大气中含氮化合物对灰霾形成机制的影响

Serious haze caused by PM2.5 covered all large and medium-sized cities in China. 24 out of 29 days in January 2013 were in haze weather, with the highest hourly mass concentration of PM2.5 in single monitoring station reached 993μg/m3 in Beijing. Haze pollution, mainly attributed to PM2.5, has become the most serious and urgent environmental problem in our country. Studies show that ammonium salts（NH4NO3 and（NH4）2SO4） have become the key components of pollution aerosol and could caused growth of fine particles due to its hygroscopic.Atmosphere ammonia and amine is the only alkaline species in the atmosphere, and ammonium salt in PM2.5 was mainly due to secondary aerosols from atmospheric ammonia and acid gas, so ammonia and ammonium salt in atmosphere is crucial to the haze pollution control. Lab studies showed acidic gas prefered to react with some amines rather than ammonia, but rare attention was focused on the amine and its salt in atmosphere. Sampling and chemical analysis of aerosols will be carried out in the main dust source regions and the typical city area and the island in China to understand the temporal and spatial distribution of ammonium salt and amine salt in the atmosphere; Emission sources of ammonia and amine will be surveyed, and based on the concentration of amine (salt) and ammonia (salt), the relationship between haze pollution and ammonia(salt), as well as amine(salt) will be elucidated. Combined with monitoring of laser radar and satellite, the optical properties of the atmosphere related ammonium salt, such as visibility, extinction coefficient, will be discussed to obtain the effects of atmospheric nitrogen compounds on the fomation machinism of haze.

严重灰霾污染覆盖了我国所有大中城市，2013年1月北京24天为灰霾天气，PM2.5小时浓度达993μg/m3，从源头控制PM2.5为解决问题的关键。铵盐（硝酸铵和硫酸铵）为PM2.5的主要成分，对促进细颗粒的吸湿长大有显著作用，成为主要的消光物质，对灰霾污染至关重要。氨和有机胺是大气中唯一的碱性物质，与酸性气体发生反应生成二次气溶胶。研究证明某些有机胺比氨更易于与酸性气体反应生成有机盐，而有机气溶胶对光具有更强的吸收作用。目前对大气及细颗粒物中有机胺（盐）鲜有报道。本研究在我国主要沙尘源区和典型城市及海岛上采样并全面化学分析，研究我国大气中铵盐和有机胺盐的时空分布和影响因素，建立大气胺（盐）的分析方法，首次追踪城市氨和胺排放源及其对PM2.5的贡献；结合激光雷达、卫星遥感观测，阐明这些含氮化物与能见度、消光系数、气象要素等的关系，分析含氮化合物对灰霾形成机制的影响。

严重灰霾污染覆盖了我国所有大中城市，2013年1月北京24天为灰霾天气，PM2.5小时浓度达993μg/m3，从源头控制PM2.5为解决问题的关键。铵盐（硝酸铵和硫酸铵）为PM2.5的主要成分，对促进细颗粒的吸湿长大有显著作用，成为主要的消光物质，对灰霾污染至关重要。氨和有机胺是大气中唯一的碱性物质，与酸性气体发生反应生成二次气溶胶。项目对大气中含氮化合物的分布、特征以及在大气转换过程进行了系统研究，包括PM2.5中的铵根、有机胺、硝酸根以及与这些组分成盐的前体物氨气（NH3），尤其是非农业源氨作了较为深入的研究。从源排放出发，首先对城市氨源作了全面筛查，定量了城市机动车和建筑人居排泄物的排放；继而依托自主建立的覆盖上海城乡区域的NH3监测网络，厘清了大气NH3的时空分布特征；首次建立了包含几乎所有氨排放源的稳定氮同位素源谱，并将之应用于北京APEC环境NH3的源解析；本研究建立了测定大气中痕量7种有机胺和15种氨基酸的有效观测方法，并将该方法成功应用于上海大气中有机胺和氨基酸的测定。基于气体（包括NH3）和颗粒物化学组分的连续监测，探究了SNA（NH4+、NO3-、有机胺）以及NH3对城市大气PM2.5污染的贡献。二次无机气溶胶的贡献比重随着PM2.5浓度的升高而持续增长，凸显出SNA对雾霾天气的重要作用。严重灰霾期间二次无机气溶胶（SNA）和比重均超过了50%，NO3-/SO42-的比值在2013年比2006年有明显的提高，预示着中国的能源消费结构正经历着以煤为主导向其它多元能源利用形式（如天然气、石油）并举的转型。在2006年冬季严重灰霾期间，硫酸盐的质量占到了19.0%，远远高于硝酸盐的占比（12.9%）；而在2013年冬季严重灰霾期间硫酸盐的占比已经下降到了10.6%，硝酸盐的质量占比上升到了20.2%，在SNA中的比例超过了50%，显示含氮组分对气溶胶爆发性增长加剧了灰霾的形成的贡献。

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