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Root colonization in mine covers and impact on their functioning Marie Guittonny, Professor at the Research Institute on Mines and the Environment of Universit du Qubec en Abitibi-Tmiscamingue (UQAT) 43rd CLRA/ACRSD National Conference and

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Root colonization in mine covers and impact on their functioning

Marie Guittonny, Professor at the Research Institute on Mines and the Environment of Université du Québec en Abitibi-Témiscamingue (UQAT) 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event, October 17

marie.guittonny@uqat.ca

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Root colonization in mine covers

Presentation schedule

  • Context
  • Problem and objectives
  • Study sites and measurements
  • Results
  • Conclusion and perspectives

2

43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

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Root colonization in mine covers

  • --Context-------------------------------------------------------------------
  • Mine covers are used to limit mine contaminated drainage

= physical barriers controlling oxygen migration and/or water infiltration towards underlying reactive wastes

(Aubertin et al. 2015)

  • For ex. Covers with capillary barrier effect (CCBE, Aubertin et al. 1995, Bussière et al. 2003),

Monolayer combined to elevated water table (EWT) (MEND 1996, Demers et al. 2008, Ouangrawa et

  • al. 2009, Pabst et al. 2017, Éthier 2018); Covers with low ksat (Daniel et Koerner 2007) or store and release

(SR, or ET) (Khire et al. 1999, 2000)

  • Adequate functionning relies on specific hydrogeological properties of materials

that control the variation of water budget components (for ex. storage, infiltration, run off, evaporation)

3

Reactive mine wastes Mine cover H2O, O2 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

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SLIDE 4
  • Revegetation or natural colonization  Vegetation presence that can change

the water budget of covers, especially storage and infiltration

  • Roots

Direct pumping of water from materials lost through transpiration (up to 50% of cover water can be lost under humid climate by transpiration, Waugh 2001)  Organic matter enrichment (OM+tailings mixture increases total porosity (+macroporosity), and decreases θ and Sr Larchevêque et al. 2013, Guittonny-Larchevêque et al. 2016)  Biopores (increasing of ksat by 103, Albright et al. 2006, DeJong

et al. 2015)

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Reactive mine wastes Mine cover H2O, O2 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Context-------------------------------------------------------------------
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  • To ensure the long-term performance of mine covers  It may be necessary to calibrate and

integrate root effects on hydrogeological properties of cover materials and on the water budget components

  • Challenges : The reference values of root colonization parameters that are used in numerical

models and their relationships with the water budget come from contexts differing from the mining context Are root architecture and intensity of colonization particular to the mining context? Knowing that: 1) Recycled mine materials are used in covers; 2) Covers have several layers of differing materials

  • Objectives of the presentation: Examples of 1) Root colonization of materials in specific mine

contexts; 2) Quantitative relationship between root characteristics and hydrogeological properties that are important for cover functionning

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43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Problem and objectives-------------------------------------------------
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Manitou Canadian Malartic Westwood Lorraine Rouyn-Noranda Val d’Or Abitibi-Témiscamingue region, QC 4 sites between 47 et 48° of latitude – Boreal forest or northern temperate forest 800-900 mm mean precipitation / year – 1-3°C mean annual temperature

Root colonization in mine covers

  • --Study sites and measurements---------------------------------------
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  • Lorraine site (Cu and Ni mine, 1999, Aubertin et Nastev 2000)
  • O2 barrier cover, CCBE multilayer (PhD Proteau)

7

  • 150
  • 100
  • 50
  • 10 cm

0-10 cm θ Sample 8 cm × 10 cm n, ρ (Bussière et al. 2009) WinRhizo Analysis RLD Sr Alnus, Salix, Picea, Populus, Herbs (17 years)

20-30 cm 35-45 cm

Root colonization in mine covers

  • --Study sites and measurements---------------------------------------
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8

y = -0.3493x + 0.9495 R² = 0.5034 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 Water saturation (Sr) Root length density (RLD, cm/cm3)

Relationship between root length density (RLD, in cm/cm3) and water saturation (Sr ) at the surface (0-10 cm) of the moisture retaining layer of a CCBE colonized by natural vegetation since 17 years (N=18) (Lorraine site)

43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Results----------------------------------------------------------------------
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  • Canadian Malartic site (Au mine)
  • Greenhouse experiment on mine tailings

(Guittonny- (Larchevêque et al. 2016a)

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Sample 100 cm3 WinRhizo analyse RLD, mean diameter Macroporosity (% vol. pores > 30 µm) 5 graminoids (2 months) : Lolium perenne, Avena sativa, Bromus inermis, Phalaris arundinacea, and Festuca rubra Biomass Sandbox 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Study sites and measurements---------------------------------------
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Relationship between root biomass of herbaceous plants grown in tailings during two months (in g/dm3) and tailings macroporosity (% volume pores > 30 µm) (N=43) (Greenhouse, Canadian Malartic tailings)

y = 6.5062x + 12.265 R² = 0.208 5 10 15 20 0.0 0.5 Tailings macroporosity (%) Root biomass (g) by tailings volume (dm3)

43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Results----------------------------------------------------------------------
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SLIDE 11
  • Canadian Malartic site
  • Plantation on mine tailings (Guittonny-Larchevêque et al. 2016b)

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50 cm or 20 cm of topsoil 2 species (2 years) : fast-growing poplar and willow 20 cm × 1m2 holes filled with topsoil Sample 8 cm × 20 cm Sample 8 cm × 10 cm Soil Tailings 0-20 cm 0-10 cm WinRhizo analyse RLD, mean diameter 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Study sites and measurements---------------------------------------
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  • Canadian Malartic site
  • Plantation on waste rocks (Remaury et al. 2018)

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50 cm topsoil, hybrid poplar (3 years) Sample 8 cm × 10 cm Soil Waste rocks 0-10 cm WinRhizo analyse RLD, mean diam. 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Study sites and measurements---------------------------------------
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  • Manitou site, TSF 2 (Zn and Cu mine)
  • O2 barrier cover = monolayer of mine tailings with EWT, 2009 (MSc Ben Khouya)

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Herbaceous seeding (7 years old) Sample 8 cm × 10 cm WinRhizo analyse RLD, mean diameter 0-10 cm 20-30 cm 30-40 cm Goldex tailings Manitou tailings 2 m Goldex tailings 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Study sites and measurements---------------------------------------
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Variation of the root colonization of vegetated mine materials – Minimal-Maximal values

Site Material type Vegetation type Age Depth RLD (cm.cm-3) Root mean

diameter (mm)

Manitou Monolayer EWT Mine tailings Seeded herbs 7 yr 0-10 cm 3,8-13,7 0,37-1,23 20-30 cm 0,2-0,9 0,34-1,14 30-40 cm 0,02-0,1 0,41-0,51 Lorraine Compacted silt Forest recolonization 17 yr 0-10 cm 0,0017-0,6 0,20-0,67 CCBE (MRL) 20-30 cm 0,0008-0,06 0,16-0,55 35-45 cm 0,0017-0,05 0,17-0,65 Canadian Malartic Plantation 2012 on tailings Plantation 2013 on w. rocks Greenhouse Mine tailings Poplar, willow 2 yr 20-30 cm 0,17-0,33 0,40-0,57 Topsoil 0-20 cm 0,36-0,55 0,41-0,47 Topsoil Poplar 3 yr 0-10 cm 0,28-1,5 Colonizing weeds 0,14-0,55 Seeded herbs 0,76-1,9 Mine tailings Herbs 2 mth 0-15 cm 0,3-0,8 0,32-0,56

Δ factor 1 to 7 Δ factor 1 to 1000 + + 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Results----------------------------------------------------------------------
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SLIDE 15
  • Westwood/Doyon site (Au mine)
  • Plantation on Doyon waste rocks

(Guittonny-Larchevêque and Lortie 2017)

15

Fast-growing willow (1-3 years) Analyse WinRhizo RLD Root profile Root occurrence (%) On a grid (75×70cm) by 5cm depth Root maximal depth 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Study sites and measurements---------------------------------------
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Variation of root colonization in superimposed layers of differing materials (Westwood site)

20 40 60 80 100

0-5 10-15 20-25 30-35 40-45 50-55 60-65 Root occurence (%) Depth class (cm)

Waste rocks - year 1

20 40 60 80 100 0-5 10-15 20-25 30-35 40-45 50-55 60-65

Waste rocks – year 3

  • Max. rooting depth = 65 cm
  • 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Results----------------------------------------------------------------------
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Variation of root colonization in superimposed layers of differing materials (Westwood site)

20 40 60 80 100 0-5 10-15 20-25 30-35 40-45 50-55 60-65

Moraine (40 cm) - year 3

20 40 60 80 100 0-5 10-15 20-25 30-35 40-45 50-55 60-65

Moraine (40 cm) - year 1

0… 1… 2… 3… 4… 5… 6… Interface avec les roches stériles +

  • Max. rooting depth = 65 cm

+ 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Results----------------------------------------------------------------------
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SLIDE 18

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Variation of root colonization in superimposed layers of differing materials (Westwood site)

20 40 60 80 100 0-5 10-15 20-25 30-35 40-45 50-55 60-65

Moraine (20 cm) then sludges (20 cm) - year 3

20 40 60 80 100 0-5 10-15 20-25 30-35 40-45 50-55 60-65

Moraine (20 cm) then sludges (20 cm) - year 1

0-5 1… 2… 3… 4… 5… 6…

Interface avec les roches stériles

+

  • 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Results----------------------------------------------------------------------
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  • Variation of root colonization intensity (RLD), depth and occurrence

among differing materials and layers.

  • Useful indicators in the mine context to calibrate root effects may be

RLD (Sr of O2 barriers) and biomass (Tailings macroporosity)

  • Root effects  it is necessary to integrate them to the design of

mine covers to ensure their performance at the long-term

  • At the medium term (7 and 17 years), roots remain concentrated at

the surface of fine grained materials of O2 barriers

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43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Conclusion-----------------------------------------------------------------
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  • Obtain reference values of root colonization specific to the mine

context

  • Multilayers

 Go further than maximal rooting depth  Take into account root development in each material layer, especially if mine materials, at the horizontal and vertical levels

  • Study the factors that control root development in mine materials to

conceive designs ensuring adequate functionning of vegetated mine covers

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43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Perspectives---------------------------------------------------------------
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  • Root effects on porosity influence on AEV of O2 barriers?

PhD Proteau : relationship between root parameters and ksat + water retention curve

  • Root effects on Sr  influence on other components of the water budget?

MSc Ben Khouya; Chevé et al. 2018 : revegetation effect on evapotranspiration and infiltration

  • Integration of plant effects in the numerical modelling of the water budget of

covers? Postdoc Botula : comparison of the ability of several numerical models to take vegetation into account

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43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event

Root colonization in mine covers

  • --Undergoing research work at RIME-UQAT-------------------------
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