关键词: 铀矿区, 农田土壤, 重金属, 赋存形态, 生物有效性

Abstract: In order to explore the bioavailability of heavy metals in farmland soil near a uranium mining area, the samples of farmland soil near mining area, smelter and tailings dam were collected as the research object to analyze the physical and chemical properties of the soil and the improved BCR four-step extraction method was applied to evaluate the bioavailability of the heavy metals (Pb, Cd, Cr, Cu) and U in the farmland soil. The results show that the farmland soil in the study area is acidic; the organic matter content of the farmland soil in different locations followed the order of: tailing dam > smelter > mining area; The forms of heavy metals in the farmland soil are dominated by the residue state; The content of bioavailable form of the heavy metal elements (Pb, Cd, Cr and Cu) accounted for 27%-42% of the total content of heavy metals, and the content of bioavailable form of radionuclide U was 43%-45% of the total content of U; the enrichment coefficients of heavy metals (Cr, Cd, Cu and Pb) for crops grown at different locations followed the order of: mining area > smelter > tailing dam; Compared with the adsorption of the other heavy metals, the adsorption of U by crops in all locations was the strongest. In summary, the bioavailability of heavy metals in farmland soil is comprehensively affected by factors such as pH, organic matter content, and bioavailable content of heavy metals. The stronger the bioavailability of heavy metals, the greater the ecological risk they cause; The bioavailability of the heavy metals (Cr, Cd, Cu, and Pb) in farmland soil of different locations followed the order of: mining area > smelter > tailing dam; U had the strongest bioavailability in farmland soils of different locations; due to the influence of uranium ore extraction, U in the smelter had a higher bioavailability than in other study areas. Though, the crops in the tailings dam farmland have poor enrichment effect on heavy metal elements, while considering the high content of heavy metals in the soil of this location, the ecological risks brought by it are also worthy of attention. The research results can provide an important theoretical basis for the scientific and biological control of heavy metal pollution in mining areas in the future.

Key words: uranium mining area, farmland soil, heavy metal, occurrence form, bioavailability