the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 28 Feb 2025
Gas-particle partitioning of m-xylene and naphthalene oxidation products: temperature and NOx influence
Abstract. Volatile organic compounds (VOCs) react with atmospheric oxidants resulting in oxygenated products of lower volatility known as semi and intermediate volatile organic compounds (S/IVOCs) forming secondary organic aerosols (SOA). Those compounds can partition between the gas and particle phases, a critical process influenced by several environmental parameters, yet poorly constrained. This study aims to evaluate the effect of temperature and VOC/NOx ratio on SOA formation and partitioning of individual SOA products from m-xylene and naphthalene OH-oxidation. Experiments are carried out in an oxidation flow reactor (OFR) and products are identified and quantified using a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) coupled to a CHemical Analysis of aeRosol ONline (CHARON) inlet. Results show that lower temperatures significantly enhance SOA formation, while lower VOC/NOx ratios reduce it. Gas-phase m-xylene major products are C3, C5 and C8 whereas particle-product distributions exhibit a progressive increase from C2 to C8. In contrast, naphthalene products partition more readily into the condensed phase, with C8-C10 products dominating. Most of the oxidation products from both precursors exhibit a volatility distribution in the SVOC regime, with fewer in the IVOC regime. The decrease in temperature shifts saturation concentration (Ci*) values towards lower values, though no clear relationship between Ci* and oxidation state is observed. A comparison between observed and estimated volatilities using SIMPOL.1 model reveals systematic deviations for both light molecules and heavy compounds, suggesting a need for improved predictive models.
- Preprint
(2657 KB) - Metadata XML
-
Supplement
(963 KB) - BibTeX
- EndNote
Status: open (until 11 Apr 2025)
-
RC1: 'Comment on egusphere-2025-833', Anonymous Referee #1, 22 Mar 2025
reply
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-833/egusphere-2025-833-RC1-supplement.pdf
-
RC2: 'Comment on egusphere-2025-833', Anonymous Referee #2, 23 Mar 2025
reply
In this paper, the effect of temperature and VOC/NOx ratio on SOA formation and partitioning of individual SOA products from m-xylene and naphthalene OH-oxidation. Experiments are carried out in an oxidation flow reactor (OFR) and products are identified and quantified using a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) coupled to a CHemical Analysis of aeRosol ONline (CHARON) inlet. Results show that lower temperatures significantly enhance SOA formation, while lower VOC/NOx ratios reduce it. Gas-phase m-xylene major products are C3, C5 and C8 whereas particle-product distributions exhibit a progressive increase from C2 to C8. In contrast, naphthalene products partition more readily into the condensed phase, with C8-C10 products dominating. Most of the oxidation products from both precursors exhibit a volatility distribution in the SVOC regime, with fewer in the IVOC regime. A comparison between observed and estimated volatilities using SIMPOL.1 model reveals systematic deviations for both light molecules and heavy compounds, suggesting a need for improved predictive models. This is a nice piece of work. However, the article, the figure and the table have to be ameliorated. In particularly, there is no uncertainties of measurements, it will be good to add it when it’s possible. Furthermore, some explanation are missing in the manuscript, as the temperature influence, the model VBS, the comparison with literature (yield and also products). The data presented are of significant importance and should be published after some minor revisions. For more explanation, see specific comments.
-
RC3: 'Comment on egusphere-2025-833', Anonymous Referee #3, 24 Mar 2025
reply
General comments
Shahin et al. used an oxidation flow reactor (OFR) to generate m-xylene and naphthalene aerosol particles at 280 K and 295 K under low and high NOx conditions. They used a suite of real-time instruments to investigate the gas- and particle-phase products. The method is overall technically sound, but the current analysis still lacks details. The main drawback of the work is that it reads like a measurement report, especially for sections 3.1 and 3.2. The associated content should be shortened and condensed for readability. It is hard to grab the take-home message from the study with good experimental design. Efforts must be made to address the following comments and highlight the novelty before the work can be considered for publication.
Major Comment
- Introduction: Previous researchers have conducted extensive studies on the effects of temperature on SOA yield and product volatility, though not all of them involve aromatics, their research works are also of great reference (Svendby et al., 2008; Clark et al., 2016; Price et al., 2016; Li et al., 2019; Li et al., 2020; Deng et al., 2021; Lannuque et al., 2023; Fan et al., 2025). The authors should give a good summary of existing studies in the introduction. Additionally, the authors should how this work differs from Lannuque et al. (2023).
- OFR: the overall input flow is 2.4 lpm, and thus, the residence time is fairly long. I am concerned about the significant vapour and particle losses inside the OFR. These artifacts will potentially affect the observed SOA yield and products. However, there is no discussion about how the results are biased by the vapour and particle losses. I also wonder if any loss correction has been applied to the results. The way to generate OH differs from that used in the widely used PAM. Some levels of simple model simulation should be provided to understand the chemistry inside the OFR and how NOx affects oxidation in the context of used OFR. This can be done by the KimSim model developed by Peng and Jimenez (2019).
- Low NOx experiments: One variable in the experiment is the NOx However, there is no discussion about the results under low-NOx conditions from section 3.2 onward. It will be interesting to see how NOx affects the chemical distribution and volatility distribution.
- AMS: What was the use of the AMS data in this study? The author should consider including the bulk elemental composition, oxidation states and organonitrate fraction based on the AMS data.
- Section 3.4: The authors gave a very good explanation about the differences between the model results and the observational data. But authors should also discuss how temperature and VOC/NOx ratios affect these differences.
Minor Comment
- Lines 63-65: “In other studies, SOA yields increase up to 60% under elevated levels of NOx .......(Srivastava et al., 2023; Zhu et al., 2021)”. Although Zhu et al., (2021) mentioned “Nevertheless, the maximum concentration of p-xylene SOA …, which was 60% higher than that without NO2 ……”, it only is related to SOA mass concentrations but not SOA yield. In addition, in Srivastava et al. (2023), though higher SOA yield was found under high NOx conditions in comparison with low NOx conditions, the ratios of VOC/NOx were not known. I suggested if the authors wanted to express the SOA yield increased with VOC/NOx, please include extra reference.
- Lines 103– 106: How was the OH radical concentration determined?
- Line 119: Does the activated charcoal affect the collection of organic aerosols?
- Line 121: Why 150 deg C was the set temperature of the TD? Is it high enough to vaporise all compounds in the particles?
- Line 135: How was diiodobenzene introduced into the PTR? Was it done by a permeation tube?
- For the yield calculation, did you use the organic mass from SMPS or AMS?
- Eq 5: Where did you take the Δ𝐻 values?
- Table 1: VOC and delta VOC are shown in different units. Could you add another column for the consumed percentage of VOC?
- Line 214: the description of “Lower initial levels of the VOC precursor increase the amount of S/IVOCs (Chen et al., 2019)” is confusing. In the reference, it only showed the decrease in the normalized signal intensity of m/z range from 50 to150 when initial toluene concentration increases from 37 ppb to 690 ppb. In addition, the reference also mentioned: “the concentrations of C7H8O increased as a function of the initial toluene concentration”. And in the reference, how many species measured by the PTR could be classified as S/IVOCs is deliberative. The authors need to be more precise when expression.
- Section 3.2: The experiment was conducted under high NOx Is there any reason there is no N-contained products observed in the m-xylene photooxidation experiments?
- Line 254-256: could the author describe how to calculate the carbon balance in SI?
- Line 267-269: Does increasing temperature promote the reactivity and ring cleavage of C8 compounds, thereby increasing the signal strength of C3 and C5 compounds?
- Lines 461 – 465: How did the author come up with that there is no volatility trend as a function of OSc for anthropogenic VOCs? Where is the plot shown in the manuscript?
- Figure 5: Are (c) and (d) only for the compound detected both in gas and particle phases? The same question applies to Figure 6.
- Line 514-515: What is the meaning of “temperature-induced volatility changes for highly oxygenated compounds”? In Fig. S5, it seems that at higher temperatures (295K), the discrepancy between the observed and calculated values was smaller than that in 280K. How did the temperature affect the discrepancy?
Technical Comment
- Line 46: There is only one time when PAHs are used. You can use its full name.
- Line 47: It is unclear what is C1
- Line 61: “alkoxy radicals (RO 2, HO 2 and HO)”. RO2, HO2 and HO were not alkoxy radicals. Change to “peroxy radical (RO2 and HO2)”.
- Section 2.2 is very long. You can try to slice it into two or more paragraphs for readability.
- Lines 215: What is the meaning of the first steps of the experiment?
- Figure 1: The authors try to summarise the literature data. It is a good attempt. However, due to the small point sizes of this study and the use of multiple colours for different studies, I found that it is hard to pinpoint the values from this study without careful reading. I would suggest using one colour but different shapes for literature and keeping the two chosen colours for this study and open and filled markers for high and low NOx The marker size should be tuned to some extent for better readability. In addition, there is no need to scale the data point by OH exposure because the authors did not discuss it in detail in the main text.
- Line 270: “Fig S3” should be “Fig S2”.
- Figure S2: What is the left and right y-axis for?
- Figure 5: Please label m-xylene and naphthalene in the plot and 280 K for the (c) and (d) plots.
- Line 445: Is it supposed to be ug m-3?
- “Fig.” and “Figure” should be used consistently.
Reference:
Clark, C. H., Kacarab, M., Nakao, S., Asa-Awuku, A., Sato, K., and Cocker, D. R., 3rd: Temperature effects on secondary organic aerosol (SOA) from the dark ozonolysis and photo-oxidation of isoprene, Environ Sci Technol, 50, 5564-5571, 10.1021/acs.est.5b05524, 2016.
Deng, Y., Inomata, S., Sato, K., Ramasamy, S., Morino, Y., Enami, S., and Tanimoto, H.: Temperature and acidity dependence of secondary organic aerosol formation from α-pinene ozonolysis with a compact chamber system, Atmos. Chem. Phys., 21, 5983-6003, 10.5194/acp-21-5983-2021, 2021.
Fan, C., Wang, W., Wang, K., Lei, T., Xiang, W., Hou, C., Li, J., Guo, Y., and Ge, M.: Temperature effects on SOA formation of n-dodecane reaction initiated by cl atoms, Atmos. Environ., 346, 10.1016/j.atmosenv.2025.121070, 2025.
Lannuque, V., D'Anna, B., Kostenidou, E., Couvidat, F., Martinez-Valiente, A., Eichler, P., Wisthaler, A., Müller, M., Temime-Roussel, B., Valorso, R., and Sartelet, K.: Gas–particle partitioning of toluene oxidation products: An experimental and modeling study, Atmos. Chem. Phys., 23, 15537-15560, 10.5194/acp-23-15537-2023, 2023.
Li, J., Wang, W., Li, K., Zhang, W., Peng, C., Zhou, L., Shi, B., Chen, Y., Liu, M., Li, H., and Ge, M.: Temperature effects on optical properties and chemical composition of secondary organic aerosol derived from <i>n</i>-dodecane, Atmos. Chem. Phys., 20, 8123-8137, 10.5194/acp-20-8123-2020, 2020.
Li, Z., Tikkanen, O.-P., Buchholz, A., Hao, L., Kari, E., Yli-Juuti, T., and Virtanen, A.: Effect of decreased temperature on the evaporation of α-Pinene secondary organic aerosol particles, ACS Earth and Space Chemistry, 3, 2775-2785, 10.1021/acsearthspacechem.9b00240, 2019.
Peng, Z. and Jimenez, J. L.: Kinsim: A research-grade, user-friendly, visual kinetics simulator for chemical-kinetics and environmental-chemistry teaching, J Chem Educ, 96, 806-811, 10.1021/acs.jchemed.9b00033, 2019.
Price, D. J., Kacarab, M., Cocker, D. R., Purvis-Roberts, K. L., and Silva, P. J.: Effects of temperature on the formation of secondary organic aerosol from amine precursors, Aerosol Sci. Technol., 50, 1216-1226, 10.1080/02786826.2016.1236182, 2016.
Svendby, T. M., Lazaridis, M., and Tørseth, K.: Temperature dependent secondary organic aerosol formation from terpenes and aromatics, J. Atmos. Chem., 59, 25-46, 10.1007/s10874-007-9093-7, 2008.
Citation: https://doi.org/10.5194/egusphere-2025-833-RC3
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 131 | 50 | 7 | 188 | 16 | 5 | 4 |
- HTML: 131
- PDF: 50
- XML: 7
- Total: 188
- Supplement: 16
- BibTeX: 5
- EndNote: 4
Viewed (geographical distribution)
| Country | # | Views | % |
|---|---|---|---|
| United States of America | 1 | 67 | 34 |
| China | 2 | 36 | 18 |
| France | 3 | 28 | 14 |
| undefined | 4 | 13 | 6 |
| South Korea | 5 | 8 | 4 |
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
- 67