Spatial and temporal variations, and source identification of toxic trace metals in atmosperic particulates in Bangkok

Abstract

Airborne particulate samples were collected in Bangkok, Thailand using High Volume air samplers for a year from March 2006 to March 2007. The sampling sites were the Chulalongkorn Hospital (CH), the Huay-Khwang Community Housing (HCH), the Ministry of Science and Technology (MST) and the Ratburana Post Office (RPO) represented as business and commercial, residential, government offices with congested traffic and industrial areas, respectively. The 11 metals, Al, Cd, Cr, Cu, Fe, K, Mn, Na, Ni, Pb and Zn are quantified by ICP-AES in the study. The average concentrations of Total Suspended Particulate (TSP) at CH, HCH, MST, and RPO are 114.96, 110.93, 111.11, and 144.47 µg/m3, respectively. Major metals found in the study are Na, K, Al, Fe and Zn, while Cd and Cr are hardly found in sites. The amount of TSP and metal compositions found at RPO are higher than other sites. The seasonal variation pattern for the concentrations of TSP and metals at all sites are quite similar. The metal concentrations are low during rainy season and increase through dry season. Na is mostly found in winter while Al, K and Zn are mostly found in summer. Cu is observed the only metal which has similar amount in all different seasons. Metals measured in the study can be classified into three groups according to their EF values using Fe as reference material. The first group with EF values lesser than 10 which indicate metals from crustal sources includes Al, Cr, K, and Mn. The second group with intermediately enriched EF (EF values between 10 and 100) is Na, and Ni. The last group is metals with EF values greater than 100 which indicate metals from anthropogenic sources include Cd, Cu, Pb, and Zn. The statistical Pearson’s correlation analysis demonstrates that most of the metals exhibit their moderate to weak relationship. Besides, the metals tend to be not correlated with the meteorological parameters. Three factors are extracted by a multivariate receptor model, principle component analysis (PCA) at the HCH and the CH, while four factors are extracted at the RPO and the MST. The results from factor analysis show the possible major sources contributing to TSP concentrations. The major sources of airborne particulate found at all sites are soil dust, biomass burning and vehicular traffic.