Particle and trace gas emission factors under urban driving conditions in Copenhagen based on street and roof-level observations

• Published in: Atmospheric environment (1994) Vol. 37; no. 20; pp. 2735 - 2749
• Main Authors: Ketzel, Matthias, Wåhlin, Peter, Berkowicz, Ruwim, Palmgren, Finn
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.06.2003; Elsevier Science
• Subjects: Air pollution; Applied sciences; Atmospheric pollution; Canyons; Diesel fuels; Driving conditions; Earth and Related Environmental Sciences; Emissions control; Emittance; Exact sciences and technology; Geovetenskap och miljövetenskap; Mathematical models; Meteorologi och atmosfärforskning; Meteorology and Atmospheric Sciences; Natural Sciences; Naturvetenskap; Particle size; Particle size distribution; Photochemistry; Pollution; Pollution sources. Measurement results; Street canyon; Streets; Traffic flow; Traffic source; Transports; Ultrafine particles; Urban aerosols; Vehicle emission factors; Vehicles; Denmark; Europe; Denmark, Copenhagen; Street canyon; Traffic source; Particle size distribution; Ultrafine particles; Urban aerosols; Vehicle emission factors; Nitrogen oxide; Emission content; Troposphere; Daily variation; Urban area; Diurnal variation; Pollutant emission; Time variation; Suspended particle; Aerosols; Air pollution; Road traffic; Carbon monoxide
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/S1352-2310(03)00245-0

Simultaneous measurements of particle size distribution (size/range 10–700 nm) inside an urban street canyon and a nearby urban background location in Copenhagen in May–November 2001 were used to separate the traffic source contribution in the street canyon from the background levels. The background concentrations are highly variable due to changing contributions from long-range transport and local sources showing a diurnal pattern with a shift to smaller particle sizes during midday hours. The average ratio background/street concentration is 0.26 for NO x and 0.35, 0.42, 0.60, 0.64, respectively, for CO, total particle number (ToN), surface and volume. The particle size distribution of the traffic source shows during daytime and evening hours (6–24) a maximum at particle sizes of 20–30 nm independent of the changing heavy-duty vehicle share during the same time interval. The particle number concentration highly correlated ( R>0.83) with NO x through a wide range of particle sizes. The method of inverse modelling was applied to estimate average fleet emission factors typical of urban conditions in Denmark. Emission factors per average vehicle were estimated as (2.8±0.5)×10 14 particles/km, (1.3±0.2) g NO x /(veh km) and (11±2) g CO/(veh km). We observe two types of ‘nanoparticle events’ (a) in background, probably due to photochemistry and (b) in the night hours when traffic is dominated by diesel taxis. During night hours (0–5), the maximum in the emitted particle size distribution is shifted to smaller sizes of about 15–18 nm. This shift to smaller particle sizes is related to an increase in the average NO x and ToN emission per vehicle by a factor of 2–3 and a reduced CO emission also by a factor of 2–3.