Thesis (Ph.D.)--Chulalongkorn University, 2008

This study has been conducted to focus on carbonyl compounds in Bangkok associated with gasohol. The objectives of the study were: to identify and quantify the carbonyl compounds present in urban air; to study the spatial distribution of carbonyl compounds in Bangkok urban area; and to determine the concentration of carbonyl compounds in relation to traffic density. In order to meet these objectives, ambient air samples were collected at 10 sites in Bangkok during 2007 to 2008, by using active cartridge sampler containing 2,4 DNPH and samples were extracted and analyzed using HPLC technique utilizing Compendium Method TO-11A of the US EPA as guideline. The results of the study indicated that there were 10 prevalent carbonyl compounds found both at the roadside and residential areas in Bangkok namely; formaldehyde, acetaldehyde, acetone, butyraldehyde, propionaldehyde, crotonaldehyde, benzaldehyde, isovaleraldehyde, valeraldehyde, and hexanaldehyde. Formaldehyde was abundant in Bangkok ambient air especially in the roadside areas which ranged from 5.14 to 17.2 µg/m³ (average 11.53 µg/m³) while, in the residential areas during the same period ranged from 3.06 to 19.9 µg/m³ (average 9.65 µg/m³). The concentration of acetaldehyde in roadside areas in Bangkok during the same period ranged from 1.59 to 7.95 µg/m³ (average 3.51 µg/m³) while at the residential areas the concentration of this compound, ranged from 1.07 to 8.05 µg/m³ (average 3.11 µg/m³). Concentration levels of other carbonyl compounds in Bangkok were low. It was also found that at the roadside areas, during high traffic density the concentration of formaldehyde and acetaldehyde increased. The correlation between formaldehyde concentration and car density was calculated which indicated good correlations (R²= 0.977). The correlation between acetaldehyde concentrations in the roadside area and car density was also calculated, and the (R²= 0.9256), which indicated good correlation.