Production of peroxy nitrates in boreal biomass burning plumes over Canada  during the BORTAS campaign

Busilacchio, Marcella; Di Carlo, Piero; Aruffo, Eleonora; Biancofiore, Fabio; Dari Salisburgo, Cesare; Giammaria, Franco; Bauguitte, Stephane; Lee, James; Moller, Sarah; Hopkins, James; Punjabi, Shalini; Andrews, Stephen; Lewis, Alistair C.; Parrington, Mark; Palmer, Paul I.; Hyer, Edward; Wolfe, Glenn M.

doi:https://doi.org/10.5194/acp-16-3485-2016

Articles | Volume 16, issue 5

https://doi.org/10.5194/acp-16-3485-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue:

Quantifying the impact of Boreal fires on tropospheric oxidants...

https://doi.org/10.5194/acp-16-3485-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 16, issue 5

Research article

|

17 Mar 2016

Research article |

| 17 Mar 2016

Production of peroxy nitrates in boreal biomass burning plumes over Canada during the BORTAS campaign

Marcella Busilacchio, Piero Di Carlo, Eleonora Aruffo, Fabio Biancofiore, Cesare Dari Salisburgo, Franco Giammaria, Stephane Bauguitte, James Lee, Sarah Moller, James Hopkins, Shalini Punjabi, Stephen Andrews, Alistair C. Lewis, Mark Parrington, Paul I. Palmer, Edward Hyer, and Glenn M. Wolfe

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Final revised paper (published on 17 Mar 2016)
Preprint (discussion started on 03 Mar 2015)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC C883: 'Review of Busilacchio et al., ACPD, 15, 6009-6040, 2015', Anonymous Referee #1, 19 Mar 2015
- AC C4340: 'Reply to Reviewer #1', Piero Di Carlo, 03 Jul 2015
RC C949: 'BORTAS fire plumes', Anonymous Referee #2, 20 Mar 2015
AC C998: 'Reply to Referee #2', Piero Di Carlo, 23 Mar 2015
RC C1133: 'Review of Busilacchio et al.', Anonymous Referee #3, 26 Mar 2015
- AC C4341: 'Reply To Reviewer #3', Piero Di Carlo, 03 Jul 2015

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Piero Di Carlo on behalf of the Authors (03 Jul 2015) Author's response Manuscript

ED: Reconsider after major revisions (12 Aug 2015) by Rob MacKenzie

Dear Marcella Busilacchio and colleagues,
Thank you for taking a great deal of care to respond to the serious missgivings expressed by the referees. Given the concerns expressed, I feel that I will have to let the referees have a chance to comment on your changes, but first I would like you to consider the comments below, so that the manuscript can go back to the referees in the best possible shape,
Sincerely,
Rob

Page 4, lines 17-19: the descriptions of R3 and R4 as propagating and terminating reactions should be reversed – i.e., R4 is the propagation reaction. Also, I would say the ozone production reactions were R4-R8, not R5-R8, as this description is written.
Figure 2 looks a bit crude. Could the Legend be reduced in size so that it doesn’t dominate?
Figure 3: I recommend that the bottom left panel be drawn with the same x-axis limits as the top-left panel. This will de-emphasise the peak in mixing ratios around 4km but, nevertheless, the text should not say that “the concentrations of the species analysed are quite constant”.
Figure 4: if the pressure/altitude of the trajectories is not shown (e.g. by colouring the trajectories) then the caption should state what altitude range they cover.
Page 18, line 2. Given the reviewers’ comments it would be best to be explicit here that Figure 6 shows a scatterplot of ozone vs PN mixing ratios. The caption to Figure 6 should state which flights are shown and if there are any filter criteria (eg altitude) applied. The main text speaks about a 3rd category of air mass: air polluted by anthropogenic pollution other than biomass burning. The authors should state where this category occurs in Fig 6 (mixed in with “background”?).
Page 19, line 6: should this ratio be O3/PN rather than O3/PAN?
Page 20, line 20: split “radicalcan”
Page 22, line 15: should this be “evaluated as for methacrolein”?
Page 23, line 10: I think you will need to justify why you fixed OH in the MCM model, rather than let the model find its own OH based on the mixing ratios of the longer-lived species.
Captions for Table 4 and Figure 8: please reiterate which flights (or portions of flights) constitute “background” and which “plume”.
Table 4: please use standard scientific notation, as in the rest of the manuscript, rather than computer-code numbers.
Table 4, flight 622: the reaction-rate-coefficient results for the production terms for this flight are very different from those of other flights and from the model-derived results. Please check and provide a discussion of why they are outliers in the main text. These results are so different from the others that it will make use of averages potentially erroneous. The fact that the factor 10 differences in P(O3) and P(PN) cancel in the ratio of these numbers is not sufficient reason to leave them in the analysis.
Page 27, lines 8-9: This sentence does not seem to follow from the previous argument (which is that production of PN is *not* consistent between plume and background air); please re-phrase.
Page 27, line 17: why is B619 included in the “plume” flights here when it seems to be in the background category for Table 4?
Page 28, line 9ff. The paragraph beginning here seems to swap between discussion of ratios of production rates and ratios of mixing ratios. The paragraph should be re-written for clarity.

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AR by Piero Di Carlo on behalf of the Authors (22 Sep 2015) Author's response Manuscript

ED: Referee Nomination & Report Request started (23 Oct 2015) by Rob MacKenzie

RR by Anonymous Referee #2 (23 Oct 2015)

Suggestions for revision or reasons for rejection

The intellectual content of this paper is not substantially different from the earlier version that I indicated should be rejected. The paper remains a collection of facts without clear organizing ideas. It fails to persuade the reader that we understand something about the atmosphere. That it continues to focus on the trivial example of benzoylnitrate instead of the major terms on the total PN budget is an indication of its lack of focus. Moreover it doesn't address the issue of PNs reaching steady-state with NOx. In circumstances where that occurs or begins to, equations 1 and 2 are not appropriate for the analysis. In addition, if there are other sinks of NOx, then these equations don't describe the production of ozone properly. It is worth pointing out that the analysis that these equations are based on, contain an implicit assumption that PN formation is not important because PNs are in steady-state with NOx. The authors should at least discuss why that assumption is not appropriate here, give an idea how they estimate a value for their alpha and discuss why alpha might or might not vary in different locations in the atmosphere.

Other indicators of the lack of focus is the abstract which is twice the length it should be and the large number of uninformative figures. Figure 2, 3, 4, 5 and 7 could all be eliminated with no loss to the reader.

A minor comment. The discussion of methylperoxynitrate added in repsonse to the other reviewer should be shortened dramatically. Methylperoxynitrate is only abundant in the atmosphere at temperatures below 250K. Whether or not it is observed as NO2 depends on the lifetime to dissociation in the sample lines, not simply the temperature. For this paper, HO2NO2 is more likely an interference than methylperoxynitrate.

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RR by Anonymous Referee #3 (07 Nov 2015)

Suggestions for revision or reasons for rejection

The revised manuscript has been considerably improved. However, I have still concern a few points described in specific comments. The manuscript will be acceptable when the authors properly response these points.

(Specific comments)

1.
>> The definition of the branching ratio is wrong. The authors estimate alpha using the rate constants for reactions R3 and R4. R3 and R4 are reactions of peroxy radicals with NO2 and NO, respectively, so that NO and NO2 concentrations influence alpha values. Moreover, the contribution of R2 should not be neglected. If the branching ratio to R2 is large, P(O3) and P(PNs) becomes small.

> The reviewer is right that the branching ratio is defined as the ratio of the rate constant for a particular product of a reaction to the rate constant for the total set of possible products. However, we are looking to the branching ratio between two reactions: the R3 and R4, to understand the competition between the main branch of the RO2 reaction that produces O3 (R4) and the minor one that produces PNs (R3). This following Atkinson et al., 1984, O’Brien et al., 1998; Day et al., 2003; Perring et al., 2010 and many others that studied the branching ratio between R2 and R4 to point out the competition between the reaction of RO2 that produces O3 (R4) and the minor branch that produces ANs (R2). Therefore for the purpose of our study we do not think that we have to include in our branching ratio calculation the R2 reaction as in the branching ratio of the ANs is never included the R3 reaction, see for example the following papers: Atkinson et al., 1984, O’Brien et al., 1998; Day et al., 2003; Perring et al., 2010; Perring et al., 2013.

I found the authors are looking to the branching ratio between R3 and R4. However, the authors do not response the first comments.
"The definition of the branching ratio is wrong. The authors estimate alpha using the rate constants for reactions R3 and R4. R3 and R4 are reactions of peroxy radicals with NO2 and NO, respectively, so that NO and NO2 concentrations influence alpha values."

2. Many mistakes and wrong descriptions (for example, fonts) still remain in the text. The authors should take care of the text again. For example,

On page 4, P(O3), reaction (R1), (R2) etc...: Change all the fonts of chemical formula from italic to roman.

Table 1, "2" in (Sigma)RONO2: Indicate "2" by a subscript.

3. Figure 8 has poor quality. The authors should improve quality of it.

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ED: Reconsider after minor revisions (Editor review) (15 Dec 2015) by Rob MacKenzie

AR by Piero Di Carlo on behalf of the Authors (24 Dec 2015) Author's response Manuscript

ED: Publish as is (19 Feb 2016) by Rob MacKenzie

AR by Piero Di Carlo on behalf of the Authors (25 Feb 2016)

Short summary

Boreal fire emissions have little effect on ozone concentrations but evident impact on some NO_x reservoirs as peroxy nitrates that we quantified. This should be taken into account since NO_x reservoirs can be efficiently transported and may influence the ozone budget far away from the fire emission. The study is based on observations carried out on board the BAe 146 aircraft during BORTAS in Canada. We used a custom laser-induced fluorescence system to measure NO₂ and NO_x reservoirs.