natural uranium and strontium isotope tracers of water sources and surface water groundwater interactions in arid wetlands pahranagat valley nevada usa summary near surface physical and chemical process can strongly affect dissolved ion concentrations and stable isotope compositions of water in wetland settings especially under arid climate conditions in contrast heavy radiogenic isotopes of strontium 87sr 86sr and uranium 234u 238u remain largely unaffected and can be used to help identify unique signatures from different sources and quantify end member mixing that would otherwise be difficult to determine the utility of combined sr and u isotopes are demonstrated in this study of wetland habitats on the pahranagat national wildlife refuge which depend on supply from large volume springs north of the refuge and from small volume springs and seeps within the refuge water budgets from these sources have not been quantified previously evaporation transpiration seasonally variable surface flow and water management practices complicate the use of conventional methods for determining source contributions and mixing relations in contrast 87sr 86sr and 234u 238u remain unfractionated under these conditions and compositions at a given site remain constant differences in sr and u isotopic signatures between individual sites can be related by simple two or three component mixing models results indicate that surface flow constituting the refuge s irrigation source consists of a 65 25 10 mixture of water from two distinct regionally sourced carbonate aquifer springs and groundwater from locally sourced volcanic aquifers within the refuge contributions from the irrigation source and local groundwater are readily determined and depend on proximity to those sources as well as water management practices

uranium isotopic evidence for groundwater chemical evolution and flow patterns in the eastern snake river plain aquifer idaho the isotopic composition and concentration of uranium and strontium in groundwater combined with solute concentration data provide important details regarding groundwater geochemical evolution and flow pathways in the eastern snake river plain aquifer the study was conducted in the vicinity of the idaho national engineering and environmental laboratory ineel idaho which has a long history of storing and disposing of radioactive waste some of which has entered the aquifer uranium concentrations in ineel groundwater range from 0 3 to 3 6 ppb and 234 u 238 u atomic ratios range between 0 000085 and 0 000168 activity ratios of 1 5 to 3 1 all of the samples have natural 235 u 238 u ratios and 236 u was not detected thus the trends delineated by the 234 u 238 u ratios reflect natural variations in the aquifer groundwater nearest the valleys that provides focused recharge to the snake river plain aquifer from the northwest has high 234 u 238 u ratios when compared to values of regional groundwater flowing southwestward in the aquifer mixing of these water masses can account for the intermediate uranium isotope ratios of some of the samples however water rock interaction must also be invoked to account for the observed trends in isotopic data uranium and 87 sr 86 sr isotope ratios are positively correlated and define a trend toward isotope ratios of the aquifer host rock these relations indicate that dissolution and or ion exchange are more important than alpha recoil or selective leaching in controlling 234 u 238 u ratios as a result 234 u 238 u ratios decrease along flow pathways toward the secular equilibrium values of the aquifer host rock uranium and strontium isotopic modification can be explained by incongruent dissolution of the host basalt lateral distributions of 234 u 238 u ratios indicate elongate zones of high 234 u 238 u ratios extending southward from the mouths of birch creek and the little lost river these elongate zones are interpreted as preferential flow paths two isolated pockets of groundwater located in the central and western parts of the study area have lower 234 u 238 u ratios than the adjacent aquifer water both of these zones are interpreted to contain stagnant waters that are relatively isolated from flow in the regional aquifer due to lower permeability physical and chemical evidence strongly suggests that the stagnant zones are dominated by water from the big lost river that infiltrated via flood control ponds spreading areas playas and the riverbed

at a station hydraulic geometry relations 1 theoretical development this paper the first of two hypothesizes that 1 the temporal variation of stream power of a river channel at a given station with varying discharge is accomplished by the temporal variation in channel form flow depth and channel width and hydraulic variables including energy slope flow velocity and friction 2 the change in stream power is distributed among the changes in flow depth channel width flow velocity slope and friction depending on the boundary conditions that the channels has to satisfy the second hypothesis is a result of the principle of maximum entropy and the theory of minimum energy dissipation or its simplified minimum stream power these two hypotheses lead to families of at a station hydraulic geometry relations the conditions under which these families of relations can occur in the field are discussed copyright 2007 john wiley sons ltd

soil water flux in the southern great basin united states temporal and spatial variations over the last 120 000 years the disposal of hazardous and radioactive waste in arid regions requires a thorough understanding of the occurrence of soil water flux and recharge soil water chemistry and isotopic data are presented from three deep vadose zone boreholes 230 m at the nevada test site located in the great basin geographic province of the southwestern united states to quantify soil water flux and its relation to climate the low water contents found in the soils significantly reduce the mixing of tracers in the subsurface and provide a unique opportunity to examine the role of climate variation on recharge in arid climates tracing techniques and core data are examined in this work to reconstruct the paleohydrologic conditions existing in the vadose zone well beyond the timescales typically investigated stable chloride and chlorine 36 profiles indicate that the soil waters deep in the vadose zone range in age from approximately 20 000 to 120 000 years secondary chloride bulges that are present in two of the three profiles support the concept of recharge occurring at or near the last two glacial maxima when the climate of the area was considerably wetter and cooler the stable isotopic composition of the soil water in the profiles is significantly more depleted in heavy isotopes than is modern precipitation suggesting that recharge under the current climate is not occurring at this arid site past and present recharge appears to have been strongly controlled by surface topography with increased incidence of recharge where runoff from the surrounding mountains may have been concentrated the data obtained from this detailed drilling and sampling program shed new light on the behavior of water in thick vadose zones and in particular show the sensitivity of arid regions to the extreme variations in climate experienced by the region over the last two glacial maxima

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

determination of 88sr 86sr mass dependent isotopic fractionation and radiogenic isotope variation of 87sr 86sr in the neoproterozoic doushantuo formation abstract we measured both mass dependent isotope fractionation of 88sr 88sr 86sr and radiogenic isotopic variation of sr 87sr 86sr for the neoproterozoic doushantuo formation that deposited as a cap carbonate immediately above the marinoan related nantuo tillite the 88sr and 87sr 86sr compositions showed three remarkable characteristics 1 high radiogenic 87sr 86sr values and gradual decrease in the 87sr 86sr ratios 2 anomalously low 88sr values at the lower part cap carbonate and 3 a clear correlation between 87sr 86sr and 88sr values these isotopic signatures can be explained by assuming an extreme greenhouse condition after the marinoan glaciation surface seawater mixed with a large amount of freshwater from continental crusts with high 87sr 86sr and lighter 88sr ratios was formed during the extreme global warming after the glacial event high atmospheric co2 content caused sudden precipitation of cap carbonate from the surface seawater with high 87sr 86sr and lighter 88sr ratios subsequently the mixing of the underlying seawater with unradiogenic sr isotope compositions and normal 88sr ratios probably caused gradual decrease of the 87sr 86sr ratios of the seawater and deposition of carbonate with normal 88sr ratios the combination of 87sr 86sr and 88sr isotope systematics gives us new insights on the surface evolution after the snowball earth

stable isotope 2h 18o and 87sr 86sr and hydrochemistry monitoring for groundwater hydrodynamics analysis in a karst aquifer gran sasso central italy this paper deals with chemical and isotope analyses of 21 springs which were monitored 3 times in the course of 2001 the monitoring program was focused on the groundwater of the gran sasso carbonate karst aquifer central italy typical of the mountainous mediterranean area based on the hydrogeological setting of the study area 6 groups of springs with different groundwater circulation patterns were distinguished the hydrogeochemistry of their main components provided additional information about groundwater flowpaths confirming the proposed classification the spatial distribution of their ion concentrations validated the assumptions underlying the hydrogeological conceptual model showing diverging groundwater flowpaths from the core to the boundaries of the aquifer geochemical modelling and saturation index computation elucidated water carbonate rock interaction contribution by alluvial aquifers at the karst aquifer boundaries as well as impacts of human activities the analysis of 18o 16o and 2h h values and their spatial distribution in the aquifer substantiated the hydrogeology based classification of 6 groups of springs making it possible to trace back groundwater recharge areas based on mean isotope elevations the latter were calculated by using two rain monitoring stations 87sr 86sr analyses showed seasonal changes in many springs in winter spring the changes are due to inflow of new recharge water infiltrating into younger rocks and thus increasing 87sr 86sr values in summer autumn when there is no recharge and spring discharge declines changes are due to base flow groundwater circulating in more ancient rocks with a subsequent drop in 87sr 86sr values the results of this study stress the contribution that spatio temporal isotope monitoring can give to the definition of groundwater flowpaths and hydrodynamics in fissured and karst aquifers taking into account their hydrogeological and hydrogeochemical setting

the dynamics of central main ethiopian rift waters evidence from δd δ18o and 87sr 86sr ratios abstract water samples from cold and geothermal boreholes hot springs lakes and rivers were analyzed for d 18o and 87sr 86sr compositions in order to investigate lake water groundwater mixing processes water rock interactions and to evaluate groundwater flow paths in the central main ethiopian rift mer of the ziway shala basin different ranges of isotopic values were recorded for different water types hot springs show 18o 3 36 to 3 69 and d 15 85 to 24 23 deep aluto langano geothermal wells show 18o 4 65 to 1 24 and d 12 39 to 9 31 groundwater wells show 18o 3 99 to 5 14 and d 19 69 to 32 27 whereas the lakes show 18o and d in the range 3 98 to 7 92 and 26 19 to 45 71 respectively the intersection of the local meteoric water line lmwl d 7 18o 11 2 r2 0 94 n 42 and the local evaporation line lel d 5 63 18o 8 n 14 r2 0 82 was used to estimate the average isotopic composition of recharge water into the basin d 5 15 and 18o 2 34 these values are depleted if compared with the modern day average precipitation presumably indicating paleo groundwater components recharged during previous humid climatic phases the measured stable isotope values indicate that the geothermal wells some of the hot springs and groundwater wells mainly consist of meteoric water the sr isotopic signatures in all waters are within the range of the sr isotopic composition of the rift basalts and rhyolites the variability of sr isotopic data also pinpoints complex water rock interaction and mixing processes in groundwater and surface water the 87sr 86sr ratio ranges from 0 70445 to 0 70756 in the hot springs from 0 70426 to 0 70537 in two deep geothermal wells and from 0 70673 to 0 70721 in the rift lakes ziway langano shala and awasa the radiogenic composition recorded by the lakes indicates that the input water was predominantly affected by progressive interaction with rhyolitic volcanics and lacustrine sediments there is a change in mer water composition between the recharge infiltration zone surrounding highlands and the discharge areas from depleted d 18o and less radiogenic sr isotope compositions to enriched d 18o and more radiogenic sr isotope compositions isotope analyses are therefore useful in providing further understanding of the hydrologeological processes occurring within a productive aquifer and the surface water system

groundwater evolution chemical sedimentation and carbonate brine formation on an island in the okavango delta swamp botswana abstract the okavango delta of semi arid northern botswana is a large alluvial fan 22 000 km2 covered by permanent and seasonal swamps from which 96 of the annual discharge is lost by evapotranspiration many small islands 1ha within the permanent swamps are the sites of accumulation of sodium carbonate salts and many contain saline pans the associated alkaline soils are toxic to vegetation an understanding of the processes involved in alkalinization could be of potential benefit to long term conservation planning in this unique ecosystem the relation between soil chemistry and mineralogy and swamp and groundwater chemistry were investigated on an island in the swamps the study revealed that the water table beneath the island is depressed and swamp water enters the groundwater regime of the island from the margins and below and flows toward the centre the water becomes progressively more saline initially owing to transpiration by trees and ultimately by evaporation in the central parts of the island as a result of increasing salinity amorphous sio2 and magnesium calcite precipitate in the soils beneath the marginal zone of the island raising the land surface while the more soluble alkali carbonates are concentrated in the centre of the island as surface crusts and brine ponds leaching of these salts into the soil during the rainy season and gravity driven flow of saline brines in the dry season causes the downward movement of al and fe in the central zone of the island k feldspar and possibly amorphous allophane develop in the deeper soils under the central zone of the island

determination of temperature dependent stable strontium isotope 88sr 86sr fractionation via bracketing standard mc icp ms stable strontium isotopes here 88sr 86sr are introduced as a new member of the nontraditional stable isotopes we have developed a bracketing standard method for the determination of 88 86sr using an axiom mc icp ms and normalizing to strontium srm nbs987 for individual measurements the external reproducibility is better than about 25 ppm 1 rsd for the iapso seawater standard a 88 86sr value of 0 381 0 010 2sem was determined for the first time a temperature dependent strontium isotope fractionation during calcium carbonate precipitation could be shown aragonite samples inorganically precipitated under temperature control between 10 and 50 c revealed a 88 86sr temperature dependency of 0 0054 5 c r2 0 987 in contrast for natural coral samples pavona clavus from a proxy calibration study 23 to 27 c we did determine 0 033 5 c r2 0 955 the processes causing this sixfold stronger temperature dependency for the natural coral samples have to be studied in more detail in future studies in a first approach the different slopes can be interpreted as effects of kinetic fractionation of strontium ions with or without a hydrate shell of 22 to 29 water molecules

strontium isotope characterization and major ion geochemistry of karst water flow shentou northern china summary karst water is the most important source of water supply for shanxi province northern china the shentou springs are representative of the 19 major karst springs at shanxi the total area of the shentou karst water system is 5316 km 2 the middle ordovician limestone being its major karst aquifer in this study data about the strontium isotope geochemistry and major ion hydrochemistry were analyzed to understand the flow patterns and hydrogeochemical processes of karst water at shentou the contour map of tds value of karst water and that of sr concentration are similar showing the general tendency of increase from the northern western and southern boundary to the discharge area the average values of 87 sr 86 sr ratios of karst water decrease from recharge 0 7107 to discharge area 0 7102 evolving towards those of limestone hostrocks comparison of 87 sr 86 sr ratios with sr content suggests that isotopic compositions of some karst water samples from the recharge and flow through area should be the result of interaction between aquifer limestone matrix and strontium poor recharge waters of meteoric origin however for samples from the discharge area that are plotted above the mixing line mixing with groundwater in the quaternary aquifers with high 87 sr 86 sr ratios may be another factor controlling sr isotope chemistry two major groundwater flow paths were discerned from hydrogeological and geochemical data along both flow paths the 87 sr 86 sr ratios of karst water show a general tendency of decrease geochemical modeling of the major ion geochemistry of karst water using phreeqc also indicates that the chemistry of springs should be affected by the incorporation of groundwater in quaternary aquifer the effect of the mixing action on the spring hydrochemistry in flow path 1 is more remarkable than that in flow path 2 according to different mixing ratios in both paths 30 in flow path 1 and 5 in flow path 2

uranium isotopes as a tracer of sources of dissolved solutes in the han river south korea abstract the uranium u content and 234u 238u activity ratio were determined for water samples collected from korea s han river in spring summer and winter 2006 to provide data that might constrain the origin of u isotope fractionation in river water and the link between u isotope systematics in river waters and the lithological nature of the corresponding bedrock the large difference in the major dissolved loads between the two major branches of the han river the north han river nhr and south han river shr is reflected in the contrasting u content and 234u 238u activity ratio between the tributaries low u content 0 08 0 75 nm average 0 34 nm and small 234u 238u activity ratio 1 03 1 22 average 1 09 in the nhr and high u content 0 65 1 98 nm average 1 44 nm and large 234u 238u activity ratio 1 05 1 45 average 1 24 in the shr the large spatial differences in u content and 234u 238u activity ratio are closely related to both lithological differences between the two tributaries and groundwater input the low u content and small 234u 238u activity ratio in the nhr arise mainly from a combination of surface and meteoric weathering of the dominant silicate rocks in this branch and congruent dissolution of already weathered secular equilibrium materials in contrast the high u content and large 234u 238u activity ratio in the shr are ascribed to the dissolution of carbonates and black shales along with significant inputs of deep groundwater

u th ra fractionation during weathering and river transport the potential of radioactive disequilibria as tracers and chronometers of weathering processes has been recognised since the 1960 s e g rosholt et al 1966 hansen and stout 1968 this interest results from the dual property of the nuclides of the u and th radioactive series 1 to be fractionated during water rock interactions and 2 to have radioactive periods of the same order of magnitude as the time constants of many weathering processes and chemical transfers to ground and river waters therefore the study of radioactive disequilibria in surface environments should help to bring information about the nature the intensity but also the time scale of the water rock interactions produced during weathering and related chemical transfers these different properties have justified many of the studies on u th series in weathering profiles and river waters rosholt 1982 scott 1982 and osmond and ivanovich 1992 gave a synthesis of the studies of u series in weathering and surface hydrology up to the 1980 s and the 1990 s respectively here we present the main directions taken in these domains over the last decade they were partly stimulated by the analytical developments made in the measurement of the medium half life nuclides of 238u series i e 234u 230th 226ra in the mid 1980 s namely the use of thermal ionisation mass spectrometry tims e g chen et al 1986 edwards et al 1987 cohen et al 1991 chabaux 1993 chabaux et al 1994 and more recently the use of mc icp ms turner et al 2001 robinson et al 2002 for u and th isotope analysis details of these developments are given in this volume goldstein and stirling 2003 compared to the radioactive counting methods previously used the new techniques permit 1 a reduction by one order of magnitude or more of the size of the sample required for

strontium stable isotopes fractionate in the soil environments abstract this study shows that the stable isotopic composition of strontium the 88sr 86sr ratio expressed as 88 86sr value relative to the nbs987 standard varies significantly in sedimentary terrestrial environments the abundances of 86sr 88sr isotopes were analyzed by mc icp ms nu plasma all studied rocks and waters show 88 86sr values that are distinctly different from the measured nbs987 standard yielding 0 01 0 05 all errors are reported as 2 modern corals from the northern gulf of aqaba red sea yielded significantly different value than seawater 88 86sr 0 22 0 07 compared to 0 35 0 06 respectively in an excellent correlation with the 88 86sr analyses reported by fietzke and eisenhauer fietzke j eisenhauer a 2006 determination of temperature dependent stable strontium isotopes 88sr 86sr fractionation via bracketing standard mc icp ms geochm geophys geosyst 7 no 8 on other coral samples all carbonate samples that originated in the marine environment corals porites and acropora from the northern gulf of aqaba cretaceous limestone and runoff from the judea mountains as well as lacustrine evaporitic aragonite dead sea and red sea and atlantic seawater yield an average 88 86sr value of 0 26 0 1 on the other hand secondary materials products of chemical weathering from the terrestrial environment of the judea mountain such as terra rossa soil and speleothem calcite that derives its sr from the above lying soil yielded significantly lower 88 86sr value of 0 17 0 06 this indicates that strontium isotopes fractionate in the soil environment calling for a possible development of strontium isotopes as a tracer for processes of chemical weathering and pedogenesis

the behavior of u and th series nuclides in groundwater groundwater has long been an active area of research driven by its importance both as a societal resource and as a component in the global hydrological cycle key issues in groundwater research include inferring rates of transport of chemical constituents determining the ages of groundwater and tracing water masses using chemical fingerprints while information on the trace elements pertinent to these topics can be obtained from aquifer tests using experimentally introduced tracers and from laboratory experiments on aquifer materials these studies are necessarily limited in time and space regional studies of aquifers can focus on greater scales and time periods but must contend with greater complexities and variations in this regard the isotopic systematics of the naturally occurring radionuclides in the u and th decay series have been invaluable in investigating aquifer behavior of u th and ra these nuclides are present in all groundwaters and are each represented by several isotopes with very different half lives so that processes occurring over a range of time scales can be studied table 1 within the host aquifer minerals the radionuclides in each decay series are generally expected to be in secular equilibrium and so have equal activities see bourdon et al 2003 in contrast these nuclides exhibit strong relative fractionations within the surrounding groundwaters that reflect contrasting behavior during release into the water and during interaction with the surrounding host aquifer rocks radionuclide data can be used within the framework of models of the processes involved to obtain quantitative assessments of radionuclide release from aquifer rocks and groundwater migration rates the isotopic variations that are generated also have the potential for providing fingerprints for groundwaters from specific aquifer environments and have even been explored as a means for calculating groundwater ages view this table table 1 radionuclides important in groundwater studies the highly fractionated nature of the

the use of environmental isotopic c sr s and hydrochemical tracers to characterize anthropogenic effects on karst groundwater quality a case study of the shuicheng basin sw china rapidly increasing populations and associated intensification of agriculture urbanization and industrialization place increased demands on water resources and increased likelihood of pollution in many areas of the world the shuicheng basin southwestern china is one such area and in order to understand water rock interactions carbonate dissolution and anthropogenic impacts on groundwater quality in this karstic landform dominated area chemical as well as c sr and s isotopic compositions of groundwater spring and well and surface water river were measured during and following rainy seasons the concentrations of various ions in groundwater were characterized by the dominant cations ca2 mg2 and anions hco3 so42 which account for more than 80 of the total ion concentration strontium isotope ratios 87sr 86sr 0 70760 0 70918 mean 0 70831 and 13cdic 14 2 to 8 4 mean 10 7 indicate that the weathering dissolution of limestone controls ca2 and hco3 the decrease in 13cdic values with increasing concentrations of anthropogenic species cl no3 and na shows that the c isotopic composition of dic can be a useful tracer of contaminants chemical compositions hydrogeological conditions and 34s analyses showed increasing so42 concentration resulting from domestic wastewater fertilizer applications atmospheric inputs through coal combustion and oxidation of sulfide minerals which typically are abundant in coal formations in the basin groundwater from the old downtown industrial and agricultural areas exhibited high concentrations of cl no3 so42 and na suggesting the groundwater is impacted by significant levels of contamination from human activities

u isotope ratios as tracers of groundwater inputs into surface waters example of the upper rhine hydrosystem major elements trace elements and sr and u isotopes were analyzed in the dissolved load of water samples collected in the main reservoirs of the rhine graben i e the rhine river its main tributaries and the shallow and deep ground waters in several different aquifers our results confirm that the variations of major elements trace elements especially sr and rb and sr isotope ratios of the water samples are mainly correlated to the lithological variations of the watershed the atmospheric inputs can be considered as a minor cause for the chemical variability of the surface waters in the rhine hydrosystem except for a few chemical elements in the mountain streams human activity in particular the pollution by the exploitation of the alsace potash mines mainly affects the na and cl concentrations of the rhine and the south alluvial groundwaters but remains negligible for the other water samples the specific study of the lauter stream located in the lower triassic sandstones buntsandstein sequences demonstrates the importance of groundwater influences onto the chemical composition of river waters up to 50 of the total dissolved load tds of this stream is supplied by deep waters this contribution significantly modifies the chemical composition of the stream especially the 238u 234u radioactive disequilibrium which in turn can be used as a specific tracer of deep water inputs into surface waters and could be useful to distinguish in the dissolved load of rivers surface weathering fluxes from deeper ones

sulfate and strontium water source identification by o s and sr isotopes and their temporal changes 1997 2008 in the region of freiberg central eastern germany abstract various waters bulk atmospheric precipitation groundwater river water flowing mine water mine drainage galleries and flooding mine water were studied in the region of freiberg to achieve an improved understanding of sources and mixing processes in the hydrological cycle and to specify the main sources that determine the isotope composition of dissolved sulfate and strontium 18 o so 4 34 s so 4 and 87 sr 86 sr in river water the combined use of isotope and chemical data led to identification of three major sulfate sources i sulfate from groundwater ii sulfate from the oxidation of local ore sulfides that remained in unflooded und flooded parts after mine decommissioning and iii industrial sulfate released from abundant waste slag and tailing deposits left behind after a long mining and industrial history of the region the same three components groundwater pore water from oxidation of residual ores and industry source were identified by analyzing sr isotope ratios however the sr isotopes pointed out a fourth yet unrecognized source that contributed to water of the flooded mine section the data show that the isotope composition of water of the river freiberger mulde was mainly determined by uncontaminated groundwater diluted with atmospheric precipitation whereas the other two end members played only a minor role for this river water however for the river triebisch the isotope compositions of dissolved sulfate and strontium record a strong impact of end members ii and iii after recharging the flooding water into the river a twelve year monitoring 1997 2008 revealed a strong decrease of 18 o so 4 values of water from bulk atmospheric precipitation as of 2006 2008 7 compared to 1997 14 while 34 s so 4 values remained constant 5 this isotope shift was probably caused by a lower contribution of primary sulfates to atmospheric precipitation in recent years groundwater and river water freiberger mulde also showed decreasing 18 o so 4 values albeit to a lower degree by 4 5 a decrease of 18 o so 4 values was again found in flowing mine water by 5 6 mainly affected by end member i uncontaminated groundwater the flood event in august 2002 likely washed out large parts of older groundwater and thus enabled the relatively large oxygen isotope decrease 18 o so 4 of groundwater and river water within a few years the previously high input from the industrial source waste and slag deposits decreased from 1997 to 2002 in some drainage galleries and flooding water that discharge their water into local rivers this led to lower 18 o and 34 s values of dissolved sulfates in these waters accompanied by a concentration decrease of several elements cl na and mg however no further decrease of the impact of this source could be detected after the storm and flood event in august 2002

slow si al interdiffusion in garnet and stagnation of subducting slabs abstract si 4 m 2 2al 3 m mg fe ca interdiffusion rates in majoritic garnet have been determined at pressure of 17 gpa and temperatures of 1550 1700 c using a kawai type high pressure apparatus the diffusion profiles were measured across the interface between pyropic garnet and majoritic garnet samples by an analytical transmission electron microscope and the rate of the si 4 m 2 2al 3 interdiffusion was determined to be a d si al m 2 s 1 2 10 10 exp 364 kj mol 1 rt we found that the diffusion rate is low compared to the si diffusion rate in other silicate minerals relevant to the deep mantle slow kinetics of the pyroxene garnet transformation due to the low diffusion rate indicates that large low density metastable regions may exist in the slab greatly contributing to the slab stagnation around the transition region stagnant slabs possibly stay in this region over 10 8 yr because of the sluggish pyroxene garnet transformation but may eventually fall into the lower mantle after the completion of the transformation

geochemistry of the maroni river french guiana during the low water stage implications for water rock interaction and groundwater characteristics abstract the maroni river draining a basin of 60 000 km 2 and flowing down to the atlantic ocean between french guiana and surinam was studied during a low flow period using the chemical and isotopic composition of its dissolved load the dissolved concentrations of major ions cl so 4 no 3 hco 3 ca na mg k trace elements rb and sr stable isotopes o and d and strontium isotopes 87 sr 86 sr were determined on samples from the main stream of the river and its tributaries and from groundwaters collected in wells and two boreholes the total dissolved solid tds and the sum of cations agree with those summarised for the major guyanan rivers the orinoco and amazon on a tds vs na na ca diagram all the data from the maroni catchment plot in the precipitation dominance field close to the plots of the tefe and negro rivers the groundwaters collected from wells largely mimic the surface waters and may represent alluvial groundwater along the maroni terraces whereas the groundwaters collected from the boreholes show clearly higher values and reflect an increase in water rock interaction the river and groundwaters of the maroni catchment have been isotopically enriched 18 o vs 2 h through evaporation and the 18 o and 2 h can be used as mixing tracers of river waters within the catchment after corrections for rainwater addition were computed for selected elements and for 87 sr 86 sr ratios using chloride as an atmospheric input reference the water rock interaction along the maroni catchment was investigated for cations and sr isotopes

preferential dissolution of 234u and radiogenic pb from α recoil damaged lattice sites in zircon implications for thermal histories and pb isotopic fractionation in the near surface environment abstract zircons from two archean samples a 2732 ma trondhjemite and a 2728 ma dacite both from the western superior province were washed in hydrofluoric acid hf at moderate temperatures zircon residues and hf wash solutions were analyzed for u pb isotope systematics and 234u 238u ratios in an attempt to study the effect of hf washing on selective dissolution of radiogenic isotopes in areas damaged by recoil on a conventional concordia diagram the datum from one analyzed wash solution plots below concordia near the array of discordant data from magnetic unabraded zircon fractions which record a lower concordia intersection of about 230 ma data points from hf wash residues of two different zircon fractions from the trondhjemite are also discordant and collinear with near concordant data from abraded unleached fractions which record the true age of crystallization however this array has a negative lower concordia intercept of 749 ma the residue and wash from hf treatment of a single zircon fraction from the dacite are collinear with the crystallization age of the sample as defined by near concordant data from unleached fractions this line has a lower concordia intersection of 1388 ma also negative but distinct from the trondhjemite residue line the discordance of strongly washed residues is proportional to the calculated recoil dosage of the grains leach residues show negative 234u 238u anomalies while the leaches themselves show 234u excess on the order of 10 these results can be explained by the bulk dissolution of altered and metamict crystal domains during the hf wash accompanied by leaching of 234u and radiogenic pb from recoil damaged lattice sites in alteration free zircon residues studies were also carried out on zircons washed in nitric acid these show small ca 0 5 negative 234u anomalies this suggests that small amounts of radiogenic pb can be leached from damaged lattice sites by nitric acid the negative age lower concordia intercepts of pb loss lines defined by hf leach residues can be explained if early radiation damage has been annealed so that only more recently formed radiogenic pb atoms are in damaged crystal lattice sites and are susceptible to leaching since this pb fraction is relatively young the residue pb is biased toward anomalously old values a model is proposed for early burial and heating of the rocks above the annealing temperature for recoil damage followed by uplift and cooling several hundred million years after crystallization this model predicts a cooling time of 2500 20 ma for the trondhjemite and 2295 35 ma for the rhyolite comparison with metamorphic and cooling histories from ar ar studies suggest that the long term annealing temperature for low levels of recoil damage in zircon is in the range 250 300 c approximately the same as for fission tracks these results demonstrate that hf and possibly to a small extent hno3 can preferentially leach radioactive daughter elements from damaged zircon lattice sites in addition to dissolving metamict domains the threshold recoil dosage for dissolution of damaged zircon appears to be slightly in excess of 1 5 1015 decay events mg the isotopic composition of the leached pb is sensitive to the annealing history of the zircon thus in addition to supplying the magmatic crystallization age of the sample the hf leaching of zircon might be useful for constraining its later low temperature thermal history leaching from recoil damaged sites also occurs in the natural environment and this may lead to significant enhancement of 206pb 204pb in groundwater

evidence for mass dependent isotopic fractionation of strontium in a glaciated granitic watershed abstract the stable isotope composition of strontium expressed as 88 86sr may provide important constraints on the global exogenic strontium cycle here we present 88 86sr values and 87sr 86sr ratios for granitoid rocks a 150 yr soil chronosequence formed from these rocks surface waters and plants in a small glaciated watershed in the central swiss alps incipient chemical weathering in this young system whether of inorganic or biological origin has no resolvable effect on the 87sr 86sr ratios and 88 86sr values of bulk soils which remain indistinguishable from bedrock in terms of sr isotopic composition although due in part to the chemical heterogeneity of the forefield the lack of a resolvable difference between soil and bedrock isotopic composition indicates that these soils have thus far witnessed minimal net loss of sr a low degree of chemical weathering is also implied by bulk soil chemistry the isotopic composition of sr in streamwater is more radiogenic than median soil reflecting the preferential weathering of biotite in the catchment streamwater 88 86sr values however are indistinguishable from bulk soil 88 86sr values implying that no resolvable fractionation of sr isotopes takes place during release to the weathering flux in the damma forefield analyses of plant tissue reveal that plants rhododendron and vaccinium preferentially assimilate the lighter isotopes of sr such that their 88 86sr values are significantly lower than those of the soils in which they grow additionally 88 86sr values of foliar and floral tissues are lower than those of roots contrary to observations for ca for which sr is often used as an analogue in weathering studies we suggest that processes that discriminate against sr in favour of ca due to the different nutritional requirement of plants for these two elements are responsible for the observed contrast

hydrogeochemistry and strontium isotopes of spring and mineral waters from monte vulture volcano italy abstract this paper describes the results of a study that was conducted to determine the relationship between hydrogeochemical composition and 87sr 86sr isotope ratios of the mt vulture spring waters forty samples of spring waters were collected from local outcrops of quaternary volcanites physico chemical parameters were measured in the field and analyses completed for major and minor elements and 87sr 86sr isotopic ratios a range of water types was distinguished varying from alkaline earth bicarbonate waters reflecting less intense water rock interaction processes to alkali bicarbonate waters probably representing interaction with volcanic rocks of mt vulture and marine evaporites the average 87sr 86sr isotope ratios suggest at least 3 different sources however some samples have average sr isotope ratios 0 70704 0 70778 well above those of the volcanites these ratios imply interaction with other rocks having higher 87sr 86sr ratios probably triassic evaporites which is substantiated by their higher content of na so4 and cl the sr isotope ratios for some samples e g toka and traficante are intermediate between the value for the vulture volcanites and that for the local mesozoic rocks the salt content of these samples also lies between the value for waters interacting solely with the volcanites and the value measured in the more saline samples these waters are thus assumed to result from the mixing of waters circulating in volcanic rocks with waters presumably interacting with the sedimentary bedrock marine evaporites

sr concentrations and isotope ratios as tracers of ground water circulation in carbonate platforms examples from san salvador island and long island bahamas abstract the depth to which seawater and fresh water circulate through modern carbonate platforms may be estimated with 87 sr 86 sr isotope ratios of dissolved sr 2 that is enriched through carbonate mineral dissolution and recrystallization in 23 water samples from onshore san salvador island and long island bahamas carbonate mineral dissolution and aragonite to calcite transformations elevate sr 2 concentrations to twice seawater values in water with near seawater salinity and to about 130 times the expected value for seawater that has been mixed with fresh water carbonate mineral dissolution enriches ca 2 concentrations to around 30 times seawater concentrations only in the mixed waters water with seawater salinity has approximately seawater ca 2 concentrations assuming two end member mixing between seawater sr 2 and mineral derived sr 2 model estimates indicate that mineral derived sr 2 of 19 samples have 87 sr 86 sr ratios equivalent to modern seawater within error of the measurement indicating alteration of shallow buried late pleistocene to holocene carbonate minerals four samples have mineral derived sr 2 with 87 sr 86 sr ratios lower than modern seawater value these low ratios reflect alteration of carbonate minerals that were deposited around 1 mybp although the measured 87 sr 86 sr values could reflect ages as great as 4 6 ma considering the analytical uncertainty of the measurements these estimated ages are likely to be minimum values because alteration of modern carbonate minerals at the surface would provide an unknown but probably large amount of sr 2 with modern seawater isotope signatures thereby overprinting any low 87 sr 86 sr ratios of non modern mineral derived sr 2 three of the four samples with low 87 sr 86 sr ratios have high salinities and were collected from the interior of the islands they reflect seawater flow paths at least tens of meters deep may link the ocean to water several kilometers inland the fourth sample is from the fresh water lens below a pleistocene beach ridge 125 ka only 100 m from the shore line this sample suggests the lens may be thicker than expected based on estimates of recharge hydraulic conductivity and size of the ridge

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

234u 238u evidence for local recharge and patterns of ground water flow in the vicinity of yucca mountain nevada usa uranium concentrations and 234u 238u ratios in saturated zone and perched ground water were used to investigate hydrologic flow and downgradient dilution and dispersion in the vicinity of yucca mountain a potential high level radioactive waste disposal site the u data were obtained by thermal ionization mass spectrometry on more than 280 samples from the death valley regional flow system large variations in both u concentrations commonly 0 6 10 g l 1 and 234u 238u activity ratios commonly 1 5 6 are present on both local and regional scales however ground water with 234u 238u activity ratios from 7 up to 8 06 is restricted largely to samples from yucca mountain data from ground water in the tertiary volcanic and quaternary alluvial aquifers at and adjacent to yucca mountain plot in 3 distinct fields of reciprocal u concentration versus 234u 238u activity ratio correlated to different geographic areas ground water to the west of yucca mountain has large u concentrations and moderate 234u 238u whereas ground water to the east in the fortymile flow system has similar 234u 238u but distinctly smaller u concentrations ground water beneath the central part of yucca mountain has intermediate u concentrations but distinctive 234u 238u activity ratios of about 7 8 perched water from the lower part of the unsaturated zone at yucca mountain has similarly large values of 234u 238u these u data imply that the tertiary volcanic aquifer beneath the central part of yucca mountain is isolated from north south regional flow the similarity of 234u 238u in both saturated and unsaturated zone ground water at yucca mountain further indicates that saturated zone ground water beneath yucca mountain is dominated by local recharge rather than regional flow the distinctive 234u 238u signatures also provide a natural tracer of downgradient flow elevated 234u 238u in ground water from two water supply wells east of yucca mountain are interpreted as the result of induced flow from 40 a of ground water withdrawal elevated 234u 238u in a borehole south of yucca mountain is interpreted as evidence that natural downgradient flow is more likely to follow southerly paths in the structurally anisotropic tertiary volcanic aquifer where it becomes diluted by regional flow in the fortymile system

use of u isotopes in exploring groundwater flow and inter aquifer leakage in the south western margin of the great artesian basin and arckaringa basin central australia abstract the distribution of uranium isotopes 238u and 234u in groundwaters of the south western margin of the great artesian basin gab australia and underlying arckaringa basin were examined using groundwater samples and a sequential extraction of aquifer sediments rock weathering the geochemical environment and recoil of daughter products control the 238u and 234u isotope distributions giving rise to large spatial variations generally the shallowest aquifer j aquifer contains groundwater with higher 238u activity concentrations and 234u 238u activity ratios close to secular equilibrium however the source input of uranium is spatially variable as intermittent recharge from ephemeral rivers passes through rocks that have already undergone extensive weathering and contain low 238u activity concentrations other locations in the j aquifer that receive little or no recharge contain higher 238u activity concentrations because uranium from localised uranium rich rocks have been leached into solution and the geochemical environment allows the uranium to be kept in solution the geochemical conditions of the deeper aquifers generally result in lower 238u activity concentrations in the groundwater accompanied by higher 234u 238u activity ratios the sequential extraction of aquifer sediments showed that recoil of 234u from the solid mineral phases into the groundwater rather than dissolution of or exchange with the groundwater accessible minerals in the aquifer caused enrichment of groundwater 234u 238u activity ratios in the boorthanna formation decay of 238u in uranium rich coatings on j aquifer sediments caused resistant phase 234u 238u activity ratio enrichment the groundwater 234u 238u activity ratio is dependent on groundwater residence time or flow rate depending on the flow path trajectory thus uranium isotope variations confirmed earlier groundwater flow interpretations based on other tracers however spatial heterogeneity and the lack of clear regional correlations made it difficult to identify recharge and inter aquifer leakage