the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 22 Sep 2023
Methods to characterize type, relevance, and interactions of organic matter and microorganisms in fluids along the flow path of a geothermal facility
Danaé Bregnard
Andrea Vieth-Hillebrand
Stefanie Poetz
Florian Eichinger
Guillaume Cailleau
Pilar Junier
Simona Regenspurg
Abstract. Dissolved organic matter and microorganisms were analyzed along the flow path of a geothermal facility in Austria. Various analytical methods were used to characterize and differentiate between natural and synthetic organic matter, characterize the microbial community composition, and determine the implications of microorganisms in an operating a geothermal site. Dissolved organic carbon (DOC) concentrations were in the range of 8.4–10.3 mg C L−1 and typically decreased from the production to the injection side. Carbonate scalings are avoided in the facility by the injection of a chemical scaling inhibitor within the production well at 500 m depth. It was calculated that the inhibitor contributes approximately 1 mg C L−1 DOC to the produced fluids. Ion chromatography (IC), liquid chromatography – organic carbon detection (LC-OCD) and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) in negative electrospray ionization (ESI(−)) and positive atmospheric pressure photoionization (APPI(+)) mode were applied to the fluid samples to characterize the dissolved organic matter (DOM) composition and distinguish between the inhibitor and the natural DOM. Depending on the applied ionization mode, FT-ICR-MS results show that between 31 % and 65 % of the macromolecular formulas detected in the fluid samples seem to originate from the inhibitor. However, the DOM is mainly composed of low molecular weight acids (LMWA), especially acetate with up to 7.4 mg C L−1. The microbial community composition varied along the flowpath with dominant phyla being Firmicutes, Proteobacteria, and Thermotogae. Based on the microorganisms found in the sample, the metabolic pathways have been assessed. Acetate might be produced by microorganisms through various fermentation processes (e.g. from lysine, pyruvate and hexitol). Assessing the presence and interaction of organic compounds and microorganisms in geothermal fluids provides a broader understanding of processes within the geothermal facility. This understanding could be beneficial for the efficient use of a geothermal power plant.
- Preprint
(3664 KB) - Metadata XML
-
Supplement
(577 KB) - BibTeX
- EndNote
Alessio Leins et al.
Status: open (until 13 Jan 2024)
-
RC1: 'Comment on bg-2023-159', Anonymous Referee #1, 09 Nov 2023
reply
The authors present a data report on the composition of fluids from a set of subsurface samples which have been mixed with a chemical additive. The compositional information is both chemical and biological assessments. I view this as a data report providing details about the water system, information which may be of interest to those who want to know what is in the water.
This manuscript will benefit from editing for grammar and language usage. There are also organization issues with the manuscript with results appearing for the first time in the discussion section, and details on methods also not appearing until the discussion. I am providing specific comments on the presentation in the sections that follow.
In the legend for figure 1 it says ‘The black dots indicate the fluid sampling points…’; I see no black dots in the figure.
Line 88: ‘exsolution of CO2’ – I don’t know what exsolution means. Is there another translation for this word?
Line 92: ‘polyelecrolytes’ ? Please check this word as it is also unknown to me.
Line 95 Are the units for CO2 really this: L L-1?
Line 107: I am unclear if six filters per site were processed, or six per day spread across the three sites.
Line 109: -20C seems a little warm to store filters for DNA analysis. How long were the filters stored at this temperature, and do the authors have evidence that there was no degradation of the DNA signal at this temperature?
Line 119: I am unclear on how you use Cl as a means to determine if the chloride concentrations are too high. Do you have an external means to measure Cl before the IC measurement? And, from the later results section it would appear that all the samples had Cl measurements that would require this pre-processing step.
Line 139: the methanol and acidified water are used to activate the resins for use and are not a cleaning step.
Line 225: ‘The DOC in the fluid samples ranges from 8.4–10.3 mg CL-1 (Table 2), showing a decrease along the pathway. In March, the DOC decreased from the production to the injection side whereas in June the concentrations seemed relatively uniform with slightly higher DOC in the heat central.’ – this is confusing because the first broad statement actually only applies in March.
Line 252: “The fluid samples are affected by inhibitor signals ranging from 31–65.3 %TMIA.” I am unclear on what this means – how can the fluid samples be ‘affected’ by the inhibitor? In the table also lists an SI amount as a percent TMIA, but I see no description of how this was defined. Perhaps this was the description starting at line 315 in the discussion, and if so that definition needs to be moved to the method section. And, if that is the description, I am still unclear on how the compounds were added – is this a count of the number of compounds in the inhibitor or is this a summing of the peak intensities? Are these the compounds that are unique to the inhibitor, or is this any compound in the inhibitor?
Table 2 – presents information with an excessive number of significant digits. Sokal and Rolf provide a nice guideline about keeping significant digits between 30 and 300 unit steps (a quick Google search provides the full description).
Line 292: ‘However, it is important to note that the top five genera at each sampling point does not represent the entire community, but only a subfraction of the most abundant members of the community.’ I am not sure why this is important to note, this seems to just be repeating the definition of the top five genera and is not a notable scientific result.
Figure 5: What date are these diversity samples from? The methods describe two dates for the chemical data, but is not clear as to when the bacterial diversity samples were obtained.
Figure 6: I am unclear what the x-tick labels are here. #s 55 to 69 are presumably sample sites, but this has not been defined. Also, what is the y-axis? Is ‘contrib’ the number of strains involved in each process? Or the relative magnitude of the amount of chemical that would be altered by this process?
Line 310: ‘identify the inhibitor-derived organic compounds’ – you did not identify the compounds as that would require additional analyses with authentic standards. I would use ‘characterize’ as a more generic phrase.
Line 311: ‘is the distinction and quantification between synthetic and natural organic matter possible?’ – this is the authors’ first question and cannot be addressed given the samples in hand. The study lacks the controls that would be required to answer this question as there is sample without the synthetic material. It is also unclear to me as to why you would want to address this question – the inhibitor will always be in these samples.
The first 1.5 pages of the discussion are results, which should not be appearing for the first time in the discussion section of this manuscript.
Line 345: ‘differ clearly’ – this is vague. Please provide the statistical tests needed to support this ascertation.
Line 420: ‘Thus, slight variations and differences such as inhibitor signals being present in the heat central and not in the other samples do not necessarily represent processes linked to the flowpath.’ This statement by the authors is odd since in the other portions of the discussion they specifically link changes in the fluid composition to the flow path. Why are they now saying that these fluids cannot be linked to the flowpath?
Line 508: ‘…make it less likely that the organic acid anion content is associated with the water-oil contact.’ This ignores the possibility that microorganisms have already consumed those anions before the water sample was collected.
Given that the biochemical predictions were used to assess the presence of acetate, why did the authors not also consider the biochemical pathways that would lead to the absences of the other compounds that could have been measured with the IC system?
Citation: https://doi.org/10.5194/bg-2023-159-RC1
Alessio Leins et al.
Data sets
Dissolved organic compounds in geothermal fluids used for energy production–part II Alessio Leins, Andrea Vieth-Hillebrand, Kristin Günther, and Simona Regenspurg https://doi.org/10.5880/GFZ.4.8.2023.005
Alessio Leins et al.
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 170 | 53 | 6 | 229 | 9 | 3 | 3 |
- HTML: 170
- PDF: 53
- XML: 6
- Total: 229
- Supplement: 9
- BibTeX: 3
- EndNote: 3
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1