Determination of Thorium-230 and Protactinum-231 in Ocean Waters by Isotope-Dilution Mass Spectrometry

这个项目的主要目标是开发一种新的海水化学分析程序，使自然产生的放射性核素钍-230（半衰期75000年）和镤-231（半衰期32000年）能够在同一样品中进行测量。新程序将采用质谱测量技术，旨在取代目前使用的基于α -光谱法的程序。预计在灵敏度、精度和分析速度方面将有显著提高。特别关注这对特殊的放射性核素的原因是：(1)它们提供了关于海洋中特定物质的通量和调节许多化学物种水平的清除过程的独特信息；(2)它们可以成为破译末次冰期气候沉积记录的重要工具。关于这两种放射性核素分布的改进数据将允许更好地测试和验证它们作为海洋学示踪剂的用途。新程序完善后，将对钍-230和镤-231在北大西洋西部的分布进行研究。该项目的这一部分将全面展示新程序，并有望揭示目前无法解决的分布特征。

9415562 BACON The primary objective of this project is to develop a new procedure for the chemical analysis of seawater that will permit the naturally occurring radionuclides thorium-230 (half-life 75,000 years) and protactinium-231 (half-life 32,000 years) to be measured in the same sample. The new procedure will employ mass- spectrometric techniques of measurement and is intended to replace currently used procedures based on alpha-spectrometry. It is expected that significant improvements in sensitivity, precision, and speed of analysis will be realized. The reasons for the special focus on this particular pair of radionuclides are that (1) they provide unique information about the flux of particular matter in the oceans and the scavenging processes that regulate the level of a number of chemical species, and (2) they can be important tools for deciphering the sedimentary record of climate over the last glacial cycle. Improved data on the distributions of the two radionuclides will permit better testing and validation of their use as oceanographic tracers. After the new procedures are perfected, a study of the distribution of thorium-230 and protactinium-231 in the western North Atlantic Ocean will be undertaken. This part of the project will provide a full-scale demonstration of the new procedures and is expected to reveal features of the distribution that cannot presently be resolved.