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Wei Jing - One of the best experts on this subject based on the ideXlab platform.
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First real-time isotopic characterisation of N2O from chemodenitrification
'Elsevier BV', 2021Co-Authors: Wei Jing, Ibraim Erkan, Brüggemann Nicolas, Vereecken Harry, Mohn JoachimAbstract:Chemodenitrification can be a substantial abiotic source of nitrous oxide (N2O) in soil. The isotopic signature of N2O from this process could support source partitioning, but it is currently unknown in sufficient detail. In this study, we determined the isotopic composition of N2O, produced by the reaction of nitrite (NO2−) with lignin, four lignin derivatives, and three types of soils, online with a quantum cascade laser absorption spectrometer (QCLAS). We present the first dataset of continuous measurements of δ15Nbulk (δ15Nbulk ≡ (δ15Nα + δ15Nβ)/2), δ18O, and site preference (SPN2O, SPN2O ≡ δ15Nα − δ15Nβ) of N2O from chemodenitrification in both chemical assays and soils. Considerable amounts of N2O were produced by chemical reduction of NO2−, indicating that chemodenitrification could dominate N2O emission in NO2−-rich environments. The values of SPN2O varied by more than 20‰ in the reactions of sodium nitrite with organic substances. Contrary to the common assumption that SPN2O values are constant for a distinct N2O source process, our results reveal a considerable shift in SPN2O over time for most experiments. The large SPN2O variability might be explained by the multiple pathways with Hyponitrous Acid or nitramide as N2O precursors. These findings provide important new information to improve our understanding about the dependency of N2O isotopic signatures on N2O production processes
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Reactions between nitrite and soil organic matter and their role in nitrogen trace gas emissions and nitrogen retention in soil
Universitäts- und Landesbibliothek Bonn, 2018Co-Authors: Wei JingAbstract:As a key intermediate of both nitrification and denitrification, nitrite (NO2-) is highly chemically reactive to soil organic matter (SOM), and it was proved previously that considerable amounts of nitrogen (N) trace gases were produced from the reactions of NO2- with SOM in chemical assays decades ago. However, the role of NO2--SOM reactions in nitrogen trace gas emissions and nitrogen retention in soils has been neglected until recently. This thesis aimed to gain a better understanding of the contribution of NO2--SOM reactions to nitrogen trace gas emissions and nitrogen retention in soil. Emissions of N2O and carbon dioxide (CO2) from the reactions of NO2- with lignin and lignin derivatives, as well as N2O isotopic signatures, were studied in chemical assays at pH 3-6. Most interestingly, N2O 15N site preference (SP) varied largely from 11.9-37.4 ‰ depending on pH and structures of lignin derivatives, which was undistinguishable from other N2O sources, such as nitrification, denitrification, and abiotic hydroxylamine oxidation. Furthermore, real-time N2O isotopic characterization revealed that SP also shifted largely during the reaction of NO with lignin derivatives. Hyponitrous Acid and nitramide pathways, which could be responsible for N2O formation, were proposed to explain the shift of N2O SP values. Nitrite-driven N2O and NOx emissions in spruce forest soils and SOM fractions were investigated online and simultaneously with a quantum cascade laser and a chemoluminescence analyzer, respectively. 17-52 % and 3.3-7.1 % of NO2- was immediately transformed to NOx and N2O, respectively, when NO2- was applied into soils. Since the SP values of N2O from NO2--SOM reactions were not distinguishable from that of microbial sources (denitrification and fungal denitrification for this experiment), end-member maps failed to distinguish abiotic from biotic N2O sources, and application of a two-end-member mixing model biased N2O source apportioning by overestimating the contributions of both bacterial and fungal denitrification. Nitrogen retention resulting from NO2--SOM reactions was investigated in forest, grassland, and agricultural soils using 15N-NO2-, and about 6 % of 15N-NO2- was immobilized by SOM within 4 d. 15N enrichment in the fulvic Acid fraction was dramatically higher compared with the humus. Solid-state CP/MAS-15N-NMR analysis revealed that nitro- and amide-N were the dominant products of abiotic N immobilization from NO2--SOM reactions. The effect of lignin content and composition on N2O emission, N retention, and mineral N pool dynamics were studied in agricultural soil after the application of organic soil amendments and 15N-labelled ammonium in a 114-d laboratory incubation experiment. Both N retention and N2O emission were dramatically promoted by the combined application of N fertilizer and organic substances. Moreover, both N retention and mineral N content were significantly (P Reaktionen zwischen Nitrit und organischer Bodensubstanz und ihre Rolle bei Spurengasemissionen von Stickstoff und bei der Stickstofffestlegung im Boden Nitrit (NO2-) ist ein wichtiges Glied in der Nitrifikations- und Denitrifikationskette und verhält sich bei Kontakt mit den organischen Substanzen des Bodens (soil organic matter, SOM) hochreaktiv. Studien haben belegt, dass bedeutende Mengen von Stickstoffspurengasen aus den Reaktionen von Nitrit mit SOM hervorgehen. Dennoch wurde bisher die Rolle der NO2--SOM Reaktionen in Bezug auf Stickstoffspurengas-Emissionen und die Retention von Stickstoff im Boden vernachlässigt. Das Ziel der vorliegenden Doktorarbeit war daher, zu einem besseren Verständnis der NO2--SOM-Reaktionen und der Stickstoff-Retention im Boden zu erlangen. Die Emissionen von N2O und Kohlenstoffdioxid (CO2), die bei der Reaktionen von Nitrit mit Lignin und Lignin-Derivaten auftreten, sowie die N2O-Isotopenzusammensetzungen, wurden in einem pH-Wertbereich von 3 bis 6 untersucht. Interessanterweise zeigte sich in Abhängigkeit vom pH-Wert und der Struktur der Lignin-Derivate eine starke Variabilität der 15N-Positionspräferenz im N2O-Molekül (15N site preference, SP) im Bereich von 11.9-37.4 ‰, welcher nicht unterscheidbar von anderen N2O-Quellen wie Nitrifikation, Denitrifikation und der abiotische Hydroxylaminoxidation war. Außerdem offenbarte die Echtzeit-N2O-Isotopen-Charakterisierung eine starke Verschiebung der SP während der Reaktion von NO2- mit den Lignin-Derivaten. Eine potentielle Ursache für diese Verschiebung könnten die unterschiedlichen chemischen Reaktionswege entweder über hyposalpetrige Säure oder Nitrylamid sein. Beides sind chemische Verbindungen, die einen wichtigen Anteil an der Bildung von N2O haben. Durch Nitrit verursachte N2O- und NOx-Emissionen in Fichtenwaldböden und deren SOM-Fraktionen wurden online und simultan mit einem Quantenkaskadenlaser-Analysator und einem Chemilumineszenz-Analysator untersucht. 17-52 % und 3.3-7.1 % des Nitrits wurden nach Applikation von Nitrit in den Boden sofort in N2O und NOx umgewandelt. Die SP-Werte von in NO2--SOM Reaktionen gebildetem N2O ließen sich nicht von den mikrobiellen Quellen (Denitrifikation und pilzliche Denitrifikation) unterscheiden. Die Einordnung der gemessenen SP-Werte in Endglied-Darstellungen lieferten keine aussagekräftigen Resultate bei der Unterscheidung zwischen abiotischen und biotischen N2O-Quellen. Die Anwendung eines Mischungsmodells mit zwei Endgliedern lieferte eine verfälschte Zuordnung der N2O-Quellen durch eine Überschätzung des Beitrags sowohl der bakteriellen als auch der pilzlichen Denitrifikation. Stickstoff-Retention infolge von NO2--SOM Reaktionen wurde in Wald-, Grasland- und landwirtschaftlichen Böden unter Verwendung von 15N-NO2- untersucht. Ungefähr 6% des applizierten 15N-NO2- waren nach vier Tagen durch SOM immobilisiert. Die 15N-Anreicherung in der Fulvinsäure-Fraktion war deutlich höher als in der Humus-Fraktion. Eine CP/MAS-15N-NMR Analyse zeigte, das Nitro- und Amid-N die vorherrschenden Produkte der abiotischen N-Immobilisierung durch NO2--SOM-Reaktionen waren. Der Einfluss von Ligningehalt und -zusammensetzung auf N2O-Emissionen, N-Retention und mineralische N-Pool-Dynamik wurde in landwirtschaftlichen Böden untersucht. In einem 114-tätigen Bodeninkubationsexperiment wurden organische Bodenzusatzstoffe und 15N-markiertes Ammonium appliziert. Sowohl die N-Retention als auch N2O-Emissionen wurden deutlich durch die kombinierte Applikation von N Dünger und organischer Substanzen gefördert. Außerdem korrelierten die N-Retention und der mineralische N-Gehalt des Bodens signifikant (P < 0.05) mit der Ligninzusammensetzung
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Reactions between nitrite and soil organicmatter and their role in nitrogen trace gasemissions and nitrogen retention in soil
Forschungszentrum Jülich GmbH Zentralbibliothek Verlag, 2018Co-Authors: Wei JingAbstract:As a key intermediate of both nitrification and denitrification, nitrite (NO$_{2}^{‒}$) is highly chemically reactive to soil organic matter (SOM), and it was proved previously that considerable amounts ofnitrogen (N) trace gases, including nitrous oxide (N$_{2}$O) and nitrogen oxides (NO$_{x}$), were produced from the reactions of NO$_{2}^{‒}$ with SOM in chemical assays decades ago. However, the role of NO$_{2}^{‒}$‒SOM reactions in nitrogen trace gas emissions and nitrogen retention in soils has been neglected until recently. It is vital to identify and quantify major sources and sinks of nitrogen trace gases for the sake of the environment. On the other hand, better understanding of N$_{2}$O sources and nitrogen retention is also essential to improve the nitrogen use efficiency and soil fertility in agriculture. Therefore, this thesis aimed to gain a better understanding of the contribution of NO$_{2}^{‒}$‒SOM reactions to nitrogen trace gas emissions and nitrogen retention in soil. Emissions of N$_{2}$O and carbon dioxide (CO$_{2}$) from the reactions of NO$_{2}^{‒}$ with lignin and ligninderivatives (4‐hydroxybenzoic Acid, 4‐hydroxybenzaldehyde, 4‐hydroxy‐3‐methoxybenzoic Acid, 4‐hydroxy‐3‐methoxybenzaldehyde, 4‐hydroxy‐3,5‐dimethoxybenzoic Acid, 4‐hydroxy‐3,5‐dimethoxybenzaldehyde), as well as N$_{2}$O isotopic signatures, were studied in chemical assays at pH 3‒6. Among the six tested lignin derivatives, the highest N$_{2}$O emission was found in the 4‐hydroxy‐3,5‐dimethoxybenzaldehyde treatment, and the dependency of N$_{2}$O and CO$_{2}$ on pH varied according to the structures of the organic substances. Most interestingly, N$_{2}$O $^{15}$N site preference (SP) varied largely from 11.9‒37.4 ‰ depending on pH and structures of lignin derivatives, which was undistinguishable from other N$_{2}$O sources, such as nitrification, denitrification, and abiotic hydroxylamine oxidation. Furthermore, real‐time N$_{2}$O isotopic characterization revealed that SP also shifted largely during the reaction of NO$_{2}^{‒}$ with lignin derivatives. Hyponitrous Acid and nitramide pathways, which could be responsible for N$_{2}$O formation, were proposed to explain the shift of N$_{2}$O SP values. [...
Gernot Friedrichs - One of the best experts on this subject based on the ideXlab platform.
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Dimerization of HNO in Aqueous Solution: An Interplay of Solvation Effects, Fast Acid–Base Equilibria, and Intramolecular Hydrogen Bonding?
2016Co-Authors: Carsten Fehling, Gernot FriedrichsAbstract:The recent unraveling of the rather complex Acid–base equilibrium of nitroxyl (HNO) has stimulated a renewed interest in the significance of HNO for biology and pharmacy. HNO plays an important role in enzymatic mechanisms and is discussed as a potential therapeutic agent against heart failure. A cumbersome property for studying HNO reactions, its fast dimerization leading to the rapid formation of N2O, is surprisingly far from being well understood. It prevents isolation and limits intermediate concentrations of nitroxyl in solution. In this study, a new mechanism for the HNO dimerization reaction in aqueous solution has been theoretically derived on the basis of DFT calculations. Detailed analysis of the initial reaction step suggests a reversal of the cis–trans isomer preference in solution compared to the corresponding gas phase reaction. In contrast to a gas phase derived model based on intramolecular rearrangement steps, an Acid–base equilibrium model is in agreement with previous experimental findings and, moreover, explains the fundamental differences between the well studied gas phase reaction and the solvent reaction in terms of polarity, cis–trans isomerizations, and Acidities of the intermediates. In the case of cis-Hyponitrous Acid, the calculated pKa values of the Acid–base equilibria were found to be significantly different from the corresponding experimental value of the stable trans isomer. Under physiological conditions, N2O formation is dominated by the decomposition of the unstable monoanion cis-N2O2H– rather than that of the commonly stated cis-HONNOH
Estrin, Dario Ariel - One of the best experts on this subject based on the ideXlab platform.
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Theoretical investigation of the mechanism of nitroxyl decomposition in aqueous solution
'Elsevier BV', 2016Co-Authors: Bringas Mauro, Semelak, Jonathan Alexis, Zeida Camacho, Ari Fernando, Estrin, Dario ArielAbstract:Nitroxyl (HNO) is a species that has been proposed recently to play different roles in nitrosative stress processes. HNO decomposition in aqueous solution leading to N2O is a fast reaction that competes with many biochemical reactions in which HNO may be involved. Since molecular determinants of this reaction are still not fully understood, we present in this work an exhaustive analysis of the mechanism in terms of electronic-structure calculations as well as state of the art hybrid quantum mechanics/molecular mechanics molecular dynamics simulations. We characterized the reaction mechanism and computed free energy profiles for the reaction steps using an umbrella sampling procedure. We propose a first dimerization step followed by an Acid-base equilibria. Afterwards, the product is formed from two main pathways involving cis-Hyponitrous Acid (cis-HONNOH) and its conjugate basis as intermediate. Our calculations show preference for the anionic pathway under physiological conditions and allow us to rationalize the results in terms of a molecular description of specific interactions with the solvent. These interactions turn out to be determinant in the stabilization of transition states and, thereby, modifying the free energy barriers. We predict a strong pH-dependence of the overall kinetics of N2O formation, related with the fraction of reactive species available in solution. Finally, we suggest experimental procedures which could validate this mechanism.Fil: Bringas, Mauro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Semelak, Jonathan Alexis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Zeida Camacho, Ari Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Estrin, Dario Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; Argentin
Carsten Fehling - One of the best experts on this subject based on the ideXlab platform.
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Dimerization of HNO in Aqueous Solution: An Interplay of Solvation Effects, Fast Acid–Base Equilibria, and Intramolecular Hydrogen Bonding?
2016Co-Authors: Carsten Fehling, Gernot FriedrichsAbstract:The recent unraveling of the rather complex Acid–base equilibrium of nitroxyl (HNO) has stimulated a renewed interest in the significance of HNO for biology and pharmacy. HNO plays an important role in enzymatic mechanisms and is discussed as a potential therapeutic agent against heart failure. A cumbersome property for studying HNO reactions, its fast dimerization leading to the rapid formation of N2O, is surprisingly far from being well understood. It prevents isolation and limits intermediate concentrations of nitroxyl in solution. In this study, a new mechanism for the HNO dimerization reaction in aqueous solution has been theoretically derived on the basis of DFT calculations. Detailed analysis of the initial reaction step suggests a reversal of the cis–trans isomer preference in solution compared to the corresponding gas phase reaction. In contrast to a gas phase derived model based on intramolecular rearrangement steps, an Acid–base equilibrium model is in agreement with previous experimental findings and, moreover, explains the fundamental differences between the well studied gas phase reaction and the solvent reaction in terms of polarity, cis–trans isomerizations, and Acidities of the intermediates. In the case of cis-Hyponitrous Acid, the calculated pKa values of the Acid–base equilibria were found to be significantly different from the corresponding experimental value of the stable trans isomer. Under physiological conditions, N2O formation is dominated by the decomposition of the unstable monoanion cis-N2O2H– rather than that of the commonly stated cis-HONNOH
Bringas Mauro - One of the best experts on this subject based on the ideXlab platform.
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Theoretical investigation of the mechanism of nitroxyl decomposition in aqueous solution
'Elsevier BV', 2016Co-Authors: Bringas Mauro, Semelak, Jonathan Alexis, Zeida Camacho, Ari Fernando, Estrin, Dario ArielAbstract:Nitroxyl (HNO) is a species that has been proposed recently to play different roles in nitrosative stress processes. HNO decomposition in aqueous solution leading to N2O is a fast reaction that competes with many biochemical reactions in which HNO may be involved. Since molecular determinants of this reaction are still not fully understood, we present in this work an exhaustive analysis of the mechanism in terms of electronic-structure calculations as well as state of the art hybrid quantum mechanics/molecular mechanics molecular dynamics simulations. We characterized the reaction mechanism and computed free energy profiles for the reaction steps using an umbrella sampling procedure. We propose a first dimerization step followed by an Acid-base equilibria. Afterwards, the product is formed from two main pathways involving cis-Hyponitrous Acid (cis-HONNOH) and its conjugate basis as intermediate. Our calculations show preference for the anionic pathway under physiological conditions and allow us to rationalize the results in terms of a molecular description of specific interactions with the solvent. These interactions turn out to be determinant in the stabilization of transition states and, thereby, modifying the free energy barriers. We predict a strong pH-dependence of the overall kinetics of N2O formation, related with the fraction of reactive species available in solution. Finally, we suggest experimental procedures which could validate this mechanism.Fil: Bringas, Mauro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Semelak, Jonathan Alexis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Zeida Camacho, Ari Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Estrin, Dario Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; Argentin