Thorium Isotopes as Indicators of Export Flux and Particle Dynamics in the Southern Ocean: Joint Global Ocean Flux Study

961-2761 Cochran本研究项目是美国联合全球海洋通量研究(JGOFS)南大洋计划的一部分，旨在(1)更好地了解南大洋有机和无机碳的通量，(2)确定调节这些通量的大小和变化的物理、生态和生物地球化学因素和过程，以及(3)将这些通量置于当代全球碳循环的背景下。这项工作是在南大洋实验中合作的44个项目之一，这是一项为期三年的努力，位于南极极地前锋地带以南，旨在追踪碳通过有机和无机路径从空气-海洋界面通过整个水柱进入海底沉积物的流动。该实验将利用RVIB纳撒尼尔·B·帕尔默和R/V汤普森号在1996年10月至11月至1998年3月期间的六次工艺巡航中进行。这一部分侧重于钍同位素(钍-234和钍-228)分布和颗粒通量的空间和时间变化。这些同位素充当海洋示踪剂，提供有关生物地球化学过程的速率的基本信息，这些过程支配着海洋水柱中生物成因颗粒的生产和命运。对钍-234的测量将在海上通过贝塔和伽马计数进行；对钍-228的测量将通过阿尔法光谱分析在岸上进行。这些数据将在生物速率测量和研究期间收集的其他数据的范围内进行解释，并将用于估计真光带的有机物质、碳酸盐和二氧化硅的出口通量；量化水柱中的聚集和解聚等转化过程；以及检验生物地球化学模型。在这种情况下，钍是一种特别有用的示踪剂，因为它的产生方式众所周知；它很快就被生物粒子吸收，而且它的S浓度可以相当精确地测量出来。因此，可以确定下落粒子对钍的去除，并且可以解决推断下落粒子的积分质量(颗粒碳通量)的逆问题。*。

961-2761 Cochran This research project is part of the US Joint Global Ocean Flux Study (JGOFS) Southern Ocean Program aimed at (1) a better understanding of the fluxes of carbon, both organic and inorganic, in the Southern Ocean, (2) identifying the physical, ecological and biogeochemical factors and processes which regulate the magnitude and variability of these fluxes, and (3) placing these fluxes into the context of the contemporary global carbon cycle. This work is one of forty-four projects that are collaborating in the Southern Ocean Experiment, a three-year effort south of the Antarctic Polar Frontal Zone to track the flow of carbon through its organic and inorganic pathways from the air-ocean interface through the entire water column into the bottom sediment. The experiment will make use of the RVIB Nathaniel B. Palmer and the R/V Thompson on six process cruises between Oct.-Nov., 1996, and March 1998. This component focuses on the spatial and temporal variations in the distributions and particulate fluxes of thorium isotopes (thorium-234 and thorium-228). These isotopes serve as ocean tracers that yield fundamental information about the rates of biogeochemical processes that govern the production and fate of biogenic particles in the oceanic water column. Measurements of thorium-234 will be made at sea by beta and gamma-counting; measurements of thorium-228 will be made ashore by alpha- spectrometry. The data will be interpreted within the context of biological rate measurements and other data to be collected during the study and will be used to provide estimates of export fluxes of organic matter, carbonate, and silica from the euphotic zone; to quantify transformation processes such as aggregation and disaggregation in the water column; and to test biogeochemical models. Thorium is a particularly useful tracer in this context because its mode of production is well known; it is taken up quickly by biogenic particles, and it s concentration can be measured quite precisely. The removal of thorium by falling particles can therefore be determined, and the inverse problem of inferring the integrated mass of falling particles (the particulate carbon flux) may be solved. *** .