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.