Evidence of biomass burning aerosols in the Barcelona urban environment during winter time

The influence of biomass burning (BB) aerosols, whether of regional or local origin, on fine aerosol levels in the Barcelona urban environment (Spain) was investigated. High-time resolved data on light-absorbing aerosols and inorganic tracers in PM2.5 were combined to this end during a dedicated sampling campaign carried out in winter 2011. The evaluation of PM inorganic components and equivalent black carbon evidenced that local-scale BB emissions were not detectable, whereas a source of K, different to vehicular traffic (road dust) and construction/demolition dust re-suspension, was detectable in the urban area. Source apportionment analysis evidenced the contribution from one source traced by S (62% of the source profile) and K (16% of the source profile), which was interpreted as regional-scale transport of secondary aerosols including BB contributions. The S/K ratio for this source (S/K = 4.4) indicated transport of the polluted air masses, as occurs from the rural areas towards the Barcelona urban environment. On average for the study period, the contribution of K-related aerosols from regional BB to PM2.5 levels in the urban environment was estimated as 1.7 μg/m3 as a daily mean, accounting for 8% of the PM2.5 mass during the winter period under study. The contribution from this source to urban aerosols should be lower on the annual scale.