Evaluation of ionic pollutants of acid fog and rain using a factor analysis and back trajectories

Fog and rain water samples were collected at the same time in the Akita Hac himantai mountain range in northern Japan from June to September in 1998 an d 1999. The various ion concentrations in these samples were analyzed, and the fog droplet sizes were measured for each fog event. As the fog droplet size increased, the ion concentration decreased. The slope of log-log plots of the concentration versus the droplet size differed with the kind of ion . In order to characterize the air pollutant, moreover, these data were qua ntitatively analyzed by an oblique rotational factor analysis. We found tha t three factors were extracted as the air pollutant source: (NH4)(2)SO4, ac ids (HNO3 + H2SO4) and sea-salt. Combining the factor analysis with the 72 h back-trajectory at 850 hPa level, we found that the contribution of each factor varied with the transport pattern of air masses.