Electron accepting capacity of dissolved organic matter as determined by reaction with metallic zinc
Electron accepting capacity of dissolved organic matter as determined by reaction with metallic zinc
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DOI：
10.1016/j.chemgeo.2008.12.016
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发表时间：
2009-03
期刊：
影响因子：
3.9
通讯作者：
C. Blodau;M. Bauer;S. Regenspurg;D. Macalady
中科院分区：
文献类型：
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作者：
C. Blodau;M. Bauer;S. Regenspurg;D. Macalady
由于缺乏适用的方法，有关溶解有机物(DOM)的化学电子接受能力(EAC)的信息很少。我们在批量实验中定量了在DOC浓度为10-100M mg-C L−1下金属锌向天然DOM的电子转移，并将其与UV、同步荧光和傅里叶变换红外光谱获得的光谱信息进行了关联。以Fe(CN)63−为电子受体，考察了DOM和预还原态DOM的给电子能力。与金属锌与水在pH 6.5下的反应相比，DOM的存在导致了溶解锌的释放、质子的消耗和氢的释放。通过与反应化学计量学的比较，证实了DOM接受来自金属锌的电子。溶解态锌的释放与pH、DOC浓度、离子强度和有机质性质有关。反应在约2 4h内完成，反应符合准一级动力学，反应速率常数为0.5~0.8h−1，单位碳的EAc为0.2 2~12.6mmolg−1C。根据DOM的不同，计算出从金属锌转移到DOM的电子中有28%-127%可以随后捐赠给Fe(CN)63−。EAC随DOC浓度的增加而降低，随DOM的芳香度、羧基和酚类含量的增加而增加。结果表明，可以通过与金属锌的反应来定量天然DOM的EAc，并且DOM的性质控制着电子的转移。该方法的缺点是实验过程中DOM的凝聚和沉淀，以及金属锌与水反应生成氢和溶解锌，这可能会影响测定的EAC。
Information about the chemical electron accepting capacity (EAC) of dissolved organic matter (DOM) is scarce owing to a lack of applicable methods. We quantified the electron transfer from metallic Zn to natural DOM in batch experiments at DOC concentrations of 10–100 mg-C L−1and related it to spectroscopic information obtained from UV-, synchronous fluorescence, and FTIR- spectroscopy. The electron donating capacity of DOM and pre-reduced DOM was investigated using Fe(CN)63−as electron acceptor. Presence of DOM resulted in release of dissolved Zn, consumption of protons, and slower release of hydrogen compared to reaction of metallic Zn with water at pH 6.5. Comparison with reaction stoichiometry confirmed that DOM accepted electrons from metallic Zn. The release of dissolved Zn was dependent on pH, DOC concentration, ionic strength, and organic matter properties. The reaction appeared to be completed within about 24 h and was characterized by pseudo first order kinetics with rate constants of 0.5 to 0.8 h−1. EAC per mass unit of carbon ranged from 0.22 mmol g−1C to 12.6 mmol g−1C. Depending on the DOM, a calculated 28–127% of the electrons transferred from metallic Zn to DOM could be subsequently donated to Fe(CN)63−. EAC decreased with DOC concentration, and increased with aromaticity, carboxyl, and phenolic content of the DOM. The results indicate that an operationally defined EAC of natural DOM can be quantified by reaction with metallic Zn and that DOM properties control the electron transfer. Shortcomings of the method are the coagulation and precipitation of DOM during the experiment and the production of hydrogen and dissolved Zn by reaction of metallic Zn with water, which may influence the determined EAC.