Articles | Volume 16, issue 10
Atmos. Chem. Phys., 16, 6453–6473, 2016
Atmos. Chem. Phys., 16, 6453–6473, 2016

Research article 27 May 2016

Research article | 27 May 2016

Simulating secondary organic aerosol from missing diesel-related intermediate-volatility organic compound emissions during the Clean Air for London (ClearfLo) campaign

Riinu Ots1,2, Dominique E. Young3,a, Massimo Vieno2, Lu Xu4, Rachel E. Dunmore5, James D. Allan3,6, Hugh Coe3, Leah R. Williams7, Scott C. Herndon7, Nga L. Ng4,8, Jacqueline F. Hamilton5, Robert Bergström9,10, Chiara Di Marco2, Eiko Nemitz2, Ian A. Mackenzie11, Jeroen J. P. Kuenen12, David C. Green13, Stefan Reis2,14, and Mathew R. Heal1 Riinu Ots et al.
  • 1School of Chemistry, University of Edinburgh, Edinburgh, UK
  • 2Natural Environment Research Council, Centre for Ecology & Hydrology, Penicuik, UK
  • 3School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK
  • 4School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA
  • 5Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, York, UK
  • 6National Centre for Atmospheric Science, University of Manchester, Manchester, UK
  • 7Aerodyne Research, Inc., Billerica, MA, USA
  • 8School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
  • 9Swedish Meteorological and Hydrological Institute, Norrköping, Sweden
  • 10Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
  • 11School of GeoSciences, University of Edinburgh, Edinburgh, UK
  • 12TNO, Department of Climate, Air and Sustainability, Utrecht, the Netherlands
  • 13MRC PHE Centre for Environment and Health, King's College London, London, UK
  • 14University of Exeter Medical School, Knowledge Spa, Truro, UK
  • anow at: Department of Environmental Toxicology, University of California, Davis, CA, USA

Abstract. We present high-resolution (5 km  ×  5 km) atmospheric chemical transport model (ACTM) simulations of the impact of newly estimated traffic-related emissions on secondary organic aerosol (SOA) formation over the UK for 2012. Our simulations include additional diesel-related intermediate-volatility organic compound (IVOC) emissions derived directly from comprehensive field measurements at an urban background site in London during the 2012 Clean Air for London (ClearfLo) campaign. Our IVOC emissions are added proportionally to VOC emissions, as opposed to proportionally to primary organic aerosol (POA) as has been done by previous ACTM studies seeking to simulate the effects of these missing emissions. Modelled concentrations are evaluated against hourly and daily measurements of organic aerosol (OA) components derived from aerosol mass spectrometer (AMS) measurements also made during the ClearfLo campaign at three sites in the London area. According to the model simulations, diesel-related IVOCs can explain on average  ∼  30 % of the annual SOA in and around London. Furthermore, the 90th percentile of modelled daily SOA concentrations for the whole year is 3.8 µg m−3, constituting a notable addition to total particulate matter. More measurements of these precursors (currently not included in official emissions inventories) is recommended. During the period of concurrent measurements, SOA concentrations at the Detling rural background location east of London were greater than at the central London location. The model shows that this was caused by an intense pollution plume with a strong gradient of imported SOA passing over the rural location. This demonstrates the value of modelling for supporting the interpretation of measurements taken at different sites or for short durations.

Short summary
This study investigates the contribution of diesel vehicle emissions to organic aerosol formation and particulate matter concentrations in London. Comparisons of simulated pollutant concentrations with observations show good agreement and give confidence in the skill of the model applied. The contribution of diesel vehicle emissions, which are currently not included in official emissions inventories, is demonstrated to be substantial, indicating that more research on this topic is required.
Final-revised paper