EESS talk on "Photoinduced reactions in sunlit surface waters"
Event details
| Date | 23.02.2016 |
| Hour | 12:15 › 13:15 |
| Speaker | Dr Davide Vione, Associate Professor, Dept. of Analytical Chemistry, University of Torino, IT |
| Location | |
| Category | Conferences - Seminars |
Abstract:
The interaction between surface waters and sunlight induces several photochemical reactions that play an important role in the transformation of naturally occurring compounds and xenobiotics, in the inactivation of pathogens and in biogeochemical cycles. These processes partially involve the direct photolysis of the target molecules (where transformation is directly triggered by absorption of sunlight, if applicable), and partially their indirect or sensitised transformation. In the latter case, sunlight is absorbed by naturally-occurring photosensitisers (e.g. chromophoric dissolved organic matter or CDOM, nitrate and nitrite) to produce a range of reactive transient species that are involved in transformation reactions. The transients include, among others, the hydroxyl (•OH) and carbonate (CO3•) radicals, singlet oxygen (1O2) and CDOM triplet states (3CDOM*). Their occurrence in surface-water environments is linked to key water parameters such as chemistry and depth [1,2].
Therefore, the phototransformation of dissolved compounds involves an interplay between molecular features (e.g. photochemical reactivity or stability toward different reaction pathways) and environmental characteristics. As far as the latter are concerned, water chemistry and depth can affect both the persistence of the relevant solutes and the possible formation of intermediates that can be more toxic than the parent molecules. In particular, if an hazardous compound is preferentially produced by a certain photoreaction pathway, the environmental conditions can enhance or prevent its formation in different surface-water environments [3,4].
A potentially very important issue that is presently poorly known is the role that climate change may have on surface-water chemistry and, as a consequence, on photochemical reactions. The main difficulty in this context is the disentangling between climate effects and other disturbance factors (e.g. wastewater inputs) that may also operate on the long term and undergo modifications with a long-time scale. In this context, it is very important to select water chemistry features that may act as climate proxies, such as alkalinity [5].
[1] M.A. Young, Environmental Photochemistry in Surface Waters, Wiley, 2005.
[2] P. Boule, D.W. Bahnemann, P.K.J. Robertson (eds.), Environmental Photochemistry Part II, Springer, 2005.
[3] D. Vione, M. Minella, V. Maurino, C. Minero, Chemistry - A European Journal 2014, 20, 10590-10606.
Short biography:
Davide Vione received his PhD in Chemistry in 2001 from the University of Torino, where he has been Assistant Professor (2002-2011) and is presently Associate Professor (from 2011) in the Department of Chemistry. His research interests mainly focus on the study and modelling of photochemical reactions in sunlit surface and atmospheric waters, with an additional interest in advanced oxidation processes for water treatment (heterogeneous photocatalysis, Fenton and photo-Fenton reactions). The modelling of photochemical reactions in surface waters has recently involved the development of a software (Aqueous Photochemistry of Environmentally-occurring Xenobiotics) to predict the occurrence of photo-induced transients, the photodegradation of xenobiotics and the formation of intermediates, as a function of water chemistry and depth. His research work resulted so far in over 170 research papers in ISI journals.
The interaction between surface waters and sunlight induces several photochemical reactions that play an important role in the transformation of naturally occurring compounds and xenobiotics, in the inactivation of pathogens and in biogeochemical cycles. These processes partially involve the direct photolysis of the target molecules (where transformation is directly triggered by absorption of sunlight, if applicable), and partially their indirect or sensitised transformation. In the latter case, sunlight is absorbed by naturally-occurring photosensitisers (e.g. chromophoric dissolved organic matter or CDOM, nitrate and nitrite) to produce a range of reactive transient species that are involved in transformation reactions. The transients include, among others, the hydroxyl (•OH) and carbonate (CO3•) radicals, singlet oxygen (1O2) and CDOM triplet states (3CDOM*). Their occurrence in surface-water environments is linked to key water parameters such as chemistry and depth [1,2].
Therefore, the phototransformation of dissolved compounds involves an interplay between molecular features (e.g. photochemical reactivity or stability toward different reaction pathways) and environmental characteristics. As far as the latter are concerned, water chemistry and depth can affect both the persistence of the relevant solutes and the possible formation of intermediates that can be more toxic than the parent molecules. In particular, if an hazardous compound is preferentially produced by a certain photoreaction pathway, the environmental conditions can enhance or prevent its formation in different surface-water environments [3,4].
A potentially very important issue that is presently poorly known is the role that climate change may have on surface-water chemistry and, as a consequence, on photochemical reactions. The main difficulty in this context is the disentangling between climate effects and other disturbance factors (e.g. wastewater inputs) that may also operate on the long term and undergo modifications with a long-time scale. In this context, it is very important to select water chemistry features that may act as climate proxies, such as alkalinity [5].
[1] M.A. Young, Environmental Photochemistry in Surface Waters, Wiley, 2005.
[2] P. Boule, D.W. Bahnemann, P.K.J. Robertson (eds.), Environmental Photochemistry Part II, Springer, 2005.
[3] D. Vione, M. Minella, V. Maurino, C. Minero, Chemistry - A European Journal 2014, 20, 10590-10606.
Short biography:
Davide Vione received his PhD in Chemistry in 2001 from the University of Torino, where he has been Assistant Professor (2002-2011) and is presently Associate Professor (from 2011) in the Department of Chemistry. His research interests mainly focus on the study and modelling of photochemical reactions in sunlit surface and atmospheric waters, with an additional interest in advanced oxidation processes for water treatment (heterogeneous photocatalysis, Fenton and photo-Fenton reactions). The modelling of photochemical reactions in surface waters has recently involved the development of a software (Aqueous Photochemistry of Environmentally-occurring Xenobiotics) to predict the occurrence of photo-induced transients, the photodegradation of xenobiotics and the formation of intermediates, as a function of water chemistry and depth. His research work resulted so far in over 170 research papers in ISI journals.
Practical information
- General public
- Free
- This event is internal
Organizer
- EESS - IIE
Contact
- Prof. Samuel Arey, LMCE