pH dependence of iron photoreduction in a rocky mountain stream affected by acid mine drainage

被引:57
作者
McKnight, DM [1 ]
Kimball, BA
Runkel, RL
机构
[1] Univ Colorado, Boulder, CO 80303 USA
[2] US Geol Survey, Salt Lake City, UT 84104 USA
[3] US Geol Survey, Denver, CO 80225 USA
关键词
mountain stream; iron; hydrous metal oxides; photoreduction; reactive transport;
D O I
10.1002/hyp.251
中图分类号
TV21 [水资源调查与水利规划];
学科分类号
081501 ;
摘要
The redox speciation of dissolved iron and the transport of iron in acidic, metal-enriched streams is controlled by precipitation and dissolution of iron hydroxides, by photoreduction of dissolved ferric iron and hydrous iron oxides, and by oxidation of the resulting dissolved ferrous iron. We examined the pH dependence of these processes in an acidic mine-drainage stream, St Kevin Gulch, Colorado, by experimentally increasing the pH of the stream from about 4.0 to 6.5 and following the downstream changes in iron species. We used a solute transport model with variable how to evaluate biogeochemical processes controlling downstream transport. We found that at pH 6.4 there was a rapid and large initial loss of ferrous iron concurrent with the precipitation of aluminium hydroxide. Below this reach, ferrous iron was conservative during the morning but there was a net downstream loss of ferrous iron around noon and in the afternoon. Calculation of net oxidation rates shows that the noontime loss rate was generally much faster than rates for the ferrous iron oxidation at pH 6 predicted by Singer and Stumm (1970. Science 167: 1121). The maintenance of ferrous iron concentrations in the morning is explained by the photoreduction of photoreactive ferric species, which are then depleted by noon. Copyright (C) 2001 John Wiley & Sons, Ltd.
引用
收藏
页码:1979 / 1992
页数:14
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