Gómez Alday, J.J.Carrey, R.Valiente, NicolásOtero, NeusSoler, A.Ayora, C.Sanz Bas, DavidMuñoz Martín, AlfonsoCastaño, S.Recio, C.Carnicero, A.Cortijo, A.2023-06-192023-06-1920140048-9697, ESSN: 1879-102610.1016/j.scitotenv.2014.07.129https://hdl.handle.net/20.500.14352/34607Agricultural 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 (δ15N, δ34S, δ13C, δ18O) 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, δ15NNO3 and δ18ONO3 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.engAtribución-NoComercial-SinDerivadas 3.0 Españajournal articlehttp://dx.doi.org/10.1016/j.scitotenv.2014.07.129open access550.4(234.1)Hypersaline lakeFreshwater–saltwater interfacemStable isotopesNitrificationDenitrificationGeodinámicaGeoquímica2507 Geofísica2503 Geoquímica