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

长期以来，重金属对水生环境的污染一直被认为是与污染水接触的生物的主要威胁。在矿区形成的酸性矿井排水（AMD）经常将大量的HMs排放到当地河流中，然后被有毒金属污染。西班牙韦尔瓦省的里约热内卢Tinto河地区被认为是世界上污染最严重的河流河口系统之一，因此引起了极大的兴趣。根据里约热内卢Tinto盆地的拓扑、地质和地球化学特征，将其划分为两个3个带：北部地区的水文地球化学参数稳定，平均pH为2.3，溶液中Fe浓度较高；河口地区的日pH梯度在2.5 ~ 6.8之间；尽管pH值偏酸，HM含量高，但里约热内卢Tinto的特点是具有高水平的微生物Fe（II）氧化活性，可以刺激Fe（III）的沉淀，从而通过与Fe（III）矿物共沉淀或吸附来加速HM的阻滞过程。本提案的第一个目标是确定时空pH波动对铁（II）氧化微生物丰度和活性的影响，并评估pH波动是否以及如何刺激或抑制过渡区嗜酸铁（II）氧化微生物的活性。第二个目标是确定过渡带的pH动态是否影响甚至控制由非生物和生物铁（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北部地区和过渡带HMs的命运和运输。这个项目的结果将帮助我们了解HM迁移的变化模式，不仅在里约热内卢Tinto的过渡带，而且在其他受HM污染的前矿区。

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.