Distributions of Fine Particulate Matter (PM2.5) in the Ambient Air of Chiang Mai-Lamphun Basin

Abstract

Twenty-four hour measurements of PM2.5 particulate matter have been carried out during the two-year period between the 1 June 2004 and the 31 May 2006 in Chiang Mai-Lamphun Basin area. PM2.5 samples were collected on 47 mm filters, with the use of low volume gravimetric samplers while a meteorological station recorded meteorological data 6 m above the ground, nearby the sampling instrumentation. The mass concentration of PM2.5 annual average was 35.6 ต g/m3 during June 2004 to May 2005 and 35.7 g/m3 during June 2005 to May 2006 higher than U.S. Environmental Pollution Agency daily limit. The mean of PM2.5 mass concentrations in rainy, winter and summer seasons between June 2004 and May 2005 were 17.8, 52.3, and 36.4 g/m3, respectively. Regression analysis was used to investigate the relationship among PM2.5 concentrations, PM10 and inorganic gaseous pollutants, and meteorological parameters. Additionally, PM2.5 mass concentrations were correlated with PM10 and other inorganic gaseous pollutants (O3, NO2, SO2) while weekly and seasonal PM2.5 variations were also investigated. The highest PM2.5 mass concentrations occur with moderate southerly winds, moderate temperature and low humidity during winter.