Characteristics of Acid Precipitation in Kanazawa City

The concentration of nitrogen dioxide in atmosphere at 200-300 sites in Kanazawa City was measured. At the same time the rain, snow, hail and dust in atmosphere were sampled and concurrently were observed and analyzed by using an X-ray powder diffractometer, scanning electron microscope-energy dispersion diffractometer, and transmission type electron microscope. In general, the concentration of nitrogen dioxide is higher in the cities than that in mountainous region and the river catchment area, and therefore it is influenced by a topography and wind direction. At an initial stage of rainfall, pH is low and a lot of acid precipitation is observed. In the dust sampled in the atmosphere of tunnel and cities, by using an X-ray powder diffractometer, the quartz, feldspar, clay mineral, gypsum and so forth were recognized. Based on an observation through the electron microscope, the sulphur constituents cover a surface of mineral grain and pollen, and moreover its microshape presents thin film shape or particle shape, and furthermore frequently is agglomerated. From these observation results, it is thought that sulfur constituent in atmosphere is one of the causes for acid rain.