THE EFFECT OF BIODIESEL ON THE RATE OF REMOVAL AND WEATHERING CHARACTERISTICS OF CRUDE-OIL WITHIN ARTIFICIAL SAND COLUMNS

The physical and chemical properties of crude oils differ greatly and these properties change significantly once oil is spilled into the mar ine environment as a result of a number of weathering processes. Quant itative information on the weathering of spilled crude is a fundamenta l requirement for a fuller understanding of the fate and behaviour of oil in the environment. Additionally, such data are also essential for estimating windows-of-opportunities, where specific response methods, technologies, equipment or products are most effective in clean-up op erations. In this study the effects of a relatively low toxicity compo und, biodiesel (rape seed oil methyl ester) on the rate of removal and weathering characteristics of crude oil within artificial sand column s are thoroughly investigated using GC/MS techniques. In the absence o f the biodiesel, the crude oil exhibits low mobility and a slow rate o f microbial degradation within the sediment and as a result, a high de gree of persistance, Brent crude oil was subject to a progressive loss of the low molecular weight n-alkanes with respect to time through ev aporation and a preferential migration of these fractions through the sediment to depth, The addition of the biodiesel led to greater recove ry of oil from the sediment if applied to relatively unweathered crude oil. This was as the result of the crude oil dissolving within the mo re mobile biodiesel, The negligible concentration of the n-C-10 to n-C -21 fraction in surface sediment samples suggests a greater solubility of these fractions within the biodiesel and that their subsequent ads orption onto subsurface sediment particles was responsible for their a bsence from water flushed through the sands, These results suggest tha t biodiesel may have an active role in the beach clean-up of spilt cru de oil. (C) 1998 Elsevier Science Ltd. All rights reserved.