Oil pollution in the Straits of Malacca, Malaysia: Application of molecular markers for source identification

The Straits of Malacca is one of the world's busiest supertanker routes, an d tanker-derived oil spills occur frequently. In addition, domestic oil spi lls have been increasing due to growing industrialization of Malaysia. The determination of the exact source of the spills is critically important. Th is paper examines the utility of biomarker compounds, triterpanes, to ident ify the source of the oil spills. Middle East crude oils (MECO), South East Asian crude oils (SEACO), tar-balls, sediments, and mussels were analyzed. The most distinctive compositional features for the crude oils are that 17 alpha 21 beta(H)C-29 norhopane and C-31-C-35 homohopanes, especially C-35 homohopanes, are depleted in SEACO. These remarkably different hopane compo sitions can be explained by the fact that MECO and SEACO are derived from c arbonate (marine) and lacustrine/deltaic shale (nonmarine) source rocks, re spectively. Two of the eight tar-balls samples collected on the coast of Pe ninsular Malaysia were identified to be derived from Middle East petroleum based on their biomarker signatures. The results of oleanane analyses imply that a low concentration of oleanane does not always indicate a Middle Eas t petroleum contribution although at high concentration oleanane can be a u seful biomarker for South East Asian oil sources. Application of the source -identifier to sediment and mussel samples showed the Middle East oil signa ture. One possible explanation is that Middle East oil is used in formulati ng Malaysian lubricating oils which are the source of oil found in sediment and mussel samples. This is consistent with the analytical results for the lubricating oil used in Malaysia and the street dust samples.