Chromium(III/VI) speciation in urban aerosol

Chromium(III/VI) speciation was measured in total suspended particulate (TSP) fraction of urban aerosol collected at five sites with different municipal structures. The results show that the highest airborne chromium(III) concentrations occurred at the industrial zone. In the other parts of city the differences between mean concentrations of total chromium were not statistically significant. The higher concentration of total Cr results, to a small extent, from higher dustiness of air. The industrial dust turned out to be almost fivefold richer in chromium(III). The level of chromium(VI) in air over the whole city was constant, which seems to exclude any presence of local sources of emission of this species of chromium. The mean Cr(VI) concentration of 6.0 ng m−3 is close to the Inhalation Reference Concentration of Cr(VI). In the industrial zone airborne chromium(VI) constitutes 11% of total chromium. However, in the city centre with the lowest concentration of airborne Cr(III), the share of Cr(VI) is 50%. The percentage of Cr(VI) remains at 30–40% in aerosol collected close to transit roads.

Research highlights
► Valence speciation of chromium in the urban air.
► Monitoring of total Cr and Cr(VI) in TSP fraction of urban aerosol.
► Impact of the local emission sources on the level of Cr(III/VI) species in the air.