Abstract
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 the 3 months of winter 2014–2015. For the deconvolution of eBC into eBC emitted from fossil fuel (BCff) and wood burning (BCwb), a method based on the spectral dependency of the absorption of pure black carbon and brown carbon was used. Thereafter, BCwb and BCff 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 a comparative analysis of the results, we additionally estimated the wood burning and fossil fuel contribution to CO, calculated on the basis of their CO ∕ NOx emission ratios. The results indicate that during wintertime BC and CO are mainly emitted by local sources within the Athens Metropolitan Area (AMA). Fossil fuel combustion, mainly from road traffic, is found to be the major contributor to both eBC in PM2.5 and CO ambient concentrations in AMA. However, wintertime wood burning makes a significant contribution to the observed eBC (of about 30 %) and CO concentrations (on average, 11 and 16 % of total CO in the suburban and urban background sites respectively). Both BC and CO from biomass burning (BCwb and COwb, respectively) present a clear diurnal pattern, with the highest concentrations during night-time, supporting the theory of local domestic heating being their main source.
Highlights
Air pollution, which originates largely from combustion processes, is a very important environmental concern in Athens, like in other large urban agglomerations around the world
It is interesting to observe that the average minimum of concentrations at National Observatory of Athens (NOA) occurs during midday due to a higher boundary layer height (BLH) and corresponding aerosol dilution during day-time, when both sampling sites are under the same well-mixed atmosphere, winds are stronger, and the pollutants are more homogeneously dispersed in the metropolitan area
As a matter of fact, widespread natural sources of carbon monoxide (CO), such as plants, oceans and oxidation of hydrocarbons, in combination with its long atmospheric lifetime, are known to maintain a significant background concentration even outside urban areas. These results show that the Black carbon (BC) / CO ratio is higher for emissions related to biomass burning compared to fossil fuel combustion, which is consistent with literature values (Pan et al, 2012)
Summary
Air pollution, which originates largely from combustion processes, is a very important environmental concern in Athens, like in other large urban agglomerations around the world. A high population (3.75 million in the metropolitan area) and the confinement of commercial and industrial activities to a relatively small area (approximately 450 km2), has led to severe environmental degradation. Combustion processes used for transportation, power generation and other human activities produce a complex mixture of chemical pollutants (Cohen et al, 2004), which at any given location have characteristics depending on the relative contributions of the different sources of pollution and on the effects of the local geo-climatic factors. Black carbon (BC) aerosol and carbon monoxide (CO) are two major products of incomplete combustion and are important atmospheric components because of their substantial impact on health (Ostro et al, 2015), including respiratory and cardiovascular effects, as well as on climate (Zanatta et al, 2016).
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