Benthic Mineralization of Organic Matter on the Continental Rise and the Dissolution of CaCo3 at the Deep Seafloor

在之前的赠款期间，开发了在船上孔隙水采样和培养期间进行现场海底通量舱测量以及在现场温度和压力下取回和保持沉积物岩芯所需的仪器。该项目将利用这些仪器研究海洋碳循环的两个重要方面，即深海表层沉积物中有机质的矿化和CaCO3的溶解动力学。具体而言，将研究与生产力高的西非边缘相邻的地点(与法国赞助的EUMELI方案合作)以及赤道西太平洋溶跃层上方和下方的地点。在每个地点，将确定有机质、蛋白石和CaCO3的颗粒输入，这些相在表层沉积物中的矿化和溶解速率，以及埋藏率。当通过模型将这些信息与诸如底水CaCO3饱和状态、扩散边界层厚度等环境参数相耦合时，将允许讨论以下问题：1.流向非洲近海海底的有机物质通量对大西洋深层碳收支是否重要？2.非洲近海的有机物质通量能否得到沉积物捕捉器测量的垂直降雨率的支持？3.西非近海深海海底的反硝化作用重要吗？4.海底CaCO_3的溶解速率常数是多少？5.沉积CaCO_3的溶解在多大程度上中和了代谢二氧化碳？6.跨扩散亚层的输运是否限制了深海CaCO_3的总溶解速率？

During the preceeding grant periods, the instrumentation required to perform in situ benthic flux chamber measurements and to retrieve and maintain sediment cores at in situ temperatures and pressures during shipboard pore water sampling and incubations were developed. This project will utilize these instruments to study two important aspects of the marine carbon cycle, the mineralization of organic matter and the kinetics of CaCO3 dissolution in deep sea surface sediments. Specifically, sites adjacent to the highly productive west African margin (in collaboration with the French-sponsored EUMELI program) and sites above and below the lysocline in the western equatorial Pacific will be studied. At each location, the particulate input of organic matter, opal, and CaCO3, the mineralization and dissolution rate of these phases in surface sediments, and the burial rate will be determined. This information, when coupled through models to environmental parameters such as bottom water CaCO3 saturation state, diffusive boundary layer thickness, etc., will permit the following questions to be addressed: 1. Are organic matter fluxes to the seafloor off Africa important to deep Atlantic carbon budgets? 2. Can organic matter fluxes off Africa be supported by vertical rain rates as measured by sediment traps? 3. Is denitrification at the deep seafloor important off west Africa? 4. What is the CaCO3 dissolution rate constant at the seafloor? 5. To what extent is metabolic CO2 neutralized by the dissolution of sedimentary CaCO3? 6. Does transport across the diffusive sublayer limit the total CaCO3 dissolution rate in the deep sea?