Radioisotope Studies to Understand Biogeochemical Processes and Particle Dynamics in the Equatorial Pacific

作为美国在赤道太平洋中部开展的联合全球海洋通量研究（JGOFS）的一部分，这项拟议中的研究是对沿横贯赤道的N-S样带上天然存在的铀和钍衰变系列核素以及铍的宇宙形成同位素的上层水柱分布进行研究。放射性同位素被用作示踪剂，以收集有关生物地球化学过程速率的信息，这些过程影响海洋中化学物种的清除和生物成因颗粒的行为/命运。具体来说，228Ra和10Be-标准化7Be活度的分布数据，加上硝酸盐和溶解碳的分布数据，将使我们能够估计海洋表面不同水平上硝酸盐的垂直通量和新产量。通过测量溶解物中的234、230、228、210Pb、210PO和7Be/10Be的比活度，P.I:s’将评估溶解的小悬浮颗粒和大沉降颗粒在海洋表面三个深度区反应的正向和反向交换速率常数，以及大颗粒在光区的清除停留时间。预计这项研究将增进我们对赤道太平洋上层海洋生物地球化学动力学和循环的了解，赤道太平洋被认为在全球碳通量中起着重要作用。

As part of the U.S. Joint Global Ocean Flux Studies (JGOFS) in the central equatorial Pacific, the proposed research is a study of the upper water-column distribution of naturally occurring uranium and thorium decay series nuclides and cosmogenic isotopes of beryllium along a N-S transect across the Equator. The radioisotopes are used as tracers to gather information about the rates of biogeochemical processes that influence the scavenging of chemical species and the behavior/fate of biogenic particles in the sea. Specifically, the data obtained from the distribution of 228Ra and 10Be- normalized 7Be activities, coupled with those of nitrate and dissolved carbon, will enable us to estimate the vertical flux of nitrate and new production at various levels in the surface ocean. By measuring the specific activities of 234Th, 230Th, 228Th, 210Pb, 210PO and 7Be/10Be in the dissolved the P.I:s' will evaluate the forward and backward exchange rate constants for reactions involving dissolved small suspended particulate large settling particulate in three depth zones of the surface ocean, and the scavenging residence time of large particulates in the euphotic zone. It is anticipated that the study will enhance our understanding of the upper ocean biogeochemical dynamics and cycling in the equatorial Pacific, an area thought to play an important role in global carbon fluxes.