The Evolution of the Interannual and Seasonal Variation of the Main Gaseous and Particulate Pollutants in Athens, Greece, for 2001–2023 †
Research Centre for Atmospheric Physics and Climatology, Academy of Athens, 11521 Athens, Greece
*
Author to whom correspondence should be addressed.
†
Presented at the 17th International Conference on Meteorology, Climatology, and Atmospheric Physics—COMECAP 2025, Nicosia, Cyprus, 29 September–1 October 2025.
Environ. Earth Sci. Proc. 2025, 35(1), 41; https://doi.org/10.3390/eesp2025035041
Published: 19 September 2025
Abstract
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.
1. Introduction
Over the past few decades, the high air pollution levels in Athens, Greece, have become a priority issue for the authorities and have been the subject of many research studies on urban primary, photochemical and particulate pollution [1,2,3,4,5,6,7,8,9], regional rural surface ozone background [10,11,12,13,14], and vertical tropospheric ozone distribution [15,16]. In general, decreasing trends for most pollutants have been reported [17].
In this study, the evolution of the interannual and seasonal variation in primary and secondary photochemical urban air pollution in Athens has been examined for the 2001–2023 period. In addition, the annual and monthly averages for 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.
2. Results and Discussion
As observed in Table 1, the most polluted stations of the Athens air pollution network regarding primary pollutants (SO2, CO, NOx) are Patission and Peireas, although with different characteristics, as CO and NOx levels are about double in Patission, while equivalent SO2 levels are observed at both stations. As far as photochemical pollution is concerned, the highest values are observed at peripheral stations, while equivalent Ox levels are observed over the urban area.
The interannual variation of the concentrations of the main pollutants will be further examined for the Patission and Peireas stations. As observed in Figure 1, SO2 concentrations show a rapid decrease between 2003 and 2010, while during the past 15 years, they remain relatively stable for both examined stations. There is a sharper reduction in pollution levels in Patission than in Peireas, and regarding CO, similar behavior is observed in general. The NO2-NOx concentrations show a different pattern: Stable concentrations between 2001 and 2009, and then a rapid decrease until 2014, followed by increase in concentrations, which is more important in Peireas, reaching almost the previous levels, while in Patission, NOx concentrations remain significantly lower.
Regarding O3-Ox, while there is no clear pattern in general, it could be argued that Ox concentrations are slightly lower during the second part of the examined period (Figure 2). There is also a sharp reduction in particulate pollution (PM10-PM2.5) after 2008–09, which has slightly continued during the recent years for PM10 in Lykovrissi, while PM2.5 shows a slightly increasing trend.
A very strong seasonal variation in SO2 is observed in Patission, especially during the 2001–2004 subperiods, with minimum in August–October and maximum in winter (Table 2). Afterwards, a substantial reduction occurred, and during recent years, the mean monthly SO2 concentrations range around 5–10 μg/m3. Regarding CO and NOx, slight seasonal variations with similar patterns are observed, while NO2 shows maximum values in June–July and minimum values in December–January. The mean monthly CO concentrations range around 0.5–1.5 mg/m3 during recent years, while the NO2 levels range around 60–80 μg/m3. A Slight decrease in Ox levels is observed between the two examined subperiods (2001–2004 and 2020–2023) followed by relatively stable concentrations, while a clear decrease in PM10 and PM2.5 concentrations for all seasons is observed during recent years, relative to the concentration levels recorded before 2010.
Looking into more detail by using percentage differences, as presented in Figure 3, the comparison between the 2001–2004 and 2020–2023 subperiods for SO2 in Patission shows a significant decrease in concentrations for all seasons (60–80%), while in Peireas the lower concentration decreases are observed during the August-October period probably influenced by the harbor activity. Almost the same pattern is observed for CO, although the maximum differences between the two stations are observed during the June–August period. The average decrease for NO2 in Patission is in the range of 20–30% and 5–15% in Peireas. The NOx decrease becomes 40–50% in Patission, while in Peireas a totally different pattern is observed with significantly smaller decreases (20–30%) during winter months followed by slight increases (up to 10%) during summer months. Ozone concentrations show an increase during recent years due to reduced NOx titration, but the Ox levels show general decreases for all months (5–20%) for both examined peripheral stations. Finally, PM10 concentrations at the peripheral station of Lykovrissi have decreased more significantly (60–70%) than in the central station of Patission (40–50%) for most months of the year. For PM2.5, the decreases are less significant in Lykovrissi and almost zero in the central station of Patission.
Author Contributions
Conceptualization, P.K.; methodology, P.K. and T.S.; formal analysis, T.S., K.D., and A.P.; writing—original draft, P.K. and T.S.; writing—review and editing, P.K., T.S., A.P., K.D., and J.K.; visualization, T.S. All authors have read and agreed to the published version of the manuscript.
Funding
This research received funding from the European Project “CAMS2_82: EVALUATION AND QUALITY CONTROL (EQC) OF GLOBAL PRODUCTS”.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
The original data used in this study are openly available through the official website of the Hellenic Ministry of Environment and Energy (MEEN), without any access restrictions, at the following link: https://ypen.gov.gr/perivallon/poiotita-tis-atmosfairas/dedomena-metriseon-atmosfairikis-rypansis/ Downloaded file: “ΥΠΕΝ (AΤΤΙΚH + AΛΙAΡΤOΣ ΒOΙΩΤΙAΣ)” (accessed on 3 September 2023).
Conflicts of Interest
The authors declare no conflicts of interest.
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Figure 1.
Percentage deviation from the mean annual concentrations of SO2 and CO (upper panels) and NO2-NOx (lower panels) for the stations of Patission (red line) and Peireas (blue line).
Figure 1.
Percentage deviation from the mean annual concentrations of SO2 and CO (upper panels) and NO2-NOx (lower panels) for the stations of Patission (red line) and Peireas (blue line).
Figure 2.
Percentage deviation from the mean annual concentrations of Ox and O3 (upper panels) and PM10-PM2.5 (lower panels) for the stations of Lykovrissi, Liossia, and Aristotelous. PM2.5 data start from 2007 in Lykovrissi and from 2016 in Aristotelous.
Figure 2.
Percentage deviation from the mean annual concentrations of Ox and O3 (upper panels) and PM10-PM2.5 (lower panels) for the stations of Lykovrissi, Liossia, and Aristotelous. PM2.5 data start from 2007 in Lykovrissi and from 2016 in Aristotelous.
Figure 3.
Percentage deviation from the mean monthly concentrations of SO2, CO, NO2, NOx, O3, Ox, PM10, and PM2.5 for various stations in Athens between the 2001–2004 and 2020–2023 time periods.
Figure 3.
Percentage deviation from the mean monthly concentrations of SO2, CO, NO2, NOx, O3, Ox, PM10, and PM2.5 for various stations in Athens between the 2001–2004 and 2020–2023 time periods.
Table 1.
Average annual atmospheric concentrations (in μg/m3) of urban air pollutants for the main stations of the air pollution monitoring network in Athens for the 2001–2023 period. The PM2.5 timeseries begin from 2007 in Peiraias, Lykovrissi, and Agia Paraskevi and from 2015 in Thrakomakedones. The PM10 data begin in 2015 in Nea Smyrni and Liosia.
Table 1.
Average annual atmospheric concentrations (in μg/m3) of urban air pollutants for the main stations of the air pollution monitoring network in Athens for the 2001–2023 period. The PM2.5 timeseries begin from 2007 in Peiraias, Lykovrissi, and Agia Paraskevi and from 2015 in Thrakomakedones. The PM10 data begin in 2015 in Nea Smyrni and Liosia.
| AIR POLLUTAN STATIONS | SO2 | CO(mg/m3) | NO2 | NOx | Ox | O3 | PM10 | PM2.5 |
|---|---|---|---|---|---|---|---|---|
| PEIRAIAS | 13.02 | 1.03 | 57.59 | 131.91 | 96.57 | 37.56 | 43.20 | 20.74 |
| NEA SMYRNI | 9.84 | 0.69 | 34.42 | 58.18 | 100.58 | 64.09 | - | -- |
| GEOPONIKI | 8.71 | 0.70 | 37.08 | 70.88 | 88.70 | 49.34 | - | - |
| ATHINAS | 7.71 | 1.37 | 49.92 | 123.38 | 87.60 | 35.34 | - | - |
| PATISION | 13.21 | 1.84 | 77.24 | 225.63 | 100.89 | 20.31 | - | - |
| MAROUSI | 7.83 | 0.63 | 28.94 | 55.12 | 90.78 | 60.56 | 41.77 | - |
| LYKOVRISI | - | - | 25.98 | 46.34 | 89.62 | 61.86 | 47.57 | 19.70 |
| LIOSIA | - | - | 27.86 | 48.60 | 93.97 | 64.25 | - | - |
| AG. PARASKEVI | - | - | 15.10 | 18.84 | 98.11 | 82.29 | 30.32 | 13.35 |
| THRAK/DONES | - | - | 9.10 | 15.27 | 97.50 | 87.81 | 29.98 | 12.69 |
Table 2.
Average monthly atmospheric concentrations of urban air pollutants for the stations of Patission (SO2, CO, NO2, NOx) and Lykovrissi (O3, Ox, PM2.5, PM10) for the 2001–2004 and 2020–2023 periods (bold and italics lines, respectively). PM2.5 data start from 2007 in Lykovrissi.
Table 2.
Average monthly atmospheric concentrations of urban air pollutants for the stations of Patission (SO2, CO, NO2, NOx) and Lykovrissi (O3, Ox, PM2.5, PM10) for the 2001–2004 and 2020–2023 periods (bold and italics lines, respectively). PM2.5 data start from 2007 in Lykovrissi.
| JAN | FEB | MAR | APR | MAY | JUN | JUL | AUG | SEPT | OCT | NOV | DEC | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| SO2 | 44.78 | 43.05 | 35.21 | 30.02 | 24.66 | 20.58 | 24.02 | 13.07 | 11.85 | 13.31 | 33.23 | 42.86 |
| 9.18 | 8.87 | 7.83 | 5.24 | 5.02 | 5.18 | 3.95 | 4.18 | 4.77 | 4.41 | 5.10 | 5.96 | |
| CO | 3.53 | 3.34 | 3.14 | 2.87 | 2.85 | 2.78 | 2.71 | 2.29 | 3.28 | 3.68 | 4.12 | 3.29 |
| 1.54 | 1.33 | 1.00 | 0.85 | 1.02 | 0.90 | 0.65 | 0.68 | 0.86 | 1.14 | 1.34 | 1.6 | |
| NO2 | 76.15 | 86.13 | 93.55 | 96.84 | 96.78 | 108.49 | 99.42 | 93.20 | 90.65 | 91.71 | 76.82 | 67.77 |
| 64.47 | 70.94 | 68.11 | 71.80 | 78.06 | 76.66 | 71.12 | 67.87 | 71.83 | 67.84 | 61.44 | 59.76 | |
| NOx | 322.72 | 322.28 | 297.84 | 270.02 | 259.78 | 261.14 | 230.91 | 213.73 | 256.06 | 313.91 | 360.42 | 305.44 |
| 231.08 | 217.72 | 157.70 | 140.13 | 162.14 | 160.30 | 128.21 | 123.19 | 156.71 | 189.54 | 206.42 | 233.35 | |
| Ox | 68.06 | 84.18 | 98.08 | 103.91 | 115.37 | 116.15 | 111.52 | 108.68 | 94.18 | 83.10 | 68.23 | 59.91 |
| 63.81 | 73.98 | 81.24 | 90.79 | 97.45 | 100.19 | 108.90 | 104.66 | 90.67 | 76.43 | 65.61 | 58.39 | |
| O3 | 32.90 | 43.14 | 53.11 | 64.97 | 79.96 | 83.30 | 78.48 | 82.67 | 57.91 | 45.11 | 28.93 | 28.96 |
| 39.23 | 47.70 | 60.84 | 71.67 | 76.50 | 81.97 | 93.24 | 89.46 | 73.39 | 57.18 | 43.98 | 34.87 | |
| PM10 | 60.47 | 59.20 | 69.17 | 63.09 | 60.04 | 58.98 | 63.25 | 55.69 | 59.78 | 66.51 | 67.78 | 48.53 |
| 33.53 | 29.78 | 24.80 | 23.89 | 24.18 | 21.64 | 24.07 | 26.40 | 25.10 | 23.87 | 24.45 | 28.44 | |
| PM2.5 | 26.95 | 26.62 | 28.61 | 29.06 | 26.69 | 32.58 | 37.21 | 32.71 | 26.90 | 25.45 | 26.27 | 23.03 |
| 26.76 | 23.59 | 19.84 | 15.90 | 15.36 | 12.26 | 14.02 | 14.92 | 14.30 | 13.23 | 16.54 | 21.85 |
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MDPI and ACS Style
Stavraka, T.; Kapsomenakis, J.; Poupkou, A.; Douvis, K.; Kalabokas, P. The Evolution of the Interannual and Seasonal Variation of the Main Gaseous and Particulate Pollutants in Athens, Greece, for 2001–2023. Environ. Earth Sci. Proc. 2025, 35, 41. https://doi.org/10.3390/eesp2025035041
AMA Style
Stavraka T, Kapsomenakis J, Poupkou A, Douvis K, Kalabokas P. The Evolution of the Interannual and Seasonal Variation of the Main Gaseous and Particulate Pollutants in Athens, Greece, for 2001–2023. Environmental and Earth Sciences Proceedings. 2025; 35(1):41. https://doi.org/10.3390/eesp2025035041
Chicago/Turabian StyleStavraka, Theodora, John Kapsomenakis, Anastasia Poupkou, Kostas Douvis, and Pavlos Kalabokas. 2025. "The Evolution of the Interannual and Seasonal Variation of the Main Gaseous and Particulate Pollutants in Athens, Greece, for 2001–2023" Environmental and Earth Sciences Proceedings 35, no. 1: 41. https://doi.org/10.3390/eesp2025035041
APA StyleStavraka, T., Kapsomenakis, J., Poupkou, A., Douvis, K., & Kalabokas, P. (2025). The Evolution of the Interannual and Seasonal Variation of the Main Gaseous and Particulate Pollutants in Athens, Greece, for 2001–2023. Environmental and Earth Sciences Proceedings, 35(1), 41. https://doi.org/10.3390/eesp2025035041
