Abstract
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.
Highlights
Traffic is a diverse and important source of air pollution and is complex to describe in terms of per vehicle emissions
We report the first onroad determination of black carbon (BC), nitrogen oxides (NOx) and particle number (PN) emission factor (EF) of passenger cars measured with the chasing method and the first BC EFs of individual diesel cars measured in real driving conditions
Eurostat does not report the number of heavy goods vehicles as N1, N2 and N3, rather it reports the number of lorries by their load capacity
Summary
Traffic is a diverse and important source of air pollution and is complex to describe in terms of per vehicle emissions. Most of the previous on-road BC emission factor measurements for individual vehicles were performed on diesel-fueled trucks and on cars with the spark ignition engine, referred to as gasoline cars (Ban-Weiss et al, 2009; Dallmann et al, 2011, 2012, 2014; Hansen and Rosen, 1990; Wang et al, 2011, 2012) Many of these studies revealed that a small percentage of vehicles – the so-called super emitters contribute disproportionately to total vehicle emissions. An extensive on-road measurement study was performed in the UK by Carslaw and Rhys-Tyler (2013) They employed a remote-sensing technique to measure the emissions of NO, NO2 and NH3 on a fleet of almost 70 000 individual vehicles which included vans, passenger cars with a compression ignition engine ( referred to as diesel cars), and gasoline cars. We report the first onroad determination of BC, NOx and PN EFs of passenger cars measured with the chasing method and the first BC EFs of individual diesel cars measured in real driving conditions
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