Tailpipe emissions of a pool of 13 Euro 6b light-duty vehicles (eight diesel and five gasoline-powered) were measured over an extensive experimental campaign that included laboratory (chassis dynamometer), and on-road tests (using a portable emissions measurement system). The New European Driving Cycle (NEDC) and the Worldwide harmonised Light-duty vehicles Test Cycle (WLTC) were driven in the laboratory following standard and extended testing procedures (such as low temperatures, use of auxiliaries, modified speed trace). On-road tests were conducted in real traffic conditions, within and outside the boundary conditions of the regulated European Real-Driving Emissions (RDE) test. Nitrogen oxides (NO_X), particle number (PN), carbon monoxide (CO), total hydrocarbons (HC), and carbon dioxide (CO₂) emission factors were developed considering the whole cycles, their sub-cycles, and the first 300 s of each test to assess the cold start effect. Despite complying with the NEDC type approval NO_X limit, diesel vehicles emitted, on average, over the WLTC and the RDE 2.1 and 6.7 times more than the standard limit, respectively. Diesel vehicles equipped with only a Lean NO_X trap (LNT) averaged six and two times more emissions over the WLTC and the RDE, respectively, than diesel vehicles equipped with a selective catalytic reduction (SCR) catalyst. Gasoline vehicles with direct injection (GDI) emitted eight times more NO_X than those with port fuel injection (PFI) on RDE tests. Large NO_X emissions on the urban section were also recorded for GDIs (122 mg/km). Diesel particle filters were mounted on all diesel vehicles, resulting in low particle number emission (~10¹⁰ #/km) over all testing conditions including low temperature and high dynamicity. GDIs (~10¹² #/km) and PFIs (~10¹¹ #/km) had PN emissions that were, on average, two and one order of magnitude higher than for diesel vehicles, respectively, with significant contribution from the cold start. PFIs yielded high CO emission factors under high load operation reaching on average 2.2 g/km and 3.8 g/km on WLTC extra-high and RDE motorway, respectively. The average on-road CO₂ emissions were ~33% and 41% higher than the declared CO₂ emissions at type-approval for diesel and gasoline vehicles, respectively. The use of auxiliaries (AC and lights on) over the NEDC led to an increase of ~20% of CO₂ emissions for both diesel and gasoline vehicles. Results for NO_X, CO and CO₂ were used to derive average on-road emission factors that are in good agreement with the emission factors proposed by the EMEP/EEA guidebook.

Pollution at gas stations due to small spills that occur during vehicle refueling have received little attention. We have performed laboratory experiments to assess evaporation and infiltration of fuel spilled onto concrete. Changes in the concrete mass after small amounts of diesel and gasoline were spilled have been analyzed. Variation in humidity, among other parameters, clearly affects the measured mass since condensed water is constantly added to or released from the concrete. This mass experiences an about exponential decay in time. The difference in behavior between both fuel types is important as the percentage of evaporated mass is much larger for gasoline, while infiltration is more significant for diesel. A statistical analysis suggests that the initial spill amount does not significantly affect the fraction of infiltrated fuel over time. This finding is in agreement with pore-scale simulations that we performed. A significant amount of fuel could be seeping into soil and groundwater underneath concrete pavement at gas stations or could be released to the atmosphere. Possible solutions for pavement and groundwater pollution are considered.