Multitracer experiment to evaluate the attenuation of selected organic micropollutants in a karst aquifer

The increasing pressure on drinking water resources necessitates an efficient management of potential and actual drinking water resources. Karst aquifers play a key role in the supply of the world's population with drinking water. Around one quarter of all drinking water is produced from these types of aquifers. Unfortunately due to the aquifer characteristics with extremely high hydraulic conductivities and short residence times, these systems are vulnerable to contamination. For successful management, a fundamental understanding of mass transport and attenuation processes with respect to potential contaminants is vital. In this study, a multitracer experiment was performed in a karst aquifer in SW-Germany for determining the attenuation capacity of a karst environment by assessing the environmental fate of selected relevant micropollutants. Uranine, acesulfame and carbamazepine were injected into a sinkhole as reference tracers together with the reactive compounds atenolol, caffeine, cyclamate, ibuprofen and paracetamol (also known as acetaminophen). The breakthrough of the tracers was monitored at a karst spring at a distance of ca. 3 km. The breakthrough curves of the reactive compounds were interpreted relative to the reference substances. No significant retardation was found for any of the investigated micropollutants. The determined half-lives of the reactive compounds range from 38 to 1,400 h (i.e. persistent within the investigation period) in the following order (from high to no observed attenuation): paracetamol>atenolol≈ibuprofen>caffeine≫cyclamate. The attenuation rates are generally in agreement with studies from other environmental compartments. The occurrence of the biotransformation product atenolol acid served as evidence for in-situ biodegradation within the aquifer system.

Investigating the dynamics of two herbicides at a karst spring in Germany: Consequences for sustainable raw water management

While karst aquifers are considered as rapid flow and transport systems, their high potential for long-term storage is often ignored. However, to achieve a sustainable raw water quality for drinking water production, the understanding of this potential is highly essential. In this study, the transport dynamics of the two herbicides metazachlor and atrazine as well as a degradation product of the latter (desethylatrazine) were investigated at a karst spring over 1 year. Even 20 years after its ban in Germany, atrazine and its degradation product were almost always detectable in the spring water in the low ng L(-1) range (up to 5.2ng L(-1)). Metazachlor could only be detected after precipitation events, and the observed concentrations (up to 82.9ng L(-1)) are significantly higher than atrazine or desethylatrazine. Comparing the dynamics of the herbicides with the inorganic ions Ca(2+), Mg(2+) and electrical conductivity, a positive correlation of atrazine with these parameters could be observed. From this observation, atrazine is concluded to be located within the aquifer matrix. To achieve a sustainable raw water management at karst springs, the rapidness of these systems needs to be highlighted as well as their long-term storage potential. Persistent substances or transformation products are prone to deteriorate the raw water quality for decades.

Occurrence and fate of the angiotensin II receptor antagonist transformation product valsartan acid in the water cycle--a comparative study with selected β-blockers and the persistent anthropogenic wastewater indicators carbamazepine and acesulfame

The substantial transformation of the angiotensin II receptor antagonist valsartan to the transformation product 2'-(2H-tetrazol-5-yl)-[1,1'-biphenyl]-4-carboxylic acid (referred to as valsartan acid) during the activated sludge process was demonstrated in the literature and confirmed in the here presented study. However, there was a severe lack of knowledge regarding the occurrence and fate of this compound in surface water and its behavior during drinking water treatment. In this work a comparative study on the occurrence and persistency of valsartan acid, three frequently used β-blockers (metoprolol, atenolol, and sotalol), atenolol acid (one significant transformation product of atenolol and metoprolol), and the two widely distributed persistent anthropogenic wastewater indicators carbamazepine and acesulfame in raw sewage, treated wastewater, surface water, groundwater, and tap water is presented. Median concentrations of valsartan acid in the analyzed matrices were 101, 1,310, 69, <1.0, and 65 ng L(-1), respectively. Treated effluents from wastewater treatment plants were confirmed as significant source. Regarding concentration levels of pharmaceutical residues in surface waters valsartan acid was found just as relevant as the analyzed β-blockers and the anticonvulsant carbamazepine. Regarding its persistency in surface waters it was comparable to carbamazepine and acesulfame. Furthermore, removal of valsartan acid during bank filtration was poor, which demonstrated the relevance of this compound for drinking water suppliers. Regarding drinking water treatment (Muelheim Process) the compound was resistant to ozonation but effectively eliminated (≥90%) by subsequent activated carbon filtration. However, without applying activated carbon filtration the compound may enter the drinking water distribution system as it was demonstrated for Berlin tap water.

The challenge of sample-stabilisation in the era of multi-residue analytical methods: a practical guideline for the stabilisation of 46 organic micropollutants in aqueous samples

Water sample storage and stabilisation may affect data quality, if samples are managed improperly. In this study three stabilising strategies are evaluated for 46 relevant organic micro-pollutants: addition of the biocides (i) copper sulphate and (ii) sodium azide to water samples directly after sampling with subsequent sample storage as liquid phase and (iii) direct solid phase extraction (SPE), stabilising the samples by reducing the activity of water. River water and treated effluent were chosen as commonly investigated matrices with a high potential of biotransformation activity. Analyses were carried out for sample storage temperatures of 4 and 28°C for water samples stored as liquid phase and for sample storage temperatures of 4, 20 and 40°C for SPE cartridges. Cooling of water samples alone was not sufficient for longer storage times (>24h). While copper sulphate caused detrimental interferences with nitrogen containing heterocyclic compounds, sodium azide proved to be a suitable stabilising agent. The best results could be obtained for SPE cartridges stored cool. Recommendations for samples preservation are provided.

Identification of the attenuation potential of a karst aquifer by an artificial dualtracer experiment with caffeine

Little is known with respect to the attenuation capacity of karst aquifers. Even less is known about the risk posed by emerging micropollutants in these systems. In order to identify the attenuation potential of karst aquifers in-situ and to estimate the risk posed by micropollutants, a dualtracer test was conducted in this study in order to investigate differential transport in the subsurface: The reactive compound caffeine was used as a tracer to indicate the attenuation capacity within the aquifer in-situ. Due to the low limit of quantification, only small amounts of caffeine needed to be injected. To calibrate a model and to visualize the attenuation of caffeine a conservative reference tracer (uranine) is injected simultaneously. The methodology is tested in a well-characterised karst system in southwest Germany. The results indicate a significantly higher attenuation rate than was expected for karst aquifers. The attenuation is decribed as a first-order process. The corresponding half-life is 104 h. This low half-life suggests that a generally assumed low natural attenuation capacity of karst aquifers is unjustified. The observed mass loss of caffeine illustrates the potential of caffeine to be used as reactive tracer for indicating in-situ attenuation capacity within highly hydraulically conductive systems, such as karst aquifers. Due to the high attenuation rate of caffeine it does not pose a threat as a long-time contaminant. In combination with a conservative reference tracer an economical and environmentally benign method is presented in this manuscript for the in-situ determination of the attenuation capacity of highly conductive aquifer systems.

Caffeine as an indicator for the quantification of untreated wastewater in karst systems

Contamination from untreated wastewater leakage and related bacterial contamination poses a threat to drinking water quality. However, a quantification of the magnitude of leakage is difficult. The objective of this work is to provide a highly sensitive methodology for the estimation of the mass of untreated wastewater entering karst aquifers with rapid recharge. For this purpose a balance approach is adapted. It is based on the mass flow of caffeine in spring water, the load of caffeine in untreated wastewater and the daily water consumption per person in a spring catchment area. Caffeine is a source-specific indicator for wastewater, consumed and discharged in quantities allowing detection in a karst spring. The methodology was applied to estimate the amount of leaking and infiltrating wastewater to a well investigated karst aquifer on a daily basis. The calculated mean volume of untreated wastewater entering the aquifer was found to be 2.2 ± 0.5 m(3) d(-1) (undiluted wastewater). It corresponds to approximately 0.4% of the total amount of wastewater within the spring catchment.

[Data processing the the RAST laboratory]

We describe a clinical laboratory information system for the RAST laboratory based on personal computers. In developing this system, we paid special attention to easy handling which does not require any computer experience on the user's side. Data storage and retrieval are managed by a relational database system with fast data access. Aside from the usual functions of a laboratory information system, the laboratory work is facilitated by a clear distribution of samples, the possible on-line connection to various analyzers, as well as the provision of cumulative results and a fast access to archive data.