Constraining the role of iron in environmental nitrogen transformations: Dual stable isotope systematics of abiotic NO2− reduction by Fe(II) and its production of N2O. (1st August 2016)

• Record Type: Journal Article
• Authors: Buchwald, Carolyn; Grabb, Kalina; Hansel, Colleen M.; Wankel, Scott D.
• Is Part Of: Geochimica et cosmochimica acta. Volume 186(2016:Aug. 01)
• Page Start: 1
• Page End: 12
• Publication Date: 2016-08-01
• Subjects: Abiotic nitrite reduction -- Iron oxidation -- Nitrous oxide -- Oxygen isotopes -- Chemodenitrification -- Isotope fractionation; Geochemistry -- Periodicals; Meteorites -- Periodicals; Géochimie -- Périodiques; Météorites -- Périodiques; Geochemie; Astrochemie; Electronic journals; 551.905
• DOI: 10.1016/j.gca.2016.04.041
• Languages: English
• ISSNs: 0016-7037

Abstract

Abstract: 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 (NO2 − ) reduction by Fe(II) or 'chemodenitrification', and its relevance to the production of nitrous oxide (N2 O), specifically focusing on dual (N and O) isotope systematics under a variety of environmental conditions. 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 NO2 − 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 N2 O also suggests a complex network of parallel and/or competing pathways. Our findings suggest that NO2 − reduction by Fe(II) may represent an important abiotic source of environmental N2 O, 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 NO2 − reduction and N2 O formation, helping future studies constrain the relative roles of abiotic and biological N2 O production pathways.