Gschwend%20thesis.pdf

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volatile. which has been studied in sufficient detail for us to have deter-
mined the major aspects of its marine geochemistry.
Numerous reports have been made concerning the occurrence of Cl to C4
hydrocarbons in seawater (Unnenbom and Swinnerton, 1970; Frank et aL., 1970;
Lamontagne et al., 1971; Brooks et al., 1973; Brooks and Sackett, 1973;
Swinn.erton and Lamontagne, 1974; Lamontagne et al., 1974; Lamontagne et al.,
1976; Scranton, 1977). Methane typically occurs at about 30 ng/kg seawater
(2.2 nM), ethane at 0.6 ng/kg (0.02 nM), and propane at 0.6 ng/kg (0.014 nM).
Even lower levels of ethene, propene, butane, isobutane, butene and pentane
are found. Methane and ethene have biological sources; all of the saturated
lower hydrocarbons have petroleum-related sources; and the unsaturated com-
pounds may arise from photochemical processes.
Some effort has been made to study the volatile halogenated hydrocar-
bons in seawater due to interest in their anthropogenic origin. Volatile
chlorinated and fluorinated hydrocarbons are produced industrially at about
35,000 MT/yr, and about 4000 MT/yr are used in directly disp.ersed manners
(NAS, 1975a). Table I-i lists the compounds reported, the concentrations
found, the suspected source (s) and the location of the samples. Only tet-
rachloroethylene (CI2C=CC1i) and hexachlorobutadiene (CI2C=CCI-CCI=CCli)
would be amenable to detection by the methods used in this thesis (but not
particularly so since aflame ionization detector is used).
Volatile organic sulfur compounds such as carbon disulfide (Lovelock,
1974) and dimethyl sulfide (Lovelock et al., 1972) have also been isolated
from seawater samples. Carbon disulfide occurred at about 0.5 ng/kg while
dimethyl sulfide was found at about 12 ng/kg. Biological sources for
these materials are suspected.
Most recently, Sauer et al. (1978) have reported the concentrations of
the volatile liquid hydrocarbons in seawater from the Gulf of Mexico.