Exploring the Variation between EC and BC in a Variety of Locations

Abstract

Despite intensive research over the past three decades, a generally accepted standard method to measure black carbon (BC) or elemental carbon (EC) still does not exist. Data on BC and EC concentrations are method specific and can differ widely. This work was motivated by the lack of any prior study that established the variability between these two measures of carbonaceous particulate matter. Measurements of BC and EC were performed at different locations across Asia and the South Pacific in both urban and suburban locations. Filter samples were collected during the winter of 2007 to the winter of 2010 and analyzed for both BC and EC. EC was measured using the Interagency Monitoring of Protected Visual Environments (IMPROVE_A) protocol. Black carbon was measured by the EELS reflectometer (Diffusion Systems, Ltd). Bangladesh had the highest correlation coefficient of 0.93. Bangkok, Thailand on the other hand had the lowest correlation coefficient of 0.34. A review of previously reported source apportionment of BC concentrations in these locations showed that New Zealand had the highest percentage (82%) of BC from biomass while Mongolia had the lowest percentage of 3.1%. The fraction of BC emissions from diesel vehicles was found predominant in Mumbai, India with values as high as 80%. Mongolia had the lowest emission of BC from diesel vehicle (5.4%) with coal-and biomass-combustion being the dominant sources.

Comparison of elemental and black carbon measurements during normal and heavy haze periods: implications for research

“…This change is likely due to differences in factors such as chemical composition, mixing state, and relative humidity (Salako et al 2012;Jeong et al 2004;Andreae and Gelencsér 2006;Redemann et al 2001).…”

“…EC represents thermally refractory carbon with a graphitic structure, whereas BC is commonly used to define the extent to which an aerosol sample exhibits light-absorbing properties (Salako et al 2012;Gray and Cass 1998;Huntzicker et al 1982;Watson et al 2005). …”

“…BC cannot be measured directly but must be inferred from the particle light absorption (b ap ) through a conversion factor that is used to translate b ap to the BC mass concentration (Chow et al 2009;Biswas et al 2003). According to the literature, both EC and BC are considered to assume a graphitic structure and are therefore thermally refractory and light-absorbing in nature (Bond and Bergstrom 2006;Salako et al 2012;Conny et al 2003;Turpin et al 1990). It seems that both EC and BC describe nearly the same fraction of carbonaceous aerosols; however, according to traditional practice, their values are dependent on specified determination methods which focus on different properties, e.g., thermal stability or light absorption (Birch 1998;Chow et al 1993;Hansen et al 1984).…”

“…It seems that both EC and BC describe nearly the same fraction of carbonaceous aerosols; however, according to traditional practice, their values are dependent on specified determination methods which focus on different properties, e.g., thermal stability or light absorption (Birch 1998;Chow et al 1993;Hansen et al 1984). This practice introduces the potential for disagreement between EC and BC measurements due to method-involved biases (Jeong et al 2004;Lavanchy et al 1999;Li et al 2006;Salako et al 2012).…”

“…Because atmospheric aerosol plays an important role in global and regional energy budgets, the recently increased incidence of heavy urban haze in China is indicative of the growing impact of urban aerosols on both air quality and climate (Engling and Gelencsér 2010;Ramanathan and Feng 2009;Seinfeld and Pandis 1998). Although a number of comparisons of simultaneous EC and BC measurements for urban or non-urban ambient aerosols have been reported (Lavanchy et al 1999;Li et al 2006;Salako et al 2012;Jeong et al 2004;Cyrys et al 2003;Nordmann et al 2009), studies specifically characterizing the EC/ BC relationship during a transition from normal air quality to heavy haze are rare.…”