The Effects of Animal-Sediment Interaction on Geochemical Processes Near the Sediment-Water Interface

9314132总体而言，海洋底栖动物的活动极大地改变了现代海底大部分地区表层沉积物中的物质运输和反应分布。这项研究的目的是继续定量研究和概念化这些活动对沉积矿床中成岩反应、沉积物-水溶质交换和有机或矿物相储存的影响。各种野外和实验室观察表明，底栖动物的颗粒改造和灌溉活动促进了有机质的再矿化。在许多同时涉及的因素中，有两个可能特别重要：(1)生物扰动区氧化还原条件的重复振荡，(2)低代谢物积累。这两个因素可能会减少海洋沉积物中有机物质或特定有机化合物组的最终储存。模拟生物扰动区氧化还原和扩散传输条件的实验扩散池将被用来进一步研究这些过程，并测试表层沉积物中再矿化的概念模型。大型底栖动物的生物扰动也提高了次级氧化剂如S、MN、O2的重要性，并控制了表层沉积物中耦合氧化还原反应的相对速率。这些循环与其他元素强烈耦合，例如各种痕量金属。详细的锰氧化还原速率的实验测量将与颗粒返工、净通量和溶质剖面的测量同时使用，以开发生物扰动沉积中的锰循环和相关的氧化还原平衡模型。生物成因结构对溶解有机碳库(DOC)组分的潜在半渗透性对沉积DOC分布、微生物活性和净沉积物-水通量的模型具有重要意义。将进行扩散池测量，以检查管壁和管壁上可能存在的DOC分馏。这项研究的长期目标是对早期成岩作用中的输送和反应平衡的类型进行定量描述(模型)，并探索相应的地球化学和生态影响。

9314132 ALLER The activities of marine bottom-dwelling animals dramatically alter material transport and reaction distributions in surface sediments over much of the modern seafloor. It is the purpose of this research to continue to quantitatively examine and conceptualize the effect of these activities on the rates of diagenetic reactions, sediment-water solute exchange, and storage of organic or mineral phases in sedimentary deposits. A variety of field and laboratory observations demonstrate that particle reworking and irrigation activities of benthic fauna promote the remineralization of organic matter. Of the many simultaneous factors involved, two may be particularly important: (1) repetitive oscillation of redox conditions in the bioturbated zone, and (2) low metabolite build- up. Both factors likely decrease eventual storage of organic matter, or specific groups of organic compounds, in marine sediments. Experimental diffusion cells which mimic redox and diffusive transport conditions in the bioturbated zone will be used to further investigate these processes and test conceptual models of remineralization in surface sediments. Macrobenthic bioturbation also enhances the importance of secndary oxidants sucha s MN O2 and controls relative rates of coupled redox reactions in surface sediments. These cycles couple strongly with other elements, such as a variety of trace metals. Detailed experimental measures of Mn oxidation and reduction rates will be used simultaneously with measures of particle reworking, net fluxes, and solute profiles to develop a model of Mn cycling and associated redox balances in bioturbated deposits. The potential semipermeability of biogenic structures to components of the dissolved organic carbon pool (DOC) has major implications for models of sedimentary DOC distributions, microbial activity, and net sediment-water fluxes. Diffusion cell measurements will be performed to examine possible DOC fractionation across tube and b urrow walls. The long term goals of this research are a quantitative description (model) of the types of transport and reaction balances during early diagenesis and the exploration of the corresponding geochemical and ecological implications.