Processes Affecting the Riverine Flux of Uranium Isotopes from Coastal Margins to the Ocean: A Study of the Mississippi River and Adjacent Shelf

沿海和大陆架环境中的地球化学过程影响 海洋中的铀浓度，并影响了 过去海洋铀同位素组成 冰期/间冰期旋回 本研究的总体目标是 提高对循环过程的理解， 铀从海岸边缘流向公海 本研究 特别关注密西西比河和邻近的 大陆架，以实现以下目标。 (1)到 描述河流/海洋混合过程中铀的行为; 为了确定控制河口行为的过程， 铀。 (2)为了确定条件和过程， 影响陆架沉积物作为净源汇的作用， 铀;以及，评估河流占主导地位的一般作用 大陆架在整个海洋铀化学中起着重要作用。 水柱和海底样本将从 靠近密西西比河的大陆架。 水样 将被分为溶解的、胶体的和颗粒的 使用过滤和超滤技术分离级分。 铀 将检查所有馏分中的浓度和同位素比 评估河流/海洋混合过程中U的命运。 间质 将从大陆架岩心中提取沃茨，并检查 成岩作用从底部沉积物中吸收或释放铀，以及 河水和海水的混合实验将被用来 研究河口混合对铀的影响。

Geochemical processes in coastal and shelf environments affect uranium concentrations in the ocean, and have influenced the uranium isotope composition of the ocean during past glacial/interglacial cycles. The overall aim of this research is to improve understanding of the cycling processes that affect the flux of uranium from coastal margins to the open ocean. This study focuses specifically on the Mississippi River and the adjacent continental shelf to achieve the following objectives. (1) To characterize the behavior of uranium during river/ocean mixing; and, to identify the processes that govern the estuarine behavior of uranium. (2) To identify the conditions and processes that influence the role of shelf sediments as net sources or sinks for uranium; and, to evaluate the general role that river dominated shelves play in the overall ocean chemistry of uranium. Water-column and Seabed samples will be collected from the continental shelf adjacent to the Mississippi River. Water samples will be partitioned into dissolved, colloidal and particulate fractions using filtration and ultrafiltration techniques. Uranium concentrations and isotope ratios will be examined in all fractions to evaluate the fate of U during river/ocean mixing. Interstitial waters will be extracted from shelf cores and examined for diagenetic uptake or release of uranium from bottom sediments, and mixing experiments between river water and seawater will be used to study effects of estuarine mixing on uranium.