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| Titel |
Monitoring induced denitrification in an artificial aquifer recharge system. |
| VerfasserIn |
Alba Grau-Martinez, Clara Torrentó, Albert Folch, Cristina Domènech, Neus Otero, 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 |
250097546
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| Publikation (Nr.) |
 EGU/EGU2014-13140.pdf |
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| Zusammenfassung |
| As demands on groundwater increase, artificial recharge is becoming a common method for
enhancing groundwater supply. The Llobregat River is a strategic water supply resource to
the Barcelona metropolitan area (Catalonia, NE Spain). Aquifer overexploitation has leaded
to both a decrease of groundwater level and seawater intrusion, with the consequent
deterioration of water quality. In the middle section of the aquifer, in Sant Vicenç del Horts,
decantation and infiltration ponds recharged by water from the Llobregat River (highly
affected from wastewater treatment plant effluents), were installed in 2007, in the
framework of the ENSAT Life+ project. At the bottom of the infiltration pond, a
vegetal compost layer was installed to promote the growth of bacteria, to induce
denitrification and to create favourable conditions for contaminant biodegradation.
This layer consists on a mixture of compost, aquifer material, clay and iron oxide.
Understanding the fate of contaminants, such as nitrate, during artificial aquifer
recharge is required to evaluate the impact of artificial recharge in groundwater
quality.
In order to distinguish the source of nitrate and to evaluate the capability of the organic
reactive layer to induce denitrification, a multi-isotopic approach coupled with
hydrogeochemical data was performed. Groundwater samples, as well as river samples, were
sampled during artificial and natural recharge periods. The isotopic analysis included: δ15N
and δ18O of dissolved nitrate, δ34S and δ18O of dissolved sulphate, δ13C of dissolved
inorganic carbon, and δ2H and δ18O of water.
Dissolved nitrate isotopic composition (δ15NNO3 from +9 to +21 oand δ18ONO3
from +3 to +16 ) demonstrated that heterotrophic denitrification induced by the reactive
layer was taking place during the artificial recharge periods. An approximation
to the extent of nitrate attenuation was calculated, showing a range between 95
and 99% or between 35 and 45%, by using the extreme literature ÉN values of
-4oand -22o respectively (Aravena and Robertson, 1998; Pauwels et al., 2000).
Ongoing denitrification batch experiments will allow us to determine the specific
nitrogen and oxygen isotopic fractionation induced by the organic reactive layer, in
order to estimate more precisely the extent of denitrification during artificial aquifer
recharge.
These results confirmed that the reactive layer induces denitrification in the recharge
ponds area, proving the usefulness of an isotopic approach to characterize water quality
improvement occurring during artificial aquifer recharge.
References
1. Aravena, R., Robertson, W.D., 1998. Use of multiple isotope tracers to evaluate
denitrification in ground water: Study of nitrate from a large-flux septic system plume.
Ground Water, 36(6): 975-982.
2. Pauwels, H., J.C., Kloppmann, W., 2000. Denitrification and mixing in a schist
aquifer: Influence on water chemistry and isotopes. Chemical Geology, 168(3-4):
307-324.
Acknowledgment
This study was supported by the projects CGL2011-29975-C04-01 from the Spanish
Government, 2009SGR-00103 from the Catalan Government and ENPI/2011/280-008 from
the European Commission. Please fill in your abstract text. |
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