the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 04 Jul 2025
Atmospheric new particle formation in the eastern region of China: a mechanistic investigation at multiple sites
Abstract. As a major source of cloud condensation nuclei, atmospheric new particle formation (NPF) events exert significant influences on the global climate. Among the various nucleation mechanisms that have been identified in diverse environments, sulfuric acid-amine nucleation is unique for its high efficiency to form stable clusters and drive intense nucleation. Despite the fact that this nucleation mechanism could explain observed NPF events at a number of megacity sites in China, its applicability to a larger regional scale remains unclear. Here, we analyzed characteristics of NPF events and influencing factors at three suburban sites in the eastern region of China based on measured and theoretically predicted particle formation rates and cluster concentrations. Results show that sulfuric acid-dimethylamine is a predominant nucleation mechanism at these sites, while atmospheric conditions including precursor concentrations and temperature causes the differences in NPF characteristics among different sites. This indicates the significance of the sulfuric acid-amine nucleation mechanism over a large spatial scale in the urban agglomerations in the eastern region of China. We also find that oxygenated organic molecules are likely involved in the formation of 1.7-nm new particles at these sites by contributing the initial growth of stable sulfuric acid clusters.
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RC1: 'Comment on egusphere-2025-2787', Anonymous Referee #1, 12 Aug 2025
This paper describes results from atmospheric nucleation studies in Chinese cities and its technical aspects appear to be at the state of the art in this area. While the manuscript is admirably succinct, it also admirably touches on all (at least most) of the aspects of the important information. Yet there are sentences that are difficult to understand, and it seems that some inferences and conclusions are not well-supported (the first may be causing some of the second.) The main conclusion of the paper is that H2SO4-DMA nucleation can explain the observations in these cities. A secondary one is that OOMs are needed to explain growth rates of newly nucleated particles. Â
Support for the main conclusion is not well presented. For example, line 165 states that SA-DMA was 'identified ' as the dominate (sic) NPF mechanism. This is not a finding if it is solely based on Figure 1 (correlation and causation are falsely linked.) The analysis presented in section 3.2 is focused on teasing out SA and temperature dependencies. Should not a dependence on DMA be important for identifying SA-DMA nucleation? Figure S3 is mentioned as supporting the SA-DMA mechanism but on the face of it the J_1.4 sim.-meas. correlation is not good. Similarly for J_1.7 (figure 7b). For both of those, it looks like the measurements range over about 1/2 the orders of magnitude that the simulations do: this is not support for the mechanisms in the simulations. Assuming SA dimer is an indicator of SA-DMA nucleation, the best support is Figure 4 but SA_2 scaled is not presented here (confused by the text on lines 220-224.) Figure 5 does present SA_2 scaled instead. Good: it does show a decently strong temperature dependence (would be helpful to have data in Figure 4 colored by temperature also.) But two things are bothersome in this analysis:  the above-mentioned dependence on DMA is washed away and details are scant on the reason behind the temperature dependence of the simulations (bond strength, and only for the SA.DMA cluster?)Â
Figure 2 also gives good indirect support to the (or a) SA-DMA mechanism but can the SA3 and SA4 signals be correlated to neutral cluster concentrations ? They are the ones with DMA in them! This would be support of a more direct nature. Also, this figure needs a bit more explanation. What is/are S-O ions? Symbol size meaning diameter or area? Since the plots are relatively clean, a few could be tagged with logSignal values. Â
Sentence on line 245 talks about dependence on DMA and mentions Figure S4 but that figure shows no (or even inverse!) difference in [DMA] between events and non-events.
There are many sentences with strange wording choices e.g. in paragraphs such as lines 59-70, lines 138-150 (also, this scaling procedure leaves the reader a bit uneasy).Â
Lines 304-315 in the conclusions are accurate and reflect the indirect nature of the evidence for SA-DMA nucleation but what does this paper add to what is already there? It seems the present day tools are inadequate to directly resolve the question. What should be improved? Looking for some more strongly worded conclusions.
Citation: https://doi.org/10.5194/egusphere-2025-2787-RC1 -
RC2: 'Comment on egusphere-2025-2787', Anonymous Referee #2, 29 Aug 2025
The paper by Jin et al. examines the role of different molecules in NPF at various sites in China. While the authors provide valuable measurements of ammonia and amine concentrations—data that are otherwise scarce—the presentation of their work and the evidence supporting their conclusions are weak. In its current form, the paper does not add substantial new findings to the literature, although the analysis of temperature effects on DMA concentrations and clustering is novel, interesting, and important. However, the manuscript often reads as if it is written primarily for scientists within China, as it includes almost no comparisons with sites outside of China (with one unclear exception). The same issue arises with self-citations, which dominate the references to existing literature. In several cases, conclusions are drawn from figures where the evidence is either unclear or missing. The title also does not accurately reflect the paper’s findings. In addition, the manuscript is difficult to follow, with several contradictory statements. I recommend that the authors substantially revise the manuscript: clarify the contradictions, sharpen the focus on their novel findings, and compare their results to observations from outside China. It is also essential to strengthen the methods section so that the results can be reproduced in other locations. Below, *some* specific comments are listed.
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Specifically:
- Article needs general grammar check e.g.
Line 25: ‘causes’ to be changed to ‘cause’ or ‘result in’
Line 67: sentence starting with ‘In particular,’ needs modification
Please make sure to use a consistent verb tense throughout the manuscript. - A map of the sites, including distances and major emission source locations (if possible), could benefit the readers. Please add it to the supplementary material.
- Line 85, is it the same mass spectrometer moved between the locations? How are the authors sure that the moving of the spectrometer does not affect the calibration factor and m/z calibration.
- Line 89: I suggest to the authors to add details about the measurements of amines using the ToFs since these are new types of measurements, and it would be good to make the method reproducible.Â
- Line 94: More info on the IC measurements is needed since the text is not available in English.Â
- Line 124: please list the different errors
- Table 2: Data source is misspelled
- How does the frequency of NPF events differ between the sites?
- Line 164-165: The statements need clarification; how can the authors be sure that the mechanism is DMA-SA driven although they mention that it is unclear whether OOMs and NH3 participate in the nucleation.Â
- Figure S2 does not support this conclusion, how do the authors explain the higher DMA and NH3 on non-NPF days?
- Figure 2: are the shown molecules the only ones observed in the CIMS, or did the authors use a specific filter for the other peaks?
- Line 200: why do the authors think that CS affects NPF at the measured locations but not in the PoValley?
- Line 200: this is the first (and only) mention of a location outside of China. The authors are encouraged to widen the comparison to polluted locations outside of China, and to refer to studies of other groups working on the topic.Â
- Line 202: do these vapors affect the growth, or intensity of nucleation? Please clarify.Â
- Line 210: please clarify the role of temperature, did it influence the intensity, occurrence, or concentration of vapors?
- Line 292: contradicts lines 164-165, please clarify.
- Line 314: Do the authors mean that the production of SA depends on SO2, and not the other way around?
- Figure S7: What information do the authors infer from the volatility distribution? There is too little text explaining this figure in the manuscript. If there is no use of this figure (or data) elsewhere, the authors are encouraged to remove this part from the manuscript.
Citation: https://doi.org/10.5194/egusphere-2025-2787-RC2 - Article needs general grammar check e.g.
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