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3D multiple-point geostatistical simulation of joint subsurface redox and geological architectures

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  • Rasmus Bødker Madsen, Geological Survey of Denmark and Greenland
  • ,
  • Hyojin Kim, Geological Survey of Denmark and Greenland
  • ,
  • Anders Juhl Kallesøe, Geological Survey of Denmark and Greenland
  • ,
  • Peter B.E. Sandersen, Geological Survey of Denmark and Greenland
  • ,
  • Troels Norvin Vilhelmsen
  • Thomas Mejer Hansen
  • Anders Vest Christiansen
  • Ingelise Møller, Geological Survey of Denmark and Greenland
  • ,
  • Birgitte Hansen, Geological Survey of Denmark and Greenland

Nitrate contamination of subsurface aquifers is an ongoing environmental challenge due to nitrogen (N) leaching from intensive N fertilization and management on agricultural fields. The distribution and fate of nitrate in aquifers are primarily governed by geological, hydrological and geochemical conditions of the subsurface. Therefore, we propose a novel approach to modeling both geology and redox architectures simultaneously in high-resolution 3D (25× 25×2m) using multiple-point geostatistical (MPS) simulation. Data consist of (1) mainly resistivities of the subsurface mapped with towed transient electromagnetic measurements (tTEM), (2) lithologies from borehole observations, (3) redox conditions from colors reported in borehole observations, and (4) chemistry analyses from water samples. Based on the collected data and supplementary surface geology maps and digital elevation models, the simulation domain was subdivided into geological elements with similar geological traits and depositional histories. The conceptual understandings of the geological and redox architectures of the study system were introduced to the simulation as training images for each geological element. On the basis of these training images and conditioning data, independent realizations were jointly simulated of geology and redox inside each geological element and stitched together into a larger model. The joint simulation of geological and redox architectures, which is one of the strengths of MPS compared to other geostatistical methods, ensures that the two architectures in general show coherent patterns. Despite the inherent subjectivity of interpretations of the training images and geological element boundaries, they enable an easy and intuitive incorporation of qualitative knowledge of geology and geochemistry in quantitative simulations of the subsurface architectures. Altogether, we conclude that our approach effectively simulates the consistent geological and redox architectures of the subsurface that can be used for hydrological modeling with nitrogen (N) transport, which may lead to a better understanding of N fate in the subsurface and to future more targeted regulation of agriculture.

OriginalsprogEngelsk
TidsskriftHydrology and Earth System Sciences
Vol/bind25
Nummer5
Sider (fra-til)2759-2787
Antal sider29
ISSN1027-5606
DOI
StatusUdgivet - maj 2021

Bibliografisk note

Funding Information:
This research has been supported by the Innovation Fund Denmark (grant no. 8855-00025B).

Publisher Copyright:
© Author(s) 2021.

Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.

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