西南极海沉积物碘的迁移与富集

REMOBILIZATION AND ACCUMULATION OF IODINE IN SEDIMENTS, WESTERN ANTARCTIC OCEAN

本文研究了西南极不同地理环境沉积碘的地球化学迁移和富集机制 ,结果表明海湾和深海表层沉积物碘主要与有机质结合 ,但在陆架和半深海 ,与氧化物结合和吸附态碘可占相当大的比例。碘在表层沉积物中迁移的环境特征与铁类似 ,即在还原环境中迁移 ,在氧化环境中转入固相 ,然而碘在沉积物中主要并不是作为电子接受者 ,而是随有机质分解或氧化物还原后被释放进入液相。沉积物表层 I/Corg值高于浮游生物是由于吸附和氧化过程的参与。沉积物 I/Corg值随深度的降低代表了有机质分解 ,氧化物还原 ,粘粒物质解析及间隙水碘扩散的综合效应。沉积物碘的扩散通量与沉积通量在同一数量级水平解释了沉积岩贫碘的原因。根据计算和讨论结果重新提出了海洋沉积物碘迁移和富集的地球化学模式。

Remobilization and accumulation mechanisms of iodine in different envirionments of the sediments are studied. The results show that iodine is characteristically rich in the organic fractions in the surface of bay and pelagic sediments. However, it may be associated with oxyhydroxide and adsorptive phases in a higher percentage at the continental shelf and hemipelagic sediments. The environmental character of remobilization of iodine in surficial sediments is similar to that of iron, that is, it is remobilized in reducing condition and converted into solid phases when it is inoxidizing condition, though the iodine does not act as the electron acceptor. The processes of adsorption and oxidation are responsible for the value of I/Corg. in excess of that of planktonic materials’ except for the organic fraction in surficial sediments. It is the comprehensive effects of organism decomposition, oxyhydroxide reduction, particulate adsorption and pore water diffusion for the decrease of the ratio of iodine to organic carbon with the increase of the depth in sedimentary column. The diffusive and depositive fluxes of the iodine are in the same magnitude, which could be the cause for the poor iodine contents of sedimentary rocks. Based on the calculation and discussion a new model for the remobilization and accumulation of iodine in the sediments is set up.