Transport processes of pharmaceuticals and personal care products during stream-aquifer interaction in the urban area of Halle/Saale, Germany

The urban aquatic environment is increasingly affected by low concentrations (but potentially harmful) of xenobiotica such as residuals of pharmaceuticals and personal care products (PPCP) and their metabolites. After release into the urban sewer system the PPCPs reach the surface water mainly by passing sewage treatment plants or by diffuse leakage from the sewer system into groundwater. In the city of Halle/Saale, Germany, we used stable isotopes (18O, 2H, 34S-SO4) along with hydrochemical investigations to assess the exchange of river water with groundwater and its impact on the transport of selected PPCPs. The results indicate that attenuation of PPCP transport is mainly related to flood events with fast infiltration of river water into the aquifer (timescale of 5 days). By contrast, during slow infiltration linked to transport of PPCPs through the colmation layer (timescale of 150 days) no concentration changes have been found. These surprising differences in transport behaviour are attributed to the different hydraulic conditions with changing flow paths and river water chemistry. (author)