Except spring mining area,the total non-carcinogenic risk of heavy metals in foliar dust of residential areas in the rest of the regional and seasonal were higher than the safety threshold,the highest was in winter.In general,As,Pb and Cr contribute significantly to non-carcinogenic risk,Cr contributes significantly to carcinogenic risk,hand-mouth intake was the main route of exposure to children.