Seasonal and diurnal variations of black carbon and organic carbon aerosols in Bangkok

Abstract

[1] Measurements of black carbon (BC) and organic carbon (OC) were conducted in Bangkok during [2007][2008]. Annual trends of BC and OC show strong seasonality with lower and higher concentrations during wet and dry seasons, respectively. Flow of cleaner air, wet removal, and negligible biomass burning resulted in the lowest concentrations of aerosols in the wet season. In addition to anthropogenic sources, long-range transport and biomass burning caused higher concentrations in the dry and hot seasons, respectively. Despite extensive biomass burning in the hot season, moderate levels of aerosols were due to the mixing with air masses from the Pacific Ocean. Diurnal distributions exhibit peaks during rush hour marked by minima in the OC/BC ratio and stagnant wind flow. The lowest concentrations in the afternoon hours could be due to deeper planetary boundary layer and reduced traffic. Overall, the concentrations of both BC and OC decrease with the increase in wind speed. The weekend effects, due to reduced emission during weekends, in the concentrations of both BC and OC were significant. Therefore, stricter abatement in vehicular emissions could substantially reduce pollution. A slope of DBC/DCO of 9.8 ngm −3 ppbv −1 for the wet season represents the emission ratio from vehicular sources. The highest of DOC/DBC (3 mg mg −1 ) in the hot season was due to the predominant influence of biomass burning and significant formation of secondary OC. The levels of BC and OC in Bangkok fall within the ranges of their concentrations measured in the major cities of East Asia.

Distribution, input pathway and mass inventory of black carbon in sediments of the Gulf of Thailand, SE Asia

“…The semi-enclosed Bohai Sea and Yellow Sea, from the moderatehigh latitude region, are mainly situated at the downwind area of the East Asian Monsoon, receiving large amounts of combustionderived substances (e.g., PAHs) through atmospheric deposition, especially in the winter season due to the extensive regional heating activities in China (Wang et al, 2014). The surrounding region of the GOT from the tropical regime is more subjected to the extensive biomass burning, especially during the hot season (Sahu et al, 2011). Although there is no extensive coal consumption around the GOT, such as that in North China, the inherent biomass burning in tropical SE Asia is also significant (Bond et al, 2004), and atmospheric deposition is expected to be an important BC vector for the Indian Ocean (Lohmann et al, 2009).…”

“…6), which could be partially explained by a decoupling of the char and soot sources as noted above. Biomass burning and forest fires have been suggested to serve as the predominant sources for BC in aerosol samples in Thailand, especially in the hot season (Sahu et al, 2011), and the larger particles of char mainly from the biomass burning residues tend to first accumulate in soils in close proximity to their site of production and then be primarily transported by surface run-off and local river inputs to the aquatic sediments (Gelinas et al, 2001;Yunker et al, 2002;Pietzsch et al, 2010;Han et al, 2015a). Actually, in addition to the sedimentassociated BC, Ding et al (2015) also demonstrated that there existed different input sources for the dissolved BC in the boreal forest streams through active removal process in soils from the local biomass burning as compared to those in the remote glacial rivers with a more atmospheric delivered fossil fuel-derived BC.…”

“…The Gulf of Thailand (GOT), a shallow and semi-enclosed shelf sea in SE Asia, has been subjected to a huge BC emission from biomass burning, forest fires and fossil fuel consumption from the adjacent regions (Saha et al, 2009;Sahu et al, 2011;Huang et al, 2013). Because of the nutrient-rich, shallow waters and their confined nature, the ecosystem of the GOT is especially vulnerable to human activities (Srisuksawad et al, 1997), and increased anthropogenic activities around the GOT have induced severe environmental pollution, especially for the upper Gulf with significant river export of land-based contaminants (e.g., the Chao Phraya River) (Wattayakorn et al, 1998).…”

Estimation of Gas-particle partitioning Coefficients (Kp) of Carcinogenic polycyclic Aromatic hydrocarbons in Carbonaceous Aerosols Collected at Chiang - Mai, Bangkok and hat-Yai, Thailand

“…Some studies have focused on the chemical composition of aerosols and their impact on the tropical/sub-tropical urban environment over the past two decades (Fang et al, 1999;Latha and Badarinath, 2003;2005;Pandey et al, 2006) while others have examined the empirical estimation of secondary organic carbon (SOC) formation (Seguel et al, 2009;Grivas et al, 2012;Kim et al, 2012;Wang et al, 2012). Only a few publications have presented indepth, quantitative evidence regarding the behavior of carbonaceous aerosols in Thailand (Pongpiachan et al, 2009;Sahu et al, 2011;Li et al, 2012).…”

“…Two observatory stations, namely Baiyoke Suit Hotel (13°45'10.65" N 100°32'24.92" E) : There have, however, been an increasing number of articles to appear in several peer-reviewed international journals over the past few years, which relate to of haze episodes on the air quality in the northern region of Thailand (Kim et al, 2011;Wiwatanadate and Liwsrisakun, 2011;Li et al, 2012). For instance, one study observed a 20% rise in the number of patients suffering from respiratory diseases in March 2007 when compared to one year earlier in 2006 (Pengchai et al, 2009 : In 1971, The Environmental Protection Agency (EPA) promulgated primary and secondary national ambient air quality standards for particulate matter measured as "total suspended particulate" or "TSP".…”