Chromium(III) Complexation to Natural Organic Matter: Mechanisms and Modeling

Abstract

Chromium is a common soil contaminant, and it often exists as chromium(III). However, limited information exists on the coordination chemistry and stability of chromium(III) complexes with natural organic matter (NOM). Here, the complexation of chromium(III) to mor layer material and to Suwannee River Fulvic Acid (SRFA) was investigated using EXAFS spectroscopy and batch experiments. The EXAFS results showed a predominance of monomeric chromium-(III)-NOM complexes at low pH (<5), in which only Cr center dot center dot center dot C and Cr-O-C interactions were observed in the second coordination shell. At pH > 5 there were polynuclear chromium(III)-NOM complexes with Cr center dot center dot center dot Cr interactions at 2.98 angstrom and for SRFA also at 3.57 angstrom, indicating the presence of dimers (soil) and tetramers (SRFA). The complexation of chromium(III) to NOM was intermediate between that of iron(III) and aluminum(III). Chromium(III) complexation was slow at pH < 4: three months or longer were required to reach equilibrium. The results were used to constrain chromium-NOM complexation in the Stockholm Humic Model (SHM): a monomeric complex dominated at pH < 5, whereas a dimeric complex dominated at higher pH. The optimized constant for the monomeric chromium(III) complex was in between those of the iron(III) and aluminum(III) NOM complexes. Our study suggests that chromium(III)-NOM complexes are important for chromium speciation in many environments.

Published in

Environmental Science and Technology
2014, volume: 48, number: 3, pages: 1753-1761

SLU Authors

• Gustafsson, Jon-Petter

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    
  • Royal Institute of Technology (KTH)

• Persson, Ingmar

  • Department of Molecular Sciences, Swedish University of Agricultural Sciences
    

• Geranmayeh Oromieh, Aidin

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

• Van Schaik, Joris

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

• Sjöstedt, Carin

  • Royal Institute of Technology (KTH)

• Berggren Kleja, Dan

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    
  • Swedish Geotechnical Institute (SGI)

UKÄ Subject classification

Geochemistry
Soil Science

Publication identifier

• DOI: https://doi.org/10.1021/es404557e

Permanent link to this page (URI)

https://res.slu.se/id/publ/56606