The present work aimed at evaluating indicators of hydrocarbon sources to sediments from the Solimões River region, in the central Amazon. The 16PAH, the alkylated homologs and molecular markers were investigated. The entire series of alkylated PAH were present and, in some cases, with a distribution observed when oil residues dominate. Nevertheless, hopanes characterizing immature environments undergoing diagenetic transformation were identified in samples from the Solimões River and in surface as well as in core sediment samples from Preto Lake, in the Coari-Manaus stretch. Investigation suggests early diagenesis of the organic matter confirmed by identifying biogenic markers produced during organic matter transformation. Some of these markers derive from incomplete combustion of biomass and are contained in particulate matter formed during forest burning. In the sediments of an industrial area near the city of Manaus, the entire series of mature hopanes was present indicating anthropogenic source of hydrocarbons. The results so far obtained point out the complexity of PAH source appraisal. region Amazon 16PAH investigated cases dominate Nevertheless Lake CoariManaus Coari Manaus stretch burning hydrocarbons appraisal

<p>Polycyclic aromatic hydrocarbons (PAHs) were identified and quantified in samples of superficial sediments of the Negro River, in the Amazon region of Brazil, through analyses performed by GC/MS. Total PAH concentration that includes parent and alkylated PAHs ranged from 6.5 to 5348 ng g^-1 of dry weight. The ∑16 PAHs prioritized in environmental studies by the U.S. Environmental Protection Agency (USEPA) ranged from 5.6 to 1187 ng g^-1. The most contaminated places were those where muddy sediments were found, with the highest concentrations of organic matter, carbon and total nitrogen. The priority PAHs with high molecular weight represented 70% of the total abundance and showed that the main source of contamination of the sediments was pyrogenic. However, petrogenic PAHs coming from oil and derivatives input is also an important contamination source to be considered.</p>