Aquatic photochemistry and transformations of multiclass emerging organic contaminants in environmental water matrices

• 10 out 18 studied contaminants showed susceptibility to direct photolysis at trace levels. • Presence of natural abiotic factors in water significantly influenced photodegradation. • Aeration increased degradation but real seawater matrices had inhibitory effects. • Transformation products were identified, ranked, and subjected to ecotoxicity prediction. • Rosuvastatin’s transformation product was detected in real water in Slovenia, Europe. This study shows a comprehensive assessment of the photodegradation of 18 multiclass contaminants of emerging concern (CECs) in simulated river and marine aquatic compartments. Degradation trends, mineralization, and defluorination of the target CECs were monitored in model matrices, artificial and real seawater, with and without aeration. Each model matrix contained a natural abiotic factor of interest, i.e., chloride, nitrate, humic acids, lignosulphonate, and iron, all naturally present in surface water. Transformation pathways were investigated by LC-MS and for the identified transformation products (TPs), their ecotoxicities were predicted in silico . Only 8 out of 18 selected CECs were found to be significantly photolabile, especially rosuvastatin. Direct photolysis was their primary degradation route, while abiotic factors either accelerated or supressed the degradation depending on the type of CEC. Real and artificial seawater mostly acted inhibitory. Oxygen aeration mostly accelerated degradation showing the effect of singlet oxygen. Low mineralization and defluorination were in most cases linked to the formation of stable and relatively more toxic TPs, which were characteristic for rosuvastatin. Main identified TPs were screened in real river water and seawater (North Adriatic Sea water basin, Slovenia, Europe). Rosuvastatin’s TP ROS-349 was detected with a high confidence level for the first time, which may raise environmental concerns. Overall, advanced assessment of aquatic photochemistry is achieved by using low concentrations, mixtures of multiclass CECs, UV light above 300 nm, more realistic matrices, as well as by identifying, ranking, and analysing the TPs in actual aquatic environment.