Case Study on the High Concentrations of Ozone and Aerosol Particles in Toyama City in May 2007

Abstract

The concentrations of ozone (O₃), nitrogen oxides (NO_X) and sulfur dioxide (SO₂) and size-separated aerosol number concentrations were measured in Toyama city during the spring and early summer in 2007. High concentrations of O₃ (› 100 ppb) were observed on 8-9 and 23 May. Especially, on the 9 May event, O₃ concentration increased up to 120 ppb in the afternoon, and a photochemical oxidant advisory was announced in Toyama. The number concentrations of coarse particles (› 2.0 μm) which might have been mainly derived from soil dust, were also high on 8-9 May, on the other hand, the coarse particles concentrations were low on 23 May. The backward trajectory analysis showed that the air mass on 9 May in Toyama originated from the arid areas and the polluted regions the Asian continent, whereas the air pollution might have been transported from the western parts of Japan.