Photogeneration of Reactive Transient Species Upon Irradiation of Natural Water Samples: Formation Quantum Yields in Different Spectral Intervals, and Implications for the Photochemistry of Surface Waters.
Articolo
Data di Pubblicazione:
2015
Abstract:
Chromophoric dissolved organic matter (CDOM) in surface waters is a photochemical
source of several transient species such as CDOM triplet states (3CDOM*), singlet oxygen
(1O2) and the hydroxyl radical (OH). By irradiation of lake water samples, it is shown here
that the quantum yields for the formation of these transients by CDOM vary depending on
the irradiation wavelength range, in the order UVB > UVA > blue. A possible explanation is
that radiation at longer wavelengths is preferentially absorbed by the larger CDOM fractions,
which show lesser photoactivity compared to smaller CDOM moieties. The quantum
yield variations in different spectral ranges were definitely more marked for 3CDOM* and
OH compared to 1O2. The decrease of the quantum yields with increasing wavelength has
important implications for the photochemistry of surface waters, because long-wavelength
radiation penetrates deeper in water columns compared to short-wavelength radiation.
The average steady-state concentrations of the transients (3CDOM*, 1O2 and OH) were
modelled in water columns of different depths, based on the experimentally determined
wavelength trends of the formation quantum yields. Important differences were found
between such modelling results and those obtained in a wavelength-independent quantum
yield scenario.
Tipologia CRIS:
03A-Articolo su Rivista
Keywords:
Indirect photochemistry, Photogeneration quantum yields, Environmental photochemistry, Sensitised photolysis, Spectral intervals
Elenco autori:
A. Marchisio; M. Minella; V. Maurino; C. Minero; D. Vione.
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