Dry deposition of particulate matter, organic carbon and toxic chemical substances e. g. heavy metals, PAHs (polycyclic aromatic hydrocarbons) on urban area and their runoff were measured and compared. The measured deposition rates differed according to the shape of the sampling plate, the setting height and the sampling duration. In order to compare with the amount of runoff, we used the deposition rate obtained by the plate with very low edge placed on the ground during no precipitation period. The runoff amounts of toxic chemical substances varied with the discharge and suspended solids (SS) concentration, whereas their contents in particulate matter were inversely proportional to SS concentrations. In the case of heavy rain, the ratios of runoff amount to dry and wet deposition rates were largely greater than unity for SS and heavy metals mainly originated from soil (Fe, Mn), and were around unity for air-originated ones (Zn, Pb). In contrast, the ratios of all substances (heavy metals, Benzo (a) pyrene, organic carbon) nearly equaled to unity in case of weak rain.
