沉积物
镉
环境化学
尾矿
酸性矿井排水
风化作用
地质学
水文学(农业)
污染
地球化学
微量金属
环境科学
金属
化学
地貌学
生态学
生物
物理化学
有机化学
岩土工程
作者
Wenjun Yang,Kengbo Ding,Peng Zhang,Hao Qiu,Christophe Cloquet,Hao Wen,Jean-Louis Morel,Rongliang Qiu,Yetao Tang
标识
DOI:10.1016/j.scitotenv.2018.07.210
摘要
The pollution of natural waters and sediments with metals derived from acid mine drainage (AMD) is a global environmental problem. However, the processes governing the transportation and transformation of AMD metals such as Cd in mountainous areas are poorly understood. In this study, the Cd isotopic composition and Cd concentration of river water and sediments (16 sampling sites) from an AMD-affected river in southern China were determined. Cd concentration in river water declined from its source at a tailings dam (304 μg L-1) to a point 14 km downstream (0.32 μg L-1). Sediment Cd concentration ranged from 0.18 to 39.9 μg g-1, suggesting that anthropogenic Cd is derived primarily from the tailing dam and easily enters the solid phase of the river. Isotopic data showed that the dissolved Cd in rivers was characterized by δ114/110Cd values ranging from 0.21‰ to 1.03‰, with a mean of 0.48‰. The greatest Cd isotope difference was observed between the water and sediments in the LW dam (Δ114/110Cdriver-sediment = 1.61‰, site 1), likely due to a rapid weathering dissolution of the ore tailings. In the river's upper reach (sites 2-3), isotope difference between river and sediment (Δ114/110Cdriver-sediment) ranged from 1.0‰ to 0.91‰. This suggests that a host of secondary processes might have impacted Cd isotope fractionation, including adsorption, ternary complexation and/or (co)precipitation of Cd on secondary oxides and hydroxides. In the middle and lower reaches, an abruptly elevated δ114/110Cd value near farmland (site 10) suggests the existence of a second Cd source. Based on the chemical properties of water samples we can attribute this heavy isotope signature to agricultural fertilizer and drainage from agricultural fields. Our results suggest that Cd isotope is a tracer for identifying and tracking Cd sources and attenuation mechanisms (adsorption/(co)precipitation) in a complex mountain watershed.
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