Copper (Cu) speciation in organic-waste (OW) amended soil: Instability of OW-borne Cu(I) sulfide and role of clay and iron oxide minerals

Thiago A. Formentini, Isabelle Basile-Doelsch, Samuel Legros, Andrew J. Frierdich, Adilson Pinheiro, Cristovão V.S. Fernandes, Fábio J.K. Mallmann, Daniel Borschneck, Milton da Veiga, Emmanuel Doelsch

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1 Citation (Scopus)


The geochemistry of copper (Cu) is generally assumed to be controlled by organic matter in soils. However, the role of clay and iron oxide minerals may be understated. Soil density fractionation, X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS) were combined to assess the long-term behavior of Cu in an agricultural soil subject to organic waste application. Two unprecedented molecular environments of natural Cu (i.e. Cu inherited from the parent rock) in soils are reported: Cu dimer in the interlayer of vermiculite and Cu structurally incorporated within hematite. Moreover, the soil naturally containing Cu-vermiculite, Cu-hematite, but also Cu-kaolinite (Cutotal = 122 mg·kg−1) was amended over 11 years with Cu-rich pig slurry in which Cu was 100 % Cu(I) sulfide. Natural Cu associated with clay and iron oxide minerals persisted in the amended soil, but the exogenous Cu(I) sulfide was unstable. The increase in Cu concentration in the amended soil to 174 mg·kg−1 was accounted for the increase of Cu sorbed to kaolinite and Cu bound to organic matter. These results are important for better understanding the natural occurrence of Cu in soils and for assessing the environmental impacts of organic waste recycling in agricultural fields.

Original languageEnglish
Article number157779
Number of pages10
JournalScience of the Total Environment
Publication statusPublished - 20 Nov 2022


  • Agricultural recycling
  • Cu dimer
  • Cu-hematite
  • Cu-kaolinite
  • Cu-vermiculite
  • Pig slurry
  • XAS

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