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| Titel |
Integrated modelling of enhanced in situ biodenitrification in a fractured aquifer: biogeochemistry and isotope geochemistry |
| VerfasserIn |
Paula Rodríguez-Escales, Albert Folch, Boris M. van Breukelen, Georgina Vidal-Gavilan, Albert Soler |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092327
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| Publikation (Nr.) |
 EGU/EGU2014-6661.pdf |
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| Zusammenfassung |
| Enhanced in-situ biodenitrification is a feasible technology to recovery groundwater polluted
by nitrates and achieves drinking water standards. Under optimum conditions, nitrate is
reduced by autochthonous bacteria trough different reactions until arrive to harmless
dinitrogen gas. Isotopic fractionation monitoring in field applications allows knowing the
exact degree and the real scope of this technology. Using the Rayleigh equation the change in
the isotope ratio of the nitrate molecule (δ15N-NO3-, δ18O-NO3-) is related to the fraction
of molecules remaining as a result of biodenitrification. However, Rayleigh application at
field scale is sometimes limited due to other processes involved during groundwater
flow such as dispersion or adsorption and geological media heterogeneities that
interferes in concentration values. Then, include isotope fractionation processes in
reactive transport models is a useful tool to interpret and predict data from in-situ
biodenitrification.
We developed a reactive transport model of enhanced in situ application at field scale in a
fractured aquifer that considers biogeochemical processes as well as isotope fractionation to
enable better monitoring and management of this technology. Processes considered were:
microbiological– exogenous and endogenous nitrate and sulfate respiration coupled with
microbial growth and decay, geochemical reactions (precipitation of calcite) and isotopic
fractionation (δ15N-NO3-; δ18O- NO3- and carbon isotope network). The 2-D simulations
at field scale were developed using PHAST code.
Modeling of nitrate isotope geochemistry has allowed determining the extent of
biodenitrification in model domain. We have quantified which is the importance in decreasing
of nitrate concentrations due to biodegradation (percentage of biodegradation, “B%”) and due
to dilution process (percentage of dilution, “D%”). On the other hand, the stable carbon
isotope geochemistry has been modeled. We have considered the isotopic carbon
fractionation of different carbon species involved in enhanced biodenitrification: external
organic carbon, biomass, inorganic carbon (in different forms) and calcite. The inclusion of
carbon isotopes in the model, which are involved in both direct (oxidation of organic carbon)
and indirect (carbonate mineral interaction) processes of enhanced biodenitrification,
improves the evaluation of the overall model consistency due to the central role of carbon in
the reaction network. |
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