Search

The importance of wood combustion to local air quality was estimated by measuring different air pollutants and conducting chemical mass balance modelling. PM10, PM2.5, PAHs and VOC concentrations in ambient air were measured in a typical Finnish residential area. Measurements were conducted in January–March 2006. For some compounds, wood combustion was clearly the main local source at this site. The effect of wood combustion was more clearly seen for organic compounds than for fine particle mass. For fine particles, background concentrations dominated. However, very high, short-lived concentration peaks were detected, when the wind direction and other weather conditions were favourable. For organic compounds, the effect of wood combustion was seen in diurnal and in two-week average concentrations. PAH-concentrations were often several times higher at the residential area than in the background. Benzene concentrations showed similar diurnal pattern as the use of wood and benzene/toluene ratios indicated that wood combustion is the most important source. A chemical mass balance model was used for studying the effect of wood combustion on the measured concentrations of VOCs. Model results showed that the main local sources for VOCs at Kurkimäki are wood combustion and traffic. Wood combustion was clearly the most important source for many compounds (e.g., benzene). [Copyright &y& Elsevier]

Abstract: Ambient air concentrations of benzene were both measured and predicted in the Helsinki Metropolitan area. Two-weekly measurements were conducted in 2000, 2002 and 2003 at seven measurement stations using diffusive adsorbent sampling; additional two-hourly measurements were also performed. An urban dispersion modelling system was utilised for modelling the spatial concentration distributions of benzene for 2000. According to both measurements and predictions, the annual mean benzene concentrations were below the upper assessment threshold (3.5μgm−3) set by the European Union, while the lower assessment threshold (2μgm−3) was exceeded at one urban station (Töölö) during the year 2000. The concentrations measured in the Helsinki Metropolitan Area were also compared with those at rural and remote stations in Finland. In the winters of 2000 and 2003, the concentrations at the remote and rural stations of Utö, Hyytiälä and Pallas were close to the concentrations at the urban background station of Kallio, while in the summers of 2000 and 2003, the concentrations at Kallio were substantially higher. The predicted concentrations in 2000 were highest in the vicinity of major roads and streets, and at their junctions. At all the stations, the predicted yearly averaged concentrations agreed fairly well with the measured data; the differences between measured and predicted values ranged from 10 to 31%. According to the measurements, and also the emission and dispersion computations, the most important source categories were exhaust emissions from local vehicular traffic, and the long-range transported background. [Copyright &y& Elsevier]