Size distributions of aerosol number concentrations and water-soluble constituents in Toyama, Japan: A comparison of the measurements during Asian dust period with non-dust period

Size-separated aerosol number concentrations and water-soluble constituents were measured in Toyama, the Hokuriku district, near the coast of the Japan Sea, during the spring and summer in 2003. The number concentrations of coarse particles were significantly high in April, which was due to Asian dust events called Kosa in Japanese. Particulate nssCa2+, which is mostly present in the coarse-mode particles, was significantly high in April. On the other hand, the concentrations of NH4+ and nssSO42−, which mainly exist as the accumulation-mode particles were not high in April. The mass-size distributions of water-soluble constituents were compared with the size-separated number concentrations of particles. Backward trajectory analysis was also employed to examine the transport process of the air mass in Toyama.