Chemical speciation and extractability of Zn, Cu and Cd in two contrasting biosolids-amended clay soils

X. L. Qiao, Y. M. Luo*, P. Christie, Ming Hung WONG

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

73 Citations (Scopus)


An incubation experiment was conducted to study the chemical speciation and extractability of three heavy metals in two contrasting biosolids-amended clay soils. One was a paddy soil of pH 7.8 and the other was a red soil of pH 4.7 collected from a fallow field. Anaerobically digested biosolids were mixed with each of the two soils at three rates: 20, 40 and 60 g kg-1 soil (DM basis), and unamended controls were also prepared. The biosolids-amended and control soils were incubated at 70% of water holding capacity at 25 °C for 50 days. Separate subsamples were extracted with three single extractants and a three-step sequential extraction procedure representing acetic acid (HOAc)-soluble, reducible and oxidisable fractions to investigate the extractability and speciation of the heavy metals. As would be expected, there were good relationships between biosolids application rate and metal concentrations in the biosolids-amended soils. The three heavy metals had different extractabilities and chemical speciation in the two biosolids-amended soils. Ethylene diamine tetraacetic acid extracted more Cu, Zn and Cd than did the other two single extractants. The oxidisable fraction was the major fraction for Cu in both biosolids-amended soils and the HOAc-soluble and reducible fractions accounted for most of the Zn. In contrast, Cd was present mainly in the reducible fraction. The results are discussed in relation to the mobility and bioavailability of the metals in polluted soils.

Original languageEnglish
Pages (from-to)823-829
Number of pages7
Issue number6
Publication statusPublished - Feb 2003

Scopus Subject Areas

  • Environmental Engineering
  • Environmental Chemistry
  • Chemistry(all)
  • Pollution
  • Health, Toxicology and Mutagenesis

User-Defined Keywords

  • Heavy metals
  • Sequential extraction
  • Sewage sludge
  • Single extraction
  • Speciation


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