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Abstract:The investigation focuses on the analysis of dissolved sulfonamides, tetracyclines, analgesics, anticonvulsants and hormones in surface water. Runoff event and baseflow samples were analysed in two small river catchments of different land use in Luxembourg. For most of the flood events, similar pollutant loads to those transported during 1 day with average baseflow discharge were observed. The maximum contents during flood events and the event mean concentrations are controlled by preevent hydro-climatological conditions. For all substances under investigation, maximum concentrations and event mean concentrations show a decrease with raising antecedent rainfall. In addition, the interstorm and intrastorm variability of the pollutant transport was determined. Runoff generation and corresponding transport of xenobiotic compounds show a complex pattern with many interrelated processes, taking place within bedrock, soil, anthropogenic facilities and channel and in different parts of the basins under investigation. Different sources of pollutants can be identified and related to particular locations in the basin. The influence of the sewer systems is obvious. In the agricultural Mess basin, higher rainfall amounts lead to greater quantities of laterally inflowing soil water with higher concentrations of dissolved oxytetracycline. This originates from veterinary medicines administered to livestock and enters the environment through the application of organic fertilisers, especially by slurry that is applied to the fields.

In many cases, only selected well-known target chemicals are analysed and used for a comparison with biological effects. Predicting the environmental impact of different chemical compounds does often fail. Effects are the result of mixture toxicity of single chemicals and their degraded products, which can have different biological potency and bioavailability. In vitro toxicity or mechanism-based assays are used as screening tools, prior to extended evaluation in animals or natural populations, or even prior to chemical monitoring. This study illustrates the use of the yeast bioassay to investigate the presence of compounds or chemicals with estrogenic activity in wastewater and surface water in Luxembourg and compares results with chemical measurements. Although the approach described in this paper has already been published in many case studies before, it confirms earlier findings and it delivers results for Luxembourg where similar analyses have not been documented so far. By comparison of the biological signal in the yeast assay, expressed as estrogen equivalents, with available results by liquid chromatography-mass spectrometry for steroid hormones we could only obtain a similar ranking for the majority of samples with low or high estrogenic activity. Measurements can therefore only be used as a screening tool for estrogenic activity. Seasonal changes as apparent for chemical results in surface waters were confirmed in the yeast assay. Dissolved estrone is diluted by higher discharge in the rivers during winter containing larger amounts of unpolluted soil water and groundwater runoff.

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Near-to-nature stormwater management aims at replicating the quasi-natural local water balance and preserving the ecosystem's integrity of affected waters. Surface waters in the urban areas of Trier-Petrisberg are managed by a separate sewer system in conjunction with a complex retention system. To investigate the effect of this alternative rainwater management practice on the local water balance, a differentiated discharge and groundwater monitoring network with a high spatio-temporal measurement resolution has been implemented within the watershed. Additional information regarding the proportion and spatial distribution of discharge-generating surfaces was provided through visual interpretation of aerial photographs. As a result of this analysis, groundwater levels were found to not be significantly affected by an increase of local sealed surfaces, and the ecologically-justifiable maximum discharge in the tributary was infrequently exceeded. Regarding further building development and climate change, the hydrological load capacity of the retention basins will provide effective rainwater management, even with respect to increasing precipitation intensities and frequencies. Water Environ. Res., 84, 441 (2012).