石膏在有机物厌氧分解中的固碳效应

摘要

本文以牛肉膏蛋白胨为厌氧微生物的营养源,研究了石膏对厌氧微生物生化系统中甲烷释放量和有机物矿化的影响.根据溶液中总有机碳(TOC)、总无机碳(TIC)、硫酸根、硫化物、pH值以及气体中CO2,CH4和H2S的释放量的观测,以及固体产物的扫描电镜(SEM)、能谱(EDS)、X-射线衍射(XRD)分析结果,探讨了石膏对抑制甲烷菌活性的影响和机制.结果表明,添加石膏能有效降低甲烷释放量达40%以上,而对于CO2的释放量没有明显影响;固体中碳酸盐矿物的含量大幅度增加.石膏在该厌氧体系中的作用主要表现在如下几个方面:(1)石膏是微溶矿物,随着硫酸根的还原,体系中石膏溶解不饱和而不断溶解,石膏起到缓释硫酸根的作用;(2)石膏缓慢溶解使溶液中有稳定的硫酸根浓度,有足够的电子受体,促使硫酸盐还原菌(SRB)成为优势微生物,SRB通过对底物和电子的竞争抑制了产甲烷菌(MPB)和产甲烷能力;(3)硫酸盐还原菌在还原硫酸根的同时消耗有机碳,加速有机物的无机矿化,有机物无机矿化产生的碳酸根与石膏中的Ca2+结合形成方解石,提高了将有机碳固定为无机碳的速率,表现出固碳效应.%This paper investigated the affect of gypsum on methane emission and organic matter mineralization in anaerobic biochemical system by using beef extract peptone as the nutrient source. To explore the effect and mechanism of gypsum on suppressing the activity of methane-producing bacteria (MPB), three kinds of chemical and physical indexes were tested: 1) TOC, TIC, SO42-, sulfide and pH values of the aqueous phase; 2) volume of CO2, CH4 and H2S emissions in the gas phase, and 3) SEM, EDS and XRD analyses of the solid phase. Our results showed that addition of gypsum could effectively reduce methane emission by more than 40 ％. However, no apparent impact on the release of CO2 was observed during this process. Furthermore, the content of carbonate minerals in solid phase increased dramatically compared with the control group. These data further suggested that the major role of gypsum in this anaerobic system is represented in the following aspects: 1) the continuous dissolution of gypsum, one of the slightly soluble minerals, played an important role in controlled release of SO42- during its sustained reduction; 2) sulfatereducing bacteria (SRB) were promoted to be the dominant microorganism under the conditions of stable SO42- concentration and sufficient electron acceptors generated by slow dissolution of gypsum, and its competition of substrates and electrons further suppressed the methane production of MPB; 3) the consumption of organic carbon by SRB accelerated mineralization of organic matter, by which the carbonate generated could combine with Ca2+ in gypsum to form CaCO3. In this way, gypsum plays a crucial role in carbon sequestration by efficiently improving the rate of organic carbon mineralization.