Gschwend%20thesis.pdf

.
~l
:.
2.
,
G
~
o;
-2-
VOLATILE ORGANIC COMPOUNDS IN SEAWATER
by
PHILIP M. GSCHWND
Submitted to the Woods Hole Oceanographic Institution on January 2Q, 1979,
in partial fulfillment of the requirements for the degree of Doctor of
Philosophy.
ABSTRACT
Vapor phase stripping and solid adsorbent trapping were applied to
seaW'ater and related samples to concentrate volatile organic compounds.
The concentrates were subsequently analyzed by glass capillary gas
chromatography and combined gas chromatography-mass spectrometry. The
compound identities and the spatial and temporal distributions of their
concentrations were used to determine some sources, transformations,
and transport mechanisms of organic matter in the sea.
Volatile organic compounds were determined in seawater samples from
the Sargasso Sea, the western Equatorial Atlantic, and the upwelling
region off Peru. Pentadecane was present in all three areas in surface
samples at 10-40ng/kg ànd decreased to 1-2 ng/kg in the deep water.
A source related to the transformation of the algal fatty acid, hexadecauRic
acid, by zooplankton is proposed since anthropogenic and direct phytoplankton
sources are unlikely. Cz-alkylated benzenes were found in the
upwelled water off Peru at about 4 ng/kg in the surface (5 and ZOrn),
3 ng/kg below the thermocline (100m), and Z ng/kg or less in deeper water.
A surface or atmospheric source is required to produce this distribution.
C6-CiO aldehydes were also found in seawater from off Peru. The direct
correlation of their concentrations with chlorophyll ~ and with oxygen
indicated that they are derived from chemical oxidation of algal metabolites,
for example, unsaturated fatty acids. Total volatiles in the oligotrophic
Sargasso Sea were about 10-30 ng/kg while the biologically productive
upwelling region off Peru contained up to 100 ng/kg.
The temporal variations of volatile organic compound concentrations
were investigated in coastal seawater from Vineyard Sound, Massachusetts.
Pentadecane and heptadecane showed large summertime concentration increases
which were ascribed to benthic algal sources. Laboratory incubations of
benthic algal samples supported this conclusion. The saturated hydrocarbons,
from C13-C17, and alkylated benzenes and naphthalenes were all
abundant after an oil spill several miles from the sampling site. Cz- and C3benzenes
were the most persistently abundant volatile compounds and their