Date of Award


Degree Type


Degree Name

Master of Science in Oceanography



First Advisor

James G. Quinn


A method which allows the measurement of the concentration of hydrocarbons and phthalic acid or phthalic acid esters in a single sea water sample is described. The average hydrocarbon concentration for 36 sea surface microlayer samples, approximately the top 300 microns was 94 μg/l with a range of <4 to 559 μg/l. The hydrocarbon concentration for 36 subsurface samples, approximately 20 cm below the surface, averaged 51 μg/l, with a range of <2 to 248 μg/l. Comparisons of sample pairs, sea surface microlayer and subsurface from each station, reveal that 71% have greater hydrocarbon concentrations in the sea surface microlayer than in the subsurface.

The average phthalic acid concentration for 10 sea surface microlayer samples was 0.9 μg/l (range of 0.1 to 3.2 μg/l), while the average value for 7 subsurface samples was 0.4 μg/l (range of <0.1 to 1.0 μg/l). The average di-2-ethylhexyl phthalate (DEHP) concentration for 3 sea surface microlayer samples was 4.0 μg/l (range for 3.2 to 4.6 μg/l) and the average concentration for 3 subsurface samples was 1.3 μg/l (range of 0.7 to 2.5 μg/l). All but one of the samples measured for phthalic acid and DEHP had greater concentrations in the sea surface microlayer than in the subsurface.

Pelagic tar was found to be a possible sources of petroleum hydrocarbons found in the Sargasso Sea waters. This material, as analysed by gas liquid chromatography, averaged 23% hydrocarbon, based on the dry weight of tar. Atmospheric transport and deposition are possible sources of phthalic acid in the open ocean samples.



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