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Root penetration through sealing layers at mine deposit sites
1Department of Botany, Stockholm University, S-106 91 Stockholm, Sweden.
Summary
Plant roots can penetrate sealing layers of mine tailings, potentially compromising their protective function. Adding nutrients to the top cover can limit root growth, but defining optimal conditions is challenging due to varied plant needs.
Area of Science:
- Environmental Science
- Geotechnical Engineering
- Plant Biology
Background:
- Mine tailings require sealing layers to prevent acid mine drainage from oxygen and water ingress.
- Plant roots can penetrate dense materials, posing a risk to the integrity of sealing layers.
Purpose of the Study:
- To evaluate the ability of plant roots to penetrate various sealing materials used in mine tailings deposits.
- To identify factors influencing root penetration through sealing layers.
Main Methods:
- Field investigation of root penetration in 3- and 10-year-old mine sites by excavating trenches.
- Greenhouse experiments studying root growth of four plant species (Betula pendula, Pinus sylvestris, Poa pratensis, Salix viminalis) over 22 months.
- Testing root penetration into diverse sealing materials including clayey moraine, bentonite fabric, lime and clay, Cefyll, and biosludge/bioash mixtures.
Main Results:
- Field results confirmed root penetration into deep cover layers (1.7 m) and various sealing materials, including hard Cefyll.
- Nutrient addition in the top cover significantly reduced deep root growth and penetration through sealing layers.
- In greenhouse studies, roots did not penetrate bentonite fabric due to low pH; clayey moraine was penetrated by all species, with Pinus sylvestris showing the highest penetration ability.
Conclusions:
- Plant roots can penetrate engineered sealing layers, potentially compromising acid mine drainage prevention.
- Controlling nutrient availability in the upper cover layer is a potential strategy to limit root penetration.
- Further research is needed to define specific nutrient conditions for different plant species to optimize sealing layer integrity.
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