Abstract
We continuously measured surface ozone (O3) concentrations on Yakushima Island, a remote site in southwest Japan, during July 2009-July 2011 to investigate the long-range transport of air pollutants from highly polluted areas of East Asia. The mean O3 concentration during the observation period was 32.0±17.3 ppbv, and the O3 concentrations showed a clear seasonal variation with higher values during spring and fall, and lower values during summer. Back trajectory analysis results showed that the air masses with higher O3 concentrations observed on Yakushima Island during October-May were of significant terrestrial origin and contained high concentrations of air pollutants from anthropogenic sources. In contrast, the lower values observed during June-September were associated with air masses of mainly oceanic origin. We discussed the effect of O3 exposure on the vegetation of Yakushima Island by the AOT40 index. For April-September 2010, the AOT40 was 8122.4 ppb·h, for April-November 2010, it was 17922.3 ppb·h, and for April-July 2011, it was 5750.1 ppb·h. A further study of plant O3 sensitivity and the complex influence of acidic deposition on plants, especially Pinus armandii var. amamiana, an endangered species on Yakushima Island, is needed to evaluate the influence of air pollutants on the island's biota. Nevertheless, a comparison of our results with the critical AOT40 level showed that the observed O3 concentrations did not immediately adversely affect the island vegetation.
