Measurement of ozone in sub-high mountain area where serious forest decline is seen

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Serious forest decline is seen around Mt. Shirane in Oku-Nikko. Not only coniferous trees but also deciduous trees are damaged. We thought that photochemical ozone or peroxides formed by the reactions of ozone with natural hydrocarbons emitted by forest trees. Thus, we measured the concentrations of ozone and/or peroxides in the sub-high mountain area where serious forest decline is observed. Near the top of high mountains it is impossible to utilize electric power supply. Therefore, we used a portable ozone sensor (a fixed potential electrolysis cell) driven with car batteries and solar panels. Data were stored in a small data-logger.Observation site was located near the top of Mt. Mae-Shirane. Since there is only an uninhabited mountain hut, it was necessary to carry instruments as well as foods on our shoulder up to the observation site. Fortunately, people of a volunteers group named "the group for saving declining forests" helped us.Observations of ozone near the top of Mt. Mae-Shirane were made in early August of 1997, 1998, and 1999 for about 10 days, respectively. In 1997 and 1998 experiments the weather was so bad for whole period that no data worth for analysis was obtained. In the 1999 experiment, good weather lasted in the former half of the experimental period. Ozone reached up to 90 pptv. At the same period concentrations of peroxides such as hydrogen peroxide and methyl hydroperoxide were measured in the Oku-Nikko Environment Observation Station of NIES. The concentration of hydrogen peroxide in the daytime showed a good correlation with ozone concentration, sunlight, and isoprene concentration.