A factor with high concentration of Ca was attributed to a construction near the urban residential site and from two plaster manufacturing factories close to the suburban residential site. Charcoal/wood burning and incineration factors were likely to be the local sources. The site was located 35 km to the north from the Gulf of Thailand and was influenced by wind from the south and southwest for most of the year. The factor containing highest concentrations of Na and Cl was attributed to sea-salt and was clearly seen in the urban atmosphere. A motorcycle factor with high concentrations of Zn and Mn were found at the urban site. The motor vehicle factor showed much higher concentration for Br in urban than in suburban area. Soil was the major source of airborne particulate matter identified for all data sets. The best solutions were found to be six factors for elemental compositions of each of the fine and coarse particulate matter fractions at the urban site and five factors each for both fine and coarse fractions at the suburban location. The data sets were then analyzed by positive matrix factorization followed by rotation to identify the possible sources of atmospheric aerosols in both areas. The samples were analyzed for elemental concentrations by instrumental neutron activation analysis. Samples of fine and coarse fractions of airborne particulate matter were collected in an urban residential area of metropolitan Bangkok from June 1995 to May 1996 and in a suburban residential area in Pathumthani, Bangkok's boundary province, from September 1993 to August 1994.

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