Assessing the phototransformation of diclofenac, clofibric acid and naproxen in surface waters: Model predictions and comparison with field data
Articolo
Data di Pubblicazione:
2016
Abstract:
Phototransformation is important for the fate in surface waters of the pharmaceuticals diclofenac (DIC)
and naproxen (NAP) and for clofibric acid (CLO), a metabolite of the drug clofibrate. The goal of this paper
is to provide an overview of the prevailing photochemical processes, which these compounds undergo in
the different conditions found in freshwater environments. The modelled photochemical half-life times
of NAP and DIC range from a few days to some months, depending on water conditions (chemistry and
depth) and on the season. The model indicates that direct photolysis is the dominant degradation
pathway of DIC and NAP in sunlit surface waters, and potentially toxic cyclic amides were detected as
intermediates of DIC direct phototransformation. With modelled half-life times in the month-year range,
CLO is predicted to be more photostable than DIC or NAP and to be degraded mainly by reaction with the
OH radical and with the triplet states of chromophoric dissolved organic matter (3CDOM*). The CLO
intermediates arising from these processes and detected in this study (hydroquinone and 4-
chlorophenol) are, respectively, a chronic toxicant to aquatic organisms and a possible carcinogen for
humans. Hydroquinone is formed with only ~5% yield upon CLO triplet-sensitised transformation, but it
is highly toxic for algae and crustaceans. In contrast, the formation yield of 4-chlorophenol reaches ~50%
upon triplet sensitisation and ~10% by $OH reaction. The comparison of model predictions with field data
from a previous study yielded a very good agreement in the case of DIC and, when using 4-
carboxybenzophenone as proxy for triplet sensitisation by CDOM, a good agreement was found for
CLO as well. In the case of NAP, the comparison with field data suggests that its direct photolysis quantum
yield approaches or even falls below the lower range of literature values.
Tipologia CRIS:
03A-Articolo su Rivista
Elenco autori:
Avetta, Paola; Fabbri, Debora; Minella, Marco; Brigante, Marcello; Maurino, Valter; Minero, Claudio; Pazzi, Marco; Vione, Davide
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