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Bankside groundwater is widely used as drinking water resource and, therefore, contamination has to be avoided. In the European Union groundwater protection is explicit subject to Water Framework Directive. While groundwater pollution may originate from different sources, this study investigated on impacts via flood events. Groundwater was sampled with increasing distance to the river Rhine near Karlsruhe, Germany. Samples were HPLC-MS-MS analyzed for the river contaminant carbamazepine to indicate river water infiltration, giving permanent presence in 250 m distance to the river (14-47 μg L⁻¹). Following a flood event, concentrations of about 16-20 μg L⁻¹ could also be detected in a distance of 750 m to the river. Furthermore, estrogenic activity as determined with the Yeast Estrogen Screen assay was determined to increase up to a 17β-ethinylestradiol equivalent concentration (E-EQ)=2.9 ng L⁻¹ near the river, while activity was initially measured following the flood with up to E-EQ=2.6 ng L⁻¹ in 750 m distance. Detections were delayed with increasing distance to the river indicating river water expansion into the aquifer. Flood suspended matter and floodplain soil were fractionated and analyzed for estrogenic activity in parallel giving up to 1.4 ng g⁻¹ and up to 0.7 ng g⁻¹, respectively. Target analysis focusing on known estrogenic active substances only explained < 1% of measured activities. Nevertheless, river water infiltration was shown deep into bankside groundwater, thus, impacting groundwater quality. Therefore, flood events have to be in the focus when aiming for groundwater and drinking water protection as well as for implementation of Water Framework Directive.

This study was carried out to determine hazards of particle-bound contaminants in rivers to retention areas close to public well fields in the context of flood events. The focus was on the assessment of soil contamination at a planned retention area. Soil core samples were chemically and biologically analyzed. Samples were fractionated to identify and compare contaminant loads and biological effects of soil and flood suspended particulate matter (SPM). Soil cores were sampled at inundated and non-inundated sites at a planned retention area. Soil was analyzed for hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs) as well as for polycyclic aromatic hydrocarbons (PAHs). The highest inducing soil sample was fractionated applying a recently developed automated fractionation method to receive further insight into contaminant loads in soil at inundated sites. Impacts on biological scale were assessed using in vitro biotests for xenometabolic activity (7-ethoxyresorufin-o-deethylase (EROD) assay) as well as for mutagenic activity (Ames fluctuation assay). EROD induction was calculated as biological equivalent concentration (bio-TEQ), and mutagenic potentials were given as no observed effect concentration (NOEC) and maximum induction factor (IFmax). Soil core samples of each site induced EROD activity. However, extracts of soil sampled at a ground swale was by far the highest inducing (topsoil bio-TEQ = 41,000 pg/g). Further, chemical analysis yielded relative increases in concentration in particular: HCB (0.05 mg/kg), PCBs (0.19 mg/kg), and EPA-PAHs (39 mg/kg). Extracts of soil samples caused no mutagenic effects. PAHs caused the bulk of EROD activity (bio-TEQ = 32,000 pg/g) with ground swale topsoil fractions. Further, fractions containing moderately polar and polar substances gave elevated effects (bio-TEQ = 8,200 pg/g). Mutagenic potentials were shown with most fractions. However, highest induction was observed with fractions containing moderately polar to polar substances reflected by a NOEC ≥0.03 mg/ml and an IFmax ≤29. Soil contamination at floodplains is heterogeneous but may reach elevated levels with soil swales giving highest chemical concentrations and biological effects with total sample extracts and fractions. The origin of floodplain soil contamination can be evaluated using lines of evidence which may result in identification of contaminant transport path from sediment, via flood SPM to soil. Taking hazard assessment of floodplain soil forward to risk evaluation may indicate a concern which highlights the need to further investigate on hazards caused by eroded sediment in flood events to avoid conflicts of interest when planning and operating retention basins.

The presented study investigated on contamination of suspended particulate matter (SPM) in rivers that was sampled long-term and with higher frequency during a flood event at the river Rhine. It was conducted to determine in vitro biological effects as well as to identify and quantify compound classes and effective contaminants. Research was part of investigation on hazards of contaminants bound to SPM to inundated sites and retention areas that are inundated during flood events. SPM was sampled in 2006 and more frequently in a flood event (August, 2007) at the river Rhine barrage of Iffezheim, Germany. SPM was GC-MS analyzed for hexachlorobenzene (HCB), several polychlorinated biphenyls (PCBs) as well as for polycyclic aromatic hydrocarbons (PAHs). Flood samples were fractionated applying a recently developed automated fractionation method to receive further insight into contaminant loads in flood SPM. Impacts on biological scale were assessed using in vitro biotests for xenometabolic 7-ethoxyresorufin-o-deethylase (EROD) assay as well as for mutagenic activity (Ames fluctuation assay). EROD induction was calculated as biological equivalent concentrations (bio-TEQs) and mutagenic potentials were shown as NOECs and maximum induction factors. Chemical analysis gave low concentrations of PCBs (2006 and 2007) and HCB (2006). HCB concentrations increased during the flood in 2007 (maximum, 110 µg/kg SPM). Concentrations of PCBs were only initially elevated in the flood (maximum, 67 µg/kg SPM). EROD induction bio-TEQs ranged from 1,160 to 6,640 pg/g SPM in 2006 and showed maximum bio-TEQ at the peak discharge in 2007. There was no mutagenic activity with SPM of both years. Fractionation indicated highest EROD induction in PAH fractions with prioritized (EPA-) PAHs contributing to less than 1% to the fractions total bio-TEQ but also fractions containing more polar-to-polar substances were shown to contribute minor. Furthermore, more polar fractions were mutagenic active with SPM sampled after the peak of discharge (IFmax = 14.7). Contaminants bound to flood SPM can be hazardous to inundated retention areas. Concentrations can be assumed to be increasing correlated with discharge and, thus, with more extreme flood events. Furthermore, biological effects are elevated or first place appearing with SPM from floods. Hazards have to be expected not only from persistent and non-polar substances but alike from less persistent and more polar ones that, furthermore, are more relevant evaluating hazards to drinking water resources from public well fields.