GEOTRACES - Intercalibration Studies of Short-lived U/Th Series Isotopes and Marine Particles

在接下来的10到12年里，来自世界各地海洋实验室的科学家将参与GEOTRACES--一项基准努力，调查化学物质在海洋中的分布和行为，从而深入了解海洋作为地球物理系统的工作方式。在这笔赠款的资助下，伍兹霍尔海洋研究所的科学家们将在2008年和2009年参加两次GEOTRACES内部校准巡航。他们将集中精力了解控制天然铀-钍衰变系列中放射性同位素时空分布的物理和化学原理。U-Th示踪剂很可能对解释具有粒子反应性和生物活性的关键地质痕量元素至关重要。从本质上讲，钍同位素将提供关于垂直通量和再矿化速率的直接信息，其时间尺度为天/周(234 tç=24.1d)至数年(228 tç=1.91年)，而228Ra(tç=5.75y)是从盆地边缘到内陆的水平运移的示踪剂，时间尺度为数月至数年。研究人员认为，这些影响，即表面清扫和再矿化以及悬浮颗粒在远离海洋边界的水平迁移，对于确定将在GEOTRACES中测量的许多痕量元素的分布是重要的，对于理解海洋过程本身也很重要。具体地说，伍兹霍尔小组将：1)与GEOTRACES的其他科学家一起参与一般颗粒痕量元素的相互校准工作，比较现场采样方法与瓶装采样方法，并进行基本的过滤和操作比较，适用于更广泛的粒子反应性痕量元素，以便分发给科学界；2)组织和领导颗粒第234和第238次分配，以便在该社区之间进行相互校准；以及3)研究一套新颖的采样和分析方法，以提高准确度，减少对这套Th和Ra同位素的用水要求。就更广泛的影响而言，这一努力显然将使海洋学研究活动受益于地球观测系统以外的领域，因为将获得有关采样和分析方法的新的实践和理论知识。该项目还将涉及美国国内和国际上重要的机构间合作，因为世界各地的海洋放射化学家将有机会参与分析间校准活动。

During the next ten to twelve years, scientists from oceanographic laboratories around the world will participate in GEOTRACES -- a benchmark effort to investigate the distribution and behavior of chemicals in the sea that can give insight into the way the ocean works as a geophysical system. With funding from this grant, scientists at the Woods Hole Oceanographic Institution will participate in a pair of GEOTRACES intercalibration cruises in 2008 and 2009. They will focus their efforts on understanding the physical and chemical principles governing the spatial and temporal distributions of radioisotopes in the natural Uranium-Thorium decay series. U-Th tracers are likely to be vital to the interpretation of key GEOTRACES trace elements that are particle- reactive and bioactive. Essentially, thorium isotopes will provide direct information on the vertical fluxes and remineralization rates on time scales of days/weeks (234Th t ½ = 24.1 d) up to several years (228Th t ½ = 1.91 yr), while 228Ra (t ½ = 5.75 y) is a tracer of horizontal transport from basin margins to the interior on time scales of months to years. The investigators contend that these effects, i.e. surface scavenging and remineralization as well as horizontal transport of suspended particles far from ocean boundaries, are important in setting the distributions of many trace elements that will be measured in GEOTRACES, and important for understanding oceanic processes in their own right. Specifically, the Woods Hole group will: 1) participate with other GEOTRACES scientists in the general particulate trace element intercalibration efforts comparing in-situ vs. bottle vs. deck based sampling methods and making basic filter and operational comparisons appropriate for a wider suite of particle reactive trace elements for distribution to the scientific community; 2) organize and lead distribution of particulate 234Th and 238Th for intercalibration among that community; and 3) work on a novel set of sampling and analytical methods to improve accuracy and reduce water requirements for this suite of Th and Ra isotopes. In terms of broader impacts, it is clear that this effort will benefit oceanographic research activites well beyond GEOTRACES inasmuch as new practical and theoretical knowledge about sampling and analytical methodologies will be obtained. The project will also involve significant inter-institutional collaboration, both within the US and internationally, as marine radiochemists around the world will have the opportunity to participate in analytical intercalibration activities.