the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 04 Dec 2023
Technical Note: A Technique to Convert NO2 to NO2– with S(IV) and its Application to Measuring Nitrate Photolysis
Abstract. Nitrate photolysis is a potentially significant mechanism for “renoxifying” the atmosphere, i.e., converting nitrate into nitrogen oxides (nitrogen dioxide (NO2) and nitric oxide (NO)) and nitrous acid (HONO). Nitrate photolysis in the environment occurs through two channels, which produce: (1) NO2 and hydroxyl radical (•OH) and (2) nitrite (NO2–) and an oxygen atom (O(3P)). Although the aqueous quantum yields and photolysis rate constants of both channels have been established, field observations suggest that nitrate photolysis is enhanced in the environment. Laboratory studies investigating these enhancements typically only measure one of the two photo-channels, since measuring both channels generally requires separate analytical methods and instrumentation. However, measuring only one channel makes it difficult to assess whether secondary chemistry is enhancing one channel at the expense of the other, or if there is an overall enhancement of nitrate photochemistry. Here, we show that the addition of S(IV), i.e., bisulfite and sulfite, can convert NO2 to NO2–, allowing measurement of both nitrate photolysis channels with the same equipment. By varying the concentration of S(IV) and exploring method parameters, we determine the experimental conditions that quantitatively convert NO2 and accurately quantify the resulting NO2–. We then apply the method to a test case, showing how an •OH scavenger in solution prevents the oxidation of NO2– to NO2 but does not enhance the overall photolysis efficiency of nitrate.
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Notice on discussion status
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.
- Preprint
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Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-2876', Anonymous Referee #1, 12 Dec 2023
The manuscript by Lieberman et al. details a method to measure dissolved nitrogen dioxide (NO2) concentrations in aqueous solutions. The method relies on the conversion of aqueous NO2 into nitrite using S(IV) (= HSO3- + SO32-), followed by quantitation of nitrite by the Griess method. This technical note is well-written and provides enough detail to easily reproduce the experiments. The method is useful and represents a novel approach to (near)simultaneously measuring nitrite and NO2 concentrations arising during nitrate photolysis. The application of this method to studying nitrate photoproduct yields is notable given the importance of elucidating renoxification pathways derived from nitrate photolysis. As pointed out by the authors, previous measurements have been limited to measuring the quantum yields of the nitrite and NO2 photolysis channels with different analytical methods. The current method will enable the use of a single method to assess whether secondary chemistry is enhancing one channel at the expense of the other or if there is an overall enhancement of the primary nitrate quantum yield. Below are some points that came up during my reading of the manusript.
Figure 1: The content of this figure / scheme really doesn’t lend itself well to its own figure. I feel it would be better to simply replace this with three separate equations (R1-R3) in the main text.
Line 99: Please specifically indicate the pH (or pH range) of the solution here.
Section 2.3: Please address the possibility that HSO3- can act as a scavenger of OH radical produced from nitrate photolysis. Also, this reaction would form sulfite radical anion and I would like to know your thoughts on whether this would interfere with the chemistry. Does one have to correct the quantum yields to account for this? In addition to this, please address the possibility that H2O2 can oxidized the Griess reaction reagents or nitrite, converting it to nitrate via peroxynitrite. I would expect for a paper such as this for the researchers to test potential interferences with the method. This is not done beyond the limited intercomparison of nitrite and NO2 quantum yields presented in the figures. If a more complex matrix was used (e.g., in the presence of organic molecules, dissolved organic matter, transition metals, etc.) could we expect the method to accurately quantitate NO2 concentrations?
Line 141: How did you determine the limit of detection?
Lines 210-218: Practically speaking, can the authors please provide some comments on how variable these results are and how stable the system is. That is, if I try to use this method, how important is it to follow the indicated timing here? If one lets the reaction go longer or doesn’t “develop” the reaction solutions soon enough, does one get a different answer? Can one store the reaction solutions in the freezer for later analysis and still get comparable answers? Any insights?
Line 263: The authors suggest there are other reactions that lead to consumption of and NO2, quantifying it ask kother. Can the authors please provide some insights into what they think this(ese) reaction(s) is(are)?
Citation: https://doi.org/10.5194/egusphere-2023-2876-RC1 -
RC2: 'Comment on egusphere-2023-2876', Anonymous Referee #2, 07 Jan 2024
This paper presents a method that converts NO2 to NO2– using S(IV) so that nitrate photolysis products can be measured by the same instrument. This method can derive total nitrate photolysis quantum yield from the two channels by one analytical method, allowing determination of whether the nitrate photolysis is impacted by one channel or both channels in different environments. This method could potentially be useful to our community in better quantifying nitrate renoxification, but there are issues that need to be addressed.
Major comments:
- This method is developed to be used for bulk nitrate solutions. However, many studies (including references cited in this paper) on enhanced nitrate photolysis were about particulate nitrates or nitrates on surfaces. The authors need to address this disconnection. How can this method be used to address particulate nitrate/surface-absorbed nitrate photolysis? With complex composition in atmospheric particles, can this method still be valid?
- Did the authors investigate whether the added H2O2 would react with NO2- and interfere with the quantum yield quantification?
Minor/technical comments
- In equation (1)(2) and (4), the x should be a multiplication sign, not letter x.
- Figure 3 caption: “Measured quantum yields of nitrite (yellow bars)”. I think the authors mean blue bars.
Citation: https://doi.org/10.5194/egusphere-2023-2876-RC2 - AC1: 'Comment on egusphere-2023-2876', Cort Anastasio, 20 Feb 2024
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-2876', Anonymous Referee #1, 12 Dec 2023
The manuscript by Lieberman et al. details a method to measure dissolved nitrogen dioxide (NO2) concentrations in aqueous solutions. The method relies on the conversion of aqueous NO2 into nitrite using S(IV) (= HSO3- + SO32-), followed by quantitation of nitrite by the Griess method. This technical note is well-written and provides enough detail to easily reproduce the experiments. The method is useful and represents a novel approach to (near)simultaneously measuring nitrite and NO2 concentrations arising during nitrate photolysis. The application of this method to studying nitrate photoproduct yields is notable given the importance of elucidating renoxification pathways derived from nitrate photolysis. As pointed out by the authors, previous measurements have been limited to measuring the quantum yields of the nitrite and NO2 photolysis channels with different analytical methods. The current method will enable the use of a single method to assess whether secondary chemistry is enhancing one channel at the expense of the other or if there is an overall enhancement of the primary nitrate quantum yield. Below are some points that came up during my reading of the manusript.
Figure 1: The content of this figure / scheme really doesn’t lend itself well to its own figure. I feel it would be better to simply replace this with three separate equations (R1-R3) in the main text.
Line 99: Please specifically indicate the pH (or pH range) of the solution here.
Section 2.3: Please address the possibility that HSO3- can act as a scavenger of OH radical produced from nitrate photolysis. Also, this reaction would form sulfite radical anion and I would like to know your thoughts on whether this would interfere with the chemistry. Does one have to correct the quantum yields to account for this? In addition to this, please address the possibility that H2O2 can oxidized the Griess reaction reagents or nitrite, converting it to nitrate via peroxynitrite. I would expect for a paper such as this for the researchers to test potential interferences with the method. This is not done beyond the limited intercomparison of nitrite and NO2 quantum yields presented in the figures. If a more complex matrix was used (e.g., in the presence of organic molecules, dissolved organic matter, transition metals, etc.) could we expect the method to accurately quantitate NO2 concentrations?
Line 141: How did you determine the limit of detection?
Lines 210-218: Practically speaking, can the authors please provide some comments on how variable these results are and how stable the system is. That is, if I try to use this method, how important is it to follow the indicated timing here? If one lets the reaction go longer or doesn’t “develop” the reaction solutions soon enough, does one get a different answer? Can one store the reaction solutions in the freezer for later analysis and still get comparable answers? Any insights?
Line 263: The authors suggest there are other reactions that lead to consumption of and NO2, quantifying it ask kother. Can the authors please provide some insights into what they think this(ese) reaction(s) is(are)?
Citation: https://doi.org/10.5194/egusphere-2023-2876-RC1 -
RC2: 'Comment on egusphere-2023-2876', Anonymous Referee #2, 07 Jan 2024
This paper presents a method that converts NO2 to NO2– using S(IV) so that nitrate photolysis products can be measured by the same instrument. This method can derive total nitrate photolysis quantum yield from the two channels by one analytical method, allowing determination of whether the nitrate photolysis is impacted by one channel or both channels in different environments. This method could potentially be useful to our community in better quantifying nitrate renoxification, but there are issues that need to be addressed.
Major comments:
- This method is developed to be used for bulk nitrate solutions. However, many studies (including references cited in this paper) on enhanced nitrate photolysis were about particulate nitrates or nitrates on surfaces. The authors need to address this disconnection. How can this method be used to address particulate nitrate/surface-absorbed nitrate photolysis? With complex composition in atmospheric particles, can this method still be valid?
- Did the authors investigate whether the added H2O2 would react with NO2- and interfere with the quantum yield quantification?
Minor/technical comments
- In equation (1)(2) and (4), the x should be a multiplication sign, not letter x.
- Figure 3 caption: “Measured quantum yields of nitrite (yellow bars)”. I think the authors mean blue bars.
Citation: https://doi.org/10.5194/egusphere-2023-2876-RC2 - AC1: 'Comment on egusphere-2023-2876', Cort Anastasio, 20 Feb 2024
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Aaron Lieberman
Julietta Picco
Murat Onder
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(731 KB) - Metadata XML
-
Supplement
(336 KB) - BibTeX
- EndNote
- Final revised paper