Phosphogenesis in Near-Surface Santa Barbara Basin Sediments

这项研究的重点是确定加州圣巴巴拉盆地沉积物中自生磷酸盐的来源、反应和时间尺度。来自盆地的初步数据表明，自生磷酸盐是从沉积柱上部25厘米范围内的孔隙水中沉淀出来的。这些数据还表明，最上面厘米处高浓度的溶解磷酸盐与覆盖着沉积物-水界面的丝状硫氧化细菌Beggiatoa spp.耦合在一起。该计划的实地部分将包括1)对垫子和下伏沉积物进行季节性采集，以进行精细的生物质、孔隙水和固相采样，以及2)现场测量孔隙水氧气和pH值的毫米级梯度。在实验室中，将对单个沉积物纹层和分离的磷酸盐相进行岩石学、矿物学、化学和同位素组成的研究。这些工作应为评估碳酸盐氟磷灰石前驱体的性质、稳定性和积累率提供明确的数据。还将确定Beggiatoa生物量对成岩磷酸盐总通量的贡献，以及垫子的化学微环境对其他磷酸盐再生机制的影响，如氢氧化铁穿梭。总体而言，这些结果将有助于我们理解将磷从海洋中转移到全球沉积水库的主要过程。

This research is focused on determining the phosphate sources, reactions and time-scales involved in the precipita- tion and aging of authigenic phosphate in sediments of Santa Barbara Basin, California. Preliminary data from the basin indicate that authigenic phosphate is precipitating from pore waters within the upper 25 cm of the sediment column. These data also suggest that high concentrations of dissolved phosphate in the uppermost centimeter are coupled to a mat of filamentous sulfur-oxidizing bacteria, Beggiatoa spp., which blankets the sediment-water interface. The field portion of the program will include 1) seasonal collections of the mat and underlying sediments for fine-scale biomass, pore water and solid phase sampling, and 2) in situ measurements of millimeter -scale gradients of pore water oxygen and pH. In the labora- tory, investigations will be conducted of the petrology, mineralogy, chemistry, and isotopic compositions of individual sediments lamina and separated phosphatic phases. These latter efforts should provide definitive data for evaluating the nature, stability, and accumulation rates of phases precursory to carbonate fluorapatite. The contribution of Beggiatoa biomass to the total diagenetic phosphate flux, as well as the influence of the chemical microenvironment of the mat on other mechanisms of phosphate regeneration, such as iron-oxyhydroxide shuttling, will also be determined. Overall, the results will contribute to our understanding of the primary processes that remove phosphorus from the ocean to the global sedimentary reservoir.