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Antioxidant effect of dissolved organic matter (DOM) on indirect photochemical transformation of contaminants in surface waters ("Oxindom 3")

Applicant Canonica Silvio
Number 140815
Funding scheme Project funding (Div. I-III)
Research institution Eawag
Institution of higher education Swiss Federal Institute of Aquatic Science and Technology - EAWAG
Main discipline Other disciplines of Environmental Sciences
Start/End 01.09.2012 - 31.08.2016
Approved amount 243'562.00
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All Disciplines (3)

Discipline
Other disciplines of Environmental Sciences
Physical Chemistry
Organic Chemistry

Keywords (7)

antioxidants; NOM; organic contaminants; excited triplet states; DOM; photosensitizers; oxidation

Lay Summary (English)

Lead
Lay summary

The accelerating and inhibiting effects ofdissolved organic matter (DOM) on the sunlight-induced transformation ofanilines and sulfonamide antibiotics, which occur as contaminants in surfacewaters, will be studied in detail. The molecular basis of the inhibiting effectwill be investigated using laser flash photolysis and phenolic antioxidants asmodel inhibitors.

 

Background

The recently characterized inhibitioneffect of DOM on triplet-induced oxidation of relevant aquatic organiccontaminants is likely to play an important role for the fate of suchcontaminants in sunlit surface waters. The effect was attributed to antioxidantmoieties present in DOM, a conclusion that was supported by the positivecorrelation between the magnitude of the inhibition of oxidation and theelectron donating capacity of DOM, and by the observation of an analogouseffect in the presence of phenols, used as model antioxidants. The proposedkinetic model, supported to date by data obtained from steady-state irradiationexperiments, implies a redox reaction between oxidation intermediates of thecontaminants and antioxidant moieties of DOM, leading to partial reformation ofthe parent contaminant. In the present proposal we address some central openquestions that concern on the one hand the mechanism of the inhibition ofoxidation and on the other hand the application of the concept of DOM-inducedinhibition of oxidation to characterize and quantify the transformation ofcontaminants, such as anilines and sulfonamides, induced by sunlight in surfacewaters.

 

Objectives and methods

Detection, bynanosecond laser flash photolysis, of the oxidation intermediates of a fewselected anilines and sulfonamides antibiotics and investigation of their decaykinetics in the presence of DOM and model antioxidants. Verification of the proposedmodel for the mechanism of inhibition of oxidation.         1.

Quantification ofthe sunlight-induced transformation rates of the selected contaminants undersurface water-like conditions. Determination of the variability of such ratesupon type and concentration of DOM.         2.

 

Significance

The expected practical result is thequantification of the sunlight-induced transformation rates of the selectedclasses of contaminants under realistic surface water conditions. Themethodology will serve to characterize the photochemical fate of furtherclasses of aquatic contaminants.

Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Quenching of an Aniline Radical Cation by Dissolved Organic Matter and Phenols: A Laser Flash Photolysis Study
Leresche Frank, Ludvíková Lucie, Heger Dominik, von Gunten Urs, Canonica Silvio (2020), Quenching of an Aniline Radical Cation by Dissolved Organic Matter and Phenols: A Laser Flash Photolysis Study, in Environmental Science & Technology, 54(23), 15057-15065.
Laser flash photolysis study of the photoinduced oxidation of 4-(dimethylamino)benzonitrile (DMABN)
Leresche Frank, Ludvíková Lucie, Heger Dominik, Klán Petr, von Gunten Urs, Canonica Silvio (2019), Laser flash photolysis study of the photoinduced oxidation of 4-(dimethylamino)benzonitrile (DMABN), in Photochemical & Photobiological Sciences, 18(2), 534-545.
Probing the photosensitizing and inhibitory effects of dissolved organic matter by using N,N-dimethyl-4-cyanoaniline (DMABN)
Frank Leresche, Urs von Gunten, Silvio Canonica (2016), Probing the photosensitizing and inhibitory effects of dissolved organic matter by using N,N-dimethyl-4-cyanoaniline (DMABN), in Environmental Science & Technology, 50(20), 10997-11007.

Collaboration

Group / person Country
Types of collaboration
Prof. Petr Klan, Masaryk University, Brno Czech Republic (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
EMEC16 - 16th European Meeting in Environmental Chemistry Talk given at a conference Antioxidant effect of dissolved organic matter on excited triplet- and radical-induced oxidation of aquatic contaminants 30.11.2015 Torino, Italy Canonica Silvio;
EMEC16 - 16th European Meeting in Environmental Chemistry Poster Triplet-induced oxidation of organic contaminants: inhibition by dissolved organic matter and model antioxidants 30.11.2015 Torino, Italy Leresche Frank;
Photochemistry Section Annual Meeting 2015 (Swiss Chemical Society) Poster Triplet-induced oxidation of organic contaminants: Inhibition by dissolved organic matter and model antioxidants 08.09.2015 Zürich, Switzerland Leresche Frank;
UV Research Frontiers Conference Poster Triplet-induced oxidation of organic contaminants: Inhibition by dissolved organic matter and model antioxidants 19.05.2015 Leeuwarden, Netherlands Leresche Frank;
Swiss Photochemistry Meeting 2013 “Frontiers in Photochemistry” Poster Triplet-induced oxidation of organic contaminants: Inhibition by dissolved organic matter and model antioxidants 25.08.2013 Les Diablerets, Switzerland Leresche Frank;


Awards

Title Year
Best Poster Award EMEC16 - 16th European Meeting in Environmental Chemistry, Torino, Italien 30.11.-03.12.2015 2015

Associated projects

Number Title Start Funding scheme
134801 The role of dissolved organic matter as an antioxidant in triplet-induced oxidation reactions 01.04.2011 Project funding (Div. I-III)
125856 Riverbank filtration under climate change scenarios (RIBACLIM) 01.01.2010 NRP 61 Sustainable Water Management
169422 Characterizing organic radical oxidants produced by photoirradiation of dissolved organic matter ("OROPHOT") 01.08.2017 Project funding (Div. I-III)
126893 Using quantum chemistry to assess reactivity of contaminants in surface waters 01.01.2010 Project funding (Div. I-III)

Abstract

The recently characterized inhibition effect of dissolved organic matter (DOM) on triplet-induced oxidation of relevant aquatic organic contaminants is likely to play an important role in the fate of such contaminants in sunlit surface waters. The effect was attributed to antioxidant moieties present in DOM, a conclusion that was supported by the positive correlation between the magnitude of the inhibition of oxidation and the electron donating capacity of DOM, and by the observation of an analogous effect in the presence of phenols, used as model antioxidants. In the present proposal we address some central open questions that concern on the one hand the mechanism of the inhibition of oxidation and on the other hand the application of the concept of DOM-induced inhibition of oxidation to characterize and quantify the indirect phototransformation of contaminants, such as anilines and sulfonamides, in surface waters.The mechanistic investigations, performed primarily using laser flash photolysis, are centered on the characterization and chemical kinetics of intermediates formed in the reaction of excited triplet model photosensitizers with selected anilines and sulfonamides. Understanding how the various reaction intermediates interact with each other, in the absence and presence of model antioxidants or DOM, is the main goal of this part of the study. Kinetic evaluation of the results will be used to assess the dominant reaction pathways under conditions of stationary irradiation, which are relevant to sunlit surface waters.The prediction of sunlight-induced transformation rates of anilines and sulfonamides is complicated by the fact that DOM acts as a photosensitizer and as an inhibitor. In cases where DOM acts exclusively as a photosensitizer (as e.g. for electron-rich phenols and phenylureas), photochemical transformation rates (corrected for inner-filter effects) increase linearly with the concentration of DOM. Using two distinct sulfonamides as the target contaminants, we could recently show that this is no longer the case if DOM also acts as an inhibitor. The methodologies developed in the preceding projects will be applied and further developed to characterize both sensitizing and inhibiting effect of DOM. The use of model photosensitizers and model antioxidants will be extended for an improved mimicking of DOM. In addition, chemical modification of DOM, which is now under investigation using various selective oxidants (ozone, chlorine, chlorine dioxide), will be employed to get hints about the chemical structure of the DOM components responsible for the photosensitizing and antioxidant activities.The main objectives of the project are:1.To characterize the mechanism of the inhibition of triplet-induced oxidation;2.To evaluate and quantify the effect of DOM as an antioxidant when the same DOM also acts as a photosensitizer for the transformation of contaminants.3.To measure the effect of DOM composition and concentration on the indirect phototransformation rates of selected contaminants, in particular anilines and sulfonamides.The expected practical result is the quantification of the sunlight-induced transformation rates of the selected classes of contaminants under realistic surface water conditions.
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