Polyaromatic hydrocarbons (PAHs) are complex carbonaceous compounds emitted to the atmosphere by various combustion processes. Because the toxicity of many of them is now well recognized and documented, the determination of their atmospheric concentrations is of great interest to better understand and develop future atmospheric pollution control strategies. Hence, a common sampling protocol has to be defined to homogenize the results. With this goal in mind, field studies were carried out under different environmental conditions (74 samples) by simultaneously operating both a conventional sampler and a sampler equipped with a denuder tube upstream from the filter. The experimental results presented in this work show that the atmospheric particulate PAH concentrations are underestimated at least by a factor of 2 using a conventional sampler. The discrepancy between the two kinds of samplers used varied a lot from one compound to another and from one field campaign to another. This discrepancy may be explained by a simple degradation of particulate PAH in the natural atmosphere and on the filter. This is particularly worrisome because, based on the results presented in this work, the atmospheric PAH concentrations measured using conventional samplers not equipped with an ozone trap can underestimate the PAH concentration by more than 200%. This is especially true when the samples are collected in the vicinity of the point source of particulate PAHs and for highly reactive compounds such as benzo[a]pyrene.
Ultrafine particle, black carbon and NOx emissions from Diesel and gasoline passenger cars have been investigated in this work, as well as influences of aftertreatment device and driving conditions (the cold start, urban, rural and motorway conditions…) on emissions. Experiments have been carried out on chassis dynamometer bench with Artemis urban, road and motorway driving cycles and NEDC (New European Driving Cycle). Exhaust from Euro 5 Diesel vehicles equipped with additive and catalysed particle filter and Euro 5 gasoline vehicle with direct injection system has been taken directly from the tailpipe and diluted by Constant Volume Sampler (CVS). Tested gasoline DI vehicle emits 25% more CO2 than Diesel vehicles for all Artemis and NEDC driving conditions. It emits 2 to 200 times more PN and BC and 5 to 150 times less NOx than Diesel vehicles. Additive DPF vehicles emit 2 times more NO2 for urban conditions (175 mg/km), comparing to Diesel catalysed DPF (80 mg/km). No significant differences have been observed between additive and catalysed DPF for CO2 and NOx emissions. The cold start induces 10 to 20% more CO2 emissions for all tested vehicles. It induces 3 to 20 times higher PN emission with a great uncertainty. For NOx and NO2, the cold start induces about 40 to 60% less emissions for additive DPF Diesel vehicles. No significant impact has been observed for gasoline and catalysed DPF Diesel vehicles. DPF regeneration was observed for Artemis motorway driving cycles, with an increase of 100 -200 times more PN emission than standard filter operation mode.
Abstract. There is currently a need of reliable experimental procedure to follow the heterogeneous processing simulating the atmospheric conditions. This work offers a new experimental approach to study the reactivity and the behaviour of SVOC associated with atmospheric particles. The heterogeneous ozonolysis of naphthalene adsorbed on silica and XAD-4 particles is investigated in specially designed flow tube reactors. The experimental procedure consists in adsorbing gaseous naphthalene on particles before exposing it to ozone. By this novel approach the kinetics is determined following the consumption of naphthalene. Using this procedure, the rate constant kO3 of naphthalene is equal to (2.26±0.09)×10−17cm3.molec−1.s−1 and (4.31±1.07)×10−19cm3.molec−1.s−1 at 25°C for silica and XAD-4, respectively. The results show both that nature of the particles significantly affects the kinetics and that heterogeneous ozonolysis of naphthalene is faster than in the gaseous phase.
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