微生物降解蒙脱石层间吸附有机质的实验研究

Experimental research on microbial degradation of organic matter adsorbed in smectite internal surface area in the interlayer of the structure

近年来,国内外学者意识到,有机质在蒙脱石结构层间的吸附是有机质保存的重要机理之一,然而,目前关于微生物能否降解蒙脱石层间吸附有机质以及降解的程度等尚没有任何实验数据的支撑。本文试图通过人工合成含有层间吸附有机质的蒙脱石,利用海洋和湖泊沉积物中常见的降解有机质的微生物对其进行降解实验,据此探讨有机质的蒙脱石层间吸附在沉积物埋藏过程中对有机质保存的贡献。有机质选择半胱氨酸和甲苯,前者是生物生长所需的一种重要氨基酸,后者大量存在于土壤和沉积物中,多种细菌可以在有碳氢化合物的环境下将其降解。实验菌种选择恶臭假单胞杆菌(Pseudomonas putida)和腐败希瓦氏菌(Shewanella putrefaciens CN32)2种细菌,它们均为海洋和湖泊沉积物中的主导微生物,前者有较强的有机质降解能力,后者为铁的还原菌,厌氧代谢过程中能将蒙脱石结构中的Fe(III)还原为Fe(II)。通过上述不同菌种对蒙脱石层间吸附不同性质有机质的降解实验,结果显示,微生物对蒙脱石层间吸附的有机质的降解方式主要有分泌有机酸直接降解和破坏层间结构释放有机物从而进行降解。代表菌种假单胞菌和希瓦氏菌对半胱氨酸绿脱石及甲苯绿脱石的作用表明,微生物通过分泌有机酸的形式对蒙脱石层间吸附的有机质降解作用很有限,该结构在恒定的有氧和无氧条件下对保存有机质有利;希瓦氏菌在严格无氧条件下通过还原Fe(III)进行代谢,实验表明,无氧条件下,希瓦氏菌可以一定程度破坏矿物结构,释放并消耗有机物,因此,铁还原微生物对蒙脱石层间吸附有机质的保存有一定的影响,但由于微生物对矿物晶体结构的破坏能力有限,故其对层间吸附有机质降解的能力也有限;不同有机物对生物降解过程也有影响,这些影响取决于有机质的特性及有机质与细菌之间的相互作用。绿脱石层间吸附的半胱氨酸对生物生长有利,从而可能促进生物还原Fe(III)作用。相反,甲苯却很明显的抑制了Fe(III)的还原。由此可见,有机质的蒙脱石层间吸附是有机质保存的重要方式之一。

It has been recognized that the adsorption of organic matter（OM）into smectite internal surface area in the interlayer of structure is one of the most important preservation mechanisms in recent years,whereas there is no experimental data to indicate whether and to what extent the microbes can degrade the OM adsorbed in the smectite internal surface area.In order to understand the contribution of the adsorption of OM in the internal surface area to preservation of OM in the burying process of the sediments,the microbial degradation to OM adsorbed in the internal surface area of smectite has been researched through experiments with the different kinds of microbes.Cysteine and toluene are selected as the experimental OM.The former is an important amino acid for growing of life,and the later ubiquitously occurs in the soils and sediments and can be degraded by many kinds of bacteria.Pseudomonas putida and Shewanella putrefaciens CN32 are common microbes in the marine and lacustrine sediments.The former has strong ability to degrade the OM,and the later is the Fe-deoxidized bacterium,which can deoxidize the Fe（III）in the crystal structure of smectite into Fe（II）in the anaerobic metabolism.Through the degradation experiments of different kinds of OM adsorbed in the internal surface area of smectite with the different kinds of microbes,some conclusions can be got from the results.The degradation process of microbes to OM is through the secretion of organic acid or destroying the crystal structure to release the adsorbed OM.The experiment results indicate that the degradation of OM adsorbed in the internal surface area through the secretion of organic acid from microbes is little,and the internal adsorption of OM in the interlayer structure is effective for the preservation of OM in the aerobic or anaerobic environments.Shewanella putrefaciens CN32 metabolizes through the deoxidization of Fe（III）in the anaerobic environment.It can destroy crystal structure of smectite to some extent and release some adsorbed OM.So the Fe-deoxidized bacteria can affect the preservation of OM in some extent,whereas due to the limited effect on crystal structure caused by microbes,the degradation ability to OM adsorbed in the internal surface area from Fe-deoxidized bacteria is not predominant yet.Character of OM is also a factor influencing on microbial degradation of OM.Cysteine is propitious to develop for microbes,and may promote deoxidization of Fe（III）,by contraries,toluene is poisonous to microbes and it obviously restrain the deoxidization of Fe（III）.Thus it can be seen that the adsorption of OM in smectite internal surface area in interlayer of structure can effectively prevent degradation from microbes and is an important preservation mode of OM in sediments.