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Abstract
A new experimental procedure and robust equipment have been developed for studying oil degradation at sea and the system has been proved under harsh environmental conditions. The degradation of three weathered crude oils, differing substantially in composition, has been examined under both winter and late spring conditions. The oils were an Athabasca synthetic crude, its parent sand tar and a North Sea Forties crude. Composition had a major effect on the extent and rate of loss of oil from the system, the lighter oils disappearing more rapidly. After 40 d at sea at a mean temperature of 5 °C, only 16% of the synthetic crude remained compared with 47% and 85% of the Forties crude and sand tar respectively. At a mean temperature of 12 °C, average degradation rates were about three times those at 5 °C. At both temperatures, a mixed bacterial population involved in the degradation process was isolated from each oil. For the Forties crude and synthetic crude, the saturate fraction was degraded most rapidly, whilst in the sand tar, this fraction was not degraded as rapidly as the monoaromatic fraction.
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