Modeling of photochemical air pollution in the Barcelona area with highly disaggregated anthropogenic and biogenic emissions

The city of Barcelona and its surrounding area, located in the western Mediterranean basin, can reach high levels of O3 in spring and summertime. To study the origin of this photochemical pollution, a numerical modeling approach was adopted and the episode that took place between 3 and 5 August 1990 was chosen. The main meteorological mesoscale flows were reproduced with the meteorological non-hydrostatic mesoscale model MEMO for 5 August 1990, when weak pressure synoptic conditions took place. The emissions inventory was calculated with the EIM-LEM model, giving highly disaggregated anthropogenic and biogenic emissions in the zone studied, an 80×80 km2 area around the city of Barcelona. Major sources of VOC were road traffic (51%) and vegetation (34%), while NOx were mostly emitted by road traffic (88%). However, emissions from some industrial stacks can be locally important and higher than those from road traffic. Photochemical simulation with the MARS model revealed that the combination of mesoscale wind flows and the above-mentioned local emissions is crucial in the production and transport of O3 in the area. On the other hand, the geostrophic wind also played an important role in advecting the air masses away from the places O3 had been generated. The model simulations were also evaluated by comparing meteorological measurements from nine surface stations and concentration measurements from five surface stations, and the results proved to be fairly satisfactory.