Accumulation of uranium and heavy metals in the soil-plant system in Xiazhuang uranium ore field, Guangdong Province, China.

Plants that have grown for many years in the special environmental conditions prevailing in mining areas are naturally screened and show strong capacity to adapt to their environment. The present study investigated the enrichment characteristics of U and other heavy metals (As, Cu, Pb, Mn, Mo, Zn, Cd, Co, and Ni) in the soil-plant system in Xiazhuang uranium mine. Four dominant plants (Castanopsis carlesii, Rhus chinensis, Liriodendron chinense, and Sapium discolor) and soil samples were collected from the mined areas, unmined areas, and background areas away from the ore field. U, As, Cu, Pb, Mn, Mo, Zn, Cd, Co, and Ni concentrations were analyzed by ICP-MS. The results demonstrate that (1) The highest concentrations of U (4.1-206.9 mg/kg) and Pb (43.3-126.0 mg/kg) with the geoaccumulation index (Igeo) greater than 1 show that they are the main soil pollutants in the research area. (2) The biological accumulation coefficient (LBAC) values for Cd, Mn, and Cu are greater than zero in S. discolor, L. chinense, and C. carlesii and these three plants indicate that they can be used for remediation of the soil in the ore field. (3) R. chinensis inhibits the accumulation of heavy metals and shows sensitive pigment responses to the accumulation of U in the leaves. L. chinense has the strongest enrichment effect on heavy metals but exhibits weak biochemical responses under U stress. C. carlesii demonstrates strong adaptation to U and can maintain healthy pigment characteristics in case of high U enrichment. (4) S. discolor, L. chinense, C. carlesii and R. chinensis have strong tolerance to U toxicity and different biochemical responses.

Biogeochemistry of Dominant Plants and Soils in Shewushan Gold Lateritic Deposit, China.

This paper describes the effect of mineral elements on dominant plants in the Shewushan lateritic gold deposit, China. For this purpose, 30 soil profile samples at different depths and 3 kinds of dominant plants including Populus canadensis (Populus X canadensis Moench), Cinnamomun camphora (Cinnamomum camphora (L.) Presl.) and Rhus chinensis (Rhus chinensis Mill.) were collected. The concentration of ore-forming elements including Au, Ag, Pb, Zn, Cu, As, Fe, and S were analyzed. Based on the investigation of two mine profiles, it can be found that Au, Pb, As, and Fe were mainly enriched in laterite layer and the brown clay layer at a depth of 5-11 m. Moreover, the biological accumulate coefficient (BAC) and the contrast coefficient (CM) were calculated to assess the sensitivity and concentrating ability of Populus canadensis and Cinnamomun camphora. To investigate the response of the two species to metal stress, the contents of chlorophyll, malondialdehyde (MDA), and activities of superoxide dismutase (SOD) and peroxidase (POD) were determined. The result showed that Populus canadensis and Cinnamomun camphora have a high tolerance to metal stress and that both of the two species can indicate the content of Au, As, Pb, and Co in topsoil.

Health risk assessment of heavy metals in the soil-water-rice system around the Xiazhuang uranium mine, China.

Heavy-metal pollutants in the soil and surface water of agricultural areas accumulate in rice and may have adverse effects on the health of consumers. In this study, we determined the levels of heavy-metal contamination in agricultural areas around the Xiazhuang uranium deposits in northern Guangdong Province, China, using equidistant sampling methods along a river near the mine tailings. The pH values of all the water samples were determined. The heavy-metal concentrations in water, bottom sludge, and rice were measured. The extent of contamination was evaluated by calculating Nemerow's pollution index, contamination factor, and hazard quotient. The result shows U transferred from mine to soil and rice with irrigation water. The main pollutants and their pollution indices in soil are U (6.31), Th (4.02), Pb (2.52), Cd (2.36), Zn (1.52), and Mn (1.39). The rice grain can hardly enrich U and Th but were susceptible to Cr and Ni. The contamination factors (CFs) of the pollutants in rice grain are Cr (1.98) and Ni (3.09). The hazard quotient (HQ) shows that Cu (HQ > 1) could pose potential risks for humans upon long-term consumption of the rice.