PHOTOCHEMICAL AIR-POLLUTION CHARACTERISTICS AT THE STATION OF THE NCSR-DEMOKRITOS, DURING THE MEDCAPHOT-TRACE CAMPAIGN IN ATHENS, GREECE (20 AUGUST 20 SEPTEMBER 1994)

In this paper the continuous meteorological and air pollution measurem ents collected at the station of the NCSR-Demokritos during the MEDCAP HOT-TRACE campaign (20 August-20 September 1994) are presented and dis cussed. The station site is located about 10 km east from the center o f Athens at 280 m altitude. The air pollution species measured were O- 3, NO, NO2 and SO2 while the meteorological parameters were recorded o n a 84 m high meteorological mast. Ozone values up to 180 ppb have bee n measured during pollution episodes. The maximum hourly average ozone mixing ratio from the western sector (urban) is about 50 ppb higher t han the corresponding value of the NE sector (rural). At the same time the average ozone rate of increase during the morning hours was about 20 ppb h(-1) and the typical wind speeds from 3 to 4 m s(-1). The cre ation oi this excess ozone amount is mainly attributed to the daily ph otochemistry. In the air masses coming from all wind directions compar able nighttime levels of O-x(NO2 + O-3) around 65 ppb are observed whi le the ozone and nitrogen dioxide values are clearly anticorrelated. T he observed mixing ratios coming from the NE rural sector vary between 50 and 80 ppb and they are almost indifferent of the wind speed. For wind speeds higher than 7 m s(-1) the average ozone value was 68 +/- 7 ppb (1.8 ppb for nitrogen dioxide). Such ozone levels despite the alt itude of our station (280 m above sea level) are considered as high ru ral concentrations, if they are compared with similar values in Centra l Europe. (C) 1998 Elsevier Science Ltd. All rights reserved.