Volatile organic compounds (VOCs) in photochemically aged air from the eastern and western Mediterranean

Derstroff, Bettina; Hüser, Imke; Bourtsoukidis, Efstratios; Crowley, John N.; Fischer, Horst; Gromov, Sergey; Harder, Hartwig; Janssen, Ruud H. H.; Kesselmeier, Jürgen; Lelieveld, Jos; Mallik, Chinmay; Martinez, Monica; Novelli, Anna; Parchatka, Uwe; Phillips, Gavin J.; Sander, Rolf; Sauvage, Carina; Schuladen, Jan; Stönner, Christof; Tomsche, Laura; Williams, Jonathan

doi:https://doi.org/10.5194/acp-17-9547-2017

Articles | Volume 17, issue 15

https://doi.org/10.5194/acp-17-9547-2017

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

https://doi.org/10.5194/acp-17-9547-2017

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

Articles | Volume 17, issue 15

Research article

|

09 Aug 2017

Research article |

| 09 Aug 2017

Volatile organic compounds (VOCs) in photochemically aged air from the eastern and western Mediterranean

Bettina Derstroff, Imke Hüser, Efstratios Bourtsoukidis, John N. Crowley, Horst Fischer, Sergey Gromov, Hartwig Harder, Ruud H. H. Janssen, Jürgen Kesselmeier, Jos Lelieveld, Chinmay Mallik, Monica Martinez, Anna Novelli, Uwe Parchatka, Gavin J. Phillips, Rolf Sander, Carina Sauvage, Jan Schuladen, Christof Stönner, Laura Tomsche, and Jonathan Williams

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Final revised paper (published on 09 Aug 2017)
Supplement to the final revised paper
Preprint (discussion started on 06 Sep 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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- Supplement

SC1: 'Regarding the Henry's law coefficient of acetic acid', D. Taraborrelli, 15 Sep 2016
- AC1: 'Reply to Taraborrelli', Bettina Derstroff, 15 Dec 2016
RC1: 'Review of "Volatile organic compounds (VOCs) in photochemically aged air from the Eastern and Western Mediterranean"', Anonymous Referee #1, 24 Oct 2016
- AC2: 'Reply reviewer 1', Bettina Derstroff, 15 Dec 2016
RC2: 'Review', Anonymous Referee #2, 03 Nov 2016
- AC3: 'Reply reviwer 2', Bettina Derstroff, 15 Dec 2016
EC1: 'Further review', Rupert Holzinger, 17 Nov 2016

Peer-review completion

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

AR by Bettina Derstroff on behalf of the Authors (29 Apr 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (15 May 2017) by Rupert Holzinger

RR by Anonymous Referee #2 (27 May 2017)

Suggestions for revision or reasons for rejection

Review of Derstroff et al., “Volatile organic compounds (VOCs) in photochemically aged air from the Eastern and Western Mediterranean.
Major comments:
1. The new draft is much improved from that previously reviewed. There is now a clear scientific story that emerges from the data set.
2. The discussion of BVOC which comprises a fairly substantial fraction of the introduction and Instrumentation sections seems largely unrelated to the study. I suggest the authors consider moving this to an appendix (“Local chemistry”) so that focus on OVOC and ozone is not diluted.
Minor comments:
1. The isoprene intercomparison (GC vs PTR) suggests that another longer-lived compound may give signal at m/z 69. Is there any GC measurement of MBO, for example?
2. The discussion of the uncertainty in acetic acid measurements is still very difficult to follow. Given the large (2.5x) difference in field and post campaign calibration, I don’t see how the uncertainty (51%) is derived. Please review lns 197-225 and clarify how the uncertainty is determined.
3. Ln 410. The MVK+MAC signal also likely includes a (small) contribution from ISOPOOH.

Suggested edits:

1. In general, the manuscript could use a significant effort to strengthen the prose. Wording is often awkward with dangling dependent clauses. These distract from the overall study needlessly. With some effort and reorganization, the manuscript could be reduced by 1/3 while enhancing both readability and impact.
2. Here, for example, is my suggestion for the abstract:
During the summertime CYPHEX campaign (CYprus PHotochemical EXperiment 2014), volatile organic compounds (VOCs) were measured from a 650 m hilltop site in western Cyprus (34.95o N 32.38o E). Periodic shifts in wind direction resulted in the site being alternately impacted by photochemically-processed emissions from Western (Spain, France, Italy) and Eastern (Turkey, Greece) Europe. On some nights, the site was situated within the residual layer/free troposphere (characterized by high ozone and low relative humidity levels). The mixing ratios of the oxygenated volatile organic compounds (OVOCs) methanol and acetone were approximately an order of magnitude higher (~ 2.5-3 ppbv) than the locally-emitted isoprene and aromatic compounds. Acetic acid was present at mixing ratios ~ 1.2 ppbv during daytime. Ozone and OVOC levels were ~ 20% and ~ 30-60% higher, respectively, in air arriving from the East. In both regimes, acetone and methanol are highly correlated (r2 = 0.68 (West) 0.73 (East)). Using transport times simulated with FLEXPART, the loss rate of methanol and acetone due to the sum of photochemical processing, sea surface contact and dilution was calculated to be ~0.75 day-1 and ~0.50 day-1, respectively. Simulations using the EMAC model underestimate this loss rates. We suggest that loss of methanol and acetone to the Mediterranean Ocean may be enhanced by microbial consumption.

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RR by Anonymous Referee #1 (31 May 2017)

ED: Reconsider after minor revisions (Editor review) (09 Jun 2017) by Rupert Holzinger

AR by Bettina Derstroff on behalf of the Authors (14 Jun 2017) Author's response Manuscript

ED: Publish as is (29 Jun 2017) by Rupert Holzinger

AR by Bettina Derstroff on behalf of the Authors (29 Jun 2017)

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Short summary

The aim of the study was to examine aged air masses being transported from the European continent towards Cyprus. Longer-lived oxygenated volatile organic compounds (OVOCs) such as methanol were mainly impacted by long-distance transport and showed higher values in air masses from eastern Europe than in a flow regime from the west. The impact of the transport through the marine boundary layer as well as the influence of the residual layer/free troposphere on OVOCs were studied.