A summer air-pollution study in Athens, Greece

During a photochemical episode in September 1994, we studied transport and distribution of primary and secondary air pollutants in Athens, Greece, using a research aircraft instrumented for meteorological and air chemistry measurements, and ground-based air-pollution-monitoring stations. We performed a total of 9 flights on 7 days under various meteorological conditions and pollution levels. We report typical pollutant mixing ratios for the background boundary layer. Sea breezes of various intensities were observed during all our noon flights. The sea breezes carried air pollution of apparently different origin and photochemical age, as indicated by the O3/NOy ratios. The pollution levels within the sea breezes were, however, low compared to those in the city of Athens. Under favorable meteorological conditions, the sea breeze could penetrate the entire Athens basin, resulting in an upward flow at the foothills of Parnitha and Pendeli Mts., and filling the lower troposphere with high levels of air pollution at altitudes of up to 2000 m and more. From these layers of high photochemical activity (O3 levels up to 200 ppb), air pollution may have been incorporated into long-range transport.