9-YEAR TREND OF AIR-POLLUTION BY CO IN ATHENS, GREECE

Air quality data obtained by the Athens air pollution monitoring syste m from the nine-year period started in 1986 were analysed to determine time variations and the effect of various meteorological parameters o n air quality by CO. From the ten monitoring stations measuring CO, th e station located in a street with high traffic was selected since thi s site had the longest time record and presented the highest values of CO during the period examined. The time variations show that higher c oncentrations of CO were measured during the winter months, on working days and between 09.00 and 23.00 hours. The long-term trend shows a d efinite decline of CO concentrations after 1990 resulting from the sub stitution of gasoline-powered vehicles with vehicles equipped with thr ee-way catalysts. Finally, it was found that during days with calm or S-SW blowing light winds the CO concentrations presented their higher values.