硫同位素分馏中的生物作用及其环境效应

BIOLOGICAL FUNCTION IN SULFUR ISOTOPE FRACTIONATION AND ENVIRONMENTAL EFFECT

自然界中硫同位素组成变化范围较大(-65‰^+120‰)。许多环境过程可以引起硫同位素分馏,表生环境下微生物还原硫酸盐是最重要的硫同位素分馏过程。在≤50℃条件下,厌氧细菌使硫酸盐SO42-还原成H2S,后者与金属离子结合形成硫化物或直接从体系中逸出,这种硫循环过程是造成地球各层圈中硫的轻、重同位素变异的最主要原因。但生物成因的硫同位素分馏过程复杂,受诸多因素的限制。本文综述了由生物作用导致的硫同素分馏的发生机理和影响因素,以及生物硫循环所导致的环境效应。

Sulfur isotopic composition varies in a wide range in nature （-65‰ ～＋120‰）. Many environmental processes can cause sulfur isotope fractionation. While microbial sulfate reduction plays a key role in sulfur isotope fractionation in surface environment. Anaerobic bacteria reduced SO4^2- to H2S at less than or equal to 50 ℃, the latter was combined with metal ions to form sulfides or directly deviated from the system. This sulfur cycle is the most important reason for sulfur isotope variation in each sphere of the Earth. But the biogenic sulfur isotopic fractionation process was complicated by many factors. This paper reviewed the occurrence mechanism, affecting factors and the environment effect of biological function leading to sulfur isotope fractionation.