Growth of organic aerosols by biogenic semi-volatile carbonyls in the forestal atmosphere

Gas and aerosol samples were collected from 13 to 15 August 2001 in Quercus and Picea mixed forest located at Uryu Experimental Forest of Hokkaido University using an annular denuder air sampling system. Gaseous concentrations of biogenic semi-volatile compounds (glycolaldehyde, hydroxyacetone, n-nonanal and n-decanal) showed a rapid increase in the morning and showed a maximum (61–105 pptv) around noontime. Then their concentrations significantly decreased in the evening, and showed a minimum at mid-night. On the other hand, these compounds in the particulate phase also showed a diurnal variation pattern similar to the gaseous compounds. However, the concentrations continued to increase until the evening and showed the maximum at nearly mid-night. The time lag of several hours in the peak of concentrations of these carbonyls in gas phase and particles indicates a gas-to-particle conversion probably through condensation and adsorption of gaseous compounds onto the pre-existing particles (growth of the aerosols).