The effects of air pollution on the growth of mountain trees were investigated at Buna-daira (1,180 m a.s.l.), about half the way up Mt. Tateyama, located in Japan. Every year, about 1 million tourists are transported by highland buses through the Tateyama-Kurobe Alpine route. Since the route opened in 1971, some tree species along the road have declined and have been blighted, suggesting that bus exhaust was the cause. However, the level of regional and long-range transboundary air pollution has also increased significantly over the last few decades. The atmospheric NO 2 concentration at the roadside in the forest was highly correlated with the traffic density of buses and penetration of the exhaust into the forest was detected. However, the maximum average NO 2 concentration was lower than 3.5 ppbv during the peak traffic period in the year. At Bunadaira, the total stem cross-sectional area at breast height (BA) of the forest was nearly unchanged from 1999 to 2006, but the BA of Fagus crenata decreased 10% and that of Cryptomeria japonica increased 6%. Neither tree growth nor tree death was significantly correlated with distance from the road. The cause of the decline of F. crenata could not be attributed to the effects of road, i.e., air pollution emitted from the buses or edge effects of the road. This area was more affected by regional, longrange transport of air pollution (O 3 , SO 2 , etc.). The average atmospheric O 3 concentration in autumn was higher than 40 ppbv and the recent increase in the O 3 concentration may be an important factor of F. crenata decline through the changes in the interspecific relationships between F. crenata and C. japonica, O 3 sensitive and tolerant species, respectively.

Measurements of the chemical composition of fog water at Murododaira (altitude, 2,450 m), on the western slope of Mt. Tateyama near the coast of the Japan Sea, were performed each autumn from 2004 through 2007. Strong acidic fogs (pH<4) containing high concentrations of nssSO 4 2− were frequently observed in the autumn of 2005, when the air mass at Mt. Tateyama originated mainly from the polluted regions of Asia. The ratio of NO 3 − /nssSO 4 2− in fog water was relatively high in 2004 and 2007. High concentrations of nssCa 2+ derived from dust particles were detected in 2006. Background Kosa particles might have been predominant in the free troposphere and could have neutralized acidic fogs in the autumn of 2006. High concentrations of sea-salt components were also observed in October 2005. The sea-salt particlesmight have been transported from the Pacific Ocean by a strong typhoon, and significant Mg 2+ loss was observed. Peroxides higher than 100 μM, which are seriously harmful to vegetation were sometimes detected.

The Kosa event was observed widely in Japan on 12 November 2002. Measurements of size-separated aerosol number concentrations and precipitation chemistry were performed in Toyama during the autumn and early winter of 2002. The number of aerosol particles larger than 3.0 mm in diameter dramatically increased during the Kosa event, whereas the number concentrations of finer particles hardly changed. The concentration of non-sea-salt calcium and pH were high in the precipitation sampled during the Kosa event.

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The ion constituents contained in fresh snow immediately after snowfall were examined at 5-10 km intervals over 50 km from the coast of Hakui city in Ishikawa Prefecture leeward of the northwestern seasonal wind to the plain in Toyama city in Toyama Prefecture. The concentrations of sodium ions and sea-salt sulfate ions that originated from the Sea of Japan decreased exponentially from Hakui city in Ishikawa Prefecture to Toyama city. The concentration of non sea-salt sulfate ions, which probably originate from human activities, also decreased exponentially, but it was lower than the concentration of sea-salt sulfate ions until 25 km from Hakui city and higher in the farther regions. We considered that this was due to additive effects of non sea-salt sulfate ions transported from a distance and local sulfate ions. The concentration of non sea-salt sulfate ions transported from the Asian Continent was estimated in each sampling station. Its contribution was 0.98 of the total at the coast of Hakui city and 0.65 at Toyama city, respectively, and showed a pattern similar to those of sodium ions and sea-salt sulfate ions. The concentrations of ammonium ions and non sea-salt calcium ions were slightly higher in the plain in Toyama than on the coast of Hakui city, suggesting that they mostly originated from the sampling regions in this study. The concentration of nitrate ions was almost constant in the regions from the coast to the inland areas, suggesting also that they mostly originated from the sampling regions.