Sources and contributions of wood smoke during winter in London: assessing local and regional influences

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.

Direct observation of aqueous secondary organic aerosol from biomass-burning emissions

“…In Europe, combustion of biomass for residential heating has increased in recent years. One study at a rural site in northern Italy showed that SOA from biomass burning in winter accounts for 10% of organic carbon and 7% of fine particle mass (43); in the urban area of Paris, processing of biomassburning emissions accounted for up to 40% of the OA during another field study (44); similarly, in rural areas nearby London, aged biomass-burning emissions are a likely important contribution to the overall OA (45). This study highlights the relevance of aqueousphase chemistry for processing of wood-burning emissions.…”

Simulating secondary organic aerosol from missing diesel-related intermediate-volatility organic compound emissions during the Clean Air for London (ClearfLo) campaign

“…Furthermore, London is a smoke control area and therefore no residential emissions of SFOA are assumed by the national emissions inventory. Recent studies have, however, suggested that there are indeed local sources of SFOA in London (Crilley et al, 2015;Young et al, 2015a).…”

“…During these periods, the observed temperature was colder than the average temperature of the winter IOP (Crilley et al, 2015) and peaks in measured SOA also coincide with elevated concentrations of SFOA (Figs. 5b and 13b).…”

Modelling carbonaceous aerosol from residential solid fuel burning with different assumptions for emissions

“…Several recent studies have reported substantial local contributions of emissions from solid fuel burning to particle concentrations in London coinciding with days of low temperature (Fuller et al, 2014;Crilley et al, 2015). This is relevant as, currently, the UK's National Atmospheric Emissions Inventory (NAEI) assumes zero residential emissions of non-approved solid fuel burning in smoke control areas (i.e.…”

“…London have shown that local contributions of SFOA coincide with days of low temperature (Fuller et al, 2014;Crilley et al, 2015). Therefore, degree-day factors were included to modulate the daily variation in emissions from the SNAP2 sector according to ambient temperature (i.e.…”