Gschwend%20thesis.pdf
Gschwend%20thesis.pdf
Gschwend%20thesis.pdf
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-3-<br />
concentrations were observed to be 2-10 times higher than average immediately<br />
after summer weekends, peak periods of tourist and recreational<br />
activities on Cape Cod. Naphthalene and its homologues were more abundant<br />
in the winter than in the summer. C6-CIO aldehydes were observed yearround,<br />
but showed a concentration maximum at the time of the late-winter<br />
phytoplankton bloom. C12-C15 aldehydes were also found in abundance at<br />
that time. Oxidation of algal matter by zooplankton or photochemicallyproduced<br />
oxidizing agents may produce the aldehydes, since laboratory<br />
cultures of phytoplankton 4id not produce these oxygenated volatiles. An<br />
alkene, structurally similar to the known benthic algal gamone, fucoser-<br />
. raten, was also found in Vineyard Sound seawater and in the upwelling<br />
region off Peru. Its appearance in Vineyard Sound samples coincided with<br />
the period of expected algal reproductive activity in February and March.<br />
Dimethyl polysulfides were found in coastal seawater. They may be<br />
produced within the water from precursors such as methyl mercaptan or other<br />
known polysulfide metabolites. Total volatile concentrations in Vineyard<br />
Sound seawater varied between ZOO and 500 ng/kg for the period from<br />
the late-winter<br />
January to June. Maximum concentrations occurred during<br />
phytoplankton bloom and again in the spring from anthropogenic inputs of<br />
hydrocarbons. .<br />
The highest concentrations of CZ- and C3-benzenes found in Vineyard Sound<br />
seawater coincided with motorboat use in the immediate vicinity of the<br />
sampling station. The average year-round isomer distribution most closely<br />
resembled distributions from gasoline and auto exhaust dissolved in seawater,<br />
consistent with an inboard or inboard/outboard motorboat source.<br />
Atmospheric and runoff delivery of CZ- and C3-benzenes to Vineyard Sound<br />
seawater during the period from spring through fall was concluded to be<br />
of lesser importance. The atmosphere may serve as a buffer for seawater<br />
concentrations of the aromatic compounds, supporting low concentrations in<br />
the winter and limiting high concentrations in the summer.<br />
Thesis Supervisors: Oliver C. Zafiriou<br />
Associate Scientist<br />
Department of Chemistry<br />
Woods Hole Oceanographic<br />
Institution<br />
Robert B. Gagosian<br />
Associate Scientist<br />
Department of Chemistry<br />
Woods Hole Oceanographic<br />
Institution<br />
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