Phosphogenesis in Near-Surface Santa Barbara Basin Sediments

本研究的重点是确定美国加州圣巴巴拉盆地沉积物中自生磷酸盐的来源、反应和沉淀和老化的时间尺度。来自盆地的初步数据表明，自生磷酸盐是从沉积物柱上部25厘米的孔隙水中沉淀下来的。这些数据还表明，最上层厘米的高浓度溶解磷酸盐与覆盖在沉积物-水界面上的丝状硫氧化细菌（Beggiatoa spp.）相结合。该计划的实地部分将包括：1)对垫层和底层沉积物进行季节性的细尺度生物量、孔隙水和固相取样；2)对孔隙水氧和ph的毫米级梯度进行现场测量。在实验室中，将进行岩石学、矿物学、化学、单个沉积物的层状和分离的磷相的同位素组成。后一项工作应为评价碳酸盐氟磷灰石前兆相的性质、稳定性和积累速率提供明确的数据。还将确定Beggiatoa生物量对总成岩磷酸盐通量的贡献，以及该垫的化学微环境对磷酸盐再生的其他机制（如铁-氢氧氧穿梭）的影响。总的来说，这些结果将有助于我们了解将磷从海洋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.