APEX (Aqueous Photochemistry of Environmentally occurring Xenobiotics): a free software tool to predict the kinetics of photochemical processes in surface waters

Abstract

The APEX software predicts the photochemical transformation kinetics of xenobiotics in surface waters as a function of: photoreactivity parameters (direct photolysis quantum yield and second-order reaction rate constants with transient species, namely• OH, CO

Long-term trends of chemical and modelled photochemical parameters in four Alpine lakes

“…The modelling of lake water photochemistry used APEX software (Aqueous Photochemistry of Environmentally-occurring Xenobiotics) that is freely available as Electronic Supplementary Information of Bodrato and Vione (2014). APEX is based on a photochemical model that predicts steady-state concentrations of transient species ( • OH, CO 3 −• , 1 O 2 , 3 CDOM*) as a function of the seasonally variable sunlight spectrum, water chemistry and depth (Vione, 2014;Bodrato and Vione, 2014).…”

“…APEX is based on a photochemical model that predicts steady-state concentrations of transient species ( • OH, CO 3 −• , 1 O 2 , 3 CDOM*) as a function of the seasonally variable sunlight spectrum, water chemistry and depth (Vione, 2014;Bodrato and Vione, 2014). APEX allows for instance for the prediction of the phototransformation kinetics of xenobiotics, on which basis the photochemical model was validated upon comparison with available field data (Maddigapu et al, 2011;De Laurentiis et al, 2012;Marchetti et al, 2013).…”

“…APEX allows for instance for the prediction of the phototransformation kinetics of xenobiotics, on which basis the photochemical model was validated upon comparison with available field data (Maddigapu et al, 2011;De Laurentiis et al, 2012;Marchetti et al, 2013). The absorption of radiation by photosensitisers (CDOM, nitrate and nitrite) and xenobiotics is computed by taking into account competition for sunlight irradiance in a Lambert-Beer approach (Braslavsky, 2007;Bodrato and Vione, 2014). Data obtained with APEX are averages over the water column (in the present case, computations were run for the upper 1 m depth), and they include the contributions of the sunlit surface layer and of darker water at the bottom.…”

“…Sunlight is not vertically incident over the water surface, but refraction at the interface deviates the light path into the water towards the vertical. Under mid-latitude conditions, the dailyaveraged ratio between the path length l of sunlight in water and the depth d varies from l/d = 1.45 in winter to 1.15 in summer (Bodrato and Vione, 2014).…”

Pesticide behavior in modified water-sediment systems

“…32) [X] ss in natural water can be estimated by the reactions with probe molecules whose rate constants for each reactive species have been determined: probe(s), [X] The k x,p value has been determined for many pesticides by the competition reaction method against k x,p -known chemicals or probe molecules: 10 28,29) and the corresponding estimation program is available. 65) Though the inclusion of indirect photolysis is very limited to simulate the fate of pesticide in the water-sediment system, the computer model EXAMS (Exposure Analysis Modeling System) considering the reaction with ·OH has been successfully applied. 1,66) Since the [X] ss values highly depend not only on the natural water to be assessed but also on irradiance, the relative contribution of direct and indirect photolysis was more conveniently examined for sixteen pesticides in the sunlit U.S. surface waters by using the probe molecules as quenchers.…”