Physical speciation of arsenic, mercury, lead, cadmium and nickel in inhalable atmospheric particles

Physical speciation of metals (size distribution) in airborne particles has been studied in 24 areas of Seville (Spain). Urban particles were collected with a high-volume sampling systems equipped with cascade impactor and PM10 inlets. Particle samples were analysed by acid digestion assisted by microwave heating using a HNO3:HClO4 (3:1,v/v) mixture. Arsenic was determined by hydride generation atomic absorption spectrometry (AAS), mercury by AAS with cold vapour atomisation and inductively coupled plasma atomic emission spectrometry was employed to determine lead, cadmium and nickel. Analyses of PM10 samples revealed that the highest mean concentration was obtained for Pb, 14.04 ng m^-3. Values of 3.42 and 2.88 ng m^-3 were obtained for As and Ni, respectively. The lowest concentrations were obtained for Cd, 0.49 ng m^-3, and especially for Hg, 0.07 ng m^-3. Their physical speciation in air concentrations (ng m^-3) showed that the toxic elements As and Pb were accumulated in the fine particles of <0.6 (mu)m diameter (PM0.6), as well as the metals Cd and Ni, with high percentages of 74.8, 69.0, 61.3 and 57.5, respectively. Hg constituted a lower percentage of 40.4%. The results in mass concentrations (mg kg^-1) demonstrated that Pb and Cd contents were clearly greater in fine particles between 1.3 and 0.6 (mu)m diameter than in PM0.6. The size interval where Hg contents were higher than in PM0.6 (4.9–0.6 (mu)m) corresponded to a fine and also a coarse mode, meanwhile Ni presented similar percentages between all size ranges. As is mainly accumulated in PM0.6 in both air and mass concentrations, revealing that it constitute the element most hazardous in relation to its size distribution.