Estimations of primary nitrogen dioxide exhaust emissions from chemiluminescence NOx measurements in a UK road tunnel

• Published in: The Science of the total environment 2012-11, Vol.438, p.248-259
• Main Authors: Simmons, W.A., Seakins, P.W.
• Format: Article
• Language: English
• Subjects: Applied sciences; Atmospheric pollution; chemiluminescence; Diurnal variations; Emission inventories; emissions; England; Environmental Monitoring - methods; Environmental Monitoring - statistics & numerical data; Exact sciences and technology; Luminescent Measurements - methods; Nitric Oxide - analysis; nitrogen dioxide; Nitrogen Dioxide - analysis; Pollution; Pollution sources. Measurement results; Primary NO2; roads; Time Factors; Transports; Tunnel measurements; Vehicle Emissions - analysis; vehicles
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2012.08.050

NO and NO2 measurements have been made using the chemiluminescence method from 115weekdays during the period 4th Jan–10th Sep 2010 in a well characterised, unventilated tunnel on the Leeds Inner Ring Road. Measurements are made at two points in the tunnel and the difference in NO and NO2 was attributed to emissions from vehicles in the tunnel. These data have been used to determine the fraction of NOx (NO+NO2) as primary NO2 (f-NO2) from vehicles using the tunnel. The average value of f-NO2 from 7am to 7pm was 0.17 −0.03+0.01 in agreement with estimations from the UK National Atmospheric Emissions Inventory (NAEI). However, during the day there was a reproducible increase in f-NO2 from approximately 0.10 at 7am to 0.21 at 7pm which is not reproduced with the current UK vehicle fleet emissions inventories. The increase in f-NO2 can be qualitatively linked to a decrease in the fraction of NOx arising from heavy goods vehicles and buses. ► UK tunnel study determining fraction of NO2 in NOx emissions, f-NO2 using extensive dataset. ► Tunnel characterisation via static and mobile measurements; f-NO2 by two approaches. ► f-NO2 shows a significant diurnal profile linked to variations in fleet composition. ► Calculated variation in f-NO2 from traffic counts and emission inventories does not match observations. ► Early morning low values of f-NO2 are below calculations from emissions inventories.