NANOPARTICLE CONCENTRATIONS IN BANGKOK AMBIENT AIR T. Thongyen 1,* , W. Limpaseni 1 , T. Prueksasit 2 , Y. Otani 3 and M. Furuuchi 3 1 Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, 10330 Thailand 2 Department of General Science, Faculty of Science, Chulalongkorn University, 10330 Thailand 3 Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192 Japan INTRODUCTION Ambient air particulate matter (PM) is the major health and environmental concern in most urban areas due to the prevalent of PM emission sources and its detrimental health effects with no threshold limit. With better understanding of PM characteristics and its reactions in the human respiratory system as well as the environment, more countries have imposed stricter environmental standards for PM as well as adopted fine particulate matter (PM 2.5 ) standards in place of coarse particulate matter (PM 10 ) standards. Various studies have shown that PM 2.5 can penetrate lower respiratory system resulting in possible damage to the most critical respiratory organ, the alveolar system. Presently, the focus is on the comparative health effects of even finer PM down to the nanometer level (less than 100 nanometers or 0.1 micron). Nanoparticles in Bangkok ambient air, the capital of Thailand, were investigated to determine their potential detrimental health effects in comparison to larger particles. Nanoparticles present possible adverse effects, both on human health and the environment. These are mostly due to their high surface area to volume ratio. Larger surface area increases gaseous pollutant adsorption on its surface resulting in greater toxic air pollutant concentrations in the smaller particles. EXPERIMENTAL METHOD The study carried out measurement of sized-selected particulate matter by Nanosampler, developed by a part of the authors [3]. Nanosampler can collect particles down to nano-size range and has the flow rate of 40 Lmin -1 . Nanosampler consists of three impactor stages, an inertial filter [4] and a backup filter. providing 5 particle size fractions, namely >10 m, 2.5-10 m, 1-2.5 m, 0.07-1 m and less than 0. 07 m (~70 nm). Quarts fibrous filters, or, donut filters (Ø 65 × 30 mm) and backup filters (Ø 47 mm) were used in the impactor stages and 9 mg of webbed SUS fibers (9.6 m diameter) was packed in a nozzle of the inertial filter cassette [3]. All filters were kept in a desiccator for 72 hours before and after sampling then weighted on a micro-balance (Sartorius) with the accuracy of 0.01 mg. Three monitoring stations were carefully chosen in order to compare particulate matter concentration with data of Pollution Control Department (PCD) in Thailand: (1) Dindaeng station, far from main road (Asok-Dindaeng road) less than 10 meters (2) Bansomdet Chaopraya Rajabhat University station, far from main road (Isaraparp road) more than 50 meters, commercial and residential area of Bangkok. and (3) Chulalongkorn University Station far from main road (Phayathai road) more than 50 meters and collecting at roof floor of Environmental Engineering Building which is 20 meters height from ground level. The samplings were carried out 24 hours in every 6 days for 2 months at each station for the period of 6 months in total during November 2008 until May 2009. Chulalongkorn University Station, nanoparticle sampler was co-located with high-volume sampler and 8-stage cascade impactor as well as comparing the data with automatic PM 10 samplers (Taper Element Oscillating Microbalance (TEOM) and Beta ray type) at Dindaeng and Bansomdet Chaopraya Rajabhat University station. RESULTS AND DISCUSSION Particulate matter was collected by nano-particle sampler in 3 sampling sites: Dindaeng station, PM concentrations increase from November to highest in midmonth of December which is the cool season, Bansomdet Chaopraya Rajabhat University Station, PM concentrations trend decrease from midmonth of January to very low concentrations in March, and Chulalongkorn university station, the highest sampling site, PM average concentrations is clearly lower than PM concentrations from ground level sampling station. The PM 10 concentrations in Dindaeng as shown in Table 1, ranged from 50.3 to 127.0 μg/m 3 and average is 81.5 μg/m 3 .The highest concentrations exceeded the national standard of air quality (120 μg/m 3 ). However, PM 10 concentrations in Dindaeng in 2000 ranged from 37.0 to 137.0 μg/m 3 with the average value of 72.0 μg/m 3 (Thongsanit et al., 2003), which indicates the pollution situation is still serious in Bangkok. The sampling at Dindaeng roadside station showed the proportions of PM 10-2.5 , PM 2.5-1 , PM 1-0.07 and PM 0.07 to the total PM 10 mass were 32.7, 20.9, 35.4 and 11.0%, respectively. Bamsomdej Chaopraya station showed the proportions of PM 10-2.5 , PM 2.5-1.0 , PM 1.0-0.07 and PM 0.07 to the total PM 10 mass were 35.9, 24.5, 29.6 and 10.0%, respectively. Chulalongkorn station showed the proportions of PM 10-2.5 , PM 2.5-1 , PM 1-0.07 and PM 0.07 to the total PM10 mass were 31.5, 22.4, 34.9 and 11.2%, respectively. Proportions trend of all stations was similarity and indicating bimodal peaks for PM 10-2.5 and PM 1-0.07 rather than PM 2.5-1 . The average PM 2.5 : PM 10 ratio in 3 stations ranged from 0.64 to 0.67. This raises the issue of targeted PM size for prescribing ambient air quality standards which now call for PM 2.5 . 土木学会中部支部研究発表会 (2010.3) VII-018 -577-