1996 Volume 31 Issue 6 Pages 282-291
The chemical components of airborne suspended particulate matter (SPM) and deposition were measured in samples collected at monthly intervals both at Happoone in the Karamatsu Mountains of the Japan Alps and in Nagano City. The contributions of several sources to SPM were estimated via the chemical mass balance (CMB) method. The amount of deposition at Happoone was compared with that in Nagano City, and its effects on stream water components was observed.
At Happoone, SO42-concentration in the SPM increased from spring to summer. In spring, Kosa aerosol was detected in the SPM and its concentration was estimatedto be 4 μg/m3. Few soil particles generated from the neighboring area were detected in the SPM. The mean pH of deposition at Happoone was 5.1, slightly lower than that (5.3) in Nagano City, and the Happoone value increased during spring. The deposition rates of nss-SO42- and NO3-at Happoone were 1.5 times greater than those in Nagano City. These results suggest that greater amounts of acidic substances fell on this mountain region, which had seemed to be a clean area.
The Hira River, a mountain stream near Happoone, had sufficient capacity to neutralize the acid deposition with pH remaining at 7.6 and alkalinity at 0.48 meq/l. However the alkalinity decreased temporarily due to dilution with rainfall during the rainy season. During the snow melt season, the concentration of NO3-increased, although pH decline was not observed.
