Willow stands as an alternative method for the reduction of leachate at contaminated sites — numerical investigations

Abstract

The commonly used multiple‐liner‐system of modern top sealings of contaminated sites is expensive and in many cases (minor hazardousness of pollutants), not necessary. As an alternative, we investigated the performance of willow stands as the only measure to reduce percolating soil water and therewith pollutant transport to underlying ground water resources. It is well accepted that willows have a high water demand and may considerably reduce percolation. On the basis of experimentally determined soil physical properties of a landfill site, we performed water balance calculations with the physically based HYDRUS‐code and a simple bucket approach. The 20 yr annual leachate rate for bare soil was calculated to vary from 336 (HYDRUS) to 451 mm yr—1 (bucket‐model). Willows were able to reduce the annual leachate to 146 (HYDRUS) and 186 mm yr—1 (bucket‐model), indicating their great performance compared to a grass‐ or beechwood cover. However, legal regulations (TASi) in Germany cannot be met with the proposed method. In minor hazardous cases, official authorities may accept willow stands as an alternative system for protection.

Water regime of mechanical—biological pretreated waste materials under fast-growing trees

“…In this study the one-dimensional simulation model HYD-RUS-1D (Simunek et al 2005) was applied to simulate the water regime and therewith the leachate of different surface cover materials. The HYDRUS-code is a numerical model that has been used frequently for the design of landfill covers (Licht et al 2001, Kahle et al 2002, Dwyer 2003. The governing differential equation for fluid flow in HYDRUS-1D is the one dimensional Richards' equation.…”

“…Water retention curve 'Compost' is given by Döberl et al (2002) for a composted waste material. As reference, a natural soil material (loamy sand, see Kahle et al 2002) is displayed. For all materials a proposed 150 cm layer cover was used to conduct the numerical modelling.…”

Yield and Water Quality Impacts of Field‐Scale Integration of Willow into a Continuous Corn Rotation System

“…Shrub willows (Salix miyabeana Seemen) are efficient bioenergy and phytoremediation candidates due to their fast perennial growth, high biomass production, and high nutrient uptake. They can tolerate a wide range of environmental conditions, including drought, saturated soils, and high toxicity (landfill leachate), as well as stressors including herbivory, rust infection, and frost (Elowson, 1999;Kahle et al, 2002;Smart et al, 2005;AILE, 2007;Nissim et al, 2014). Taking into account soil and climate effects on denitrification and soil immobilization, the literature suggests that ~200 kg N ha −1 yr −1 could be treated through a soil-willow system (AILE, 2007).…”