The seasonal variations of the chemical components in airborne aerosols in a mountainous area were investigated. Field observations were made at Happo at an altitude of 1,850m in the central mountainous region of Japan. Airborne aerosol was collected for 12hours or 24hours from May 1998 to September 1999 and the chemical components (Na+, Mg2+, K+, Ca2+, NH4+, Cl-, SO42-, NO3- and oxalic acid) in the aerosol were measured. In addition, gaseous pollutants, such as ozone and SO2 were monitored simultaneously. The concentrations of Na+ were much higher from autumn to spring than those in summer. Cl- increased in winter and the seasonal variation differed from Na+. The concentrations of Mg2+, K+ and Ca2+, especially Ca2+ increased in spring. It suggests that the increase in this Ca2+ concentration is based on the influence of Kosa aerosol (yellow sand) transported from continental Asia. The concentrations of SO42- and oxalic acid produced by photochemical reaction increased from spring to summer, and NH4+ which is the neutralization ingredient of sulfuric acid showed also the same seasonal variation. The concentration ratios of Cl-/Na+ were quite low compared with that of sea water. This is based on Cl- loss reaction. There was almost no influence of sea salt in the mountainous area, because most of K+, Ca2+ and SO42- were non-sea salt. The sulfate conversion ratio, i.e., SO42- -[S]/(SO2-[S] + SO42--[S]), was as high as 0.8 in summer. In summer and winter, when the concentration of SO42- was high, total equivalent concentration of anions (Cl-, NO3- and SO42-) was much higher than that of cations (Na+, NH4+, K+, Mg2+ and Ca2+), which suggests that a portion of the SO42- existed in the form of acidic aerosols such as H3SO4 and NH4HSO4. It suggests that a part of sulfuric acid produced by the photochemical reaction is transported to the mountainous area without being neutralized by alkali substances, such as NH3.

Characteristics of the components of suspended particulate mater (SPM) were investigated, as well as their seasonal variations and compositions in the mountainous and urban areas. The mountainous sampling site was Happo Ridge at an altitude of 1850m and the urban site was the city area in Nagano, the both being in the central mountainous region in inland area of Japan. SPM was sampled by filtering air on a quartz fiber filter set in a low volume air sampler, with a flow rate of 20 1 min E-1 and for a period of one month. In the mountainous area, SO42- concentrations were much higher in spring and summer than those in fall and winter. Almost all of SO42- were considered to be produced by the photooxidation of SO2 and transported for a long distance into that area. Ca2+ concentration increased particularly in March and April in which yellow sand from the Asia Continent arrived at those sites. The seasonal variation of elemental carbon (EC) concentration was small, while organic carbon (OC) increased in spring and summer. This suggested that OC in spring and summer was produced by photochemical reaction. In the urban area, SO42- concentration increased in spring and summer. This seasonal variation was similar to that in the mountainous area, but that level was smaller. Ca2+ concentration increased in winter as a result of the road dust raised by cars. SO42- was most abundant in the mountainous area and attained more than 10 % of the SPM. EC, OC and SO42- were abundant in the urban area and all these components, respectively, were more than 10 % of the SPM. The total concentrations of chemical components analyzed attained 43 % and 68% of SPM in the mountainous and urban areas, respectively. Secondary components occupied 41% and 34% of the total components in the mountainous and urban areas, respectively. The contribution of secondary components in the mountainous area is larger than that in the urban area.