Role of Ammonia on the Feedback Between AWC and Inorganic Aerosol Formation During Heavy Pollution in the North China Plain
Role of Ammonia on the Feedback Between AWC and Inorganic Aerosol Formation During Heavy Pollution in the North China Plain
复制标题
华北平原重污染期间氨对AWC与无机气溶胶形成的反馈作用
DOI：
10.1029/2019ea000799
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发表时间：
2019-09-12
影响因子：
3.1
通讯作者：
Wang, Zifa
中科院分区：
文献类型：
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作者：
Ge, Baozhu;Xu, Xiaobin;Wang, Zifa
大气中的NH3不仅在环境生态系统中发挥着至关重要的作用，而且在大气化学中也发挥着至关重要的作用。为了进一步了解NH3对北京雾霾污染形成的影响，在2016年冬季空气污染与人体健康-北京（APHH-Beijing）活动期间，对大气中的NH3及相关物种进行了高分辨率测量和模拟。我们发现，在我们的活动期间，总NHx（气态NH3+颗粒NH4+）大部分超出了SO42−NO3−NH4+−水平衡系统。 NHx 过量使气溶胶呈中等酸性，污染和非污染条件下的中值 pH 值分别为 3.6 和 4.5，并增强了颗粒相硝酸盐的形成。我们的分析表明，NH4NO3 是驱动气溶胶水含量增加的最重要因素，NO3− 控制污染前期，NH4+ 控制污染最严重的阶段。在过量的NHx下，NH4NO3的形成增加，特别是在夜间，可能会引发气溶胶潮解相对湿度的降低，甚至降至低于50%，因此即使在低于50%的RH条件下也会导致吸湿生长，湿气溶胶颗粒成为快速非均相反应的更好介质。 RH的进一步增加促进了“气溶胶含水量-非均质反应”的正反馈，最终导致严重霾的形成。嵌套空气质量预测监测系统（NAQPMS）的模拟结果显示，在华北平原目前的排放条件下，控制20%的NH3排放可能会影响5%~11%的颗粒物PM2.5形成。
Atmospheric NH3 plays a vital role not only in the environmental ecosystem but also in atmosphere chemistry. To further understand the effects of NH3 on the formation of haze pollution in Beijing, ambient NH3 and related species were measured and simulated at high resolutions during the wintertime Air Pollution and Human Health‐Beijing (APHH‐Beijing) campaign in 2016. We found that the total NHx (gaseous NH3+particle NH4+) was mostly in excess of the SO42−‐NO3−‐NH4+‐water equilibrium system during our campaign. This NHx excess made medium aerosol acidity, with the median pH value being 3.6 and 4.5 for polluted and nonpolluted conditions, respectively, and enhanced the formation of particle phase nitrate. Our analysis suggests that NH4NO3 is the most important factor driving the increasing of aerosol water content with NO3− controlling the prior pollution stage and NH4+ the most polluted stage. Increased formation of NH4NO3 under excess NHx, especially during the nighttime, may trigger the decreasing of aerosol deliquescence relative humidity even down to less than 50% and hence lead to hygroscopic growth even under RH conditions lower than 50% and the wet aerosol particles become better medium for rapid heterogeneous reactions. A further increase of RH promotes the positive feedback “aerosol water content‐heterogeneous reactions” and ultimately leads to the formation of severe haze. Modeling results by Nested Air Quality Prediction Monitor System (NAQPMS) show the control of 20% NH3 emission may affect 5–11% of particulate matter PM2.5 formation under current emissions conditions in the North China Plain.