Dry deposition fluxes of ambient particulate heavy metals in a small city, Korea

Daytime and nighttime dry deposition fluxes of particulate heavy metals were measured in Kunpo, a small city in the Seoul metropolitan area in Korea. Samples were collected by dry deposition plates during four measurement periods in 2000. The average fluxes of total mass and elements measured during daytime were higher than the nighttime fluxes due to higher wind speeds and higher ambient concentrations. The average fluxes of Al and Ca, typical crustal species, were 1-2 orders of magnitude higher than Mn and anthropogenic elements such as As, Cd, Cu, Ni, Pb, and Zn. Possible anthropogenic source of Ca is suggested. Particle size distributions were measured by a cascade impactor and a coarse particle rotary impactor to estimate the importance of the particle size on the deposition fluxes. The Sehmel-Hodgson model was used to estimate dry deposition velocities as a function of particle size for the multi-step deposition model calculation. The calculated fluxes agreed fairly well with the measured fluxes and it was shown that large particles (D_p>9 μm) are more important than small particles (D_p>9 μm) in particulate dry deposition of heavy metals.