tially no detectable gas phase any more for the latter compounds. Therefore, it seems reasonable to explain the observed alternation of the higher n-alkanes by the natural contributions of vegetation to the ambient aerosol. Besides the odd carbon number predominance of n-alkanes which is most pronounced in our background samples, we have also identified on several occasions (7) diterpenoid compounds such as abietic, pimaric, and dehydroabietic acids which are typical of resinous plants. This is again in agreement with Simoneit’s remarks. No stable carbon isotope analysis has been performed on our samples, but it is important to stress that both the seasonal dependency of the carbon preference index (8)and its variation with particle size (using fractionated samples) sustain the natural origin of the higher n-alkanes. If dispersion of plant debris is the major source of generation of these aerosols, the carbon preference index for a size-fractionated sample should peak at the larger particle sizes, which is in contrast to the normal size distribution expected for condensation aerosols. This is precisely the case for most of our samples, as can be seen from Table I. Finally, we agree the word “pollutants” may not be appropriate for hydrocarbons and fatty acids derived from natural biogenic sources. However, even these naturally occurring compounds may have adverse health effects: thus, long-chain alkanes have been shown to behave as cocarcino-
gens in the experimental animal and to enhance the development of tumors, originally induced by polycyclic aromatic hydrocarbons. Therefore, the release of higher n-alkanes from natural sources into an atmosphere where several known carcinogens are present does constitute an additional health hazard and should be further evaluated.
Literature Cited (1) Broddin, G., Cautreels, W., Van Cauwenberghe, K., Atmos. Enuiron., in press. (2) Pupp, C., Lao, R. C., Murray, J. J., Pottie, R. F., Atmos. Enuiron., 8,915 (1974). (3) de Wiest, F., Della Fiorentina, M., Atmos. Enuiron., 10, 951 (1975). ( 4 ) de Wiest, F., Rondia, D., Atmos. Enuiron., 10,487 (1976). (5) Janssens, J., Van Vaeck, L., Van Cauwenberghe, K., unpublished results. (6) Van Vaeck, L., Van Cauwenberghe, K., Adu. Mass Spectrom., in press. (7) Broddin, G., Ph.D. Thesis, University of Antwerp, 1980. (8) Eichmann, R., Neuling, P., Ketseridis, G., Hahn, J., Jaenicke, R., Junge, C., Atrnos. Enuiron., 13,587 (1979).
L. Van Vaeck* G. Broddin K. Van Cauwenberghe Chemistry Department University of Antwerp (U.I.A.) 8-2610 Wilrijk, Belgium
Correction 1981, Volume 15
James L. Lake,* Roger F. Rogerson, and Curtis B. Norwood: A Polychlorinated Dibenzofuran and Related Compounds in an Estuarine Ecosystem. Page 551. The last sentence of footnote b to Table I should read as follows: Concentrations are not corrected for procedural losses.
1106
Environmental Science & Technology
