基于同位素异位体结构研究水稻土DNRA途径的N2O排放

氧化亚氮（N2O）是一种重要的温室气体，稻田土壤作为大气中N2O的重要来源备受关注。传统观点认为，厌氧条件下反硝化过程是土壤N2O产生的主要途径。我们前期研究发现，硝态氮异化还原为铵(DNRA)是水稻土中一个重要的氮转化途径，且在纯培养条件下可以产生N2O排放。然而，由于DNRA发生的环境条件和底物与反硝化过程相同，导致DNRA过程对水稻土N2O排放的贡献难以区分。本项目拟采用基于N2O同位素异位体SP值的Monte Carlo定量分析方法结合选择性抑制技术，定量区分水稻土DNRA和反硝化途径对N2O排放的贡献，分析影响DNRA过程N2O产生的主导因素；同时利用Real-time PCR等生物学技术手段测定DNRA菌功能基因（nrfA）丰度，验证相关研究结果。项目研究有助于深入认识水稻土N2O排放规律和产生机制，为准确评估N2O排放及减排措施制订提供理论依据，具有较高的学术价值和实践意义。

Nitrous oxide (N2O) is an important greenhouse gas with a global warming potential approximately 300times greater than that of the equivalent amount of CO2 and promotes ozone destruction in the stratosphere. Paddy soil is one of the important sources of N2O in the atmosphere. Generally, it is considered that denitrification is the most important N2O emission pathway in the soil under anaerobic conditions. However, dissimilatory nitrate reduction to ammonium (DNRA) may occur simultaneously with denitrification. We have shown that DNRA is an important nitrogen transformation pathway in paddy soils, and contributes to N2O production in a pure culture experiment. However, its contribution to N2O production in soils under field conditions is not fully understood. We propose to improve our understanding of this process and its contribution in relation to other pathways of N2O production through use of the isotopomer distribution of 15N in the N2O molecule (known as site preference, SP), combined with the use of Selective Inhibition Technology. Additionally, Real-time PCR will be used to detect the abundance of the functional genes (nrfA) of the Nitrite reductase to cross-validate the results. The outputs of this study will improve our understanding of paddy soil N2O emissions and provide basic theory for the development of control measures.