Traffic-related polycyclic aromatic hydrocarbons (PAHs) occurrence in a tropical environment.

Traffic-related PAH emissions over the urban area of Natal, Brazil, have shown a significant increase because of automobile usage and have become a major concern due to their potential effects on human health and the environment. Therefore, this research measured PAH contamination on major roads and river compartments in a tropical catchment (Pitimbu River) over an expanding urban area. Road PAH concentrations spanned from 692 to 2098 ng g-1 and suggest the predominance of heavy (diesel-powered) and light-duty (gasoline plus alcohol-powered) vehicle emission sources. High concentrations of naphthalene (515 ng g-1) and acenaphthylene (145 ng g-1) were found in river sediments, indicating oil-related spillage and low-temperature combustion sources. Diagnostic ratios indicated the prevalence of biomass, coal and petroleum combustion processes and refined oil products. The ecological risk assessment indicated an ecological contamination risk ranging between low and moderate because of naphthalene and acenaphthylene concentrations higher than ERL threshold values. Toxicity risks caused by PAHs were assessed by using the BaP-equivalent carcinogenic power (BaPE). Results indicated that both RDS and riverbed sediment samples are at low toxicity risk.

Metagenome enrichment approach used for selection of oil-degrading bacteria consortia for drill cutting residue bioremediation.

Drill cuttings leave behind thousands of tons of residues without adequate treatment, generating a large environmental liability. Therefore knowledge about the microbial community of drilling residue may be useful for developing bioremediation strategies. In this work, samples of drilling residue were enriched in different culture media in the presence of petroleum, aiming to select potentially oil-degrading bacteria and biosurfactant producers. Total DNA was extracted directly from the drill cutting samples and from two enriched consortia and sequenced using the Ion Torrent platform. Taxonomic analysis revealed the predominance of Proteobacteria in the metagenome from the drill cuttings, while Firmicutes was enriched in consortia samples. Functional analysis using the Biosurfactants and Biodegradation Database (BioSurfDB) revealed a similar pattern among the three samples regarding hydrocarbon degradation and biosurfactants production pathways. However, some statistical differences were observed between samples. Namely, the pathways related to the degradation of fatty acids, chloroalkanes, and chloroalkanes were enriched in consortia samples. The degradation colorimetric assay using dichlorophenolindophenol as an indicator was positive for several hydrocarbon substrates. The consortia were also able to produce biosurfactants, with biosynthesis of iturin, lichnysin, and surfactin among the more abundant pathways. A microcosms assay followed by gas chromatography analysis showed the efficacy of the consortia in degrading alkanes, as we observed a reduction of around 66% and 30% for each consortium in total alkanes. These data suggest the potential use of these consortia in the bioremediation of drilling residue based on autochthonous bioaugmentation.