Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6328796 | Science of The Total Environment | 2014 | 13 Pages |
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 NO3â pollution by the Regional Government in 1998, and the hypersaline lake was classified as a heavily modified body of water. The study assessed groundwater NO3â 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 NO3â from slightly volatilized ammonium synthetic fertilizers is only partially denitrified. The natural attenuation of NO3â 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 NO3â attenuation. Tritium data suggest that the absence of NO3â 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.
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Authors
J.J. Gómez-Alday, R. Carrey, N. Valiente, N. Otero, A. Soler, C. Ayora, D. Sanz, A. Muñoz-MartÃn, S. Castaño, C. Recio, A. Carnicero, A. Cortijo,