Contribution of Explicit SVOC and IVOC Emissions from the Transportation Sector on Particulate Matter Concentrations in Europe

Road transportation is a significant contributor to air pollution across Europe, especially in urban areas, and the resulting impacts on public health are highly uncertain. Pollutants are emitted in both the gas and particle phases from several operational modes including combustion exhaust, non-combustion evaporation, and mechanical brake and tire wear. Conventional air emission inventories used to inform policy in Europe have included inert fine and coarse particle emissions as well as emissions of light hydrocarbons, or volatile organic compounds. But recent laboratory studies have demonstrated that particle emissions are far more dynamic than originally thought, and that key reactive gas-phase compounds have probably been missing from existing inventories. 

As part of the Effects on Air quality of Semi-VOLatile Engine Emissions (EASVOLEE) project, state-of-the-science laboratory measurements have been used to develop a new inventory for present-day European air emissions that explicitly considers semivolatile and intermediate volatility organic compounds (SVOCs and IVOCs) from road transportation. This inventory is used to drive simulations with the European Monitoring and Evaluation Programme (EMEP) MSC-W regional-scale chemical transport model. With this new model platform, we assess the comprehensive primary and secondary contributions of road transport emissions to European particulate matter (PM). We show results from a broad series of chemical sensitivity tests along with measurements of organic aerosol across Europe to build confidence in the model’s predictions and characterize the role of uncertainty in processes like oxidation of IVOCs and multigenerational oxidative aging of second-generation products. We also compare the burden of road transport PM to that from other key sources like residential wood-burning and wildfires to better understand the role of road transport in future policy scenarios.