Analysis of precipitation chemistry at a rural site in Hiroshima Prefecture, Japan

Event basis measurements of precipitation chemistry at Shobara, the rural area of the northeastern part in Hiroshima Prefecture in Japan, during the period 1984–1988, were assessed for determining the sources of major ions, and for understanding the relation between ionic concentrations and synoptic meteorological situations. Seasonal patterns of the volume-weighted mean concentrations for major ions except H + could be characterized by winter maxima and summer minima. Principal component analysis was performed on monthly ionic deposition. Varimax rotated three principal components accounting for approximately 90% of the total variance in the data set, could be interpreted to be acid, seasalt and soil. From back-trajectories for an event using 850 hPa winds, it was found that the volume-weighted mean concentration of non-sea-salt (nss−) SO 2− 4 for the air-mass transported from the northern part of Asian Continent was highest, and that the majority of high nss-SO 2− 4 concentrations for an event were observed for the continental air-mass under the condition of light precipitation amount.