UBIQUITOUS OCCURRENCE OF SEMIVOLATILE CARBONYL-COMPOUNDS IN TROPOSPHERIC SAMPLES AND THEIR POSSIBLE SOURCES

The levels of semi-volatile aldehydes with 4-10 carbon atoms and a ket one identified as 6-methyl-5-hepten-2-one by mass spectrometry have be en measured in some urban, suburban and forest areas together with imp ortant hydrocarbons emitted by man-made (benzene, toluene) and biogeni c sources (alpha-pinene). The results obtained show the ubiquitous occ urrence of these carbonyl compounds in the atmospheric environment. Di urnal profiles obtained at various sites and a vertical gradient measu red in a pine forest seem to be consistent with their natural origin. Direct emission from plants seems to be a major source for these compo nents in the atmospheric boundary layer. The levels measured indicate that they are among the most abundant gaseous organic components prese nt in natural environments.