Photodegradation of bisphenol A in water and ice: identification of products using three photosensitizers

Bisphenol A (BPA) is a widespread organic micro-pollutant, found in most environments, including alpine and Arctic regions, and several matrices such as waters and aerosols. Polar regions are characterized by periods of intense irradiation with no sunset due to the continuous sunlight, while alpine areas, despite following the day-night cycle of mid-latitudes, also undergo strong irradiation. For such conditions, it is possible that a fraction of the BPA present in snow may degrade through direct photolysis, producing other unknown species with different environmental mobility and possible ecotoxic effects. Furthermore, the snowpack is rich in species (known as photosensitizers) that facilitate indirect photodegradation processes through reactions involving hydroxyl radicals  $\left(·,\mathrm{OH}\right)$ , singlet oxygen (¹O₂), excited triplet states of the organic fraction (³CDOM*), and nitrite/nitrate. In this study, we investigated both direct and indirect photodegradation of BPA in the presence of specific photosensitizers producing  $·\mathrm{OH}$ , ¹O₂, ³CDOM*, and NO₂^- to specifically explore the products of the reaction. The study was conducted in both liquid water and ice, under light and dark conditions. Results, obtained by HPLC-HRMS, revealed that the matrix in which the reaction takes place, in addition to the photosensitizer used, may influence the degradation by-products. This allows for the possibility of distinguishing the reaction environment based on the identified product.