Surficial weathering of iron sulfide mine tailings under semi-arid climate.
Surficial weathering of iron sulfide mine tailings under semi-arid climate.
复制标题
DOI：
10.1016/j.gca.2014.05.030
复制
发表时间：
2014-09-15
影响因子：
5
通讯作者：
Chorover, Jon
中科院分区：
文献类型：
--
作者：
Hayes, Sarah M.;Root, Robert A.;Perdrial, Nicolas;Maier, Raina M.;Chorover, Jon
矿山废弃物将人为风化剖面引入临界带，该临界带在采矿停止后的几十年里往往没有植被。因此，它们很容易受到风和水的影响，颗粒物会扩散到邻近的生态系统和居民社区。在富硫化物尾矿中，氧化风化锋向深度的扩展控制着主微量元素形态的深度变化。尽管全球干旱地区普遍存在地表矿山废弃物，但对半干旱气候下硫化矿尾矿近地表风化剖面的研究较少。在美国亚利桑那州中部半干旱地区的一个EPA超级基金站点，研究了半干旱气候下风化尾矿中铁和硫分子形态与氧化反应锋传播的关系。本文采用湿化学和同步加速器x射线衍射（XRD）和x射线吸收近边光谱（XANES）相结合的多方法数据集，分析了尾矿顶部2 m中铁（Fe）和硫(S)地球化学变化的紧密耦合。尽管Fe和S浓度随深度（分别为130-140和100-120 g kg - 1）几乎不变，但在顶部0.5 m内观察到明显的氧化还原梯度和明显的形态变化，这与硫化铁逐渐氧化转变为（氧）氧化物和（羟基）硫酸盐有关。表面样品的转变几乎完成。分子尺度变化的趋势与pH从7.3降至2.3以及化学萃取测量的铁和硫稳定性的变化同时发生。最初的风化产物水合铁和石膏转变为许氏锰矿，然后随着pH值的降低而转变为黄钾铁矾群矿物。有趣的是，在任何样品中都没有检测到针铁矿和赤铁矿等热力学稳定相，但即使在最低pH值的样品中也观察到水合铁，表明其在这些半干旱尾矿中的亚稳持久性。由此产生的靠近尾矿表面的尖锐的地球化学物种形成梯度对植物定植以及共同相关的有毒金属（样金属）的流动性和生物利用度具有重要意义。
Mine wastes introduce anthropogenic weathering profiles to the critical zone that often remain unvegetated for decades after mining cessation. As such, they are vulnerable to wind and water dispersion of particulate matter to adjacent ecosystems and residential communities. In sulfide-rich ore tailings, propagation to depth of the oxidative weathering front controls the depth-variation in speciation of major and trace elements. Despite the prevalence of surficial mine waste deposits in arid regions of the globe, few prior studies have been conducted to resolve the near-surface profile of sulfide ore tailings weathered under semi-arid climate. We investigated relations between gossan oxidative reaction-front propagation and the molecular speciation of iron and sulfur in tailings subjected to weathering under semi-arid climate at an EPA Superfund Site in semi-arid central Arizona (USA). Here we report a multi-method data set combining wet chemical and synchrotron-based X-ray diffraction (XRD) and X-ray absorption near-edge spectroscopy (XANES) methods to resolve the tight coupling of iron (Fe) and sulfur (S) geochemical changes in the top 2 m of tailings. Despite nearly invariant Fe and S concentration with depth (130–140 and 100–120 g kg−1, respectively), a sharp redox gradient and distinct morphological change was observed within the top 0.5 m, associated with a progressive oxidative alteration of ferrous sulfides to (oxyhydr)oxides and (hydroxy)sulfates. Transformation is nearly complete in surficial samples. Trends in molecular-scale alteration were co-located with a decrease in pH from 7.3 to 2.3, and shifts in Fe and S lability as measured via chemical extraction. Initial weathering products, ferrihydrite and gypsum, transform to schwertmannite, then jarosite-group minerals with an accompanying decrease in pH. Interestingly, thermodynamically stable phases such as goethite and hematite were not detected in any samples, but ferrihydrite was observed even in the lowest pH samples, indicating its metastable persistence in these semiarid tailings. The resulting sharp geochemical speciation gradients in close proximity to the tailings surface have important implications for plant colonization, as well as mobility and bioavailability of co-associated toxic metal(loid)s.
登录
查看更多内容
影响因子：
3.3
作者：
Fittschen, U. E. A.;Meirer, F.;Pepponi, G.
通讯作者：
Pepponi, G.
影响因子：
11.4
作者：
Hayes, Sarah M.;Webb, Sam M.;Bargar, John R.;O'Day, Peggy A.;Maier, Raina M.;Chorover, Jon
通讯作者：
Chorover, Jon
影响因子：
5
作者：
COMBES, JM;MANCEAU, A;BOTTERO, JY
通讯作者：
BOTTERO, JY
影响因子：
5
作者：
Couture, Raoul-Marie;Gobeil, Charles;Tessier, Andre
通讯作者：
Tessier, Andre
影响因子：
9.8
作者：
Csavina, Janae;Field, Jason;Taylor, Mark P.;Gao, Song;Landazuri, Andrea;Betterton, Eric A.;Saez, A. Eduardo
通讯作者：
Saez, A. Eduardo