Gschwend%20thesis.pdf

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Finally, the diesel-exhause-dissolved-in-seawater pattern differs from
the gasoline-exhaust-dissolved-in-seawater pattern in that the former
showed Cz- and C3-benzenes at similar levels while the latter had relatively
more C2- than C3-benzenes. This is probably due to the relatively facile
transfer of C2-benzenes on the one hand, and to the original enrichment of
C3 -benzenes in the heavier diesel on the other hand. This C3 ~benzene
enrichment is particularly evident for l, 2, 3-trimethyl benzene relative to
the other lower-boiling isomers.
The average year-round isomer distribution is indicated by the dots in
figure 4-2 and most resembles the patterns for auto-exhaust~dissolved-in-
seawater and September 2 boat exhaust at CD. The linear correlation coeffi-
cients for the isomer distributions found in the lab studies versus the
average year-round, Idistribution values were: gasoline, O. 9l; auto exhaus t,
0.46; auto exhaust dissolved in seawater, 0.95; gasoline/oil for outboards,
0.88; outboard exhaust dissolved in seawater, 0.61; Sept. 2, 1978 ski
boats, 0.94; diesel exhaust dissolved in seawater, 0.80; and #2 fuel oil,
0.44. The most notable discrepancies in these distributions are found for
the peaks containing para substituents (para-xylene, p-ethyl methyl benzene,
and 1,2, 4-trimethyl benz ene; the first 2 were not resolved from the meta
isomers by GC and appear as a single peak in the isomer distributions) .
These compounds were found to be the most rapidly degraded of the. alkylated
benzenes by Kappeler (1976) in his studies of the microbial degradation of
the alkyla ted benzenes in groundwater. Thus, the discrepancies may reveal
the importance of a similar biochemical degradation in these coastal seawaters.
Utilizing o-xylene as an internal standard, the other C2- and C3-
benzenes may be studied for their relative variations during the year