Aliphatic hydrocarbons and 39 PAH (parental and alkylated homologs) determined in ca. 100 sediment
samples from the Guanabara Bay, Rio de Janeiro, were evaluated for source discrimination using new
approaches. Concentrations of total PAH were in the range of 96–135,000 lg kg1 similar to other coastal
urbanized embayment. Traditional diagnostic ratios were not as efficient PAH source indicators, e.g. biomass
combustion was assigned as the major source of the pyrolytic PAH although the hydrographic basin
is highly industrialized and urbanized. It is proved petrogenic imprint cannot be detected if only the 16
USEPA PAH are determined. The high production in the eutrophic system is not apparent in the aliphatic
fraction dominated by land derived n-alkanes due to the effectiveness of microbial degradation. The present
work demonstrates the complexity of hydrocarbon forensics when applied to chronically contaminated
environments.