RUI: Photobiogeochemistry of resuspended sediments in coastal environments: Impacts on organic matter and trace metal cycling

河口和河流的沉积物被风、浪和水流自然地重新悬浮和调动。在典型的浅水河口和沿海水域，沉积物-水的相互作用可以显著影响各种重要的生物地球化学过程，如痕量金属动员、营养物质和有机质循环以及人为污染物的释放。虽然早期的研究已经证明了重新悬浮的河口沉积物暗释放的重要性，但它们还没有解决光化学转化在从这些沉积物中动员有机质和金属方面潜在的更重要的作用。来自北卡罗来纳大学威尔明顿分校的科学家计划进行一系列野外和实验室实验，以研究光转化的机制以及它们对两个有机丰富的沿海平原河口再悬浮沉积物中有机氮、有机碳、铜(铜)和铅(铅)的动员的影响，其中一个受到人类活动的影响。具体地说，这项研究计划解决以下问题：(1)再悬浮河口沉积物的光解产生多少溶解有机氮(DON)、溶解有机碳(DOC)、铜和铅，以及光化学通量如何随季节和地点的变化而变化？(2)产生的DON和DOC的生物可利用性是什么？它如何随季节和地点的变化而变化？(3)来源物质的无机和有机成分以及照射波长如何影响再悬浮沉积物的光反应性？(4)在再悬浮物质变化中，DON、DOC、铜和铅作为主要的有机质再矿化过程(硫酸盐还原和产甲烷)的通量如何变化？这项研究的结果解决了根本上重要的和具有全球意义的问题，因为它考虑了盐度变化时有机物和金属的通量如何反应，例如海平面上升时可能发生的变化。此外，这项工作将提供关于光诱导反应对河口系统中有机氮、有机碳和痕量金属的分布和形态的作用的信息。与该项目相关的教育影响包括对博士后以及研究生、本科生和高中生的支持和培训。此外，预计一名高中教师将在暑期参加这项研究。

Estuarine and riverine sediments are naturally resuspended and mobilized by wind, waves, and water currents. In typically shallow estuaries and coastal waters, sediment-water interactions can significantly impact a variety of important biogeochemical processes such as trace metal mobilization, nutrient and organic matter cycling, and release of anthropogenic contaminants. While earlier studies have demonstrated the importance of dark release from resuspended estuarine sediments, they have not addressed the potentially more significant role that photochemical transformations play in the mobilization of organic matter and metals from these sediments.Scientists from the University of North Carolina, Wilmington plan to carry out a series of field and laboratory experiments to examine the mechanisms of phototransformations and the impacts they have on the mobilization of organic nitrogen, organic carbon, copper (Cu), and lead (Pb) from resuspended sediments in two organic-rich coastal plain estuaries, one of which is impacted by anthropogenic activities. Specifically, the study plans to address the following questions: (1) How much dissolved organic nitrogen (DON), dissolved organic carbon (DOC), Cu, and Pb are produced upon photolysis of resuspended estuarine sediments and how do the photochemical fluxes vary seasonally and by location?; (2) What is the bioavailability of the DON and DOC produced and how does that vary by season and location?; (3) How is the photoreactivity of resuspended sediments impacted by the inorganic and organic composition of the source material and irradiation wavelength?; and (4) How do fluxes of DON, DOC, Cu, and Pb change as the dominant organic matter remineralization processes (sulfate reduction vs. methanogenesis) in the resuspended material change?. Results from this research addresses fundamentally important and globally significant questions because it considers how fluxes of organics and metals respond during changes in salinity, such as those that could occur in rising sea levels. In addition, the work would provide information regarding the role of light-induced reactions on the distributions and speciation of organic nitrogen, organic carbon, and trace metals in estuarine systems. Educational impacts associated with this project include support and training for a postdoc, as well as graduate, undergraduate, and high school students. In addition, it is anticipated that a high school teacher would participate in the study during the summer months.