Use of sequential extraction and mercury stable isotope analysis to assess remobilization of sediment-bound legacy mercury,Environmental Science: Processes & Impacts

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Use of sequential extraction and mercury stable isotope analysis to assess remobilization of sediment-bound legacy mercury
Environmental Science: Processes & Impacts ( IF 4.3 ) Pub Date : 2021-4-29 , DOI: 10.1039/d1em00019e
Elizabeth R. Crowther _{1,

2,

3,

4} , Jason D. Demers _{1,

2,

3,

4} , Joel D. Blum _{1,

2,

3,

4} , Scott C. Brooks _{4,

5,

6,

7} , Marcus W. Johnson _{1,

2,

3,

4}

Affiliation

The goal of this project was to assess how anthropogenic legacy mercury (Hg) retained in streambed sediment may be remobilized to stream water. To do this, we performed sequential extractions and Hg isotope analyses on streambed sediment collected along the length of East Fork Poplar Creek, a point-source contaminated stream in Oak Ridge, Tennessee, USA. Legacy Hg within streambed sediment appears to have been isotopically fractionated by equilibrium isotope effects driven by isotope exchange between co-existing Hg(0) and Hg(II) species, potentially over-printing fractionation patterns that would have been imparted by kinetic redox reactions. Weakly-bound and recalcitrant sediment Hg pools were isotopically similar to one another, suggesting that small amounts of recalcitrant Hg may be released and then rapidly and weakly re-adsorbed onto the sediment. This weakly-bound Hg pool appears to contribute dissolved Hg to the hyporheic pore water, which may subsequently enter the surface flow. The isotopic composition of the organically-bound sediment Hg pools, as well as biofilm and suspended particulates, converged with that of the weakly-bound and recalcitrant sediment Hg pools along the flow path. This appears to be indicative of both physical mixing with streambed sediment and the transfer of weakly-bound sediment Hg into biofilm and suspended particulates, followed by re-incorporation into the organically-bound sediment Hg pool. Overall, these results provide evidence that legacy Hg in the streambed is remobilized, enters the stream water as dissolved Hg, and may be incorporated into streambed biofilm, which constitutes a basal resource within the stream ecosystem.

中文翻译：

使用顺序萃取和汞稳定同位素分析来评估与沉积物结合的传统汞的迁移

该项目的目的是评估如何将流化沉积物中残留的人为遗留汞（Hg）转移到流水中。为此，我们对沿美国东田纳西州橡树岭受点源污染的东叉白杨溪长度收集的河床沉积物进行了连续萃取和汞同位素分析。河床沉积物中的传统Hg似乎已通过平衡同位素效应进行了同位素分馏，该平衡同位素效应是由共存的Hg（0）和Hg（II）之间的同位素交换驱动的）物种，可能是由动力学氧化还原反应赋予的可能过度印刷的分馏图案。弱结合和顽固的沉积物汞池在同位素上彼此相似，这表明少量的顽固性汞可能会释放出来，然后迅速而微弱地重新吸附到沉积物上。该弱结合的汞池似乎为溶解的孔隙水贡献了溶解的汞，该水随后可能进入地表流。有机结合的沉积物汞池，生物膜和悬浮颗粒的同位素组成与沿流动路径弱结合的顽固性沉积物汞池的同位素组成趋同。这似乎表明与流化沉积物进行了物理混合，以及弱结合的沉积物Hg转移到生物膜和悬浮颗粒中，然后将其重新结合到有机结合的沉积物汞池中。总体而言，这些结果提供了证据，表明河床中的残留Hg被清除，以溶解的Hg的形式进入河水中，并可能并入河床生物膜中，而河床生物膜构成了河水生态系统的基础资源。

更新日期：2021-05-10

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