the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Biogenically driven marine organic aerosol production over the Northwest Pacific Ocean
Abstract. Marine organic aerosols play crucial roles in cloud formation and climate regulation within the marine boundary layer. However, the abundance of marine primary organic carbon (MPOC) emitted from marine bubble bursting or secondary organic carbon (MSOC) formed via gas-to-particle conversion remains poorly quantified, which hinders our understanding on the climate effects of marine aerosols. In this work, two shipboard cruises were conducted over the Northwest Pacific Ocean to estimate abundance and compositions of marine organic aerosols. We propose an observation-based approach to quantify the MPOC and MSOC using combined parameterization of the observed Na+ in fine aerosol particles and the surface chlorophyll-a, an indicator of marine biological activity. The parameterization approach was validated through comparing with the water-insoluble organic carbon in the aerosol samples. The estimated MPOC averagely accounted for 56 %−66 % of the total organic carbon in the collected marine aerosol samples, which was mainly attributed to the protein-like substances transferred into the sea spray aerosols from seawater. Over the Northwest Pacific Ocean, the MPOC and MSOC displayed peak concentrations over the regions 5° S–5° N and 35° N–40° N. The variation and spatial distribution of MPOC and MSOC along the latitude were driven by the marine biological activities. High MSOC concentrations were also observed over the region of 15° N–20° N, which was due to an additional contribution by the oxidation of volatile organic precursors from the photochemical production of seawater organics. This study proposes a parameterization approach to quantify the MPOC and MSOC over the Pacific Ocean or other oceanic areas. Our results highlight the marine biogenically driven formation of marine organic aerosols and different quantitative relations of MPOC with seawater chlorophyll-a and other parameters are needed based on the in-situ observations across oceanic regions.
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Status: open (until 17 Oct 2025)
- RC1: 'Comment on egusphere-2025-3951', Anonymous Referee #1, 23 Sep 2025 reply
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RC2: 'Comment on egusphere-2025-3951', Anonymous Referee #2, 07 Oct 2025
reply
Review Report of the manuscript titled "Biogenically driven marine organic aerosol production over the Northwest Pacific Ocean by Yujue Wang et al., ( MS No.: egusphere-2025-3951 MS type: Research article)
General Comment: This paper is based on the analysis of PM2.5 samples collected over the Northwest Pacific Ocean during two campaigns in the spring season during 19 Feb.−9 April, 2022, and in the summer during 19 June−30 July, 2022. The chemical composition data have been investigated to the spatial/regional variability but mainly of Marine organic aerosol (MOA) fractions (WSOC and WIOC, primary and secondary), and Chl-a data as a supporting parameter. While the paper presents a quality data set, the discussion of the results is not up to mark. The basis or tracer data is not enough to quantify the contributions of WSOC and WIOC, primary and secondary to MOA. Another concern is the ignoring/undermining of the impact of terrestrial biogenic outflow on the OC levels and their composition. Though the impact of long-range transport is mentioned, evidence (like back trajectory analysis) is not provided. The data have been further utilised to parameterise the marine sources. But it is not well presented or summarized how seasonality in sea surface parameters and prevailing environmental conditions could impact the seasonal MOA composition. Further, following specific comments provide the issues to be addressed.
Line 57-58: "regions with high emission rates of MOA are largely related to the spatial" Why high emissions rates only? You may revise "regional emission rates of MOA are largely related to the spatial"
Line 60: "Due to the relationship between sea surface phytoplankton and MOA" I feel this phrase is not required.
Line 64: "Observation-based parameterization..." Provide a reference to support this sentence.
Line 77: As shown in Figure 1(a) the track covers between 02S-34 N, so it would be appropriate to mention the region as "Northwest Pacific Ocean"? covering southern latitudes
Line 80-81: "suspended particles (TSP) samples and PM2.5" can be revised as "suspended particles (TSP) and PM2.5"
Line 114: "observation, and" should be "observation and"
Figure 1(b) . I suggest to mention the year of the campaigns. You may provide a common x-axis title as (Date/Year).
Line 131: "r = 0.67, p < 0.01, Fig. 1)," r= 0.67 may not represent a strong correlation. Also I dont find correlation plots in Figure 1, perhaps referring to Fig 2?
Line 136: But how about the impact/outflow of terrestrial biogenic emissions. ?
Line 138-139: "spring 138 (0.09 ± 0.06 μg L-1) than in summer (0.07 ± 0.05 μg L-1)." I think the values are not very different. So the explanation for the differences in OC levels is not robust. I feel the transport from regions of Papua New Guinea and Indonesia needs a consideration. Following works may provide more insights.
https://doi.org/10.1038/s41612-022-00311-0
https://doi.org/10.5194/essd-15-5403-2023
Line 141-142 and other places: "mass ratios of 70% ± 27% in spring and 48% ± 35% in" should be "mass ratios of 70 ± 27% in spring and 48 ± 35% in"
Line 145: "WSPC in marine aerosols." should be "WSOC in marine aerosols."
Line 147-148: "and transferred to atmospheric aerosols over the ocean." Rewrite with a better phrase.
Line 152: "marine reactive organic gases (Boreddy et al., 2018; De Jonge et al., 2024; Miyazaki et al., 2010)." Here I would suggest citing studies which provide measurements of reactive trace gases implying the roles in SOA in marine air. Following works may be cited:
Sources and distribution of light NMHCs in the marine boundary layer of the northern Indian Ocean during winter: Implications to aerosol formation. Journal of Geophysical Research: Atmospheres, 129, e2023JD039433. https://doi.org/10.1029/2023JD039433
Elevated levels of biogenic nonmethane hydrocarbons in the marine boundary layer of the Arabian Sea during the intermonsoon. Journal of Geophysical Research: Atmospheres, 125, e2020JD032869. https://doi.org/10.1029/2020JD032869..
Further, in this section, I suggest comparing the composition of WSOC, WISOC, and other species presented in typically continentally influenced air over this region. The following work may be useful in this regard (It would be good if you can find some other similar works and highlight those)
Anthropogenic aerosols observed in Asian continental outflow at Jeju Island, Korea, in spring 2005, J. Geophys. Res., 114, D03301, doi:10.1029/2008JD010306.
Line 155: "..through the ocean bubble bursting." why through bubble bursting only as other air-sea exchange processes can also contribute?. Please explain and revise accordingly.
Line 158-160: "in th present .." I think similar discussion is presented in previous section (line 143-144). I suggest to concise the discussion related to correlation in one section only.
Line 170: "concentrations of OC or WIOC in PM2.5 did not show obvious correlations with" I disagree here. The levels OC and WIOC tend to decrease rapidly with wind speed (may not be linear). The discussion should be based on dependencies or trend (with Chl-a and wind speed) but not strictly in terms of correlation/ anti-correlation (as data points are scattered)
Line 172: "which was due to the elevated proportions of inorganic sea salts in the marine aerosols under the high-wind" This justification is not convincing. That can change only the magnitude of the slope but not the direction (positive/negative), check.
Line 185: "Under certain marine environment conditions (e.g., Chl-a, wind speed, SST etc.)," What is certain here , as values of these parameters are not given. And why MPOC should be constant anyway?
Line 188: "Based on the shipboard observations in present study," Should be "In the present study,"
Line 191: "contribution of SOA (e.g., methanesulfonic acid from DMS oxidation," Check if DMS oxidation provides SOA, I know it gives sulfate. But then do you consider sulfate as SOA ? Check following and other papers on DMS
Processes controlling DMS variability in marine boundary layer of the Arabian Sea during post-monsoon season of 2021. Journal of Geophysical Research: Atmospheres, 130, e2024JD042547. https://doi.org/10.1029/2024JD042547
Line213-214: "Based on the correlation analysis above," should be "Based on the correlation analysis"
Line 215-219: "In the classic OC/EC ratio method...Yu et al., 2021)." These sentences appear out of context , may be removed.
Figure 4 (a-d): Y-axis should be Latitude . Also check Fig 4 (e-f) if axes titles are correct (latitude /longitude or vice versa) .
Line 272:"high concentrations over the oceanic regions among 5°S–5°N and 35°N–40°N," Here for these two region, why the contributions from the land vegetation should also be discussed (due to vicinity to land/island regions)
LIne 279-280" "from surface seawater as well as the production of biologic VOCs (e.g., isoprene, DMS, etc.) from phytoplankton" should be revised as "from seawater as well as the production of VOCs from phytoplankton" but again terrestrial contributions should be discussed.
Line 284-286: "The strong.." This sentence seems speculative also Chl-a map does not support this localized feature.
Citation: https://doi.org/10.5194/egusphere-2025-3951-RC2
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This study presents a very detailed analysis of the organic aerosol fraction in the marine atmosphere. The author made efforts to try to find a better way of parameterizing the primary and secondary OC in marine aerosols using common measurements of seawater (chl-a and Na+). However, it is not clear about the main conclusion of applying the proposed new method and its performance. Key gaps in interpreting the fluorescent components are missing. I expect further elaborations on these issues together with other major comments. Please see the following comments for details.
Major comments:
How about the primary OC and gas precursors transported from the terrestrial environments?
In summary, it is unclear what does “marine” mean here. Does it only refer to marine atmosphere?
Minor comments: