Quantifying the Photochemical Reactivity of Deep Ocean Water

由于70%的海洋溶解有机碳(DOC)存在于深海，因此确定DOC的来源和汇对于了解其在全球碳循环中的作用非常重要。不幸的是，深度DOC的汇在很大程度上仍然是未知的；然而，有限的数据表明，光化学可能会影响深层难降解DOC的去除。佐治亚大学的一位科学家将利用现场和实验室辐照实验来量化控制(1)DOC的直接损失和一氧化碳(DOC氧化的重要产物)的光产生的光化学速率，(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褪色；以及(3)反映氧在DOC光化学中的作用的两种活性氧物种(过氧化氢和超氧化物)。这项研究将集中在北太平洋，在那里发现了深海DOC浓度最低的地方，这很可能反映了一个古老而难处理的碳库的存在。在这个深度DOC上方1000米的顶部，有一个浓度梯度，可以比较不同DOC浓度、年龄和表观折射率的水域。这项研究的结果将被用来定量地重新评估这个目前制约全球DOC模型的基本问题：光化学在去除汇集在深海中的大量难降解DOC方面是否发挥了重要作用？在更广泛的影响方面，根据与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，介绍他们的科学，并建立一个名为“询问海洋学家”的网站，并在巡航期间保持现场博客。这项研究的结果将包括在有关碳循环的课程材料中。作为该项目的一部分，一名研究生和三名本科生将得到支持和培训。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暑期本科生研究计划招收。

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.