Abstract
Abstract. Determining the contribution of wood smoke to air pollution in large cities such as London is becoming increasingly important due to the changing nature of domestic heating in urban areas. During winter, biomass burning emissions have been identified as a major cause of exceedances of European air quality limits. The aim of this work was to quantify the contribution of biomass burning in London to concentrations of PM2.5 and determine whether local emissions or regional contributions were the main source of biomass smoke. To achieve this, a number of biomass burning chemical tracers were analysed at a site within central London and two sites in surrounding rural areas. Concentrations of levoglucosan, elemental carbon (EC), organic carbon (OC) and K+ were generally well correlated across the three sites. At all the sites, biomass burning was found to be a source of OC and EC, with the largest contribution of EC from traffic emissions, while for OC the dominant fraction included contributions from secondary organic aerosols, primary biogenic and cooking sources. Source apportionment of the EC and OC was found to give reasonable estimation of the total carbon from non-fossil and fossil fuel sources based upon comparison with estimates derived from 14C analysis. Aethalometer-derived black carbon data were also apportioned into the contributions from biomass burning and traffic and showed trends similar to those observed for EC. Mean wood smoke mass at the sites was estimated to range from 0.78 to 1.0 μg m−3 during the campaign in January–February 2012. Measurements on a 160 m tower in London suggested a similar ratio of brown to black carbon (reflecting wood burning and traffic respectively) in regional and London air. Peaks in the levoglucosan and K+ concentrations were observed to coincide with low ambient temperature, consistent with domestic heating as a major contributing local source in London. Overall, the source of biomass smoke in London was concluded to be a background regional source overlaid by contributions from local domestic burning emissions. This could have implications when considering future emission control strategies during winter and may be the focus of future work in order to better determine the contributing local sources.
Highlights
A number of detrimental health effects have been associated with exposure to airborne particles (Cohen et al, 2005; Kampa and Castanas, 2008)
Recent work has shown that the contribution of biomass burning to the organic carbon (OC) fraction in an urban environment derived from radiocarbon, levoglucosan and aerosol mass spectrometry results gave similar estimates, ranging from 0.3 to 0.7 μg m−3, and indicates that these techniques can give comparable results (Minguillón et al, 2011)
Wind rose plots for the winter intensive observation period (IOP) are given in the Supplement
Summary
A number of detrimental health effects have been associated with exposure to airborne particles (Cohen et al, 2005; Kampa and Castanas, 2008). These techniques include the chemical analysis of filter samples for elemental carbon (EC) and organic carbon (OC) (Gelencsér et al, 2007), the radioisotope of carbon (14C; Heal, 2014; Heal et al, 2011; Szidat et al, 2006) and chemical tracers such as levoglucosan and potassium (Harrison et al, 2012a; Viana et al, 2013; Wagener et al, 2012) Instruments such as aethalometers (Sandradewi et al, 2008a, b; Herich et al, 2011) and aerosol mass spectrometers (Allan et al, 2010; Lanz et al, 2010; Crilley et al, 2014) have been useful for determining the contribution of biomass burning with the added advantage of measurements at a high time resolution. Recent work has shown that the contribution of biomass burning to the OC fraction in an urban environment derived from radiocarbon, levoglucosan and aerosol mass spectrometry results gave similar estimates, ranging from 0.3 to 0.7 μg m−3, and indicates that these techniques can give comparable results (Minguillón et al, 2011)
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