Natural organic matter affects arsenic speciation and sorption onto hematite
Natural organic matter affects arsenic speciation and sorption onto hematite
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DOI：
10.1021/es0112801
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发表时间：
2002-07-01
影响因子：
11.4
通讯作者：
Ahmann, D
中科院分区：
文献类型：
--
作者：
Redman, AD;Macalady, DL;Ahmann, D
自然环境中砷的流动性主要由金属氧化物表面的吸附控制，并且这种吸附的程度可能会受到与表面或砷本身相互作用的其他溶解物质的存在的强烈影响。天然有机物（NOM）是天然沃茨的主要成分，对金属和表面具有高度反应性，因此是影响砷迁移率的明显候选物。因此，本研究的目的，是揭示不同的，NOM样品上的吸附的影响，砷到赤铁矿，模型金属氧化物，以及揭示砷对NOM的吸附的影响，使用的条件和浓度相关的天然淡水环境的六个NOM样品测试，四个形成的水络合物与砷酸盐和亚砷酸盐。络合的程度随NOM来源而变化，特别是随NOM样品的阳离子金属（主要是Fe）含量而增加。此外，每个NOM样品对砷物种表现出活跃的氧化还原行为，表明NOM可能会极大地影响淡水环境中砷的氧化还原和络合形态。当NOM和As与赤铁矿一起孵育时，NOM显著延迟了吸附平衡的实现，并降低了砷酸盐和亚砷酸盐的吸附程度。与此结果相一致，当NOM和作为顺序引入时，所有NOV样品从赤铁矿表面置换吸附的砷酸盐和亚砷酸盐，砷物种同样显示从赤铁矿吸附NOM的显着数量。NOM和As之间的吸附竞争，因此似乎是，在自然沃茨中的一个潜在的重要过程，这表明NOM可能发挥更大的作用，砷的流动性比以前认识到的。此外，在所有的吸附实验中，亚砷酸盐始终解吸或阻止吸附到更大的程度比砷酸盐，表明与NOM的相互作用也可以部分解释一般更大的流动性亚砷酸盐在自然环境中。
Arsenic mobility in natural environments is controlled primarily by 'sorption onto-metal oxide surfaces, and the extent of this sorption may be influenced strongly by the presence of other dissolved substances that interact with surfaces or with arsenic itself. Natural organic matter (NOM), a prevalent constituent of natural waters, is highly reactive toward both metals and surfaces and is thus a clear candidate to influence arsenic mobility. The objectives of this study, were therefore to reveal the influences of diverse,NOM samples on the sorption,of arsenic onto hematite, a model metal oxide, as well as to reveal influences of arsenic on the sorption of NOM, using conditions and concentrations relevant to natural freshwater environments Of the six NOM samples tested, four formed aqueous complexes with arsenate and arsenite. The extent of complexation varied with NOM origin and, in particular, increased with the cationic metal (primarily Fe) content of the NOM sample. In addition, every NOM sample showed active redox behavior toward arsenic species, indicating that NOM may greatly influence redox as well as complexation speciation of arsenic in freshwater environments. When NOM and As were incubated together with hematite, NOM,dramatically delayed the attainment of sorption equilibrium and diminished the extent of sorption of both arsenate and arsenite. Consistent with this result, when NOM and As were introduced sequentially, all NOV samples displaced sorbed arsenate and arsenite from hematite surfaces, and arsenic species similarly displayed sorbed NOM from hematite in significant quantities. Competition between NOM and As for sorption thus appears to be,a potentially important process in natural Waters, suggesting that NOM may play a greater role in arsenic mobility than previously recognized. In addition, in all,sorption experiments, arsenite was consistently desorbed or prevented from sorbing to a greater extent than arsenate, indicating that interactions with NOM may also partially explain the generally greater mobility of arsenite in natural environments.