Determination of sorption coefficients of pharmaceutically active substances carbamazepine, diclofenac, and ibuprofen, in sandy sediments

Laboratory batch studies were conducted to characterize the sorption behavior of three pharmaceutically active substances (carbamazepine, diclofenac, and ibuprofen) in different sediment types. The sediments were natural sandy sediments from the water saturated zone and the unsaturated zone in the Berlin (Germany) area. They are characterized as medium and fine-grained sands, both with low organic carbon content. The results of the experiments show that sorption coefficients were generally quite low. Distribution coefficients (Kd values) determined by the batch experiments varied from 0.21 to 5.32 for carbamazepine, 0.55 to 4.66 for diclofenac, and 0.18 to 1.69 for ibuprofen. Comparison of the organic carbon normalized sorption coefficient KOC values based on correlation equations with actual experimental data revealed that the calculated data for carbamazepine is of the same order as the experimental data. For diclofenac and ibuprofen the calculated values are much higher than the experimental data, showing a much higher mobility of diclofenac and ibuprofen in natural aquifer sediments than indicated by correlation equations based on octanol water distribution coefficients.