Study On Hygroscopic Properties And Dynamic Processing Of Aerosol By FTIR-ATR

Aerosol plays a very important role in atmospheric environment, so it is significant in reality for environment to understanding the basic property parameters and dynamic process of aerosol. In this paper, we studied the hygroscopic properties of Na₂SO₄ and C12H22O11 aerosols with linearly changeable relative humidity?RH? by FTIR-ATR.The FTIR-ATR spectra of mixed glycerol/Na₂SO₄ aerosols with various mole ratios have been measured. From the feature bands of solution and crystal, it can be found that the amount of Na₂SO₄ crystals decreased and the appearance of Na₂SO₄ crystalsis delayed with the increasing glycerol content. The efflorescence relative humidity?ERH? of Na₂SO₄ decreases with more glycerol in the mixed particles, indicating that the contact ion pairs Na+SO42- have been blocked by glycerol molecules. The saturation of mixed aerosols corresponding to each RH could be obtained from the Extended Aerosol Inorganics Model?E-AIM?. By combination of ERH and saturation, it was found that the nucleation saturation became higher with the increasing glycerol content. Based on FTIR-ATR spectra and classical nucleation theory, the nucleation rate of Na₂SO₄ in mixed glycerol/Na₂SO₄ droplets has been calculated. The results show that the heterogeneous uncleation rate of Na₂SO₄ was decreased with the glycerol increasing.We measured the spectra of Hexadecyltrimethyl ammonium bromide?CTAB? and mixed CTAB/Na₂SO₄ aerosols. In the humidification process, the AH2 O of the CTAB changes continuously with RH and no ERH found. The addition of CTAB had little effect on nucleation of Na₂SO₄,however, decreased the nucleation ratios of Na₂SO₄.The FTIR-ATR spectra of sucrose?C12H22O11? and mixed C12H22O11/NaCl aerosols with mole ratios 1:1also have been measured. In the humidification process, AH2 O changes gradually. At 23% RH, the C12H22O11 entered into the glassy state, reflected by the limiting water-transfer. The addition of the NaCl has little effect on the FTIR-ATR spectra of sucrose. However, NaCl prevent sucrose from forming the glass state, which should be attributed to the lower viscosity of sucrose in C12H22O11/NaCl aerosols.