Chemical Controls on Bioavailability of Riverine Particulate Phosphorus and Changes in Riverine Particulate Phosphorus Chemistry Across the Continent-Ocean Interface

本提案的总体目标是：(1)使用选择性浸出程序（SEDEX方法）来识别和量化密西西比河下游和阿查法拉亚河、密西西比河与三角洲海洋陆架之间的界面以及近表层三角洲海洋沉积物中的颗粒- p的化学成分；(2)确定河流运输过程中颗粒物- p变化过程的时空控制因素；(3)确定大陆-海洋界面化学修饰的时空控制因素。磷(P)是限制淡水、半咸水和咸水生物生产力的必需营养物。天然水体中磷与颗粒物质的结合将在一定程度上提高生物生产力，使其能够被吸收。确定与颗粒物质相关的生物可利用磷对于限制水生系统中生物循环的磷来源至关重要。体磷浓度不是一个有用的参数，因为磷的形态是评估颗粒磷的生物可利用性所必需的。SEDEX方法分别量化了Fe-P、自生沉积磷灰石（ASAP）、有机磷、松散吸附磷和碎屑磷灰石（可能控制天然水体中可溶磷和生物可利用磷的相）。河流悬浮颗粒物（RSPM）中的磷分布将在一系列河流站点进行测定，这些站点选择用于比较农业和工业用地的投入，以及征收的密西西比河下游和Atchafalaya硬木沼泽之间的投入。将通过季节性地重新访问河流研究地点来评估时间变异性。这项工作将与美国地质勘探局正在进行的监测项目一起进行，该项目提供了一系列有价值的支持数据和长期记录。河口过程对RSPM磷分布的影响将通过耦合现场测量和p解吸实验来检验。后者将涵盖在河口观测到的盐度范围。混合前后测定的RSPM的P分布应该允许直接识别固相P储集层，将可溶性（因此是生物可利用的）P释放到溶液中。这些结果将与河口原位RSPM的p分布进行比较。通过对比这两条河流中RSPM的p分布与近岸表层海洋沉积物中的p分布，以及通过对比单独量化的RSPM p库的p负荷计算与近岸陆架沉积物中的p埋藏率，来评估沿海海洋生物有效磷的河流来源。这项工作的重点是一个具有全球意义的系统、转化机制以及应该广泛适用的物理和化学控制。

9406585 Ruttenberg The overall objectives of this proposal are (1) to use selective leaching procedure (the SEDEX Method) to identify and quantify the chemical from of particulate-P in the lower Mississippi and Atchafalaya Rivers, at the interface between the Mississippi River and the deltaic marine shelf, and in proximal surficial deltaic marine sediments; (2) to identify spatial and temporal controls on processes modifying particulate-P during riverine transport; and (3) to identify spatial and temporal controls on chemical modification at the continent-ocean interface. Phosphorus (P) is an essential nutrient which can limit biological productivity in fresh, brackish, and saline natural waters. P associated with particulate matter in natural waters will enhance biological productivity to the extent that the P can be assimilated. Determining the bioavailable P associated with particulate matter is essential for placing constraints on sources of P for biological cycling in aquatic systems. Bulk P concentration is not a useful parameter as P-speciation is required for assessment of the fraction of particulate P which is bioavailable. The SEDEX method separately quantifies Fe-P, authigenic sedimentary apatite (ASAP), (phases likely to control soluble, and therefore bioavailable-P in natural waters), organic- P, loosely sorbed-P, and detrital apatite. P-distribution in Riverine Suspended Particulate Matter (RSPM) will be determined at a series of river stations chosen to permit comparisons of input from agricultural versus industrial land and between the levied lower Mississippi and the Atchafalaya hard-wood swamps. Temporal variability will be assessed by re-visiting the river study sites seasonal. This work will be carried out in conjunction with ongoing USGS monitoring programs, which provided an array of valuable supporting data and a long-term record. The effect of estuarine processes on RSPM P-distribution will be examined by coupling field measurements with P-desorption experiments. The latter will cover the range of salinity observed in the estuary. P-distribution of RSPM determined before and after mixing should permit direct identification of solid-phase P-reservoirs which liberate soluble (and therefore bioavailable ) P to solution. These results will be compared to P-distribution of in situ RSPM from the estuary. The riverine source of bioavailable-P to the coastal ocean will be assessed by contrasting the P-distribution of RSPM from these two rivers with that in proximal surficial marine sediments, and by contrasting P-loading calculations of separately quantified RSPM P-reservoirs to P-burial rates in proximal shelf sediments. The work focusses on a globally significant system, mechanisms of transformation, and physical and chemical controls that should be broadly applicable.