| Mineral resources are necessary to the human society, but it’s inevitably to lead all kinds of environmental problems, especially heavy metal pollution during its exploitation. Some pyrite mine in the west of Guangdong was selected as the research object in this paper. Water, sediments, soils, peanut of mining area and its downstream were collected. Total amount of elements in all the samples, speciation of elements in sediments and root soils were analyzed. Distribution and migration characteristics of Cd, Cr, Cu, Pb and Zn in mining area and its downstream were studied. The pollution degrees of heavy metals in different media were evaluated by utilizing different assessment method. The primary results of this study as follows:(1) Compared to The standards for Irrigation Water Quality, all the concentrations of Cd, Cr, Cu, Pb and Zn in mining area exceeded both, and pH of water lied between2.4-3.7which is acid. Content of Cd in polluted river downstream of mine tailing exceeded the both two standards.(2) The results of single factor and comprehensive pollution index showed that, Cd, Cr, Cu, Pb and Zn in mining area and polluted river downstream mine tailing were seriously pollution; Cd, Zn downstream of mining area were slight pollution. Surface soils were not polluted by Cr; mining area and its downstream were polluted by Cd, Cu, Pb and Zn; farmland downstream of mine tailing was polluted by Cd, Cu and Zn. Soils of different levels in the farmland downstream of mine tailing were polluted by Cd and Cu, and Cd pollution was more serious; Cd was only enriched in surface soil downstream of quarry, and Cd was slight pollution.(3) Compared to background values of elements in Guangdong Province and China, concentrations of Cd, Cu, Pb and Zn in sediments downstream of mine tailing exceeded both, and superstandard multiple of Cd was the highest; concentrations of Cd, Cu, Pb and Zn in sediments of Xijiang River didn’t exceed background values. Cr in root soils didn’t exceed both; concentrations of Cd, Cu, Pb and Zn in root soils downstream of mining area and mine tailing were higher than others.(4) Cd, Cr, Cu, Pb and Zn in sediments were dominated by residual fraction; available state of Pb and Zn in polluted river downstream of mine tailing were higher, and the environment risk of five elements is:Zn>Pb>Cr>Cd>Cu; available state of Cd in Xijiang River was higher, and the environment risk of five elements is:Cd>Zn> Pb>Cu>Cr; the results of RAC and SQG showed that, heavy metal pollution in sediments downstream of mine tailing was more serious than Xijiang River. Cd, Cr, Cu, Pb and Zn in root soils were dominated by residual fraction; the sum of carbonate, Fe-Mn oxides and organic matter form was larger in some samples; labile phases proportion of the five elements as followed:Pb>Cu>Zn>Cr>Cd.(5) With the increase of depth, most elements in the soil profile changed little; Pb downstream of quarry was declining trend.(6) The geochemical migration of heavy metals in mining area and its downstream showed that, the influence of the three probable polluted sources:mining area, mine tailing and quarry, to the downstream were limited; concentrations of Cd, Cr, Cu, Pb and Zn in water and surface soils outside of the three sources were lower, and the pollution level of the five elements was low.(7) Compared to Sanitary Standard of Food, content of Cr in fruit didn’t exceed the standard; content of Cd in fruit downstream of mine tailing exceeded the standard; contents of Cu and Pb in fruit downstream of mining area and mine tailing exceeded the standard; content of Zn in fruit nearby the city exceeded the standard.(8) The total amount of elements in root soils more higher, the higher content of various form. The content of various forms in root soil was strongly influenced by the total amount of element.(9) Assessment of potential ecological risk of heavy metals in root soil showed that, the pollution degree of Cd, Cr, Cu, Pb and Zn in the farmland downstream of mine tailing were different, and pollution of Cd was serious.(10) content of Cr, Pb in fruit changed with their total amount, effective state in root soils a little. On the contrary, content of Cd, Cu, Zn in fruit change with their total amount, effective state in root soils greatly. |
