TY - JOUR
T1 - Oxidation of Dissolved Tetravalent Selenium by Birnessite
T2 - Se Isotope Fractionation and the Effects of pH and Birnessite Structure
AU - Dwivedi, Pranjal
AU - Schilling, Kathrin
AU - Wasserman, Naomi
AU - Johnson, Thomas M.
AU - Pallud, Celine
N1 - Publisher Copyright:
Copyright © 2022 Dwivedi, Schilling, Wasserman, Johnson and Pallud.
PY - 2022/7/6
Y1 - 2022/7/6
N2 - Redox reactions control the mobility and bioavailability of selenium (Se) in biogeochemical systems, both modern and ancient. Se isotope ratio measurements (e.g., 82Se/76Se) have been developed to enhance understanding of biogeochemical transformations and transport of Se. Stable isotope ratios of many elements are known to be powerful indicators of redox reactions, and shifts in 82Se/76Se have been observed for Se reduction reactions. However, Se isotope shifts caused by naturally relevant oxidation reactions have not been published. Here, we report Se isotope fractionation factors for oxidation of Se(IV) by birnessite. Experiments were conducted at pH = 4.0 and 5.5, with two types of birnessite of contrasting composition at two concentrations of suspended birnessite. The results are consistent with a single 82Se/76Se fractionation factor, for all times during all experiments, of 0.99767 (±0.0035 2 s.d.). Expressed as ε, the fractionation is 2.33‰ (±0.08‰).
AB - Redox reactions control the mobility and bioavailability of selenium (Se) in biogeochemical systems, both modern and ancient. Se isotope ratio measurements (e.g., 82Se/76Se) have been developed to enhance understanding of biogeochemical transformations and transport of Se. Stable isotope ratios of many elements are known to be powerful indicators of redox reactions, and shifts in 82Se/76Se have been observed for Se reduction reactions. However, Se isotope shifts caused by naturally relevant oxidation reactions have not been published. Here, we report Se isotope fractionation factors for oxidation of Se(IV) by birnessite. Experiments were conducted at pH = 4.0 and 5.5, with two types of birnessite of contrasting composition at two concentrations of suspended birnessite. The results are consistent with a single 82Se/76Se fractionation factor, for all times during all experiments, of 0.99767 (±0.0035 2 s.d.). Expressed as ε, the fractionation is 2.33‰ (±0.08‰).
KW - Rayleigh fractionation
KW - isotope geochemistry
KW - manganese oxides
KW - paleoredox
KW - selenium oxidation
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U2 - 10.3389/feart.2022.909900
DO - 10.3389/feart.2022.909900
M3 - Article
AN - SCOPUS:85134576829
SN - 2296-6463
VL - 10
JO - Frontiers in Earth Science
JF - Frontiers in Earth Science
M1 - 909900
ER -