Articles | Volume 15, issue 8
Atmos. Chem. Phys., 15, 4373–4387, 2015
Atmos. Chem. Phys., 15, 4373–4387, 2015

Research article 29 Apr 2015

Research article | 29 Apr 2015

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

H. L. DeWitt1, S. Hellebust1, B. Temime-Roussel1, S. Ravier1, L. Polo2,3, V. Jacob2, C. Buisson3, A. Charron3, M. André3, A. Pasquier3, J. L. Besombes4, J. L. Jaffrezo2, H. Wortham1, and N. Marchand1 H. L. DeWitt et al.
  • 1Aix Marseille Université, CNRS, LCE FRE 3416, 13331 Marseille, France
  • 2Université Grenoble Alpes, CNRS, LGGE, 38000 Grenoble, France
  • 3IFSTTAR, Case 24, 69675 Bron CEDEX, France
  • 4Université de Savoie, LCME, 73376 Le Bourget du Lac, France

Abstract. 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 factorization 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 NOx, 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.

Short summary
By performing source-apportionment modeling, the amount of primary and secondary organic emissions was resolved from a bulk aerosol data set measured adjacent to a major highway in France. Over 70% of vehicles on this highway were diesel, and a high concentration of BC and NOx were measured. Even close to a major highway, the bulk of the aerosol mass was secondary in nature. Radiocarbon data revealed that most of the fossil organic carbon was from primary vehicular emissions and not from SOA.
Final-revised paper