Transfer of greenhouse gases in the soil – vadose zone – groundwater – river – atmosphere system.

Name : Nikolenko Olha

Promotor : S. Brouyère

Thèse Ohla 1000 

The presented work consists of four chapters complemented by an introduction and a final section presenting general conclusions and research perspectives.
The first chapter reviews available evidence about the variability of 15N isotopic signature of nitrate (NO3-), ammonium (NH4+) and nitrous oxide (N2O) in groundwater affected by agricultural activities. It summarizes information regarding factors and processes affecting the isotopic composition of NO3-, NH4+ and N2O in subsurface, and discusses the use of 11B, 18O, 13C, 34S, 87Sr/86Sr isotopes to support the analysis of δ15N values. This chapter shows that previous studies have accumulated rich data on isotopic composition of NO3- in groundwater, but evidence remains scarce in the cases of NH4+ and N2O.
The second chapter presents the results of regional investigations which explored the variability in concentrations of greenhouse gases (GHGs) (N2O, CO2 and CH4) across lateral and vertical dimensions of the Hesbaye chalk aquifer located in the eastern part of Belgium. At first, this chapter describes the approach applied to the regional survey. In brief, groundwater samples from 29 locations across the aquifer were analyzed for a range of parameters including: 1) concentrations of GHGs; 2) hydrochemical controls (dissolved oxygen (DO), dissolved organic matter (DOC), sulfate (SO42-), pH etc.); 3) concentration of nitrogen (N) species (NO3-, NH4+, NO2-) and 4) isotope signatures of NO3-, N2O, SO42-, DOC, 11B and H2O. Afterwards, based on the results of chemical and isotope/isotopomer analysis this chapter presents information about sources of N and C input to groundwater and processes that govern N2O, CO2 and CH4 biochemistry in the aquifer.
The next, third chapter, discusses the research work undertaken in order to specify the impact of nitrification and denitrification processes, occurrence of which was identified during the regional survey, on N2O dynamics in groundwater. At first, the results of chemical and isotope/isotopomer analyses of groundwater samples collected from the shallow and deep parts of the aquifer are examined to obtain more information about the variability of hydrochemical conditions with depth. Afterwards, this chapter presents the results of laboratory stable isotope incubation experiments using NO3- and NH4+ compounds labeled with heavy 15N isotope, which
were applied in order to quantify the rates of nitrification and denitrification processes in shallow and deep groundwater. Moreover, it discusses challenges encountered during quantification of N transformation processes in subsurface.
The final, fourth chapter, is devoted to the discussion of the findings of microbiological explorations conducted to detect the activity of bacteria (expression of genes) involved into denitrification and nitrification pathways. This chapter describes in detail the methodology used to target functional markers of bacterial nitrifiers (amoA) and denitrifies (nirK, nirS, norB, norC, nosZ) including DNA and RNA extraction, 16S amplicon profiling, polymerase chain reaction (PCR) design and Sanger sequence analyses of PCR products. Afterwards, the experimental results are presented with the following conclusions about the occurrence of N2O production and consumption via nitrification and/or denitrification mechanisms within the aquifer. Finally, data obtained from isotope/isotopomer analyses are compared to the information received from microbiological explorations in order to discuss the N2O transformations in subsurface in the area of study.
Conclusions. Conclusions address the research questions determined as objectives of this research and presented in the introductory part. Firstly, it summarizes the evidence about the variability of GHGs concentration in groundwater and explains its causes. Secondly, it compares the results of isotope and isotopomers analysis of groundwater samples collected during regional and local scale campaigns with the results of laboratory 15N stable isotope experiments and mRNA studies to identify the processes of N2O production and consumption in the aquifer. Finally, it discusses the variations in SP values obtained from the analysis of ambient groundwater samples.
Perspectives. In the discussion of research perspectives the need to study GHGs dynamics simultaneously in different environmental components is emphasized as a key to get conclusive evidence about the role of subsurface as indirect source of GHGs emission and identify the hotspots of GHGs emissions. In addition, it discusses the importance of studying the dynamics of N2O fluxes occurring in the contrasting hydrological/meteorological conditions and under different land management practices in order to address the problem of upscaling of point estimates of N compounds concentrations by developing catchment scale models.

iconeDocumentPublications :

List of publications:

  • Nikolenko, O., Brouyѐre, S., Goderniaux, P., Robert, T.,. & Morana, (2020).Dynamics of nitrous oxide with depth in groundwater: insights from ambient groundwater and laboratory incubation experiments (Hesbaye chalk aquifer, Belgium). Journal of Contaminant Hydrology. (under a review)
  • Nikolenko, O., Jurado, A., Morana, C., Jamin, P., Robert, T., … & Brouyѐre, S. (2019). Dynamics of greenhouse gases in groundwater: hydrogeological and hydrogeochemical controls. Applied Geochemistry,105,31-44.

10.1016/j.apgeochem.2019.04.009;

  • Nikolenko, O., Borges, A., Orban, P., & Brouyère, S. (2019). Analysing N sources and transformation processes in groundwater under agricultural areas (chalk aquifer, Belgium). CL: AIRE Library.

http://hdl.handle.net/2268/239471;

  • Nikolenko, O., Jurado, A., Borges, A. V., Knӧller, K., & Brouyѐre, S. (2018). Isotopic composition of nitrogen species in groundwater under agricultural areas: A review. Science of the Total Environment, 621,1415-1432. 1016/j.scitotenv.2017.10.086;
  • Jurado, A., Borges, A. V., Pujades, E., Briers, P., Nikolenko, O., Dassargues, A., & Brouyère, S. (2018). Dynamics of greenhouse gases in the river–groundwater interface in a gaining river stretch (Triffoy catchment, Belgium). Hydrogeology journal, 26(8), 2739-2751.

10.1007/s10040-018-1834-y;

Conference abstracts:

  • Nikolenko, O., Morana, C., Taminiau, B., Borges, A. V., Robert, T., Goderniaux, P., ... & Brouyere, S. (2020, May). Vertical interval dynamics of greenhouse gases in groundwater (Hesbaye chalk aquifer, Belgium). In EGU General Assembly Conference Abstracts (p. 4958).
  • Nikolenko, O., Orban, P., Morana, C., Borges, A. V., Jamin, P., B., Brouyere, S. (2019, September). Effects of the hydrogeochemical stratification on the distribution of greenhouse gases concentrations and their production/consumption processes in groundwater. 10th International Groundwater Quality Conference (GQ 2019).
  • Jurado, A., Nikolenko, O., Orban, P., Borges, A., & Brouyère, S. (2018, September). Dynamics of greenhouse gases in the aquifers of two agricultural catchments of Belgium. IAH 2018.
  • Nikolenko, O., Orban, P., Jurado, A., Borges, A., Brouyère, S., Jamin, P., ... & Morana, C. (2018, April). Dynamics of nitrous oxide in groundwater under agricultural areas: insights from multi-isotopic studies (15N, 34S, 18O, 13C, 3H). BASIS Symposium 2018.
  • Nikolenko, O., Orban, P., Jamin, P., Jurado, A., Borges, A. V., & Brouyère, S. (2018, April). Biogeochemistry of greenhouse gases in groundwater under agricultural area (the Geer catchment, Belgium). In EGU General Assembly Conference Abstracts(Vol. 20, p. 16102).

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