SORPTION AND TRANSPORT OF VARDENAFIL IN NATURAL SOILS

Pharmaceutical pollutants are increasingly discovered in natural stream systems around the world and is an environmental concern. In this study we focus on vardenafil (active ingredient in Levitra, an erectile dysfunction drug) sorption and transport in natural soils. Vardenafil hydrochloride is a complex organic molecule with nonpolar (aromatic) and polar (amines) functionalities and has relatively low water solubility and an acid-base character with multiple pKa’s. It is estimated that some consumed vardenafil will enter the wastewater system, undergo partial removal and ultimately discharged into the natural environment. In natural systems, reactive components in soil are likely to sorb vardenafil and remove it from solution. The polar nature of vardenafil is likely to preferentially sorb to permanently charged clay minerals in soils. To test this hypothesis, we conducted laboratory batch sorption and column transport experiments in soils with different clay mineral (B-horizon soils) and organic matter content (A-horizon soils).

Our preliminary results in batch sorption studies show that vardenafil sorption to soil followed a linear trend and sorption was stronger to clay mineral-rich soil. This behavior was confirmed in column transport experiments as well. Vardenafil was strongly retarded compared with a nonsorbing tracer in glass columns packed with quartz sand particles. This indicated that charged soil and sediment surfaces may be key to strong sorption or that soils with higher clay mineral concentrations are likely to filter vardenafil from water. These data are useful in management of water resources and tracking geochemical fate of emerging contaminants in the environment.