Experimental Evidence for Abiotic Sulfurization of Marine Dissolved Organic Matter
Experimental Evidence for Abiotic Sulfurization of Marine Dissolved Organic Matter
复制标题
DOI：
10.3389/fmars.2017.00364
复制
发表时间：
2017-11
影响因子：
3.7
通讯作者：
Anika M Pohlabeln;Gonzalo V. Gomez-Saez;Beatriz E. Noriega‐Ortega;T. Dittmar
中科院分区：
文献类型：
--
作者：
Anika M Pohlabeln;Gonzalo V. Gomez-Saez;Beatriz E. Noriega‐Ortega;T. Dittmar
溶解有机硫是海洋中最大的有机硫库，是全球硫循环的重要组成部分。海洋中的DOS对微生物降解具有抵抗力，并在千年时间尺度上翻转。然而，其稳定性背后的来源和机制在很大程度上是未知的。在这里，我们假设，在硫酸盐还原沉积物中，硫被非生物性地纳入溶解有机物（DOM）并释放到海洋中。我们将天然海水和浮游生物培养物的滤液暴露在硫化物条件下。在20 °C下一小时后，DOS浓度在这些实验中增加了4倍，在50 °C下4周后增加了14倍，表明有机物质在天然硫化物环境中不需要长的停留时间就能受到硫化作用的影响。通过超高分辨率质谱的分子分析表明，硫是共价和非选择性地结合DOM。实验产生的和天然的DOS沉积物是高度相似的分子和结构水平。通过结合我们的数据与发表的底栖DOC通量，我们估计，30 - 200 Tg DOS每年从厌氧和硫酸盐还原沉积物输送到海洋。在这第一次推测性评估中，不确定性很大。然而，这第一次尝试表明，底栖DOS通量可能比河流大一个数量级，表明这可以平衡估计的全球净去除难降解DOS。
Dissolved organic sulfur (DOS) is the largest pool of organic sulfur in the oceans, and as such it is an important component of the global sulfur cycle. DOS in the ocean is resistant against microbial degradation and turns over on a millennium time scale. However, sources and mechanisms behind its stability are largely unknown. Here, we hypothesize that in sulfate-reducing sediments sulfur is abiotically incorporated into dissolved organic matter (DOM) and released to the ocean. We exposed natural seawater and the filtrate of a plankton culture to sulfidic conditions. Already after one hour at 20 °C, DOS concentrations had increased 4-fold in these experiments, and 14-fold after 4 weeks at 50 °C, indicating that organic matter does not need long residence times in natural sulfidic environments to be affected by sulfurization. Molecular analysis via ultrahigh-resolution mass spectrometry showed that sulfur was covalently and unselectively bound to DOM. Experimentally produced and natural DOS from sediments were highly similar on a molecular and structural level. By combining our data with published benthic DOC fluxes we estimate that 30 – 200 Tg DOS are annually transported from anaerobic and sulfate reducing sediments to the oceans. Uncertainties in this first speculative assessment are large. However, this first attempt illustrates that benthic DOS flux is potentially one order of magnitude larger than that via rivers indicating that this could balance the estimated global net removal of refractory DOS.