Kristyna Kantnerova

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Kantnerova

First Name

Kristyna

ORCID

0000-0001-6259-3225

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Publications 1 - 7 of 7

Clumped isotope signatures of nitrous oxide formed by bacterial denitrification
Kantnerova, Kristyna; Hattori, Shohei; Toyoda, Sakae; et al. (2022)
Geochimica et Cosmochimica Acta
Multiply substituted isotopic species of nitrous oxide (N2O), referred to as clumped isotopes, represent a promising new tool for distinguishing production pathways of this potent greenhouse gas. This work presents the first determination of enrichment factors of N2O clumped isotopes during bacterial denitrification. Samples of N2O obtained after 1-, 3-, and 7-day incubations of a pure culture of the denitrifier Pseudomonas aureofaciens at 20 °C and 30 °C were analysed by the recently developed quantum cascade laser absorption spectroscopy (QCLAS) method. Enrichment factors εp/s of the cumulative product (p) relative to the substrate (s) were determined using a Rayleigh model for the seven most abundant isotopically substituted molecules (isotopocules) of N2O. Values of the enrichment factors εp/s (with uncertainty expressed as expanded standard uncertainty at the 95% confidence interval) at the two incubation temperatures (20 °C/30 °C) are:14N15N16O (456): ε456 = (−40.3 ± 2.6)‰/(−35.1 ± 0.7)‰15N14N16O (546): ε546 = (−38.1 ± 3.4)‰/(−31.2 ± 0.6)‰14N14N17O (447): ε447 = (21.3 ± 1.2)‰/(24.5 ± 0.5)‰14N14N18O (448): ε448 = (38.8 ± 1.5)‰/(46.4 ± 1.2)‰14N15N18O (458): ε458 = (−8.9 ± 2.0)‰/(−11.7 ± 0.6)‰15N14N18O (548): ε548 = (−3.4 ± 1.1)‰/(−1.8 ± 0.5)‰15N15N16O (556): ε556 = (−85.9 ± 1.5)‰/(−63.9 ± 1.4)‰Temporal evolutions of the abundances of singly substituted N2O isotopocules during nitrate reduction agree with previously published experiments: there is normal isotope effect associated with the production of 14N15N16O and 15N14N16O; i.e., intermediates leading to 14N14N16O react faster than intermediates leading to 14N15N16O and 15N14N16O. However, the production of 14N14N17O and 14N14N18O is associated with inverse isotope effect; i.e., intermediates leading to 14N14N16O react slower than intermediates leading to 14N14N17O and 14N14N18O due to preferential cleavage of 16O during nitrate reduction to N2O. Isotopic fractionation at the incubation temperature of 30 °C was significantly lower compared to 20 °C. We observed a large kinetic isotope effect of the 15N site preference (SP) and the 15N–18O site preference (SP18) at the onset of the reaction. SP18 was found to be closer to 0‰ than SP, which is thought to arise from similar rates of breakage of the 15N–O and 14N–O bonds in the reaction intermediates. The 15N–18O clumped isotope anomalies in two isotopic isomers (isotopomers) 14N15N18O and 15N14N18O (Δ458+548avg) follow a temporal trend similar to those of SP and SP18. The 15N–15N clumped isotope anomalies in 15N15N16O are greater than 0‰ and show no clear temporal trend or influence of incubation temperature, suggesting no strong combinatorial effects involved during the N–N bond formation. Overall, our data illustrate that clumped N2O isotopes may be used as independent tracers for reaction mechanisms of N2O conversion and may establish themselves as a worthwhile tool to study the biogeochemical cycle of N2O.
Quantifying Isotopic Signatures of N₂O Using Quantum Cascade Laser Absorption Spectroscopy
Kantnerova, Kristyna; Tuzson, Béla; Emmenegger, Lukas; et al. (2019)
Chimia
Nitrous oxide, N2O, is the environmentally most relevant constituent of the biogeochemical nitrogen cycle. Human activities, e.g. the agricultural use of mineral fertilizers, accelerate nitrogen transformations, leading to higher emissions of this strong greenhouse gas. Investigating the stable isotopic composition of N2O provides a better understanding of formation mechanisms to disentangle its variable source and sink processes. Mid-infrared (mid-IR) laser spectroscopy is a highly attractive technique to analyze N2O isotopocules based on their specific ro-vibrational absorption characteristics. Specifically, quantum cascade laser absorption spectroscopy (QCLAS) in combination with preconcentration has shown to be powerful for simultaneous and high-precision analysis of the main N2O isotopocules. Recently, in the scope of my PhD project, we have been advancing this analytical technique for the analysis of the very rare doubly substituted N2O isotopic species 15N14N18O, 14N15N18O, and 15N15N16O, also known as clumped isotopes. Currently, we are investigating the potential of these novel isotopic tracers to track the complex N2O production and consumption pathways. Improved understanding of the nitrogen cycle will be a major step towards N2O emission reduction.
Photolytic fractionation of seven singly and doubly substituted nitrous oxide isotopocules measured by quantum cascade laser absorption spectroscopy
Kantnerova, Kristyna; Jespersen, Malte F.; Bernasconi, Stefano M.; et al. (2020)
Atmospheric Environment: X
There is strong interest in using isotopic analysis to better constrain the budget of atmospheric nitrous oxide (N2O). This interest is supported by emerging instruments that allow analysis of multiply substituted species. We have studied fractionation during UV photolysis of singly and doubly isotopically substituted molecules (isotopocules) of N2O. N2O was photolyzed in an electropolished stainless-steel reactor using a broadband laser-driven light source with bandpass filters. Isotopocule ratios were quantified at different stages of photolysis using a quantum cascade laser absorption spectroscopy (QCLAS) system. Wavelength-dependent fractionation constants were determined using the Rayleigh distillation model. The fractionation constants for photolysis with 200 nm and 214 nm bandpass filters, respectively, for the seven most abundant isotopocules of N2O (after 14N14N16O) are: 14N15N16O (456): (−48.9 ± 7.4) ‰ /(−82.4 ± 22.3) ‰, 15N14N16O (546): (−22.2 ± 5.3) ‰ /(−36.1 ± 19.6) ‰, 14N14N17O (447): (−12.7 ± 4.5) ‰ /(−21.9 ± 15.7) ‰, 14N14N18O (448): (−33.5 ± 12.0) ‰ /(−44.1 ± 29.8) ‰, 14N15N18O (458): (−80.9 ± 6.5) ‰ /(−120.9 ± 23.7) ‰, 15N14N18O (548): (−52.7 ± 10.8) ‰ /(−79.1 ± 28.5) ‰, 15N15N16O (556): (−66.9 ± 9.8) ‰ /(−110.9 ± 27.5) ‰. The fractionation constants determined here for isotopocules 456, 546, 447, 448, and 556 are in agreement with previous theoretical models employed in this study and previous experiments. For 458 and 548, the fractionation constants were determined for the first time, confirming the prediction of more negative fractionation for 15N substitution in the central position. The effect of stratospheric photolysis on the clumped isotope Δ values of tropospheric N2O was found to be modest with Δ458 = (4.0 ± 1.0) ‰, Δ548 = (−4.0 ± 1.0) ‰, and Δ556 = (−1.5 ± 1.0) ‰ at 9% photolysis. Therefore, atmospheric variations of doubly substituted N2O isotopocules will likely be dominated by the characteristics of the N2O sources, which strongly supports their value for source attribution and quantification.
Analysis of Clumped Isotopes in Nitrous Oxide: Method Development and First Applications
Kantnerova, Kristyna (2020)
First investigation and absolute calibration of clumped isotopes in N₂O by mid-infrared laser spectroscopy
Kantnerova, Kristyna; Yu, Longfei; Zindel, Daniel; et al. (2020)
Rapid Communications in Mass Spectrometry
Rationale: Unravelling the biogeochemical cycle of the potent greenhouse gas nitrous oxide (N2O) is an underdetermined problem in environmental sciences due to the multiple source and sink processes involved, which complicate mitigation of its emissions. Measuring the doubly isotopically substituted molecules (isotopocules) of N2O can add new opportunities to fingerprint and constrain its cycle. Methods: We present a laser spectroscopic technique to selectively and simultaneously measure the eight most abundant isotopocules of N2O, including three doubly substituted species – so called “clumped isotopes”. For the absolute quantification of individual isotopocule abundances, we propose a new calibration scheme that combines thermal equilibration of a working standard gas with a direct mole fraction-based approach. Results: The method is validated for a large range of isotopic composition values by comparison with other established methods (laser spectroscopy using conventional isotopic scale and isotope ratio mass spectrometry). Direct intercomparison with recently developed ultrahigh-resolution mass spectrometry shows clearly the advantages of the new laser technique, especially with respect to site specificity of isotopic substitution in the N2O molecule. Conclusions: Our study represents a new methodological basis for the measurements of both singly substituted and clumped N2O isotopes. It has a high potential to stimulate future research in the N2O community by establishing a new class of reservoir-insensitive tracers and molecular-scale insights. © 2020 John Wiley & Sons, Ltd.
Stable Isotope Analysis of Greenhouse Gases Requires Analyte Preconcentration
Kantnerova, Kristyna; Barthel, Matti; Six, Johan; et al. (2022)
Chimia
Nitrous oxide (N2O) is an important trace gas contributing to global warming and depletion of ozone in the stratosphere. Its increasing abundance is caused mainly by anthropogenic sources, such as application of fertilizers in agriculture or emissions from industry. To understand the N2O global budget, its sources and sinks need to be well-described and quantified. In this project, a new method for N2O source appointment was de-veloped that can help with this task. The method is based on analysis of the eight most abundant isotopic mol-ecules of N2O, using quantum cascade laser absorption spectroscopy (QCLAS). The applicability of the method towards the N2O biogeochemical cycle was demonstrated on a prominent N2O source (bacterial denitrification) and the most important N2O sink (UV photolysis) on samples prepared in laboratory experiments. An extension of the QCLAS method to natural samples can be achieved by hyphenation with a preconcentration technique that increases concentration of the analyte and standardizes the sample matrix. This article provides an overview of currently applied preconcentration techniques in the field of greenhouse-gas analysis and a description of the preconcentration device TREX that will be employed in future projects with the developed QCLAS method.
The use of stable isotopes in soil science: Low atomic number elements
Pistocchi, Chiara; Bertrand, Isabelle; Kantnerova, Kristyna; et al. (2023)
Reference Module in Earth Systems and Environmental Sciences
In this chapter, we focus on low atomic mass stable isotopes that are widely used in soil and environmental studies. These include carbon (C), nitrogen (N), oxygen (O), and sulfur (S). We elucidate how such stable isotopes are used to infer processes, estimate mean residence time of an element in an environmental compartment, and identify sources or relative contribution to a pool. In addition, we describe the basis of the most widespread analytical methods for isotope analyses and report relevant technical advances, which are expected to provide unique insight into biogeochemistry of key elements of life in the near future.

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