4.4 Article

Tracing the Origin and Evolution of Geochemical Characteristics of Waters from the Candiota Coal Mine Area (Southern Brazil): Part I

期刊

MINE WATER AND THE ENVIRONMENT
卷 35, 期 1, 页码 29-43

出版社

SPRINGER HEIDELBERG
DOI: 10.1007/s10230-015-0330-z

关键词

Acid mine drainage (AMD); Water-rock interaction; Hydrogeochemistry; Geochemical modeling; Brazilian coal mine

资金

  1. Brazilian National Research Council (CNPQ) [472766/2003-1]

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This work correlates surface and ground water composition to the substrata, and traces how water chemistry evolves at Brazil's largest coal mine, the Candiota Mine. The water is dominated by SO4, Fe, Ca, and Mg. A pH range of 2.7-3 in the pit lakes is attributed through chemical models to concomitant pyrite oxidation and carbonate dissolution along with slow hydrolysis of aluminosilicate minerals and buffering provided by several iron oxy-hydroxide species. The Fe deficit of the surface water relative to the expected values is mainly due to precipitation of Fe sulfate salts, hydroxysulfates, and oxyhydroxides in the waste piles and their runoff. A progressive decrease in oxygen partial pressure with increased lake depth leads to destabilization of the iron oxyhydroxides/hydroxysulfates formed near the surface, which explains their absence from the lake sediment. Although interacting with similar rock types, the groundwater has a significantly different composition than the surface water, with less salinity and a pH of 5-6.5, due to limited oxygen and its evolution in a nearly closed system that stabilizes at higher pH values, which is controlled by carbonate/bicarbonate buffering.

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