The Soil Heavy Metals Analysis And Risk Assessment In The Replacement Process Of Qing Dao Former Industrial Sites

With the rapid development of city economy and the acceleration of urbanization,city soil pollution problems have become increasingly prominent. under thebackground of the increasingly scarce land resources, to carry urban land replacement,change the pollution plots of land use function is an effective way to take the road ofsustainable development. Therefore, to find out the source of contamination of thesoil to be replaced, analysis of the potential threat to human health and ecologicalenvironment of contaminated soil is the focus and the premise of the urban landreplacement work.This paper selects Qingdao eastern coast of Jiao Zhou Bay typical region, basedon understanding the characteristics of pollutants, sources for soil pollution, physicaland chemical properties of pollutants, using mathematical and statistical tools such asthe polluted soil samples collected, analyzed, indirectly infer the sources of heavymetals in soil. At the same time, Combined with land-use type, this article selectedmain pollution factor to carry out the research from the contaminated sources,pollution classification and risk assessment.The main conclusions of this study are as follows:(1) The various activities of the venue makes the soil was polluted to a certainextent. The overall environmental quality of the study site is poor. Pb, Ni pollution isserious，the spatial range of Ni pollution is wide, all surface soil and most subsurfacesoil was detected in nickel elements exceed the standard. Surface soil heavy metalvariation than subsurface, indicates the pollution sources with exogenous. In addition,the heavy metal content in surface soil was significantly higher than that in subsurface,description of soil pollutants from external factors, but also with contaminated soilalkaline environment the chemical properties of heavy metals showed certain "inert"and water soluble, reducing the possibility of heavy metals in the surface to the deeplayer of soil on migration. (2) Enrichment coefficient method is used to analyze the degree of enrichment ofheavy metals in the soil so as to further understanding of soil pollution. The resultsshowed that6kinds of heavy metal elements have a certain degree of accumulation,of which elements Pb, Ni and Cu reaches to sever enrichment. Especially, Pb and Niin the most significant, indicate that Ni and Pb is the main contribution of thepollution factor. According to field conditions in the study area, combining with sitesurrounding environment analysis, The cause leading to the accumulation of heavymetals in soil is related to the following factors：Industrial activities，hardwareenterprise production as well as dry wet subsidence of road vehicle exhaust emission.(3) Correlation analysis and principal component analysis were used to discussthe correlation among the heavy metal elements. The results show that the fourelements nickel, lead, chromium and zinc content was significantly positively relatedto each other under0.01test level; elements such as lead, zinc, copper, nickel, amongor between any two showing a significant correlation at the0.05test level. Thecorrelation results suggest that soil at the site is mostly incidental pollution, and thatpollution occurred with similar contamination pathways.(4) Based on the classification of contaminated sites randomness, fuzziness andnon-linear relationship between the characteristics of uncertainty coexist orcross-exist, using in the analytic hierarchy process (AHP) to establish the sitepollution hierarchies of set pair analysis model. According to the value research ofcomprehensive evaluation index, the pollution area risk level is divided into low,medium, heavy, heavy and serious5classes. At the same time, the level of studyfield contamination is divided.(5) Take into account the sources of pollution potential negative effects on theecological environment and endanger human health, accumulation index method andRBCA health risk assessment model were used to study the environmental risk of soilpollution and human health risk in the evaluation of the pollution caused byenvironmental risks. The results of accumulation index method show that there existcertain ecological risk in the study area, the degree of risk in general belong tomoderate pollution, portion of the location with moderate pollution risk. Human health risk evaluation results show that Pb, Cd, Zn, Ni, Cu, Cr level of health risk isrelatively low, there are no more than a risk alert value. However, the combinednon-carcinogenic risk can not be ignored, and need to attract enough attention.