Gefährdung des Grundwassers durch Freisetzung organischer Schadstoffe: Methoden zur Berechnung der in-situ-Schadstoffkonzentrationen

The release of pollutants from contamined soils can be due to desorption and dissolution from residual phase blobs or pools. Volatile compounds can diffuse from contaminated soil air into the groundwater. This paper discusses the basic release processes and presents methods for the calculation of the rates of desorption, dissolution and diffusion. These rates are a prerequisite for the determination of the in-situ contaminant concentration in groundwater. The necessary parameters can be estimated from empirical correlations or may be measured directly in laboratory experiments. Column experiments, e. g., yield maximum release rates in the case of slow diffusion limited desorption whereas dissolution of contaminants from blobs of residual phase results in maximum concentration (solubility) in the column effluent.     

Abschätzung der Subsidenz im Einflussbereich Geothermischer Anlagen

The estimate of possibly occurring subsidence within the vicinity of geothermal heating plants is indispensable for the judgement of their operational safety and environmental impact. In this study exploitation of a sandstone aquifer using a production and re-injection well was examined with the groundwater simulation program MODFLOW ( Harbaugh &; McDonald 1996) and the accompanying Interbed-Storage-Package ( Leake &; Prudic 1991). Parameter studies of a typical northern German geothermal aquifer showed that the hydraulic characteristics of the clay stone layer, which is sensitive to subsidence, have little influence on the absolute values of the subsidence. In contrast thereto, the hydraulic characteristics of the geothermally used sandstone layer have great impact on the subsidence. Subsidence will be on no account within the magnitude of meters, but most likely in the range of centimeters (2–3 cm), for both the production and the re-injection well. The results are in agreement with field observations.     

Abschätzung der horizontalen Bettung mittels dynamischer Pfahlprüfung

Estimation of the horizontal subgrade reaction by means of dynamic pile testing. Considering monopile foundations for offshore wind power plants as example a dynamic procedure for the determination of the dynamic subgrade reaction is presented (H-DPT: Horizontal-Dynamic Pile Testing). With the aid of diagrams it is possible to deriv e the modulus of subgrade reaction by the measured oscillation period. Afterwards the first natural frequency of the entire offshore wind power plant can be evaluated by further diagrams.     

Grundwassermodellierung zur Gefährdungsabschätzung eines phenolverseuchten Tagebaurestsees

For decades the open-pit mining lake Vollert-South in Saxony-Anhalt was filled with phenolic wastewater from lignite smouldery. In the groundwater downstream of the lake, used for drinking water, measurements indicated up to 1 mg/l phenol and 15 mg/l ammonium, which is far above drinking water limits. Nevertheless the monitored phenol plume effects only a small area. A three-dimensional groundwater flow model with mass transport was developed to determine the phenol input and to estimate natural attenuation due to sorption and microbial decay. Besides the dilution due to dispersion the microbiological decay plays the most decisive part. Sorption is only of minor importance. A prognosis until 2030 as a worst-case scenario shows no direct danger to the groundwater despite the huge potential of pollution by the lake Vollert-South. The phenol plume will not exceed a length of 250 m. There-fore an active remediation of the groundwater seems not to be necessary.     

Zur Absch?tzung von W?rmeleitf?higkeiten der oberfl?chennahen Lockergesteinsschichtenfolge in Norddeutschland

In the course of a groundwater investigation program in east Schleswig-Holstein, groundwater temperature measurements were performed in groundwater observation wells. First, the heat flux density of the investigation area was determined. The heat flow ranged from 20 to 77?mW?m^?2. Near the boundaries of the area, subsurface salt structures cause an increase in heat flow to the earth’s surface. In the centre of this region the heat flow is due to convective processes, and is somewhat low. Here the groundwater recharge as well as the influx from top to bottom affects the temperature field. By means of heat flux densities and the measured temperature gradients, the thermal conductivity was estimated. For clays in the study area the thermal conductivity averaged 1.4?W?m^?1?K^?1 ranging between 1.1 and 1.7?W?m^?1?K^?1. For the coarse grained sand the conductivity was 3.0?W?m^?1?K^?1 and for the fine sands it was 2.8?W?m^?1?K^?1. Due to its heterogeneity, the thermal conductivity of the till ranged between 1.6 and 2.8?W?m^?1?K^?1, depending on the mineralogical composition, the bulk density and the water content of the till. The average thermal conductivity was 2.1?W?m^?1?K^?1.     

Herkunft der Salinität in Tiefenwässern des Grundgebirges – unter besonderer Berücksichtigung der Kristallinwässer des Schwarzwaldes

Deep groundwater in fractured crystalline basement has been reported from deep mines and scientific wells. Highly saline brines have been described from several km depth in the continental basement worldwide. The origin of salinity is unknown and many different possibilities have been presented ( Emmermann et al. 1995, Pauwels et al. 1993, Edmunds &;: Savage 1991, Frape &;: Fritz 1987, Kozlovsky 1984, Banks et al. 1996, Stober 1986, 1995, Kanz 1987, Stober &; Bucher 1999). We compare the compositional evolution of deep waters in the Black Forest basements, SW-Germany, with those of other deep crystalline waters and use the halogen systematics (e. g. Cl/Br ratios) and other parameters of the waters to deduce the origin of their salinity. In teh Black Forest the composition of deep thermal waters results from chemical interaction of surface water with the rock matrix and from mixing of the reacted water with stagnant saline deep water of marine origin.     

Isotopenphysikalische Beiträge zur Beurteilung des Grundwasserschutzes im Buntsandstein

The complex application of isotope physical measuring methods together with model calculations for groundwater flow and hydrochemistry is helpful to estimate groundwater vulnerability. Thereby Tritium is used as a natural tracer of local groundwater input indicating a possible groundwater vulnerability, and the far-reaching, long-term groundwater migration is derived from Carbon-14 ages of dissolved inorganic carbon. For the case “double-porosity aquifer (Finne Bunter Sandstone, Saxonia-Anhalt)” the derivation of hydrogeological parameters as groundwater recharge, groundwater flow and the water exchange rate of an aquifer is demonstrated. Especially information on the groundwater vulnerability can be obtained without any real groundwater contamination.     

Eine Sensitivitätsanalyse zur Berechnung der Grundwasserneubildung aus Niederschlag

Input data for the calculation of groundwater recharge show natural variations. Thus their estimation is coupled with appropriate uncertainties. The resulting error for the values of groundwater recharge can be estimated by sensitivity analysis. The possible maximum range of variation of input data in most cases an be derived from published data. The factors most sensitive for the procedure are precipitation, as well as evapotranspiration and interception, when the portion of wood at land use is significant.     

Missstände bei der Vollziehung des Baurechts. Aktuelle Fälle aus der Volksanwaltschaft 2007

Aufgabe der Volksanwaltschaft ist es, auf Grund von Beschwerden oder von Amts wegen Missst?nde in der Verwaltung des Bundes und – auf der Grundlage landesverfassungsrechtlicher Erm?chtigungen (Bgld, Krnt, N?, O?, Sbg, Stmk, Wien) – der L?nder einschlie?lich des eigenen Wirkungsbereichs der Gemeinden zu prüfen. In diesem Zusammenhang hat die Volksanwaltschaft auch wichtige, praxisrelevante Rechtsfragen des Baurechts zu kl?ren. Die Ergebnisse sollen ein- bis zweimal pro Jahr bundesl?nderweise und in Leitsatzform dokumentiert werden.     

Markierungsversuche und Modellierung zur Bewertung der Gefährdung eines Trinkwasserbrunnens

A tracer experiment with uranine in a gravel aquifer aimed to assess the risk of a drinking water well near Pratteln, Switzerland, resulting from a contaminated site 760?m further upgradient. The experiment revealed a maximum linear flow velocity of 127?m/d and a mass recovery of 0.93?%. The tracer was also detected at two intermediate monitoring wells. This paper discusses the causes of this high flow velocity. Three different analytical models allowed simulation of the breakthrough curves and determination of transport parameters. A two-dimensional numerical model (FEFLOW) with simplified geometry provided a hydrogeologically consistent and probable explanation of all results. The aquifer is most likely relatively homogeneous, the steep hydraulic gradient (6?‰) and high conductivity (3?·?10^–2?m/s) cause high flow velocities, and most of the tracer passed northeast of the wells. Recently conducted small scale pumping tests largely confirmed this conceptual model. These findings should be considered for future protection measures.     

Ein neues Verfahren zur Berechnung des räumlichen passiven Erddrucks vor Trägern

A calculation method for the spatial passive earth pressure acting on girders. This paper presents a calculation method for vertical girders in cohesionsless soils. Measurements on buildings and model experiments are the basis. The Distinct Element Method (DEM) was extended and improved to enable the numerical simulation of load tests. Based on this knowledge, conditions not covered by experiments was simulated by means of the DEM. Accordingly, the test matrix could be extended. With the results of these simulations a new calculation method was derived.     

Anwendung des Neutralisationspotenzials bei der Bilanzierung von Säure-Base-Reaktionen im Umfeld des Braunkohlebergbaues

Acidic conditions of seepage and groundwater originating from open pit minings in Lusatia are described using the neutralization potential, which is based on the concept of acidity. Acid formation and buffer reactions can be reduced to three elemental reactions: oxidation of pyrit/reduction of sulfate, dissolution of carbonate and gypsum equilibrium. These reactions are combined in a genetic model in order to interpret the origin of mineral and acid contents of different groundwaters influenced by lignite mining. The statistical results of these calculations are summarised in order to calibrate parameters of a prognostic model. The method described here is used to prepare restoration measures.     

Missstände bei der Vollziehung des Baurechts. Aktuelle Fälle aus der Volksanwaltschaft 2008/1

Aufgabe der Volksanwaltschaft ist es, auf Grund von Beschwerden oder von Amts wegen Missst?nde in der Verwaltung des Bundes und – auf der Grundlage landesverfassungsrechtlicher Erm?chtigungen (Bgld, Krnt, N?, O?, Sbg, Stmk, Wien) – der L?nder einschlie?lich des eigenen Wirkungsbereichs der Gemeinden zu prüfen. In diesem Zusammenhang hat die Volksanwaltschaft auch wichtige, praxisrelevante Rechtsfragen des Baurechts zu kl?ren. Die Ergebnisse sollen ein- bis zweimal pro Jahr bundesl?nderweise und in Leitsatzform dokumentiert werden.     

Modellansätze zur langfristigen Entwicklung der Grundwasserqualität im Bourtanger Moor (Emsland)

Agricultural activities and atmospheric acid deposition are responsible for a significant decline of shallow groundwater quality in the Bourtanger Moor area near the German city Haren (Ems). The main indicators of acidification are low soil and groundwater pH and elevated aluminium concentrations. Agricultural nutrient concentrations, e. g. for potassium and nitrate commonly exceed drinking water limits. Polluted water has partially reached deeper layers where drinking water wells are screened. Contaminant spreading is retarded due to geochemical interactions with reactive aquifer material. Cation exchange and autotrophic denitrification are the main processes. Mass balance calculations, colums experiments and hydrogeochemical modelling show that the vertical propagation velocities of the contaminants are in the range of several centimetres per year.     

Tiefengestaffeltes Wasserprobennahmesystem zur spezifischen Beprobung der ungesättigten Zone, dem Kapillarsaum und der gesättigten Zone

Flow and transport processes in the transition area between the unsaturated and the saturated zone can influence the quality and properties of the groundwater. Special hydraulic properties have to be considered throughout the entire transition zone, which is a physically and bio-chemically highly active reaction chamber. Using the available measuring techniques, the present processes cannot be fully comprehended or, on the other hand, require significant effort. Thus, the influence of the transition zone is often neglected (Ronen and Sorek, The Unsaturated Zone—A Neglected Component of Nature. Water Quality Division, Israel Water Commision, Tel-Aviv, 2005). Utilizing laboratory experiments and numerical simulations, an innovative concept for a depth-specific measuring technique was evaluated. Results show that with some modifications of the actual design, the device is capable of sampling the entire transition zone between the unsaturated and the saturated zone, including the capillary fringe, with high temporal and spatial resolution.