TY - JOUR

T1 - Role of Ammonia on the Feedback Between AWC and Inorganic Aerosol Formation During Heavy Pollution in the North China Plain

AU - Ge, B.

AU - Xu, Xiaobin

AU - Ma, Zhiqiang

AU - Pan, X.

AU - Wang, Zhe

AU - Lin, Weili

AU - Ouyang, B.

AU - Xu, D.

AU - Lee, J.

AU - Zheng, M.

AU - Ji, D.

AU - Sun, Y.

AU - Dong, Huabin

AU - Squires, F.A.

AU - Fu, P.

PY - 2019/9/30

Y1 - 2019/9/30

N2 - 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.

AB - 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.

KW - aerosol water content

KW - ammonia

KW - APHH-Beijing

KW - NCP

KW - partition

KW - PM2.5

U2 - 10.1029/2019EA000799

DO - 10.1029/2019EA000799

M3 - Journal article

VL - 6

SP - 1675

EP - 1693

JO - Earth and Space Science

JF - Earth and Space Science

SN - 2333-5084

IS - 9

ER -