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Title: Characterization of Minerals and Organic Phosphorus Species in Marine Sediments using Soft X-ray Fluorescence Spectromicroscopy

Abstract

Phosphorus Near Edge X-ray Fluorescence Spectroscopy (P-NEXFS) data were collected on phosphorus containing phases including organic and inorganic compounds and minerals. Although phases containing P in the plus five oxidation state P(V) in a tetrahedral PO{sub 4} structure have similar primary fluorescence peak positions, the size, shape, and positions of secondary spectral features are diagnostic for different compounds and minerals. In particular, calcium phosphates exhibited a notable post-peak shoulder at 2154.5 eV, while oxidized iron phosphates had a distinctive pre-peak feature at 2148 eV. Polyphosphates have a broad secondary peak located approximately 2 eV higher in energy than a similar feature in phosphate esters and diesters. Compounds containing P(V) in structures other than PO{sub 4} tetrahedra such as phosphonates have a primary peak shifted about 1 eV lower than corresponding organo-phosphates. Organo-phosphates with P in the plus three oxidation state P(III) such as phosphines had primary fluorescence peaks shifted still further down in energy (2-3 eV). The substitution of aromatic carbon groups in close proximity to P structures in organic compounds generated both pre- and post-peak features as well as a number of secondary peaks. In addition, X-ray fluorescence mapping of P, Si, Al, Mg, and Na was conducted onmore » a marine sediment sample with sub-micron spatial resolution. Phosphorus was heterogeneously distributed in the sample and not correlated on a broad scale with any other element examined. Much of the P present in the sample was located in small, 0.6-8 {mu}m size, P-rich domains. Several P-rich regions were examined with P-NEXFS using a focused beam with 60 nm resolution and were found to consist of either calcium phosphate or polyphosphate phases. The presence of significant polyphosphate-dominated regions in a marine sediment sample supports the recent observations that such phases can play an important role in marine P cycling. The combination of fluorescence mapping and P-NEXFS data collection on fine particles provides a powerful new tool for environmental phosphorus studies.« less

Authors:
; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930429
Report Number(s):
BNL-81172-2008-JA
Journal ID: ISSN 0304-4203; MRCHBD; TRN: US200904%%539
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Marine Chemistry; Journal Volume: 103; Journal Issue: 39511
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; CALCIUM PHOSPHATES; IRON PHOSPHATES; ORGANIC PHOSPHORUS COMPOUNDS; PHOSPHINES; PHOSPHONATES; SEDIMENTS; SPATIAL RESOLUTION; X-RAY FLUORESCENCE ANALYSIS; MINERALS; national synchrotron light source

Citation Formats

Brandes,J., Ingall, E., and Paterson, D. Characterization of Minerals and Organic Phosphorus Species in Marine Sediments using Soft X-ray Fluorescence Spectromicroscopy. United States: N. p., 2007. Web. doi:10.1016/j.marchem.2006.09.004.
Brandes,J., Ingall, E., & Paterson, D. Characterization of Minerals and Organic Phosphorus Species in Marine Sediments using Soft X-ray Fluorescence Spectromicroscopy. United States. doi:10.1016/j.marchem.2006.09.004.
Brandes,J., Ingall, E., and Paterson, D. Mon . "Characterization of Minerals and Organic Phosphorus Species in Marine Sediments using Soft X-ray Fluorescence Spectromicroscopy". United States. doi:10.1016/j.marchem.2006.09.004.
@article{osti_930429,
title = {Characterization of Minerals and Organic Phosphorus Species in Marine Sediments using Soft X-ray Fluorescence Spectromicroscopy},
author = {Brandes,J. and Ingall, E. and Paterson, D.},
abstractNote = {Phosphorus Near Edge X-ray Fluorescence Spectroscopy (P-NEXFS) data were collected on phosphorus containing phases including organic and inorganic compounds and minerals. Although phases containing P in the plus five oxidation state P(V) in a tetrahedral PO{sub 4} structure have similar primary fluorescence peak positions, the size, shape, and positions of secondary spectral features are diagnostic for different compounds and minerals. In particular, calcium phosphates exhibited a notable post-peak shoulder at 2154.5 eV, while oxidized iron phosphates had a distinctive pre-peak feature at 2148 eV. Polyphosphates have a broad secondary peak located approximately 2 eV higher in energy than a similar feature in phosphate esters and diesters. Compounds containing P(V) in structures other than PO{sub 4} tetrahedra such as phosphonates have a primary peak shifted about 1 eV lower than corresponding organo-phosphates. Organo-phosphates with P in the plus three oxidation state P(III) such as phosphines had primary fluorescence peaks shifted still further down in energy (2-3 eV). The substitution of aromatic carbon groups in close proximity to P structures in organic compounds generated both pre- and post-peak features as well as a number of secondary peaks. In addition, X-ray fluorescence mapping of P, Si, Al, Mg, and Na was conducted on a marine sediment sample with sub-micron spatial resolution. Phosphorus was heterogeneously distributed in the sample and not correlated on a broad scale with any other element examined. Much of the P present in the sample was located in small, 0.6-8 {mu}m size, P-rich domains. Several P-rich regions were examined with P-NEXFS using a focused beam with 60 nm resolution and were found to consist of either calcium phosphate or polyphosphate phases. The presence of significant polyphosphate-dominated regions in a marine sediment sample supports the recent observations that such phases can play an important role in marine P cycling. The combination of fluorescence mapping and P-NEXFS data collection on fine particles provides a powerful new tool for environmental phosphorus studies.},
doi = {10.1016/j.marchem.2006.09.004},
journal = {Marine Chemistry},
number = 39511,
volume = 103,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}