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Title: Sulfur and nitrogen speciation in humic substances by x-ray absorption near-edge structure spectroscopy

Abstract

Understanding the chemical composition and structure of complex macromolecules in the geosphere, such as humic substances and kerogen, poses a challenging analytical problem. Widely used chromatographic techniques, such as the pyrolysis GC-MS, cause severe changes in structure during preparation and analysis of the sample, and thus, may not give accurate information. An important non-destructive technique that is becoming popular in speciation studies of environmental and geochemical samples is x-ray absorption fine structure spectroscopy. We used the x-ray absorption near-edge structure (XANFS) spectroscopy for examining the speciation of sulfur and nitrogen in humic substances of different origins, including soil and marine sediments. XANES provides information on the characteristics of the functional groups containing these atoms because of its sensitivity to the electronic structure, oxidation state, and the geometry of the neighboring atoms. Organic sulfides, di- and poly-sulfides, sulfonates and organic sulfates are the major forms of sulfur detected in all the humics we examined. The oxidized sulfonate-sulfur dominates the composition of sulfur species in soil humics accounting for more than 60% of the total sulfur. In marine humics, although sulfonates are abundant in near-surface sediments, reduced sulfur species, particularly di-and poly-sulfides, also constitute an important fraction. The nitrogen XANES indicates themore » dominance of amino and amide groups among nitrogen functionalities, although porphyrinic and pyridinic groups also are present. The significance of these results for the transformations of nitrogen and sulfur in soil and sedimentary systems will be presented.« less

Authors:
; ;  [1]
  1. Brookhaven National Lab., Upton, NY (United States); and others
Publication Date:
OSTI Identifier:
539000
Report Number(s):
CONF-960807-
TRN: 97:004029-0068
Resource Type:
Conference
Resource Relation:
Conference: 212. national meeting of the American Chemical Society (ACS), Orlando, FL (United States), 25-30 Aug 1996; Other Information: PBD: 1996; Related Information: Is Part Of 212th ACS national meeting; PB: 1830 p.
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 04 OIL SHALES AND TAR SANDS; 40 CHEMISTRY; KEROGEN; CHEMICAL COMPOSITION; HUMIC ACIDS; ABSORPTION SPECTRA; ELECTRONIC STRUCTURE; FINE STRUCTURE; PYROLYSIS; SEDIMENTS; SULFATES; ENVIRONMENTAL MATERIALS

Citation Formats

Vairavamurthy, M A, Wang, Shenghe, and Maletic, D. Sulfur and nitrogen speciation in humic substances by x-ray absorption near-edge structure spectroscopy. United States: N. p., 1996. Web.
Vairavamurthy, M A, Wang, Shenghe, & Maletic, D. Sulfur and nitrogen speciation in humic substances by x-ray absorption near-edge structure spectroscopy. United States.
Vairavamurthy, M A, Wang, Shenghe, and Maletic, D. 1996. "Sulfur and nitrogen speciation in humic substances by x-ray absorption near-edge structure spectroscopy". United States.
@article{osti_539000,
title = {Sulfur and nitrogen speciation in humic substances by x-ray absorption near-edge structure spectroscopy},
author = {Vairavamurthy, M A and Wang, Shenghe and Maletic, D},
abstractNote = {Understanding the chemical composition and structure of complex macromolecules in the geosphere, such as humic substances and kerogen, poses a challenging analytical problem. Widely used chromatographic techniques, such as the pyrolysis GC-MS, cause severe changes in structure during preparation and analysis of the sample, and thus, may not give accurate information. An important non-destructive technique that is becoming popular in speciation studies of environmental and geochemical samples is x-ray absorption fine structure spectroscopy. We used the x-ray absorption near-edge structure (XANFS) spectroscopy for examining the speciation of sulfur and nitrogen in humic substances of different origins, including soil and marine sediments. XANES provides information on the characteristics of the functional groups containing these atoms because of its sensitivity to the electronic structure, oxidation state, and the geometry of the neighboring atoms. Organic sulfides, di- and poly-sulfides, sulfonates and organic sulfates are the major forms of sulfur detected in all the humics we examined. The oxidized sulfonate-sulfur dominates the composition of sulfur species in soil humics accounting for more than 60% of the total sulfur. In marine humics, although sulfonates are abundant in near-surface sediments, reduced sulfur species, particularly di-and poly-sulfides, also constitute an important fraction. The nitrogen XANES indicates the dominance of amino and amide groups among nitrogen functionalities, although porphyrinic and pyridinic groups also are present. The significance of these results for the transformations of nitrogen and sulfur in soil and sedimentary systems will be presented.},
doi = {},
url = {https://www.osti.gov/biblio/539000}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Dec 31 00:00:00 EST 1996},
month = {Tue Dec 31 00:00:00 EST 1996}
}

Conference:
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