Contamination And Health Risk Assessment Of Soil Heavy Metals In Residential Communities Built On Brownfields

Nine residential communities which were built on different brownfields in a city of east HenanPlain were chosen to investigate the health risks of heavy metals (As, Hg, Cd, Pb, Ni, Zn, Cr and Cu) insurface soils. Concentrations of heavy metals in soils were measured by the national standard methods.Contamination levels of these heavy metals were evaluated using Pollution Index (Pi), Integrated PollutionIndex (IPI) and Geoaccumulation Index. Based on the health risk models recommended by U. S.Environmental Protection Agency (US EPA), non-carcinogen and carcinogen health risks of heavy metalsin soils were assessed. The main results were as follows:(1) Compared with the original brownfield, concentrations of heavy metals in soils and theirhealth risks in the residential communities built on brownfields have been significantly reduced after soilremediation.(2) Heavy metal concentrations in the surface soil of each residential community are higher thanits reference background values. Heavy metal concentrations in soils and their health risks in residentialcommunities built on brownfields are higher than residential communities built on non-brownfield. Theproductions of the original enterprises which were built on the brownfields were different, which resulteddifferent heavy metal concentrations in surface soil of each residential community built on brownfields.The distribution of heavy metals in different soil profiles are varied, the concentrations of heavy metal indeeper soil (20~40cm or40~60cm) remain high. In addition to Cr, heavy metal concentrations in deepersoil (20~40cm or40~60cm) are higher than those in the soils at the corresponding depth of theresidential communities built on non-brownfield.(3) According to Standard of Soil Quality Assessment for Exhibition Site (HJ305-2007), theassessment by Integrated Pollution Index indicates that among nine sampling sites, TX indicates thepresence of critical pollution, the rest eight sampling sites have none pollution level. The values ofPollution Index indicates that pollution level of the eight heavy metals in the surface soil of the samplingsites WY, XT, D1, D2and D3belong to none pollution level. The soils of the sampling site YH areconsidered to be uncontaminated with respect to Hg, Cd, Pb, Ni, Zn, Cr and Cu, some soil samples are considered to be practically contaminated with respect to As. The soils of the sampling site TX areconsidered to be uncontaminated with respect to As, Cd, Pb, Ni, Zn and Cu, some soil samples areconsidered to be practically contaminated with respect to Hg, Cr. The soils of the sampling site XH areconsidered to be uncontaminated with respect to As, Hg, Cd, Pb, Ni, Zn and Cr, some soil samples areconsidered to be practically contaminated with respect to Cu. The soils of the sampling site DS areconsidered to be uncontaminated with respect to As, Hg, Cd, Pb, Ni, Zn and Cr, some soil samples areconsidered to be practically contaminated with respect to Cu;According to its reference background values, the assessment by Geoaccumulation indexindicates that the soils of all the residential communities built on brownfields are uncontaminated withrespect to Pb and Ni. The soils of the sampling site YH are considered to be uncontaminated to moderatelycontaminated with respect to As, Cr, Cd, Zn, and Cu, and uncontaminated with respect to Hg, some soilsamples are considered to be moderately contaminated with respect to As. The soils of the sampling siteXH are considered to be uncontaminated to moderately contaminated with respect to Cd and As, anduncontaminated with respect to Cr, Cu, Zn and Hg. The soils of the sampling site WY are considered to bemoderately contaminated with respect to Cd, Cr, As and Zn, and uncontaminated with respect to Cu and Hg,some soil samples are considered to be moderately contaminated with respect to Cd. The soils of thesampling site TX are considered to be moderately contaminated with respect to Hg and Cr, uncontaminatedto moderately contaminated with respect to As, Cd and Zn, and uncontaminated with respect to Cu, somesoil samples are considered to be heavily to extremely contaminated with Hg. The soils of the sampling siteDS are considered to be uncontaminated to moderately contaminated with respect to As, Cr, Cd, Zn, Hgand Cu, some soil samples are considered to be heavily contaminated with respect to Hg, and moderatelycontaminated with respect to Cd, Zn and Cu. The soils of the sampling site XT are considered to beuncontaminated to moderately contaminated with respect to Cr, Cd, Cu, Zn and As, and uncontaminatedwith respect to Hg, some soil samples are considered to be moderately contaminated with respect to Cr andCu. The non-brownfield control site D1are considered to be uncontaminated to moderately contaminatedwith respect to Cd and Cr, and uncontaminated with respect to As, Hg, Pb, Ni, Zn and Cu. D2areconsidered to be uncontaminated to moderately contaminated with respect to Hg and Cr, anduncontaminated with respect to As, Cd, Pb, Ni, Zn and Cu. The original brownfield control site D3are considered to be heavily contaminated with respect to Hg, moderately contaminated with respect to Cu, Cr,Pb, Zn and Cd, and uncontaminated to moderately contaminated with respect to As and Ni.(4) The HQ and HI values of soil heavy metals in each residential community are lower than1,which indicates that there are no non-carcinogenic risks in these communities. The HI value of the heavymetals for children is exactly six times higher than for adults. The contribution rate of HQAsto HI is about53%,arsenicisthe crucial factor for non-carcinogenic risk in the residential communities of the city. Thecontribution rate of oral exposure (ingestion) to HI is about93.04%, the highest levels of non-carcinogenicrisks is associated with the route of ingestion of soil for all the heavy metals.(5) The values of CR and TCR are lightly higher than the standards suggested by US EPA,which indicate that slight carcinogenic risks might exist in the communities, but lower than the lenientstandard proposed by some experts,.The contribution rate of CRASto TCR is about80%, and thereforearsenic is the crucial factor for carcinogenic risk in the residential communities of the city. The contributionrate of oral exposure (ingestion) to TCR is about98.14%, the highest levels of carcinogenic risks isassociated with the route of ingestion of soil for all the heavy metals.