Long-term fate and persistence of the spilled Metula oil in a marine salt marsh environment - Degradation of petroleum biomarkers

Three coastal sites, heavily oiled from the 1974 Metula oil spill in the St rait of Magellan [two are salt marshes (East and West) and the third, an in tertidal asphalt pavement], were examined during May 1998. Complete 'total oil analyses' were performed on the oil samples collected from these sites. Chemical fingerprinting data reveal, except for those samples from the Eas t Marsh untreated plots which were only lightly to moderately weathered, th at the spilled oil has undergone significant alteration in chemical composi tion after 24 years. There are no fundamental differences between the heavi ly weathered West Marsh and treated East Marsh samples. However, the effect of experimental filling action conducted in 1993 has been to substantially promote plant recolonization. The asphalt pavement samples indicate extrem ely high degradation of oil hydrocarbons, evidenced by a complete loss of n -alkanes from n-C-8 to n-C-41 and by depletion of greater than 98% of the a lkylated polycyclic aromatic hydrocarbon homologues. Even the most refracto ry biomarker compounds showed some degree of biodegradation. The biomarkers were generally degraded in the declining order of importance as follows: d iasteranes >C-27 steranes > tricyclic terpanes > pentacyclic terpanes > nor hapanes similar toC(29)-alpha beta beta -steranes. (C) 2001 Elsevier Scienc e B.V. All rights reserved.