§ANKA Synchrotron Radiation Facility, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany.
Environ Sci Technol. 2015 May 5;49(9):5441-9. doi: 10.1021/es505531u. Epub 2015 Apr 21.
The reactivity of natural dissolved organic matter toward sulfide and has not been well studied with regard to electron transfer, product formation, and kinetics. We thus investigated the abiotic transformation of sulfide upon reaction with reduced and nonreduced Sigma-Aldrich humic acid (HA), at pH 6 under anoxic conditions. Sulfide reacted with nonreduced HA at conditional rate constants of 0.227-0.325 h(-1). The main transformation products were elemental S (S0) and thiosulfate (S2O3(2-)), yielding electron accepting capacities of 2.82-1.75 μmol e- (mg C)(-1). Native iron contents in the HA could account for only 6-9% of this electron transfer. About 22-37% of S reacted with the HA to form organic S (Sorg). Formation of Sorg was observed and no inorganic transformation products occurred for reduced HA. X-ray absorption near edge structure spectroscopy supported Sorg to be mainly zerovalent, such as thiols, organic di- and polysulfides, or heterocycles. In conclusion, our results demonstrate that HA can abiotically reoxidize sulfide in anoxic environments at rates competitive to sulfide oxidation by molecular oxygen or iron oxides.
天然溶解有机质对硫化物的反应性在电子转移、产物形成和动力学方面尚未得到很好的研究。因此，我们在缺氧条件下、pH 值为 6 时，研究了在还原态和非还原态西格玛-奥尔德里奇腐殖酸（HA）存在的情况下，硫化物的非生物转化。非还原态 HA 与硫化物的反应条件速率常数为 0.227-0.325 h(-1)。主要的转化产物是元素 S（S0）和硫代硫酸根（S2O3(2-)），其电子接受能力为 2.82-1.75 μmol e- (mg C)(-1)。HA 中的天然铁含量仅占这种电子转移的 6-9%。大约 22-37%的 S 与 HA 反应形成有机 S（Sorg）。在还原态 HA 中观察到 Sorg 的形成，没有发生无机转化产物。X 射线吸收近边结构光谱支持 Sorg 主要为零价，如硫醇、有机二硫化物和多硫化物或杂环化合物。总之，我们的结果表明，HA 可以在缺氧环境中以与分子氧或氧化铁氧化硫化物相当的速率进行非生物再氧化。
