Significant formation of sulfate aerosols contributed by the heterogeneous drivers of dust surface
- 1Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, IRDR international Center of Excellence on Risk Interconnectivity and Governance on Weather, Department of Environmental Science & Engineering, Fudan University, Shanghai, 200433, Peoples’ Republic of China
- 2Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, Peoples’ Republic of China
- 1Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, IRDR international Center of Excellence on Risk Interconnectivity and Governance on Weather, Department of Environmental Science & Engineering, Fudan University, Shanghai, 200433, Peoples’ Republic of China
- 2Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, Peoples’ Republic of China
Abstract. The importance of dust heterogeneous chemistry in the removal of atmospheric SO2 and formation of sulfate aerosols is not adequately understood. In this study, the Fe, Ti, Al-bearing components, Na+, Cl-, K+, and Ca2+ of the dust surface were discovered to be closely associated with the heterogeneous formation of sulfate. Regression models were then developed to accurately predict the heterogeneous reactivity by the particle chemical compositions. Further, the recognized gas-phase, aqueous-phase and heterogeneous oxidation routes were quantitatively assessed and kinetically compared by combining the laboratory work with modeling study. In the presence of 55 μg m-3 airborne dust, heterogeneous chemistry accounts for approximately 28.6 % of the secondary sulfate aerosols during nighttime, while the proportion decreases to 13.1 % in the presence of solar irradiation. On the dust surface, heterogeneous drivers (e.g. transition metal constituents, water-soluble ions) are more efficient than surface adsorbed oxidants (e.g. H2O2, NO2, O3) in the conversion of SO2, particularly during nighttime. Dust heterogeneous chemistry offers an opportunity to explain the missing sulfate source during severe haze pollution events, and its contribution proportion in the complex atmospheric environments could be even higher than the current calculation results. Overall, the dust surface drivers are responsible for the significant formation of sulfate aerosols and have profound impacts on the atmospheric sulfur cycling.
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Tao Wang et al.
Status: open (until 04 Jun 2022)
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RC1: 'Comment on acp-2022-227', Anonymous Referee #2, 04 May 2022
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This paper discusses the correlation of atmospheric mineral dust, and heterogeneous chemistry with the lifetime of SO2 and would give a closer prediction of the formation of sulfate aerosols. Therefore this will be a good addition to our current knowledge in this field of atmospheric chemistry.
I have a few comments and suggestions.
1. Abstract: I think we shouldn't say accurately predict - This is because it is still a prediction. Maybe with near accuracy, some rewording would be good.
2. Authors discuss at several points that the differences of dust surfaces can affect their heterogeneous reactivities. (Under driving factors of dust surface, line 265). Another addition to this section: TiO2 and other titanium-bearing minerals such as ilmenite showed night-time thermal reactions that involve redox cycling with nitrates, as well as pH dependency.
3. Figure 2: why do some minerals have lower sulfates in the daytime while the others have lower sulfates in the nighttime? Can this be explained with the change of particle pH?
what is the pH of each sample before the reaction? Fig 2b shows only the pH after reactions.
4. Is chemistries a real word?
5. Figure 3: why does the reactive uptake coefficient drastically increases after particle acidity reached ~4.5/ 5?
6. For daytime chemistry, did you consider the possibility of the formation of sulfate radicals on surfaces with high Ti content?
7. Figure 5: Why the kinetics has increased drastically after pH 5? within the statistical error, do you see any difference between the aq phase and heterogeneous chemistry?
8. Figure 7: Can you better label the y-axes to explain what % contribution?
Panel b: why does the heterogeneous sulfate contribution for a daytime peak at a certain dust concentration and lowers, whereas it reaches a plateau at night time?
9. Why is more SSA formed during nighttime, but more sulfate is formed during the daytime?
Tao Wang et al.
Tao Wang et al.
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