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: 0403842
• 负责人: Jennifer Cherrier
• 金额: --
• 依托单位: Florida Agricultural and Mechanical 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 2009-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0403842&HistoricalAwards=false
• 关键词: Collaborative; Research; Carbon; Fluxes; Marine

0403842CherrierThe 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).

沿海海洋沉积物中的碳通量可能受到海底地下水排放（SGD）的影响，这可能会增强埋藏碳的再矿化作用并将其输送到水柱中。以往的研究表明，SGD既包括来自大陆含水层的大气水，也包括通过波浪和潮汐泵送、密度驱动流和生物灌溉等过程混合成浅层沉积物的地表水。地表水含氧量饱和，因此应该再矿化有机碳，否则将被隔离在沉积物中。混合和强化再矿化过程将在印度河泻湖系统（佛罗里达东部）进行研究，在此之前已经使用了水柱盐度和孔隙水的变化，并将在本研究中使用，以追踪将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、222Rn活性和温度）来确定混合的时空尺度，以及区域含水层排放的时空变化。结合氯离子和电导率比单独使用任何一种都能获得更高的时间和空间分辨率。同时测量Cl-浓度、电导率和222Rn活度提供了独特的信息，因为它们在端元水源中的组成不同。水文研究将结合沉积物中C的再矿化研究，使用C浓度和13C和14C作为C来源的示踪剂，混合带中的碳将在14C中耗尽，因为碎屑有机碳的年龄将高达几千年，具体取决于埋藏深度。根据流动路径和速率的不同，大气水中的碳在14C中会消耗得更多。d13C值将由碳酸盐或有机物中的C来源控制，并为14C测量提供有力的补充。研究结果应提供有关碳转化效率、沿海沉积物中碳转化和通量的水文控制的时空变化以及水文过程中海洋沉积物中碳循环的信息，这是定量估计全球碳循环来源的重要第一步。该研究还将开发新的同位素示踪技术来研究这些过程。该研究对当地的研究地点具有重要的管理意义，该地点属于国家河口计划，是美国生物多样性最丰富的河口之一，也是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（一所研究机构）、佛罗里达农工大学（一所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，既通过课程作业，也通过与佛罗里达海洋科学教育卓越中心（FCOSEE）门户网站链接，直接在项目中。它提供了广泛的学习机会（水文学和生物地球化学）。