Quantifying the Photochemical Reactivity of Deep Ocean Water

由于70%的海洋溶解有机碳（DOC）是在深海中发现的，因此确定其来源和汇对了解其在全球碳循环中的作用非常重要。不幸的是，深海DOC的沉降量在很大程度上仍然未知；然而，有限的数据表明光化学可能影响深层难降解DOC的去除。佐治亚大学的一名科学家将利用现场和实验室的辐照实验来量化光化学速率控制(1)DOC的直接损失和一氧化碳的光产生，一氧化碳是DOC氧化的重要产物；(2)有机碳的常见光学示踪剂，如有色溶解有机物和荧光溶解有机物的褪色；(3)反映氧在DOC光化学中的作用的两种活性氧（过氧化氢和超氧化物）。这项研究将集中在北太平洋，那里的深海DOC浓度最低，这很可能反映了一个古老而难降解的碳库的存在。在深度DOC上方1000米的地方有一个浓度梯度，可以比较不同DOC浓度、年龄和视折射率的水域。该研究的结果将用于定量地重新评估目前限制全球DOC模型的基本问题：光化学是否在去除深海中聚集的大量难降解DOC方面发挥了重要作用？就更广泛的影响而言，基于与K-12教师建立的联系，这位科学家和他的学生计划访问当地学校，展示他们的科学成果，并建立一个名为“询问海洋学家”的网站，并在他们的巡航期间维护一个实时博客。本研究的结果将被纳入碳循环的课堂材料。作为该项目的一部分，将支持和培训一名研究生和三名本科生。预计来自历史上代表性不足的群体的本科生将通过佐治亚大学的夏季本科生研究计划被招募。

Because 70% of marine dissolved organic carbon (DOC) is found in the deep ocean, it is important to determine its sources and sinks to understand its role in the global carbon cycle. Unfortunately, the sinks for DOC at depth remain largely unknown; however, limited data has suggested that photochemistry may influence the removal of deep refractory DOC. A scientist from the University of Georgia will use field and laboratory irradiation experiments to quantify the photochemical rates controlling (1) direct loss of DOC and photoproduction of carbon monoxide, a significant product resulting from DOC oxidation, (2) common optical tracers of organic carbon such as colored dissolved organic matter and fluorescent dissolved organic matter fading; and (3) two reactive oxygen species (hydrogen peroxide and superoxide) that reflect the role of oxygen in DOC photochemistry. The study will focus on the north Pacific, where the lowest deep ocean DOC concentrations are found which most likely reflect the presence of an aged and refractory carbon pool. Layered in the top 1000m above this deep DOC is a concentration gradient that will allow comparison of waters with different DOC concentrations, ages and apparent refractivity. Results from the study will be used to quantitatively reevaluate this basic question that now constrains global DOC models: Does photochemistry have a significant role in the removal of the massive amount of refractory DOC that is pooled in the deep sea? In terms of the broader impacts, based on established links with K-12 teachers, the scientist and his students plan visits to local schools to present their science, as well as have a website entitled "ask the oceanographer" and maintain a live blog during their cruise. Results from this study will be included into class materials dealing with the carbon cycle. One graduate and three undergraduate students would be supported and trained as part of this project. It is anticipated that undergraduate students from historically underrepresented groups would be recruited via the University of Georgia's Summer Undergraduate Research Program.