Heterogeneous formation of particulate nitrate under ammonium-rich regimes during the high-PM2.5 events in Nanjing, China

• Published in: Atmospheric chemistry and physics 2020-04, Vol.20 (6), p.3999-4011
• Main Authors: Yu-Chi, Lin, Yan-Lin, Zhang, Mei-Yi, Fan, Bao, Mengying
• Format: Article
• Language: English
• Subjects: Acidification; Aerosol content; Aerosol formation; Aerosols; Air quality; Airborne particulates; Ammonia; Ammonium; Ammonium compounds; Aquatic ecosystems; Cities; Climate; Emissions; Equilibrium; Gases; Humidity; Ions; Moisture content; Nitrates; Nitrogen compounds; Nitrogen dioxide; Nitrogen oxides; Nitrogen oxides emissions; Particulate matter; Pollution; Ratios; Regional climates; Terrestrial environments; Water; Water chemistry; Water content
• ISSN: 1680-7316; 1680-7324
• DOI: 10.5194/acp-20-3999-2020

Particulate nitrate (NO3-) not only influences regional climates but also contributes to the acidification of terrestrial and aquatic ecosystems. In 2016 and 2017, four intensive online measurements of water-soluble ions in PM2.5 were conducted in Nanjing City in order to investigate the potential formation mechanisms of particulate nitrate. During the sampling periods, NO3- was the predominant species, accounting approximately for 35 % of the total water-soluble inorganic ions, followed by SO42- (33 %) and NH4+ (24 %). Significant enhancements of nitrate aerosols in terms of both absolute concentrations and relative abundances suggested that NO3- was a major contributing species to high-PM2.5 events (hourly PM2.5≥150 µg m-3). High NO3- concentrations mainly occurred underNH4+-rich conditions, implying that the formation of nitrate aerosols in Nanjing involved NH3. During the high-PM2.5 events, the nitrogen conversion ratios (Fn) were positively correlated with the aerosol liquid water content (ALWC; R>0.72 and p