Date of Award

1984

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Oceanography

Department

Oceanography

First Advisor

Michael Pilson

Abstract

The fates of two four-ringed polycyclic aromatic hydrocarbons (PAH), benz(a) anthracene and 7,12-dimethylbenz(a) anthracene, were examined in the large marine microcosms of the Marine Ecosystems Research Laboratory (MERLa) at the University of Rhode Island. The microcosms contain ecosystems that are representative of the conditions in lower Narragansett Bay. Two experiments with carbon-14 labeled benz(a)anthracene lasted 230 and 202 days and were begun in the summer and winter respectively. A summer experiment with carbon-14 labeled 7,12-benz(a)anthracene lasted 62 days. The parent compounds and their degradation products were examined in the water and sediments.

At the end of the two benz(a)anthracene experiments the distribution of the radiolabel was quite similar with 10-20% found as parent compound, 25-40% as CO2, and 45-55% as intermediate breakdown products. The disappearance of benz(a) anthracene from the water column was 3 to 5 times faster in the summer than in the winter. The rate of benz(a)anthracene biodegradation became very slow after about 50 to 100 days, indicating that the portion of the parent compound remaining at the end of the experiments may persist indefinitely. Significant portions (up to 30%) of the activity were found as water soluble intermediates. The 7,12-dimethylbenz(a)anthracene was rapidly photodegraded during the first few hours of the experiment, followed by slow remineralization of intermediates to CO2.

The results of the large microcosm experiments were compared to predictions based on laboratory experiments or predictive models. The photodegradation and sedimentation models provided good predictions. Also, one of a number of partitioning models provided a good prediction of the experimental results. Laboratory measurements of PAH biodegradation and remineralization rates did not predict the complex patterns of biodegradation and remineralization in the microcosm experiments.

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