开放式奶牛运动场与粪污堆贮设施N2O排放规律研究

It is recognized that the over emission of greenhouse gas, CO2, CH4 and N2O in particular, from animal production systems to the atmosphere is a major contributor to the global warming. More and more attention is increasingly being paid on N2O emission because of its high global warming potential (GWP), which is about 298 times of CO2 with a very significant effect on global warming. In this project, the method will be optimized by using the closed non-through-flow chamber to measure the gas emission under lower gas concentration and emission rate. And then a systemic solution combing the chamber technique and tracer gas method, will be developed to quantify and characterize the N2O emission from open outdoor exercising yard and manure storages of typical dairy cattle farms in China. The effects of the key factors including ambient temperature, manure properties and manure managements, etc., on N2O emission will be analyzed. Based on the simulation experiment on N2O generating and emitting from the yard and manure storage, the generation path and emission pattern of N2O will be majorly studied, and the mechanism of the emission will be revealed. A sensitivity analysis will be carried out to find out the most important factors on the emission, and finally a strategy to mitigate N2O emission will be given based on the practical condition of the dairy farm in China. The project will provide fundamental data of N2O emission from dairy cattle farms. It will be very helpful in developing the method to measure and estimate greenhouse gas emission from animal production operations and making the mitigation strategies as well.

畜牧业中的CO2、CH4、N2O等温室气体过度排放是全球气候变暖的重要原因，而其中N2O的全球增温潜势是CO2的298倍，增温效果异常显著。本项目以我国典型的规模化奶牛场为对象，在优化低浓度气体环境动态箱检测技术的基础上，通过箱法与示踪法相结合，对奶牛开放式运动场、临时粪便堆贮设施等N2O排放的重点源头进行监测，研究我国奶牛场温室气体N2O排放通量与排放特征，分析环境参数、粪便特性与管理措施等对N2O排放的影响；试验模拟开放式运动场与粪污堆贮设施N2O的产生与释放过程，研究氮素转化形态及其与N2O产生途径及规律，揭示排放机理与关键影响因素；在进行敏感性分析的基础上，制定符合我国规模化奶牛场实际的减排策略与技术方案。通过对奶牛场N2O排放特征的研究和排放过程的模拟，为掌握我国奶牛场温室气体N2O排放提供基础数据，对发展畜禽场温室气体排放测试与模拟方法、制定减排措施提供理论依据和技术。

畜牧业中温室气体过度排放是全球气候变暖的重要原因，而其中N2O的全球增温潜势是CO2的265倍，增温效果异常显著。本项目通过对我国典型开放式奶牛运动场和粪污临时堆贮设施N2O排放特征的研究和排放过程的模拟，对掌握我国奶牛场N2O排放基础数据，发展畜禽场N2O排放测试与预估方法，制定减排措施提供了理论依据和技术指导。.项目构建了箱法和梯度法以测算我国典型开放式奶牛运动场和粪污堆贮设施N2O排放通量，研究了N2O排放通量与特征，分析了环境参数对N2O排放通量的影响。设计搭建了粪污临时堆贮设施模拟系统，模拟了开放式奶牛运动场在不同表面温度、风速、降水、地面类型等条件下的N2O排放特征与规律，并对奶牛粪便堆贮过程中微生物菌群变化和氮素形态转化过程进行了探究；制定了我国开放式奶牛运动场和粪污堆贮设施N2O减排策略与技术方案。通过研究得到如下主要结论：（1）使用静态箱检测时，N2O和SF6排放通量在不同试验水平下均被低估。推荐在排放源表面风速低于2.00m/s时，采用D300×H400的静态箱检测CH4应密闭20~30min，检测N2O应密闭10~20min。（2）梯度法测试N2O、SF6气体的准确度主要受风速和上下边界距离的影响，当风速大于1m/s时，梯度法可能会有15%左右的高估；当主风向与测试边界长度方向偏角为45°时测试结果最为准确，偏差率约-8.86±2.39%。（3）春季奶牛运动场N2O的排放通量为3.60mg/(m2·h)。环境温度显著影响N2O的排放量，风速在一定范围内会促进N2O的排放。（4）运动场的年均N2O排放量为0.13 kg/(hd·yr)，粪堆的年均N2O排放量为2.3 kg/(hd·yr)。运动场和堆粪场的温室气体排放均受外界温度的影响，存在显著的季节性差异，粪便在堆粪场堆放的时间的长短影响气体的排放量。（5）N2O排放受季节温度影响显著，主要集中于春、夏两季。单位质量奶牛粪便在春、夏、秋季的N2O排放总量分别为5.86mg、9.43mg、0.81mg。（6）素土地面N2O的排放速率显著高于立砖地面，立砖地面能够有效阻止粪污氮素下沉。不同地面类型的牛粪微生物含量基本一致。