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Nitrate sources and transformation processes in groundwater of a coastal area experiencing various environmental stressors

Boumaiza Lamine, Ben Ammar Safouan, Chesnaux Romain, Stotler Randy L., Mayer Bernhard, Huneau Frederic, Johannesson Karen H., Levison Jana, Knöller Kay et Stumpp Christine. (2023). Nitrate sources and transformation processes in groundwater of a coastal area experiencing various environmental stressors. Journal of Environmental Management, 345, e118803.

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URL officielle: http://dx.doi.org/10.1016/j.jenvman.2023.118803

Résumé

In coastal salinized groundwater systems, contamination from various nitrate (NO3) inputs combined with complex hydrogeochemical processes make it difficult to distinguish NO3 sources and identify potential NO3 transformtation processes. Effective field-based NO3 studies in coastal areas are needed to improve the understanding of NO3 contamination dynamics in groundwater of such complex coastal systems. This study focuses on a typical Mediterranean coastal agricultural area, located in Tunisia, experiencing substantial NO3 contamination from multiple anthropogenic sources. Here, multiple isotopic tracers (δ18OH2O, δ2HH2O, δ15NNO3, δ18ONO3, and δ11B) combined with a Bayesian isotope MixSIAR model are used (i) to identify the major NO3 sources and their contributions, and (ii) to describe the potential NO3 transformation processes. The measured NO3 concentrations in groundwater are above the natural baseline threshold, suggesting anthropogenic influence. The measured isotopic composition of NO3 indicates that manure, soil organic matter, and sewage are the potential sources of NO3, while δ11B values constrain the NO3 contamination to manure; a finding that is supported by the results of MixSIAR model revealing that manure-derived NO3 dominates over other likely sources. Nitrate derived from manure in the study area is attributed to organic fertilizers used to promote crop growth, and livestock that deposit manure directly on the ground surface. Evidence for ongoing denitrification in groundwaters of the study area is supported by an enrichment in both 15N and 18O in the remaining NO3, although isotopic mass balances between the measured and the theoretical δ18ONO3 values also suggest the occurrence of nitrification. The simultaneous occurrence of these biogeochemical processes with heterogeneous distribution across the study area reflect the complexity of interactions within the investigated coastal aquifer. The multiple isotopic tracer approach used here can identify the effect of multiple NO3 anthropogenic activities in coastal environments, which is fundamental for sustainable groundwater resources management.

Type de document:Article publié dans une revue avec comité d'évaluation
ISSN:03014797
Volume:345
Pages:e118803
Version évaluée par les pairs:Oui
Date:2023
Identifiant unique:10.1016/j.jenvman.2023.118803
Sujets:Sciences naturelles et génie > Génie
Sciences naturelles et génie > Sciences appliquées
Sciences naturelles et génie > Sciences naturelles > Sciences de la terre (géologie, géographie)
Département, module, service et unité de recherche:Départements et modules > Département des sciences appliquées > Unité d'enseignement en sciences de la Terre
Unités de recherche > Centre d’étude sur les Ressources minérales (CERM)
Mots-clés:nitrate, aquifer, denitrification, nitrification, stable isotopes, MixSIAR, aquifère, dénitrification, isotopes stables
Déposé le:06 sept. 2023 15:08
Dernière modification:06 sept. 2023 15:08
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