(1) My major concern lies within the question of the sensitivity of the instrument. Regarding the detection limits of the instruments and partly some time ranges where concentrations were below the LOD, I am wondering how applicable is the method for amine measurements in low concentrated (e.g. remote marine) areas. The concentrations reported here are in part significantly higher that reported in other marine regions and I think with the LODs of the here applied method, the amines would not be detectable. Please comment on the limits of the here presented technique! In this context, please compare the concentration values achieved here with literature data (especially of marine locations).

 

Response: Thank the comments. The limits of detection (LOD) for ions in AIM-IC are largely adjustable and almost completely determined by the user-chosen volume of the loop installed on the low-pressure injection valve. We adopted the loop volume at 250 -2000 μL for measurements in different atmospheres to lower the LOD and gain reasonably accurate concentrations of these species. In this study, 250 μL loop was used by considering that high NH_3gas concentrations may occur in the marine atmosphere. The information has been added in the revision. The reviewer’s comments are valid by considering measurements made by the use of the deputy loop volume.   

 

In the revision, more comparisons with those values reported in the literature had been added. For example, Gibb et al.(1999) measured DMA_gas and TMA_gas on November 16 to December 19 in 1994 over Arabian Sea, which were 8.8 ng m^-3 and 0.48 ng m^-3 respectively. The values were approximately one-two orders smaller than the concentrations of DMA_gas and TMA_gas measured in this work. Including the concentrations of DMAH⁺ and TMAH⁺ in atmospheric particles reported by Gibb et al. (1999), we also made tens of cruise off-line measurements of DMAH⁺ and TMAH⁺ in size-segregated atmospheric particles. Their concentrations varied largely from a few ng m^-3 to ~1 μg m^-3 in PM₁₀. The comparison has also been added in the revision.  

 

(2) Line 20 “we identified marine emissions of the gas species originating from continental transport…” sounds confusing. Is it marine or continental? Please clarify (and shorten the sentence) 

 

Response: We have changed the word “identified” into “differentiated”.

 

(3) Line 35: please add which numbers (16%, 34%) belong to which species.

 

Response: We have added the corresponding species in the revision.

 

(4) The introduction mixed amine sources in seawater and in the atmosphere. Please be more correct. For example, the first sentence of the intro states that the atmospheric amines are derived from the degradation of glycine betanine…. But the latter processes happen in the seawater (not in the atmosphere as appears from the sentence). 

 

Response: Thank you. The sentence is indeed confusing and corrected in the revision.

 

(5) Line 57: Please explain, why this is not the case for the continental atmosphere.

 

Response: The sentence has been revised as “However, measuring gaseous amines in real-time simultaneously to their particulate counterparts in the marine atmosphere over the ocean remains challenging because of artifact signals related to self-vessel emissions and amine-contained dew evaporation from outside surfaces of the vessel with sunrise in morning, although this is not the case in the continental atmosphere (VandenBoer et al., 2011).”

 

(6) Line 82: Do you mean, that 1) higher concentration levels of nutrients result in higher concentrations of amines?

 

Response: This is what we expected prior to the study. Yes. We have added the description for explanation. In the revision, it has been revised as “Winter cruise campaigns provide great opportunities for observational studies due to the 1) higher concentration levels of nutrients in the seas at a lower sea surface water temperature which may emit a large amount of gaseous amines and/or particulate aminium-contained sea spray aerosols from the seas (Guo et al., 2020);”

 

(7) Line 83: why is 3) “… periodically enhance long-range transport…” an advantage here?

 

Response: In the revision, it has been revised as “periodically enhanced long-range transport of anthropogenic pollutants from continents to the seas which may enhance formation of secondary ammonium and aminium aerosols (Guo et al., 2016; Wang et al., 2019).”

 

(8) Line 89: unclear expression: “identifying marine sources from continental transport…” do you mean distinguish the sources?

 

Response: Yes. Corrected to “distinguishing” in the revision.

 

(9) Line 118: in Context with my main comment: please give the LOD converted to the atmospheric measurements (in µg/m^3)

 

Response: The limit of detection of NH₄⁺, DMAH⁺, and TMAH⁺ were 0.4, 4 and 2 ng m^-3 in ambient air, respectively.

 

(10) Line 150: is 0.002 µg/m^3 the LOD?

 

Response: Yes. The data of 0.002 µg m^-3 was the average values of TMA which approached the LOD of TMA.

 

(11) Line 155: “extremely low” please be more precise here and give numbers. Also, please compare with other published amine measurements in marine regions (see main comment).

 

Response: In the revision, it reads as “The TMA_gas and TMAH⁺ concentrations at 0.002±0.001 μg m^-3 in the upwind continental and coastal atmospheres were much lower than most of observed values over tens of ng m^-3 reported in the literature. However, Gibb et al. (1999) reported even lower values of TMA_gas (0.5 ng m^-3) and particulate TMAH⁺ (0.5 ng m^-3) in the marine atmosphere over Arabian Sea on November 16 to December 19 in 1994.”

 

(12) Line 161: Explain the amines in relation to “onshore” and “offshore” winds more detailed and refer to the corresponding Figures.

 

Response: To be clear, the sentence has been changed to “The DMA_gas and DMAH⁺ in PM_2.5 concentrations with north offshore winds were substantially higher than those with south or southeast onshore winds (Fig 1), suggesting that their continental emissions and related secondary sources were stronger.” in the revision.

 

(13) Line 175: I am wondering if the times when the concentrations were below LOD are included in the given average values (e.g. for example setting the concentration to ½ LOD for times when the analytes could not be detected). Otherwise the mean data represent too high concentrations. A Table listing the mean (min-max) values for the gas and particulate amines for the different “campaigns” would help.

 

Response: The concentrations below LOD are included in the given average values. The min-max values have been added in the revision. 

 

(14) Line 185: From Fig.1 is looks as if DMA_gas shows a similar behaviour as TMA_gas. Please show the correlations reported in this passage (e.g in the supporting information). Otherwise, the differences between TMA_gas and DMA_gas are not easily understandable.

 

Response: In the revised SI, the correlations between TMA_gas and DMA_gas were added in SI, in which three periods such as Peak 1, Peak 2 and Peak 3 were highlighted in different markers. 

 

(15) Line 192: Please define “campaign A” and “campaign B” and the “costal station” more concise. Use the same descriptions concerning these separate “campaigns” consistently in the text and in the Figures. 20-22. Dec is “campaign B” = “port-anchoring period”?

 

Response: Agree. Revised accordingly. Campaign A was conducted on 9-19 December, 2019. Port-anchoring occurred on December 19-22. Campaign B started from 27 December, 2019 to 17 January, 2020, organized by another research team.

 

(16) Line 227/228: Do these references state that the amines (or TMA) are transferred via primary sea spray? Please state this more clear. Connected to this: has a primary sea spray transfer (Line 236) been shown for (gaseous and/or particulate) amines?

 

Response: The sentence has been revised as “This suggests that the observed TMAH⁺ may not be derived from the neutralization reactions of TMA_gas with acids in the marine atmosphere, and may have been derived from primary sea-spray organic aerosols (Hu et al., 2015, 2018). Primary sea-spray organic aerosols mainly contained primary and degraded organics (Ault et al., 2013; Prather et al., 2013; Quinn et al., 2015; Dall’Osto et al., 2019).”

 

(17) Line 256: It is highly speculative to comment on changing amine concentrations in the seawater, if such values were not measured. What means not “directly”? Same for line 265

 

Response: Agree. The regression equation can allow to argue the emission potential, but it is highly speculated to argue the concentrations of TMAH⁺ concentrations. In the revision, the sentence has been revised as “However, the measured concentrations of TMAH⁺ and seawater pH in the surface seawater were needed to confirm this”.

 

(18) Line 270: What is meant with “scenarios”? Do you mean “hypothesis”? Please explain. 

 

Response: Hypothesis is better and used in the revision.

 

(19) Line 278: What is meant with “increasing” and “decreasing” period? 

 

Response: The sentence has been clarified as “The purple-red and dark-green markers represent the data obtained at 10:00 on 14 December - 22:59 on 16 December with increasing concentrations and at 23:00 on 16 December -19:59 on 17 December with decreasing concentrations of the species during Peak 3, respectively, which were analyzed separately.”

 

(20) Line 276 and following (chapter 4.2 and 4.3): I find it difficult to follow and understand the estimations and conclusions from the given information. I suggest adding some more details. Why is it justified to estimate the DMA_gas in this way? This part is very descriptive and little explanatory. For example: The good correlation is mentioned (Line 280) but what can be concluded from that and why? What is the explanation that TMAH⁺ decomposed into DMAH⁺ (Line 283)? I have the feeling that the interrelationships and conclusion in 4.2 and 4.3 should be elaborated more strongly. The connections were much better illustrated in chapter 4.4.

 

Response: We had revised two parts accordingly to clarify our approaches and findings. 

 

(21) Line 360: Did you exclude emissions of seabirds because the peaks were persistent for a long time under strong winds? Or what else is the reason? If so, maybe add “.. were therefore unlikely to be derived…” (Line 361) 

 

Response: Agree and revised accordingly.

 

(22) Line 362: why “alternatively”? 

 

Response: The word has been removed.

 

(23) Line 369: undetectable chemical conversion? What is meant by that?

 

Response: It has been revised “Chemical conversion of particulate TMAH⁺ by AIM-IC likely occurred and the products were undetectable by the AIM-IC. This requires further investigation.”

(1) Between lines 140-145, the comparison was made between two different time periods and this might be meaningless unless the authors can provide strong rationale to do so. Also, conclusions made on the origin of the particulate TMAH⁺ between lines 177-178 were based on similar comparison. Can the authors be sure that the TMAH⁺ concentration was highest in summer than in any other seasons?

 

Response: The measurement data at the same coastal site during the period on November 15 to December 1 in 2019, two weeks before the campaign, were added in supplement material. The data also showed that the concentrations of TMA_gas were extremely low and close to the limit of detection. The corresponding concentrations of TMAH⁺ observed were also extremely low and mostly undetectable during the cold period. Both the summer and the cold season data allow to draw the conclusion, i.e., the continental transport of TMA_gas and particulate TMAH⁺ to downwind marine atmosphere was likely negligible.

 

(2) What are the backgrounds or interferences for both NH₃ and NH₄⁺, the gaseous amines, aminum from the URG and potentially affect the measurement results?

 

Response: We speculate that the comments related to the deputy loop volume installed on the low-pressure injection valve. The limits of detection (LOD) for ions in AIM-IC are largely adjustable and almost completely determined by the user-chosen volume of the loop. We adopted the loop volume at 250 -2000 μL for measurements in different atmospheres to lower the LOD and gain reasonably accurate concentrations of these species. In this study, 250 μL loop was used by considering that high NH_3gas concentrations may occur in the marine atmosphere. The information has been added in the revision. 

 

In our measurements, the major interference to aminium measurements was derived from the unexpected occurrence of K⁺ interference. This had been mentioned in the method section and more data has been added in the revision. 

 

Since 2014, we tried to measure NH_3gas and amine gases in various marine atmospheres. However, no reasonable data can be gained until 2018. We combined multiple NH_3gas analyzers and off-line denuder samplings during two cruise campaigns in 2016-2017, and found dew evaporation on the vessel surface with sunrise in the morning to be the major positive sampling artifacts of these basic gases. To solve the problem, we designed a specific container to house the AIM-IC and set the container on the front deck, where human activities were rare, to measure NH₃, DMA_gas, TMA_gas and their particulate counterparts in PM_2.5. The approach works well based on simultaneous measurements made by the AIM-IC and denuder samplers in other cruise campaigns. In addition, we made intercomparison between the AIM-IC and denuder samplers in various coastal atmospheres since 2012. We didn’t find high background and other interferences, except K⁺ interference (Teng et al., 2017).   

 

(3) The authors claim that the TMA and TMAH⁺ are mainly from sea spray aerosols and hence they can be used as tracers for other basic compounds. Do the authors have any evidences between concentrations of the above two species and concentrations of sea spray aerosols or their makers? In addition, how confidence is for the measurements of the above two species?

 

Response: Na⁺ in PM_2.5 over the marine atmosphere far away from the continents should be mainly derived from marine sources, especially the increased concentrations of Na⁺ in PM_2.5 with increasing wind speeds at 10 m s^-1. In the revision, the sentence has changed to “while accompanying with high concentrations of Na+ under high wind speeds as commonly assumed to be indicators of sea spray aerosols (Feng et al., 2017).”

 

The increased TMA_gas with increasing wind speeds in the remote marine atmosphere is also an important evidence to release TMA_gas through the air-sea exchange. Theoretically, increasing wind speeds in the remote marine atmosphere should decrease concentrations of TMA_gas derived from those emissions other than the air-sea exchange. 

 

Please see our response to Comment 2.

 

(4) Rather minor: there are no section numbers for introduction and the second section.

 

Response: Sorry for this and corrected.

(1) The data presented in this paper could add to our understanding of TMA and DMA in gas and in particulate phase, in China’s marginal seas. This should be also reflected in the title since the word “amines” is misleading because it is discussed only two compounds. Furthermore, some technical details, especially in the analytical protocol, are not presented adequately.

 

Response: Agree. The title has been changed to “Mapping gaseous dimethylamine, trimethylamine, ammonia, and their particulate counterparts in marine atmospheres of China’s marginal seas: Part 1 - Differentiating marine emission from continental transport”.

 

The technical details of our analytical protocol have been added in the revised experimental section.

 

(2) The different sections have not the correct numbers e.g. the section “4. Conclusions” should be 5, while the sections “Introduction” and “Experimental” do not have numbers.

 

Response: Sorry for this. It has been corrected in the revision.

 

(3) In the Experimental section: I propose to split it into the sampling and analysis part.

 

Response: Agree. Done. 

 

(4) The introduction is focused on the biogenic sources of amines. What about anthropogenic emissions? Is there any information from the literature, especially for the area?

 

Response: Ge et al.(2011) reviewed anthropogenic emissions of DMA and TMA such as animal husbandry, fishing processing, manufacturing, industry, etc. This has been added in the revision. Anthropogenic sources of DMA and TMA in the continental atmosphere upwind of the Yellow sea, Bohai sea and Eastern China sea are poorly understand. This has been also added in the revision.  

 

(5) Lines 114-118. More details regarding the analysis should be added here, such as the eluent, the type and time of elution, injection volume, the detection limit for anions.

 

Response: Agree. Done. 

 

(6) Line 123. What exactly the author means by the term contamination of K⁺? Is it related to the overlapping of the peaks? If yes, the term “interference” is more appropriate. I propose to present a chromatograph in the supplement material with and without K⁺ interference.

 

Response: Thanks. The word “interference”should be better and changed accordingly. Figures with and without K⁺ interference have been added in the supplement material.

 

(7) Line 174. What are those values?

 

Response: Those values are referred to “The observed concentrations of TMA_gas”, which have been clarified in the revision. 

 

(8) Line 187. “Negatively correlated” please refer r² and p.

 

Response: R² and p value have been given in the revision.

 

(9) Line 221. SO₄^2- anions are non-sea salt? If not, it should be clarified for continental sources.

 

Response: Nss-SO₄^2- instead of SO₄^2- has been used for the tracer of continental sources in the revised Figure 2(d).

 

(10) Line 223. Na is sea salt Na? If not it should be for marine sources.

 

Response: We had no additional data to confirm sea-salt Na. However, Na⁺ in PM_2.5 over the marine atmosphere far away from the continents should be mainly derived from marine sources, especially the increased concentrations of Na⁺ in PM_2.5 with increasing wind speeds at 10 m s^-1. In the revision, the sentence has changed to “while accompanying with high concentrations of Na⁺ under high wind speeds as commonly assumed to be indicators of sea spray aerosols (Feng et al., 2017).”

 

(11) It would be nice to change the order of Figures 1 and 2, in order to help the reader to follow the discussion.

 

Response: Agree. Done.

 

(12) Fig. 2 (b) where is wind speed? Please explain how the direction of arrows is connected with the wind direction.

 

Response: Agree. The length of arrows was superimposed on the top of (a) represents wind speed. We have added a legend for reference in Fig. 2(a) to shown the speed and direction of wind. 

 

(13) Fig.3. The legends are missing from the graph.

 

Response: Added in the revision.

 

(14) Fig.3. “only some data were used in (e) and (f) to avoid clustering”. Which was the criterion of “some data”?

 

Response: In the revision, we added “to better show spatiotemporal distributions of TMAH⁺ and NH₄⁺ during Peak 1, Peak 2 and Peak 4, only data during periods shaded in (a-d) were used in (e) and (f) to avoid clustering.”

 

(15) Fig.4. Remove the single bracket.

 

Response: Sorry. We can’t get the point.