Risk Assessment Of Heavy Metal Contaminated Sites

Along with the economic development, some companies will move out of the city center, the original industrial land will become commercial or residential land use. And there is a certain degree of such land contamination, if necessary assessment and treatment is not conducted, it will pose a great threat to people’s health and ecological environment. Therefore, the relocation of enterprises legacy of contaminated sites has already attracted people’s attention.This text takes the contaminated sites of an electroplating factory in Wuxi, Jiang su as its research object. Based on careful assessment of contaminated soil, the findings we have got are as follows:four kinds of heavy metals, which including Cr, Cu, Ni, Zn, are contaminated to some degree; Cr is the most highly contaminated heavy metal, reaching down as far as 3m and weighing the contamination index up to 44.5; Overall, we can see that topsoil is more likely to be contaminated than deep soil, besides, north central areas of this factory are presenting higher contamination index.This article then adopts Hakanson potential ecological risk index method to conduct ecological risk assessment, results are as follows:(1) The total potential ecological risk index (here in after referred to as RI) decreases with the increase of depth. Top soil in four points (A 16, A17, A21, A32) is presenting higher ecological risk, of which A17 has reached 2542.2 in terms of its value at risk; (2) Potential ecological risk coefficient (here in after referred to as Eτ1) for single heavy metal:Cr, Cu and Ni are presenting higher ecological risk in 6 points which including A17, A20, A24, A31, A32, A33, with its Eτ1 rising up to 1846.5.We have conducted health risk assessments with Technical Guidelines of Risk Assessment in Contaminated Sites (draft). The results are as follows:(1) Cr is the major factor of carcinogenic risk. Cr is presenting high carcinogenic risk in 8 points when the land is used as residential purpose, while the rest of them are presenting moderate level of carcinogenic risk. And when the land is used as commercial purpose, Cr is presenting high carcinogenic risk in 7 points and moderate level carcinogenic risk in 12 points respectively, with the remaining land presenting low carcinogenic risk. Carcinogenic risk of Ni is only presented in some individual points; (2) Cr is presenting non-carcinogenic risk in 17 points when the land is used as residential purpose, which is higher than that of 8 points when the land is used as commercial purpose; (3) Due to the consideration of the pediatric population, both the carcinogenic risk and non-carcinogenic risk in residential sites are higher than that in commercial sites.This text has marked out different risk zones according to different risk level, and as for the heavy contaminated soil, it adopts soil replacement method to fundamentally solve the problem of soil pollution.