Olav Hillebrand

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.

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.

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 worlds 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.

Potenziale der Nutzung organischer Spurenstoffe als Indikatoren in Grundwasserleitern

ZusammenfassungDie Bewertung von Risiken für die Trinkwasserversorgung erfordert eine grundlegende hydrogeologische Modellvorstellung des Einzugsgebiets. Aufgrund der großen Heterogenität ist in Kluft- und Karstgrundwasserleitern die Anwendung ergänzender hydrogeochemischer Methoden unumgänglich. Die Aussagekraft und Anwendbarkeit der üblicherweise genutzten künstlichen Markierungsstoffe, Umwelttracer oder stabilen Isotope ist häufig limitiert. Eine Vielzahl von Studien belegt die Anwesenheit von anthropogenen organischen Verbindungen wie Pestiziden, Arzneimitteln, Rostschutzmitteln oder auch Koffein im Nano- bis Mikrogramm-pro-Liter-Bereich im Grundwasser. Dieser Beitrag zeigt beispielhaft, wie das Vorkommen sowie die Konzentrationsverteilung organischer Spurenstoffe die hydrogeologischen Eigenschaften von Grundwasserleitern reflektieren und diese damit für die Beantwortung bestimmter hydrogeologischer Fragestellungen herangezogen werden können.AbstractRisk assessment for drinking water requires a conceptual hydrogeological model of the catchment as well as an understanding of flow pathways, residence times and processes on the catchment scale. In fractured and karst aquifers, this is a challenging task, in part because the application of artificial tracers, environmental tracers or stable isotopes for understanding processes on the catchment scale is limited. Recently, a large number of organic compounds with different properties in very small concentrations have been detected in groundwater, including pesticides, pharmaceuticals, corrosion inhibitors and caffeine. In this article, we use a case study to demonstrate the potential of employing these compounds as indicators to reflect selected aquifer characteristics and properties, and to answer specific questions on the hydrogeological system.

Charakterisierung zweier Karstsysteme mithilfe organischer Spurenstoffe

ZusammenfassungIn der vorliegenden Arbeit wird das Auftreten organischer Spurenstoffe in zwei hinsichtlich der geologischen Verhältnisse und der Flächennutzung unterschiedlichen Karstgebieten diskutiert.In einem urban geprägten, moderat verkarsteten Quelleinzugsgebiet mit einer hohen Anzahl lokaler Eintragsquellen (beispielsweise Altlasten, Kanalleckagen) ist gegenüber einem landwirtschaftlich dominierten Gebiet das Spektrum der gefundenen Stoffe breiter. Die Konzentrationen der meisten dieser Stoffe nehmen auf der Fließstrecke zu den Quellaustritten bis unter die Bestimmungsgrenzen ab und können daher nur über ein flächendeckendes Messstellennetz erfasst werden. In den Quellen finden sich vorwiegend Stoffe, die entweder durch eine weite rezente Anwendungsverbreitung oder hohe Persistenz charakterisiert sind.In der Quelle eines stärker verkarsteten und somit höher durchlässigen Grundwasserfließsystems werden zeitlich variierend auch biologisch leicht abbaubare Substanzen detektiert. Aufgrund hoher Fließgeschwindigkeiten erfordern Untersuchungen dieses Fließsystems ein zeitlich hochaufgelöstes Monitoring organischer Spurenstoffe.Somit haben neben den jeweiligen Stoffeigenschaften auch die hydrogeologischen Systemcharakteristika erheblichen Einfluss auf das Spektrum der nachweisbaren Stoffe.AbstractIn the presented work the occurrence of organic micro-pollutants is discussed for two karst areas with different geological characteristics and land-use patterns.Within an urban moderately karstified catchment with a large number of local input sources (e.g. contaminated sites, sewer leakages), a greater variety of micro-pollutants is found compared to a rural area. Mostly the concentrations of these compounds decrease below quantification limits before emerging at the spring and can therefore only be detected by a comprehensive network of sampling points. Springs show the presence of micro-pollutants, either recently applied in large amounts or characterized by high persistence.At the outlet of a highly karstified and consequently highly permeable aquifer readily biodegradable compounds are detected. Due to high groundwater flow velocities investigations of micro-pollutants require a highly resolved monitoring.Therefore, beside substance properties, also hydrogeological characteristics affect the spectrum of detectable micro-pollutants.