RESUMO

This study assessed the occurrence and ecological potential risk of nine selected pharmaceuticals in water samples from the Juquehy River. The river flows continuously to Juquehy Beach, known as "the jewel of the north coast" of São Paulo, Brazil. Samples were collected during Christmas and the New Year (period of December 2023-January 2024), in addition to a previous baseline weekend, to compare the loads during "celebratory parties" versus "normal operational conditions." The findings indicated that the "mass gathering" during Christmas and New Year holidays contributed significantly to an increase of the mass load of the nine pharmaceuticals flowing along to the Juquehy River, i.e., caffeine (14.40-633.00 ng/L) > losartan ( furosemide (< LOQ to 9.16 ng/L) > diclofenac (0.61-4.55 ng/L) > carbamazepine (< LOQ to 0.73 ng/L) > orphenadrine (< LOQ to 0.11 ng/L) showed higher concentrations during the New Year holiday. Conversely, atenolol (< LOQ to 13.10 ng/L) > benzoylecgonine (0.33-7.23 ng/L) > cocaine (0.12-6.59 ng/L) showed higher concentrations during the Christmas day. The individual ecological risk assessment in the Juquehy River revealed a clear environmental concern for the aquatic ecosystem. The threat to the aquatic biota is significant, with caffeine and losartan presenting a moderate level of risk. Moreover, the mixture ecological risk assessment of nine compounds indicates acute moderate risks to algae, crustaceans, and fishes, as well as chronic low risks to fishes.