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Identifying the influential aquifer heterogeneity factor on nitrate reduction processes by numerical simulation

Jang, E. and He, W. and Savoy, H. and Dietrich, P. and Kolditz, O. and Rubin, Y. and Schüth, Christoph and Kalbacher, T. (2017):
Identifying the influential aquifer heterogeneity factor on nitrate reduction processes by numerical simulation.
In: Advances in Water Resources, Elsevier, pp. 38-52, 99, ISSN 03091708, DOI: 10.1016/j.advwatres.2016.11.007, [Online-Edition: https://www.sciencedirect.com/science/article/pii/S030917081...],
[Article]

Abstract

Nitrate reduction reactions in groundwater systems are strongly influenced by various aquifer heterogeneity factors that affect the transport of chemical species, spatial distribution of redox reactive substances and, as a result, the overall nitrate reduction efficiency. In this study, we investigated the influence of physical and chemical aquifer heterogeneity, with a focus on nitrate transport and redox transformation processes. A numerical modeling study for simulating coupled hydrological-geochemical aquifer heterogeneity was conducted in order to improve our understanding of the influence of the aquifer heterogeneity on the nitrate reduction reactions and to identify the most influential aquifer heterogeneity factors throughout the simulation. Results show that the most influential aquifer heterogeneity factors could change over time. With abundant presence of electron donors in the high permeable zones (initial stage), physical aquifer heterogeneity significantly influences the nitrate reduction since it enables the preferential transport of nitrate to these zones and enhances mixing of reactive partners. Chemical aquifer heterogeneity plays a comparatively minor role. Increasing the spatial variability of the hydraulic conductivity also increases the nitrate removal efficiency of the system. However, ignoring chemical aquifer heterogeneity can lead to an underestimation of nitrate removals in long-term behavior. With the increase of the spatial variability of the electron donor, i.e. chemical heterogeneity, the number of the �hot spots� i.e. zones with comparably higher reactivity, should also increase. Hence, nitrate removal efficiencies will also be spatially variable but overall removal efficiency will be sustained if longer time scales are considered and nitrate fronts reach these high reactivity zones.

Item Type: Article
Erschienen: 2017
Creators: Jang, E. and He, W. and Savoy, H. and Dietrich, P. and Kolditz, O. and Rubin, Y. and Schüth, Christoph and Kalbacher, T.
Title: Identifying the influential aquifer heterogeneity factor on nitrate reduction processes by numerical simulation
Language: English
Abstract:

Nitrate reduction reactions in groundwater systems are strongly influenced by various aquifer heterogeneity factors that affect the transport of chemical species, spatial distribution of redox reactive substances and, as a result, the overall nitrate reduction efficiency. In this study, we investigated the influence of physical and chemical aquifer heterogeneity, with a focus on nitrate transport and redox transformation processes. A numerical modeling study for simulating coupled hydrological-geochemical aquifer heterogeneity was conducted in order to improve our understanding of the influence of the aquifer heterogeneity on the nitrate reduction reactions and to identify the most influential aquifer heterogeneity factors throughout the simulation. Results show that the most influential aquifer heterogeneity factors could change over time. With abundant presence of electron donors in the high permeable zones (initial stage), physical aquifer heterogeneity significantly influences the nitrate reduction since it enables the preferential transport of nitrate to these zones and enhances mixing of reactive partners. Chemical aquifer heterogeneity plays a comparatively minor role. Increasing the spatial variability of the hydraulic conductivity also increases the nitrate removal efficiency of the system. However, ignoring chemical aquifer heterogeneity can lead to an underestimation of nitrate removals in long-term behavior. With the increase of the spatial variability of the electron donor, i.e. chemical heterogeneity, the number of the �hot spots� i.e. zones with comparably higher reactivity, should also increase. Hence, nitrate removal efficiencies will also be spatially variable but overall removal efficiency will be sustained if longer time scales are considered and nitrate fronts reach these high reactivity zones.

Journal or Publication Title: Advances in Water Resources
Volume: 99
Publisher: Elsevier
Divisions: 11 Department of Materials and Earth Sciences > Earth Science
11 Department of Materials and Earth Sciences > Earth Science > Hydrogeology
11 Department of Materials and Earth Sciences
Date Deposited: 17 Apr 2018 12:46
DOI: 10.1016/j.advwatres.2016.11.007
Official URL: https://www.sciencedirect.com/science/article/pii/S030917081...
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