Comment on acp-2022-364

Abstract

Nitrate uptake into particles is an important feature of thermodynamic equilibriums responsible for the high-concentration particle formation in East Asia. However, key processes including the gas-particle partitioning of HNO3-NO3- and the deliquescence of particles, are not scrutinized in thermodynamic model simulations used in field studies. Using a humidified tandem differential mobility analyzer (HTDMA), we investigated water uptake and gas-particle partitioning of nitrates for inorganic and inorganic-organic aerosols as we simulated thermodynamic models (ISORROPIA-II and E-AIM). For the best-fit to HTDMA measurements, we revised thermodynamic model simulations and conducted linear regressions. Results demonstrated that ammonium nitrate aerosols maintained deliquescence in the entire range of 10–90 % relative humidity (RH) and in the range of 30–70 % RH the aerosol liquid water content (ALWC) and nitrates in ammonium-sulfate-nitrate aerosols simultaneously evaporated. Glyoxal exhibited hygroscopicity and a synergetic effect on ALWC formation with ammonium sulfates. In ammonium-sulfate-nitrate-glyoxal aerosols, more ALWC and nitrates formation above 50 % RH is likely due to the synergetic effect among ammonium, sulfates and nitrates. Considering that 30–80 % RH is haze conditions in East Asia, we propose that pronounced nitrate formation in particles beyond the description of current thermodynamic model simulations includes deliquescent nature of ammonium nitrate aerosols that undergo hysteresis with an unclear efflorescence RH point due to incomplete equilibriums, the evaporation of ALWC, nitrates and ammoniums in sulfate-rich aerosols, and the synergetic effect between organic and inorganic components on ALWC formation at high RH.