Photochemical Fate of Carbamazepine in Surface Freshwaters: Laboratory Measures and Modeling

Abstract

It is shown here that carbamazepine (CBZ) would undergo direct photolysis and reaction with • OH as main phototransformation pathways in surface waters. Environmental lifetimes are expected to vary from a few weeks to several months, and predictions are in good agreement with the available field data. Acridine (I) and 10,11-dihydro-10,11-trans-dihydroxy-CBZ (V) are the main quantified phototransformation intermediates upon direct photolysis and • OH reaction, respectively. The photochemical yield of mutagenic I from CBZ is in the 3-3.5% range and, being similar for both direct photolysis and • OH reaction, it would undergo limited variation with environmental conditions. In contrast, the yield of V would vary in the 4-8.5% range depending on the conditions, because V is formed from CBZ by • OH (9.0% yield) more effectively than upon direct photolysis (1.4% yield). Other important photointermediates, mostly formed from CBZ upon • OH reaction are an aromatic-ring-dihydroxylated CBZ (VI) and N,N-di(2-carboxyphenyl)urea (VII). Compounds VI and VII are formed by photochemistry and are not reported as human metabolites, thus they could be used as tracers of CBZ phototransformation in surface waters. Interestingly, VI has recently been detected in river water.

Photoenhanced transformation of nicotine in aquatic environments: Involvement of naturally occurring radical sources

“…The used model approach has been validated against available data of pollutant photodegradation in the field Vione et al, 2011;De Laurentiis et al, 2012 Figure 2 gives the second-order rate constants …”

Photochemical processes involving the UV absorber benzophenone-4 (2-hydroxy-4-methoxybenzophenone-5-sulphonic acid) in aqueous solution: Reaction pathways and implications for surface waters

“…An alternative approach that overcomes this difficulty is the prediction of the photodegradation kinetics of organic xenobiotics in surface waters on the basis of water chemistry and depth and of photochemical reactivity parameters (direct photolysis quantum yields and reaction rate constants with • OH, CO 3 •− , 1 O 2 and 3 CDOM*). We have recently developed a photochemical model that helps performing this task and that has been validated against the transformation of several organic pollutants in fresh and estuarine (brackish) water (Maddigapu et al, 2011;Vione et al, 2011a;De Laurentiis et al, 2012a;Sur et al, 2012). In this context, the purpose of the present paper is to predict the photochemical transformation kinetics of BP-4 in natural water systems, to gain insight into its environmental persistence.…”

Modelling photochemical transformation of emerging organic pollutants in surface waters: effect of water level fluctuations following outflow or evaporation, relevant to arid and semi-arid environments

“…In contrast, the much lower quantum yield of 24DNP is largely compensated for by the substrate ability to absorb sunlight between 300 and 500 nm [53]. In the case of CBZ, IBU and DCNP, the model has been validated for its ability to predict substrate transformation kinetics under field conditions [48,49,51]. In the case of outflow, where concentration values of solutes would not vary, it was possible to extend the model to near-zero depth.…”