Dear authors,

First of all, sorry for long delay on the final decision. Since the manuscript got
split opinions in the first round review, I invited the third referee in this round.
Now, I receive the opinions from the third referee that may be attached
(shown) in this mail. Based on the third referee's opinion, I have to make this
decision. Again, I am sorry that I cannot be more positive on this manuscript.
After reflecting all the comments made from three referees, please revisit acp.

Best regards,

Chul H. Song

Dear Dr. Kelly Peireira,

Could you uplaod the revised manuscript and your relpies? Thank you!

Chul H. Song

Dear authors,

It is the time to finalize. I invited the third reviewer to review the revised manuscript and authors' replies as well as two previous reviewers' decisions at the first & second rounds of acpd (not asking to make more comments). Particularly, I asked the third reviewer to determine whether the first reviewer's negative points made at the first stage of acpd were proper.

Based on the third reviewer's opinion, it appears that the current form of acp-2017-603 has an obvious limitation in covering the emission profiles of intermediate VOCs (roughly, C12-C22 alkane compounds) from diesel engine. Currently, in the air quality modeling, the formation of secondary organic aerosols (SOAs) is a hot issue. In this context, the IVOCs and SVOCs emissions and/or emission profiles are of great importnace. However, this manuscript provides only limited spectrum of VOC emissions profiles from diesel engine. Taking all reviewers' opinions into account, I have no choice but to make this decision. I am sorry that I cannot be more positive. Also, I am sorry that it takes a long time for this final decision.

Best regards,

Chul H. Song

Editor report from 22 May 2018:

Dear Dr. Pereira,

Following up on the appeal against the editorial decision not to accept manuscript acp-2017-603 for final publication, the ACP executive committee has carefully re-assessed the review process and the manuscript.

We regret that the process was not as efficient and swift as intended and usually achieved in the journal’s interactive open access publishing approach with public peer review and discussion. Accordingly, we will do our best to further improve the guidelines for all involved parties and further minimize the potential for such inconveniences and controversies. In particular, we intend to encourage authors, editors and reviewers to critically check whether a manuscript actually fits within the scientific scope of the journal before it is posted for public review and discussion.

In the present case, it seems that all involved parties overlooked during manuscript preparation, submission, and access review that the subject and results of the reported investigations are not within the scope of ACP, which “is focused on studies with general implications for atmospheric science rather than investigations that are primarily of local or technical interest” as specified on the journal homepage and re-emphasized under “Aims and scope” and “Manuscript types”.
https://www.atmospheric-chemistry-and-physics.net/
https://www.atmospheric-chemistry-and-physics.net/about/aims_and_scope.html
https://www.atmospheric-chemistry-and-physics.net/about/manuscript_types.html

The title and abstract of manuscript acp-2017-603 clearly indicate that the reported investigations are focused on combustion and emission control technologies rather than atmospheric science:

“The Effect of Varying Engine Conditions on Unregulated VOC-IVOC Diesel Exhaust Emissions:
… investigate the effect of different engine conditions (i.e. load, speed, 15 ‘driving scenarios’) and emission control devices (with/without diesel oxidative catalyst, DOC) on the composition and abundance of unregulated exhaust gas emissions from a light-duty diesel engine,
… further technologies are required to reduce emission rates, specifically from cold engine conditions (i.e. poor engine combustion efficiencies) and below the working temperature of the DOC.
… this is the first study which attempts to decouple the effect of the DOC and combustion efficiency on the exhaust gas composition.”

Accordingly, most key references at the end of the introduction, where the scope of the study is outlined, and at the end of the results and discussion section, where the key findings are summarized, go to environmental and combustion technology-oriented journals like Environmental Science & Technology or Energy & Fuels rather than to atmospheric science journals like Atmospheric Chemistry and Physics:

Chin, J.-Y., Batterman, S. A., Northrop, W. F., Bohac, S. V., and Assanis, D. N.: Gaseous and Particulate Emissions from Diesel Engines at Idle and under Load: Comparison of Biodiesel Blend and Ultralow Sulfur Diesel Fuels, Energy & Fuels, 26, 6737-6748, 10.1021/ef300421h, 2012.

Cross, E. S., Sappok, A. G., Wong, V. W., and Kroll, J. H.: Load-Dependent Emission Factors and Chemical Characteristics of IVOCs from a Medium-Duty Diesel Engine, Environmental science & technology, 49, 13483-13491, 10.1021/acs.est.5b03954, 2015.

Gentner, D. R., Worton, D. R., Isaacman, G., Davis, L. C., Dallmann, T. R., Wood, E. C., Herndon, S. C., Goldstein, A. H., and Harley, R. A.: Chemical Composition of Gas-Phase Organic Carbon Emissions from Motor Vehicles and Implications for Ozone Production, Environmental science & technology, 47, 11837-11848, 10.1021/es401470e, 2013.

Gentner, D. R., Jathar, S. H., Gordon, T. D., Bahreini, R., Day, D. A., El Haddad, I., Hayes, P. L., Pieber, S. M., Platt, S. M., de Gouw, J., Goldstein, A. H., Harley, R. A., Jimenez, J. L., Prévôt, A. S. H., and Robinson, A. L.: Review of Urban Secondary Organic Aerosol Formation from Gasoline and Diesel Motor Vehicle Emissions, Environmental science & technology, 51, 1074-1093, 10.1021/acs.est.6b04509, 2017.

Gordon, T. D., Presto, A. A., Nguyen, N. T., Robertson, W. H., Na, K., Sahay, K. N., Zhang, M., Maddox, C., Rieger, P., 25 Chattopadhyay, S., Maldonado, H., Maricq, M. M., and Robinson, A. L.: Secondary organic aerosol production from diesel vehicle exhaust: impact of aftertreatment, fuel chemistry and driving cycle, Atmos. Chem. Phys., 14, 4643-4659, 10.5194/acp-14-4643-2014, 2014.

Yamada, H., Misawa, K., Suzuki, D., Tanaka, K., Matsumoto, J., Fujii, M., and Tanaka, K.: Detailed analysis of diesel vehicle exhaust emissions: Nitrogen oxides, hydrocarbons and particulate size distributions, Proceedings of the Combustion Institute, 20 33, 2895-2902, http://dx.doi.org/10.1016/j.proci.2010.07.001, 2011.

Yang, L., Franco, V., Mock, P., Kolke, R., Zhang, S., Wu, Y., and German, J.: Experimental Assessment of NOx Emissions from 73 Euro 6 Diesel Passenger Cars, Environmental science & technology, 49, 14409-14415, 10.1021/acs.est.5b04242, 2015.

Yao, Y.-F. Y.: Oxidation of Alkanes over Noble Metal Catalysts, Industrial & Engineering Chemistry Product Research and 25 Development, 19, 293-298, 10.1021/i360075a003, 1980.

Zhao, Y., Nguyen, N. T., Presto, A. A., Hennigan, C. J., May, A. A., and Robinson, A. L.: Intermediate Volatility Organic Compound Emissions from On-Road Diesel Vehicles: Chemical Composition, Emission Factors, and Estimated Secondary Organic Aerosol Production, Environmental science & technology, 49, 11516-11526, 10.1021/acs.est.5b02841, 2015.

Zhu, L., Cheung, C. S., Zhang, W. G., Fang, J. H., and Huang, Z.: Effects of ethanol–biodiesel blends and diesel oxidation catalyst (DOC) on particulate and unregulated emissions, Fuel, 113, 690-696, https://doi.org/10.1016/j.fuel.2013.06.028, 2013.

One of the few key references to an atmospheric science journal is Gordon et al. ACP 2014. Unlike Pereira et al. ACPD 2017, however, Gordon et al. ACP 2014 studied atmospheric processes (SOA formation) rather than the effects of combustion and oxidation catalyst efficiency on the diesel exhaust emissions of a specific type of diesel engine and oxidation catalyst.

In accordance with the comments of Referees #1 and #3, the atmospheric implications of the reported investigations appear limited and the manuscript would appear much better suited for publication in a journal focusing on environmental, combustion, and emission control technologies like ES&T or Energy & Fuels rather than in an atmospheric science journal like ACP.

Normally, manuscripts that are not within the scope of ACP should not be posted for public review and discussion in ACPD. Unfortunately, the editorial pre-selection has not worked out in the present case, and we sincerely regret the resulting complications. While we normally recommend that manuscripts outside the scope of the journal are submitted to alternative publication venues, we feel that this may be particularly inconvenient and difficult in the present case. If you would still prefer to have your manuscript published in ACP rather than submitting it to a more technology-oriented journal, we could thus offer to accept your manuscript for publication in ACP as a technical note.

In this case, the title should be changed into “Technical Note: Speciation of unregulated VOC-IVOC diesel engine emissions using an atmospheric chamber system” (or something similar) and the manuscript text should be adjusted accordingly. In particular, the following and related aspects should be emphasized and extended in the abstract, introduction and conclusions:
… In contrast to previous studies, this work combines both detailed chemical speciation and groupings of VOC–IVOCs based on their structure and functionality,
… Exhaust dilution ratios were varied to represent a range of ambient conditions from near to downwind of an emission source, capturing the chemical and physical transformations of semi-volatiles in the exhaust emissions with varying ambient dilutions.

Alternatively, you could of course also pursue publication of your manuscript in a more technology-oriented journal (https://www.atmospheric-chemistry-and-physics.net/about/faqs.html, FAQ Point 7, Option C):
“The authors can submit the manuscript to an alternative journal. In many scientific journals, prepublication in a scientific discussion forum (like ACPD) is considered equivalent to prepublication on a scientific preprint server (like arXiv.org) and is not regarded as a reason for exclusion from (re)submission for fully peer-reviewed publication. We expect that in the long run most if not all scientific journals will adopt this policy. Normally, even very good manuscripts can be further improved by revision. In the unlikely event that a very good manuscript cannot achieve publication in ACP, a revised and further improved version is very likely to achieve publication in an alternative journal.”
If desired or required, the discussion paper can also be formally withdrawn from ACPD to facilitate acceptance in alternative publication venues (https://www.atmospheric-chemistry-and-physics.net/about/publication_policy.html, Corrections & Retractions):
“Retraction: authors or, in specific cases, editors can decide to formally withdraw a published journal article. The article stays online but the reader is notified about the retraction. … The retraction also includes the withdrawal of discussion papers that are not accepted for further review after discussion or where a revised manuscript was not accepted for final journal publication.”

Please let us know how you would like to proceed and if you have any questions or comments.

Many thanks and best regards,
Uli Pöschl
(on behalf of the ACP executive editors)

Dear Dr. Pereira and Colleagues,

Following up on our preceding exchange and for consistency with the journal scope of ACP (atmospheric science rather than environmental technology), please adjust the abstract and conclusions of the revised manuscript as suggested in the attached file or in a similar way, further emphasizing the atmospheric science approach applied and described in this study and technical note (use of atmospheric simulation chamber and measurement techniques) rather than particular aspects of combustion technology (efficiency of a single Euro 4 engine and DOC).

Many thanks and best regards,
Uli Pöschl

Dear Dr. Pereira and Colleagues,

Thanks and yes, a couple of editing suggestions were apparently missed. Please consider specifying the nature of the values reported in the abstract (arithmetic mean +/- standard deviation, correct?) and implement a final clarification of the match between manuscript contents and journal scope in the last sentence of the abstract as follows:

“To our knowledge, this is the first study using an atmospheric simulation chamber to separate the effects of the DOC and combustion efficiency on the exhaust gas composition.”

Many thanks and best regards,
Uli Pöschl

Dear Dr. Pereira and Colleagues,

Thanks for the revised submission. It seems, however, that a couple of adjustments and clarifications are still missing. (1) Please define the term "experimental uncertainty" in the main text. It seems not appropriate to introduce such a term in the abstract without specifying it in the main text. (2) Please implement a final clarification of the match between the content/message of the technical note and the journal scope of ACP in the last sentence of the abstract as follows: “To our knowledge, this is the first study using an atmospheric simulation chamber to separate the effects of the DOC and combustion efficiency on the exhaust gas composition.”

Many thanks and best regards,
Uli Pöschl