the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Driving and limiting factors of CH4 and CO2 emissions from coastal brackish-water wetlands in temperate regions
Emilia Chiapponi
Sonia Silvestri
Denis Zannoni
Marco Antonellini
Beatrice Maria Sole Giambastiani
Abstract. Coastal wetlands are fundamental for climate-change mitigation thanks to their ability to store large amounts of organic carbon in the soil. They also represent the first natural emitter of methane (CH4). Salinity is known to inhibit CH4 production, but its effect in brackish ecosystems is still poorly understood. Our study aims to understand how environmental variables may affect greenhouse gas emissions (GHGs) in coastal temperate wetlands. We present the results of over one year of measurements performed in four wetlands located along a salinity gradient on the northeast Adriatic coast near Ravenna, Italy. Soil properties were determined by collecting soil samples, while carbon dioxide (CO2) and methane (CH4) fluxes from soils and standing waters, water levels, surface, and groundwater physical-chemical parameters (temperature, pH, electrical conductivity, and sulphate concentrations of water) were monthly monitored by a portable gas flux-meter and multiparametric probes, respectively. Principal component analysis (PCA) was used to investigate emergent relationships between GHGs fluxes and environmental variables. Our results suggest that, among all variables, temperature and irradiance play a significant role in CH4 emissions from water and soil whereas water column depth and salinity are limiting factors of GHGs emissions.
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Emilia Chiapponi et al.
Status: open (until 07 Jul 2023)
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RC1: 'Comment on egusphere-2023-605', Anonymous Referee #1, 19 May 2023
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Comments to the Manuscript egusphere-2023-605 “Driving and limiting factors of CH4 and CO2 emissions from coastal brackish-water wetlands in temperate regions”
General Comments
- This interesting study addresses the relevant scientific question of the quantifications of possible emission of GHGs (CO2 and CH4) from coastal wetlands.
- The attention is focused on a study area at the Italian Adriatic Seaside, even comprehensive of four different study sites. This study area can be considered representative of possible conditions referable to the relevant Mediterranean Area.
- It should be positively pointed out the overall methodological approach to combine the fundamental method of the accumulation chamber to monitor the CO2 and CH4 flux emissions with a large number of complementary and needed measures in terms of soil properties and water levels, surface, and groundwater physical-chemical parameters (as temperature, pH, electrical conductivity, and sulphate concentrations of water).
- The statistical elaboration and the evaluation and discussion of all these monitoring data sets are appropriate.
- The English style and grammar are appropriate.
- Some Figures, that contain a deep visualization of interesting data and elaborations, could be eventually reorganized to favour their increased readability.
- In the following, some specific suggestions to improve the expected final revised version of the manuscript.
Specific Comments
“Abstract”:
- Page 1, line 11: it should be “…. greenhouse gas (GHG) emissions…”
- Page 1, line 13: no need to repeat again the complete wording “… methane (CH4)…” as it was already extensively introduced at page 1, line 9
“Introduction”:
- Page 2, line 27: “gases” instead of “gasses”
- Page 2, line 34: please, be consistent with a selected format only for the units throughout the manuscript and related Tables and Figures. Therefore, for instance 0.109 g/m2/day or 0.109 g m-2 day-1, make a choice only.
- Page 2, line 35: it should be “… CH4…”
- Page 2, line 53: it should be “… on GHG emissions…” instead of “… on GHGs emissions…”
- Page 2, line 59: it should be better specified as “… CH4 and CO2 emission fluxes…”
- Page 3, line 64: “modelling” and “models” in “… modelling the C cycle accounting in temperate coastal wetlands models…”, please try to avoid wording repetitions in a sentence
Section 2.1:
- Page 3, line 73: to be consistent with the Section title, it should be here “study area” instead of “study site”
- Page 3, line 76: The citations “EEC 1979; 1992” should clearly appear with the same acronym (EEC) in the “References” Section
- Page 3, lines 77-78: Please verify that, according to the Journal Editing Style, pertaining web site links should be reported along the manuscript text or, differently, properly listed in the “References” Section
- Page 3, lines 79: please, provide a pertaining citation for the reported mean annual temperature of 13.3°C in the study area
Section 2.1.1:
- Page 5, lines 112 and 114: the acronym citation “RER” should be properly reported as “RER (Regione Emilia Romagna)” in the “References” Section
Section 2.2.1:
- Page 6, lines 161-162: the meaning of the following sentence should be explained better: “… a value of 0.05 mol/m2/day was assigned to all fluxes larger than zero and lower than this value to avoid over estimation.”
- Page 6, lines 162-163: concerning the negative or zero measurements, is it eventually possible to have effective absence of CH4 or CO2 emissions from some points of a wetland?
- Page 6, line 166: is it suggested to write “… loss-on-ignition analysis: …”
Section 2.2.2:
- Page 7, line 176: please report extensively the meaning of the acronym “ARPAE”
Section 2.5:
- Page 7, lines 182-183: is it appropriate the comma in “… and, for homoscedasticity…”
- Page 7, line 188: “plain” or, better, “plane”?
Section 3.1:
- Page 7, line 200: it is suggested “GHG fluxes” instead of “GHGs fluxes” (see also the title of Section 3.1.2)
- Page 8, lines 231-233: please, specify that the mentioned mean values refer to CE site
Fig.1:
- Eventually, to increase in particular the visibility and readability of the four EC diagrams at the selected piezometers, the authors could consider the alternative option to split the original figure into two separated figures (one with the overall map even specifying the identifying numbers of these piezometers, the other with the mentioned four diagrams)
Table 2
- Not “DV. ST.” while “ST. DV.” or even better only “SD”
- Moreover, please add a legend by specifying that: ST. DV. (or SD) = standard deviation; CV = coefficient of variation
Section 3.2.1:
- Page 10, line 249: please specify the meaning of “In the first case” (it should be referring to CH4 ?)
Figg. 3, 4, and 5:
- Eventually, to increase the overall readability of these interesting figures, the authors could consider the alternative option to insert and combine in all the respective histograms and scree plot as an independent figure.
- Discussion:
- Page 18, line 362: please delete one of the “..”.
- and 5. Sections:
- Page 19, lines 422-431: indeed, this paragraph should be included and harmonized within the final “5. Conclusions” Section
The Reviewer, May 2023
Citation: https://doi.org/10.5194/egusphere-2023-605-RC1
Emilia Chiapponi et al.
Emilia Chiapponi et al.
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