Collaborative Research (USC and Caltech): Evaluation of Opal Dissolution Kinetics and Factors that May Regulate Opal Accumulation in Margin Sediments

海洋碳和硅的生物地球化学循环是通过硅藻的活动直接联系在一起的，因此，如果不明确是什么因素调节了海洋硅的收支平衡，就无法预测碳循环的行为。很明显，从海洋中去除Si主要是通过蛋白石（bSi =生物源二氧化硅）埋藏发生的，并且基于深海环境的观测，已经提出了几种将bSi掩埋与bSi降雨率联系起来的算法。不幸的是，这些算法的效用有限，因为我们对bSi溶解与到达海底的bSi雨之间的联系因素没有机制上的理解，而且因为它们不能在边缘环境中工作。边缘环境最近被认为是整个海洋中埋藏的bSi的30-45%的汇。沉积物堆积的相对速率和bSi与铝硅酸盐相互作用的动力学似乎是调节bSi溶解的关键因素，尽管其他因素也可能起作用。在这项研究中，南加州大学和加州理工学院的研究人员将使用一种相对较新的技术，搅拌流反应器，来测量边缘沉积物中bSi溶解和Al释放的动力学，以努力评估这些因素如何影响bSi的埋藏。将对新收集的样本（浮游生物物质、落入陷阱的颗粒和沉积物）进行测量，这些样本代表了加州两个边缘盆地的整个颗粒输出路径。结果将与通过模拟硅酸和溶解铝的孔隙水剖面推断出的动力学进行比较。目标是开发一种基于易于测量的沉积物特征的算法，该算法将提供可靠的bSi埋藏敏感性测量。这些信息将有助于解释bSi沉积记录的意义，并有助于开发包含Si循环对碳动力学影响的生物地球化学模型。该项目还将为研究生和本科生提供支持和培训。

ABSTRACTOCE - 0351169 / OCE - 0351498The marine biogeochemical cycles of carbon and silicon are directly linked through the activities of diatoms, so the behavior of the carbon cycle cannot be predicted without a firm understanding of what factors regulate the oceanic Si budget. It is clear that Si removal from the ocean occurs primarily through opal (bSi = biogenic silica) burial, and several algorithms that relate bSi burial to bSi rain rate have been proposed, based on observations in deep sea environments. Unfortunately, these algorithms have limited utility because we do not have a mechanistic understanding of the factors linking bSi dissolution to the bSi rain reaching the seabed, and because they fail to work in margin environments. Margin environments have recently been recognized as the sink for 30-45% of the bSi buried in the entire ocean. The relative rates of sediment accumulation and the kinetics of bSi interaction with aluminosilicates appear to be critical factors that regulate bSi dissolution, although other factors may play a role.In this study, researchers at the University of Southern California and the California Institute of Technology will use a relatively new technique, stirred flow reactors, to measure the kinetics of bSi dissolution and Al release from margin sediments, in an effort to evaluate how these factors may govern bSi burial. Measurements will be made on freshly collected samples (planktonic material, particles falling into traps, and the sediments) representing the entire particle export pathway in two California borderland basins. Results will be compared with kinetics deduced from modeling pore water profiles of silicic acid and dissolved Al. The goal is to develop an algorithm based on readily measured characteristics of sediments that will provide a reliable measure of bSi burial susceptibility. This information will be of value for interpreting the significance of the bSi sedimentary record and for developing biogeochemical models that incorporate the effect of the Si cycle on carbon dynamics. The project will also provide for the support and training of graduate and undergraduate students.