Sorption and Photodegradation Processes Govern Distribution and Fate of Sulfamethazine in Freshwater−Sediment Microcosms

The antibiotic sulfamethazine can be transported from manured fields to surface water bodies. We investigated the degradation and fate of sulfamethazine in pond water using 14C-phenyl-sulfamethazine in small pond water microcosms containing intact sediment and pond water. We found a 2.7-day half-life in pond water and 4.2-day half-life when sulfamethazine was added to the water (5 mg L–1 initial concentration) with swine manure diluted to simulate runoff. Sulfamethazine dissipated exponentially from the water column, with the majority of loss occurring via movement into the sediment phase. Extractable sulfamethazine in sediment accounted for 1.9–6.1% of the applied antibiotic within 14 days and then declined thereafter. Sulfamethazine was transformed mainly into nonextractable sediment-bound residue (40–60% of applied radioactivity) and smaller amounts of photoproducts. Biodegradation, as indicated by metabolite formation and 14CO2 evolution, was less significant than photodegradation. Two photoproducts accounted for 15–30% of radioactivity in the water column at the end of the 63-day study; the photoproducts were the major degradates in the aqueous and sediment phases. Other unidentified metabolites individually accounted for \u3c7% of radioactivity in the water or sediment. Less than 3% of applied radioactivity was mineralized to 14CO2. Manure input significantly increased sorption and binding of sulfamethazine residues to the sediment. These results show concurrent processes of photodegradation and sorption to sediment control aqueous concentrations and establish that sediment is a sink for sulfamethazine and sulfamethazine-related residues. Accumulation of the photoproducts and sulfamethazine in sediment may have important implications for benthic organisms

Determination of antibiotic residues in Southern Baltic Sea sediments using tandem solid-phase extraction and liquid chromatography coupled with tandem mass spectrometry

The main objective of this study was to adapt analytical procedures for determining antibiotic residues in solid and aquatic samples to marine sediments and to investigate the occurrence of 9 sulfonamides, trimethoprim and 2 quinolones in southern Baltic Sea sediments. The analytical procedure was applied to sediment samples characterized as sand and silty sand. The validation results showed that a sensitive and efficient method applying tandem solid-phase extraction (SPE) and liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) was obtained. Analytes were determined in the lower ng g−1 range with good accuracy and precision. The proposed analytical procedure was applied to the analysis of 13 sediment samples collected from the Baltic Sea along the Polish coast. Concentrations of antibiotic residues in environmental samples were calculated based on external matrix-matched calibration. Residues of nine out of twelve of the above antibiotics were detected in sediment samples in a concentrations of up to 419.2 ng g−1 d.w. (dry weight). Sulfamethoxazole and sulfachloropyridazine were the most frequently detected compounds (58% of the analyzed samples). The occurrence frequency of trimethoprim was 42% and it was always detected simultaneously with sulfamethoxazole. Preliminary studies on the spatial distribution of the analyzed antibiotics indicate a high level of antibiotics occurring in the Pomeranian Bay and close to the mouths of Polish rivers. The study is the first one to demonstrate the occurrence of antibiotic residues in sediments of the Polish coastal area. The obtained results suggest that sediment can be an important secondary source of antibiotic residues in the marine environment