the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 23 Jan 2024
Analysis of secondary inorganic aerosols over the Greater Area of Athens using the EPISODE-CityChem source dispersion and photochemistry model
Abstract. Secondary inorganic aerosols (SIA) are major components of fine particulate matter (PM2.5), having substantial implications for climate and air quality in an urban environment. In this study, a state-of-the-art thermodynamic model has been coupled to the source dispersion and photochemistry city-scale chemistry transport model EPISODE-CityChem, able to simulate pollutants on a horizontal resolution of 100 x 100 m2, to determine the equilibrium between the inorganic gas and aerosol phases over the Greater Area of Athens, Greece, for the year 2019. In agreement with in-situ observations, sulfate (SO42-) is calculated to have the highest annual mean surface concentration (2.15 ± 0.88 μg m-3) among SIA in the model domain, followed by ammonium (NH4+; 0.58 ± 0.14 μg m-3) and fine nitrate (NO3-; 0.24 ± 0.22 μg m-3). Simulations denote that NO3- formation strongly depends on the local nitrogen oxide emissions, along with the ambient temperature, the relative humidity, and the photochemical activity. Additionally, we show that anthropogenic combustion sources may have an important impact on the NO3- formation in an urban area. During the cold period, the combined effect of decreased temperature in the presence of non-sea salt potassium favors the partitioning of HNO3 in the aerosol phase in the model, raising the NO3- formation in the area. Overall, this work highlights the significance of atmospheric composition and the local meteorological conditions for the equilibrium distribution of nitrogen-containing semivolatile compounds and the acidity of inorganic aerosols, especially in urban areas where atmospheric trace elements from natural and anthropogenic sources coexist.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(4967 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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- Final revised paper
Journal article(s) based on this preprint
A state-of-the-art thermodynamic model has been coupled with the city-scale chemistry transport model EPISODE–CityChem to investigate the equilibrium between the inorganic gas and aerosol phases over the greater Athens area, Greece. The simulations indicate that the formation of nitrates in an urban environment is significantly affected by local nitrogen oxide emissions, as well as ambient temperature, relative humidity, photochemical activity, and the presence of non-volatile cations.
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-2798', Anonymous Referee #2, 19 Feb 2024
The paper addresses an interesting topic related to the physical and chemical processes that determine the atmospheric levels of the secondary inorganic aerosols (SIA) in urban scale. The manuscript is very well written. The scientific tools used (i.e. Eulerian modeling and PM chemical composition measurements) and methodological approach are robust, while the conclusions are clear.
The paper can be accepted for publication. The main minor comment is that the authors should provide maps with the chemical speciated total emission fields (precursors of SIA and SIA), so as to be easier to associate the impact of emission sources on the spatial distribution of SIA concentrations. For the same reason, the relative contribution of emission sectors on the precursors of SIA and SIA total emissions should be presented.
Citation: https://doi.org/10.5194/egusphere-2023-2798-RC1 - AC1: 'Reply on RC1', Stylianos Myriokefalitakis, 29 Apr 2024
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RC2: 'Comment on egusphere-2023-2798', Anonymous Referee #1, 30 Mar 2024
The manuscript describes the coupling of the EPISODE-CityChem cityscale CTM with the ISORPPIA thermodynamic model to account for SIA and acidity levels over the Greater Athens Area for a year of simulations in 2019. The manuscript is easy to follow and well-structured. However, it lacks description and discussion of two major factors that influence the interpretation of the results, being the emissions and meteorology, which I list in my below comments. The manuscript can be published in ACP when these are addressed.
Line 199: the improved spatial distribution of the CAMS emissions should be shortly described.
Lines 212-213: Representation of sea-salt as purely NaCl vs. explicit composition could be a bit further explained. Why is it not represented with explicit composition throughout the model?
How about biomass burning emissions other than domestic wood burning, i.e. forest fires? The area of interest is largely impacted by fires in certain periods. Same question for biogenic VOCs, are they taken into account?
Are local and international shipping emissions taken into account? The area is highly influenced by maritime emissions.
How about the vertical distribution of anthropogenic emissions? Are they all assumed to be all emitted at the surface?
How about the temporal distribution of emissions into hourly variation represented in the model?
Section 2.1.5: Are the meteorological simulations evaluated against observations? In particular wind speed can be very challenging over urban areas. How the WRF model is setup in terms of physics should be documented.
Section 3.1.1:
Can the reasons for low temporal correlation (r=0.46) be explained? Are they attributed to the temporal variation of the anthropogenic emissions for example?
Overall, the temporal and spatial distribution and performance of the model in SIA and acidity is strongly linked with meteorology and further discussions are needed on how the WRF model represents the meteorological conditions (see comment for section 2.1.5).
Citation: https://doi.org/10.5194/egusphere-2023-2798-RC2 - AC2: 'Reply on RC2', Stylianos Myriokefalitakis, 29 Apr 2024
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-2798', Anonymous Referee #2, 19 Feb 2024
The paper addresses an interesting topic related to the physical and chemical processes that determine the atmospheric levels of the secondary inorganic aerosols (SIA) in urban scale. The manuscript is very well written. The scientific tools used (i.e. Eulerian modeling and PM chemical composition measurements) and methodological approach are robust, while the conclusions are clear.
The paper can be accepted for publication. The main minor comment is that the authors should provide maps with the chemical speciated total emission fields (precursors of SIA and SIA), so as to be easier to associate the impact of emission sources on the spatial distribution of SIA concentrations. For the same reason, the relative contribution of emission sectors on the precursors of SIA and SIA total emissions should be presented.
Citation: https://doi.org/10.5194/egusphere-2023-2798-RC1 - AC1: 'Reply on RC1', Stylianos Myriokefalitakis, 29 Apr 2024
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RC2: 'Comment on egusphere-2023-2798', Anonymous Referee #1, 30 Mar 2024
The manuscript describes the coupling of the EPISODE-CityChem cityscale CTM with the ISORPPIA thermodynamic model to account for SIA and acidity levels over the Greater Athens Area for a year of simulations in 2019. The manuscript is easy to follow and well-structured. However, it lacks description and discussion of two major factors that influence the interpretation of the results, being the emissions and meteorology, which I list in my below comments. The manuscript can be published in ACP when these are addressed.
Line 199: the improved spatial distribution of the CAMS emissions should be shortly described.
Lines 212-213: Representation of sea-salt as purely NaCl vs. explicit composition could be a bit further explained. Why is it not represented with explicit composition throughout the model?
How about biomass burning emissions other than domestic wood burning, i.e. forest fires? The area of interest is largely impacted by fires in certain periods. Same question for biogenic VOCs, are they taken into account?
Are local and international shipping emissions taken into account? The area is highly influenced by maritime emissions.
How about the vertical distribution of anthropogenic emissions? Are they all assumed to be all emitted at the surface?
How about the temporal distribution of emissions into hourly variation represented in the model?
Section 2.1.5: Are the meteorological simulations evaluated against observations? In particular wind speed can be very challenging over urban areas. How the WRF model is setup in terms of physics should be documented.
Section 3.1.1:
Can the reasons for low temporal correlation (r=0.46) be explained? Are they attributed to the temporal variation of the anthropogenic emissions for example?
Overall, the temporal and spatial distribution and performance of the model in SIA and acidity is strongly linked with meteorology and further discussions are needed on how the WRF model represents the meteorological conditions (see comment for section 2.1.5).
Citation: https://doi.org/10.5194/egusphere-2023-2798-RC2 - AC2: 'Reply on RC2', Stylianos Myriokefalitakis, 29 Apr 2024
Peer review completion
Journal article(s) based on this preprint
A state-of-the-art thermodynamic model has been coupled with the city-scale chemistry transport model EPISODE–CityChem to investigate the equilibrium between the inorganic gas and aerosol phases over the greater Athens area, Greece. The simulations indicate that the formation of nitrates in an urban environment is significantly affected by local nitrogen oxide emissions, as well as ambient temperature, relative humidity, photochemical activity, and the presence of non-volatile cations.
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Matthias Karl
Kim Andreas Weiss
Dimitris Karagiannis
Eleni Athanasopoulou
Anastasia Kakouri
Aikaterini Bougiatioti
Eleni Liakakou
Iasonas Stavroulas
Georgios Papangelis
Georgios Grivas
Despina Paraskevopoulou
Orestis Speyer
Nikolaos Mihalopoulos
Evangelos Gerasopoulos
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(4967 KB) - Metadata XML