Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 15, 11011-11026, 2015
https://doi.org/10.5194/acp-15-11011-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
05 Oct 2015
Black carbon, particle number concentration and nitrogen oxide emission factors of random in-use vehicles measured with the on-road chasing method
I. Ježek1, T. Katrašnik2, D. Westerdahl3, and G. Močnik1,4 1Aerosol d.o.o., Ljubljana, Slovenia
2University of Ljubljana, Faculty of Mechanical engineering, Ljubljana, Slovenia
3Cornell University, Sibley School of Mechanical and Aerospace Engineering, Ithaca, New York 14853, USA
4Jožef Stefan Institute, Condensed Matter Physics Department, Ljubljana, Slovenia
Abstract. The chasing method was used in an on-road measurement campaign, and emission factors (EF) of black carbon (BC), particle number (PN) and nitrogen oxides (NOx) were determined for 139 individual vehicles of different types encountered on the roads. The aggregated results provide EFs for BC, NOx and PN for three vehicle categories: goods vehicles, gasoline and diesel passenger cars. This is the first on-road measurement study where BC EFs of numerous individual diesel cars were determined in real-world driving conditions. We found good agreement between EFs of goods vehicles determined in this campaign and the results of previous studies that used either chasing or remote-sensing measurement techniques. The composition of the sampled car fleet determined from the national vehicle registry information is reflective of Eurostat statistical data on the Slovenian and European vehicle fleet. The median BC EF of diesel and gasoline cars that were in use for less than 5 years decreased by 60 and 47 % from those in use for 5–10 years, respectively; the median NOx and PN EFs of goods vehicles that were in use for less than 5 years decreased from those in use for 5–10 years by 52 and 67 %, respectively. Surprisingly, we found an increase of BC EFs in the newer goods vehicle fleet compared to the 5–10-year old one. The influence of engine maximum power of the measured EFs showed an increase in NOx EF from least to more powerful vehicles with diesel engines. Finally, a disproportionate contribution of high emitters to the total emissions of the measured fleet was found; the top 25 % of emitting diesel cars contributed 63, 47 and 61 % of BC, NOx and PN emissions respectively. With the combination of relatively simple on-road measurements and sophisticated post processing, individual vehicle EF can be determined and useful information about the fleet emissions can be obtained by exactly representing vehicles which contribute disproportionally to vehicle fleet emissions; and monitor how the numerous emission reduction approaches are reflected in on-road driving conditions.

Citation: Ježek, I., Katrašnik, T., Westerdahl, D., and Močnik, G.: Black carbon, particle number concentration and nitrogen oxide emission factors of random in-use vehicles measured with the on-road chasing method, Atmos. Chem. Phys., 15, 11011-11026, https://doi.org/10.5194/acp-15-11011-2015, 2015.
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Short summary
On-road measurement of black carbon (BC), NOx and particle number (PN) emission factors (EF) by chasing vehicles is the first such study where BC EFs of many individual diesel cars were determined in real-world conditions. Median BC EF of diesel and gasoline cars in use for <5 years, decreased by 60% and 47% from those in use for 5–10 years. Reductions for goods vehicles' NOx and PN EFs were 52% and 67%. We found an increase of BC EFs in newer goods vehicle fleet compared to 5 – 10 year old one.
On-road measurement of black carbon (BC), NOx and particle number (PN) emission factors (EF) by...
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