Korea Institute of Ocean Science & Technology, Busan, 49111, Republic of Korea.
Department of Geology, Wayne State University, Detroit, Detroit, MI, 48201, USA.
J Environ Radioact. 2019 Nov;208-209:106024. doi: 10.1016/j.jenvrad.2019.106024. Epub 2019 Jul 31.
The disequilibrium of the grandparent-daughter pair Pb (t=)-Po (t) has been used to estimate the export fluxes of particulate organic carbon in the ocean using particulate-matter-associated Po. Po is produced from Bi, not from Pb. The half-life of Bi (t) is sufficiently long compared to the rates of biological particle formation and decomposition or dissolution occurring at sea. The role of Bi has not yet been assessed quantitatively in the apparent disequilibrium between Pb and Po, partly due to the non-existence of Bi depth profile measurements at sea up to now. However, greater affinity of Bi over Po and Pb was found recently in coastal waters and phytoplankton Bi uptake experiments. Build upon these findings, we developed a primitive and simple analytical approach to elucidate the role of Bi in the Po-Pb pair in the ocean using a simplified two-box irreversible steady-state ocean model. We assumed that the activity concentrations in the dissolved and particulate phases of Pb, Bi, and Po in a given water column are solely determined by the concentration of the particles, their input and output, the distribution coefficients between dissolved and particulate phases, and decay constants of these radionuclides in the steady-state ocean. The Bi contribution to the Pb-Po activity difference in seawater is found to be significant, therefore, it needs to be considered in estimating particle fluxes using Pb-Po secular equilibrium at sea.
利用与颗粒物质相关的 Po，已经将祖孙对 Pb(t)-Po(t) 的不平衡状态用于估算海洋中颗粒有机碳的输出通量。Po 是由 Bi 而不是 Pb 产生的。与海洋中发生的生物颗粒形成、分解或溶解的速率相比，Bi(t) 的半衰期足够长。由于迄今为止在海洋中尚未进行 Bi 深度剖面测量，因此 Bi 在 Pb 和 Po 之间的明显不平衡中的作用尚未得到定量评估。然而，最近在沿海水域和浮游植物 Bi 吸收实验中发现，Bi 比 Po 和 Pb 具有更大的亲和力。在此发现的基础上，我们开发了一种原始而简单的分析方法，利用简化的两箱不可逆稳态海洋模型来阐明海洋中 Po-Pb 对中 Bi 的作用。我们假设在给定水柱中 Pb、Bi 和 Po 的溶解相和颗粒相的活度浓度仅由颗粒的浓度、它们的输入和输出、溶解相和颗粒相之间的分配系数以及这些放射性核素在稳态海洋中的衰变常数决定。在海水中，Bi 对 Pb-Po 活度差的贡献是显著的，因此，在使用 Pb-Po 长期平衡估算颗粒通量时，需要考虑这一点。
