the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Organosulfate Produced from Consumption of SO3 Speeds up Sulfuric Acid-Dimethylamine Atmospheric Nucleation
Xiaomeng Zhang
Yongjian Lian
Shendong Tan
Shi Yin
Abstract. Although sulfuric acid (SA) and dimethylamine (DMA) driven nucleation mainly dominants the new particle formation (NPF) process in the atmosphere, seeking the involvement of other gaseous species remains crucial to better understand the NPF. Organosulfate has been detected in gas phase and abundantly in atmospheric fine particles. However, its molecular formation mechanism and its impact on the NPF are still much less understood. Here, we explored the gas phase reaction of Glycolic acid (GA) with SO3, and evaluated the enhancing potential of its products on the SA-DMA driven NPF using a combination of quantum chemical calculations and kinetics modeling. We found that the considerable concentration of glycolic acid sulfate (GAS) is thermodynamically accessible from the reaction of GA with SO3, efficiently catalyzed by SA or H2O molecules. The produced GAS can form stable clusters with SA and DMA, and speeds up the nucleation rate of SA-DMA system obviously. Notably, the enhancement by GAS on the SA-DMA-based particle formation rate can be up to ~ 800 times in the region where the concentration of SA is about 104 molecules cm-3. Supported by observations of atmospheric NPF events at Mt. Tai in China, our proposed ternary GAS-SA-DMA nucleation mechanism further indicates that the organosulfates produced from the consumption of SO3 may play an important role for the unexpected high NPF rates observed in areas with relatively low concentrations of SA. The presented reaction and nucleation mechanisms provide a new feasible source of organosulfates in atmospheric new particles. Based on our findings, the impact of organosulfates on the atmospheric NPF in multiple regions around the world was estimated and discussed.
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Xiaomeng Zhang et al.
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RC1: 'Comment on egusphere-2023-1649', Anonymous Referee #1, 14 Aug 2023
The manuscript entitled ‘Organosulfate produced from consumption of SO3 speeds up sulfuric acid-dimethylamine atmospheric nucleation’ by Zhang et al. presents a detailed theory of the potential role of gas-phase glycolic acid (and its organosulfate derivatives) in new particle formation (NPF). The authors rely on quantum chemical calculations to define the most reasonable pathway and formation product of the reaction between glycolic acid and SO3, leading to organosulfates. Also, kinetic modeling is used to understand the most efficient clustering with dimethyl amines. Their findings are backed up with atmospheric observations from Mt. Tai in China where intense NPF events have been observed. The authors also report observations from other locations around the world where the role of glycolic acid in NPF might be important but has been not evaluated earlier. First of all, I would like to acknowledge the authors for a very detailed, easy to follow manuscript. As mentioned by the authors, there are very few studies which tackle the role of organic acids in NPF, mainly due to the scarcity of their measurements. The results presented in this manuscript improve our understanding of the formation pathway of organosulfates from glycolic acid and sulfate and the role of the most stable organosulfate product in clustering with dimethyl amine and its role in NPF. The paper calls for an inclusion of organosulfate chemistry in global models when evaluating NPF and for more studies tackling hydroxyl acids in the gas phase from an observational and measurement point of view. The paper is well written and the finding are sound, I recommend publication after tackling the suggestions listed below.
General comments:
1. Could the authors comment on the role of relative humidity (availability of H2O clusters) and how these affect the formation of GAS and GASA. Please see results by Tsona et al. (https://doi.org/10.1016/j.atmosenv.2019.116921)
2. Could the authors comment on the role of coagulation sink? Eg. Line 134, it is a reasonable assumption to use the values from Hyytiälä for Mt. Tai for example?
3. The products GAS and GASA are better introduced in the main text. Could the authors move page S3 from the supplementary information to the main text in the methods section?
4. References to studies who tackled the role of organosulfates and other similar organic acids in NPF are missing e.g. Katz et al. (https://doi.org/10.5194/acp-23-5567-2023) and Zhang et al. (https://doi.org/10.5194/acp-22-2639-2022)
Technical comments:
1. In figure 3, could the authors write in the figure caption that the GA-SA-DMA lines are the same in a and b, but the y scale is different?
2. References format needs to be checked. In some cases, e.g. line 149, 150 the citation is starting the sentence.
3. Line 369, ‘sight’. I guess the authors mean ‘slight’?Citation: https://doi.org/10.5194/egusphere-2023-1649-RC1 -
AC1: 'Reply on RC1', Shi Yin, 18 Sep 2023
Thanks very much for the comments on our paper “egusphere-2023-1649”. We appreciate the referee’s valuable suggestions, agree with the referee, and have addressed referee’s all issues and questions. We list below the corresponding changes and explanations we have added to the text, as requested by the referee. A pdf version of the response is also uploaded in the Supplement.
Response to referee #1:
Referee's Comments to Author:
The manuscript entitled ‘Organosulfate produced from consumption of SO3 speeds up sulfuric acid-dimethylamine atmospheric nucleation’ by Zhang et al. presents a detailed theory of the potential role of gas-phase glycolic acid (and its organosulfate derivatives) in new particle formation (NPF). The authors rely on quantum chemical calculations to define the most reasonable pathway and formation product of the reaction between glycolic acid and SO3, leading to organosulfates. Also, kinetic modeling is used to understand the most efficient clustering with dimethyl amines. Their findings are backed up with atmospheric observations from Mt. Tai in China where intense NPF events have been observed. The authors also report observations from other locations around the world where the role of glycolic acid in NPF might be important but has been not evaluated earlier. First of all, I would like to acknowledge the authors for a very detailed, easy to follow manuscript. As mentioned by the authors, there are very few studies which tackle the role of organic acids in NPF, mainly due to the scarcity of their measurements. The results presented in this manuscript improve our understanding of the formation pathway of organosulfates from glycolic acid and sulfate and the role of the most stable organosulfate product in clustering with dimethyl amine and its role in NPF. The paper calls for an inclusion of organosulfate chemistry in global models when evaluating NPF and for more studies tackling hydroxyl acids in the gas phase from an observational and measurement point of view. The paper is well written and the finding are sound, I recommend publication after tackling the suggestions listed below.
General comments:- Could the authors comment on the role of relative humidity (availability of H2O clusters) and how these affect the formation of GAS and GASA. Please see results by Tsona et al. (https://doi.org/10.1016/j.atmosenv.2019.116921)
Author reply:
Thanks for the referee’s question and suggestions. In order to comment the role of relative humidity (availability of H2O clusters) and how these affect the formation of GAS and GASA, we further explored hydration process of glycolic acid (GA) in the gas phase, according to the method reported by Tsona et al. (Tsona and Du, 2019) at tropospheric temperatures (258 K, 278 K, 298 K) and ambient pressure. The lowest-energy structure of clusters GA-n(H2O) (n = 0 - 3) (Figure S2), equilibrium distribution of GA hydrates (Figure S3), thermodynamic data of the stepwise hydration of GA (Table S2), and relative equilibrium abundance of GA hydrates at different degrees of humidity (Table S3) were obtained and added to the revised supporting information of the manuscript. Following discussions were added to page S6 in our modified supporting information materials.
“As shown in Table S2, the first water addition to GA at 298 K, with a Gibbs free energy change of -0.71 kcal mol-1, are more favorable compared to the second and the third water additions, having free energy changes of 2.98 and 0.18 kcal mol-1, respectively. Additionally, the energies decrease as the temperature decreases, and the energy of first water addition reaches to -1.96 kcal mol-1 at 258 K. Although the abundances of hydrated GA clusters, including mono-, di- and tri-hydrates, are slightly increased with increasing RH (relative humidity) (Figure S3 and Table S3), the hydration of GA is still weak at high RH. For example, the relative equilibrium abundance of GA hydrates is less than 7% at RH = 90% and 298 K. Therefore, the relative abundance of unhydrated GA is dominant at varying temperature and RH considered.”
Following sentences were also added to line 173 in page 6 in our modified manuscript.
“These results indicate that both reaction pathways for GA + SO3 are favorable with the catalysis of H2O to generate GAS and GASA, respectively. Therefore, as the relative humidity (RH) increases, it should be conducive to the formation of GAS and GASA. The abundances of hydrated GA clusters GA-n(H2O) (n = 0 - 3) were also calculated at different RH (Figure S3 and Table S3). The relative equilibrium abundance of GA hydrates is less than 7% at RH = 90% and 298 K. Since the hydration of GA is weak, the effect of the hydrated GA clusters to the formation of GAS and GASA is not further considered.”
Figure S2 Lowest energy geometries of (GA)(H2O)n, optimized with the M06-2X/6-311++G(3df,3pd) method. The color coding is red for oxygen, grey for carbon, and white for hydrogen. The number of water molecules increases from (a) where n = 0 to (d) where n = 3.
Figure S3 Equilibrium distribution of glycolic acid hydrates at different degrees of humidity (RH = 10%, 50% and 90%) and different temperatures (258 K, 278 K, and 298 K).
Table S2 Thermodynamic data (in kcal mol-1) of the stepwise hydration of glycolic acid (GA) calculated by the M06-2X/6-311++G(3df,3pd) method.
n
ΔG
258 K
278 K
298 K
(GA)(H2O)n-1 + H2O (GA)(H2O)n
1
-1.96
-1.33
-0.71
2
1.77
2.38
2.98
3
-1.07
-0.44
0.17
Table S3 Relative equilibrium abundance of GA hydrates at different degrees of humidity (RH = 10%, 20%, 40%, 50%, 90% and 100%) and different temperatures (258 K, 278 K, and 298 K)
258 K
RH
10%
20%
40%
50%
90%
100%
n=0
0.98970000
0.97970000
0.96020000
0.95070000
0.91460000
0.90600000
n=1
0.01026766
0.02032661
0.03984325
0.04931278
0.08539284
0.09398853
n=2
0.00000006
0.00000025
0.00000098
0.00000151
0.00000472
0.00000577
n=3
0.00000002
0.00000018
0.00000139
0.00000268
0.00001504
0.00002044
278 K
RH
10%
20%
40%
50%
90%
100%
n=0
0.99050000
0.98120000
0.96310000
0.95430000
0.92070000
0.91260000
n=1
0.00948502
0.01879180
0.03689036
0.04569154
0.07934438
0.08738994
n=2
0.00000001
0.00000004
0.00000015
0.00000023
0.00000073
0.00000089
n=3
0.00000000
0.00000001
0.00000009
0.00000017
0.00000095
0.00000130
298 K
RH
10%
20%
40%
50%
90%
100%
n=0
0.99260000
0.98530000
0.97100000
0.96400000
0.93700000
0.93050000
n=1
0.00741927
0.01472926
0.02903091
0.03602716
0.06303219
0.06954867
n=2
0.00000000
0.00000000
0.00000001
0.00000002
0.00000006
0.00000008
n=3
0.00000000
0.00000000
0.00000000
0.00000000
0.00000002
0.00000003
Reference
Tsona, N. T., and Du, L.: Hydration of glycolic acid sulfate and lactic acid sulfate: Atmospheric implications, Atmospheric Environment, 216, 116921, https://doi.org/10.1016/j.atmosenv.2019.116921, 2019.
- Could the authors comment on the role of coagulation sink? Eg. Line 134, it is a reasonable assumption to use the values from Hyytiälä for Mt. Tai for example?
Author reply:
Thanks for the referee’s question. According to the reviewer’s suggestion, the following detail descriptions about coagulation sink were clarified and modified in line 153 page 6 in our revised manuscript. “A constant coagulation sink of 2.6 × 10-3 s-1 was applied to account for scavenging by larger particles. The simulations were mainly run at 278 K, with additional runs at 258 K and 298 K to investigate the influence of temperature. These conditions correspond to a typical sink value and temperature in the boreal forest environment (Olenius et al., 2013; Maso et al., 2008).” A constant coagulation sink was applied in the cluster distribution dynamics simulations to account for scavenging by larger particles. The coagulation sink used in this work is the major loss by particles in the assumed atmospheric conditions. Mt. Tai is located in northern China, and its landscape is dominated by forests. Unfortunately, we did not find the measurement coagulation sink report in Mt. Tai. We chose a constant coagulation sink coefficient of 2.6 × 10−3 s−1, which is the median condensation sink coefficient of sulfuric acid vapor on pre-existing aerosol particles, based on measurements in the boreal forest environment in Hyytiälä, Finland (Maso et al., 2007). On the other hand, the cluster size dependent coagulation sink coefficient did not have a significant effect on the steady-state cluster concentrations, according to the parametrized formula from Kulmala et al. (Kulmala et al., 2001; Kulmala and Wagner, 2001). Additionally, this coagulation sink value is widely used for a typical sink for molecular sized clusters in continental background areas (Paasonen et al., 2012), and taking into account external losses of organic compound-sulfuric acid-dimethylamine cluster system (Li et al., 2017). Therefore, we think it is a reasonable assumption to use this coagulation sink value in this work.
Reference
Maso, M. D., Sogacheva, L., Aalto, P. P., Riipinen, I., Komppula, M., Tunved, P., Korhonen, L., Suur-Uski, V., Hirsikko, A., KurtéN, T., Kerminen, V.-M., Lihavainen, H., Viisanen, Y., Hansson, H.-C., and Kulmala, M.: Aerosol size distribution measurements at four Nordic field stations: identification, analysis and trajectory analysis of new particle formation bursts, 660 Tellus B, 59, 350-361, https://doi.org/10.1111/j.1600-0889.2007.00267.x, 2007.
Kulmala, M. and Wagner, P. E.: Mass accommodation and uptake coefficients – a quantitative comparison , J. Aerosol Sci., 32, 833–841, https://doi.org/10.1016/S0021-8502(00)00116-6, 2001.
Kulmala, M., Maso, M. D., Mäkelä, J. M., Pirjola, L., Väkevä, M., Aalto, P., Miikkulainen, P., Hämeri, K., And O'dowd, C. D.: On the formation, growth and composition of nucleation mode particles, Tellus B, 53, 479-490, https://doi.org/10.1034/j.1600-0889.2001.530411.x, 2001.
Li, H., Kupiainen-Määttä, O., Zhang, H., Zhang, X., and Ge, M.: A molecular-scale study on the role of lactic acid in new particle formation: Influence of relative humidity and temperature, Atmospheric Environment, 166, 479-487, https://doi.org/10.1016/j.atmosenv.2017.07.039, 2017.
Paasonen, P., Olenius, T., Kupiainen, O., Kurtén, T., Petäjä, T., Birmili, W., Hamed, A., Hu, M., Huey, L. G., Plass-Duelmer, C., Smith, J. N., Wiedensohler, A., Loukonen, V., McGrath, M. J., Ortega, I. K., Laaksonen, A., Vehkamäki, H., Kerminen, V. M., and Kulmala, M.: On the formation of sulphuric acid - amine clusters in varying atmospheric conditions and its influence on atmospheric new particle formation, Atmos. Chem. Phys., 12, 9113-9133, 10.5194/acp-12-9113-2012, 2012.
- The products GAS and GASA are better introduced in the main text. Could the authors move page S3 from the supplementary information to the main text in the methods section?
Author reply:
We appreciated the referee’s suggestion. According to the suggestion, we moved the page S3 to the methods section of main text in our revised manuscript.
- References to studies who tackled the role of organosulfates and other similar organic acids in NPF are missing e.g. Katz et al. (https://doi.org/10.5194/acp-23-5567-2023) and Zhang et al. (https://doi.org/10.5194/acp-22-2639-2022)
Author reply:
Thanks for the referee’s comments. According to the suggestion, we have read articles, introducing the role of organosulfates and other similar organic acids in NPF by Katz et al. and Zhang et al. The following sentences and references were added to line 37 and line 51 page 2 in the Introduction part of the revised manuscript, respectively.
“Organosulfates have been identified as the most abundant class of organosulfur compounds, accounting for 5-30% of the organic mass fraction in atmospheric particles (Brüggemann et al., 2017; Tolocka and Turpin, 2012; Shakya and Peltier, 2015; Froyd et al., 2010; Mutzel et al., 2015; Glasius et al., 2018). Katz et al. measured the presence of organosulfates and identified its importance to new particle formation (Katz et al., 2023).”
“Organic acids, which are frequently observed in the atmosphere, have been expected to participate in the process of atmospheric nucleation, with a focus on the thermochemical properties of clusters between organic acids and common atmospheric nucleation precursors (Zhang et al., 2022).”
Reference
Brüggemann, M., Poulain, L., Held, A., Stelzer, T., Zuth, C., Richters, S., Mutzel, A., van Pinxteren, D., Iinuma, Y., Katkevica, S., Rabe, R., Herrmann, H., and Hoffmann, T.: Real-time detection of highly oxidized organosulfates and BSOA marker compounds during the F-BEACh 2014 field study, Atmos. Chem. Phys., 17, 1453-1469, https://doi.org/10.5194/acp-17-1453-2017, 2017.
Tolocka, M. P., and Turpin, B.: Contribution of organosulfur compounds to organic aerosol mass, Environ. Sci. Technol., 46, 7978-7983, https://doi.org/10.1021/es300651v, 2012.
Shakya, K. M., and Peltier, R. E.: Non-sulfate sulfur in fine aerosols across the United States: Insight for organosulfate prevalence, Atmos. Environ., 100, 159-166, https://doi.org/10.1016/j.atmosenv.2014.10.058, 2015.
Froyd, K. D., Murphy, S. M., Murphy, D. M., de Gouw, J. A., Eddingsaas, N. C., and Wennberg, P. O.: Contribution of isoprene-derived organosulfates to free tropospheric aerosol mass, Proc. Natl. Acad. Sci. U.S.A., 107, 21360, https://doi.org/10.1073/pnas.1012561107, 2010.
Mutzel, A., Poulain, L., Berndt, T., Iinuma, Y., Rodigast, M., Böge, O., Richters, S., Spindler, G., Sipilä, M., Jokinen, T., Kulmala, M., and Herrmann, H.: Highly Oxidized Multifunctional Organic Compounds Observed in Tropospheric Particles: A Field and Laboratory Study, Environ. Sci. Technol., 49, 7754-7761, https://doi.org/10.1021/acs.est.5b00885, 2015.
Glasius, M., Hansen, A. M. K., Claeys, M., Henzing, J. S., Jedynska, A. D., Kasper-Giebl, A., Kistler, M., Kristensen, K., Martinsson, J., Maenhaut, W., Nøjgaard, J. K., Spindler, G., Stenström, K. E., Swietlicki, E., Szidat, S., Simpson, D., and Yttri, K. E.: Composition and sources of carbonaceous aerosols in Northern Europe during winter, Atmos. Environ., 173, 127-141, https://doi.org/10.1016/j.atmosenv.2017.11.005, 2018.
Katz, D. J., Abdelhamid, A., Stark, H., Canagaratna, M. R., Worsnop, D. R., and Browne, E. C.: Chemical identification of new particle formation and growth precursors through positive matrix factorization of ambient ion measurements, Atmos. Chem. Phys., 23, 5567–5585, https://doi.org/10.5194/acp-23-5567-2023, 2023.
Zhang, R., Shen, J., Xie, H. B., Chen, J., and Elm, J.: The Role of Organic Acids in New Particle Formation from Methanesulfonic Acid and Methylamine, Atmos. Chem. Phys. Discuss., 2021, 1-18, https://doi.org/10.5194/acp-2021-831, 2022.
Technical comments:
- In figure 3, could the authors write in the figure caption that the GA-SA-DMA lines are the same in a and b, but the y scale is different?
Author reply:
Thanks for the referee’s suggestion. In our modified manuscript, we made a detailed description in the figure caption of Figure 3 that the GA-SA-DMA lines are same in a and b, but the Y-axis scale is different.
Figure 3. Simulated cluster formation rates J (cm-3s-1) as a function of monomer concentrations ([GA], [GAS], and [GASA], respectively) at (a) (b) 278 K and (c) (d) 258 K under the condition of [DMA] = 108 molecules cm-3 and [SA] = 105 molecules cm-3. Note that the simulated JGA-SA-DMA are the same data, but the Y-axis scale are different at (a) (b) and (c) (d), individually.
2. References format needs to be checked. In some cases, e.g. line 149, 150 the citation is starting the sentence.Author reply:
Thanks for the referee’s comment. According to the comment, we made an effort to check and correct all reference format in our modified manuscript. The sentence of line 149,150 “With high abundance (~1017 cm−3) being detected in the troposphere,(Huang et al., 2015) H2O has been reported to effectively act as a catalyst in chemical reactions.(Liu et al., 2019)” was corrected to “With high abundance (~1017 cm−3) being detected in the troposphere (Huang et al., 2015), H2O has been reported to effectively act as a catalyst in chemical reactions (Liu et al., 2019).” in line 169 page 6 of our revised manuscript.
- Line 369, ‘sight’. I guess the authors mean ‘slight’?
Author reply:
Thanks for the referee’s suggestion. According to the suggestion, we corrected the above spelling error. The sentence of “Given the fact that GA has only a sight influence on the nucleation and growth processes of atmospheric clusters, the reaction between GA and SO3 may provide a secondary source of the potential precursor since high concentrations of sulfur oxides being detected.” in line 394 page 15 was corrected to “Given the fact that GA has only a slight influence on the nucleation and growth processes of atmospheric clusters, the reaction between GA and SO3 may provide a secondary source of the potential precursor since high concentrations of sulfur oxides being detected.” in our revised manuscript.
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AC1: 'Reply on RC1', Shi Yin, 18 Sep 2023
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RC2: 'Comment on egusphere-2023-1649', Anonymous Referee #2, 14 Sep 2023
The paper investigates if organic acids, organic sulfates or organic sulfuric anhydrides could enhance new particle formation driven only by sulfuric acid (SA) and dimethyl amine (DMA). The authors present quantum chemical calculations of the reaction of SO3 with glycolic acid to glycolic acid sulfate (GAS) and glycolic acid sulfuric anhydride (GASA). They demonstrate that the addition of a catalyst (e.g. water) makes this reaction almost barrierless and thus could be a potential pathway to form GAS and GASA in the gas phase. Furthermore, lowest free energy structures of (GA)x-(SA)y-(DMA)z, (GAS)x-(SA)y-(DMA)z, and (GASA)x-(SA)y-(DMA)z clusters, their formation Gibbs Free Energies and evaporation rates have been calculated. It is shown that (GA)x-(SA)y-(DMA)z clusters are least stable, while mixed clusters with GAS and GASA are similar to or more stable than pure SA-DMA clusters. In a next step the authors calculate mixed cluster formation rates and determine an enhancement effect of GAS on SA-DMA driven new particle formation (NPF). Cluster growth pathways are then shown for different concentrations of SA, GAS and DMA. Finally, the authors compare their theoretical results with ambient observations at Mount Tai in China and conclude, that GAS could explain deviations between pure SA-DMA driven NPF and observations. Furthermore, they propose that the formation of organosulfates by this gas phase reaction may be a source of organosulfates often observed in secondary organic aerosols.
The first part of the manuscript including the quantum chemical calculations of the thermodynamic parameters of the organosulfates, as well as the mixed cluster geometries and stabilities is fine. However, the second part has some serious issues. There are no quantitative measurements of GAS and GASA in the atmosphere. Thus, the authors assume for SO3 a concentration of 105 cm-3 and a range of measured ambient GA concentrations to calculate potential equilibrium concentrations for GAS and GASA. GASA levels would be negligibly small while GAS concentrations could reach 103-105 cm-3. The authors do not give a reference for their assumed SO3 concentration of 105 cm-3. In fact, SO3 is very rapidly converted by water vapor to sulfuric acid, which in turn is condensing on aerosol. Let’s assume a condensation sink for SA of 0.01 s-1, k(s-1) = 3.90 x 10-41 exp(6830.6/T)[H2O]2 (J.Phys. Chem. A 1997, 101,10000-10011), [H2O]= 2.1017 cm-3, an SO3 level of 105 cm-3 would then yield a steady state concentration of SA = 5.6 ppb. Ambient SA levels are at least a factor 1000 lower. Therefore, possible GAS concentrations would be much lower in the ambient. Furthermore, SO3 and SA scale with each other. It is very unlikely that [SO3]=[SA]=105cm-3 as assumed in Figure 3. The simulated cluster formation rates in Figures 3 and S6 are only a theoretical exercise but not at all relevant for ambient conditions.
The authors also argue that measured new particle formation rates at Mt. Tai could not be explained by pure SA-DMA nucleation. For the comparison the authors use theoretical NPF-rates from ACDC calculations at a cluster size of only about 1.2-1.4 nm, while the measurements were made at 3 nm. The authors apparently assume that the nucleation rate at the two different cluster sizes should be the same. That is not at all the case. J(3nm) is probably more than a factor of 10 slower than J(1.3nm) (see e.g. Xiao et al., ACP 21, 14275–14291, 2021). Thus, this comparison does not provide evidence that GAS could explain the fast NPF rate.
Overall, I think the second part of the paper about the potential role and importance of GAS for ambient NPF is untenable. I do not see how this hypothesis could be substantiated. Since the first part is only QC calculations, I think the first part alone is not suited for ACP.
Minor comments
Line 57: it is not proven so far that SO3 is a major oxidant in the atmosphere. It is also not emitted but formed as an intermediate species through oxidation of SO2.
Figure 3: For J rates you should say at what cluster size they have been calculated
Line 311: high mountain sites and polar regions are usually not places with high amine concentrations, do you have references?
Figure S1: there is no red line. The blue line should read green. “the pathway to form H2SO4 with as a catalyst” should read “the pathway to form H2SO4 with H2O as a catalyst”
Table S1: how do you get the ΔG values from Figure 1?
Citation: https://doi.org/10.5194/egusphere-2023-1649-RC2
Xiaomeng Zhang et al.
Xiaomeng Zhang et al.
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