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

Abstract

The scope of this study was to estimate the contribution of fossil fuel and wood burning combustion to black carbon (BC) and carbon monoxide (CO) during wintertime, in Athens. For that purpose, in-situ measurements of equivalent Black Carbon (eBC) and CO were simultaneously conducted in a suburban and an urban background monitoring site in Athens during three months of winter 2014-2015. For the deconvolution of eBC into eBC emitted from fossil fuel (BC ff ) and wood burning 15 (BC wb ), a method based on the spectral dependency of the absorption of pure black carbon and brown carbon was used.Thereafter, BC wb and BC ff estimated fractions were used along with measured CO concentrations in a multiple regression analysis, in order to quantify the contribution of each one of the combustion sources to the ambient CO levels. For an independent evaluation of the results, we additionally estimated the wood-burning and fossil fuel contribution to CO, calculated on the basis of their CO/NO x emission ratios. The results indicate that during wintertime BC and CO are mainly 20 emitted by local sources within the Athens Metropolitan Area (AMA), and are only occasionally affected by long-range transport. Fossil fuel combustion, mainly from road traffic, is found to be the major contributor to both eBC in PM 2.5 and CO ambient concentrations in AMA. However, wintertime wood burning makes a significant contribution of about 30% to the observed eBC and the CO concentrations (on average, 11 % and 16 % of total CO in the two sites, respectively). Both, BC and CO from biomass burning (BC wb and CO wb , respectively) present a clear diurnal pattern with highest concentrations 25 during night, supporting the local domestic heating as their main source.

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

“…The relative contributions of fossil fuel (FF) and wood burning (WB) to aerosol absorption at 880 nm, as estimated by the use of the different α wb values, over the whole year and during the warm and cold period, are presented in Table 1. All further analysis was performed with α wb equal to 2.0, since this is the value proposed by most studies [35,38]. This value is also very similar to the maximum Ångström exponent values during the winter period (2.03-2.04), observed during nighttime hours when wood-burning contributions are expected to be significant.…”

“…An average MAC equal to 4.1 m 2 g −1 was calculated for the entire study period, with 24-h values ranging from 2.0-9.9 ( Figure S2). [38]. The lower MAC value found in the present work relates to the different study period.…”

“…Mean relative contribution of wood burning during these months was calculated equal to 27%. Kalogridis et al reported a contribution from BC wb of 34% for the winter months of the following year (2014-2015) [38]. It should be noted that the period of 2013-2014 was characterised by an exceptionally mild winter, which may explain the slightly lower BC wb contributions.…”

“…The Aethalometer model has been applied in several studies for apportioning carbonaceous aerosol to fossil fuel combustion and biomass burning [33][34][35][36][37][38], despite certain uncertainties, mainly associated with the selection of appropriate values for α ff and α wb . In the present study, calculations were performed for the 470 (UV) and 950 nm (IR).…”

“…A series of tests were therefore conducted with the value of α ff ranging between 0.8 and 1.2, by a step of 0.1, based on typical values for fossil fuel combustion aerosol found in the literature [4,32,33,39]. The value of α wb was set at this point equal to 2.0, which is considered a typical value of the Ångström exponent for wood burning aerosol [38]. The estimated absorption coefficients for wood burning at 950 nm (b abs (950) wb ) were averaged over 24 h and were correlated with concentrations of levoglucosan measured at the site during the same period.…”