elliptical inhomogeneities in groundwater flow an analytical description abstract in order to be able to decide whether and how heterogeneities should be taken into account for modelling a groundwater flow problem the magnitude of those disturbances must be estimated therefore in this paper we solve the problem of a uniform flow in a homogeneous medium with an elliptical shaped inhomogeneity with a different value for the permeability and positioned under an arbitrary angle with respect to the undisturbed flow we calculate the ratio of the flow rate through this body with respect to the undisturbed case besides its use in solving groundwater flow problems this formula may be helpful for problems relevant to field reconnaisance

migration of contaminants in groundwater at a landfill a case study 3 tritium as an indicator of dispersion and recharge abstract since the beginning of the era of major atmospheric tests of nuclear weapons in 1953 rain and snow has contained concentrations of 3 h that have been above the natural levels that existed prior to 1953 as a consequence 3 h now serves as an identifier or tracer of post 1952 water in groundwater flow systems in this study the distribution of 3 h in and near the contaminant plume at the borden landfill was determined by analysis of samples from multilevel point samplers and from bundle piezometers the contaminant plume which was delineated using cl and so 2 4 patterns was found to contain a large zone of tritiated water and a smaller zone with no detectable 3 h much of the zone of untritiated water exists in the frontal segment of the plume this is consistent with the fact that landfilling operations at the site began in 1940 and that as the plume developed in the period from 1940 to 1952 any natural 3 h that may have existed in the plume during this period is now below the detection level an estimate of the 3 h concentrations in water that has recharged the aquifer beneath the landfill was developed using the nearly continuous record for 3 h in precipitation at ottawa ontario with comparisons to less frequent data from other sampling stations the ottawa record indicates that during the years in the 1960 s in which peak 3 h concentrations occurred values of thousands of tu in precipitation were common and levels of many hundreds of tu or higher existed almost continuously in the zone of tritiated water in the plume and in the tritiated zone in the natural groundwater up and downgradient of the plume all of the sample points except three in the plume had concentrations below 150 tu two of these three have concentrations below 290 tu the general occurrence in the aquifer of 3 h levels that are much below the high levels that existed in precipitation prior to the 1970 s is attributed to radioactive decay and to the effect of longitudinal hydrodynamic dispersion that has caused mixing of the tritiated groundwater with older untritiated water an analytical solution to the one dimensional form of the advection dispersion equation was used with the method of superposition to simulate the distribution of 3 h along the central flow path in the contaminant plume simulated 3 h distributions using longitudinal dispersivity values in the range of 30 60 m gave 3 h distributions similar to the field values although the longitudinal dispersivity range of 30 60 m is far above the range reported from laboratory experiments on sand and although it is much above the range obtained in a small scale tracer test at the borden site it is within the range reported in the literature based on the calibration of models to regional contaminant migration patterns in glaciofluvial or alluvial aquifers the strong longitudinal dispersion is believed to be caused by mixing between the ubiquitous layers of fine and medium grained sand and silty sand that comprise the aquifer an estimate of the average annual rate of recharge that has contributed to the groundwater zone beneath the landfill during the bomb tritium period was obtained by comparing the input of 3 h to an area segment of the landfill with the 3 h contained within a groundwater flow tube leading from the specified area along the centerline of the contaminant plume this approach yielded a minimum average annual recharge rate of 50 with the main cause of uncertainty being the extent of the area in which recharge occurs

borehole dilution tests in the vicinity of an extraction well abstract a mathematical solution is derived for a borehole dilution test conducted in the proximity of an extraction well under conditions where the theis assumptions are applicable the solution is similar to the steady state velocity case except for a factor that accounts for the transient response of the aquifer to pumping curves calculated from the derived solution show a delay in response that increases with the specific storage of the aquifer and with the radius from the extraction well the delay decreases with increasing values of hydraulic conductivity and aquifer thickness deviations of the response curves from the straight line steady state velocity case can be used to calculate the hydraulic diffusivity while the limiting slope at late time can be used to calculate groundwater flux when borehole dilution tests are conducted at several intervals over the thickness of the aquifer under steady state velocity conditions k z can in principle be calculated using several equations depending on the type of information available two existing methods to account for the distortion of the flow lines near the open test interval are related to well construction and development reasonable estimates of borehole factors can only be obtained for minimally developed wells

geostatistical analysis of the borden aquifer hydraulic conductivity field abstract a total of 11 vertical cores spaced 1 m apart along a single transect were extracted from the borden aquifer at a location 60 m north northeast from the site studied by sudicky previously examination of these cores shows the upper 1 5 2 0 m of the aquifer to be comprised of relatively unstructured fine to medium sands underlain by a 0 1 0 8 m thick peaty layer and a 0 1 m thick organic rich horizon between depths of 3 05 and 6 10 m the aquifer is comprised of clean horizontally bedded fine to medium sands similar to those examined by sudicky previously statistical analysis of 642 subsamples of 5 cm length from this interval suggests that the permeability data may follow a log normal distribution with a mean lntransformed permeability m 2 of 25 67 and a variance of 0 585 no consistent trend with depth was detected for ln k or for the mean and variance of ln k on a core by core basis exponential spherical and gaussian models all provided excellent fits to the vertical experimental variogram calculated using the classical estimator without the removal of outliers these fits produced correlation scales ranging from 0 16 to 0 23 m of the three theoretical models only the gaussian model produced a reasonable fit to the horizontal experimental variogram with a correlation scale of 4 8 m a linear model was also found to fit the experimental variogram data well in comparison with earlier results of sudicky and woodbury and sudicky it can be concluded that similar deposits were examined in this study particularly with respect to correlation structure on the basis of statistical tests however it cannot be concluded that the mean and variance of ln k are stationary over the 60 m distance between the cores examined in this study and those of sudicky the results of this study indicate that the borden hydraulic conductivity field is relatively uniform over the scale examined but that it cannot be characterized by a single spatially invariant statistical distribution

analytical solutions to non fickian subsurface dispersion in uniform groundwater flow abstract analytical solutions are obtained by the fourier transform technique for the one two and three dimensional transport of a conservative solute injected instantaneously in a uniform groundwater flow these solutions account for dispersive non linearity caused by the heterogeneity of the hydraulic properties of aquifer systems and can be used as building blocks to construct solutions by convolution principle of superposition for source conditions other than slug injection the dispersivity is assumed to vary parabolically with time and is thus constant for the entire system at any given time two approaches for estimating time dependent dispersion parameters are developed for two dimensional plumes they both require minimal field tracer test data and therefore represent useful tools for assessing real world aquifer contamination sites the first approach requires mapped plume area measurements at two specific times after the tracer injection the second approach requires concentration versus time data from two sampling wells through which the plume passes detailed examples and comparisons with other procedures show that the methods presented herein are sufficiently accurate and easier to use than other available methods

determination of migration rates of contaminants in a hydrocarbon polluted site using non reactive tracer test in the niger delta nigeria a natural gradient tracer test with sodium chloride as the injectate was conducted using one injection well and eleven observation wells in an oil contaminated site in the study area the aim was to characterize the site and to determine migration rates of the contaminants to provide information on their fate in groundwater resources in the area the migration of the tracer was constantly monitored by sampling all the observation wells spaced 5 m from each other at 15 30 min intervals for a period of 6 days the test soil layer is a clayey silty sand consisting of 50 sand 30 silt and 20 clay the average static water level at the site is about 2 5 m gas chromatography fingerprinting showed that kerosene and diesel are the dominant fractions within the soil matrix the arrival times of the breakthrough moments of the migrating tracer plume from two observation piezometers situated 2 0 and 7 22 m away from the injection well showed that the mean velocity in the longitudinal direction in the aquifer is 1 403 10 3 ms 1 121 m day the longitudinal and transverse dispersion coefficients of 2 45 10 3 m2s 1 and 2 3 10 3 m2s 1 were used to obtain longitudinal and transverse dispersivities of 1 78 and 1 64 m respectively high hydraulic conductivity denoted by the high migration rate of the tracer implies that contaminant at the site will migrate through the aquifer with relative ease however the significant clay fraction within the soil provides the medium for adsorption and partitioning of contaminants to the soil

an experimental and numerical study of evaporite mineral dissolution and density driven flow in porous media abstract subsurface mineral dissolution problems exhibit complex behaviors which are difficult to model and validate numerically controlled physically validated experimental problems can be used to better understand mineral dissolution and subsequent numerical representation bridging the gap between numerical models and field observations the objective of this work was to collect the first controlled physical measurements in a porous aquifer overlying an evaporite mineral and to create a numerical model of the system the problem studied was modified from the classic hydrocoin level 1 case 5 problem three flow gradients in a porous aquifer were investigated in duplicate in a 2 d box problem the duplicate measurements had high variability shown by numerical modeling to be a result of initial conditions variable flux representing dissolution sharp gradients and variable dispersivity the physical measurements of parameters and fields were important for calibration success the numerical models including sensitivity analyses were capable of simulating flow patterns observed concentrations and peaks resulting from observed initial conditions the numerical models were a key tool in understanding factors influencing the flow and spread of salt within the system the models were limited by the ability to detail physical observations difficult in both the laboratory and for potential field applications the results provided insight in the hydrocoin level 1 case 5 numerical simulations with flow appearing to be swept forward however observed concentrations were lower than commonly modeled

space local spectral texture segmentation applied to characterizing the heterogeneity of hydraulic conductivity 1 spatial variability of hydraulic conductivity exerts a predominant control on groundwater flow by influencing advective pathways hydrodynamic dispersion and density dependent instabilities space local spectral texture segmentation aids in the macroscale characterization of the spatial heterogeneity of natural porous media via an outcrop analogue approach detailed photographic data sets were obtained for a 45 m 3 m vertical section of glacial fluvial sand and gravel deposit in the fanshawe delta area ontario canada high resolution texture maps of the sedimentary exposure are generated using a texture segmentation routine based on the space local s transform with the photographic data sets used as input geostatistical analyses of the texture maps reveal similarity between the spatial correlation structures of spectral texture and hydraulic conductivity as determined from constant head permeameter testing of sediment cores conditioned on the permeameter measurements texture maps can be used to provide local continuous estimates of the hydraulic conductivity field at a spatial resolution equal to the sediment core dimensions

transition zone width in ground wateron ocean atolls an analytical solution for the thickness of the transition zone between fresh and seawater in aquifers on ocean islands is presented the interface is treated as a mixing layer similar to a laminar boundary layer between fluids moving at different velocities the method requires assumptions of homogeneous isotropic dispersion uniform hydraulic conductivity and steady flow all water withdrawal is assumed to occur at the water table the slope of the sharp interface is used in the solution for the mixing layer and the sharp interface is determined using dupuit forchheimer assumptions of horizontal flow the method presented efficiently estimates the transition zone thickness thus providing information not available from sharp interface models the method is illustrated by application to the freshwater lens on an island of the tarawa atoll in the pacific ocean and is used to show the effects of different pumping arrangements on the width of the mixing layer

migration of contaminants in groundwater at a landfill a case study 2 groundwater monitoring devices abstract six types of devices for groundwater monitoring were used on an experimental basis in the investigation of the plume of contamination in the unconfined sandy aquifer at the borden landfill these include standpipe piezometers water table standpipes an auger head sampler suction type and positive displacement type multilevel point samplers and bundle piezometers with the exception of the first two each of these devices provides a means of obtaining vertical sample profiles of groundwater from a single borehole the auger head sampler which is a device that is attached to the cutting head of conventional continuous flight hollow stem augers yields samples from relatively undisturbed aquifer zones as the augers are advanced downward in the borehole from one depth of sampling to another this method is a rapid means of aquiring water quality profiles for mapping the distribution of a contaminant plume the other three profiling devices can be used to establish permanent networks for groundwater quality monitoring a suction type multilevel sampler consists of twenty or more narrow polyethylene or polypropylene tubes contained in a pvc casing that is capped at the bottom each tube extends to a different depth and is attached to a small screened sampling point that extends through the casing to draw water from the aquifer when suction is applied a positive displacement multilevel sampler is similar except that each sampling point is connected to a positive displacement pumping device located inside the pvc casing adjacent to the screen use of the suction type multilevel sampler is limited to zones where the water table is less than the suction lift depth of 8 or 9 m the positive displacement sampler can be used even if the water table is at a much greater depth a bundle piezometer consists of 1 2 cm o d flexible polyethylene tubes each with a short screened section at the bottom fastened as a bundle around a semi rigid center piezometer constructed of thick walled 2 cm o d pvc pipe in shallow water table areas water is withdrawn from each of the tubes and from the pvc piezometer by suction in areas with a deep water table samples are obtained by bailing with a narrow tube with a check valve on the bottom or by displacement using a double or triple tube gas drive sampler the positive displacement multilevel sampler or use of the gas drive samplers in the bundle piezometers provide the best opportunities for collecting samples that can be filtered and have preservatives added without the water being influenced excessively by degassing or by oxygen invasion networks of these three types of devices for multilevel groundwater monitoring were installed in the borden aquifer by means of hollow stem augers the devices are particularly well suited for use in aquifers composed of cohesionless sand or gravel that have little or no clay and groundwater flow that is primarily horizontal when 8 cm diameter hollow stem augers are used as many as eight polyethylene tubes are included conveniently in each bundle piezometer if augers with a larger hollow stem are used more tubes can be assembled in each bundle

the significance of viscosity in density dependent flow of groundwater abstract many modeling studies of variable density groundwater flow have been performed in the last few decades in most of these studies fluid density is considered to vary with concentration while the variation of viscosity with concentration is neglected the consequences of this negligence is not completely known the present study uses a numerical simulation approach to investigate the density viscosity concentration relationship during groundwater flow and solute transport through a density stratified system fluid density is assumed to increase with depth from freshwater at the surface through brackish and saline waters to brines at the bottom half of the system the system mimics field observations at the atikokan research area ara in northwestern ontario canada hypothetical unit basin models consisting of recharge midline and discharge area regimes are employed simulations with the density concentration equation of state and a constant freshwater viscosity in the density stratified system causes groundwater to sink against the buoyancy forces of the system more water is recharged into the system than necessitated by the buoyancy the configurations and lengths of travel paths and travel time of conservative contaminants are inaccurately predicted accounting for concentration in the viscosity equation causes groundwater floating in agreement with the expected buoyancy physics of the system overestimation of concentration dependent density causes sinking whereas overestimation of viscosity results in overfloating and underestimation of groundwater recharge even in density stratified fluids with salinity of seawater recharge and through flow of water may be slightly overestimated if a concentration dependent depsity is used along with a constant freshwater viscosity the concentration dependence of both density and viscosity are to be analyzed carefully during groundwater flow and solute transport simulations in systems with considerable fluid density variations

migration of contaminants in groundwater at a landfill a case study 6 hydrogeochemistry multilevel point samplers located on a longitudinal cross section through the plume of contaminated groundwater in the sand aquifer at the abandoned borden landfill were used to obtain a suite of small volume samples for analysis of major ions and of minor and trace level inorganic constituents calcium is the dominant cation and sulphate and bicarbonate are the dominant anions in the contaminant plume with maximum concentrations of 400 2000 and 1200 mg l 1 respectively beneath the landfill the most highly contaminated water in the aquifer has total dissolved solids of 4000 mg l 1 sulphate and iron are the only inorganic constituents that exceed the recommended limits for drinking water the plume contains above background concentrations of dissolved zinc and manganese no heavy metals or other hazardous inorganic trace elements occur at levels above the maximum limits for drinking water the plume contains levels of total dissolved organic carbon that are above background levels ranging from 30 mg l 1 beneath the landfill to 5 mg l 1 near the front of the plume the landfill which is almost entirely above the water table contains high partial pressures of carbon dioxide and methane the high carbon dioxide levels induce substantial dissolution of calcite which occurs in sand layers in the landfill and in the aquifer immediately below the landfill calcite dissolution is the origin of much of the dissolved inorganic carbon and some of the calcium in the plume most of the sulphate and much of the calcium in the plume appears to be derived from gypsum in construction debris in the landfill groundwater beneath the landfill is saturated with respect to gypsum and slightly supersaturated with respect to calcite some of the dissolved iron in the plume results from the release under reducing conditions of iron from ferric iron coatings on sand grains located in the aquifer beneath the landfill and in the layers in the refuse dissolved iron concentrations appear to be limited by the solubility of siderite dissolved sulphide is present at only very low concentrations and is probably controlled by ferrous sulphide solubility exchange of cations between the aquifer material and the leachate contaminated groundwater is an apparent cause of calcium release and subsequent precipitation of calcite in the plume as much of 80 of the k 20 of the mg2 and 15 of the na in the plume exists on the exchange sites the effects of dispersive and geochemical attenuation were evaluated from the ratios of chloride to other species along a central flow path from the landfill to the front of the plume platinum electrode measurements and electrochemical potentials calculated from equilibrium speciation of analysed constituents varied over a wide range of values and provided poor agreement among methods for the same sample only potentials derived from the iron redox couples and pt electrode measurements exhibited fair agreement for any one sample the rather narrow range of pt electrode potential values along the central flow line through the plume suggest that the electrochemical potentials are buffered apparently as a result of fe oh 3 s ag feco3 s equilibria

migration of contaminants in groundwater at a landfill a case study 7 dc vlf and inductive resistivity surveys abstract we report here the results of direct current dc very low frequency vlf and inductive resistivity surveys of the abandoned landfill at canadian forces base borden these surveys were undertaken initially to assist in mapping the migration of contaminants and continued to assess the relative usefulness of the three techniques for the task all three techniques were successful in outlining the regions of highest landfill derived dissolved constituents in the sand aquifer but the electromagnetic methods have a significant advantage over dc resistivity in both resolution and cost this conclusion is very site specific however we emphasize the importance of evaluating geophysical methods through preliminary modelling before undertaking field work at a new site where the contaminant levels at borden are less than about twice background mapping their distribution with surface geophysics became unreliable as has been noted in previous case histories of this type surface surveys are ultimately limited in their usefulness by natural scatter in the apparent resistivity variations which are unrelated to the variations in contaminant level this lithological and topographical noise can easily mask the detail of a contaminant pattern and is generally inseparable from contaminant related variations if geophysical monitoring is to be useful it is essential that resistivity surveys be undertaken as part of the pre landfill hydrogeological studies in order to separate the natural scatter from post landfill surveys

reply to comment on a natural gradient experiment on solute transport in a sand aquifer spatial variability of hydraulic conductivity and its role in the dispersion process by e a sudicky

migration of contaminants in groundwater at a landfill a case study 4 a natural gradient dispersion test abstract a natural gradient tracer test using a chloride solution with an initial injection volume of 0 7 m 3 was performed in the sandy aquifer at the borden site the solution was injected into five well points set 1 m below the water table in an uncontaminated zone situated above the contaminant plume at a location 450 m downflow from the landfill under conditions of natural groundwater flow the tracer slug was monitored for a period of 4 months by withdrawing small volume samples from points in a three dimensional array of bundle type multilevel samplers measurements of hydraulic head were obtained from a network of miniature piezometers soon after injection the tracer slug gradually split into two halves one half moving horizontally at an average velocity of 2 9 10 6 ms 1 and the other horizontally at 8 2 10 7 ms 1 although the split has been attributed to local lateral heterogeneity the nature of the heterogeneity and its influence on the hydraulic head distribution were not clearly distinguishable in the field data obtained before during or after the test the chloride patterns for each of the two halves of the tracer slug evolved into gaussian forms although the patterns demonstrated some irregularity at early time the relatively smooth gaussian forms were unexpected because the aquifer has numerous small scale heterogeneities observed in vertical cores obtained from the tracer zone and because the glaciofluvial origin of the aquifer suggests that heterogeneities are not laterally continuous simulated chloride distributions from a three dimensional analytical solution to the advection dispersion equation were fitted to the field data to obtain best fit estimates of the values of longitudinal transverse horizontal and transverse vertical dispersivity at various travel distances for each of the two halves of the tracer zone this is the first known field test that has permitted the estimation of three principal dispersion coefficients in layered media the longitudinal dispersivity was found to increase from 0 01 m at a distance of 0 75 m from the source to 0 08 m at 11 0 m the transverse horizontal dispersivity increased also to a value of 0 03 m at 11 0 m transverse vertical dispersion was very weak and was accounted for by molecular diffusion the relative lack of vertical dispersion is consistent with the shape of the plume of leachate contamination from the landfill it was concluded that the observed increase in dispersivity along the path of migration is likely caused by heterogeneities information on the dispersion controlling heterogeneities is not yet available as practical field methodologies for their identification and description have not yet been developed until such information is incorporated into mass transport models a realistic solution of the dispersion problem in heterogeneous media will remain elusive

leaching surfaces to characterize transport in a heterogeneous aquifer comparison between flux concentrations resident concentrations and flux concentrations estimated from temporal moment analysis 1 for subsurface solute transport flux concentrations are key while usually resident concentrations are measured flux concentrations are frequently estimated from resident concentrations by temporal moment analysis we tested this approach by simulating transport of an injected tracer during steady flow in an aquifer with a heterogeneous saturated hydraulic conductivity we constructed grid cell scale breakthrough curves btcs from flux concentrations and approximated btcs from resident concentrations and estimated flux concentrations we assembled these btcs into spatiotemporal leaching surfaces at various aquifer cross sections for subsequent analysis resident concentrations were unsuitable to assess solute movement in the aquifer temporal moment analysis worked well when the entire aquifer cross section was considered but performed poorer at the grid cell scale because it approximates the local velocity by the trajectory average the leaching surfaces served as valuable tools to demonstrate and quantify the limitations of temporal moment analysis

observations of grain scale interactions and simulation of dry granular flows in a large scale flume a series of 30 tests on dry granular flows were performed using a large scale flume under varying source volumes and basal friction conditions to capture grain scale interactions and their impact o

role of aquitards in hydrogeochemical systems a synopsis abstract aquitards exert significant influence on the hydrogeochemistry of aquifer systems this influence is manifested somewhat differently depending on the relative position of aquitards within a system in the deeper regimes they are influential in the origin and distribution of brines and the development of geopressured zones in intermediate regimes they form multi layered aquifer systems and provide a source of reactive minerals and exchangeable ions in shallow regimes aquitards can influence the topography and drainage patterns this influences the relationship between the water table and the potentiometric surface of confined aquifers controls the rates of infiltration and discharge and controls whether the geochemical system is open or closed to exchange of carbon dioxide gas in coastal areas aquitards can determine the depth of the saltwater freshwater interface its distance from the shoreline and the position of the mixing zone that causes geochemical alteration of minerals and development of porosity

migration of contaminants in groundwater at a landfill a case study 1 groundwater flow and plume delineation abstract a landfill derived contaminant plume with a maximum width of 600 m a length of 700 m and a maximum depth of 20 m in an unconfined sand aquifer was delineated by means of a monitoring network that includes standpipe piezometers multilevel point samplers and bundle piezometers the extent of detectable contamination caused by the landfill which began operation in 1940 and which became inactive in 1976 was determined from the distributions of chloride sulfate and electrical conductance in the sand aquifer all of which have levels in the leachate that are greatly above those in uncontaminated groundwater the maximum temperature of groundwater in the zone of contamination beneath the landfill is 12 c which is 4 5 c above background the thermal plume in the aquifer extends 150 m downgradient from the centre of the landfill a slight transient water table mound exists beneath the landfill in the late spring and summer in response to snowmelt and heavy rainfall beneath the landfill the zone of leachate contamination extends to the bottom of the aquifer apparently because of transient downward components of hydraulic gradient caused by the water table mound and possibly because of the higher density and lower viscosity of the contaminated water values of hydraulic conductivity which show variations due to local heterogeneity were obtained from slug tests of piezometers from pumping tests and from laboratory tests because of the inherent uncertainty in the aquifer parameter values the 38 yr frontal position of the plume calculated using the darcy equation with the assumption of plug flow can differ from the observed frontal position by many hundreds of metres although the use of mean parameter values produces a close agreement the width of the plume is large relative to the width of the landfill and can be accounted for primarily by variable periods of lateral east and westward flow caused by changes in water table configuration due to the variable nature of recharge northward from the landfill the vertical thickness of the plume decreases and the top of the plume is farther below the water table the thickness of the zone of uncontaminated groundwater above the plume increases northward as the area of recharge of uncontaminated water downflow from the landfill increases because dispersion in the vertical direction is weak there is very little mixing between the overlying zone of recharge water and the contaminant plume concentration profiles are irregular beneath and near the landfill and become smooth downgradient where the maximum concentrations are much less than those beneath landfill these features are attributed to a strong influence of longitudinal dispersion the plume passes beneath a small shallow stream near the landfill without significant influence on the stream

geochemical and palaeohydrological controls on the composition of shallow groundwater in the netherlands with the exception of the south of the country the netherlands has a strong bipartite hydrogeology the holocene part with a coastal dune belt and confining top layer of clay and peat further inland and the pleistocene where thick phreatic aquifers dominate this research aimed to ascertain the geochemical and palaeohydrological controls on the composition of shallow groundwater in 27 regions close to 6000 groundwater analyses were grouped and interpreted in terms of 1 salinity 2 redox status 3 acid base and carbonate status and 4 natural nutrients nh4 and po4 the a priori classification into geographical regions and geological formations revealed many statistically significant differences in medians even for geologically or geographically related data groups the compound specific interpretation indicates that there are geogenically controlled systematic differences in groundwater composition at the regional scale the imprint of the geological sediments on the groundwater composition decreases in the order marine estuarine via limnological fluvial to aeolian the imprints with respect to ph and carbonate status natural nutrients and redox status are not necessarily interrelated the vertical stratification in groundwater composition turns out to be often limited at the regional scale due to mutual occurrence of infiltrating and exfiltrating groundwater in regions and either the presence of a highly reactive holocene confining top layer or temporal changes in contamination in the holocene part the salinity is controlled by the palaeoenvironmental conditions during the holocene and by the recharge origin the average cl concentration decreases from estuarine via lagoonal to the former zuider sea which was a bay the most reduced states and also the highest nutrient concentrations and highest co2 pressure are related to the presence of holocene marine sediments in the confining top layer degradation of marine derived organic matter as a nutrient source is likely more intense in the holocene deposits than that of peat and sedimentary remnants of terrestrial plants a broad range in ph carbonate status and redox status is encountered in the pleistocene part here the palaeohydrological evolution in terms of carbonate leaching together with the geological controls on the calcareous nature of the shallow sedimentary deposits cause regional differences in ph calcite saturation and silicate weathering one region with late pleistocene limnological deposits has deviating groundwater characteristics and appears more similar to the holocene part of the netherlands furthermore reactive fe is not abundant in all pleistocene fluvial sediments nor is it maximally mobilised as not all anoxic groundwater in these sediments is siderite saturated this leads to considerable intra and inter region variability 2013 elsevier ltd

an analytical model for solute transport in an infiltration tracer test in soil with a shallow groundwater table summary it is recommended that an in situ infiltration tracer test is considered for simultaneously determining the longitudinal and transverse dispersion coefficients in soil analytical solutions have been derived for two dimensional advective dispersive transport in a radial geometry in the literature which can be used for interpreting the result of such a tracer test however these solutions were developed for a transport domain with an unbounded radial extent and an infinite thickness of vadose zone which might not be realistically manifested in the actual solute transport during a field infiltration tracer test especially the assumption of infinite thickness of vadose zone should be invalid for infiltration tracer tests conducted in soil with a shallow groundwater table this paper describes an analytical model for interpreting the results of an infiltration tracer test based on improving the transport domain with a bounded radial extent and a finite thickness of vadose zone the analytical model is obtained with the successive application of appropriate integral transforms and their corresponding inverse transforms a comparison of the newly derived analytical solution against the previous analytical solutions in which two distinct sets of radial extent and thickness of vadose zone are considered is conducted to determine the influence of the radial and exit boundary conditions on the solute transport the results shows that both the radial and exit boundary conditions substantially affect the trailing segment of the breakthrough curves for a soil medium with large dispersion coefficients previous solutions derived for a transport domain with an unbounded radial and an infinite thickness of vadose zone boundary conditions give lower concentration predictions compared with the proposed solution at late times moreover the differences between two solutions are amplified when the observation positions are near the groundwater table in addition we compare our solution against the approximate solutions that derived from the previous analytical solution and has been suggested to serve as fast tools for simultaneously estimating the longitudinal and transverse dispersion coefficients the results indicate that the approximate solutions offer predictions that are markedly distinct from our solution for the entire range of dispersion coefficient values thus it is not appropriate to use the approximate solution for interpreting the results of an infiltration tracer test

the use of tritium in groundwater to determine fluid mean residence times of valles caldera hydrothermal fluids new mexico usa abstract naturally and artificially produced 3 h in precipitation is used to place limits on mean residence times of fluids associated with the valles caldera geothermal reservoir the 3 h concentrations in precipitation are used to calculate fluid mean residence times using two end member cases piston flow and well mixed reservoirs these simplified models using 3 h yield relative fluid mean residence times in different portions of the system in situ 3 h production in the reservoir through neutron interaction with 6 li is considered and only very low levels of 3 h 0 01 t u are contributed to the waters by this process calculations using the end member cases at valles caldera indicate that mean residence times of geothermal waters in the reservoir are between 3000 and 10 000 years the results also show that the two distinct subsystems of the main reservoir are associated with different fluid mean residence times waters in the redondo creek subsystem are older 4300 to 10 000 years than waters in the sulphur springs subsystem 2000 4400 years comparison of the results of the end member cases with those obtained using more sophisticated methods indicates that the two end member cases with the use of 3 h can provide acceptable limits order of magnitude on a fluid s mean residence time and volumes within a reservoir

hydrological characteristics of an alpine glacial valley in the north italian dolomites abstract hydrogeological characteristics of alpine regions generally are determined to a large extent by the geomorphological development during the quaternary period pleistocene and holocene this development and the hydrogeological characteristics were studied for a glacial trough valley san vigilio developed in a dolomite limestone complex in the alps of north italy geo electrical soundings were successful for detecting the shape of the glacial valley bottom and to interpret the depth and sediment type distribution of the glacial valley fill composed of ground moraine fluvio glacial deposits fluvial fans talus cones and lake deposits hydrochemical analyses and environmental isotopes 3 h and 18 o were used to further interpret the groundwater flow systems