Size-fractionated aerosol composition at Gent, Belgium. Results from a one-year study

The ''Gent'' stacked filter unit (SFU) sampler was used to collect aerosols in separate coarse (2-10 mu m) and fine (<2 mu m) size fractions at an urban residential site in Gent, Belgium. The samplings were done from May 1993 to July 1994, and two daily samples were taken per week. The samples were analyzed for the particulate mass (PM), black carbon (BC) and up to 29 elements. The elements were measured by PIXE and short-irradiation INAA. The crustal and sea-salt elements were predominantly associated with the coarse particles, but PM, the halogens Br and I, and the typical anthropogenic elements BC, S, V, Ni, Zn, In and Pb exhibited average FINE/COARSE ratios of over 2 (up to 7 for BC and I). The fine and PM10 median concentrations were compared with median levels in the respirable size fraction (<5 mu m), as measured at the same site in fall 1986. Overall, the airborne particulate element levels did not seem to have changed much since 1986. Notable exceptions were Pr and Pb, which were reduced to one third of the 1986 levels, but both elements were still predominantly attributable to automotive emissions. The fine and coarse multielemental data sets were subjected to multivariate receptor modelling, and the results were compared with the receptor model results from the 1986 fall study.