Sulfonamide antibiotics in groundwater and their migration in the vadose zone: A case in a drinking water resource

Abstract Vadose zone is an important channel for sulfonamide contamination into groundwater, and the processes of adsorption and migration in the vadose zone are complicated. In this study, we focused on three sulfonamide antibiotics (sulfamethoxazole, sulfamethazine and sulfamethoxypyridazine) in the groundwater of Limin drinking water resource in northeastern China and assessed their migration potential in aquifers. Analysis was based on adsorption batch tests, a column experiment. Some key influencing factors including pH, iron, manganese and ammonia were considered. The results showed that the concentration of sulfamethoxypyridazine in groundwater is higher, ranging between 7 and 30 ng/L, the concentrations of sulfamethoxazole and sulfamethazine are relatively lower and no more than 1 ng/L. The adsorption capacity of the three antibiotics on vadose zone materials shows the following order: sulfamethoxypyridazine > sulfamethazine > sulfamethoxazole. Furthermore, for the three sulfonamides, the adsorption is higher in the medium of 0–20 cm (finer particle size, higher clay content and lower sand content) than that in 80–100 cm. Coexisting ions (iron, manganese and ammonia) promote the adsorption of sulfonamides, and the adsorption of sulfonamides decreases as the water pH increases. The column experiment also shows that the three sulfonamides have strong migration abilities and pose a considerable risk to groundwater.