strontium isotopes and rare earth elements as tracers of groundwater lake water interactions lake naivasha kenya abstract strontium isotope compositions and rare earth element ree concentrations are presented for groundwater and surface water samples collected from the lake naivasha watershed in the east african rift kenya the chief objective of the study is to test the suitability of rees in conjunction with sr isotopes as tools for investigating groundwater lake water interactions in general the ree concentrations and 87 sr 86 sr ratios support the authors earlier investigations where cl mass balance 18 o d and he isotopes were employed to study groundwater lake water interactions in the naivasha watershed the ree data suggest that a significant amount of the groundwater south of lake naivasha i e 50 85 consists of lake water recharge to the aquifer system specifically mixing calculations conducted using ree data of lake naivasha water and groundwaters indicate that between 70 and 85 of groundwater directly south of the lake is likely lake water these values are somewhat higher than the authors previous estimates determined with conservative stable h isotopes d 50 70 for both cases however the data demonstrate that water originating in lake naivasha contributes significantly to the underlying groundwater flow system hence supporting earlier evidence that the lake s freshness reflects rapid loss of water and dissolved solutes to the local groundwater system overall lake and groundwater sr isotope compositions support seepage of lake water into the underlying aquifer along the lake s south shore the 87 sr 86 sr data also provide additional insight into the geochemical evolution of waters of the lake naivasha watershed indicating that the initial source of sr to these waters is likely chemical weathering reactions involving basaltic rocks within the recharge zones of the watershed along the rift valley flanks furthermore with increasing residence time of groundwaters within the aquifer system and flow down and along the rift valley floor sr isotope compositions of groundwaters become more radiogenic reflecting rock water interactions with chemically differentiated and radiogenic peralkaline rhyolite volcanic rocks the importance of the longer aquifer residence times and radiogenic source rocks is especially apparent for geothermal waters of the olkaria geothermal field that have 87 sr 86 sr ratios i e 0 70747 similar to local comendites

the origin and mechanisms of salinization of the lower jordan river the chemical and isotopic 87 sr 86 sr 11 b 34 ssulfate 18 owater 15 nnitrate compositions of water from the lower jordan river and its major tributaries between the sea of galilee and the dead sea were determined in order to reveal the origin of the salinity of the jordan river we identified three separate hydrological zones along the flow of the river 1 a northern section 20 km downstream of its source where the base flow composed of diverted saline and wastewaters is modified due to discharge of shallow sulfate rich groundwater characterized by low 87 sr 86 sr 0 7072 34 ssulfate 2 high 11 b 36 15 nnitrate 15 and high 18 owater 2 to 3 values the shallow groundwater is derived from agricultural drainage water mixed with natural saline groundwater and discharges to both the jordan and yarmouk rivers the contribution of the groundwater component in the jordan river flow deduced from mixing relationships of solutes and strontium isotopes varies from 20 to 50 of the total flow 2 a central zone 20 50 km downstream from its source where salt variations are minimal and the rise of 87 sr 86 sr and so4 cl ratios reflects predominance of eastern surface water flows 3 a southern section 50 100 km downstream of its source where the total dissolved solids of the jordan river increase particularly during the spring 70 80 km and summer 80 100 km to values as high as 11 1 g l variations in the chemical and isotopic compositions of river water along the southern section suggest that the zarqa river 87 sr 86 sr0 70865 11 b25 has a negligible affect on the jordan river instead the river quality is influenced primarily by groundwater discharge composed of sulfate rich saline groundwater cl 31 180 mm so4 cl0 2 0 5 br cl2 310 3 87 sr 86 sr0 70805 11 b30 15 nnitrate 17 34 ssulfate4 10 and ca chloride rift valley brines cl 846 1500 mm br cl 6 8 10 3 87 sr 86 sr0 7080 11 b40 34 ssulfate4 10 mixing calculations indicate that the groundwater discharged to the river is composed of varying proportions of brines and sulfate rich saline groundwater solute mass balance calculations point to a 10 contribution of saline groundwater cl282 to 564 mm to the river a high nitrate level up to 2 5 mm in the groundwater suggests that drainage of wastewater derived irrigation water is an important source for the groundwater this irrigation water appears to leach pleistocene sediments of the jordan valley resulting in elevated sulfate contents and altered strontium and boron isotopic compo sitions of the groundwater that in turn impacts the water quality of the lower jordan river copyright 2004 elsevier ltd

strontium and carbon isotope constraints on carbonate solution interactions and inter aquifer mixing in groundwaters of the semi arid murray basin australia abstract strontium and carbon isotopes are used to study the effect of carbonate mineral dissolution and inter aquifer mixing on the chemical evolution of groundwater from the murray group limestone aquifer in semi arid se australia the 87 sr 86 sr ratio of groundwater evolves from 0 7097 at the basin margin to a less radiogenic value of 0 7084 about 250 km down gradient which is similar to the 87 sr 86 sr ratio of the aquifer carbonate matrix the concomitant increase in 13 c dic sr ca and mg ca ratios in the groundwater along a 250 km transect suggests that incongruent dissolution of high mg calcite controls the carbonate geochemistry in this aquifer further down gradient the groundwater is characterized by a relatively more radiogenic 87 sr 86 sr ratio caused by upward leakage and mixing with more radiogenic groundwater from the renmark group sand aquifer a mixing model using 87 sr 86 sr ratio suggests that the fraction of water that contribute to the murray group aquifer through upward leakage from underlying renmark group aquifer ranges from 15 to 85

estimating groundwater exchange with lakes 1 the stable isotope mass balance method groundwater inflow and outflow contributions to the hydrologic budget of lakes can be determined using a stable isotope 18o 16o mass balance method the stable isotope method provides a way of integrating the spatial and temporal complexities of the flow field around a lake thereby offering an appealing alternative to the traditional time and labor intensive methods using seepage meters and an extensive piezometer network in this paper the method is applied to a lake in northern wisconsin demonstrating that it can be successfully applied to lakes in the upper midwest where thousands of similar lakes exist inflow and outflow rates calculated for the wisconsin lake using the isotope mass balance method are 29 and 54 cm yr respectively which compare well to estimates derived independently using a three dimensional groundwater flow and solute transport model of 20 and 50 cm yr such a favorable comparison lends confidence to the use of the stable isotope method to estimate groundwater exchange with lakes in addition utilization of stable isotopes in studies of groundwater lake systems lends insight into mixing processes occurring in the unsaturated zone and in the aquifer surrounding the lake and verifies assumed flow paths based on head measurements in piezometers

dissolved constituents and sr isotopes in river waters from a mountainous island the danshuei drainage system in northern taiwan abstract taiwan is a typical active orogenic belt situated at the collision boundary between the eurasian continental plate and the philippine sea plate dissolved major and trace constituents as well as sr and sr isotopes in river waters collected from the danshuei river basin in northern taiwan have been studied to evaluate chemical weathering processes the results of principal component analysis show that the ion sources in these river waters can be categorized into 3 major components chemical weathering seasalt contribution and local anthropogenic input the chemical weathering is the most dominant factor that contributes about 85 of total variances significantly increased na cl and ca cl as well 87 sr 86 sr were observed in most upper stream samples the na cl and ca cl ratios in the dahan stream however are much higher than the shindien stream even though average rainfall is stronger in the shindien drainage basin chemical evidence from river waters supports less intense weathering in the region selective dissolution of secondary calcites explains the observed high ca cl sr cl and ca na in the dahan stream these results highlight the potential importance of tectonic factors such as uplift and physical erosion in studying chemical weathering in an active orogenic belt the variations of 87 sr 86 sr in the danshuei river are quite large reflecting some strata that released sr most of the upstream waters exhibit more radiogenic 87 sr 86 sr 0 713243 0 714338 due to weathering of ambient low grade metamorphic rocks 0 71678 0 72216 the distributions of cl sr and 87 sr 86 sr in the main stream were affected by somewhat conservative mixing with sources varing between ambient rocks and seasalt in the upper dahan stream heavy 87 sr 86 sr ratios were coincident with large deviations of na cl from the average seawater value as high as 40 the degree of chemical weathering in ambient rocks plays a dominant role in affecting the distribution of sr and 87 sr 86 sr in the danshuei river this isotopic characteristic makes 87 sr 86 sr an invaluable tracer for studying source mixing migration pathways and chemical weathering in an active orogenic belt

a multi isotope δd δ18o 87sr 86sr and δ11b approach for identifying saltwater intrusion and resolving groundwater evolution along the western caprock escarpment of the southern high plains new mexico abstract declining water levels in arid and semi arid regions increase an aquifer s vulnerability to natural and anthropogenic influences a multi isotope d 18 o 87 sr 86 sr and 11 b approach was used to resolve the geochemical evolution of groundwater in a declining aquifer in a semi arid region of the southwestern usa as groundwater composition reacts to source water mixing cross formational flow including saltwater intrusion water rock interaction and likely agricultural recharge sub aquifers or local flow systems are present in the southern high plains aquifer along the western caprock escarpment in new mexico and the study site s local flow system contains a na cl high dissolved solids groundwater that flows from the escarpment until it mixes with a high quality regional aquifer or regional flow system the local flow system contains water that is similar in composition to the underlying upper dockum group aquifer saltwater found in the upper dockum group aquifer likely originates in the adjacent pecos river basin and crosses beneath or possibly through the hydrologic divide of the western caprock escarpment strontium concentrations of 0 9 31 mg l and a 87 sr 86 sr range of 0 70845 0 70906 were sufficient to estimate source water fractions mixing patterns and contributions from chemical weathering through mass balance inverse calculations boron concentrations 59 1740 mg l and 11 b values 6 0 46 0 were used to confirm source water mixing further evaluate water rock interaction and examine the influence of possible agricultural recharge alteration of b concentrations and 11 b values in an area of likely agricultural recharge indicated the loss of b and decrease in 11 b values likely from plant uptake adsorption and weathering contributions in the soil vadose zone prior to recharge the effectiveness of 87 sr 86 sr and 11 b for resolving the geochemical influences in groundwater in the southern high plains along the western caprock escarpment allowed for the reinterpretation of the isotopic composition of water that has been shown to be highly variable in the southern high plains this study shows the utility of a multi isotope approach for resolving the geochemical evolution of groundwater in an aquifer that has a complex relationship with underlying aquifers and the applicability of these isotopes as indicators of the alteration of source waters from natural or anthropogenic influences

new isotopic evidence for the origin of groundwater from the nubian sandstone aquifer in the negev israel the geochemistry and isotopic composition h o s osulfate c sr of groundwater from the nubian sandstone kurnub group aquifer in the negev israel were investigated in an attempt to reconstruct the origin of the water and solutes evaluate modes of water rock interactions and determine mean residence times of the water the results indicate multiple recharge events into the nubian sandstone aquifer characterized by distinctive isotope signatures and deuterium excess values in the northeastern negev groundwater was identified with deuterium excess values of 16 which suggests local recharge via unconfined areas of the aquifer in the negev anticline systems the d 18 oh2o and d 2 h values 6 5 and 35 4 of this groundwater are higher than those of groundwater in the sinai peninsula and southern arava valley 7 5 and 48 3 that likewise have lower deuterium excess values of 10 based on the geochemical differences between groundwater in the unconfined and confined zones of the aquifer a conceptual geochemical model for the evolution of the groundwater in the nubian sandstone aquifer has been reconstructed the isotopic composition of shallow groundwater from the unconfined zone indicates that during recharge oxidation of pyrite to so4 d 34 sso4 13 d 18 oso4 7 7 and dissolution of caco3 87 sr 86 sr 0 70787 d 13 cdic 3 7 occur in the confined zone of the aquifer bacterial so4 reduction removes a significant part of dissolved so 2

evidence for high salinity of early cretaceous sea water from the chesapeake bay crater chemical isotopic and physical evidence indicate that some of the groundwater in the chesapeake bay crater is remnant early cretaceous north atlantic sea water probably 100 145 million years old with an average salinity of about 70 which is twice that of modern sea water geologists and oceanographers generally have to rely on indirect evidence from the analysis of solid materials in deep sediment cores when estimating temperature and salinity levels of the ancient oceans but now a team from the us geological survey has identified a body of underground water that is actually a remnant of a past ocean water a body of early cretaceous north atlantic sea water deep drilling at the site of the chesapeake bay impact crater has yielded groundwater with an isotope and chemical composition signature that together with model analysis suggests that it was trapped in the sediments before the impact occurred around 35 million years ago the water may have lain undisturbed for much longer it has an average salinity of about 70 parts per thousand twice that of modern sea water and is probably 100 145 million years old high salinity groundwater more than 1 000 metres deep in the atlantic coastal plain of the usa has been documented in several locations1 2 most recently within the 35 million year old chesapeake bay impact crater3 4 5 suggestions for the origin of increased salinity in the crater have included evaporite dissolution6 osmosis6 and evaporation from heating7 associated with the bolide impact here we present chemical isotopic and physical evidence that together indicate that groundwater in the chesapeake crater is remnant early cretaceous north atlantic ecna sea water we find that the sea water is probably 100 145 million years old and that it has an average salinity of about 70 per mil which is twice that of modern sea water and consistent with the nearly closed ecna basin8 previous evidence for temperature and salinity levels of ancient oceans have been estimated indirectly from geochemical isotopic and palaeontological analyses of solid materials in deep sediment cores in contrast our study identifies ancient sea water in situ and provides a direct estimate of its age and salinity moreover we suggest that it is likely that remnants of ecna sea water persist in deep sediments at many locations along the atlantic margin

strontium isotopes as tracers to delineate aquifer interactions and the influence of rainfall in the basalt plains of southeastern australia summary to better understand the spatial distribution of groundwater salinisation in western victoria southeast australia the interactions between a surficial basalt aquifer and an underlying extensive palaeodrainage deep lead system were studied using a multi disciplinary approach combining strontium isotope analyses with major ion chemistry and the interpretation of geological and hydrogeological data the strontium isotopes proved particularly useful in delineating flow paths and hydraulic connections between the two aquifers which have contrasting 87sr 86sr ratios the freshest basalt groundwaters lie beneath volcanoes and have 87sr 86sr signatures close to the whole rock strontium isotope ratios of the basalts 0 7045 indicating the strong influence of basalt weathering with increasing distance from the eruption points basalt groundwaters become progressively more saline and the strontium isotope ratios evolve towards the more radiogenic signatures of local rainfall 0 710 0 711 due to the slow addition of infiltration concentrated by evapotranspiration during its passage through the thick clay rich soils developed on the basalt lavas overall the influence of rainwater on the strontium isotope signatures of the basalt groundwater is much greater than that of basaltic weathering indicating that rainwater can play a greater role in determining groundwater strontium composition than is often realised most parts of the palaeodrainage system beneath the basalt are preferentially recharged through the volcanoes as shown by strong downwards hydraulic gradients and groundwater 87sr 86sr ratios similar to the least radiogenic basalt groundwaters however in the northwestern part groundwater 87sr 86sr ratios are closer to those of the source material of the sediments palaeozoic bedrock indicating that here recharge occurs predominantly in the headwaters where the basalts are absent in the southern and western sections of the palaeodrainage system there is an upward flux into the overlying basalts as shown by strong upward hydraulic gradients and elevated strontium isotope signatures in basalt groundwaters this occurs because lateral groundwater flow in the palaeodrainage system is restricted by shallow subsurface basement ridges and ultimately discharges to the surface as salt lakes

acidification processes and soil leaching influenced by agricultural practices revealed by strontium isotopic ratios abstract in natural river systems the chemical and isotopic composition of stream and ground waters are mainly controlled by the geology and water rock interactions the leaching of major cations from soils has been recognized as a possible consequence of acidic deposition from atmosphere for over 30 years moreover in agricultural areas the application of physiological acid fertilizers and nitrogen fertilizers in the ammonia form may enhance the cation leaching through the soil profile into ground and surface waters this origin of leached cations has been studied on two small and adjacent agricultural catchments in brittany western france the study catchments are drained by two first order streams and mainly covered with cambisoils issued from the alteration and weathering of a granodiorite basement precipitations soil water and nh4 acetate leachates separated minerals and stream waters have been investigated chemical element ratios such as ba sr na sr and ca sr ratios as well as sr isotopic ratios are used to constrain the relative contribution from potential sources of stream water elements based on sr isotopic ratio and element concentration soil water and nh4 acetate leaching indicates 1 a dominant manure slurry contribution in the top soil representing a cation concentrated pool with low 87sr 86sr ratios 2 in subsoils mineral dissolution is enhanced by fertilizer application becoming the unique source of cations in the saprolite the relatively high weathering rates encountered implies significant sources of cations which are not accessory minerals but rather plagioclase and biotite dissolution stream water has a very different isotopic and chemical composition compared to soil water leaching suggesting that stream water chemistry is dominated by elements issued from mineral and rock weathering agriculture by applications of chemical and organic fertilizers can influence the export of major base cations such as na plagioclase dissolution rather than anthropogenically controlled soil water seems to be the dominant source of na in streams however ca2 in streams is mostly derived from slurries and manures deposited on top soils and transferred into the soil ion exchange pool and stream waters less than 10 of na 5 40 of sr2 and 20 100 of ca2 found in streams can be directly derived from the application of organic fertilizers

application of multi isotope ratios to study the source and quality of urban groundwater in metro manila philippines abstract to characterize water quality in terms of dissolved elements and to investigate both the origin of the water and the source and behavior of groundwater contaminants in metro manila 33 water groundwater and surface water samples were analyzed for ion and element concentrations h and o isotope ratios d h2o and 18o h2o so 4 2 isotope ratios 34s so 4 2 and 18o so 4 2 and sr isotope ratio 87sr 86sr the chemical measurements showed that the primary important environmental concerns within metro manila are groundwater salinization for both shallow and deep aquifers and as concentrations up to 22 5 g l in shallow groundwaters comparison of so 4 2 and sr isotope values with possible source materials revealed that contamination by man made materials such as fertilizers and detergents are present in some shallow groundwaters shallow groundwater having higher d h2o and 18o h2o values av 44 5 6 and 6 8 0 6 respectively n 15 than deep groundwater av 48 4 4 and 7 4 0 7 respectively n 7 suggests that the origins of h2o in both groundwaters are different from each other since the mixing of shallow and deep groundwater does not commonly occur under metro manila the contaminants in the shallow aquifers are unlikely to be transported into the deep aquifers sulfate reduction by bacterial activity was observed for some groundwaters resulting in a maximum elevation in 34s so 4 2 values of around 10 by using so 4 2 isotope ratios as an indicator of changes in redox conditions and sr isotope ratio as a source indicator it was shown that as was dissolved from unconsolidated sedimentary deposits of volcanic origin which enclose shallow unconfined aquifers but was not the result of changes in redox conditions the study demonstrated that multi isotope ratios are useful for evaluating water quality problems in urban groundwaters

solute sources and chemical weathering in the owens lake watershed eastern california 1 chemical and strontium isotope analyses of solutes in a series of streams representing the bulk of the water reaching the 8500 km2 owens lake watershed provide a unique opportunity to evaluate factors that control stream chemistry on a regional scale the streams drain terrain that is dominated by mesozoic granitoids of the sierra nevada batholith but that also contains irregularly distributed roof pendants of paleozoic metasedimentary sequences mass balance modeling indicates that plagioclase feldspar weathering is the dominant contributor to stream chemistry and that carbonate dissolution is also a significant source of solutes for most streams the calculated ratio of plagioclase to carbonate is highly sensitive to the assumed weathering product of plagioclase kaolinite versus smectite and we suggest that the importance of carbonate could be exaggerated in cases where only the plagioclase to kaolinite reaction is considered strontium isotope 87sr 86sr ratios range from 0 70685 to 0 71958 with a flow weighted mean of 0 70911 to the extent that this value represents the water that would be flowing into owens lake were it not diverted by the los angeles aqueduct system the flow weighted mean 87sr 86sr ratio is consistent with ratios measured in owens lake core carbonates ranging in age up to 25 kyr the overall sr budget of the watershed is determined by the relative contributions of carbonate dissolution and plagioclase feldspar weathering and is dominated by reactions related to pyrite oxidation and hydrothermal fluid input from just two subbasins the impact of these processes needs to be considered when modeling regional and global riverine sr budgets climate related shifts in the relative importance of silicate mineral weathering reactions appear to be only second order effects on a regional scale

fluctuations of the svalbard barents sea ice sheet during the last 150 000 years abstract on spitsbergen western svalbard three major glacial advances have been identified during the weichselian all three reached the continental shelf west of the svalbard archipelago radiocarbon luminescence and amino acid dating of interbedded interstadial and interglacial sediments indicate that these glacial advances have early isotope stage 5d middle stage 4 and late weichselian ages stage 2 an additional more local advance has been dated to isotope stage 5b the late weichselian ice sheet expanded across the entire barents sea however in the south western barents sea the late weichselian till is the only till above eemian sediments indicating that the early and middle weichselian ice advances were restricted to the svalbard archipelago and the northern barents sea a major problem with the onshore sites is the dating of events beyond the range of the radiocarbon method to overcome this the onshore record has been correlated with marine cores from the continental slope and the deep sea west of svalbard where a chronology has been established by oxygen isotope stratigraphy ice rafted detritus ird was used as the main monitor of glaciation the ird record closely mirrors the glaciation history as interpreted from the onshore sections during the late weichselian the largest ird peak occurred during deglaciation a pattern also postulated for the earlier events given this the results from the marine cores indicate that the ages for the first glacial advances during the weichselian were a few thousand years older than interpreted from the onshore stratigraphy

seasonal variations in the geochemistry of shallow groundwater hosted in granitic till the groundwater chemistry in a small catchment in northern sweden has been studied for a period of 15 months including two snowmelt events the groundwater was sampled from two wells in a slope

weathering rates and 87sr 86sr ratios an isotopic approach the 87sr 86sr ratios of precipitation throughfall groundwater streamwater and mineral matter were analyzed precipitation strontium ratios are around 0 71 throughfall which is affected by strontium from the mineral soil has ratios of 0 72 0 73 and shallow groundwater in a drug well and runoff have ratios around 0 73 0 74 there is a tendency for this relationship to be reversed for discharge higher ratios are associated with lower discharges water from a fracture zone gave the highest value 0 78 approaching the value of the bedrock around 0 85 a calcium budget which reflects the mean conditions over a few years has been calculated this budget indicates that weathering should be of the order of 8 kg ca ha 1yr 1 to maintain the pool of exchangeable calcium at a constant level the major anion in the runoff is suphate which has entered the system in the form of acid rain sulphur deposition has been rather constant over the last two decades if acidification had an effect on weathering of silicates this would have shown up in a tendency of the strontium isotope ratios toward higher values in the soil pool and in runoff water thus its seems from the observed ratios that at least a major portion of the excess calcium export resulting from sulphur deposition is taken from the soil pool resulting in a gradual acidification of the soil

surface water groundwater interactions in an alluvial plain chemical and isotopic systematics our work on the loire river forms part of a french national research program dedicated to wetlands and aims to better understand the global functioning of the system from the hydrological geochemical ecological and sociological aspects the present study using a coupled hydrological and geochemical stable and sr isotopes approach focuses on the soulangy site with its secondary anastomosing channels just below the confluence of the loire and allier rivers and also on the dorna nt site with two unconnected oxbow lakes 50 km upstream of the confluence the stable isotopes of water 18o 2h show that the alluvial or riverbank aquifer feeds the loire river during the summer but is not recharged by the river during flood periods in the winter the alluvial groundwater thus has a purely local origin from precipitation the major elements reveal an anthropogenic input of cl and more importantly of no3 especially near farms the 87sr 86sr isotopes identify different groundwater layers in the alluvium i e an upper and a lower alluvial aquifer and a perched aquifer at dornant that have relatively complex relationships with the surface water the two main rivers loire and allier present distinct geochemical characteristics reflecting the different lithologies that they drain upstream in addition the secondary channels lying parallel to the loire main stream at the soulangy site give different geochemical signatures which shows that they are not fed by the same overflows of the loire they are more or less well connected to the upper level of the alluvial plain and a longitudinal study of one of these channels has revealed a loire river influence progressively replaced by a water contribution from the upper alluvial aquifer similarly the two oxbow lakes at the dornant site are not supplied by the same water during the summer months a conceptual scheme of the loire hydrosystem based on 18o and 87sr 86sr suggests that the isotopic variations of the loire river can be related to a massif central surface water supply for the loire and allier main streams and to a groundwater supply from the alluvial plains

the water balance of a small lake using stable isotopes and tritium abstract a small maar lake known as the blue lake set in a karstic region of southeastern australia provides the municipal water supply for a population of 20 000 the lake has a volume of 3 6 10 7 m 3 of which 10 15 is pumped from it each year the lake is recharged almost entirely from groundwater and the main objective of this study was to estimate the total groundwater inflow and outflow rates estimation of groundwater throughflow in a lake is difficult to assess using classical hydrological techniques and an alternative method involving measurement of the concentrations of the environmental isotopes 3 h 18 o 2 h and 14 c in the lake water and in the recharging groundwater was used to establish the lake water balance the water balance calculations indicated a total groundwater inflow to blue lake of between 5 0 10 6 and 6 5 10 6 m 3 yr 1 corresponding to a residence time of water in the lake of 6 yr it was not possible to derive the relative proportions of inflow to the lake from the two possible source aquifers using these isotopes because their concentrations did not show a sufficiently large contrast to distinguish the two water sources

residence time mineralization processes and groundwater origin within a carbonate coastal aquifer with a thick unsaturated zone this study aims at establishing groundwater residence times identifying mineralization processes and determining groundwater origins within a carbonate coastal aquifer with thick unsaturated zone and lying on a granitic depression a multi tracer approach major ions sio2 br ba sr2 18o 2h 13c 3h ne ar combined with a groundwater residence time determination using cfcs and sf6 allows defining the global setting of the study site a typical mineralization conditioned by the sea sprays and the carbonate matrix helped to validate the groundwater weighted residence times from using a binary mixing model terrigenic sf6 excesses have been detected and quantified which permits to identify a groundwater flow from the surrounding fractured granites towards the lower aquifer principally the use of cfcs and sf6 as a first hydrogeological investigation tool is possible and very relevant despite the thick unsaturated zone and the hydraulic connexion with a granitic environment

hydrogeochemistry and strontium isotopes in the arno river basin tuscany italy constraints on natural controls by statistical modeling summary in this paper the chemistry of major and trace elements and for the first time strontium isotopic ratios measured in running waters from the arno river basin tuscany central northern italy and thermal springs discharging in the same hydrographic system are presented and discussed classical graphical methods e g mixing diagrams have here been improved to identify in a correct statistical sample space extreme chemical compositions attributable to the action of geochemical processes and or inherited from specific lithologies namely contributions or components 1 2 and 3 to be used in inverse modeling procedures due to the absence of clear end members a linear least squares problem with non negativity constraints and distances as required for compositional data convex linear mixing was solved by considering the contribution of the most discriminant variables given by the 87 sr 86 sr isotopic ratios and the concentration of ca 2 mg 2 sr and rb following such approach it can be assumed p 2 mg 2 hco 3 radiogenic rich 87 sr 86 sr 0 71274 rb sr 0 039 represents a dominant feature at basin scale with a weight ranging from 69 to 100 much lower percentages are related to component 2 represented by a ca 2 mg 2 so 4 2 facies with intermediate 87 sr 86 sr 0 70874 and low rb sr 2 8 10 4 ratios and component 3 identified by ca 2 hco 3 facies with less radiogenic 87 sr 86 sr 0 70827 and low mg 2 ca 2 0 011 ratios these components are mainly dominated by the dissolution of evaporitic rocks and or mixing with thermal waters in the southern part of the arno river basin and by dissolution of the carbonatic fraction kinetically favored with respect to that of the silicatic minerals in the upper reaches of the main course and its tributaries respectively

vadose zone infiltration rate at hanford washington inferred from sr isotope measurements i sr isotope ratios were measured in the pore water acid extracts and sediments of a 70 m vadose zone core to obtain estimates of the long term infiltration flux for a site in the hanford doe complex in eastern washington state the 8 7 sr 8 6 sr values for the pore waters decrease systematically with depth from a high value of 0 721 near the surface toward the bulk sediment average value of 0 711 estimates of the bulk weathering rate combined with sr isotopic data were used to constrain the long term century to millenial scale natural diffuse infiltration flux for the site given both steady state and nonsteady state conditions the models suggest that the infiltration flux for the site is 7 3 mm yr the method shows potential for providing long term in situ estimates of infiltration rates for deep heterogeneous vadose zones

impact of glacial activity on the weathering of hf isotopes observations from southwest greenland abstract data for the modern oceans and their authigenic precipitates suggest incongruent release of hafnium hf isotopes by chemical weathering of the continents the fact that weathering during recent glacial periods is associated with more congruent release of hf isotopes has led to the hypothesis that the incongruency may be controlled by retention of unradiogenic hf by zircons and that glacial grinding enhances release of hf from zircons here we study the relationship between glacial weathering processes and hf isotope compositions released to rivers fed by land terminating glaciers of the greenland ice sheet as well as neighbouring non glacial streams the weathered source rocks in the studied area mostly consist of gneisses but also include amphibolites of the same age 1 9 ga hafnium and neodymium isotope compositions in catchment sediments and in the riverine suspended load are consistent with a predominantly gneissic source containing variable trace amounts of zircon and different abundances of hornblende garnet and titanite glacially sourced rivers and non glacial streams fed by precipitation and lakes show very unradiogenic nd isotopic compositions in a narrow range nd 42 8 to 37 9 hafnium isotopes on the other hand are much more radiogenic and variable with hf between 18 3 and 0 9 in glacial rivers and even more radiogenic values of 15 8 to 46 3 in non glacial streams although relatively unradiogenic hf is released by glacial weathering glacial rivers actually fall close to the seawater array in hf nd isotope space and are not distinctly unradiogenic based on their abundance in rocks and sediments and their isotope compositions different minerals contribute to the radiogenic hf in solution with a decreasing relevance from garnet to titanite hornblende and apatite neodymium isotopes preclude a much stronger representation of titanite hornblende and apatite in solution such as might result from differences in dissolution rates than estimated from mineral abundance the strong contrast in hf isotope compositions between glacial rivers and non glacial streams results mostly from different contributions from garnet and zircon where zircon weathering is more efficient in the subglacial environment a key difference between glacial and non glacial waters is the water rock interaction time while glacial rivers receive continuous contributions from long residence time waters of distributed subglacial drainage systems non glacial streams are characterized by fast superficial drainage above the permafrost horizon therefore the increased congruency in hf isotope weathering in glacial systems could simply reflect the hydrological conditions at the base of the ice sheet and glaciers with zircon weathering contributions increasing with water rock interaction time

archaeology tree trail to chaco canyon strontium isotopes have been used to identify the sources of timber in buildings around one thousand years old the method can now help to solve a range of other problems

investigation of geochemical indicators to evaluate the connection between inland and coastal groundwater systems near kaloko honokōhau national historical park hawai i abstract kaloko honok hau national historical park kaho is a coastal sanctuary on the western side of the island of hawai i that was established in 1978 to preserve interpret and perpetuate traditional native hawaiian culture and activities kaho contains a variety of culturally and ecologically significant water resources and water related habitat for species that have been declared as threatened or endangered by the u s fish and wildlife service or are candidate threatened or endangered species these habitats are dependent on coastal unconfined groundwater in a freshwater lens system the coastal unconfined groundwater system is recharged by local infiltration of rainfall but also may receive recharge from an inland groundwater system containing groundwater impounded to high altitudes the area inland of and near kaho is being rapidly urbanized and increased groundwater withdrawals from the inland impounded groundwater system may affect habitat and water quality in kaho depending on the extent of connection between the coastal unconfined groundwater and inland impounded groundwater an investigation of the geochemistry of surface water and groundwater samples in and near kaho was performed to evaluate the presence or absence of a connection between the inland impounded and coastal unconfined groundwater systems in the area analyses of major ions selected trace elements rare earth elements and strontium isotope ratio results from ocean fishpond anchialine pool and groundwater samples were consistent with a linear mixing process between the inland impounded and coastal unconfined groundwater systems stable isotopes of water in many samples from the coastal unconfined groundwater system require an aggregate recharge altitude that is substantially higher than the boundary between the coastal unconfined and inland impounded systems a further indication of a hydrologic connection between the two systems the stable isotope composition of the freshwater component of water samples from kaho indicates that about 25 70 of the freshwater is derived from the inland impounded system

mapping 87sr 86sr variations in bedrock and water for large scale provenance studies abstract although variation in 87sr 86sr has been widely pursued as a tracer of provenance in environmental studies forensics archeology and food traceability accurate methods for mapping variations in environmental 87sr 86sr at regional scale are not available in this paper we build upon earlier efforts to model 87sr 86sr in bedrock by developing gis based models for sr isotopes in rock and water that include the combined effects of lithology and time using published data we fit lithology specific model parameters for generalized equations describing the concentration of radiogenic sr in silicate and carbonate rocks the new model explained more than 50 of the observed variance in measured sr isotope values from independent global databases of igneous metaigneous and carbonate rocks but performed more poorly explaining 33 of the variance for sedimentary and metasedimentary rocks in comparison a previously applied model formulation that did not include lithology specific parameters explained only 20 and 8 of the observed variance for igneous and sedimentary rocks respectively and exhibited an inverse relationship with measured carbonate rock values building upon the bedrock model we also developed and applied equations to predict the contribution of different rock types to 87sr 86sr variations in water as a function of their weathering rates and strontium content the resulting water model was compared to data from 68 catchments and shown to give more accurate predictions of stream water 87sr 86sr r2 0 70 than models that did not include lithological weathering parameters we applied these models to produce maps isoscapes predicting 87sr 86sr in bedrock and water across the contiguous usa and compared the mapped sr isotope distributions to data on sr isotope ratios of us marijuana crops although the maps produced here are demonstrably imperfect and leave significant scope for further refinement they provide an enhanced framework for lithology based sr isotope modeling and offer a baseline for provenance studies by constraining the 87sr 86sr in strontium sources at regional scales

the combined use of 87sr 86sr and carbon and water isotopes to study the hydrochemical interaction between groundwater and lakewater in mantled karst abstract the hydrochemical interaction between groundwater and lakewater influences the composition of water that percolates downward from the surficial aquifer system through the underlying intermediate confining unit and recharges the upper floridan aquifer along highlands in florida the 87sr 86sr ratio along with the stable isotopes d 18o and 13c were used as tracers to study the interaction between groundwater lakewater and aquifer minerals near lake barco a seepage lake in the mantled karst terrane of northern florida upgradient from the lake the 87sr 86sr ratio of groundwater decreases with depth mean values of 0 71004 0 70890 and 0 70852 for water from the surficial aquifer system intermediate confining unit and upper floridan aquifer respectively resulting from the interaction of dilute oxygenated recharge water with aquifer minerals that are less radiogenic with depth the concentrations of sr2 generally increase with depth and higher concentrations of sr2 in water from the upper floridan aquifer 20 35 g l relative to water from the surficial aquifer system and the intermediate confining unit result from the dissolution of sr bearing calcite and dolomite in the eocene limestone dissolution of calcite 13c 1 6permil is also indicated by an enriched 13cdic 8 8 to 11 4 in water from the upper floridan aquifer relative to the overlying hydrogeologic units 13cdic groundwater downgradient from lake barco was enriched in18o and d relative to groundwater upgradient from the lake indicating mixing of lakewater leakage and groundwater downgradient from the lake the 87sr 86sr ratio of groundwater and aquifer material become less radiogenic and the sr2 concentrations generally increase with depth however sr2 concentrations are substantially less than in upgradient groundwaters at similar depths the lower sr2 concentrations result from the influence of anoxic lakewater leakage on the mobility of sr2 from clays based on results from mass balance modeling it is probable that cation exchange plays the dominant role in controlling the 87sr 86sr ratio of groundwater both upgradient and downgradient from lake barco even though groundwater from the three distinct hydrogeologic units displays considerable variability in sr concentration and isotopic composition the dominant processes associated with the mixing of lakewater leakage with groundwater as well as the effects of mineral water interaction can be ascertained by integrating the use of stable and radiogenic isotopic measurements of groundwater lakewater and aquifer minerals

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

constraining the groundwater flow system and aquifer properties using major ions environmental traces and a simple physical model in china s jilantai basin this study uses major ions and environment isotopes 87sr 86sr 13c and 14c together with a proposed physical model to constrain hydrogeochemical processes groundwater ages recharge rates and physical parameters in china s jilantai basin the major processes are identified using major ions which include calcite dissolution and the exchange of na for ca in upstream areas and gypsum dissolution carbonate incongruent dissolution and silicate weathering in downstream areas sr and major ions indicate the dissolution of carbonate minerals or gypsum and silicate weathering 87sr 86sr variations indicate that shallow groundwater in discharge areas consists of more than 90 groundwater from rainfall in the ulan buh desert ubd and middle groundwater comes entirely from the helan mountains the major ions 87sr 86sr ratio and physical model reflect that inter aquifer mixing has occurred between shallow unconfined and upper confined aquifers but not in middle confined formations the 14c ages range from the present to 15 ka and the distribution of 14c residence times indicate that inter aquifer flow occurs on a regional scale and over the long term between shallow unconfined and upper confined aquifers the travel times using the physical model proposed in this paper are comparable to the 14c ages indicating that this model is suitable for calculating travel times for the middle confined aquifers that have effective aquitards the vertical leakage rates are 0 01 0 03 m day and the long term recharge rates are 15 mm year approximately 5 of annual rainfall the groundwater from this region is a locally valuable resource and the correct understanding of groundwater flow systems inter aquifer mixing and recharge rates is critical to managing these groundwater resources

mineralogic controls on the composition of natural waters dominated by silicate hydrolysis a detailed mineral solute mass balance spreadsheet model has been developed to improve understanding of mineralogic controls on water composition in surface waters and groundwater systems dominated by silicate lithologies the spreadsheet based approach is used to investigate mass balance solutions over a range of mineral compositions for predominant multi element phases such as plagioclase biotite chlorite amphibole and dioctahedral smectite the mass balance technique has been applied to a variety of hydrogeologic environments including calibrated watersheds springs and groundwater systems lithologic settings include plutonic metamorphic minor volcanic and sedimentary alluvial and glacial deposits materials sites investigated most of which allowed comparison with earlier work include ephemeral and perennial springs of the central sierra nevada mountains california the loch vale colorado high altitude watershed four catchments in the inyo mountains california and nevada watersheds in the catoctin mountain maryland area and ground water flow systems in vekol valley arizona and in the trout lake area wisconsin analytical mass balances were derived with a novel approach that permits graphic analysis of the functional dependency of mineral mass transfer coefficients on variations in major silicate composition a 10 x 10 matrix of mineral solute reaction equations was used to solve for the best mass balances alternative methods were developed to investigate cases where the number of mineral phases exceeds the number of solute constraints 10 that are commonly found in clastic silicate dominated systems with diverse sources and or phase mixtures of variable chemistry such as an assortment of plagioclase compositions techniques were also developed to allow for important structurally controlled compositional variation in clay minerals final mass balance choices were tempered by thermodynamic stability calculations for various minerals under near surface weathering conditions mineral mass transfer ratios were also found to be useful in restricting mass balances additional constraints were provided by establishing consistent sets of similar mineral assemblages and mineral compositions for a series of wells along a ground water flow path or through comparison of multiple nearby watersheds subject to similar climatic and vegetative conditions whereas unique analytical solutions from spreadsheet mass balances were not always possible a surprisingly limited range was obtained for mineral assemblages and compositions satisfying observed mineral occurrences and thermodynamic stability conditions our results demonstrate the importance of having well characterized mineral compositions for both reactant and product phases the mass balance results are particularly sensitive to the compositions of plagioclase dioctahedral smectite and a few primary mafic mineral groups trioctahedral mica amphibole and pyroxene in addition to mineral controls the specific examples studied demonstrate effects of dolomite and calcite overprints on silicate weathering biomass fluctuations road salt contamination and on buried evaporite salts a comparison of the mass balance results from surface and groundwater systems indicates strong similarities suggesting that similar processes dominate the mineral controls in both settings and that under soil weathering conditions ion exchange might have been overemphasized except under conditions where pre existing waters are displaced by solutions of significantly different composition

tracking multiple sr sources through variations in 87sr 86sr ratios of surface waters from the aljustrel massive sulphide mining area geological versus anthropogenic inputs abstract this study presents major and trace element data and 87sr 86sr ratios for surface waters from a small watershed draining the aljustrel sulphide mining area south portugal the watershed is located in a geologically complex area comprising two main compartments the northern compartment is dominated by cenozoic formations and does not bear any mining activity whilst the southern compartment is underlain by rocks from both the cenozoic sedimentary cover and the mineralized sequences of the variscan paleozoic basement of the south portuguese zone based on the available geochemical and isotopic data the analysed water samples can be roughly divided into five main groups a group 1 corresponds to amd contaminated water drainages from the southern part of the catchment showing ph 8 marked depletions in so4 and heavy metals and displaying sr isotopic compositions similar to rainwater 87sr 86sr 0 7097 0 7098 c group 3 includes mixed type stream waters with ph and elemental isotopic signatures intermediate between those of groups 1 and 2 d group 4 comprises the samples collected at two lime treated water dams from the mining area that are clearly distinguished from the impacted waters of group 1 by their elevated ca mg and sr concentrations and low 87sr 86sr ratios 87sr 86sr 0 7085 0 7091 e group 5 includes clean waters from two dams located upstream of the ore processing site which are dominantly supplied by direct precipitation and surface runoff and have ph 6 very low so4 and metal concentrations and 87sr 86sr ratios varying between 0 7094 and 0 7108 variations in the 87sr 86sr ratios and sr concentrations of the analysed waters are attributed to mixing of two main end members atmospheric meteoric waters local rainfall runoff with low sr contents and 87sr 86sr ratios 0 7095 and more radiogenic waters derived from the aljustrel mining area the highly radiogenic signatures of the southern tributaries appear to have been controlled by weathering of plagioclase from the acid volcanic rocks of the paleozoic basement enhanced by mining activities pyrite oxidation although released strontium from gangue carbonates could have locally contributed to the fluctuations of sr contents and 87sr 86sr ratios observed in some of these water samples by contrast the low 87sr 86sr ratios and relatively high sr cl and na concentrations shown by the surface waters draining the northern compartment suggest that these tributaries correspond to meteoric waters that have gained cl na and sr through wash out of cenozoic deposits containing finely disseminated halite layers finally the decrease in the 87sr 86sr ratios and elevation of sr contents observed in the samples from the lime treated water dams support the involvement of an anthropogenic source of sr with 87sr 86sr ratios lower than that of rainfall

pb sr and nd isotopic features in organic matter from china and their implications for petroleum generation and migration to better understand processes and sources of crude oil and bitumen generation from kerogen rocks a comprehensive study of pb sr and nd isotopic systematics was undertaken for bitumen crude oil and kerogen from two large oil fields karamay and liaohe and two paleo oil deposits tarim and guizhou in china the bitumen samples from the karamay oil field have present day 143nd 144nd ratios pointing to a depleted mantle origin 0 5126 0 5130 they define a rb sr isochron age of 286 12 ma pb isotopic compositions for bitumen and crude oil from karamay liaohe and tarim all show features of crust mantle mixing they are evidently different from pb isotopic compositions of kerogen that occurred in the same strata of the various oil fields which mostly show crustal signatures sr isotopic compositions in crude oil from liaohe are consistent with those of carbonate sediments and volcanic rocks in island arc environments 0 7065 0 7100 radiometric isotope systems can be preserved in the bitumen with low vitrinite reflectance r0 0 5 and therefore allow us to date petroleum generation both isotopic data and the geologic setting of the oil fields indicate that petroleum generation was associated with fluid action from deep sources including the mantle lower crust and buried strata in rift basins and buried foreland basins at craton margins or subduction zones

application of multiple isotopic and geochemical tracers for investigation of recharge salinization and residence time of water in the souss massa aquifer southwest of morocco summary groundwater and surface water in souss massa basin in the west southern part of morocco is characterized by a large variation in salinity up to levels of 37 g l 1 the high salinity coupled with groundwater level decline pose serious problems for current irrigation and domestic water supplies as well as future exploitation a combined hydrogeologic and isotopic investigation using several chemical and isotopic tracers such as br cl 18 o 2 h 3 h 87 sr 86 sr 11 b and 14 c was carried out in order to determine the sources of water recharge to the aquifer the origin of salinity and the residence time of water stable isotope 3 h and 14 c data indicate that the high atlas mountains in the northern margin of the souss massa basin with high rainfall and low 18 o and 2 h values 6 to 8 and 36 to 50 is currently constitute the major source of recharge to the souss massa shallow aquifer particularly along the eastern part of the basin localized stable isotope enrichments offset meteoric isotopic signature and are associated with high nitrate concentrations which infer water recycling via water agricultural return flows the 3 h and 14 c data suggest that the residence time of water in the western part of the basin is in the order of several thousands of years hence old water is mined particularly in the coastal areas the multiple isotope analyses and chemical tracing of groundwater from the basin reveal that seawater intrusion is just one of multiple salinity sources that affect the quality of groundwater in the souss massa aquifer we differentiate between modern seawater intrusion salinization by remnants of seawater entrapped in the middle souss plains recharge of nitrate rich agricultural return flow and dissolution of evaporate rocks gypsum and halite minerals along the outcrops of the high atlas mountains the data generated in this study provide the framework for a comprehensive management plan in which water exploitation should shift toward the eastern part of the basin where current recharge occurs with young and high quality groundwater in contrast we argued that the heavily exploited aquifer along the coastal areas is more vulnerable given the relatively longer residence time of the water and salinization processes in this part of the aquifer

constraining groundwater recharge and the rate of geochemical processes using tritium and major ion geochemistry ovens catchment southeast australia summary constraining recharge is essential for understanding and managing groundwater systems this study uses high precision tritium 3 h concentrations together with major ion and environmental isotope sr c o h geochemistry to constrain rates of recharge and geochemical processes in the ovens catchment of the southeast murray basin australia 3 h concentrations of groundwater in the ovens catchment decline with depth but not with position in the catchment implying that recharge occurs over broad areas recharge rates calculated using an exponential piston flow model are 120 180 mm yr in the coarse grained alluvial gravels of the upper and middle ovens and 30 45 mm yr in the finer grained sediments of lower ovens these recharge rates are similar to those calculated from the response of shallow bore hydrographs to rainfall the geochemistry of groundwater with low 60 160 mg l total dissolved solids tds from the upper and middle ovens indicates that dissolution of both silicate minerals and calcite has occurred major ion geochemistry 87 sr 86 sr ratios and 13 c values in the upper and middle ovens groundwater are correlated with groundwater residence times and constrain the progress of mineral reactions dissolution of silicates with high 87 sr 86 sr ratios biotite and k feldspar occurs prior to dissolution of silicates with low 87 sr 86 sr ratios plagioclase and calcite mineral dissolution mainly occurs in the upper 20 m of the aquifer system with relatively little change in geochemistry deeper in the flow system groundwater from the lower ovens has higher tds contents 600 9600 mg l due to higher degrees of evapotranspiration although a correlation between tds and groundwater residence times exists it is more likely to reflect differential recharge rates and not the rate of evapotranspiration the conclusion that recharge occurs across the ovens catchment indicates that protection of groundwater from surface contamination is dependent on the protection and management of large areas

assessing response of local moisture conditions in central brazil to variability in regional monsoon intensity using speleothem 87 sr 86 sr values abstract delineating the controls on hydroclimate throughout brazil is essential to assessing potential impact of global climate change on water resources and biogeography an increasing number of monsoon reconstructions from 18 o records provide insight into variations in regional monsoon intensity over the last millennium the strength however of 18 o as a proxy of regional climate limits its ability to reflect local conditions highlighting the need for comparable reconstructions of local moisture conditions here speleothem 87 sr 86 sr values are developed as a paleo moisture proxy in central brazil to complement existing 18 o based reconstructions of regional monsoon intensity speleothem 87 sr 86 sr values are resolved using laser ablation and conventional solution mass spectrometry at high resolution relative to existing non 18 o based paleo moisture reconstructions to allow comparisons of centennial variability in paleo monsoon intensity and paleo moisture conditions variations in speleothem 87 sr 86 sr values from tamboril cave are interpreted to reflect varying extents of water interaction with the carbonate host rock with more interaction resulting in greater evolution of water isotope values from those initially acquired from the soil to those of the carbonate bedrock increasing speleothem 87 sr 86 sr values over the last millennium suggest progressively less interaction with the carbonate host rock likely resulting from higher infiltration rates expected under wetter conditions increasingly wetter conditions over the last millennium are consistent with an overall trend of increasing monsoon intensity decreasing 18 o values preserved in many existing 18 o records from the region such a trend however is absent in 18 o records from our site central brazil and cristal cave southeast brazil suggesting the existence of divergent relevant to 18 o precip shifts in the climate patterns within and outside the core monsoon region

hydrochemical assessment of the rochefort marsh role of surface and groundwater in the hydrological functioning of the wetland abstract the interaction between a wetland the rochefort agricultural marsh and its underlying aquifers was studied using both geochemical and isotopic approaches water from the various components of the hydrosystem water from ditches shallow bri groundwater silty clay deposits deep bri groundwater and groundwater in the kimmeridgian aquifer confined and unconfined was sampled and analysed for major and trace elements sr br stable water isotopes 18 o and 2 h and sr isotopes the salinity of groundwater in the marsh cl up to 15 5 g l can be attributed to seawater trapped in the clay sediments during the flandrian 12 000 6400 bp the groundwater has since undergone more or less major chemical evolution due to water rock interactions and mixing with fresh water rainwater ditch water and kimmeridgian groundwater from the edge of the marsh the chemical characteristics of the groundwater in the confined kimmeridgian underlying the bri formation exclude the possibility of a salt wedge the combined use of 18 o 2 h cl br and sr contents and 87 sr 86 sr ratios enabled exchanges between surface water in marsh canals and ditches and groundwater in the shallow bri aquifer 7 m and in the confined kimmeridgian 18 m aquifers to be defined and quantified during the summer the ditches recharge the shallow bri aquifer by sub irrigation gravity flow by up to 26 the presence of a very compact layer of clay 1 2 m deep prevents the rapid recharge of the deep bri aquifer by rainfall and direct hydraulic connections between the ditches and the deep bri aquifer on the scale of the marsh the confined kimmeridgian groundwater recharges the bri aquifer by upward flow maximum contribution estimated to be 76 13 this flow being relatively limited and preferentially on the edge of the marsh the deep bri groundwater contributes very locally to recharging the confined kimmeridgian aquifer maximum contribution estimated to be 61 36 this study demonstrates the interest in combining hydrological and geochemical tools in order to identify and quantify the hydraulic interconnections between a wetland and its groundwater components a prior understanding of how wetlands function is crucial for the sustainable management of such ecosystems

boron sr o and h isotope geochemistry of groundwaters from mt etna sicily hydrologic implications combined b o h and sr isotopic studies of groundwaters from mt etna provide new constraints on their origin and the consequences of fluid rock interaction within this hydrologic system variations in d 18 o 29 7 to 27 2 and d d 262 to 223 mainly lie along the regional meteoric water line and suggest that most waters originated as local precipitation however small shifts in d 18 o and variable 87 sr 86 sr 0 70355 to 0 70879 and d 11 b 25 2 to 125 8 indicate that subsequent interactions occurred between the fluids and local rocks high b cl ratios in all samples seemingly preclude direct involvement of seawater in the hydrologic system despite the proximity to the coast and in some samples elevated 87 sr 86 sr and d 11 b two general end member water types are recognized on the basis of their chemistry these apparently are produced by interactions of local meteoric waters with the dominant reservoir rocks either basaltic lavas of etna or the underlying sediments respectively high d 11 b in the sediment hosted end member points to a significant marine carbonate contribution subsequent mixing between these or similar end members produced a range of intermediate composition groundwaters certain anomalous water compositions require the presence locally of a distinct component with high b and moderate d 11 b ca 110 but relatively low 87 sr 86 sr an anthropogenic source for this component is plausible one unusual sample has b and sr isotopic compositions similar to the other volcanic rock hosted waters but anomalously high cl content that likely reflects local magmatic outgassing near this sampling locality in general this study indicates that groundwater b and sr isotopic compositions are rock dominated these data provide useful constraints on the origin and evolution of groundwaters copyright 2000 elsevier science ltd

fe and mn levels regulated by agricultural activities in alluvial groundwaters underneath a flooded paddy field abstract iron and mn concentrations in fresh groundwaters of alluvial aquifers are generally high in reducing conditions reflecting low so4 concentrations the mass balance and isotopic approaches of this study demonstrate that reduction of so4 supplied from agricultural activities such as fertilization and irrigation is important in lowering fe and mn levels in alluvial groundwaters underneath a paddy field this study was performed to investigate the processes regulating fe and mn levels in groundwaters of a point bar area which has been intensively used for flood cultivation four multilevel groundwater samplers were installed to examine the relationship between geology and the vertical changes in water chemistry the results show that fe and mn levels are regulated by the presence of no3 at shallow depths and by so4 reduction at the greater depths isotopic and mass balance analyses revealed that no3 and so4 in groundwater are mostly supplied from the paddy field suggesting that the fe and mn rich zone of the study area is confined by the agricultural activities for this reason the geologic conditions controlling the infiltration of agrochemicals are also important for the occurrence of fe mn rich groundwaters in the paddy field area

pyroxene selective impact smelting in ureilites abstract a characteristic feature of ureilite meteorites is reduction of feo but the reduction is usually confined to the rims of olivine in the lar 04315 lap 03587 and almahata sitta ureilites pyroxene was extensively reduced by impact smelting in lar 04315 the impact caused nearly all of the original pigeonite to melt or otherwise become sufficiently structurally compromised to allow smelting and yet a minor proportion of the pyroxene escaped smelting and survived with its original composition en 74 1 wo 10 2 olivine mosaicism confirms that lar 04315 experienced a major shock event the smelted pyroxenes also show a distinctive patchiness in their interference colors although each grain s basic optical continuity often including twinning is still discernible they also have reduced compositions are ubiquitously porous 15 and contain sprinklings of fe metal and felsic glass for the most part the olivine underwent only very slight reduction much of the small pyroxene component of lap 03587 shows the same oddly porous texture lar 04315 also contains large traces of silica and felsic glass with a typical composition of in wt 61 sio 2 23 al 2 o 3 11 cao 3 7 na 2 o glass these two phases together form selvages that line the walls of many of the largest voids in the rock silica is a by product of pyroxene smelting the felsic glass probably derives largely from interstitial basaltic melt that predated the impact however the comparatively stiff surrounding included silica may have promoted unusually high melt retention within lar 04315 through the smelting episode one aspect of which was a major stream out through the same large voids of co x gas the impact smelted pyroxene of lap 03587 is enigmatic because this ureilite also features little shocked euhedral graphite laths and no olivine mosaicism the fine grained ureilitic component of almahata sitta appears to have likewise formed by impact smelting but with more extensive melting of pyroxene especially a ca rich pyroxene component more pulverization and melting of olivine and more displacement of both however in places the original coarse equant ureilite texture is still discernible in relict form ordinarily an impact shock melts olivine before or at least no later than pyroxene but in the case of lar 04315 and lap 03587 the great shock event evidently occurred when the material was already anatectic or very nearly so and thus the difference in melting temperature between pyroxene and olivine 300 degrees lower for pyroxene was decisive if literature inferences of extremely fast cooling rates implying shallow burial depths are accurate the proportion of co x gas generated by ureilite smelting exceeded by a very large factor of order 10 3 but possibly much greater the volume represented as porosity in the final ureilites the outflow of so much gas may have by near surface explosive expansion and jetting enhanced the thoroughness of the impact triggered catastrophic impact disruption of the parent asteroid

chemical weathering of a soil chronosequence on granitoid alluvium ii mineralogic and isotopic constraints on the behavior of strontium the use of strontium isotopes to evaluate mineral weathering and identify sources of base cations in catchment waters requires an understanding of the behavior of sr in the soil environment as a function of time our approach is to model the temporal evolution of 87sr 86sr of the cation exchange pool in a soil chronosequence developed on alluvium derived from central sierra nevada granitoids during the past 3 ma with increasing soil age 87sr 86sr of ammonium acetate extractable sr initially decreases from values typical of k feldspar to those of plagioclase and hornblende and then remains constant even though plagioclase and hornblende are absent from the soils after approximately 1 ma of weathering the temporal variation of 87sr 86sr of exchangeable sr is modeled by progressively equilibrating sr derived from mineral weathering and atmospheric deposition with sr on exchange sites as waters infiltrate a soil column observed decreases in quartz normalized modal abundances of plagioclase hornblende and k feldspar with time and the distinct87sr 86sr values of these minerals can be used to calculate sr flux from weathering reactions hydrobiotites in the soils have nearly constant modal abundances chemistry and 87sr 86sr over the chronosequence and provide negligible sr input to weathering solutions the model requires time and soil horizon dependent changes in the amount of exchangeable sr and the efficiency of sr exchange as well as a biologic cycling term the model predicts that exchangeable sr initially has 87sr 86sr identical to that of k feldspar and thus could be dominated by sr leached from k feldspar following deposition of the alluvium the maximum value of 87sr 86sr observed in dilute stream waters associated with granitoids of the yosemite region is likewise similar to that of the k feldspars suggesting that k feldspar and not biotite may be the dominant source of radiogenic sr in the streams this study reveals that when attempting to use strontium isotopes to identify sources of base cations in catchment waters and biomass both preferential leaching of sr from minerals during incipient soil development and changing sr exchange efficiency must be considered along with chemical contributions due to mineral dissolution

importance of accessory minerals for the control of water chemistry of the pampean aquifer province of buenos aires argentina abstract the pampean aquifer in south east argentina is mainly constituted of loess like sediments these are clastic sediments mainly composed of quartz and aluminosilicates and calcrete concretions its hydrochemistry is generally studied assuming a chemical equilibrium between mineral phases and the aqueous fluids the phases forming the matrix of this aquifer are considered to be the reactive phases responsible for the chemistry of the groundwater in the present study batch dissolution experiments were performed on calcrete and loess to better understand the source of the pampean aquifer water chemistry and to measure the benefit of applying water rock interaction models that use kinetic rate laws instead of thermodynamic equilibria the different minerals composing the loess and calcrete samples were calculated using quantitative rietveld refinement of x ray powder diffraction xrd patterns this analysis showed that the major phases of loess are quartz 30 wt and feldspars 70 wt the main components of calcrete are calcite 95 wt and quartz 5 wt scanning electron microscopy with energy dispersive x ray microanalysis sem edxs was used to provide detailed information about the chemical composition of the powder samples revealing the presence of traces of minerals like halite barite and fluorapatite which were not detected by xrd the kinetic code kindis was used to carry out simulations using the minerals identified previously in their relative proportions to identify the signature of those geochemical phases on water chemistry experimental data from batch dissolution experiments were compared to simulated data this investigation showed that water reached pseudo steady state concentrations due to the presence of fast dissolving phases like halite barite gypsum plant phytolith these phases appeared to be of major importance in controlling the chemical composition of the pampean groundwater furthermore this work showed that the kindis software can be used on all kinds of aquifers as it is very easy to modify the parameters of the simulation to adapt it to numerous situations the modeling is a very important tool for thermodynamic and kinetic studies of groundwater chemistry it enables the prediction of water quality and can help to understand the impact of anthropic or natural contamination on the groundwater

strontium isotope geochemistry of groundwaters and streams affected by agriculture locust grove md the effects of agriculture on the isotope geochemistry of sr were investigated in two small watersheds in the atlantic coastal plain of maryland stratified shallow oxic groundwaters in both watersheds contained a retrievable record of increasing recharge rates of chemicals including no3 cl mg ca and sr that were correlated with increasing fertilizer use between about 1940 and 1990 the component of sr associated with recent agricultural recharge was relatively radiogenic 87sr 86sr 0 715 and it was overwhelming with respect to sr acquired naturally by water rock interactions in the oxidized non calcareous portion of the saturated zone agricultural groundwaters that penetrated relatively unoxidized calcareous glauconitic sediments at depth acquired an additional component of sr from dissolution of early tertiary marine caco3 87sr 86sr 0 708 while undergoing o2 reduction and denitrification ground water discharge contained mixtures of waters of various ages and redox states two streams draining the area are considered to have higher 87sr 86sr ratios and no3 concentrations than they would in the absence of agriculture however the streams have consistently different 87sr 86sr ratios and no3 concentrations because the average depth to calcareous reducing denitrifying sediments in the local groundwater flow system was different in the two watersheds the results of this study indicate that agriculture can alter significantly the isotope geochemistry of sr in aquifers and streams and that the effects could vary depending on the types sources and amounts of fertilizers added the history of fertilizer use and groundwater residence times

strontium isotopic composition of the po river dissolved load insights into rock weathering in northern italy abstract strontium isotopic composition 87sr 86sr of river water provides insight on the nature of rocks involved in the weathering processes and important constraints for reconstructing silicate versus carbonate weathering in large scale basins new data presented in the context of a geochemical map of the po river basin highlight that the po river water evolves from the upper part of the catchment where 87sr 86sr approaching 0 7097 relates to the weathering of igneous and metamorphic silicate rocks to the middle part where less radiogenic compositions 87sr 86sr 0 7089 are driven by the confluence of the tributaries draining mesozoic carbonate rocks of the south alpine domain and from inflow of apennine streams characterized by less radiogenic sr signatures due to weathering of marly sediments and mafic magmatic rocks down flow the sr isotopic compositions of po river water rises at 0 7091 either by the confluence of the last apennine tributary panaro 87sr 86sr 0 7095 and or by the possible contribution from hyporheic exchanges po river isotopic signatures reveal slightly more radiogenic 87sr 86sr in comparison to other important alpine river systems e g danube rhine and rhone likely suggesting that silicate rocks are comparatively contributing more weathering byproducts in the po basin

formation waters from mississippian pennsylvanian reservoirs illinois basin usa chemical and isotopic constraints on evolution and migration we have analyzed a suite of seventy four formation water samples from mississippian and pennsylvanian carbonate and siliciclastic strata in the illinois basin for major minor and trace element concentrations and for strontium isotopic composition a subset of these samples was also analyzed for boron isotopic composition data are used to interpret origin of salinity and chemical and sr isotopic evolution of the brines and in comparison with a similar data set from an earlier study of basin formation waters from silurian devonian reservoirs systematics of cl br na show that present mississippian pennsylvanian brine salinity can be explained by a combination of subaerial seawater evaporation short of halite saturation and subsurface dissolution of halite from an evaporite zone in the middle mississippian st louis limestone along with extensive dilution by mixing with meteoric waters additional diagenetic modifications in the subsurface interpreted from cation br ratios include k depletion through interaction with clay minerals ca enrichment and mg depletion by dolomitization and sr enrichment through caco3 recrystallization and dolomitization ste genevieve limestone middle mississippian formation waters show 87sr86sr ratios in the range 0 70782 0 70900 whereas waters from the siliciclastic reservoirs are in the range 0 70900 0 71052 inverse correlations between 87sr86sr and b li and mg concentrations suggest that the brines acquired radiogenic 87sr through interaction with siliciclastic minerals completely unsystematic relations between 87sr86sr and 1 sr are observed sr concentrations in ste genevieve and aux vases middle mississippian waters appear to be buffered by equilibrium with respect to srso4 although there are many similarities in their origin and evolution these formation waters are distinguished from silurian devonian brines in the basin by elevated clbr and nabr ratios and by unsystematic sr isotope relationships thus waters from these two major segments of the illinois basin stratigraphic column form distinct geochemical regimes which are separated by the new albany shale group devonian mississippian regional aquitard geochemical evolution appears to have been influenced significantly by paleozoic and mesozoic hydrologic flow systems in the basin

groundwater s dynamic role in regulating acidity and chemistry in a precipitation dominated lake abstract the role of groundwater in regulating the hydrologic and chemical regime ofan acid susceptible lake situated in a sandy silicate aquifer in northern wisconsin was determined by direct groundwater measurements using a network of 68 piezometers groundwater inputs were compared with precipitation and dryfall components of the hydrologic and chemical budgets for the lake groundwater contributed only 10 of the water to crystal lake in 1982 but was the major source of alkalinity calcium magnesium sodium potassium silicon and chloride precipitation contributed 90 of the water and was the major source of hydrogen and sulfate ions continuing analyses suggest that groundwater consistently supplies the bulk of the inoorganic constituents to the lake on annual basis the flux of groundwater and dissolved solids to the lake is highly seasonal with large pulses of groundwater inflow occuring after spring snowmelt and in the fall for certain nonconservative elements such as silicon the periodic influx of chemically concentrated groundwater can trigger significant changes in the chemical and biological balance in the lake despite the fact that the aquifer contains no carbonate minerals and the area experiences acid precipitation ph 4 6 the alkalinity of the small amount of groundwater entering crystal lake is more than enough to neutralize all of the acidity contributed by precipitation in lake sulfate reduction may generate an equal amount of alkalinity this buffering of ph helps to regulate aluminum concentrations at low levels thus minimizing potential aluminum toxicity in the lake most lakes in the region probably receive even larger amounts of alkalinity rich groundwater than crystal lake because most lie further downgradient in the regional flow system this may help to explain why most lakes in this acid susceptible area are no more acidic today than they were 50 years ago

seafloor fluid seeps on kimki ridge offshore southern california links to active strike slip faulting abstract the kimki ridge fluid seeps are located in western catalina basin about 60 km southwest of the southern california mainland and at a water depth of approximately 1100 m multichannel seismic reflection profiles collected by the u s geological survey usgs in 2014 show acoustic transparency within the kimki ridge suggesting the possibility of fluid seeps and possible sub seafloor fluid pathways subsequent multibeam bathymetric and backscatter intensity data collected during a cooperative university of washington usgs cruise in early 2016 show subtle seafloor buildups with high acoustic backscatter reflectivity in three places along kimki ridge supporting the existence of fluid seepage a remotely operated vehicle rov dive conducted as part of the nautilus exploration program took place in august 2016 to confirm the presence of these previously unknown seeps and document their characteristics as well as those of any associated biological communities two of the three seeps were explored by rov and showed abundant evidence of fluid seepage including characteristic algal mats chemosynthetic clams and authigenic carbonate formation the seeps are comprised of carbonate buildups 1 3 m thick and 300 500 m across within these areas we interpret broad crater like depressions 30 50 m across and 1 2 m deep to be individual seep vents the seep areas appear to be broad zones of diffuse seepage that support chemosynthetic biologic communities however active venting was not observed geochemical analyses of rock samples collected from the seeps indicate microbially driven anaerobic oxidation of methane at or near the sediment water interface seismic reflection profiles show chimney like fluid pathways along the limbs and in the axis of the fold forming kimki ridge and evidence of methane in shallow sediments can be traced into the adjacent catalina basin a system of closely spaced faults located at the axis of the kimki ridge anticline may serve as pathways to allow fluid flow to the seafloor our data are consistent with other studies that suggest that transpression is an important component in the formation and localization of fluid seeps in a strike slip setting implying that seep formation may be a common occurrence at fault stepovers or transpressional bends in strike slip systems

delineation of groundwater flow paths using hydrochemical and strontium isotope composition a case study in high arsenic aquifer systems of the datong basin northern china summary strontium isotopic compositions and major ion chemistry were used to delineate flow paths in an arsenic affected groundwater flow system in the datong basin china total of 28 samples including one spring and one river water were collected for major ions and strontium isotopic compositions and concentration analysis the ion ratios indicate that dissolution of silicates and carbonates is the dominant geochemical process controlling the hydrochemistry of groundwater from two recharge areas at the basin margins while the water chemistry in the center of the basin is affected by the dissolution of evaporites including gypsum and halite groundwater from eastern and western margin areas have relatively high 87 sr 86 sr values ranging from 0 72114 to 0 72604 and from 0 71119 to 0 71151 which are consistent with expected values for groundwater dominantly affected by dissolution of silicates however in the discharge area the groundwater samples had lower 87 sr 86 sr values and varied between 0 71016 and 0 71753 the contour map of 87 sr in groundwater shows the general tendency of decrease from the western and eastern margin areas to the discharge area the plot of 87 sr 86 sr vs sr na indicates that interactions between quaternary aquifer sediment and groundwater in the recharge areas along the flow paths control the hydrochemistry and strontium isotopic compositions of groundwater by contrast groundwater samples from the discharge area are plotted on the mixing line indicating that mixing of groundwater from recharge area with low 87 sr 86 sr values groundwater could be the controlling factor on their hydrochemistry and strontium isotopic compositions four main flow paths of groundwater were inferred from hydrochemical and isotopic data the results of phreeqc inverse modeling matched quite well with the results of strontium isotopic and ion compositions along the flow paths the distribution of high arsenic groundwater in this area could be attributed to the combined effect of the vertical flow and local groundwater flow on the redox conditions of the groundwater system

tracing effects of decalcification on solute sources in a shallow groundwater aquifer nw germany summary 87 sr values and ca sr ratios were employed to quantify solute inputs from atmospheric and lithogenic sources to a catchment in nw germany the aquifer consists primarily of unconsolidated pleistocene eolian and fluviatile deposits predominated by 90 quartz sand accessory minerals include feldspar glauconite and mica as well as disperse calcium carbonate in deeper levels decalcification of near surface sediment induces groundwater ph values up to 4 4 that lead to enhanced silicate weathering consequently low mineralized ca na cl and ca cl groundwater types are common in shallow depths while in deeper located calcareous sediment ca hco 3 type groundwater prevails 87 sr values and ca sr ratios of the dissolved pool range from 7 3 to 2 6 and 88 to 493 respectively positive 87 sr values and low ca sr ratios indicate enhanced feldspar dissolution in shallow depths of less than 20 m below soil surface bss while equilibrium with calcite governs negative 87 sr values and elevated ca sr ratios in deep groundwater 30 m bss both positive and negative 87 sr values are evolved in intermediate depths 20 30 m bss for groundwater that is undersaturated with respect to calcite atmospheric supplies range from 4 to 20 while feldspar weathering accounts for 8 26 and calcium carbonate for 62 90 of dissolved sr 2 in contrast more than 95 of sr 2 is derived by calcium carbonate and less than 5 by feldspar dissolution in ca hco 3 type groundwater the surprisingly high content of carbonate derived sr 2 in groundwater of the decalcified portion of the aquifer may account for considerable contributions from ca containing fertilizers complementary tritium analyses show that equilibrium with calcite is restricted to old groundwater sources

the use of strontium and lead isotopes to identify sources of water beneath the fresh kills landfill staten island new york usa abstract a study was undertaken to explore whether the isotopic compositions of pb and sr are useful to distinguish mixtures of uncontaminated groundwater seawater and landfill leachate at the fresh kills landfill staten island new york ratios of 87sr 86sr ranged from 0 7088 to 0 7137 and could be used to distinguish sr that was derived from seawater from that in uncontaminated groundwater lead isotopic abundances did not vary systematically among the different water sources plots of 87sr 86sr versus dissolved organic c b and nh4 defined perpendicular trends documenting where leachate or sea water mixed with uncontaminated groundwater and demonstrating that leachate has not contaminated groundwater in aquifers beneath the landfill

characterization of calcium isotopes in natural and synthetic barite abstract the mineral barite baso4 accommodates calcium in its crystal lattice providing an archive of ca isotopes in the highly stable sulfate mineral holocene marine pelagic barite samples from the major ocean basins are isotopically indistinguishable from each other 44 40ca 2 01 0 15 but are different from hydrothermal and cold seep barite samples 44 40ca 4 13 to 2 72 laboratory precipitated synthetic barite samples are more depleted in the heavy ca isotopes than pelagic marine barite and span a range of ca isotope compositions 44 40ca 3 42 to 2 40 temperature saturation state a ba 2 a so 4 2 and aca2 aba2 each influence the fractionation of ca isotopes in synthetic barite however the fractionation in marine barite samples is not strongly related to any measured environmental parameter first principles lattice dynamical modeling predicts that at equilibrium ca substituted barite will have much lower 44ca 40ca than calcite by 9 at 0 c and 8 at 25 c based on this model none of the measured barite samples appear to be in isotopic equilibrium with their parent solutions although as predicted they do record lower 44 40ca values than seawater and calcite kinetic fractionation processes therefore most likely control the extent of isotopic fractionation exhibited in barite potential fractionation mechanisms include factors influencing ca2 substitution for ba2 in barite e g ionic strength and trace element concentration of the solution competing complexation reactions precipitation or growth rate temperature pressure and saturation state as well as nucleation and crystal growth rates these factors should be considered when investigating controls on isotopic fractionation of ca2 and other elements in inorganic and biogenic minerals

constraining groundwater flow residence times inter aquifer mixing and aquifer properties using environmental isotopes in the southeast murray basin australia environmental isotopes particularly d 18 o d 2 h and d 13 c values 87 sr 86 sr ratios and a 14 c constrain geochemical processes recharge distribution and rates and inter aquifer mixing in the riverine province of the southern murray basin due to methanogenesis and the variable d 13 c values of matrix calcite d 13 c

strontium isotope geochemistry of groundwater in the central part of the dakota great plains aquifer usa abstract the dakota aquifer of the central and eastern great plains of the united states is an important source of water for municipal supplies irrigation and industrial use although the regional flow system can be characterized generally as east to northeasterly from the rocky mountains towards the missouri river locally the flow systems are hydrologically complex this study uses sr isotopic data from groundwater and leached aquifer samples to document the complex subsystems within the dakota aquifer in nebraska and kansas the interaction of groundwater with the geologic material through which it flows has created spatial patterns in the isotopic measurements that are related to long term water rock interaction during which varying degrees of isotopic equilibrium between water and rock has been achieved and the alteration of nacl fluids by water rock interaction specifically sr isotopic data distinguish brines from kansas and western nebraska from those in eastern nebraska the former are interpreted to reflect interaction with permian rocks whereas the latter record interaction with pennsylvanian rocks the sr isotopic composition of groundwater from other parts of nebraska and kansas are a function of the dynamic interaction between groundwater and unlithified sediments e g glacial till and loess followed by interaction with oxidized and unoxidized sediments within the dakota formation this study illustrates the power of combining sr chemistry with more conventional geochemical data to obtain a more complete understanding of groundwater flow systems within regional aquifer systems where extensive monitoring networks do not exist

investigation of a dynamic seawater intrusion event using strontium isotopes 87sr 86sr summary a seawater intrusion experiment was carried out in a shallow coastal unconfined aquifer at skansehage denmark the aquifer consists of 6 10 m of postglacial holocene eolian and marine sands and gravels resting on pleistocene glacial sequence of tills and glacio fluviatile sediments on a basement of palaeocene danian limestone stable isotopes 18 o and 2 h strontium isotopes 87 sr 86 sr and the elements sr and cl were measured to delineate the mixing of seawater and groundwater in the shallow aquifer and to determine the contribution from different water sources along the flow paths the stable isotopes reflect recharge conditions and mixing between groundwater and seawater the 87 sr 86 sr isotope ratios are controlled by aquifer matrix chemistry the 87 sr 86 sr ratio distribution and sr content reveal a ternary mixing system in the shallow aquifer encompassing brackish seawater fresh shallow groundwater and deep groundwater from the underlying limestone aquifer as end members a mixing analysis is performed using the cl contents and the 87 sr 86 sr ratios the mixing analysis indicates a zone with leakage of deep groundwater from the limestone aquifer into the lower part of the shallow sandy aquifer through the pleistocene sedimentary sequence the upper part of the sandy aquifer is thoroughly dominated by mixing processes between infiltrating fresh groundwater and brackish seawater from isefjord prior to the intrusion experiment there appeared to be limited mixing between the upper and lower part of the water body in the shallow sandy aquifer the leakage of deep groundwater increased during the intrusion experiment as a result of the large abstraction of groundwater following the ceasing of the groundwater pumping the interface went from being vertical to being predominantly horizontal due to density flow as a consequence the deep groundwater from the limestone aquifer was pushed by the seawater into the upper part of the aquifer to mix with the upper fresh groundwater

hydrogeochemical evolution of confined groundwater in northeastern osaka basin japan estimation of confined groundwater flux based on a cation exchange mass balance method abstract a confined aquifer system has developed in argillaceous marine and freshwater sediments of pliocene holocene age in the northeastern osaka basin neob in central japan the shallow groundwater 3 type water which changes as it flows toward the sw to mg hco 3 type and then to na hco 3 type water comparison of the chemical and sr isotopic compositions of the groundwater with those of the bulk and exchangeable components of the underground sediments indicates that elements leached from the sediments contribute negligibly to the neob aquifer system moreover model calculations show that contributions of paleo seawater in the deep horizon and of river water at the surface are not major factors of chemical change of the groundwater instead the zonal pattern of the hco 3 dominant groundwater is caused by the loss of ca 2 from the water as it is exchanged for mg 2 in clays followed by loss of mg ca as they are exchanged for na k in clays between the ca hco 3 type recharge water and the exchangeable cations in the clay layers which were initially enriched in na part of this process was reproduced in a chromatographic experiment in which na type water with high 87 sr 86 sr was obtained from mg type water with low 87 sr 86 sr by passing it through marine clay packed in a column the flux of recharge water into the confined aquifer system according to this chromatographic model is estimated to be 0 99 mm day which is compatible with the average recharge flux to unconfined groundwater in japan 1 mm day

anhydrite and the sr isotope evolution of groundwater in a carbonate aquifer major element concentrations and 87 sr 86 sr ratios were measured in groundwaters and bedrock from the madison aquifer in western south dakota in this region the madison aquifer is primarily comprised of dolomite belonging to the madison limestone group the purpose of the study was to investigate controls on the downgradient evolution of dissolved sr 2 in a carbonate groundwater system that is recharged by waters with high 87 sr 86 sr ratios draining precambrian basement rocks and to establish the sources of sr 2 added to the waters by reaction with the aquifer lithology a mass balance model following previous workers was used to calculate amounts and effective rates of mineral dissolution and precipitation during groundwater transport along a 240 km flow path both the calculated reaction rates and data for the sr isotope geochemistry of the reacting phases were then used to develop a self consistent and quantitative description of the concentration and isotopic composition of dissolved sr 2 in the aquifer waters the major ion chemistry of madison aquifer groundwater is known to evolve according to dolomite dissolution anhydrite dissolution calcite precipitation and ion exchange with clay minerals dissolved 87 sr 86 sr ratios in the madison aquifer decrease downgradient input waters draining the igneous black hills have 87 sr 86 sr ratios of 0 723 while highly evolved waters in the aquifer have 87 sr 86 sr ratios of 0 708 dissolved sr 2 concentrations undergo a concurrent increase from 1200 to 66 000 nmol l model results indicate that dolomite dissolution exerts a critical control on the major ion chemistry but is not the primary source of nonradiogenic sr 2 as both the dissolution rate and sr concentration of dolomite are very low anhydrite is readily soluble in water has a low 87 sr 86 sr ratio 0 708 and a very high sr concentration 50 000 nmol g anhydrite is also greatly undersaturated in the groundwaters and the downgradient evolution of sr 2 accompanies an 80 fold increase in dissolved so 4 2 while anhydrite has a very low abundance in the aquifer rocks the flow model indicates that anhydrite dissolution provides 300 times more sr 2 per liter of water relative to dolomite dissolution these findings suggest that anhydrite dissolution governs the sr 2 geochemistry of madison aquifer groundwaters whereas dolomite dissolution and calcite precipitation control the bulk chemistry lastly it is shown that the calculation of net mineral masses transferred to solution requires very high relative proportions of anhydrite and clay to dolomite mineral masses obtained by this approach actually represent bulk contributions without consideration of the intrinsic reaction rates of the phases or their modal abundances in the aquifer rocks however consideration of these parameters in a transport equation for flow through porous media shows that the high apparent abundances are not a real requirement this latter approach is consistent with laboratory experiments and indicates that as little as 0 04 wt of very soluble anhydrite and 0 3 wt of exchangeable clay in the aquifer rock are sufficient to produce the observed groundwater chemistry in most of the flow path

strontium 87 strontium 86 as a tracer of mineral weathering reactions and calcium sources in an alpine subalpine watershed loch vale colorado sr isotopic ratios of atmospheric deposition surface and subsurface water and geologic materials were measured in an alpine subalpine watershed to characterize weathering reactions and identify sources of dissolved ca in stream water previous studies have noted an excess of ca in stream water above that expected from stoichiometric weathering of the dominant bedrock minerals mixing calculations based on 87 sr 86 sr indicate that on an annual basis 26 67 of ca export in streams is atmospherically derived 23 61 is from weathering of plagioclase and the remainder is from weathering of calcite present in trace amounts in the bedrock a potential source of error when applying sr isotopes in catchment studies is determination of the 87 sr 86 sr of sr released by mineral weathering which is complicated by the wide range of mineral isotopic compositions particularly in older rocks and the variable rates at which the minerals weather in this study base flow stream chemistry was used to represent the 87 sr 86 sr of sr derived from mineral weathering because it effectively integrates the potentially variable isotopic composition of sr released by weathering in the alpine environment

hydrochemical variation in the springs water between jerusalem ramallah mountains and jericho fault palestine the spatial and temporal changes of the composition of the groundwater from the springs along the wadi qilt stream running from the jerusalem ramallah mountains towards the jericho plain is studied during the hydrological year 2006 2007 the residence time and the intensity of recharge play an important role in controlling the chemical composition of spring water which mainly depends on distance from the main recharge area a very important factor is the oxidation of organics derived from sewage and garbage resulting in variable dissolved co2 and associated hco3 concentration high co2 yields lower ph values and thus under saturation with respect to calcite and dolomite low co2 concentrations result in over saturation only at the beginning and at the end of the rainy season calcite saturation is achieved the degradation of dissolved organic matter is a major source for increasing water hardness besides dissolution of carbonates dissolved species such as nitrate chloride and sulfate are leached from soil and aquifer rocks together with only small amounts of mg mg not only originates from carbonates but also from mg cl waters are leached from aquifer rocks leaching of mg cl brines is particularly high at the beginning of the winter season and lowest at its end two zones of recharge are distinguishable zone 1 represented by ein fara and ein qilt is fed directly through the infiltration of meteoric water and surface runoff from the mountains along the eastern mountain slopes with little groundwater residence time and high flow rate the second zone is near the western border of jericho at the foothills which is mainly fed by the under groundwater flow from the eastern slopes with low surface infiltration rate this zone shows higher groundwater residence time and slower flow rate than zone 1 groundwater residence time and the flow rate within the aquifer systems are controlled by the geological structure of the aquifer the amount of active recharge to the aquifer and the recharge mechanism the results of this study may be useful in increasing the efficiency of freshwater exploitation in the region some precautions however should be taken in future plans of artificial recharge of the aquifers or surface water harvesting in the wadi because of evaporation and associated groundwater deterioration the runoff water should be artificially infiltrated in zones of wadis with high storage capacity of aquifers natural infiltration along the wadis lead to evaporation losses and less quality of groundwater

strontium and its isotopes in canadian rivers fluxes and global implications systematic sampling of the 39 largest canadian rivers shows that the weighted average 87sr86sr ratio in the dissolved load is 0 7111 similar to previous measurements on such large rivers as the amazon and mississippi consequently we believe that the above estimate is likely representative of the global average this imposes a limit of 6 5 1011g yr 1 on the amount of sr exchanged with basalts in hydrothermal cells on mid oceanic ridges evaluation of geological information suggests that sr from silicate sources is of considerable importance for all but the largest canadian rivers the latter have chemical and isotopic composition consistent with 4 1 carbonate vs silicate derivation of sr but such interpretation is not unique in terms of their water discharge the 39 canadian rivers studied account for 4 2 of the world total and their weighted average concentrations for other dissolved solutes are tds 176 ppm ca 18 ppm cl 6 8 ppm and sr 84 ppb

kinetic and mineralogic controls on the evolution of groundwater chemistry and 87sr 86sr in a sandy silicate aquifer northern wisconsin usa abstract substantial flowpath related variability of 87sr 86sr is observed in groundwaters collected from the trout lake watershed of northern wisconsin in the extensive shallow aquifer composed of sandy glacial outwash groundwater is recharged either by seepage from lakes or by precipitation that infiltrates the inter lake uplands 87sr 86sr of groundwater derived mainly as seepage from a precipitation dominated lake near the head of the watershed decreases with progressive water chemical evolution along its flowpath due primarily to enhanced dissolution of relatively unradiogenic plagioclase in contrast 87sr 86sr of groundwater derived mainly from precipitation that infiltrates upland areas is substantially greater than that of precipitation collected from the watershed due to suppression of plagioclase dissolution together with preferential leaching of sr from radiogenic phases such as k feldspar and biotite the results of a column experiment that simulated the effects of changing residence time of water in the aquifer sand indicate that mobile waters obtain relatively unradiogenic sr whereas stagnant waters obtain relatively radiogenic sr nearly the entire range of strontium isotope composition observed in groundwaters from the watershed was measured in the experimental product waters the constant mobility of water along groundwater recharge flowpaths emanating from the lakes promotes the dissolution of relatively unradiogenic plagioclase perhaps due to effective dispersal of clay mineral nuclei resulting from dissolution reactions in contrast episodic stagnation in the unsaturated zone along the upland recharge flowpaths suppresses plagioclase dissolution perhaps due to accumulation of clay mineral nuclei on its reactive surfaces differences in redox conditions along these contrasting flowpaths probably enhance the observed differences in strontium isotope behavior this study demonstrates that factors other than the calculated state of mineral saturation must be considered when attempting to simulate chemical evolution along flowpaths and that reaction models must be able to incorporate changing contributions from reacting minerals in the calculations

mineral dissolution in the cape cod aquifer massachusetts usa i reaction stoichiometry and impact of accessory feldspar and glauconite on strontium isotopes solute concentrations and rey distribution abstract to compare relative reaction rates of mineral dissolution in a mineralogically simple groundwater aquifer we studied the controls on solute concentrations sr isotopes and rare earth element and yttrium rey systematics in the cape cod aquifer this aquifer comprises mostly carbonate free pleistocene sediments that are about 90 quartz with minor k feldspar plagioclase glauconite and fe oxides silica concentrations and ph in the groundwater increase systematically with increasing depth while sr isotopic ratios decrease no clear relationship between 87sr 86sr and sr concentration is observed at all depths the 87sr 86sr ratio of the groundwater is considerably lower than the sr isotopic ratio of the bulk sediment or its k feldspar component but similar to that of a plagioclase rich accessory separate obtained from the sediment the si 87sr 86sr depth relationships are consistent with dissolution of accessory plagioclase in addition solutes such as sr ca and particularly k show concentration spikes superimposed on their respective general trends the k sr 87sr 86sr systematics suggests that accessory glauconite is another major solute source to cape cod groundwater although the authigenic glauconite in the cape cod sediment is rich in rb it is low in in grown radiogenic 87sr because of its young pleistocene age the low 87sr 86sr ratios are consistent with equilibration of glauconite with seawater the impact of glauconite is inferred to vary due to its variable abundance in the sediments in the cape cod groundwater the variation of rey concentrations with sampling depth resembles that of k and rb but differs from that of ca and sr shale normalized rey patterns are light rey depleted show negative ce anomalies and super chondritic y ho ratios but no eu anomalies rey input from feldspar therefore is insignificant compared to input from a k rb bearing phase inferred to be glauconite these results emphasize that interpretation of groundwater chemistry even in relatively simple aquifers may be complicated by solute contributions from exotic accessory minerals such as glauconite to detect such peculiarities groundwater studies should combine the study of elemental concentration and isotopic composition of several solutes that show different geochemical behavior

the geochemistry of groundwater resources in the jordan valley the impact of the rift valley brines the chemical composition of groundwater in the jordan valley along the section between the sea of galilee and the dead sea is investigated in order to evaluate the origin of the groundwater resources and in particular to elucidate the role of deep brines on the chemical composition of the regional groundwater resources in the jordan valley samples were collected from shallow groundwater in research boreholes on two sites in the northern and southern parts of the jordan valley adjacent to the jordan river data is also compiled from previous published studies geochemical data e g br cl na cl and so4 cl ratios and b o sr and s isotopic compositions are used to define groundwater groups to map their distribution in the jordan valley and to evaluate their origin the combined geochemical tools enabled the delineation of three major sources of solutes that differentially affect the quality of groundwater in the jordan valley 1 flow and mixing with hypersaline brines with high br cl 2 10 3 and low na cl 0 8 ratios 2 dissolution of highly soluble salts e g halite gypsum in the host sediments resulting in typically lower br cl signal 2 10 3 and 3 recharge of anthropogenic effluents primarily derived from evaporated agricultural return flow that has interacted e g base exchange reactions with the overlying soil it is shown that shallow saline groundwaters influenced by brine mixing exhibit a north south variation in their br cl and na cl ratios this chemical trend was observed also in hypersaline brines in the jordan valley which suggests a local mixing process between the water bodies

dissolution rates and vadose zone drainage from strontium isotope measurements of groundwater in the pasco basin wa unconfined aquifer abstract strontium isotope ratios 87sr 86sr measured in groundwater samples from 273 wells in the pasco basin unconfined aquifer below the us department of energy hanford site show large and systematic variations that provide constraints on groundwater recharge weathering rates for saturated zone dissolution of the aquifer host rocks communication between unconfined and deeper confined aquifers and vadose zone groundwater interaction the impact of millions of cubic meters of wastewater discharged to the vadose zone 103 105 times higher than ambient drainage shows up strikingly on maps of groundwater 87sr 86sr extensive access through the many groundwater monitoring wells at the site allows for an unprecedented opportunity to evaluate the strontium geochemistry of a major aquifer hosted primarily in unconsolidated sediments and relate it to both long term properties and recent disturbances groundwater 87sr 86sr increases systematically from 0 707 to 0 712 from west to east across the hanford site in the general direction of groundwater flow as a result of addition of sr from the weathering of aquifer sediments and from diffuse drainage through the pasco basin vadose zone the lower 87sr 86sr groundwater reflects recharge waters that have acquired sr from columbia river basalts based on a steady state model of sr reactive transport and drainage there is an average natural drainage flux of 0 1 4 mm yr near the western margin of the hanford site and ambient drainage may be up to 30 mm yr in the center of the site assuming an average bulk rock weathering rate of 10 7 5 g g yr the weathering rates cannot be higher than those assumed by more than a factor of 2 3 in order to match sr isotope data

87sr 86sr as a tracer of groundwater discharge and precipitation recharge in the glacial lake agassiz peatlands northern minnesota a contrast in the 87sr 86sr ratio of atmospherically derived sr 0 710 and sr from regional bedrock 0 730 allows quantification of the proportions of precipitation recharge and groundwater discharge into peat columns of bogs and fens in the glacial lake agassiz peatlands two contrasting bog fen pairs were studied the lost river peatland located over a regional groundwater discharge zone and the red lake peatland situated atop a hydrologic divide where recharge is expected to occur bog pore waters consist of 90 100 precipitation in the upper 2 m below which they mix with groundwater adjacent fens consist mostly of groundwater ranging from 30 near the surface to 100 with depth at the red lake peatland mixing relations suggest an additional sr source that may be peat mineralization distinct 87sr 86sr and ca sr ratios for groundwater discharging into bog and fen sites are indicative of distinct groundwater sources and are likely indicative of flow paths at two different length scales

the transport and fate of fe mn cu zn cd pb and so4 in a groundwater plume and in downstream surface waters in the coeur d alene mining district idaho u s a abstract the controls on metal concentrations in a plume of acidic ph 3 29 5 55 groundwater in the moon creek watershed in idaho u s a were investigated with the use of property property plots a plot of ca vs s demonstrated that a plume of contaminated groundwater was being diluted by infiltration of rain and creek water at shallow depths and by ambient groundwater near bedrock the small amount of dissolved fe 2 1 mg l was removed while dissolved pb was added reaching a maximum concentration of 0 37 mg l the other metals zn 16 al 6 2 cu 2 1 and cd 0 077 mg l in the shallow groundwater were essentially conserved until they emerged as a seep along the creek bank upon mixing with the creek water groundwater was diluted by factors between 11 and 50 and the ph of the mixture became neutral metals originating from the contaminated groundwater were removed in the creek in the following order fe al pb cu mn zn cd pb and cu continued to be removed from solution even as the creek passed adjacent to a tailings pile in contrast zn concentrations in the creek increased adjacent to the tailings area presumably as a result of the reemergence of the upgradient plume as the creek lost elevation below the tailings dam contaminated creek water 400 800 g zn l was diluted by both smaller side streams and a creek of equal flow the presence of 3 distinctive water masses required the use of two tracers dissolved si and s to distinguish between mixing and geochemical reactions the removal of metals was greater during low flow conditions pb was removed to the greatest extent falling below detection limits 0 5 l at the first sampling location copper and mn were removed to a lesser extent during low flow conditions and approached conservative behavior during high flow conditions during a 5 km journey through two hydrological regimes less than 10 of the dissolved zn and cd was lost

isotopic identification of natural vs anthropogenic sources of pb in laramie basin groundwaters wyoming usa water well samples precipitation and leachates of aquifer rock samples from the laramie basin wyoming were analyzed to test the suitability of pb isotopes for tracing hydrologic processes in a basin where sr isotopes had proven effective leachable pb from host rocks to aquifers in this basin have isotopically distinct compositions and isotopic tracing would be effective in differentiating natural sources of pb however in almost all cases this natural signal is apparently swamped by anthropogenic pb sources in drilled water wells the isotopic compositions of these samples cannot be produced by any combination of pb in precipitation and leached pb from the aquifers alone but are consistent with mixtures of anthropogenic pb thorogenic 208pb vs uranogenic 206pb 207pb pb was especially useful for discriminating natural from anthropogenic sources for these samples it is strongly recommended that all four pb isotopes be reported in hydrologic and environmental studies that employ this approach

strontium isotopic evolution of oil field waters from carbonate reservoir rocks in bindley field central kansas u s a abstract oil field waters produced from mississippian carbonate reservoir rocks in bindley field kansas had an average salinity of about 42 8 mg l they were enriched in ca sr na k rb and li and depleted in mg relative to sea water at the same level of either cl or br concentration the average abundances of different elements are as follows na 13 460 mg l k 325 mg 1 rb 0 9 mg l li 12 mg l ca 1 515 mg l sr 42 mg l mg 430 mg l cl 23 000 mg l so4 2 630 mg l br 32 mg l the 87 sr 86 sr values of the waters ranged between 0 7221 and 0 7230 whereas the values of the host carbonate rocks were between 0 7090 and 0 7093 the very high 87 sr 86 sr values of the waters probably occurred as a result of their reaction with alkali feldspar minerals in buried precambrian crystalline rocks to the east of the bindley field the study demonstrates that despite their residence in carbonate reservoir rocks oil field waters can retain sufficiently distinct isotopic memory that may provide important dues about mineral water interactions in the chemical evolutionary history of the waters the study further indicates that very late diagenetic reactions in many carbonate rocks are of minor extent difference in the sr isotopic data among the oil field waters suggests that the sr isotopic data can be used as a reliable guide in recognising existence of separate pools in an oil field

geochemical and isotopic characteristics of shallow groundwater within the lake qinghai catchment ne tibetan plateau abstract major ions isotopic ratios of strontium 87 sr 86 sr hydrogen d and oxygen 18 o of groundwater samples were analyzed to decipher spatial variation controlling factors solute sources and the recharge source of shallow groundwaters within the lake qinghai catchment shallow groundwaters in this area are slightly alkaline with 97 being fresh water of good quality though there are high concentrations of nitrate and sulfide in buha and lakeside groundwaters most of the shallow groundwaters are of the ca 2 hco 3 type whereas part of groundwaters surrounding the lake ls belongs to the na cl type as lake water qhl groundwater geochemistry is controlled by regional lithological association ion exchange and mineral precipitation the dissolved sr concentrations and 87 sr 86 sr ratios vary from 1 0 to 15 6 mol l and from 0 709859 to 0 715779 respectively the first quantitative calculation in groundwater using a forward model shows that 40 of dissolved sr is from carbonate weathering 33 from evaporite dissolution 17 from silicate weathering and the remainder from atmospheric input for the whole catchment carbonate weathering dominates groundwater geochemistry in shaliu sl hargai hg and buha bh samples while evaporite dissolution dominates ls and daotang dt samples d and 18 o data show that rain water is the major recharge source of both river water and shallow groundwater within the lake qinghai catchment qinghai lake water is characterized by buha type water but its sr geochemistry is different from the shallow groundwater due to carbonate precipitation although shallow groundwater contributes 5 of the dissolved sr to the qhl groundwater must be taken into account when the chemistry and budget of lake water are characterized

implications of carbonate like geochemical signatures in a sandstone aquifer radium and strontium isotopes in the cambrian jordan aquifer minnesota usa water rock interaction in sandstone aquifers can potentially mobilize u and th series radionuclides resulting in elevated levels of radioactive constituents such as radium ra in groundwater previous studies have delineated the sources of ra in groundwater by assuming that 228ra 226ra of groundwater parallels the 232th 238u activity ratio of aquifer solids we present an integrated geochemical and isotopic study of groundwater and aquifer solids for major and trace elements radium 224ra 226ra 228ra strontium isotopes 87sr 86sr and tritium in the cambrian jordan quartz sandstone aquifer of southeastern minnesota usa the jordan aquifer part of the cambrian ordovician aquifer system of the upper midwestern usa is characterized by a wide range of ra activities in groundwater uniform ca mg hco3 major element composition and patterns in 87sr 86sr indicate that interaction with carbonate minerals controls water chemistry at least one contributing sr source is radiogenic yielding 87sr 86sr ratios up to 0 71347 radium 226 activities exhibit especially large variations 1 418 mbq l 1 and the highest radium activities occupy a 100 km long north south region consistent with the carbonate like elemental and sr isotope signatures 226ra activity median 85 mbq l 1 is higher than 228ra median 47 mbq l 1 yielding low 228ra 226ra ratios median 0 5 that would be expected from a lithology preferentially containing u relative to th such as carbonate rocks collectively results indicate the primary source of radium to the aquifer is alpha recoil from aquifer solids rather than external inputs of high ra waters indicated by 1 similar 228ra 226ra ratios in aquifer solids and groundwater including low carbonate like values in the high 226ra samples 2 some association between whole rock 226ra levels and groundwater 226ra activities and 3 groundwater 224ra 228ra averaging near unity furthermore hydrogeologic setting e g presence or absence of overlying carbonate units is inconsistent with systematic inputs of high ra waters from overlying carbonate aquifers the most proximate source of carbonate material in the sandstone aquifer seems to be the calcite and dolomite cement that yields different geochemical and isotopic fingerprints than silicate minerals would impart whole rock 226ra 238u 1 implies that any u enrichment in the carbonate cement occurred at least 350 000 years ago high groundwater ra activities relative to solids are attributable to anoxic conditions that play a role in maintaining inefficient radium removal for a fresh groundwater system indicated by the estimated dimensionless whole rock ra distribution coefficient of 150 920 median 560 coprecipitation of ra into barite is a potential but unquantified ra removal mechanism overall radium in the jordan aquifer provides an example of a naturally occurring trace element of health significance that may be derived not mainly from the quartz sandstone matrix but from carbonate material such as calcite and dolomite cement especially when combined with complementary tracers such as 87sr 86sr this study demonstrates the usefulness of the 228ra 226ra ratio as an indicator of the key mineral phases silicate vs carbonate involved in supplying radium to groundwater

trace elements and environmental isotopes as tracers of surface water groundwater interaction a case study at xin an karst water system shanxi province northern china in this case study silica concentration oxygen and strontium isotopes of water samples were used to study surface water groundwater interaction at the xin an karst water system the silica concentration in rain water is commonly less than 1 mg l in the areas around the south tributary of the zhuozhang river silica concentrations in the groundwater in quaternary aquifers range between 4 04 and 7 66 mg l while that of the surface water varies from 1 49 to 6 9 mg l silica concentrations of most surface water samples increase with tds indicating the effect of groundwater recharge on river water chemistry on the contour map of silica concentration of groundwater in quaternary aquifers samples located close to surface water often have lower silica concentrations as a result of surface water recharge both overland flow and surface water have impact on karst water according to our hydrogeochemical study of stable oxygen isotope sr isotope and strontium contents calculation results of three end member mixing model show that the contribution of karst water surface water and overland flow water is 45 28 and 27 respectively

obtaining parsimonious hydraulic conductivity fields using head and transport observations a bayesian geostatistical parameter estimation approach 1 flow path delineation is a valuable tool for interpreting the subsurface hydrogeochemical environment different types of data such as groundwater flow and transport inform different aspects of hydrogeologic parameter values hydraulic conductivity in this case which in turn determine flow paths this work combines flow and transport information to estimate a unified set of hydrogeologic parameters using the bayesian geostatistical inverse approach parameter flexibility is allowed by using a highly parameterized approach with the level of complexity informed by the data despite the effort to adhere to the ideal of minimal a priori structure imposed on the problem extreme contrasts in parameters can result in the need to censor correlation across hydrostratigraphic bounding surfaces these partitions segregate parameters into facies associations with an iterative approach in which partitions are based on inspection of initial estimates flow path interpretation is progressively refined through the inclusion of more types of data head observations stable oxygen isotopes 18o 16o ratios and tritium are all used to progressively refine flow path delineation on an isthmus between two lakes in the trout lake watershed northern wisconsin united states despite allowing significant parameter freedom by estimating many distributed parameter values a smooth field is obtained