Gschwend%20thesis.pdf

-14-
background ~ the next two chapters report investigations into the sources of
some anthropogenic and some natural volatile compounds.
These studies have provided insight into several aspects of marine
organic chemistry. First, organic compounds and their concentrations in sea-
water have been determined, allowing speculations concerning their chemical.
biochemical, and photochemical transformations. Next, additional insight
into the quantity and lability of the volatile fraction has been obtained
and can be put into the context of the larger carbon cycle. Also, informa-
tion pertinent to the feasibility of proposed transport mechanisms. for
example, from land via the atmosphere to the sea, has been acquired. Evi-
dence for chemical signals from marine organisms has been obtained and sug-
gests the strength and timing of these signals. Finally, data describing
"Man's infringement" on the sea have been procured and reveal not only the
presence of anthropogenic volatile compounds, but Have also suggested their
mode of introduction, their longevity, and tàeir potential for biological
interference.
Definition of Volatiles
The volatile fraction which is the subject of this thesis is described
by an operational definition. Three criteria are used to limit this frac-
tion. First, a compound must be "stripable", that is, it must be of suf-:
ficiently low water solubility and high vapor pressure to be purged from
the seawater sample by bubbling with an inert gas. Next, the component must
be retained at room temperature by a solid adsorbent such as charcoal or
Tenax. Lastly, the volatile must be amenable to gas chromatographic analy-
sis. It must be separable from interfering low-boiling compounds. it must
be thermally stable within the gas chromatograph, and it must be detectable
with the flame ionization detector.