Developing receptor-oriented methods for non-methane hydrocarbon characterisation in urban air. Part II: source apportionment

The methods and the results of non-methane hydrocarbon (NMHC) source apportionment are described at urban scale on a spatial and temporal basis. Here, hourly ambient concentrations of nearly 40 C2–C9 NMHC are used. Methods are based on the knowledge of the wintertime NMHC vehicle-exhaust emission ratio generally determined by simple regression analysis taking acetylene, ethylene, propene and 1,3-butadiene as auto-exhaust tracers. The RSD of the estimated source contributions is lower than 20%; the developed receptor-oriented methods are flexible and easily transposable to other areas. In winter, vehicle-exhaust emissions explain 100% of the NMHC majority levels and even isoprene. From May to November, our models revealed the temperature-dependent contribution of additional sources (0.71