Project

Back to overview

Characterizing organic radical oxidants produced by photoirradiation of dissolved organic matter ("OROPHOT")

Applicant Canonica Silvio
Number 169422
Funding scheme Project funding
Research institution Swiss Federal Institute of Aquatic Science and Technology (EAWAG)
Institution of higher education Swiss Federal Institute of Aquatic Science and Technology - EAWAG
Main discipline Other disciplines of Environmental Sciences
Start/End 01.08.2017 - 31.10.2021
Approved amount 258'054.00
Show all

All Disciplines (3)

Discipline
Other disciplines of Environmental Sciences
Physical Chemistry
Organic Chemistry

Keywords (7)

DOM; oxidation; phenoxyl radicals; NOM; phenols; organic contaminants; photosensitizers

Lay Summary (German)

Lead
Das in Oberflächengewässern natürlich vorkommende gelöste organische Material ist unter Einwirkung des Sonnenlichts eine Quelle von reaktiven chemischen Spezies. Diese können verschiedene Schadstoffe abbauen und sind somit an der Selbstreinigung der Gewässer beteiligt. Unter diesen reaktiven Spezies befinden sich organische Radikale, deren Wirkung auf im Wasser gelöste Schadstoffe bisher noch wenig bekannt ist. Für den Abbau von gewissen Klassen von Schadstoffen, die zur oxidativen Transformation neigen, könnten oxidierende organische Radikale (OOR) eine entscheidende Rolle spielen.
Lay summary

Inhalt und Ziel desForschungsprojekts

Dieses Projekt soll dazu dienen, die Bedeutung von OOR in sonnenbelichteten Gewässern besser zu verstehen, vor allem in Bezug auf den Abbau von im Wasser gelösten Schadstoffen. Die Hauptziele bestehen darin, (i) wichtige Klassen von Schadstoffen zu identifizieren, deren Abbau massgeblich von OOR bestimmt wird, (ii) chemische Eigenschaften der OOR zucharakterisieren, und (iii) die Hypothese zu überprüfen, dass chemisch genau definierte Phenoxyradikale als Modelle für OOR dienen können. Wir konnten während den letzten zehn Jahren zeigen, dass phenolische Bestandteile des organischen Materials für die Hemmung von Licht-induzierten Transformationsprozessen bestimmter Schadstoffe verantwortlich sind. Dieses Projekt soll das Gegenstück aufzeigen, nämlich dass eine Gruppe solcher phenolischen Bestandteile unter Lichteinwirkung den Abbau von Schadstoffen beschleunigen kann.

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Unser Projekt wird neue wichtige Erkenntnisse im wissenschaftlichen Gebiet der Umwelt-Photochemie liefern. Diese können von Behörden und interessierten Kreisen dazu verwendet werden, um die Abbauwege und Abbauraten von verschiedenen Mikroverunreinigungen besser als nach heutigem Stand zu beurteilen, und so einen verbesserten Schutz von aquatischer Umwelt und Bevölkerung zu erreichen.

Direct link to Lay Summary Last update: 19.07.2017

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
Photochemical oxidation of phenols and anilines mediated by phenoxyl radicals in aqueous solution
Remke Stephanie C., Bürgin Tobias H., Ludvíková Lucie, Heger Dominik, Wenger Oliver S., von Gunten Urs, Canonica Silvio (2022), Photochemical oxidation of phenols and anilines mediated by phenoxyl radicals in aqueous solution, in Water Research, 213, 118095.
Enhanced transformation of aquatic organic compounds by long-lived photooxidants (LLPO) produced from dissolved organic matter
Remke Stephanie C., von Gunten Urs, Canonica Silvio (2021), Enhanced transformation of aquatic organic compounds by long-lived photooxidants (LLPO) produced from dissolved organic matter, in Water Research, 190, 116707-116707.

Collaboration

Group / person Country
Types of collaboration
Prof. Dominik Heger, Masaryk University, Brno Czech Republic (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
Prof. Oliver Wenger, Universität Basel Switzerland (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
8th Late Summer Workshop (Wasserchemische Gesellschaft) Talk given at a conference The role of “long-lived” photooxidants in the transformation of aquatic organic contaminants photosensitized by dissolved organic matter 22.09.2019 Haltern am See, Germany Remke Stephanie; Canonica Silvio; von Gunten Urs;
17th International Conference on Chemistry and Environment Talk given at a conference The role of “long-lived” photooxidants in the transformation of aquatic organic contaminants photosensitized by dissolved organic matter 16.06.2019 Thessaloniki, Greece Canonica Silvio; von Gunten Urs; Remke Stephanie;


Associated projects

Number Title Start Funding scheme
181975 Reactions of ozone with water matrix components: reactive sites and oxidation by-product formation 01.11.2018 Project funding
140815 Antioxidant effect of dissolved organic matter (DOM) on indirect photochemical transformation of contaminants in surface waters ("Oxindom 3") 01.09.2012 Project funding

Abstract

The ubiquitous and in its chemical composition extremely complex dissolved organic matter (DOM) is a source of various reactive intermediates when exposed to ultraviolet (UV) light. Such intermediates induce the transformation of many aquatic contaminants in sunlit surface waters or UV-based water treatment systems. The reactive intermediates produced from photoirradiated DOM comprise well-defined chemical entities, such as the hydroxyl radical, carbonate radical or singlet oxygen, as well as excited states or radical species that are often elusive to precise chemical identification because derived from and still attached to the DOM backbone. Excited triplet states of the DOM (3DOM*) have been recognized (with decisive contributions by the applicants) as pivotal photooxidants affecting the fate of organic contaminants in surface waters. Besides 3DOM*, the existence of DOM-derived photooxidants having longer lifetimes than 3DOM* and therefore termed "long-lived photooxidants" (LLPOs) was demonstrated based on the transformation kinetics of probe compounds. Although there has been little research about these photooxidants, for the the phototransformation of certain contaminant classes, such as electron-rich phenols and anilines, the contribution of LLPOs is expected to be high and even override the effect of 3DOM*. Based on the fact that DOM carries many phenolic groups which, when oxidized (e.g. by 3DOM*), lead to the formation of phenoxyl radicals, we hypothesize that DOM-attached phenoxyl radicals are substantial components of LLPOs. With the present proposal we intend to characterize the reactivity of LLPOs with various classes of contaminants and identify their chemical nature.The main objectives of the project are: (1) To identify the classes and types of contaminants prone to transformation induced by LLPOs with the goal of a broader evaluation of the role and relevance of LLPOs in the fate of aquatic contaminants in surface waters; (2) To characterize the chemical nature of LLPOs by means of diagnostic chemical kinetic methods; (3) To verify the hypothesis that photochemically produced phenoxyl radicals are able to mimic the phototransformation of organic contaminants induced by LLPOs.To pursue these objectives, a kinetic methodology developed by the applicants will be used and further improved to measure the effect of LLPOs on the transformation of selected contaminants. The reactivity of phenoxyl radicals will be mainly studied using laser flash photolysis.Besides clarifying the questions of the objectives, the present project is expected to provide an improved understanding of the role of phenolic moieties in the photochemistry and redox chemistry of DOM. It also offers stimulating links to the topic of DOM as an antioxidant, which was addressed in two preceding SNF proposals. The part of the study regarding the reactivity of phenoxyl radicals, which will be performed using model phenols, is expected to fill a gap in the aqueous chemical kinetics of these radicals, which might, in addition to aquatic environments, also be of interest for biochemical systems.The present project will also achieve the education of a PhD student and offer the opportunity for a continued international collaboration and exchange in the fields of photochemistry and kinetics of transient intermediates (Prof. Petr Klan and Prof. Dominik Heger, Masaryk University, Brno, Czech Republic).
-