Occurrence and spatial distribution of organic micro-pollutants in a complex hydrogeological karst system during low flow and high flow periods, results of a two-year study.

Fifty-four different organic micro-pollutants (OMPs) including pharmaceuticals, pesticides, corrosion inhibitors and other typical wastewater compounds such as caffeine are repeatedly analyzed in approximately fifty groundwater observation points in a complex faulted and fractured carbonate aquifer system consisting of three spring catchment areas. With the applied HPLC-MS/MS method, achieving method quantification limits (MQL) of 1.2-28 ng L(-1), forty-four of the OMPs are detected in groundwater. Regarding the vertical distribution in the aquifer system the highest variety of OMPs occurs in the shallow aquifer. Most frequently detected compounds are atrazine together with the metabolites of several triazines, desethylatrazine (DEA) and desisopropylatrazine (DIA), the corrosion inhibitors 1H-benzotriazole and tolytriazoles and as pharmaceutical residues the anti-epileptic drug carbamazepine as well as the analgesic drug phenazone. Median OMP concentrations are in the range of 20-40 ng L(-1) with occasionally and locally higher concentrations of up to 6000 ng L(-1). Defined combinations of OMPs occur repeatedly in the same observation wells and allow to distinguish different input functions. The comparison of detection frequency with the number of prescribed doses gives information about the specific persistence of pharmaceuticals. The analgesic phenazone exhibits a peculiar high detection frequency, although it is recently not prescribed in significant amounts. The detection of the estrogen antagonist tamoxifen (6-17 ng L(-1)) in a groundwater flow system is reported for the first time.