Heavy metal geochemistry of the acid mine drainage discharged from the Hejiacun uranium mine in central Hunan, China

Effect of weathering on abundance and release of potentially toxic elements in soils developed on Lower Cambrian black shales, P. R. China

“…Deposits exploited in the county include P, Mn, V, U, W, Au, Sb, and stone coals, and most of these ore deposits are hosted in the lower Cambrian black shales (Peng et al 2005(Peng et al , 2009b. Because the black shales were formed under anoxic seawater conditions, they are generally enriched with several metals including Cd, Mo, Sb, V, U, Ba, Cu, Pb, and Zn, which were precipitated or fixed into sulfide minerals and organic materials during deposition (Horan et al 1994;Ž ák et al 2003;Peng et al 2005Peng et al , 2009a. The black shales are mostly organic-rich carbonaceous or siliceous shales.…”

“…The black shales are mostly organic-rich carbonaceous or siliceous shales. The mineral composition constitutes mainly of quartz, muscovite, kaoline, clinochlore, dolomite, calcite, organic matter, and sulfide (mainly pyrite), with minor microcline, albite, opal, limonite, goethite, and gibbsite (Fan et al 1973;Huang 1989;Peng et al 2009a). Two black shale areas, the Dongping and the Yanxi areas of the county, were selected for this study (Fig.…”

“…In the Anhua county, located within this area, the black shale is an organic-rich carbonaceous shale and/or slate of the Lower Cambrian Niutitang Formation, with strata thickness of more than 260 m (Hrgi 1972) and an age of 541-560 Ma (Mao et al 2002;Horan et al 1994). After identification of spatial relationship between prevalence of endemics and black shale (Peng et al 2004), there have been studies focusing on chemical weathering of this bedrock type (Peng et al 2004(Peng et al , 2009a, analyses of acid rock drainage (Peng et al 2009b), the environmental impacts of waste rocks Peng et al 2007), and the enrichment of toxic elements in black shale soils Yu et al 2008Yu et al , 2009Peng et al 2009a). …”

“…Consequently, the toxic trace elements pose a threat to local human health by entering the food chain. These kinds of issues have previously been addressed by: (1) assessing the environmental contamination caused by black shale soils distributed in different parts of the world (e.g., Lee et al 1998a, b;Pašava et al 2003;Peng et al 2007Peng et al , 2009aYu et al 2008Yu et al , 2009); (2) determining the phases and species of the toxic metals in the soils (Poňavič et al 2006;Lee et al 1998b);and (3) assessing the possible impacts on ecological systems (Lee et al 1998a;Fang et al 2002;Pašava et al 2003;Peng et al 2009a) and on human health (Lee et al 1998b;Fang et al 2002;Peng et al 2004;Poňavič et al 2006).…”

Geochemistry of major and trace elements and Pb–Sr isotopes of a weathering profile developed on the Lower Cambrian black shales in central Hunan, China

“…Because of their high organic carbon and sulphide contents, black shales are susceptible to alteration when exposed, and thus mining in shales throughout the world has accelerated the weathering of these sedimentary rocks. The weathering of black shale is an important environmental concern because of the dispersion of toxic metals hosted by the shales; the production of acid mine drainage, which can harm the ecosystem due to oxidation of sulphides (e.g., Lee et al, 1998a,b;Pašava et al, 2003;Peng et al, 2004Peng et al, , 2009a; and the release of CO 2 , which may contribute to the global http://dx.doi.org/10.1016/j.apgeochem.2014.09.007 0883-2927/Ó 2014 Elsevier Ltd. All rights reserved. carbon cycle (e.g., Petsch et al, 2000Petsch et al, , 2001Jaffe et al, 2002).…”