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捉器的技术，用于确定整个海洋水柱中的颗粒通量。它是基于溶解在海水中的铀同位素衰变产生的230和231pa的已知产生率，在概念上类似于使用第234来确定真光区的出口通量。不同大小范围的颗粒将通过大容量(1000-2000升)、现场过滤和分析两种放射性核素及其主要成分(有机质、碳酸盐、蛋白石、铝硅酸盐)进行采样。将对整个水柱进行采样，但主要重点将放在中深海带(~150-1500米)的有机质再矿化上，那里的通量随着深度的下降很大，但用沉积物捕捉器直接测量通量是困难的，容易产生很大的误差。夏威夷海洋时间序列(热)站Aloha之所以被选为这项初步研究的地点，是因为它远离海洋边缘的复杂影响，也因为正在进行的时间序列计划提供的后勤便利和支持数据。近年来，电感耦合等离子体质谱(ICPMS)用于小样品中~(230)Th和~(231)Pa的高灵敏度分析方法的发展，使该方法成为可能。如果这一概念在这个项目中被证明是成功的，该方法可以应用于其他海洋地区，并可以扩展到各种特定的元素和化合物。

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.