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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. 2016. "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 = 2016,
month = 8
}

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

Citation Metrics:
Cited by: 4works
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
  • Excessive phosphorus loss from soils poses a threat to surface-water quality. Soils comprise assemblages of multiple minerals, with Fe- and Al-oxides being important for phosphate sorption. Our objective was to measure reductive dissolution of an Fe-oxide and sorbed orthophosphate as affected by the presence of an Al-(hydr)oxide mineral. Aqueous suspensions containing 0.5 g ferrihydrite kg{sup -1} and up to 0.7 g boehmite kg{sup -1} and KH2PO4 added at 750 mmol kg{sup -1} of ferrihydrite were abiotically reduced at pH 6.0 for 72 h using 0.5% H2(g) in the presence of a Pt catalyst. A sharp decrease in zero-order Fe(II) dissolutionmore » rate coefficients was observed between 0 and 0.008 g kg{sup -1} of added boehmite, whereas net Fe(II) dissolution was essentially null for boehmite additions {ge} 0.02 g kg{sup -1}. Although net dissolution of PO{sub 4} occurred over time in the absence of boehmite, a net uptake occurred in the presence of boehmite. Auxiliary experiments suggested that Al(III) dissolved from boehmite decreased Fe(II) dissolution during reduction by sorbing to the ferrihydrite surface and blocking electron transfer. Because PO{sub 4} was taken up in excess of the maximum boehmite sorption capacity in systems with {le} 0.008 g boehmite kg{sup -1}, results suggested the formation of Al-phosphate or an Al(III)-PO{sub 4} complex on ferrihydrite surfaces. Phosphorus K-XANES spectroscopy of samples collected during reduction of a 1:1 ferrihydrite/boehmite mixture showed no consistent change in sorbed PO{sub 4} associated with Fe(III) versus Al(III).« less