污泥堆肥过程中N2O形成与释放影响因素及减排机制研究

The very sensitive greenhouse gas nitrous oxide (N2O) has a 296 times higher impact than CO2 and is also responsible for ozone depletion. Composting are known to be important sources of N2O emissions. To devise a strategy to mitigate N2O emissions, it is essential to understand its sources in detail and the country specific emission factor(EF). However, the sources of N2O emissions during the sludge composting process are still largely unclear and there is still no country EF report of China. A high-precision analytical technique for determining intramolecular 15N site preference in asymmetric molecules of N2O was developed.The site preference enabled us to identify the source and sinks of N2O in the environment and distinguish the relative contributions of nitrification and denitrification sources to N2O emissions. Thus, molecular analysis of betaproteobacterial ammonia oxidizers and a N2O isotopomer analysis will be conducted to study the sources of N2O emissions during the sludge composting process.On-site monitoring of N2O emission of 3-5 sluge composting plant will be implemented.Lab scale experiment will be conducted to find the proper measurement(C/N ration, dosing of different component, additives, DO, etc.) to reduce the N2O emission. Finally, all the data will be statistically analyzed and the reasonable EF of China will be proposed. The result of this project could provide data for establishing a strategy of mitigating N2O emissions.

污泥堆肥过程中N2O的释放是各国最主要N2O排放源之一，本项目拟针对生物污水厂污泥堆肥工艺过程中N2O产生的影响因素及释放机制不清楚、相关温室气体核算参数缺失、N2O的减排方法不完善等问题，拟针对国内3-5个生活污水污泥堆肥工艺开展各阶段N2O排放监测，获取实测数据；借鉴土壤中N2O 产生和排放的经验与方法，在实验室条件下应用稳定同位素标记法和优先点位值分析法，对污泥好氧堆肥过程氮素迁移转化方式和 N2O 产生机理进行系统研究，利用现代分子生物学方法，研究堆肥中硝化与反硝化微生物的群落变化及其与N2O排放的关系，力图揭示污泥堆肥过程中N2O的形成机制和主要影响因素。最后通过实验室研究，获取堆肥物料配比、供氧方式和时机、添加剂添加方法等N2O减排控制方法，并提出我国的污泥堆肥过程中N2O释放系数的合理范围。为我国污泥堆肥过程中氧化亚氮的核算和减排提供基础数据。

好氧堆肥是我国污泥处理处置的主要技术路线之一。污泥好氧堆肥过程伴随着氧化亚氮的排放，已经成为全球N2O的潜在来源。本项目针对生活污水处理厂污泥堆肥工艺过程中N2O产生影响因素及释放机制不清楚、相关温室气体核算参数缺失的问题。在国内2个污泥堆肥厂进行了N2O的排放监测，数据表明：仓式工艺中，夏季N2O的释放集中于腐熟堆垛区，取样通量分别达到 47.1~863.2 mg N2O-N/ (m2·d)和611.3~890.6 mg N2O-N/ (m2·d)，一次堆肥期仅监测到极低的N2O释放。并利用15N同位素比率值方法（δ15N）对N2O的产生机理进行初步探讨。同时利用PCR-DGGE、荧光定量PCR等现代分子微生物学技术，研究堆肥过程中微生物群落的变化及其与N2O释放的关系。在堆肥前期硝化螺旋菌的数量均要明显多于亚硝化侏儒菌，而在堆肥后期亚硝化侏儒菌则成为优势菌群。堆肥10天后，两个对照组中硝化螺旋菌的数量均达到峰值；亚硝化侏儒菌数量则在第18天时达到峰值，分别为9.1×109个/g和9.0×109个/g。堆肥初期硝化作用主要贡献了N2O的释放；而在堆肥腐熟期，亚硝化侏儒菌的数量较多说明此时反硝化作用主要贡献了N2O的释放。添加生物炭可以促进泥堆肥过程中N2O的减排。

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