Measuring NOx Emissions of Road Vehicles and Detection of Manipulated Emission Systems with the ICAD Instrument

Ulrich Platta,b), Tim Adlera), Christopher Krufczika), Martin Horbanskia,b), Johannes Lampela,b), Jan-Lukas Tirpitza) and Denis Pöhlera,b)

aInstitute of Environmental Physics, University of Heidelberg, INF 229, Heidelberg, Germany

bAiryx GmbH, Justus-von-Liebig-Str. 14, 69214 Eppelheim, Germany

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Road vehicles, driven by internal combustion engines, in particular with Diesel engines, are the most relevant NOx (NO + NO2) sources in urban areas and cause large environmental problems. Therefore, vehicle NOx emissions are regulated in the EU with the EURO Norm Standard (e.g. EURO VI since 1.1.2013 for trucks with 400mg/kWh). All EURO VI and most EURO V trucks use the selective catalytic reduction (SCR) after treatment system, which consumes AdBlue to reduce the NOx emissions below the limits. Nowadays also most EURO VI diesel passenger cars use SCR systems.

Here we describe a novel system for real driving emission (RDE) measurements using the newly developed mobile NOx-ICAD (Iterative Cavity Enhanced DOAS) + CO2 –instrument. It measures the NOx and CO2 concentrations and the ratios of the gases in the emission plume of the target vehicle for several minutes at high temporal resolution (plume chasing measurement principle). The data are converted to NOx emission factors to be compared to the EURO standard.

As examples we show (1) RDE of more than 250 randomly chosen trucks on German highways showing that about 20-25% of the EURO V and VI foreign trucks (mainly from Eastern Europe) feature very high emissions of up to 10.000 mg/kWh, much higher than any EURO norm. These trucks feature a defect emission treatment system most likely caused by an illegal AdBlue emulator.

Also we present (2) studies of emissions from about 100 buses in three German cities, which show a large range of emissions. Especially older buses exhibit high emissions. EURO VI buses have in most cases very low emissions, but there are also some strong outliers.

Finally (3) we present data on personal NO2 exposure of cyclists and car passengers from several German cities showing considerable exceedance of the air pollution limits.