Purpose: Psychoactive compounds-meprobamate, pyrithyldione, primidone, and its metabolites, phenobarbital, and phenylethylmalonamide-were detected in groundwater within the catchment area of a drinking water treatment plant located downgradient of a former sewage farm in Berlin, Germany. The aim of this study was to investigate the distribution of the psychoactive compounds in anoxic groundwater and to assess the risk of drinking water contamination. Groundwater age was determined to achieve a better understanding of present hydrogeological conditions.
Methods: A large number of observation and production wells were sampled. Samples were analyzed using solid-phase extraction and ultrahigh-performance liquid chromatography-tandem mass spectrometry. Groundwater age was estimated using the helium-tritium ((3)He-(3)H) dating method.
Results: Concentrations of psychoactive compounds up to 1 μg/L were encountered in the contamination plume. Generally, concentrations of phenobarbital and meprobamate were the highest. Elevated concentrations of the analytes were also detected in raw water from abstraction wells located approximately 2.5 km downgradient of the former sewage farm. Concentrations in the final drinking water were below the limit of quantification owing to dilution. The age of shallow groundwater samples ranged from years to a decade, whereas groundwater was up to four decades old at 40 m below ground. Concentrations of the compounds increased with groundwater age.
Conclusions: Elevated concentrations of psychoactive drugs indicate a strong persistence of these compounds in the environment under anoxic aquifer conditions. Results suggest that the heritage of sewage irrigation will affect raw water quality in the area for decades. Therefore, further monitoring of raw and final drinking water is recommended to ensure that contaminant concentrations remain below the health-based precautionary value.