Near-highway aerosol and gas-phase measurements in a high-diesel environment

Hl. Dewitt (1, 2) , S Hellebust (1, 2) , B Temime-Roussel (1, 2) , S Ravier (1, 2) , L Polo (3, 4) , V Jacob (5, 6) , C Buisson (4) , A Charron (4) , M André (4) , A Pasquier (4) , Jean-Luc Besombes (7) , Jean-Luc Jaffrezo (3, 5) , Henri Wortham (1) , Nicolas Marchand (1)

1 LCE - Laboratoire Chimie de l'environnement
2 AMU - Aix Marseille Université
3 UGA [2016-2019] - Université Grenoble Alpes [2016-2019]
4 IFSTTAR - Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux
5 LGGE - Laboratoire de glaciologie et géophysique de l'environnement
6 UNIC - Unité de neurosciences intégratives et computationnelles
7 LCME - Laboratoire de Chimie Moléculaire et Environnement

Diesel-powered passenger cars currently outnumber gasoline-powered cars in many countries, particularly in Europe. In France, diesel cars represented 61 % of light duty vehicles in 2011 and this percentage is still increasing (French Environment and Energy Management Agency, ADEME). As part of the September 2011 joint PM-DRIVE (Particulate Matter – DiRect and Indirect on-road Vehicular Emissions) and MOCOPO (Measuring and mOdeling traffic COngestion and POllution) field campaign, the concentration and high-resolution chemical composition of aerosols and volatile organic carbon species were measured adjacent to a major urban highway south of Grenoble, France. Alongside these atmospheric measurements, detailed traffic data were collected from nearby traffic cameras and loop detectors , which allowed the vehicle type, traffic concentration , and traffic speed to be quantified. Six aerosol age and source profiles were resolved using the positive matrix fac-torization model on real-time high-resolution aerosol mass spectra. These six aerosol source/age categories included a hydrocarbon-like organic aerosol (HOA) commonly associated with primary vehicular emissions, a nitrogen-containing aerosol with a diurnal pattern similar to that of HOA, oxidized organic aerosol (OOA), and biomass burning aerosol. While quantitatively separating the influence of diesel from that of gasoline proved impossible, a low HOA : black carbon ratio, similar to that measured in other high-diesel environments , and high levels of NO x , also indicative of diesel emissions, were observed. Although the measurement site was located next to a large source of primary emissions, which are typically found to have low oxygen incorporation , OOA was found to comprise the majority of the measured organic aerosol, and isotopic analysis showed that the measured OOA contained mainly modern carbon, not fossil-derived carbon. Thus, even in this heavily vehicular-emission-impacted environment, photochemical processes, biogenic emissions, and aerosol oxidation dominated the overall organic aerosol mass measured during most of the campaign.

Domaines: Sciences de l'environnement

Hl. Dewitt, S Hellebust, B Temime-Roussel, S Ravier, L Polo, et al.. Near-highway aerosol and gas-phase measurements in a high-diesel environment. Atmospheric Chemistry and Physics Discussions, 2015, 15, pp.4373-4387. ⟨10.5194/acp-15-4373-2015⟩. ⟨insu-01164691⟩