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| Titel |
Natural attenuation processes of nitrate in a saline lake-aquifer system: Pétrola Basin (Central Spain) |
| VerfasserIn |
Nicolas Valiente, Alfonso Menchen, Franz Jirsa, Thomas Hein, Wolfgang Wanek, Juan Jose Gomez-Alday |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250126508
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| Publikation (Nr.) |
 EGU/EGU2016-6240.pdf |
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| Zusammenfassung |
| Saline wetlands associated with intense agricultural activities in semi-arid to arid climates are
among the most vulnerable environments to NO3− pollution. The endorheic Pétrola Basin
(High Segura River Basin, Central Spain) was declared vulnerable to NO3− pollution by the
Regional Government of Castilla-La Mancha in 1998. The hypersaline lake was classified as
a heavily modified waterbody, due to the inputs of pollutants from agricultural sources and
urban waste waters, the latest are discharged directly into the lake without proper
treatment.
Previous studies showed that the aquifer system has two main flow components: regional
groundwater flow from recharge areas into the lake, and a density-driven flow from the lake
to the underlying aquifer. The NO3− inputs derived from agriculture originate from
nitrification of synthetic ammonium fertilizers, and afterwards, NO3− is expected to be
attenuated by denitrification (up to 60%) in the saltwater-freshwater interface around the lake.
However, the spatial and temporal pattern of nitrate reduction in lake sediments is not
known.
In this study, an isotope pairing technique was used in order to clarify the main pathways for
the NO3− attenuation linked to the sediment-water interface. For that purpose mesocosm
experiments were performed: organic-rich lake sediment (up to 23% organic carbon
content) was incubated for 96 hours with the addition of 15N nitrate tracer. During
the experiments two factors were modified: light and oxic conditions. Analyzing
inorganic N-species (n=20) over time (72 hours) showed that NO3− attenuation was
coupled with an increment in the NH4+ concentration (from 0.8 mg/L up to 5.3
mg/L) and a decrease in redox values (from 135.1 mV up to -422 mV) in the water
column.
The main outcome of this study was to elucidate the importance of different microbial
pathways denitrification, dissimilatory nitrate reduction to ammonium (DNRA) and
anaerobic ammonium oxidation (Anammox), in controlling the fate of NO3− in Pétrola Lake.
The complete attenuation of 250 μmol of NO3− occurred during the first 30 hours of
incubation under all the treatments, coupled to a temporal increase in the NO2−
concentration. The results will support the understanding how hypersaline lakes are able to
respond to elevated nutrient loads. |
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