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Water Res. 2018 Feb 1;129:94-104. doi: 10.1016/j.watres.2017.10.064. Epub 2017 Oct 30.

Simulation of photoreactive transients and of photochemical transformation of organic pollutants in sunlit boreal lakes across 14 degrees of latitude: A photochemical mapping of Sweden.

Author information

1
Department of Ecology and Genetics/Limnology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, 75236 Uppsala, Sweden.
2
Department of Chemistry, University of Torino, Via Pietro Giuria 5, 10125 Torino, Italy.
3
Swedish Meteorological and Hydrological Institute, Atmospheric Remote Sensing, Folkborgsvägen 1, 60176 Norrköping, Sweden.
4
Department of Chemistry, University of Torino, Via Pietro Giuria 5, 10125 Torino, Italy. Electronic address: davide.vione@unito.it.

Abstract

Lake water constituents, such as chromophoric dissolved organic matter (CDOM) and nitrate, absorb sunlight which induces an array of photochemical reactions. Although these reactions are a substantial driver of pollutant degradation in lakes they are insufficiently understood, in particular on large scales. Here, we provide for the first time comprehensive photochemical maps covering a large geographic region. Using photochemical kinetics modeling for 1048 lakes across Sweden we simulated the steady-state concentrations of four photoreactive transient species, which are continuously produced and consumed in sunlit lake waters. We then simulated the transient-induced photochemical transformation of organic pollutants, to gain insight into the relevance of the different photoreaction pathways. We found that boreal lakes were often unfavorable environments for photoreactions mediated by hydroxyl radicals (OH) and carbonate radical anions (CO3-), while photoreactions mediated by CDOM triplet states (3CDOM*) and, to a lesser extent, singlet oxygen (1O2) were the most prevalent. These conditions promote the photodegradation of phenols, which are used as plastic, medical drug and herbicide precursors. When CDOM concentrations increase, as is currently commonly the case in boreal areas such as Sweden, 3CDOM* will also increase, promoting its importance in photochemical pathways even more.

KEYWORDS:

Boreal lakes; Browning; Modeling; Photochemical transients; Photochemistry; Pollutants

PMID:
29132125
DOI:
10.1016/j.watres.2017.10.064
[Indexed for MEDLINE]

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