Mixing state of oxalic acid containing particles in the rural area of Pearl River Delta, China: implications for the formation mechanism of oxalic acid

Cheng, Chunlei; Li, Mei; Chan, Chak K.; Tong, Haijie; Chen, Changhong; Chen, Duohong; Wu, Dui; Li, Lei; Wu, Cheng; Cheng, Peng; Gao, Wei; Huang, Zhengxu; Li, Xue; Zhang, Zhijuan; Fu, Zhong; Bi, Yanru; Zhou, Zhen

doi:https://doi.org/10.5194/acp-17-9519-2017

Articles | Volume 17, issue 15

https://doi.org/10.5194/acp-17-9519-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-17-9519-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 17, issue 15

Research article

|

08 Aug 2017

Research article |

| 08 Aug 2017

Mixing state of oxalic acid containing particles in the rural area of Pearl River Delta, China: implications for the formation mechanism of oxalic acid

Chunlei Cheng, Mei Li, Chak K. Chan, Haijie Tong, Changhong Chen, Duohong Chen, Dui Wu, Lei Li, Cheng Wu, Peng Cheng, Wei Gao, Zhengxu Huang, Xue Li, Zhijuan Zhang, Zhong Fu, Yanru Bi, and Zhen Zhou

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Preprint (discussion started on 21 Dec 2016)
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Interactive discussion

Status: closed

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

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RC1: 'Reviewer's cooments on the paper by Cheng et al', Anonymous Referee #1, 09 Jan 2017
- AC1: 'response letter to RC1', Mei Li, 06 Apr 2017
RC2: 'Review', Anonymous Referee #2, 11 Jan 2017
- AC2: 'response letter to RC2', Mei Li, 06 Apr 2017
RC3: 'Review', Anonymous Referee #3, 19 Jan 2017
- AC3: 'response letter to RC3', Mei Li, 06 Apr 2017

Peer-review completion

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

AR by Mei Li on behalf of the Authors (07 Apr 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (11 Apr 2017) by Kimitaka Kawamura

RR by Anonymous Referee #2 (14 Apr 2017)

RR by Anonymous Referee #3 (14 Apr 2017)

ED: Reconsider after major revisions (25 Apr 2017) by Kimitaka Kawamura

AR by Mei Li on behalf of the Authors (24 May 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (14 Jun 2017) by Kimitaka Kawamura

RR by Anonymous Referee #3 (15 Jun 2017)

Suggestions for revision or reasons for rejection

Main comment:
Throughout the manuscript, the authors state that ‘acidic aqueous phase chemical processing’ leads to oxalic acid. I still do not understand why the authors keep emphasizing the role of acidity. In general, the rate constants of dicarboxylates (e.g. glyoxylate, pyruvate) decrease with acidity. Or are the authors saying that the LOSS PROCESSES of oxalic acid are slowed down at higher acidity and therefore oxalic acid accumulated? If so, that should be mentioned somewhere that the pH was sufficiently low that indeed oxalic acid (H2C2O4) and not its anions (HC2O4-, C2O42-) was predominant. However, this only occurs at extremely low pH, i.e. if pH ~ pKa(H2C2O4) ~ 1.25.

l. 55: replace ‘was’ by ‘were’

l. 60 – 62: This sentence seems meaningless and redundant “The strong acidity… indicated an acidic environment…”

l. 111: The formation MECHANISM of oxalic acid is realtively well constrained, i.e. the facts that glyoxal is oxidized to glyoxylic acid and further to oxalate. However, the oxidation RATES are associated with uncertainties as they are the product of the reactants (organics and oxidants) and the rate constants.

l. 342: As mentioned in my previous comments, the figure does not DISCUSS the influence of the pH. A discussion would include a line of arguments on the various processes that include RH, inorganic ions etc and how and to what extent they affect pH. Since this information cannot be gathrered form Fig. S5, it is not a discussion but merely the representation of temporal trends of pH, RH, inorganic ions etc.

l. 349: Remove ‘of’

l. 352: replace ‘aerosols-related’ by ‘aerosol-related’

l. 383: Why ‘likely correlated’? There are robust statistical methods that can be applied to confirm (or refuse) a statistical correlation.

l. 389: replace ‘extreme’ by ‘extremely’

l. 390: What do you mean by ‘above asynchronous variation’? I suggest replacing it by a more common expression.

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ED: Reconsider after minor revisions (Editor review) (28 Jun 2017) by Kimitaka Kawamura

AR by Mei Li on behalf of the Authors (06 Jul 2017) Author's response Manuscript

ED: Publish as is (10 Jul 2017) by Kimitaka Kawamura

AR by Mei Li on behalf of the Authors (10 Jul 2017) Manuscript

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Short summary

Oxalic acid is an abundant and ubiquitous constituent in secondary organic aerosol (SOA) and can be an effective tracer for the oxidative processes leading to the formation of SOA. In this work photochemical reactions have a significant contribution to oxalic acid formation in summer, while in winter the formation of oxalic acid is closely associated with the oxidation of organic precursors in the aqueous phase.