Contribution of wood burning to PM10 in London

Ahead of measures to incentivise wood heating, the current level of wood burning in London was assessed by two tracer methods; i) a six week campaign of daily measurements of levoglucosan along a 38 km transect across the city during winter 2010, ii) a three year (2009–2011) measurement programme of black carbon and particulate matter from wood burning using differential IR and UV absorption by Aethalometer. Mean winter levoglucosan concentrations were 160 ± 17 ng m−3 in central London and 30 ± 26 ng m−3 greater in the suburbs, with good temporal correlation (r2 = 0.68–0.98) between sampling sites. Sensitivity testing found that the aethalometer wood burning tracer method was more sensitive to the assumed value of the Ångström coefficient for fossil fuel black carbon than it was to the Ångström coefficient for wood burning PM, and that the model was optimised with Ångström coefficient for fossil fuel black carbon of 0.96. The aethalometer and levoglucosan estimates of mean PM from wood burning were in good agreement during the winter campaign; 1.8 μg m−3 (levoglucosan) and 2.0 μg m−3 (aethalometer); i.e. between 7% and 9% of mean PM10 across the London transect. Analysis of wood burning tracers with respect to wind speed suggested that wood burning PM was dominated by sources within the city. Concentrations of aethalometer and levoglucosan wood burning tracers were a greatest at weekends suggesting discretionary or secondary domestic wood burning rather than wood being used as a main heating source. Aethalometer wood burning tracers suggests that the annual mean concentration of PM10 from wood burning was 1.1 μg m−3. To put this in a policy context, this PM10 from wood burning is considerably greater than the city-wide mean PM10 reduction of 0.17 μg m−3 predicted from the first two phases of the London Low Emission Zone which was introduced to reduce PM from traffic sources.