the role of perched aquifers in hydrological connectivity and biogeochemical processes in vernal pool landscapes central valley california relatively little is known about the role of perched aquifers in hydrological biogeochemical and biological processes of vernal pool landscapes the objectives of this study are to introduce a perched aquifer concept for vernal pool formation and maintenance and to examine the resulting hydrological and biogeochemical phenomena in a representative catchment with three vernal pools connected to one another and to a seasonal stream by swales a combined hydrometric and geochemical approach was used annual rainfall infiltrated but perched on a claypan duripan and this perched groundwater flowed downgradient toward the seasonal stream the upper layer of soil above the claypan duripan is 0 6 m in thickness in the uplands and 0 1 m in thickness in the vernal pools some groundwater flowed through the vernal pools when heads in the perched aquifer exceeded 0 1 m above the claypan duripan perched groundwater discharge accounted for 30 60 of the inflow to the vernal pools during and immediately following storm events however most perched groundwater flowed under or around the vernal pools or was recharged by annual rainfall downgradient of the vernal pools most of the perched groundwater was discharged to the outlet swale immediately upgradient of the seasonal stream and most water discharging from the outlet swale to the seasonal stream was perched groundwater that had not flowed through the vernal pools therefore nitrate nitrogen concentrations were lower e g 0 17 to 0 39 mg l 1 and dissolved organic carbon concentrations were higher e g 5 97 to 3 24 mg l 1 in vernal pool water than in outlet swale water discharging to the seasonal stream though the uplands vernal pools and seasonal stream are part of a single surface water and perched groundwater system the vernal pools apparently play a limited role in controlling landscape scale water quality copyright 2005 john wiley sons ltd

comment on helium isotope fluxes and groundwater ages in the dogger aquifer paris basin by b marty t torgersen v meynier r k o nions and g de marsily

p wave tomographic imaging of the crust and upper mantle beneath the japan islands more than 50 000 high accuracy arrival times from 1200 shallow and deep earthquakes selected from the japan university network earthquake catalog are used to investigate the three dimensional 3 d seismic velocity structure beneath japan travel times and ray paths are accurately calculated by using an efficient 3 d ray tracing technique p wave tomographic images of the crust and upper mantle to a depth of 500 km beneath the japan islands are determined with spatial resolutions of 25 50 km the obtained p wave velocity in the crust and uppermost mantle is slightly higher and relatively homogeneous in western japan in contrast with an average lower velocity and a large heterogeneity in eastern japan where many active volcanoes exist this feature correlates well with the distributions of heat flow and gravity anomalies low velocity low v zones are imaged in the crust and uppermost mantle beneath active volcanoes the low v zones in the mantle wedge dip toward the west and extend continuously to a depth of about 200 km a high velocity high v zone corresponding to the subducted pacific plate is delineated the thickness of the high v zone is estimated to be 80 90 km in southwestern japan the descending philippine sea plate is also delineated its thickness is estimated to be 30 km

impact of permeable conduits on solute transport in aquitards mathematical models and their application 1 the migration of contaminants through porous conduits for example sand layers in aquitards or any preferential flow feature within a low permeability matrix can be significantly retarded via diffusion into the matrix and processes such as sorption and decay previous solutions for simulating contaminant transport in these types of environments have been limited to a parallel plate approach such as that used in studies of fractured rock aquifers a major drawback of using these approaches is that they cannot account for the radial component of diffusion that occurs from circular or elliptical sectioned conduits we have developed solutions for both of the latter cases and compared results from generic simulations to those obtained with a conventional parallel plate model the results demonstrated using a circular conduit approach can produce concentration profiles for both the conduit and surrounding matrix that are up to several orders of magnitude lower than those predicted using parallel plate models the solutions for elliptical section conduits provide concentration profiles that are bounded by the circular and parallel plate models we also present several generic simulations to demonstrate the effects of conduit radius and average groundwater flow velocity on concentration profiles finally the circular conduit model is applied to a clay rich till aquitard in southern saskatchewan canada to provide insight into an anomalous dissolved chloride peak in the vertical pore water profile the model demonstrates that the source of the high cl could be as far as 10 100 km from the site although this distance may be unrealistic and allows estimation of the cl concentration at the source we envisage that the solutions for conduit diffusion will have far wider applications than just aquitard studies and future uses may include tracer tests in karstic and fractured aquifers

simulations of anomalous seismogram envelopes at coda portions abstract two models of coda wave envelope formation based on single isotropic scattering in complicated inhomogeneous structures are tested to explain anomalous seismogram envelopes observed at the coda portion one is a hybrid model with a reflector embedded in a scattering medium the seismogram envelope composed of scattered waves is calculated from the summation of the energy density of coda waves for the real source and the mirror image source the size of the reflector affects the duration of the anomalously large amplitude coda envelope following the reflected wave the second model is a simulation of coda waves in a medium which is composed of many small cubic blocks three dimensional variation of the attenuation and scattering intensity is represented adequately by combination of blocks the energy density of coda waves is calculated with the scattering coefficient of the block which includes the scattering point and the attenuation factor integrated along the ray path of each scattered wave coda envelopes based on the two models are simulated in order to explain anomalous seismogram envelopes which are observed in japan in the kanto area central part of japan reflected s waves from the upper boundary of the subducting pacific plate are observed for shallow events and generate large amplitude wave trains in the coda portion the parallel distribution of coda decay curves following the direct s wave and the reflected s wave is explained by the large extension of the reflector the large amplitude offset requires a two layer structure in the distribution of the scattering and attenuation intensity in awaji island western part of japan the coda amplitude does not decrease for about 10 s after the arrival of the direct s wave for shallow local events the simulation of coda waves with a two layer strong scattering body for s waves ranging from about 20 to 30 km in depth might explain the flat portion of the observed s coda envelope the simulation of p wave seismogram envelopes for the artificial blast suggests that there exists a strong scattering body for p waves ranging from 20 to 25 km in depth the lower crust beneath the northern part of awaji island might be strongly inhomogeneous not only for s waves but also for p waves

a multi isotope b sr o h and c and age dating 3h 3he and 14c study of groundwater from salinas valley california hydrochemistry dynamics and contamination processes 1 the chemical and isotope 11b 10b 87sr 86sr 18o 16o 2h h 13c 12c 14c and 3he 3h compositions of groundwater from the upper aquifer system of the salinas valley in coastal central california were investigated in order to delineate the origin and processes of groundwater contamination in this complex system the salinas valley has a relatively deep confined 400 foot aquifer overlain by a 180 foot aquifer and a shallower perched aquifer all made up of alluvial sand gravel and clay deposits groundwater from the aquifers have different 14c ages fossil 14c 21 3 percent modern carbon pmc for the 400 foot aquifer and modern 14c 72 2 98 2 pmc for the 180 foot aquifer fresh groundwater in all aquifers is recharged naturally and artificially through the salinas river the two modes of recharge can be distinguished chemically we identified several different saline components with distinguishable chemical and isotopic fingerprints 1 saltwater intrusion in the northern basin has c1 concentrations up to 1700 mg l a na cl ratio less than seawater a marine br cl ratio a ca cl ratio greater than seawater 11b between 17 and 38 and 87sr 86sr between 0 7088 and 0 7096 excess dissolved ca relative to the expected concentration for simple dilution of seawater correlates with 87sr 86sr ratios suggesting base exchange reaction with clay materials 2 agriculture return flow is high in no3 and so4 with a 87sr 86sr 0 7082 11b 19 and 13c between 23 and 17 the 3h 3he ages 5 17 years and 14c data suggest vertical infiltration rates of irrigation water of 3 10 m yr 3 nonmarine saline water in the southern part of the valley has high total dissolved solids up to 3800 mg l high so4 na cl ratio 1 11b between 24 and 30 and 87sr 86sr 0 70852 this groundwater may have acquired its geochemical signature from leaching of sedimentary rocks associated with the coast range marine deposits of mesozoic to early cenozoic age the combination of different geochemical and isotopic fingerprints enables us to delineate the impact of salt sources in different areas of the valley and to reconstruct the origin of the so4 enriched no3 depleted saline plume that is located west of the city of salinas we suggest that the latter is derived from a mixture of different natural saline waters rather than from anthropogenic contamination

seismic structure of the northeastern japan convergent margin a synthesis many studies recently made on the basis of seismic observations have revealed a detailed structure of the crust and the upper mantle beneath the northeastern japan arc and its relationship to seismic and volcanic activity spatial distributions of the depths to the conrad and the moho discontinuities estimated from shallow earthquake data and seismic explosion data show that both discontinuities are deep in the middle of the land area and shallow toward the coastlines of the japan sea and the pacific ocean the pn velocity has a lateral variation it is as low as 7 5 km s beneath the land area while that beneath the japan sea and the pacific ocean is 8 0 8 2 km s it changes abruptly at the transition zones which are located along the coastlines precise structure and location of the subducted pacific plate beneath the land area is inferred from converted or reflected seismic waves at the top or bottom of the plate the pacific plate is composed of a thin 5 km low velocity upper layer and a thick high velocity lower layer its total thickness being 80 90 km the upper plane seismicity of the double seismic zone is confined to the thin low velocity upper layer which probably corresponds to the subducted former oceanic crust the lower plane seismicity lies at the middle of the high velocity lower layer and the lower half of the plate below it is incapable of generating earthquakes the shallower portion of the upper surface of the plate beneath the pacific ocean along which major seismicity with low angle thrust faultings is actually occurring is also located by seismic observations on land and in the sea the pacific plate subducts at an extremely low angle of 5 for the first 25 km depth and then the dip steepens rather abruptly to 30 normal fault type events at the top of the plate have not been detected in the portion where the downward bending is the largest but have been ditected near the trench axis where it is rather small tomographic inversions for seismic velocity structure clearly delineate the inclined high velocity pacific plate with a thickness of 80 90 km and low velocity zones in the crust and the mantle wedge beneath active volcanoes seismic attenuation tomography also shows similar zones of low q value beneath active volcanoes although its spatial resolution is much lower the low velocity zones with 2 6 velocity lows are continuously distributed from the upper crust just beneath active volcanoes to a depth of 100 150 km in the mantle wedge and are approximately parallel to the dip of the underlying pacific plate these low velocity zones probably reflect the pathway of magma ascent from a depth in the mantle wedge to the earth s surface corresponding to a portion of the subduction induced secondary mantle wedge flow

seismic wave conversion near the upper boundary of the pacific plate beneath the kanto district japan summary a detailed structure of the pacific plate beneath the kanto district japan was studied by the use of conspicuous sp converted waves that are generated near the upper boundary of the pacific plate these sp waves are observed for earthquakes occurring in the lower plane of the double seismic zone of the subducted pacific plate the location of the conversion interface is estimated by inverting the observed tsp p times 293 seismic traces recorded at 42 stations for 49 earthquakes are used for analysis the conversion interface is located above the upper seismic plane of the double seismic zone and is equivalent to the upper boundary of the pacific plate within the estimated uncertainty in general the conversion interface coincides well with the zone of low angle thrust fault type earthquakes in the entire area studied comparison with the result of 3 d tomographic inversion reveals that the conversion interface is probably located in the low velocity layer on the top of the pacific plate which is interpreted as the oceanic crust of the pacific plate

light stable isotope systematics of large scale hydrologic regimes in california and nevada surface waters shallow groundwaters and precipitation samples were collected along three traverses which begin at the california coast and are oriented in an east west manner roughly parallel to the atmospheric flow path of meteoric water the hydrogen isotope compositions from short term precipitation records varied as much as 40 at one location and were not representative of the average annual isotopic composition of precipitation the hydrogen isotope ratios of surface waters and shallow groundwaters distinguish segments with isotopic variations that correlate with measured vertical fluxes of meteoric water one coastal segment appears to closely approximate an open system in which precipitation dominates over evapotranspiration most segments are described by rather regular variations in d 3 45 per 100 km which represent different degrees of closure of the hydrologic system caused by variable partitioning of precipitation between runoff and evapotranspiration all partially closed systems imply terrestrial recycling of water a simple model estimates this amount to be about 20 across northern and central california three segments representing the great basin show virtually no geographic variation and appear to represent isotopically closed systems

influence of matrix diffusion and exchange reactions on radiocarbon ages in fissured carbonate aquifers the parallel fissure model coupled with the equation of diffusion into the matrix and with exchange reaction equations has been used to derive a simple formula for estimating the influence of matrix porosity and reaction parameters on the determination of radiocarbon ages in fissured carbonate rocks examples of evidently too great radiocarbon ages in carbonate formations which are not explainable by models for the initial sup 14 c corrections can easily be explained by this formula parameters obtained for a chalk formation from a known multitracer experiment combined with a pumping test suggest a possibility of sup 14 c ages more than three orders of magnitude greater than the ages which would be observed if the radiocarbon transport took place only in the mobile water in the fissures it is shown that contrary to the solute movement on a small scale and with a variable input the large scale movement characteristic for the sup 14 c dating does not necessarily require the knowledge of kinetic parameters because they may be replaced by the distribution coefficient discordant tritium and sup 14 c concentrations are commonly interpreted as a proof of mixing either in the aquifer or at the discharge site for fissured carbonate formations however anmore alternative explanation is given by the derived model showing a considerable delay of sup 14 c with respect to nonsorbable tracers less

isotopic imaging of surface water groundwater interactions sacramento valley california groundwater isotope data across the sacramento valley california establish two types of groundwater mining 1 overdraft of ancient groundwater with limited recharge by surface waters producing cones of depression 2 ancient groundwater withdrawal followed by rapid recharge of irrigation water reducing groundwater quality the first type occurs in the sacramento metropolitan area where meteoric runoff is unnaturally high and 40 years of pumping have depressed water levels to 25 m below sea level inducing recharge from losing reaches of the sacramento and american rivers lateral migration rates are quantified by the binary mixing between river water 18o 10 8 and natural groundwater 18o 7 0 the second type of mining occurs in agricultural regions to the west where 14c ages indicate that irrigation waters constitute more than 80 of modern recharge this recharge has several characteristics of evaporated irrigation water including 1 high 18o values to 6 0 that define closed contour patterns 2 elevated no3 concentrations to 100 ppm 3 low 14c ages of less than 500 years stable isotope contours augmented by 14c data provide dynamic recharge patterns in this profoundly disturbed giant alluvial aquifer on a large scale 100 km2 the lateral permeabilities of alluvial aquifers are essentially isotropic whereas on a smaller scale 25 km2 anisotropy is evident and isotope values can be geographically complex and seasonally transient groundwater flow patterns implied by the isotope data can differ substantially from steady state models based on head measurements

regional extent of the s wave reflector beneath the kanto district japan an s wave reflector was found near the upper plane of the double seismic zone associated with the subducting pacific plate beneath the southern kanto district of japan here the areal extent of the reflector is confirmed for a region ranging from 34 5 n to 36 7 n from the analysis of the travel times of the reflected s waves on 8 hz band seismograms a bend of the reflector is found at about 36 n it is coincident with the bend of the upper boundary of the subducting pacific plate obtained from the seismicity analysis in the middle of the kanto district the reflector extends to a depth of 120 km whereas in the northern kanto district it extends just beneath the volcanic front the reflector could not be verified for depths shallower than 60 km depth because the reflected s wave cannot be identified at the eastern most stations of the network

study of seismogram envelopes based on scattering by random inhomogeneities in the lithosphere a review abstract instead of the precise examination of individual phases in seismograms we will focus on the relation between random inhomogeneities in the lithosphere and the systematic change in seismogram envelopes recent developments in the study of high frequency seismogram envelopes are briefly reviewed the smooth amplitude decay of coda envelopes of local earthquakes first attracted seismologists interest in scattering and was investigated based on the single scattering assumption with a uniform distribution of point like scatterers subsequently the importance of multiple scattering was recognized and theoretical models were introduced as a bridge between conventional seismology and the scattering approach a hybrid model in which a large impedance contrast plane was embedded in a scattering medium was proposed for the interpretation of a reflected s phase in the coda for shallow events around a volcanic front in japan next three component seismogram envelopes of a small local earthquake were synthesized using the born approximation in inhomogeneous media the s coda is excited in all directions from the hypocenter the p coda appears even in the nodal direction of the p wave radiation mostly owing to sp scattering near the hypocenter both pseudo p and s phases appear even on the null axis these synthetic seismogram envelopes are in harmony with characteristics of observed seismogram envelopes of local earthquakes scattering due to random inhomogeneities quantitatively explains the frequency dependence of s wave attenuation from the analysis of seismogram envelopes around direct s waves of earthquakes with intermediate hypocentral distances it was recently found that the time lag of the maximum amplitude arrival from the s wave onset increased and the envelope broadened with travel distance diffraction due to slowly varying velocity inhomogeneities is modeled using the parabolic approximation and is used to explain the envelope around the s wave arrival observed at intermediate distances a nonlinear inversion of the full seismogram envelope is used for the evaluation of randomness thus the analysis of seismogram envelopes offers us useful information on the randomly inhomogeneous structure of the lithosphere complementary to the array observation analysis of individual phases

vertical distribution of as iii and as v in a coastal sandy aquifer factors controlling the concentration and speciation of arsenic in the stuarts point groundwater system northern new south wales australia arsenic species were measured in a bundled piezometer installed in the holocene barrier of the stuarts point coastal sands aquifer northern new south wales australia vertical distribution shows two peaks of elevated as concentration at a depth of 10 11 m concentrations of as tot as v and as iii are in the range of 52 85 38 67 and 14 18 mg l respectively and the ratio of as v as iii is well above 1 at 3 7 2 7 the second peak at a depth of 25 m shows the highest concentrations of as tot as v and as iii with values reaching 337 125 and 212 mg l respectively the as v as iii ratio is below 1 at 0 6 0 7 high as tot and as v concentrations at shallower depths are associated with acidic conditions and very low concentrations of all ions desorption of as from al hydroxides and as enriched feoxyhydroxides are plausible mechanisms releasing as into the groundwater system the elevated concentration of as tot and as iii at 25 m is potentially related to the leaching of the clay surfaces elevated hco3 and alkaline ph conditions at this depth cause desorption of as which is later present as as iii species in the reducing environment the high concentrations of hco3 further reduce the possible extent of as sorption on fe and mn oxyhydroxides the identification of as in a groundwater system associated with the coastal barrier sand dune environment raises serious questions of the suitability of human consumption of untreated groundwater drawn from these aquifer types further investigation both in australia and globally are needed to classified the extent of this hydrogeochemical occurrence near coastal communities that rely on groundwater 2003 elsevier science ltd all rights reserved

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

contamination of groundwater under cultivated fields in an arid environment central arava valley israel the purpose of this study is to obtain a better understanding of groundwater contamination processes in an arid environment precipitation of 50 mm year due to cultivation additional aims were to study the fate of n k and other ions along the whole hydrological system including the soil and vadose zone and to compare groundwater in its natural state with contaminated groundwater through the drilling of several wells a combination of physical chemical and isotopic analyses was used to describe the hydrogeological system and the recharge trends of water and salts to the aquifers the results indicate that intensive irrigation and fertilization substantially affected the quantity and quality of groundwater recharge low irrigation efficiency of about 50 contributes approximately 3 5 4 million m 3 year to the hydrological system which corresponds to 0 65 m per year of recharge in the irrigated area by far the

three dimensional fine velocity structure and hypocentral distribution of earthquakes beneath the kanto tokai district japan we determine the three dimensional p wave velocity structure beneath the kanto tokai district central japan and simultaneously relocated by inverting travel time data for 91 events that were observed at 61 stations operated by the national research center for disaster prevention the variance of the travel time data is reduced by 75 as compared to the variance for the routinely used laterally homogeneous model in general our velocity model is consistent with tectonic models of the kanto tokai district our velocity model is also in good agreement with seismic explosion data and bouguer gravity anomalies the uppermost layer from 0 to 16 km depth is characterized by lateral velocity differences of more than 20 we find low velocity zones beneath tokyo bay the middle of the boso peninsula and omae zaki where there are thick sedimentary layers a marked 30 km thick high velocity zone extends to the northeast and the west of the izu peninsula this zone dips gradually from the surface to a depth of 70 km in the eastern region and to a depth of 40 km in the western region and is interpreted as the philippine sea phs plate which is being subducted at the sagami and the suruga troughs the data unquestionably require a high velocity zone beneath mount tsukuba that cannot be explained in terms of present tectonic models we use our three dimensional velocity model to relocate about 23 000 earthquakes that took place from 1983 through 1985 the accuracy of the hypocentral parameters improved considerably as a result the double seismic zone within the subducting pacific plate is more clearly delineated than in previous studies the inclined seismic zone for the subducting phs plate coincides fairly well with the high velocity zone of our three dimensional velocity model

seismic detection of the untransformed basaltic oceanic crust subducting into the mantle summary subcrustal earthquakes occur in a slab like zone beneath sw japan in association with the subduction of the philippine sea plate they generate a distinct pair of p and s later phases with anomalously low apparent velocities of about 7 and 4 km s 1 which cannot be explained by a laterally homogeneous velocity structure these later phases are observed for particular source receiver geometries the sources at depths shallower than 50 60 km and the receivers beneath which the subcrustal seismic zone comes in contact with the bottom of the continental crust we examined the nature of these later phases using two methods one is to determine two types of apparent velocities an event common apparent velocity and a station common apparent velocity which may be different from one another for a laterally inhomogeneous velocity structure the other is to trace seismic rays numerically for a laterally heterogeneous velocity model an extensive analysis using these two methods leads to a conclusion that the slab like seismic zone constitutes a low velocity channel in the uppermost mantle with p and s velocities comparable to those of the lower continental crust beneath sw japan the waves trapped within the low velocity channel escape from it through its contact with the continental moho and are observed as a distinct pair of later phases the head waves guided by the bottom boundary of the low velocity channel are observed as weak arrivals of initial phases the thickness 10 km and the velocities vp 7 km s 1 vs 4 km s 1 of the subcrustal seismic zone indicates that it is made up of the untransformed basaltic oceanic crust subducted with the underlying lithospheric mantle and that the transformation of basalt to eclogite does not take place in the subducting slab at least down to depths of 50 60 km we present laterally heterogeneous structural models of the crust and the uppermost mantle along two profiles in sw japan the models are characterized by an apparent thickening of the lower continental crust in particular regions due to a direct contact of the subducting oceanic crust to the continental moho such features are qualitatively consistent with the results of explosion seismology and with the bouguer anomaly pattern in the relevant regions the oceanic lithosphere with the untransformed light oceanic crust at its top might still be buoyant after subduction a factor which must be taken into account in considering the driving mechanisms of plate tectonics the slab geometry and the earthquake related tectonic process

low velocity oceanic crust at the top of the philippine sea and pacific plates beneath the kanto region central japan imaged by seismic tomography 1 we construct fine scale three dimensional p and s wave velocity structures beneath the kanto region central japan by seismic tomography with a spatial correlation of velocities the philippine sea and pacific plates subduct beneath the eurasian plate in this area and are imaged with high velocities oceanic crust at the uppermost part of these subducting plates is a low velocity layer low velocity oceanic crust of the philippine sea plate subducts to a depth of approximately 80 km there are also two low velocity bodies with relatively high v p v s ratios of 1 80 1 90 in the mantle wedge above the oceanic crust of the philippine sea plate we speculate that the westernmost of these two low velocity bodies consists of 20 partially serpentinized peridotite continuous with gabbro in the oceanic crust of the uppermost philippine sea plate while the eastern body is composed of 30 partially serpentinized peridotite we trace the subducting oceanic crust of the pacific plate to a depth of 120 km the estimated v p v s ratio of this layer is 1 85 1 90 which indicates a low probability of molten rock the gabbroic oceanic crust may have been metamorphosed to garnet granulite

radiocarbon dating of groundwater of the aquifer confined in the lower triassic sandstones of the lorraine region france abstract blavoux b and olive ph 1981 radiocarbon dating of groundwater of the aquifer confined in the lower triassic sandstones of the lorraine region france in w back and r letolle guest editors symposium on geochemistry of groundwater 26th international geological congress j hydrol 54 167ndash 183 stable isotope and groundwater chemistry analyses on samples from about 40 boreholes in the lorraine region eastern france are used to evaluate the paleohydrological regime of the lower triassic sandstone aquifer in the study of the mechanisms of the general water dynamics of the aquifer at present in this sandstone aquifer the estimation of the 14 c activity a 14 in the total dissolved carbon tdc to 100 of modern carbon is justified by the absence of carbonates in the reservoir and by the 13 c contents in the tdc a significant relation could be determined between the 14 c activity in the tdc and 13 c a 14 7 7 13 59 6 this gradual enrichment of the tdc with 13 c results from the escape of the dissolved co 2 the meaning of the radiometric age is discussed as a function of piston and exponential type flows the study of the stable isotopes 18 o and 2 h revealed two water families the most recent waters have 18 o values higher by 1 0 than the more than 10 4 yr old waters this 1 0 discontinuity corresponds to the improvement of weather conditions during the holocene which amounts to 2 5 c the isochrons of the aquifer reveal the existence of hydrogeological sections bounded by faults where the rates of circulation are different

a 40 year record of carbon 14 and tritium in the christchurch groundwater system new zealand dating of young samples with carbon 14 summary knowledge of the sources and flowpaths of water in the christchurch groundwater system will be vital to future management of the system to gain such knowledge oxygen 18 18 o tritium 3 h carbon 14 14 c and chemical concentrations have been measured on deep and shallow groundwaters since 1970 18 o measurements show that seepage from the waimakariri river is the dominant source of the groundwater early 3 h measurements in the 1970s showed non zero concentrations in the deep groundwaters but these were discounted at the time as due to at most a few percent of very young water however reinterpretation in light of the 14 c ages in this work has revealed much younger ages for the deep waters than was previously believed with average ages of 38 years in 1971 71 years in 1976 98 years in 1985 greater than 120 years in 1986 and greater than 150 years in 1993 1994 because the waimakariri river was identified as the major source of the deep groundwater the river s 14 c concentration between 1986 and 2006 was modelled by combining the records of its two carbon sources biogenic carbon and atmospheric co 2 this allowed the initial 14 c concentrations of the groundwaters to be unequivocally determined and their mean 14 c ages estimated using the same flow model as was applied to the 3 h measurements the resulting mean 14 c ages are in the range 5 1500 years the long sequence of measurements reveals that the mean ages of the deep christchurch groundwater have changed markedly during the study the pre exploitation rate of turnover of water in the system is not known but was probably quite slow by the 1970s ages in the deep system aquifers 4 and 5 had become relatively young right across christchurch with mean ages of 60 70 years indicating mainly lateral inflow of young waimakariri river water because of groundwater abstraction mean ages measured since have gradually increased showing increasing upflow of much older water from depth this water has 10 15 rainfall recharge and is sourced from the inland plains region there is now in 2006 a steep gradient in age from west to east across christchurch from 300 years to 1400 years showing that a large body of much older deeper water is stored on the seaward side of the system where the deep aquifers are blind this body will yield good quality water for many years but eventually it is likely to be replaced or bypassed by younger a few hundred years old waimakariri river dominated but surface recharge bearing water from inland

chemical and isotopic signature of old groundwater and magmatic solutes in a costa rican rain forest evidence from carbon helium and chlorine 1 c he and cl concentrations and isotopes in groundwater and surface water in a lowland costa rican rain forest are consistent with the mixing of two distinct groundwaters 1 high solute bedrock groundwater representing interbasin groundwater flow igf into the rain forest and 2 low solute local groundwater recharged in the lowlands in bedrock groundwater high 13c 4 89 low 14c 7 98 pm high r ra for he 6 88 and low 36cl cl 17 10 15 suggest that elevated tracer concentrations are derived from magmatic outgassing and or weathering of volcanic rock beneath nearby volcan barva in local groundwater the magmatic signature is absent and data suggest atmospheric sources for he and cl and a biogenic soil gas co2 source for dissolved inorganic carbon dating of 14c suggests that the age of bedrock groundwater is 2400 4000 years most likely at the lower end of the range local groundwater has 14c 100 pm indicating the presence of bomb carbon and thus ages less than 55 years overall data are consistent with a conceptual hydrologic model originally proposed on the basis of water budget and major ion data 1 large variation in solute concentrations can be explained by mixing of the two distinct groundwaters 2 bedrock groundwater is much older than local groundwater 3 elevated solute concentrations in bedrock groundwater are derived from volcanic fluids and or rock and 4 local groundwater has not interacted with volcanic rock tracers with different capabilities converge on the same hydrologic interpretation also transport of magmatic co2 into the lowland rain forest via igf seems to be significant relative to other large ecosystem level carbon fluxes

catastrophic and dangerous inflows to salt mines in poland as related to the origin of water determined by isotope methods tritium 14c 13c 18o and d measurements indicated as early as 1973 the existence of inflows of modern meteoric water to the wapno salt mine in a zechstein diapir in spite of these early warnings the continuation of improper exploitation led in 1977 to sudden flooding of the mine followed by catastrophic land subsidence the lesson learned from that catastrophe as well as the results of isotope investigations performed in the inowroclaw salt mine led to the decision to flood the mine artificially in order to avoid a similar land subsidence the klodawa mine was not regarded to be in danger of flooding due to a thick clay cap in fact a large number of usually short lasting water occurrences had the isotopic composition characteristic for evaporated ocean water however since 1956 an inflow has existed with 18o and d values close to that of pre quaternary saline waters and brines in the mesozoic formations adjacent to the diapir two other inflows have recently occurred with the initial 18o and d values of modern waters as a consequence the mine is regarded to be in danger and the exploitation of salt in the areas of inflows has been stopped the wieliczka mine southern poland exploits miocene salts overthrusted together with the carpathian flysch from the south the most dangerous and catastrophic inflows were caused by human errors isotope data show the water to be of glacial or holocene age stored in tertiary slightly cemented rocks of low permeability which neighbor the mine from the north owing to specific geology the mine has survived for a long time in spite of relatively large and long lasting inflows however its existence is in permanent danger

using hydrogeochemistry to understand inter aquifer mixing in the on shore part of the gippsland basin southeast australia groundwater in the latrobe valley in the gippsland basin of southeast australia is important for domestic agricultural and industrial uses this sedimentary basin contains a number of aquifers that are used for water supply dewatered for open pit coal mining and which are potentially influenced by off shore oil and gas production major ion chemistry together with stable and sr isotope data imply that the main hydrogeochemical processes are evapotranspiration with minor silicate and carbonate weathering methanogenesis and so4 reduction in reduced groundwater associated with coal deposits have also occurred groundwater has estimated 14c ages of up to 36ka and is largely 3h free carbon 14 ages are irregularly distributed and poorly correlated with depth and distance from the basin margins the observations that the geochemistry of groundwater in aquifers with different mineralogies are similar and the distribution of 14c ages is irregular implies that the aquifers are hydraulically connected and horizontal as well as vertical inter aquifer mixing occurs the connection of shallow and deeper aquifers poses a risk for the groundwater resources in gippsland as contaminants can migrate across aquifers and dewatering of shallow units may impact deeper parts of the groundwater system

radiocarbon in dissolved organic carbon a possible groundwater dating method case studies from western canada this paper explores the feasibility of using 14c in dissolved organic carbon doc as an alternative isotopic ground water dating method two hydrogeologically contrasting groundwater systems were tested the cretaceous age milk river aquifer and low permeability organic rich wisconsinan age prairie tills in southern alberta canada comparisons of radiocarbon data were made between doc fractions dissolved inorganic carbon dic and several dic geochemical age correction models along well defined flow paths the data presented demonstrate that 14c dating of doc fractions can indeed provide an alternative method for determining isotopic groundwater ages under suitable conditions however detailed information may be required regarding 1 the geologic nature of the aquifer and its flow system 2 the isotopically conservative behavior of doc 3 the initial 14c activity of doc in recharge and 4 the effect of bacterial redox processes on the 14c activity of doc in the milk river aquifer doc 14c ages were successfully used to estimate groundwater residence times as well as to further refine input parameter assumptions for the dic method in the prairie tills doc 14c ages were used to establish a maximum age for the pore waters in an environment where the dic method is especially problematic

d 18o enriched waters of the coast range mountains northern california connate and ore forming fluids abstract d and 18o enriched waters of several weight percent salinity issue from hot and cold springs in franciscan complex and great valley sequence rocks in the northern coast range mountains of california although these waters have been described separately in the past and called metamorphic connate and serpentinizing fluids this study shows that the hot and cold springs are all fed by one source of water trapped cretaceous seawater modified by a variety of reactions the district is an example of the complexities of subsurface waters and their importance for our understanding of metamorphic fluid sources oil field waters and ore transport problems the subsurface waters have a range of 34s values including some near marine sulfate values 20 and 13c near marine calcite values 0 strontium isotopic signatures in the spring waters are derived from the great valley sequence 87 sr 86 sr values near 0 705 the most saline spring pool is lined with serpentine phases found together as a fine white precipitate and has a ph of 11 one portion of the subsurface water is heated and reduced it transports au ag sb as and hg to the surface gold grades of the hot spring precipitates range from less than 1 ppm to over 10 ppm these heated waters are chemically and isotopically similar to the fluids which formed au mineralization at the nearby mclaughlin gold mine the hot springs precipitate pyrite and native sulfur and are supersaturated with respect to calcite other springs are less saline and are oxidized cooler and diluted versions of the hot spring fluid they do not carry ore metals but they are supersaturated with respect to silica and calcite 3 he 4 he ratios of the springs gases are all above atmospheric values and indicate a possible magmatic component consistent with the presence of quaternary clear lake volcanics 129i data yield a minimum age of 60 80 ma for the source of the iodide in the waters consistent with the connate nature of the source fluid fehn et al 1992

500 000 year stable carbon isotopic record from devils hole nevada the record of carbon 13 delta 13 c variations in dh 11 vein calcite core from devils hole nevada shows four prominent minima near glacial terminations glacial interglacial transitions v to ii the delta 13 c time series is inversely correlated with the dh 11 oxygen isotope ratio time series and leads it by as much as 7000 years the delta 13 c variations likely record fluctuations in the delta 13 c of dissolved inorganic carbon of water recharging the aquifer how such variations are transported 80 kilometers to devils hole without obliteration by water rock reaction remains an enigma the record may reflect i global variations in the delta 13 c of atmospheric co 2 and hence the delta 13 c of continental biomass or ii variations in extent and density of vegetation in the southern great basin in the latter case delta 13 c minima at 414 334 246 and 133 thousand years ago mark times of maximum vegetation

geochemistry of tectonically expelled fluids from the northern coast ranges rumsey hills california usa tectonic compression has created abnormally high pressure on deep basinal fluids causing their expulsion from areally exposed upper cretaceous rock along the eastern margin of the california coast ranges the fluids emerge as near neutral perennial sodium chloride springs at high elevations with flow rates as high as 10 l per min higher spring discharges are more common around the exposure of a west vergent fault propagation fold axis spring waters range from 1000 to 27 000 mg l tds the least saline water 18o 7 5 closely represents local meteoric water that mixes with saline fluid 18o 5 3 and forms a slope of 3 5 on a d vs 18o plot a na 125 to 8000 mg l vs cl 150 to 17 000 mg l plot shows a linear dilution trend that extends close to but below the values for modern seawater calcium 75 3000 mg l is considerably enriched relative to seawater and forms a nonlinear trend with chloride in detail the na deficit defined by the difference between the measured na content and the na concentration on a hypothetical seawater dilution line is approximately balanced by the ca excess similarly defined by the seawater dilution line this relationship strongly suggests that the fluid is diluted seawater that is being modified by active albitization of plagioclase at different depths simultaneous b and 18o enrichment of the fluids accompanied by deuterium depletion further suggest that the seawater modification is influenced by clay diagenesis bicarbonate and sio2 concentrations show an inverse correlation with cl with most waters being saturated or slightly oversaturated with calcite and quartz at the discharge temperatures some freshwater springs with near meteoric stable isotope values may represent mixing of young groundwater from perched aquifers but in many cases the freshwater springs emerge along the same structures and have the same perennial nature as the saline fluids and expulsion of an older fresh groundwater component that is under abnormal fluid pressures cannot be ruled out basinal fluids elsewhere commonly show dilution trends with local meteoric water and in the case of the rumsey hills some of the dilute saline waters may indicate deep penetration of meteoric water 1 km in the pleistocene before the latest tectonic uplift geothermometry of the spring waters maximum 90 c suggest an origin from as deep as 4 0 km this depth is consistent with the depth of the core of a fault propagation anticline below the surface of the rumsey hills developed by active internal deformation of an east tapering wedge beneath the southwestern sacramento valley active tectonic compression causes near lithostatic fluid pressures in the shallow subsurface below the rumsey hills and volume strain within the core of the anticline that results in upward expulsion of the saline fluids from the indicated depths

sweden s first forest hydrology field study 1905 1926 contemporary relevance of inherited conclusions and data from the rokliden hillslope during the last decades of the 19th century a great worry arose about forest landscape paludification in northern sweden this was the original impetus for forest hydrological research in sweden and the swedish institute of experimental forestry established the first field research site in 1905 at rokliden close to pitea in north sweden it comprised 8 64 ha located 2 km down a 3 km long gently sloping 4 north facing norway spruce covered till slope interspersed with small mires by 1931 it was concluded that paludification was not spreading across northern sweden at an appreciable rate within the rokliden research site 22 groundwater wells were installed and levels measured weekly until 1926 a map with 0 5 m equidistance ten vegetation classes and soil profiles was established groundwater flow velocity was estimated by tracing added sodium chloride hydraulic conductivity was measured on undisturbed soil cores while mechanical and chemical analyses were carried out on other samples groundwater was collected and analysed for dissolved compounds including oxygen hydrology was found important for soil types and vegetation development the necessary profile drainage for podzol soil development was identified as vein drainage at the bedrock surface modern measurements in the re established groundwater observation network and re analysis of old data confirmed the plausibility of these original conclusions partial catchment area could explain rates of both groundwater level rise and recession revisiting this field study reveals that many issues in contemporary hillslope hydrology were already established a century ago even though the provenance of that knowledge is not generally recognized copyright 2014 john wiley sons ltd

conceptualizing lateral preferential flow and flow networks and simulating the effects on gauged and ungauged hillslopes 1 one of the greatest challenges in the field of hillslope hydrology is conceptualizing and parameterizing the effects of lateral preferential flow our current physically based and conceptual models often ignore such behavior however for addressing issues of land use change water quality and other predictions where flow amount and components of flow are imperative dominant runoff processes like preferential subsurface flow need to be accounted for in the model structure this paper provides a new approach to formalize the qualitative yet complex explanation of preferential flow into a numerical model structure we base our examples on field studies of the well studied maimai watershed new zealand we then use the model as a learning tool for improved clarity into the old water paradox and reasons for the seemingly contradictory findings of lateral preferential flow of old water where applied line sources of tracer appear very quickly in the stream following application we evaluate the model with multiple criteria including ability to capture flow hydrograph composition and tracer breakthrough we generate output ensembles with different pipe network geometries for model calibration and validation analysis surprisingly the range of runoff response among the ensembles is narrow indicating insensitivity to specific pipe placement our new model structure shows that high transport velocities for artificial line source tracers can be reconciled with the dominance of preevent water during runoff events even when lateral pipe flow dominates response the work suggests overall that preferential flow can be parameterized within a process based model structure via the structured dialog between experimentalist and modeler

sulfur isotopic study of sulfate in the aquifer of costa de hermosillo sonora mexico in relation to upward intrusion of saline groundwater irrigation pumping and land cultivation abstract groundwater from the costa de hermosillo aquifer has been used extensively for irrigation over the past 60 a in the sonora region of northwestern mexico resulting in salinization of fresh groundwater resources salinization of groundwater is most pronounced on the western coastal side of the aquifer with an aerial extent of 26 7 km2 where maximum values are reported for conductivity 31 ms cm and cl concentrations 16 271 mg l salinization is likely to increase if groundwater pumping continues at levels comparable to the present time upward incursion of marine water into the aquifer is inferred from 2h 7 2 and 18o 1 6 compositions of groundwater samples with the highest conductivity compared to modern seawater in the gulf of california ratios of so4 cl and cl br are small 0 01 and 33 respectively and the s isotopic composition of so 4 2 is high 32 7 in the most saline portions of the costa de hermosillo this saline groundwater is inferred to result from an earlier phase of dissimilatory bacterial so 4 2 reduction coupled to decomposition of organic matter in marine blue clays deposited during the miocene pliocene transgression the isotopic composition of present day surface discharge from agricultural fields is substantially enriched in 32s due to widespread application of nh4 2so4 fertilizers and potential mobilization of s from mineral resources surface water discharging from irrigated fields has 34s values ranging from 2 1 to 3 3 which are distinctly different from groundwater and surface water in adjacent non agricultural areas with 34s values ranging from 5 2 to 13 5 prolonged irrigation pumping that promotes the incursion of air to the subsurface could enhance the weathering of s bearing minerals such as magmatic sulfides producing 32s enriched so 4 2

a graphical method to evaluate predominant geochemical processes occurring in groundwater systems for radiocarbon dating a graphical method is described for identifying geochemical reactions needed in the interpretation of radiocarbon age in groundwater systems graphs are constructed by plotting the measured 14c 13c and concentration of dissolved inorganic carbon and are interpreted according to specific criteria to recognize water samples that are consistent with a wide range of processes including geochemical reactions carbon isotopic exchange 14c decay and mixing of waters the graphs are used to provide a qualitative estimate of radiocarbon age to deduce the hydrochemical complexity of a groundwater system and to compare samples from different groundwater systems graphs of chemical and isotopic data from a series of previously published groundwater studies are used to demonstrate the utility of the approach ultimately the information derived from the graphs is used to improve geochemical models for adjustment of radiocarbon ages in groundwater systems

using groundwater geochemistry and environmental isotopes to assess the correction of 14c ages in a silicate dominated aquifer system summary the use of 14c to constrain groundwater residence times requires careful correction of 14c activities a14c and an assessment of the degree of inter aquifer mixing in groundwater of the campaspe valley in the southern murray basin australia 13c values of dissolved inorganic carbon dic range from 18 to 2 using these 13c values to correct 14c ages assuming that dissolution of or exchange with matrix calcite had occurred implies that locally 90 of the dic is derived from carbonates in turn this suggests that low salinity groundwater in the deeper confined calivil renmark formation up to 50 60 km from the basin margins in the campaspe valley has a component of modern recharge which would require that widespread leakage from the overlying shepparton formation had occurred however 87sr 86sr ratios and major ion geochemistry of groundwater imply that negligible inter aquifer mixing has occurred and that calcite dissolution is a very minor process the variable 13c values are most probably due to methanogenesis via reduction of co2 in the groundwater that results in the residual dic being enriched in 13c as methanogenesis by this mechanism has only a minor impact on a14c uncorrected 14c ages are a better estimate of groundwater residence times groundwater in the north of the campaspe valley has a residence time of 9 13 ka which agrees with ages calculated from head gradients and hydraulic conductivities calivil renmark groundwater from the adjacent pyramid hill region in an area where the aquifers contain lower hydraulic conductivity sediments is substantially older up to 20 25 ka the age of groundwater from the shepparton formation increases irregularly with depth with ages of in excess of 25 ka recorded at its base this study illustrates the need to fully understand hydrogeological processes in order to correct 14c ages especially in silicate dominated aquifers where dissolution of carbonates may not be the major process controlling 13c values

age distribution estimation for karst groundwater issues of parameterization and complexity in inverse modeling by convolution summary convolution modeling is useful for investigating the temporal distribution of groundwater age based on environmental tracers the framework of a quasi transient convolution model that is applicable to twodomain flow in karst aquifers is presented the model was designed to provide an acceptable level of statistical confidence in parameter estimates when only chlorofluorocarbon cfc and tritium 3 h data are available we show how inverse modeling and uncertainty assessment can be used to constrain model parameterization to a level warranted by available data while allowing major aspects of the flow system to be examined as an example the model was applied to water from a pumped well open to the madison aquifer in central usa with input functions of cfc 11 cfc 12 cfc 113 and 3 h and was calibrated to several samples collected during a 16 year period a bimodal age distribution was modeled to represent quick and slow flow less than 50 years old the effects of pumping and hydraulic head on the relative volumetric fractions of these domains were found to be influential factors for transient flow quick flow and slow flow were estimated to be distributed mainly within the age ranges of 0 2 and 26 41 years respectively the fraction of long term flow 50 years was estimated but was not dateable the different tracers had different degrees of influence on parameter estimation and uncertainty assessments where

reconstructing the oxygen isotope composition of late cambrian and cretaceous hydrothermal vent fluid oxygen isotope analyses 18o of 16 quartz epidote pairs from late cambrian betts cove and mings bight newfoundland ordovician thetford mines quebec canada and cretaceous troodos cyprus ophiolites are used to calculate the 18o of the hydrothermal fluids from which they crystallized we combine these with 3 quartz fluid inclusion measurements and 3 quartz magnetite measurements from the cambrian ophiolites to explore how the range in the 18o of submarine hydrothermal vent fluid has varied between the late cambrian cretaceous and today the range of calculated 18o values of vent fluid 4 to 7 4 is larger than that of modern seafloor hydrothermal vent fluid 0 to 4 we employ two numerical models to ascertain whether this range is most consistent with changes in paleo seawater 18o or with changes in the reactive flow path in ancient hydrothermal systems a static calculation of the vent fluid oxygen isotope composition as a function of the water rock ratio suggests that in an ocean with a lower 18o than today the range of vent fluid 18o should be larger our data however show little evidence that the 18o of the ocean was much lower than the global ice free value of 1 2 a dual porosity model for reactive flow through fractured and porous media is used to model the relative evolution of the 87sr 86sr and 18o of vent fluid in contact with rock our 87sr 86sr and 18o for cretaceous epidotes suggest the strontium concentration of the cretaceous oceans may have been much higher than at present the 87sr 86sr and 18o data from cambrian epidotes are strikingly different from the younger samples and are difficult to model unless fluid rock interaction in the cambrian hydrothermal systems was substantially different it is also possible that some of the quartz epidote veins have been reset by obduction related metamorphism our data suggest that the high calcium to sulfate ratio in early and cretaceous seawater may have affected the degree of strontium isotope exchange causing hydrothermal fluids to have 87sr 86sr closer to that of seawater than in modern systems

a review of single sample based models and other approaches for radiocarbon dating of dissolved inorganic carbon in groundwater abstract numerous methods have been proposed to estimate the pre nuclear detonation 14c content of dissolved inorganic carbon dic recharged to groundwater that has been corrected adjusted for geochemical processes in the absence of radioactive decay 14c0 a quantity that is essential for estimation of radiocarbon age of dic in groundwater the models approaches most commonly used are grouped as follows 1 single sample based models 2 a statistical approach based on the observed curved relationship between 14c and 13c data for the aquifer and 3 the geochemical mass balance approach that constructs adjustment models accounting for all the geochemical reactions known to occur along a groundwater flow path this review discusses first the geochemical processes behind each of the single sample based models followed by discussions of the statistical approach and the geochemical mass balance approach finally the applications advantages and limitations of the three groups of models approaches are discussed the single sample based models constitute the prevailing use of 14c data in hydrogeology and hydrological studies this is in part because the models are applied to an individual water sample to estimate the 14c age therefore the measurement data are easily available these models have been shown to provide realistic radiocarbon ages in many studies however they usually are limited to simple carbonate aquifers and selection of model may have significant effects on 14c0 often resulting in a wide range of estimates of 14c ages of the single sample based models four are recommended for the estimation of 14c0 of dic in groundwater pearson s model ingerson and pearson 1964 pearson and white 1967 han plummer s model han and plummer 2013 the iaea model gonfiantini 1972 salem et al 1980 and oeschger s model geyh 2000 these four models include all processes considered in single sample based models and can be used in different ranges of 13c values in contrast to the single sample based models the extended gonfiantini zuppi model gonfiantini and zuppi 2003 han et al 2014 is a statistical approach this approach can be used to estimate 14c ages when a curved relationship between the 14c and 13c values of the dic data is observed in addition to estimation of groundwater ages the relationship between 14c and 13c data can be used to interpret hydrogeological characteristics of the aquifer e g estimating apparent rates of geochemical reactions and revealing the complexity of the geochemical environment and identify samples that are not affected by the same set of reactions processes as the rest of the dataset the investigated water samples may have a wide range of ages and for waters with very low values of 14c the model based on statistics may give more reliable age estimates than those obtained from single sample based models in the extended gonfiantini zuppi model a representative system wide value of the initial 14c content is derived from the 14c and 13c data of dic and can differ from that used in single sample based models therefore the extended gonfiantini zuppi model usually avoids the effect of modern water components which might retain bomb pulse signatures the geochemical mass balance approach constructs an adjustment model that accounts for all the geochemical reactions known to occur along an aquifer flow path plummer et al 1983 wigley et al 1978 plummer et al 1994 plummer and glynn 2013 and includes in addition to dic dissolved organic carbon doc and methane ch4 if sufficient chemical mineralogical and isotopic data are available the geochemical mass balance method can yield the most accurate estimates of the adjusted radiocarbon age the main limitation of this approach is that complete information is necessary on chemical mineralogical and isotopic data and these data are often limited failure to recognize the limitations and underlying assumptions on which the various models and approaches are based can result in a wide range of estimates of 14c0 and limit the usefulness of radiocarbon as a dating tool for groundwater in each of the three generalized approaches single sample based models statistical approach and geochemical mass balance approach successful application depends on scrutiny of the isotopic 14c and 13c and chemical data to conceptualize the reactions and processes that affect the 14c content of dic in aquifers the recently developed graphical analysis method is shown to aid in determining which approach is most appropriate for the isotopic and chemical data from a groundwater system

tracing water cycle in regulated basin using stable δ18o δ2h isotopes the ebro river basin spain abstract variations in the stable isotope compositions of o and h in a catchment s water balance are mainly caused by natural variations in the isotopic composition of rainfall through mixing with pre existing waters and evaporation stable isotopes were analysed in surface waters along the main course of the ebro river spain in its main tributaries and in some groundwaters as part of a year long monthly survey at the outlet meteoric input data over the basin from five iaea gnip stations surrounding the ebro catchment showed that the mean weighted 18 o 2 h rain input showing enriched values for four stations and a depleted value for the fifth most surface and ground waters collected in the ebro catchment plot close to the global and local meteoric water lines reflecting a meteoric origin and a lack of significant evaporation or oxygen isotope exchanges between water and the rock matrix although the main tributaries show large variations of 18 o and 2 h signatures respectively 5 0 to 9 6 and 38 5 to 63 6 only the guadalope river shows an evaporated signal all tributaries have more depleted 18 o and 2 h values than the mean rainwater 18 o and 2 h signal for the ebro catchment given by local rain monitoring stations the depleted values in the ebro tributaries originate from runoff from the pyrenees whereas normal mediterranean rains yield mostly enriched values the ebro river itself shows 18 o and 2 h values that fall between those of its tributaries and no variation is related to the location along the river course the river water at the outlet amposta display a range of 18 o 2 h values from respectively 7 2 to 8 4 and 47 5 to 53 9 though with a few enriched values there is no link between river discharge and cl content temporal 18 o 2 h variations at the ebro outlet reflect input of enriched water from mediterranean rains and of depleted waters from pyrenean runoff the geochemical signal at the ebro basin outlet was deconvolved through a conceptual scheme of the ebro hydro system highlighting the major role played by dam impoundments not only on water quantity but also on its quality

upper mantle velocity structure estimated from ps converted wave beneath the north eastern japan arc summary the upper boundary of the descending oceanic plate is located by using ps waves converted from p to s at the boundary in the tohoku district the north eastern part of honshu japan the observed ps p time data are well explained by a two layered oceanic plate model composed of a thin low velocity upper layer whose thickness is less than 10 km and a thick high velocity lower layer the upper and lower layers respectively have 6 per cent lower and 6 per cent higher velocity than the overriding mantle the estimated location of the upper boundary is just above the upper seismic plane of the double planed deep seismic zone this result indicates that events in the upper seismic plane at least in the depth range from 60 to 150 km occur within the thin low velocity layer on the surface of the oceanic plate

a study of the interrelation between surface water and groundwater using isotopes and chlorofluorocarbons in sanjiang plain northeast china surface water and groundwater are the main water resources used for drinking and production assess ments of the relationship between surface water and groundwater provide information for water resource man agement in sanjiang plain northeast china the surface water river lake and wetland and groundwater were sampled and analyzed for stable isotopic dd d 18 o composition tritium and chlorofluorocarbons concentra tions the local meteoric water line is dd 7 3d 18 o 6 7 the tritium t and chlorofluorocarbon cfc contents in groundwater were analyzed to determine the groundwater ages most groundwater were modern water with the ages 50 years the groundwaters in mountain area and near rivers were younger than in the central plain the oxygen isotope d 18 o was used to quantify the relationship between surface water and groundwater the songhua heilongjiang and wusuli rivers were gaining rivers but the shallow groundwater recharged from rivers at the confluence area of rivers at the confluence of songhua and heilongjiang rivers 88 of the shallow groundwater recharged from songhua river the combination of stable isotopes tritium and cfcs was an effectively method to study the groundwater ages and interrelation between sur face water and groundwater practically the farmlands near the river and under foot of the mountain could be culti vated but the farmlands in the central plain should be controlled

effective matrix diffusion in kilometer scale transport in fractured crystalline rock concentrations of tritium 3h and dichlorodifluoromethane cfc 12 in water samples taken from glacial drift and fractured crystalline rock over 4 km2 in central new hampshire are interpreted to identify a conceptual model of matrix diffusion and the magnitude of the diffusion coefficient dispersion and mass transfer to and from fractures has affected the 3h concentration to the extent that the peak 3h concentration of the 1960s is no longer distinguishable because of heterogeneity in the bedrock the sparsely distributed chemical data do not warrant a three dimensional transport model instead a one dimensional model of cfc 12 and 3h migration along flow lines in the glacial drift and bedrock is used to place bounds on the processes affecting kilometer scale transport arid model parameters are varied to reproduce the measured relation between 3h and cfc 12 rather than their spatial distributions a model of mass exchange to and from fractures that is dependent on the time varying concentration gradient at fracture surfaces qualitatively reproduces the measured relation between 3h and cfc 12 with an upper bound for the fracture dispersivity approximately equal to 250 m and a lower bound for the effective matrix diffusion coefficient equal to 1 m2 yr 1 the diffusion coefficient at the kilometer scale is at least 3 orders of magnitude greater than laboratory estimates of diffusion in crystalline rock the large diffusion coefficient indicates that diffusion into an immobile fluid phase rock matrix is masked at the kilometer scale by advective mass exchange between fractures with large contrasts in trarismissivity the measured transmissivity of fractures in the study area varies over more than 6 orders of magnitude advective mass exchange from high permeability fractures to low permeability fractures results in short migration distances of a chemical constituent in low permeability fractures over an extended period of time before reentering high permeability fractures viewed at the kilometer scale this process is analogous to the chemical constituent diffusing into and out of an immobile fluid phase

moho depth variation in the central part of northeastern japan estimated from reflected and converted waves abstract we detected reflected p and s waves at the moho in seismograms of shallow crustal earthquakes in the central part of northeastern ne japan p to s and s to p mode converted waves at the moho are also detected in seismograms of intermediate depth earthquakes in the subducted pacific slab the depth distribution of the moho in the central part of ne japan is estimated by using travel time differences between these later phases and the first p and s arrivals we collected travel time data of 496 reflected waves from 67 shallow earthquakes and 200 converted waves from 65 intermediate depth earthquakes the depth to the moho estimated is deep beneath the land and becomes shallower toward the eastern and western coastlines the moho depth is about 34 km in the middle of the land area about 30 km under the coastline of the japan sea and 27 29 km under the coastline of the pacific ocean

carbon 14 study of groundwater in the sedimentary rocks at the tono study site central japan isotopic investigations using 14c of groundwater were carried out to understand the hydraulic conditions in the sedimentary rocks at the tono study site central japan 14c activities of groundwater observed range from 2 to 32 modern carbon pmc measured 14c activities of groundwater are corrected by the isotopic mass balance model based on 14c activities 13c values concentrations of the dissolved inorganic carbon dic and 13c values of non active carbon dissolved into the groundwater from carbonate minerals and organics assuming that the groundwater reservoir is comparable to the piston flow situation the relative 14c ages of groundwaters were calculated from the corrected 14c activity the relative 14c age suggests that the groundwater infiltration from the upper part of the sedimentary rocks to the lower part takes several thousands of years or that the groundwater in the lower part of sedimentary rocks is derived from long distance flow from the surface through the unconformity between the sedimentary rocks and basement granite the flow rate calculated by relative 14c ages shows similar values to those estimated by computer simulation using hydraulic pressure and conductivity data hydraulic conditions at the tono study site inferred from 14c activity agree with those suggested from hydrogeological analyses isotopic approaches using 14c activity can be applied as geochemical evaluation for interpretations from the hydraulic study

reconstruction of palaeoinfiltration during the holocene using porewater data laxemar sweden abstract the interaction between fracture groundwater and crystalline rock matrix was explored by extracting the porewater residing today in the low permeability saturated rock matrix about 100 m below surface concentrations of the natural tracers cl 18 o 2 h in the porewater along a 11 m long profile from a water conducting fractured deformation zone into the intact rock matrix are the result of superimposed changes in the fracture groundwater composition the tracer profiles have evolved by diffusive exchange of the porewater in the rock matrix with groundwater flowing in fractures of high and low transmissivity since the retreat of the last weichselian glacier from the laxemar investigation area sweden numerical simulations indicate the necessity of a diachronic arrival of surface infiltration signals in the two fractures at the sampling location and of heterogeneous transport properties in the rock matrix as determined for the individual rock samples stringent conclusions regarding the palaeoinfiltration conditions can only be obtained when at least two tracers with independent source terms i e salinity and temperature moisture source are simulated simultaneously quantification of the porewater fracture groundwater interaction allows modification of the different evolutionary stages of the palaeoinfiltration conditions over holocene times most prominently this suggests the absence of any influence of brackish water from the yoldia sea and littornia sea in the area and the requirement for warmer climate precipitation from 8 ka to 4 5 ka bp coinciding with the holocene thermal maximum the ability to interpret the natural tracer profiles in accordance with independent geological hydrological and climatic constraints indicates that matrix diffusion in crystalline rocks is effective over decametres within timescales of 10 14 ka the impact of matrix diffusion on the fracture groundwater composition will become measurable over these timescales especially in low transmissivity fractures these data demonstrate that porewater indeed acts as an archive for palaeohydrologic variations although the resolution is still limited

application of tritium in precipitation and in groundwater of the kouris catchment cyprus for description of the regional groundwater flow abstract the kouris catchment is located in the south of the troodos massif in cyprus it constitutes one of the biggest catchments of the island with important freshwater resources geologically the catchment includes an ophiolitic complex outcropping in the north which is overlaid by sedimentary rocks in the south the hydrology is driven by a mediterranean climate a mountainous topography and a complex distribution of the hydrogeological properties resulting from the complex geology to improve the understanding of groundwater hydrology of the kouris catchment 176 groundwater and precipitation samples were collected and their 3 h contents were analyzed the three dimensional 3 h transport in the groundwater was simulated by the pmpath code for numerical modelling a regional input function of 3 h in precipitation was constructed from a linear regression between data for cyprus and for neighboring meteorological stations the calculated residence times for the groundwaters in the sedimentary aquifer and pillow lavas were greater than 48 a and were considerably greater than those of the ophiolitic complex 14 30 a the calibrated aquifer porosities were in a range of 0 05 0 06 the pmpath model was applied for delineation of spring catchments that were represented by quite narrow zones of lengths up to 5 km another contribution resulting from the 3 h analysis was a better understanding of the river aquifer interactions in most of the southern part the lithified sediments received only negligible amounts of water from the rivers while the alluvial aquifer contained mostly water infiltrated from rivers the largest springs in the southern part associated with the alluvial aquifer also discharged water identical to that in the rivers

estimating recharge in fractured aquifers of a temperate humid to semiarid volcanic island jeju korea from water table fluctuations and cl cfc 12 and 3h chemistry summary groundwater table fluctuations wtf chloride mass balance cmb apparent groundwater chlorofluorocarbon cfc 12 ages and tritium 3 h mean residence times were used to assess recharge rates on jeju island korea where groundwater is the main source of potable water given the limitations of various techniques and the respective data the methods yield median values of 687 mm yr wtf 429 mm yr cmb 423 mm yr cfc 12 and 394 mm yr 3 h which are lower than the multi annual 1993 2002 average value calculated using the soil water budget swb method 911 mm yr these underestimates are mainly due to most groundwater samples used for the analyses being located in the more arid lowland areas of the island all methods yield highest recharge rates in the southern and eastern districts of jeju implying a strong control of rainfall on the spatial recharge distribution the spatial variability of recharge at the catchment scale is caused by spatially and temporally variable rainfall and evapotranspiration as well as the wide range in effective porosity and specific yield values of the aquifer lithologies the wtf method yields reliable results in the coastal regions where low hydraulic gradients prevail the cmb technique underestimates the recharge values of the swb in all geographic districts probably as a result of anthropogenic cl additions to groundwater and unaccounted for atmospheric cl dry deposition median recharge estimates from the cfc 12 and 3 h data show the lowest spatial correlation with those from the swb mainly as a result of vertical anisotropies and uncertainties in the determination of effective aquifer thicknesses particularly in the perched high level areas the here applied methods are useful for local calibration and validation of swb estimates in lower parabasal regions where thin unsaturated zones prevail however due to their inability to predict recharge in the more remote upslope areas from which as of yet no groundwater data could be obtained they cannot be applied to predict average recharge values representative for the whole island

teleseismic evidence for lateral heterogeneities in the northeastern japan arc we have measured and analyzed 4211 p wave first arrival times from 100 teleseismic events recorded by 67 high sensitivity seismic stations in the northeastern japan arc the relative travel time residuals show regional variations of about 1 6 s the mean relative residuals averaged for all 100 events produce a spatial pattern of early arrivals at stations near the pacific coast and delayed arrivals in the central part of the island arc and along the japan sea coast large delayed arrivals are observed at stations in volcanic areas this pattern is generally consistent with the heat flow distribution and the major structural features that have been determined by local and regional earthquake studies large early arrivals appear in northern kanto and southern tohoku for the rays from the teleseismic events in the southwestern direction using a simple and plausible model of plate subduction we have shown that this anomalous pattern can be explained by the change of the geometry of the subducting pacific plate beneath kanto the observed teleseismic residual distributions can be explained with a 3 d velocity model which includes the high velocity subducting pacific plate and low velocity anomalies in the crust and mantle wedge beneath active volcanoes suggesting that the 3 d model represents well the velocity structure in this region these teleseismic observations provide a new piece of information on the significant lateral heterogeneities of seismic velocity structure in the northeastern japan arc

basin induced love waves observed using the strong motion array at fuchu japan phases have been observed in the s wave coda of local earthquakes recorded at the fuchu strong motion array located in the kanto basin in the western suburbs of tokyo japan these phases are often larger than the direct s wave at a period of 1 sec because these phases are observed only on horizontal components at surface sites and are weakly observed at only the shallowest 150 m of a number of borehole sites they are interpreted as love waves particle motions indicate significantly off azimuth travel directions the fuchu array is too sparse to allow the application of standard array analysis to determine the origin of these phases instead we use a combination of three component polarization enveloping and slant stack techniques that allows propagation directions to be reasonably well determined 10 however group slownesses are more difficult to obtain precisely 1 to 2 sec km using these results and assuming that the love waves are generated by the scattering of s waves at the earth s surface we estimate locations of scattering points we find that the scattering occurs along a short segment of the kanto basin boundary for widely distributed earthquake source locations we believe that this segment is important because it is the closest part of the basin boundary to the observation sites the existence of these basin induced love waves violates backscattering models for the generation of the coda of local earthquakes this must be kept in mind when applying coda techniques to sediment basin sites at periods of 1 sec or more

age dating of groundwater in fissured rock influence of water volume in micropores age dating of groundwater by 14c measurements is sometimes used to indicate the residence time of the water in fissured rock with a porous rock matrix the flow is in the fissures the water filled pores of the rock may however be accessed by the tracer by diffusion the residence time for a tracer can then be longer than the flow time model calculations were performed using data for granitic rock for flow in large fissures 1 mm the 14c age is 10 70 times larger than the water residence time for small fissures 0 01 mm the 14c age may be more than 1000 times larger

study of multi aquifer groundwater interaction in a coal mining area in china using stable isotopes and major ion chemical data investigations have been undertaken to determine the interactions between the main aquifers in a coal mining area near the taihang mountains in china to determine the sources of water environmental isotopes 18o 2h 3h 34s and water chemistry ions ca2 mg2 na k hco3 so42 cl were used as tracers furthermore batch sampling and testing were conducted on mountain spring water and karst water in the aquifers of the taiyuan group fengfeng group and majiagou group on the seatearth of the coal mining area via field observations and laboratory experimental analysis the 18o and 2h values of the mountain spring water and karst water in the coal mining area showed a common distribution with the local meteoric water line el1 of karst water in the majiagou group but significantly deviated from the surface water evaporation line el2 in the coal mining area when combined with the distribution of karst water level values thus karst water in the coal mining area is mainly supplied by groundwater from mountainous areas furthermore the concentration of sulfate ions increased dramatically in the groundwater flow of karst water from mountain spring water to karst water in the fengfeng group and majiagou group of the coal mining area when equivalent concentrations of ca2 mg2 hco3 and so42 hco3 reached their peak the chemical type of groundwater gradually evolved from ca mg hco3 to ca mg so4 hco3 in addition significant positive correlation was found between the 34s and so42 values of the water samples indicating that gypsum is involved in groundwater lixiviation in contrast the relationships of ca na versus mg na na hco3 versus total dissolved solids tds and na versus cl revealed that tds and salinity accumulate from the mountain spring water and karst water in the taiyuan group of the coal mining area furthermore the chemical type of groundwater gradually evolved from ca mg hco3 to na hco3 as revealed by a piper trilinear diagram

matrix porosity as the most important parameter of fissured rocks for solute transport at large scales simple considerations show that tracer and or pollutant velocity at large scales in fissured rocks can be described by the formula vtnp h x k where vt is the mean velocity of a conservative tracer or pollutant np is the matrix porosity h x is the hydraulic gradient and k is the hydraulic conductivity the applicability of the formula is discussed and its validity tested in several case studies in which hydraulic conductivities calculated from either pollutant transport velocity or environmental tracer ages were compared with those known or estimated from other determinations the influence of matrix diffusion on the environmental tracer ages can also be proved independently by comparison of the rock volume vrock estimated from the hydrogeologic map with that calculated from volumetric flow rate q age of tracer tt and matrix porosity vrock qttnp

sulfur isotope signatures in gypsiferous sediments of the estancia and tularosa basins as indicators of sulfate sources hydrological processes and microbial activity abstract in order to reconstruct paleo environmental conditions for the saline playa lakes of the rio grande rift we investigated sediment sulfate sources using sulfur isotope compositions of dissolved so 4 2 ions in modern surface water groundwater and so 4 2 precipitated in the form of gypsum sediments deposited during the pleistocene and holocene in the tularosa and estancia basins the major sulfate sources are lower and middle permian marine evaporites 34s of 10 9 14 4 but the diverse physiography of the tularosa basin led to a complex drainage system which contributed sulfates from various sources depending on the climate at the time of sedimentation as inferred from sulfur isotope mass balance constraints weathering of sulfides of magmatic hydrothermal and sedimentary origin associated with climate oscillations during last glacial maximum contributed about 35 50 of the sulfates and led to deposition of gypsum with 34s values of 1 2 to 2 2 which are substantially lower than permian evaporates in the estancia basin microbial sulfate reduction appears to overprint sulfur isotopic signatures that might elucidate past groundwater flows a rayleigh distillation model indicates that about 3 18 of sulfates from an inorganic groundwater pool 34s of 12 6 13 8 have been metabolized by bacteria and preserved as partially to fully reduced sulfur bearing minerals species elemental sulfur monosulfides disulfides with distinctly negative 34s values 42 3 to 20 3 compared to co existing gypsum 3 8 to 22 4 for the tularosa basin microbial sulfate reduction had negligible effect on 34s value of the gypsiferous sediments most likely because of higher annual temperatures 15 33 c and lower organic carbon content median 0 09 in those sediments leading to more efficient oxidation of h2s and or smaller rates of sulfate reduction compared to the saline playas of the estancia basin 5 28 c median 0 46 of organic carbon the white sands region of the tularosa basin is frequently posited as a hydrothermal analogue for mars high temperatures of groundwater 33 3 c and high 18o h2o values 1 1 in white sands however are controlled predominantly by seasonal evaporation rather than the modern influx of hydrothermal fluids nevertheless it is possible that some of the geochemical processes in white sands such as sulfide weathering during climate oscillations and upwelling of highly mineralized waters might be considered as valid terrestrial analogues for the sulfate cycle in places such as meridiani planum on mars

existence of an s wave reflector near the upper plane of the double seismic zone beneath the southern kanto district japan the amplitude of coda from local shallow earthquakes in the southern kanto district of japan does not decay smoothly with time a clear phase appears in the s coda at lapse time from 15 to 45 s measured from the s wave arrival and it is predominant for frequencies around 8 hz this phase seems to be an s wave reflected from a discontinuity inclined westward at upper mantle depths since it is predominantly on the horizontal components and propagated westward with a high apparent velocity applying an inversion method to the travel times of the phases read from 8 hz band seismograms we locate the s wave reflector near the upper plane of the double seismic zone associated with the subducting pacific plate the s wave reflector is resolved east of the volcanic front at a depth of 80 100 km if we put qs l 10 3 the reflection coefficient is estimated to be around 0 5 however the scatter is large the s wave impedance contrast at the interface seems to be very large it may suggest the existence of a zone containing many liquid bodies

detection of the subducting crust of oceanic plates beneath the kanto district japan abstract low velocity crustal layers on the top of the subducting slabs beneath the kanto district central japan were detected by a travel time inversion using 40 763 p wave arrival times from 3038 local earthquakes recorded by a local network of 41 seismic stations the inversion covered 188 228 110 km volume of the target region and the model was parameterized by 47 57 18 rectilinear blocks measuring 4 0 km per side horizontally and 4 10 km varying thickness in depth a prominent e w directed low velocity band of about 25 km width appeared in the central kanto region at a depth of 30 km moving north or northwestward gradually with depth this band can be traced to the depth of about 60 km at a depth of 60 km a slightly lower amplitude nearly n s directed low velocity band was observed at the east coast of the kanto region moving westward with depth these low velocity bands are thin layers attached to the top of the inclined thick layers with relatively high velocity in the kanto district the philippine sea phs plate subducts under the eurasian eur plate and the pacific pac plate also underthrusts beneath both the eur and phs plates some authors already suggested low velocity anomalies near the surface of those descending plates in this region mainly from the analyses of later phases and focal mechanisms of local earthquakes the shapes of the low velocity bands are similar to the depth distribution of the upper boundary of the phs and pac plates proposed by other authors the thrust earthquakes that occur at the boundaries between the eur and phs plates and between the phs and pac plates are almost located in the low velocity layers described above we conclude that these low velocity layers are the crusts that exist at the top of the subducting phs and pac plates while high velocity layers are subducting slabs themselves for the phs plate low density crust of the izu bonin arc is probably stacking at the range from 139 25 e to 139 55 e at 35 55 n which is observed as a thick low velocity region to the south of the range and in a steep inclination to the north of it this is also recognized from the gravity anomaly

the ribe formation in western denmark holocene and pleistocene groundwaters in a coastal miocene sand aquifer the ribe formation is a regionally extensive miocene sand aquifer that is present in western denmark at depths ranging from 100 to 300 m below ground surface groundwater chemistry and isotope data collected from more than 40 wells show that the ribe formation mainly contains high quality ca bicarbonate type groundwater of holocene age 100 10 000 a bp pleistocene age groundwaters identified on the basis of stable isotopes noble gases and corrected 14c values are present below the island of r0m in discharge areas near the coast and in hydraulically isolated inland areas the groundwater age distribution in the ribe formation was successfully simulated with a numerical groundwater flow model and particle tracking only when the 14c content in groundwater was corrected for both geochemical reactions and diffusion the results indicate that geochemical and physical processes significantly influence the 14c content of groundwater and that the correction factors required for the two processes are of the same magnitude flow modelling results indicate that pleistocene groundwaters were emplaced at depth within the ribe fromation under low base level conditions that prevailed throughout the late pleistocene near the coast these waters are essentially isolated from the present flow system and pleistocene freshwater may be present offshore seismic surveys show that conditions offshore are favourable for the presence of pleistocene freshwater within the ribe formation and other aquifers

evolution of chemical and isotopic composition of inorganic carbon in a complex semi arid zone environment consequences for groundwater dating using radiocarbon abstract estimating groundwater age is important for any groundwater resource assessment and radiocarbon 14 c dating of dissolved inorganic carbon dic can provide this information in semi arid zone i e water limited environments there are a multitude of reasons why 14 c dating of groundwater and traditional correction models may not be directly transferable some include 1 the complex hydrological responses of these systems that lead to a mixture of different ages in the aquifer s 2 the varied sources origins and ages of organic matter in the unsaturated zone and 3 high evaporation rates these all influence the evolution of dic and are not easily accounted for in traditional correction models in this study we determined carbon isotope data for dic in water carbonate minerals in the sediments sediment organic matter soil gas co 2 from the unsaturated zone and vegetation samples the samples were collected after an extended drought and again after a flood event to capture the evolution of dic after varying hydrological regimes a graphical method han et al 2012 was applied for interpretation of the carbon geochemical and isotopic data simple forward mass balance modelling was carried out on key geochemical processes involving carbon and agreed well with observed data high values of dic and 13 c dic and low 14 c dic could not be explained by a simple carbonate mineral co 2 gas dissolution process instead it is suggested that during extended drought water sediment interaction leads to ion exchange processes within the top 10 20 m of the aquifer which promotes greater calcite dissolution in saline groundwater this process was found to contribute more than half of the dic which is from a mostly dead carbon source dic is also influenced by carbon exchange between dic in water and carbonate minerals found in the top 2 m of the unsaturated zone this process occurs because of repeated dissolution precipitation of carbonate that is dependent on the water salinity driven by drought and periodic flooding conditions this study shows that although 14 c cannot be directly applied as a dating tool in some circumstances carbon geochemical isotopic data can be useful in hydrological investigations related to identifying groundwater sources mixing relations recharge processes geochemical evolution and interaction with surface water

the relationship between and evolution of surface water and groundwater in songnen plain northeast china to improve water management the relation and the hydrochemical evolution of surface water and groundwater were studied in the songnen plain the surface water and groundwater samples were evaluated for stable isotopes and hydrochemistry analyses the stable isotopic compositions 18o d indicate the groundwater recharges from the precipitation however the connectivity between surface water and groundwater is weak because of the clay layer and the interrupted aquifer the water evolution is from ca mg hco3 to na hco3 by the evaporation water rock interaction and ion exchange processes the water evaporation and leaching of saline alkaline soil are the main reasons for water salinity further the leaching of salts in the soil during recharging from backwater and irrigation water intensifies the salinization the relationship between and evolution of surface water and groundwater provide important guidance for water management not only in the arid and semi arid area but also in the soda saline alkali soil regions of the world

deep structure of japan subduction zone as derived from local regional and teleseismic events we have determined a detailed three dimensional p wave velocity structure of the japan subduction zone to 500 km depth by inverting local regional and teleseismic data simultaneously we used 45 318 p wave arrivals from 1241 shallow and deep earthquakes which occurred in and around the japan islands the arrival times are recorded by the japan university seismic network which covers the entire japan islands densely and uniformly we also used 4211 travel time residuals from 100 teleseismic events which are read from seismograms recorded by seismic stations in northeastern japan in comparison with the previous results obtained from only local and regional events the present result for the area around the lower plate boundary and the mantle below the plate is determined more reliably because of the addition of 7035 data from 100 teleseismic events and 41 very deep earthquakes in the crust and uppermost mantle low velocity zones are clearly visible beneath active volcanoes in the mantle wedge the low velocity zones generally parallel with the slab and exist continuously to a depth of about 200 km which is consistent with the petrological geochemical and geodynamic studies we consider that the existence of volcanism related low velocity anomalies in the mantle wedge is a general seismological characteristic of subduction zones in light of all the available tomographic results for many subduction zones in the world the pacific slab beneath japan is imaged more clearly than in previous studies as a high velocity zone with a thickness of 80 90 km and a p wave velocity 4 6 higher than the normal mantle lower velocity anomalies are found in the mantle below the slab

pathogen and chemical transport in the karst limestone of the biscayne aquifer 2 chemical retention from diffusion and slow advection 1 a tracer experiment using a nonreactive tracer was conducted as part of an investigation of the potential for chemical and pathogen migration to public supply wells that draw groundwater from the highly transmissive karst limestone of the biscayne aquifer in southeastern florida the tracer was injected into the formation over approximately 1 h and its recovery was monitored at a pumping well approximately 100 m from the injection well the first detection of the tracer occurred after approximately 5 h and the peak concentration occurred at about 8 h after the injection the tracer was still detected in the production well more than 6 days after injection and only 42 of the tracer mass was recovered it is hypothesized that a combination of chemical diffusion and slow advection resulted in significant retention of the tracer in the formation despite the high transmissivity of the karst limestone the tail of the breakthrough curve exhibited a straight line behavior with a slope of 2 on a log log plot of concentration versus time the 2 slope is hypothesized to be a function of slow advection where the velocities of flow paths are hypothesized to range over several orders of magnitude the flow paths having the slowest velocities result in a response similar to chemical diffusion chemical diffusion due to chemical gradients is still ongoing during the declining limb of the breakthrough curve but this process is dwarfed by the magnitude of the mass flux by slow advection

source and path of magma for volcanoes in the subduction zone of northeastern japan the assumption that the source of magma for volcanoes in subduction zones is located in the mantle immediately above the top of the subducting slab at approximately 100 km depth and straight beneath the volcanoes is incorrect in northeastern japan the combination of evidence from velocity tomography in the mantle wedge above the slab and mapping of earthquake size distribution within it strongly points to a source of fluids at the top of the slab at 140 to 150 km depth from where material rises along an inclined path to the volcanoes

subducting oceanic crusts of the philippine sea and pacific plates and weak zone normal compression in the kanto district japan summary oceanic crusts subducting into the mantle were detected by analyses of mantle earthquakes in the kanto district central japan earthquakes in a depth range of 30 80 km in the southwestern ibaraki prefecture were relocated by a modified method of joint hypocentre determination we obtained a good distribution map of hypocentres and focal mechanisms a boundary layer between the eurasian and philippine sea plates was found where thrust earthquakes with p axes in the nw se direction and of which low angle nodal planes dip northward occurred in a layer with a thickness of about 4 km the p wave velocity in this layer is estimated to be less than about 7 0kms l another boundary layer between the philippine sea and pacific plates exists about 15 km beneath the above boundary layer thrust earthquakes with p axes in the ew direction and of which low angle nodal planes dip westward occurred in this layer that also has a thickness of about 4km furthermore normal faulting earthquakes of which the p axes are almost perpendicular to the boundary layers were found immediately outside the boundary layers combining these results we can conclude that the boundary layers are oceanic crusts that exist at the top of the subducting philippine sea and pacific plates weak zone normal compression was proposed to result from the existence of low velocity oceanic crusts at plate boundaries this hypothesis can be explained because only stress caused by relative motion of the two plates is consumed inside the weak oceanic crust the remnant stress after subtracting the above stress from the tectonic one applied at the plate boundary is the stress of which the p axis is normal to the plate boundary

tracage par 13c 2h i et uranine dans la nappe de la craie senonienne en ecoulement radial convergent bethune france abstract the behaviour of four labelled solutions h213co3 2h2 o i and uranine is analysed through a field experiment solutions are injected using a pulse condition into a dynamic radial flow runs are performed on 10 22m of a semi confined aquifer senonian chalk aquifer in the bethune s france institute of technology area using the form and position parameters of the break through curves pure convective transfer time tc mean residence time t and the dispersivity it is shown that 1 i and 2h2o have a nearly identical behaviour 2 uranine presents a faster convective and dispersive transfer than the other tracers specially 2h2o and 3 the retardation of 13c h13co 3 is greater than those of 2h2 o and i this retardation suggests a fixation of h13co 3 onto the solid matrix furthermore the transfer disparity of these compounds is due to the difference of their diffusion rates to the stationary liquid phase of the chalk matrix which lead to apparent distinct mean velocity for each tracer

near surface and deep groundwaters abstract groundwater occurs in all climatic zones and differs in hydrodynamic isotopic and chemical terms according to its activity within the water cycle and its interaction with rocks among the many chemical components in groundwaters tritium concentrations allow differentiation between groundwater of high and low mobility and thus permit the distinction between shallow and deep groundwaters in germany shallow groundwaters range in depth between 10 and 100 m and account for more than 85 of groundwater recharge deep groundwaters in contrast participate in the water cycle only at intervals of hundreds or thousands of years and reach depths of several hundred metres both types of groundwater overlie connate waters that have been isolated from the water cycle since the accumulation of the sediments in which they occur the exploitation of deep groundwaters mostly causes long term non steady state conditions large scale changes of flow patterns of the groundwaters and hydraulic short circuits to shallow aquifers thus persistent contaminants may penetrate extraction wells in deep groundwaters even if the wells are believed to be well protected against pollution in deep groundwaters it is difficult to apply the conventional use of groundwater protection zones to prevent this kind of intrusion of contaminants

water storage in a till catchment ii implications of transmissivity feedback for flow paths and turnover times this paper explores the flow paths and turnover times within a catchment characterized by the transmissivity feedback mechanism where there is a strong increase in the saturated hydraulic conductiv

geochemical and isotopic investigations on groundwater residence time and flow in the independence basin mexico abstract the independence basin in the semi arid guanajuato state of central mexico is facing serious groundwater resources deficiency due to an increasing demand linked to a rapid population growth and agricultural development this problem is aggravated by an inadequate evaluation of groundwater resources in the region geochemistry and isotopic tracers were used in order to investigate the groundwater flow system and estimate the groundwater residence time the groundwater is characterized by low salinity with some exceptions associated to a contribution of more saline groundwater from deep formations the predominant reactions are co 2 gas dissolution carbonate dissolution albite weathering kaolinite and chalcedony precipitation six principal hydrochemical zones were recognized which provided information on plausible recharge sources and groundwater chemical evolution the 14 c concentration varies between 19 and 94 pmc the high 14 c values indicating recent recharge are observed at the basin margins and a trend to lower 14 c values is observed along the modern groundwater flow paths the groundwater residence time according to radiocarbon estimations ranges between recent and 11 ka the residence time distribution matches the regional important discharge zones west in the basin center from dolores hidalgo and southwest from doctor mora hydrochemical tracers are in general agreement with the predeveloped and current hydraulic head configuration however show some inconsistencies with the predeveloped head in the downgradient areas which means that the impact by gradually increasing groundwater extraction during the last decades is reflected on radiocarbon age distribution geochemical evidences imply that the recharge input from the northern basin area is insignificant

anthropogenic sulfate loads in the rio grande new mexico usa abstract the sources of so 4 along a 550 km stretch of the rio grande in new mexico and western texas were investigated using stable s isotopes during 2007 and 2008 the 34 s of dissolved so 4 in the rio grande surface water varied over a narrow range from 1 6 to 0 9 which was consistent with the 34 s of local fertilizers 2 1 to 1 6 and was not consistent with paleozoic evaporite sources of so 4 in regional bedrock 7 6 to 12 9 this is likely due the fact that so 4 is the major component of n p k fertilizers used in the rio grande valley constituting about half of the total fertilizers by mass the so 4 cl ratios of the groundwater system are relatively low 0 06 to 3 compared to the fertilizer source suggesting that more cl is added to the rio grande from geological sources as compared to so 4 in the mesilla basin in southern new mexico we identified zones of mixing between recharging irrigation water with groundwater within the depth range of 50 200 m below the ground surface for this aquifer principal component analysis pca indicated that na k cl concentrations were largely attributable to geological sources and so 4 mg ca concentrations to anthropogenic sources here an additional anthropogenic source of so 4 with a 34 s of 2 7 was linked to anaerobic decomposition of manure on a horse farm in this case so 4 concentrations 800 mg l increased by about three times compared to background so 4 concentrations in groundwater 2 so 4 in fertilizer manufacturing anthropogenic so 4 fluxes to rivers and shallow aquifers from irrigation waters can be significant worldwide

carbon 14 dating of groundwater in confined aquifers implications of aquitard diffusion the influence of diffusive losses into fine grained aquitards on the 14c age interpretation of groundwater in long thin confined aquifers is examined an analytical model is developed by coupling two one dimensional steady state differential equations one representing advective dispersive transport in the aquifer and the other representing diffusion into the aquitards the results indicate that aquitard diffusion is a mechanism that can cause a significant reduction in 14c concentrations in a confined aquifer groundwater velocities derived from 14c measurements that are unadjusted for diffusion would therefore be underestimated the error that ensues is highly sensitive to the aquifer thickness and the magnitude of the diffusion coefficient in contrast the steady state distribution of 14c is shown to be relatively insensitive to the magnitude of the longitudinal dispersivity value of the aquifer dispersivities representative of the upper range of values that have been reported in the literature produced a negligible difference in steady state 14c concentration compared to results obtained using small dispersivities an equation is presented which permits the adjustment of 14c data to account for diffusion providing that the aquifer aquitard system is not stratigraphically complex and heterogeneous the analysis can be extended to include age dating isotopes that have half lives different from that of 14c the results of this study also apply to age dating in fractured porous media

regional variations of amplitudes of scsp phases observed in the japanese islands summary scsp phases are examined with special reference to their amplitude variations over seismograph networks in the japanese islands scsp of rela tively large amplitude are observed along the pacific side of the japanese islands amplitude ratios of the scsp with respect to scs are explained in terms of scs to p conversion at the upper boundary of a descending pacific plate which dips at about 30 and whose seismic wave velocity is between 5 and 10 per cent higher than that of the surrounding mantle large amplitude scsp are observed at stations nearest the kurile or japan trench the ampli tude ratios of scsp scs are found to decrease rapidly with distance inland from the trench an estimate is made of the effects of sharpness of the con version interface the incident angle of scs upon it and lateral variations of anelasticity within the asthenosphere overlying the descending pacific plate upon the scsp scs ratios we show that the sharpness of the conversion inter face is the dominant factor this result implies that the nature of the scs to p conversion interface varies with distance from the trench or equivalently with depth the presence of a low velocity zone in the vicinity of the conversion interface is inferred from the relative polarity between scsp and scs observed at the stations on the outermost side of north eastern japan scsp arrivals from shallower conversions at depths less than about 80 km observed in central and south western japan are also examined to elucidate the structure of the philippine sea plate descending beneath this region a discussion is made on the correlations between dipping subcrustal seismicity and the scs to p conversion interfaces except for the chugoku region the scs to p conversion interfaces correlate well with the dipping subcrustal seismicity our scsp observations indicate the presence of a dipping dis continuity in the uppermost mantle beneath the chugoku region where no subcrustal earthquakes have been detected

stable isotope imaging of a dynamic groundwater system in the southwestern sacramento valley california usa abstract a dynamic image of a shallow 45 160 m below the surface aquifer in a 25km2 area in the southwestern sacramento valley california has been obtained by 18 o 16 o and d h determinations of groundwater from municipal wells the regular summertime drawdown of the water table is strongly correlated with municipal wide increases in the 18o values particularly in wells with shallow perforation levels thus demonstrating that the high 18o water resides in the upper reaches of the aquifer and penetrates more deeply with increased discharge rates these 1 5 enrichments in the 18o values are primarily attributed to infiltration of irrigation water that has penetrated to depths of at least 80 m the increased 18o values correlate with increased deviation from the meteoric water line and with increased nitrate levels indicating that the high 18o groundwater component represents local meteoric water that has been enriched by soil evaporation processes in nitrogen fertilized flood irrigated cropland isotopic gradients provide a new method for qualitatively determining subsurface permeability zones of low isotopic gradients interpreted as high 18o plumes probably follow coarse textured deposits of ancient stream channels the 18o gradients are primarily controlled by subsurface permeability although additional influences may include 1 the heterogeneous distribution of the high 18o groundwater 2 isotopic contributions from deeper groundwater 3 variable perforation depths of the wells 4 local differences in the water table level deeper sodium bicarbonate groundwaters 300 650 m below the surface have lower 18o values to 9 4 than the more shallow magnesium bicarbonate groundwaters suggesting derivation from 18o depleted meteoric groundwaters of the sierra nevada minor mixing of the deeper groundwater into the municipal discharge occurs even though previous workers considered the deeper groundwater to be confined

a multi tracer study of groundwater origin and transit time in the aquifers of the venice region italy located in the northeastern region of italy the venetian plain vp is a sedimentary basin containing an extensively exploited groundwater system the northern part is characterised by a large undifferentiated phreatic aquifer constituted by coarse grain alluvial deposits and recharged by local rainfalls and discharges from the rivers brenta and piave the southern plain is characterised by a series of aquitards and sandy aquifers forming a well defined artesian multi aquifer system in order to determine origins transit times and mixing proportions of different components in groundwater gw a multi tracer study 3