Non-aromatic hydrocarbons in recent sediments of sepetiba and Ilha Grande Bays, Brazil

Abstract

An investigation was conducted in Ilha Grande and Sepetiba Bays aiming at identifying the nature of non-aromatic hydrocarbons (NAH) in surface sediments. NAH concentrations ranged from 2.5 μg g-1 to 193.8 μg g -1 of which the major fraction (53 to 93%) was composed by unresolved complex mixture (UMC). In most samples n-alkane distribution was dominated by compounds of odd carbon number showing maxima in nC29 and nC 31. Mono-olefins were at low concentrations and the polyolefins including highly branched isoprenoids and squalene varied from 0.099 μg g-1 to 1.387 μg g-1 with lower values relative to NAH appearing in areas of strong terrestrial and anthropogenic influence. Hopanes between C27 and C33 were observed in all samples with the predominant configuration 17α(H),21β(H), characteristic of a petrogenic origin. ©2008 Sociedade Brasileira de Química.