GAW Report No. 205 - IGAC Project

CHAPTER 3 - ASIAand Kim Oanh, 2002]. Meteorological conditions, averaged over 1981-2007 period, show theannual average temperature of Bangkok ranges between 26.7-28.0 o C and average annual rainfallbetween 1,320-1,950 mm. Low wind, average of 1.3 m/s and mostly below 3 m/s, is observedthroughout the year [TMD, 2009]. Monthly windroses of a 10-year period, 1991 – 2000, show highpercentages of calm conditions, ranging from 30% in March to 61% in October [Zhuang, 2001].Monthly meteorological variables in Bangkok, averaged for 1971 to 2000, are presented in Figure 3.Figure 3 - Monthly observed average meteorological conditions in Bangkok, Thailand (1971-2000)[Zhang, 2001]Emission sources of air pollutantsMajor sources of air pollution in BMR include traffic, power plants, industries andincinerators. In addition, agroresidue field open burning also contributes significantly to urban airpollution but has not yet been properly quantified. Point sources (industry, power plants) are themajor source of SO 2 , whereas mobile source contributes significantly to NO X , CO, VOC/HC, andPM emission. Area sources also contribute a remarkable amount to CO emission.The average growth rate of vehicles in Bangkok, over an 18-year period starting from 1989,is around 7% per year. There were approximately six million vehicles registered in Bangkok as ofMay 2009 [Department of Land Transport, 2007]. A high growth rate of vehicles and inadequateroad infrastructures are major causes of traffic congestion in Bangkok that lead to high air pollutionemissions. In recent years, in order to improve air quality, the European standards have beenimposed for new vehicles progressively. For example, in 1998 new heavy-duty diesel vehiclesregistered in Thailand had to meet EURO1 standards. The EURO2 standard was implemented in2003 and since 2007, new heavy-duty diesel vehicles have to meet the EURO-3 standard [PCD,2009]. For over a decade, development of fuel specification has been continuously implemented inThailand. Leaded gasoline was phased out as of January 1996. Sulphur content in diesel fuel isbeing reduced, e.g. 500 ppm sulphur was enacted on July 1998; 350 ppm sulphur was enacted onJanuary 2004; and 50 ppm sulphur is currently proposed for 2010 [ESMAP, 2008]. Thailand has apolicy of encouraging use of compressed natural gas (CNG) and ethanol in transport [ESMAP,2008]. Nowadays, the CNG use is widely spread, especially in taxis and trucks.For point sources, there are two thermal power plants under EGAT operated in BMR.Fortunately one is oil-based and the other is natural gas (NG) based, which are cleaner thancoal-based power plants. Around 38,593 industries of different types and sizes are registered inBMR [DIW, 2007]. Half of them (19,082 industries) are located in Bangkok city. Most of theseindustries are of small scales and potentially more polluting. A few waste incinerators are also inoperation in BMR to treat the hygiene and hospital wastes [IPEP, 2006] and also emit air pollutants.64