Ecological and human health risk of sulfonamides in surface water and groundwater of Huixian karst wetland in Guilin, China

Sulfonamide antibiotics are contaminants of emerging concern (CEC). These CECs raise considerable alarm because they are commonly present in water environments. Studies on the environmental existence of CECs in karst areas of Guilin (Southern China) have yet to be reported. Thus, this study aims to investigate the presence, temporal and spatial distributions of sulfonamides in surface water and groundwater of four major aquatic environments (i.e., aquafarm water, ditch water, wetland water, and groundwater) in the Huixian karst wetland system of Guilin. Furthermore, this study aims to determine the ecological and human health risks of individual sulfonamides and their mixtures. Ten sulfonamides (i.e., sulfadiazine, sulfapyridine, sulfamerazine, trimethoprim, sulfamethazine, sulfamethoxypyridazine, sulfachloropyridazine, sulfamethoxazole, sulfadimethoxine, and sulfaquinoxaline) were observed in the study area. The highest average concentrations of aquafarm water, ditch water, wetland water, and groundwater were those of sulfadiazine (48.24 μg/L), sulfamethoxypyridazine (1281.50 μg/L), sulfamethoxazole (51.14 μg/L), and sulfamethazine (20.06 μg/L), respectively. The potential ecological risks of the detected compounds were much higher in ditch water than in aquafarm water, wetland water, and groundwater. The most ecological risks were observed for sulfachloropyridazine with a risk quotient (RQ) reaching 335.5 to green algae and 152 to Daphnia magna in ditch water. Similarly, sulfachloropyridazine posed the highest ecological risks to green algae among the ten sulfonamides in aquafarm water (RQ = 3.39), wetland water (RQ = 2.98), and groundwater (RQ = 3.6). Human health risk for age groups<12 months was observed from sulfonamide in drinking groundwater. Ecological and human health risks caused by sulfonamide mixtures were larger than the individual risks. Overall, ecological and human health risks caused by sulfonamides were observed in the study area.