Abstract：
Seasonal and daily variations of gaseous emissions from naturally ventilated dairy cattle barns are important figures for the establishment of effective and specific mitigation plans. The present study aimed to measure methane (CH4) and ammonia (NH3) emissions in three naturally ventilated dairy cattle barns covering the four seasons for two consecutive years. In each barn, air samples from five indoor locations were drawn by a multipoint sampler to a photoacoustic infrared multigas monitor, along with temperature and relative humidity. Milk production data were also recorded. Results showed seasonal differences for CH4 and NH3 emissions in the three barns with no clear trends within years. Globally, diel CH4 emissions increased in the daytime with high intra-hour variability. The average hourly CH4 emissions (g h-1 livestock unit-1 (LU)) varied from 8.1 to 11.2 and 6.2 to 20.3 in the dairy barn 1, from 10.1 to 31.4 and 10.9 to 22.8 in the dairy barn 2, and from 1.5 to 8.2 and 13.1 to 22.1 in the dairy barn 3, respectively, in years 1 and 2. Diel NH3 emissions highly varied within hours and increased in the daytime. The average hourly NH3 emissions (g h-1 LU-1) varied from 0.78 to 1.56 and 0.50 to 1.38 in the dairy barn 1, from 1.04 to 3.40 and 0.93 to 1.98 in the dairy barn 2, and from 0.66 to 1.32 and 1.67 to 1.73 in the dairy barn 3, respectively, in years 1 and 2. Moreover, the emission factors of CH4 and NH3 were 309.5 and 30.6 (g day-1 LU-1), respectively, for naturally ventilated dairy cattle barns. Overall, this study provided a detailed characterization of seasonal and daily gaseous emissions variations highlighting the need for future longitudinal emission studies and identifying an opportunity to better adequate the existing mitigation strategies according to season and daytime.
摘要：
自然通风的奶牛场的气体排放量的季节性和每日变化是建立有效和具体的缓解计划的重要数据。本研究旨在连续两年测量三个自然通风的奶牛谷仓中的甲烷（CH4）和氨（NH3）排放量。在每个谷仓里，通过多点采样器将来自五个室内位置的空气样本绘制到光声红外多气体监测器上，随着温度和相对湿度。还记录了牛奶生产数据。结果表明，三个谷仓中CH4和NH3排放的季节性差异在几年内没有明显的趋势。全球范围内,dielCH4的排放量在白天增加，小时内变化很高。平均每小时CH4排放量（gh-1牲畜单位1（LU））在奶牛场1中从8.1到11.2和6.2到20.3，在奶牛场2中从10.1到31.4和10.9到22.8，在奶牛场3中从1.5到8.2和13.1到22.1，在第1年和第2年。DielNH3排放量在数小时内变化很大，在白天增加。平均每小时NH3排放量（gh-1LU-1）在奶牛场1中从0.78到1.56和0.50到1.38，在奶牛场2中从1.04到3.40和从0.93到1.98，在奶牛场3中从0.66到1.32和从1.67到1.73，在第1年和第2年。此外，CH4和NH3的排放因子分别为309.5和30.6(gday-1LU-1)，分别,用于自然通风的奶牛谷仓。总的来说,这项研究提供了季节性和每日气体排放量变化的详细特征，强调了未来纵向排放研究的必要性，并根据季节和白天确定了更好地适应现有减排策略的机会。
