NOAA/WDS Paleoclimatology - Anderson et al 2001 Sed. Concentrations of Phosphorus and Carbon

Defining the transformations of phosphorus (P) in sediments is critical to assessing the geochemical behavior of sedimentary P and the behavior of reactive P (Preactive= Poxide-associated + Pauthigenic + Porganic) relative to organic carbon (Corganic). This study includes the determination of P components and Corganic concentrations on samples from sites in the California Current region (Ocean Drilling Program (ODP) leg 167, sites 1010, 1011, 1012, 1014, 1016, and 1021), in the Benguela Current region (ODP leg 175, sites 1082, 1084, and 1085), and on Blake Nose in the western Atlantic (ODP leg 17 1B, sites 1050 and 1052). Sample depths range up to 650 m, and ages range up to 65 Ma. Our data demonstrate the transformation of labile forms of P (Porganic and Poxide-associated) to Pauthigenic throughout the sediment column in all redox states and at all sedimentation rates investigated, until a substantial portion of reactive P is in the authigenic form (>80%). (C/P)organic ratios are always greater than or equal to the Redfield Ratio in all of the sediments we studied. Sediments with Corganic concentrations ≤2 wt % have Corganic/Preactive ratios less than the Redfield Ratio, and Corganic/Preactive ratios increase linearly with Corganic, consistent with degradation of Corganic with age. In general, Corganic/Preactive ratios for sediments with Corganic concentrations ≥2 wt %, from a variety of redox states and sedimentation rates, center around the Redfield Ratio, although some ratios are as high as 3 times the Redfield Ratio. However, Corganic/ Preactive ratios (up to 400) do not approach the high ratios observed for (C/P)organic ratios (up to 4500). Because of the efficient transfer of labile forms of P to Pauthigenic, Corganic/Preactive ratios better describe the geochemical behavior of sedimentary P.

明确沉积物中磷（phosphorus, P）的转化过程，对于评估沉积磷的地球化学行为，以及活性磷（Preactive，即结合氧化物态磷（Poxide-associated）+自生磷（Pauthigenic）+有机磷（Porganic））相对于有机碳（Corganic）的演化特征至关重要。本研究对以下区域的沉积物样品开展了磷组分与有机碳（Corganic）浓度测定：加利福尼亚流海域（大洋钻探计划（Ocean Drilling Program, ODP）167航次，站位1010、1011、1012、1014、1016及1021）、本格拉流海域（ODP 175航次，站位1082、1084及1085），以及西大西洋布雷克岬（Blake Nose）区域（ODP 171B航次，站位1050及1052）。样品的埋藏深度可达650米，沉积年代跨度可达65百万年（Ma）。本研究数据表明，在所考察的所有氧化还原环境与沉积速率条件下，沉积物柱中不稳定态磷（即有机磷（Porganic）与结合氧化物态磷（Poxide-associated））均可转化为自生磷（Pauthigenic），直至活性磷中有相当比例（>80%）以自生磷形式存在。本研究涉及的所有沉积物中，有机碳磷比（(C/P)organic）始终大于或等于雷德菲尔德比值（Redfield Ratio）。有机碳浓度≤2重量百分比（wt%）的沉积物，其有机碳与活性磷比（Corganic/Preactive）小于雷德菲尔德比值，且该比值随有机碳含量呈线性增长，这与有机碳随沉积年代发生降解的规律一致。总体而言，有机碳浓度≥2重量百分比（wt%）的沉积物（涵盖各类氧化还原环境与沉积速率），其有机碳与活性磷比的平均值接近雷德菲尔德比值，不过部分样品的该比值可达雷德菲尔德比值的3倍。然而，有机碳与活性磷比的最大值仅为400，远低于有机碳磷比的最高值（可达4500）。由于不稳定态磷可高效转化为自生磷，有机碳与活性磷比能够更准确地反映沉积磷的地球化学行为。