isotopic constraints on the origin of groundwater in the ordos basin of northern china despite its extreme aridity the ordos basin in northern china is rich in groundwater many artesian wells or springs with large fluxes are utilized for drinking irrigation and industrial production in a search for the origin of the groundwater a detailed investigation of the stable isotopes of oxygen and hydrogen in the local precipitation the river water the springs the well water as well as the soil water extracted from six soil profiles in the ordos basin was carried out the data show that d 18o and tds values of the river water are similar to those of groundwater while the tds values of the soil water are about ten times greater than those of groundwater furthermore the mean isotopic compositions of the local precipitation are significantly higher than those of river water and groundwater based on the chloride mass balance method the estimated recharge rates range from 5 2 to 17 2 mm year with a mean value of 10 5 mm year the results show that the main source of recharge of the groundwater in the ordos basin is not the local precipitation but must come from a region where the precipitation is characterized by much lower d and 18o values in addition the groundwater in the ordos basin contains a component of mantle derived 3he and crust derived 4he suggesting that the groundwater may partly derive from flows through basement faults beneath the ordos basin

stable isotope compositions of waters in the great basin united states 3 comparison of groundwaters with modern precipitation 1 groundwater samples from wells and springs scattered over most of the great basin province were collected and analyzed for their isotopic makeup they were augmented by previously published isotopic data on groundwaters from southeast california and by several hundred unpublished isotopic analyses the ratio of 2h deuterium d to 1h in water samples from valleys in parts of california idaho nevada oregon and utah are here compared with the winter summer and annual isotopic compositions of precipitation falling in or near the sampled areas the main goal of this study was to identify basins where the groundwaters have isotopic compositions that are lighter depleted in the heavier isotope d relative to modern winter precipitation where these basins do not adjoin substantially higher terrain we consider those light groundwaters to be of pleistocene age and thus more than 10 000 years old where the groundwater is 10 to 19 lighter than local winter precipitation we consider it to be possibly an indication of pleistocene water where the d makeup is 20 lighter we consider it to be probably pleistocene water more than 80 sites underlain by waters of possible or probable pleistocene age were identified

catchment scale surface water groundwater connectivity on china s loess plateau abstract thick loess deposits up to 200 m deep and a large unsaturated zone up to 100 m below the soil surface complicate the interactions between surface water and groundwater in china s loess plateau especially in catchments characterized by tableland gully topography in this region in the heihe watershed electrical conductivity ec chloride cl concentrations and stable water isotope data d and 18 o obtained during dry and wet seasons in the period of 2012 2014 are used to determine the relationship between surface water and groundwater ec and cl concentrations are found to be unsuitable for analyzing the relationship between surface water and groundwater in this watershed due to the impacts of chemical weathering the stable water isotope data indicate a gaining surface water system i e groundwater and gully runoff both recharge streamflow further groundwater appears to dominate the hydrologic cycle in the watershed therefore water resources management on china s loess plateau should pay more attentions to groundwater protection

groundwater recharge circulation and geochemical evolution in the source region of the blue nile river ethiopia geochemical and environmental isotope data were used to gain the first regional picture of groundwater recharge circulation and its hydrochemical evolution in the upper blue nile river basin of ethiopia q mode statistical cluster analysis hca was used to classify water into objective groups and to conduct inverse geochemical modeling among the groups two major structurally deformed regions with distinct groundwater circulation and evolution history were identified these are the lake tana graben ltg and the yerer tullu wellel volcanic lineament zone ytvl silicate hydrolysis accompanied by co2 influx from deeper sources plays a major role in groundwater chemical evolution of the high tds na hco3 type thermal groundwaters of these two regions in the basaltic plateau outside these two zones groundwater recharge takes place rapidly through fractured basalts groundwater flow paths are short and they are characterized by low tds and are ca mg hco3 type waters despite the high altitude mean altitude 2500 masl and the relatively low mean annual air temperature 18 c of the region compared to sahelian africa there is no commensurate depletion in d 18 o compositions of groundwaters of the ethiopian plateau generally the highland areas north and east of the basin are characterized by relatively depleted d 18 o groundwaters altitudinal depletion of d 18 o is 0 1 100 m the meteoric waters of the blue nile river basin have higher d excess compared to the meteoric waters of the ethiopian rift and that of its white nile sister basin which emerges from the equatorial lakes region the geochemically evolved groundwaters of the ytvl and ltg are relatively isotopically depleted when compared to the present day meteoric waters reflecting recharge under colder climate and their high altitude 2005 elsevier ltd all rights reserved 1 background surface water of the blue nile river basin of ethiopia is not widely used for water supply because of its marked seasonality and lack of proper technology to retain it in the basin groundwater is the most important source of water and is the dominant source for domestic

the ichnogenus dictyodora from late silurian deposits of central western argentina ichnotaxonomy ethology and ichnostratigrapical perspectives from gondwana abstract the association of trace fossils from the late silurian rio seco de los castanos formation in central western argentina san rafael block is mainly composed of dictyodora including dictyodora scotica dictyodora tenuis and a new ichnospecies named dictyodora atuelica the latter shows a tendency to migrate to a deeper level analogous to dictyodora liebeana s which reflects more sophisticated behavioural patterns the dictyodora ichnospecies one of the most diverse assemblages in gondwana coexists with nereites sem observations and eds analyses suggest that the wall structure of dictyodora could be the result of an activity other than the traditional suggestion of respiration e g feeding the succession including some of the levels containing dictyodora presents microbially induced sedimentary structures miss that would indicate a photic zone this discovery favours previous deltaic interpretations instead of the deep sea fan deposits traditionally suggested for the siluro devonian greywackes of the cuyania terrane and particularly for this unit the abundant dictyodora nereites zoophycos and undermat miners ichnofossils as well as the scarce arthropod trackways resemble older records in europe and north america the studied section is very well age constrained and the autochthonous gondwana ichnofauna permits to cast doubt on previous interpretations suggesting that after the ordovician microbial mats retreated to marginal marine environments and then spread later in the carboniferous more importantly the occurrence of dictyodora and nereites in beds that bear abundant wrinkle structures or records of biofilms in some places is challenging with regard to deep sea interpretations dictyodora is probably not a good stratigraphic indicator and the provincialism suggested for this ichnogenus may be an artefact of the lack of more complete records in gondwana

holocene vegetation and climate in the puerto blanco mountains southwestern arizona abstract plant macrofossils from 21 pack rat neotoma sp middens at 535 605 m from the puerto blanco mountains southwestern arizona provide and excellent history of vegetation and climate for the last 14 120 yr b p in the sonoran desert a late wisconsin juniper joshua tree woodland gave way to a transitional early holocene desertscrub with sparse juniperus californica california juniper by 10 540 yr b p important sonoran desert plants including carnegiea gigantea saguaro and encelia farinosa brittle bush were dominants riparian trees such as acacia greggii catclaw acacia prosopis velutina velvet mesquite and cerdicium floridum blue palo verde grew on dry south facing slopes in a middle holocene sonoran desertscrub in a warm wet summer climate with frequent winter freezes modern subtropical sonoran desertscrub formed about 4000 yr b p as summer rainfall and winter freezes declined cercidium microphyllum foothills palo verde sapium biloculare mexican jumping bean olneya tesota ironwood and stenocereus thurberi organ pipe cactus became dominant as riparian trees retreated to wash habitats the inferences of a latest wisconsin early holocene summer monsoonal maximum by j e kutzbach 1983 modeling of holocene climates in late quaternary environments of the united states vol 2 the holocene h e wright ed pp 271 277 univ of minnesota press minneapolis are not supported for the southwest apparently the persistence of late wisconsin circulation patterns offset any increases in insolation

stable isotopic and geochemical characteristics of groundwater in kherlen river basin a semi arid region in eastern mongolia summary inorganic solute ion concentrations and stable isotopes of oxygen and hydrogen in groundwater river water and precipitation were investigated to gain insight into the groundwater recharge process in the kherlen river basin a semi arid region in eastern mongolia the solute constituents in the river water main stream were of ca hco3 type spatially invariant and low in concentration groundwater in the upstream region was also characterized by a ca hco3 type though all ion concentrations were higher than in the river water on the other hand the chemical composition of the groundwater in the midstream region southern and eastern was spatially variable and the na mg2 cl and hco 3 concentrations were considerably higher than in the river water and upstream groundwater the stable isotopic compositions showed an evaporation effect on the groundwater and river water as well as an altitude effect in the precipitation and river water preferential recharge by relatively large rainfall events is thought to have caused the depleted isotopic ratio in the groundwater in the dry regions the stable isotope chemical and hydrological data suggest that the main stream water of the kherlen river is recharged by precipitation that falls in a headwater region at an altitude of more than 1650 m and that the interaction between the groundwater and river water is not dominant in the midstream and downstream regions of the river basin

assessment and estimation of groundwater recharge for a catchment located in highland tropical climate in central ethiopia using catchment soil water balance swb and chloride mass balance cmb techniques two commonly applied groundwater recharge estimation techniques namely soil water balance swb and the chloride mass balance cmb methods were applied and compared to quantify and analyse groundwater recharge in the akaki catchment located in central ethiopia the semi distributed swb method estimated natural groundwater recharge at 105 mm a 10 of the mean annual areal precipitation maap the chloride mass balance method applied to the same catchment estimated mean annual groundwater recharge at 273 mm a 25 of the maap the swb recharge value is much less than the recharge estimated by cmb method highlighting the importance of preferential flow path recharge mechanism which is not captured by the swb method in situ permeability measurements undertaken as part of this research and an earlier investigation based on environmental isotopes have demonstrated that the catchment gets recharged both from direct and preferential flow recharge mechanisms which explains the discrepancy between recharge estimated through the two methods therefore swb model result which only takes into consideration the piston type flow recharge mechanism should be taken as the minimum possible groundwater recharge for the catchment characterized by fractured aquifers the mean recharge estimate from the two methods represents the maximum possible recharge estimate for the catchment investigated although calibration of the recharge estimates was not possible the swb recharge estimate is found to be highly sensitive to changes in precipitation input the findings of this research underline the fact that multiple recharge estimation methods are important to understand and capture possible recharge mechanisms and to reach to an acceptable recharge estimate

major ion hydrochemistry and environmental isotope signatures as a tool in assessing groundwater occurrence and its dynamics in a fractured volcanic aquifer system located within a heavily urbanized catchment central ethiopia summary hydrochemical and environmental isotope 2 h 18 o and 3 h data were used to characterize the groundwater flow occurrence and major ion chemistry in a complex fractured volcanic aquifer system located at the edge of the ethiopian rift the study has been supported by conventional hydrogeological mapping the result clearly indicates the presence of two distinct groundwater systems 1 the shallow groundwater characterized by low ionic concentration and in places isotopically enriched younger waters and 2 the deep thermal waters with relatively older age showing negative 18 o shifts and higher ionic concentration the deep groundwaters are manifested as thermal springs and deep confined and artisan wells mainly aligned along major regional faults the first group of groundwater is further divided into four subgroups indicating clear geo hydrological patterns along the groundwater flow path representing different lithologies residence time and anthropogenic influences the classification shows different degrees of rock water interaction and aquifer composition there are indications of aquifer recharge from highly evaporated surface waters this integrated study enabled to conceptualize the groundwater flow system vertically in to three zones namely shallow fast circulating fresh water mixed and moderately mineralized groundwaters representing the majority of wells and the deep old and mineralized thermal waters this study has very important implications on possible location and depth of future boreholes well head protection and in understanding the spread of pollutants that may originate from urban areas

morphology and stable and radiogenic isotope composition of pedogenic carbonates in late quaternary relict soils new mexico u s a an integrated record of pedogenic overprinting abstract this petrographic and stable 13c and 18o and radiogenic 14c isotope study of pedogenic carbonates from late quaternary soils in the rio grande rift region of new mexico documents that carbonate formation in semiarid to arid soils aridisols occurs principally by overprinting and can result in a complex petrographic and isotopic record with increasing duration of exposure 7 to 900 ky of the four studied profiles pedogenic carbonates exhibit 1 an increase in the degree of intraprofile 13c and 18o heterogeneity 2 increased development of down profile 13c and 18o trends 3 an increase in the degree of intermorphologic and intramorphologic stable isotope variation commonly in samples distributed laterally within narrow depth intervals and 4 development of covariation between 13c and 18o values radiocarbon ages of the carbonates permit assessment of the degree of isotope heterogeneity in contemporaneous carbonates and recognition of temporal isotopic trends the range of exposure times recorded by the studied soils are analogous to those associated with the formation of fossil soils this makes the studied soils ideal for evaluating the origin of stable isotope heterogeneity in paleosol carbonates and the implications of those heterogeneities for the use of stable isotopes as paleoenvironmental proxies specific implications of this study include the following 1 pedogenic carbonates that form by overprinting are a cumulative record of the soil conditions present during their accumulation thus isotope analysis of overprinted carbonates can result in time averaging of changing climatic paleoenvironmental and paleoecologic conditions 2 carbonates may record only a fraction of the duration of development of their host profile 3 there is a high level of uncertainty associated with using the sequence of morphologic development of carbonate as a function of time or maturity in paleosols 4 an exponential decrease in carbonate 13c values with depth in a paleosol does not imply that the carbonates are contemporaneous or accumulated under invariant soil conditions 5 shifts in soil and paleoclimatic conditions may be recorded by the 13c and 18o values of carbonates distributed within narrow depth intervals of a given soil in addition to those distributed down profile or even from within individual carbonate samples

ichnotaxonomy and ichnostratigraphy of chambered trace fossils in palaeosols attributed to coleopterans ants and termites

groundwater recharge in the akaki catchment central ethiopia evidence from environmental isotopes δ18o δ2h and 3h and chloride mass balance recharge patterns possible flow paths and the relative age of groundwater in the akaki catchment in central ethiopia have been investigated using stable environmental isotopes 18o and 2h and radioactive tritium 3h coupled with conservative chloride measurements stable isotopic signatures are encoded in the groundwater solely from summer rainfall thus groundwater recharge occurs predominantly in the summer months from late june to early september during the major ethiopian rainy season winter recharge is lost through high evaporation evapotranspiration within the unsaturated zone after relatively long dry periods of high accumulated soil moisture deficits chloride mass balance coupled with the isotope results demonstrates the presence of both preferential and piston flow groundwater recharge mechanisms the stable and radioactive isotope measurements further revealed that groundwater in the akaki catchment is found to be compartmentalized into zones groundwater mixing following the flow paths and topography is complicated by the lithologic complexity an uncommon highly depleted stable isotope and zero 3h groundwater observed in a nearly east west stretch through the central sector of the catchment is coincident with the filwoha fault zone here deep circulating meteoric water has lost its isotopic content through exchange reactions with co2 originating at deeper sources or it has been recharged with precipitation from a different rainfall regime with a depleted isotopic content copyright 2006 john wiley sons ltd

infiltration in layered loessial deposits revised numerical simulations and recharge assessment summary the objective of this study is to assess recharge rates and their timing under layered loessial deposits at the edge of arid zones particularly this study is focused on the case of the coastal plain of israel and gaza first results of a large scale field infiltration test were used to calibrate the van genuchten parameters of hydraulic properties of the loessial sediments using hydrus 2d 3d second optimized soil hydraulic parameters were used by hydrus 1d to simulate the water balance of the sandy loess sediments during a 25 year period 1990 2015 for three environmental conditions bare soil and soil with both sparse and dense natural vegetation the best inverse parameter optimization run fitted the infiltration test data with the rmse of 0 27 d with respect to a moisture front arrival and r 2 of 96 the calibrated model indicates that hydraulic conductivities of the two soil horizons namely sandy loam and sandy clay loam are 81 cm d and 17 5 cm d respectively these values are significantly lower than those previously reported based on numerical simulations for the same site hydrus 1d simulation of natural recharge under bare soil resulted in recharge estimates to the aquifer in the range of 21 93 mm yr with an average recharge of 63 mm yr annual precipitation in the same period varied between 100 and 300 mm yr with an average of 185 mm yr for semi stabilized dunes with 26 of the soil surface covered by local shrub artemisia monosperma the mean annual recharge was 28 mm for the stabilized landscape with as much as 50 vegetation coverage it was only 2 3 mm yr in other words loessial sediments can either be a source of significant recharge or of no recharge at all depending on the degree of vegetative cover additionally the time lag between specific rainy seasons and corresponding recharge events at a depth of 22 m increased from 2 5 to 5 years and to about 20 years respectively with an increasing vegetative cover for this reason and also likely due to a great depth of loessial sediments no correlation was found between annual recharge and annual precipitations of the same year or subsequent years similarly no differences were found between summer and winter recharge fluxes instead numerical simulations indicated continuous year round recharge of the aquifer we conclude that the layered subsurface acts as a short term annual and long term multi annual buffer to smooth sudden precipitation infiltration events vegetation conditions can help in predicting long term recharge rates as percentage of annual precipitation which in turn need to be considered when assigning recharge characteristics in regional assessments and models

morphology and isotope heterogeneity of late quaternary pedogenic carbonates implications for paleosol carbonates as paleoenvironmental proxies abstract stable isotope values and radiocarbon ages were determined for pedogenic carbonate microsamples from relict soils and palaeosols from the rio grande rift region of new mexico carbonate nodules and clusters were sampled from fluvial and piedmont soils and palaeosols with widely varying exposure durations 7 900 ky pedogenic carbonates from individual soils exhibited irregular relationships between age and depth ranging in radiocarbon age by 13 ky at individual depths 18 o values and to a lesser extent 13 c values likewise had wide ranges within soils however comparing the stable isotope values of carbonates with similar radiocarbon ages within and between soils revealed consistent trends in stable isotope values over time 18 o values of pedogenic carbonates tended to decrease with decreasing age 25 17 radiocarbon ka and increased with decreasing age 13 c values with either depth or age although the oldest palaeosol piedmont carbonates radiocarbon ages of 24 5 19 2 ka are 1 more negative than the younger piedmont palaeosol carbonates pedogenic carbonates in the relict fluvial soil which has by far the longest exposure period showed the greatest range in 13 c values comparing the 13 c values of samples of similar radiocarbon age from the relict fluvial soil indicates a transition from a mixed c 3 c 4 ecosystem at 11 ka to an effectively pure c 3 ecosystem at 9 ka followed by a return to mixed vegetation by 5 ka thus although c 4 vegetation persisted in southern new mexico through the last glaciation drought resistant c 3 vegetation became dominant at 9 ka prior to significant strengthening of the summer monsoon this study illustrates that the stable isotope values of carbonate nodules and clusters from relict soils and or slowly buried palaeosols can be used for palaeoenvironmental reconstructions in the context of a detailed chronologic framework

geological control on the origin of fresh groundwater in the otindag desert china abstract the present study has explored the origin of fresh groundwater in the otindag desert china using environmental tracers the results characterize hydrochemical and isotopic properties of groundwater in this middle latitude desert of arid asia clarifying their spatial distribution and linkage with climatic topographic and geologic settings and interpreting the groundwater source and chemical evolution hydrogeochemical and isotopic signals suggest that groundwater recharge in the desert is isolated from seasonal and regional variations in meteorological forcing stable isotopic data 2h 18o and radioactive isotopic data 3h indicate that the desert aquifer is dominated by high altitude cold water originating from the highland mountains that border the desert to the east and south variography shows that the dip of the main xilamulun fault is a dominant control on the groundwater flow implying that the tectonic settings are more important than climatic and topographical settings to explain the origin of groundwater in the desert this means that the origin of fresh groundwater in the desert is maily controlled by geological structures this study provides a new perspective into the origin and evolution of groundwater resources in the middle latitude deserts of the arid asia

pedogenic carbonate stable isotope record of environmental change during the neogene in the southern great plains southwest kansas usa oxygen isotopes and paleoclimate during the evolution of c4 dominated grasslands neogene strata in the meade basin southwest kansas preserve numerous superposed calcareous paleosols in sections that range in age from the clarendonian north american land mammal age nalma 12 0 9 0 ma early late miocene to the early irvingtonian nalma ca 2 5 ca 1 ma early pleistocene the carbon isotope compositions 13 c relative to vienna peedee belemnite vpdb of pedogenic carbonates from these sections record the protracted regional increase in the abundance of grasses using the c 4 photosynthetic pathway over this interval with the first appearance of a modern like grassland ecosystem having 70 c 4 biomass around 1 3 ma we use the stable oxygen isotope composition 18 o relative to vienna standard mean ocean water vsmow of 194 paleosol carbonates from 19 measured sections to reconstruct the climatic conditions in the meade basin during the rise of c 4 grasses to ecological dominance in the region pedogenic carbonate 18 o values are sensitive to soil temperature and the 18 o of soil water and hence they are a paleoclimate proxy carbonate 13 c values do not exhibit consistent trends in relation to 18 o values indicating no consistent relationship between short term climatic conditions in terms of temperature or aridity and the abundance of c 4 biomass mean carbonate 18 o values within biostratigraphic intervals decrease from the clarendonian 25 3 0 72 to the early and middle blancan 21 8 0 87 and 22 1 0 69 respectively and they also exhibit a decreasing trend in the late blancan early irvingtonian from 25 to 21 the increase in 18 o values between the end of the middle blancan and the beginning of the late blancan early irvingtonian sections could reflect the onset of northern hemisphere glaciation and a change in the isotope composition of the hydrosphere due to increased ice volume the long term trend in 18 o values suggests that c 4 biomass increased coincident with some combination of decreasing temperature increasing proportion of winter precipitation recharge of soil water and or increasing soil moisture thus the ecological dominance of c 4 grasses in the region today does not seem to be linked to warmer temperatures or increased aridity

sediment management with submerged vanes i theory recent research results with the submerged vane technique for sediment control in rivers are described submerged vanes are small flow training structures foils designed to modify the near bed flow pattern and redistribute flow and sediment transport within the channel cross section the structures are installed at an angle of attack of 15 25 with the flow and their initial height is 0 2 0 4 times local water depth at design stage the vanes function by generating secondary circulation in the flow the circulation alters magnitude and direction of the bed shear stresses and causes a change in the distributions of velocity depth and sediment transport in the area affected by the vanes as a result the river bed aggrades in one portion of the channel cross section and degrades in another the vanes can be laid out to develop and maintain any desired bed topography vanes have been used successfully for protection of stream banks against erosion and for amelioration of shoaling problems at water inta

sediment control by submerged vanes a procedure is developed for a rational design of a system of submerged vanes for depth control in alluvialriver channels the vanes are vertical smallaspect ratio foils installed on the channel b

the influence of biological soil crusts on dew deposition in gurbantunggut desert northwestern china dew is an important source of moisture for plants biological soil crusts invertebrates and small vertebrates in desert environments in this paper measurements were taken to investigate the effects of three different types of biological soil crusts cyanobacteria lichen and moss and bare sand on dew deposition in the gurbantunggut desert dew quantities were measured using micro lysimeters with a diameter of 6 cm and a height of 3 5 cm the results showed that the total amount of dew deposited increased with the development of soil crusts from bare sand to cyanobacterial crust to lichen crust to moss crust the average amount of dew deposited daily on the moss crust was the highest of all and it was significant higher than the other three soil surfaces lichen crust cyanobacterial crust and bare sand p l 0 05 during the period of the study for each type of crust studied the maximum amount of dew recorded was several times greater than the minimum moss crust was characterized by having the greatest amount of dew at dawn and also the maximum amount of dew deposited whereas bare sand yielded the lowest amount of dew with lichen crust and cyanobacterial crust exhibiting intermediate values however this was not the case for dew duration as bare sand retained moisture for the longest period of time followed by cyanobacterial crust moss crust and finally lichen crust dew continued to condense even after sunrise furthermore the differences in dew deposition may be partially attributed to an effect of the biological soil crusts on surface area this study demonstrates the important effect of biological soil crusts upon dew deposition and may assist in evaluating the role of dew in and and semi arid environments c 2009 elsevier b v all rights reserved

climatic and environmental controls on speleothem oxygen isotope values variations in speleothem oxygen isotope values d 18 o result from a complicated interplay of environmental controls and processes in the ocean atmosphere soil zone epikarst and cave system as such the controls on speleothem d 18 o values are extremely complex an understanding of the processes that control equilibrium and kinetic fractionation of oxygen isotopes in water and carbonate species is essential for the proper interpretation of speleothem d 18 o as paleoclimate and paleoenvironmental proxies and is best complemented by study of site specific cave processes such as infiltration flow routing drip seasonality and saturation state and cave microclimate among others this review is a process based summary of the multiple controls on d 18 o in the atmosphere soil epikarst and speleothem calcite illustrated with case studies primary controls of d 18 o in the atmosphere include temperature and relative humidity through their role in the multiple isotope effects variability and modifications of water d 18 o values in the soil and epikarst zones are dominated by evaporation mixing and infiltration of source waters the isotopically effective recharge into a cave system consists of those waters that participate in precipitation of caco3 resulting in calcite deposition rates which may be biased to time periods with optimal dripwater saturation state recent modeling experimental and observational data yield insight into the significance of kinetic fractionation between dissolved carbonate phases and solid caco3 and have implications for the hendy test to assist interpretation of speleothem d 18 o time series quantitative and semi quantitative d 18 o climate calibrations are discussed with an emphasis on some of the difficulties inherent in using modern spatial and temporal isotope gradients to interpret speleothems as paleoclimate proxy records finally several case studies of globally significant speleothem paleoclimate records are discussed that show the utility of d 18 o to reconstruct past climate

reconstruction of groundwater flows and chemical water evolution in an amagmatic hydrothermal system la lechere french alps summary a detailed picture of the hydrogeochemistry of an alpine thermal area la lechere french alps was drawn up from new and complete analyses of shallow and deep groundwater including major and trace elements gases and stable 18 o d 13 c 34 s and radiogenic isotopes 14 c combined with data on the trace and stable isotope 18 o 34 s contents of the aquifer rocks three different groundwater facies were recognized 1 the shallow groundwater in the carbonate and crystalline rocks presents a poorly mineralized ca hco 3 facies 2 the shallow groundwater from the evaporitic fault zone presents a mineralized ca mg so 4 facies 3 and the deep thermal water presents a highly mineralized ca na so 4 facies the evolution from facies 2 to facies 3 is controlled by three phenomena i the presence or absence of evaporitic deposits along the fault which governs whether or not the water can interact with carbonates and dolomites ii interactions with micaschists and permo carboniferous rocks which lead to ca na exchanges and enrichment in some trace elements and gases co 2 ch 4 and h 2 s and iii the long residence time several thousand years and high temperature 90 c of the thermal water

effects of sand burial on dew deposition on moss soil crust in a revegetated area of the tennger desert northern china summary sand burial and dew deposition are two fundamental phenomena profoundly influencing biological soil crusts in desert areas however little information is available regarding the effects of sand burial on dew deposition on biological soil crusts in desert ecosystems in this study we evaluated the effects of sand burial at depths of 0 control 0 5 1 2 and 4 mm on dew formation and evaporation of three dominant moss crusts in a revegetated area of the tengger desert northern china in 2010 the results revealed that sand burial significantly decreased the amount of dew deposited on the three moss crust types by acting as a semi insulator retarding the dew formation and evaporation rates the changes in surface temperature cannot fully explain the variations of the formation and evaporation rates of dew by moss crusts buried by sand the extension of dew retention time was reflected by the higher dew ratios the ratio of dew amount at a certain time to the maximum value in a daily course in the daytime and may to some extent have acted as compensatory mechanisms that diminished the negative effects of the reduction of dew amount induced by sand burial of moss crusts the resistances to reduction of dewfall caused by sand burial among the three moss crusts were also compared and it was found that bryum argenteum crust showed the highest tolerance followed by crusts dominated by didymodon vinealis and syntrichia caninervis this sequence corresponds well with the successional order of the three moss crusts in the revegetated area thereby suggesting that resistance to reduction of dewfall may act as one mechanism by which sand burial drives the succession of moss crusts in desert ecosystems this side effect of dew reduction induced by sand burial on biological soil crusts should be considered in future ecosystem construction and management of desert area

study of stable isotopes in the kouris catchment cyprus for the description of the regional groundwater flow the stable isotopes of oxygen and hydrogen in groundwater and precipitation were integrated for the description of groundwater flow in the kouris catchment cyprus the catchment consists of an ophiolitic complex in the north and sediments in the south it is characterized by strong heterogeneity of the underground media and steep slopes of the topography the regression line constructed from the data of 70 rainfall samples is described by the equation ddz6 6d 18 oc10 9 which shows evaporation during precipitation the altitude gradients in the precipitation were estimated to be k1 7 100 m for dd and 0 27 100 m for d 18 o the stable isotope analysis of 234 groundwater samples reflected fractionation due to evaporation the origin of groundwaters in the catchment was described based on the regression equation between surface elevations and dd contents for 33 selected springs of the ophiolitic complex it was found that the groundwaters in the ophiolitic aquifer and in the consolidated sediments originated from local recharge at high and low altitudes respectively on the contrary the groundwater in the alluvium aquifer originates from the high altitudes in the ophiolitic complex additionally dd data were used for the calibration of the recharge rates for a steady state groundwater flow and transport model the resulting calibrated total steady state recharge rate was 100 130 mm per year

oxygen isotope evidence of climate change from pedogenic clay minerals in the himalayan molasse abstract in this study we examine the oxygen isotope ratios of smectite and kaolinite in a stratigraphic sequence of paleosols in the siwalik himalayan molasse on the potwar plateau northern pakistan there is a 3 4 o increase in the smectite 18 o values synchronous with a 3 5 o increase in 18 o values of pedogenic calcite at 8 5 6 5 ma previously observed by quade et al 1989 the covariation of the 18 o values of smectite with calcite gd 18 o values through time strongly suggests a pedogenic origin of smectite and that its 18 o values reflect the oxygen isotope ratio of the soil water present during pedogenesis these data show that the 18 o values of clay minerals in paleosols in aggrading sedimentary sequences are viable paleoclimate indicators kaolinite 18 o values are similar to smectite 18 o values as would be expected for pedogenic kaolinite but there is greater variation in these data which we attribute to incomplete mineral separation the measured permil oxygen isotope fractionation between calcite and smectite within individual paleosols is on average 3 o higher than the equilibrium fractionation this isotopic disequilibrium can be explained by the calcite forming predominantly during the dry winter season and the smectite forming predominantly during the wet summer season the synchronous 3 5 o increase in oxygen isotope ratios of smectite and calcite at 8 5 6 5 ma indicates that this 18 o 16 o increase is not due to diagenesis but rather results from a climate change the most likely causes of the 18 o 16 o increase in smectite and calcite are either increased aridity resulting in increased soil water evaporation thus 18 o enrichment and or a change from more continental to more marine sourced precipitation the tibetan plateau which is suggested to have undergone rapid uplift around 8 ma e g harrison et al 1992 may have acted as an effective orographic barrier to low 18 o precipitation originating from central asia causing higher 18 o values of the precipitation falling on the potwar plateau currently it is impossible to distinguish between these two potential causes of the 18 o 16 o increase at 8 5 6 5 ma but these clay mineral 18 o values support that there was a significant climate change in this region

the mid cretaceous water bearer isotope mass balance quantification of the albian hydrologic cycle a latitudinal gradient in meteoric n 18 o compositions compiled from paleosol sphaerosiderites throughout the cretaceous western interior basin kwib 34 75 n paleolatitude exhibits a steeper more depleted trend than modern predicted values 3 0x 34 n latitude to 9 7x 75 n lighter furthermore the sphaerosiderite meteoric n 18 o latitudinal gradient is significantly steeper and more depleted 5 8x 34 n to 13 8x 75 n lighter than a predicted gradient for the warm mid cretaceous using modern empirical temperature n 18 o precipitation relationships we have suggested that the steeper and more depleted relative to the modern theoretical gradient meteoric sphaerosiderite n 18 o latitudinal gradient resulted from increased air mass rainout effects in coastal areas of the kwib during the mid cretaceous the sphaerosiderite isotopic data have been used to constrain a mass balance model of the hydrologic cycle in the northern hemisphere and to quantify precipitation rates of the equable greenhouse albian stage in the kwib the mass balance model tracks the evolving isotopic composition of an air mass and its precipitation and is driven by latitudinal temperature gradients our simulations indicate that significant increases in albian precipitation 34 52 and evaporation fluxes 76 96 are required to reproduce the difference between modern and albian meteoric siderite n 18 o latitudinal gradients calculations of precipitation rates from model outputs suggest mid high latitude precipitation rates greatly exceeded modern rates 156 220 greater in mid latitudes 2600 3300 mm yr 99 greater at high latitudes 550 mm yr the calculated precipitation rates are significantly different from the precipitation rates predicted by some recent general circulation models gcms for the warm cretaceous particularly in the mid to high latitudes our mass balance model by no means replaces gcms however it is a simple and effective means of obtaining quantitative data regarding the mid cretaceous hydrologic cycle in the kwib our goal is to encourage the incorporation of isotopic tracers into gcm simulations of the midcretaceous and to show how our empirical data and mass balance model estimates help constrain the boundary conditions

effects of microbiotic crusts on dew deposition in the restored vegetation area at shapotou northwest china information regarding dew deposition on microbiotic crusts is scarce in chinese desert areas an area of restored vegetation where microbiotic crusts with different developmental levels are distributed in the revegetated enclosures of different ages provides an ideal opportunity to study the hydrological issues related to the development processes of microbiotic crusts in a temporal sequence the effects of microbiotic crusts on dew condensation were studied during the late summer and autumn of 2004 the results show that the amount of dew increases with the level of development of the microbiotic crusts the physical crust which is an initial form of microbiotic crust and is composed of sand with a higher proportion of clay and silt because of its aeolian origin collects more dew than sand soil in addition the microorganisms adhering to the crusts cause the amounts of dew on the algae and moss crust to increase dramatically anova analysis results also indicate a significant difference between well developed microbiotic crusts algal and moss crusts initial microbiotic crusts physical crust and sandy soil it is potential that dew acts as a driving factor for restored vegetation succession through its benefits in the development of microbiotic crust

compositional multivariate statistical analysis of the hydrogeochemical processes in a fractured massif la linea tunnel project colombia abstract hydrogeochemical and isotopic data were used to improve the understanding of 1 groundwater flow in a complex fractured aquifer system 2 surface water groundwater interactions and 3 groundwater evolution within the la linea massif in the cordillera central of the colombian andes using two roadway tunnels drilled there as a natural laboratory the la linea massif is a crystalline structure formed by two igneous metamorphic fractured complexes cajamarca group and quebradagrande group plus andesitic porphyry rocks from the cenozoic period the tunnels traverse eight main fault zones where higher infiltrations of groundwater into the tunnels were reported water samples were collected at the surface and within the tunnels in three different sampling rounds in 2010 2014 and 2015 major ion concentrations and 18 o and 2 h stable isotopic ratios were measured this database is a unique opportunity to investigate water rock interaction processes through time in a dewatering crystalline rock massif in such an important area in the colombian andes compositional data analysis coda techniques were implemented on the major ion data before a multivariate statistical analysis msa the msa included a compositional principal component analysis pca and a compositional hierarchical cluster analysis hca combined with more classical graphical methods for the classification of water chemistry data such as piper and stiff diagrams according to the compositional hca and pca the obtained components and clusters are first related to the location of the samples surface or tunnel samples followed by the geochemical processes the geochemical variability of the massif is associated with the weathering of silicates and pyrite oxidation that generates carbonate dissolution as a result of the drainage caused by the tunnels a temporal evolution characterized by a decrease in ph conductivity and mg2 concentrations was observed the analysis of the stable isotopes 2h and 18o suggests that the sampled groundwater has a common origin recharge waters with specific signatures for the east and west watersheds that exhibit alterations due to hydration because of the dissolution of plagioclases and rock water interactions with materials exposed to hydrothermal fluids

groundwater recharge and evolution of water quality in china s jilantai basin based on hydrogeochemical and isotopic evidence we investigated major ions stable isotopes and radiocarbon dates in a quaternary aquifer in semi arid northwestern china to gain insights into groundwater recharge and evolution most deep and shallow groundwater in the helan mountains was fresh with total dissolved solids 1 000 mg l 1 and cl 250 mg l 1 the relationships of major ions with cl suggest strong dissolution of evaporites however dissolution of carbonates albite weathering and ion exchange are also the major groundwater process in jilantai basin the shallow desert groundwater is enriched in 18o and intercepts the local meteoric water line at 18o 13 4 indicating that direct infiltration is a minor recharge source the isotope compositions in intermediate confined aquifers resemble those of shallow unconfined groundwater revealing that upward recharge from intermediate formations is a major source of shallow groundwater in the plains and desert the estimated residence time of 10 0 kyr at one desert site indicating that some replenishment of desert aquifers occurred in the late pleistocene and early holocene with a wetter and colder climate than at present

estimating groundwater recharge in hebei plain china under varying land use practices using tritium and bromide tracers summary tritium and bromide were used as applied tracers to determine groundwater recharge in hebei plain north china to evaluate the impacts of different soil types land use irrigation and crop cultivation practice on recharge additional objectives were to evaluate temporal variability of recharge and the effect on results of the particular tracer used thirty nine profiles at representative locations were chosen for investigation average recharge rates and recharge coefficient determined by tritium and bromide tracing for different sites were 0 00 1 05 mm d and 0 0 42 5 respectively the results showed relative recharge rates for the following paired influences items within each pair are listed with the influence producing greater recharge first flood irrigated cropland and non irrigated non cultivation land flood irrigation 0 42 0 58 mm d and sprinkling irrigation 0 17 0 23 mm d no stalk mulch 0 56 0 80 mm d and stalk mulch 0 44 0 60 mm d vegetable e g chinese cabbage and garlic 0 70 mm d and wheat maize 0 38 mm d peanut 0 51 mm d and peach 0 43 mm d the results also showed greater recharge for the first year of tracer travel than for the second because total precipitation and irrigation were greater in the first year than in the second this may reflect temporal variability of recharge the method may not be applicable where the water table is shallow less than 3 m a comparison of the near ideal tritium tracer with the more common but less ideal bromide showed that bromide moved approximately 23 faster than tritiated water perhaps because of anion exclusion

evaluation of evaporation rate from forested soil surface using stable isotopic composition of soil water in a headwater basin the stable isotopic composition of rain water and soil water was analysed and the soil surface evaporation rate was evaluated using the isotope value of soil water taken from a forested headwater basin in central japan rainfall throughfall soil water groundwater and discharge water were sampled at intervals of one month to determine the isotopic compositions of deuterium d and oxygen 18 18 o therein in addition tensiometric observation of soil water was performed continuously the stable isotopic ratio of soil water was homogenized between the soil surface and a depth of 100 cm by means of active soil water movement above 100 cm in depth the mean 18 o in deep soil water below a depth of 100 cm was 0 24 higher than the volume weighted mean 18 o in throughfall consequently the mean evaporation rate from the soil surface was calculated as 5 of the evapotranspiration rate using the difference between the 18 o in throughfall and in deep soil water based on the rayleigh equation under equilibrium condition

groundwater recharge estimation using chloride stable isotopes and tritium profiles in the sands of northwestern senegal a study of environmental chloride deuterium oxygen 18 and tritium in deep sand profiles 35 m has been carried out in order to estimate their relative value for measuring average groundwater recharge the investigation was located at a 0 1 km2 site in quaternary sands near the northwestern coast of senegal in a zone of rainfed agriculture by using a steady state model for duplicate unsaturated zone chloride profiles the long term average recharge at the site was estimated to be 30 mm yr 1 or around 10 of the average precipitation 290 mm the chloride concentration of adjacent shallow groundwater was relatively uniform and comparable to the unsaturated zone average while the spatial variability in the depth distribution of cl in the unsaturated zone was considerable stable isotope deuterium and oxygen 18 data show that there is some isotopic enrichment due to direct evaporation through the soil surface the degree of heavy isotope enrichment is proportional to the extent of evaporative loss and there is good correspondance with the chloride enrichment nevertheless stable isotopes cannot be used quantitatively to estimate the recharge the excellent preservation of the peak in thermonuclear tritium in precipitation in the unsaturated zone at depths between 12 and 20 m enables an estimated annual recharge of 24 mm yr 1 in this area to be calculated using the piston flow model agreement therefore between cl and3h as tools for recharge measurement is reasonable over the site

multi isotopic study 15n 34s 18o 13c to identify processes affecting nitrate and sulfate in response to local and regional groundwater mixing in a large scale flow system the integrated use of hydrogeologic and multi isotopic approaches 15n 18ono3 34s 18oso4 and 13chco3 was applied in the selva basin area ne spain to characterize no3 and so42 sources and to evaluate which geochemical processes affect no3 in groundwater the studied basin is within a basin and range physiographic province where natural hydrodynamics have been modified and different scale flow systems converge as a consequence of recent groundwater development and exploitation rates as a result groundwaters related to the local recharge flow system affected by anthropogenic activities and to the generally deeper regional flow system recharged from the surrounding ranges undergo mixing processes the 15n 18ono3 and 34s indicated that the predominant sources of contamination in the basin are pig manure and synthetic fertilizers hydrochemical data along with 15n 18ono3 34s 18oso4 and 13chco3 of some wells confirmed mixing between regional and local flow systems apart from dilution processes that can contribute to the decrease of no3 concentrations the positive correlation between 15n and 18ono3 agreed with the occurrence of denitrification processes the 34s and 18oso4 indicated that pyrite oxidation is not linked to denitrification and 13chco3 did not clearly point to a role of organic matter as an electron donor therefore it is proposed that the mixing processes between deeper regional and local surface groundwater allow denitrification to occur due to the reducing conditions of the regional groundwater thus isotopic data add useful complementary information to hydrochemical studies especially in those areas where hydrochemical data is not conclusive

the early paleozoic development of bioturbation evolutionary and geobiological consequences abstract bioturbation the physical and chemical mixing of sediments by burrowing animals is a critical engineering process in modern seafloor environments and exerts an important control on not only benthic ecology and sediment properties but also ocean wide biogeochemical cycling well mixed sediments have long been assumed to appear at the precambrian cambrian boundary with the first occurrence of the index fossil and three dimensional burrow treptichnus pedum however field based analyses synthesizing ichnological stratigraphic sedimentological and taphonomic data collected from lower paleozoic successions worldwide indicate that sediment mixing in marine shelf environments remained limited until at least the late silurian 120 million years after the precambrian cambrian transition in spite of early advances in complex modes of infaunalization mixed layer development had a much more gradual trajectory and did not occur in step with the first appearance of three dimensional burrows the delayed appearance of modern style intensities of sediment reworking postdating both the cambrian explosion and the great ordovician biodiversification event may be due to the late stage radiation of mobile infaunal deposit feeders biological bulldozers the organisms which are in modern marine settings the most efficient bioturbators the protracted development of the sediment mixed layer holds important implications for contemporaneous biogeochemical cycling and oxygenation of the ocean atmosphere system the delayed development of intensive sediment mixing may have also mediated exceptional preservation of both fossilized soft tissues and shallow tier trace fossils and may therefore have contributed to the anomalous preponderance of konservat lagerstatten and exceptionally preserved shallow tier trace fossils and bioglyphs characteristic of the lower paleozoic stratigraphic record

the response of infiltration depth evaporation and soil water replenishment to rainfall in mobile dunes in the horqin sandy land northern china to understand the relationships among rainfall infiltration evaporation replenishment in mobile dunes in the semi arid areas of china we used the container of water distribution 100 100 120 cm3 to examine rainfall infiltration soil water redistribution and soil surface evaporation under natural and simulated rainfall conditions the results showed that infiltration depth was linearly related to rainfall amount and intensity rainfall amounts larger than 13 4 mm could replenish soil water at 60 cm depth after redistribution while with rainfalls larger than 39 8 mm infiltration depth could exceed 120 cm rainfall amounts larger than 50 mm produced saturated soil water at 120 cm depth and replenishment amount accounted for 40 4 of the total amount of rainfall soil surface evaporation exhibited a relatively minor change with increases in rainfall when rainfall was larger than 11 8 mm the amount of evaporation and soil water content were significantly correlated at 0 60 cm soil depth but not below these results suggest that the maximum effective depth of evaporation is 60 cm below the ground surface and that rainfall of 13 4 mm is a threshold distinguishing effective from ineffective rainfall in the mobile dunes of the horqin sandy land

origin of the shallow groundwater system in the southern voltaian sedimentary basin of ghana an isotopic approach the development and management of groundwater resources require an ability to understand and identify the recharge source to the groundwater system stable and radioactive isotope data have been used to investigate the source of recharge and the age of the shallow groundwater system within the southern voltaian sedimentary basin svsb of ghana as part of an on going groundwater development project the tritium concentrations in the groundwater samples are very low and range from less than 1 7 2 t u while measured 14c content ranges from 43 to 108 modern carbon the tritium concentration of rainfall ranges from less than 1 4 t u the 18o values of groundwater samples range from 4 2 to 2 6 while the d values range from 21 to 10 stable isotopic data of the groundwater samples lie either on or close to the global meteoric water line gmwl on the d 18o plot and indicate that the shallow groundwater in the area is derived from meteoric water that has undergone no significant degree of kinetic evaporation during recharge no indication of paleo recharge can be inferred from the 18o and 2h composition of the groundwater current tritium concentration in the groundwater is generally low however it proved useful in the qualitative identification of modern recharge radiocarbon deduced ages range from about b p to modern and indicate young recharge to the shallow groundwater system

influence of rainfall quantity on the isotopic composition 18o and 2h of water in mountainous areas application for groundwater research in the yunquera nieves karst aquifers s spain abstract the isotopic composition 18 o and 2 h of rainwater and groundwater was determined in the yunquera nieves hydrogeological unit a karstic massif in s spain with complex orography and hydrogeology the aims were to identify 1 the source of the water 2 the main factors determining the isotopic content 3 the catchment area of the springs and 4 the aquifer behaviour the isotopic content of the sampled waters is of mixed atlantic mediterranean origin and is opposite to the quantity of rainwater distribution both in space and time spatially water is isotopically less depleted toward the eastern sector where rainwater quantity is lower which is locally affected by the orography thus it is possible to differentiate the catchment areas of the main springs aquifer recharge is produced by winter precipitation when rainfall water is isotopically more negative and evaporation is lower the decrease in rainfall quantity during the study period provoked an increase in 18 o and 2 h values both in rainwater and in groundwater the recorded variations of the isotopic content of the rainfall are rapidly evident in the spring waters which demonstrates a well developed karst network inside the carbonate aquifers and thus the existence of conduit flow systems

understanding recharge in soil groundwater systems in high loess hills on the loess plateau using isotopic data abstract the topography on the eastern and western sides of the liupan mountains northwestern china is characterized by hilly and gully loess deposits with elevations above 1000 m this study aims to uncover the mechanisms governing loess groundwater and soil water recharge in these relatively arid to semiarid higher loess hills on the basis of temporal soil profiles the results show that during the four monitoring periods the distinct variations of soil water and cl contents in soil water at different times in the upper parts of loess profiles particularly the increasing water content after the rainy season above 7 5 m indicate that temporal precipitation can at least infiltrate to 7 5 m in depth these variations attenuate as depth increases discernable variations in 18 o and 2 h values in soil water can also be identified at different times and even in deeper parts of the soil profiles however based on the average values in the steady state hydrologic layer ssl in the soil profiles very small temporal variations in average 18 o and 2 h values in the soil water in the ssl are observed if the analytical uncertainties of 2 h and 18 o are considered the 18 o and 2 h values in groundwater show relatively similar temporal fluctuations as the average values of soil water in the ssl at the same times they are also close to the local weighted average annual precipitation groundwater sampled in may 2013 revealed elevated tritium concentrations in both the monitoring well and the springs or wells the monitoring well displays a lower tritium isotope content 2 26 tu and others show higher contents in lower areas the radio carbon 14 isotope in the monitoring well also shows a lower content of approximately 25 95 pmc thus it can be inferred that in a general year temporal precipitation can rapidly infiltrate and reach the depth below 7 5 m of the loess profile through various preferential conduits preventing the water from evaporating near the surface then the soil water slowly percolates downwards mimicking a piston like flow and finally recharges groundwater these dual flow modes that exist inside loess deposits are the main mechanisms that maintain soil water and relatively abundant groundwater resources

the role of soil processes in δ18o terrestrial climate proxies a paleoclimate interpretation of a terrestrial hydrologic proxy such as the 18o of tree cellulose or speleothem calcite may be biased or misinterpreted if the isotopic composition of the soil water from which the proxy originated undergoes isotopic exchange or fractionation in this study we use a global isotope enabled land surface model to investigate how the 18o of precipitation may be altered in a soil column due to evaporation and vertical moisture transport in order to assess how precipitation and evaporation contribute to the soil water isotopic variability we compare seasonal and interannual changes in simulated xylem water 18o within a control simulation and in a suite of sensitivity experiments where the effects of precipitation 18o water vapor 18o and soil water evaporation are independently removed the simulations carried out for the period 1979 to 2004 reveal that in semiarid regions such as the southwest united states the seasonal cycle in xylem water 18o is strongly affected by evaporative loss during the dry season and evaporation can also constitute as much as 50 of the interannual 18o variance additional simulations including soil water tagging experiments indicate that upward fluxes of soil water occur during drier periods for soil water 18o profiles that are isotopically more depleted in 18o at depth this imparts a low isotopic signature to xylem water 18o during such dry intervals hence without taking into account vertical moisture transport in the soils low 18o years could be misinterpreted as wet conditions due to decreased evaporative enrichment when instead drier conditions are equally as likely

identification of different groundwater flowpaths within volcanic aquifers using natural tracers for the evaluation of the influence of lava flows morphology argnat basin chaine des puys france hydrochemical and stable isotopic 2h 18o data were used to characterize the groundwater flow and major chemical features within a complex fractured volcanic aquifer system the argnat basin which is located in the chaine des puys french massif central from 10 sampling points the study of the transfer into the saturated zone from upstream to downstream given the geological context and topography allows to estimate the role of supply from high and low altitudes to the recharge processes this work shows the existence of different types of supply between pahoehoe and a a flows therefore the morphology of volcanic flows impacts the chemical and isotopic signatures of groundwater enhancing or reducing the influence of the unsaturated zone on the pathways of infiltrated water pahoehoe flows imply horizontal water flows of low discharge at the top of the lava whereas a a flows seems to be much more heterogeneous and locally able to promote the existence of perched water bodies and further vertical circulations taking into account these two types of behaviour a conceptual scheme of the functioning of this heterogeneous environment is proposed which will help towards a sustainable management of volcanic aquifers in relation with the european union groundwater directive 2006 118 ce 2006

sustainability of groundwater usage in northern china dependence on palaeowaters and effects on water quality quantity and ecosystem health a synthesis of groundwater ages recharge rates and information on processes affecting groundwater quality in northern china highlights the major challenges faced for sustainable management of the region s groundwater direct recharge rates range from hundreds of millimetres per year in the north china plain to tens of millimetres per year in the loess plateau to less than 4 mm year in the arid northwest recharge rates and mechanisms to deep semiconfined and confined aquifers are poorly constrained however on the basis of available data these are likely to be mostly negligible severe groundwater level declines 0 53 m year have occurred throughout northern china in the last three to four decades particularly in deep aquifers radiocarbon dating stable isotope and noble gas data show that the most intensively extracted deep groundwater is palaeowater recharged under different climate and land cover conditions to the present reservoir construction has reduced surface runoff in mountain front areas that would naturally recharge regional quaternary aquifers in many basins in combination with intensive irrigation practices this has resulted in the main recharge source shifting from surface runoff and mountain front recharge to irrigation returns this has reduced infiltration of fresh recharge at basin margins and rapidly increased nitrate concentrations and overall mineralisation in phreatic groundwater over wide areas in some cases to 400 mg l and 10 g l respectively in some basins there is evidence that poor quality shallow water has leaked into deep layers 200 m via preferential flow mixing with palaeowaters stored in semiconfined aquifers high concentrations of naturally occurring fluoride and arsenic locally 8 5 and 4 mg l respectively have recently lead to the abandonment of numerous supply wells in northern china creating further pressure on stressed water resources increasing water demand from direct and indirect consumption poses major challenges for water management in northern china which must consider the full water cycle copyright c 2012 john wiley sons ltd

hydrogeology of palm valley central australia a pleistocene flora refuge abstract the palm valley oasis finke gorge national park in arid central australia is characterised by large stands of red cabbage palm trees livistona mariae how these unique plants over 1000 km away from nearest relatives in the tropical parts of northern australia persist has long fascinated visitors the hydrogeology of this area helps explain this phenomenon stable isotope 2h 8o analyses shows groundwater to have a uniform composition that plots on or near a local meteoric water line carbon 14 results are observed to vary throughout this aquifer from effectively dead 100 ka along some flow paths indicate groundwater discharge would endure through arid phases associated with quaternary climate oscillations such a flow system can explain the persistence of this population of palms and also highlight the possibility that palm valley has acted as a flora refuge since at least the mid pleistocene

review on soil water isotope based groundwater recharge estimations groundwater recharge estimations are necessary for sustainable management of groundwater resources among various hydraulic hydrogeological and hydrological approaches tracer methods are proposed to improve groundwater recharge estimations soil water isotope based estimates of groundwater recharge rates were developed in the 1960s and have been applied in more than 40 studies reviewed within this manuscript this comprehensive review research distinguishes three fundamental research approaches 1 labelling method with tritium or deuterium which can be used to trace unsaturated zone water movement 2 tracing soil water movement using a seasonal signal of stable isotopes in precipitation mainly applied in humid zones and 3 interpretation of an evaporation signal that impacts soil water stable isotope composition mainly applicable in arid and semiarid regions more recently advances in soil water extraction and analytical methods allow a higher sampling resolution and in situ measurements of soil water stable isotopes analytical advances may strengthen and improve the applicability of stable isotope methods for quantitative recharge we present compare and discuss studies of unsaturated zone isotope profiles with an emphasis on necessary prerequisites such as a substantial thick porous sedimentary layer or negative influences through high clay and silt contents or dry soil conditions copyright 2015 john wiley sons ltd

determining the origin of groundwater elements using hydrochemical data case study kerman water conveyance tunnel pollution by heavy metals and potentially toxic elements is one of the main problems in tunneling construction in geothermal and volcanic areas kerman tunnel located in the central parts of iran average base level of 2370 m and length of 38 km plays a key role in water transportation from safa dam to kerman city the tunnel is located at the kerman cenozoic volcanic belt as a southern part of urmia dokhtar volcanic belt the overburden of basement rocks above the tunnel axis is up to 850 m thick and the tunnel cuts across granite diorite andesite trachyandesite and flysch rocks based on the geothermal fluids evidences in the area this study made an attempt to determine the hydrochemical characteristics and the origin of the elements in groundwater this can identify the geological hazards in the tunnel route to this end 31 groundwater samples were collected from 12 boreholes and were then chemically analyzed the results showed that the cations and anions had widely varying concentrations high to ultra high concentrations of as b fe al hco3 and so4 were significant properties of the water samples the results of different diagrams ion ratios and multivariate statistical analysis especially principal component analysis pca and hierarchical cluster analysis hca confirmed that the unique water compositions and characteristics resulted from rock water interaction and mixing of geothermal and meteoric water

the variation of morphological features and mineralogical components of biological soil crusts in the gurbantunggut desert of northwestern china increasingly complex life forms were found in older biological soil crusts in the gurbantaunggut desert in northwestern china these crusts may play a critical role in mineral erosion and desert soil formation by modifying the weathering environment and ultimately affecting mineralogical variance to test this hypothesis variations in the morphological features and mineralogical components of successional biological soil crusts at 1 cm were studied by optical microscopy sem and grain size analysis concentrations of erosion resistant minerals decreased with crust succession while minerals susceptible to weathering increased with crust development neogenetic minerals were found in late stage crusts but not in early stage crusts silt and clay concentrations were highest in early formation crusts and soil mean particle size decreased with crust succession cyanobacteria lichen and moss were shown to erode and etch rocks and secondary minerals produced by weathering were localized with the living organisms thus more developed crusts appeared to contribute to greater mineral weathering and may be a major cause of mineralogical variance seen in the gurbantunggut desert the greater activity and complexity of older crusts as well as their improved moisture condition may function to accelerate mineral weathering therefore protection and recovery of biological crusts is vital for desert soil formation

characterization of water and solute transport in the unsaturated zone of a hypersaline environment we present a methodology for the analysis of chemical profiles from the unsaturated zone where ions from the sediment are extracted by two methods centrifugation and water addition the methodology enables one to 1 assess the ion amounts present in two different phases pore water and minerals 2 determine the depth in the unsaturated profile where the degree of saturation of each mineral is reached 3 establish the principal direction of water flow and 4 differentiate between upward transport of water either as vapor or as a saline solution the methodology was applied to the unsaturated zone of the dead sea coastal area where the original salinity of interstitial water in these sediments was 300 g l our analysis of the field data suggests that reduction of interstitial water salinity is the result of vertical upward transport of fresh water from a confined aquifer at a depth of 7 m flushing up to the potentiometric surface depth of 3 5 m is due to the positive pressure head of the aquifer above the potentiometric surface upward water transport is due to capillary forces and flow is maintained by evaporation at the soil surface evaporation leads to an increase in the salinity of the rising interstitial solution and to the sequential deposition of salts such as nacl and kmgcl3 6h2o

salt crust development in paddy fields owing to soil evaporation and drainage contribution of chloride and deuterium profile analysis summary in northeast thailand lowlands with shallow saline watertable rainfed paddy fields often present high salt concentration in the dry season forming patches or spots of salt crusts on the soil surface in this context the mechanisms implied in salt concentration during dry season were studied by establishing salt budget with evaporation and drainage estimates inside and outside a saline patch drainage was estimated by hydrus 1d modelling constrained by an hydrodynamic characterization and the profile of water contents at the end of dry season evaporation rates at the end of the dry season were computed by interpreting natural detailed profiles of deuterium d and chloride cl contents because of the drastic diminution of hydraulic conductivity at saturation with depth and the decrease of groundwater level at the end of the cropping season simulated hydrological balance with hydrus 1d pointed out zero cumulated fluxes for depths of 39 5 cm outside the saline patch and 37 5 cm inside the saline patch therefore all the chloride accumulated in the very upper layers during dry season comes from the chloride that was present in the 0 39 5 cm layers before the beginning of the drying inside the saline patch the tentative cl budget is coherent with the hypothesis of saturation of the profile by aquifer saline water during the flooding evaporation rates computed from the diffusion of chloride and deuterium at the end of the drying season when the aquifer level was 1 4 m deep range between 0 121 and 0 378 mm d 1 this does not sustain the assumption of a considerable salinity contribution from the aquifer during the dry season moreover evaporation estimates based on cl and d diffusion equilibrium showed depleted rates 38 63 inside the saline patch due to salt accumulation in the first 12 cm of the soil in the vapour transfer layer estimated evaporation rate based on the vapour movement of d was in the same order of magnitude than computed rate assuming liquid cl diffusion this coincidence is attributed to the liquid fluxes that occurred during the expansion of the vapour transfer layer during the progression of the evaporation front

stable carbon and oxygen isotopes in quaternary soil carbonates as indicators of ecogeomorphic changes in the northern chihuahuan desert usa stable carbon and oxygen isotopes in soil carbonates provide an additional technique for investigating quaternary ecogeomorphic changes in arid and semiarid regions this study presents 13c and 18o values in surface and buried soils in a basin and range region of southern new mexico and west texas three landform categories were investigated for their isotopic content 1 middle piedmont slopes 2 a lower piedmont slope and adjacent playa depressions and 3 an intermontane basin floor soils of the middle piedmont slopes had greatest 13c variability ranging from 0 6 in buried soils to 11 1 pdb in surface soils soils of the basin floor had greatest variability in 18o values ranging from 0 6 to 7 6 pdb fossil pollen patterns roughly paralleled 13c shifts with cheno am pollen exhibiting greatest changes both isotope and pollen data across stratigraphic discontinuities suggest that a conversion from c4 grasses to c3 desert shrubs accompanied holocene erosion

tritium profiles of pore water in the chinese loess unsaturated zone implications for estimation of groundwater recharge summary within the framework of the iaea research contract no 9402 two cores were taken in 1997 and 1998 in the loess unsaturated zone in inner mongolia and shanxi province respectively where the tritium profiles of pore water from a test pit and a core taken in 1980 s had already been reported it has been shown that even in the late 1990 s the tritium profiles of pore water still showed clearly defined peaks as those formerly reported this is because both sampling sites were located at rather high latitudes of the northern hemisphere this is also thanks to the very special characteristics of the loess deposit providing slow infiltration rate of pore water in the unsaturated zone average infiltration rate obtained from these tritium profiles was 0 30 m a the values of annual groundwater recharge were 47 and 68 mm a for inner mongolia and shanxi province respectively however the tritium content of the groundwater aquifers near both sampling sites was higher than expected consequently it can be concluded that the vertical infiltration in the soils of the semi arid loess region perhaps is not the only mechanism of groundwater recharge the unconfined aquifers may also be recharged by surface flow through deep valleys or through vertical cleavages which are generally developed in the loess deposit therefore the values of groundwater recharge obtained by using tritium profiles in the loess unsaturated zone may be underestimated

evidence for chlorine recycling hydrosphere biosphere atmosphere in a forested wet zone on the canadian shield abstract the ability to measure environmental levels of 36 cl by accelerator mass spectrometry and 3 h by 3 he ingrowth mass spectrometry has made it possible to use the pulses of these two isotopes released into the atmosphere during nuclear weapons testing as tracers of cl and water movement in soils and groundwater the authors have investigated the movement of these tracers below a forested wet zone and have found that both are retarded to a differing extent in the near surface because of vegetative uptake and recycling adsorption by clay particles followed by slow release to the groundwater may also be significant the data accumulated in this region of near vertical recharge have gone a considerable distance towards explaining the anomalously low concentrations of 36 cl measured in the 5 laurentian great lakes as well as indicating possible mechanisms for large scale cl recycling in the atmosphere and biosphere identification of the near term non conservative behaviour of the cl is significant since such a phenomenon could introduce errors in many watershed calculations e g water residence times evaporation rates and mixing calculations

chemical and sr isotopic compositions of rainwater on the ordos desert plateau northwest china the major ions and sr concentrations and the sr isotopic compositions of rainwater from four weather stations in the ordos desert northwest china were measured in this study in the studied rainwater ca2 was the most abundant cation with a volume weighted mean vwm value of 387 mol l and so4 2 was the dominant anion with a vwm value of 229 mol l the sr concentrations varied from 0 1 to 72 mol l and the strontium isotopic ratios 87sr 86sr range from 0 7098 to 0 7110 with an average of 0 7106 which are higher than that of seawater the 87sr 86sr ratios showed the potential to trace sources of rainwater solutes when combined with other chemical composition data the covariation between mg ca vs ca na and sr isotopic ratios vs ca sr in the rainwater suggested the mixture of at least three sources soil dust derived from the local area and or desert and loess areas in northwest china 87sr 86sr values of 0 7114 seawater 87sr 86sr value of 0 70917 and anthropogenic inputs 87sr 86sr value of 0 7110 and high ca sr due to coal combustion or automobile exhausts the human activity inputs are likely the major sources of atmospheric contaminants in the ordos rainwater from back trajectory analysis principal component analysis and a comparison between the major ion compositions of other selected sites in china we conclude that the ordos rainwater ion composition is more significantly influenced by desert and soil dust and anthropogenic sources primarily industrial and traffic emissions from the surrounding cities than by marine sources

recharge mechanisms and geochemical processes in a semi arid sedimentary basin eastern cape south africa abstract stable isotope 18 o and 2 h and geochemical signatures are used to gain some insight into recharge processes and groundwater salinization mechanisms in a semi arid rangeland catchment the 665 km 2 catchment is underlain by fractured lower beaufort sandstones and mudstones and is intruded by several dolerite dykes chloride and isotopic relationships suggest that chloride ions in ground water are of meteoric origin the hypothesized recharge and salinization mechanism is that large storm events periodically dissolve accumulated surficial meteoric salts and after a period of evaporative enrichment at or near the soil surface leach them into the ground water geochemical variations imply that spatial differences exist in recharge volumes in evaporative enrichment or in the extent of leaching of surficial salts meteoric sodium chloride contributes greater than 90 of the dissolved sodium except at low salinities where cation exchange processes yield additional sodium inputs in exchange for dissolved calcium and magnesium at high salinities this process reverses and sodium is adsorbed releasing calcium and magnesium this process accounts for up to 40 of the dissolved calcium and magnesium contributions from geochemical weathering are relatively uniform in spite of highly variable salinities which implies that residence times are also relatively uniform

influx and efflux of moisture in a desert soil during a 1 year period spatial and temporal variation of moisture flux in soil over a 1 year period was studied in the thar desert of india tritium was injected at a depth of 0 8 m at 18 sites distributed over an area of 50 km2 and at 20 adjacent points at a single site over a sand dune before the 1994 monsoon vertical soil profiles were collected from the 18 sites after the end of monsoon and at the end of the year and from the multiple injections site at different time intervals throughout the year moisture flux values computed from tritium and moisture distribution in soil profiles show that the moisture influx at a site depends upon the grain size of the top 20 cm layer and that about 68 of the total influx of water below the injection depth is lost during the summer months the data for the multiple injections site show that the tritium spike was displaced to a depth of 4 m by the end of the monsoon and it remained stationary during the postmonsoon period of 8 months although about 64 of the soil moisture was lost the spiked layer showed enrichment in the specific activity of tritium during summer months these observations suggest that vapor diffusion is the dominant process for moisture loss from the thar desert soil the net input natural recharge to groundwater due to 1994 precipitation was 62 mm

bed topography in bends of sand silt rivers a mathematical model for defining the lateral bed topography in bends of sand silt rivers is presented the model includes the effects of suspended sediment that have not been considered in the existing models the major agency for defining the lateral bed profile is found to be the force balance between the fluid force and the gravitational force exerting on bed materials the theory suggests that the lateral convective transport of suspended sediment induced by secondary flow may considerably affects the bed profile at the outer region of river bends while the lateral diffusion due to turbulence has negligible effect on the profile everywhere the new model is applied to an actual river suggesting the adequacy of the present model within the possible error

determining the origin circulation path and residence time of geothermal groundwater using multiple isotopic techniques in the heyuan fault zone of southern china abstract medium low temperature geothermal resources are abundant in southern china but their heat source and link to fault zones is poorly understood consequently geothermal energy is only used at small scale in order to broaden the footprint of geothermal energy use in southern china it is first necessary to understand and track the geothermal groundwater circulation pattern associated with fault zones the heyuan fault zone serves as a typical medium low temperature geothermal system of south china here we show that the geothermal groundwater circulation pattern can be traced by using stable hydrogen and oxygen isotopes helium and neon isotopes carbon 13 and carbon 14 as well as hydrochemical parameters the results show that in the heyuan fault zone the main hydrochemical type of the hot springs is hco3 na k while the shallow cold groundwater is mainly enriched in hco3 ca the results of the helium isotope and neon isotope indicate that the geothermal groundwater of this area is derived from the crust thus excluding the possibility of extremely deep paths of groundwater tapping into mantle helium sources furthermore the characteristics of the stable hydrogen and oxygen isotopes imply that geothermal groundwater is of local meteoric origin and the recharge area located at the hilly area of the hanging wall of the heyuan main fault with the recharge elevations ranging from about 440 m to 670 m the hot spring geothermometer shows that the highest reservoir temperature is about 157 c and the deepest circulation depth is about 6500 m carbon 14 isotope age dating suggests that the geothermal groundwater ages are mostly from 9 9 kyr bp to 12 3 kyr bp according to the geological structural characteristics of the study area the main upward channel for geothermal groundwater is the heyuan main fault generally the hot springs in this area are mixed with shallow cold groundwater and surface water which raises the ratio of the ca2 in water and dilutes the heavy hydrogen and oxygen isotopes

uncertainties around modelling of steady state phreatic evaporation with field soil profiles of δ18o and chloride summary the application of the general advection diffusion equation to model phreatic evaporation flux rates from solute concentration soil profiles has been applied to a variety of arid zone locations but the effects of heterogeneous and uncertain field data on modelling performance are rarely described we revisit and extend the model by accounting for the effects of variable water content and sediment type on the impedance factor and in turn effective diffusion coefficient we explore the local sensitivity of the extended model to its major assumptions and parameter values the mean diffusion coefficient of the soil profile data is most sensitive to the volumetric water content close to the evaporation front and so modelled evaporation results can be very sensitive to uncertainty around the position of the evaporation front the uncertainty in the position of the groundwater reservoir and its concentration has little effect where the lower part of the profile shows an asymptotic trend towards a representative value of groundwater concentration but can vary substantially with different values of groundwater depth and concentration if this is not the case field data from the southern margin of the great artesian basin are shown to exhibit considerable uncertainty around the boundary conditions of the advection diffusion model e g position of evaporation front depth and concentration of lower groundwater boundary condition resulting phreatic evaporation flux estimates show a wide range that needs to be considered when using these data in water balance studies of groundwater systems

stable carbon and oxygen isotopes of pedogenic carbonates ajo mountains southern arizona implications for paleoenvironmental change abstract in this study we compare the stable isotope composition of late holocene pedogenic carbonate from a late holocene soil developed on the pediment below the ajo mountains in southern arizona usa with measurements of the 18 o of the soil water throughout the seasonal cycle and with 18 o and 13 c measurements on older dated soils the comparison with the soil water composition shows that the pedogenic carbonate is forming in equilibrium with highly evaporated soil water at the highest summer temperatures the 13 c of the carbonate apparently reflects equilibrium with co 2 of an isotopic composition consistent with the present mixture of c3 desert shrubs and cam cactus comparison with glacial period soil carbonates shows that there has been little change in the 18 o but that the 13 c was about 4 5 heavier independent evidence indicates that glacial period summer temperatures were probably much cooler and that the 18 o of precipitation was also lighter the increase in the carbonate water fractionation factor with decreasing temperature probably counteracted the decrease in the 18 o of precipitation producing little net change in the 18 o of the soil carbonate we attribute the decrease in the 13 c to replacement of a glacial period c4 grassland by holocene c3 cam desert shrubs and succulents this replacement was probably in response to an increase in temperature and reduction in summer precipitation at the end of the last glacial period the 13 c of older soil carbonates indicates that landscape was dominated by grassland for most of the past 700 ka and that the present vegetation likely represents a relatively brief anomaly

spatio temporal variations of δ2h and δ18o in precipitation and shallow groundwater in the hilly loess region of the loess plateau china groundwater is of utmost significance to socio economic development and ecological recovery for the loess plateau however studies regarding the mechanism governing groundwater recharge over this area appear to be inadequate this study is to examine the spatio temporal variations of 2h and 18o in precipitation and shallow groundwater on the basis of this the mechanisms governing shallow groundwater recharge were explored precipitation and groundwater were sampled monthly from may to october during the period 2004 2006 at 13 sites in the chabagou catchment 187 km2 in the caopingxigou experimental watershed 0 1 km2 meteorological variables were observed and rainfall larger than 5 mm was sampled immediately after each rain event across the area 90 of the precipitation occurred from may to september primarily in the form of heavy rains or rainstorms with great spatial variability there were about 30 localized rains in each year it was indicated that there existed notable seasonality and pronounced spatial variability in precipitation isotopic compositions contributing factors and indications of isotopic compositions as well as their climatic indications such as monsoon intensities and mixing processes of water vapor were investigated the 2h 18o relation of groundwater was found to be 2h 3 22 18o 38 1 deviating from the local meteoric water line 2h 7 57 18o 3 9 the range of values in groundwater is shrunken to be 15 21 of that in individual precipitations and groundwater in the middle reaches shows a wider range of values isotopic results showed that groundwater originates from precipitation with hydrogen and oxygen isotopic compositions being 69 and 9 7 respectively and most groundwater experiences serious evaporation and adequate mixing with old water during infiltration or percolation in the aerated zone it was also founded that obvious fluctuations of isotopic compositions in groundwater mainly appear in the middle reaches especially at sites that are close to valleys suggesting varying sources of groundwater from precipitation precipitation runoff isotopically enriched surface water and or lateral recharge of adjacent groundwater

transition between terrestrial submerged walking and swimming revealed by early permian amphibian trackways and a new proposal for the nomenclature of compound trace fossils abstract exceptionally preserved early permian tetrapod trackways from the orobic basin central western southern alps offer a unique opportunity to investigate in detail locomotion in fossil vertebrates that lived on continental european landmasses herein are reported the results of a study on several tetrapod trackways that display a large variety of behavioral gait and substrate related extramorphologies they clearly document the transition from terrestrial underwater walking to swimming and are assigned to the compound ichnotaxon batrachichnus c lunichnium the use of the c symbol is here introduced for the first time as nomenclatural indication of a compound trace producers were probably small sized temnospondyl or lepospondyl microsaurs amphibians comparisons with living urodelan anatomy and mechanics provide evidence for conservatism of locomotor mechanics in evolutionary history among amphibians the derived model for locomotor kinematics in early permian amphibians provides a reference for interpreting transitional land to water trackways the shift from walking to swimming behavior in early tetrapods as in extant urodelan amphibians is described as a complex balance between different dynamics

perchlorate accumulation and migration in the deep vadose zone in a semiarid region summary for 25 years a plant in israel manufacturing ammonium perchlorate disposed of untreated wastewater in four unlined ponds this study explores the transport mechanisms of perchlorate infiltrated from 1965 to 1990 from one of these active storage ponds into a deep 40 m layered vadose zone and the underlying israeli coastal aquifer perchlorate migration from 1990 when wastewater disposal ceased until today with infiltration due only to natural rain 500 mm y 1 was also studied several indirect methods were used including mass balance in the unsaturated zone profile 18 o and 2 h profiles below the pond and a comparison of the same sediment profiles in 2005 and 2007 the isotopic composition of the pore water could be divided into two separate groups lighter depleted and heavier enriched samples all samples in the lighter group were from the shallow vadose zone above two clayey layers and represent natural infiltration of rainwater the enriched samples were from the deeper section of the unsaturated zone 20 40 m and represent water used for perchlorate manufacturing 14 years prior to drilling consequently the overall maximum infiltration rate was estimated to be 1 4 m y 1 below the clayey layer almost identical perchlorate concentrations were found along the sediment profile in 2005 and 2007 two boreholes 3 m apart very different perchlorate profiles were observed above the clayey layers this suggests that perchlorate below the clay layers 20 40 m is practically stagnant under the current natural conditions the reduction in perchlorate concentration in groundwater below the ponds vs its increased concentration further downgradient supports the contention that the current migration of perchlorate from the vadose zone to the groundwater is very small we estimate that perchlorate concentration in the groundwater under the infiltration pond which was 187 mg l 1 in 2004 will reach 10 g l 1 within about 14 years the existence of a clayey layer crossing the thick vadose zone was thus found to significantly change the infiltration rate when ponded conditions were replaced with natural precipitation

seasonal bias in the formation and stable isotopic composition of pedogenic carbonate in modern soils from central new mexico usa in order to better calibrate pedogenic carbonate as a proxy for past environments we compared the stable isotopic composition of soil co 2 soil water and pedogenic carbonate in young soils from central new mexico usa seasonal changes in the 13 c value of soil co 2 the 18 o value of soil water and the soil temperature were monitored to establish the timing of isotopic equilibrium with the carbonate calcite solubility was calculated from measured temperatures and co 2 concentrations in the soil this approach allowed us to determine the conditions associated with pedogenic carbonate formation carbon isotope equilibrium oxygen isotope equilibrium and minimum calcite solubility all occurred simultaneously during warm dry conditions in may 2008 when soil co 2 concentrations were low it is therefore concluded that pedogenic carbonate forms during warm dry periods and does not record mean growing season conditions as typically assumed the seasonal bias in pedogenic carbonate formation may explain the occurrence of pedogenic carbonate in monsoon climates and its absence in regions where annual precipitation is more uniformly distributed the implications of the seasonal bias for stable isotope based paleoenvironmental reconstructions are that paleoelevations may have been previously over or underestimated paleoatmospheric co 2 concentrations likely have been signifi cantly overestimated and pedogenic carbonate provides a c 4 biased record of paleovegetation especially in dry soils

a chlorine 36 study of regional groundwater flow and vertical transport in southern nevada chlorine 36 data for groundwater from the death valley regional flow system is interpreted in the context of existing conceptual models for regional groundwater flow in southern nevada chlorine 36 end member compositions are defined for both recharge and chemically evolved groundwater components the geochemical evolution of 36cl is strongly controlled by water rock interaction with paleozoic carbonate rocks that comprise the regional aquifer system resulting in chemically evolved groundwater that is characteristically low in 36cl cl and high in cl groundwater from alluvial and volcanic aquifers that overlie the regional carbonate aquifer are generally characterized by high 36cl cl and low cl signatures and are chemically distinct from water in the regional carbonate aquifer this difference provides a means of examining vertical transport and groundwater mixing processes in combination with other geochemical and hydrogeologic data the end members defined here provide constraints on aquifer residence times and mixing ratios

a 700 year history of groundwater recharge in the drylands of nw china a 700 year semi quantitative history of diffuse groundwater recharge in the badain jaran desert inner mongolia is proposed on the basis of solute data from multiple unsaturated zone groundwater profiles using mass balance of chloride to establish recharge rates and profile chronologies four relatively humid 1330 1430 1500 1620 1700 1780 and 1950 1990 and three relatively arid phases 1430 1500 1620 1700 and 1900 1950 are discernable across the profiles the recharge history broadly reflects multidecadal to centurial timescale precipitation changes in the northern tibetan plateau and suggests that variations in east asian summer monsoon intensity affect desert recharge rates uncertainties in the records owing to assumptions about the cl inputs are examined by comparing deterministic and stochastic cl input scenarios such records are valuable for assessing spatial aspects of climate changes in the region as well as for informing sustainable water resource management strategies for northwestern china s drylands

arthrophycus in the silurian of alabama usa and the problem of compound trace fossils arthrophycus brongniartii harlan 1832 is common in marginal marine deposits in the silurian red mountain formation of alabama the ichnospecies the second to be named in north america is revived and emended after long disuse transitional forms to rusophycus isp and other morphologic evidence indicate that the maker of arthrophycus was an arthropod perhaps a trinucleine raphiophorid trilobite interconnection of arthrophycus and nereites biserialis as well as intergradation of arthrophycus with cruziana aff quadrata phycodes flabellum and asterosoma ludwigae indicate that these red mountain trace fossils were made by the same species of arthropod possible relationships with arthrophycus alleghaniensis harlan 1831 in the silurian belt from ontario to tennessee are also explored ichnofamily arthrophycidae schimper 1879 is emended the ichnofamily is interpreted as chiefly the work of arthropods arthrophycus and other trace fossils from the silurian of alabama constitute a test case to build criteria for recognizing the members of complexes of trace fossils in general criteria such as interconnection of different forms intergradation among unconnected forms similarity of size similarity of morphologic elements and co occurrence should be examined in order to determine the biologic and ethologic interrelationships of trace fossils 7 2003 elsevier science b v all rights reserved

groundwater recharge in the victoria nile basin of east africa support for the soil moisture balance approach using stable isotope tracers and flow modelling across equatorial africa increasing demand for groundwater has raised concerns about resource sustainability and has highlighted the need for reliable estimates of groundwater recharge recharge investigations in this environment are typically inhibited by a shortage of good quality meteorological and hydrogeological records moreover when recharge studies are attempted they tend to rely on a single technique and frequently lack corroborating evidence to substantiate recharge predictions in recent studies undertaken in the aroca catchment of the victoria nile basin in central uganda the timing and magnitude of recharge determined by a soil moisture balance approach are supported by stable isotope data and groundwater flow modelling the soil moisture balance study reveals that recharge averages in the order of 200 mm year 1 and is more dependent on the number of heavy more than 10 turn day 1 rainfall events than the total annual volume of rainfall stable isotope data suggest independently that recharge occurs during the heaviest rains of the monsoons and further establish that recharge stems entirely from the direct infiltration of rainfall an assumption implicit in the soil moisture balance approach deforestation over the last 30 years is shown to have more than doubled the recharge estimate aquifer flow modelling supports the recharge estimates but demonstrates that the vast majority over 99 of recharging waters must be transmitted by the aquifer in the regolith rather the underlying bedrock fractures which have traditionally been developed for rural water supplies

residence time indicators in groundwater the east midlands triassic sandstone aquifer the east midlands triassic sherwood sandstone aquifer which has been the subject of detailed radiometric age studies is used to investigate both inert and reactive constituents of groundwater as indicators of residence time detailed resampling of the aquifer in 1992 has provided a considerable body of new inorganic geochemistry data though without radiocarbon several inert indicators are defined including the isotopic ratios 18o 2h 36cl noble gas ratios as well as the halogen elements cl br f i and their element ratios these form a group of essentially unreactive tracers primarily reflecting changing rainfall inputs and palaeoclimatic conditions except at outcrop where human impacts are also seen clearly the concentrations of cl mainly from atmospheric sources remain below 25 mg l 1 cl over a distance of some 30 km from outcrop reactive indicators the result of time dependent water rock interactions include 13c mg ca sr ca na cl and show diagnostic trends along the flow lines however the concentrations of certain trace elements li rb cs mn and mo which are not limited by solubility constraints show linear trends along the present day flow gradient this water rock interaction is taking place in groundwaters with low total mineralisation and it can be demonstrated that reactions involving these elements and isotopes are occurring entirely within the aquifer since high salinity groundwaters are found below the sherwood sandstone there is good correlation between some of the elements and 14c activities in the 1977 data set and this has been used to derive a concentration age relationship for the 1992 set of data a chemical timescale for the aquifer is then established using a li and b a combination of five trace elements the age of the fresh groundwater is thus shown to be up to 100 ka bp indicating the likelihood of semi continuous recharge during the devensian glacial period preceding the glacial maximum when no recharge occurred 10 20 ka bp this approach may be of value in extending groundwater dating beyond the radiocarbon timescale as well as interpreting sites where no radiocarbon data are available the scatter from the mean age line indicates those groundwaters which are derived from either rapid or slower than average flow zones within the aquifer as well as age stratification this stratification is borne out by a depth profile of groundwater from a new borehole near to outcrop which is shown by a combination of chemical and isotopic tracers to contain holocene overlying late pleistocene water

soil profile evolution following land use change implications for groundwater quantity and quality soil and vadose zone profiles are used as an archive of changes in groundwater recharge and water quality following changes in land use in an area of the loess plateau of china a typical rain fed loess terrace agriculture region in hequan guyuan is taken as an example and multiple tracers chloride mass balance stable isotopes tritium and water chemistry are used to examine groundwater recharge mechanisms and to evaluate soil water chloride as an archive for recharge rate and water quality results show that groundwater recharge beneath natural uncultivated grassland used as a baseline is about 94 100 mm year 1 and that the time it takes for annual precipitation to reach water table through the thick unsaturated zone is from decades to hundreds of years tritium free this recharge rate is 2 3 orders of magnitude more than in the other semiarid areas with similar annual rainfall but with deep rooted vegetation and relatively high temperature most of the water that eventually becomes recharge originally infiltrated in the summer months the conversion from native grassland to winter wheat has reduced groundwater recharge by 42 50 50 55 mm year 1 for recharge and the conversion from winter wheat to alfalfa resulted in a significant chloride accumulation in the upper soil zone which terminated deep drainage the paper also evaluates the time lag between potential recharge and actual recharge to aquifer and between increase in solute concentration in soil moisture and that in the aquifer following land use change due to the deep unsaturated zone copyright 2012 john wiley sons ltd

recharge history and controls on groundwater quality in the yuncheng basin north china environmental isotopes and water quality indicators e g tds and no 3 contents were used to characterize the age recharge history and controls on the quality of groundwater resources in the yuncheng basin north china where extensive extraction occurs for agriculture and domestic supply delta 18 o and delta 2 h values as low as 10 6 and 73 parts per thousand respectively together with low radiocarbon activities 70 pmc indicating a significant component of modern post 1950s recharge the shallow groundwater has higher delta 18 o and delta 2 h values up to 8 1 and 54 parts per thousand that are similar to those in modern summer monsoon rainfall indicating that current recharge is via direct infiltration and or leakage of ephemeral streams during heavy rain events historic recharge rates estimated using radiocarbon ages are between 1 and 10 mm year corresponding to 20 mg l in some deep wells 180 m preferential leakage has occurred near the linyi fault in the northern sushui river basin salinisation nitrate contamination and excessive drawdown of deep groundwater are major concerns for the future of the groundwater resources in this region c 2010 elsevier b v all rights reserved

investigation on the dimensions and shape of a submerged vane for sediment management in alluvial channels a submerged vane is a flow training facility mounted vertically on the channel bed to control the sediment movement in the channel cross section and has been utilized in various applications such as prevention of bank erosion sediment exclusion at water intakes and deepening channels for navigation the performance of a submerged vane is related to its dimensions and shape this study aims to investigate a vane s sediment control effectiveness as a function of its size and shape with the expectation of an optimal combination of dimensions and shape a model for the calculation of the transverse bed profile in a cross section of a straight alluvial channel induced by a single submerged vane is developed the model is utilized to investigate the performances for three types of vanes 1 rectangular plates with various height and length 2 tapered plates with linear decreasing in length from the base to the top and 3 plates of parallelogram with the top of the plates swept forward or backward design guidelines and suggestions on the dimensions and shape of the vane are provided based on the results

estimating paleorecharge and paleoclimate from unsaturated zone profiles unsaturated zone solute and isotope profiles may be interpreted in terms of past changes in recharge rate in cases where water movement can be approximated by piston flow a model is presented which describes water movement in terms of piston flow below a surface mixing layer below the mixing layer diffusion and dispersion occur in the liquid phase in the case of solutes and in both the liquid and gas phases in the case of isotopically labeled water climatic events of 4 5 years duration may be preserved in the unsaturated zone for more than 50 years if the recharge rate is greater than approximately 20 mm yr 1 longer term fluctuations in climatic conditions century scale might be preserved for over 1000 years provided the recharge rate is greater than approximately 2 mm yr 1 and the unsaturated zone is sufficiently deep profiles from cyprus and northern senegal appear to record changes in recharge rate over periods up to 400 years the profiles are well correlated with known variations in rainfall and fluctuations in lake levels the model provides limiting conditions to be applied to the interpretation of profiles

temporal variation of stable isotopes in a precipitation groundwater system implications for determining the mechanism of groundwater recharge in high mountain hills of the loess plateau china

groundwater recharge estimation using chloride deuterium and oxygen 18 profiles in the deep coastal sands of western australia the depth distributions of environmental chloride deuterium and oxygen 18 in the deep sands 20 m were monitored with a view to estimate average recharge to groundwater the investigated area is located on the southwestern coast of western australia and supports a perennial native woodland vegetation by using a steady state model based on the conservation of chloride the average areal recharge was estimated to be approximately 15 of the average precipitation 775 mm yr 1 whilst the cl concentration of groundwater was relatively uniform there was a considerable spatial variability in the depth distribution of cl in the unsaturated zone an approximate method of data analysis is developed application of this to cl data shows that possibly some 50 of the total annual recharge occurs via movement of water through preferred pathways thus bypassing the soil matrix stable isotope deuterium and oxygen 18 data show that there has been some isotopic enrichment due to evaporation of the rainfall but the extent of enrichment appears to be too small to estimate recharge rates reliably it is argued that relatively small isotopic enrichment occurs in the system studied since the direct evaporation from soil is a rather small component of the total evapotranspiration the observations on the depth distribution of isotopes qualitatively support the presence of a bimodal system for water movement through the profile as was suggested by the analysis of chloride data

hydrogeochemical evolution of groundwater in a mediterranean coastal aquifer mersin erdemli basin turkey in this study hydrogeologic and hydrochemical information from the mersin erdemli groundwater system were integrated and used to determine the main factors and mechanisms controlling the chemistry of groundwaters in the area and anthropogenic factors presently affecting them the phreeqc geochemical modeling demonstrated that relatively few phases are required to derive water chemistry in the area in a broad sense the reactions responsible for the hydrochemical evolution in the area fall into four categories 1 silicate weathering reactions 2 dissolution of salts 3 precipitation of calcite amorphous silica and kaolinite 4 ion exchange as determined by multivariate statistical analysis anthropogenic factors show seasonality in the area where most contaminated waters related to fertilizer and fungicide applications that occur during early summer season

identification of probable groundwater paths in the amargosa desert vicinity in this study the hydrogeochemical program phreeqc was used to determine the chemical speciation and mineral saturation indices sis of groundwater in the vicinity of the proposed high level nuclear waste repository at yucca mountain nevada usa in turn these data were used to interpret the origin and recharge mode of groundwater to elucidate the mechanisms of flow and transport and to determine potential sources of groundwater contamination phreeqc was run to determine aqueous dissolved species and minerals that would be in equilibrium with the study area s groundwater selected major ions associated si f and ca na ion exchange were then examined using the multivariate statistical methods of principal component factor analysis and k means cluster analysis analysis of dissolved ion concentrations sis and ca na ion exchange allows simultaneous consideration of arithmetic raw concentrations and logarithmic si ion exchange variables that describe the hydrochemical system and therefore can provide further insight into the system s behavior the analysis indicates that the dominant processes and reactions responsible for the hydrochemical evolution in the system are 1 evaporative concentration prior to infiltration 2 carbonate equilibrium 3 silicate weathering reactions 4 limited mixing with saline water 5 dissolution precipitation of calcite dolomite and fluorite and 6 ion exchange principal component factor analysis and k means cluster analysis of factor scores allow the reduction of dimensions describing the system and the identification of hydrogeochemical facies and the processes that defined and govern their evolution statistical analysis results indicate that the northern west face and southern yucca mountain groundwater is fresh water with low concentrations of ca2 mg2 cl ca2 na 2 and caf2 the fortymile wash groundwater is dilute the carbonate signature is shown in the ash meadows and death valley waters with high fluorite si finally the crater flat stripped hills and skeleton hills are dominated by ca na ion exchange mg and ca the hydrochemical and statistical analyses showed three main groundwater signatures or hydrochemical processes indicating groundwater evolution potential flowpaths and recharge areas the flowpaths are the trace of the amargosa river the trace of fortymile wash and its convergence with the amargosa river this appears to represent not just a groundwater flow path but traces of surface runoff infiltration as well

tracing infiltration and recharge using stable isotope in taihang mt north china the groundwater in headwater region is an important recharge source for the adjacent mountain front plain in order to reveal the relationship among precipitation soil water and groundwater from june to september in 2004 stable isotopes deuterium and oxygen 18 in precipitation and soil waters at the depths of 10 20 30 50 70 90 and 110 cm were analyzed at two sites covered by black locust robinia pseudoacia l site a and grass predominated by themeda triandra t japonica willd tanaka and bothriochloa ischaemum b ischaemum l keng site b in an experimental catchment at taihang mt north china respectively the 18o of precipitation in daily rain events shows large variations 13 3 to 4 3 with a mean of 8 1 the 18o and d of soil waters along profiles in two sites suggest that the influence of canopy cover was just up to 10 cm in top soil water the soil water moved over the zero flux plane at 70 cm in depth is expected to escape the evaporative effect at the end of september in both sites the results show that the stable isotope instead of tritium as tradition can be used to trace the soil water behaviors based on the movement of isotopic peak along the vertical profiles in this semi arid and semi humid mountainous region the infiltration depths of soil water in taihang mt are 12 and 10 mm day from june to september in 2004 in site a and site b respectively tracing by stable isotope recharge fluxes of soil water to local groundwater are of 3 8 and 3 2 mm day in site a and site b respectively the results provide desirable information for assessment of local groundwater resources

water movement in desert soil traced by hydrogen and oxygen isotopes chloride and chlorine 36 southern arizona abstract understanding soil water movement is important for water resource management and for analyzing pollutant transport in the vadose zone seasonal variations in shallow soil profiles may have profound effects on deep soil water and solutes we have investigated seasonal soil water movement in the top meter of undisturbed desert soil in the southern arizona using 2 h 18 o cl and bomb 36 c1 six soil profiles were sampled from a young terrace holocene during 1991 to 1992 on a seasonal basis one soil profile was sampled from an older terrace latest pleistocene in october 1992 and one from a yet older fan surface late pleistocene in march 1992 the results indicate that repeated seasonal cyclic movement of soil water in the top 60 80 cm active zone tends to produce a consistent stable isotope composition for the soil water below the active zone in different seasons the deep 18 o on the oldest surface is about 6 heavier than on the younger surfaces probably resulting from greater evaporative loss due to the larger proportion of fines in the older soil this deep isotopic composition is closely related to the composition of the local average annual precipitation an annual average evaporation rate of 35 mm year 1 was estimated using a steady state diffusion model whereas the actual regional evapotranspiration rate is 175 250 mm year 1 this suggests that about 80 of the soil water is lost through transpiration and first stage evaporation before quasi steady state is reached the long term average infiltration rate below the active zone is about 4 mm year 1 for the younger terrace based on both chloride mass balance and bomb 36 cl and 0 02 mm year 1 for the older terrace and the fan surface based on chloride mass balance the correlation between the deep 18 o the reduction of downward flux and the surface age suggests that increasing soil development has resulted in a significant decrease of soil water infiltration and hence an increase in evaporation and surface runoff

a four component mixing model for water in a karst terrain in south central indiana usa using solute concentration and stable isotopes as tracers the study area lies in a highly karstified carbonate terrain in south central indiana sinkholes conduits and caves form large secondary pathways for the subsurface flow as a result the discharge from a main emergence point for the subsurface flow system the orangeville rise quickly responds to the storm events and shows wide variations in flow rate water chemistry and stable isotopic compositions these responses are attributed to the mixing of water in secondary pathways in the study area recharge occurs through the thick mantled karst plain and the sinkhole plains and the role of soil layer and epikarst in the recharge process is of great importance rain dic 2 hco3 mg l 13cdic 7 soil water dic 544 hco3 mg l 13cdic 14 7 epikarstic water dic 224 hco3 mg l 13cdic 13 6 and phreatic diffuse flow water dic 299 hco3 mg l 13cdic 11 8 generally showed unique and constant dissolved inorganic carbon dic and 13cdic values over time using dic and 13cdic as tracers a four component mixing model was established for the karstic flow system by constructing the discharge hydrograph separation curves the mixing ratio of each component rain 10 6 soil 3 1 epikarstic 52 3 and phreatic 34 0 water was determined for the orangeville rise discharge over the testing period of 104 h after the storm event of 10 4 90 vadose water occupied 55 4 of spring discharge and this demonstrates the importance of the unsaturated zone especially the epikarst in the karstic flow systems

shelf paralic and fluvial environments and eustatic sea level fluctuations in the origin of the tuscarora formation lower silurian of central pennsylvania abstract the tuscarora formation lower silurian of central pennsylvania owes its origin to a combination of tectonic eustatic and depositional events tuscarora deposition began at the beginning of the silurian period at the time of both glacioeustatic sea level rise and renewed tectonic elevation of the taconic source terrain braided alluvial systems transported coarse sediment northwestward to a wave dominated coast yet sea level rise was so rapid that the shoreline retrograded from western to eastern pennsylvania at the time of transgression shoreline characteristics varied from high energy beaches in central pennsylvania to estuaries along the south central border region of pennsylvania seaward of the shoreline sand was fashioned into shelf sand wave complexes analogous to moder shoreface connected sand ridges much of the tuscarora formation west of the susquehanna river accumulated in this shallow marine shelf environment later in the early silurian eustatic sea level fall resulted in progradation of lower energy coastal sand mud flats northwestward over the former shelf shortly before a subsequent sea level rise terminated tuscarora development with the return of the sea in which the rose hill formation was deposited the basis for these interpretations is the analysis of five major lithofacies in the exposed tuscarora formation of central pennsylvania the basal part of the tuscarora consists of two lithofacies of coastal origin the horizontally laminated lithofacies high energy beach and the pink transitional lithofacies estuary the main body of the tuscarora comprises the eastern cross laminated lithofacies braided fluvial and the western cross laminated lithofacies shelf sand wave complexes capping the tuscarora is the red skolithos burrowed lithofacies coastal sand mud flats

trace fossils versus body fossils oldhamia recta revisited new discoveries in north carolina s neoproterozoic carolina terrane combined with a reexamination of the holotype of oldhamia recta and other material from the yale peabody museum reveal these specimens as body fossils of a rod like organism rather than ichnofossils close examination of fossils originally identified as o recta lack levees made by movement of a tracemaker through a sediment internal structures indicating backfilling or fecal material scratch marks denoting a recumbent lifestyle or evidence of peristaltic movement crossovers of rods in some instances also indicate rigidity in the fossils most importantly quantitative analyses indicate gaussian size distributions and narrow ranges of alignment for the fossils with each respective line of evidence interpreted as body fossils aligned by currents because this newly discerned evidence favors a body fossil origin for these specimens we propose that o recta is invalid as an ichnospecies our research supports more quantitative approaches to augment qualitative descriptions when evaluating whether ediacaran age structures are trace or body fossils 2010 elsevier b v all rights reserved