Degradation of Bunker C oil under different coastal environments of Chedabucto Bay, Nova Scotia

Abstract

The results given in this paper tend to indicate that the extent of degradation of spilled oil in marine areas depends, in a large measure, upon the environmental conditions of coastal areas. The degradation is rapid in the high energy environment but is relatively slow in protected areas. Bacterial as well as oxidative processes appear to alter the composition of oil. Oils exposed to high energy shoreline environments lose n-alkanes more rapidly. This loss is probably due to bacterial degradation because no other known physical or chemical process can account for this. With weathering the saturated and aromatic hydrocarbons decrease with a corresponding increase in the non-hydrocarbons, particularly in resins and NSO compounds. These changes which are possibly due to microbial and oxidative degradation processes are prominent in the oils of high energy environment. The rates of degradation of saturated and aromatic fractions appear to be the same. The specific gravity increases with an increase in degradation of oil. The viscosity values show a marked increase with weathering. The increased viscosity of the oil residues in the high energy environment has reduced its mobility. The data suggest that the residual oils present in varying amounts on nearly all contaminated beaches of the protected areas of low and moderate energy environments will persist for several years. In high energy environments the residual oils are substantially altered due to the loss of n-alkanes and a parallel increase in resins and NSO compounds. The resulting residues are highly viscous and remain adhering to sand and pebble substrate.