Particle Flux and Remineralization at Hawaii Ocean Time-Series Station ALOHA: Development of a New Estimation Method Based on 230Th and 231Pa

在这个项目中，伍兹霍尔海洋研究所的研究人员将开发一种独立于沉积物捕集器的技术，用于确定整个海洋水柱中的粒子通量。它是基于溶解在海水中的U同位素衰变产生230 Th和231 Pa的已知速率，在概念上类似于使用234 Th来确定真光层的输出通量。将通过大体积（1000-2000升）原位过滤对各种尺寸范围的颗粒进行采样，并分析两种放射性核素及其主要成分（有机物、碳酸盐、蛋白石、铝硅酸盐）。将对整个水体进行采样，但主要重点是中层（~150 - 1500 m）有机物的再矿化，该区域的通量随着深度的增加而大幅减少，但直接测量通量沉积物陷阱很困难，并且误差很大。选择夏威夷海洋时间序列（HOT）站ALOHA进行这项初步研究，因为它远离海洋边缘的复杂影响，并且由于后勤便利和正在进行的时间序列方案提供的支持数据。所提出的方法是可行的，最近发展的高灵敏度的分析方法，用于测量小样品中的230 Th和231 Pa的电感耦合等离子体质谱（ICP-MS）。如果这一概念在该项目中证明是成功的，该方法可应用于其他海洋区域，并可扩展到各种特定元素和化合物。

ABSTRACTOCE-0117922In this project, researchers at the Woods Hole Oceanographic Institution will develop a technique independent of sediment traps for determining particle flux throughout the oceanic water column. It is based on the known rate of production of 230Th and 231Pa from decay of U isotopes dissolved in seawater and is similar in concept to the use of 234Th to determine export flux from the euphotic zone. Particles of various size ranges will be sampled by large- volume (1000-2000 liters), in-situ filtration and analyzed for the two radionuclides and for their major components (organic matter, carbonate, opal, aluminosilicate). The whole water column will be sampled, but a major emphasis will be on remineralization of organic matter in the mesopelagic zone (~150 - 1500m), where there is a large decrease of the flux with depth but where direct measurement of the flux with sediment traps is difficult and subject to large errors. The Hawaii Ocean Time-series (HOT) Station ALOHA is the site chosen for this initial study because it is remote from the complicating effects of ocean margins and because of the logistical ease and the supporting data provided by the ongoing time-series program. The proposed method is made feasible by the recent development of high-sensitivity analytical methods for measurement of 230Th and 231Pa in small samples by inductively-coupled plasma mass spectrometry (ICP-MS). If the concept proves in this project to be successful, the method could be applied to other oceanic areas and could be extended to a variety of specific elements and compounds.