Size Distributions of Aerosol Number Concentrations and Water-soluble Constituents and Precipitation Chemistry in Toyama, Japan

Abstract

Size-separated aerosol number concentrations and water-soluble constituents as well as precipitation chemistry were simultaneously measured in Toyama, the Hokuriku district, near the coast of the Japan Sea, in 2004. The number concentrations of coarse particles were significantly high in the spring, which was due to Asian dust events called Kosa in Japanese. Particulate Ca²⁺, which was mostly present in the coarse-mode particles, was also significantly high in March and April. On the other hand, the concentration of NH₄⁺ and SO₄^2-, which mainly exists as the accumulation-mode particles was higher in the summer. The concentration of SO₄^2- in the coarse-mode particles also was not higher in the spring than in the summer. The pollutants adsorbed on Kosa particles, may not significantly affect the air quality in the Hokuriku district. High concentration of Ca²⁺ in the precipitation was observed from February to April. The acidic species in the precipitation were neutralized by the Kosa particles.