field measurements of the flux and speed of wind blown sand a field experiment was conducted to measure the flux and speed of wind blown sand under known conditions in a natural setting the experiment run at pismo beach california involved a tract 100 m long parallel with the wind by 20 m wide the site was instrumented with four arrays of anemometers to obtain wind velocity profiles through the lower atmospheric boundary layer temperature probes to determine atmospheric stability and wind vanes to determine wind direction from these measurements wind friction speeds were derived for each experimental run in order to measure sand saltation flux a trench 3 m long by 10 m wide transverse to the wind direction by 0 5 m deep was placed at the downwind end of the tract and lined with 168 collector bins forming an egg box pattern the mass of particles collected in each bin was determined for four experimental runs in order to assess various sand trap systems used in previous experiments 12 leatherman traps one fryberger trap and one array of ames traps were deployed to collect particles concurrently with the trench collection particle velocities were determined from analysis of high speed 3000 and 5000 frames per second motion pictures and from a particle velocimeter sand samples were collected from the trench bins and the various sand traps and grain size distributions were determined fluxes for each run were calculated using various previously published expressions and then compared with the flux derived from the trench collection results show that bagnold s 1941 model and white s 1979 equation most closely agree with values derived from the trench comparison of the various collector systems shows that the leatherman and ames traps most closely agree with the flux derived from the trench although these systems tended to under collect particles particle speeds were measured from analysis of motion pictures for saltating particles in ascending and descending parts of their trajectories results show that particle velocities from the velocimeter are in the range 0 5 7 0 m s 1 compared to a wind friction velocity of 0 32 0 43 m s 1 and a wind velocity of 2 7 3 9 m s 1 at the height of the particle measurements descending particles tended to exceed the speeds of ascending particles by 0 5 m s 1

successive aeolian saltation studies of idealized collisions as observed by bagnold and experimentally reconfirmed by other workers the impact angles of saltating grains are remarkably constant over a wide range of conditions lying between 10 and 16 it can be shown that successive saltation contains a mechanism which very effectively confines impact angles to that range this control mechanism is most effective at windspeeds less than about 15 30 m s 1 depending on grain diameter and mass the control mechanism is evaluated from model calculations of grain populations saltating over a level bed consisting of a layer of loose grains the grains are assumed to be spherical and uniform in size and mass also rigid and perfectly elastic the model also describes distributions of maximum height of grain paths and of lift off angles compared to other processes involved in aeolian saltation successive saltation is the only process with a high probability of transferring energy from horizontal into vertical grain movement this fact together with the calculations presented strongly suggests that successive saltation plays a major role in saltation in air successive saltation of uniform grains is theoretically impossible if the ground over which saltation occurs is tilted by about 15 against wind direction values of tilt angles in this range are observed in nature as stoss side angles of dunes and ripples leading to the concept that stoss sides are tilted up by deposition until successive saltation is subdued

comment on piezometric response in shallow bedrock at cb1 implications for runoff generation and landsliding by david r montgomery william e dietrich and john t heffner

the grain bed collision in sand transport by wind in the last decade much progress has been made toward the development of a comprehensive model of aeolian sediment transport in which the grain bed collision has been identified as having a significant role the grain bed collision has been studied by both physical experiments and numerical simulation a principal objective of these studies has been to gather sufficient data to characterize the collision in order that it may be represented as an empirical function in numerical models of the sand transport system thus the study of the exact physical mechanism of the collision has to some extent been neglected the transport of larger particles in saltation over a loose surface is known to promote the release of finer particles from that surface into suspension thus the precise physics of the grain bed collision become highly significant with regard to the physics of dust release from a surface this paper re examines previous collision data and compares them with a simple collision model this model proposed that the impinging grain strikes a single surface grain and rebounds an alternative mechanism might be that the impinging grain ploughs through the surface striking a number of bed grains before rebounding the collision data are shown to support the model first because the duration of the collisions observed on the high speed film supports a short contact time with the surface and second because the data fit well with the model

sources of basinal and mississippi valley type mineralizing brines mixing of evaporated seawater and halite dissolution brine abstract origins of basinal brines and mississippi valley type mvt mineralizing fluids have been separately attributed to evaporation of seawater or dissolution of halite although brines originating from the two processes are not mutually exclusive in basins this study shows that the na br cl br diagram cannot distinguish between evaporated seawater and halite dissolution fluid using the na deficit ca excess diagram which was previously proposed to characterize fluid rock interactions of basinal brines it is shown that most basinal brines including wt mineralizing fluids of the viburnum trend deposits were probably initially a mixture of halite dissolution fluid and evaporated seawater using the same diagram we suggest that the mineralizing brines of the gays river mvt deposit were derived from an aquifer of clastics underlying a thick succession of evaporites where halite dissolution fluid and evaporated seawater could have mixed

dating groundwater in the bohemian cretaceous basin understanding tracer variations in the subsurface the northern section of the bohemian cretaceous basin has been the site of intensive u exploitation with harmful impacts on groundwater quality the understanding of groundwater flow and age distribution is crucial for the prediction of the future dispersion and impact of the contamination state of the art tracer methods 3h 3he 4he 85kr 39ar and 14c were therefore used to obtain insights to ageing and mixing processes of groundwater along a north south flow line in the centre of the two most important aquifers of cenomanian and middle turonian age dating of groundwater is particularly complex in this area as i groundwater in the cenomanian aquifer is locally affected by fluxes of geogenic and biogenic gases e g co2 ch4 he and by fossil brines in basement rocks rich in cl and so4 ii a thick unsaturated zone overlays the turonian aquifer iii a periglacial climate and permafrost conditions prevailed during the last glacial maximum lgm and iv the wells are mostly screened over large depth intervals large disagreements in 85kr and 3h 3he ages indicate that processes other than ageing have affected the tracer data in the turonian aquifer mixing with older waters 50 a was confirmed by 39ar activities an inverse modelling approach which included time lags for tracer transport throughout the unsaturated zone and degassing of 3he was used to estimate the age of groundwater best fits between model and field results were obtained for mean residence times varying from modern up to a few hundred years the presence of modern water in this aquifer is correlated with the occurrence of elevated pollution e g nitrates an increase of reactive geochemical indicators e g na and radiogenic 4he and a decrease in 14c along the flow direction confirmed groundwater ageing in the deeper confined cenomanian aquifer radiocarbon ages varied from a few hundred years to more than 20 ka initial 14c activity for radiocarbon dating was calibrated by means of 39ar measurements the 14c age of a sample recharged during the lgm was further confirmed by depleted stable isotope signatures and near freezing point noble gas temperature radiogenic 4he accumulated in groundwater with concentrations increasing linearly with 14c ages this enabled the use of 4he to validate the dating range of 14c and extend it to other parts of this aquifer in the proximity of faults 39ar in excess of modern concentrations and 14c dead co2 sources elevated 3he 4he ratios and volcanic activity in oligocene to quaternary demonstrate the influence of gas of deeper origin and impeded the application of 4he 39ar and 14c for groundwater dating

limits on the validity of infinite length assumptions for modelling shallow landslides the infinite slope method is widely used as the geotechnical component of geomorphic and landscape evolution models its assumption that shallow landslides are infinitely long in a downslope direction is usually considered valid for natural landslides on the basis that they are generally long relative to their depth however this is rarely justified because the critical length depth l h ratio below which edge effects become important is unknown we establish this critical l h ratio by benchmarking infinite slope stability predictions against finite element predictions for a set of synthetic two dimensional slopes assuming that the difference between the predictions is due to error in the infinite slope method we test the infinite slope method for six different l h ratios to find the critical ratio at which its predictions fall within 5 of those from the finite element method we repeat these tests for 5000 synthetic slopes with a range of failure plane depths pore water pressures friction angles soil cohesions soil unit weights and slope angles characteristic of natural slopes we find that 1 infinite slope stability predictions are consistently too conservative for small l h ratios 2 the predictions always converge to within 5 of the finite element benchmarks by a l h ratio of 25 i e the infinite slope assumption is reasonable for landslides 25 times longer than they are deep but 3 they can converge at much lower ratios depending on slope properties particularly for low cohesion soils the implication for catchment scale stability models is that the infinite length assumption is reasonable if their grid resolution is coarse e g 25 m however it may also be valid even at much finer grid resolutions e g 1 m because spatial organization in the predicted pore water pressure field reduces the probability of short landslides and minimizes the risk that predicted landslides will have l h ratios less than 25

origin and mixing history of brines palo duro basin texas u s a formation waters in the palo duro basin texas u s a fall into four major groups based on integrated chemical and isotopic characteristics 1 interbed brines within the major permian evaporite aquitard these are the most chemically concentrated and18o rich fluids in the basin and are interpreted as evaporatively concentrated sea water which has been hydrologically isolated since the permian 2 brines below the salt on the eastern side of the basin have clbr divalent cation and isotopic systematics indicating a mixture of evaporatively concentrated sea water and meteoric water of d 20 3 brines below the salt on the western side of the basin have chemical and isotopic systematics suggesting a mixture of two pulses of meteoric water one with d 20 and the other with d 55 and 4 waters above the salt have the isotopic composition of meteoric waters diagenetic alteration of the cation chemistry has occurred for brines within and below the salt aquifers below the salt on the eastern side are interpreted as having been charged with dense permian evaporite brines which subsequently mixed in various amounts with a basin wide pulse of triassic meteoric water on the western side the descending triassic meteoric waters became saline by dissolution of halite and are currently mixing with a tertiary pulse of meteoric water initiated by the laramide uplift to the west the hydrochemistry suggests flow on the western side of the basin and static conditions on the eastern side an unrecognized approximately n s permeability restriction or discontinuity in the potentiometric flow surface is inferred for major aquifers in the central area of the basin

the impact process in aeolian saltation two dimensional simulations a critical event in the trajectory of a sand grain saltating in air is its interaction with the surface we examine the phenomenon of grain bed impacts in two dimensions using a combination of dynamical computer simulations analytical models and physical reasoning the results indicate that the grain bed collisions can be treated as two body collisions with the bed particle assuming an effective mass greater than its true mass also the presence of geometrical surface irregularities has a strong bearing on the interaction between saltating and surface grain populations as well as on the formation of small scale bedforms

numerical simulation of saltating particles in atmospheric boundary layer over flat bed and sand ripples 1 in this work we numerically simulated the saltating particles in a turbulent boundary layer over flat bed and sand ripples by using natural sand grains in a wind tunnel we obtained the initial conditions for the simulation and also verified the correctness of the numerical model we carefully analyzed the numerically simulated saltating particle movement over the two sand beds and we found the following 1 the aeolian sand transport is a dynamic equilibrium process on both sand beds and it took longer to reach equilibration on the sand ripples than on the flat bed 2 according to the mass flux profile at the trough of the sand ripples there is a maximum mass flux at about 4 cm height in the leeward section the mass flux increases with height below 4 cm and decreases with height above 4 cm 3 the wind profile near the surface is modified by saltating particles on the two different sand beds and the flow field characteristics of the sand ripples are more complex than that of the flat bed

reply to comment by richard m iverson on piezometric response in shallow bedrock at cb1 implications for runoff generation and landsliding 1 iverson 2004 has offered a useful commentary on our paper and we appreciate this opportunity to offer corrections and to raise some important questions the issue he raises deals with a subsidiary part of the paper and none of our primary conclusions are affected by these corrections 2 iverson 2000 proposed a useful scaling argument for understanding the relative role in pore pressure development during a rainstorm of lateral flow from upslope contributing areas versus slope normal flow he suggests that the ratio a d0 approximates the minimum time necessary for strong lateral pore pressure transmission from the area a to the point x y h whereas h d0 approximates the minimum time necessary for strong slope normal pore pressure transmission from the ground surface to depth h iverson argues that a must be approximated by some readily measurable property and states that a is the area enclosed by the upslope topographic divide and hypothetical flow lines that run normal to topographic contours and bound the region that can contribute surface runoff to point x y iverson defines d0 as the maximum characteristic diffusivity given by the ratio of saturated conductivity ksat to c0 the minimum value of c y defined as the change in volumetric water content per unit change in pressure head i e c y dq dy where q is the volumetric water content and y is pressure head iverson introduces d0 to give a useful reference time and argues that comparison of these two timescales demonstrates that the slope normal component must control slope instability because it delivers a pore pressure response much quicker we argued in this article and in our previous reports on our study site torres et al 1998 montgomery and dietrich 2002 that rapid pore pressure response that controls both slope instability and general hydrologic response is driven by vertical flow not lateral flow hence there is no disagreement between iverson and us on this important finding we both agree too that the lateral flow contribution is nonetheless important in that it affects the propensity for landsliding iverson 2000 because it strongly influences the pore pressure field antecedent to a burst of rain that could initiate a landslide 3 iverson correctly points out that we miscalculate d0 instead we mistakenly calculated the dimensionally equivalent transmissivity saturated conductivity times depth which we often use in subsurface runoff modeling there is no point in clarifying how we arrived at our estimated timescales for site response as they were based on an erroneous definition and are simply wrong old habits sometimes blind one and we are thankful that iverson caught this foolish mistake 4 there are however some issues in regard to the application of iverson s scaling ratios to the coos bay data that are worth reviewing in his comment iverson argues that an effective depth averaged dq dy for the wet region q 0 2 of the soil water retention curve of coos bay soil is about 0 1 m the soil water retention curves of coos bay soils are strongly nonlinear such that while not at saturation small changes in y require large changes in q as the pressure head nears zero but before the soil reaches saturation torres et al 1998 figure 5 show that soil tensions were nearly all less than 0 1 m in response to irrigation and a median value of about 0 03 m typified the pressure head for wet conditions the values of dq dy for the change in y between 0 1 and a hinge beyond which dq dy increases greatly as y approaches 0 for the six soil water retention curves reported by torres et al 1998 for cb1 range from 0 1 to 0 7 m or up to seven times the value assumed by iverson for winter conditions when landslides are most likely y will be near zero and the soil moisture retention curves for cb1 torres et al 1998 show that dq dy may be even larger this means that d0 assuming ksat of 10 4 m s is from 10 3 m s 1 to a value of 1 4 10 4 m s 7 times smaller than assumed by iverson 2000 table 1 using these values of d0 h d0 ranges from about 20 min to 1 9 hr for a 1 m thick soil and from 1 1 to 7 8 hr for a 2 m thick soil due to the squared dependency on soil depth copyright 2004 by the american geophysical union 0043 1397 04 2003wr002815 09 00

helium isotopes at the rainbow hydrothermal site mid atlantic ridge 36 14 n the 3he 4he ratio and helium concentration have been measured in the vent fluids and the dispersing plume of the rainbow hydrothermal site on the mid atlantic ridge mar the 3he 4he ratio 7 51 ra and 3he end member concentration 25 pmol kg are in the range of observed values elsewhere on mid ocean ridges pointing to the relative homogeneity of the upper mantle with respect to helium isotope geochemistry 3he is linearly correlated with methane and manganese throughout the plume with ch4 3he and mn 3he ratios identical to those measured in the hot fluids the bulk residence time of the plume in the rift valley estimated from the plume 3he budget is v20 days the 3he flux transported by the plume calculated from current meter data is 12 3 3 nmol s requiring a flux of 490 kg s of high temperature fluid the scaling of the heat flux emitted by the rainbow site to that of 3he using the 3he heat ratio measured in the hydrothermal fluids 9 3 2u10318 mol j indicates a heat output of 1320 mw with a regional spreading rate of v25 mm year we calculate that the annual 3he flux for this section of the mar is of the order of 0 5 0 2 mmol per kilometre of ridge per millimetre of newly formed crust this figure compares well with the flux calculated for the neighbouring lucky strike segment although the uncertainties remain large both fluxes are v40 50 above the world average 0 33 mmol km mm thus supporting earlier suggestions that the intensity of the hydrothermal activity south of the azores is higher than expected from the regional spreading rate

nitrate and colloid transport through coarse hanford sediments under steady state variably saturated flow 1 at the u s department of energy s hanford reservation colloid facilitated transport is a potential mechanism for accelerated movement of radionuclides like cs 137 here we investigate the transport of colloids through hanford sediments under steady state unsaturated flow conditions we isolated colloids from hanford sediments by dispersion and sedimentation and determined colloid breakthrough curves in packed sediment columns a column system was developed with which we could control volumetric water contents with accuracy better than 0 01 effective saturation and the water potentials to better than 0 06 cm h2o inflow and outflow boundary conditions had to be meticulously controlled to ensure uniformity of water contents and water potentials inside the column colloid breakthrough curves were determined under a series of water contents ranging from 0 2 to 1 0 effective saturation colloids were mobile under all water saturations but the total amount of colloids transported decreased with decreasing water saturation colloid behavior was described with the mobile immobile model concept including first order deposition from the mobile phase only

formation of saline groundwaters in the baltic region through freezing of seawater during glacial periods typical ca cl brines occur in crystalline and metamorphic rocks below freshwater horizons at various localities in sweden and finland total dissolved solids tds range in concentration between 2 and 120 gl 1 and have long been thought to derive from water rock interactions the relationships between na cl and br in these brines suggest however that they were derived from freezing of seawater during glacial periods the brines were subsequently diluted by meteoric waters and their ca mg ratio was increased through water rock interactions in the subsurface the hydrogeological model for both the formation of freeze derived marine brines and their lateral intrusion involves restricted inland marine basins in recent and subrecent polar climatic belts seawater in such basins gradually freezes in response to glaciation the solutes which concentrate in the remaining water body are residual after precipitation of a sequence of minerals which include carbonates mirabilite and hydrohalite hydraulic pressure of the growing ice sheet over the frozen seas is gradually added to the ambient hydrostatic pressure exerted on the brines this together with their increased density increases the intrusional potential of the brines as the land ice cannot exert hydraulic pressure on continental groundwater in the aquifers the balance of pressure favours deep landward intrusion of brines post glacial processes cause the subsurface dilution and replacement of the brines both by seawater and fresh waters the presence of such brines also far from present day coastal settings reflects the shifting of coastlines as a result of isostatic movements and eustatic sea level changes associated with glaciation and deglaciation

a comparison of groundwater dating with 81kr 36cl and 4he in four wells of the great artesian basin australia the isotopic ratios 81 kr kr and 36 cl cl and the 4 he concentrations measured in groundwater from four artesian wells in the western part of the great artesian basin gab in australia are discussed based on radioactive decay along a water flow path the 81 kr kr ratios are directly converted to groundwater residence times results are in a range of 225 400 kyr with error bars in the order of 15 primarily due to counting statistics in the cyclotron accelerator mass spectrometer measurement additional uncertainties from subsurface production and or exchange with stagnant porewaters in the confining shales appear to be of the same order of magnitude these 81 kr ages are then used to calibrate the 36 cl and the 4 he dating methods based on elemental analyses of rock samples from the sandstone aquifer as well as from the confining bulldog shale the in situ flux of thermal neutrons and the corresponding 3 he 4 he and 36 cl cl ratios are calculated from a comparison of i the 3 he 4 he ratios measured in the groundwater samples with the calculated in situ ratios in rocks and ii the measured n 37 cl ratios with the 4 he concentrations measured in groundwater it is concluded that both helium and chloride are most likely added to the aquifer from sources in the stagnant porewaters of the confining shale by diffusion and or mixing based on this working hypothesis the 36 cl transport equation in groundwater is solved taking into account i radioactive decay ii subsurface production in the sandstone aquifer with an in situ 36 cl cl ratio of 6u10 315 and iii addition of chloride from a source in the confining shale with a 36 cl cl ratio of 13u10 315 lacking better information it is assumed that the chloride concentration increased linearly with time from an unknown initial value ci to its

height profile of the mean velocity of an aeolian saltating cloud wind tunnel measurements by particle image velocimetry abstract the velocity of saltating particles is an important parameter in studying the aeolian sand movement we used particle image velocimetry to measure the variation with height of the mean particle velocity of a saltating cloud over a loose sand surface in a wind tunnel the results suggest that both the horizontal and vertical particle velocities fit the gaussian distribution well and that the mean particle velocity of a saltating cloud varies with wind velocity particle size and the height above bed the mean horizontal velocity is mainly the result of acceleration by the wind and increases with an increase in friction wind velocity but decreases with an increase in grain size because greater wind velocity causes more acceleration and finer particles are more easily accelerated at a given wind velocity it also increases with an increase in height by a power function in agreement with previous results obtained by other methods such as the high speed multi flash photographic method and particle dynamics analyzer pda reflecting first the increase in wind velocity with height through the boundary layer and second the longer trajectory particle path length increases with height and affords a longer time for acceleration by the wind an empirical model relating the mean horizontal particle velocity and height friction wind velocity as well as particle size is developed the ratio of the mean horizontal particle velocity to the clean wind velocity at the same height increases with height but decreases with grain size the magnitude of mean vertical velocity is much less one or two orders less compared with the mean horizontal velocity the average movement in the vertical direction of a saltating cloud is upward the mean vertical velocity is positive although the upward velocity of a saltating particle should decrease with height due to gravity the mean vertical upward velocity the average of both ascending and descending particles generally shows a tendency to increase with height it seems that at higher elevations the data are more and more dominated by the high flyers the underlying mechanism for the mean vertical velocity distribution patterns needs to be clarified by further study

origin and age of saline waters in busko spa southern poland determined by isotope noble gas and hydrochemical methods evidence of interglacial and pre quaternary warm climate recharges abstract in the busko and solec spas saline sulphide and sulphate waters are exploited at different depths the shallow water system in busko is related to an interglacial or interstadial period shown by the lack of tritium and 14 c and its 18 o and d values equal to that of modern water the noble gas temperatures ngt are somewhat lower than the present air temperatures but the 4 he and 40 ar ages of about 90 480 ka confirm a pleistocene recharge the 18 o and d values of the deep system are much heavier than those of local modern waters which may mean the recharge of a warm pre quaternary climate the 4 he 40 ar and 21 ne contents and the ngt values confirm the deep system to be recharged at the pre quaternary stages of the present hydrologic cycle i e after the sea transgression in the badenian high so 4 2 contents indicate that the cl and so 4 2 in both systems originated from simultaneous leaching of nacl and gypsum other components can be explained by cation exchange between water and badenian clay minerals in marls e g ca 2 for mg 2 and na for k and by the decay of marine organic matter supplying br i and b

the isotopic composition of radiogenic helium and its use to study groundwater movement in confined aquifers abstract the 3 he 4 he ratio for radiogenic he is shown to be primarily determined by the abundance of li and neutron absorbing elements in the host formations and is almost independent of the radioelement abundance the 3 he 4 he ratios have been computed for various li contents in rock matrices with average abundances of other elements the 3 he 4 he ratio is specific for each formation and may therefore be used to study crustal diffusion of he it is shown however that both the 3he and 4he contents of continental basements are likely to exceed those of the mantle so that diffusion of mantle he through continental crust is not likely to occur changes in the 3 he 4 he ratio for dissolved he have potential for studying groundwater movement and mixing processes atmospheric he which was dissolved at recharge is progressively diluted by radiogenic he with an isotopic ratio characteristic of the aquifer as the groundwater migrates down dip mixing proportions for formation he and atmospheric he in aquifers for which there is admixture of fracture borne water and interstitially stored water can also be estimated from isotopic measurements these processes are discussed in relation to two aquifers in eastern england

dating ultra deep mine waters with noble gases and 36cl witwatersrand basin south africa abstract concentrations and isotopic ratios of dissolved noble gases 36cl d and 18o in water samples from the ultra deep gold mines 0 718 to 3 3 km below the surface in the witwatersrand basin south africa were investigated to quantify the dynamics of these ultra deep crustal fluids the mining activity has a significant impact on the concentrations of dissolved gases as the associated pressure release causes the degassing of the fissure water the observed under saturation of the atmospheric noble gases in the fissure water samples 70 98 normalized to asw at 20 c and 1013 mbar is reproduced by a model that considers diffusive degassing and solubility equilibration with a gas phase at sampling temperature corrections for degassing result in 4he concentrations as high as 1 55 10 1cm3stp4he g 1 40ar 36ar ranging between 806 and 10331 and 134xe 132xe and 136xe 132xe ratios above 0 46 and 0 44 respectively corrected 134 136 xe 132xe and 134 136 xe 4he ratios are consistent with their production ratios whereas the nucleogenic 4he 40ar and 134 136 xe 40ar ratios generally indicate that these gases are produced in an environment with an average u th k content 2 3 times above that of crustal average in two scenarios one considering only accumulation of in situ produced noble gases the other additionally crustal flux components the model ages for 14 individual water samples range from 13 to 168 ma and from 1 to 23 ma respectively the low 36cl ratios of 4 37 10 15 and comparatively high 36cl concentrations of 8 350 10 15 atoms 36cl l 1 reflect subsurface production in secular equilibrium indicating an age in excess of 1 5 ma or 5 times the half life of 36cl in combination the results suggest residence times of the fluids in fissures in this region up to 3 3 km depth are of the order of 1 100 ma we cannot exclude the possibility of mixing and that small quantities of younger water have been mixed with the very old bulk

an experimental study of multiple grain size ejecta produced by collisions of saltating grains with a flat bed collision data are presented from coloured high speed films of three size fractions of sand grains saltating over a bed of the total grain population each fraction was colour tagged and the proportion of each size ejected by grains colliding with the surface was recorded on a number of films taken as the bed was progressively eroded the results confirm earlier findings that v3 v1 0 5 0 6 vn v1 08 and the rebound angle increases with decreasing grain size ejected grains are examined in relation to their size the impactor size ejection speed and angle and the number of ejecta per collision in addition changes in grain parameters are observed with time for fine impactors ejection speeds generally increase with a decrease in ejecta size but the fine fraction does not follow this trend for the coarse and medium impactors ejection angles are typically between 40 and 60 with coarse grains having shallower mean angles than fine ejecta the number of ejections per collision increases with a decrease in particle size for each impactor size the general tendency for coarse particles to be ejected at lower speeds and shallower angles than fine particles will lead to sorting of the grain sizes there is poor correlation between the forward momentum loss of the saltating grams at collision and both the forward momentum of the ejected grains and the number of ejected grains much of the forward momentum of the saltating grains is transfered to creeping grains the composition and geometry of the bed are considered to be important factors in the evolution of the saltation cloud

evidence for bacterially generated hydrocarbon gas in canadian shield and fennoscandian shield rocks hydrocarbon rich gases found in crystalline rocks on the canadian and fennoscandian shields are isotopically and compositionally similar suggesting that such gases are a characteristic feature of precambrian shield rocks gases occure in association with saline groundwaters and brines in pressurized pockets formed by sealed fracture systems within the host rocks when released by drilling activities gas pressures as high as 5000 kpa have been recorded typical gas flow rates for individual boreholes range from 0 25 l min to 4 l min the highest concentrations of ch4 are found in the deepest levels of the boreholes associated with ca na cl and na ca cl brines n2 is the second major component of the gases and with ch4 accounts for up to 80 to 90 vol higher hydrocarbon c2 concentrations range from 1 to 10 vol with c1 c2 c3 ratios from 10 1000 isotopically the gases show a wide range of values overall 13c 57 5 to 41 1 d 245 to 470 but a relatively tight cluster of values within each sampling locality the enonkoski mine methanes are unique with 13c values between 65 4 and 67 3 and d values between 297 and 347 the shield gases are not readily reconcilable with conventional theories of methanogenesis the range of c1 c2 c3 ratios for the shield gases is too low to be consistent with an entirely bacterial origin in addition dch4 values are in general too depleted in the heavy isotope to be produced by thermogenic methanogenesis or by secondary alteration processes such as bacterial oxidation or migration however isotopic and compositional evidence indicates that bacterially derived gas can account for a significant component of the gas at all shield sites conventional bacterial gas accounts for 75 94 vol of the occurrences at enonkoski mine in finland at each of the other shield sites bacterial gas can account for up to 30 50 vol of the total gas accumulation this study and other recent evidence of active bacterial communities in deep hydrogeological environments emphasize the need for more comprehensive investigation of the role of microorganisms in the deep subsurface

steady state saltation in air coupled equations of motion for steady state saltation over an infinite plane are derived and solved for a simplified model of the grain surface impact process experimentally observed features of the wind velocity profile in saltation are qualitatively reproduced including a diminution of the sub saltation layer mean wind speed as the friction speed increases in this model the surface impact velocity of the saltating grains remains relatively constant over a wide range of free stream shear stresses and the grain mass flux increases with friction speed uf less rapidly than uf3

modelling the probability of occurrence of shallow landslides and channelized debris flows using geotop fs this paper describes a coupled distributed hydrological geotechnical model geotop fs which simulates the probability of occurrence of shallow landslides and debris flows we use a hydrological distributed model geotop which models latent and sensible heat fluxes and surface runoff and computes soil moisture in 3 d by solving richards equation numerically together with an infinite slope geotechnical model geotop fs the combined model allows both the hydraulic and geotechnical properties of soil to be considered and realistically modelled in particular the model has been conceived to make direct use of field surveys geotechnical characteristics and soil moisture measurements in the model the depth of available sediments is also used to characterize the hydraulic properties of the area examined to account for the uncertainty related to the natural variability in the factors influencing the stability of natural slopes the safety factor is computed with a probabilistic approach in order to determine the likelihood of slope failures soil parameters are assigned distributions instead of single deterministic values the analysis presented was carried out for an alpine watershed located in the friuli region italy for which some geological and geotechnical data were available in the past this watershed experienced landslides and debris flows during intense storms following long and moderate intensity rainfall events the distributed coupled geotop fs model was calibrated by reproducing some of these events and validated in order to map future failure probabilities

helium accumulation in groundwater ii a model for the accumulation of the crustal 4he degassing flux abstract a model of 4 he accumulation in a confined aquifer is presented which includes in situ production and a crustal degassing flux of 4 he into the bottom of a confined aquifer the model is consistent with the measurements of 4 he concentration in the great artesian basin australia torgersen and clarke 1985 and also with the measurements of 4 he concentration in the auob sandstone of namibia heaton 1981 the measured value of the crustal degassing flux of 4 he from these two areas is comparable with the 4 he degassing flux calculated from the atmospheric budget of 4 he wasserburg et al 1963 ozima and podosek 1983 a literature review suggests that a crustal degassing 4 he source may account for the 4 he accumulation in many other groundwater systems it is concluded from the literature review the detailed modelling of 4 he accumulation in gab and the auob sandstone and the atmospheric budget that crustal degassing of 4 he may be a common and widespread phenomena

particle dislodgement from a flat sand bed by wind the rate with respect to area and time at which grains are dislodged from a sand bed for given wind conditions is an important factor in determining the grain transport rate and the intensity of grain activity in each of the transport modes the literature of the subject contains little direct information about particle dislodgement the paper describes a series of experiments in which dyed sand grains spread on the surface of quartz dune sand in a wind tunnel were photographed at five second intervals while the sand was exposed to wind the data on rate of loss of coloured grains was used for two of three chosen size fractions to deduce the dislodgement rate for each size fraction the variation of this dislodgement rate with shear velocity is shown graphically for values of u between 24 cm s 1 and 50 cm s 1 because of the artificial method of distribution of the coloured sand grains the results should be applied with caution to natural conditions the interpretation of the observations of dyed grain loss involved the numerical simulation of the process which comprises removal of coloured grains slightly offset by replenishment as upwind coloured grains settle briefly in the observed zone an estimation of grain excursion length has to be incorporated in the simulation this estimation was made by trial but general corroboration was found from earlier work comparisons are made between dislodgement rates obtained thus and rates estimated by anderson 1986 and by jensen and sorensen 1986 reasonable agreement with the latter is found in the u range 30 cm s 1

geochemistry of halogens in the milk river aquifer alberta canada abstract analytical data are presented for cl br and i on a regional scale for the milk river aquifer the three halides show strikingly similar spatial distributions and are highly correlated concentrations are low in the freshwater portions of the aquifer but increase by as much as two orders of magnitude along the margins however halide ratios reach nearly constant values moving down gradient suggesting the dominance of a common subsurface source for these ions ratios of cl i and cl br are less than those of seawater and fit an origin derived from the diagenesis of organic matter in the sediments halide ratios rule out leakage and or diffusion from the underlying colorado group as a major influence on the chemistry the favored hypothesis is altered connate seawater diffusing from low permeability units within the milk river formation as the primary source of salts this hypothesis of an internal source has important implications for solute sources in other aquifers affected by saline waters because it does not require the importation of a distant fluid the129i i ratio has a meteoric value in groundwater collected near the recharge area but ratios for downflow waters are only 8 70 of this value due to the 16 ma half life of129i these data indicate that most of the increase in dissolved i cannot derive from concentration of a meteoric source by ion filtration but must have a subsurface origin concentrations of129i producedin situ by spontaneous fission of238u attain measurable levels only in the oldest waters sampled ages 105a in which it may account for nearly 90 of the total dissolved129i concentration water ages based upon36cl cl data range up to 2 ma if uncorrected for any dilution by subsurface sources of dead cl if one assumes that the subsurface contributions of cl contribute at least 90 of total cl in the distal portion then the36cl based ages are reduced to 1ma somewhat greater than those estimated by hydrodynamic modeling

neon identifies two billion year old fluid component in kaapvaal craton abstract the deep gold mines of the witwatersrand basin south africa have gained recent attention not only because of investigations of the deep fracture water and associated ch4 and h2 rich gases found there but because of recent reports of deep microbial communities persisting to depths of almost 3 km an exotic outpost of the earth s deep biosphere while shallower fluids in the basin to approximately 1 km were found to contain abundant populations of methanogens and sulphate reducing bacteria the deepest oldest most saline fracture waters in the basin hosted hitherto unrecognised low biomass and low biodiversity chemoautotrophic ecosystems independent from the photosphere shallow and deep fluids also show distinct differences in gas and fluid geochemistry paleometeoric waters are dominated by hydrocarbon gases with compositional and isotopic characteristics consistent with production by methanogens utilising the co2 reduction pathway in contrast the deepest most saline fracture waters contain gases that are dominated by high concentrations of h2 gas and ch4 and higher hydrocarbon gases with isotopic signatures attributed to abiogenic processes of water rock reaction the high salinities up to hundreds of g l highly altered 18o and 2h signatures and both 36cl and measurements of co occurring nucleogenic noble gases for these fracture waters are consistent with extensive water rock interaction over geologically long time scales in these high rock water ratio environments while the ultimate origin of these fluids has been attributed alternately to saline waters that penetrated the crystalline basement formation water or hydrothermal fluids in some cases their 18o and 2h isotopic signatures have typically been so profoundly overprinted by the effects of long term water rock interaction that for the most saline end members little evidence of their primary composition remains the key objective of the present study is to further investigate the origin of these fluids by integrating for the first time detailed neon isotope analyses on the dissolved gases helium isotopic analysis confirmed that there is no significant mantle derived component associated with these fluids and gases neon isotope results show distinct differences in neon composition that correspond to the different fluid geochemical end members previously identified typical crustal neon signatures type a are identified in the paleometeoric waters populated with abundant methanogens in contrast the deep more saline fracture waters contain an enriched nucleogenic neon signature unlike any previously reported in crustal fluids these samples show the highest 21ne 22ne ratios 0 160 0 003 ever reported in groundwater fluid inclusions in these rocks yield even higher 21ne 22ne ratios between 0 219 and 0 515 consistent with an extrapolated 21ne 22ne value of 3 3 0 2 at 20ne 22ne 0 we show that this enriched nucleogenic neon end member represents a fluid component that was produced in the fluorine depleted archaean formations and trapped in fluid inclusions 2 ga ago the observation of enriched nucleogenic neon signatures in deep fracture water implies the release of this billion year old neon component from the fluid inclusions and its accumulation in exceptionally isolated fracture water systems the observed association of this archean neon signature with h2 hydrocarbon rich geogases of proposed abiogenic origin dissolved in the same deep groundwater suggests that the fracture systems have also allowed for the accumulation of various products of water rock reactions throughout geologic times one of these fracture systems contained the deepest characterised microbial ecosystems on earth chemolithotrophs eking out an existence at maintenance levels independent from sunlight consequently the enriched nucleogenic neon isotope signature may indicate regions in the archaean crust where investigations of the deep biosphere might be focused

identification of he sources and estimation of he ages in groundwater of the north china plain abstract dissolved helium concentrations and 3 he 4 he ratios were measured for 18 groundwater samples collected from the quaternary confined aquifers in the north china plain ncp the dissolved helium concentrations ranged from 1 10 7 to 1 10 6 cm 3 stp g 1 in the 14 samples from the central plain but was approximately two orders of magnitude higher between 6 10 6 and 9 10 5 cm 3 stp g 1 in 4 samples from the coastal plain based on these concentrations and the corresponding 3 he 4 he ratios varying from 0 09 to 0 55 r a where r a is the 3 he 4 he ratio of air the dissolved helium in groundwater in the central plain was identified to be primarily a mixture of atmospheric helium with radiogenic helium and a representative radiogenic helium ratio was estimated to be 0 035 r a despite the high fraction of terrigenic 4 he in the samples from the coastal plain their 3 he 4 he ratios were found to be significantly above this radiogenic value ranging between 0 20 and 0 37 r a indicating the presence of a mantle derived he component in this area about 2 4 mantle helium was estimated to be present in the groundwater of the coastal plain which probably is associated with the regional cangdong fault and tectonic activities based on the radiogenic he component 4 he ages of the groundwater in the central plain were calculated by assuming either pure in situ production or an external helium flux j 0 of 4 7 10 8 cm 3 stpcm 2 a 1 the estimated 4 he ages fall between 9 5 and 51 4 ka and are comparable to the 14 c ages suggesting that the results of 4 he dating are reasonable and can be an effective tool to estimate groundwater residence times under suitable conditions

alabama gulf coast groundwaters 4he and 14c as groundwater dating tools analyses of 4 he and 1 4 c in groundwaters from a miocene quartz aquifer on the alabama gulf coast show the usefulness of 4 he for dating these holocene groundwaters in this aquifer system of low alkalinities and low phs radiocarbon ages can be used without model correction the groundwaters studied ranged from 42 3 to 95 5 modern carbon and yielded uncorrected ages of 375 6790 yr radiogenic 4 he ages ranged from 50 7500 yr

sources of chloride and implications for 36cl dating of old groundwater southwestern great artesian basin australia we investigate the relative importance of a number of processes that affect cl and 36cl distribution in the southwestern flow systems of the great artesian basin australia to provide more precise estimates of age and flow and recharge rates in situ production of 36cl secular variations in the rate of production of 36cl and its subsequent fallout as well as rates of diffusion of stable cl from adjacent aquitards mask the interpretation of rates of decay of 36cl cl along hydraulic gradients and can preclude estimating absolute groundwater ages however mean flow velocities calculated from absolute cl concentrations are 0 24 0 03 m yr and are a more reliable parameter than calculated ages because fewer assumptions and approximations are required recharge rates to the main cadna owie formation and algebuckina sandstone aquifer of the great artesian basin estimated from cl mass balance in the unconfined aquifers are 0 16 0 08 mm yr and were probably up to a factor of 3 higher 30 kyr ago as indicated by decreasing cl and 18o concentrations along the head gradient

saltating particles over flat beds measurements of ejection and impact velocities trajectory lengths and maximum rise heights of sand grains median diameters 118 and 188 m in saltation over a flat sand bed in a wind tunnel have been obtained from the digitization of multiple image photo graphs the mean angle of ejection is found to be about 30 o from the horizontal rather than 90 o with mean vertical ejection velocity of about 2u where u is the friction velocity trajectories of saltating grains have been computed using the measurements of the initial ejection velocities and the mean velocity profile of the air flow

using 81kr and noble gases to characterize and date groundwater and brines in the baltic artesian basin on the one million year timescale abstract analyses for 81 kr and noble gases on groundwater from the deepest aquifer system of the baltic artesian basin bab were performed to determine groundwater ages and uncover the flow dynamics of the system on a timescale of several hundred thousand years we find that the system is controlled by mixing of three distinct water masses interglacial or recent meteoric water 18 o 10 4 with a poorly evolved chemical and noble gas signature glacial meltwater 18 o 18 with elevated noble gas concentrations and an old high salinity brine component 18 o 4 5 90 g cl l with strongly depleted atmospheric noble gas concentrations the 81 kr measurements are interpreted within this mixing framework to estimate the age of the end members deconvoluted 81 kr ages range from 300 ka to 1 3 ma for interglacial or recent meteoric water and glacial meltwater for the brine component ages exceed the dating range of the atta 3 instrument of 1 3 ma the radiogenic noble gas components 4 he and 40 ar are less conclusive but also support an age of 1 ma for the brine based on the chemical and noble gas concentrations and the dating results we conclude that the brine originates from evaporated seawater that has been modified by later water rock interaction as the obtained tracer ages cover several glacial cycles we discuss the impact of the glacial cycles on flow patterns in the studied aquifer system

helium accumulation in groundwater iii limits on helium transfer across the mantle crust boundary beneath australia and the magnitude of mantle degassing abstract the groundwaters of the great artesian basin australia have been previously shown to be accumulating in situ production helium for groundwaters ages 100 kyr 1 2 new helium isotope measurements show that the observed in situ production helium 3he 4he 1 6 10 8 is isotopically distinct from the crustal degassing helium flux 3he 4he 6 6 10 8 furthermore the crustal degassing helium isotope ratio is marginally in excess of the whole crustal production ratio 3he 4he 3 5 10 8 and the production ratio in a variety of continental rock types this suggests that the upper limit on volatile transport across the mantle crust boundary beneath the relatively stable and complacent australian continent can be characterized by a conductive diffusive helium heat flux ratio of 2 6 1064he atoms mw 1 s 1 which is two orders of magnitude less than the intrusive volcanic ratio of 2 9 1084he atoms mw 1 s 1 measured at the galapagos 16 these results constrain the transcrustal mantle degassing fluxes of4he and40ar to be much less than the mid ocean ridge degassing fluxes which are much less than the degassing of4he and40ar from continental crust thus the degassing of the earth s interior is dominated by magmatic processes but the dominant fluxes of4he and40ar to the atmosphere must come from the continental crust

environmental isotopes and noble gases in the deep aquifer system of kazan trona ore field ankara central turkey and links to paleoclimate abstract environmental isotopes and noble gases in groundwater samples from the kazan trona ore field are studied to establish the temperature change between the holocene and the late pleistocene noble gas temperatures ngts presented in this study add an important facet to the global paleotemperature map in the region between europe and north africa the groundwater system under investigation consists of three different aquifers named shallow middle and deep in which 18 o and 2 h vary from 8 10 to 12 80 and from 60 89 to 92 60 vsmow respectively the average isotopic depletion between unconfined and confined parts of the system is 2 5 in 18 o and 20 in 2 h it is not possible to explain this depletion solely with the elevation effect recharge temperatures derived from dissolved atmospheric noble gases reflect the current average yearly ground temperatures 13 c for samples collected near the recharge area but are 3 to 8 c lower than today s temperatures in the deep aquifer system low 14 c activities and high he excesses in the confined parts of the aquifer system suggest that the water in the deep aquifer was recharged during the last pleistocene under considerably cooler climatic conditions

geochemical and isotopic evidence for a genetic link between canadian shield brines dolomitization in the western canada sedimentary basin and devonian calcium chloridic seawater hypersaline brines of marine origin deep within fractured crystalline rocks of the canadian shield are characterized by calcium chloride compositions with relatively low concentrations of magnesi

sediment transport by wind toward a general model a general model of eolian sediment transport by both saltation and suspension is developed saltation is analyzed through calculations of single trajectories given initial conditions of liftoff speed angle and spin profiles of particle concentration and mass flux generated by assuming that all trajectories are identical display distinct maxima at the top of the trajectory by incorporating the realistic distribution of trajectories that arises from the stochastic nature of grain impacts with a granular bed the model yields monotonic decreases in particle concentration and mass flux with height in accordance with published empirical data the analysis of suspension as the balance between downward advective flux as a result of the settling of grains and their upward diffusive flux as a result of turbulence results in concentration profiles that fall off as power laws with height also in accordance with empirical data a relation for reference level concentrations is presented for both blowing snow and dust profiles the solutions for saltation and suspension are combined to yield mass flux profiles for the entire range of grain sizes in the bed the saltation layer emerges naturally as that region where the total flux of saltating grains exceeds that of suspended grains the model points clearly to the need for further research on the stochastic grain bed interactions which control both the probability distribution of liftoff velocities in saltation and the production of fine particles in suspension

on the effect of mid air collisions on aeolian saltation the effect of mid air collisions on aeolian saltation is investigated using concentration profiles and grain velocities predicted by a numerical saltation model the probability of a mid air collision is found to be greater at high wind speeds it is also found that mid air collisions tend to reduce the number of grain bed impacts and thus reduce the number of ejecta near the bed this in turn reduces the intensity of mid air collisions it is suggested that this feed back mechanism significantly influences transport rates at high wind speeds

fossil brines preserved in the st lawrence lowlands quebec canada as revealed by their chemistry and noble gas isotopes abstract brines in cambrian sandstones and ordovician dolostones of the st lawrence lowlands at becancour quebec canada were sampled for analysis of all stable noble gases in order to trace their origin and migration path in addition to quantifying their residence time major ion chemistry indicates that the brines are of na ca cl type possibly derived from halite dissolution 87 sr 86 sr ratios and ca excess indicate prolonged interactions with silicate rocks of the proterozoic grenville basement or the cambrian potsdam sandstone the brines constrain a 2 3 contribution of mantle 3 he and large amounts of nucleogenic 21 ne and 38 ar and radiogenic 4 he and 40 ar 4 he 40 ar and 21 ne 40 ar ratios corrected for mass fractionation during incomplete brine degassing are identical to their production ratios in rocks the source of salinity halite dissolution plus the occurrence of large amounts of 40 ar in brines constrain the residence time of becancour brines as being older than the cretaceous evaporites in the st lawrence lowlands likely existed only during devonian silurian time brines might result from infiltration of devonian water leaching halite penetrating into or below the deeper cambrian ordovician aquifers during the devonian the basin reached temperatures higher than 250 c allowing for thermal maturation of local gas prone source rocks utica shales and possibly facilitating the release of radiogenic 40 ar into the brines the last thermal event that could have facilitated the liberation of 40 ar into fluids and contributed to mantle 3 he is the cretaceous monteregian hills magmatic episode for residence times younger than the cretaceous it is difficult to find an appropriate source of salinity and of nucleogenic radiogenic gases to the becancour brines

collisions of quartz grains with a sand bed the influence of incident angle the velocities with which grains were observed to emerge from a sand bed after an intersaltation collision at u 40 cm s 1 are reported for four bed attitudes from horizontal bed to adverse bed slope 15 the principal effect of bed angle is to alter the magnitude and direction of the ricochet velocity however emergent velocities of dislodged grains are consistent with reptation path lengths comparable to the length of the upwind face of ripples in the corresponding wind calculations of the loss of forward momentum at collision using the data for the range of bed attitudes studied suggest that creep is most vigorous on the sloping upwind face of the ripple and diminishes at the crest as a result the crest would be expected to accumulate the coarse material which moves predominantly by creep the saltations originating in ricochet from the sloping back of the ripple are more vigorous and more concentrated in plan than are those originating at the crest however the saltation path length is at least an order of magnitude greater than the ripple wavelength and the probability distribution of path lengths is quite dispersed consequently it is very unlikely that these spatial patterns of ricochet are preserved sufficiently distinctly in the saltation cloud and subsequent collision distribution to be the agent of ripple development this study therefore supports a view of moving grain interaction with the bed in which saltation provides the power to mobilize grains but ripple growth is associated with reptation and particularly with a pattern of impact which develops with the bed relief creep is more active on upwind facing slopes than at the crest which therefore is a zone of net creep grain deposition

the rapid yet uneven turnover of earth s groundwater the turnover of groundwater through recharge drives many processes throughout earth s surface and subsurface yet groundwater turnover rates and their relationship to regional climate and geology remain largely unknown we estimated that over 200 million km3 of groundwater has recharged since the last glacial maximum lgm which is ten times the volume of global groundwater storage however flushing is very unevenly distributed throughout earth s one million watersheds with some aquifers turned over thousands of times to others with 1 turnover the median global groundwater turnover of 5 3 times since the lgm highlights groundwater s active role in earth system processes incomplete groundwater turnover since the lgm beneath a third of land areas reveals the imprint of relict climate conditions on modern day groundwater resources the bulk groundwater turnover calculated here enable better quantification of groundwater s impact in dynamic global water budgets and the transport of nutrients contaminants and geologic weathering products

the evolution of alkaline groundwaters in the continental intercalaire aquifer of the irhazer plain niger this paper discusses the hydrochemical evolution of groundwaters in the multilayer artesian aquifer of the continental intercalaire the mainly jurassic agadez dabla sandstones aquifer of northern niger isotopic and chemical changes in relation to the geological setting suggest that the increasing hco3 alkalinity of the groundwaters is caused by interaction of deep co2 with the aquifer matrix alteration of feldspars by co2 with a 13c value of 3 0 accounts for the observed alkalinity and isotopic and trends carbon 14 ages have been estimated for recent and holocene groundwaters which have a distinct stable isotopic 2h and 18o signature compared with 14c dead groundwaters from further west on the irhazer plain recharge temperatures estimated by analysis of noble gas contents show that the 14c dead waters were recharged under conditions cooler than present averages in the region possibly at the beginning of deglaciation 16 ka b p or during the period 23 30 ka b p trends in the hydrochemistry of u are related to the deep co2 alteration process radiogenic he contents increase along the flow direction and extremely high values occur in the proximity of u ores denitrification in the paleowaters of the irhazer was assessed by measurements of nitrogen argon ratios

correlation between dissolved 4he concentration and 36cl in groundwater at aspo sweden abstract tunnel excavation at aspo island sweden has caused severe groundwater disturbance gradually extending deeper into the tunnel as present day baltic seawater intrudes through fractures connecting to the surface however the paleo hydrogeochemical conditions have remained in the deep highly saline waters that have avoided mixing a correlation has been observed between dissolved 4he concentration and cl ion concentration measured every two years from 1995 to 2001 at aspo groundwater mixing conditions can be examined by the correlations between 1 cl 36cl cl and 3h concentrations subsurface production is responsible for the majority of the 36cl and excess dissolved 4he of interstitial groundwater in fractures the secular equilibrium ratio of 36cl cl in rock was theoretically estimated to be 5 05 0 82 10 14 based on the neutron flux intensity a value comparable to the measured 36cl cl ratio in rock and groundwater the degassing crustal 4he flux was estimated to be 2 9 10 8 1 3 10 6 ccstp cm2a using the hto diffusion coefficient for the aspo diorite the 4he accumulation rate ranges from 6 8 10 10 for the in situ accumulation rate to 7 0 10 9 ccstp gwater a considering both 4he in situ production and the degassing flux assuming 4he is accumulated constantly in groundwater by comparing the subsurface 36cl increase with 4he concentrations in groundwater the 4he accumulation rate was determined from data for groundwater arriving at the secular equilibrium of 36cl cl the 4he accumulation rate was found to be 1 83 0 72 10 8 ccstp gwater a without determining the magnitude of degassing 4he flux

radioelements radiogenic helium and age relationships for groundwaters from the granites at stripa sweden abstract the solution of radioelements and radiogenic 4he by groundwaters in fractured rocks is dependent upon the radioelement distribution in the rock matrix and the extent of the rock water interface the 234 u 238 u activity ratio and the dissolved u rn and he contents of such groundwaters respond to changes in the flow regime with time although 234 u 238 u activity ratios change with groundwater residence time as a consequence of 234th recoil induced solution of 234u the activity ratio is strongly influenced by the u distribution within fractures by the extent of the rock water interface and by the amount of 238u in solution a model for the quantitative evaluation of these effects is presented groundwaters from depths up to 880 m in the stripa granite have variable dissolved uranium contents and 234 u 238 u activity ratios the uranium geochemistry is primarily determined by variations in flow path rather than by groundwater age dissolved radiogenic 4he in the groundwaters increases with their depth of origin and is dependent upon the u content of the granite and upon its fracture porosity it increases with groundwater residence time but movement of 4he by diffusion and transport processes make the actual groundwater age indeterminate

the relationship between he and cl as a criterion for the formation of groundwater composition abstract the analysis of the relationship between 1611 parallel determinations of helium and chloride concentrations in the groundwater of crystalline shields and sedimentary basins was performed the comparison showed that groundwaters have helium and chlorides concentrations in the range of 1 8 10 8 to 6 8 mol m3 and of 5 6 10 3 to 6488 mol m3 respectively and relatively stable he rcl ratios equal to 5 5 10 5 in sedimentary basins and 7 5 10 4 in crystalline shields such behavior of helium and chlorides shows that the formation of the groundwater composition is determined primarily by the processes of mixing fresh meteoric and saline sea waters with ancient brines from great depths during sedimentation sea water penetrates the subsurface and mixes with ancient brines on land fresh meteoric waters dilute the mixtures of seawater and ancient brines most of the radiogenic 4he and chlorides comes from the subsurface ancient brine the radiogenic 4he in the host rocks plays a secondary role therefore the concentration of 4he in saline groundwater reflects the size of the impurities of the ancient brine with a very high content of 4he rather than the residence time within the subsurface

canadian shield brine from the con mine yellowknife nt canada noble gas evidence for an evaporated palaeozoic seawater origin mixed with glacial meltwater and holocene recharge abstract dissolved noble gas concentrations were measured in high salinity 270 g l ca na cl groundwaters from the con mine yellowknife canada in an effort to discriminate between two possible origins as either a brine generated by evaporative enrichment in a paleozoic inland sea or marine water concentrated by freezing during glacial times major ion and isotope geochemistry indicate that brines from the deepest level remain relatively undisturbed by mixing with modern water introduced by mining mixing calculations are used to quantify fractions of brine glacial meltwater and modern water from this noble gas concentrations were corrected for excess air with ne and normalized to 100 brine solution over pressuring of helium and argon in the brine provide age constraints based on the accumulation of geogenic 4he and 40ar radiogenic age calculations together with the local geological history suggest brine emplacement during early palaeozoic time likely during the devonian when evaporitic inland seas existed in this region the concentrations of the atmospherically derived noble gases in the brine fraction kr 1 4e 8 xe 8 5e 10 cc stp cc h 2 o are close to atmospheric equilibrium for brine at 25 c kr 7 3e 9 xe 8 0e 10 cc stp cc h 2 o but are far lower than would be expected for closed system concentration of seawater by freezing kr 2 8e 6 xe 4 2e 7 cc stp cc h 2 o thus despite the complicated mixing history of the brine the atmospheric and geogenic noble gases provide strong evidence for an origin as air equilibrated brine from evaporated paleozoic seawater which infiltrated via density displacement through existing fractures and faults into the canadian shield

basin scale natural gas source migration and trapping traced by noble gases and major elements the pakistan indus basin he ne and ar concentrations he and ar isotopic ratios carbon isotopic ratios and chemical compositions of hydrocarbon gases were measured in natural gas samples from gas producing wells in the indus basin pakistan where no oil has ever been found 3he 4he ratios are in the range 0 01 0 06 ra ra is the atmospheric value of 1 38 10 6 indicating the absence of mantle derived helium despite the trias extension 40ar 36ar ratios range from 296 to 800 consistent with variable additions of radiogenic argon to atmospheric groundwater derived argon rare gas concentrations show large variations from 6 10 5 to 1 10 3 mol mol for 4he and from 3 10 7 to 3 10 5 mol mol for 36ar in general 36ar concentrations are high compared to literature data for natural gas co2 and n2 concentrations are variable ranging up to 70 and 20 respectively mantle derived he is not observed therefore co2 and n2 are not mantle derived either hydrocarbon gas maturity is high but accumulation efficiency is small suggesting that early produced hydrocarbons including oil were lost as well as mantle helium this is consistent with the generally late pliocene trap formation and explains the high n2 concentrations since n2 is the final species generated at the end of organic matter maturation based on 13c data co2 originates from carbonate decomposition very elevated 20ne 36ar ratios are found reaching a maximum of 1 3 compared to 0 1 0 2 for air saturated water and 0 5 for air and these high values are related to the lowest rare gas concentrations we suggest that this highly fractionated signature is the trace of the past presence of oil in the basin and appeared in groundwater we propose a model where oil water contact is followed by gas water contact both with rayleigh distillation for rare gas abundance ratios thereby generating the fractionated 20ne 36ar signature in groundwater first and transferring it to gas later assuming the gas water contact occurred shallower than present reservoir depths this model explains the generally high 36ar concentrations and low ch4 36ar ratios compared to other studies on younger basins it thus provides a historical perspective on fluid transfer in a sedimentary basin where a gas accumulation may have been buried to greater depth since formation rare gas and major element data point to mixing between two gas pulses produced successively the very co2 n2 rich gases are terminal products of organic matter maturation which have been trapped after important migration this gas was followed by a more typical thermogenic gas which mixed with it

retracted the influence of sand diameter and wind velocity on sand particle lift off and incident angles in the windblown sand flux the problem of impact entrainment is one of the central issues in understanding the process of saltation in this paper through improving the experimental scheme of particle image velocimetry piv and data processing methods using wind tunnel data the measurement of sand particle lift off and incident angles near the sand bed was achieved based on experimental data we analyze the probability distribution of sand particle lift off and incident angles and the influence of wind velocity and sand diameter on the probability distribution as well as the relation between incident angle and lift off angle the results demonstrate that wind velocity and sand diameter have no obvious influence on the distribution shape of sand particle lift off and incident angles however wind velocity will influence the decay constant and amplitude of the probability distribution c 2013 elsevier b v all rights reserved

observations of collisions of saltating grains with a granular bed from high speed cine film high speed photography was used to record saltating sand grains colliding with a horizontal noncohesive bed of similarly sized grains impacting grain bed interaction is discussed in general the process as observed from the films is then described in terms of the apparent bed contact length abcl and various parameters of the impacting grains and any ejected grains examples are given of typical behaviour of bed grains in response to impacting grains of different sizes saltating grains that are large in comparison to the bed grains they encounter at collision can churn up the surface layers of soils and sediments so that previously buried grains become available for entrainment this process is discussed in relation to the potential release of dust particles into the airflow

modeling subsurface flow in sedimentary basins groundwater flows that arise in sedimentary basins from the effects of topographic relief buoyant convection sediment compaction erosional unloading and combinations of these driving forces can be described using quantitative modeling techniques models can be constructed to consider the effects of heat and solute transport petroleum migration and the chemical interaction of water and rocks the accuracy of model predictions however is limited by the difficulty of predicting hydrologic properties of sediments on regional dimensions estimating past conditions such as topographic relief and knowledge of how physical and chemical processes interact over gelogic time scales progress in basin modeling will accelerate as hydrologic research efforts are better integrated with those of other specialities such as sedimentology rock mechanics and geochemistry

the distribution of velocity and energy of saltating sand grains in a wind tunnel abstract sand transport by wind is a special case of two phase flow of gas and solids with saltating grains accounting for about 75 of the transport rate this form of flow is not only the main external agent moulding aeolian landforms but also the motive force responsible for transport sorting and deposition of aeolian sediments high speed multiflash photography is an effective method of studying the distribution of velocity and energy of saltating grains within the boundary layer of wind tunnel the experimental wind shear velocities were set at 0 63 0 64 0 74 and 0 81 ms 1 the statistical study of the results showed that there is a power function relation between mean velocity and height of saltating grains as the height is divided into 0 5 cm intervals the sand grain velocities at various levels are consistent with the pearson vii distribution pattern the variations in kinetic energy and total energy of sand grains with height accord with the pulse peak modified with power term pulsepow law the maximum values occur at heights of 6 cm or so and tend to shift upward with increasing wind velocity

establishing constraints on groundwater ages with 36cl 14c 3h and noble gases a case study in the eastern paris basin france abstract groundwaters from the tithonian kimmeridgian oxfordian and upper dogger aquifers within the eastern part of the paris basin france were characterised using 3 h 14 c and 36 cl and noble gases tracers to evaluate their residence times and determine their recharge period this information is an important prerequisite to evaluating the confinement properties of the callovo oxfordian clay formation sandwiched between the oxfordian aquifer and the dogger aquifer currently being investigated by the french nuclear waste management agency andra for radioactive waste disposal data presented in this paper are used to test 4 hypotheses 1 the oxfordian limestone is isolated from the overlying tithonian kimmeridgian surface aquifer this first hypothesis is supported by the presence of measurable 3 h activities in groundwaters from the surface aquifer 6 11 tu and by its absence in groundwaters derived from deeper aquifers 2 the callovo oxfordian clay sequence in the vicinity of the url serves as an effective barrier to advective flow and transport between the underlying upper dogger aquifer and the overlying oxfordian limestone aquifer this second hypothesis is supported by relatively low concentrations of cl 3 5 78 mg l 1 na 15 145 mg l 1 br 0 08 0 4 mg l 1 and 4 he rad 0 2 2 3 ccstp g 1 and slightly higher 36 cl cl ratios 2 7 59 10 15 at at 1 in groundwaters from the oxfordian aquifer compared to those from the upper dogger aquifer 345 4027 mgcl l 1 402 2390 mgna l 1 1 8 22 2 mgbr l 1 1 6 37 2 ccstp he g 1 1 5 10 15 at 36 cl at 1 cl 3 groundwaters from the oxfordian aquifer in the vicinity of url are pre holocene with residence times exceeding 10 ka geochemical and isotopic lines of evidence for this hypothesis include a 13 c values measured on oxfordian aquifer waters that are close to 13 c of the aquifer matrix reflecting strong isotopic exchange over several thousand years b noble gas temperatures that indicate recharge temperatures between 3 and 8 6 c lower by 2 7 c than the modern average temperature in this area c radiogenic 4 he concentrations between 0 16 10 5 and 2 3 10 5 ccstp g 1 of water about 2 3 orders of magnitude greater than the 4 he concentration of air equilibrated water 4 groundwater residence time for the upper dogger aquifer in the vicinity of the url probably exceed several hundred thousand years such long residence times are indicated by the accumulation of radiogenic he up to 37 10 5 ccstp g 1 assuming a closed system primary contributors to uncertainties in interpretation of the data presented in this paper are the lack of well defined 36 cl cl input ratio knowledge about the 4 he rad sources for oxfordian and dogger aquifers knowledge about transport processes occurring through the dogger aquifer and the extensive dilution of initial 14 c activities by dissolution exchange with aquifer matrix overall however although the data presented in this paper remain semi quantitative due to inevitable intrinsic limitations of the methods none contradict the hypotheses of long residence times and aquifer isolation in the vicinity of the url

geochemical evidence for efficient aquifer isolation over geological timeframes aquitards layers of rock having low permeability have been suggested as potential long term reservoirs for toxic materials such as nuclear or chemical waste but information about the isolation properties of aquitard layers is essential to evaluate whether they can indeed be used safely as reservoirs here we investigate the long term mobility of groundwaters between two aquifers surrounding an aquitard layer in the eastern recharge area of the paris basin france using helium isotopes as a geochemical tracer the deeper trias sandstone aquifer which lies above the crystalline basement accumulates radiogenic 4he and primordial 3he from large regions of the crust and mantle at rates comparable to the degassing of the whole crust1 and of mid ocean ridges2 we show that the overlying carbonate dogger aquifer which is separated from the trias aquifer by an aquitard layer consisting of a 600 m succession of shales and clays is stagnant and has been extremely well isolated from the trias over the past several million years this finding together with previous studies at the centre of the paris basin3 4 shows that diffusive mass transfer across aquitards is negligible and that cross formational flow in basins takes place preferentially in faulted areas

helium 4 characteristics of groundwaters from central australia comparative chronology with chlorine 36 and carbon 14 dating techniques summary helium isotope and concentration characteristics were determined for a suite of groundwater samples from the amadeus basin in central australia two study areas include a wellfield south of alice springs and the dune plains and mututjulu aquifers near uluru measurements of 36cl cl and 14c on the same sample suite enable us to assess the relative applicability of the three groundwater chronometers over a range of anticipated groundwater residence times ages and to investigate possible causes of discordant ages derived from the different groundwater dating techniques results from the analyses of 39 groundwater samples reveal helium 4 4he concentrations that range from 0 80 to 98 8 10 7 cm3 stp g 1 h2o in the alice springs samples and from 0 47 to 65 6 10 7 cm3 stp g 1 h2o in the uluru samples 4he concentrations yield uncorrected groundwater residence times i e time since recharge of between modern to 2500 ka near alice springs and modern to 1600 ka near uluru assuming an effective porosity of 20 and uranium and thorium contents of 1 7 and 6 1 ppm respectively 36cl cl ratios on the same samples range from 93 to 158 10 15 near alice springs and from 80 to 335 10 15 near uluru representing groundwater residence times near alice springs from modern to 200 ka and from modern to 300 ka near uluru percent modern carbon pmc on the same samples ranged from 64 9 to 12 5 pmc near alice springs and from 93 5 to 30 ka for the amadeus basin groundwater samples the 4he method uncorrected over estimates groundwater residence time compared to 36cl and 14c techniques this implies the presence of an extraneous he component or basal flux of he j0 to reconcile groundwater 4he and 14c residence times it is necessary to adopt j0 values between 0 and 30 10 8 cm3 stp he cm 2 a 1 which supplements in situ produced he within the aquifer adoption of j0 values over this range lowers 4he residence times relative to 36cl and produces closer agreement between the 4he and 14c chronometers the extraneous he component basal flux in amadeus basin samples is dominated by radiogenic crustal 4he without a detectable amount of mantle derived 3he we conclude that the stable tectonic regime albeit with the presence of major faults within the basin inhibits the input of mantle volatiles to the groundwater system so that in this region diffusion is the dominant transport mechanism for he in the crust

a steady state model of wind blown sand transport a model for steady state eolian saltation is presented in which computation of sand grain trajectories in the wind and of the wind velocity profile modified by saltating grain drag forces is combined with experimental data on grain bed collisions in an iterative simulation scheme which resembles the time development of natural saltation qualitative features of eolian saltation are reproduced in the simulations including a height in the saltating layer at which the wind velocity remains roughly constant with changing free stream friction velocity and an approximate separation of the saltating population into successively hopping grains and reptating or creeping grains the numerical solutions give rise to more general arguments in support of the conclusions that fluid entrainment of grains is unimportant in steady state saltation that the mass flux profile obeys roughly an inverse power law dependence on height and that the vertically integrated mass flux dependence on the free stream friction velocity

helium isotope fluxes and groundwater ages in the dogger aquifer paris basin the dogger aquifer of the paris basin has been shown to be first order homogeneous in its helium concentration and its helium isotopic ratio although slight differences are noted in relation to specific chemical water types the helium isotopic composition of the dogger aquifer contains a small component of mantle helium that is associated with a magmatic input although the heat accompanying this magma is small constraints on the age of the overlying albien aquifer are used to calculate the flux of helium out of the dogger this constraint allows a calculation of the residence time of waters in the dogger aquifer of 4 myr 50 which is significantly longer than estimates derived from hydrologic models and hydrologic testing it is possible that the hydrologic ages and the helium ages can be reconciled by a vertically layered dogger aquifer with gradients in he salinity and fluid flow vertical profiles of fluid composition helium concentration and permeability are required in the paris basin to resolve this question

the origin of helium in deep sedimentary aquifers and the problem of dating very old groundwaters noble gases inert elements having isotopes produced by the decay of long half life radionuclides offer a powerful approach for tracing fluid circulation and dating groundwaters the u th 4he water ages calculated from the accumulation rate in water of radiogenic 4he produced by decay of u and th contained in the aquifer rocks is frequently higher than the hydrological ages this discrepancy is generally interpreted by two contrasting models i heterogeneities of the aquifers which allow water stagnation and accumulation of large amounts of radiogenic 4he or ii addition of 4he produced in deeper regions of the continental crust in this contribution we propose that the apparent contrast between u th 4he ages and hydrological ages in the paris basin reflects the mixing of different types of water having different residence times we show using the helium isotopic signatures of waters that this mixing occurs between three aquifers the middle jurassic the triassic and the palaeozoic basement which have contrasting helium contents and heterogeneous chemical compositions and permeabilities the difference of radiogenic 4he 4 ratios between the aquifers of triassic and middle jurassic strongly suggests that a significant fraction of helium is produced in the aquifer rocks this implies residence times for groundwaters circulating in the middle jurassic carbonate aquifer much longer than those obtained from hydrological studies independent fluid age estimates based on the ground palaeotemperatures recorded in the same groundwaters by the atmospherederived noble gases seem to confirm the presence of very old groundwaters in the paris basin the estimation of the residence time of ancient groundwaters is the most challenging problem in basin hydrology e g chapman 1987 typical water residence times of 104 108 years outreach the range of half lives of most of the geochronometers available in hydrology e g 3h 14c and prolonged water rock interactions alter the chemical and isotopic signature of water preventing the identification of the fluid sources on the other hand hydrological modelling faces serious problems of estimating space and time variations of critical parameters such as the permeability due to the petro physical heterogeneities of the aquifers and fluid velocity estimates can be valid only on a local scale e g alexander et al 1987 because noble gases are inert and have isotopes produced by natural decay of long halflife radionuclides these elements have received increasing attention as tracers of groundwater movements in deep aquifers e g marine 1979 andrews et al 1982 1985 bottomley et at 1984 1990 torgersen clarke 1985 zaikowski et al 1987 ballentine et al 1991 stute et al 1992 marty et al 1993 o nions ballentine 1993 groundwaters contain noble gases derived from the atmosphere the crust and the mantle fig 1 studies on water dating are focused mainly on the crustal derived radiogenic noble gas component for obvious reasons although the mantle derived component has the capacity of tracing fluid sources oxburgh et al 1986 and the atmosphere derived component can provide independent estimates on the water residence times pinti et al 1997 in continental environments mantle derived noble gases are generally observed in regions of active volcanism or extensional tectonics ballentine et al 1991 the source is probably sub continental magma intrusion and underplating with successive episodic and tectonically controlled advective transport in the crust torgersen 1993 mantle derived helium can be easily identified from its isotopic signature indeed the mantle is enriched in primordial 3he as indicated by 3he 4he ratios greater than 10 5 whereas the atmospheric ratio is l a x 10 6 and crustalderived radiogenic helium has 3he 4he ratios in the range of 10 8 consequently the geographical distribution of the 3he 4he ratios in sedimentary fluids can be used to identify the fluids pinti d l marty b 1998 the origin of helium in deep sedimentary aquifers and the problem of dating very old groundwaters in parnell j ed 1998 dating and duration of fluid flow and fluid rock interaction geological society london special publications 144 53 68 by guest on january 5 2014 http sp lyellcollection org downloaded from

estimation of some aeolian saltation transport parameters a re analysis of williams data a new method for analysing observed aeolian sand transport rate profiles of the kind obtained by williams is presented the method involves a mathematical model of aeolian saltation detailed information about the saltation process can be calculated from the transport rate profile by means of this model the method is used to perform a re analysis of williams trap data among the main findings of this analysis is that the grain borne shear stress appears to be a smaller fraction of the total shear stress than assumed by bagnold owen in their theories of aeolian saltation other findings are that the probability distribution of the jump height of the grains does not depend much on the wind speed once the saltation is established and that the vertical component of the mean launch velocity decreases with the grain size it is approximately inversely proportional to the grain diameter our estimates of the landing angles indicate that estimates of the impact angles obtained from photographically recorded trajectories are too small due to biased sampling the influence of grain shape on the transport characteristics is mainly due to changes in the grains ability to jump when hitting the bed it is found that angular grains have a lower mean jump height than spherical grains

eemian sea level highstand in the eastern baltic sea linked to long duration white sea connection abstract revised diatom and new dinoflagellate cyst and benthic foraminiferal data from the eastern baltic sea have refined our understanding of eemian last interglacial 131 119 5 ka sea level change on the russian karelia a former seaway linking the baltic to the white sea results from peski eastern baltic show the initiation of marine conditions just before 131 ka in the latest saalian after the opening of a connection to the north sea following the onset of the eemian marine highstand and the opening of the white sea connection at around 130 25 ka near fully marine conditions persisted in the eastern baltic area for ca 6 kyr until ca 124 ka for most of the eemian a strong thermal stratification in the eastern baltic resulted from an arctic and possible north atlantic water component from the white sea merging with warmer waters from the north sea from ca 124 ka decreasing salinity indicates the end of the marine highstand and a simultaneous closure of the baltic sea white sea connection i e a duration of ca 6 kyr for this seaway the main influence of white sea inflow appears to be restricted to the eastern baltic area although a large submerged area in the russian karelia associated with temperate atlantic waters could have assisted in creating a more oceanic climate for central europe

noble gas composition of deep brines from the palo duro basin texas deep groundwaters in sedimentary basins can be sufficiently old 10 m y to have accumulated both radiogenic 4he and 40ar differences in the ratio of u th k for aquifer lithologies lead to variations for 4he40ar in the groundwater these variations can be used to resolve chronologically significant noble gas components application of a binary model to brine samples from the palo duro basin texas yields u th 4he residence times of 100 to 300 m y concentrations of two non radiogenic noble gases 20ne and 36ar provide information on the salinities of the water that recharged these aquifers

the noble gas isotope record of hydrocarbon field formation time scales abstract noble gases may be considered as the most prominent tracers of natural fluids including hydrocarbons the atmosphere is the only source of 20ne 36ar 84kr 130xe in subsurface environments and their concentrations in pore waters after recharge are known from the solubility data this allows modelling of noble gas partitioning between coexisting gas oil and water phases in the course of hydrocarbon formation migration and storage radiogenic isotopes 4he 21ne 40ar 136xe after being released from source rocks are mixed with air derived noble gases already present in the pore space concentrations of radiogenic species in the pore space of typical hydrocarbon fields are generally so high that they can hardly be accumulated in situ and thus indicate noble gas transfer from ground waters the time bearing ratios 4he 20ne 21ne 20ne 4he 40arair 40ar 40arair in hydrocarbon fields are thus proportional to the time interval between the ground water recharge and noble gases partitioning into the hydrocarbon phase s the recharge partition interval the largest available data set allows the recharge partition intervals to be constrained for a large number of hydrocarbon fields situated in different tectonic settings ancient plates young plates mobile belts these intervals increase systematically with the ages of hydrocarbon source and trap lithologies and are comparable with these ages this important feature valid in general for different hydrocarbon fields implies i local sources of radiogenic noble gas isotopes in ground waters ii relatively recent formation of hydrocarbon fields and iii their short formation time scales in some cases the duration of formation of a hydrocarbon field can be constrained for example nearly constant 21ne 20ne 40ar 40arair ratios measured in samples from the magnus oil field north sea give an accumulation time scale 10 ma it should be emphasized that the above noble gas isotope ratios give the time estimates which are independent of geological reconstructions sometimes the noble gas inventory in a hydrocarbon field and ground waters allows characterization of the source rock volume involved in formation of the field generally this volume exceeds that of the hydrocarbon field rocks by orders of magnitude

application of combined 81kr and 4he chronometers to the dating of old groundwater in a tectonically active region of the north china plain abstract groundwater dating by radio krypton 81kr half life of about 229 000 years was applied to the sedimentary basin aquifer of the north china plain ncp krypton gas extracted from deep groundwater in the coastal plain was analyzed for 81kr kr ratios by atom trap trace analysis which yielded normalized ratios of 0 05 to 0 20 corresponding to groundwater residence times of 0 5 1 million years helium isotope compositions were determined on groundwater samples collected from the central plain and the coastal plain along a flow path of about 200 km helium dissolved in the groundwater samples are a mixture of atmospheric crustal radiogenic and mantle derived sources mantle derived 3he contributes up to 30 of the total and the area of occurrence coincides with zones of previous magmatic tectonic activities by contrast 90 of 4he is derived from crustal reservoirs and correlates with 81kr ages the absolute groundwater ages 81kr and radiogenic 4he concentrations permit us to calibrate the 4he flux into the aquifer as well as the vertical diffusion rate of 4he to utilize the radiogenic 4he in groundwater as a quantitative age tracer previously groundwater showed 14c activities near the limit of detection 30 40 k yr in contrast kr and radiogenic 4he data reveal progressively older ages from the recharge area to the coastal plain from

the geochemistry age and origin of groundwater in a mafic pluton east bull lake ontario canada abstract the geochemistry of groundwater in the east bull lake gabbro anorthosite pluton near elliot lake ontario canada has been investigated three chemical types of groundwater are present to depths of about 650 m and are controlled by the nature of the groundwater flow systems and the water rock interactions in the fractures ca hco 3 water is present in the recharge area of the local flow system and evolves rapidly along the direction of groundwater flow to a high ph na hco 3 water primarily by cation exchange reactions saline na cl water is present below a depth of about 350 m on the basis of its chemistry and hydraulic head measurements the na cl water is believed to be part of a deep regional groundwater flow system carbon 14 measurements of the na hco 3 water suggest that this water was recharged shortly after the last pleistocene deglaciation this is supported by 18o values that are as much as 6 lighter than shallow modern groundwater despite the high mg content of the enclosing rocks mg2 concentrations in the groundwater of this unit are na hco 3 and na cl waters and hence could still be forming under the present low temperature conditions the stable isotope composition of the na cl water suggests that this water type is not a geochemically evolved product of the overlying waters although present day albitization of the anorthosite could be responsible for the increased ca na ratio in the na cl water compared to the other water types the salinity of this water appears to have been derived outside the pluton possibly as an ancient infiltration into crystalline basement rocks of saline formation waters present in paleozoic sedimentary rocks which formerly overlay the pluton or from nearby proterozoic formations this hypothesis is supported by br cl ratios that are similar to sea water and many present day formation waters and the isotopic composition of the dissolved sulphate the he age of the saline water is of the order of 108 years therefore both the saline water and many of its solutes appear to have ancient origins

a two species model of aeolian sand transport the transport of sand by wind results from the equilibrium between the erosion of grains dragged by the flow and the resulting slow down of the wind velocity the dynamical mechanisms governing the saturation of the sand flux are investigated theoretically we first demonstrate that previous models based on the assumption that all the grains have the same trajectory are either not self consistent or lead to unstable solutions a model based on a discrete number of states is derived which solves these problems two well defined species of grain appear which correspond to saltons high energy grains and reptons grains ejected from the sand bed by the impact of saltons they play specific roles the negative feedback of the transport on the wind is limited to the reptation layer while most of the transport is due to saltation the model is further simplified benefiting from the existence of these two species and the dependencies of the threshold velocity the saturated flux the aerodynamic roughness and the saturation length are derived and compared to experimental measurements

dissolved gases in the milk river aquifer alberta canada abstract geochemical relations between the noble gases 40 ar 36 ar ratio n 2 and ch 4 contents of groundwaters from the milk river aquifer albert canada have been investigated the ch 4 contents for many of the groundwaters are several times their n 2 contents and cause degassing to occur as the hydrostatic pressure decreases during their ascent in the wells recharge temperatures derived for those groundwaters that were not degassed indicate that the youngest groundwaters were recharged under cooler climatic conditions than prevailed during earlier recharge this conclusion is supported by the stable isotope compositions of the groundwater the 4 he concentration in the groundwater varies with depth according to the theoretical concentration depth profile for accumulated radiogenic 4 he in the aquifer and its adjacent shales the corresponding flux of 4 he to the atmosphere is 4 he production rate excess radiogenic 40 ar is associated with ch 4 and both gases originated within the adjacent shales the ch 4 is biogenic and was produced in an aqueous environment which ranged from marine to freshwater as the connate fluids in these marine shales were replaced the degassing process has been modelled to explain the residual dissolved gas contents of the groundwater and to show that the ch 4 n 2 ratio in situ was 12

cross checking groundwater age by 4he and 14c dating in a granite tono area central japan abstract groundwater dating was performed simultaneously by the 4he and 14c methods in granite of the tono area in central japan groundwater was sampled at 30 packed off sections of six 1000 m boreholes 4he concentrations increased and 14c concentrations decreased along a groundwater flow path on a topographic gradient 4he ages were calculated by using the in situ 4he production rate derived from the porosity density and u and th content of the rock neglecting external flux 14c ages were calculated with a noncorrected model in which the initial 14c content was 100 percent of the modern radiocarbon level co 100 pmc a statistical model using the average 14c content of tritium bearing samples co 46 4 pmc and a 13c model based on the isotopic mass balance although the absolute 14c ages calculated by the models were different the relative 14c ages were almost identical the relative 14c ages were considered reliable because dissolved inorganic carbon has no significant geochemical reactions in granite the relation between the 4he ages and the noncorrected 14c ages was 4he age 1 15 14c age 7200 r2 0 81 except in the discharge area the slope of this relation was equivalent to unity which indicates that the 4he accumulation rate is confirmed by the relative 14c ages moreover the accumulated 3he 4he ratio was equivalent to that derived from the 6li n 3h reaction in granite these results show that the accumulated he is of crustal origin produced in situ without external flux except in the discharge area the intercept value of 7200 a implies that the 14c concentrations were diluted due to geochemical reactions tritium bearing samples supported this result simultaneous measurements make it feasible to estimate the accumulation rate of 4he and initial dilution of 14c which cannot be done with a single method cross checking groundwater dating has the potential to provide more reliable groundwater ages the circulation time of the groundwater flow in the tono area may be several tens of thousands of years and the groundwater age calculated from the 4he and 14c ages appears to be consistent with geochemical information such as groundwater types d and 18o

hydrogeology of sedimentary basins abstract hydrogeologic environments in sedimentary basins are as variable as are the different types of basins important hydrologic characteristics can be used to distinguish the different types of basin 1 the topographic setting as determined by the geologic and structural history of the basin 2 permeability distribution within the basin and 3 potential energy distributions and flow mechanisms these parameters control residence times of waters rates and directions of saline groundwater flow and the origin and chemical composition of the saline waters the gulf coast and palo duro basins texas exemplify two end member types of sedimentary basins the gulf coast basin is a relatively young tertiary age basin which is presently compacting fluid movement is from the overpressured undercompacted sediments up the structural dip or up fault zones into the hydrostatic section natural fluid pressures are either hydrostatic or overpressured the palo duro is an older paleozoic age basin that has been tectonically uplifted fluid flow is gravity driven from topographically high recharge areas to discharge in topographically low areas fluid pressures are subhydrostatic fluids discharge more easily than they are recharged not all flow is derived by a simple recharge discharge model brines may flow from other basins into the palo duro basin and waters may discharge from the palo duro basin into other basins areal differences in the chemical composition of the basin brines may be the result of different origins

groundwater dating by estimation of groundwater flow velocity and dissolved 4he accumulation rate calibrated by 36cl in the great artesian basin australia abstract we tested two methods for dating groundwaters that cannot be reliably measured by 36cl dating alone one based on groundwater flow velocity plus distance along a flow path and the other based on 4he accumulation rates calibrated with 36cl dates we sampled groundwaters along six inferred regional groundwater flow paths in the great artesian basin gab of australia we selected three groundwater paths where the decrease in 36cl was largely controlled by cosmogenic 36cl radioactive decay without a significant increase in chloride concentration the extrapolated groundwater velocities were 0 133 0 018 m y to 0 433 0 140 m y the estimated residence time of 1 06 106 y at the discharge area around lake eyre was comparable to the estimate of 1 2 2 106 y in previous studies on the other hand our estimated 4he accumulation rates for the selected three groundwater flow paths 1 85 0 31 10 11 to 1 51 0 63 10 10 ccstp cm3 y were approximately 2 15 times lower than previously reported rates for the central gab our estimated rate of 1 51 10 10 ccstp cm3 y 1 in the western gab is compatible with previous estimates based on 81kr ages the groundwater residence time estimated from the 4he accumulation rate was approximately 7 105 y near the discharge area at lake eyre finally both estimations were mutually compatible with a 30 error

wind tunnel experimental investigation of sand velocity in aeolian sand transport sand velocity in aeolian sand transport was measured using the laser doppler technique of pdpa phase doppler particle analyzer in a wind tunnel the sand velocity profile probability distribution of particle velocity particle velocity fluctuation and particle turbulence were analyzed in detail the experimental results verified that the sand horizontal velocity profile can be expressed by a logarithmic function above 0 01 in while a deviation occurs below 0 01 m the mean vertical velocity of grains generally ranges from 0 2 m s to 0 2 m s and is downward at the lower height upward at the higher height the probability distributions of the horizontal velocity of ascending and descending particles have a typical peak and are right skewed at a height of 4 turn in the lower part of saltation layer the vertical profile of the horizontal rms velocity fluctuation of particles shows a single peak the horizontal rms velocity fluctuation of sand particles is generally larger than the vertical rms velocity fluctuation the rms velocity fluctuations of grains in both horizontal and vertical directions increase with wind velocity the particle turbulence intensity decreases with height the present investigation is helpful in understanding the sand movement mechanism in windblown sand transport and also provides a reference for the study of blowing sand velocity c 2007 elsevier b v all rights reserved