Global modeling of lake-water indirect photochemistry based on the equivalent monochromatic wavelength approximation: The case of the triplet states of chromophoric dissolved organic matter
Chromophoric dissolved organic matter (CDOM) plays key role as photosensitizer in sunlit surface-water environments, and it is deeply involved in the photodegradation of contaminants. It has recently been shown that sunlight absorption by CDOM can be conveniently approximated based on its monochromatic absorption at 560 nm. Here we show that such an approximation allows for the assessment of CDOM photoreactions on a wide global scale and, particularly, in the latitude belt between 60◦S and 60◦N. Global lake databases are currently incomplete as far as water chemistry is concerned, but estimates of the content of organic matter are available. With such data it is possible to assess global steady-state concentrations of CDOM triplet states ( 3 CDOM*), which are predicted to reach particularly high values at Nordic latitudes during summer, due to a combination of high sunlight irradiance and elevated content of organic matter. For the first time to our knowledge, we are able to model an indirect photochemistry process in inland waters around the globe. Implications are discussed for the phototransformation of a contaminant that is mainly degraded by reaction with 3 CDOM* (clofibric acid, lipid regulator metabolite), and for the formation of known products on a wide geographic scale.
AGG acknowledges Spanish Ministry of Education for her FPU grant (FPU17/04333). AGG and JM gratefully acknowledge the financial support of the Spanish State Research Agency (AEI), the Spanish Ministry of Science and Innovation through the project AQUAENAGRI (PID2021–126400OB-C32), and Comunidad de Madrid through the program REMTAVARES (P2018/EMT-4341). LC and DV acknowledge support from the Project CH4.0 under the MUR program "Dipartimenti di Eccellenza 2023–2027″ (CUP: D13C22003520001). DV also acknowledges financial support by Next Generation EU – PNRR project GRINS (Growing Resilient, INclusive, and Sustainable), PE9 - spoke 6.
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