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Title: Constraining the role of iron in environmental nitrogen transformations: Dual stable isotope systematics of abiotic NO 2 − reduction by Fe(II) and its production of N 2 O

Authors:
; ; ; ORCiD logo
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1326433
Grant/Contract Number:
SC0006681
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 186; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-06 15:01:41; Journal ID: ISSN 0016-7037
Publisher:
Elsevier
Country of Publication:
United States
Language:
English

Citation Formats

Buchwald, Carolyn, Grabb, Kalina, Hansel, Colleen M., and Wankel, Scott D.. Constraining the role of iron in environmental nitrogen transformations: Dual stable isotope systematics of abiotic NO 2 − reduction by Fe(II) and its production of N 2 O. United States: N. p., 2016. Web. doi:10.1016/j.gca.2016.04.041.
Buchwald, Carolyn, Grabb, Kalina, Hansel, Colleen M., & Wankel, Scott D.. Constraining the role of iron in environmental nitrogen transformations: Dual stable isotope systematics of abiotic NO 2 − reduction by Fe(II) and its production of N 2 O. United States. doi:10.1016/j.gca.2016.04.041.
Buchwald, Carolyn, Grabb, Kalina, Hansel, Colleen M., and Wankel, Scott D.. Mon . "Constraining the role of iron in environmental nitrogen transformations: Dual stable isotope systematics of abiotic NO 2 − reduction by Fe(II) and its production of N 2 O". United States. doi:10.1016/j.gca.2016.04.041.
@article{osti_1326433,
title = {Constraining the role of iron in environmental nitrogen transformations: Dual stable isotope systematics of abiotic NO 2 − reduction by Fe(II) and its production of N 2 O},
author = {Buchwald, Carolyn and Grabb, Kalina and Hansel, Colleen M. and Wankel, Scott D.},
abstractNote = {},
doi = {10.1016/j.gca.2016.04.041},
journal = {Geochimica et Cosmochimica Acta},
number = C,
volume = 186,
place = {United States},
year = {Mon Aug 01 00:00:00 EDT 2016},
month = {Mon Aug 01 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.gca.2016.04.041

Citation Metrics:
Cited by: 9works
Citation information provided by
Web of Science

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  • Redox reactions involving nitrogen and iron have been shown to have important implications for mobilization of priority contaminants. Thus, an understanding of the linkages between their biogeochemical cycling is critical for predicting subsurface mobilization of radionuclides such as uranium. Despite mounting evidence for biogeochemical interactions between iron and nitrogen, our understanding of their environmental importance remains limited. Here we present an investigation of abiotic nitrite (NO 2 -) reduction by Fe(II) or ‘chemodenitrification,’ and its relevance to the production of nitrous oxide (N 2O), specifically focusing on dual (N and O) isotope systematics under a variety of environmentally relevant conditions.more » We observe a range of kinetic isotope effects that are regulated by reaction rates, with faster rates at higher pH (~8), higher concentrations of Fe(II) and in the presence of mineral surfaces. A clear non-linear relationship between rate constant and kinetic isotope effects of NO 2 - reduction was evident (with larger isotope effects at slower rates) and is interpreted as reflecting the dynamics of Fe(II)-N reaction intermediates. N and O isotopic composition of product N 2O also suggests a complex network of parallel and/or competing pathways. Our findings suggest that NO 2 - reduction by Fe(II) may represent an important abiotic source of environmental N 2O, especially in iron-rich environments experiencing dynamic redox variations. This study provides a multi-compound, multi-isotope framework for evaluating the environmental occurrence of abiotic NO 2 - reduction and N 2O formation, helping future studies constrain the relative roles of abiotic and biological N 2O production pathways.« less
  • Fe[(CH{sub 3}(CH{sub 2}){sub 2}PO{sub 3})(H{sub 2}O)] (1) and Fe[(CH{sub 3}(CH{sub 2}){sub 17}PO{sub 3})(H{sub 2}O)] (2) were synthesized by reaction of FeCl{sub 2}.6H{sub 2}O and the relevant phosphonic acid in water in presence of urea and under inert atmosphere. The compounds were characterized by elemental and thermogravimetric analyses, UV-visible and IR spectroscopy. The crystal structure of (1) was determined from X-ray single crystal diffraction studies at room temperature: monoclinic symmetry, space group P2{sub 1}, a=5.707(1)A, b=4.811(1)A, c=11.818(2)A, and {beta}=98.62(3){sup o}. The compound is lamellar and the structure is hybrid, made of alternating inorganic and organic layers along the c direction. Themore » inorganic layers consist of Fe(II) ions octahedrally coordinated by five phosphonate oxygen atoms and one from the water molecule, separated by bi-layers of propyl groups. A preliminary structure characterization of compound (2) suggests a similar layered structure, but with an interlayer spacing of 40.3A. The magnetic properties of the compounds were both studied by a dc and ac SQUID magnetometer. Fe[(CH{sub 3}(CH{sub 2}){sub 2}PO{sub 3})(H{sub 2}O)] (1) obeys the Curie-Weiss law at temperatures above 50K (C=3.81cm{sup 3}Kmol{sup -1}, {theta}=-62K), indicating a Fe +II oxidation state, a high-spin d{sup 6} (S=2) electronic configuration and an antiferromagnetic exchange couplings between the near-neighbouring Fe(II) ions. Below T=22K, Fe[(CH{sub 3}(CH{sub 2}){sub 2}PO{sub 3})(H{sub 2}O)] exhibits a weak ferromagnetism. The critical temperature of T{sub N}=22K has been determined by ac magnetic susceptibility measurements. Compound (2) shows the same paramagnetic behaviour of the iron (II) propyl derivative. The values of C and {theta} were found to be 3.8cm{sup 3}Kmol{sup -1} and -44K, respectively, thus suggesting the presence of Fe +II ion in the S=2 spin state and antiferromagnetic interactions between Fe(II) ions at low temperatures. Zero-field and field cooled magnetic susceptibility vs. T plots do not overlap below T=30K, suggesting the presence of an ordered magnetic state. The critical temperature, T{sub N}, has been located by the peaks at T{sub N}=26K from the ac susceptibility ({chi}'and {chi}'') vs. T plots. Below T{sub N} hysteresis loops recorded in the temperature region 16<T<26K show an S-shape, while below 15K assume an ellipsoid form. They reveal that compound (2) is a weak ferromagnet. The critical temperature T{sub N} in these layered Fe(II) alkylphosphonates is independent of the distance between the inorganic layers.« less
  • The effects of the concentrntions of ferric and ferrous ions, isobutyl alcohol, and oxygen on the radioinduced oxidation and reduction reactions of the iron ions were observed during the irradiation. Measurements were taken in 0.lN H/sub 2/SO/sub 4/ solutions. The results point out the importance of the concentration of ferrous ions in reactions terminating the chain as well as that of alcohol in reactions of the reduction of ferric ions. The steady-state, observed at low concentrations of the ferrous ions, may be attributed to the presence of oxygen inhibiting the reduction. A decisive factor on the whole process of oxidationmore » and reduction turns out to be oxygen, whose presence helps to stant the oxidation of ferrous and absence enables the reduction of the ferric ions. (auth)« less
  • The authors have investigated the mechanism and determined the enthalpy of crystallization of x-ray amorphous iron garnets of rare-earth elements and their solid solutions. The authors have established a relation between the mechanism of the solid-phase reaction of formation of the iron garnets and the decrease in the ionic radius of the rare-earth element in the dodecahedral positions. A rise in the temperature during crystallization of amorphous phases facilitates a rapid completion of the reaction in which double oxides with a complex three-sublattice structure are released.