Effect of long-range transport of air mass on the ionic components in radiation fog in northern Japan.

Water samples from radiation and upslope types of fog were collected at Takanosu Basin and Hachimantai mountain range of Akita Prefecture in northern Japan, respectively. The effect of the long-range transport of pollutants from the Asian Continent to the basin and the mountain range on the chemical characteristics of two types of fog was studied using chemical analysis data for the water samples as well as the back-trajectories of the air mass. In particular, non-sea-salt (nss)-SO4(2-) of radiation fog provided a much higher concentration than that of upslope fog, which suggests that nss-SO4(2-) might be transported mainly from the Asian Continent. The transport and uptake mechanism of pollutants in the radiation fog water were explained based on their accumulation in the basin due to anticyclonic subsidence and by the long-lasting fog behavior.