城市生活垃圾填埋初期N2O的释放机制及其影响因素

The existing results showed that significant N2O emissions happened on the working face of landfill sites. Extensive studies were more concerned with the CH4 emitting from the deposited refuse, while few systemic and in-depth studies with respect to N2O. To explore the involved mechanisms, influencing factors and mitigating strategies of N2O emission from newly deposited waste during the initial landfill stage, this project presents a study of the corresponding relationships among N2O emission intensity, waste compositions and environmental factors in a laboratory-scale simulated landfill. Then, Response surface methodology (RSM) would be employed to distinguish the principal factors affecting the N2O release, and further put forward the optimum conditions under which N2O emissions are minor according to the RSM analysis. Moreover, using the 15N isotope labeling method and strictly controlling the performance of batch experiments, the quantifying contribution of nitrification and denitrification to the N2O emissions would be conducted under different environmental conditions during landfill time, for the sake of accurately evaluating the influence of relevant environmental factors (e.g. temperature, oxygen content, moisture content and bioavailable carbon content) on N2O fluxes. At the same time, molecular biological approaches would be applied to investigate the effect of environmental factors on the variation of microbial community structures and the abundances and expressions of functional genes involved in N2O emissions, which would shed light on molecular mechanism of N2O emission in the early stage of landfill. Last but not least, different types of soils covering the simulated landfill cells would be carried out to evaluate N2O mitigation capacity and its corresponding reduction mechanism. The project implementation will provide a scientific basis of N2O emission control in landfills.

现有的研究表明垃圾填埋作业面有高强度的N2O释放。与填埋场CH4排放的研究相比，针对垃圾填埋场中N2O排放的研究还不够系统和深入。为了探明垃圾填埋初期N2O的释放机制、影响因素及调控原理，本项目拟通过模拟填埋实验研究N2O释放通量与垃圾成分及环境因子的相关关系，应用响应曲面法研究影响N2O释放的主要因素；利用15N标记稳定同位素手段，通过严格控制条件的批次实验，获得不同环境因子影响下不同填埋时间段硝化和反硝化过程对N2O释放量的贡献，从而探明温度、O2含量、含水率、生物可利用碳等微生物环境因子对N2O释放的影响机制；同时应用分子生物学技术研究填埋过程环境因子对微生物群落结构、与N2O释放相关的功能基因的丰度及其表达量的影响，阐明填埋初期N2O释放的分子机制。通过模拟实验比较不同类型土壤覆盖控制N2O的效果及其影响机制。本项目的实施将为控制垃圾填埋场N2O的排放提供科学依据。

为了探明垃圾填埋初期N2O的释放机制、影响因素及调控原理，本项目首先对漳州垃圾填埋场N2O的释放开展了整年的监测；通过模拟填埋实验研究了填埋初期N2O的释放规律，并考察了氧气浓度、填埋温度和含水率对N2O释放通量的影响；利用15N标记稳定同位素手段获得不同环境因子影响下不同填埋时间段硝化和反硝化过程对N2O释放量的贡献，同时应用分子生物学技术研究填埋过程环境因子对反硝化功能菌群演替的影响。取得如下主要研究结果：. 1. 通过地统计学结合ArcGIS反演垃圾填埋场N2O释放通量的时空变化，发现N2O的释放热区与新鲜垃圾填埋作业面高度重合，说明新鲜垃圾填埋作业面是填埋堆体N2O的主要释放源。. 2. 敞口培养条件下N2O释放总量为27.3±9.8 mg N kg-1 waste；密闭培养条件下N2O释放总量为33.9±8.7 mg N kg-1 waste。. 3. 不同氧气浓度条件下填埋初期N2O释放量顺序为0%> 21%> 5%> 10%。0%氧气条件下模拟填埋垃圾产生N2O释放量最大；N2O的释放峰值随着培养温度和含水率的升高而增大，25C、含水率30%时最低（3.192 µg N kg-1waste h-1），45C、含水率60%时最高（19.687 µg N kg-1 waste h-1）。. 4. 在各种培养条件下，反硝化作用均是N2O释放的主要途径，其贡献比例平均为57.51%90.51%不等，硝化作用和硝化-反硝化作用贡献的N2O仅占很小比例。。. 5. 生活垃圾在收运阶段阶段的N2O释放水平甚至超过填埋。厨余垃圾的N2O释放通量最高，最大可达1469.59±1004.32 µg N·kg-1 wet waste·h-1。厨余垃圾的N2O释放通量比非厨余垃圾高出12倍。