Fate and bioavailability of sulfamethazine in freshwater ecosystems

Abstract

The antibiotic sulfamethazine can be transported from manured fields to surface water bodies. We investigated the degradation, fate, and bioavailability of sulfamethazine in surface water using 14C-U-phenyl-sulfamethazine in small pond water microcosms. Sulfamethazine dissipated exponentially from the water column, with the majority of loss occurring via movement into the sediment phase. Manure input significantly increased sorption and binding of sulfamethazine residues to the sediment. These results indicate sediment is a potential sink for sulfamethazine and sulfamethazine-related residues, which could have important implications for benthic organisms. Understanding the bioavailability of pharmaceuticals in environmental matrices is particularly important considering they are often in a bioactive form. The bioavailability of sulfamethazine in surface water microcosms was evaluated using Lumbriculus variegatus in a bioassay. Bioconcentration factors (BCFs) were calculated, and a log BCF >2 was observed during aquatic exposure (0.05 mg/l). Interestingly, a significant inverse relationship between exposure concentration and BCF was also noted. Our results indicate the need for further assessment of the bioaccumulation potential of SMZ residues as a result of sediment exposure of benthic invertebrates.