Gschwend%20thesis.pdf

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study in some summer samples (Schwarzenbach et al., 1978; chapter 3)
and in the August and October control seawater samples of this study.
Two dihalomethanes were also found. These were produced at
about 0.1 times the rate of the trihalomethanes. This may reflect
the greater difficulty of cleavage of the dihalo-2-keto-compounds
relative to that of the trihalo analogues. The presence of iodine
in both of these dihalocompounds would serve to' enhance this cleavage.
o "
X3C--C--R
o
" k/10?
HX C--C--R
,.
2
k
)i
o
"
X3 CH + HOCR
o "
X2 CH2 + HOCR
Release rates on the order of several nglgm dry weight/day sug-
gest that standing stocks of less than 1 ng/liter seawater would re-
suIt. Thus detection by the FID would not be expected and indeed
the CD year-round samples did not reveal the presence of these com-
pounds. However, future work utilizing an electron capture detec-
tor may be fruitful, since thia detector is particularly sensitive
to halogenated compounds.
Undoubtedly, many other compounds substituting halogens for one
another were present in the algae of this investigation, but were
not seen due to limitations of the methodology (e.g., iodoform may be
too soluble and have too high a boiling point to be stripped).
One potential problem with this study is that algae may be
artificially induced to release. the volatiles to seawater by
the experimental conditions. However, since algae do not have root
systems, they do not die upon disengagement from the seafloor.