Quantifying alkane emissions in the Eagle Ford Shale using boundary layer enhancement

Roest, Geoffrey; Schade, Gunnar

doi:https://doi.org/10.5194/acp-17-11163-2017

Articles | Volume 17, issue 18

https://doi.org/10.5194/acp-17-11163-2017

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

https://doi.org/10.5194/acp-17-11163-2017

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

Articles | Volume 17, issue 18

Research article

|

20 Sep 2017

Research article |

| 20 Sep 2017

Quantifying alkane emissions in the Eagle Ford Shale using boundary layer enhancement

Geoffrey Roest and Gunnar Schade

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Final revised paper (published on 20 Sep 2017)
Supplement to the final revised paper
Preprint (discussion started on 15 Dec 2016)
Supplement to the preprint

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review of Roest and Schade (2016)', Anonymous Referee #1, 15 Dec 2016
- AC1: 'Response to RC1: 'Review of Roest and Schade (2016)', Anonymous Referee #1', Geoffrey Roest, 23 Mar 2017
RC2: 'Review of Roest and Schade', Anonymous Referee #2, 29 Dec 2016
- AC2: 'Response to RC2: 'Review of Roest and Schade', Anonymous Referee #2', Geoffrey Roest, 23 Mar 2017

Peer-review completion

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

AR by Geoffrey Roest on behalf of the Authors (21 Apr 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (22 Apr 2017) by Steven Brown

RR by Anonymous Referee #2 (05 May 2017)

Suggestions for revision or reasons for rejection

The authors have addressed most of the issues raised by the original reviewers. However, one main issue remains that must be addressed before I would recommend publication. The issue I have is with the authors’ treatment of the PBL height and its related uncertainties. In their response to reviewers, page C5, the authors refer to an average PBL height of 1789 ± 164 m, or an uncertainty of 9.2%. First, in the supplementary materials provided, there is no Table S3, so it is difficult to ascertain the authors’ treatment of the PBL height uncertainty. It is also not explicitly stated in the text, which it probably should be. Second, for the Barnett region, Karion et al. (2015) estimated the PBL height uncertainty between 12 and 31%, with an average of 24%, and that was from actual measurements of the PBL height. I find it difficult to believe that the NARR model would be more than twice as certain as actual measurements, especially since both study regions are relatively flat. I think the modeled PBL height should have at least a 25% uncertainty, if not more. While increasing the PBL height in the Monte Carlo analysis likely won’t change the conclusions of the manuscript (although the IQR of the emission rate will likely increase), I think it would make it more defensible scientifically.

Other comments:

page 1, line 11: uncapitalize n-Butane

page 2, lines 16 to 21: the volumes reported should be in SI units

page 5, line 34: can the authors quantify the “major source of uncertainty” that has been introduced? How do the authors know it is “major”? If the authors ignore it, then it really introduces no additional uncertainty other than what are stated in the conclusions. If the authors accounted for this uncertainty, they should state what it is. Otherwise, I would change “a major source of uncertainty” to “an unquantified uncertainty”.

page 7, line 17: remove “the” to read “as outlined in Sect. 2.4.”

Figure 2: why wouldn’t ethane mixing ratios from the south be expected to be as great as when the winds are from the southeast or west?

Figure 4: does this map include the county that Floresville is in, and is it colored on the grey scale? If not, I’d add it; if so, I’d state that in the caption and in the main body where the discussion of how far Floresville is from the nearest well.

Figure S7: change to “correlations were weak”

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ED: Reconsider after minor revisions (Editor review) (13 May 2017) by Steven Brown

AR by Geoffrey Roest on behalf of the Authors (14 Jun 2017) Manuscript

ED: Publish subject to technical corrections (27 Jul 2017) by Steven Brown

AR by Geoffrey Roest on behalf of the Authors (02 Aug 2017) Author's response Manuscript

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Short summary

We used atmospheric concentrations of hydrocarbons to estimate emissions from regional oil and gas activities in the Eagle Ford Shale in southern Texas to better understand their air quality impacts. While higher hydrocarbons emissions are underestimated, emissions of methane from raw natural gas sources appear lower than the US EPA's current estimate. However, we identified liquid storage tanks as an additional source of methane and as the dominant source of regional hydrocarbon emissions.