preferential flow in a sandy vadose zone 2 mechanism and implications abstract field experiments conducted at the hancock agricultural research station during the 1987 growing season showed that preferential flow paths were the dominant flow pattern in the central sand area of wisconsin csaw the observed preferential flow was different from other preferential flow patterns mentioned in the literature e g short circuiting flow and fingering flow this paper presents a detailed discussion of the mechanism of this preferential flow and its influence on groundwater contamination soil solution sampling and solute transport modeling four factors that will determine the occurrence of a funneled flow are a conductivity of the upper finer layer k b slope of the inclined layer sin c retention potential of the upper finer layer 2 r and d ponding potential g l

interstitial water studies of late quaternary eastern mediterranean sediments with emphasis on early diagenetic reactions and evaporitic salt influences interstitial waters of five piston cores from the eastern mediterranean were recovered by shipboard squeezing and analyzed for their major elements additionally organic carbon caco3 and hcl extractable mg were determined in the sediments from these cores three cores contain sapropels which are considered to be the sedimentary expression of anoxic periods during the quaternary the ph in the interstitial waters extracted from the sapropels is significantly lower than the ph of the interstitial waters from the surrounding sediment it is suggested that the low ph in sapropel interstitial waters is induced by bacterial activity other dissolved elements are not influenced by these sapropel layers core t83 46 taken in the hypersaline anoxic tyro basin shows a strong downward so4 decrease accompanied by a strong nh4 increase the interstitial water chemistry of the tyro basin sediment is attributed to selective leaching of evaporitic salt first halite dissolution later followed by gypsum dissolution the interstitial water chemistry of core t83 45 taken in the adjacent kretheus basin is dominated by diffusive processes which became important after oxic conditions returned in this formerly anoxic hypersaline basin

assessing preferential flow through an unsaturated waste rock pile using spectral analysis 1 waste rock piles are an outcome of open pit and underground mining operations unprocessed low grade rock is disposed of in piles from several meters high to 100 m high waste rock piles may still contain sufficient concentrations of metals to be a potential source of pollution the evaluation of the potential risk involves properly characterizing flow through these piles under unsaturated conditions the main flow characteristic of the piles is the presence of a large range of grain and pore sizes based on data from an instrumented rock pile located in saskatchewan canada unsaturated flow through the pile is modeled as a linear system after separating a fast and a slow component water reaching the base of the pile is monitored by 16 contiguous zero tension lysimeters the fast component flowing through macropores is assumed to be released instantaneously while the slow component is simulated using a linear reservoir model that assumes the presence of an interconnected porous matrix an empirical transfer function tf is computed as the ratio of the spectra of signals between the output basal outflow and the input rainfall time series determination of a parametric transfer function model provides information on the characteristic time of water storage in the matrix and on the fraction of the water within each subsection of the experimental pile that is channeled through the macropores an analysis of the output signal at different support scales is performed indicating the nonlinearity of the macropore fraction scaling processes

microstructure and poro mechanical performance of haubourdin chalk abstract large chalk deposits are to be found in the north of france and as a result developing chalk as a load bearing aggregate is considered by french road building companies due to its limited mechanical performance chalk is subjected to a medium heat treatment process up to 500 c in this context microstructure and poro mechanical performance of haubourdin chalk are characterized before and after heat treatment the investigation of the so called water weakening effect is associated to that of heat treatment mainly to show to what extent the strength of haubourdin chalk decreases at a given water saturation state prior to or after heat treatment in terms of microstructure analysis sem and fib sem observations show the initial weak cementation of haubourdin chalk in direct relation with its moderate mechanical performance after heat treatment minor re crystallisation of calcium carbonate is observed which should be confirmed further the specific behavior of haubourdin chalk is highlighted under partial water saturation and after heat treatment by using uniaxial compressive tests and triaxial drained and undrained compressive tests pore collapse is quantified directly under increasing hydrostatic stress by measuring coupled gas permeability and porosity change a heat hardening effect is identified which is counter balanced by the water weakening effect the latter makes natural haubourdin chalk unsuitable as load bearing road aggregate without further binding matter

overview of inert tracer experiments in key belgian soil types relation between transport and soil morphological and hydraulic properties to investigate relations between solute transport soil properties and experimental conditions we summarize results from leaching experiments that we carried out in a range of soils at different scales column 0 3 1 0 m id 1 0 m length and field plot scale and using different leaching rates 0 5 30 cm d 1 the lateral mixing regime and longitudinal dispersion were derived from time series of tracer concentrations at several depths in the soil field and column scale transport were similar in loam and silt loam soils the mixing regime was related to soil morphological features such as vertical tongues stratification macropores and a water repellent layer the dispersion increased in all soils more than linearly with increasing leaching rate implying that the dispersivity is not an intrinsic soil characteristic the change of dispersivity with leaching rate was linked to the unsaturated hydraulic conductivity using a multidomain conceptualization of the pore space

discovery of an anoxic basin within the strabo trench eastern mediterranean we report here the discovery of a basin which we call the tyro basin in the eastern mediterranean in which anoxic conditions exist and organic rich sediments are accumulating bottom water samples show extremely high salt concentrations a horizontal midwater sound reflector about 70 m above the basin floor was observed in a seismic reflection profile across the basin from shipboard observations we conclude that dissolution of messinian evaporites exposed by faulting in the sides of the basin causes stagnant bottom conditions this basin provides an opportunity to test some of the hypotheses concerning the formation of sapropels present in cores collected from the same area cores taken in an adjacent similar basin for which we propose the name kretheus basin indicate a recent change from anoxic to oxygenated conditions which was probably caused by tectonic activity associated with the strabo trench

a new interpretation of kinematic stormflow generation the paper reviews a number of possible fast and slow hydrological flow mechanisms to account for rapid runoff generation within a catchment a new interpretation of the kinematic wave process is proposed which develops some of these concepts to explain rapid subsurface flow from a watershed evidence for the process is provided by the results from a laboratory soil core experiment and an investigation of the hydrology of a dartmoor hillslope a tension response was monitored in the soil core in which pressure waves were propagated downwards and expelled water from the base the transmission of the wave down the core was considerably faster than the movement of a chloride tracer the concept of this kinematic wave process and associated water flux was then extended to the dartmoor watershed raindrops reaching the wet soil surface caused pressure waves to travel laterally downslope during large rainstorms the hillslope became hydrologically highly connected and the pressure waves forced existing water from seepage faces into the saturated area adjacent to the stream contributing substantially to the stream discharge a kinematic contributing area was defined as determined by both rainfall runoff ratios and geostatistical analyses of hillslope soil moisture contents which extended over at least 65 of the catchment area this kinematic wave theory is consistent with results of translatory flow and macropore flow models and stable isotope field studies of old new water copyright 2002 john wiley sons ltd

deposition of sapropel s1 sediments in oxic pelagic and anoxic brine environments in the eastern mediterranean differences in diagenesis and preservation sediments from a boxcore in the previously anoxic brine filled poseidon basin eastern mediterranean have been studied and compared to sediments deposited in a normal eastern mediterranean environment the boxcore can be divided into three main sedimentary intervals based on ams radiocarbon ages foraminiferal and geochemical zonations from the base of the core upwards these are 1 12 3 31 2 cm organic rich sediments redeposited from within the brine 2 6 6 12 3 cm sediment containing a cold foraminifera fauna redeposited from above the brine into the basin while the brine was still present 3 0 6 6 cm oxic pelagic sediment accumulated since the reoxygenation of poseidon basin which occurred1800 yrs bp near the base of the latter unit a mn oxide peak has formed and it marks the present boundary between oxic and suboxic environments a progressive downward oxidation front which is usually found in normal sapropel s1 sediments has never formed in poseidon basin sediments this has resulted in the preservation of the relationship between organic carbon and organic related trace elements e g se in the organic rich sediments of poseidon basin whereas such a relationship has been obliterated in normal sapropel s1 sediments on the basis of the carbonate content as well as the sr ca ratio preservation of carbonates appears to be better in the brine sapropel sediments of bc15 than it is in normal sapropel s1 sediments the high opal content of bc15 shows that biogenic opal is also much better preserved the overall lower corg ba ratio in bc15 suggests a better preservation of barite relative to that of organic carbon in shallow brine sediments but is as yet inconclusive for the organic carbon preservation potential of brine relative to normal unoxidised sediments 1999 elsevier science b v all rights reserved

controls of grain size distribution on geomechanical properties of reservoir rock a case study cretaceous khafji member zuluf field offshore arabian gulf abstract the khafji member of the cretaceous wasia formation in zuluf field offshore saudi arabia is an important siliciclastic hydrocarbon reservoir the reservoir consists of a lower main sand and an upper stringer sand the present study investigated the relationships between the geomechanical attributes young s modulus and poisson s ratio of the reservoir and its grain size distribution in addition an attempt was also made to relate the reservoir quality with the depositional environments deduced from factor analysis of the grain size distribution data the young s modulus for the khafji reservoir range from a low of 8 43 105 psi at 1000 psi confining pressure 1 13 106 psi at 2900 psi confining pressure to a high of 1 27 106 psi at 1000 psi 1 91 106 psi at 2900 psi the study shows that there is no significant relationship between grain size parameters mean median skewness and kurtosis and geomechanical properties however a good correlation was observed between geomechanical parameters and sands deposited in different environments the clean sand showing moderate to good sorting and interpreted as beach sand showed low young s modulus average 1 07 106 psi and poisson s ratio average 0 16 while the parameters were higher average of 1 57 106 psi young s modulus and 0 204 poisson s ratio for the fine grained sediments representing possible lagoonal or offshore environment

rainy periods and bottom water stagnation initiating brine accumulation and metal concentrations 1 the late quaternary a working hypothesis is proposed to account for the present accumulation of brines in isolated pockets of the ocean floor and for the formation of the underlying organic and metal rich sediments these are the tyro and bannock basins in the east mediterranean the red sea deeps and the orca basin in the northern gulf of mexico initiation of brine derived deposition in the red sea deeps and orca basin occurred between 12 000 and 8000 years b p this time bracket also encompasses the formation of the latest east mediterranean sapropel and the wettest global climate since the last glacial maximum this wet period first appeared in the tropics around 12 000 years b p then in the subtropical and middle latitudes during the same period the 23 000 year precession cycle brought the summer insolation of the northern hemisphere to its peak at 11 000 years b p with retreating northern hemisphere ice sheets the red sea deeps and the orca basin became anoxic during this humid period and metal rich sapropel deposition then began in contrast the tyro and bannock basins began accumulating a brine long before and persisted beyond this climatic stage the hypothesis involves two propositions 1 as in the eastern mediterranean sea marine anoxia was mainly the consequence of the large influx of continental runoff and local precipitation longer residence time of bottom waters so called stagnation in silled rimmed basins would have resulted from lower salinity at the sea surface in areas of deep water formation in the eastern mediterranean the red sea and the gulf of mexico and 2 miocene or older evaporites underlie these basins or outcrop on their flanks leaching from these evaporites was an ongoing process before the quasi stagnation phase but the initial leachate much less saline than the present brines was continuously flushed by bottom circulation the climate induced quiescence of bottom waters in these basins enabled the leachate to accumulate the feedback of stagnation by increased density progressively raised the salinity of entrapped bottom waters to the present brine concentration the high density has resisted brine removal by bottom circulation until present time long after cessation of the initiating wet period the brines therefore are stagnant fossil waters

effects of layering on triggering mechanisms of rainfall induced landslides in unsaturated pyroclastic granular soils1 rainfall induced landslides are widespread in shallow layered granular soil deposits in many cases slope instability is related to the decrease of suction during rainwater infiltration however

messinian salt fluxes into the present day eastern mediterranean implications for budget calculations and stagnation abstract although messinian evaporites underly almost the entire mediterranean fluxes related to these evaporites have not been included in water and salt budget calculations recently long piston cores recovered in the eastern mediterranean were sampled for pore waters in sufficient detail to allow a semi quantitative study of the sedimentary fluxes six different salt sources can be distinguished namely those coming from 1 normal pore waters 2 mud diapirs 3 sediments of formerly brine filled basins 4 brine filled basins 5 sediments from areas with a cobblestone topography and 6 salt dissolution holes based on the chloride versus depth profiles chloride fluxes from the sediment to the seafloor can be calculated the fluxes were multiplied by the estimated areas for the different salt sources to obtain the total flux these calculations show that mud diapirs and normal pore waters are the most important presently known salt sources in the eastern mediterranean compared with the salt input by evaporation the sedimentary salt input is rather small and has little influence on the models used for the water and salt budgets salt input from the sediment has a similar effect on the circulation of the eastern mediterranean water column as the introduction of huge amounts of fresh water at the surface the latter process may have resulted in the formation of sapropels the known sedimentary salt input is too low to be directly responsible for stagnation of the water column however once stagnation is initiated by other factors e g decrease of excess evaporation the extra salt input into the deep water will enhance the stagnation process therefore the circulation mechanism may be more sensitive to external changes than assumed until now

solute mixing during imbibition and drainage in a macroscopically heterogeneous medium 1 we studied the flow of water and the transport of solutes in a heterogeneously packed sand tank by performing transport experiments with a fluorescent tracer the packing consisted of an inclined layered sand bedding characterized by a large number of thin layers of three quartz sands of different grain sizes the purpose was to evaluate to which extent the preceding wetting draining history affects the mixing of solutes in presence of textural heterogeneities we irrigated the surface at stepwise increased flow rates imbibition and afterward at stepwise decreased flow rates drainage at each step the flow rate was kept constant to monitor the transport and spreading of several tracer plumes in the stationary flow field the results show that during imbibition mixing at the textural boundaries is hindered and the solutes are funneled through connected preferential flow paths during drainage we observed enhanced mixing resulting in a definitely less heterogeneous transport regime these results stress the role of the preceding wetting draining history for determining the characteristics of solute transport in heterogeneous media we demonstrate this using the integral mixing characteristics dilution index and reactor ratio which quantify the degree of preferentiality of flow and transport

the diversion capacity of capillary barriers an arrangement of unsaturated fine grained soil overlying unsaturated coarse grained soil along a sloping contact can under appropriate circumstances divert infiltrating water away from the coarser material such an arrangement is called a capillary barrier the water diverted by a capillary barrier flows downdip above the contact the volume of water moving laterally increases in the downdip direction as additional infiltration is diverted by the barrier sufficiently far downdip the laterally moving water wets the contact to the point that an amount of water equal to the infiltration flows downward through the coarse soil the lateral flow at such a point represents the diversion capacity of the capillary barrier because this flow will not increase farther downdip if the width measured in the direction of dip of the system is large enough that total infiltration exceeds the diversion capacity the downdip portion of the barrier will not be effective the diversion capacity can be calculated exactly in the quasi linear approximation where the relationship between relative permeability krel and pressure potential takes the form krel e this calculation shows that an upper bound on the width of capillary barriers is ks tan o q where ks is the saturated hydraulic conductivity of the fine soil o is the dip angle of the contact and q is the infiltration rate

reconstructing the palaeoenvironment at the early mesolithic site of lake duvensee ground penetrating radar and geoarchaeology for 3d facies mapping we investigate the landscape development of the early mesolithic hunter gatherer sites of duvensee 10000 6500 cal bce based on ground penetrating radar gpr and geoarchaeological drillings we

strength of jointed rock masses jointed rock masses comprise interlocking angular par ticles or blocks of hard brittle material separated by discontinuity surfaces which may or may not be coated with weaker materials the strength of such rock masses depends on the strength of the intact pieces and on their freedom of movement which in turn depends on the number orientation spacing and shear strength of the discontinuities a complete understanding of this problem presents formidable theoretical and experi mental problems and hence simplifying assumptions are required in order to provide a reasonable basis for estimating the strength of jointed rock masses for engineering design purposes this paper summarizes some of the basic information upon which such simplifying assumptions can be made a simple empirical failure criterion is presented and its application in engineering design is illustrated by means of a number of practical examples des masses jointives de rochers comprennent des particules angulaires enchevetrees ou des

porosity of sediments in accretionary prisms and some implications for dewatering processes rapid dewatering largely through loss of porosity is one of the most striking changes affecting deformed sediments in accretionary prisms analysis of porosity from sample and seismic data confirms that porosity in accretionary prisms is significantly less than that in basinal strata of similar lithology more specifically the porosity depth gradient increases arcward across the prism until porosities less than 10 occur within a few kilometers of the surface in deeper parts of the prism dewatering and volume reduction occur not only during loss of porosity but also during dehydration and metamorphic reactions calculations involving volume change lead us to define a function which reflects total volume reduction the distribution of the relative intensity of dewatering within the prism can be calculated from the porosity contours and trajectories of sediment elements an initial attempt indicates that in the toe region the rate of dewatering is accelerated at depth relative to the basinal section and may be greatest near the base of the prism toward the rear of the prism the maximum rate of dewatering occurs at progressively shallower depths several lines of evidence suggest that in addition to gradual diffuse dewatering localized zones of strong dewatering are associated with zones of intense shear this model of shear dewatering based on critical state soil mechanics suggests that sediments adjacent to the basal decollement should be strongly dewatered

detecting the vulnerability of groundwater in semi confined aquifers using barometric response functions summary the use of barometric response functions brfs for detecting the presence of fully penetrating highly conductive bodies within aquifer confining layers that present potential pathways for contaminants is explored brfs are determined from borehole water level wl and barometric pressure bp records past studies have shown that confining layer properties can be estimated from brfs providing a potential link between brfs and the concept of groundwater vulnerability existing analytical models that predict the brf from system properties assume homogeneity within the aquifer and its confining layer conditions which are seldom satisfied in nature the impact of partially and fully penetrating high diffusivity heterogeneities within a confining layer representing potential high flow pathways for contaminants on the brf is investigated through a suite of three dimensional transient numerical simulations of the confining layer aquifer system the results are interpreted through comparison with a modified pre existing analytical model for the brf comparison of numerically and analytically calculated brfs reveals that the key effect of a localised fully penetrating high diffusivity heterogeneity within a low diffusivity confining layer is to reduce the brf gain with only minor changes to the phase this impact on the brf decreases with increasing distance from the heterogeneity the importance of heterogeneity size is secondary to distance from the borehole and partially penetrating heterogeneities affect the brf to only a minor extent data from a study of the chalk aquifer e yorkshire england which is semi confined by heterogeneous glacial sediments display variations in brfs which are qualitatively similar to those shown by the numerical results it is suggested that the variation in brfs estimated from borehole records across a semi confined aquifer could be used to assess the degree of spatial continuity of low diffusivity lithologies within the confining layer which protect the aquifer against surface sourced contamination and thus provide a tool to improve groundwater vulnerability assessment

sediment chemistry and magnetic properties in an anomalously reducing core from the eastern mediterranean sea abstract in core kc19c 19 6 m long recovered in the abyssal plain between crete and cyprus in the eastern mediterranean a large number of organic rich layers sapropels occur which correlate to maxima in the insolation curve in contrast to other sites in the eastern mediterranean porewaters contain sulfide below a few meters below seafloor mbsf geochemical analyses were performed on the porewaters ammonium alkalinity sulfate manganese iron bisulfide chloride eh ph and sediments organic carbon barium total sulfur total iron manganese pyrite dithionite extractable iron in addition a series of magnetic parameters and ratios nrm arm irm in arm irm s ratio arm 20mt arm in were determined in the top of the sediments fe and mn hydr oxides occur at the oxic suboxic boundary just above the youngest sapropel si2 these hydr oxides appear to be more easily demagnetized by means of alternating fields than deeper hydr oxides which presumably are of detrital origin the transition from suboxic to anoxic sediments is located at 2 mbsf sulfide is produced possibly during sulfate reduction through anoxic methane oxidation at 17 5 mbsf from 17 5 mbsf sulfide migrates upward titrating reactive fe resulting in pyrite formation in the entire sediment column up to 2 mbsf at this depth the upward sulfide flux has been totally consumed by reaction with solid phase fe and dissolved fe ii diffusing downward from the suboxic zone above from 2 mbsf downward magnetic intensities are significantly reduced indicating reductive dissolution of fe oxide minerals and pyrite formation as a consequence no reliable nrm data can be obtained in the lower half of the core

the influence of connected heterogeneity on groundwater flow and salinity distributions in coastal volcanic aquifers abstract geological heterogeneity is a key factor affecting rates and patterns of groundwater flow and the evolution of salinity distributions in coastal aquifers the hydrogeologic systems of volcanic aquifers are characterized by lava flows that can form connected geologic structures in the subsurface surface based geostatistical techniques were adopted to generate geologically realistic statistically equivalent model realizations of a hydrogeologic system based on that of the big island of hawaii conduit models the density dependent groundwater flow and solute transport code seawat was used to perform 3d simulations to investigate subsurface flow and salt transport through these random realizations statistically equivalent geological systems generated with sequential indicator simulation sis and equivalent homogeneous systems were also simulated for comparison simulation results show that conduit realizations tend to have more complex salinity distributions with larger mixing zones for which the center of mass is farther offshore compared to homogeneous and sis realizations the zone of groundwater discharge is also farther offshore than for homogeneous and sis models with higher point fluxes of both fresh and saline water and greater spatial variability this highlights the importance of the geometry of geologic features in coastal groundwater flow and solute transport processes in highly heterogeneous aquifers it also points to the importance of preferential flow with implications for both coastal groundwater resource management and solute fluxes to the ocean

assessment of preferential flow processes in a forest reclaimed lignitic mine soil by multicell sampling of drainage water and three tracers abstract predictions of the long term development of newly established forest reclaimed ecosystems are required for land use planning of post mining landscapes the geological and mineralogical composition the small distance heterogeneity and inclined structures of the mine spoil s overburden sediment mixtures as well as the physical and chemical properties of acidic and lignitic mine soil components have raised questions about the water flow and solute transport processes in these soils the objective of this study was to quantify preferential flow processes and spatially resolved solute transport in order to better distinguish between dominating processes for such soils the experimental study was carried out by determining spatially resolved rates of throughfall drainage and tracer leaching from underneath a 110 cm deep mine soil block drainage water was collected using 45 contiguous suction cells of 27 cm edge length a tracer cocktail consisting of bromide terbuthylazine and deuterium was applied at the soil surface and subjected to natural infiltration tracer concentrations in drainage waters were analysed for a period of about 10 months then the mine soil block was sampled completely in the form of 225 cubes of about 27 cm edge length to determine the residual bromide content tracer labelled drainage in 110 cm depth occurred in spring 2001 over about 71 and in autumn 2001 over 35 of the total cross sectional drainage area respectively local drainage maxima shifted from spring to autumn but also within drainage periods by 1 2 cell lengths bromide concentrations of drainage effluents varied by a factor of 4 between individual cells bypass type preferential flow seems not to be a dominating transport mechanism since terbuthylazine in drainage waters occurred only singularly in spring with concentrations just above the detection limit perhaps the dilution in relatively large cells was too effective to detect modest contributions of tracer through preferential flow paths relative concentrations of deuterium and of bromide were akin during both drainage periods indicating similar transport behaviour of both tracers in the mine soil the spatial distribution of residual bromide concentrations in the subsoil seemed to correspond with the inclined spoil ripple structures the spatial patterns of leached bromide suggest a funnelling type flow concentration in this lignitic mine soil preferential flow is presumably caused by the temporarily varying effects of multiple determinants such as inclined dumping structures spatial variability of hydraulic properties water repellence and the properties of lignitic dust and fragments with some immobile porosity

laboratory and numerical modeling of water balance in a layered sloped soil cover with channel flow pathway over mine waste rock macropores developed in barrier layers in soil covers overlying acid generating waste rock may produce preferential flow through the barrier layers and compromise cover performance however little has been published on the effects of preferential flow on water balance in soil covers in the current study an inclined layered soil cover with a 10 cm wide sand filled channel pathway in a silty clay barrier layer was built over reactive waste rock in the laboratory the channel or preferential flow pathway represented the aggregate of cracks or fissures that may occur in the barrier during compaction and or climate induced deterioration precipitation runoff interflow percolation and water content were recorded during the test a commercial software vadose w was used to simulate the measured water balance and to conduct further sensitivity analysis on the effects of the location of the channel and the saturated hydraulic conductivity of the channel material on water balance the maximum percolation 80 1 of the total precipitation was obtained when the distance between the mid point of the channel pathway and the highest point on the slope accounted for 71 of the total horizontal length of the soil cover the modeled percolation increased steadily with an increase in the hydraulic conductivity of the channel material percolation was found to be sensitive to the location of the channel and the saturated hydraulic conductivity of the channel material confirming that proper cover design and construction should aim at minimizing the development of vertical preferential flow in barrier layers the sum of percolation and interflow was relatively constant when the location of the channel changed along the slope which may be helpful in locating preferential flow pathways and repairing the barrier

shoaling of the eastern mediterranean pycnocline due to reduction of excess evaporation implications for sapropel formation a simple two layered model is applied to assess the relation between variations in the depth of the permanent pycnocline and changes in the excess of evaporation over freshwater input in the eastern mediterranean this study is performed to estimate the magnitude of the excess evaporation at times of sapropel formation in the eastern mediterranean pycnocline shoaling from a depth below the euphotic layer to a depth within that layer at times of sapropel formation has been inferred from the planktonic foraminiferal record by rohling and gieskes 1989 the model suggests that a decrease in the eastern mediterranean excess evaporation defined as evaporation minus total freshwater input by about 8 5 1011 m yr 1 would suffice to invoke shoaling of the pycnocline to a depth within the euphotic layer a consideration of the effects exerted by concomitant changes in the thermal balance suggests that the necessary decrease of excess evaporation may even be smaller than the above estimate

oxygen influx and geochemistry of percolate water from reactive mine waste rock underlying a sloping channelled soil cover an ideal engineered soil cover can mitigate acid rock drainage ard by limiting water and gaseous o2 ingress into an underlying waste rock pile however the barrier layer in the soil cover almost invariably tends to develop cracks or fractures after placement these cracks may change water flow and o2 transport in the soil cover and decrease performance in the long run the present study employed a 10 cmwide sand filled channel installed in a soil barrier layer silty clay to model the aggregate of cracks or fractures that may be present in the cover the soil cover had a slope of 20 oxygen transport through the soil cover and oxidation of the underlying waste rock were investigated and compared to a controlled column test with bare waste rock without soil cover moreover gaseous o2 transport in the soil cover with channel and its sensitivity to channel location as well as the influence of the saturated hydraulic conductivity of the channel material were modeled using the commercial software vadose w the results indicted that the waste rock underlying the soil cover with channel had a lower oxidation rate than the waste rock without cover because of reduced o2 ingress and water flushing in the soil cover with channel which meant a partial soil cover might still be effective to some extent in reducing ard generation gaseous o2 ingress into the covered waste rock was more sensitive to the channel location than to the saturated hydraulic conductivity of the material filling the channel aqueous equilibrium speciation modeling and scanning electron microscopy with energy dispersive x ray analysis indicated that secondary minerals formed as a result of the oxidation of the waste rock included gypsum and goethite in the covered waste rock and schwertmannite and other fe oxides in the uncovered waste rock the findings of the study provided insight into the effect of channel flow on o2 transport and oxidation of the covered waste rock which may help to improve soil cover design and construction to minimise the generation of preferential flow in the barrier layer

a mechanistic model for water seepage through thick unsaturated zones in fractured rocks of low matrix permeability the theme developed in this paper is that water seepage in thick unsaturated zones in fractured rocks of low matrix permeability cannot be understood by considering spatial and temporal averages we suggest that most such seepage proceeds in an unsteady episodic manner in localized preferential pathways mechanisms are proposed and explored which permit water to flow relatively freely in networks of interconnected fractures in the presence of strong suction pressures from an unsaturated rock matrix imbibition into the rock matrix is reduced by limited wetted area the episodic nature of flow and possibly also by the presence of mineral coatings of low permeability on the fracture walls these effects and conditions combine to limit total imbibition rates to values less than saturated matrix hydraulic conductivity leaving the rock matrix in partially saturated conditions even as water is flowing freely in portions of the fracture network the proposed conceptual model is elaborated and substantiated with analytical estimates and numerical simulation studies mechanisms are demonstrated that can funnel distributed seepage into spatially localized preferential paths subsequent horizontal broadening from dispersive mechanisms is found to be a slow process for fractures of high intrinsic permeability the presence of an unsaturated rock matrix provides constraints on fracture matrix interface areas for imbibition and on the frequency of episodic deep seepage events further studies are needed to test the proposed model

the application of resin impregnation to the three dimensional study of chalk pore geometry abstract asp art of a wider study of the hydraulic properties of upper cretaceous chalk from east yorkshire and the north sea a method of pore space casting is being employed thus with the aid of the scanning electron microscope it is possible to obtain by direct visual observation information about the shape and size of pores and grains the connectedness and roughness of pore channels the fluid flow in porous rocks a more detailed understanding of the nature of hydrocarbon of water bearing rock is becoming increasingly important in pursuance of studies of oil exploration oil exploitation and geotechnics in this paper a method of impregnation and casting the pore space in chalk is described together with some preliminary observations of chalk pore geometry

preferential flow in a sandy vadose zone 1 field observation abstract field experiments of water movement in the lower portion of an unsaturated zone i e vadose zone are far more difficult to conduct than those in the root zone thus our concept of the transport mechanism in the vadose zone is still primitive and mainly an extrapolation of our understanding of transport in the root zone recent results from field experiments conducted at the hancock agricultural research station indicated that water and solute applied uniformly to soil surfaces did not flow through the entire vadose zone by using dye tracing and profile excavation field experiments were conducted during the 1987 growing season to examine water flow patterns in the unsaturated zone of the central sand area of wisconsin csaw the results confirmed that preferential flow paths constitute the dominant flow pattern at this location water flowing through the root zone was funneled into concentrated flow paths that occupied only a small portion of the soil matrix in the vadose zone yet accounted for most of the transport the observed phenomena of preferential flow in a sandy vadose zone are discussed in this paper the mechanism and implications of preferential flow are presented in a companion paper

reconstructing the paleotopography beneath the loess cover with the aid of an electromagnetic induction sensor abstract during the last glacial period weichselian wind blown loess was deposited over the undulating landscape of central belgium which had been formed in surfacing tertiary marine sediments since valleys were filled up with a thicker loess layer than hill tops the present topography is much smoother this smoothing was enhanced by subsequent erosion processes reconstructing the paleolandscape at a detailed scale is almost impossible by conventional procedures based on soil augerings therefore the use of the electromagnetic induction sensor em38dd was evaluated as an alternative for mapping the depth to the tertiary clay substrate on our 2 7 ha study site located in the loess belt of central belgium a strong non linear relationship r 2 0 86 was found between the apparent electrical conductivity eca measured by the vertical dipole orientation of the em38dd and the depth to a tertiary clay substrate these predictions were validated by independent observations of the depth to the tertiary clay and a correlation coefficient of 0 83 with an average error of 0 22 m was found so our dense eca measurements 2 by 2 m resolution allowed us to build a three dimensionall surface of the depth to the tertiary substrate reconstructing the paleotopography beneath the loess cover this paleotopography revealed distinct erosion patterns on the surface of the tertiary clay the continuity of these was confirmed by an analysis of surface flow patterns conducted on the reconstructed paleotopography the non invasive time and cost effective electromagnetic induction sensor was found to offer new perspectives to reconstruct and analyse in detail the quaternary paleotopography beneath the loess cover

water vapor transport in the vicinity of imbibing saline plumes homogeneous and layered unsaturated porous media 1 water vapor transport in the vicinity of imbibing saline solutions was investigated in two dimensional 2 d chambers using a light transmission technique concentrated nano3 solutions brines were applied as point sources to the surface of homogenous packs of prewetted silica sand for four different sand grades the same solutions were applied to layered systems where two horizontal fine layers were embedded within a coarser matrix mimicking stratified sedimentary deposits water vapor transport from the residually saturated sand into the imbibing brine was observed in all sand grades and geometries pure water applied to sand prewetted with brine migrated into the surrounding residual brine water vapor stripping was found to enhance the lateral transport of brine in layered sand where capillary barrier effects play a major role our observations suggest that osmotic potential and vapor density lowering in saline solutions often neglected in predictive models should be taken into account when predicting the transport of brines in the vadose zone

funneled flow mechanisms in layered soil field investigations abstract the movement of water and potential pollutants in the vadose zone of fluvial deposits is often difficult to predict because fine over coarse layers may behave as capillary barriers funneling water and dissolved solutes into concentrated preferential flow paths capillary barriers have been studied in laboratory experiments and by mathematical analysis with well defined boundaries but little is known about water and solute movement in naturally layered soils this paper demonstrates how naturally occurring capillary barriers affect water and solute movement experiments were carried out in a river valley near amherst ma and on a prehistoric beach near cornell university in ithaca ny dye tracer and chloride were initially applied near the soil surface followed by intermittent rainfall over several weeks after 2 6 weeks the blue dye soil water content and chloride concentration distributions in the soil profile were examined by excavating a trench and photographing and sampling the exposed soil face at both sites the infiltrating water was diverted and flowed laterally over a relatively coarse layer at the cornell site flow broke through the fine coarse interface into the coarse layer at a few points along the barrier the primary breakthrough at the cornell site occurred at a horizontal section of the interface 2 m down slope from the point of dye application the capillary diversions generally agreed with current theory however the flow patterns were difficult to predict accurately without more detailed information about the soil layering characteristics

application of high frequency ground penetrating radar to the reconstruction of 3d sedimentary architecture in a flume model of a fluvial system abstract ground penetrating radar gpr offers a fast and efficient method for visualizing three dimensional 3d images of shallow subsurface structures we investigated the application of gpr to nondestructive imaging of deposits formed in a small experimental flume using a high frequency gpr antenna the gpr measurements made with a 1 6 ghz antenna were conducted on flume models of sandy fluvial systems we conducted two experiments one to reveal the penetration depth and resolution of the gpr antenna and to reconstruct the 3d architecture of fluvial deposits created in a flume and the other to examine the characteristics of reflection boundaries the experimental materials were mainly loamy soil the first experiment showed that a 1 6 ghz antenna was suited to laboratory use offering a depth resolution of 2 3 cm in full penetration of a bed 15 24 cm thick gpr scanning yielded an accurate reconstruction of the 3d architecture of a fluvial channel using magnetite marker beds the second experiment also successfully imaged a 3d architecture using quartz sand instead of magnetite and loamy soil which have different relative permittivities this research shows that gpr is a feasible technique for 3d analysis of experimental flume deposits

water flow in unsaturated soil in layered slopes abstract the water flow in unsaturated soil in layered slopes sandwiching coarse materials was measured using inclined soil containers placed under a rain simulator the refraction law of water flow in saturated soils was extended to the flow in unsaturated soils the extended refraction law of water flow in saturated and unsaturated soils was applied to the flow at the interface between the masa sandy loam and either the plant or gravel layer using a jump condition and particular assumptions of hydraulic conductivity of materials the data obtained on infiltration steady percolation and drainage in the soil containers could be well explained by the proposed new concept of saturated and unsaturated refraction flow so far as we know the work reported here is the first specifically designed to elucidate the effects of abrupt change of hydraulic conductivity on the flow of water in unsaturated soil slopes

preferential flow first results of a full scale flow model the main goal of a joint project undertaken by the geophysical and hydrological research units of kiel university is to study preferential flow in a large open air full scale model looking in particular at near surface penetration and flow of water through the unsaturated vadose zone an artificial irrigation device is installed in place of natural rain and a homogeneous sand body is used instead of natural soil this provides a reference model for future field experiments inside the sand body there are a large number of geophysical and hydrological sensors to measure dc resistivity using various electrode configurations water content and water potential using tdr and tensiometer instruments respectively a ground penetrating radar gpr system is installed at the surface whereas at the bottom several containers and a thin gravel layer are embedded to measure the flow arrival and the discharge of water irrigation is varied in intensity time area and salt content tracer results of the first six experiments show that the percolation of intruding water can be followed by all techniques and percolation is finally controlled by the discharge measurements these display some undulations and variations of the water front and agree with the measurements of all other sensors the redundancy achieved by the use of multiple methods was intended to enable an assessment of the reliability of the techniques used the true values of electrical resistivity before and after irrigation reflect the distribution of water saturation within the sand body a numerical 3 d inversion of the apparent resistivity provides information regarding future field experiments in which it will be possible to install only some of the sensors in order to preserve the natural structure of the soil

laboratory experiments on heat driven two phase flows in natural and artificial rock fractures water flow in partially saturated fractures under thermal drive may lead to fast flow along preferential localized pathways and heat pipe conditions at the potential high level nuclear waste repository at yucca mountain water flowing in fast pathways may ultimately contact waste packages and transport radionuclides to the accessible environment sixteen experiments were conducted to visualize heat driven liquid flow in fracture models that included 1 assemblies of roughened glass plates 2 epoxy replicas of rock fractures and 3 a fractured specimen of topopah spring tuff continuous rivulet flow was observed for high liquid flow rates intermittent rivulet flow and drop flow for intermediate flow rates and film flow for lower flow rates and wide apertures heat pipe conditions vapor liquid counterflow with phase change were identified in five of the seven experiments in which spatially resolved thermal monitoring was performed but not when liquid vapor counterflow was hindered by very narrow apertures and when inadequate working fluid volume was used

tracing solute infiltration using a combined method of dye tracer test and electrical resistivity tomography in an undisturbed forest soil profile an accurate prediction of solute infiltration in a soil profile is important in the area of environmental science groundwater and civil engineering we examined the infiltration pattern and monitored the infiltration process using a combined method of dye tracer test and electrical resistivity tomography ert in an undisturbed field soil 1 m 1 m a homogeneous matrix flow was observed in the surface soil a horizon but a preferential flow along macropores and residual rock structure was the dominant infiltration pattern in the subsurface soil saturated interflow along the slopping boundaries of a and c1 horizons and of an upper sandy layer and a lower thin clay layer in the c horizon was also observed the result of ert showed that matrix flow started first in a horizon and then the infiltration was followed by the preferential flows along the sloping interfaces and macropores the ert did not show as much detail as the dye stained image for the preferential flow however the area with the higher staining density where preferential flow was dominant showed a relatively lower electrical resistivity the result of this study indicates that ert can be applied for the monitoring of solute transportation in the vadose zone copyright 2010 john wiley sons ltd

movements of water solutes and stable isotopes in the unsaturated zones of two sand plains in the upper midwest four month long field experiments investigated movements of water and solutes through unsaturated sand plains near princeton minnesota and oakes north dakota atrazine and bromide were applied to bare soils and soils planted with corn the field plots were irrigated according to local farming practices at the end of each experiment unsaturated soils were analyzed for atrazine and bromide concentrations and oxygen and hydrogen isotope compositions of soil water most soil water was affected by evaporation but groundwater beneath the plots had no evaporative isotopic signature therefore most recharge consisted of water that was unaffected by evaporation sources of such water may have included snowmelt prolonged or high intensity rainfalls that were not interrupted by periods of drying and water that moved through preferential flow paths preferential flow also was suggested by the detection of atrazine deethylatrazine and bromide in groundwater shortly after each application of irrigation water at princeton and by isolated concentrations of atrazine and bromide in soil well below the main masses of chemicals at oakes

the influence of diagenesis on some index properties of chalk in england the chalk in england is a highly variable material and much of its variability stems from the wide variety of diagenetic processes which have been identified from lithological studies this paper reviews those processes and presents results of laboratory index tests to determine their significance the variability of the unweathered chalk is judged on the basis of approximately 600 tests to determine dry density and 200 atterberg limit tests the influence and extent of a number of diagenetic processes are examined the degree to which the index properties are predictable both stratigraphically and geographically is discussed en angleterre la craie est un materiau qui varie beaucoup cette variabilite est le resultat d une grande variete de phenomenes diagenetiques qui ont ete identifies a partir des etudes lithologiques cet article passe en revue ces phenomenes et puis presente les resultats des essais des proprietes caracteristiques faits dans le laboratoire avec le but de determiner leur signifi

setting and tectonic evolution of some eastern mediterranean deep sea basins abstract nine discrete deep sea basins seven from the calabrian and mediterranean ridges and two from the strabo trench were explored geologically during several cruises carried out from 1978 to 1984 in the eastern mediterranean the seven basins displaying similar geological features calabrian and mediterranean ridges may be divided into three groups on the basis of their size 1 very small basins botticelli and raffaello basins whose area ranges from 1 1 to 4 3 km 2 2 small basins ares aphrodite and katia basins from 7 to 13 km 2 and 3 large basins bannock and cleft basins from 22 to 74 km 2 the two basins from the strabo trench tyro and kretheus basins whose areas range from 16 to 20 km 2 are considered separately tectonics is the most important element affecting basin formation processes progressive folding and faulting of messinian pliocene and quaternary sediments in the calabrian and mediterranean ridges allows the infiltration of water into the subbottom and dissolution of messinian evaporites so that collapse of the overlying unconsolidated plio quaternary cover creates local distensive tectonics superimposed on the regional compressive tectonic setting the size of the basins reflects different steps in this process very small basins are related to the fracturing occurring at the top of anticlines small basins originate when anticlines are faulted and large amounts of water are able to reach the evaporites and increase the intensity of leaching finally large basins are related to regional tectonic lineaments both compressive large reverse faults overthrusts and strike slip salt diapirism may be associated with some of these situations the process responsible for the tyro and kretheus basins formation is the pull apart mechanism connected with the strike slip motion occurring in that area the geometric position of subaqueously dissolved evaporites seems to influence the environment on the basin floor brines originating from the dissolution of buried evaporites are thought to disperse in the subbottom whereas brines originating from dissolution of evaporites cropping out on the basin walls can flow to the floor and cause stagnation only if the shape of the basin prevents the action of bottom currents

after the deluge mediterranean stagnation and sapropel formation in an east mediterranean marine core the upper sapropel begins soon after the start of a global event a very heavy precipitation which occurred in the equatorial latitudes during the late glacial early holocene this heavy precipitation in africa channelled by the nile river across 35 of latitude produced a low salinity surface layer in the east mediterranean in this confined basin with high bottom salinity the steep salinity gradient stratified the water column the stagnant bottom waters triggered the sapropel formation cretaceous sapropels in the tropical oceans may result from the same chain of events in warm humid climates with contrasting wet and dry seasonal rhythm

fluvio pedogenic processes in an ephemeral stream channel nahal yael southern negev israel abstract a detailed stratigraphic survey conducted in the alluvial fill of the channel of nahal yael a small catchment in the southern negev desert indicates the existence of a continuous compacted red colored unit at an average depth of 50 cm beneath the surficial grey non cohesive alluvium granulometric distinction between the grey and the red alluvium is evident only within the fine

gypsum precipitation from cold brines in an anoxic basin in the eastern mediterranean in 1968 hot brines from which gypsum had precipitated were discovered in the red sea in a divergent plate boundary setting with hydrothermal activity1 we now report the discovery of cold brines in an entirely different geodynamic situation a convergent plate boundary in the eastern mediterranean where the heatflow is very low2 and no hydrothermal activity occurs decimetric pure gypsum crystals precipitate from the cold brines which occupy the bottom of a rimmed anoxic basin near the southern edge of the mediterranean ridge close to the sirte abyssal plain nucleation of the crystals does not occur at the surface but from the deep brines because the salinity of the water is normal down to the depth of 3 000 m we propose the name bacino bannock for this basin after the consiglio nazionale delle ricerche r v bannock from which the bottom water brines were surveyed and sampled

effect of groundwater and sea weathering cycles on the strength of chalk rock from unstable coastal cliffs of nw france abstract the aim of this paper is to evaluate the role of groundwater and sea weathering on the strength of the chalk rocks exposed on the coastline of the english channel in normandy nw france we present a study of the rock strength variations of three representative chalk units lewes chalk seaford chalk and newhaven chalk exposed at various locations on the coastal chalk cliffs the combination of ucs tests and sem observations have been used 1 on dry natural chalk samples 2 on chalk samples at various moisture contents 3 on dry chalk samples submitted to a 10 day cycle of alternating wetting and drying by distilled water and by sea water dry chalk samples show low ucs strength 3 46 4 mpa indicative of very weak rocks when chalk samples are submitted to progressive water wetting they present a decrease of ucs strength and young s modulus of 40 to 50 this behaviour begins at low values of water content within the chalk i e for a degree of water saturation ranging between 10 and 17 when chalk samples are submitted to an artificial weathering cycle with distilled water a decrease in strength is observed whereas the young s modulus increases sem observations indicate the occurrence of microcracks and particle aggregates in the sample when chalk samples are submitted to an artificial weathering with sea water the decrease of ucs strength and young s modulus achieves a minimum sem observations indicate salt crystals within the chalk on the coastal cliffs of nw france weathering processes depend both on chalk lithology which show a range of sensitivity to weathering and on the location of the chalk in the coastal area processes allied to the degree of weathering e g salt crystallisation or fresh water disaggregation differ in the chalk massif on the cliff face and on the shore platform

lateral flow in loamy to sandy kandiudults of the upper coastal plain of georgia usa abstract interest in site specific agronomic management in intensively cropped regions necessitates characterization of subsurface water movement for efficient water management irrigation timing and control of off site agrichemical movement soils formed in fluvial sediments in portions of the upper coastal plain of georgia usa are extensively used for peanut cotton and corn production certain proximate soils in this region possess contrasting subsoil properties and it was hypothesized that these differences would have major effects on water redistribution across the landscape this could be important in irrigation management where soils possessing increased impedance to vertical flow could require decreased irrigation as opposed to soils without vertical flow restrictions at a site near plains ga usa hydraulic properties of soils with differences in overlying sand thickness and contrasting argillic horizon textures sandy vs loamy were evaluated the soils were predominantly in loamy and sandy families of typic arenic and grossarenic kandiudults laboratory measurements field monitoring of matric potentials under simulated and natural rainfall and modeling vs2dt were utilized to evaluate soil hydraulic properties reduction in vertical k s occurred in horizons containing higher clay argillic horizon changes in tension and build ups in hydraulic gradients associated with infiltration and redistribution events existed above and within horizons with low k s evidence suggested there was less groundwater recharge occurring in the loamy than in the sandy pedons suggesting more pronounced lateral flow occurred in the loamier soils model simulations of water movement across a slightly sloping 1 simulated landscape indicated lateral gradients of flow existed within the solum of these soils analyses of tracer br movement suggested a very slight lateral redistribution occurred within a relatively short monitoring period within the sandy pedon s bt1 horizon and the bt2 and bt3 horizons of the loamy pedon evidence suggested both loamy and sandy argillic horizons slightly but not overwhelmingly induced lateral flow on these landscapes

ground penetrating radar of northern lacustrine deltas ground penetrating radar gpr was used in several selected deltaic sedimentary environments to better understand subsurface stratigraphy and reconstruct former depositional environments the profiles provide high resolution continuous subsurface data on facies thickness and depths orientation of major sedimentary structures postdepositional failure planes and depth of peat deposits field experiments were carried out on six river deltas records from four of the deltas exhibit sedimentary facies a record from one delta shows a possible slump and records from another delta reveal the thickness and stratigraphic relationships of peat deposits the delta types are i sandy wave influenced ii sandy immature wave influenced steeper middle and lower shoreface iii sandy braided and iv gravelly fan foreset in areas of limited subsurface control stratigraphic logs from drill core cutbank exposure or geophysical logs radar profiles can provide big picture perspectives of the subsurface

geological and geotechnical characterisation for offshore wind turbine foundations a case study of the sheringham shoal wind farm abstract this paper characterises the soil conditions at the sheringham shoal wind farm in the north sea in the context of designing foundations for offshore wind turbines the purpose is to provide a realistic reference case study for research and practice in the emerging field of offshore wind energy the soil data was obtained between 2005 and 2008 in an investigation program involving field measurements and laboratory experiments the characterisation focuses on soil properties which are relevant for evaluating the performance of foundations for offshore wind turbines the soil profile at the sheringham shoal site consists of four main units two clay strata interbedded with a sand layer and underlain by a chalk bed the heavily overconsolidated state of the clays and the densely compacted state of the sand dictate the behaviour of these soils the chalk bed is characterised by varying degrees of weathering leading to significant variation in properties ranging from those typical for stiff soil to soft rock these four main units though differ considerably in soil composition share several common characteristics including high shear strength and high stiffness but their shear stiffnesses reduce significantly both at high mobilised static shear strength and at medium to high mobilised strength under cyclic loading the soil stiffness is an important input parameter for the design of offshore wind turbine foundations and hence the degradation of stiffness is an important issue at this wind farm a number of soil properties at the site show considerable variability which requires a specific foundation design tailored for each location in order to be both safe and cost effective

effect of structure and texture on infiltration flow pattern during flood irrigation understanding the flow pattern of water and solute in subsurface soils is critically important in the fields of agricultural and environmental sciences dye tracer tests using a flood irrigation of brilliant blue fcf solution 5 g l 1 and excavation method was performed to investigate the effect of texture and structure on the infiltration pattern at three different field soils developed from granite gr gneiss gn and limestone ls the gr soil showed a homogeneous matrix flow in the surface soil with weak medium granular structure and a macropore flow along pegmatitic vein and plant root in c horizon the surface horizon a1 of gn soil with moderate medium granular structure and many fine roots had matrix flow the fingering occurred at the interfaces of sandy loam a horizon and loamy sand c horizon in gr soil and loam a1 horizon and sandy loam a2 horizon in gn soil the ls soil with strong coarse prismatic structure and the finest texture showed a macropore flow along cracks and had the deepest penetration of the dye tracer the macropore crack and vein layer interface and plant root induced the preferential flow in the studied soils

an engineering approach to fingered vadose pollutant transport abstract results of many independent experimental findings related to fingered preferential flow are combined into a concise conservative engineering methodology for predicting pollutant transport through fingered flow paths preferential flow can occur in all textures of soil with fingering occurring in less structured coarse soils giving over to macropore flow in finer textured soil regimes a simple example comparing groundwater loading of naphthalene using plug flow and fingered flow assumptions illustrates that fingered flow can increase contaminant loading to groundwater aquifers by over two orders of magnitude at sites with coarse vadose zone materials

using ground penetrating radar to detect layers in a sandy field soil abstract pollutant transport in sandy soils can be very complex due to the presence of coarse sand lenses water flows laterally over the coarse material and subsequently breakthrough occurs in concentrated pathways called fingers this funneled flow process is a form of preferential flow reducing solute travel time and degradation of organic chemicals in this paper we test ground penetrating radar gpr as a tool for detecting layers in the soil several gpr transects were established on a fine sandy loam soil throughout the growing season and subsequent fall period to find the best time to reveal layer structures the effect of the spatially varying moisture content on the radar velocity was determined from actual measurements with soil samples and by using the common mid point cmp technique the optimal time to find coarse layers with gpr in this soil was at the end of the fall season when the soil was wetted and evaporation had decreased the depth of layers as indicated by gpr was highly sensitive to the soil moisture content and could be in error by as much as 0 4 m on a depth scale of 1 5 to 2 m if an average propagation velocity was used a satisfactory depth prediction of textural interfaces was obtained non destructively by collecting data in both reflection and cmp mode

hydropedological investigations with ground penetrating radar gpr estimating water table depths and local ground water flow pattern in areas of coarse textured soils in coarse textured soils ground penetrating radar gpr can provide continuous high resolution records that chart the depth to water tables the use of this information can increase confidence in hydropedological site assessments and reduce the number of wells needed for water table depth and ground water flow determinations ground penetrating radar was used to map spatial and temporal variations in water table depths and ground water flow patterns within an unconfined aquifer located beneath an eolian landscape in northwestern indiana compared with the data collected at a limited number of wells the greater number of observations with gpr provided more comprehensive site coverage and mapped more intricate local ground water flow patterns over a 2 year period gpr revealed systematic temporal and spatial variations in water table depths and local ground water flow patterns

shipboard routine and pressure filtration system for pore water extraction from suboxic sediments abstract a shipboard working procedure for the handling and porewater extraction of suboxic sediments is outlined in addition a detailed description is given of the shipboard pressure filtration system that has been used to extract porewater this procedure in combination with the pressure filtration system has been demonstrated to produce reliable porewater from suboxic sediments

boron isotope and geochemical evidence for the origin of urania and bannock brines at the eastern mediterranean effect of water rock interactions the origin of hypersaline brines from urania and bannock deep anoxic basins in the eastern mediterranean sea has been investigated by integrating geochemical data and boron isotopic ratios bottom brines from urania basin have chloride contents up to 4200 mmole kg h2o and a marine na cl ratio 0 87 all the other ionic ratios are different from the marine ratios and show a relative enrichment in ca k br and b and depletion in mg and so4 as normalized to the chloride ion the 11b values of the urania brines 11b 29 8 2 9 n 7 are lower than that of mediterranean seawater 39 the concentrations of cl and na which make up 95 of the total dissolved ions in molal units suggest that the urania brines were derived from eightfold evaporated seawater the relative enrichment of ca and depletion of mg and so4 reflect dolomitization gypsum precipitation and sulfate reduction processes which modified the original evaporated seawater while the brines were entrapped as interstitial waters in the sedimentary section of the mediterranean the relative enrichments of br b and k and the low 11b value of the urania brines suggest high temperatures interactions of the evaporated sea water with sediments mass balance calculations suggest that desorption of exchangeable b from the sediments 11b 20 modified the marine b isotopic composition of the original eightfold evaporated seawater potassium was also leached from clay minerals whereas br was contributed from degradation of organic matter in the sediments this is consistent with a thermal anomaly up to 45 c recorded at depth in the region of urania basin in contrast bottom brines and shallow interstitial fluids from bannock basin with low temperatures 15 c show marine 11b 11b 39 6 2 8 n 5 38 5 2 2 n 5 respectively and b cl ratios 7 10 4 the b isotope data confirm that the bannock brines were derived from twelvefold evaporated seawater we argue that the brines from both basins are relics of fossil evaporated seawater that was entrapped in late miocene sediments and accumulated in the deep basins of the mediterranean seafloor

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

mediterranean functioning and sapropel formation respective influences of climate and hydrological changes in the atlantic and the mediterranean abstract during ocean drilling program odp legs 160 and 161 sapropels were recovered both in the western and eastern mediterranean this obliges to a reassessment of the previous studies focused on sapropels from only the eastern mediterranean and to consider the changes which occurred in the mediterranean climate but also in the water characteristics both in the atlantic and in the western mediterranean in the north atlantic the position of the polar front which migrated southwards during glacial times and the melting of northern ice caps during interglacial periods together with the convection in the labrador and norwegian seas appear essential to control the salinities of the waters facing the strait of gibraltar the salinities of the surface and intermediate layers constitute the first driving force of the mediterranean dynamics the second driving force being the mediterranean climate the stagnation of deep waters leading to sapropel deposition in the western mediterranean may be explained by a drastic weakening of the density difference between mediterranean outflow and atlantic intermediate waters facing the strait of gibraltar this weakening was induced primarily by the salinity decrease of atlantic surface water and secondly by a rather high salinity in the atlantic intermediate layer rather than by a drastic deterioration of the mediterranean climate this scenario probably concerns most of the sapropel events and it may be used for the knowledge of atlantic and mediterranean functioning over climatic changes

unraveling chalk microtextural properties from indentation tests abstract the petrographical petrophysical and geomechanical properties of the less commonly studied low permeability or tight chalks are presented in this study the latter are relevant as potential unconventional reservoirs or intra reservoir seals tight chalks encompass different lithotypes in which the main factors controlling the petrophysical properties as shown in this study are the non carbonate content and the degree of cementation those parameters strongly modify chalk microtexture and thus its porous network reducing pore sizes hence altering poroperm properties in order to better understand the characteristics of tight chalks an integrated petrographical petrophysical and geomechanical study was carried out on a set of 65 chalk samples from northwestern european outcrops covering a wide range of lithotypes the dataset gathered covers a broad spectrum of values for the determined petrophysical e g porosities from 9 to 45 and geomechanical properties e g strengths from 3 to 60 mpa in the framework of this study indentation tests were performed on the chalk samples this technique proved to be a successful method to quickly estimate rock strength indeed a good linear correlation r2 0 90 has been established between indentation strength and ucs furthermore indentation tests yielded valuable information about the chalk properties both in terms of petrographical cementation clay content petrophysical exponential relationship with porosity and geomechanical in relation to the elastic parameter and plasticity index properties this cheap and easy to operate method is a promising tool to indirectly estimate the mechanical parameters of chalks when core samples are unavailable for laboratory testing in oil field wells

sedimentary and hydraulic characterization of a heterogeneous glaciofluvial deposit application to the modeling of unsaturated flow abstract flows in the unsaturated zones of alluvial deposits are often poorly understood at the scale of structures such as stormwater infiltration basins the heterogeneous nature of the sediment inherent to this type of formation can lead to preferential flows the difficulty of quantifying them lies in obtaining hydrodynamic parameters representative of the soil structure in situ when the latter is inaccessible this study proposes a method of estimating the hydrodynamic parameters of the lithofacies composing a glaciofluvial deposit east lyon france and their integration in a 2d flow model to model flow in the unsaturated zone the approach developed comprises a sedimentological study based on the miall code carried out to determine the analogy between the lithofacies of the study site and those of two glaciofluvial reference sites currently in the process of formation chamonix france breidamerkurjokull iceland thereby permitting easy access to all the lithofacies identified on the study site the water retention and hydraulic conductivity curves were obtained on the reference sites by using beerkan type infiltration tests for finely textured materials completed by the arya and paris model and data from the literature for coarser materials thus hydrofacies corresponding to all the lithofacies were characterized these hydrofacies were used to model a drainage phase on the study site at the scale of a trench 13 50 m long 2 50 m deep the model highlighted the importance of the role played by the spatial distribution of hydrofacies on flows with a pronounced capillary barrier effect of the very coarse lithofacies and a sand lens leading to funneled flows by assuming that there is a direct link between the sedimentary lithological heterogeneity and the unsaturated hydrodynamic properties of the materials composing its different structures it was possible to perform a detailed hydrodynamic characterization of the unsaturated zone that could then be used to model flows and in particular highlight preferential flows

full wave calibration of time and frequency domain ground penetrating radar in far field conditions full wave modeling of ground penetrating radar gpr data using green s functions for wave propagation in planar layered media and antenna characteristic global reflection and transmission functions for describing far field antenna effects including antenna medium interactions has shown a great potential for nondestructive characterization of soils and materials the accuracy of the retrieved parameters in the gpr data inversion depends on the accuracy of the gpr external calibration in this research we studied the stability and the repeatability of two different gpr systems namely frequency and time domain systems a combination of a vector network analyzer and 800 5200 mhz horn antenna was used as a frequency domain gpr fd gpr whereas a gssi gpr system using a 900 mhz bowtie antenna was used as a time domain gpr td gpr both gpr systems including their antennas were calibrated several times using measurements with the antennas at different heights over a perfect electric conductor pec in the laboratory as well as over a water layer in addition measurements were performed over a thin water layer and a relatively thick sandy soil layer as validating medium the results showed that the fd gpr is relatively stable while the td gpr presents a significant drift which can be accounted for using corrections based on the air direct coupling waves free space measurements water and pec based calibrations provided very similar results for the gpr calibration functions inversions for the water layer and the sandy soil layer provided reliable results and showed a high degree of the repeatability for both radar systems the error on the calibration based on inaccurate antenna heights over pec showed the significant errors on the inversion results for the directive antenna horn antenna but less error for the bowtie antenna this analysis demonstrated the general validity of the proposed far field radar modeling approach not only with respect to frequency and time domain radars but as well with respect to the calibrating medium

effect of antecedent soil moisture on preferential flow in a texture contrast soil summary the effect of soil moisture status on preferential flow in a texture contrast soil was investigated by applying 25 mm brilliant blue dye tracer to soil profiles at high and low antecedent soil moisture differences in soil morphology and chemistry between soil profiles had little effect on the depth of dye infiltration and dye distribution down the profile antecedent soil moisture strongly influenced the type depth and rate of dye tracer movement in the wet treatment the dye tracer infiltrated to depths between 0 24 and 0 40 m at an average rate of 120 mm h 1 whilst in the dry treatment the same volume of dye tracer infiltrated to between 0 85 and 1 19 m depth at an average rate of 1160 mm h 1 in dry antecedent conditions finger flow developed in the a1 horizon as a result of water repellency in the wet treatment the wetting front developed permutations but did not break into fingers despite similar particle size distributions flow in the a2 e was slower than the a1 horizon due to the absence of macropores in the dry treatment the dye tracer ponded on the upper surface of the b21 horizon which then spilled down the sides of the large clay columns as rivulets at rates of between 2000 and 3000 mm h 1 the dye tracer accumulated at the base of the columns resulting in backfilling of the inter column shrinkage cracks at an estimated rate of 750 mm h 1 in the subsoil water movement occurred via shrinkage cracks which resulted in flow by passing 99 of the soil matrix in the b21 horizon and 94 of the soil matrix in the b22 horizon evidence of rapid and deep infiltration in dry texture contrast soils has implications for water and solute management this knowledge could be used to i improve irrigation and fertilizer efficiency ii explain variations in crop yield iii reduce salinity through improved leaching practices iv reduce the risk of agrochemicals contaminating shallow groundwater

the origin of mediterranean interstitial waters relics of ancient miocene brines a re evaluation re examination of interstitial waters from sixteen mediterranean dsdp sites reveals that the high salinity values of these waters up to 350 g l do not reflect dissolution of underlying evaporites but are rather related to miocene evaporated sea water trapped in the sediments and modified by diagenetic reactions and advection diffusion only in two shallow sites was the chemical composition of the interstitial waters controlled by evaporite dissolution the large variations in the chemistry of the interstitial waters among different sites suggests that the mediterranean was divided into separate sub basins with different chemical compositions the composition of interstitial waters records the history of the mediterranean since early miocene as follows 1 salinization of the western mediterranean during the early and middle miocene 2 intrusion of low salinity water in the eastern basin during the middle miocene 3 desiccation by evaporation of the mediterranean during the messinian late miocene other processes such as sulphate reduction and dolomitization took place along the sedimentary section the diffusion advection processes in the interstitial water in addition to smoothing the contrasts within vertical profiles of chemical concentrations caused an upward shift in the liquid phase profile in respect to the solid phase changed the vertical trend in the case of an end member which became exhausted and brought about vertical changes associated with the porosity structure

geological evidence for mud diapirism on the mediterranean ridge accretionary complex abstract a mud breccia has been repeatedly cored from four mud diapir fields located on the crest of the mediterranean ridge this breccia is composed of subrounded clasts supported by a clay rich matrix and ranges in age from cretaceous to early miocene sedimentological analysis allows identification of a primitive intrusive and a reworked mud breccia the latter being formed by mud extrusion and gravitational reworking of the former homogeneous mud sorted by grain size which occurs at the top of the diapirs has been interpreted as a lake deposit based on composition and carbon isotopic ratios gases present within the diapiric material suggest a partial thermogenic origin and gas escape structures have been identified in the mud breccia and host sediments carbonate crusts occurring in the host sediments are not related to bacterial oxidation of methane and consequent authigenic calcite precipitation their carbon and oxygen isotopic ratios reveal that they are characteristic of early deep sea lithification in the mediterranean sea the presence of a marker bed composed of mn nodules and bacterial colonies the mud lake deposits showing lower carbonate content than primitive mud breccia and the gas escape structures suggest the presence of active fluid vents in the vicinity of the diapiric structures evidence of active mud diapirism can be found from about 300 000 yrs b p to the present

funneled flow mechanisms in a sloping layered soil laboratory investigation artificial capillary barriers are being used to divert water away from sensitive underground regions conversely funneled flow over natural capillary barriers may increase the danger of groundwater contamination by decreasing the travel time and contact area there have been relatively few experimental studies of capillary barrier flow patterns in this study water was applied uniformly across the top surface of a backlit tilting chamber 1 cm thick 110 cm high and 180 cm long in which a coarse sand layer was imbedded in a fine sand bedding slope and water application rates were varied between 0 and 12 and 1 and 3 cm h 1 respectively after attaining steady state matric potential was measured along the textural interface and photos of dye traces were taken in order to visualize streamlines the funneled flow was characterized by three discrete regions an initial capillary diversion a breakthrough region and a toe diversion the breakthrough region consisted of a significant zone of partial breakthrough where the vertical flux into the coarse layer was less than the water application rate the lateral distance of the capillary diversion was explained well by previously published relationships when the water entry value at the textural interface was replaced by lower observed matric potential at which breakthrough occurred at the most upslope point the length of the capillary diversion was overpredicted using the air entry value finally the toe of the coarse layer had significant observed effects on funneled flow patterns which have previously received little if any attention the results of this study imply that the slope of the coarse layer and infiltration rate will largely govern the effectiveness of capillary barriers and that capillary barriers are less effective than previously assumed

hydrologic issues in arid unsaturated systems and implications for contaminant transport analysis of unsaturated flow and transport in arid regions is important not only in water resource evaluation but in contaminant transport as well partic ularly in siting waste disposal facilities and in remediat ing contaminated sites the water fluxes under consid eration have a magnitude close to the errors inherent in measuring or in calculating these water fluxes which makes it difficult to resolve basic issues such as direction and rate of water movement and controls on unsaturated flow the purpose of this paper is to review these issues on the basis of unsaturated zone studies in arid settings because individual techniques for estimating water fluxes in the unsaturated zone have limitations a variety of physical measurements and environmental tracers should be used to provide multiple independent lines of evidence to quantify flow and transport in arid regions the direction and rate of water flow are affected not only by hydraulic head gradients but also by temperature and air pressure gradients the similarity of water fluxes in a variety of settings in the southwestern united states indicates that vegetative cover may be one of the pri mary controls on the magnitude of water flow in the unsaturated zone however our understanding of the role of plants is limited most unsaturated flow in arid systems is focused beneath topographic depressions and diffuse flow is limited thick unsaturated sections and low water fluxes typical of many arid regions result in preservation of paleoclimatic variations in water flux and suggest that deep vadose zones may be out of equilib rium with current climate whereas water movement along preferred pathways is common in humid sites field studies that demonstrate preferential flow are restricted mostly to fractured rocks and root zones in arid regions results of field studies of preferential flow in humid sites generally restricted to the upper 1 2 m because of shallow water tables cannot be applied readily to thick vadose zones in arid regions

recent sapropel formation in the eastern mediterranean during the 1983 expedition of the rv tyro in the eastern mediterranean a combined programme of seismological micropalaeontological and geochemical research was performed the geochemical research focused mainly on the interstitial water and the chemical composition and origin of sapropels for this purpose box cores piston cores and bottom water samples were collected we report here that some of these cores showed clear evidence of long term stagnant bottom water conditions in a small basin south of crete for which we propose the name tyro basin 1 the bottom water is strongly anoxic whereas the sediment down to at least 400 cm is sapropel to sapropelic as salt concentrations in the bottom water are eight times higher than in normal seawater the anoxic conditions in this basin are probably due indirectly to dissolution of salt from a nearby diapir

dissolution and collapse features on the eastern mediterranean ridge abstract morphologic features similar to subaerial karstic dolines and zanjones have been observed on the eastern mediterranean ridge using a near bottom towed geophysical instrument package these features are found only on the floors of certain large depressions which lie above the crests of subcropping evaporite diapirs the coincidence of dissolution controlled morphology with the subcropping soluble evaporite confirms earlier suggestions that the large depressions result from dissolution of the evaporites and collapse of the overlying strata

modeling fingered flow of water in soils owing to wetting front instability a review abstract fingered flow in the unsaturated zone caused by wetting front instability enhances solute leaching to the groundwater this paper reviews recent progress in fingered flow research focusing on theoretical results and model development a variety of stability criteria have been derived to predict wetting front instability mainly through linear and sometimes non linear stability analysis but also by theoretically analyzing infiltration into dry soils and by stochastic methods that take into account random variations of the soil properties fluid pressure and front location these stability criteria are discussed and compared eight expressions for finger size are presented they fall into three categories based on the dependence on the ratio of the infiltration rate to the soil hydraulic conductivity in the finger next the modeling of finger growth is discussed because of its relevance to solute transport recent advances in the measurement and modeling of finger behavior in moist soils are thoroughly reviewed various models ranging from easily applied closed form equations for risk assessment to sophisticated transient numerical codes have been developed over the past 15 years these are discussed and selected results are shown finally some remaining gaps in our understanding are given among these are the role of the initial water content the nature of the flow in the distribution zone above the fingers the effect of soil heterogeneity on wetting front instability and the combined effect of soil heterogeneity and wetting front instability on field scale solute transport

a review of selected engineering geological characteristics of english chalk abstract chalk is a variable material the properties of which are dependent upon its composition textural features and diagenetic history with the exception of certain horizons in the lower chalk that contain appreciable amounts of clayey material the english chalk is a remarkably pure micritic carbonate rock that generally can be divided into coarse and fine fractions the latter comprises 70 80 of chalk cementation took place more or less contemporaneously with deposition so that the sediment was able to support relatively high overburden pressures hence high values of porosity were retained chalk varies appreciably in density and hardness the harder chalks are the result of diagenetic processes and bioturbation that brought about densification in soft chalks the grains are only bound together at the points of contact by thin films of calcite the latest classification of chalk is based on an assessment of intact dry density discontinuity aperture and discontinuity spacing chalk tends to vary from moderately weak to moderately strong and its strength is significantly reduced on saturation under triaxial loading conditions diagonal shear failure tends to occur at lower confining pressures but at higher confining pressures barrel shaped failure occurs indicating plastic deformation and textural disaggregation similarly at low loading chalk exhibits low volume compressibility but much more significant consolidation occurs if the yield stress is exceeded chalk undergoes dissolution and so solution features are found throughout its outcrop mineworkings in the chalk extend back into the distant past the most ancient being those excavated in the neolithic age for flint several types of workings exist collapse of old mineworkings most of which are unrecorded is difficult to predict the potential for subsidence caused by the collapse of both mineworkings and dissolution features affects development and its occurrence can lead to the abandonment of property or worse the loss of lives

soil moisture and dry bulk density patterns in bare dune sands abstract recent research has shown that irregular wetting and preferential flow may occur in heterogeneous field soils bare dune sands which at first sight show the greatest homogeneity were sampled volumetrically at nine locations in temperate and arid areas to determine the spatial distribution of soil moisture content and dry bulk density soil moisture patterns were irregular even in extremely dry situations as functions for dune sands are very steep in the dry range small differences in water content result in huge differences in hydraulic conductivity these differences induced by soil moisture variability may result in anisotropy of the system and hysteresis tends to magnify this phenomenon so if soil moisture differences exist they will be consolidated and even amplified during new rain events at one site on a recently deposited dune sand infiltrating water was able to transform a one layer soil system into a two layer soil system inducing preferential flow at the layer interface at another site preferential flow paths appeared at the soil surface as sand columns as a result of the displacement of the dry sand between the flow paths caused by wind erosion in all the dunes studied dry bulk density patterns were irregular and tended to be slightly vertically orientated spatial distributions of volumetric and gravimetric soil water content showed great similarity