The Evolution of the Interannual and Seasonal Variation of the Main Gaseous and Particulate Pollutants in Athens, Greece, for 2001–2023

The densely populated city of Athens has been facing air pollution problems over the past few decades due to the high population density associated with an intense emission load constrained by the local topography causing poor ventilation. In this study, the evolution of the interannual and seasonal variation in primary and secondary gaseous as well as particulate urban air pollution in Athens was examined for the 2001–2023 period and for the following pollution parameters: SO2, CO, NO2, NOx (NO + NO2), O3, Ox (O3 + NO2), PM10, and PM2.5. For this purpose, the annual and monthly averages from the Athens air pollution monitoring stations of Peireas (SO2, CO, NO2, NOx), Patission (SO2, CO, NO2, NOx), Aristotelous (PM10, PM2.5), Lykovrissi (PM10, PM2.5, O3, Ox), and Liossia (O3, Ox) in the selected periods of 2001–2004 and 2020–2023 were examined. There was a clear reduction in most air pollution parameters at all stations during the period examined, relative to the average values. The ozone and Ox values, presenting a high interannual variability, remained generally unchanged. The smallest reductions are observed for NO2 and NOX (about −10% to −20%), while the highest reductions are observed for SO2, CO, and PM10 (about −50% to −60%). The change in pollutant concentrations for every month of the year between the 2001–2004 and 2020–2023 time periods is also examined, and the observed seasonal differences are discussed.