Soils and sediments can serve as potential sinks for residual antimicrobial drugs that are discharged from farms and wastewater treatment plants. Conversely, they can also act as reservoirs for these compounds once the bound antimicrobials leach out. In this research, we investigated the sorption kinetics of three priority antimicrobials, namely lincomycin, sulfamethazine, and tetracycline in soils and river sediments collected from three relatively undisturbed environments in the Grand River watershed, which is a main contributor of pollutants in eastern Lake Erie. The soils and sediments were characterised for their organic fraction, cation exchange capacity, pH and particle size distribution. To explore the effects of seasonal temperature changes, sorption kinetics was studied using batch tests carried out at three temperatures (4°C, 20°C, and 35°C) and with varying initial antimicrobial concentrations (50-1000 ug/L). Aliquots were taken at defined time intervals and analytes were quantified using liquid-chromatography with mass spectrometry under electrospray ionization. Results show that the sorption of the antimicrobials can be best described by the Freundlich sorption model (R<sup>2</sup> &gt; 0.7). In all soil and sediment samples, equilibrium was achieved in less than 24 hours at temperatures of 20°C and 35°C for all initial antimicrobial concentrations, while equilibrium was achieved in less than 48 hours for the 4°C batch runs. Generally, sorption rates were in the order tetracycline &gt; lincomycin &gt; sulfamethazine. Despite the high CEC of the river sediment, its sorption capacity for antimicrobials was lower likely because of its lower carbon content and higher particle size compared to the soil samples. Over-all, our findings provide insights, especially in the temperate regions, on the attenuation of antimicrobials in the environment via sediment sorption and should be coupled with knowledge on seasonal changes in farming practices and contaminant removal rates at treatments plants. These findings should also be further evaluated in relation to other studies that found the environmental occurrence of antimicrobials in aqueous media in the studied watershed.<br/>

Sorption of human and veterinary antimicrobials in soils and sediments

250th National Meeting (2015)

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