SIZE DISTRIBUTIONS AND CHEMICAL-COMPOSITION OF ATMOSPHERIC AEROSOLS IN A SUBURB OF BANGKOK, THAILAND

A survey of atmospheric aerosols in a suburban area of Bangkok, Thaila nd was conducted using an Andersen sampler. Significant amounts of Na and Cl collected in the area were considered to be derived from sea sa lt. Difference of the Na/Cl ratio in the area to that of sea salt indi cated a considerable amount of Cl loss which is assumed to be caused b y the chemical reaction to form NaNO3 which is the main nitrate specie s present. Most of the sulfate in the sample was found to be (NH4)(2)S O4, in the form of fine particles which is different from the sulphate derived from sea salt and soil. Another characteristic noticed is tha t CaCO3 seems to play an influential role in causing a cation rich ben d in the aerosols which is a particular contrast to aerosols in Tokyo, Japan. This could be one of the strongest factors determining the cha racteristics of the atmospheric environment around Bangkok. The size d istribution of K and Mg particles are also discussed in particular rel ation to sources.