Root colonisation effects on the key hydrogeological properties of a reclamation cover with an elevated water table

ABSTRACT

The performance of reclamation cover systems could be affected by the colonization of plant roots, which may modify the hydrogeological properties of the construction materials. A four-year field investigation was conducted using six experimental cells with various soil layering designs over AMD-generating tailings reclaimed with an oxygen-barrier cover combined with an elevated water table. Both herbaceous and woody vegetation were installed on top of the cells to compare the influence on the properties of the cover material. Consecutive and undisturbed cores were collected from the cover’s functional layer in 2020 and 2021, respectively. Root parameters, such as root length density, and hydrogeological properties were measured on the core samples to assess the possible relationships between the two categories of variables. Root observation trenches were also cut in each cell to better analyze the root density and occurrence profiles. Results showed that, within the four-year monitoring period of the study, both herbaceous and woody vegetation roots mostly colonized the top overburden layer of the cell (>86% visible roots) and barely occupied the functional layer of the reclamation cover (<10% visible roots). The observed maximum desorption rates for the functional layer were lower than the predicted values, which could be a short-term effect of the fine roots. No significant impact of roots on the main hydrogeological variables controlling the oxygen barrier efficiency were noted. At the end of the four-year study period, the hydrogeological behavior of the functional layer in all cells with/without vegetation/additional soil layers was found to be similar.

KEYWORDS:

• Oxygen-barrier cover systems
• root colonization effects
• hydrogeological properties
• reclamation of acid generating mine wastes

Acknowledgments

The authors would like to acknowledge the collaboration of the Westwood mine IAMGOLD Corporation, as well as the technical support of the URSTM team for their help in realisation of the experimental field setups and follow-ups. This work was funded by a collaborative research grant (CRD) between the Natural Sciences and Engineering Research Council (NSERC) of Canada and the Research Institute on Mines and the Environment (RIME-UQAT-Polytechnique) granted to M. Guittonny and coll. (RDCPJ 531237).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All data, models, and code generated or used during the study appear in the submitted article.

Additional information

Funding

This work was supported by the Natural Sciences and Engineering Research Council of Canada [RDCPJ 531237].