Geochemical distribution of arsenic in waters, sediments and weathered gold mineralized rocks from Iron Quadrangle, Brazil
Geochemical distribution of arsenic in waters, sediments and weathered gold mineralized rocks from Iron Quadrangle, Brazil
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DOI：
10.1007/s00254-002-0733-6
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发表时间：
2003-05-01
期刊：
影响因子：
--
通讯作者：
Matschullat, J
中科院分区：
文献类型：
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作者：
Borba, RP;Figueiredo, BR;Matschullat, J
铁四合院一直是巴西最重要的黄金生产地。据估计，在铁四合院三个世纪的金矿开采过程中，至少有39万吨砷被排放到排水系统中。本研究提供了该地区三个河流流域的地球化学数据，重点是地表水和河流沉积物监测。还研究了主要金矿的原生和氧化硫化矿以及尾矿和地下水样品。水和水系沉积物中砷浓度最高的地方是矿区附近。在地表水中，发现的砷含量高达300微克/升，而溪流沉积物中的砷含量在20至4，000毫克/公斤范围内。某些水样的As ~（3+）/As ~（5+）浓度比为1.10（-1）~ 4.10（-2）。通过观察黄铁矿和毒砂的原位氧化、臭葱石和三斜方铝石的沉淀、As在针铁矿上的吸附以及As最终释放到地下和地表沃茨中的过程，可以追踪到与矿床风化有关的As的活动性。这一过程可能会产生大量的矿井废水，其中总砷和三价砷分别高达1,960和60 mug/l。河流沉积物和尾矿堆样品提交的浸出过程中显示最大的砷释放量从1至4%的原始总砷的样品。在某些地区，存在砷危害的潜在风险，例如，老尾矿因洪水而分散，定居点占用有毒土壤，以及偶尔消耗受污染的地表水和地下水。
The Iron Quadrangle has been the scenery of the most important gold production in Brazil. It is estimated that during the three centuries of gold mining in the Iron Quadrangle, at least 390,000 t of arsenic was discharged into the drainage system. This study presents geochemical data for the three river basins in the region, with focus on surface water and stream sediment monitoring. Samples of primary and oxidized sulfide ores as well as of tailings and groundwater from the major gold mines were also studied. The highest As concentrations in water and stream sediments occur in the vicinity of mining areas. In surface water, up to 300 mug As/l were found whereas the As contents in stream sediments were in the range of 20 to 4,000 mg/kg. The As3+/As5+, concentration ratios obtained for some water samples range from 1.10(-1) to 4.10(-2). The As mobility associated with ore-deposit weathering could be traced in some closed gold mines by observation of in-situ pyrite and arsenopyrite oxidation, precipitation of scorodite and gippsite, As adsorption onto goethite, and final liberation of As into underground and surface waters. This process is likely to produce large volumes of mine effluents containing total As and trivalent As up to 1,960 and 60 mug/l, respectively. River sediments and tailings pile samples were submitted to a leaching procedure showing maximal arsenic release from 1 to 4% of the original total As in the samples. There are potential risks for As hazards in some areas induced by, for instance, the dispersion of old tailings by flooding, occupation of poisoned soils for settlements, and occasional consumption of contaminated surface and groundwater.