Pollution Characteristics Of Soils In The Typical Industrial Area In Baoan District Of Shenzhen And Its Health Risk Assessment Of Heavy Metals

With the increasing development of urbanization and industrialization,heavy metals,polychlorinated biphenyls?PC Bs?and phthalic acid ester?PAEs?contents in industrial soils are increased continuously,which can cause serious damage to regional eco-environmental quality and residential health.At present,our country has carried out comprehensive investigation of soil heavy metals and organic pollutants in the environment of big city and megalopolis area.This is meaningful for soil environmental protection,as well as ensuring the human health.Reports showed that,the soil pollution of heavy metals,PCBs and PAEs in Baoan District has being increased,there is important practical significance to carry out comprehensive survey of soil pollution and to elucidate the potential ecological and healthy risks.In this paper,industrial soils in Baoan District in Shenzhen C ity were subjects to be investigated,and the forestry soils were used as comparing background points to get out the pollution characteristics of heavy metal,PCBs and PAEs in the industrial soils.Then the single pollution index combined with Nemerow's integrated index was adopted for pollution evaluation.The ecological risk assessment was done by risk quotients and the preliminary health risk assessment was evaluated by the model recommended by USEPA,sothat to provide reference for the local soil environment regulation and remediation.The resultsare as follows:?1?Heavy metal contents in industrial soils were significantly higher than that in forestry soils.Except Pb,heavy metal contents in forestry soil samples were conformed to the first grade values of the soil standard in China?GB 15618—1995?.Cu,N i,Pb,Cd and As were exceeded the standard values in industrial soils,and few sampling points were severely polluted by heavy metals,which presents potential hazard to human health.?2?PCBs contents of industrial soils were significantly higher than that in forestry soils.In forestry soils,PCB101 and PCB118 were detected.In industrial soils,just PCB118was detected.PCBs mainly come from air.In the study area,PC Bs in 23 soil samples were all below the first grade level of the soil standard in C hina?GB 15618—2008,exposure draft?.?3?PAEs contents in industrial soils were significantly higher than that in forestry soils.In forestry soils,just the DEP in soil samples collected from the Pingluan Mountain Park were higher than the limit value of the control standards in the USA,probably because the park is nearby the factory using PAEs.In industrial soils,DMP and DBP for different sampling points exceeded standard values,with a percentage being 7.7%and 61.5%to the total sampling points,respectively for DMP and DBP,and the highest content was 1.56 and5.88 times to the standard limit.This may be related to that the enterprises apply this kind of materials in the production process but there is no strict controlling its waste discharge.?4?The decreasing order of pollution index of 8 heavy metals in the industrial soils was N i>C u>As>Pb>Cd>Zn>Hg>Cr,while the intergreated pollution index was 1.33,meaning the pollution of heavy metals in the industrial soils is at the low grade.There is very low ecological risk from heavy metals,except N i which presents low ecological risk.?5?The heavy metals?C u,N i,Pb,Cd and As?which concentration at 95%probability was higher than the second standard limit were subjected to do health risk assessment.The assessment result showed that the decreasing order of the total non-carcinogenic hazard index of 5 heavy metals were Pb>As>N i>C u>Cd,and the importance of exposure was hand-mouth intake>skin absorption>breathe inhale.The order of carcinogenic risk of 3heavy metals followed As>N i>Cd.The total non-carcinogenic hazard index of Cu,N i,Pb,Cd and As is 0.648 and the total carcinogenic risk index was 4.79×10^-15,so it is considered that the non-carcinogenic hazard or carcinogenic risk from heavy metals are all negligible for the industrial soils.?6?The result of principal component analysis showed that Zn,N i,Cr and Pb mainly came from industrial production such as the metal surface treatment,electroplating,meanwhile,traffic also contributed to Pb pollution.Hg and As came from coal and garbage burning and also from printing and dyeing wastewater discharge.C u and Cd came from electronical production and metal processing.