Efficient Heterogeneous Formation of Ammonium Nitrate on the Saline Mineral Particle Surface in the Atmosphere of East Asia during Dust Storm Periods

Abstract

To understand the chemical evolution of dust in the current East Asian atmosphere, the chemistry of PM2.5 and size-resolved aerosols in Shanghai, China, during the 2019 dust storm event was investigated. Our results showed that concentrations of SO4 2– in the city during the event highly correlated with Ca2+ and Na+ due to the direct emissions of CaSO4 and Na2SO4 from the upwind deserts. In contrast, during the event, NO3 – linearly correlated with NH4 + at a molar ratio close to 1:1, and both almost entirely stayed in coarse particles, suggesting they accumulated on the dust surface as NH4NO3. Based on the field observations and laboratory smog chamber simulations, we found that NO2 and O3 in Shanghai during the dust period reacted to form N2O5, which subsequently hydrolyzed into HNO3 on the surface of saline mineral dusts (e.g., CaSO4 and Na2SO4) and was further neutralized by NH3 as NH4NO3. The relative abundances of NO3 – and NH4 + in Shanghai during the dust event were notably higher than those a decade ago, indicating that this heterogeneous formation of NH4NO3 on dust was enhanced by the abundantly coexisting NO x , O3, and NH3 in the current East Asian atmosphere, which should be considered in future modeling studies.

Surface solvation of Martian salt analogues at low relative humidities

“…[4][5][6][7][8][9] An important and dynamic source of salt aerosols is saline lakes and playas, 10,11 which produce salt particles mixed with mineral dust that are transported over long distances. 5,7,[12][13][14][15][16][17][18] Furthermore, saline lakes and playas are becoming more relevant as they are continuously develop, in particular in the context of climate change. 19 Salt particles are also associated with haze formation in more populated regions.…”

N<sub>2</sub>O<sub>5</sub> uptake onto saline mineral dust: a potential missing source of tropospheric ClNO<sub>2</sub> in inland China

“…A very recent study (Wu et al, 2020) showed that N 2 O 5 uptake onto saline mineral dust contributed significantly to particulate nitrate formation during a dust storm event in Shanghai, China. One may further expect that it may have a profound effect on ClNO 2 , especially considering that vast areas in China are heavily affected by both mineral dust and NO x .…”

Synergetic effects of NH<sub>3</sub> and NO<sub><i>x</i></sub> on the production and optical absorption of secondary organic aerosol formation from toluene photooxidation

“…Furthermore, the acid-base reactions between NH 3 / NH + 4 and the carboxyl groups in SOA molecules might enhance SOA formation (Qi et al, 2020;Liu et al, 2015). The condensable ammonium salts formed from the reaction between NH 3 and organic acids reduce the volatility of the organic acids by several orders of magnitude (Paciga et al, 2014), and they act as particle-phase organics that further promote SOA formation (Na et al, 2007;Huang et al, 2012;Chen et al, 2019;Qi et al, 2020;Wu et al, 2020). In addition, carbonyls can undergo nucleophilic attack by NH 3 through the Maillard reactions and form the corresponding iminium intermediates (Noziere et al, 2009;Laskin et al, 2015;Liu et al, 2015).…”