Collaborative Research: Are Carbon Fluxes from Marine Sediments Enhanced by Submarine Ground Water Discharge?

合作研究：海底地下水排放是否增强了海洋沉积物中的碳通量？

• 批准号: 0403515
• 负责人: Jaye Cable
• 金额: $ 21.35万
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-08-01 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0403515&HistoricalAwards=false
• 关键词: Collaborative; Research; Carbon; Fluxes; Marine

0403515CableThe flux of C from coastal marine sediments is likely to be influenced by submarine ground water discharge (SGD), which may enhance remineralization of buried C and transport it to the water column. Previous studies reveal that SGD includes both meteoric water from continental aquifers and surface water mixed into shallow sediment through processes such as wave and tidal pumping, density driven flow, and bioirrigation. Surface water is saturated with oxygen, and thus should remineralize organic carbon that otherwise would be sequestered in the sediments. The process of mixing and enhanced remineralization will be studied in the Indian River Lagoon System (eastern Florida), where changes in water column salinity and pore waters have been used previously, and will be used in this study, to trace pumping of oxygenated surface water into the sediments. The study will use time-series measurements and monitoring of conservative tracers (conductivity, Cl- concentration, 222Rn activity, and temperature) to determine the temporal and spatial scales of mixing, as well as variations through time and space of discharge from the regional aquifers. Combining Cl- and conductivity allows greater temporal and spatial resolution than either one alone. Simultaneous measurements of Cl- concentration, conductivity, and 222Rn activity provide unique information because of their distinct compositions in end-member water sources. The hydrologic studies will be coupled with studies of remineralization of C in the sediments using C concentrations and 13C and 14C as tracers of the sources of C. Carbon in the mixed zone will be depleted in 14C because detrital organic carbon will be up to several thousand years old depending on depth of burial. Carbon in the meteoric water will be even more depleted in 14C depending on the flow paths and rates. The d13C values will be controlled by the source of C from carbonate or organic matter and provides a powerful complement to the 14C measurements. Results of the study should provide information on the efficiencies of C transformation, spatial and temporal variations of hydrologic controls on those transformations and fluxes in coastal sediments, and information on C cycling in marine sediments from hydrologic processes, an important first step toward quantitative estimates of sources to the global C cycle. The study will also develop new isotopic tracing techniques to study these processes. The study has important management implications for the local study site, which is in the National Estuaries Program, is one of the most biologically diverse estuaries in the nation, and home to 21 endangered or threatened species. The project impacts the educational missions of the University of Florida (a Research I institution), Florida A&M University (a Historically Black and Minority Serving College/University), and Louisiana State University (located in an EPSCoR state) through involvement of high school to graduate students, both through course work that will be linked to the Florida Center for Ocean Science Education Excellence (FCOSEE) web portal, and directly in the project, which offers a broad range of learning opportunities (hydrology and biogeochemistry).

0403515电缆来自沿海海洋沉积物的C通量可能会受到海底地下水排放（SGD）的影响，这可能会增强埋藏C的矿化并将其输送到水柱中。 以往的研究表明，SGD包括从大陆含水层和地表水混合成浅沉积物的过程，如波浪和潮汐抽水，密度驱动流，生物灌溉的大气降水。 地表水充满了氧气，因此应该使有机碳矿化，否则这些有机碳将被封存在沉积物中。 将在印度河泻湖系统（佛罗里达东部）研究混合和强化矿化的过程，在该系统中，以前曾使用过水柱盐度和孔隙沃茨的变化，并将在本研究中使用，以跟踪含氧地表水泵入沉积物的情况。 该研究将使用时间序列测量和监测保守示踪剂（电导率、Cl-浓度、222 Rn活性和温度），以确定混合的时间和空间尺度，以及区域含水层排放的时间和空间变化。 结合Cl-和电导率允许更大的时间和空间分辨率比任何一个单独。 Cl-浓度，电导率和222 Rn活性的同时测量提供了独特的信息，因为它们在端元水源的独特组合物。 水文研究将与利用C浓度和13 C和14 C作为C来源示踪剂的沉积物中C的矿化研究相结合。 混合带中的碳将在14 C时耗尽，因为碎屑有机碳将长达数千年，这取决于埋藏深度。 根据流动路径和速率，大气水中的碳将在14 C中消耗得更多。 d13 C值将由碳酸盐或有机质中的C源控制，并为14 C测量提供了有力的补充。 研究结果应提供有关C转化效率、水文控制对这些转化和沿海沉积物通量的空间和时间变化的信息，以及水文过程中海洋沉积物中C循环的信息，这是对全球C循环来源进行定量估计的重要的第一步。 该研究还将开发新的同位素示踪技术来研究这些过程。 这项研究对当地研究地点具有重要的管理意义，该研究地点位于国家河口计划中，是全国生物多样性最丰富的河口之一，是21种濒危或受威胁物种的家园。 该项目影响了佛罗里达大学（一个研究机构）、佛罗里达A M大学（一个历史上为黑人和少数民族服务的学院/大学）和路易斯安那州立大学（位于EPSCoR州）的教育使命，通过高中到研究生的参与，既通过将与佛罗里达海洋科学教育卓越中心（FCOSEE）门户网站链接的课程工作，也直接参与该项目，该项目提供了广泛的学习机会（水文学和地球化学）。