The degradation of fatty acid methyl esters (FAMEs) has been characterized in selected biodiesels exposed to sunlight and seawater, and markers are identified that can be used to match a weathered biodiesel spill to its source. Samples of one synthetic and three commercial biodiesels were subjected to a regime of controlled weathering for 71 days. Experiments were designed to promote photo-oxidation, biodegradation or a combination of both processes. The FAME compositions of the biodiesels were measured by GC-MS at various times. Unsaturated FAMEs were preferentially degraded by photo-oxidation. Saturated C16 and C18 FAMEs were the most persistent compounds. The diagnostic ratio C16:0/(C16:0 + C18:0), calculated from the peak area of the total ion chromatograms (TICs), varied by less than 2% (RSD) during 71 days of weathering and could be used to distinguish among the biodiesels studied.
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- Biodegradation of biodiesel
- Gas chromatography mass spectrometry
- Oil spills
- Photo-oxidation of biodiesel