Comparison of high mileage LPG cars in different technical condition in Czechia: Particle-bound PAHs

Liquefied petroleum gas (LPG) is represented in the literature as a transport fuel with lower regulated and non-regulated emissions compared to petrol. For the purpose of this paper, real-world emissions measurements were performed on a random sample of four commonly operated passenger vehicles with higher mileage (over 200 thousand km) and on a new one. The aim is to compare the emission factors of particle-bound polycyclic aromatic hydrocarbons (PAHs) in dual-fuelled passenger cars running on LPG and petrol, or rather to compare the emission factors of the two fuel types. PAH concentrations are determined by gas chromatography based on the analysis of particles captured on a filter during isokinetic sampling of the exhaust gas during driving in real traffic. In terms of the sum of the 8 most hazardous PAHs analysed, LPG fuelling reduced the total (summary) emission factor of only two of the vehicles analysed, by 22% and 26% respectively compared to petrol. For the remaining vehicles, there was an increase in the total emission factor ranging from 4.4 to 68.8%. The results show that in terms of particle-bound PAHs, the benefit of LPG fuel in terms of vehicle emissions may not be so clear-cut in real-world tests and it depends very much on whether a suitable propulsion system is fitted to the vehicle, how it is set up and how the vehicle is serviced (i.e. the vehicle overall condition).