Influence of Seasonal Variation in Antibiotic Concentration on the Fate and Transport of Antibiotics Within an Artificial Pond System

Seasonal variability significantly influences the fate and transport of antibiotics (Abs) in wastewater stabilization ponds by affecting their concentration, degradation kinetics, sorption behavior, and ecological interactions. This study investigated the influence of seasonal variability for a large number of Ab classes—eleven sulfonamides (SAs), eight fluoroquinolones (FQs), five macrolides (MLs), one diaminopyrimidine (DIA), two tetracyclines (TETs), two lincosamides (LICs), and three phenicols (Phens)—on their fate and transport in an artificial stabilization pond system (SPS) receiving treated WWTP effluent. Two sampling campaigns were conducted during China’s long-lasting seasons (summer and winter). The detection frequency for sulfamethoxazole (SMX), sulfapyridine (SPY), and ofloxacin (OFX) was 100%, for sulfamethazine (SMZ) 63.3%, and for clindamycin (CLN) 83.3% in both seasons. The detection frequency for the other Abs was equal or below 50% in both seasons. In addition, the maximum concentration of SMX, SMZ, SPY, OFX, and CLN in summer was 10.51, 19.37, 6.93, 22, and 4.04 ng/L, respectively, and 4.27, 0.14, 3.15, 9.29, and 8.78, respectively, in winter). The rest of the Abs were either detected in summer or winter. It was observed that environmental fluctuations (such as temperature, precipitation, SPS flow patterns, light intensity), differences in antibiotic use and consumption between seasons, and differences in physicochemical properties of the Abs were the main factors influencing their fate and transport within the SPS. The potential environmental risks of Abs detected in the SPS were assessed using the risk quotient (RQ) approach. Typically, RQs in summer were remarkably higher than in winter. Norfloxacin and chlortetracycline posed a medium risk in summer; however, ofloxacin posed a medium risk in winter and a high risk in summer. Therefore, management strategies should consider the dynamic nature of antibiotic contamination, accounting for seasonal influences on fate and transport within the studied SPS and maybe for other wastewater stabilization ponds by adjusting operational practices, optimizing treatment processes, and implementing source control measures to mitigate the environmental impacts of seasonal antibiotic variability.