The role of natural biogeochemical barriers in limiting metal loading to a stream affected by mine drainage
The role of natural biogeochemical barriers in limiting metal loading to a stream affected by mine drainage
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DOI：
10.1016/j.apgeochem.2016.11.020
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发表时间：
2017-01-01
影响因子：
3.4
通讯作者：
Kimball, B. A.
中科院分区：
文献类型：
--
作者：
De Giudici, Giovanni;Pusceddu, Claudia;Kimball, B. A.
圣乔治河（意大利撒丁岛伊格莱西恩特）是一条受废弃矿山废弃物影响的河流，其特征是河床植被茂密，主要由芦苇和灯心草组成。这些植被形成了天然的生物地球化学屏障，推动了矿化过程，并削弱了溪流中的金属负荷。采用了从微米到千米的几种技术来调查地球化学过程：水化学、注入的水文示踪剂、矿物学、显微镜调查和X射线光谱学。从这种多尺度和多方法的方法，我们认识到两个主要的生物地球化学过程：微生物驱动的金属硫化物沉淀，主要导致黄铁矿的形成;和植物吸收的金属，导致形成氧化铁氢氧化物和锌的根和地上部分（茎和叶）。里奥圣乔治河床中茂密的植被控制着其形态、水流速度，并且正如观察到的溴化物示踪剂损失所反映的那样，增强了河床和自流区之间的水交换。这些植物控制的综合作用是建立地球化学屏障，大大阻碍了微量金属的流动性在潜流带。我们估计这种效应可以导致锌负荷明显下降高达60%。(C)2016爱思唯尔有限公司版权所有
Rio San Giorgio (Iglesiente, Sardinia, Italy), a stream affected by abandoned mine wastes, is characterized by dense vegetation in the streambed, mainly comprised of Phragmites australis and Juncus acutus. This vegetation creates natural biogeochemical barriers that drive mineralization processes and attenuate metals load in the stream. Several techniques, covering scales from micrometres to kilometres, were applied to investigate the biogeochemical processes: water chemistry, injected hydrologic tracer, mineralogy, microscopic investigation and X-ray spectroscopy. From this multiscale and multimethod approach, we recognized two predominant sets of biogeochemical processes: microbially driven metal sulphide precipitation, mainly resulting in pyrite formation; and plant uptake of metals that leads to formation of iron oxide-hydroxide and incorporation of Zn within the roots and aerial part (stem and leaves). The dense vegetation in the Rio San Giorgio streambed controls its morphology, velocity of streamflow, and, as reflected by observed bromide-tracer loss, enhanced water exchange between the streambed and the hyporheic zone. The combined effect of these vegetative controls is to establish biogeochemical barriers that greatly retard trace-metal mobility in the hyporheic zone. We estimated this effect can lead to an apparent decrease in Zn load up to 60%. (C) 2016 Elsevier Ltd. All rights reserved.