Variations in time and space of trace metal aerosol concentrations in urban areas and their surroundings
Using an unprecedentedly large geochemical database, we compare temporal and spatial variations in in-halable trace metal background concentrations in a major city (Barcelona, Spain) and at a nearby mountainous site (Montseny) affected by the urban plume. Both sites are contaminated by technogenic metals, with V, Pb, Cu, Zn, Mn, Sn, Bi, Sb and Cd all showing upper continental crust (UCC) normalised values >1 in broadly increasing order. The highest metal concentrations usually occur during winter at Barcelona and summer in Montseny. This seasonal differ-ence was especially marked at the remote mountain site in several elements such as Ti and Rare Earth Elements, which recorded campaign maxima, exceeding PM 10 concentrations seen in Barcelona. The most common metals were Zn, Ti, Cu, Mn, Pb and V. Both V and Ni show highest concen-trations in summer, and preferentially fractionate into the finest PM sizes (PM 1 /PM 10 > 0.5) especially in Barcelona, this being attributed to regionally dispersed contamination from fuel oil combustion point sources. Within the city, hourly metal concentrations are controlled either by traf-fic (rush hour double peak for Cu, Sb, Sn, Ba) or indus-trial plumes (morning peak of Ni, Mn, Cr generated outside the city overnight), whereas at Montseny metal concentra-tions rise during the morning to a single, prolonged after-noon peak as contaminated air transported by the sea breeze moves into the mountains. Our exceptional database, which includes hourly measurements of chemical concentrations, demonstrates in more detail than previous studies the spa-tial and temporal variability of urban pollution by trace met-als in a given city. Technogenic metalliferous aerosols are Correspondence to: T. Moreno (firstname.lastname@example.org) commonly fine in size and therefore potentially bioavailable, emphasising the case for basing urban background PM char-acterisation not only on physical parameters such as mass but also on sample chemistry and with special emphasis on trace metal content.