Sorption and Desorption of Pharmaceuticals in Soils.

Fate of pharmaceuticals (PCs) in soils and its potential redistributions to crops irrigated with reused water is an emerging environmental concern. Sorption and desorption of PCs in soils may play important roles in plant availability of the compounds under different conditions. We studied the effects of soil type, soil water content (θ), and initial drug concentration (C) on sorption and desorption of Atenolol (β-blocker), Diclofenac (anti-inflammatory) and Ofloxacin (antibiotic). Three levels of drug concentrations were applied to three soils varying in organic carbon (OC) and θ. Samples were placed in air-tight containers and stored at room temperature in the dark. Subsamples were taken after 1, 45, and 90 days. Samples were extracted and analyzed for drug concentration using LC-MS. Atenolol detected in 24-hr samples ranged from 10 to 40% of C, depending on the soils. However, no Atenolol desorption was detected when the samples were further extracted with water: methanol (2:1 by volume). Less than 10% and 2% of C was detected in 45-day and 90-day samples, respectively. Diclofenac sorption was related to OC with more sorption to soils that contain a higher OC. Approximately, 99% of C was sorbed in soils with higher OC but ~ 50% of C remained in sand at the end of experiments. Only ~ 1% of Ofloxacin was detected in soil extracts and no significant desorption was found in any samples. Results suggested that sorption and desorption of the drugs were significantly influenced by soil type and C; however, the effect of θ varied with soils and types of drugs.