Concentrations and Elemental Analysis of Airborne Particulate Matter in Chiang Mai, Thailand

Air pollution, especially airborne particulate matter, is becoming a major problem in Chiang Mai. The present study reports findings on total suspended particulate matter (TSP) loading as well as its spatial and daily variation in Chiang Mai ambient air. Limited elemental analysis of airborne particulate matter was also performed. Samples were collected at four different sites, representative of urban, industrial, residential and rural areas during day time between October 2003 and April 2004. TSP mass concentrations ranged from 50 – 370 μg/m, with average concentration of 149 μg/m. A similar order of magnitude was observed for mass concentrations at different sites. The maximum monthly averaged TSP concentration observed at a busy commercial site was about 2-fold higher than the maximum TSP found at a suburban residential site. A daily variation of TSP concentrations was found to be significant, with occasional peaks well above Thailand’s national ambient air quality standards (NAAQS) for 24 h TSP of 330 μg/m, observed during the morning rush hours. Elemental analysis results showed that the likely TSP sources were crustal matter from soil and road dust (Fe, Ca, Al and K) as well as vehicular and industrial emissions (Pb, Zn and Cr).