Concentration Variations of Air Pollutants Observed at Kashiwazaki Environmental Air Quality Monitoring Station

摘要

Concentration variations of air pollutants observed from April 1990 through December 2007 at the Kashiwazaki Air Quality Monitoring Station in Niigata Prefecture were analyzed. While annual mean concentrations of NO and NO_2 showed no remarkable trends, those of SPM were in clear downward trends, and Ox was in an upward trend. On the other hand, those of SO_2 decreased remarkably from 1990 to 2001, however, they have increased slightly in recent years. Monthly averaged concentrations of Ox are higher from February through May and hourly concentrations show a peak around 2 to 3 pm. The daily average concentrations of Ox were higher on Saturdays and Sundays, which is known as the weekend effect. Monthly average concentrations of NO and NO_2 were higher from November through December and hourly concentrations showed diurnal variations with peaks in the morning and evening. Monthly mean concentrations of SPM were higher from April through August and hourly concentrations are higher from 7 to 9 pm. The maximum concentrations of SO_2, SPM and Ox during the period investigated were recorded at an exceptional time, influenced by the eruption of the Miyake-jima volcano, by the Kosa phenomenon, and also the occurrence of the long-range transport of air pollutants from the continental area.