Chemical composition of fine particles (PM2.5): water-soluble organic fraction and trace metals

The chemical composition of the atmosphere changes rapidly due to the amount of air pollutants released every day. The aim of this research was to make an exploratory study on the chemical composition (metals and water-soluble organic fraction) of fine particulate matter (PM 2.5 ) in a region with tropical climate. Multiple sites, with and without the influence of the construction works for the World Cup and Olympic Games, were selected in Rio de Janeiro State, RJ, Brazil. PM 2.5 samples were collected every 6 days from January to December 2011. This is the first PM 2.5 data generated by RJ’s monitoring network. The PM 2.5 annual average concentrations in Rio de Janeiro ranged from 9 to 32 μg m −3 . Metals originated from industrial (Cu, Cd, Pb) and traffic (Cr, Mn, Ni, V, and Zn) emissions, as well as those from natural emissions (Na, K, Ca, Ti, Al, Mg, Fe), were quantified. The concentrations of the metals analyzed ranged from 0.4 to 13,000 ng m −3 . The highest concentrations found were related to metals present in the crust, such as Al (1.6 to 6.7 μg m −3 ). In the places where there was the presence of railroad minerals, Ca and Mg appeared in higher concentrations than in the other sites. Fe and PM 2.5 annual and daily average were higher in areas under construction for urban mobility improvements or the Olympic arenas. Even though, the results for Ni, Pb, and Cu were 50% below WHO guidelines. Water-soluble organic carbon (WSOC) concentrations ranged from 0.8 to 4.9 μg m −3 . The highest concentrations (2.4 to 4.9 μg m −3 ) were observed in urban areas with intense light vehicle fleet traffic as well as in areas of large industrial influence near highways with intense circulation of heavy vehicles. This is due to the fact that WSOC is mainly formed by the emissions from combustion processes. Studies are needed in order to assess to which extent the WSOC can increase the bioavailability of these and other metals.