Seminar

Abstract

Volatile Organic Compounds (VOC) affect urban air quality and regional climate change by contributing to ozone formation and the build-up of Secondary Organic Aerosols (SOA). Quantification of VOC emissions is a first critical step to design effective abatement strategies and to predict VOC environmental impacts. Indeed, the quality of ozone and SOA forecasts strongly depends on the accurate knowledge of the primary VOC emissions. However, commonly used bottom-up approaches are highly uncertain due to source multiplicity (combustion processes, storage and distribution of fossil fuels, solvent use, etc.) because of numerous controlling factors (driving conditions, fuel type, temperature, radiation, etc.) and their great variability in time and space. Field observations of VOC and other air quality tracers can provide valuable constraints to assess and evaluate VOC emission inventories at urban scale. In addition, the implementation of emission reduction measures raises the question of the gaining importance of VOC sources other than traffic. Here, I will present an overview of urban VOC emissions in mid-latitude urban areas inferred from field observations of VOCs over the last decade. These observations include long-term monitoring from French Air Quality Networks and recent intensive campaigns in two megacities of the Northern Hemisphere: Paris (Europe) and Los Angeles (USA) in the framework of the MEGAPOLI (EU FP7) and CalNex 2010 projects, respectively. These data as a whole have provided a unique opportunity to assess and discuss the seasonality of VOC emissions, their spatial variability regarding regional characteristics and control policies (ie. European vs. Californian) and to evaluate the accuracy of up-to-date emission inventories.