1996 Volume 33 Issue 4 Pages 131-136
In the Seto Inland Sea District, high NO2 concentration are recorded on seaside mountain slope, usually, at the altitude of 100-150m, and it is thought to be one of the causes of forest decline. In this study, temperature profile was determined by the captive balloon at the Miyajima Service Area (140m above sea level) of Sanyo Express Highway on south-facing of the Mt. Gokurakuji, Hiroshima Prefecture, in summer and winter of 1995 in order to investigate the relationship between the inversion layer and atmospheric NOx on the slope of forest decline area. It was found that a clear inversion layer was present at the height of 20m (160m above sea level) during night through early morning. The 12 hours concentration during night-time was 32.2 ppb at an altitude of 150m and 10.7 ppb at 300m in summer, and it was 27.2 ppb at 150m and 4.3 ppb at 300m in winter. These results show that the night-time concentration difference was fairly strong, and it means that the air pollutants are hard to diffuse to the outside of the inversion layer and are trapped below the layer during night-time. It suggests that the chain chemical reactions associated with NO2 are probably promoted in the night-time, and the reactions might cause the forest decline at the low elevation area (100-150m) .
