Journal of Environmental Sciences 2011, 23(6) 904–911 Distribution and origin of polycyclic aromatic hydrocarbons in surface sediments from an urban river basin at the Metropolitan Region of Curitiba, Brazil Natalicio Ferreira Leite 1 , Patricio Peralta-Zamora 2 , Marco Tadeu Grassi 2, ∗ 1. Instituto de Tecnologia do Paran´ a (TECPAR), 81350-010 Curitiba, Brazil 2. Departamento de Qu´ ımica, Universidade Federal do Paran´ a (UFPR), C.P. 19081, 81531-990 Curitiba, Brazil. E-mail: mtgrassi@ufpr.br Received 21 July 2010; revised 15 October 2010; accepted 01 November 2010 Abstract The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in surface sediment samples from nine sites located at the Iguac ¸u River Basin in the Metropolitan Region of Curitiba, Brazil to evaluate their distribution and sources. The total concentration of the PAHs was greater for sediments from highly urbanized areas, while the sediments from the Ira´ ı Environmental Protection Area (Ira´ ı EPA) showed significantly low concentrations. The sediments from the Iguac ¸u and Barigui rivers were classified as highly contaminated, while those from the Cercado and Curralinho rivers were classified as moderately contaminated. The predominance of PAHs containing two to four aromatic rings in most of the samples suggested the direct input of raw sewage into the water resources evaluated. Benzo[g,h,i]perylene, dibenzo[a,h]anthracene and indeno[1,2,3-cd]pyrene were predominant in sediments from the areas under the greatest urban and industrial development. The correlation between thermodynamic stability and the kinetics of evolution presented by the isomeric pairs indicated that combustion is the predominant source of PAHs in the sediments because the combustion of fossil fuels affected most of the points evaluated, followed by combustion of biomass and eventually combustion of oil product inputs. In general, the results showed that areas under strong urban influence, as well as the Ira´ ı EPA, receive contributions of PAHs from similar sources. Key words: PAHs; trace level analysis; river sediment; isomeric ratio; Iguac ¸u River Basin DOI: 10.1016/S1001-0742(10)60496-2 Citation: Natalicio F L, Patricio P Z, Marco T G, 2011. Distribution and origin of polycyclic aromatic hydrocarbons in surface sediments from an urban river basin at the Metropolitan Region of Curitiba, Brazil. Journal of Environmental Sciences, 23(6): 904–911 Introduction Polycyclic aromatic hydrocarbons (PAHs) are ubiqui- tous environmental contaminants primarily produced by exposure of organic matter to temperatures exceeding 700°C. Production of PAHs occurs in natural and anthro- pogenic processes of incomplete pyrolysis and combustion (WHO, 1998) in addition to the geochemical formation of fossil fuels (Yang et al., 1991). Anthropogenic emissions, including domestic and industrial wastes, by-products of incineration of industrial and urban wastes, oil spills and their derivatives and, particularly, the combustion of biomass and fossil fuels (WHO, 1998; Baird and Cann, 2008), are responsible for the most significant contribution of PAHs to the environment. In developing countries like Brazil the burning of vegetation from both forests and agricultural practices represents a significant source of PAHs in the environment (Godoi et al., 2004). The stationary sources are responsible for approximate- ly 80% of the total emission of PAHs, while the exhaust * Corresponding author. E-mail: mtgrassi@ufpr.br of vehicles powered by diesel and gasoline are the most prominent mobile sources (Yang et al., 1991; Mostafa et al., 2009). While most of the physicochemical properties of PAHs vary considerably, the semi-volatile behavior presented by some PAHs makes them highly mobile in the environment, resulting in re-volatilization after deposition and favoring their distribution through air, soil and water bodies. Atmosphere is the environmental compartment that receives most of the discharge of PAHs, which occurs in the gas phase or, predominantly, in association with the particulate material. PAHs are pollutants that are strongly implicated in the degradation of human health in some cities because their concentration in the outdoor air in ur- banized areas commonly has a range from 1 to 500 ng/m 3 . PAH levels can even reach ten times this concentration in heavily polluted environments (WHO, 1998). Usually, after spending several hours or even days in suspension in the atmosphere, where these compounds can be transported over long distances (Wania and Mackay, 1996), they eventually precipitate by dry or wet deposi- tion (Dickhut et al., 2000; Baird and Cann, 2008). The