Christoph Merz

Sulfide oxidation and sulfate reduction in a shallow groundwater system (Oderbruch Aquifer, Germany)

Abstract Detailed groundwater monitoring was carried out over a period of two years in an anoxic, river recharged aquifer of the Oderbruch polder, north-eastern Germany. Isotope data from wells located in a 5 km transect along the flow direction was used to determine sources and sinks of SO 4 2− in the aquifer. The SO 4 2− originates from river water infiltration and from oxidative dissolution of FeS 2 within the alluvial loam covering the aquifer sands. A change of confined hydraulic conditions near the river to unconfined conditions in the central polder effects the hydrochemistry of the aquifer. The confined areas are dominated by sulfate reduction. Increasing δ 34 S −SO 4 values suggest continuous but slow ( t 1/2 =50 years) sulfate reduction from the beginning of inflow onwards with δ 34 S −SO 4 values ranging from +1.8 to +44.7‰ versus CDT and an enrichment factor of −33‰. A zone with a strong sulfate depletion ( δ 34 S −SO 4 of up to +85.7‰) exists in a shallow microenvironment rich in solid-phase organic carbon between river and levee. In the unconfined areas of the central polder, a SO 4 2− plume with concentrations exceeding the original river water content indicates FeS 2 oxidation by O 2 and/or NO 3 − within the alluvial loam. The lowered δ 34 S −SO 4 value reflects the input of the isotopically lighter SO 4 2− from the sulfide.

Influence of organic material on mineralization processes in the Permian Kupferschiefer formation, Poland

Abstract The Permian Kupferschiefer horizon in Southwest Poland acted as a geochemical trap by accumulating metals from an ascending oxidizing brine. The hydrogen-rich organic material in the Kupferschiefer supplied sufficient reduction equivalents for the precipitation of base and precious metals from these brines by redox reactions. This is indicated by regular changes in the molecular composition of the extractable organic material in a set of samples collected from a 1.4 m thick horizon in a Polish mine. The degree of oxidation is shown to change drastically from the bottom to the top of the horizon. In the bottom section, saturated hydrocarbons are diminished and heteroaromatic systems containing oxygen and sulphur are enriched significantly; alkylated aromatic hydrocarbon abundances are relatively low. The ratio of phenanthrene/sum of methylphenanthrenes varies with the degree of oxidation. Spectral fluorescence measurements reveal an increase in fluorescence intensities of the extracts with increasing oxidation. Moreover, the green shift of fluorescence maxima is related to oxidation effects. Parallel to the intensity of oxidation, as observed from changes in the extractable organic matter, the content of copper and silver changes within the horizon. The results confirm that organic matter in sediments, under appropriate geological conditions, can play a significant role in ore formation processes.

Behavior of organophosphates and hydrophilic ethers during bank filtration and their potential application as organic tracers. A field study from the Oderbruch, Germany

The behavior of organophosphates and ethers during riverbank filtration and groundwater flow was assessed to determine their suitability as organic tracers. Four sampling campaigns were conducted at the Oderbruch polder, Germany to establish the presence of chlorinated flame retardants (TCEP, TCPP, TDCP), non-chlorinated plasticizers (TBEP, TiBP, TnBP), and hydrophilic ethers (1,4-dioxane, monoglyme, diglyme, triglyme, tetraglyme) in the Oder River, main drainage ditch, and anoxic aquifer. Selected parameters were measured in order to determine the hydro-chemical composition of both, river water and groundwater. The results of the study confirm that organophosphates (OPs) are more readily attenuated during bank filtration compared to ethers. Both in the river and the groundwater, TCPP was the most abundant OP with concentrations in the main drainage ditch ranging between 105 and 958 ng L(-1). 1,4-dioxane, triglyme, and tetraglyme demonstrated persistent behavior during bank filtration and in the anoxic groundwater. In the drainage ditch concentrations of 1,4-dioxane, triglyme, and tetraglyme ranged between 1090 and 1467 ng L(-1), 37 and 149 ng L(-1), and 496 and 1403 ng L(-1), respectively. A positive correlation was found for the inorganic tracer chloride with 1,4-dioxane and tetraglyme. These results confirm the possible application of these ethers as environmental organic tracers. Both inorganic and organic compounds showed temporal variability in the surface- and groundwater. Discharge of the river water, concentrations of analytes at the time of infiltration and attenuation were identified as factors influencing the variable amounts of the analytes in the surface and groundwater. These findings are also of great importance for the production of drinking water via bank filtration and natural and artificial groundwater recharge as the physicochemical properties of ethers create challenges in their removal.

Funktionalanalyse versus Trendanalyse zur Abschätzung anthropogener Einflüsse auf Grundwasserganglinien

ZusammenfassungAls erster Schritt zur Abschätzung eines etwaigen negativen anthropogenen Einflusses auf den quantitativen Zustand des Grundwassers wird in der Europäischen Wasserrahmenrichtlinie empfohlen, eine Trendanalyse durchzuführen. In der Praxis stößt dieser Ansatz auf erhebliche Probleme und wurde deshalb in dieser Studie überprüft. Der weit verbreitete Mann-Kendall-Test berücksichtigt nicht die Wechselwirkungen zwischen Trends und der Autokorrelation der Daten, wie sie gerade für Grundwasserganglinien typisch sind. Dadurch kam es zu einer massiven Überschätzung der Signifikanz der beobachteten Trends. Signifikanz, Stärke und Vorzeichen der Trends hingen sehr stark von dem jeweils gewählten Zeitraum ab.Dagegen lieferte die als Alternative hier vorgestellte Funktionalanalyse auf Basis einer Hauptkomponentenanalyse von Ganglinien für verschiedene Zeiträume fast identische Werte. Abweichungen beobachteter Ganglinien von dem regionstypischen Verhalten konnten quantitativ erfasst werden, um Art, Zeitraum und Stärke des anthropogenen Einflusses auf die beobachteten Ganglinien zu erfassen. Der rechnerische und datentechnische Aufwand dieses Verfahrens ist vergleichbar mit dem der Trendanalyse.AbstractThe European Water Framework Directive recommends investigating trends in groundwater head time series by means of trend analysis in order to assess possible harmful anthropogenic impacts. This approach encounters substantial problems. Usually the Mann-Kendall test is applied which does not consider interactions between trends and auto-correlation in the data. These are very common in groundwater head time series. As a consequence, trend significance has been substantially overestimated. In addition, significance, magnitude and trend sign depend strongly on the selected time span. A functional analysis based on a principal component analysis of groundwater head time series was introduced as an alternative. It yielded very robust results, independent from the selected periods. To determine anthropogenic impacts on groundwater heads, deviations of observed data from the expected behaviour could be investigated. Data requirements and the computational effort of this approach are about the same compared to trend analysis.

Forensic hydrology: what function tells about structure in complex settings

Abstract Facing the challenges of the European Water Framework Directive and competing demands requires a sound knowledge of the hydrological system. This is a major challenge in regions like Northeast Germany. The landscape has been massively reshaped during repeated advances and retreats of glaciation during the Pleistocene. This resulted in a complex setting of unconsolidated sediments with high textural heterogeneity and with layered aquifer systems, partly confined, but usually of unknown number and extent of single aquifers. The Institute of Landscape Hydrology aims both at a better understanding of hydrological processes and at providing a basis for sustainable water resources management in this region. That would require sound information about the respective regions of interest that are rarely available at sufficient degree of detail. Thus, there is urgent need for alternative approaches. For example, time series of groundwater head, lake water level and stream runoff do not only depend on (unknown) geological structures, but in turn can reveal information about major geological features. To that end, different approaches have been developed and successfully applied at different scales, based both on advanced time series analysis and dimension reduction approaches and on well-known and rather simple methods. This approach has been coined “forensic hydrology”: Like in a crime story, numerous pieces of evidence are combined in a systematic way to end up with a consistent conceptual model about the prevailing cause–effect relationships. An example is given for the Quillow catchment in Northeast Germany in a rather complex geological setting.

A review on missing hydrological data processing

Like almost all fields of science, hydrology has benefited to a large extent from the tremendous improvements in scientific instruments that are able to collect long-time data series and an increase in available computational power and storage capabilities over the last decades. Many model applications and statistical analyses (e.g., extreme value analysis) are based on these time series. Consequently, the quality and the completeness of these time series are essential. Preprocessing of raw data sets by filling data gaps is thus a necessary procedure. Several interpolation techniques with different complexity are available ranging from rather simple to extremely challenging approaches. In this paper, various imputation methods available to the hydrological researchers are reviewed with regard to their suitability for filling gaps in the context of solving hydrological questions. The methodological approaches include arithmetic mean imputation, principal component analysis, regression-based methods and multiple imputation methods. In particular, autoregressive conditional heteroscedasticity (ARCH) models which originate from finance and econometrics will be discussed regarding their applicability to data series characterized by non-constant volatility and heteroscedasticity in hydrological contexts. The review shows that methodological advances driven by other fields of research bear relevance for a more intensive use of these methods in hydrology. Up to now, the hydrological community has paid little attention to the imputation ability of time series models in general and ARCH models in particular.

Ephemeral kettle hole water and sediment temporal and spatial dynamics within an agricultural catchment

1 Institute of Landscape Biogeochemistry, Leibniz Center for Agricultural Landscape Research (ZALF), Eberswalder Str. 84, 15374 Muencheberg, Germany Department of Soil and Water Systems, University of Idaho, 875 Perimeter Ave, Moscow, ID 83843, USA Beuth University of Applied Sciences, Luxemburger Str. 10, 13353 Berlin, Germany Federal Institute for Geosciences and Natural Resources (BGR), Stilleweg 2, 30655 Hanover, Germany 5 Institute of Landscape Hydrology, Leibniz Center for Agricultural Landscape Research (ZALF), Eberswalder Str. 84, 15374 Muencheberg, Germany 6 Institute of Geological Sciences, Workgroup Hydrogeology, Freie Universität Berlin, Malteserstr. 74‐100, D‐12249 Berlin, Germany Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zuercherstrasse 111, 8903 Birmensdorf, Switzerland Berlin‐Brandenburg Institute of Advanced Biodiversity Research (BBIB), 14915 Berlin, Germany Correspondence Zachary E. Kayler, Department of Soil and Water Systems, University of Idaho, 875 Perimeter Ave, Moscow, ID 83843, USA. Email: zkayler@uidaho.edu Present Address Research Institute for Humanity and Nature (RIHN), 457‐4 Motoyama, Kamigamo, Kita‐ku, Kyoto 603‐8047, Japan Funding information Bundesministerium für Bildung und Forschung, Grant/Award Number: 01LC1406E BASIL

Einfluß mikrobieller Aktivitäten auf die Migrationseigenschaften redox-sensitiver Elemente (Technetium und Selen)

Technetium (Tc) ist das leichteste Element des Periodensystems der Elemente, das nur in Form radioaktiver Isotope existiert. In nennenswerten Mengen entsteht Tc heute nur im Brennstoffkreislauf von Kernkraftwerken (Tc-99) und es wird fur die medizinische Diagnostik hergestellt (Tc-99m). Tc-99 hat, bezogen auf die Endlagersicherheit, zwei ungunstige Eigenschaften: a) eine Halbwertzeit von 213 000 Jahren und b) in oxidierter Form als Pertechnetat (TcO4 -) ist Technetium sehr mobil. Es wurde fruher sogar als Tracer in der Hydrogeologie verwendet. In der reduzierten Form (vierwertig) ist Tc sehr immobil und wird ausgefallt. In fruheren Untersuchungen zum Migrationsverhalten von Technetium und Selen (bei spezieller Berucksichtigung des Tc) wurde eine starke Tc-Festlegung gemessen, die durch thermodynamische Vorgange nicht erklarbar war (Bruhl et al. 1991). In diesen Laborexperimenten konnte eine mit der Zeit zunehmende Fixierung des Tc, auch unter oxidierenden Bedingungen, beobachtet werden. Das Transportverhalten von redox-sensitiven Elementen wie Tc und Se wird also nicht ausschlieslich durch thermodynamische “Rahmenbedingungen” gesteuert, wie sie im Ma-kromilieu mit Sonden gemessen werden konnen, sondern zu einem grosen Anteil durch Mikromilieus und mikrobiellen Metabolismus (Winkler 1989; Henrot 1989; Pignolet et al. 1986; Schulte u. Scoppa 1987). Eine Festlegung kann durch Mikromilieus verursacht werden, die ihrerScits beeinflust oder erzeugt werden durch bakterielle Aktivitaten auf Partikeloberflachen oder in Biofilmen.