Collaborative Research: Tracing the Transformations of Organic Carbon in Marine Sediments using Natural C Isotopes

孔隙水溶解有机碳（DOC）是海洋中特征最少的有机碳库之一。因此，其在海洋碳循环中的生物地球化学作用仍不清楚。旧金山州立大学和奥多明尼恩大学的科学家提议测试这一假设，即孔隙水 DOC 不仅由不稳定颗粒有机碳 (POC) 水解而成的材料组成，而且还由 14C 耗尽的顽固 POC 溶解产生的抗性部分组成。为了检验他们的假设，将确定圣莫尼卡盆地沉积物岩心中 DOC、溶解无机碳、POC 和碳酸盐的 '13C 和 '4C 特征的垂直剖面。使用同位素质量平衡模型对这些岩心的结果进行分析，以确定向孔隙水提供 DOC 的 POC 成分、氧化成溶解无机碳的 DOC 成分，以及在孔隙水中积累并随后作为底栖通量从沉积物中释放的成分。这项研究的结果将为了解缺氧大陆边缘沉积物中 DOC 积累和流出的来源和反应性提供新的见解。就更广泛的影响而言，这项研究的结果不仅会影响我们对海底 DOC 通量对海洋 DOC 循环的重要性的理解，而且还将进一步加深我们对海洋沉积物中有机碳矿化控制的理解。这项研究包括资助研究生和本科生的众多教育和培训机会，以及通过 SEED 项目夏季项目为高中生提供实践研究经验，该项目是美国化学会的一个项目，旨在鼓励低收入家庭的学生从事化学科学职业。这项研究的结果还将通过教师研讨会和开放活动等外展活动传播到专业科学界之外。

Pore-water dissolved organic carbon (DOC) is one of the least characterized pools of organic carbon in the ocean. Thus, its biogeochemical role in the marine carbon cycle remains unclear. Scientists from San Francisco State University and Old Dominion University propose to test the hypothesis that pore water DOC consists not only of material hydrolyzed from labile particulate organic carbon (POC), but also of resistant moieties derived from the solubilization of 14C-depleted, recalcitrant POC. To test their hypothesis, vertical profiles of '13C and '4C signatures of DOC, dissolved inorganic carbon, POC, and carbonates in sediment cores from Santa Monica Basin would be determined. Results from these cores would be analyzed using an isotope mass balance model to determine the component of POC that supplies DOC to pore waters, the component of DOC that is oxidized to dissolved inorganic carbon, and the component that is accumulated in pore water and subsequently released from sediments as a benthic flux. Results of this research would provide new insight into the sources and reactivity of DOC accumulating in, and effluxing from, anoxic continental margin sediments. As regards broader impacts, the outcome of this research would not only impact our understanding of the significance of benthic DOC fluxes on the cycling of DOC in the oceans, but would also further our understanding of the controls on organic carbon mineralization in marine sediments. This research includes funding to support numerous education and training opportunities for graduate and undergraduate students as well as hands on research experiences for high school students through the Project SEED summer programs, an American Chemical Society program created to encourage students from low-income families to pursue a career in the chemical sciences. Findings from this study would also be disseminated beyond the professional scientific community through outreach activities such as teacher workshops and open-house events.