Deep tree roots at risk of accelerating groundwater pollution beneath clay-rich aquitards
Abstract
Glacial aquitards from the last Pleistocene glaciation cover vast areas of the Northern Hemisphere. Due to their clay-rich composition, these aquitards are considered to protect underlying aquifers from surface contaminations, provided they are not penetrated by widespread deep fractures. In this study we combine ancient DNA (aDNA) with detailed hydrological techniques to investigate contaminant transport in the aquitards – an interdisciplinary approach that was not possible when the current understanding of the dominant role of fractures was established. We show that deep fractures (> 2 m below surface) in the glacial aquitards across Denmark are closed or marginal as pathways of dissolved contaminant transport unless they contain flow channels from deep modern and ancient tree roots. Our study reveals that deep tree roots can compromise natural groundwater protection and accelerate groundwater pollution by opening fractures and generating deep macropores. The results highlight that thorough attention needs to be paid to land-use history and widespread legacy and future soil pollution prior to reforestation and afforestation of aquitards above drinking water resources. We furthermore demonstrate that the protection of aquitard areas with less thickness than historical rooting depths and high degrees of lithological heterogeneity (related to aquitard glacial till types) is crucial to preserve drinking water resources and to restore groundwater quality beneath glacial aquitards.
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BibTeX
@article{jorgensen2026deep,
title = {{Deep tree roots at risk of accelerating groundwater pollution beneath clay-rich aquitards}},
author = {Peter R Jørgensen and Klaus Mosthaf and Paul Henning Krogh and Anders J Hansen and Ida B Nielsen and Frederik Seersholm and Natascha D Wagner and Jesper Olsen and Jiayi Qin and Luca Modesti and Jens Aamand and Una Pétursdóttir and Rasmus Thalund-Hansen and Carsten T Petersen and Bjarne W Strobel and Marine Lacoste and Massimo Rolle},
journal = {Nature Communications},
year = {2026},
month = may,
doi = {10.1038/s41467-026-73299-3},
url = {https://hal.inrae.fr/hal-05769242v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Deep tree roots at risk of accelerating groundwater pollution beneath clay-rich aquitards
AU - Peter R Jørgensen
AU - Klaus Mosthaf
AU - Paul Henning Krogh
AU - Anders J Hansen
AU - Ida B Nielsen
AU - Frederik Seersholm
AU - Natascha D Wagner
AU - Jesper Olsen
AU - Jiayi Qin
AU - Luca Modesti
AU - Jens Aamand
AU - Una Pétursdóttir
AU - Rasmus Thalund-Hansen
AU - Carsten T Petersen
AU - Bjarne W Strobel
AU - Marine Lacoste
AU - Massimo Rolle
PY - 2026
DA - 2026/05/28
JO - Nature Communications
DO - 10.1038/s41467-026-73299-3
UR - https://hal.inrae.fr/hal-05769242v1
AB - Glacial aquitards from the last Pleistocene glaciation cover vast areas of the Northern Hemisphere. Due to their clay-rich composition, these aquitards are considered to protect underlying aquifers from surface contaminations, provided they are not penetrated by widespread deep fractures. In this study we combine ancient DNA (aDNA) with detailed hydrological techniques to investigate contaminant transport in the aquitards – an interdisciplinary approach that was not possible when the current understanding of the dominant role of fractures was established. We show that deep fractures (> 2 m below surface) in the glacial aquitards across Denmark are closed or marginal as pathways of dissolved contaminant transport unless they contain flow channels from deep modern and ancient tree roots. Our study reveals that deep tree roots can compromise natural groundwater protection and accelerate groundwater pollution by opening fractures and generating deep macropores. The results highlight that thorough attention needs to be paid to land-use history and widespread legacy and future soil pollution prior to reforestation and afforestation of aquitards above drinking water resources. We furthermore demonstrate that the protection of aquitard areas with less thickness than historical rooting depths and high degrees of lithological heterogeneity (related to aquitard glacial till types) is crucial to preserve drinking water resources and to restore groundwater quality beneath glacial aquitards.
SN - 2041-1723
SN - 2041-1723
ER -