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Characteristics of atmospheric ammonia and its impacts on SNA formation in PM2.5 of Nanchang, China
Atmospheric Pollution Research ( IF 4.5 ) Pub Date : 2024-01-24 , DOI: 10.1016/j.apr.2024.102059 Yue Liang , Hong Jiang , Xiaozhen Liu
Atmospheric Pollution Research ( IF 4.5 ) Pub Date : 2024-01-24 , DOI: 10.1016/j.apr.2024.102059 Yue Liang , Hong Jiang , Xiaozhen Liu
Atmospheric NH is the only alkaline inorganic gas, and plays a important role to the formation of secondary inorganic aerosols (SNA). The high-time resolution of NH levels were measured throughout a year in Nanchang city in central China. Combined with the conversion rates of SO2/NO2/NH3 and the water-soluble inorganic ions in fine particulate matter (PM), the effect of NH on SNA formation were analyzed. The results showed that NH levels ranged from 0.71 μg/m to 17.15 μg/m with mean 5.83 ± 3.45 μg/m, and high value in summer (7.85 ± 2.39 μg/m) and spring (7.14 ± 2.16 μg/m) and low value in autumn (4.96 ± 1.43 μg/m) and winter (3.10 ± 0.39 μg/m). NH levels were strongly influenced by temperature (R = 0.83), while weak negative correlation with relative humidity (R = −0.24) and not correlated with wind speed (P > 0.05). In the rainy spring and summer, NH concentration increased on the first day of rain and after rain stopped, whereas continuous or heavy rain had obvious scavenging effect on NH concentration. The removal efficiency of rain on NH was greater in agricultural activities periods than that in non-agricultural activities periods. In autumn and winter, intermittent rain was dominant and little impact on NH levels. Levels of NO2, SO2 and NH3 had similar significant increase attributed to the biological and agricultural source in spring, while in other seasons variations of these trace gases levels were different due to their different sources and conversion mechanisms. Higher NH3 conversion rate (NHR = 0.56) and [NH4+]excess>0 only occurred in winter, early spring and late autumn, and NH4+ had a significant correlation with 2SO42−+NO3−+Cl− (R2 = 0.91) with a slope close to 1, indicated the generation of SNA in winter was limited by NH3 levels. SO42- concentration was mainly controlled by SO2 and SOR, while NO3- was controlled not only by NO2 and NOR but also influenced by NH3 and temperature. NH3/NHx (NH3+NH4+) had obvious seasonal differences, NHx deposition was mainly by form of NH3 deposition (NH3/NHx = 0.73) in summer while by NH4+ in winter (NH3/NHx = 0.27).
更新日期：2024-01-24
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