the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 01 Sep 2022
Chemical characterization of organic compounds involved in iodine-initiated new particle formation from coastal macro-algal emission
Abstract. Iodine-initiated new particle formation (I-NPF) has long been recognized in coastal hotspot regions. However, no prior work has studied the exact chemical composition of organic compounds and their role in the coastal I-NPF. Here we present an important complementary study to the ongoing laboratory and field researches of iodine nucleation in coastal atmosphere. Oxidation and NPF experiments with vapor emissions from real-world coastal macroalgae were simulated in a bag reactor. On the basis of comprehensive mass spectrometry measurements, we reported for the first time a variety of volatile precursors and their oxidation products in gas and particle phases in such a highly complex system. Organic compounds overwhelmingly dominated over iodine in the new particle growth initiated by iodine species. The identity and transformation mechanisms of organic compounds were proposed in this study to provide a more complete story of coastal NPF from low-tide macroalgal emission.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Interactive discussion
Status: closed
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CC1: 'Comment on egusphere-2022-838', Juan Carlos Gomez Martin, 02 Sep 2022
Wan et al. have performed an interesting laboratory study showing that the organic compounds co-emitted with iodine bearing molecules by exposed tidal macroalgae dominate particle growth in iodine-triggered NPF events. The chemical evolution of the emitted organic precursors is investigated by means of iodide-CIMS, showing that alkene ozonolysis and criegee intermediate gas-phase reactions and particle-phase accretion reactions increase the number of carbon and oxygen atoms of the organic compounds observed. Some information about inorganic iodine molecular cluster precursors is also obtained.
I have listed a few comments below that the authors may want to consider to improve their manuscript.
Page 2, line 35. Here and elsewhere: Martín et al., 2020 -> Gómez Martín et al., 2020
Page 2, line 38. A previous study also examined the growth of iodine oxide clusters in the presence of condensable vapours such as H2SO4 or oxalic acid (Saunders et al., 2010)
Page 2, line 47. An opening sentence indicating that organic compounds have been observed in particles formed in I-NPF events (Vaattovaara et al., 2006; Yu et al., 2019) would be useful.
Page 2, line 48. More common names for this compound are iodomethane and methyl iodide
Page 3, line 81. Indicate in this paragraph an estimate of water vapour concentration or RH in the experiment.
Page 3, line 84. Note that even though up to 10% of O1D may end up as OH under atmospheric conditions, the rest will be quenched to O3P, and that O3P reacts both with I2 and iodomethane to make IO. Moreover, it is well known that OH reacts quickly with I2 to make HOI. Therefore, in these experiments additional photolytic sources of IO are present, plus a source of HOI. This may obscure the interpretation of the "OH-enhanced" experiments.
Page 4, line 117. Indicate ultrasonication time and power.
Page 5, line 145. It is likely that this effect is rather due to the presence of ground state oxygen atoms in the flow. O3P will free additional iodine atoms by reaction with I2 and CH3I.
Page 6, line 171. Is HNO3 then emitted by algae? I think explaining a bit more about the source of HNO3 is necessary, since it indirectly allows detection of most of the inorganic compounds reported. In fact the iodide CIMS in practice operates in these experiments as a nitrate CIMS for inorganic iodine compounds.
Page 6, line 174. While iodide CIMS maybe a good technique for detecting organics, it is probably not be the best technique for detecting inorganic iodine compounds, for the obvious reason that the source of charge is the iodide anion, which may obscure the interpretation of the observed ion clusters. No discussion of this potential interference has been included in this paper.
Page 6, line 177. Alongside Figure 4, it would be very useful showing a table with the correspondences between observed anions and proposed parent neutral molecules. Such correspondence is not always straightforward, as we have argued recently (Gómez Martín et al., 2022).
Page 6, line 182. What about I2 and HOI photolysis? Why are you ruling out I2 and HOI as iodine sources?
Page 6, line 184. Unlikely. Much faster reactions are:
Cl+I2->ICl+I
Cl+ICl->Cl2+I
The time traces in Figure 2b are qualitatively consistent with this sequence of reactions
Page 6, line 188. These experiments employ UHP air.What is then the source of NO2 in this system? There is no easy route from HNO3 to NO2.
Page 7, line 193. Again, what is the source of NO2 in this system? This must be discussed, since you are concluding that IONO2 is contributing to particle growth. In our recent work on the nitrate CIMS system in the context of I-NPF (Gomez Martin et al., 2022), we have found that IO3-, HIO3.NO3- (or rather HNO3.IO3-) and IONO2.NO3- are products of the reaction between NO3- and I2O3. I am skeptical about the presence of IONO and IONO2 in this system because of the unlikely presence of NO and NO2, and I suspect that IONO.NO3- and IONO2.NO3- could be products of IxOy+NO3- also in these experiments.
Page 7, line 193. Following my previous comment, at least part of the signal attributed to HIO3 results from I2Oy+NO3- (Gómez Martín et al., 2022)
Page 7, line 194. Note that Gomez Martin et al., 2020 never argued in that HOIO2 would form from I + H2O +O3 -they rather argued the opposite. The source of HOIO2 remains to be confirmed, although the reaction between I2O5 and the water dimer is currently our best candidate, where I2O5 would be a photolysis product of a higher iodine oxide (Gómez Martín et al., 2022).
Page 7, line 196. This is in disagreement with the observations by He et al. 2022 using a Br-CIMS FIGAERO. They did observe HIO3 in the particles. This disagreement should be discussed.
Heating of HIO3 between 100ºC and 200ºC results in dehydration and formation of I2O5 (Selte and Kjekshus 1968\), so the desorption temperature in is critical.
The IO- and IO2- signals may be secondary products of the reaction between I2O5 and I-.
Citation: https://doi.org/10.5194/egusphere-2022-838-CC1 - AC1: 'Reply on CC1', Huan Yu, 31 Oct 2022
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RC1: 'Comment on egusphere-2022-838', Anonymous Referee #1, 26 Sep 2022
Manuscript entitled “Chemical characterization of organic compounds involved in iodine-initiated new particle formation from coastal macro-algal emission” studied the identity and transformation mechanisms of organic compounds from low-tide macroalgal emission. This manuscript simulates vapor emission oxidation and new particle formation (NPF) experiments of real coastal macroalgae in a bag-reactor. Based on the integrated mass spectrometry measurements, the authors report for the first time a variety of volatile precursors and their oxidation products in the gas and particle phases in such a highly complex system. The results show that organic compounds dominate the growth of new particles induced by iodine species.
This paper falls in an active field of research, and I believe it brings interesting insights to the study of the ongoing laboratory and field researches of coastal I-NPF. The paper could be published in the journal assuming some minor corrections.
- Page 4 Lines 96-98: What is the proportion of VOCs and O3 in the VOCs/O3 flow of the dynamic mode, respectively?
- Page 4 Lines 98-99: Does the residence time of 67min refer to the sampling time of particulate matter?
- Page 5 Lines 133-134: How can we see from Figure 2a when O3 is injected? And when to add light? Why only see the figure of SMPS under static conditions of the ozonolysis experiment.
- Page 5 Line 157: Please indicate what kind of macroalgae you choose and how to preserve the algae and seawater. And why you choose this type of macroalgae?
- Page 8 Lines 225-229: Does accretion reactions or dimer formation change particle size? Please describe the accretion reaction in detail.
- Page 8 Lines 230-232: Why do ESI-Orbitrap MS and FIGAERO-iodide-CIMS use quartz fiber filter and PTFE membrane filter, respectively? Is filter inconsistency the reason why ESI-Orbitrap MS did not measure bimodal distribution?
Citation: https://doi.org/10.5194/egusphere-2022-838-RC1 - AC2: 'Reply on RC1', Huan Yu, 31 Oct 2022
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RC2: 'Comment on egusphere-2022-838', Anonymous Referee #2, 24 Oct 2022
The authors reported the chemical composition and evolution of volatile precursors emitted from macro-algae and their oxidation products in the gas and particle phase using a suite of mass spectrometers. But it was shallow and simple about the discussion of the transformation mechanisms of organic compound. I recommend that the authors could make more detailed explanations about the results and explore more precise reaction formulas.
Here are some questions about the methods and results in the following.
Method
81: “In the three ozonolysis experiments”
It seems that only one result (without error bar) is shown in this paper. What is about the remaining two experiments?
84: “In an additional OH-enhanced experiment”
The authors conducted this experiment for simulating atmospheric oxidation process, however, you didn’t even give the concentration of additional OH and the limitation of the experimental design compared with the real environment wasn’t discussed.
120: “TI or TOC in the particles was obtained by subtracting the amount on the back filter from that on the front filter”
I am confused about the calculation. As you said that “The front filter of the double filter pack collected the particles, while the back filter placed downstream of the front filter was supposed to adsorb the same amount of volatile species as the front filter”, may I think of it this way: particles in the front filter and volatile species in the back filter. Why the TI in the particle is not the amount on the front filter? Why it needs to subtracting the amount on the back filter?
128: “Only the compounds that existed solely in the front filter or with ion intensity in the front filter higher than that in the back filter by a factor of 3 were regarded as the organic compounds in the particle phase”
Please cite suitable literature.
Results and discussion
135, 138: “new particles larger than 14 nm were observed only 58 minutes after the injection of ozone flow”, “With a prolonged residential time of 67 min…”
The authors talked about the results after 58 or 67 minutes. But the maximum of axis about the elapsed time in the Figure. 2 was 50.
136: “No particles were formed in the absence of room light or ozone”.
I don’t see the relevant results (table or figure) shown in the paper.
154: “But those small new particles are expected to grow into CCN active sizes, given longer residence time and uptake of more condensing vapors in the atmosphere”.
Please cite suitable literature.
156: “3.2 Macroalgal emission”
I think it is more suitable to remove this section to the first part of the Results and discussion
187, 188: “IO, IO2 and ClIO could be from the reactions between I, ClI and O3”, “ClNO2 was likely to form upon similar reaction between Cl and NO2 in the bag reactor”
Give the reaction mechanisms or cite literatures.
195: “which is contrary to the observation by HPLC-ICP-MS that total iodine was mostly dominated IO3- peak”
Could the authors explain the contrast?
259: Scheme II
The formulas are too simple to understand the mechanism of particle formation. It might be meaningful to give formulas like Scheme I for several specific species.
Citation: https://doi.org/10.5194/egusphere-2022-838-RC2 - AC3: 'Reply on RC2', Huan Yu, 31 Oct 2022
Interactive discussion
Status: closed
-
CC1: 'Comment on egusphere-2022-838', Juan Carlos Gomez Martin, 02 Sep 2022
Wan et al. have performed an interesting laboratory study showing that the organic compounds co-emitted with iodine bearing molecules by exposed tidal macroalgae dominate particle growth in iodine-triggered NPF events. The chemical evolution of the emitted organic precursors is investigated by means of iodide-CIMS, showing that alkene ozonolysis and criegee intermediate gas-phase reactions and particle-phase accretion reactions increase the number of carbon and oxygen atoms of the organic compounds observed. Some information about inorganic iodine molecular cluster precursors is also obtained.
I have listed a few comments below that the authors may want to consider to improve their manuscript.
Page 2, line 35. Here and elsewhere: Martín et al., 2020 -> Gómez Martín et al., 2020
Page 2, line 38. A previous study also examined the growth of iodine oxide clusters in the presence of condensable vapours such as H2SO4 or oxalic acid (Saunders et al., 2010)
Page 2, line 47. An opening sentence indicating that organic compounds have been observed in particles formed in I-NPF events (Vaattovaara et al., 2006; Yu et al., 2019) would be useful.
Page 2, line 48. More common names for this compound are iodomethane and methyl iodide
Page 3, line 81. Indicate in this paragraph an estimate of water vapour concentration or RH in the experiment.
Page 3, line 84. Note that even though up to 10% of O1D may end up as OH under atmospheric conditions, the rest will be quenched to O3P, and that O3P reacts both with I2 and iodomethane to make IO. Moreover, it is well known that OH reacts quickly with I2 to make HOI. Therefore, in these experiments additional photolytic sources of IO are present, plus a source of HOI. This may obscure the interpretation of the "OH-enhanced" experiments.
Page 4, line 117. Indicate ultrasonication time and power.
Page 5, line 145. It is likely that this effect is rather due to the presence of ground state oxygen atoms in the flow. O3P will free additional iodine atoms by reaction with I2 and CH3I.
Page 6, line 171. Is HNO3 then emitted by algae? I think explaining a bit more about the source of HNO3 is necessary, since it indirectly allows detection of most of the inorganic compounds reported. In fact the iodide CIMS in practice operates in these experiments as a nitrate CIMS for inorganic iodine compounds.
Page 6, line 174. While iodide CIMS maybe a good technique for detecting organics, it is probably not be the best technique for detecting inorganic iodine compounds, for the obvious reason that the source of charge is the iodide anion, which may obscure the interpretation of the observed ion clusters. No discussion of this potential interference has been included in this paper.
Page 6, line 177. Alongside Figure 4, it would be very useful showing a table with the correspondences between observed anions and proposed parent neutral molecules. Such correspondence is not always straightforward, as we have argued recently (Gómez Martín et al., 2022).
Page 6, line 182. What about I2 and HOI photolysis? Why are you ruling out I2 and HOI as iodine sources?
Page 6, line 184. Unlikely. Much faster reactions are:
Cl+I2->ICl+I
Cl+ICl->Cl2+I
The time traces in Figure 2b are qualitatively consistent with this sequence of reactions
Page 6, line 188. These experiments employ UHP air.What is then the source of NO2 in this system? There is no easy route from HNO3 to NO2.
Page 7, line 193. Again, what is the source of NO2 in this system? This must be discussed, since you are concluding that IONO2 is contributing to particle growth. In our recent work on the nitrate CIMS system in the context of I-NPF (Gomez Martin et al., 2022), we have found that IO3-, HIO3.NO3- (or rather HNO3.IO3-) and IONO2.NO3- are products of the reaction between NO3- and I2O3. I am skeptical about the presence of IONO and IONO2 in this system because of the unlikely presence of NO and NO2, and I suspect that IONO.NO3- and IONO2.NO3- could be products of IxOy+NO3- also in these experiments.
Page 7, line 193. Following my previous comment, at least part of the signal attributed to HIO3 results from I2Oy+NO3- (Gómez Martín et al., 2022)
Page 7, line 194. Note that Gomez Martin et al., 2020 never argued in that HOIO2 would form from I + H2O +O3 -they rather argued the opposite. The source of HOIO2 remains to be confirmed, although the reaction between I2O5 and the water dimer is currently our best candidate, where I2O5 would be a photolysis product of a higher iodine oxide (Gómez Martín et al., 2022).
Page 7, line 196. This is in disagreement with the observations by He et al. 2022 using a Br-CIMS FIGAERO. They did observe HIO3 in the particles. This disagreement should be discussed.
Heating of HIO3 between 100ºC and 200ºC results in dehydration and formation of I2O5 (Selte and Kjekshus 1968\), so the desorption temperature in is critical.
The IO- and IO2- signals may be secondary products of the reaction between I2O5 and I-.
Citation: https://doi.org/10.5194/egusphere-2022-838-CC1 - AC1: 'Reply on CC1', Huan Yu, 31 Oct 2022
-
RC1: 'Comment on egusphere-2022-838', Anonymous Referee #1, 26 Sep 2022
Manuscript entitled “Chemical characterization of organic compounds involved in iodine-initiated new particle formation from coastal macro-algal emission” studied the identity and transformation mechanisms of organic compounds from low-tide macroalgal emission. This manuscript simulates vapor emission oxidation and new particle formation (NPF) experiments of real coastal macroalgae in a bag-reactor. Based on the integrated mass spectrometry measurements, the authors report for the first time a variety of volatile precursors and their oxidation products in the gas and particle phases in such a highly complex system. The results show that organic compounds dominate the growth of new particles induced by iodine species.
This paper falls in an active field of research, and I believe it brings interesting insights to the study of the ongoing laboratory and field researches of coastal I-NPF. The paper could be published in the journal assuming some minor corrections.
- Page 4 Lines 96-98: What is the proportion of VOCs and O3 in the VOCs/O3 flow of the dynamic mode, respectively?
- Page 4 Lines 98-99: Does the residence time of 67min refer to the sampling time of particulate matter?
- Page 5 Lines 133-134: How can we see from Figure 2a when O3 is injected? And when to add light? Why only see the figure of SMPS under static conditions of the ozonolysis experiment.
- Page 5 Line 157: Please indicate what kind of macroalgae you choose and how to preserve the algae and seawater. And why you choose this type of macroalgae?
- Page 8 Lines 225-229: Does accretion reactions or dimer formation change particle size? Please describe the accretion reaction in detail.
- Page 8 Lines 230-232: Why do ESI-Orbitrap MS and FIGAERO-iodide-CIMS use quartz fiber filter and PTFE membrane filter, respectively? Is filter inconsistency the reason why ESI-Orbitrap MS did not measure bimodal distribution?
Citation: https://doi.org/10.5194/egusphere-2022-838-RC1 - AC2: 'Reply on RC1', Huan Yu, 31 Oct 2022
-
RC2: 'Comment on egusphere-2022-838', Anonymous Referee #2, 24 Oct 2022
The authors reported the chemical composition and evolution of volatile precursors emitted from macro-algae and their oxidation products in the gas and particle phase using a suite of mass spectrometers. But it was shallow and simple about the discussion of the transformation mechanisms of organic compound. I recommend that the authors could make more detailed explanations about the results and explore more precise reaction formulas.
Here are some questions about the methods and results in the following.
Method
81: “In the three ozonolysis experiments”
It seems that only one result (without error bar) is shown in this paper. What is about the remaining two experiments?
84: “In an additional OH-enhanced experiment”
The authors conducted this experiment for simulating atmospheric oxidation process, however, you didn’t even give the concentration of additional OH and the limitation of the experimental design compared with the real environment wasn’t discussed.
120: “TI or TOC in the particles was obtained by subtracting the amount on the back filter from that on the front filter”
I am confused about the calculation. As you said that “The front filter of the double filter pack collected the particles, while the back filter placed downstream of the front filter was supposed to adsorb the same amount of volatile species as the front filter”, may I think of it this way: particles in the front filter and volatile species in the back filter. Why the TI in the particle is not the amount on the front filter? Why it needs to subtracting the amount on the back filter?
128: “Only the compounds that existed solely in the front filter or with ion intensity in the front filter higher than that in the back filter by a factor of 3 were regarded as the organic compounds in the particle phase”
Please cite suitable literature.
Results and discussion
135, 138: “new particles larger than 14 nm were observed only 58 minutes after the injection of ozone flow”, “With a prolonged residential time of 67 min…”
The authors talked about the results after 58 or 67 minutes. But the maximum of axis about the elapsed time in the Figure. 2 was 50.
136: “No particles were formed in the absence of room light or ozone”.
I don’t see the relevant results (table or figure) shown in the paper.
154: “But those small new particles are expected to grow into CCN active sizes, given longer residence time and uptake of more condensing vapors in the atmosphere”.
Please cite suitable literature.
156: “3.2 Macroalgal emission”
I think it is more suitable to remove this section to the first part of the Results and discussion
187, 188: “IO, IO2 and ClIO could be from the reactions between I, ClI and O3”, “ClNO2 was likely to form upon similar reaction between Cl and NO2 in the bag reactor”
Give the reaction mechanisms or cite literatures.
195: “which is contrary to the observation by HPLC-ICP-MS that total iodine was mostly dominated IO3- peak”
Could the authors explain the contrast?
259: Scheme II
The formulas are too simple to understand the mechanism of particle formation. It might be meaningful to give formulas like Scheme I for several specific species.
Citation: https://doi.org/10.5194/egusphere-2022-838-RC2 - AC3: 'Reply on RC2', Huan Yu, 31 Oct 2022
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Yibei Wan
Xiangpeng Huang
Chong Xing
Qiongqiong Wang
Xinlei Ge
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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