the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 Apr 2024
Investigating Carbonyl Compounds above the Amazon Rainforest using PTR-ToF-MS with NO+ Chemical Ionization
Abstract. The photochemistry of carbonyl compounds significantly influences tropospheric chemical composition by altering the local oxidative capacity, free radical abundance in the upper troposphere, and formation of ozone, PAN, and secondary organic aerosol particles. Carbonyl compounds can be emitted directly from the biosphere into the atmosphere and are formed through photochemical degradation of various precursor compounds. Aldehydes have atmospheric lifetimes of hours to days, in contrast to ketones, which persist for up to several weeks. While standard operating conditions for proton transfer time‑of‑flight mass spectrometer (PTR-ToF-MS) using H3O+ ions are unable to separate aldehydes and ketones, the use of NO+ reagent ions allows for the differential detection of isomeric carbonyl compounds with a high time resolution. Here we study the temporal (24 h) and vertical (80–325 m) variability of individual carbonyl compounds in the Amazon rainforest atmosphere with respect to their rainforest-specific sources and sinks. We found strong sources of ketones within or just above the rainforest canopy (acetone, MEK, and C5-ketones). A common feature of the carbonyls was nocturnal deposition observed by loss rates, most likely since oxidized volatile organic compounds are rapidly metabolized and utilized by the biosphere. With NO+ chemical ionization, we show that the dominant carbonyl species include acetone and propanal, which are present at a ratio of 1:10 in the wet–to–dry transition and 1:20 in the dry season.
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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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Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-1210', Anonymous Referee #1, 21 May 2024
In this work, Ringsdorf et al. describe atmospheric measurements of carbonyl containing OVOCs in the Amazon Rainforest using PTR-ToF-MS and NO+ CIMS. The use of PTR-ToF-MS and reagent switching enables differentiation between ketones and aldehydes which in turn enables the determination of their atmospheric fate, including reactivity and dry deposition. This includes vertically resolved measurements at 80-325 m of multiple species.
The paper exploits reagent ion switching to obtain information about ketones and aldehydes separately which is relatively novel.
The OVOC behavior described in this article is consistent with previous data, so although the measurements are somewhat novel there are no significant new conclusions.
The methods are described thoroughly, including calibrations or sensitivity estimates as well as possible interferences from isomers or decomposition of other species such as peroxides.
The authors do a very good job in contextualizing the measurements of each individual OVOC being reported. They cite the literature extensively and pose multiple hypotheses for observed diurnal and height variations in measurements.
Although reproducibility is impossible with field data, the authors do a great job detailing instrumental parameters such as E/N and sensitivity calculations which will enable future measurements to directly compare their results to the ones herein.
In terms of structure and presentation, the article has a good title and abstract which reflects the contents. The abstract and sections are logical and well organized, and the writing is great. Regarding content, most of the text is dedicated to previous work about the observed OVOCs making it seem more like a merge between a review and a measurement report. This level of background detail makes for a nice introductory read but it is not new science per se.
Regarding the supplementary data, I think the paper would benefit from some time series data. The only measurements presented in the article are averaged diurnal profiles and correlation tables. Presenting some time series data could provide further insight into the sampling height differences, reagent ion switching and differences between seasons which would strengthen the article.
As of now the article can be published with technical corrections.
Minor comments:
Line 333: reference to chapter 4 should be removed.
Figures S3-S5 are incorrectly ordered.
Figure S2 text boxes are illegible.
Figure S4 could benefit should be replaced with a higher resolution version.
Figure S5 shows a plot of benzene with no data and non-sensical axes.
Citation: https://doi.org/10.5194/egusphere-2024-1210-RC1 -
AC1: 'Reply on RC1', Akima Ringsdorf, 04 Jun 2024
Dear Editor Frank Keutsch,
Thank you for the review provided. We are very grateful to the reviewer for the constructive, positive evaluation of the manuscript. All points raised by the reviewer have been addressed in the revised manuscript and the supplementary material.
The individual detection of carbonyl compound mixing ratios with a high temporal resolution in the Amazon presents a unique dataset, that advances the characterization of the BVOC diversity found in rainforest environments. By comparing this dataset to background literature the impression is created that all species were observed before, however, it is important to note that the instrumental methods did not allow the individual measurement of isomeric carbonyl compounds. To stress this point we adopted the following passages:
Line 467: Accordingly, in 2013, measurements of acetaldehyde using a PTR-quadrupole-MS (nominal m/z 45) vertical gradients below 80 m at ATTO showed increasing acetaldehyde between 24 m (inside the canopy, high influence by surrounding trees) and 79 m.
Line 512: Both studies deployed PTR-quadrupole-MS operated with H3O+ reagent ions with a nominal mass resolution.
We added time series of the carbonyl compounds discussed in the manuscript as suggested by reviewer 1 to the supplementary (Fig. S6-S15), to illustrate reagent ion switching and day-to-day variabilities.
Line 345: Time series of the aldehydes and ketones are provided in the supplementary (Fig. S6-S15).
During the review process, we noted that Fig. 4 included the Pearson correlation coefficients of the carbonyl species and ethanol for the dry season 2019, although ethanol mixing ratios were found below the detection limit (see Fig. S17). We changed the figure and its introduction in the manuscript accordingly:
Line 390: Figures 3-4 show the Pearson correlation coefficients (p) for both seasons divided into day (10:00–17:00 LT) and nighttime (22:00–05:00 LT) between the carbonyl compounds and between carbonyls and other selected VOC, including terpenes (isoprene, sum of monoterpenes), alkenes (C5-alkenes, benzene), and oxygenated compounds (ethanol, furan, acetic acid, C5H4O3), when measured above the detection limit.
Minor comments:
Line 333: reference to chapter 4 should be removed.
Under the reasonable assumption of a carbonyl source at canopy level (based on emission inventories discussed in section 4)…
Figures S3-S5 are incorrectly ordered.
We thank the reviewer for noticing that detail, the numbers of figures S3 and S5 are changed accordingly.
Figure S2 text boxes are illegible.
We decided to show an enlarged view of the ATTO site on the map without the extra information provided in the text boxes, as those are only interesting from a logistical point of view.
Figure S4 could benefit should be replaced with a higher resolution version.
We agree, Fig. S4 is now replaced by a higher resolution figure.
Figure S5 shows a plot of benzene with no data and non-sensical axes.
We thank the reviewer for pointing this out, we removed the concerning subplot (C5-alkenes) as suggested.
-
AC1: 'Reply on RC1', Akima Ringsdorf, 04 Jun 2024
-
RC2: 'Comment on egusphere-2024-1210', Anonymous Referee #2, 26 Jun 2024
Review of “Investigating Carbonyl Compounds above the Amazon Rainforest using PTR-ToF-MS with NO+ Chemical Ionization” by Akima Ringsdorf et al. The manuscript analyzes the characteristics of different carbonyl compounds and emphasizes the necessity of supplementing the NO+ CIMS method to measure carbonyl compounds. The authors examine the sources and sinks in the Amazon rainforest of the selected carbonyl species in combination with a sufficient literature review. The article is substantial, with many citations and argumentation work. However, the writing focus of the discussion section of the manuscript is not clear enough, and the data analysis method is relatively simple. I recommend a major revision before its publication. My concerns in the manuscript are mainly listed below:
Specific comments:
- Line 99-100: What is the temporal variation of humidity during the observation? Even with NO+ ionizing chemistry, the reported C2-C9 carbonyl compounds are greatly affected by humidity. The author needs to specify whether the signal of these compounds has been calibrated for humidity.
- Line 101-121: What is the delay time of measured compounds？Does the time resolution of 20 s for NO+ PTR-ToF-MS be able to guarantee that the measured signal of speciated compounds was from the actual atmosphere, not the tube residue?
- Line 141-143: The author needs to specify the parameter setting for NO+ mode, including the ion source voltage and drift tube voltage since the difference of parameter setting will affect the abundance of impurity ions (H3O+, O2+, and NO2+). And the author also needs to give the abundance of impurity ions during the campaign, especially for the ratio of O2+/NO+, due to O2+will cause interference when using NO+ ionization for measurement.
- Line 187-197: It seems that the parameterized quantitative method proposed by Cappellin et al. is based on the proton transfer reaction between organic compounds and H3O+ I wonder if this method is suitable for NO+ chemistry. Because NO+ ions can react with organic compounds with multiple ways and occur simultaneously. I think the author needs to reconsider this issue. In addition, it is suggested that the author use a formula to explain how to obtain the sensitivity for those compounds not included in the gas standard based on k-rate.
- Table 1 and Table S1: According to previous studies for the reaction pathway of NO+ to organic compounds, the multiple reactions of NO+ to organic compounds (Charge transfer (M+), hydride abstraction (M+- H), association reaction (MNO+) or hydroxide ion transfer (M+- OH)) should occur simultaneously. However, the differences in ionization energy (IE) and the chemical bond can cause species to react more easily with NO+ in one particularly pathway, associated with the formation of fragments. Therefore, we need to identify the characteristic product ions (which refers to the ion formula the author shown in the table) according to the contribution of each product ion after reaction. The author should show this contribution here, which also be better explain the influence of different E/N conditions to measurements.
- Line 268-285: What is the contribution of local emissions and long-range transport during the measurement in dry season? As mentioned above that region is affected by long-range transport from African biomass burning pollution. And I prefer to see an overall picture of carbonyl emissions with concentrations and contributions.
- Line 298-309: Just a suggestion, maybe the author could further quantify the influence of biomass burning from Africa and South America based on PAN, which is basically present in aging plumes.1
- Line 334: Short-lived aldehydes do not include isoprene.
- Line 440-443: The authors believe that ethanol was formed by anaerobic reactions on the surface, but why does the ethanol concentration decrease with increasing altitude during the transition season?
- Line 498-545: During the daytime, acetone and C5-ketones have stronger vertical gradients than the more reactive isoprene and monoterpenes. This phenomenon is very important for analyzing the sources and sinks of ketones. On a well-mixed daytime, it is difficult to understand the strong vertical gradient of ketones, even though the ketones have a strong source at the surface, as the authors believe.
Technical Corrections:
- Table 1: The references involved in the table may be annotated separately.
- The picture can be named (for example, Fig. 1(a)), which can avoid the description of upper, lower, etc.
- S6 and S7: The naming format used for each species in the figures should be unified, now there are both species names, molecular formulas and ionic formulas
- S7: Why is the first picture empty?
Reference
- Liang, Y.; Weber, R. J.; Misztal, P. K.; Jen, C. N.; Goldstein, A. H., Aging of Volatile Organic Compounds in October 2017 Northern California Wildfire Plumes. Environ Sci Technol 2022, 56, (3), 1557-1567.
Citation: https://doi.org/10.5194/egusphere-2024-1210-RC2 -
AC2: 'Reply on RC2', Akima Ringsdorf, 19 Jul 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1210/egusphere-2024-1210-AC2-supplement.pdf
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-1210', Anonymous Referee #1, 21 May 2024
In this work, Ringsdorf et al. describe atmospheric measurements of carbonyl containing OVOCs in the Amazon Rainforest using PTR-ToF-MS and NO+ CIMS. The use of PTR-ToF-MS and reagent switching enables differentiation between ketones and aldehydes which in turn enables the determination of their atmospheric fate, including reactivity and dry deposition. This includes vertically resolved measurements at 80-325 m of multiple species.
The paper exploits reagent ion switching to obtain information about ketones and aldehydes separately which is relatively novel.
The OVOC behavior described in this article is consistent with previous data, so although the measurements are somewhat novel there are no significant new conclusions.
The methods are described thoroughly, including calibrations or sensitivity estimates as well as possible interferences from isomers or decomposition of other species such as peroxides.
The authors do a very good job in contextualizing the measurements of each individual OVOC being reported. They cite the literature extensively and pose multiple hypotheses for observed diurnal and height variations in measurements.
Although reproducibility is impossible with field data, the authors do a great job detailing instrumental parameters such as E/N and sensitivity calculations which will enable future measurements to directly compare their results to the ones herein.
In terms of structure and presentation, the article has a good title and abstract which reflects the contents. The abstract and sections are logical and well organized, and the writing is great. Regarding content, most of the text is dedicated to previous work about the observed OVOCs making it seem more like a merge between a review and a measurement report. This level of background detail makes for a nice introductory read but it is not new science per se.
Regarding the supplementary data, I think the paper would benefit from some time series data. The only measurements presented in the article are averaged diurnal profiles and correlation tables. Presenting some time series data could provide further insight into the sampling height differences, reagent ion switching and differences between seasons which would strengthen the article.
As of now the article can be published with technical corrections.
Minor comments:
Line 333: reference to chapter 4 should be removed.
Figures S3-S5 are incorrectly ordered.
Figure S2 text boxes are illegible.
Figure S4 could benefit should be replaced with a higher resolution version.
Figure S5 shows a plot of benzene with no data and non-sensical axes.
Citation: https://doi.org/10.5194/egusphere-2024-1210-RC1 -
AC1: 'Reply on RC1', Akima Ringsdorf, 04 Jun 2024
Dear Editor Frank Keutsch,
Thank you for the review provided. We are very grateful to the reviewer for the constructive, positive evaluation of the manuscript. All points raised by the reviewer have been addressed in the revised manuscript and the supplementary material.
The individual detection of carbonyl compound mixing ratios with a high temporal resolution in the Amazon presents a unique dataset, that advances the characterization of the BVOC diversity found in rainforest environments. By comparing this dataset to background literature the impression is created that all species were observed before, however, it is important to note that the instrumental methods did not allow the individual measurement of isomeric carbonyl compounds. To stress this point we adopted the following passages:
Line 467: Accordingly, in 2013, measurements of acetaldehyde using a PTR-quadrupole-MS (nominal m/z 45) vertical gradients below 80 m at ATTO showed increasing acetaldehyde between 24 m (inside the canopy, high influence by surrounding trees) and 79 m.
Line 512: Both studies deployed PTR-quadrupole-MS operated with H3O+ reagent ions with a nominal mass resolution.
We added time series of the carbonyl compounds discussed in the manuscript as suggested by reviewer 1 to the supplementary (Fig. S6-S15), to illustrate reagent ion switching and day-to-day variabilities.
Line 345: Time series of the aldehydes and ketones are provided in the supplementary (Fig. S6-S15).
During the review process, we noted that Fig. 4 included the Pearson correlation coefficients of the carbonyl species and ethanol for the dry season 2019, although ethanol mixing ratios were found below the detection limit (see Fig. S17). We changed the figure and its introduction in the manuscript accordingly:
Line 390: Figures 3-4 show the Pearson correlation coefficients (p) for both seasons divided into day (10:00–17:00 LT) and nighttime (22:00–05:00 LT) between the carbonyl compounds and between carbonyls and other selected VOC, including terpenes (isoprene, sum of monoterpenes), alkenes (C5-alkenes, benzene), and oxygenated compounds (ethanol, furan, acetic acid, C5H4O3), when measured above the detection limit.
Minor comments:
Line 333: reference to chapter 4 should be removed.
Under the reasonable assumption of a carbonyl source at canopy level (based on emission inventories discussed in section 4)…
Figures S3-S5 are incorrectly ordered.
We thank the reviewer for noticing that detail, the numbers of figures S3 and S5 are changed accordingly.
Figure S2 text boxes are illegible.
We decided to show an enlarged view of the ATTO site on the map without the extra information provided in the text boxes, as those are only interesting from a logistical point of view.
Figure S4 could benefit should be replaced with a higher resolution version.
We agree, Fig. S4 is now replaced by a higher resolution figure.
Figure S5 shows a plot of benzene with no data and non-sensical axes.
We thank the reviewer for pointing this out, we removed the concerning subplot (C5-alkenes) as suggested.
-
AC1: 'Reply on RC1', Akima Ringsdorf, 04 Jun 2024
-
RC2: 'Comment on egusphere-2024-1210', Anonymous Referee #2, 26 Jun 2024
Review of “Investigating Carbonyl Compounds above the Amazon Rainforest using PTR-ToF-MS with NO+ Chemical Ionization” by Akima Ringsdorf et al. The manuscript analyzes the characteristics of different carbonyl compounds and emphasizes the necessity of supplementing the NO+ CIMS method to measure carbonyl compounds. The authors examine the sources and sinks in the Amazon rainforest of the selected carbonyl species in combination with a sufficient literature review. The article is substantial, with many citations and argumentation work. However, the writing focus of the discussion section of the manuscript is not clear enough, and the data analysis method is relatively simple. I recommend a major revision before its publication. My concerns in the manuscript are mainly listed below:
Specific comments:
- Line 99-100: What is the temporal variation of humidity during the observation? Even with NO+ ionizing chemistry, the reported C2-C9 carbonyl compounds are greatly affected by humidity. The author needs to specify whether the signal of these compounds has been calibrated for humidity.
- Line 101-121: What is the delay time of measured compounds？Does the time resolution of 20 s for NO+ PTR-ToF-MS be able to guarantee that the measured signal of speciated compounds was from the actual atmosphere, not the tube residue?
- Line 141-143: The author needs to specify the parameter setting for NO+ mode, including the ion source voltage and drift tube voltage since the difference of parameter setting will affect the abundance of impurity ions (H3O+, O2+, and NO2+). And the author also needs to give the abundance of impurity ions during the campaign, especially for the ratio of O2+/NO+, due to O2+will cause interference when using NO+ ionization for measurement.
- Line 187-197: It seems that the parameterized quantitative method proposed by Cappellin et al. is based on the proton transfer reaction between organic compounds and H3O+ I wonder if this method is suitable for NO+ chemistry. Because NO+ ions can react with organic compounds with multiple ways and occur simultaneously. I think the author needs to reconsider this issue. In addition, it is suggested that the author use a formula to explain how to obtain the sensitivity for those compounds not included in the gas standard based on k-rate.
- Table 1 and Table S1: According to previous studies for the reaction pathway of NO+ to organic compounds, the multiple reactions of NO+ to organic compounds (Charge transfer (M+), hydride abstraction (M+- H), association reaction (MNO+) or hydroxide ion transfer (M+- OH)) should occur simultaneously. However, the differences in ionization energy (IE) and the chemical bond can cause species to react more easily with NO+ in one particularly pathway, associated with the formation of fragments. Therefore, we need to identify the characteristic product ions (which refers to the ion formula the author shown in the table) according to the contribution of each product ion after reaction. The author should show this contribution here, which also be better explain the influence of different E/N conditions to measurements.
- Line 268-285: What is the contribution of local emissions and long-range transport during the measurement in dry season? As mentioned above that region is affected by long-range transport from African biomass burning pollution. And I prefer to see an overall picture of carbonyl emissions with concentrations and contributions.
- Line 298-309: Just a suggestion, maybe the author could further quantify the influence of biomass burning from Africa and South America based on PAN, which is basically present in aging plumes.1
- Line 334: Short-lived aldehydes do not include isoprene.
- Line 440-443: The authors believe that ethanol was formed by anaerobic reactions on the surface, but why does the ethanol concentration decrease with increasing altitude during the transition season?
- Line 498-545: During the daytime, acetone and C5-ketones have stronger vertical gradients than the more reactive isoprene and monoterpenes. This phenomenon is very important for analyzing the sources and sinks of ketones. On a well-mixed daytime, it is difficult to understand the strong vertical gradient of ketones, even though the ketones have a strong source at the surface, as the authors believe.
Technical Corrections:
- Table 1: The references involved in the table may be annotated separately.
- The picture can be named (for example, Fig. 1(a)), which can avoid the description of upper, lower, etc.
- S6 and S7: The naming format used for each species in the figures should be unified, now there are both species names, molecular formulas and ionic formulas
- S7: Why is the first picture empty?
Reference
- Liang, Y.; Weber, R. J.; Misztal, P. K.; Jen, C. N.; Goldstein, A. H., Aging of Volatile Organic Compounds in October 2017 Northern California Wildfire Plumes. Environ Sci Technol 2022, 56, (3), 1557-1567.
Citation: https://doi.org/10.5194/egusphere-2024-1210-RC2 -
AC2: 'Reply on RC2', Akima Ringsdorf, 19 Jul 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1210/egusphere-2024-1210-AC2-supplement.pdf
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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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