CO₂, CH₄, and CO Emission Sources and Their Characteristics in the Lamto Ecological Reserve (Côte d’Ivoire)

Round 1

Reviewer 1 Report

1. What is the main question addressed by the research?

Analyzing the temporal relationships between local meteorological parameters and CO2, CH4 and CO levels will allow us to verify if the high levels observed at Lamto ecological reserve result from distant emission sources or from local areas. If local, which sources are: dam? human activities? Collecting data at this level will allow to feed models on dynamics of emission of gases, climate changes and impacts.
2. Do you consider the topic original or relevant in the field? Does it
address a specific gap in the field?  There are many gaps in this field. One of them is exactly to understand the meteorological dynamics behind pollution data observed in an ecological reserve, which, by principle and law, should have clean air. Measurement of pollutants is quite scarce in Africa, so, this manuscript brings important results for public polities, either to plan and control land use in the surrounding areas, or to negotiate with other countries regarding transboundary pollution. 
3. What does it add to the subject area compared with other published
material? Data collection in various points during 4 years and in different stations for CO2, CH4, CO using innovative techniques as the bivariate polar diagram, through the package Openair, adds to other published studies based mainly in modeling techniques.
4. What specific improvements should the authors consider regarding the
methodology? What further controls should be considered? As I have already suggested, a map of the studied area (the Lamto Ecological Reserve and surroundings) would contribute to the understanding of the readers.
5. Are the conclusions consistent with the evidence and arguments presented
and do they address the main question posed? Yes. Yes.
6. Are the references appropriate? Yes. As mentioned, there are some self-references, which are acceptable as this manuscript follows others published with results from the same investigation, but with different data.
7. Please include any additional comments on the tables and figures. Seasons GSS, GSP, PSS, PSP should be expressed in full names

Good quality of English language

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding corrections in red and suggestions of the manuscript revised.

Comments and Suggestions for Authors

 

Comments 1: What is the main question addressed by the research?

Analyzing the temporal relationships between local meteorological parameters and CO2, CH4 and CO levels will allow us to verify if the high levels observed at Lamto ecological reserve result from distant emission sources or from local areas. If local, which sources are: dam? human activities? Collecting data at this level will allow to feed models on dynamics of emission of gases, climate changes and impacts.

 

Response 1: We agree with this comment and thank you. There are many sources of GHG emissions in the area given its geographical location. These sources are: (1) the hydroelectric dam of Taabo located less than 8 km from the measurement point, (2) the A3 highway linking the city of Abidjan to that of Yamoussoukro and which records very dense road traffic during the day , is located 14 km northwest of the station, (3) livestock activities, (4) seasonal bush fires and burning, and (6) distant sources controlled by regional atmospheric dynamics, etc. ., thus this work seeks to know the location of dominant sources responsible for the significant levels of concentrations recorded ((see Line 90, version revised). Furthermore, in addition to feeding the gas emissions dynamics models that you rightly highlighted, Lamto data could also be used to validate satellite measurements. To this end, an EM27/SUN project for measuring the total column (i.e., the vertical profile) will be carried out in Lamto in a few months to provide better quality GHG monitoring.

 

Comments 2: Do you consider the topic original or relevant in the field? Does it
address a specific gap in the field?  There are many gaps in this field. One of them is exactly to understand the meteorological dynamics behind pollution data observed in an ecological reserve, which, by principle and law, should have clean air. Measurement of pollutants is quite scarce in Africa, so, this manuscript brings important results for public polities, either to plan and control land use in the surrounding areas, or to negotiate with other countries regarding transboundary pollution.

 

Response 2:  Due to the scarcity of quality data and ground measurements, the results of inversions used to deduce the distribution of GHG sources and sinks present large uncertainties throughout the African region. When such studies are carried out, they use emission inventories that are significantly biased towards under- and/or over-estimation. 

Monitoring the temporal evolution of these atmospheric GHGs using in situ and continuous data is an observable that can both help diagnose the impact of human activities on the atmosphere and model the various components of the carbon cycle in Africa with less error. For example, against all expectations, we found that the growth rates and concentration values of these GHGs observed at Lamto were similar to the global trend (see Tiemoko et al., 2020 and 2021), even though the 2700 ha Lamto reserve is not, a priori, a carbon emission zone.

By contributing in the same way as you; these different works using original and quality data are contributing to the understanding of this field of research in Africa.

 

3. What does it add to the subject area compared with other published
   material? Data collection in various points during 4 years and in different stations for CO2, CH4, CO using innovative techniques as the bivariate polar diagram, through the package Openair, adds to other published studies based mainly in modeling techniques.

 

Response 3: The back-trajectory analysis with the FLEXPART model with its global wind fields on the station data induced specific conclusions and highlighted the impact of distant emitting sources on in situ measurements of CO2 concentrations, CH4 and CO (see Tiemoko et al. (2020)). This modeling method was only able to explain part of the variance in the concentration levels of these GHGs. The Openair method based on local meteorological parameters (temperature, wind speed and direction) makes it possible to take local impacts into account to explain all of the variations in CO2, CH4 and CO on the site.

 

Comment 4: What specific improvements should the authors consider regarding the
methodology? What further controls should be considered? As I have already suggested, a map of the studied area (the Lamto Ecological Reserve and surroundings) would contribute to the understanding of the readers.

Response 4: In the revised version of the manuscript, we have added a new figure (Figure 1) showing the location of the station and its vegetation. Consequently, Figures 1, 2, 3, 4, 5 and 6 have become Figure 2, 3, 4, 5, 6 and 7 in the new version.

 

Comment 5: Are the conclusions consistent with the evidence and arguments presented
and do they address the main question posed? Yes. Yes.

Response 6: Thank you for evaluating and valorizing this research work.

 

Comment 6:  Are the references appropriate? Yes. As mentioned, there are some self-references, which are acceptable as this manuscript follows others published with results from the same investigation, but with different data.

Response 6: We would thank you for your interest and for the very constructive comments which have added value to this work.

 

Comment 7. Please include any additional comments on the tables and figures. Seasons GSS, GSP, PSS, PSP should be expressed in full names

Response 7: Done. Please refer to the revised manuscript

Please see the attachment

 

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript submitted for review is extremely interesting. Perhaps the authors should better emphasize the research hypotheses, although the purpose of the work is correctly defined and obvious. The research methodology and its nature are modern. Therefore, I have no doubts about the necessity of publishing the manuscript almost in its original form. The only remarks relate to the editorial aspects of the text. Detailed notes are below:

 

155 The partial parenthesis and space in the equation looks weird.

Figure 1 appears that the font size can be reduced; The notation of brackets (1,3] looks strange, the comma should be replaced with a dot; "Wind Speed" - the unit of measurement is missing.

316, 325, 329, 334, 364, 442 superscript.

387 what is OH•?

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding corrections in red and suggestions of the manuscript revised. Comments and Suggestions for Authors Comment 1: The manuscript submitted for review is extremely interesting. Perhaps the authors should better emphasize the research hypotheses, although the purpose of the work is correctly defined and obvious. The research methodology and its nature are modern. Therefore, I have no doubts about the necessity of publishing the manuscript almost in its original form. The only remarks relate to the editorial aspects of the text. Detailed notes are below: Response 1: We would thank you for your interest and for the very constructive comments which have added value to this work. However, the main question addressed by this research is to know the location of the dominant sources responsible for the significant levels of concentrations recorded. In the revised version, we have added a sentence to better highlight the research question (see Line 90, version revised)   Comment 2: L155: The partial parenthesis and space in the equation looks weird. Response 2: We have removed the parenthesis and revised the formatting of the equation. Comment 3: (a) Figure 1 appears that the font size can be reduced; (b) The notation of brackets (1,3] looks strange, the comma should be replaced with a dot; (c) "Wind Speed" - the unit of measurement is missing. Response 3: (a) The font size of Figure 1 has been reduced (see Figure 2, version revised); (c) Done: Wind Speed (m/s) (see Figure 2, version revised). I had specified in the legend of the figure.  Comment 4:  316, 325, 329, 334, 364, 442 superscripts. Response 4: Done (see Line 3018, Line 327, Line 331, Line 368, Line 323, Line 373, Line 443 version revised). In addition, to this we also corrected an entry error by replacing change throughout the manuscript 85th with 75th. Comment 5: 387 what is OH•? Response 5: OH• means OH radical.  OH• replaced by OH-radical (see Line 388, version revised).  Please see the attachment

 

Author Response File: Author Response.pdf