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Environ Monit Assess (2014) 186:47434751 DOI 10.1007/s10661-014-3734-5
Attribution of aerosol light absorption to black carbon and volatile aerosols
Rijana Shrestha & Sang-Woo Kim &
Soon-Chang Yoon & Ji-Hyoung Kim
Received: 19 August 2013 /Accepted: 18 March 2014 /Published online: 2 April 2014 # Springer International Publishing Switzerland 2014
Abstract We investigated the contribution of volatile aerosols in light-absorption measurement by three filter-based optical instruments [aethalometer, continuous light-absorption photometer (CLAP), and continuous soot monitoring system (COSMOS)] at Gosan Climate Observatory (GCO) from February to June 2012. The aerosol absorption coefficient (abs) and the equivalent
black carbon (BC) mass concentration (MBC) measured by the aethalometer and CLAP showed good agreement with a difference of 9 %, which is likely due to the instrumental uncertainty. However, abs and MBC mea
sured by the COSMOS with a heated inlet were found to be approximately 44 and 49 % lower than those measured by the aethalometer and CLAP under ambient conditions, respectively. This difference can be attributed to the light absorption by the volatile aerosols coexisting with the BC. Even considering inherent observational uncertainty, it suggests that approximately 3540 % difference in the abs and MBC can be contrib
uted by volatile aerosols. Increase in the difference of MBC measured by the aethalometer and COSMOS with the increasing thermal organic carbon (OC) measured by Sunset OC/EC analyzer further suggests that the filter-based optical instruments without the use of a heater are likely to enhance the value of abs and MBC,
because this sample air may contain both BC and volatile aerosols.
Keywords Blackcarbon .Volatileaerosols .Filter-based optical instruments . Aethalometer. Light absorption
Introduction
Aerosol light absorption plays an important role in the earths atmosphere in terms of direct and semidirect radiative forcing (Bond et al. 2013). Wind-blown mineral dust, brown carbon (BrC), and black carbon (BC) are well-known as major light-absorbing aerosols in the atmosphere. Mineral dusts refer to strong or weak light absorbers depending on their mineralogical composition (Linke et al. 2006). BrC refers to moderate-to-weak light-absorbing organic matter in the atmosphere of various origins with a brownish appearance (Andreae and Gelencser 2006). BC is operationally defined as the carbonaceous aerosol with a deep black appearance, based on the measurement of light absorption. BC is formed by incomplete combustion of...