Chromium(III) complexation to natural organic matter: Mechanisms and modeling
2014 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 48, no 3, 1753-1761 p.Article in journal (Refereed) Published
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··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···Cr interactions at 2.98 Å and for SRFA also at 3.57 Å, 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.
Place, publisher, year, edition, pages
American Chemical Society (ACS), 2014. Vol. 48, no 3, 1753-1761 p.
X-Ray Absorption Spectroscopy, Humic Substances, Ion Binding, Exafs Spectroscopy, Condensed Matter, Proton-Binding, Cation-Binding, Soils, Metal
IdentifiersURN: urn:nbn:se:kth:diva-142807DOI: 10.1021/es404557eISI: 000331015100049ScopusID: 2-s2.0-84893606291OAI: oai:DiVA.org:kth-142807DiVA: diva2:704735
FunderKnut and Alice Wallenberg FoundationSwedish Research Council
QC 201403132014-03-132014-03-122015-03-24Bibliographically approved