Fog water chemistry at Mt. Oyama and its dominant factors

M. Igawa*, K. Matsumura, H. Okochi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


We have observed acid fog in Mt. Oyama since 1988. Fog events occur frequently in Mt. Oyama; 47% of the time the mountain top is covered with fog. The pH of fog is lower than that of rain collected at the fog sampling station by about 1 unit and the lowest pH was 1.95. We have also collected gas and aerosol components at the station and observed fog events by a video camera from the mountain base, where there is an air pollution monitoring station. The air quality at the fog sampling station was affected by not only the air quality at the base but also the wind direction, valley or mountain wind. It is ascertained by using back trajectory analyses that polluted air masses are transported to the base from the Kanto plains or other big urban areas, Osaka and Nagoya. When the base is polluted, the relative humidity increases, and the valley wind blows, acid fog is formed at the mountainside. In the acid fog, nitrate ion is the most abundant anion. Nitrate ion concentration correlates well with hydrogen ion concentration. The annual mean total ion concentration has not changed much since 1988, but the concentration ratio of nitrate ion to sulfate ion has increased in recent years. The nitric acid gas concentration in the station is comparable to that in urban areas, while other gas concentrations are much lower.

Original languageEnglish
Pages (from-to)607-612
Number of pages6
JournalWater, Air, and Soil Pollution
Issue number1-4 II
Publication statusPublished - 2001 Nov 10
Externally publishedYes


  • Acid fog
  • Back trajectory
  • Mt. Oyama
  • Nitric acid
  • Valley wind

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Ecological Modelling
  • Water Science and Technology
  • Pollution


Dive into the research topics of 'Fog water chemistry at Mt. Oyama and its dominant factors'. Together they form a unique fingerprint.

Cite this