Role of biogenic Fe(III) minerals as a sink and carrier of heavy metals in the Rio Tinto, Spain.
Role of biogenic Fe(III) minerals as a sink and carrier of heavy metals in the Rio Tinto, Spain.
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DOI：
10.1016/j.scitotenv.2020.137294
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发表时间：
2020-02
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通讯作者：
S. Abramov;J. Tejada;Lars Grimm;Franziska Schädler;A. Bulaev;E. Tomaszewski;J. Byrne;D. Straub;H. Thorwarth;R. Amils;S. Kleindienst;A. Kappler
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作者：
S. Abramov;J. Tejada;Lars Grimm;Franziska Schädler;A. Bulaev;E. Tomaszewski;J. Byrne;D. Straub;H. Thorwarth;R. Amils;S. Kleindienst;A. Kappler
伊比利亚硫铁矿带地区硫化矿石的氧化导致力拓酸性水中存在极高浓度的溶解重金属(HMS)。Fe(II)被微生物氧化，形成由微生物细胞和Fe(III)矿物与共沉淀HMS组成的悬浮颗粒物(SPM)。虽然大量含HM的SPM可能沉积到河流沉积物中，但仍有一部分可以通过河口输送到沿海海洋。因此，滨海-河口带底泥的形成和运移机制是非常重要的。为了揭示这些机制，我们对力拓河水进行了每日采样，并对中游和河口的沉积物进行了矿物学和元素分析。我们确定了两条不同但相互关联的HM转移途径。第一条纵向途径是As(6.58g/L)、Pb(3.51g/L)和Cr(1.30gμg/L)等与颗粒物相关的金属向近海的迁移。第二条沉积路径有助于HMS在整个河流的沉积物中持续埋藏。在中期，沉积物在早期成岩过程中经历了矿物学转化，并圈闭了HMS(如1.6 mg/g As、1.23 mg/g Pb和0.1 mg/g Cr)。在河口，HMS积累在一个明显的缺氧层中(例如，As 1.5 mg/g，Pb2.09 mg/g，Cr0.04 mg/g)。我们的结果表明，微生物沉淀的Fe(III)矿物(被鉴定为亚铁水合物和施维特曼尼特)在维持这些不同的HM途径方面发挥了关键作用，因此对力拓HM的流动性至关重要。
Oxidation of sulfide ores in the Iberian Pyrite Belt region leads to the presence of extremely high concentration of dissolved heavy metals (HMs) in the acidic water of the Rio Tinto. Fe(II) is microbially oxidized resulting in the formation of suspended particulate matter (SPM) consisting of microbial cells and Fe(III) minerals with co-precipitated HMs. Although substantial amount of HM-bearing SPM is likely deposited to river sediment, a portion can still be transported through estuary to the coastal ocean. Therefore, the mechanisms of SPM formation and transport along the Rio Tinto are important for coastal-estuarine zone. In order to reveal these mechanisms, we performed diurnal sampling of Rio Tinto water, mineralogical and elemental analysis of sediment from the middle course and the estuary of the river. We identified two divergent but interrelated pathways of HM transfer. The first longitudinal pathway is the transport of SPM-associated metals such as As (6.58 μg/L), Pb (3.51 μg/L) and Cr (1.30 μg/L) to the coastal ocean. The second sedimentation pathway contributes to the continuous burial of HMs in the sediment throughout the river. In the middle course, sediment undergoes mineralogical transformations during early diagenesis and traps HMs (e.g. 1.6 mg/g of As, 1.23 mg/g of Pb and 0.1 mg/g of Cr). In the estuary, HMs are accumulated in a distinct anoxic layer of sediment (e.g. 1.5 mg/g of As, 2.09 mg/g of Pb and 0.04 mg/g of Cr). Our results indicate that microbially precipitated Fe(III) minerals (identified as ferrihydrite and schwertmannite) play a key role in maintaining these divergent HM pathways and as a consequence are crucial for HM mobility in the Rio Tinto.