WIRC member Dr Jannis Wenk, together with colleagues from Eawag and ETH Zurich in Switzerland, recently published a new study in ACS Environmental Science and Technology elucidating the interactions of sunlight with water contaminants and naturally occurring antioxidants. You can read the paper here: Effect of Solution pH on the Dual Role of Dissolved Organic Matter in Sensitized Pollutant Photooxidation.
A wide range of water contaminants, for example antibiotics, pesticides and other trace contaminants released into lakes and rivers degrade through natural sunlight that penetrates the water surface. Light-induced degradation is an important sink for many environmentally concerning compounds. The photochemical processes in surface water can be complex, while the exact mechanisms underlying the transformation of contaminants often remains unknown.
In their study Wenk and co-workers have conducted several hundred kinetic irradiation experiments with anilines and sulfonamide antibiotics as target pollutants to shed light on the dual role that naturally occurring dissolved organic matter (DOM) plays on contaminant attenuation in surface water.
While DOM performs as photosensitizer promoting phototransformation, it also acts as inhibitor of photochemical reactions via intrinsic antioxidants. Understanding and quantifying the role of these antioxidants as inhibitors of photochemical transformations is critical to accurately assess the environmental fate of aquatic pollutants.
This study significantly improves the understanding of the role of DOM on transformation rates of contaminants in natural surface water, ultimately allowing a better prediction of environmental contaminant attenuation processes. In addition, this study presents the first comprehensive collection of kinetic data on the pH dependence of the photosensitized transformation of aromatic amines, including several high-usage antibiotics, under conditions relevant to sunlit surface waters.