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Journal of Environmental Quality Abstract - Heavy Metals in the Environment

Phytoextraction of Heavy Metals by Willows Growing in Biosolids under Field Conditions


This article in JEQ

  1. Vol. 41 No. 1, p. 134-143
    Received: July 8, 2011

    * Corresponding author(s): wlaidlaw@unimelb.edu.au
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  1. W. S. Laidlaw *a,
  2. S. K. Arndtb,
  3. T. T. Huynhad,
  4. D. Gregoryc and
  5. A. J. M. Bakera
  1. a School of Botany, The Univ. of Melbourne, Grattan St, Parkville, Victoria 3010, Australia
    b Dep. of Forest and Ecosystem Science, The Univ. of Melbourne, 500 Yarra Blvd., Richmond, Victoria 3121, Australia
    d current address: Centre for Mined Land Rehabilitation, The University of Queensland, Brisbane, QLD 4072, Australia. Assigned to Associate Editor Brett Robinson
    c Research and Technology Division, Melbourne Water Corporation, 100 Wellington Parade, East Melbourne, Victoria 3002, Australia


Biosolids produced by sewage treatment facilities can exceed guideline thresholds for contaminant elements. Phytoextraction is one technique with the potential to reduce these elements allowing reuse of the biosolids as a soil amendment. In this field trial, cuttings of seven species/cultivars of Salix (willows) were planted directly into soil and into biosolids to identify their suitability for decontaminating biosolids. Trees were irrigated and harvested each year for three consecutive years. Harvested biomass was weighed and analyzed for the contaminant elements: As, Cd, Cu, Cr, Hg, Pb, Ni, and Zn. All Salix cultivars, except S. chilensis, growing in soils produced 10 to 20 t ha−1 of biomass, whereas most Salix cultivars growing in biosolids produced significantly less biomass (<6 t ha−1). Salix matsudana (30 t ha−1) and S. × reichardtii A. Kerner (18 t ha−1) had similar aboveground biomass production in both soil and biosolids. These were also the most successful cultivars in extracting metals from biosolids, driven by superior biomass increases and not high tissue concentrations. The willows were effectual in extracting the most soluble/exchangeable metals (Cd, 0.18; Ni, 0.40; and Zn, 11.66 kg ha−1), whereas Cr and Cu were extracted to a lesser degree (0.02 and 0.11 kg ha−1). Low bioavailable elements, As, Hg, and Pb, were not detectable in any of the aboveground biomass of the willows.

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