秸秆分解过程中二甲基硫醚释放及其微生物学机制

Dimethyl sulfide (DMS) play an important role in acid precipitation and sulfate aerosols. Recently, more and more studies focus on its terrestrial sources,among which plant residues are of importance to DMS emssion. Crop straw are important components of plant residues. However, no study was conducted on the emission fluxes and emission profiles of DMS from crop straw and its microbiological mechanism. In the present project, three typical crop straw including straw of rice, wheat and maize will be selected in the field experiment. They will be returned field and left on soils, respectively, and the emission fluxes of DMS from crop straw will be measured. Biological activity, environmental factors and chemical components of crop straw will be also determined simultaneously. To obtain the precursors and the key microorganism of DMS released from crop straw, crop straw will be added with sulfur compounds presented in crop straw and key microorganism separated from field samples, and incubated under controlled conditions in laboratory and under uncontrolled conditions in field, respectively. The emission fluxes of DMS from crop straw will be determined. Moreover,environment factors and chemical components of crop straw, which control the emission of DMS from crop straw, will be setup at different levels during the decomposition of crop straw in laboratory to study the effects of key factors on the emission fluxes of DMS from crop straw. Combined with the results obtained in field experiments,we will try to set up a model or method that can estimate the emission fluxes of DMS from crop straw during the decomposition process. The project can get the emission fluxes of DMS from crop straw, and is also of significance to understand the emission profiles of DMS from crop straw and reveal its microbiological mechanism. The results obtained will help to supplement the gobal emission inventory of DMS and study the biogeochemical cycle of sulfur.

二甲基硫醚(DMS)对酸沉降和硫酸盐气溶胶具有重要贡献。DMS的陆地源越来越受到关注，植物残体是DMS重要陆地源之一，秸秆是重要的植物残体，但是有关秸秆分解过程中DMS排放通量、排放规律和微生物学机制的研究尚未见报道。本研究拟选水稻、小麦和玉米三种主要秸秆为研究对象，野外观测三种秸秆还田和被弃置分解过程中DMS的排放通量，同步观测微生物活动、环境因子和秸秆质量因子。室内和野外模拟秸秆分解，通过分别添加秸秆中已有硫源和野外样品中分离培养的关键菌株，筛选出DMS的前体物和关键功能微生物；室内模拟秸秆分解，调节环境因子和秸秆质量因子，结合野外原位观测结果，获得秸秆分解释放DMS的影响机理，并尝试建立秸秆分解过程中DMS排放通量的估算模型和方法。研究可获得秸秆分解过程中DMS排放通量和排放规律，并揭示其微生物学机制，可为完善全球DMS排放清单和深入研究硫生物地球化学循环提供基础数据和理论依据。

围绕DMS的生物地球化学循环主题，开展了野外观测和室内模拟试验，取得了以下成果：（1）获得了秸秆还田稻田DMS的排放通量数据，在非淹水和淹水条件下排放量分别为93.8和58.1 μg kg-1，初略估算全球秸秆还田DMS排放量为19.6×10-3 Tg yr-1，与种植水稻田和生物质燃烧对全球DMS贡献量相当。（2）发现秸秆还田DMS排放通量在非淹水条件下与Desulfitobacterium dehalogenans丰度呈显著线性正相关，在淹水条件下与Clostridium cavendishii、Clostridium hungatei、Flavitalea populi 和Holophaga foetida丰度呈显著线性正相关，而与Methylobacterium radiotolerans丰度呈显著线性负相关；在此基础上，进一步筛选获得了4株稻田DMS高产菌，且其产量受温度、pH等环境因子的影响，揭示了秸秆还田DMS释放的微生物学机制。（3）开展了与DMS相关的其它VOCs的观测，获得了秸秆还田过程中其它挥发性有机硫化物（VSCs）、含氧挥发性有机物（OVOCs）、非甲烷碳氢化合物（NMHCs）等成分排放通量和排放规律，发现DMS占总VOCs排放量比例小于2%，其它VOCs排放量不可忽视。指导撰写了6篇硕士论文，已发表论文11篇，其中SCI收录7篇以上（二区论文3篇），国内核心4篇，为进一步理解硫生物地球化学循环提供了依据。