the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Effects of OH radical and SO2 concentrations on photochemical reactions of mixed anthropogenic organic gases
- 1State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
- 2Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
- 3Environment Research Institute, Shandong University, Qingdao 266237, China
- 4State Key Laboratory for Structural Chemistry of Unstable and Stable Species Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- 1State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
- 2Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
- 3Environment Research Institute, Shandong University, Qingdao 266237, China
- 4State Key Laboratory for Structural Chemistry of Unstable and Stable Species Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
Abstract. Vehicle exhaust, as a major source of air pollutants in urban areas, contains a complex mixture of organic vapors including long-chain alkanes and aromatic hydrocarbons. The atmospheric oxidation of vehicle emissions is a highly complex system as the co-existing inorganic gases (e.g., NOx and SO2) from other urban sources, and therefore remains poorly understood. In this work, the photooxidation of n-dodecane, 1,3,5-trimethylbeneze, and their mixture are studied in the presence of NOx and SO2 to mimic the atmospheric oxidation of urban vehicle emissions (including diesel and gasoline vehicles), and the formation of ozone and secondary aerosols are investigated. It is found that ozone formation is enhanced by higher OH concentration and higher temperature, but is influenced little by SO2 concentration. However, SO2 can largely enhance the particle formation in both number and mass concentrations, likely due to the promoted new particle formation and acid-catalyzed heterogeneous reactions from the formation of sulfuric acid. In addition, organo-sulfates and organo-nitrates are detected in the formed particles, and the presence of SO2 can promote the formation of organo-sulfates. These results provide a scientific basis for systematically evaluating the effects of SO2, OH concentration, and temperature on the oxidation of mixed organic gases in the atmosphere that produce ozone and secondary particles.
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Junling Li et al.
Status: open (until 06 Jun 2022)
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RC1: 'Comment on acp-2022-294', Anonymous Referee #1, 24 May 2022
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The manuscript entitled “Effects of OH radical and SO2 concentrations on photochemical reactions of mixed anthropogenic organic gases” presents new findings of the atmospheric processing of the anthropogenic pollutants, represented by n-dodecane, 1,3,5-trimethylbeneze, which are associated with the vehicular traffic pollution. The paper is scientifically sound; for the most part, methods and experimental details are adequately presented. The equipment and methodology used in the simulation chamber experiments are adequate and provide valuable information about the reactions under investigation. The length of sections 1 and 2 is well balanced, providing sufficient details and discussion without adding too much volume to the final manuscript.
At the same time, the article would benefit from major revisions. Generally, the use of the English language should be improved because it is frequently awkward, even from the point of view of a non-native speaker of English.
My technical comments are provided below. Regarding the scientific comments, I believe that the article would benefit greatly from a more in-depth analysis of the results. The is a lack of a broader context in the presented discussion. The discussion in section 3 discusses the data but without providing any broader insights into the processes under investigation. In connection with this comment, there is no quantitative information presented in section 4, which almost reads like a literature review section. I would recommend constructing a kinetic model (perhaps MCM can be utilized in some way) and attempting to reproduce the experimental temporal profiles of the reactants from the chamber experiments and the measured yields of SOAs. All of the elements are here; rate coefficients for the two molecules under investigation are available or can be estimated with SAR parameter if needed. The author should attempt to construct a mechanism explaining the experimental observations and the use of this mechanism to discuss and explain the atmospheric implications of their findings in section 4 (Atmospheric Implications).
See also:
Environ. Sci. Technol. 2001, 35, 1394-1405
https://acp.copernicus.org/articles/22/215/2022/acp-22-215-2022.pdf
Technical comments.
Line 36-37, 41-45 These sentences are not well constructed and read awkwardly, please revise.
etc. is used a little bit too much in the introduction, please avoid such abbreviations in the scientific writing.
Line 61 Consider removing “in combination with the corresponding equipment”
Lines 74-77 Can you please clarify why the temperature inside the chamber during wintertime is within 15-30 °C range?
Line 80 Consider removing “classics”
Line 80 NO was introduced from a 500 ppm standard gas cylinder, I understand that this cylinder contained a 500 ppm mixture of NO in nitrogen? Similar comment to Line 84 (SO2 cylinder).
Line 82 Consider removing “home-made”
Line 92 Consider removing “solid” and changing adsorbent to sorbent
Line 99 Can you provide some more details about the experimental conditions for the ESI-MS measurements? Perhaps in the SI? What was the difference between the measured and expected elemental formula? What was the mass resolution of the used instrument? Note also that the elemental composition provides little information about the molecular structure.
Line 111 Referring to OH as the hydroxyl free radical is rather uncommon.
Lines 271-272 more as a higher number or larger concentration?
Figures S2 and S3 – the labels on these plots are completely unreadable, can you please make the fonts larger?
Figures 2 and 4 are difficult to read, perhaps consider presenting some of these results in a form of a bar plot?
Junling Li et al.
Junling Li et al.
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