Impact of Roots on the Hydrogeological Properties of Silty Soil Covers

Abstract

Mine tailings storage poses significant environmental risks such as the formation of acid mine drainage (AMD). Engineered covers offer a solution by controlling water ingress. Their performance is based on specific soil hydrogeological properties (SHPs). They must support vegetation which can impact saturated hydraulic conductivity (ksat) and water retention curve (WRC). This study assesses the impact of four-year-old willow root colonization on silty soil covers using flexible wall permeameters and water retention tests. The obtained SHPs were compared with root traits. Results suggested that the hydrogeological properties of the studied in situ samples were not significantly affected by roots. The variation of measured and predicted ksat values spanned an order of magnitude, regardless of the root colonization intensity, up to a root length density (RLD) of 2.98 cm/cm3. RLD showed a significant and positive linear relationship with measured ksat values (R2 = 0.54). However, when root colonization was low (RLD < 1 cm/cm3), RLD was negatively correlated to the nvg (R2 = 0.44) parameter of the van Genuchten WRC model, while the opposite relationship was observed for samples with RLD > 1 cm/cm3 (R2 = 0.61). Additionally, RLD and the coarse root (diameter > 1 mm) volume to fine root volume (C/F ratio) influenced WRCs. Over time, coarser roots may have a more pronounced impact on SHPs; further research is needed