Environ. Sci. Technol. 1996, 30, 3646
Comment on “Global Mass Balance for Polychlorinated Dibenzo-p-dioxins and Dibenzofurans” SIR: Possibly there is an explanation for the fact that, for chlorinated dioxins and dibenzofurans, Brzuzy and Hites find global deposition rates to be four times greater than human-induced emissions (1). A reasonable explanation is that the total emission calculations should also include natural biomass metabolism products, volcanic gases, and naturally caused forest fires (probably ignited by lightning). The importance of these three sources has been pointed out by G. W. Gribble (2-4). Although the emissions from these might be difficult to estimate, some quantitative information about them is reported in the literature referred to by Gribble. Each natural source sometimes produces aerosols that are visible over vast areas of the earth, and the amounts of halocarbons and furans could be very large. Since, as Gribble mentions, the natural biomass emission
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of chloromethane is estimated to be about 5 billion kg/yr, it seems reasonable that the naturally produced dioxinlike materials might turn out to be a significant part of the 13 thousand kg/yr deposition rate estimated by Brzuzy and Hites. It is therefore appropriate that future calculations on the global mass balance should attempt to include these natural sources.
Literature Cited (1) Brzuzy, L. P.; Hites, R. A. Environ. Sci. Technol. 1966, 30, 17971804. (2) Gribble, G. W. Environ. Sci. Technol. 1994, 28, 310A-319A. (3) Gribble, G. W. Environ. Sci. Technol. 1995, 29, 8A. (4) Gribble, G. W. Environ. Sci. Technol. 1996, 30, 184A.
Daniel J. Shanefield Ceramics Engineering Department Rutgers University Piscataway, New Jersey 08855-0909 ES9604929
S0013-936X(96)00492-0 CCC: $12.00
1996 American Chemical Society
