title: Denitrification in a hypersaline lake-aquifer system (Pétrola Basin, Central Spain): the role of recent organic matter and Cretaceous organic rich sediments.
abstract: Agricultural regions in semi-arid to arid climates with associated saline wetlands are one of the most vulnerable environments to nitrate pollution. The Pétrola Basin was declared vulnerable to NO3(-) pollution by the Regional Government in 1998, and the hypersaline lake was classified as a heavily modified body of water. The study assessed groundwater NO3(-) through the use of multi-isotopic tracers (δ(15)N, δ(34)S, δ(13)C, δ(18)O) coupled to hydrochemistry in the aquifer connected to the eutrophic lake. Hydrogeologically, the basin shows two main flow components: regional groundwater flow from recharge areas (Zone 1) to the lake (Zone 2), and a density-driven flow from surface water to the underlying aquifer (Zone 3). In Zones 1 and 2, δ(15)NNO3 and δ(18)ONO3 suggest that NO3(-) from slightly volatilized ammonium synthetic fertilizers is only partially denitrified. The natural attenuation of NO3(-) can occur by heterotrophic reactions. However, autotrophic reactions cannot be ruled out. In Zone 3, the freshwater-saltwater interface (down to 12-16 m below the ground surface) is a reactive zone for NO3(-) attenuation. Tritium data suggest that the absence of NO3(-) in the deepest zones of the aquifer under the lake can be attributed to a regional groundwater flow with long residence time. In hypersaline lakes the geometry of the density-driven flow can play an important role in the transport of chemical species that can be related to denitrification processes.
authors.affiliation: Hydrogeology Group, Institute for Regional Development (IDR), University of Castilla-La Mancha (UCLM), Campus Universitario s/n, 02071 Albacete, Spain. Electronic address: JuanJose.Gomez@uclm.es.
authors.forename: J J
authors.initials: JJ
authors.lastname: Gómez-Alday
authors.affiliation: Grup d'Mineralogia Aplicada i Medi Ambient, Dep. Cristal·lografia, Mineralogia i Dipòsits Minerals, Facultat de Geologia, Universitat de Barcelona, C/ Martí i Franquès s/n, 08028, Barcelona, Spain. Electronic address: raulcarrey@ub.edu.
authors.forename: R
authors.initials: R
authors.lastname: Carrey
authors.affiliation: Hydrogeology Group, Institute for Regional Development (IDR), University of Castilla-La Mancha (UCLM), Campus Universitario s/n, 02071 Albacete, Spain. Electronic address: Nicolas.Valiente@uclm.es.
authors.forename: N
authors.initials: N
authors.lastname: Valiente
authors.affiliation: Grup d'Mineralogia Aplicada i Medi Ambient, Dep. Cristal·lografia, Mineralogia i Dipòsits Minerals, Facultat de Geologia, Universitat de Barcelona, C/ Martí i Franquès s/n, 08028, Barcelona, Spain. Electronic address: notero@ub.edu.
authors.forename: N
authors.initials: N
authors.lastname: Otero
authors.affiliation: Grup d'Mineralogia Aplicada i Medi Ambient, Dep. Cristal·lografia, Mineralogia i Dipòsits Minerals, Facultat de Geologia, Universitat de Barcelona, C/ Martí i Franquès s/n, 08028, Barcelona, Spain. Electronic address: albertsolergil@ub.edu.
authors.forename: A
authors.initials: A
authors.lastname: Soler
authors.affiliation: Grup d'Hidrologia Subterrània (GHS), Institut de Diagnóstic Ambiental i Estudis de l'Aigua (IDAEA-CSIC), C/Jordi Girona 18, 08028 Barcelona, Spain. Electronic address: cayora1@gmail.com.
authors.forename: C
authors.initials: C
authors.lastname: Ayora
authors.affiliation: Hydrogeology Group, Institute for Regional Development (IDR), University of Castilla-La Mancha (UCLM), Campus Universitario s/n, 02071 Albacete, Spain.
authors.forename: D
authors.initials: D
authors.lastname: Sanz
authors.affiliation: Applied Tectonophysics Group, Departamento de Geodinámica, Universidad Complutense de Madrid, C/José Antonio Novais 2, 28040 Madrid, Spain. Electronic address: amunoz@geo.ucm.es.
authors.forename: A
authors.initials: A
authors.lastname: Muñoz-Martín
authors.affiliation: Hydrogeology Group, Institute for Regional Development (IDR), University of Castilla-La Mancha (UCLM), Campus Universitario s/n, 02071 Albacete, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Castaño
authors.affiliation: Stable Isotope Laboratory, University of Salamanca, Plz. De los Caídos s/n, 37008 Salamanca, Spain. Electronic address: crecio@usal.es.
authors.forename: C
authors.initials: C
authors.lastname: Recio
authors.affiliation: Stable Isotope Laboratory, University of Salamanca, Plz. De los Caídos s/n, 37008 Salamanca, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Carnicero
authors.affiliation: Hydrogeology Group, Institute for Regional Development (IDR), University of Castilla-La Mancha (UCLM), Campus Universitario s/n, 02071 Albacete, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Cortijo
mesh_terms: D058440:Denitrification; D004784:Environmental Monitoring; D060587:Groundwater; D060106:Lakes / Q000737:chemistry*; D009566:Nitrates / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D009566:Nitrates; D014874:Water Pollutants, Chemical
keywords: Denitrification; Freshwater–saltwater interface; Hypersaline lake; Nitrification; Stable isotopes