Annual Variability of Black Carbon Concentrations Originating from Biomass and Fossil Fuel Combustion for the Suburban Aerosol in Athens, Greece

Abstract

Abstract:The objective of this work was to assess the yearly contribution of fossil fuel combustion (BC ff ) and wood burning (BC wb ) to equivalent black carbon (eBC) concentrations, in Athens, Greece. Measurements were conducted at a suburban site from March 2013 to February 2014 and included absorption coefficients at seven wavelengths and PM 2.5 chemical composition data for key biomass burning markers, i.e., levoglucosan, potassium (K) and elemental and organic carbon (EC, OC). A well-documented methodology of corrections for aethalometer attenuation coefficients was applied with a resulting annual dataset of derived absorption coefficients for the suburban Athens' atmospheric aerosol. The Aethalometer model was applied for the source apportionment of eBC. An optimum Ångström exponent for fossil fuel (α ff ) was found, based on the combined use of the model with levoglucosan data. The measured eBC concentrations were equal to 2.4 ± 1.0 µg m −3 and 1.6 ± 0.6 µg m −3 , during the cold and the warm period respectively. The contribution from wood burning was significantly higher during the cold period (21 ± 11%, versus 6 ± 7% in the warm period). BC ff displayed a clear diurnal pattern with a morning peak between 8 and 10 a.m. (during morning rush hour) and a second peak during the evening and night hours, due to the shallowing of the mixing layer. Regression analysis between BC wb concentrations and biomass burning markers (levoglucosan, K and OC/EC ratio) supported the validity of the results.

Assessment of wood burning versus fossil fuel contribution to wintertime black carbon and carbon monoxide concentrations in Athens, Greece

“…Recently, Zotter et al (2017) recommended to use α ff = 0.9 and α wb = 1.68, obtained by fitting the model outputs (calculated with the absorption coefficients at 470 and 950 nm) against the fossil fraction of EC derived from 14 C measurements. At DEM site, a previous study showed that values of a wb below 1.7 were not appropriate for the specific site (Diapouli et al, 2017b). On top of that, during fire events, Ångström exponent values up to 2 have been observed at DEM.…”

Authors Responses to referees' 1 & 2 comments

“…Differences in the absorption coefficients calculated using f λ values calculated for an SSA of 0.8 (e.g. f 6 = 1.166) and those found in Drinovec et al, (2015) were found to be lower than 1 %. The performance of the loading compensation algorithm was examined using the approach described in Drinovec et al, (2015), where the dependence of the absorption Ångström exponent α to the attenuation of light is analysed.…”

“…The aerosol light absorption coefficient, b abs , was retrieved at each station by means of a seven-wavelength (370,470,520,590,660,880 and 950 nm) Aethalometer (Magee Scientific Corp., Berkeley, CA 94703, USA) with a 5 min temporal resolution. At DEM, the new generation AE33 Aethalometer model was used, which provides a real-time compensation for multiple scattering in the filter matrix and loading effects using the DualSpot Technology ® (Drinovec et al, 2015). The AE33 sampled aerosol through a PM 2.5 cut-off inlet.…”

“…where SSA λ is the aerosol single scattering albedo and α a constant parameter, varying in the range 0.82-0.88 for the different wavelengths (950-370 nm). Since no simultaneous scattering coefficient measurements were available during this campaign, f λ values (f 370 = 1.319, f 470 = 1.288, f 520 = 1.244, f 590 = 1.213, f 660 = 1.213, f 880 = 1.203, f 950 = 1.203) given in Drinovec et al (2015) for an urban site with a single scattering albedo of about 0.75 were used for loading compensation at the urban background Alves et al, 2002), Barcelona (year 2009, Reche et al, 2011, Paris (summer 2009(summer , Zhang et al, 2013 and Helsinki (winter 2000, Hitzenberger andTohno, 2001); (red) in urban background/residential areas such as Milan (summer 2010, Invernizzi et al, 2011), London (year 2009, Reche et al, 2011 and Lugano (year 2009, Reche et al, 2011; and (green) a suburban area of Paris (Laborde et al, 2013) along with the results from this study at NOA and DEM stations in winter 2014-2015. site. In order to estimate uncertainties related to the chosen f λ values, absorption coefficients calculated with f λ values taken from Drinovec et al (2015) were compared with those using f λ values calculated for a SSA value of 0.8.…”

Carbonaceous Aerosols in the Atmosphere

“…Analysis of these variabilities could bring information regarding the impact of the main carbon sources to particulate matter. In Diapouli et al [31], seasonal, weekly, and diurnal variability of equivalent black carbon (eBC) concentrations were investigated at a suburban site in Athens (Greece). A dataset was collected between 2013 and 2014 including absorption coefficients (at seven wavelengths), and PM 2.5 chemical composition data for key biomass burning markers (levoglucosan, K, EC, and OC).…”