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
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
Root colonization in mine covers H 2 O, O 2 ---Context------------------------------------------------------------------- • Mine covers are used to limit mine contaminated drainage Mine cover = physical barriers controlling oxygen migration and/or Reactive mine wastes 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 k sat (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 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event
Root colonization in mine covers ---Context------------------------------------------------------------------- • 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 H 2 O, O 2 increases total porosity (+macroporosity), and decreases θ and S r Larchevêque et al. 2013, Guittonny-Larchevêque et al. 2016 ) Mine cover Biopores (increasing of k sat by 10 3 , Albright et al. 2006, DeJong Reactive mine wastes et al. 2015 ) 4 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event
Root colonization in mine covers ---Problem and objectives------------------------------------------------- • 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 5 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event
Root colonization in mine covers ---Study sites and measurements--------------------------------------- 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 Westwood Rouyn-Noranda Canadian Malartic Manitou Val d’Or Lorraine
Root colonization in mine covers ---Study sites and measurements--------------------------------------- • Lorraine site (Cu and Ni mine, 1999, Aubertin et Nastev 2000 ) • O 2 barrier cover, CCBE multilayer (PhD Proteau) - 150 - θ - 0-10 cm - Sr - 20-30 cm - 100 n, ρ - 35-45 cm (Bussière et al. 2009) - - - - 50 - RLD - - - 10 cm Alnus, Salix, Picea, Populus, Herbs WinRhizo Analysis Sample 7 (17 years) 8 cm × 10 cm
Root colonization in mine covers ---Results---------------------------------------------------------------------- 1.0 Relationship between root Water saturation (Sr) length density (RLD, in cm/cm 3 ) 0.8 and water saturation (S r ) at the surface (0-10 cm) of the 0.6 moisture retaining layer of a y = -0.3493x + 0.9495 R² = 0.5034 CCBE colonized by natural 0.4 vegetation since 17 years (N=18) 0.2 (Lorraine site) 0.0 0.0 0.2 0.4 0.6 Root length density (RLD, cm/cm3) 8 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event
Root colonization in mine covers ---Study sites and measurements--------------------------------------- • Canadian Malartic site (Au mine) • Greenhouse experiment on mine tailings (Guittonny- (Larchevêque et al. 2016a) Sample Macroporosity 100 cm 3 (% vol. pores > 30 µm) Sandbox 5 graminoids (2 months) : RLD, mean diameter Lolium perenne, Avena sativa, Bromus inermis, Phalaris arundinacea, Biomass and Festuca rubra WinRhizo analyse 9 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event
Root colonization in mine covers ---Results---------------------------------------------------------------------- Relationship between root 20 Tailings macroporosity (%) biomass of herbaceous plants grown in tailings during two 15 months (in g/dm3) and tailings macroporosity (% y = 6.5062x + 12.265 10 volume pores > 30 µm) R² = 0.208 (N=43) 5 (Greenhouse, Canadian Malartic tailings) 0 0.0 0.5 Root biomass (g) by tailings volume (dm3) 10 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event
Root colonization in mine covers ---Study sites and measurements--------------------------------------- • Canadian Malartic site • Plantation on mine tailings (Guittonny-Larchevêque et al. 2016b) Sample 8 cm × 20 cm Soil 0-20 cm 0-10 cm Tailings Sample 8 cm × 10 cm WinRhizo analyse 20 cm × 1m 2 holes filled with topsoil 50 cm or 20 cm of topsoil RLD, mean diameter 2 species (2 years) : fast-growing poplar and willow 11 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event
Root colonization in mine covers ---Study sites and measurements--------------------------------------- • Canadian Malartic site • Plantation on waste rocks (Remaury et al. 2018) 0-10 cm RLD, Soil mean diam. Waste rocks Sample WinRhizo analyse 8 cm × 10 cm 50 cm topsoil, hybrid poplar (3 years) 12 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event
Root colonization in mine covers ---Study sites and measurements--------------------------------------- • Manitou site, TSF 2 (Zn and Cu mine) • O 2 barrier cover = monolayer of mine tailings with EWT, 2009 (MSc Ben Khouya) Goldex 0-10 cm tailings 20-30 cm 2 m 30-40 cm WinRhizo analyse Goldex tailings Manitou Sample tailings RLD, mean 8 cm × 10 cm diameter Herbaceous seeding (7 years old) 13 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event
Root colonization in mine covers ---Results---------------------------------------------------------------------- Variation of the root colonization of vegetated mine materials – Minimal-Maximal values RLD Root mean (cm.cm -3 ) Site Material type Vegetation type Age Depth diameter (mm) Manitou Mine tailings Seeded herbs 7 yr 0-10 cm 3,8-13,7 0,37-1,23 Δ factor Monolayer EWT + 20-30 cm 0,2-0,9 0,34-1,14 1 to 7 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 Δ factor + CCBE (MRL) 20-30 cm 0,0008-0,06 0,16-0,55 1 to 1000 35-45 cm 0,0017-0,05 0,17-0,65 Canadian Malartic 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 Plantation 2012 on tailings Topsoil Poplar 3 yr 0-10 cm 0,28-1,5 Colonizing weeds 0,14-0,55 Plantation 2013 on w. rocks Seeded herbs 0,76-1,9 Mine tailings Herbs 2 mth 0-15 cm 0,3-0,8 0,32-0,56 Greenhouse 14 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event
Root colonization in mine covers ---Study sites and measurements--------------------------------------- Fast-growing willow • Westwood/Doyon site (Au mine) (1-3 years) • Plantation on Doyon waste rocks (Guittonny-Larchevêque and Lortie 2017) Root profile Root occurrence (%) Analyse WinRhizo On a grid (75×70cm) by 5cm depth Root maximal depth RLD 15 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event
Root colonization in mine covers ---Results---------------------------------------------------------------------- Variation of root colonization in superimposed layers of differing materials (Westwood site) Waste rocks – year 3 Waste rocks - year 1 Root occurence (%) 0 20 40 60 80 100 0 20 40 60 80 100 Depth class (cm) 0-5 0-5 10-15 10-15 - 20-25 - 20-25 - 30-35 30-35 40-45 40-45 50-55 50-55 60-65 60-65 Max. rooting depth = 65 cm 16 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event
Root colonization in mine covers ---Results---------------------------------------------------------------------- Variation of root colonization in superimposed layers of differing materials (Westwood site) Moraine (40 cm) - year 3 Moraine (40 cm) - year 1 0 20 40 60 80 100 0 20 40 60 80 100 0-5 0-5 10-15 10-15 + 20-25 20-25 + - 30-35 30-35 40-45 40-45 50-55 50-55 60-65 60-65 0 6… Interface avec les roches Max. rooting depth = 65 cm 1… 0… 2… 3… 5… 4… stériles 17 43rd CLRA/ACRSD National Conference and AGM /ARC 2018 Event
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