硫酸盐还原菌粘附作用对硬石膏分解的影响

Effect of Adhered Sulfate-Reducing Bacteria on Decomposition of Anhydrite

硫酸盐还原菌(SRB)分解硫酸盐矿物对C、S、Fe、Sr、Ba等元素的循环起着重要制约作用,二者相互作用机制的阐明具有重要的矿物学、地球化学及地质微生物学意义。通过设计厌氧实验,本文探讨了SRB与硬石膏的作用过程及机理。结果表明,较之无菌体系,SRB体系中氧化还原电位(EORP)显著降低;可挥发性硫(AVS)与蛋白质浓度则不断增大;硬石膏中总溶出硫含量增加;硬石膏表面SRB粘附位置出现明显溶蚀现象。分析表明SRB通过两种机制促进硬石膏分解:SRB还原代谢消耗溶解态SO42-,降低SO42-浓度,进而促使硬石膏持续溶解;SRB粘附于硬石膏表面,其自身及代谢产物通过络合硬石膏中的Ca加速矿物分解,此种机制在前人的研究中被普遍忽略,而通过此机制SRB亦可促进难溶硫酸盐(天青石、重晶石等)及铁氧化物的溶解,进而制约相关元素的地球化学行为。

Sulfate-reducing bacteria （SRB） substantially constrains the cycles of C, S, Fe, St, and Ba. One important step for SRB＇s impact on elemental cycle is their function in decomposing sulfate minerals; thus to understand the mechanism of SRB-sulfate mineral interaction has important mineralogical, geochemical and geomicrobiological significances. In this study, anaerobic experiments were designed to investigate the process and mechanism of the decomposition of anhydrite by SRB. Results show that comparing with sterile experiment, obvious changes were happened in SRB experiment： the values of oxidation-reduction potential （Eo~） decreased significantly; the concentrations of acid volatile sulfur （AVS） and protein increased; the decomposition of anhydrite was strengthened; popular dissolution pits and holes can be observed on the surface of anhydrite where SRB was adhered. Results demonstrate that anhydrite was decomposed by SRB through two processes. The first one is through using dissolved SO42＂ as electron acceptor; according to this process anhydrite can be dissolved consistently. The second one, which is generally neglected in previous studies, is through adhesion, where adhered SRB and their metabolic products can complex structural Ca and strengthen the decomposition. And SRB can also promote the dissolution of insoluble sulfate minerals（celestite, barite, et al.） and iron oxides by the adhesion mechanism, thereby restricting the geochemical behaviors of relevant elements.