Study On Characterizations Of Organic Micro-Pollutants And Heavy Metals In Soil At Typical Industrial District

In the present study, soil and plant samples were collected in typical industrial district inNorthwest China. The contamination levels, spatial distribution, isomeric composition,possible sources and potential ecological risk of OCPs, and PAHs, as well as heavy metalsrfom soil and plant were systematically investigated using soxhlet extraction, hydrochloricacid-nitric acid-hydrolfuoric acid-perchloric acid digestion, GC/ECD，GC/MS detectionmethod and atomic absorption spectrophotometry.The results showed that the total concentrations of8kinds of OCPs （^OCPs） rangedrfom18.34to125.34(ag-k₁g with a mean value of54.84jag-k₁g in soil samples. Among thedifferent sampling areas, the higher levels of OCPs were detected in the roadside, followed bygreenbelt and thizosphere soil samples when the lowest concentration was found in theagricultural soils. The isomeric ratios of OCPs indicated that OCPs，as the residues in soil，were generally originated rfom the typical industrial district and historical application. Thesoils in the typical industrial district in this studiy could be classiifed as the low pollution dueto the concentrations of OCPs. The risk assessment showed that DDTs residues in the soilsposed some risk to birds and geobiont.The results showed that the total concentrations of22PAHs （^PAHs） in topsoil rangedrfom855.2to2254₁.7(ag-kg in typical industrial district and, the total concentrations of thevertical distribution in soil had an salience diffusion and transfer. The higher levels of PAHswere found near the heating and power plant. The composition of PAHs was characterized bythe low moleculor weight PAHs. The correlation analysis showed that the contents of PAHswere poorly correlated with soil total organic carbon （TOC） and pH in soil in the typicalindustrial district. The principal component analysis （PCA） and isomeric ratios of PAHsindicated that PAHs in soil rfom typical industrial district mainly originated rfom combustionsources. The risk assessment suggested that exposure of PAHs needed an attention at presentcarcinogenic level in typical industrial instrict.In the soil surfaces of typical industrial district, the mean concentrations of lead （Pb）,chromium （Cr），zinc （Zn），copper （Cu） and cadmium （Cd） were111.03,78.99,64.60,43.11and01.32mg-k"g, respectively. The concentrations of heavy metals in topsoil showed a tread in anorder: Pb>Cr>Zn>Cu>Cd, moreover, showed a tread in an order: Pb>Cr>Zn>Cu in verticaldistribution. Through description of spatial variation of heavy metals in different areas,industrial activities and transports were the important sources of heavy metal pollution in soilin the study area. The single pollution index，Nemerow synthetical pollution index andgeo-accumulation index （Igeo） were adapted to evaluate the pollution status and the soilquality contaminated by heavy metals in the study area. The results showed that the soil was none to moderately pollute by Cu, Zn，Pb and Cr，but the soil was severely polluted by Cd.The concentrations of Cu, Pb, Cr and Zn in plants rfom the investigated sites had aconsiderable variance, the accumulation ability for heavy metals showed a tread in an order:Zn>Cu>Cr>Pb. The higher concentrations of Zn was found in plant samples. The availablecontents of heavy metals in soils showed that Zn element is easy to accumulate rfom soil toplant, but Pb element was hard to be uptaken by plants.