Article

Environmental Geochemistry and Health

, Volume 21, Issue 2, pp 157-173

First online:

An Investigation Into the Mechanism by Which Synthetic Zeolites Reduce Labile Metal Concentrations in Soils

  • Robert EdwardsAffiliated withSchool of Pharmacy and Chemistry, Liverpool John Moores University
  • , Irina RebedeaAffiliated withSchool of Pharmacy and Chemistry, Liverpool John Moores University
  • , Nicholas W. LeppAffiliated withSchool of Biological and Earth Science, Liverpool John Moores University
  • , Anthony J. LovellAffiliated withCrosfield Chemicals, Warrington

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Abstract

The addition of synthetic zeolites and similar materials to metal contaminated soils has been shown to reduce soil phytotoxicity and to improve the quality of plant growth on such amended soils. To gain an understanding of the mechanism by which the phytotoxicity of contaminated soils is reduced when treated with synthetic zeolites, sequential extraction procedures and soil solution techniques have been used to identify changes associated with metal speciation in amended soils. Sequential extraction data and changes in soil solution composition are presented for three different contaminated soils, amended with three synthetic zeolites (P, 4A and Y) at concentrations of 0.5%, 1% and 5% w/w, or lime at 1%. The soils were collected from the site of a metal refinery, an old lead zinc mine spoil tip and from a field which had been treated with sewage sludge. After incubation of the zeolite treated soils for between one and three months, results showed a reduction in the metal content of the ammonium acetate fraction between 42% and 70%, depending on soil, zeolite and rate of addition, compared with the unamended soils. In addition, soil solution experiments indicated that synthetic zeolite amendments were more efficient at reducing metal content than comparable lime treatment. The mechanism by which synthetic zeolites reduce metal bioavailability in contaminated soils is discussed and compared to other amendments.

contaminated land in situ remediation heavy metals bioavailability zeolites