Objectives This paper describes the resuspension of road dust in an urban subarctic environment and focuses especially on the effect of wind speed on the formation of resuspended dust episodes.

Methods The study was conducted in Kuopio, Finland, in the spring of 1995. There were 36 daily measurements of mass concentrations of fine particulate matter (PM_2.5), inhalable particulate matter (PM₁₀), total suspended particulate matter, black carbon and carbon monoxide; size-segregated number concentrations of particles (diameter range 0.01-10 µm); and meteorological parameters. Total elemental compositions of PM_2.5 and PM₁₀ samples were analyzed with inductively coupled plasma mass spectrometry.

Results The mass and number concentrations of particles in all size ranges and the concentrations of soil-derived (iron) and combustion-derived (vanadium and lead) elements in the PM_2.5 and PM₁₀ increased during the dust episodes. The daily average wind speed dually affected the episodes. The pollutant concentrations increased at wind speeds of <4 m/s and >5 m/s. The former was related to inversion-type conditions characterized by low wind speeds, while the latter was likely to be due to wind-blown resuspended dust. Resuspended lead accounted for an average of 27% of the total lead, and resuspended vanadium for 46% of the total vanadium in PM_2.5.

Conclusions Resuspended dust episodes were related to both low and high wind speeds and therefore suggest that factors other than wind speed, such as turbulence induced by traffic, affect the emergence of these episodes. The contribution of elevated levels of crustal material and toxic metals in resuspended PM2.5 to human adverse health effects should be investigated.

Key terms air pollution; air quality; black carbon; dust; elemental composition; particle size distribution; particulate matter; resuspension; subarctic region; urban air quality