摘要
Glyoxal, (CHO)2, is one of the major products in the oxidation of isoprene, and it can be easily transformed to the fully hydrated from, dihydrated glyoxal (CH(OH)2)2, when dissolved in water. In this work, the hygroscopic growth of glyoxal aqueous aerosol was examined from the extinction infrared spectra by using in situ Fourier-transform infrared spectrometry as the glyoxal aqueous aerosols were generated by nebulization of the glyoxal solutions at different concentrations (1–10 wt %). The most characteristic bands of the glyoxal aqueous aerosols appeared at 3600–3000 cm–1 and 1200–900 cm–1, attributed to the O–H stretching modes of liquid-like water and the C–O stretching modes of glyoxal dihydrate, respectively. The partitioning of the liquid water and the glyoxal dihydrate in the glyoxal aqueous aerosols from nebulization of the concentrated glyoxal solution is similar to that from diluted glyoxal solution, in concomitance with the increase in the aerosol particle size, indicating the hygroscopic growth of the concentrated glyoxal aqueous aerosol. When the ambient temperature was increased to 55 °C from 35 °C in the presence of sufficient H2O vapor, the glyoxal aerosol preserved 40% of its H2O content with respect to that at 35 °C, whereas the aerosols from nebulizing pure water did not manifest the liquid-like water IR features. These results implied the inhomogeneous nucleation capability of the glyoxal aqueous aerosol. On the basis of these observations, the hydration/dehydration of glyoxal or other carbonyls should be explicitly taken into consideration in the aerosol chemistry of glyoxal, especially in highly humid environments.