Ectomycorrhizal seedling response to selected components of landfill leachate

Abstract

The threshold toxicity concentrations of seven landfill leachate components (acetic, propionic, butyric, isobutyric, valeric, isovaleric and hexanoic acids) were determined with respect to the growth of three ectomycorrhizal fungi (Laccaria proxima, Hebeloma crustuliniforme and Paxillus involutus) and to the survival of mycorrhizal and mycorrhizal-free Betula pendula seedlings. Inoculation increased tree seedling tolerance to the acids, with the exception of the susceptibilities of L. proxima and H. crustuliniforme to valerate and isovalerate. Interacting microbial associations catabolically active against the acids were isolated from three different source materials (refuse, subsoil, topsoil). Minimum inhibitory acid concentrations exceeded the threshold toxicity concentrations to B. pendula seedlings, fungal isolates and mycorrhizal associations. Thus, provided that the acid concentrations were not toxic to the microbial associations and the hydraulic loading rates were lower than the maximum specific growth rates of the associations, concentrations should be reduced by microbial intervention during vertical migration. The potential for the routine use of mycorrhizal tree seedlings in landfill site restoration is discussed in the context of site-specific variables.