Source apportionment and potential source locations of PM2.5 and PM2.5–10 at residential sites in metropolitan Bangkok

Fine and coarse fractions of PM10 (PM2.5 and PM2.5–10, respectively) were collected from January 2003 to December 2007 at an urban Bangkok site (Chatuchak district) and a suburban site (Klongha district, Pathumthani) in Thailand. The filter samples were analyzed for mass, black carbon, and up to 28 elements were determined using instrumental neutron activation analysis and Particle–Induced X–ray Emission (PIXE). The long–term database shows that PM mass at the urban area had higher mass, black carbon, and some elements than the one at the suburban area. Furthermore, it is found that mass and elemental concentrations were generally elevated in the coarse fractions whereas black carbon was the major content in fine fractions. Positive Matrix Factorization (PMF) and multiple linear regression were applied to investigate for PM source fingerprints and apportionment. Source contributions and wind direction influence were also examined by use of conditional probability function (CPF) and potential source contribution function (PSCF). The PMF results indicated that major sources contributed to coarse fractions were soil, construction, whereas traffic and biomass burning were the major sources for fine fractions. CPF and PSCF models assisted in determining of the potential locations and/or the preferred pathways of these possible sources.