Downstream patterns of bed sediment-borne metals,minerals and organic matter in a stream system receiving acidic mine effluent: A preliminary study |
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| Authors: | Yingqun Ma Wenzhou Lu Chuxia Lin |
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| Institution: | 1. Centre for Ecological and Environmental Technologies, South China Agricultural University, Guangzhou 510642, China;2. South China Institute of Environmental Science, Guangzhou 510655, China;3. Australian Centre for Sustainable Catchments, University of Southern Queensland, Toowoomba, QLD 4350, Australia |
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| Abstract: | Different downstream variation patterns were observed for a range of bed sediment-borne metals (aqua regia-extractable fraction) in a subtropical stream system receiving acid mine drainage. Mine-originated Fe tended to be deposited in the acidic (mean pH < 4.9) upstream reach in forms of goethite and/or hematite. In contrast, other metals tended to be transported farther downstream and settled in a low-gradient reach with high pH (mean pH > 5.6). The peak of sediment-borne Al, Be, Ca, Cd, Co, Cu, La, Mn, Ni and Zn corresponded very well with the peak of the sediment-borne organic matter, suggesting a close association between the water-borne organic colloids and the inorganic metal oxides/hydroxides during their transport. The marked increase in the sediment-borne Al and Pb started more upstream than the other metals, suggesting that the water-borne Al and Pb were more susceptible to pH rise-induced precipitation, as compared to the other metals. It appeared that the organic colloids played no important role in Pb transport and settlement. The iron precipitates had a limited role to play in affecting the transport and fates of other metals since they were predominantly formed and deposited in the acidic reach, which made them incapable of scavenging cationic metals by co-precipitation or adsorption. |
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| Keywords: | Streambed sediment Acid mine drainage Heavy metal Spatial variation Mineral Organic matter |
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