| In order to understand the pollution status of heavy metals in polluted areas in Xi’an,the content level, spatial distribution and their sources of As, Pb, Cr, Cd, Hg, Zn and Cuwere studied. And health risk assessment of kinds of industries was conducted based onthe technique of “Polluted site risk assessment guideline”, the main conclusions were asfollow:(1)The results of potential ecological index assessment showed Cd and Hg locatedto extremely heavy ecological level, Pb in the non-ferrous metals smelting industryfell heavy ecological risk level, while As and Pb in mechanical ranged middle risk, andAs in the thermal power plant ranged middle risk.(2)The spatial distribution of heavy metal concentrations indicating concentrations were strongly related to their producing processes. With the maximum concentration of As, Pb, Cr, Cd and Cu was69.54mg·kg-1,944.78mg·kg-1,247.22mg·kg-1,84.42mg·kg-1,314.86mg·kg-1, respectively, the nitrogen factory where coupled withnon-ferrous metals smelting process was the most remarkable contaminated. Thepretreatment of metal structure, welding process and mechanical product thermeltreatment process in cane factory would generate large amounts of "three wastes" which contain As, Pb, Cd and Cu, and their maximum values were45.74mg·kg-1,705.01mg·kg-1,41.93mg·kg-1,306.94mg·kg-1, respectively. The main heavy metalpollutants in iron-steel industry was the ash that contain particle of As which emitted from blast furnace smelting, and chromium workshop section and filteringsection of metal leaching brought up waste water(contains Cr ions), their biggest values were37.68mg·kg-1,236.84mg·kg-1for As and Cr, respectively. The highest content of As was53.23mg·kg-1generated by ash in thermal power plant whichstands for its major pollution. However, the calcium carbide process of polyvin yl chloride(PVC) in chemical industry produces contained Hg "three wastes", with the maximum value of1.98mg·kg-1.(3)Results of source identification of heavy metals revealing these elementsoriginated from different industrial activities, the main origins were metal smelting,galvanization passivation, chimneys and polyvinyl chloride process.(4)The health risk assessment showed that if the polluted areas were planned asresidential and public land, chemical industry and iron-steel industry both should payattention to the noncarcinogenic and carcinogenic risk of As and Cr. Theirnoncarcinogenic risk or carcinogenic risk is2.17,2.07and1.09,1.80or1.49×10-4,1.43×10-4and1.09×10-2,1.80×10-2. And thermal power industry should pay attention tothe noncarcinogenic and carcinogenic risk of As due to its high value of2.93and2.02×10-4, respectively. While the non-ferrous metal smelting industry should addattention to the noncarcinogenic and carcinogenic risk for As, Cr and Cd, andnoncarcinogenic risk for Pb. However, As for both noncarcinogenic(2.52) andcarcinogenic risk(1.73×10-4), Cd for carcinogenic risk(3.45×10-5) and Pb fornoncarcinogenic risk(2.82) should be focused on in cane factory. In the case that theseareas were planned as commercial service and industrial land, chemical industry,iron-steel industry should pay attention to the carcinogenic risk for As(3.83×10-5、2.08×10-5) and Cr(2.76×10-3、4.54×10-3). Moreover, the thermal power industry andmachinery industry should pay attention to carcinogenic risk for As(2.93×10-5and2.52×10-5, respectively), non-ferrous metals smelting industry for As(3.83×10-5),Cr(4.74×10-3) and Cd(1.78×10-5). |
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