Comparison of the Photodegradation of Pharmaceuticals and Personal Care Products (PPCPs) in Water and Ice

Abstract Photochemical reactions are prevalent in natural aquatic environments and play a crucial role in aquatic ecosystems. Sunlight-induced photodegradation is particularly effective in degrading various pharmaceuticals and personal care products (PPCPs). However, the photochemical behavior of pollutants within surface ice in cold regions remains unclear. This review synthesizes current research advances regarding the photochemical transformation mechanisms and associated environmental risks of PPCPs in ice, highlighting the significance of these transformations in evaluating the environmental impact of PPCPs in such contexts. In ice or snow, PPCPs may undergo transformation pathways (e.g., photolysis and free radical reactions), which differ from those in aquatic environments. Factors including ice crystal structure, pH, dissolved organic matter, and light conditions can influence their transformation efficiency and the resulting degradation products. This review systematically elucidates the photochemical reaction pathways, key influencing factors, and potential ecotoxicological effects of PPCPs in ice. These transformation processes may generate secondary products that are more persistent or toxic than the parent compounds, posing potential threats to aquatic ecosystems and food chains in cold regions. Therefore, there is an urgent need to thoroughly explore the environmental behavior and ecological risks of PPCPs to provide a scientific basis for pollution control and ecological protection in cold environments.