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Using nitrogen isotope fractionation to assess redox reactions of organic contaminants

English title Using nitrogen isotope fractionation to assess redox reactions of organic contaminants
Applicant Hofstetter Thomas
Number 134720
Funding scheme Project funding
Research institution Umweltchemie Eawag
Institution of higher education Swiss Federal Institute of Aquatic Science and Technology - EAWAG
Main discipline Other disciplines of Environmental Sciences
Start/End 01.04.2011 - 29.02.2012
Approved amount 56'754.00
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All Disciplines (2)

Discipline
Other disciplines of Environmental Sciences
Geochemistry

Keywords (8)

compound-specific isotope analysis; CSIA; kinetic isotope effect; isotope fractionation; redox reactions; groundwater contaminants; organic micropollutants; transformation processes

Lay Summary (English)

Lead
Lay summary
Compound-specific stable isotope analysis (CSIA) offers new avenues for assessing transformation pathways of organic micropollutants. Fractionation of stable isotopes in individual compounds is usually indicative for an ongoing (bio)chemical reaction and thus allows one to identify such processes in complex environments as well as studying the mechanisms of degradation. However, a more comprehensive exploitation of stable isotope analysis in contaminant studies is currently hampered as both isotope effects and reaction pathways of many organic pollutants, especially those with N-containing functional groups, are not understood adequately on a mechanistic level. In fact, reactions at N-containing structural moieties (e.g., nitro-, amino-, and azo-compounds, amides, ureas) are often the initial site of attack for transformation processes of contaminants such as pesticides, pharmaceuticals, or explosives.
In this project, we will develop approaches to study isotope effects during the oxidation of substituted anilines. Our principal goal is to investigate the multielement isotope fractionation of aromatic N-alkyl amines for a comprehensive application of CSIA to enzyme- and mineral-catalyzed oxidations and addition reactions of this compound class.From the combined evaluation of carbon, hydrogen, and nitrogen isotope fractionation and the corresponding apparent kinetic isotope effects, we will be able to identify the typical bonding changes at the reactive atoms in a set of probe compounds covering substituted aromatic N-methyl and N,N-dimethyl amines as well as N,N-dimethyl di- and triazines. On the basis of the interpretation of multielement isotope effects we will be able to delinate the different, sometimes competing transformation processes of micropollutants containing reactive N-alkyl amine moieties.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Carbon, Hydrogen, and Nitrogen Isotope Fractionation Associated with Oxidative Transformation of Substituted Aromatic N-Alkyl Amines
Skarpeli-Liati Marita, Pati Sarah G., Bolotin Jakov, Eustis Soren N., Hofstetter Thomas B. (2012), Carbon, Hydrogen, and Nitrogen Isotope Fractionation Associated with Oxidative Transformation of Substituted Aromatic N-Alkyl Amines, in Environmental Science & Technology, 46(13), 7179-7198.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Isotopes 2011, Poster presentation 20.06.2011 Gréoux-les-Bains, Frankreich


Self-organised

Title Date Place

Awards

Title Year
2011 SCNAT/SCS Chemistry Travel Award 2011
Best poster award 2011

Associated projects

Number Title Start Funding scheme
116447 Using nitrogen isotope fractionation to assess redox reactions of organic contaminants 01.03.2008 Project funding
142500 A density functional theory study on the kinetic isotope effect associated with the oxidative N-dealkylation of aromatic N-methyl amines 01.07.2012 International short research visits
139111 Expanding Compound-Specific Isotope Analysis Towards Polar Organic Micropollutants and Chlorine Isotopes 01.09.2012 R'EQUIP
140545 Tracking Water Disinfection By-Product Formation by Multi-Element Isotope Fractionation Analysis 01.08.2012 Project funding

Abstract

Compound-specific stable isotope analysis (CSIA) offers new avenues for assessing transformation pathways of organic micropollutants. Fractionation of stable isotopes in individual compounds is usually indicative for an ongoing (bio)chemical reaction and thus allows one to identify such processes in complex environments as well as studying the mechanisms of degradation. However, a more comprehensive exploitation of stable isotope analysis in contaminant studies is currently hampered as both isotope effects and reaction pathways of many organic pollutants, especially those with N-containing functional groups, are not understood adequately on a mechanistic level. In fact, reactions at N-containing structural moieties (e.g., nitro-, amino-, and azo-compounds, amides, ureas) are often the initial site of attack for transformation processes of contaminants such as pesticides, pharmaceuticals, or explosives. In our current, SNF-funded project (no. 200020-116447/1), we provide the basis for assessing reductions of nitroaromatic compounds at contaminated sites using CSIA and we have developed approaches to study isotope effects during the oxidation of substituted anilines. Here, we propose to investigate the multielement isotope fractionation of aromatic N-alkyl amines to enable a comprehensive application of CSIA to enzyme- and mineral-catalyzed oxidations and addition reactions of this compound class. The requested one-year follow-up project for the termination of a PhD thesis takes full advantage of the model systems set up so far for studying oxidative N-dealkylation processes that are mediated by manganese oxides or peroxidase-enzymes. From the combined evaluation of carbon, hydrogen, and nitrogen isotope fractionation and the corresponding apparent kinetic isotope effects, we will be able to identify the typical bonding changes at the reactive atoms in a set of probe compounds covering substituted aromatic N-methyl and N,N-dimethyl amines as well as N,N-dimethyl di- and triazines. On the basis of the interpretation of multielement isotope effects we will be able to delinate the different, sometimes competing transformation processes of micropollutants containing reactive N-alkyl amine moieties. Finally, the proposed research will also benefit from the international collaboration, which was established during the current project, to obtain theoretical support from density functional theory calculations for the interpretation of observed kinetic and equilibrium isotope effects.
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