| Continuous recirculation of two municipal solid waste landfill leachates from Ontario, Canada, through a vegetated clay surface cover was field tested in 39 bottom-draining hysimeters over two field seasons. The degree of leachate constituent attenuation, the reduction in leachate volume, the vigour of the vegetative cover, and the influence of leachate on clay hydraulic conductivity were examined. Vegetation tested included reed canarygrass (Phalaris arundinacea L.), meadow foxtail (Alopecurus pratensis L.), weeping willow (Salix babylonica L.) and hybrid poplar (Populus sp. nigra x maximowiczii). The clay soil significantly buffered leachate pH, lowered the EC 76% to 3.22 mS cm{dollar}sp{lcub}-1{rcub}{dollar}, lowered the COD:Cl ratio 90% to 1.08, and attenuated Ca, Fe, Mn, and Zn. Anaerobic decomposition within the holding tanks lowered volatile organic concentrations by 80-100%, which was as effective as application to the clay soil. Leachate stimulated height growth 36 to 141% in the four species tested relative to the growth in the water-irrigated plants. (Abstract shortened by UMI.)... |
