Modelled and observed ozone urban background concentrations in the metropolitan area of Buenos Aires, Argentina

PINEDA ROJAS, A.L.; VENEGAS, L.E.

Amsterdam

Conferencia; Urban Environmental Pollution. Creating Healthy, Liveable Cities; 2012

Elsevier

Ozone (O3) is an urban atmospheric pollutant of increasing concern given that its ground-level concentrations have remained relatively stable in many cities of the world despite the great efforts made to reduce anthropogenic emissions of its precursor species (NOx and VOC). The Metropolitan Area of Buenos Aires (MABA) is the third megacity of Latin America and the tenth worldwide. There are few studies on O3 concentrations at some places in this region. In order to evaluate the O3 concentration distribution in the MABA, we have recently coupled the atmospheric dispersion model DAUMOD (which has been extensively used to study the air quality in the MABA) with the GRS model (a widely used simplified scheme of the most complete photochemical mechanisms). This work presents the first evaluation of the spatial distribution of ground-level O3 concentrations resulting from area source emissions of NOx and VOC in the MABA. Modelled hourly ozone concentrations are compared with observations (N=4666) including new available data from 20 sites. Statistical measures obtained from this comparison (NMSE=0.38, FA2=0.668, FB=0.022) show that the performance of DAUMOD-GRS is good. Results improve for diurnal hours, showing NMSE=0.22, FA2=0.82, FB=-0.022. During summer, diurnal maximum 1-h O3 concentration ranges between 14.9-52.8 ppb (Fig.1). Greater O3 levels are found in the suburbs, as expected. In addition, several runs were performed assuming different scenarios aiming to evaluate the impact of possible future reductions of NOx and VOC emissions on O3 levels across the MABA. The results show that the variation of diurnal O3 peak levels will not be significant. The maximum hourly value obtained for the MABA (52.8 ppb) could be reduced up to 4%.