Publication Details
Category Text Publication
Reference Category Journals
DOI 10.1016/j.scitotenv.2024.178265
Title (Primary) Multiple environmental tracers combined with a constrained Bayesian isotope mixing model to elucidate nitrate and sulfate contamination in a coastal groundwater system
Author Boumaiza, L.; Chesnaux, R.; Stotler, R.L.; Zahi, F.; Mayer, B.; Leybourne, M.I.; Otero, N.; Johannesson, K.H.; Huneau, F.; Schüth, C.K.; Knoeller, K.; Ortega, L.; Stumpp, C.
Source Titel Science of the Total Environment
Year 2025
Department CATHYD
Volume 959
Page From art. 178265
Language englisch
Topic T4 Coastal System
Supplements Supplement 1
Supplement 2
Supplement 3
Keywords Mediterranean region; Aquifer Anthropogenic activities; Stable isotope; MixSIAR
Abstract Several groundwater quality investigations have been conducted in coastal regions that are commonly exposed to multiple anthropogenic stressors. Nonetheless, such studies remain challenging because they require focused-diagnostic approaches for a comprehensive understanding of groundwater contamination. Therefore, this study integrates a multi-tracer approach to acquire comprehensive information allowing for an improved understanding of the origins of groundwater contamination, the relative contribution of contaminants, and their biogeochemical cycling within a coastal groundwater system. This multi-tracer approach, focusing on nitrate (NO3) and sulfate (SO4) groundwater contamination, is applied to a Mediterranean coastal aquifer underlying an important economically strategic agricultural area. Dissolved NO3 in groundwater has concentrations up to 89 mg/L, whereas SO4 concentrations in groundwater are up to 458 mg/L. By integrating isotope tracers (i.e., δ15NNO3, δ18ONO3, δ11B, δ34SSO4, and δ18OSO4), NO3 and SO4 in the groundwater are found to have originated from multiple anthropogenic and natural sources including synthetic fertilizers, manure, sewage, atmospheric deposition, and marine evaporites. Chemical and isotopic data are coupled to identify the dominant hydro(geo)logic processes and the major subsurface biogeochemical reactions that govern the NO3 and SO4 occurrences. Nitrate and SO4 concentrations are identified to be respectively controlled by nitrification/denitrification and by bacterial dissimilatory SO4 reduction. Identifying these subsurface biogeochemical processes constrained the Bayesian isotope MixSIAR model, that is used for apportioning the relative contributions of the identified groundwater contamination sources, by informed site-specific isotopic fractionation effects. Results from MixSIAR indicate that manure is distinguished as the predominant source for NO3 (61 %), whereas SO4 in groundwater is mostly supplied from two sources (i.e., synthetic fertilizers and soil-derived sulfate) identified with similar contributions (30 %). This study particularly demonstrates the utility of initially describing the subsurface processes, not only to predict the fate of NO3 and SO4 concentrations within the groundwater system, but also to constrain the MixSIAR model with justified site-specific isotopic fractionation effects for subsurface transformation processes affecting NO3 and SO4.
Persistent UFZ Identifier https://www.ufz.de/index.php?en=20939&ufzPublicationIdentifier=31977
Boumaiza, L., Chesnaux, R., Stotler, R.L., Zahi, F., Mayer, B., Leybourne, M.I., Otero, N., Johannesson, K.H., Huneau, F., Schüth, C.K., Knoeller, K., Ortega, L., Stumpp, C. (2025):
Multiple environmental tracers combined with a constrained Bayesian isotope mixing model to elucidate nitrate and sulfate contamination in a coastal groundwater system
Sci. Total Environ. 959 , art. 178265 10.1016/j.scitotenv.2024.178265