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研究报告

Atmospheric ammonia pollution in the traffic environment of Beijing city in spring

摘要：当前，机动车作为大气PM_2.5的重要污染源，越来越受到人们的关注.机动车运行中产生的氨气能与大气中的酸性气体相结合，形成二次污染物，也是PM_2.5的重要组成成分.因此，为监测北京市交通环境中大气氨的排放情况，探索交通环境氨浓度与机动车运行情况以及大气环境等因素间的关系，本实验在通过对学院路（北航东门天桥下）和城市环境点（北京市环境保护监测中心楼顶）采用DOAS仪器对大气中氨的浓度进行持续2个月的观测.通过对监测数据的分析得到学院路空气中氨的总体浓度水平（日平均浓度24.39μg·m^-3）高于城市环境点（日平均浓度17.80μg·m^-3）.从相关性分析可以看出，NH₃与PM_2.5、NO、CO、NO₂相关性较高，与PM₁₀、SO₂相关性较弱.而对氨和交通流量和流速的分析得到，NH₃浓度与车流量和车速关系密切，随着车流量的增加，大气中NH₃的浓度也在不断增加.车速越高，NH₃的浓度越低.

Abstract：As an important source of atmospheric PM_2.5, vehicle emission has drawn great attention. Ammonia (NH₃) generated from vehicles can react with the acidic gases in the atmosphere to produce ammonium salt, which accounts for a significant fraction of PM_2.5. To understand the emission of atmospheric NH₃ in the traffic environment of Beijing City, a two-month observatory experiment was conducted to collect NH₃ concentration and related traffic data. The relationships between NH₃ and vehicle operation conditions as well as atmospheric and environmental factors were discovered. One observation site was located in a typical traffic environment close to the eastern gate of BeiHang University (BH), the other one on the top of the seven-floor building in a typical downtown environment (BMEMC). One DOAS instrument was mounted at each of the two observation sites. The analytical result showed that the 24-hr NH₃ concentration of 24.39 μg·m^-3 at the BH site was higher than that at the BMEMC site (17.80 μg·m^-3). The correlation analysis indicated that NH₃ concentration was well correlated with the concentrations of PM_2.5, NO, CO and NO₂, but only weakly correlated with the concentrations of PM₁₀ and SO₂. The statistical analysis proved that NH₃ concentration had a close relationship with the vehicle conditions:the atmospheric NH₃ concentration increased with the vehicle flow while decreased with the traffic speed.