Stduy On Heavy Metal Pollution Of Urban Surface Dust In Wuhu City Area

Because of the special characteristic of urban surface dust environment interface,heavy metals which exited in unban sueface dust easily become a potential souce to impact on the urban environment.On the one hand,surface dust is easy to scatter under the conditions of certain extermal force,and is absorbed by the body through the respiratory tract and skin,so,it has bad impact on the humans.On the other hand,surface dust go into river under the condition of its precipitation,which can cause the urban water environment pollution.In present,study on the surface dust mainly concentrated in urban street dust migration,partical size composition heavy metal spatial distribution, occurrence form, source analysis and environment effects, however,there were little report on the heavy metal distribution and enrichment in different size and their impact on human health risk assessment,This paper selected WUHU city as the object,study heavy metals spatial distribution,particl size and its health risk assessment,it has certain practical significance.In this paper,heavy metals were analized by ICP-AES.Based on ARCGIS statistical analysis module,heavy metals spatial distribution and its reasons were studied,combined with statistical analysis methods,the sources of surface dust heavy metals were analized.Through the heavy metals enrichment ratios change of different partical size,this paper preliminary study the partical size distribution of heavy metals.On this basis,heavy metals health risk assessment of Wuhu urban surface dust were carried out,The main findings were as follows:(1)The rang of pH value of Wuhu urban surface dust was7.65-12.36,with the average of 9.75,rang of organic matter contents was 1.25%-16.84%,with the average of 4.86%. The content of Zn,Cd,Pb,Co,Ni,Mn,Cr,V and Cu were 313.53,1.95,138.61,8.19,21.38,589.87,110.31,55.19 and 135.42mg/kg,respectively.Cd,Pb,Cu and Zn pollutions were more serious,their contents were 10.3,5.2,4.2,4.1 times of the soil background value,respectively.However,Cd pollution was the most serious.(2)Spatial distribution of heavy metals of Wuhu urban surface dust had large differences.Heavy metals content had contact with the distance away from the industrial area and traffic areas.The closer distance,the higher contents.Heavy metals of the economic and technological development zones which had the center of industrials and the central city which had the center of transport activities were moer higher,while in college park-oriented high-tech development zone,heavy metals contents were low relatively.The different spatial distribution was mainly due to the differences of regional function.(3)Statistical analysis showed that industial emissions and urban transport activities were t the mian sources of surface dust heavy metals.Co,Ni,Mn,Cu and V were mainly come from industrial emissions,Zn,Cd,Cr and Pb were mainly influenced by transport activities.(4)Heavy metals contens showed a significant size effect.When the partical size decreased,heavy metals contents showed a trend of increasing.160-200 mesh size was the main pollution size.In the >200 mesh size,heavy metals enrichment ratios were about 50%,the order was:Cd>Cu>Zn>Cr>Ni>Pb>Co>V>Mn.(5)The order of chirdren exposure to heavy metals of surface dust <75um-level in WUHU city was:hand-mouth intake ways>skin inhalation means>breath inhalation channel,hand-mouth intake ways was the main way of the risk of surface dust heavy metals.The non-carcinogenic risk of heavy metals was in order of Pb>Cr>Mn>V>Cu>Cd>Co>Ni>Zn,their risk were all lower than the non-carcinogenic threshold.But the risk of all heavy metals in the superposition of multi-channel intake was upto 0.753,it indicated that the health risks from the compound heavy metal pollution can not be ignored.Non-carcinogenic risk had greater different spatial distribution.In economic and technological development zone,because of the coal-fired power plants,industrial emissions and traffic activities,the overlay heavy metals non-cancer risk was moer high than 1,there was a serious hazard in this area.Cr,Cd,Co and Ni cancer risk was lower than the risk threshold,it indicated that,they had a low risk of cancer.Although urban dust effect on human health risks were not outstanding,as urban industrial emissions and transport activities were more and more strengthen,it was necessary to control the emissions of heavy metals,in particular,the multiple heavy metals composite pollution and spatial distribution differences should be concerned.