Characterization of laboratory and real driving emissions of individual Euro 6 light-duty vehicles - Fresh particles and secondary aerosol formation.

Emissions from passenger cars are one of major sources that deteriorate urban air quality. This study presents characterization of real-drive emissions from three Euro 6 emission level passenger cars (two gasoline and one diesel) in terms of fresh particles and secondary aerosol formation. The gasoline vehicles were also characterized by chassis dynamometer studies. In the real-drive study, the particle number emissions during regular driving were 1.1-12.7 times greater than observed in the laboratory tests (4.8 times greater on average), which may be caused by more effective nucleation process when diluted by real polluted and humid ambient air. However, the emission factors measured in laboratory were still much higher than the regulatory value of 6 × 1011 particles km-1. The higher emission factors measured here result probably from the fact that the regulatory limit considers only non-volatile particles larger than 23 nm, whereas here, all particles (also volatile) larger than 3 nm were measured. Secondary aerosol formation potential was the highest after a vehicle cold start when most of the secondary mass was organics. After the cold start, the relative contributions of ammonium, sulfate and nitrate increased. Using a novel approach to study secondary aerosol formation under real-drive conditions with the chase method resulted mostly in emission factors below detection limit, which was not in disagreement with the laboratory findings.

A study on the CO2 and NOx emissions performance of Euro 6 diesel vehicles under various chassis dynamometer and on-road conditions including latest regulatory provisions.

The current study presents a detailed analysis of the gaseous emissions, focusing on CO2 and NOx, of diesel vehicles under several operating conditions. An assessment is also made on the impact and effectiveness of the Real Driving Emissions (RDE) test, which is mandatory by the European Union (EU) type approval regulation for passenger cars since September 2017. The method followed comprises emissions measurement tests on three Euro 6 diesel vehicles, under laboratory and various on-road operation conditions. Chassis dynamometer tests in the laboratory showed that emissions over the current type approval test (World-wide harmonized Light-duty Test Procedure or WLTP), and over the former one (New European Driving Cycle or NEDC), poorly reflect real-world levels. However, the most demanding CADC testing comes closer to real drive emissions. Comparison of driving conditions on the chassis dynamometer over different driving cycles and on the road reveals that the emission performance substantially varies between different tests, even for apparently similar operation conditions. The NOx emissions reduction strategy of pre-RDE monitoring Euro 6 vehicles seems to be optimized for the NEDC driving conditions, which are not representative of the real-world driving conditions. The real-world emissions during normal driving conditions are effectively captured with the new RDE test, however driving the vehicle dynamically, at conditions outside the RDE regulation boundaries, results to disproportional high emissions. This is a significant shortcoming which might be critical for populations living on hilly areas or those close to specific micro-environments, such as highway entrance ramps, traffic lights, etc.