PAHs in SD:Polycyclic aromatic hydrocarbons levels in street dust in the central area of Niterói City, RJ, Brazil

Polycyclic aromatic hydrocarbons (PAHs) were studied in street dust (SD) samples collected in the center of Niterói, a tropical city located in the State of Rio de Janeiro, Brazil, at the margins of Guanabara Bay. Sampling was carried out monthly during the year of 2002 in order to evaluate seasonal variation of PAH concentrations. Samples were extracted by ultrasonic treatment with dichloromethane, cleaned up by solid phase extraction and analyzed by gas chromatography-mass spectrometry. The concentrations of the twenty one analyzed PAHs ranged from 3.2 to 132 ng/g. Of all PAHs, pyrene, fluoranthene and naphthalene showed the highest geometric means. Total PAH concentration (σPAH) ranged from 434 to 1247 ng/g with levels of carcinogenic PAHs (σCARC) representing 29 to 45% of σPAHs. The highest value of σPAH occurred in July 2002, when the lowest temperatures were measured in the Central Area of Niterói City. σPAH and σCARC showed significant correlations with daily mean and minimum temperature, as well as with temperature during sampling, indicating that both are influenced by these parameters. The obtained results suggest that a seasonal variation of total PAH levels in SD may occur in the studied area.