Epsilon Archive for Student Projects

Abstract

Willow short rotation coppice (SRC) is a perennial gricultural crop used for the production of biomass for energy in Sweden. Environmental applications of willow SRC became of interest in the last years, such as the use of willow phytoremediation systems for the treatment of andfill leachate. Landfill leachate is generated after percolation of water through waste deposited in a landfill. The resulting effluent is a hazardous mixture of dissolved organic matter, inorganic components such as ammonium and chloride, heavy metals and xenobiotic compounds. This study investigates the longterm impact of landfill leachate application on the accumulation of heavy metals, as well as the carbon and nitrogen content in soil. In 2005 a field trial was established on an arable field next to a landfill operated by Ragnsells Avfallsbehandling AB, at Högbytorp, Upplands-Bro (Sweden). Two different Salix sp. clones (Gudrun and Tora) were planted in double rows in sixteen 400 m2 square plots. The treatments consisted of three different concentrations of landfill leachate and a control. In 2011 soil samples were taken from every treatment plot and from the surrounding grassland and
analysed for heavy metal concentrations and total carbon and nitrogen content. Moreover, samples of willow shoots were taken from the treatments and analysed for heavy metal concentrations and nitrogen content. Cd, Pb and Ni concentrations were significantly lower in the topsoil of the willow treatments compared to the reference. Moreover, Zn tended to decrease in the topsoil of the treatments compared to the reference. The total carbon and nitrogen content in the topsoil was significantly lower in the willow treatments compared to the surrounding grassland. Although willows showed potential for the accumulation of some heavy metals, biomass production is important for an efficient treatment. Plant growth was negatively affected by the leachate overload on the treatment with the highest supply resulting in low offtake of heavy metals. Although no
substantial accumulation of heavy metals was reported in this study, application of heavy metals with the leachate should be within recommended application loads in order to prevent accumulation of metals that might not be taken up by the plants.