Fate of four pharmaceuticals in aquatic ecosystems : Investigating the role of UV- light and animal assimilation as dissipation factors

Abstract: Pharmaceuticals in the aquatic environment are of concern due to its possible negative consequences for non-target species. Pharmaceuticals can be found in many parts of the environment and especially in the effluent from sewage treatment plants where pharmaceuticals can be found in significant quantities. Therefore it is important to acquire knowledge of the fate of these pharmaceuticals in the aquatic environment. In this study two experimental ponds, one was covered by a tarp to avoid degradation by UV-light, were spiked with ~400 ng/l of diclofenac, diphenhydramine, hydroxyzine and trimethoprim. Water samples were taken regularly during 224 days. Animals from the uncovered pond was sampled weekly for the first 66 days. The aim was to investigate the degradation rate, the importance of UV-light for degradation and the uptake of pharmaceuticals by animals. The results showed that diclofenac and hydroxyzine had the fastest degradation rate and degraded to under 10 ng/l within 14 days and had the shortest calculated half-life of ~5 and ~10 days, respectively. Trimethoprim and diphenhydramine were more recalcitrant towards degradation and still had concentrations at 18 ng/l and ~8 ng/l respectively after 128 days and had half-life of ~23 and 24~days respectively. There were no significant difference between degradation rate between the pond covered with a tarp and the one which received UV-light. Only diphenhydramine and hydroxyzine were assimilated into the sampled animals. This study shows the different behavior of pharmaceuticals concerning their degradation rate and their ability to accumulate into animals.