Microbial Fe(II) oxidation and heavy metal co-precipitation in the Rio Tinto region, Spain

长期以来，重金属(HMS)对水环境的污染一直被认为是与受污染水接触的生物的主要威胁。在矿区形成的酸性矿山废水(AMD)经常将大量HMS排放到当地河流中，然后被有毒金属污染。位于西班牙韦尔瓦省的里约热托河地区被认为是世界上污染最严重的河流-河口系统之一，因此引起了人们的极大兴趣。根据里约热内卢盆地的拓扑、地质和地球化学特征，将其划分为两个三个带：北部带，水文地球化学参数稳定，平均pH值为2.3，溶液中铁含量较高；河口带，pH日梯度在2.5~6.8之间；尽管酸碱度高，HM含量高，但力拓的特点是微生物Fe(II)氧化活性高，可以刺激Fe(III)沉淀，从而通过与Fe(III)矿物共沉淀或吸附在Fe(III)矿物上来加速HM的迟滞过程。本提案的第一个目标是确定空间和时间上的pH波动对Fe(II)氧化微生物的丰度和活性的影响，并评估pH波动是否以及如何刺激或抑制过渡带中嗜酸性Fe(II)氧化微生物的活动。第二个目标是确定过渡带的pH动态是否影响甚至控制非生物和生物Fe(II)氧化产生的原生矿物的特性和组成。第三个目标是确定关键的生物地球化学过程(微生物和非生物Fe(II)氧化)和沉淀矿物的组成如何控制HMS在北部地区和过渡带的去向和运输。该项目的结果将帮助我们了解HM流动的变化模式，不仅在力拓过渡区，而且在HMS污染的其他前矿区也是如此。

Pollution of aquatic environments by heavy metals (HMs) has long been considered a major threat to living organisms that are in contact with contaminated water. Acid mine drainage (AMD) forming in mining regions often discharges substantial loads of HMs into local rivers, which then become contaminated with toxic metals. The Rio Tinto river region in the province of Huelva, Spain, is of great interest as it is considered to be one of the most polluted fluvial-estuarine systems in the world. The Rio Tinto basin is divided into two three zones based on topological, geological and geochemical characteristics: the northern region characterized by stable hydrogeochemical parameters with a mean pH of 2.3 and high concentrations of Fe in solution, the estuary with a daily pH gradient in the range of 2.5-6.8 and the transitional zone. Despite acidic pH and high HM content, the Rio Tinto is characterized by a high level of microbial Fe(II)-oxidizing activity that can stimulate Fe(III) precipitation and thus accelerate the process of HM retardation by co-precipitation with or by sorption onto Fe(III) minerals. The first goal of the present proposal is to determine the influence of the spatial and temporal pH fluctuations on the abundance and the activity of Fe(II)-oxidizing microorganisms and to evaluate if and how pH fluctuations stimulate or supress the activity of acidophilic Fe(II)-oxidizing microorganisms in the transitional zone. The second goal is to determine whether the pH dynamics in the transitional zone influence or even control the identity and composition of the primary minerals that are produced by abiotic and biotic Fe(II) oxidation. The third goal is to determine how the key biogeochemical processes (microbial and abiotic Fe(II) oxidation) and the composition of precipitated minerals control the fate and transport of HMs in the northern region and transitional zones. The results from this project will help us to understand changing patterns in HM mobility not only in the transitional zone of the Rio Tinto but also in other former mining areas contaminated with HMs.