Abstract. Changes in engine technologies and after-treatment devices can profoundly alter the chemical composition of the emitted pollutants. To investigate these effects, we characterized the emitted particles' chemical composition of three diesel and four gasoline Euro 5 light-duty vehicles tested at a chassis dynamometer facility. The dominant emitted species was black carbon (BC) with emission factors (EFs) varying from 0.2 to 7.1 mg km−1 for direct-injection gasoline (GDI) vehicles, from 0.02 to 0.14 mg km−1 for port fuel injection (PFI) vehicles, and 0.003 to 0.9 mg km−1 for diesel vehicles. The organic matter (OM) EFs varied from 5 to 103 µg km−1 for GDI gasoline vehicles, from 1 to 8 µg km−1 for PFI vehicles, and between 0.15 and 65 µg km−1 for the diesel vehicles. The first minutes of cold-start cycles contributed the largest PM fraction including BC, OM, and polycyclic aromatic hydrocarbons (PAHs). Using a high-resolution time-of-flight mass spectrometer (HR-ToF-AMS), we identified more than 40 PAHs in both diesel and gasoline exhaust particles including methylated, nitro, oxygenated, and amino PAHs. Particle-bound PAHs were 4 times higher for GDI than for PFI vehicles. For two of the three diesel vehicles the PAH emissions were below the detection limit, but for one, which presented an after-treatment device failure, the average PAHs EF was 2.04 µg km−1, similar to the GDI vehicle's values. During the passive regeneration of the catalysed diesel particulate filter (CDPF) vehicle, we measured particles of diameter around 15 nm mainly composed of ammonium bisulfate. Transmission electron microscopy (TEM) images revealed the presence of ubiquitous metal inclusions in soot particles emitted by the diesel vehicle equipped with a fuel-borne-catalyst diesel particulate filter (FBC-DPF). X-ray photoelectron spectroscopy (XPS) analysis of the particles emitted by the PFI vehicle showed the presence of metallic elements and a disordered soot surface with defects that could have consequences on both chemical reactivity and particle toxicity. Our findings show that different after-treatment technologies have an important effect on the emitted particles' levels and their chemical composition. In addition, this work highlights the importance of particle filter devices' condition and performance.

Abstract. Changes in engine technologies and after-treatment devices can profoundly alter the chemical composition of the emitted pollutants. To investigate these effects, we characterized the chemical composition of particles emitted from three diesel and four gasoline Euro 5 light duty vehicles on a chassis dynamometer facility. Black carbon (BC) was the dominant emitted species with emission factors (EFs) varying from 0.2 to 7.1 mg km−1 for gasoline cars and 0.003 to 0.08 mg km−1 for diesel cars. For gasoline cars, the organic matter (OM) EFs varied from 5 to 103 µg km−1 for direct injection (GDI) vehicles, and from 1 to 8 µg km−1 for port fuel injection (PFI) vehicles, while for the diesel cars it ranged between 0.15 and 65 µg km−1. Cold-start cycles and more specifically the first minutes of the cycle, contributed the largest fraction of the PM including BC, OM and Polycyclic Aromatic Hydrocarbons (PAHs). More than 40 PAHs, including methylated, nitro, oxygenated and amino PAHs were identified and quantified in both diesel and gasoline exhaust particles using an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS). The PAHs emissions from the GDI technology were a factor of 4 higher compared to the vehicles equipped with a PFI system during the cold start cycle, while the nitro-PAHs fraction was much more appreciable in the GDI emissions. For two of the three diesel vehicles the PAHs emissions were close to the detection limit, but for one, which presented an after-treatment device failure, the average PAHs EF was 2.04 µg km−1. Emissions of nanoparticles (below 30 nm), mainly composed by ammonium bisulfate, were measured during the passive regeneration of the catalyzed diesel particulate filter (CDPF) vehicle. TEM images confirmed the presence of ubiquitous nanometric metal inclusions into soot particles emitted from the diesel vehicle equipped with a fuel borne catalyst – diesel particulate filter (FBC-DPF). XPS analysis of the particles emitted by the PFI car revealed both the presence of heavy elements (Ti, Zn, Ca, Si, P, Cl), and disordered soot surface with a significant concentration of carbon radical defects having possible consequences on both chemical reactivity and particle toxicity. Our findings show that different after-treatment technologies have an important effect on the level and the chemical composition of the emitted particles. In addition, this research highlights the importance of the particle filter devices condition and their regular checking.

Abstract. Aromatic hydrocarbons represent a large fraction of anthropogenic volatile organic compounds and significantly contribute to tropospheric ozone and secondary organic aerosol (SOA) formation. Toluene photooxidation experiments were carried out in an oxidation flow reactor (OFR). We identified and quantified the gaseous and particulate reaction products at 280, 285 and 295 K using a proton-transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) coupled to a CHemical Analysis of aeRosol ONline (CHARON) inlet. The reaction products accounted for both ring-retaining compounds such as cresols, benzaldehyde, nitrophenols, nitrotoluene, bicyclic intermediate compounds, as well as ring-scission products such as dicarbonyls, cyclic anhydrides, small aldehydes and acids. The chemical system exhibited a volatility distribution mostly in the semi-volatile (SVOCs – semi-volatile organic compounds) regime. The saturation concentration (Ci*) values of the identified compounds were mapped onto the two-dimensional volatility basis set (2D-VBS). Temperature decrease caused a shift of Ci* towards lower values while there was no clear relationship between Ci* and oxidation state. The CHARON PTR-ToF-MS instrument identified and quantified approximately 70–80 % of the total organic mass measured by an aerosol mass spectrometer (AMS). The experiments were reproduced by simulating SOA formation with the SSH-aerosol box model. A semi-detailed mechanism for toluene gaseous oxidation was developed. It is based on the MCM and GECKO-A deterministic mechanisms modified following the literature in particular to update cresols and ring-scission chemistry. The new mechanism improved secondary species representation with an increment of the major identified species (+35 % in number). Light compounds formation (i.e. m/z < 100) is enhanced and accumulation of heavy compounds (i.e. m/z ≥ 100) is reduced, especially in the gas phase. Additional tests on (i) partitioning processes such as condensation into aqueous phase, (ii) interactions of organic compounds between themselves and with inorganics and (iii) wall losses were also performed. When all these processes were taken into account the simulated SOA mass concentration showed a much better agreement with the experimental results. Finally, an irreversible partitioning pathway for methylglyoxal was introduced and considerably improved the model results, opening a way to further developments of partitioning in models. Our results underline that the volatility itself is not sufficient to explain the partitioning between gas and particle phase: the organic and the aqueous phases need to be taken into account as well as interactions between compounds in the particle phase.

Part 1: Instrumentation and experiments Part 2: Modeling and chemical mechanisms 141.054 (C7H8O3)H + 1.88±0.14 1.33±0.10 0.55 155.034 (C7H6O4)H+ 1.62±0.14 0.90±0.11 0.70 157.050 (C7H8O4)H 1.37±0.50 1.08±0.17 0.29 171.029(C7H6O5)H+ 1.45±0.60 0.70±0.10 0.75 127.041 (C6H6O3)H + 1.46±0.25 0.83±0.05 0.63 143.034 (C6H6O4) H + 1.26±0.03 0.93±0.02 0.33 125.029 (C6H4O2) H + 1.40±0.30 1.10±0.30 0.30 129.057 (C6H8O3)H + 1.62±0.13 1.07±0.02 0.55 111.045 (C6H6O2)H + 2.10±0.03 1.56±0.05 0.55 140.039 (C6H5NO3)H+ 3.10±0.24 2.70±0.15 0.40 113.057(C6H8O2)H + 2.71±0.35 1.64±0.25 1.07 141.019 (C6H4O4)H + 1.75±0.13 1.38±0.03 0.37 95.050 (C6H6O)H+ 2.60±0.20 2.08±0.05 0.52 109.030 (C6H4O2)H + 3.04±0.16 2.72±0.10 0.32 115.042 (C5H6O3)H + 1.81±0.34 1.43±0.02 0.39 101.060 (C5H8O2)H + 4.75±0.94 4.25±0.34 0.50 113.025 (C5H4O3)H + 2.69±0.36 2.41±0.14 0.28 99.046 (C5H6O2)H + 2.62±0.13 2.19±0.05 0.43 117.021 (C4H4O4)H + 2.50±0.60 1.89±0.05 0.65 103.042 (C4H6O3)H + 1.69±0.02 1.21±0.04 0.47 85.031 (C4H4O2)H + 2.66±0.12 2.29±0.05 0.38 87.046 (C4H6O2)H + 2.59±0.11 2.03±0.03 0.56 101.026 (C4H4O3)H + 2.35±0.24 1.87±0.04 0.48 83.014 (C4H2O2)H + 2.30±0.61 1.78±0.22 0.52 89.026 (C3H4O3)H + 2.24±0.11 1.83±0.02 0.42 71. 015(C3H2O2)H + 1.99±0.27 1.83±0.02 0.16 75.043 (C3H6O2)H + 4.40±0.52 2.55±0.19 0.85 73.030 (C3H4O2)H + 2.85±0.02 2.55±0.08 0.30 77.025 (C2H4O3)H+ 3.88±0.18 3.52±0.06 0.36 61.028 (C2H4O2)H + 3.76±0.49 3.04±0.06 0.72 47.013 (CH2O2)H + 3.63±0.32 3.32±0.09 0.31