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Claire Richard - One of the best experts on this subject based on the ideXlab platform.
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The role of triplet state keto-enol tautomerism in the photodeamination of Metamitron.
The journal of physical chemistry. A, 2011Co-Authors: Sofia Kouras-hadef, Pascal De Sainte-claire, Alexandra Ter Halle, Amina Amine-khodja, Claire RichardAbstract:Substituted 4-amino-1,2,4-triazin-5-ones undergo photodeamination through cleavage of the N-NH(2) bond in the presence of oxygen and water. To elucidate the mechanism of this reaction, we investigated the photolysis of Metamitron (4-amino-6-phenyl-3-methyl-1,2,4-triazin-5-one) by nanosecond laser flash photolysis, steady-state irradiation, and ab initio calculations. Upon pulsed laser excitation of deoxygenated aqueous Metamitron, two transient species are clearly detected. The predictions of ab initio results are consistent with experimental results: (i) it is proposed here that the transient species are, respectively, the keto and diradical forms of the Metamitron keto-enol tautomerism in the triplet state, and (ii) in water, the activation free energy barrier of enolization is drastically decreased. Thus, the formation of the diradical triplet is enabled in aqueous solvent. A detailed analysis of the intermediate structures that lead to the final products (HNO(2) and deaminoMetamitron) is provided.
Sofia Kouras-hadef - One of the best experts on this subject based on the ideXlab platform.
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The role of triplet state keto-enol tautomerism in the photodeamination of Metamitron.
The journal of physical chemistry. A, 2011Co-Authors: Sofia Kouras-hadef, Pascal De Sainte-claire, Alexandra Ter Halle, Amina Amine-khodja, Claire RichardAbstract:Substituted 4-amino-1,2,4-triazin-5-ones undergo photodeamination through cleavage of the N-NH(2) bond in the presence of oxygen and water. To elucidate the mechanism of this reaction, we investigated the photolysis of Metamitron (4-amino-6-phenyl-3-methyl-1,2,4-triazin-5-one) by nanosecond laser flash photolysis, steady-state irradiation, and ab initio calculations. Upon pulsed laser excitation of deoxygenated aqueous Metamitron, two transient species are clearly detected. The predictions of ab initio results are consistent with experimental results: (i) it is proposed here that the transient species are, respectively, the keto and diradical forms of the Metamitron keto-enol tautomerism in the triplet state, and (ii) in water, the activation free energy barrier of enolization is drastically decreased. Thus, the formation of the diradical triplet is enabled in aqueous solvent. A detailed analysis of the intermediate structures that lead to the final products (HNO(2) and deaminoMetamitron) is provided.
Karolina M. Nowak - One of the best experts on this subject based on the ideXlab platform.
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Microbial activity and Metamitron degrading microbial communities differ between soil and water-sediment systems.
Journal of hazardous materials, 2020Co-Authors: Shizong Wang, Anja Miltner, A.m. Muskus, Karolina M. NowakAbstract:Abstract The herbicide Metamitron is frequently detected in the environment, and its degradation in soil differs from that in aquatic sediments. In this study, we applied 13C6-Metamitron to investigate the differences in microbial activity, Metamitron mineralization and Metamitron degrading microbial communities between soil and water-sediment systems. Metamitron increased soil respiration, whereas it suppressed respiration in the water-sediment system as compared to controls. Metamitron was mineralized two-fold faster in soil than in the water-sediment. Incorporation of 13C from 13C6-Metamitron into Phospholipid fatty acids (PLFAs) was higher in soil than in sediment, suggesting higher activity of Metamitron-degrading microorganisms in soil. During the accelerated mineralization of Metamitron, biomarkers for Gram-negative, Gram-positive bacteria and actinobacteria dominated within the 13C-PLFAs in soil. Gram-negative bacteria dominated among the Metamitron degraders in sediment throughout the incubation period. Actinobacteria, and actinobacteria and fungi were the main consumers of necromass of primary degraders in soil and water-sediment, respectively. This study clearly showed that microbial groups involved in Metamitron degradation depend on the system (soil vs. water-sediment) and on time. It also indicated that the turnover of organic chemicals in complex environments is driven by different groups of synthropic degraders (primary degraders and necromass degraders) rather than by a single degrader.
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Transformation of Metamitron in water-sediment systems: Detailed insight into the biodegradation processes
The Science of the total environment, 2016Co-Authors: Shizong Wang, Anja Miltner, Matthias Kästner, Andreas Schäffer, Karolina M. NowakAbstract:Metamitron and its main metabolite desamino-Metamitron are frequently detected in surface waters. To date, there are no studies targeting Metamitron degradation in water-sediment systems. Therefore, the aim of this study was to trace the fate of Metamitron in a water-sediment system using 13C-isotope labeling. Mineralization of Metamitron was high and accounted for 49% of 13C6-Metamitron equivalents at the end. In contrast, only 8.7% of 13C6-Metamitron equivalents were mineralized in the water only system demonstrating the key role of sediment for biodegradation. Metamitron disappeared from the water on day 40 and was completely removed from the sediment on day 80. This agrochemical was utilized as carbon source by microorganisms as shown by the incorporation of the 13C label into microbial amino acids and finally into biogenic residues. The latter amounted to 24% of 13C6-Metamitron equivalents at the end. However, 17% of 13C6-Metamitron equivalents were detected in xenobiotic non-extractable residues (NER) with a release potential and delayed risk for the environment. Metamitron was degraded via two pathways, initially via 4-(dimethylimino)-3-methyl-6-phenyl-1,2,4-triazin-5(4H)-one, which might be related to growth, and later via desamino-Metamitron, which can be attributed to starvation.
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Identification of degradation routes of Metamitron in soil microcosms using 13C-isotope labeling.
Environmental pollution (Barking Essex : 1987), 2016Co-Authors: Shizong Wang, Anja Miltner, Karolina M. NowakAbstract:Metamitron is one of the most commonly used herbicide in sugar beet and flower bulb cultures. Numerous laboratory and field studies on sorption and degradation of Metamitron were performed. Detailed biodegradation studies in soil using 13C-isotope labeling are still missing. Therefore, we aimed at providing a detailed turnover mass balance of 13C6-Metamitron in soil microcosms over 80 days. In the biotic system, Metamitron mineralized rapidly, and 13CO2 finally constituted 60% of the initial 13C6-Metamitron equivalents. In abiotic control experiments CO2 rose to only 7.4% of the initial 13C6-Metamitron equivalents. The 13C label from 13C6-Metamitron was incorporated into microbial amino acids that were ultimately stabilized in the soil organic matter forming presumably harmless biogenic residues. Finally, 13C label from 13C6-Metamitron was distributed between the 13CO2 and the 13C-biogenic residues indicating nearly complete biodegradation. The parallel increase of 13C-alanine, 13C-glutamate and 13CO2 indicates that Metamitron was initially biodegraded via the desamino-Metamitron route suggesting its relevance in the growth metabolism. In later phases of biodegradation, the "Rhodococcus route" was indicated by the low 13CO2 evolution and the high relevance of the pyruvate pathway, which aims at biomolecule synthesis and seems to be related to starvation. This is a first report on the detailed degradation route of Metamitron in soil.
Jan Petersen - One of the best experts on this subject based on the ideXlab platform.
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Sensitivität verschiedener Herkünfte von Matricaria inodora und Matricaria chamomilla gegenüber Metamitron
Gesunde Pflanzen, 2003Co-Authors: Jan PetersenAbstract:In recent years it was observed that sugar beet fields showed more weeds left after Metamitron treatments, especially Matricaria-species, than in the past. This leads to the question, if there is a shift within the species towards biotypes that are less sensitive to Metamitron, caused by repeated sequential applications of Metamitron in the last decades. In the greenhouse dose response experiments were conducted comparing several different origins of M. chamomilla and M. inodora in their Metamitron sensitivity. There were significant differences within the species. For M. inodora it could be shown that biotypes never received any Metamitron application were more sensitive than biotypes from sugar beet fields with Metamitron treatments. Furthermore, comparison between M. chamomilla and M. inodora showed that M. chamomilla was much more sensitive.
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Sensitivität verschiedener Herkünfte von Matricaria inodora und Matricaria chamomilla gegenüber Metamitron
Gesunde Pflanzen, 2003Co-Authors: Jan PetersenAbstract:Beobachtungen in Zuckerrübenfeldern zeigten in den vergangenen Jahren mehr Restverunkrautung insbesondere von Kamille-Arten trotz eines Einsatzes von Metamitron. Dies führte zur Frage, ob durch den langjährigen Metamitroneinsatz in Zuckerrüben eine Verschiebung innnerhalb der Arten hin zu weniger sensitiven Biotypen stattgefunden hat. Im Gewächshaus wurden mit verschiedenen Herkünften von Matricaria chamomilla und M. inodora Dosis-Wirkungsversuche durchgeführt. Es zeigten sich sigfikante Unterschiede innerhalb der Arten zwischen den verschiedenen Herkünften. Herkünfte aus Zuckerrüben mit Metamitronbehandlung waren weniger empfindlich als Kontrollherkünfte ohne Metamitronbehandlung in der Vergangenheit. Beim Vergleich zwischen den beiden Kamillearten wurde deutlich, dass M. chamomilla wesentlich empfindlicher reagiert als M. inodora . In recent years it was observed that sugar beet fields showed more weeds left after Metamitron treatments, especially Matricaria-species , than in the past. This leads to the question, if there is a shift within the species towards biotypes that are less sensitive to Metamitron, caused by repeated sequential applications of Metamitron in the last decades. In the greenhouse dose response experiments were conducted comparing several different origins of M. chamomilla and M. inodora in their Metamitron sensitivity. There were significant differences within the species. For M. inodora it could be shown that biotypes never received any Metamitron application were more sensitive than biotypes from sugar beet fields with Metamitron treatments. Furthermore, comparison between M. chamomilla and M. inodora showed that M. chamomilla was much more sensitive.
Pascal De Sainte-claire - One of the best experts on this subject based on the ideXlab platform.
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The role of triplet state keto-enol tautomerism in the photodeamination of Metamitron.
The journal of physical chemistry. A, 2011Co-Authors: Sofia Kouras-hadef, Pascal De Sainte-claire, Alexandra Ter Halle, Amina Amine-khodja, Claire RichardAbstract:Substituted 4-amino-1,2,4-triazin-5-ones undergo photodeamination through cleavage of the N-NH(2) bond in the presence of oxygen and water. To elucidate the mechanism of this reaction, we investigated the photolysis of Metamitron (4-amino-6-phenyl-3-methyl-1,2,4-triazin-5-one) by nanosecond laser flash photolysis, steady-state irradiation, and ab initio calculations. Upon pulsed laser excitation of deoxygenated aqueous Metamitron, two transient species are clearly detected. The predictions of ab initio results are consistent with experimental results: (i) it is proposed here that the transient species are, respectively, the keto and diradical forms of the Metamitron keto-enol tautomerism in the triplet state, and (ii) in water, the activation free energy barrier of enolization is drastically decreased. Thus, the formation of the diradical triplet is enabled in aqueous solvent. A detailed analysis of the intermediate structures that lead to the final products (HNO(2) and deaminoMetamitron) is provided.