GEOCHEMICAL FATE AND TRANSPORT OF PHARMACEUTICAL CHEMICALS IN NATURAL SOILS

The use of prescription antidepressant medications has increased significantly around the world and is becoming a more common pollutant in surface water and drinking water. In this study we investigated three of the most commonly prescribed antidepressant chemicals - bupropion (BUP), fluoxetine (FLX), and sertraline (SER). The main objective of our research was to measure competitive sorption and transport behaviors of these chemicals in natural soils. All compounds have relatively high water solubility and exhibit acid-base functionality, indicating the possibility that they can interact with water, soil, and aquifer materials. In our previous studies we investigated sorption and transport behavior of each of these compounds individually in soils. In this study we investigated if these compounds would compete with each other when sorbing to soil minerals. To study this competitive transport behavior we injected solution containing all pharmaceutical chemicals through glass chromatography columns packed with different soil types. Effluent solutions were analyzed using a high-pressure liquid chromatograph. Column breakthrough curves that showed each of the studied pharmaceutical chemical’s transport behavior were plotted. Batch reactor sorption experiments were also conducted using the same soils with various concentrations of solution containing all three pharmaceutical chemicals.

The strength of sorption in both batch and column experiments were in the following order: SER > FLX > BUP. FLX and SER sorbed strongly to the clay-rich soil than to the organic-rich soil. BUP was shown to also sorb stronger to the organic-rich soil. These results indicate that polar nature of SER and FLX most strongly influenced sorption to clay minerals present in soils. In contrast, the more nonpolar nature of BUP strongly preferred soils that had higher organic matter. These results were comparable to experiments where sorption was measured individually, but it was clear that sorption was stronger when each compound was reacted with soil alone. These compounds were likely competing for the same reaction sites present in the soil. These results have implications for water resources management.