Comparison of methods for evaluation of wood smoke and estimation of UK ambient concentrations

R M Harrison,J Yin,L Hu,D C S Beddows

doi:10.5194/acp-12-8271-2012

Abstract

Abstract. Airborne concentrations of the wood smoke tracers, levoglucosan and fine potassium have been measured at urban and rural sites in the United Kingdom alongside measurements with a multi-wavelength aethalometer. The UK sites, and especially those in cities, show low ratios of levoglucosan to potassium in comparison to the majority of published data. It is concluded that there may be two distinct source types, one from wood stoves and fireplaces with a high organic carbon content, best represented by levoglucosan, the other from larger, modern appliances with a very high burn-out efficiency, best represented by potassium. Based upon levoglucosan concentrations and a conversion factor of 11.2 from levoglucosan to wood smoke mass, average concentrations of wood smoke including winter and summer sampling periods are 0.23 μg m−3 in Birmingham and 0.33 μg m−3 in London, well below concentrations typical of other northern European urban areas. There may be a further contribution from sources of potassium-rich emissions amounting to an estimated 0.08 μg m−3 in Birmingham and 0.30 μg m−3 in London. Concentrations were highly correlated between two London sites separated by 4 km suggesting that a regional source is responsible. Data from the aethalometer are either supportive of these conclusions or suggest higher concentrations, depending upon the way in which the data are analysed.

Highlights

The enforcement of legislation internationally is acting to reduce airborne concentrations of particulate matter, measured as PM2.5 and PM10
The weekday diurnal pattern for estimated wood burning smoke (PMwb) and the different diurnal profile and higher concentrations seen on weekends are in line with expectations, but the average concentrations far exceed those measured by the other techniques
This work is suggesting that annual mean concentrations of biomass smoke at UK sites are very low at well below 1 μg m−3 and very much lower than some other estimates for the UK (Fuller et al, 2011)

Summary

Introduction

The enforcement of legislation internationally is acting to reduce airborne concentrations of particulate matter, measured as PM2.5 and PM10. In the European Union, member states have to meet an air quality objective of 25 μg m−3 for PM2.5 as an annual mean by 2015, as well as an exposure reduction target to be met by 2020 whose magnitude depends upon the annual average concentration across qualifying sites in the years 2009–2011 (Harrison et al, 2012). Amongst the sources most difficult to quantify by receptor modelling, and for which emissions inventory data are least reliable, wood smoke stands out as posing particular problems. Since the estimation of emissions poses such large difficulties, most estimates of the source contribution are based upon receptor modelling methods. These may be based upon a CMB modelling approach using a range of compositional components (e.g. Chow et al, 2007), or more often upon individual source tracers.

Results

Discussion

Conclusion