During the last Olympic Games ‘82 in Barcelona (July 25th - August 9th), 1) the city council of Barcelona adopted special traffic restriction measures in some areas (several streets were closed and there were parking limitations) and 2) some traffic jams were expected between 1100and 1300LST, and between 1900 and 2100 LST in several highways going into the city. The aim of this contribution is to present the results of a numerical simulation to forecast the influence that these traffic conditions could have on the air quality over the city with respect to the normal situation existing before the Olympic Games.The simulations have been performed for a typical summer non-workable day (24 hours) within a 39x39x6-km3 region with a horizontal grid spacing of 1 km x 1 km.Concentration fields for NOx and O3 have been calculated for selected scenarios on the Olympic Games ‘92 in Barcelona by applying the Eulerian dispersion model for reactive species MARS.1 For the numerical modeling of photochemical oxidant formation the chemical transformation of pollutants should be considered together with their transport in the atmospheric boundary layer. 3D wind fields necessary to run the model were calculated by the non-hydrostatic mesoscale model MEMO2 and the emission inventory calculated was done by the model EMITEMA-EIM.3This work has been supported by the Servei de Control del Medi de l’Area Metropolitana de Barcelona, IBM España, S.A., and Comisión Interministerial de Ciencia y Tecnología (CICYT) grant no. NAT91-0987.The following discussion refers to differences in the pollutant concentration levels between the situation forecast during the Olympic Games ‘92 and the normal situation existing before the Olympics.Because of the traffic restrictions, surface concentration patterns obtained by simulation show lower ozone concentrations. From 900to 1400 LST, a spread area of lower ozone concentrations appears (minus 5–20 ppbv O3), which is originated in Barcelona Downtown Area (BDA) and driven towards the sea. Due to the sea breeze the afternoon ozone concentration patterns also show lower ozone concentrations (minus 5–10 ppbv O3) in the North-western part of the modelling domain and in the Llobregat valley. It can be said that the decrease of emissions due to traffic restrictions leads to decreased ozone concentrations in widely spread areas, whereas significant decrease of NO and NO2 concentrations (minus 5–20 ppbv), are located almost only near BDA, except in the morning hours (until 1000 LST), when differences of NO and NO2 concentrations are also observed above the sea. During the whole day lower NO2 concentration levels in BDA are promoted by decreased NO2 formation which is caused by less NO and O3 reactions.As to the influence of traffic jams, it can be said that at the beginning of the traffic jams higher ozone and lower NO concentrations can be seen only in a small area surrounding the concerned highway sections. Noon concentration patterns show lower NO concentrations (minus 5–20 ppbv) in the surroundings of concerned highway sections and higher ozone concentrations (plus 3–10 ppbv) in more widely spread regions. At 1300and 1400 LST the sea breeze is stronger and thus transports air with higher ozone concentrations (plus 3-10 ppbv) along the Llobregat valley. Ozone concentrations in Barcelona and above the sea are slightly higher in the 1300 LST concentration pattern. These ozone concentration levels are almost fully dilluted by fresh air in the afternoon. The influence of the evening traffic jams can be seen in the concentration patterns between 1900 and 2100 LST. Again higher ozone concentrations (plus 3-20 ppbv) are observed near the concerned highway sections, but also in the valley of Llobregat and above the sea.As conclusion, the influences of both lower emissions due to traffic restrictions in BDA and higher VOC emissions caused by traffic jams on some highway sections, are almost spatially separated, except for a small region in BDA where decrease of ozone due to traffic restrictions is almost counterbalanced by an increase of ozone formation due to traffic jams. In the evening lower ozone concentrations in the Llobregat valley because of traffic restrictions are overcompensated by higher ozone concentrations due to the traffic jams.These preliminary results are now being validated.
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- Influence of the Traffic Conditions on the Air Quality of Barcelona During the Olympic Games ‘82
J. M. Baldasano
- Springer US