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Title: Studies of the nature of Cu{sup 2+} and Pb{sup 2+} binding sites in soil humic substances using x-ray absorption spectroscopy

Abstract

We have investigated the binding environments of Cu{sup 2+} and Pb{sup 2+} complexed by soil humic substances using synchrotron-based X-ray absorption spectroscopy. With the assistance of bond network analysis, analysis of X-ray absorption near edge structure (XANES) and radial structure functions derived from extended X-ray absorption fine structure (EXAFS) spectra of Cu-humate at pH 4, 5, and 6 yielded a tetragonally-distorted octahedral binding environment for Cu with 4 O atoms at an average distance of 1.94 {angstrom}, 20 atoms at an average distance of 2.02 {angstrom}, and 4 C atoms at an average distance of 3.13 {angstrom}. Analysis of Pb-humate samples at pH 4, 5, and 6 yielded 4 O atoms at average distances between 2.46 {angstrom} to 2.32 {angstrom} and 2 C atoms at an average distance of 3.26 {angstrom} for Pb. We interpret the presence of C atoms in the second atomic shell of the metal binding site as evidence that both C{sup 2+} and Pb{sup 2+} form innersphere complexes with soil humic substances. Within the pH range 4-6, there is no significant change in the structure of the binding sites for either Cu or Pb. 65 refs., 8 figs., 5 tabs.

Authors:
; ;  [1]
  1. Univ. of Wisconsin, Madison, WI (United States)
Publication Date:
OSTI Identifier:
576338
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 61; Journal Issue: 11; Other Information: PBD: Jun 1997
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 36 MATERIALS SCIENCE; 58 GEOSCIENCES; HUMIC ACIDS; COPPER; LEAD; NSLS; RESEARCH PROGRAMS; GEOCHEMISTRY; TRACE AMOUNTS; ELEMENTS; ENVIRONMENTAL TRANSPORT; SOILS

Citation Formats

Xia, Kang, Bleam, W, and Helmke, P A. Studies of the nature of Cu{sup 2+} and Pb{sup 2+} binding sites in soil humic substances using x-ray absorption spectroscopy. United States: N. p., 1997. Web. doi:10.1016/S0016-7037(97)00079-3.
Xia, Kang, Bleam, W, & Helmke, P A. Studies of the nature of Cu{sup 2+} and Pb{sup 2+} binding sites in soil humic substances using x-ray absorption spectroscopy. United States. https://doi.org/10.1016/S0016-7037(97)00079-3
Xia, Kang, Bleam, W, and Helmke, P A. 1997. "Studies of the nature of Cu{sup 2+} and Pb{sup 2+} binding sites in soil humic substances using x-ray absorption spectroscopy". United States. https://doi.org/10.1016/S0016-7037(97)00079-3.
@article{osti_576338,
title = {Studies of the nature of Cu{sup 2+} and Pb{sup 2+} binding sites in soil humic substances using x-ray absorption spectroscopy},
author = {Xia, Kang and Bleam, W and Helmke, P A},
abstractNote = {We have investigated the binding environments of Cu{sup 2+} and Pb{sup 2+} complexed by soil humic substances using synchrotron-based X-ray absorption spectroscopy. With the assistance of bond network analysis, analysis of X-ray absorption near edge structure (XANES) and radial structure functions derived from extended X-ray absorption fine structure (EXAFS) spectra of Cu-humate at pH 4, 5, and 6 yielded a tetragonally-distorted octahedral binding environment for Cu with 4 O atoms at an average distance of 1.94 {angstrom}, 20 atoms at an average distance of 2.02 {angstrom}, and 4 C atoms at an average distance of 3.13 {angstrom}. Analysis of Pb-humate samples at pH 4, 5, and 6 yielded 4 O atoms at average distances between 2.46 {angstrom} to 2.32 {angstrom} and 2 C atoms at an average distance of 3.26 {angstrom} for Pb. We interpret the presence of C atoms in the second atomic shell of the metal binding site as evidence that both C{sup 2+} and Pb{sup 2+} form innersphere complexes with soil humic substances. Within the pH range 4-6, there is no significant change in the structure of the binding sites for either Cu or Pb. 65 refs., 8 figs., 5 tabs.},
doi = {10.1016/S0016-7037(97)00079-3},
url = {https://www.osti.gov/biblio/576338}, journal = {Geochimica et Cosmochimica Acta},
number = 11,
volume = 61,
place = {United States},
year = {Sun Jun 01 00:00:00 EDT 1997},
month = {Sun Jun 01 00:00:00 EDT 1997}
}