Fluorescence of dissolved organic matter un marine sediments

The fluorescence of porewaters from marine sediment cores from six different areas was measured. In most cases, fluorescence was affected primarily by the diagenesis of organic carbon first through sulfate reduction and subsequently by methane generation. Typically, fluorescence, dissolved organic carbon (DOC), absorbance, alkalinity, and ammonium ion concentrations correlate quite well, increasing in the upper sections of anoxic sediments and co-varying in deeper sections of these cores. The good correlation of DOC with fluorescence in the three cores in which DOC was measured indicates that fluorescence can be used to make a first order estimate of DOC concentration in anoxic porewaters. Data are consistent with a model in which labile organic matter in the sediments is broken down by sulfur reducing bacteria to low molecular weight monomers. These monomers are either remineralized to CO2 or polymerize to form dissolved, fluorescent, high molecular weight molecules. The few exceptions to this model involve hydrothermally generated hydrocarbons that are formed in situ in the Guaymas Basin or are horizontally advected along the decollement in the Nankai Trench.

对取自6个不同区域的海洋沉积物岩芯的孔隙水荧光特性进行了测定。多数情况下，荧光特性主要受有机碳成岩作用调控：首先通过硫酸盐还原过程，随后由甲烷生成过程主导。
通常而言，荧光特性、溶解有机碳（dissolved organic carbon, DOC）、吸光度、碱度以及铵离子浓度之间呈现良好相关性：在缺氧沉积物的上层区段，上述指标均呈上升趋势，而在岩芯的深层区域则协同变化。在3个完成溶解有机碳测定的岩芯中，DOC与荧光特性的良好相关性表明，可通过荧光特性对缺氧孔隙水中的DOC浓度开展一阶近似估算。
本数据集的观测结果与下述模型相符：沉积物中的易降解有机质被硫酸盐还原菌（sulfur reducing bacteria）分解为低分子量单体。这些单体要么被再矿化生成二氧化碳，要么发生聚合反应形成溶解性、具有荧光特性的高分子量物质。
该模型仅存在少数例外情况，涉及瓜伊马斯盆地原位生成的热液成因烃类，或是沿南海海沟滑脱层水平平流输送的烃类。