Gschwend%20thesis.pdf

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an atmospheric source did not control these levels. Also air concentrations
of o-xylene (measured directly, calculated from rain data, and calculated
from Oyster Pond data) were below values expected for equilibrium with
observed seawater levels.
Analyses of inland freshwater samples from Oyster Pond, the Quashnet
River, and Sippewissett Marsh also revealed that runoff, through these
relatively undeveloped areas, diluted the coastal seawater with respect to
the aromatic hydrocarbons. This is not to say that runoff entering the
Sound through, for example, Falmouth Harbor, does not contain high concen-
trations of these pollutants.
The relative constancy of concentrations and isomer ratios of the
C2- and C3-benzenes in coastal seawater may indicate that a "buffer" controlled
the background levels of these materials. The metropolitan northeastern U. S.
may provide a continuous background of aromatic hydrocarbons and this, in
conjunction with the prevailing south westerly w~nd pattern, may maintain the
background levels observed at CD. This was supported by the November rain
sample which indicated that the atmosphere was near equilibrium with seawater
with respect to the C2- and C3~benzenes at that time.
Superimposed on this background, there may have been short-term effects
related to tourist and recreational activities on Cape Cod.
Additional work is required to study the "off season" effects. Also,
many assumptions concerning the sinks of these relatively refractory hydro-
carbons have been made and need to be investigated. Finally, the development
of dependable analytical methods for air samples is needed to complement
the reliable procedures already available for water samples.