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Sample records for stable water isotope

  1. Tritium and stable isotopes of magmatic waters

    NASA Astrophysics Data System (ADS)

    Goff, F.; McMurtry, G. M.

    2000-04-01

    To investigate the isotopic composition and age of water in volcanic gases and magmas, we analyzed samples from 11 active volcanoes ranging in composition from tholeiitic basalt to rhyolite: Mount St. Helens (USA), Kilauea (USA), Pacaya (Guatemala), Galeras (Colombia), Satsuma Iwo-Jima (Japan), Sierra Negra and Alcedo (Ecuador), Vulcano (Italy), Parı´cutin (Mexico), Kudryavy (Russia), and White Island (New Zealand). Tritium at relatively low levels (0.1-5 T.U.) is found in most emissions from high-temperature volcanic fumaroles sampled, even at discharge temperatures >700°C. Although magmatic fluids sampled from these emissions usually contain high CO 2, S total, HCl, HF, B, Br, 3He R/ RA, and low contents of air components, stable isotope and tritium relations of nearly all such fluids show mixing of magmatic volatiles with relatively young meteoric water (model ages≤75 y). Linear δD/ δ18O and 3H/ δ18O mixing trends of these two end-members are invariably detected at arc volcanoes. Tritium is also detected in fumarole condensates at hot spot basalt volcanoes, but collecting samples approaching the composition of end-member magmatic fluid is exceedingly difficult. In situ production of 3H, mostly from spontaneous fission of 238U in magmas is calculated to be <0.001 T.U., except for the most evolved compositions (high U, Th, and Li and low H 2O contents). These values are below the detection limit of 3H by conventional analytical techniques (about 0.01 T.U. at best). We found no conclusive evidence that natural fusion in the Earth produces anomalous amounts of detectable 3H (>0.05 T.U.).

  2. STABLE ISOTOPES AS INDICATORS OF SOIL WATER DYNAMICS IN WATERSHEDS

    EPA Science Inventory

    Stream water quality and quantity depend on discharge rates of water and nutrients from soils. However, soil-water storage is very dynamic and strongly influenced by plants. We analyzed stable isotopes of oxygen and hydrogen to quantify spatial and temporal changes in evaporati...

  3. Using stable isotopes of water to infer wetland hydrological dynamics

    NASA Astrophysics Data System (ADS)

    Clay, A.; Bradley, C.; Gerrard, A. J.; Leng, M. J.

    This paper considers the potential of oxygen and hydrogen isotope ratios to identify spatial and temporal changes in the water source of a lowland headwater wetland situated adjacent to the River Tern in Shropshire, UK. Stable isotope composition (d18O) of end-members varied between -7.5 and -8.0‰ for groundwater, -7.3 and -8.5‰ for river-water and -4.5 and -8.0‰ for precipitation. Water samples were extracted from six nests each comprising three porous cup samplers at depths of 0.2 m, 0.5 m and 1.0 m between June 2000 and October 2001, and their isotope compositions determined. Groundwater appears to be the main source of water to the wetland, but stable isotope ratios enable seasonal variations in the contribution of precipitation to be determined, and indicate the extent of precipitation storage within the wetland.

  4. Stable isotopes in leaf water of terrestrial plants.

    PubMed

    Cernusak, Lucas A; Barbour, Margaret M; Arndt, Stefan K; Cheesman, Alexander W; English, Nathan B; Feild, Taylor S; Helliker, Brent R; Holloway-Phillips, Meisha M; Holtum, Joseph A M; Kahmen, Ansgar; McInerney, Francesca A; Munksgaard, Niels C; Simonin, Kevin A; Song, Xin; Stuart-Williams, Hilary; West, Jason B; Farquhar, Graham D

    2016-05-01

    Leaf water contains naturally occurring stable isotopes of oxygen and hydrogen in abundances that vary spatially and temporally. When sufficiently understood, these can be harnessed for a wide range of applications. Here, we review the current state of knowledge of stable isotope enrichment of leaf water, and its relevance for isotopic signals incorporated into plant organic matter and atmospheric gases. Models describing evaporative enrichment of leaf water have become increasingly complex over time, reflecting enhanced spatial and temporal resolution. We recommend that practitioners choose a model with a level of complexity suited to their application, and provide guidance. At the same time, there exists some lingering uncertainty about the biophysical processes relevant to patterns of isotopic enrichment in leaf water. An important goal for future research is to link observed variations in isotopic composition to specific anatomical and physiological features of leaves that reflect differences in hydraulic design. New measurement techniques are developing rapidly, enabling determinations of both transpired and leaf water δ(18) O and δ(2) H to be made more easily and at higher temporal resolution than previously possible. We expect these technological advances to spur new developments in our understanding of patterns of stable isotope fractionation in leaf water. PMID:26715126

  5. Stable isotopic composition of bottled mineral waters from Romania

    NASA Astrophysics Data System (ADS)

    Bădăluţă, Carmen; Nagavciuc, Viorica; Perșoiu, Aurel

    2015-04-01

    Romania has a high potential of mineral waters resources, featuring one of the largest mineral resources at European and global level. In the last decade, due to increased in consumption of bottled water, numerous brands have appeared on the market, with equally numerous and variable sources of provenance. In this study we have analyzed the isotopic composition of bottled mineral waters from Romania in order to determine their source and authenticity. We have analysed 32 carbonated and 24 non-carbonated mineral waters from Romania. and the results were analysed in comparison with stable isotope data from precipitation and river waters. Generally, the isotopic values of the mineral waters follow those in precipitation; however, differences occur in former volcanic regions (due to deep circulation of meteoric waters and increased exchange with host rock and volcanic CO2), as well as in mountainous regions, where high-altitude recharge occurs.

  6. Modelling of stable water isotopes in Central Europe with COSMOiso

    NASA Astrophysics Data System (ADS)

    Christner, Emanuel; Pfahl, Stephan; Schädler, Gerd

    2016-04-01

    Atmospheric water in form of vapor or clouds is responsible for ˜75 % of the natural greenhouse effect and carries huge amounts of latent heat. For this reason, a best possible description of the hydrological cycle is a prerequisite for reliable climate modelling. As the stable isotopes H216O, H218O and HDO differ in vapor pressure, they are fractionated during phase changes and contain information about the formation of precipitation, evaporation from the ground, etc. Therefore, the isotopic composition of atmospheric water is an useful tracer to test and improve our understanding of the extremely complex and variable hydrological cycle in Earth's atmosphere. Within the project PalMod the isotope-enabled limited-area model COSMOiso will be used for high-resolution isotope simulations of paleo-climates. For validation with modern observations we compare 12 years of modelled isotope ratios from Central Europe to observations of the Global Network of Isotopes in Precipitation (GNIP) and to observations of isotope ratios of water vapor at different locations in Germany. We find a good agreement of modelled and observed isotope ratios in summer. In winter, we observe a systematic overestimation of modelled isotope ratios in precipitation and low-level water vapor. We relate those differences to specific circulation regimes with predominantly easterly moisture transport and the corresponding strong dependence of modelled isotope ratios on lateral boundary data. Furthermore, we investigate the dependence of modelled isotope ratios in winter on the type of isotope fractionation during surface evaporation at skin temperatures close to the freezing point.

  7. Stable isotope geochemistry of East African waters. [Abstract only

    SciTech Connect

    Sayer, M.D.; Cerling, T.E.; Bowman, J.R.

    1983-03-01

    Lakes and Rivers in East Africa have varied stable isotopic compositions. Lakes exhibit enriched delta13-C values (-2 to +5%), while their inflowing rivers show depleted values (-15 to -8%). Hot springs and standing pools of water have intermediate values. Some small lakes are extremely variable in delta18-0 or deltaD (+2 to +8% and +20 to +40%, respectively for Lake Naivasha), whereas larger lakes are relatively constant for long periods of time (+5.6 to 6.1 and +36 to 40, respectively for Lake Turkana). Isotopic values are unrelated to salinity for comparison between lakes. Stable isotopes also reveal the sources of hot spring discharges: the Kapedo hot springs probably originate from Maralel and not from Lake Baringo as local legend has it; the hot springs north of Lake Naivasha are of meteoric origin while those to the south of Lake Naivasha have similar isotopic compositions to Lake Naivasha.

  8. Spatial distribution of stable water isotopes in alpine snow cover

    NASA Astrophysics Data System (ADS)

    Dietermann, N.; Weiler, M.

    2013-07-01

    The aim of this study was to analyse and predict the mean stable water isotopic composition of the snow cover at specific geographic locations and altitudes. In addition, the dependence of the isotopic composition of the entire snow cover on altitude was analysed. Snow in four Swiss catchments was sampled at the end of the accumulation period in April 2010 and a second time during snowmelt in May 2010 and analysed for stable isotope composition of 2H and 18O. The sampling was conducted at both south-facing and north-facing slopes at elevation differences of 100 m, for a total altitude difference of approximately 1000 m. The observed variability of isotopic composition of the snow cover was analysed with stepwise multiple linear regression models. The analysis indicated that there is only a limited altitude effect on the isotopic composition when considering all samples. This is due to the high variability of the isotopic composition of the precipitation during the winter months and, in particular in the case of south-facing slopes, an enrichment of heavy isotopes due to intermittent melting processes. This enrichment effect could clearly be observed in the samples which were taken later in the year. A small altitudinal gradient of the isotopic composition could only be observed at some north-facing slopes. However, the dependence of snow depth and the day of the year were significant predictor variables in all models. This study indicates the necessity to further study the variability of water isotopes in the snow cover to increase prediction for isotopic composition of snowmelt and hence increase model performance of residence time models for alpine areas in order to better understand the accumulation processes and the sources of water in the snow cover of high mountains.

  9. Spatial distribution of stable water isotopes in alpine snow cover

    NASA Astrophysics Data System (ADS)

    Dietermann, N.; Weiler, M.

    2013-03-01

    The aim of this study was to analyze and predict the mean stable water isotopic composition of the snow cover at specific geographic locations and altitudes. In addition, the dependence of the isotopic composition of the entire snow cover on altitude was analyzed. Snow in four Swiss catchments was sampled at the end of the accumulation period in April 2010 and a second time in Mai 2010 and analyzed for stable isotope composition of 2H and 18O. The sampling was conducted at both south-facing and north-facing slopes at elevation differences of 100 m for a total altitude difference of approximately 1000 m. The observed variability of isotopic composition of the snow cover was analyzed with stepwise multiple linear regression models. The analysis indicated that there is only a limited altitude effect on the isotopic composition when considering all samples. This is due to the high variability of the isotopic composition of the precipitation during the winter months and, in particular in the case of south-facing slopes, an enrichment of heavy isotopes due to intermittent melting processes. This enrichment effect could clearly be observed in the samples which were taken later in the year. A small altitudinal gradient of the isotopic composition could only be observed at some north-facing slopes. However, the dependence of snow depth and the day of the year were significant predictor variables in all models. This study indicates the necessity to further study the variability of water isotopes in the snow cover to increase prediction for isotopic composition of snowmelt and hence increase model performance of residence time models in alpine areas and to better understand the accumulation processes and the sources of water in the snow cover of high mountains.

  10. Water vapor stable isotope observations from tropical Australia

    NASA Astrophysics Data System (ADS)

    Parkes, Stephen; Deutscher, Nicholas; Griffith, David; McCabe, Matthew

    2015-04-01

    The response of the tropical hydrological cycle to anthropogenically induced changes in radiative forcing is one of the largest discrepancies between climate models. Paleoclimate archives of the stable isotopic composition of precipitation in the tropics indicate a relationship with precipitation amount that could be exploited to study past hydroclimate and improve our knowledge of how this region responds to changes in climate forcing. Recently modelling studies of convective parameterizations fitted with water isotopes and remote sensing of water vapor isotopes in the tropics have illustrated uncertainty in the assumed relationship with rainfall amount. Therefore there is a need to collect water isotope data in the tropics that can be used to evaluate these models and help identify the relationships between the isotopic composition of meteoric waters and rainfall intensity. However, data in this region is almost non-existent. Here we present in-situ water vapor isotopic measurements and the HDO retrievals from the co-located Total Column Carbon Observing Network (TCCON) site at Darwin in Tropical Australia. The Darwin site is interestingly placed within the tropical western pacific region and is impacted upon by a clear monsoonal climate, and key climate cycles including ENSO and Madden Julian Oscillations. The analysis of the data illustrated relationships between water vapor isotopes and humidity which demonstrated the role of precipitation processes in the wet season and air mass mixing during the dry season. Further the wet season observations show complex relationships between humidity and isotopes. A simple Rayleigh distillation model was not obeyed, instead the importance of rainfall re-evaporation in generating the highly depleted signatures was demonstrated. These data potentially provide a useful tool for evaluating model parameterizations in monsoonal regions as they demonstrate relationships with precipitation processes that cannot be observed with

  11. Dynamic simulation of stable water isotopes during the last interglacial

    NASA Astrophysics Data System (ADS)

    Gierz, P.; Lohmann, G.; Brocas, W.; Felis, T.

    2014-12-01

    Using the novel isotope module of the global fully coupled climate model COSMOS, we simulate the climate of the last interglacial for three time slices at 120, 125, and 130 kiloyears before present. The inclusion of stable water isotopes allows us to not only have a comprehensive picture of the climate state during a warm interglacial, but also allows for a direct comparison with climate proxy records. We compare our simulation with isotope data gathered from fossilized corals, which have an excellent temporal resolution and well constrained dating. A model data comparison allows us to see that there was an enhanced seasonality of both temperature and rainfall during the Eemian. While the data tends to produce a stronger winter cooling than the model, we suggest that this may be due to an incomplete climatology, as the measurements taken from the coral only encompasses a few decades. If the data happens to fall during an usually cool decade, the mismatch could be rectified. Alternatively, the data may include the cooling signal associated with centennial scale cold stadials during the Eemian. We test this by performing a freshwater perturbation experiment during the peak interglacial, which causes a pronounced cooling at the core site while the ocean circulation is depressed.

  12. Stable Isotope Mixing Models as a Tool for Tracking Sources of Water and Water Pollutants

    EPA Science Inventory

    One goal of monitoring pollutants is to be able to trace the pollutant to its source. Here we review how mixing models using stable isotope information on water and water pollutants can help accomplish this goal. A number of elements exist in multiple stable (non-radioactive) i...

  13. System for high throughput water extraction from soil material for stable isotope analysis of water

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A major limitation in the use of stable isotope of water in ecological studies is the time that is required to extract water from soil and plant samples. Using vacuum distillation the extraction time can be less than one hour per sample. Therefore, assembling a distillation system that can process m...

  14. Lake Louise Water (USGS47): A new isotopic reference water for stable hydrogen and oxygen isotope measurements

    USGS Publications Warehouse

    Qi, Haiping; Lorenz, Jennifer M.; Coplen, Tyler B.; Tarbox, Lauren V.; Mayer, Bernhard; Taylor, Steve

    2014-01-01

    RESULTS: The δ2H and δ18O values of this reference water are –150.2 ± 0.5 ‰ and –19.80 ± 0.02 ‰, respectively, relative to VSMOW on scales normalized such that the δ2H and δ18O values of SLAP reference water are, respectively, –428 and –55.5 ‰. Each uncertainty is an estimated expanded uncertainty (U = 2uc) about the reference value that provides an interval that has about a 95-percent probability of encompassing the true value. CONCLUSION: This isotopic reference material, designated as USGS47, is intended as one of two isotopic reference waters for daily normalization of stable hydrogen and stable oxygen isotopic analysis of water with a mass spectrometer or a laser absorption spectrometer. "

  15. Isotopic tracing of clear water sources in an urban sewer: A combined water and dissolved sulfate stable isotope approach.

    PubMed

    Houhou, J; Lartiges, B S; France-Lanord, C; Guilmette, C; Poix, S; Mustin, C

    2010-01-01

    This paper investigates the potential of stable isotopes of both water (deltaD and deltaOH(2)O18) and dissolved sulfate (delta(34)S and deltaOSO(4)18) for determining the origin and the amount of clear waters entering an urban sewer. The dynamics of various hydrological processes that commonly occur within the sewer system such as groundwater infiltration, rainwater percolation, or stormwater release from retention basins, can be readily described using water isotope ratios. In particular, stable water isotopes indicate that the relative volumes of infiltrated groundwater and sewage remain approximately constant and independent of wastewater flow rate during the day, thus demonstrating that the usual quantification of parasitic discharge from minimal nocturnal flow measurements can lead to completely erroneous results. The isotopic signature of dissolved sulfate can also provide valuable information about the nature of water inputs to the sewage flow, but could not be used in our case to quantify the infiltrating water. Indeed, even though the microbial activity had a limited effect on the isotopic composition of dissolved sulfate at the sampling sites investigated, the dissolved sulfate concentration in sewage was regulated by the formation of barite and calcium-phosphate mineral species. Sulfate originating from urine was also detected as a source using the oxygen isotopic composition of sulfate, which suggests that deltaOSO(4)18 might find use as a urine tracer. PMID:19822346

  16. Assessment of water sources to plant growth in rice based cropping systems by stable water isotopes

    NASA Astrophysics Data System (ADS)

    Mahindawansha, Amani; Kraft, Philipp; Racela, Heathcliff; Breuer, Lutz

    2016-04-01

    Rice is one of the most water-consuming crops in the world. Understanding water source utilization of rice will help us to improve water use efficiency (WUE) in paddy management. The objectives of our study are to evaluate the isotopic compositions of surface ponded water, soil water, irrigation water, groundwater, rain water and plant water and based on stable water isotope signatures to evaluate the contributions of various water sources to plant growth (wet rice, aerobic rice and maize) together with investigating the contribution of water from different soil horizons for plant growth in different maturity periods during wet and dry seasons. Finally we will compare the water balances and crop yields in both crops during both seasons and calculate the water use efficiencies. This will help to identify the most efficient water management systems in rice based cropping ecosystems using stable water isotopes. Soil samples are collected from 9 different depths at up to 60 cm in vegetative, reproductive and matured periods of plant growth together with stem samples. Soil and plant samples are extracted by cryogenic vacuum extraction. Root samples are collected up to 60 cm depth from 10 cm intercepts leading calculation of root length density and dry weight. Groundwater, surface water, rain water and irrigation water are sampled weekly. All water samples are analyzed for hydrogen and oxygen isotope ratios (d18O and dD) using Los Gatos Research DLT100. Rainfall records, ground water level, surface water level fluctuations and the amount of water irrigated in each field will be measured during the sampling period. The direct inference approach which is based on comparing isotopic compositions (dD and d18O) between plant stem water and soil water will be used to determine water sources taken up by plant. Multiple-source mass balance assessment can provide the estimated range of potential contributions of water from each soil depth to root water uptake of a crop. These

  17. A new method of snowmelt sampling for water stable isotopes

    USGS Publications Warehouse

    Penna, D.; Ahmad, M.; Birks, S. J.; Bouchaou, L.; Brencic, M.; Butt, S.; Holko, L.; Jeelani, G.; Martinez, D. E.; Melikadze, G.; Shanley, J.B.; Sokratov, S. A.; Stadnyk, T.; Sugimoto, A.; Vreca, P.

    2014-01-01

    We modified a passive capillary sampler (PCS) to collect snowmelt water for isotopic analysis. Past applications of PCSs have been to sample soil water, but the novel aspect of this study was the placement of the PCSs at the ground-snowpack interface to collect snowmelt. We deployed arrays of PCSs at 11 sites in ten partner countries on five continents representing a range of climate and snow cover worldwide. The PCS reliably collected snowmelt at all sites and caused negligible evaporative fractionation effects in the samples. PCS is low-cost, easy to install, and collects a representative integrated snowmelt sample throughout the melt season or at the melt event scale. Unlike snow cores, the PCS collects the water that would actually infiltrate the soil; thus, its isotopic composition is appropriate to use for tracing snowmelt water through the hydrologic cycle. The purpose of this Briefing is to show the potential advantages of PCSs and recommend guidelines for constructing and installing them based on our preliminary results from two snowmelt seasons.

  18. Stable water isotope patterns in a climate change hotspot: the isotope hydrology framework of Corsica (western Mediterranean).

    PubMed

    van Geldern, Robert; Kuhlemann, Joachim; Schiebel, Ralf; Taubald, Heinrich; Barth, Johannes A C

    2014-06-01

    The Mediterranean is regarded as a region of intense climate change. To better understand future climate change, this area has been the target of several palaeoclimate studies which also studied stable isotope proxies that are directly linked to the stable isotope composition of water, such as tree rings, tooth enamel or speleothems. For such work, it is also essential to establish an isotope hydrology framework of the region of interest. Surface waters from streams and lakes as well as groundwater from springs on the island of Corsica were sampled between 2003 and 2009 for their oxygen and hydrogen isotope compositions. Isotope values from lake waters were enriched in heavier isotopes and define a local evaporation line (LEL). On the other hand, stream and spring waters reflect the isotope composition of local precipitation in the catchment. The intersection of the LEL and the linear fit of the spring and stream waters reflect the mean isotope composition of the annual precipitation (δP) with values of-8.6(± 0.2) ‰ for δ(18)O and-58(± 2) ‰ for δ(2)H. This value is also a good indicator of the average isotope composition of the local groundwater in the island. Surface water samples reflect the altitude isotope effect with a value of-0.17(± 0.02) ‰ per 100 m elevation for oxygen isotopes. At Vizzavona Pass in central Corsica, water samples from two catchments within a lateral distance of only a few hundred metres showed unexpected but systematic differences in their stable isotope composition. At this specific location, the direction of exposure seems to be an important factor. The differences were likely caused by isotopic enrichment during recharge in warm weather conditions in south-exposed valley flanks compared to the opposite, north-exposed valley flanks. PMID:24437609

  19. Stable water isotope and surface heat flux simulation using ISOLSM: Evaluation against in-situ measurements

    NASA Astrophysics Data System (ADS)

    Cai, Mick Y.; Wang, Lixin; Parkes, Stephen D.; Strauss, Josiah; McCabe, Matthew F.; Evans, Jason P.; Griffiths, Alan D.

    2015-04-01

    The stable isotopes of water are useful tracers of water sources and hydrological processes. Stable water isotope-enabled land surface modeling is a relatively new approach for characterizing the hydrological cycle, providing spatial and temporal variability for a number of hydrological processes. At the land surface, the integration of stable water isotopes with other meteorological measurements can assist in constraining surface heat flux estimates and discriminate between evaporation (E) and transpiration (T). However, research in this area has traditionally been limited by a lack of continuous in-situ isotopic observations. Here, the National Centre for Atmospheric Research stable isotope-enabled Land Surface Model (ISOLSM) is used to simulate the water and energy fluxes and stable water isotope variations. The model was run for a period of one month with meteorological data collected from a coastal sub-tropical site near Sydney, Australia. The modeled energy fluxes (latent heat and sensible heat) agreed reasonably well with eddy covariance observations, indicating that ISOLSM has the capacity to reproduce observed flux behavior. Comparison of modeled isotopic compositions of evapotranspiration (ET) against in-situ Fourier Transform Infrared spectroscopy (FTIR) measured bulk water vapor isotopic data (10 m above the ground), however, showed differences in magnitude and temporal patterns. The disparity is due to a small contribution from local ET fluxes to atmospheric boundary layer water vapor (∼1% based on calculations using ideal gas law) relative to that advected from the ocean for this particular site. Using ISOLSM simulation, the ET was partitioned into E and T with 70% being T. We also identified that soil water from different soil layers affected T and E differently based on the simulated soil isotopic patterns, which reflects the internal working of ISOLSM. These results highlighted the capacity of using the isotope-enabled models to discriminate

  20. Using water stable isotopes to assess evaporation and water residence time of lakes in EPA’s National Lakes Assessment.

    EPA Science Inventory

    Stable isotopes of water (18O and 2H) can be very useful in large-scale monitoring programs because water samples are easy to collect and water isotopes integrate information about basic hydrological processes such as evaporation as a percentage of inflow (E/I), w...

  1. Spatial and temporal analysis of stable isotopes in tap water across China

    NASA Astrophysics Data System (ADS)

    Zhao, S.; Hu, H.; Tian, F.; Tie, Q.

    2015-12-01

    Stable isotopes in water (δ2H and δ18O) are important indicators of hydrological and ecological pattern and process. Water isotopes have been used to trace atmospheric moisture source, identify source of groundwater and surface water charge, reconstruct paleoclimate, and so on. Tap water appears to reflect pervasive features of regional integrated hydrological process. China is a large-size country with high variations in both environmental and geographical factors including temperature, precipitation amount, relative humidity, latitude, altitude et al. Here we present a first national-scale survey on stable isotope of tap water across China. More than 1000 tap water samples have been collected from 93 cities across China by monthly between December 2014 and November 2015. Stable isotope composition of tap water ranged from -132.1‰ to -25.6‰ (δ2H) and from -17.5‰ to -4.2‰ (δ18O). The Meteoric Water Line is δ2H = 7.77 δ18O + 5.79 (r2 = 0.95) and the LMWL of Chinese precipitation is δ2H =7.6δ18O+ 9.94 (r2= 0.97). Spatial distribution of stable isotopes present typical "continental effect", isotope values generally decrease from coastal regions to inland. Isotopes in different regions present different correlations with temperature, precipitation amount, latitude and altitude as a result of varied moisture source and local water supply. The results of the study could provide mapping information of tap water for fundamental isotope hydrological studies in different regions of China.

  2. Deuterium stable isotope ratios as tracers of water resource use: an experimental test with rock doves.

    PubMed

    McKechnie, Andrew E; Wolf, Blair O; Martínez del Rio, Carlos

    2004-07-01

    Naturally-occurring deuterium stable isotope ratios can potentially be used to trace water resource use by animals, but estimating the contribution of isotopically distinct water sources requires the accurate prediction of isotopic discrimination factors between water inputs and an animal's body water pool. We examined the feasibility of using estimates of water fluxes between a bird and its environment with a mass-balance model for the deuterium stable isotope ratio of avian body water (deltaDbody) to predict isotopic discrimination factors. Apparent fractionation and thus discrimination factors were predicted to vary with the proportion of an animal's total water losses than could be attributed to evaporative processes. To test our ability to predict isotopic discrimination, we manipulated water intake and evaporative water loss in rock doves (Columba livia) by providing them with fresh water or 0.15 M NaCl solution in thermoneutral or hot environments. After we switched the birds from drinking water with deltaD=-95 per thousand VSMOW (Vienna Standard Mean Ocean Water) to enriched drinking water with deltaD=+52 per thousand VSMOW, steady-state deltaDbody was approached asymptotically. The equilibrium deltaDbody was enriched by 10-50 per thousand relative to water inputs. After isotopic equilibrium was reached, the degree of enrichment was positively related (r2=0.34) to the fraction of total water loss that occurred by evaporation (revap/rH2O)supporting the major prediction of the model. The variation we observed in discrimination factors suggests that the apparent fractionation of deuterium will be difficult to predict accurately under natural conditions. Our results show that accurate estimates of the contribution of different water sources to a bird's body water pool require large deuterium isotopic differences between the sources. PMID:15185137

  3. Estimating plant water uptake source depths with optimized stable water isotope labeling

    NASA Astrophysics Data System (ADS)

    Seeger, Stefan; Weiler, Markus

    2016-04-01

    Depth profiles of pore water stable isotopes in soils in conjunction with measurements of stable water isotopes (SWI) in plant transpiration allow the estimation of the contributions of different soil depths to plant water uptake (PWU).
 However, SWI depth profiles that result from the variations of SWI in natural precipitation may lead to highly ambiguous results, i.e. the same SWI signature in transpiration could result from different PWU patterns or SWI depth profiles. The aim of this study was to find an optimal stable water isotope depth profile to estimate plant water uptake patterns and to compare different PWU source depth estimation methods. We used a new soil water transport model including fractionation effects of SWI and exchange between the vapor and liquid phase to simulate different irrigation scenarios. Different amounts of water with differing SWI signatures (glacier melt water, summer precipitation water, deuterated water) were applied in order to obtain a wide variety of SWI depth profiles. Based on these simulated SWI depth profiles and a set of hypothetical PWU patterns, the theoretical SWI signatures of the respective plant transpiration were computed. In the next step, two methods - Bayesian isotope mixing models (BIMs) and optimization of a parametric distribution function (beta function) - were used to estimate the PWU patterns from the different SWI depth profiles and their respective SWI signatures in the resulting transpiration. Eventually, the estimated and computed profiles were compared to find the best SWI depth profile and the best method. The results showed, that compared to naturally occurring SWI depth profiles, the application of multiple, in terms of SWI, distinct labeling pulses greatly improves the possible spatial resolution and at the same time reduces the uncertainty of PWU estimates.
 For the PWU patterns which were assumed for this study, PWU pattern estimates based on an optimized parametric distribution function

  4. [Characteristics of stable isotopes in soil water under several typical land use patterns on Loess Tableland].

    PubMed

    Cheng, Li-Ping; Liu, Wen-Zhao

    2012-03-01

    In this study, the precipitation over the Loess Tableland in Changwu County of Shaanxi Province and the soil water in 0-20 m loess profiles under different land use patterns on the Tableland were sampled, and their isotope compositions were analyzed, aimed to understand the characteristics of stable isotopes in the soil water and the mechanisms of the soil water movement. In the study area, the equation of the local meteoric water line (LMWL) was deltaD = 7.39 delta180 + 4.34 (R2 = 0.94, n = 71), and the contents of the stable isotopes in the precipitation had an obvious seasonal variation of high in winter and spring and low in summer and autumn. The contents of the stable isotopes in the soil water were fell on the underside of the LMWL, and higher than those in the precipitation from July to October, indicating that the soil water was mainly replenished by the precipitation with lower stable isotope contents in summer and autumn. In the soil profiles of different land use patterns, the stable isotope contents in soil water tended to be the same with the increasing soil depth; while under the same land use patterns, the water's stable isotope composition in shallow soil layers changed greatly with time, but changed less with increasing depth. Through the comparison of the stable isotope contents in precipitation and in soil water, it was observed that the piston flow and preferential flow on the Tableland were coexisted in the process of precipitation infiltration, and the occurrence of the preferential flow had a certain relation with land use pattern. Generally, the soil desiccation caused by the negative water balance resulted from the artificial plantations of high water consumption could reduce the probability of preferential flow occurrence, whereas the precipitation infiltration in the form of preferential flow could easily occur on the farmland or natural grassland so that the soil water in deep layers or the ground water could be replenished. PMID

  5. [Stable Isotope Characteristics in Different Water Bodies in Changsha and Implications for the Water Cycle].

    PubMed

    Li, Guang; Zhang, Xin-ping; Zhang, Li-feng; Wang, Yue-feng; Deng, Xiao-jun; Yang, Liu; Lei, Chao-gui

    2015-06-01

    Analysis of the variation characteristics of different water bodies is the basis of applying isotopic tracer technique in regional water cycle research. Based on the samples of atmospheric precipitation, surface water (river water) and groundwater (spring water and well water) in Changsha from January 2012 to December 2013, the study analyzed the variation characteristics of δD and δ(18)O in different water bodies. The results showed that the values of D and 18O in precipitation of Changsha showed obvious seasonal variation because of the seasonal difference of the water vapor source, and it showed significant negative correlation between δ(18)O in precipitation and some meteorological factors such as the temperature and the amount, the local meteoric water line revealed the climatic characteristic of humid and rainy in Changsha; the fluctuation of 8D and 80 in surface water was more moderate than those in precipitation, and the seasonal variation of stable isotope value showed lagging characteristic compared with that in precipitation, the difference of river water line (RWL) indicated that the main supply sources of surface water were changing in different seasons; the fluctuation of δD and δ(18)O in groundwater was the least, the variation ranges and mean values of δD and δ(18)O in spring water and well water were very close, it showed that there were some hydraulic connections in the two water bodies, the values of δD and δ(18)O in groundwater were constantly lower during drought months, this phenomenon might have a certain relationship with the increasing absorbency of tree roots from groundwater. The results of the study have certain guiding significance for rational utilization of water resources in the region. PMID:26387312

  6. Exploring water cycle dynamics through sampling multitude stable water isotope pools in a small developed landscape of Germany

    NASA Astrophysics Data System (ADS)

    Orlowski, N.; Kraft, P.; Breuer, L.

    2015-02-01

    Conducting a dual stable water isotope (δ2H and δ18O) study in the developed landscape of the Schwingbach catchment (Germany) helped to unravel connectivity and disconnectivity between the different water cycle components. The two-year weekly to biweekly measurements of precipitation, stream, and groundwater isotopes revealed that surface and groundwater are decoupled from the annual precipitation cycle but showed bidirectional interactions between each other. Seasonal variations based on temperature effects were observed in the precipitation signal but neither reflected in stream nor in groundwater isotopic signatures. Apparently, snowmelt played a fundamental role for groundwater recharge explaining the observed differences to precipitation δ-values. A spatially distributed snapshot sampling of soil water isotopes in two soil depths at 52 sampling points across different land uses (arable land, forest, and grassland) revealed that top soil isotopic signatures were similar to the precipitation input signal. Preferential water flow paths occurred under forested soils explaining the isotopic similarities between top and subsoil isotopic signatures. Due to human-impacted agricultural land use (tilling and compression) of arable and grassland soils, water delivery to the deeper soil layers was reduced, resulting in significant different isotopic signatures. However, the land use influence smoothed out with depth and soil water approached groundwater δ-values. Seasonally tracing stable water isotopes through soil profiles showed that the influence of new percolating soil water decreased with depth as no remarkable seasonality in soil isotopic signatures was obvious at depth > 0.9 m and constant values were observed through space and time. Little variation in individual isotope time series of stream and groundwater restricted the use of classical isotope hydrology techniques e.g. mean transit time estimation or hydrograph separation. Still, tracing stable water

  7. The use of stable isotopes in quantitative determinations of exogenous water and added ethanol in wines

    NASA Astrophysics Data System (ADS)

    Magdas, D. A.; Moldovan, Z.; Cristea, G.

    2012-02-01

    The application of oxygen isotope ratios analysis to wine water according to EU regulation no. 822/97 to determine wine's origin and also, the possible water addition to wines, gained great importance in wines authenticity control. In the natural cycle of water isotopic fractionation, during water evaporation process, the water vapors are depleted in heavy isotopes. On the other hand inside the plants take place an isotope enrichment of heavy stable isotopes of water compared with meteoric water due to photosynthesis and plants transpiration. This process makes possible the detection of exogenous water from wines 18O/16O ratios. Carbon isotopic ratios were used to estimate the supplementary addition of ethanol obtained from C4 plants (sugar cane or corn). This work presents the way in which the isotopic fingerprints (δ13C and δ18O) were used to determine the content of exogenous water from wines and the added supplementary ethanol coming from C4 plants. By using this method, the calculated values obtained for the degree of wine adulteration were in a good agreement with the real exogenous percent of water and ethanol from investigated samples.

  8. Stable isotope ratios of tap water in the contiguous United States

    NASA Astrophysics Data System (ADS)

    Bowen, Gabriel J.; Ehleringer, James R.; Chesson, Lesley A.; Stange, Erik; Cerling, Thure E.

    2007-03-01

    Understanding links between water consumers and climatological (precipitation) sources is essential for developing strategies to ensure the long-term sustainability of water supplies. In pursing this understanding a need exists for tools to study and monitor complex human-hydrological systems that involve high levels of spatial connectivity and supply problems that are regional, rather than local, in nature. Here we report the first national-level survey of stable isotope ratios in tap water, including spatially and temporally explicit samples from a large number of cities and towns across the contiguous United States. We show that intra-annual ranges of tap water isotope ratios are relatively small (e.g., <10‰ for δ2H) at most sites. In contrast, spatial variation in tap water isotope ratios is very large, spanning ranges of 163‰ for δ2H and 23.6‰ for δ18O. The spatial distribution of tap water isotope ratios at the national level is similar to that of stable isotope ratios of precipitation. At the regional level, however, pervasive differences between tap water and precipitation isotope ratios can be attributed to hydrological factors in the water source to consumer chain. These patterns highlight the potential for monitoring of tap water isotope ratios to contribute to the study of regional water supply stability and provide warning signals for impending water resource changes. We present the first published maps of predicted tap water isotope ratios for the contiguous United States, which will be useful in guiding future research on human-hydrological systems and as a tool for applied forensics and traceability studies.

  9. Comparing Stable Water Isotope Variation in Atmospheric Moisture Observed over Coastal Water and Forests

    NASA Astrophysics Data System (ADS)

    Lai, C. T.; Rambo, J. P.; Welp, L. R.; Bible, K.; Hollinger, D. Y.

    2014-12-01

    Stable oxygen (δ18O) and hydrogen (δD) isotopologues of atmospheric moisture are strongly influenced by large-scale synoptic weather cycles, surface evapotranspiration and boundary layer mixing. Atmospheric water isotope variation has been shown to empirically relate to relative humidity (Rh) of near surface moisture, and to a less degree, air temperature. Continuous δ18O and δD measurements are becoming more available, providing new opportunities to investigate processes that control isotope variability. This study shows the comparison of δ18O and δD measured at a continental location and over coastal waters for 3 seasons (spring to fall, 2014). The surface moisture isotope measurements were made using two LGR spectroscopy water vapor isotope analyzers (Los Gatos Research Inc.), one operated in an old-growth coniferous forest at Wind River field station, WA (45.8205°N, 121.9519°W), and another sampling marine air over seawater at the Scripps Pier in San Diego, CA (32.8654°N, 117.2536°W), USA. Isotope variations were measured at 1Hz and data were reported as hourly averages with an overall accuracy of ±0.1‰ for δ18O, ±0.5‰ for δ2H. Day-to-day variations in δ18O and δD are shown strongly influenced by synoptic weather events at both locations. Boundary layer mixing between surface moisture and the dry air entrained from the free troposphere exerts a midday maximum and a consistent diel pattern in deuterium excess (dx). At the forest site, surface moisture also interacts with leaf water through transpiration during the day and re-equilibration at night. The latter occurs by retro-diffusion of atmospheric H2O molecules into leaf intercellular space, which becomes intensified as Rh increaes after nightfall, and continues until sunrise, to counter-balance the evaporative isotopic enrichment in leaf water on a daily basis. These vegetation effects lead to negative dx values consistently observed at nighttime in this continental location that were not

  10. Investigating surface water-well interaction using stable isotope ratios of water

    USGS Publications Warehouse

    Hunt, R.J.; Coplen, T.B.; Haas, N.L.; Saad, D.A.; Borchardt, M. A.

    2005-01-01

    Because surface water can be a source of undesirable water quality in a drinking water well, an understanding of the amount of surface water and its travel time to the well is needed to assess a well's vulnerability. Stable isotope ratios of oxygen in river water at the City of La Crosse, Wisconsin, show peak-to-peak seasonal variation greater than 4??? in 2001 and 2002. This seasonal signal was identified in 7 of 13 city municipal wells, indicating that these 7 wells have appreciable surface water contributions and are potentially vulnerable to contaminants in the surface water. When looking at wells with more than 6 sampling events, a larger variation in ??18O compositions correlated with a larger fraction of surface water, suggesting that samples collected for oxygen isotopic composition over time may be useful for identifying the vulnerability to surface water influence even if a local meteoric water line is not available. A time series of ??18O from one of the municipal wells and from a piezometer located between the river and the municipal well showed that the travel time of flood water to the municipal well was approximately 2 months; non-flood arrival times were on the order of 9 months. Four independent methods were also used to assess time of travel. Three methods (groundwater temperature arrival times at the intermediate piezometer, virus-culture results, and particle tracking using a numerical groundwater-flow model) yielded flood and non-flood travel times of less than 1 year for this site. Age dating of one groundwater sample using 3H-3He methods estimated an age longer than 1 year, but was likely confounded by deviations from piston flow as noted by others. Chlorofluorocarbons and SF6 analyses were not useful at this site due to degradation and contamination, respectively. This work illustrates the utility of stable hydrogen and oxygen isotope ratios of water to determine the contribution and travel time of surface water in groundwater, and

  11. Tritium and Stable Isotopes of Precipitation and Surface Water in California

    NASA Astrophysics Data System (ADS)

    Harms, P.; Moran, J. E.; Visser, A.; Esser, B. K.

    2014-12-01

    Tritium (3H) and stable isotopes (2H and 18O) are effective natural tracers of water molecules through the hydrologic system. The strong topographic gradient in California results in distinct isotopic signatures that are particularly effective in watershed studies. Past studies of meteoric tritium distribution within the United States have focused on large-scale trends, at low spatial resolution. Globally, tritium in precipitation is monitored by the International Atomic Energy Agency contributing to the Global Network of Isotopes in Precipitation (GNIP) database. The two tritium monitoring stations in California contributing to the GNIP database were discontinued in 1976 (Santa Maria) and 1993 (Menlo Park). Surface water studies have focused on time series in major rivers nationwide or localized studies. Our study focuses on high spatial resolution water isotope data collection in California. Over 140 tritium and stable water isotope samples were collected from surface water and direct precipitation during the 2013 Summer/Fall and 2014 Winter/Spring flow regimes and analyzed by helium accumulation and noble gas mass spectrometry. Surface water samples are collected as a proxy for precipitation and to investigate trends related to water residence times. Tritium concentrations in precipitation show strong spatial trends, with higher concentrations at inland high elevation locations. Surface water tritium trends with spatial location (latitude and longitude) and elevation (reflecting the precipitation signal) and distance downstream (reflecting water residence times). A local meteoric water line (MWL) for California is developed from stable isotope data and analyzed in comparison to the global MWL. Results have implications for tritium tracer and water provenance studies.

  12. A new isotopic reference material for stable hydrogen and oxygen isotope-ratio measurements of water—USGS50 Lake Kyoga Water

    USGS Publications Warehouse

    Coplen, Tyler B.; Wassenaar, Leonard I; Mukwaya, Christine; Qi, Haiping; Lorenz, Jennifer M.

    2015-01-01

    This isotopic reference material, designated as USGS50, is intended as one of two reference waters for daily normalization of stable hydrogen and oxygen isotopic analysis of water with an isotope-ratio mass spectrometer or a laser absorption spectrometer, of use especially for isotope-hydrology laboratories analyzing freshwater samples from equatorial and tropical regions.

  13. Stable isotope studies

    SciTech Connect

    Ishida, T.

    1992-01-01

    The research has been in four general areas: (1) correlation of isotope effects with molecular forces and molecular structures, (2) correlation of zero-point energy and its isotope effects with molecular structure and molecular forces, (3) vapor pressure isotope effects, and (4) fractionation of stable isotopes. 73 refs, 38 figs, 29 tabs.

  14. Tracing Water Sources of Terrestrial Animal Populations with Stable Isotopes: Laboratory Tests with Crickets and Spiders

    PubMed Central

    McCluney, Kevin E.; Sabo, John L.

    2010-01-01

    Fluxes of carbon, nitrogen, and water between ecosystem components and organisms have great impacts across levels of biological organization. Although much progress has been made in tracing carbon and nitrogen, difficulty remains in tracing water sources from the ecosystem to animals and among animals (the “water web”). Naturally occurring, non-radioactive isotopes of hydrogen and oxygen in water provide a potential method for tracing water sources. However, using this approach for terrestrial animals is complicated by a change in water isotopes within the body due to differences in activity of heavy and light isotopes during cuticular and transpiratory water losses. Here we present a technique to use stable water isotopes to estimate the mean mix of water sources in a population by sampling a group of sympatric animals over time. Strong correlations between H and O isotopes in the body water of animals collected over time provide linear patterns of enrichment that can be used to predict a mean mix of water sources useful in standard mixing models to determine relative source contribution. Multiple temperature and humidity treatment levels do not greatly alter these relationships, thus having little effect on our ability to estimate this population-level mix of water sources. We show evidence for the validity of using multiple samples of animal body water, collected across time, to estimate the isotopic mix of water sources in a population and more accurately trace water sources. The ability to use isotopes to document patterns of animal water use should be a great asset to biologists globally, especially those studying drylands, droughts, streamside areas, irrigated landscapes, and the effects of climate change. PMID:21209877

  15. Tracing water sources of terrestrial animal populations with stable isotopes: laboratory tests with crickets and spiders.

    PubMed

    McCluney, Kevin E; Sabo, John L

    2010-01-01

    Fluxes of carbon, nitrogen, and water between ecosystem components and organisms have great impacts across levels of biological organization. Although much progress has been made in tracing carbon and nitrogen, difficulty remains in tracing water sources from the ecosystem to animals and among animals (the "water web"). Naturally occurring, non-radioactive isotopes of hydrogen and oxygen in water provide a potential method for tracing water sources. However, using this approach for terrestrial animals is complicated by a change in water isotopes within the body due to differences in activity of heavy and light isotopes during cuticular and transpiratory water losses. Here we present a technique to use stable water isotopes to estimate the mean mix of water sources in a population by sampling a group of sympatric animals over time. Strong correlations between H and O isotopes in the body water of animals collected over time provide linear patterns of enrichment that can be used to predict a mean mix of water sources useful in standard mixing models to determine relative source contribution. Multiple temperature and humidity treatment levels do not greatly alter these relationships, thus having little effect on our ability to estimate this population-level mix of water sources. We show evidence for the validity of using multiple samples of animal body water, collected across time, to estimate the isotopic mix of water sources in a population and more accurately trace water sources. The ability to use isotopes to document patterns of animal water use should be a great asset to biologists globally, especially those studying drylands, droughts, streamside areas, irrigated landscapes, and the effects of climate change. PMID:21209877

  16. Correcting Laser-Based Water Stable Isotope Readings Biased by Carrier Gas Changes.

    PubMed

    Gralher, Benjamin; Herbstritt, Barbara; Weiler, Markus; Wassenaar, Leonard I; Stumpp, Christine

    2016-07-01

    Recently, laser-based water stable isotope spectrometers have become popular as they enable previously impossible approaches of environmental observations. Consequently, they have been subjected to increasingly heterogeneous atmospheric conditions. However, there is still a severe lack of data on the impact of nonstandardized gas matrices on analyzer performances. Against this background, we investigated the influence of changing proportions of N2, O2, and CO2 in the carrier gas on the isotope measurements of a typical laser-based water stable isotope analyzer (Picarro L2120-i). We combined environmentally relevant mixtures of N2, O2, and CO2 with referenced, flash-evaporated water and found that isotope readings of the same water were altered by up to +14.57‰ for δ(18)O and -35.9‰ for δ(2)H. All tested relationships between carrier gas changes and respective isotope readings were strongly linearly correlated (R(2) > 0.99). Furthermore, an analyzer-measured variable allowed for reliable postcorrection of the biased isotope readings, which we additionally tested on field data. Our findings are of importance for environmental data obtained by analyzers based on the same technology. They are relevant for assays where inconsistent gas matrices or a mismatch in this regard between unknown and reference analyses cannot be excluded, which is in particular common when investigating the soil-vegetation-atmosphere continuum. PMID:27291718

  17. Quantifying Irrigation Return Flows Using Stable Isotopes of Water along the South Platte River, Colorado USA

    NASA Astrophysics Data System (ADS)

    Sanford, W. E.; Davila Olmo, K.; Stednick, J. D.

    2011-12-01

    As the South Platte River flows from Denver, CO to the Nebraska border it crosses urban and agricultural settings which affect water quality and quantity. This reach of the river is highly regulated, with numerous diversions, off-channel reservoirs, and flow-augmentation projects. Water in the river is used 7 different times between Denver and the state line. Much of the water diverted from the river is used for irrigation. A significant portion of this water returns to the river as groundwater flow, often during times of low stream flow. Groundwater return flows, coupled with wastewater treatment plant and reservoir storage, have turned the once ephemeral river into a perennial one. The goal of this research was to determine if the stable isotopes of water (δ 2H and δ18O) in the river can be used to identify and to help quantify groundwater return flows to the river. Water samples were collected and analyzed for their isotopic signature at 17 sites from Denver to Julesburg. Nine rounds of samples were collected from June 2009 to June 2010. Well defined linear patterns of isotope ratios are observed on individual sampling events indicating that the water in the river is becoming enriched as it moves downstream. The enrichment is caused by evaporation from irrigation waters and their discharge to the river as groundwater return flows. These promising results indicate that it may be possible to quantify irrigation return flow to the South Platte River using the stable isotopes of water.

  18. Stable Isotope Analyses of water and Aqueous Solutions by Conventional Dual-inlet Mass Spectrometry

    SciTech Connect

    Horita, Juske; Kendall, C.

    2004-01-01

    The foundation of various analytical methods for the stable isotope composition of water and other aqueous samples (natural abundance, {sup 1}H : {sup 2}H (D) = 99.985 : 0.015 atom%, and {sup 16}O : {sup 17}O : {sup 18}O = 99.762 : 0.038 : 0.200 atom%) was established during the Manhatten Project in the U.S.A., when large amounts of heavy water were produced for nuclear reactors (see Kirshenbaum, 1951, for a detailed account). From early on, there was great interest in the oxygen and hydrogen isotopic compositions of water, because they are the ideal tracers of water sources and reactions. The increased analytical precisions made possible by the subsequent development of modern gas-source isotope-ratio mass spectrometers with dual-inlets and multi-collectors, have caused the proliferation of new analytical methods and applications for the oxygen and hydrogen isotopic compositions of water. These stable isotopes have found wide applications in basic as well as applied sciences (chemistry, geology, hydrology, biology, medical sciences, and food sciences). This is because water is ubiquitous, is an essential and predominant ingredient of living organisms, and is perhaps the most reactive compound in the Earth.

  19. A method to extract soil water for stable isotope analysis

    USGS Publications Warehouse

    Revesz, K.; Woods, P.H.

    1990-01-01

    A method has been developed to extract soil water for determination of deuterium (D) and 18O content. The principle of this method is based on the observation that water and toluene form an azeotropic mixture at 84.1??C, but are completely immiscible at ambient temperature. In a specially designed distillation apparatus, the soil water is distilled at 84.1??C with toluene and is separated quantitatively in the collecting funnel at ambient temperature. Traces of toluene are removed and the sample can be analyzed by mass spectrometry. Kerosene may be substituted for toluene. The accuracy of this technique is ?? 2 and ?? 0.2???, respectively, for ??D and ??18O. Reduced accuracy is obtained at low water contents. ?? 1990.

  20. Selenium stable isotope ratios in California agricultural drainage water management systems

    USGS Publications Warehouse

    Herbel, M.J.; Johnson, T.M.; Tanji, K.K.; Gao, S.; Bullen, T.D.

    2002-01-01

    Selenium stable isotope ratios are known to shift in predictable ways during various microbial, chemical, and biological processes, and can be used to better understand Se cycling in contaminated environments. In this study we used Se stable isotopes to discern the mechanisms controlling the transformation of oxidized, aqueous forms of Se to reduced, insoluble forms in sediments of Se-affected environments. We measured 80Se/76Se in surface waters, shallow ground waters, evaporites, digested plants and sediments, and sequential extracts from several sites where agricultural drainage water is processed in the San Joaquin Valley of California. Selenium isotope analyses of samples obtained from the Tulare Lake Drainage District flow-through wetland reveal small isotopic contrasts (mean difference 0.7%o) between surface water and reduced Se species in the underlying sediments. Selenium in aquatic macrophytes was very similar isotopically to the NaOH and Na2SO3 sediment extracts designed to recover soluble organic Se and Se(O), respectively. For the integrated on-farm drainage management sites, evaporite salts were slightly (approximately 0.6%o) enriched in the heavier isotope relative to the inferred parent waters, whereas surface soils were slightly (approximately 1.4%o) depleted. Bacterial or chemical reduction of Se(VI) or Se(IV) may be occurring at these sites, but the small isotopic contrasts suggest that other, less isotopically fractionating mechanisms are responsible for accumulation of reduced forms in the sediments. These findings provide evidence that Se assimilation by plants and algae followed by deposition and mineralization is the dominant transformation pathway responsible for accumulation of reduced forms of Se in the wetland sediments.

  1. Stable water isotope simulation by current land-surface schemes:Results of IPILPS phase 1

    SciTech Connect

    Henderson-Sellers, A.; Fischer, M.; Aleinov, I.; McGuffie, K.; Riley, W.J.; Schmidt, G.A.; Sturm, K.; Yoshimura, K.; Irannejad, P.

    2005-10-31

    Phase 1 of isotopes in the Project for Intercomparison of Land-surface Parameterization Schemes (iPILPS) compares the simulation of two stable water isotopologues ({sup 1}H{sub 2} {sup 18}O and {sup 1}H{sup 2}H{sup 16}O) at the land-atmosphere interface. The simulations are off-line, with forcing from an isotopically enabled regional model for three locations selected to offer contrasting climates and ecotypes: an evergreen tropical forest, a sclerophyll eucalypt forest and a mixed deciduous wood. Here we report on the experimental framework, the quality control undertaken on the simulation results and the method of intercomparisons employed. The small number of available isotopically-enabled land-surface schemes (ILSSs) limits the drawing of strong conclusions but, despite this, there is shown to be benefit in undertaking this type of isotopic intercomparison. Although validation of isotopic simulations at the land surface must await more, and much more complete, observational campaigns, we find that the empirically-based Craig-Gordon parameterization (of isotopic fractionation during evaporation) gives adequately realistic isotopic simulations when incorporated in a wide range of land-surface codes. By introducing two new tools for understanding isotopic variability from the land surface, the Isotope Transfer Function and the iPILPS plot, we show that different hydrological parameterizations cause very different isotopic responses. We show that ILSS-simulated isotopic equilibrium is independent of the total water and energy budget (with respect to both equilibration time and state), but interestingly the partitioning of available energy and water is a function of the models' complexity.

  2. Winds, Water Budgets and Stable Isotopes in Tropical Cyclones using TRMM and QUICKSCAT

    NASA Technical Reports Server (NTRS)

    Lawrence, James R.

    2004-01-01

    Water vapor is the most abundant greenhouse gas in the atmosphere. Changes in its concentration and distribution are controlled by the hydrologic cycle. Because of its capacity to absorb and emit long wave radiation, release latent heat during condensation in storms and reflect short wave radiation when clouds form it has a major impact on Global climate change. The stable isotope ratios of water are H20 H2l6O and H0 H2l6O. These ratios change whenever water undergoes a phase change. They also change in both rain and water vapor whenever an air parcel is exposed to rain. In addition the relative changes in the two ratios differ as a &nction of the relative humidity. In short, the stable isotope ratios in water vapor in the atmosphere contain an integrated history of the processes affecting the concentration and distribution of water vapor in the atmosphere. Therefore the measurement and interpretation of changes in these stable isotope ratios are a powerful tool matched by no other method in tracing the transport history of water in the atmosphere. Our initial studies under this grant focused on the changes of the stable isotope ratios of precipitation and water vapor in tropical cyclones. The changes in time and space were found to be very large and to trace the transport of water in the storms reflecting changes in basic structural features. Because the stable isotope ratios of rains from tropical cyclones are so low flooding associated with land falling tropical cyclones introduces a negative isotopic spike into the coastal surface waters. In addition the stable isotope ratios of water vapor in the vicinity of tropical cyclones is anomalously low. This suggests that carbonate shelled organisms such as ostracoda living in coastal waters have the potential to record the isotopic spike and thereby provide a long term record of tropical storm activity in sediment cores containing fossil shells. Likewise, tree rings in coastal environments offer a similar potential

  3. Winds, Water Budgets and Stable Isotopes in Tropical Cyclones using TRMM and QUICKSCAT

    NASA Technical Reports Server (NTRS)

    Lawrence, James R.

    2004-01-01

    Water vapor is the most abundant greenhouse gas in the atmosphere. Changes in its concentration and distribution are controlled by the hydrologic cycle. Because of its capacity to absorb and emit long wave radiation, release latent heat during condensation in storms and reflect short wave radiation when clouds form it has a major impact on Global climate change. The stable isotope ratios of water are H20 H2l6O and H0 H2l6O. These ratios change whenever water undergoes a phase change. They also change in both rain and water vapor whenever an air parcel is exposed to rain. In addition the relative changes in the two ratios differ as a &nction of the relative humidity. In short, the stable isotope ratios in water vapor in the atmosphere contain an integrated history of the processes affecting the concentration and distribution of water vapor in the atmosphere. Therefore the measurement and interpretation of changes in these stable isotope ratios are a powerful tool matched by no other method in tracing the transport history of water in the atmosphere. Our initial studies under this grant focused on the changes of the stable isotope ratios of precipitation and water vapor in tropical cyclones. The changes in time and space were found to be very large and to trace the transport of water in the storms reflecting changes in basic structural features. Because the stable isotope ratios of rains from tropical cyclones are so low flooding associated with land falling tropical cyclones introduces a negative isotopic spike into the coastal surface waters. In addition the stable isotope ratios of water vapor in the vicinity of tropical cyclones is anomalously low. This suggests that carbonate shelled organisms such as ostracoda living in coastal waters have the potential to record the isotopic spike and thereby provide a long term record of tropical storm activity in sediment cores containing fossil shells. Likewise, tree rings in coastal environments offer a similar potential

  4. Modelling stable water isotopes during "high-precipitation" events at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Schlosser, Elisabeth; Masson-Delmotte, Valérie; Risi, Camille; Stenni, Barbara; Valt, Mauro; Powers, Jordan G.; Manning, Kevin W.; Duda, Michael G.; Cagnati, Anselmo

    2014-05-01

    For a correct paleoclimatologic interpretation of stable water isotopes from ice cores both pre- and post-depositional processes and their role for isotope fractionation have to be better understood. Our study focusses on "pre-depositional processes", namely the atmospheric processes that determine moisture transport and precipitation formation. At the deep ice core drilling site "Dome C", East Antarctica, fresh snow samples have been taken since 2006. These samples have been analysed crystallographically, which enables us to clearly distinguish between blowing snow, diamond dust, and "synoptic precipitation". Also the stable oxygen/hydrogen isotope ratios of the snow samples were measured, including measurements of 17-O. This is the first and only multi-year fresh-snow data series from an Antarctic deep drilling site. The Antarctic Mesoscale Prediction System (AMPS) employs Polar WRF for aviation weather forecasts in Antarctica. The data are archived and can be used for scientific purposes. The mesoscale atmospheric model was adapted especially for polar regions. The horizontal resolution for the domain that covers the Antarctic continent is 10 km. It was shown that precipitation at Dome C is temporally dominated by diamond dust. However, comparatively large amounts of precipitation are observed during several "high-precipitation" events per year, caused by synoptic activity in the circumpolar trough and related advection of relatively warm and moist air from lower latitudes to the interior of Antarctica. AMPS archive data are used to investigate the synoptic situations that lead to "high-precipitation" events at Dome C; in particular, possible moisture sources are determined using back-trajectories. With this meteorological information, the isotope ratios are calculated using two different isotope models, the Mixed Cloud Isotope Model, a simple Rayleigh-type model, and the LMDZ-iso (Laboratoire de Météorologie Dynamic Zoom), a General Circulation Model (GCM

  5. Estimating flow and transport parameters in the unsaturated zone with pore water stable isotopes

    NASA Astrophysics Data System (ADS)

    Sprenger, M.; Volkmann, T. H. M.; Blume, T.; Weiler, M.

    2014-10-01

    Determining the soil hydraulic properties is a prerequisite to physically model transient water flow and solute transport in the vadose zone. Estimating these properties by inverse modelling techniques has become more common within the last two decades. While these inverse approaches usually fit simulations to hydrometric data, we expanded the methodology by using independent information about the stable isotope composition of the soil pore water depth profile as a single or additional optimization target. To demonstrate the potential and limits of this approach, we compared the results of three inverse modelling strategies where the fitting targets were (a) pore water isotope concentrations, (b) a combination of pore water isotope concentrations and soil moisture time series, and (c) a two-step approach using first soil moisture data to determine water flow parameters and then the pore water stable isotope concentrations to estimate the solute transport parameters. The analyses were conducted at three study sites with different soil properties and vegetation. The transient unsaturated water flow was simulated by numerically solving the Richards equation with the finite-element code of Hydrus-1D. The transport of deuterium was simulated with the advection-dispersion equation, and the Hydrus code was modified to allow for deuterium loss during evaporation. The Mualem-van Genuchten and the longitudinal dispersivity parameters were determined for two major soil horizons at each site. The results show that approach (a) using only the pore water isotope content cannot substitute hydrometric information to derive parameter sets that reflect the observed soil moisture dynamics, but gives comparable results when the parameter space is constrained by pedotransfer functions. Approaches (b) and (c) using both, the isotope profiles and the soil moisture time series resulted in satisfying model performances and good parameter identifiability. However, approach (b) has the

  6. Temporal and Spatial Variation of Surface Water Stable Isotopes in the Marys River Basin, Oregon

    NASA Astrophysics Data System (ADS)

    Nickolas, L. B.; Segura, C.; Brooks, J. R.

    2015-12-01

    Understanding the temporal and spatial variability of water sources within a basin is vital to our ability to manage the impacts of climate variability and land cover change. Water stable isotopes can be used as a tool to determine geographic and seasonal sources of water at the basin scale. Previous studies in the Coastal Range of Oregon reported that the variation in the isotopic signatures of surface water does not conform to the commonly observed "rainout effect", which exhibits a trend of increasing isotopic depletion with rising elevation. The primary purpose of this research is to investigate the mechanisms governing seasonal and spatial variations in the isotopic signature of surface waters within the Marys River Basin, located in the Oregon Coastal Range. We hypothesize that catchment orientation, drainage area, geology, and topography act as controlling factors on groundwater flow, storage, and atmospheric moisture cycling, which explain variations in source water contribution. Surface water and precipitation samples were collected every 2-3 weeks for isotopic analysis of δ18O and δ2H for one year. Preliminary results indicate a significant difference (p<0.001) in isotopic signature between watersheds underlain by basalt and sandstone. The degree of separation is the most distinct during the summer when low flows likely reflect deeper groundwater sources, whereas isotopic signatures during the rainy season (fall & winter) show a greater degree of similarity between the two lithologies. These findings indicate that the more permeable sandstone formations may be hydrologically connected to enriched water sources on the windward side of the Coastal Range that sustain baseflow within catchments on the leeward side, while streams draining basalt catchments are fed by a more depleted source of water (e.g. precipitation originating within the Marys River Basin).

  7. A stable isotope approach and its application for identifying nitrate source and transformation process in water.

    PubMed

    Xu, Shiguo; Kang, Pingping; Sun, Ya

    2016-01-01

    Nitrate contamination of water is a worldwide environmental problem. Recent studies have demonstrated that the nitrogen (N) and oxygen (O) isotopes of nitrate (NO3(-)) can be used to trace nitrogen dynamics including identifying nitrate sources and nitrogen transformation processes. This paper analyzes the current state of identifying nitrate sources and nitrogen transformation processes using N and O isotopes of nitrate. With regard to nitrate sources, δ(15)N-NO3(-) and δ(18)O-NO3(-) values typically vary between sources, allowing the sources to be isotopically fingerprinted. δ(15)N-NO3(-) is often effective at tracing NO(-)3 sources from areas with different land use. δ(18)O-NO3(-) is more useful to identify NO3(-) from atmospheric sources. Isotopic data can be combined with statistical mixing models to quantify the relative contributions of NO3(-) from multiple delineated sources. With regard to N transformation processes, N and O isotopes of nitrate can be used to decipher the degree of nitrogen transformation by such processes as nitrification, assimilation, and denitrification. In some cases, however, isotopic fractionation may alter the isotopic fingerprint associated with the delineated NO3(-) source(s). This problem may be addressed by combining the N and O isotopic data with other types of, including the concentration of selected conservative elements, e.g., chloride (Cl(-)), boron isotope (δ(11)B), and sulfur isotope (δ(35)S) data. Future studies should focus on improving stable isotope mixing models and furthering our understanding of isotopic fractionation by conducting laboratory and field experiments in different environments. PMID:26541149

  8. Spectral analysis software improves confidence in plant and soil water stable isotope analyses performed by isotope ratio infrared spectroscopy (IRIS).

    PubMed

    West, A G; Goldsmith, G R; Matimati, I; Dawson, T E

    2011-08-30

    Previous studies have demonstrated the potential for large errors to occur when analyzing waters containing organic contaminants using isotope ratio infrared spectroscopy (IRIS). In an attempt to address this problem, IRIS manufacturers now provide post-processing spectral analysis software capable of identifying samples with the types of spectral interference that compromises their stable isotope analysis. Here we report two independent tests of this post-processing spectral analysis software on two IRIS systems, OA-ICOS (Los Gatos Research Inc.) and WS-CRDS (Picarro Inc.). Following a similar methodology to a previous study, we cryogenically extracted plant leaf water and soil water and measured the δ(2)H and δ(18)O values of identical samples by isotope ratio mass spectrometry (IRMS) and IRIS. As an additional test, we analyzed plant stem waters and tap waters by IRMS and IRIS in an independent laboratory. For all tests we assumed that the IRMS value represented the "true" value against which we could compare the stable isotope results from the IRIS methods. Samples showing significant deviations from the IRMS value (>2σ) were considered to be contaminated and representative of spectral interference in the IRIS measurement. Over the two studies, 83% of plant species were considered contaminated on OA-ICOS and 58% on WS-CRDS. Post-analysis, spectra were analyzed using the manufacturer's spectral analysis software, in order to see if the software correctly identified contaminated samples. In our tests the software performed well, identifying all the samples with major errors. However, some false negatives indicate that user evaluation and testing of the software are necessary. Repeat sampling of plants showed considerable variation in the discrepancies between IRIS and IRMS. As such, we recommend that spectral analysis of IRIS data must be incorporated into standard post-processing routines. Furthermore, we suggest that the results from spectral analysis be

  9. Stable water isotopic composition of the Antarctic subglacial Lake Vostok: implications for understanding the lake's hydrology.

    PubMed

    Ekaykin, Alexey A; Lipenkov, Vladimir Y; Kozachek, Anna V; Vladimirova, Diana O

    2016-01-01

    We estimated the stable isotopic composition of water from the subglacial Lake Vostok using two different sets of samples: (1) water frozen on the drill bit immediately after the first lake unsealing and (2) water frozen in the borehole after the unsealing and re-drilled one year later. The most reliable values of the water isotopic composition are: -59.0 ± 0.3 ‰ for oxygen-18, -455 ± 1 ‰ for deuterium and 17 ± 1 ‰ for d-excess. This result is also confirmed by the modelling of isotopic transformations in the water which froze in the borehole, and by a laboratory experiment simulating this process. A comparison of the newly obtained water isotopic composition with that of the lake ice (-56.2 ‰ for oxygen-18, -442.4 ‰ for deuterium and 7.2 ‰ for d-excess) leads to the conclusion that the lake ice is very likely formed in isotopic equilibrium with water. In turn, this means that ice is formed by a slow freezing without formation of frazil ice crystals and/or water pockets. This conclusion agrees well with the observed physical and chemical properties of the lake's accreted ice. However, our estimate of the water's isotopic composition is only valid for the upper water layer and may not be representative for the deeper layers of the lake, so further investigations are required. PMID:26862787

  10. Reducing and correcting for contamination of ecosystem water stable isotopes measured by isotope ratio infrared spectroscopy.

    PubMed

    Schmidt, Markus; Maseyk, Kadmiel; Lett, Céline; Biron, Philippe; Richard, Patricia; Bariac, Thierry; Seibt, Ulli

    2012-01-30

    Concern exists about the suitability of laser spectroscopic instruments for the measurement of the (18)O/(16)O and (2)H/(1)H values of liquid samples other than pure water. It is possible to derive erroneous isotope values due to optical interference by certain organic compounds, including some commonly present in ecosystem-derived samples such as leaf or soil waters. Here we investigated the reliability of wavelength-scanned cavity ring-down spectroscopy (CRDS) (18)O/(16)O and (2)H/(1)H measurements from a range of ecosystem-derived waters, through comparison with isotope ratio mass spectrometry (IRMS). We tested the residual of the spectral fit S(r) calculated by the CRDS instrument as a means to quantify the difference between the CRDS and IRMS δ-values. There was very good overall agreement between the CRDS and IRMS values for both isotopes, but differences of up to 2.3‰ (δ(18)O values) and 23‰ (δ(2)H values) were observed in leaf water extracts from Citrus limon and Alnus cordata. The S(r) statistic successfully detected contaminated samples. Treatment of Citrus leaf water with activated charcoal reduced, but did not eliminate, δ(2)H(CRDS) - δ(2)H(IRMS) linearly for the tested range of 0-20% charcoal. The effect of distillation temperature on the degree of contamination was large, particularly for δ(2)H values but variable, resulting in positive, negative or no correlation with distillation temperature. S(r) and δ(CRDS) - δ(IRMS) were highly correlated, in particular for δ(2)H values, across the range of samples that we tested, indicating the potential to use this relationship to correct the δ-values of contaminated plant water extracts. We also examined the sensitivity of the CRDS system to changes in the temperature of its operating environment. We found that temperature changes ≥4 °C for δ(18)O values and ≥10 °C for δ(2)H values resulted in errors larger than the CRDS precision for the respective isotopes and advise the use of such

  11. Seasonal Water Usage by Juniperus Ashei: Assessment With Stable Isotopes of Hydrogen and Oxygen

    NASA Astrophysics Data System (ADS)

    McCole, A. A.

    2003-12-01

    The recent expansion of Juniperus ashei (Ashe juniper) on the Edwards Plateau of Central Texas has important implications for the ecosystem structure, productivity and hydrology of the region. Ashe juniper expansion may negatively impact the ecology and hydrology of the Edwards Plateau. The Ashe juniper's morphology, rooting habit, and ability to photosynthesize throughout the year suggests greater water loss will occur in areas where Ashe juniper is prevalent compared to areas dominated by grasses. However, past studies have reached conflicting conclusions regarding Ashe juniper's effect on the water budget. A better understanding of the patterns of Ashe juniper's water use will aid in the understanding of how the Ashe juniper affects groundwater recharge, herbaceous productivity and evapotranspirational water loss. Stable isotopes of hydrogen and oxygen from precipitation, soil water, plant xylem water, and groundwater reveal the current ecosystem hydrology. A comparison of the isotopic compositions of potential water sources and juniper stem water indicates the source water utilized by the Ashe juniper. At the Honey Creek State Natural Area, Comal County, Texas the plant, soil and spring water as representative groundwater were sampled at approximately two month intervals over an annual cycle from two adjacent watersheds and analyzed for hydrogen and oxygen isotope composition. Soils were sampled at depth intervals of 5 to 10 cm and soil water content measured. Mass balance calculations using oxygen isotope data from the dry periods of the year, late summer and winter, indicate the Ashe juniper derives between 72% and 100% of it water from groundwater. In contrast, during the wet periods of the year, spring and fall, mass balance calculations indicate that between 45% and 100% of Ashe juniper's water is derived from soil water. Hydrogen isotope data from a subset of samples are consistent with these results. Bowens ratio measurements of evapotranspiration were

  12. Stable isotopes in river waters in the Tajik Pamirs: regional and temporal characteristics.

    PubMed

    Meier, Christiane; Knoche, Malte; Merz, Ralf; Weise, Stephan M

    2013-01-01

    The Gunt River catchment in the Central Pamirs is a representative of the headwater catchments of the Aral Sea Basin. It covers 14,000 km(2), spanning altitudes between 2000 and 6700 m a.s.l. In a monitoring network, water samples were taken at 30 sampling points every month and analysed for the stable water isotopes ((18)O and (2)H). Our first results show δ(2)H values in the range from-131.2 to-94.9 ‰ and δ(18)O values from-18.0 to-14.0 ‰. The stable isotope patterns in the catchment seem to follow a systematic way, dominated by an altitude effect with a mean Δ δ(2)H=-3.6 ‰/100 m. The observed seasonal variations can be explained by geographical aspects such as the influence of different wind systems as well as melting processes. PMID:24313375

  13. Precipitation water stable isotope measurements and analyses in Middle and Polar Ural

    NASA Astrophysics Data System (ADS)

    Stukova, Olga; Gribanov, Konstantin; Zakharov, Vyacheslav; Cattani, Olivier; Jouzel, Jean

    2015-11-01

    In this paper, we present results of precipitation (rain, snow) water stable isotope measurements, which were collected on two places. Measuring was made on laser spectroscopy analyzer PICARRO L2130-i equipped with liquid auto sampler. We describe method of sample collecting, preparing, measuring and continuing analysis of experimental data. Stored data include results of 177 samples measuring from Kourovka collected from November 2012 to March 2014 and 73 samples from Labytnangi collected from March 2013 to December 2013.

  14. Calculations of evaporative losses using stable water isotope composition in dry climates

    NASA Astrophysics Data System (ADS)

    Skrzypek, Grzegorz; Mydlowski, Adam; Dogramaci, Shawan; Hedley, Paul; Gibson, John; Grierson, Pauline

    2014-05-01

    Evaporative loss from surface waters is a major component of the hydrological cycle in arid zones, restricting recharge to aquifers and limiting the persistence of surface water bodies. Calculation of evaporative loss is founded on the so-called Craig-Gordon model (C-G), and the stable hydrogen and oxygen isotope composition of water can be successfully used to estimate progressive evaporation. The advantage of this approach is that it does not require monitoring of water levels, inflow and outflow rates. However, the precision and reliability of calculations in very hot and dry climates can be compromised by variable isotope composition of air moisture, which thus needs to be calibrated for C-G model calculations. In this study, we tested the range of uncertainty in the estimation of evaporative losses by cross-validating a simplified stable isotope model with field pan evaporation experiments. The use of standardized pans (1.2 m diameter, max volume 300 dm3) allowed simulation of fast evaporation from shallow water bodies in hot and dry climates (mean daily temperature 29° C and relative humidity between 19 and 26% RH during an 11 day experiment). The stable isotope composition of water in pans changed from -8.23o (δ18O) and -56o (δ2H) to approximately +6.0o (δ18O) and +2.4o (δ2H), reflecting evaporative losses of 56% in sun and 53% in shade. The maximum difference between observed (measured in the field) and calculated evaporative losses was

  15. Evapotranspiration partitioning in a semi-arid African savanna using stable isotopes of water vapor

    NASA Astrophysics Data System (ADS)

    Soderberg, K.; Good, S. P.; O'Connor, M.; King, E. G.; Caylor, K. K.

    2012-04-01

    Evapotranspiration (ET) represents a major flux of water out of semi-arid ecosystems. Thus, understanding ET dynamics is central to the study of African savanna health and productivity. At our study site in central Kenya (Mpala Research Centre), we have been using stable isotopes of water vapor to partition ET into its constituent parts of plant transpiration (T) and soil evaporation (E). This effort includes continuous measurement (1 Hz) of δ2H and δ18O in water vapor using a portable water vapor isotope analyzer mounted on a 22.5 m eddy covariance flux tower. The flux tower has been collecting data since early 2010. The isotopic end-member of δET is calculated using a Keeling Plot approach, whereas δT and δE are measured directly via a leaf chamber and tubing buried in the soil, respectively. Here we report on a two recent sets of measurements for partitioning ET in the Kenya Long-term Exclosure Experiment (KLEE) and a nearby grassland. We combine leaf level measurements of photosynthesis and water use with canopy-scale isotope measurements for ET partitioning. In the KLEE experiment we compare ET partitioning in a 4 ha plot that has only seen cattle grazing for the past 15 years with an adjacent plot that has undergone grazing by both cattle and wild herbivores (antelope, elephants, giraffe). These results are compared with a detailed study of ET in an artificially watered grassland.

  16. Estimating flow and transport parameters in the unsaturated zone with pore water stable isotopes

    NASA Astrophysics Data System (ADS)

    Sprenger, M.; Volkmann, T. H. M.; Blume, T.; Weiler, M.

    2015-06-01

    Determining the soil hydraulic properties is a prerequisite to physically model transient water flow and solute transport in the vadose zone. Estimating these properties by inverse modelling techniques has become more common within the last 2 decades. While these inverse approaches usually fit simulations to hydrometric data, we expanded the methodology by using independent information about the stable isotope composition of the soil pore water depth profile as a single or additional optimization target. To demonstrate the potential and limits of this approach, we compared the results of three inverse modelling strategies where the fitting targets were (a) pore water isotope concentrations, (b) a combination of pore water isotope concentrations and soil moisture time series, and (c) a two-step approach using first soil moisture data to determine water flow parameters and then the pore water stable isotope concentrations to estimate the solute transport parameters. The analyses were conducted at three study sites with different soil properties and vegetation. The transient unsaturated water flow was simulated by solving the Richards equation numerically with the finite-element code of HYDRUS-1D. The transport of deuterium was simulated with the advection-dispersion equation, and a modified version of HYDRUS was used, allowing deuterium loss during evaporation. The Mualem-van Genuchten and the longitudinal dispersivity parameters were determined for two major soil horizons at each site. The results show that approach (a), using only the pore water isotope content, cannot substitute hydrometric information to derive parameter sets that reflect the observed soil moisture dynamics but gives comparable results when the parameter space is constrained by pedotransfer functions. Approaches (b) and (c), using both the isotope profiles and the soil moisture time series, resulted in good simulation results with regard to the Kling-Gupta efficiency and good parameter

  17. Water masses along the OVIDE 2010 section as identified by oxygen and hydrogen stable isotope values

    NASA Astrophysics Data System (ADS)

    Voelker, Antje; Salgueiro, Emilia; Thierry, Virginie

    2016-04-01

    The OVIDE transect between the western Iberian Peninsula and the southern tip of Greenland is one of the hydrographic sections in the North Atlantic that is measured regularly to identify changes in water mass formation and transport and thus to evaluate the state of the Atlantic Meridional Overturning Circulation (Mercier et al., 2015; García-Ibáñez et al., 2015; both in Progr. in Oceanography). During the OVIDE 2010 campaign seawater samples covering the complete water column were collected on the section between Portugal and the Reykjanes ridge for stable isotope analyses. Oxygen (δ18O) and hydrogen (δD) stable isotope values were measured simultaneously by cavity ring-down laser spectroscopy using a L1102-i Picarro water isotope analyser at the Godwin Laboratory for Paleoclimate Research (Univ. Cambridge, UK). Within the upper water column the stable isotope values clearly mark the positions of the Portugal Current (40.3°N 11°W), the North Atlantic Drift (46.2°N 19.4°W) and of the subarctic front (51°N 23.5°W). Up to Station 36 (47.7°N 20.6°W) an upper (around 600 m) and lower (around 1000 m) branch of the Mediterranean Outflow water (MOW) can clearly be distinguished by high oxygen (0.5-0.7‰) and hydrogen (3-5‰) values. At Station 28 (42.3°N 15.1°W) strong MOW influence is also indicated between 1400 and 1600 m. In the west European Basin, lower oxygen isotope values reveal the presence of Labrador Sea Water (LSW) below the MOW (down to 2200 m). Close to and west of the subarctic front this water mass shallows and occupies the complete interval between 1000 and 2000 m water depth. In the Iceland basin, two additional levels with lower oxygen isotope values are observed. The deeper level (2200-3500 m) marks Iceland Scotland Overflow Water (ISOW) that based on its distinct isotopic signature (δ18O ≤ 0.25‰) can be traced as far east as 18.5°W (down to at least 3500 m). Close to the Reykjanes ridge both, the ISOW and LSW, are also

  18. Stable isotopes of water in estimation of groundwater dependence in peatlands

    NASA Astrophysics Data System (ADS)

    Isokangas, Elina; Rossi, Pekka; Ronkanen, Anna-Kaisa; Marttila, Hannu; Rozanski, Kazimierz; Kløve, Bjørn

    2016-04-01

    Peatland hydrology and ecology can be irreversibly affected by anthropogenic actions or climate change. Especially sensitive are groundwater dependent areas which are difficult to determine. Environmental tracers such as stable isotopes of water are efficient tools to identify these dependent areas and study water flow patterns in peatlands. In this study the groundwater dependence of a Finnish peatland complex situated next to an esker aquifer was studied. Groundwater seepage areas in the peatland were localized by thermal imaging and the subsoil structure was determined using ground penetrating radar. Water samples were collected for stable isotopes of water (δ18O and δ2H), temperature, pH and electrical conductivity at 133 locations of the studied peatland (depth of 10 cm) at approximately 100 m intervals during 4 August - 11 August 2014. In addition, 10 vertical profiles were sampled (10, 30, 60 and 90 cm depth) for the same parameters and for hydraulic conductivity. The cavity ring-down spectroscopy (CRDS) was applied to measure δ18O and δ2H values. The local meteoric water line was determined using precipitation samples from Nuoritta station located 17 km west of the study area and the local evaporation line was defined using water samples from lake Sarvilampi situated on the studied peatland complex. Both near-surface spatial survey and depth profiles of peatland water revealed very wide range in stable isotope composition, from approximately -13.0 to -6.0 ‰ for δ18O and from -94 to -49 ‰ for δ2H, pointing to spatially varying influence of groundwater input from near-by esker aquifer. In addition, position of the data points with respect to the local meteoric water line showed spatially varying degree of evaporation of peatland water. Stable isotope signatures of peatland water in combination with thermal images delineated the specific groundwater dependent areas. By combining the information gained from different types of observations, the

  19. Stable isotopes in leaf water and transpiration - tools to assess leaf physiology and water uptake

    NASA Astrophysics Data System (ADS)

    Gessler, Arthur; Roddy, Adam; Volkmann, Till; Haberer, Kristine

    2014-05-01

    New laser based isotope technology allows online determination of the isotopic composition of water transpired from leaves. With this tool we can get new insights into leaf water physiology during day-night-cycles but also track the dynamics of plant water uptake with high temporal resolution. This talk we will give an overview on the following emerging topics - Leaf level physiology: The isotopic non-steady state of leaf water during the diel course - Plant-soil-atmosphere coupling: Dynamics of water uptake by plants Brought together both topics allow to get deeper insights into the effects of environmental parameters on the water balance of ecosystems bridging temporal and spatial scales. The findings from this research might help integrating plant physiological information, soil hydrological processes and the interaction between plant and soil processes in hydrological models.

  20. Stable isotope and salinity systematics in estuarine waters and carbonates - San Francisco Bay

    SciTech Connect

    Ingram, B.L.; Conrad, M.E.; Ingle, J.C.

    1995-01-31

    Salinities, {delta}D and {delta}{sup 18}O values of water samples collected bimonthly from two stations in San Francisco Bay estuary during 1991-1993, and along a salinity transect in March of 1992, indicate a linear mixing relation between the isotopic compositions of the waters and their salinities. The salinities and stable isotope compositions of samples from two locations in San Francisco Bay vary in response to changes in freshwater inflow. The data from these locations indicate simple mixtures of Pacific Ocean water (salinity approximate to 33, {delta}{sup 18}O approximate to 0 to -1 parts per thousand, {delta}D approximate 0 to -10 parts per thousand) and Sacramento-San Joaquin River water (salinity approximate to 0, {delta}{sup 18}O = -10 to -12 parts per thousand, {delta}D = -75 to -85 parts per thousand). Preliminary water balance estimates, using isotopic differences between local and upland runoff, suggest that local runoff (including waste water) comprises less than 20 percent of total freshwater entering the bay. The average {delta}{sup 18}O values of mussel shells (Mytilus edulis) collected live from eight locations in San Francisco Bay primarily reflect the {delta}{sup 18}O of the water in which they grew. Shells subsampled along growth bands show that seasonal shifts in salinity and delta(18)O are recorded in the shells. Therefore, the use of stable isotope measurements should be useful in reconstructing pre-instrumental bay salinity and associated freshwater inflow (both annual average values and seasonal variations) to the San Francisco Bay, as well as potentially other estuarine systems.

  1. A stable isotope study of water movements with typical vegetation cover in the North China Plain

    NASA Astrophysics Data System (ADS)

    Ma, Bin; Liang, Xing; Liu, Shaohua; Jin, Menggui; Li, Jing

    2015-04-01

    The stable isotope 2H and 18O are often used as natural tracers in subsurface water pathways in semi-arid areas. The stable isotopic compositions in precipitation, soil water and groundwater were observed to assess the temporal variations in soil water flow at three sites covered by grass (Carex humili and Carex lanceolata) (site A), poplar (Ponulus hopeiensis) (site B) and winter wheat (Triticum asetivum) and summer maize (Zea mays) (site C) in the shallow groundwater area in the North China Plain (NCP) from April 2012 to October 2013. Precipitation isotopes resulted in a meteoric water line of δ2H =7.6δ18O -3.7 and showed a typical seasonal variation for δ2H (-98.9 to -13.3) and δ18O (-12.0 to -1.7). The seasonality in the shallow groundwater was further subdued due to the evaporation and mixing and diffusional exchange with stored water held in the soil pores within the unsaturated zone. Shallow groundwater was mainly recharged by precipitation in the rainy season. Soil water isotope profiles were sampled at depths of 10 cm down to 150 cm every 10 cm for the three sites. The vertical profiles of soil water δ18O showed large variations in the superficial 10 cm layer under the precipitation input and evapotranspiration effects. The soil water δ18O decreased and soil moisture increased with depth ( 70 cm) due to continuously evapotranspiration for the three sites though that at site B showed more positive δ18O values and smaller soil moisture than those at site A and C. The signal of individual rainstorm event in the summer with low δ18O values could be traced down to a depth of 40 cm that mixed with antecedent mobile soil water and to 120 cm due to a fast and direct preferential infiltration of the input rainwater that bypassed the upper soil layer at sites B and C. Keywords: stable isotopes; soil water pathways; groundwater recharge; North China Plain

  2. Multisample conversion of water to hydrogen by zinc for stable isotope determination

    USGS Publications Warehouse

    Kendall, C.; Coplen, T.B.

    1985-01-01

    Two techniques for the conversion of water to hydrogen for stable isotope ratio determination have been developed that are especially suited for automated multisample analysis. Both procedures involve reaction of zinc shot with a water sample at 450 ??C. in one method designed for water samples in bottles, the water is put in capillaries and is reduced by zinc in reaction vessels; overall savings in sample preparation labor of 75% have been realized over the standard uranium reduction technique. The second technique is for waters evolved under vacuum and is a sealed-tube method employing 9 mm o.d. quartz tubing. Problems inherent with zinc reduction include surface inhomogeneity of the zinc and exchange of hydrogen both with the zinc and with the glass walls of the vessels. For best results, water/zinc and water/glass surface area ratios of vessels should be kept as large as possible.

  3. Cloud water in windward and leeward mountain forests: The stable isotope signature of orographic cloud water

    USGS Publications Warehouse

    Scholl, M.A.; Giambelluca, T.W.; Gingerich, S.B.; Nullet, M.A.; Loope, L.L.

    2007-01-01

    Cloud water can be a significant hydrologic input to mountain forests. Because it is a precipitation source that is vulnerable to climate change, it is important to quantify amounts of cloud water input at watershed and regional scales. During this study, cloud water and rain samples were collected monthly for 2 years at sites on windward and leeward East Maui. The difference in isotopic composition between volume-weighted average cloud water and rain samples was 1.4??? ??18O and 12??? ??2H for the windward site and 2.8??? ??18O and 25??? ??2H for the leeward site, with the cloud water samples enriched in 18O and 2H relative to the rain samples. A summary of previous literature shows that fog and/or cloud water is enriched in 18O and 2H compared to rain at many locations around the world; this study documents cloud water and rain isotopic composition resulting from weather patterns common to montane environments in the trade wind latitudes. An end-member isotopic composition for cloud water was identified for each site and was used in an isotopic mixing model to estimate the proportion of precipitation input from orographic clouds. Orographic cloud water input was 37% of the total precipitation at the windward site and 46% at the leeward site. This represents an estimate of water input to the forest that could be altered by changes in cloud base altitude resulting from global climate change or deforestation.

  4. High-resolution profiling of the stable isotopes of water in unsaturated coal waste rock

    NASA Astrophysics Data System (ADS)

    Barbour, S. Lee; Hendry, M. Jim; Carey, Sean K.

    2016-03-01

    Characterization of the rate of water migration through unsaturated mine waste rock dumps is an essential element in assessing the chemical loading from these landforms; yet our understanding of how water moves into, through and out of waste rock is incomplete. To further understand the rates and magnitude of percolation through waste rock, deep high-resolution (every 0.1-4.5 m) depth profiles of the stable isotopes of water (δ2H and δ18O) at two coal waste rock dumps and a natural alluvial deposit down-gradient of one of the dumps were collected in the Elk Valley, British Columbia, Canada. The profiles were generated using vapor equilibrium techniques applied to continuous core samples collected using dry sonic drilling methods. Elevated core temperatures (up to 80 °C) were measured during sonic coring. The isotopic values of pore waters measured in the core samples were corrected for water loss to the atmosphere attributed to the elevated core temperatures. The average isotopic composition of the core samples were compared to water collected from rock drains discharging from the base of the dumps. The results indicate that high-resolution profiles of δ2H and δ18O can be measured to depths of 86 m in coal waste rock dumps and, based on the seasonal cycles in the isotopic composition of recharging water, can be used to characterize the migration of recharge water within these dumps. These profiles also suggest that recharge into these dumps occurs from both rain as well as snow melt and may be as high as 400-600 mm/yr (60-75% of annual precipitation). Combined with the relatively low volumetric water contents of these dumps (5-10%) the rates of water migration through the dumps are tens of meters each year.

  5. [Monitoring and Analysis of Stable Isotopes of the Near Surface Water Vapor in Changsha].

    PubMed

    Xie, Yu-long; Zhang, Xin-ping; Yao, Tian-ci; Huang, Huang

    2016-02-15

    Based on the monitored atmospheric water vapor stable isotopes and observed meteorological elements at Changsha during the period from November 12, 2014 to April 13, 2015, the variations of water vapor stable isotopes and the relationships between isotope ratios and temperature, absolute humidity, precipitation amount were analyzed in this paper. The results indicated that: (1) Seasonal variations of delta18O and 82H in atmospheric water vapor at Changsha were remarkable, with high values in winter. delta18O and delta2H in atmospheric water vapor were positively correlated with absolute humidity in winter. There were some fluctuations of the delta18O and delta2H in atmospheric water vapor, especially when the precipitation events occurred. Precipitation events had a significant effect on the variations of delta18O and delta2H in atmospheric water vapor, and low values were often accompanied with precipitation events; (2) Diurnal Variations of delta18O and delta2H in atmospheric water vapor had a close correlation with the atmospheric water vapor content, whereas the absolute humidity was mainly controlled by the strength of the local evapotranspiration and atmospheric turbulence. The "precipitation amount effect" was observed during the process of a single precipitation event; (3) Values of delta18O and delta2H in atmospheric water vapor were always lower than those of precipitation in Changsha, but he variation trends were completely consistent, the average difference values were 8.6% per hundred and 66.82% per hundred, respectively; (4) The meteoric vapor line (MVL) in cold months was delta2H =7.18 delta18O + 10.58, the slope and intercept of MVL were always lower than those of MWL, and the slope and intercept of MVL in spring were significantly higher than those of winter. PMID:27363133

  6. Stable isotope investigation of the Columbus, Ohio, water supply by examining precipitation, tap water, and surface/reservoir waters

    NASA Astrophysics Data System (ADS)

    Leslie, D. L.; Lyons, W. B.

    2011-12-01

    Management of our water resources requires that human intervention as well as natural processes in the hydrologic cycle be fully understood, and integrated watershed management strategies be implemented to monitor variation and to maximize water resources. In this study of regional water supply, we utilize the stable isotopes of water to characterize the flow and relative residence time of water within a human-dominated watershed-reservoir system. Tap water, precipitation, and water from three reservoirs used for domestic water supply were collected in Franklin County, Ohio, from August 2010 until July 2011. Samples were analyzed for δ18O and δD by a Picarro WS-CRDS Analyzer for Isotopic Water - Model L1102-i at The Ohio State University. Reservoir waters (δ18O= -9.0% to -4.8% and δD= -61% to -30%) are more enriched during the spring/summer months and more depleted during the fall/winter months, following changes in precipitation and capacity of each reservoir. Tap water samples (δ18O= -9.1% to -4.3% and δD= -58% to -29%), distributed from the Dublin Road Water Plant (DRWP) which utilizes surface water from Griggs and O'Shaughnessy Reservoirs on the Scioto River, display an isotopic mixture of these reservoir waters and precipitation. These data demonstrates how quickly precipitation moves through the water conveyance system. Previously collected Columbus, Ohio, tap water samples reported by Bowen et al. (2007) demonstrated a seasonal lag in the city's water supply with more enriched precipitation from the summer months showing up in the water supply during the fall/winter seasons, and more depleted precipitation from winter months being part of the water supply in the spring/summer seasons. The tap water samples from the Bowen et al. (2007) study were distributed by Hap Cremean Water Plant (HPWP) that utilizes surface water from Hoover Reservoir on Big Walnut Creek. This isotopic signature of seasonal enrichment and depletion in the tap water that does not

  7. Partitioning of Evapotranspiration Using a Stable Water Isotope Technique in a High Temperature Agricultural Production System

    NASA Astrophysics Data System (ADS)

    Lu, X.; Liang, L.; Wang, L.; Jenerette, D.; Grantz, D. A.

    2015-12-01

    Agricultural production in the hot and arid low desert systems of southern California relies heavily on irrigation. A better understanding of how much and to what extent the irrigation water is transpired by crops relative to being lost through evaporation will contribute to better management of increasingly limited agricultural water resources. In this study, we examined the evapotranspiration (ET) partitioning over a field of forage sorghum (S. bicolor) during a growing season with several irrigation cycles. In several field campaigns we used continuous measurements of near-surface variations in the stable isotopic composition of water vapor (δ2H). We employed custom built transparent chambers coupled with a laser-based isotope analyzer and used Keeling plot and mass balance methods for surface flux partitioning. The preliminary results show that δT is more enriched than δE in the early growing season, and becomes less enriched than δE later in the season as canopy cover increases. There is an increase in the contribution of transpiration to ET as (1) leaf area index increases, and (2) as soil surface moisture declines. These results are consistent with theory, and extend these measurements to an environment that experiences extreme soil surface temperatures. The data further support the use of chamber based methods with stable isotopic analysis for characterization of ET partitioning in challenging field environments.

  8. Mapping Precipitation Patterns from the Stable Isotopic Composition of Surface Waters: Olympic Peninsula, Washington State

    NASA Astrophysics Data System (ADS)

    Anders, A. M.; Brandon, M. T.

    2008-12-01

    Available data indicate that large and persistent precipitation gradients are tied to topography at scales down to a few kilometers, but precipitation patterns in the majority of mountain ranges are poorly constrained at scales less than tens of kilometers. A lack of knowledge of precipitation patterns hampers efforts to understand the processes of orographic precipitation and identify the relationships between geomorphic evolution and climate. A new method for mapping precipitation using the stable isotopic composition of surface waters is tested in the Olympic Mountains of Washington State. Measured δD and δ18O of 97 samples of surface water are linearly related and nearly inseparable from the global meteoric water line. A linear orographic precipitation model extended to include in effects of isotopic fractionation via Rayleigh distillation predicts precipitation patterns and isotopic composition of surface water. Seven parameters relating to the climate and isotopic composition of source water are used. A constrained random search identifies the best-fitting parameter set. Confidence intervals for parameter values are defined and precipitation patterns are determined. Average errors for the best-fitting model are 4.8 permil in δD. The difference between the best fitting model and other models within the 95% confidence interval was less than 20%. An independent high-resolution precipitation climatology documents precipitation gradients similar in shape and magnitude to the model derived from surface water isotopic composition. This technique could be extended to other mountain ranges, providing an economical and fast assessment of precipitation patterns requiring minimal field work.

  9. Optimization of post-run corrections for water stable isotope measurements by laser spectroscopy

    NASA Astrophysics Data System (ADS)

    van Geldern, Robert; Barth, Johannes A. C.

    2013-04-01

    Light stable isotope analyses of hydrogen and oxygen of water are used in numerous aquatic studies from various scientific fields. The advantage of using stable isotope ratios is that water molecules serve as ubiquitous and already present natural tracers. Traditionally, the samples were analyzed in the laboratory by isotope ratio mass spectrometry (IRMS). Within recent years these analyses have been revolutionized by the development of new isotope ratio laser spectroscopy (IRIS) systems that are said to be cheaper, more robust and mobile compared to IRMS. Although easier to operate, laser systems also need thorough calibration with international reference materials and raw data need correction for analytical effects. A major issue in systems that use liquid injection via a vaporizer module is the memory effect, i.e. the carry-over from the previous analyzed sample in a sequence. This study presents an optimized and simple post-run correction procedure for liquid water injection developed for a Picarro water analyzer. The Excel(TM) template will rely exclusively on standard features implemented in MS Office without the need to run macros, additional code written in Visual Basic for Applications (VBA) or to use a database-related software such as MS Access or SQL Server. These protocols will maximize precision, accuracy and sample throughput via an efficient memory correction. The number of injections per unknown sample can be reduced to 4 or less. This procedure meets the demands of faster throughput with reduced costs per analysis. Procedures were verified by an international proficiency test and traditional IRMS techniques. The template is available free for scientific use from the corresponding author or the journals web site (van Geldern and Barth, 2012). References van Geldern, R. and Barth, J.A.C. (2012) Limnol. Oceanogr. Methods 10:1024-1036 [doi: 10.4319/lom.2012.10.1024

  10. Cellular Metabolic Activity and the Oxygen and Hydrogen Stable Isotope Composition of Intracellular Water and Metabolites

    NASA Astrophysics Data System (ADS)

    Kreuzer-Martin, H. W.; Hegg, E. L.

    2008-12-01

    Intracellular water is an important pool of oxygen and hydrogen atoms for biosynthesis. Intracellular water is usually assumed to be isotopically identical to extracellular water, but an unexpected experimental result caused us to question this assumption. Heme O isolated from Escherichia coli cells grown in 95% H218O contained only a fraction of the theoretical value of labeled oxygen at a position where the O atom was known to be derived from water. In fact, fewer than half of the oxygen atoms were labeled. In an effort to explain this surprising result, we developed a method to determine the isotope ratios of intracellular water in cultured cells. The results of our experiments showed that during active growth, up to 70% of the oxygen atoms and 50% of the hydrogen atoms in the intracellular water of E. coli are generated during metabolism and can be isotopically distinct from extracellular water. The fraction of isotopically distinct atoms was substantially less in stationary phase and chilled cells, consistent with our hypothesis that less metabolically-generated water would be present in cells with lower metabolic activity. Our results were consistent with and explained the result of the heme O labeling experiment. Only about 40% of the O atoms on the heme O molecule were labeled because, presumably, only about 40% of the water inside the cells was 18O water that had diffused in from the culture medium. The rest of the intracellular water contained 16O atoms derived from either nutrients or atmospheric oxygen. To test whether we could also detect metabolically-derived hydrogen atoms in cellular constituents, we isolated fatty acids from log-phase and stationary phase E. coli and determined the H isotope ratios of individual fatty acids. The results of these experiments showed that environmental water contributed more H atoms to fatty acids isolated in stationary phase than to the same fatty acids isolated from log-phase cells. Stable isotope analyses of

  11. Multiphase Reactive Transport modeling of Stable Isotope Fractionation of Infiltrating Unsaturated Zone Pore Water and Vapor Using TOUGHREACT

    SciTech Connect

    Singleton, Michael J.; Sonnenthal, Eric L.; Conrad, Mark E.; DePaolo, Donald J.

    2003-08-28

    Numerical simulations of transport and isotope fractionation provide a method to quantitatively interpret vadose zone pore water stable isotope depth profiles based on soil properties, climatic conditions, and infiltration. We incorporate the temperature-dependent equilibration of stable isotopic species between water and water vapor, and their differing diffusive transport properties into the thermodynamic database of the reactive transport code TOUGHREACT. These simulations are used to illustrate the evolution of stable isotope profiles in semiarid regions where recharge during wet seasons disturbs the drying profile traditionally associated with vadose zone pore waters. Alternating wet and dry seasons lead to annual fluctuations in moisture content, capillary pressure, and stable isotope compositions in the vadose zone. Periodic infiltration models capture the effects of seasonal increases in precipitation and predict stable isotope profiles that are distinct from those observed under drying (zero infiltration) conditions. After infiltration, evaporation causes a shift to higher 18O and D values, which are preserved in the deeper pore waters. The magnitude of the isotopic composition shift preserved in deep vadose zone pore waters varies inversely with the rate of infiltration.

  12. Stable isotopes in mineralogy

    USGS Publications Warehouse

    O'Neil, J.R.

    1977-01-01

    Stable isotope fractionations between minerals are functions of the fundamental vibrational frequencies of the minerals and therefore bear on several topics of mineralogical interest. Isotopic compositions of the elements H, C, O, Si, and S can now be determined routinely in almost any mineral. A summary has been made of both published and new results of laboratory investigations, analyses of natural materials, and theoretical considerations which bear on the importance of temperature, pressure, chemical composition and crystal structure to the isotopic properties of minerals. It is shown that stable isotope studies can sometimes provide evidence for elucidating details of crystal structure and can be a powerful tool for use in tracing the reaction paths of mineralogical reactions. ?? 1977 Springer-Verlag.

  13. Results from stable isotope investigations of river waters in Western Croatia

    NASA Astrophysics Data System (ADS)

    Häusler, H.; Frančišković-Bilinski, S.; Rank, D.; Stadler, P.; Bilinski, H.

    2012-04-01

    During a campaign lasting from 27 October to 21 November 2010, sixty-one water samples were taken from the Kupa River, the catchment of which is about ten thousand square kilometres in size. Due to the fact that the upper tributaries of e.g. the Čabranka-, Dobra-, Korana-, Mrežnica- and Petrinjčica River comprise karstified Mesozoic carbonate formations, the hydrogeologic catchment of Kupa River extends the hydrologic one by far. The upper Kupa River is mainly charged by springs from big karst reservoirs in the Gorski Kotar mountain range, where a mean groundwater residence time of up to one year has to be considered. The rapid increase of discharge of these tributary rivers results from the rapid increase of discharge of karst wells after melting in springtime as well as from storm events. In general, the minimum mean discharge for all hydrographs in July reveals a dry summer season, with the maximum discharge in August/September resulting from an increase in precipitation. We interpret the d O-18 values of the Čabranka River (of about -8, 07‰) as signals from maritime precipitation in this karstified catchment area. The d O-18 value of upper Kupa River diminishes along its course from -8,09‰ near Osilnica to -9,06‰ west of Karlovac. After the inflow of tributaries south of Karlovac, the oxygen isotope ratio of Kupa River water reveals a significant change because the d O-18 values of the Dobra-, Korana- and Mrežnica River range from -10,45‰ to -9,58‰ . Due to the fact that the catchment of Dobra- and Korana River rises between 400 and 880 metres, we interpret the lower d O-18 values of river waters from recharge areas at those low mean altitudes as not caused by an altitude effect, but instead by precipitation out of more continental air masses. Our interpretation of stable isotope ratios in river waters is based on the relation between the weighted mean d O-18 and the altitude obtained from stations of the Global Network of Isotopes in

  14. Partitioning water and carbon fluxes in a Mediterranean oak woodland using stable oxygen isotopes

    NASA Astrophysics Data System (ADS)

    Dubbert, Maren; Piayda, Arndt; Cuntz, Matthias; Correia, Alexandra; Silva, Filipe Costa e.; Pereira, Joao; Werner, Christiane

    2014-05-01

    Water is a key factor driving ecosystem productivity, especially in water-limited ecosystems. A separation of the component fluxes is needed to gain a functional understanding on the development of net ecosystem water fluxes and their coupling with biogeochemical cycles. Oxygen isotope signatures are valuable tracers for water movements within the ecosystem because of the distinct isotopic compositions of water in soil and vegetation. In the past, determination of isotopic signatures of evaporative or transpirational fluxes has been challenging since measurements of water vapor isotopes were difficult to obtain using cold-trap methods, delivering data with low time resolution. Recent developments in laser spectroscopy now enable direct high frequency measurements of the isotopic composition of atmospheric water vapor (δv), evapotranspiration (δET), and its components and allow validations of common modeling approaches for estimating δE and δT based on Craig and Gordon (1965). Here, a novel approach was used, combining a custom build flow-through gas-exchange branch chamber with a Cavity Ring-Down Spectrometer in a Mediteranean cork-oak woodland where two vegetation layers respond differently to drought: oak-trees (Quercus suber L.) avoid drought due to their access to ground water while herbaceous plants survive the summer as seeds. We aimed at 1) testing the Craig and Gordon equation for soil evaporation against directly measured δE and 2) quantifying the role of non-steady-state transpiration under natural conditions. Thirdly, we used this approach to quantify the impact of the understory herbaceous vegetation on ecosystem carbon and water fluxes throughout the year and disentangle how ET components of the ecosystem relate to carbon dioxide exchange. We present one year data comparing modeled and measured stable oxygen isotope signatures (δ18O) of soil evaporation, confirming that the Craig and Gordon equation leads to good agreement with measured δ18O of

  15. On-line high-precision stable hydrogen isotopic analyses on nanoliter water samples.

    PubMed

    Morrison, J; Brockwell, T; Merren, T; Fourel, F; Phillips, A M

    2001-08-01

    We describe a new on-line chromium reduction technique for the measurement of stable hydrogen (deltaD) isotopes in waters using continuous-flow isotope ratio mass spectrometry. The on-line Cr reduction method has low intersample memory effects (< 1%) and excellent precision and accuracy for deltaD (+/-0.5% and was used to analyze waters samples as small as 50 nL. The on-line Cr method has a number of significant advantages over conventional offline Zn and U reduction and on-line carbon-based pyrolysis techniques. A single Cr reactor can be used to analyze approximately 1,000 water samples using an injection volume of 0.5 microL, with an individual sample analysis time of 4 min. Intersample memory effects are negligible. The Cr reactor temperature of 1050 degree C is easily attainable on standard elemental analyzers and so does not require the specialized and costly high-temperature furnaces of carbon-based pyrolysis reactors. Furthermore, hydrogen isotopes in extremely small water samples in the 100-nL range or less can be easily measured; hence, this new method opens up a number of exciting application areas in earth and environmental sciences, for example, natural abundance deltaD measurements of individual fluid inclusions in geologic materials using a laser source and measurements of body fluids in physiological and metabolic research. PMID:11510820

  16. Preliminary identification of ground-water nitrate sources using nitrogen and carbon stable isotopes, Kansas

    USGS Publications Warehouse

    Townsend, M.A.; Macko, S.A.

    2007-01-01

    Increasing nitrate-N in ground water is a problem in areas with limited ground-water supplies, such as central Kansas. Nitrate-N concentrations in ground water in the study area in Ellis County range from 0.9 to 26 mg/L. Calculated mean values observed in soil cores are 1.2-15 mg/kg. The ??15N signatures of the ground waters are more enriched (+16.8 to +28.7???) than those of the soils (+8.4 to +1 3.7???), strongly suggesting that nitrate-N sources are not from mineralized and labile nitrogen present in the unsaturated zone. Soil cores were collected near municipal wells to determine if soil nitrogen was a contributing source to the ground water. Increased ??15N of total nitrogen with depth suggests that microbial mineralization processes and possible denitrification or volatilization isotope enrichments have affected the observed ?? 15N signatures in the soil. However, the observed soil-nitrogen values are not of sufficient magnitude to explain the nitrate-N concentrations or associated ??15N values observed in the ground water. Stable carbon isotopes provide some supporting evidence that soils are not a major contributor to the observed nitrate-N concentration in the ground water. ?? 13C values of the dissolved organic carbon (DOC) in soils generally become more enriched with depth while corresponding ground-water ??13C (DOC) values are more depleted than in the overlying soils. Carbon isotope values of the soils are indicative of a C4 plant source that is enriched by microbial processes. The ??13C (DOC) of ground water indicates C3 values that may reflect impacts from animal-waste sources.

  17. A new stable water isotope-salinity dataset from the central tropical Pacific

    NASA Astrophysics Data System (ADS)

    Conroy, J. L.; Cobb, K.; Lynch-Stieglitz, J.

    2013-12-01

    The central tropical Pacific is home to key water isotope-based paleoclimate proxies that reveal past interannual to millennial-scale ocean variability. In particular, the stable oxygen isotope ratio of seawater (henceforth δ18Osw), which is strongly correlated with salinity, is often interpreted as a proxy for past surface forcing (precipitation-evaporation). However, very few modern δ18Osw measurements exist in this region, and a clear understanding of the drivers of δ18Osw variability on mean, seasonal, and interannual timescales needs to be investigated. This is a particularly important region to understand these dynamics: central tropical Pacific oceanography is complex, defined by three surface currents, upwelling, and zonal shifts in the boundary defining the fresher waters of the western tropical Pacific and the more saline waters of the central tropical Pacific. In addition, this region also experiences the seasonal migration of the intertropical convergence zone and associated changes in precipitation-evaporation. Here we present 177 paired stable water isotope and salinity measurements taken in May 2012 from the Line Islands Ridge, tripling the number of available stable isotope observations from the region. We find a δ18Osw-salinity slope of 0.35 across the main surface currents as well as water masses of the surface and subsurface. The May 2012 δ18Osw-salinity relationship is not significantly different from previous measurements in the region, supporting the integrity of these datasets. The highest δ18Osw-salinity values of the new dataset occur in the core of the Equatorial Undercurrent. Salinity and δ18Osw values throughout the North Equatorial Countercurrent (NECC) are higher compared to previous data from the region. This may be due to a weaker NECC during the boreal spring, as the previous data are biased toward boreal winter, but more data are needed to understand temporal δ18Osw-salinity variability. We have also increased the number of

  18. Tracing subarctic Pacific water masses with benthic foraminiferal stable isotopes during the LGM and late Pleistocene

    NASA Astrophysics Data System (ADS)

    Cook, Mea S.; Ravelo, A. Christina; Mix, Alan; Nesbitt, Ian M.; Miller, Nari V.

    2016-03-01

    As the largest ocean basin, the Pacific helps to set the global climate state, since its circulation affects mean ocean properties, air-sea partitioning of carbon dioxide, and the distribution of global oceanic poleward heat transport. There is evidence that during the Last Glacial Maximum (LGM) the subarctic Pacific contained a better-ventilated, relatively fresh intermediate water mass above ~2000 m that may have formed locally. The source and spatial extent of this water mass is not known, nor do we know how formation of this water mass varied during Pleistocene glaciations with different orbital and ice sheet boundary conditions. Here we present a 0.5 My multi-species benthic stable isotope record from Site U1345 (1008 m) on the northern Bering slope and a 1.0 My record from U1339 (1868 m) from the Umnak Plateau in the southeastern basin. We find that the relatively well-ventilated low-δ18O intermediate water reaches 1000 m in the Bering Sea during MIS2, but that the hydrographic divide between this water mass and poorly-ventilated deep water was shallower than 1000 m for earlier glaciations. We also compare Bering Sea piston core and IODP Expedition 323 Uvigerina data from the Holocene and LGM with the modern hydrography, and to previously published profiles from the Okhotsk Sea and Emperor Seamounts. We find that the carbon and oxygen stable isotope signatures of well-ventilated water in the Bering and Okhotsk Seas are distinct, suggesting that there may have been intermediate water formation in both basins during the LGM.

  19. Estimation of evaporative loss based on the stable isotope composition of water using Hydrocalculator

    NASA Astrophysics Data System (ADS)

    Skrzypek, Grzegorz; Mydłowski, Adam; Dogramaci, Shawan; Hedley, Paul; Gibson, John J.; Grierson, Pauline F.

    2015-04-01

    Accurate quantification of evaporative losses to the atmosphere from surface water bodies is essential for calibration and validation of hydrological models, particularly in remote arid and semi-arid regions, where intermittent rivers are generally minimally gauged. Analyses of the stable hydrogen and oxygen isotope composition of water can be used to estimate evaporative losses from individual pools in such regions in the absence of instrumental data but calculations can be complex, especially in highly variable systems. In this study, we reviewed and combined the most recent equations required for estimation of evaporative losses based on the revised Craig-Gordon model. The updated procedure is presented step-by-step, increasing ease of replication of all calculations. The main constraints and sources of uncertainties in the model were also evaluated. Based on this procedure we have designed a new software, Hydrocalculator, that allows quick and robust estimation of evaporative losses based on isotopic composition of water. The software was validated against measures of field pan evaporation under arid conditions in northwest Australia as well as published data from other regions. We found that the major factor contributing to the overall uncertainty in evaporative loss calculations using this method is uncertainty in estimation of the isotope composition of ambient air moisture.

  20. Patterns of local and nonlocal water resource use across the western U.S. determined via stable isotope intercomparisons

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The stable isotope ratios of hydrogen (H) and oxygen (O) are valuable tracers of the origin of biological materials and water sources. Application of these environmental tracers is largely based on the distinct and pervasive spatial patterns of precipitation isotopes, which are preserved in many hy...

  1. Plant Water Use and Environmental Stress on Two Opposite Slopes: from Water and Carbon Stable Isotopic Perspective

    NASA Astrophysics Data System (ADS)

    Guan, H.; Xu, X.; Skrzypek, G.; Simmons, C. T.

    2014-12-01

    Climate-soil-vegetation dynamics are among key research focuses in the emerging ecohydrology discipline. Topographic relieves on landscapes provide various hydroclimatic conditions to examine vegetation functions and its responses to climate variation and changes in a short distance. In this study, we investigate ecohydrologic processes on two slopes of contrasting orientation and soil conditions in a native vegetation catchment with mean annual precipitation of 716 mm in South Australia, using water and carbon stable isotopes. Throughfall, soil water, twig water, and groundwater stable isotopes were measured and integrated into an isotope incorporated soil-plant-atmosphere model to examine different plant water use patterns on two slopes with different environmental conditions. The focuses are on how ecosystems on the two slopes receive, store, and use soil moisture in different manners. On these two slopes, trees are under different water stresses. Both leaf and soil 13C/12C ratio were measured for the two slopes to examine if δ13C can be used as an water stress indicator in this small catchment, and if the potential difference in δ13C can be observed in the soil organic matter. We monitored one-year leaf δ13C of two tree species, Eucalyptus leucoxylon and Acacia pycnantha. Our results indicate that leaf δ13C reflects different water stress conditions between slopes, seasons, and different locations on the slopes.

  2. Stable isotope geochemistry of pore waters from the New Jersey shelf - No evidence for Pleistocene melt water

    NASA Astrophysics Data System (ADS)

    van Geldern, Robert; Hayashi, Takeshi; Böttcher, Michael E.; Mottl, Michael J.; Barth, Johannes A. C.; Stadler, Susanne

    2013-04-01

    Scientific drillings in the 1970s revealed the presence of a large fresh water lens below the New Jersey Shelf. The origin and age of this fresh water body is still under debate. Groundwater flow models suggest that the water mainly originates from glacial melt water that entered the ground below large continental ice sheets during the last glacial maximum (LGM), whereas other studies suggest an age up to late Miocene. In this study, interstitial water was sampled during the Integrated Ocean Drilling Program (IODP) expedition 313 "New Jersey Shallow Shelf" (Mountain et al., 2010) and analyzed for water chemistry and stable isotope ratios (van Geldern et al, 2013). The pore fluid stable isotope values define a mixing line with end members that have oxygen and hydrogen isotope values of -7.0‰ and -41‰ for fresh water, and -0.8‰ and -6‰ for saltwater, respectively. The analyses revealed the following sources of fluids beneath the shelf: (1) modern rainwater, (2) modern seawater, and (3) a brine that ascends from deep sediments. The stable isotope composition of the water samples indicates modern meteoric recharge from New Jersey onshore aquifers as the fresh-water end member. This contradicts earlier views on the formation of the New Jersey fresh water lens, as it does not support the ice-age-origin theory. The salt-water end member is identical to modern New Jersey shelf seawater. Lower core parts of the drilling sites are characterized by mixing with a brine that originates from evaporites in the deep underground and that ascends via faults into the overlying sediments. The geochemical data from this study may provide the basis for an approach to construct a transect across the New Jersey shallow shelf since they fill a missing link in the shelf's geochemical profile. They also lay foundations for future research on hardly explored near-shore freshwater resources. References Mountain, G. and the Expedition 313 Scientists, 2010, Proceedings of the Integrated

  3. Stable isotopes in water vapor and precipitation for a coastal lagoon at mid latitudes

    NASA Astrophysics Data System (ADS)

    Zannoni, Daniele; Bergamasco, Andrea; Dreossi, Giuliano; Rampazzo, Giancarlo; Stenni, Barbara

    2016-04-01

    The stable oxygen and hydrogen isotope composition in precipitation can be used in hydrology to describe the signature of local meteoric water. The isotopic composition of water vapor is usually obtained indirectly from measurements of δD and δ18O in precipitation, assuming the isotopic equilibrium between rain and water vapor. Only few studies report isotopic data in both phases for the same area, thus providing a complete Local Meteoric Water Line (LMWL). The goal of this study is to build a complete LMWL for the lagoon of Venice (northern Italy) with observations of both water vapor and precipitation. The sampling campaign has started in March 2015 and will be carried out until the end of 2016. Water vapor is collected once a week with cold traps at low temperatures (‑77°C). Precipitation is collected on event and monthly basis with a custom automatic rain sampler and a rain gauge, respectively. Liquid samples are analyzed with a Picarro L1102-i and results are reported vs VSMOW. The main meteorological parameters are continuously recorded in the same area by the campus automatic weather station. Preliminary data show an LMWL close to the Global Meteoric Water Line (GMWL) with lower slope and intercept. An evaporation line is clearly recognizable, considering samples that evaporated between the cloud base and the ground. The deviation from the GMWL parameters, especially intercept, can be attributed to evaporated rain or to the humidity conditions of the water vapor source. Water vapor collected during rainfall shows that rain and vapor are near the isotopic equilibrium, just considering air temperature measured at ground level. Temperature is one of the main factor that controls the isotopic composition of the atmospheric water vapor. Nevertheless, the circulation of air masses is a crucial parameter which has to be considered. Water vapor samples collected in different days but with the same meteorological conditions (air temperature and relative humidity

  4. Understanding patterns of water use in a subtropical woodland using stable isotopes

    NASA Astrophysics Data System (ADS)

    Grierson, Pauline; Page, Gerald; Skrzypek, Grzegorz; Dogramaci, Shawan; Luccitti, Samuel; O'Donnell, Alison

    2015-04-01

    Vegetation structure in the arid subtropics is often highly variable across the landscape, reflecting at least in part the high spatial and temporal heterogeneity of rainfall, groundwater and soil moisture. Here, we investigated how patterns of water uptake by trees and shrubs differed across landscape positions in the Pilbara region of northwest Australia and assessed the responsiveness of trees and shrubs to large (cyclonic) rainfall events. We sampled water stable isotope compositions of xylem, soil, rain and groundwater as well as soil water content and root distributions of eucalypt and mulga woodlands in the Pilbara region over three years. Based on the 18O results, we found that the sampled plant taxa (mulga, Eucalyptus victrix) were using water originally derived from a large rainfall event (Cyclone Heidi), both at lowland and upland sites. Trees and shrubs such as mulga were accessing shallow soil water of meteoric origin. Eucalyptus victrix accessed water deeper in the profile (8-10 m) as surface soils dried out. Mulga appeared to store water for many months after the recharge event. This ability to take up and likely store a large proportion of shallow soil water after rainfall is a key feature enabling mulga to survive through the period of greatest water demand and to acclimate to the spatiotemporal changes to water conditions in the soil profile. Alternatively, episodic cyclonic recharge maintains deep soil and groundwater resources that maintain deeper-rooted species such as E. victrix throughout the prolonged drought periods.

  5. Determining the Hydrological Importance of Coastal Fog in Northern California Using Stable Isotopes of Water

    NASA Astrophysics Data System (ADS)

    Scholl, M. A.; Torregrosa, A.; Coplen, T. B.

    2014-12-01

    Fog and cloud water can be an important part of the water cycle in mountainous coastal areas. In coastal California's Mediterranean climate, fog is the predominant precipitation source during the summer months. Here we report initial results of a study utilizing stable hydrogen and oxygen isotopes of water to investigate the role of fog in the hydrology of two ecosystems in Sonoma County, CA. The two study sites were the Bodega Marine Laboratory (BML) at 13 m elevation at the coast, and the Pepperwood Preserve at 375 m elevation in the North Coast Range, 44 km inland to the northeast. During a 1-week period in July 2014, fog samples were collected at 30-minute intervals using small active-strand cloudwater collectors (mini-CASCCs) and automated precipitation samplers. Four overnight fog events were collected at the Pepperwood site, while at the BML site, the liquid water content of the fog was very low, and only one cumulative sample was obtained. Groundwater samples from five wells and seven springs, and surface water samples from two streams were collected in and around the Pepperwood Preserve and on Bodega Head near BML. Droplet size distribution of the fog at BML was monitored, and at both sites, air temperature was measured at 10-minute intervals to assess variation in the δ 18O and δ 2H values of fog related to temperature. Relative humidity, wind speed, and wind direction were obtained from weather stations at each site. Previous work in this area (Coplen et al., in prep) documented the isotopic signatures of winter precipitation from frontal systems and landfalling Pacific storms. These results will be combined with the isotopic signature of summer fog water to determine whether fog contributes to shallow groundwater recharge or streamflow at the two sites.

  6. Influence of environmental factors on dissolved nitrate stable isotopes under denitrifying conditions - carbon sources and water isotopes

    NASA Astrophysics Data System (ADS)

    Wunderlich, A.; Meckenstock, R.; Einsiedl, F.

    2012-04-01

    Stable isotopes in dissolved nitrate are regularly used to identify sources of nitrate contamination in aquifers and water bodies. A dual isotope plot of 15N and 18O in nitrate can provide good evidence of the origin of such pollution as various sources have different isotopic signatures. Microbial denitrification changes both isotopic values by removing nitrate with lighter isotopes first, thereby increasing δ18O as well as δ15N. This change can distort the determination of sources but also has the potential to be used to identify and quantify microbial denitrification. Previous studies found a wide range of enrichment factors (ɛ) that did not allow conclusions towards the extent of microbial denitrification. However, it was found that during denitrification at each respective field site or laboratory experiment, there was a constant ratio in increase of the values of δ18O in relation to δ15N. That ratio was, however, not constant across field sites and the values published range from below 0.5 to more than 1.0. The reasons for these variations in enrichment factors and relative enrichment of oxygen compared to nitrogen are yet unknown. We conducted microcosm experiments with three different bacterial species to elucidate possible influences of environmental factors on these parameters. As a result we conclude that the type of carbon source available to denitrifying bacteria can play a role in the value of the enrichment factors, but not in the relative enrichment of the two isotopes. Specifically we found that complex hydrocarbons (toluene, benzoate) produce significantly different enrichment factors in nitrate than a simple hydrocarbon substrate (acetate). The relative enrichment of δ18O compared to δ15N was 0.86. We hypothesise that this influence is based on a variation in process kinetics of cross-membrane nitrate transport in relation to intracellular nitrate reduction. The core of the hypothesis is that nitrate transport into the cell becomes rate

  7. Forensic Stable Isotope Biogeochemistry

    NASA Astrophysics Data System (ADS)

    Cerling, Thure E.; Barnette, Janet E.; Bowen, Gabriel J.; Chesson, Lesley A.; Ehleringer, James R.; Remien, Christopher H.; Shea, Patrick; Tipple, Brett J.; West, Jason B.

    2016-06-01

    Stable isotopes are being used for forensic science studies, with applications to both natural and manufactured products. In this review we discuss how scientific evidence can be used in the legal context and where the scientific progress of hypothesis revisions can be in tension with the legal expectations of widely used methods for measurements. Although this review is written in the context of US law, many of the considerations of scientific reproducibility and acceptance of relevant scientific data span other legal systems that might apply different legal principles and therefore reach different conclusions. Stable isotopes are used in legal situations for comparing samples for authenticity or evidentiary considerations, in understanding trade patterns of illegal materials, and in understanding the origins of unknown decedents. Isotope evidence is particularly useful when considered in the broad framework of physiochemical processes and in recognizing regional to global patterns found in many materials, including foods and food products, drugs, and humans. Stable isotopes considered in the larger spatial context add an important dimension to forensic science.

  8. Water stable isotope measurements of Antarctic samples by means of IRMS and WS-CRDS techniques

    NASA Astrophysics Data System (ADS)

    Michelini, Marzia; Bonazza, Mattia; Braida, Martina; Flora, Onelio; Dreossi, Giuliano; Stenni, Barbara

    2010-05-01

    In the last years in the scientific community there has been an increasing interest for the application of stable isotope techniques to several environmental problems such as drinking water safeguarding, groundwater management, climate change, soils and paleoclimate studies etc. For example, the water stable isotopes, being natural tracers of the hydrological cycle, have been extensively used as tools to characterize regional aquifers and to reconstruct past temperature changes from polar ice cores. Here the need for improvements in analytical techniques: the high request for information calls for technologies that can offer a great quantity of analyses in short times and with low costs. Furthermore, sometimes it is difficult to obtain big amount of samples (as is the case for Antarctic ice cores or interstitial water) preventing the possibility to replicate the analyses. Here, we present oxygen and hydrogen measurements performed on water samples covering a big range of isotopic values (from very negative antarctic precipitation to mid-latitude precipitation values) carried out with both the conventional Isotope Ratio Mass Spectrometry (IRMS) technique and with a new method based on laser absorption techniques, the Wavelenght Scanned Cavity Ringdown Spectroscopy (WS-CRDS). This study is focusing on improving the precision of the measurements carried out with WS-CRDS in order to extensively apply this method to Antarctic ice core paleoclimate studies. The WS-CRDS is a variation of the CRDS developed in 1988 by O'Keef and Deacon. In CRDS a pulse of light goes through a box with high reflective inner surfaces; when there is no sample in the box the light beam doesn't find any obstacle in its path, but the reflectivity of the walls is not perfect so eventually there will be an absorption of the light beam; when the sample is injected in the box there is absorption and the difference between the time of absorption without and with sample is proportional to the quantity

  9. A lab in the field: real-time measurements of water quality and stable isotopes

    NASA Astrophysics Data System (ADS)

    Kirchner, J. W.; von Freyberg, J.

    2015-12-01

    Hydrological and bio-geochemical processes in catchments are largely determined by the flow pathways of water through the subsurface. While the properties of the input (precipitation) and the output (streamflow) can be monitored with relatively low expenditure, subsurface flow processes and travel times remain difficult to quantify. A comprehensive understanding of these physical mechanisms is, however, crucial for a sustainable management of water resources. Natural tracers, such as stable isotopes of water (18O and 2H), in combination with other water quality parameters allows for studying various hydrological and associated processes in great detail. To follow the dynamics in rapidly changing hydrologic systems, high temporal resolution measurements of water isotopes and other constituents is required. Here, we present first results from an extensive field experiment in Switzerland where rain- and river water samples are sampled and analyzed directly in the field every 30 minutes. With this, sample degradation during storage and transportation can be minimized. At the same time, errors due to the collection and handling of numerous water samples are avoided. The fully automated monitoring system is comprised of the newly developed Continuous Water Sampler Module (CoWS), which was coupled to a Picarro L2130-i Cavity Ring-Down Spectrometer (Picarro Inc., USA), to continuously measure 18O and 2H. Optical and electrochemical sensors together with a spectrometer probe monitor NO3-, DOC and physico-chemical parameters, such as oxygen content, pH, electrical conductivity (s::can Messtechnik GmbH, Vienna). An ion chromatograph (Metrohm, Switzerland) allows for precise measurements of the major anions and cations. For quality control, additional water samples are taken automatically at the same frequency and analyzed in the laboratory.

  10. Constraints in calculations of evaporative losses in arid climates using the stable isotope composition of water

    NASA Astrophysics Data System (ADS)

    Skrzypek, G.; Mydlowski, A.; Dogramaci, S.; Hedley, P.; Gibson, J. J.; Grierson, P. F.

    2014-12-01

    Accurate quantification of evaporative losses to the atmosphere from surface water bodies is essential for calibration and validation of hydrological models, particularly in remote arid and semi-arid regions, where rivers and lakes are generally minimally gauged. In this study, we reviewed and combined the most recent equations for estimation of evaporative losses based on the revised Craig-Gordon model. We designed new software, called Hydrocalculator, which allows quick and robust estimation of evaporative losses based on the isotopic composition of water. We validated Hydrocalculator by testing the range of uncertainty in the estimation of evaporative losses in arid climates by cross-validating a simplified stable isotope model with field pan evaporation experiments. The use of standardized pans (1.2 m diameter, volume 300 dm3) in hot and dry climates (temperature 29°C and relative humidity between 19 and 26%) allowed simulation of fast evaporation from shallow water bodies. Several factors may contribute to the uncertainty in the evaporative loss calculations. The analytical uncertainty in the determination of the stable isotope composition of water may contribute to ~0.6% for δ18O and ~1.4% for δ2H. The model is less sensitive to uncertainty in climatic variables and an uncertainty of 1°C in air temperature will result only in the ~0.1% uncertainty in δ18O and δ2H. However, uncertainty in relative humidity of 10% will result in an uncertainty in the final outcome of 0.4% (δ18O) and 1.0% (δ2H). Significantly higher uncertainty in evaporative loss estimation is thus associated with uncertainty in ambient air moisture estimation or analysis. An error of 20‰ in δ2H and 5.0‰ in δ18O will result in a maximum difference of 2.4% (δ2H) and 1.7% (δ18O) in the final calculations. Hydrocalculator can thus provide accurate, rapid and cost-effective insight into the water balance of surface water pools. We used the new software to determine the origin of

  11. Geochemistry and origin of formation waters in the western Canada sedimentary basin-I. Stable isotopes of hydrogen and oxygen

    USGS Publications Warehouse

    Hitchon, B.; Friedman, I.

    1969-01-01

    Stable isotopes of hydrogen and oxygen, together with chemical analyses, were determined for 20 surface waters, 8 shallow potable formation waters, and 79 formation waters from oil fields and gas fields. The observed isotope ratios can be explained by mixing of surface water and diagenetically modified sea water, accompanied by a process which enriches the heavy oxygen isotope. Mass balances for deuterium and total dissolved solids in the western Canada sedimentary basin demonstrate that the present distribution of deuterium in formation waters of the basin can be derived through mixing of the diagenetically modified sea water with not more than 2.9 times as much fresh water at the same latitude, and that the movement of fresh water through the basin has redistributed the dissolved solids of the modified sea water into the observed salinity variations. Statistical analysis of the isotope data indicates that although exchange of deuterium between water and hydrogen sulphide takes place within the basin, the effect is minimized because of an insignificant mass of hydrogen sulphide compared to the mass of formation water. Conversely, exchange of oxygen isotopes between water and carbonate minerals causes a major oxygen-18 enrichment of formation waters, depending on the relative masses of water and carbonate. Qualitative evidence confirms the isotopic fractionation of deuterium on passage of water through micropores in shales. ?? 1969.

  12. Analysis of the hydrogen and oxygen stable isotope ratios of beverage waters without prior water extraction using isotope ratio infrared spectroscopy.

    PubMed

    Chesson, Lesley A; Bowen, Gabriel J; Ehleringer, James R

    2010-11-15

    Hydrogen (δ(2)H) and oxygen (δ(18)O) stable isotope analysis is useful when tracing the origin of water in beverages, but traditional analytical techniques are limited to pure or extracted waters. We measured the isotopic composition of extracted beverage water using both isotope ratio infrared spectroscopy (IRIS; specifically, wavelength-scanned cavity ring-down spectroscopy) and isotope ratio mass spectrometry (IRMS). We also analyzed beer, sodas, juices, and milk 'as is' using IRIS. For IRIS analysis, four sequential injections of each sample were measured and data were corrected for sample-to-sample memory using injections (a) 1-4, (b) 2-4, and (c) 3-4. The variation between δ(2)H and δ(18)O values calculated using the three correction methods was larger for unextracted (i.e., complex) beverages than for waters. The memory correction was smallest when using injections 3-4. Beverage water δ(2)H and δ(18)O values generally fit the Global Meteoric Water Line, with the exception of water from fruit juices. The beverage water stable isotope ratios measured using IRIS agreed well with the IRMS data and fit 1:1 lines, with the exception of sodas and juices (δ(2)H values) and beers (δ(18)O values). The δ(2)H and δ(18)O values of waters extracted from beer, soda, juice, and milk were correlated with complex beverage δ(2)H and δ(18)O values (r = 0.998 and 0.997, respectively) and generally fit 1:1 lines. We conclude that it is possible to analyze complex beverages, without water extraction, using IRIS although caution is needed when analyzing beverages containing sugars, which can clog the syringe and increase memory, or alcohol, a known spectral interference. PMID:20941769

  13. Identifying Hydrological Controls in the Lower Nelson River Basin utilizing Stable Water Isotopes

    NASA Astrophysics Data System (ADS)

    Delavau, C. J.; Smith, A. A.; Stadnyk, T.; Koenig, K.

    2012-12-01

    In 2010 a Stable Water Isotope (SWI) Monitoring Network was established within the lower Nelson River Basin (LNRB) (approximately 90,000 km2) in northern Manitoba, Canada, through a joint collaboration between the University of Manitoba and Manitoba Hydro (MH). The monitoring network encompasses over 60 sites where surface waters are regularly sampled, four sites sampling isotopes in precipitation, two sites utilizing drive point piezometers for the isotopic sampling of baseflow waters, and one site collecting evaporatively enriched water samples from an evaporation pan. In addition, two synoptic surveys have been completed in June 2011 and July 2012 to obtain annual snapshots of the monitoring network at a point in time. Currently, over 700 samples have been collected and analyzed. The LNRB contains approximately 9% of the total Nelson River Basin (NRB) drainage area, which encompasses an area of over 1 million km2. A diversion from the Churchill River through the Rat/Burntwood system routes an additional portion of flow into the northwest portion of the LNRB. The LNRB is significant to MH's network as it represents 75% of their power generation potential through six generating stations, thus resulting in a large portion of the basin being regulated. The watershed is topographically flat, therefore the movement and runoff of water, as well as isotopic composition of streamflow, is suspected to be highly impacted by changes in landscape and hydrography. The LNRB is a coniferous and wetland dominated basin, with almost 35% of the land cover composed of coniferous forest and 40% comprised of wetlands and lakes. Interpretation of the LNRB isotope framework shows that the major water sources (rainfall, snowfall, groundwater and surface waters) and rivers are isotopically distinct from one another. The main stem of the Nelson River shows little spatial or temporal variability, with an average δ18O of -10.6‰ and a standard deviation of 0.5‰ throughout the sampling

  14. Discrepancies between isotope ratio infrared spectroscopy and isotope ratio mass spectrometry for the stable isotope analysis of plant and soil waters.

    PubMed

    West, Adam G; Goldsmith, Gregory R; Brooks, Paul D; Dawson, Todd E

    2010-07-30

    The use of isotope ratio infrared spectroscopy (IRIS) for the stable hydrogen and oxygen isotope analysis of water is increasing. While IRIS has many advantages over traditional isotope ratio mass spectrometry (IRMS), it may also be prone to errors that do not impact upon IRMS analyses. Of particular concern is the potential for contaminants in the water sample to interfere with the spectroscopy, thus leading to erroneous stable isotope data. Water extracted from plant and soil samples may often contain organic contaminants. The extent to which contaminants may interfere with IRIS and thus impact upon data quality is presently unknown. We tested the performance of IRIS relative to IRMS for water extracted from 11 plant species and one organic soil horizon. IRIS deviated considerably from IRMS for over half of the samples tested, with deviations as large as 46 per thousand (delta(2)H) and 15.4 per thousand (delta(18)O) being measured. This effect was reduced somewhat by using activated charcoal to remove organics from the water; however, deviations as large as 35 per thousand (delta(2)H) and 11.8 per thousand (delta(18)O) were still measured for these cleaned samples. Interestingly, the use of activated charcoal to clean water samples had less effect than previously thought for IRMS analyses. Our data show that extreme caution is required when using IRIS to analyse water samples that may contain organic contaminants. We suggest that the development of new cleaning techniques for removing organic contaminants together with instrument-based software to flag potentially problematic samples are necessary to ensure accurate plant and soil water analyses using IRIS. PMID:20552579

  15. Stable isotopes of water as a natural tracer for infiltration into urban sewer systems

    NASA Astrophysics Data System (ADS)

    Kracht, O.; Gresch, M.; de Bénédittis, J.; Prigiobbe, V.; Gujer, W.

    2003-04-01

    An adequate understanding of the hydraulic interaction between leaky sewers and groundwater is essential for the sustainable management of both sewer systems and aquifers in urbanized areas. Undesirable infiltration of groundwater into sewers can contribute over 50% of the total discharge and is detrimental to treatment plant efficiency. On the other hand, in many European cities groundwater surface levels seem to be particularly controlled by the drainage effect of permeable sewer systems. However, nowadays methods for the quantification of these exchange processes are still subject to considerable uncertainties due to their underlying assumptions. The frequently used assumption that the night time minimum in the diurnal wastewater hydrograph is equal to the "parasitic discharge" has to be reconsidered to today's patterns of human life as well as to the long residence time of wastewater in the sewer networks of modern cities. The suitability of stable water isotopes as a natural tracer to differentiate the origin of water in the sewer ("real" wastewater or infiltrating groundwater) is currently investigated in three different catchment areas. The studies are carried out within the framework of the European research project APUSS (Assessing Infiltration and Exfiltration on the Performance of Urban Sewer Systems): 1) The village of Rümlang (Zürich, Switzerland) is predominantly served with drinking water from the Lake Zürich. A large fraction of the lakes water is derived from precipitation in the Alps. This drinking water represents the intrinsic provenience of the wastewater with an δ18O value around -11,5 per mill and δ^2H value around -82 per mill vs. SMOW. In contrast, the local groundwater is originating from precipitation in a moderate altitude of about 450 m above sea level and shows comparatively enriched mean δ18O values of -9,7 per mill and δ^2H values of -70 per mill with only small natural variations. The isotopic separation between these

  16. The influence of environmental water on the hydrogen stable isotope ratio in aquatic consumers.

    PubMed

    Solomon, Christopher T; Cole, Jonathan J; Doucett, Richard R; Pace, Michael L; Preston, Nicholas D; Smith, Laura E; Weidel, Brian C

    2009-08-01

    Aquatic food webs are subsidized by allochthonous resources but the utilization of these resources by consumers can be difficult to quantify. Stable isotope ratios of hydrogen (deuterium:hydrogen; deltaD) potentially distinguish allochthonous inputs because deltaD differs between terrestrial and aquatic primary producers. However, application of this tracer is limited by uncertainties regarding the trophic fractionation of deltaD and the contributions of H from environmental water (often called "dietary water") to consumer tissue H. We addressed these uncertainties using laboratory experiments, field observations, modeling, and a literature synthesis. Laboratory experiments that manipulated the deltaD of water and food for insects, cladoceran zooplankton, and fishes provided strong evidence that trophic fractionation of deltaD was negligible. The proportion of tissue H derived from environmental water was substantial yet variable among studies; estimates of this proportion, inclusive of lab, field, and literature data, ranged from 0 to 0.39 (mean 0.17 +/- 0.12 SD). There is a clear need for additional studies of environmental water. Accounting for environmental water in mixing models changes estimates of resource use, although simulations suggest that uncertainty about the environmental water contribution does not substantially increase the uncertainty in estimates of resource use. As long as this uncertainty is accounted for, deltaD may be a powerful tool for estimating resource use in food webs. PMID:19471971

  17. Using Water Vapor Isotope Observations from above the Greenland Ice Sheet to improve the Interpretation of Ice Core Water Stable Isotope Records

    NASA Astrophysics Data System (ADS)

    Steen-Larsen, H. C.; Masson-Delmotte, V.; Risi, C. M.; Yoshimura, K.; Werner, M.; Butzin, M.; Brun, E.; Landais, A.; Bonne, J. L.; Dahl-Jensen, D.

    2014-12-01

    Water stable isotope data from Greenland ice cores provide key paleoclimatic information. For the purpose of improving the climatic interpretation from ice core records, a monitoring of the isotopic composition δ18O and δD at several height levels (up to 13 meter) of near-surface water vapor, precipitation and snow in the first 0.5 cm surface layer has been conducted during three summers (2010-2012) at NEEM, NW Greenland. We compare the observed water vapor isotopic composition with model outputs from three isotope-enabled general circulation models: LMDZiso, isoGSM, ECHAM-wiso. This allows us to benchmark the models and address effect of model resolution, effect of transport, effect of isotope parameterization, and representation of significant source region contributions. We find for all models that the simulated isotopic value δD are significantly biased towards too enriched values. A bias, which is only partly explained by the air temperature. The simulated amplitude in d-excess variations is ~50% smaller than observed and the simulated average summer level is ~10‰ lower than in observations. Using back trajectories we observe water vapor of Arctic origin to have a high d-excess fingerprint. This fingerprint is not observed in the GCMiso simulations indicating a problem of simulating accurately the Arctic hydrological cycle. The bias in the simulated δD and d-excess water vapor is similar to the already-documented bias in the simulated δD and d-excess of Greenland ice core records. This suggests that if we improve the simulation of the water vapor isotopic composition we might also improve the simulation of the ice core isotope record. During periods between precipitation events, our data demonstrate parallel changes of δ18O and d-excess in surface snow and near-surface vapor. The changes in δ18O of the vapor are similar or larger than those of the snow δ18O. It is estimated using the CROCUS snow model that 6 to 20% of the surface snow mass is

  18. Detailed assessment of isotope ratio infrared spectroscopy and isotope ratio mass spectrometry for the stable isotope analysis of plant and soil waters.

    PubMed

    Zhao, Liangju; Xiao, Honglang; Zhou, Jian; Wang, Lixin; Cheng, Guodong; Zhou, Maoxian; Yin, Li; McCabe, Matthew F

    2011-10-30

    As an alternative to isotope ratio mass spectrometry (IRMS), the isotope ratio infrared spectroscopy (IRIS) approach has the advantage of low cost, continuous measurement and the capacity for field-based application for the analysis of the stable isotopes of water. Recent studies have indicated that there are potential issues of organic contamination of the spectral signal in the IRIS method, resulting in incorrect results for leaf samples. To gain a more thorough understanding of the effects of sample type (e.g., leaf, root, stem and soil), sample species, sampling time and climatic condition (dry vs. wet) on water isotope estimates using IRIS, we collected soil samples and plant components from a number of major species at a fine temporal resolution (every 2 h for 24-48 h) across three locations with different climatic conditions in the Heihe River Basin, China. The hydrogen and oxygen isotopic compositions of the extracted water from these samples were measured using both an IRMS and an IRIS instrument. The results show that the mean discrepancies between the IRMS and IRIS approaches for δ(18) O and δD, respectively, were: -5.6‰ and -75.7‰ for leaf water; -4.0‰ and -23.3‰ for stem water; -3.4‰ and -28.2‰ for root water; -0.5‰ and -6.7‰ for xylem water; -0.06‰ and -0.3‰ for xylem flow; and -0.1‰ and 0.3‰ for soil water. The order of the discrepancy was: leaf > stem ≈ root > xylem > xylem flow ≈ soil. In general, species of the same functional types (e.g., woody vs. herbaceous) within similar habitats showed similar deviations. For different functional types, the differences were large. Sampling at nighttime did not remove the observed deviations. PMID:21953962

  19. Detailed assessment of isotope ratio infrared spectroscopy and isotope ratio mass spectrometry for the stable isotope analysis of plant and soil waters

    NASA Astrophysics Data System (ADS)

    Zhao, L.; Xiao, H.; Zhou, J.; Wang, L.; Cheng, G.; Zhou, M.; Yin, L.; McCabe, M. F.

    2011-12-01

    As an alternative to isotope ratio mass spectrometry (IRMS) the isotope ratio infrared spectroscopy (IRIS) approach has the advantage of low cost, continuous measurement and capacity for field based application for the analysis of stable water isotopes. Recent studies have indicated that there are potential issues of organic contamination of the spectral signal in the IRIS method, resulting in errant readings for leaf samples. To gain a more thorough understanding of the effects of sample type (e.g., leaf, root, stem and soil), sample species, sampling time and climatic condition (dry vs. wet) on water isotope estimates using IRIS, we collected soil samples and plant components from a number of major species at a fine temporal resolution (every two hours for 24-48 hours) across three locations with different climatic conditions in the Heihe River Basin, China. The hydrogen and oxygen isotopic composition of the extracted water from these samples was measured using both an IRMS and IRIS instrument. Results show that the mean discrepancy between the IRMS and IRIS approach, for δ18O and δD respectively, was: -5.6% and -75.7% for leaf water; -4.0% and -23.3% for stem water; -3.4% and -28.2% for root water; -6.7% and -0.5% for xylem water; -0.06% and -0.3% for xylem flow; and -0.1% and 0.3% for soil water. The order of the discrepancy followed: leaf > stem ≈ root > xylem > xylem flow ≈ soil. In general, species of the same functional types (e.g., woody vs. herbaceous) within similar habitats showed similar deviations. For different functional types, the differences were large. Sampling during the nighttime did not remove the observed deviations.

  20. Origin and Fate of Organic Compounds in Water: Characterization by Compound-Specific Stable Isotope Analysis

    NASA Astrophysics Data System (ADS)

    Schmidt, Torsten C.; Jochmann, Maik A.

    2012-07-01

    Within the past 15 years, compound-specific stable isotope analysis has continued to increase in popularity in the area of contaminant hydrology of organic molecules. In particular, in cases where concentration data alone are insufficient to elucidate environmental processes unequivocally, the isotope signature can provide additional unique information. Specifically, it can help answer questions about contaminant source apportionment, quantification of biotic and abiotic processes, and identification of transformation reactions on a mechanistic level. We review advances in laboratory and field investigations and exemplary applications in contaminant hydrology via stable isotope analysis. We also highlight future directions in the field.

  1. Seasonal variation of water level, water and soil temperature, chemistry, and stable isotopes in hyporheic zone of Korea

    NASA Astrophysics Data System (ADS)

    Jeon, W. H.; Lee, J. Y.

    2015-12-01

    The purpose of study was to evaluate interaction between groundwater and stream water in hyporheic zone using water level, water temperature, soil temperature, chemistry, and stable isotopes. We installed seven piezometers (IYHW1 to 7) in the streambed that across stream in every 10 m and in depth of 0.85 to 1.54 m, a device that measure stage level nearby IYHW1, and devices that measure soil temperature in every 10 cm down to 50 cm nearby each piezometer was installed. We monitored water level and water temperature every hour from automatic transducers at the piezometers and the stage level, and soil temperatures were monitored every two hours. We took samples from the hyporheic water, stream water, and nearby groundwater to analysis chemical and isotopic compositions. The water level difference between stream water and hyporheic waters indicated that groundwater was downwelling in wet season and upwelling in dry season. The groundwater temperature remained steady in different seasons, but the stream water represented a frequent fluctuation with large amplitude. The hyporheic waters and soil temperature represented intermediate variation characteristics. The chemical compositions were not able to indicate in interaction of groundwater and stream water because no distinctive difference in seasonal variation in waters. The quantity of isotopic compositions of oxygen and hydrogen determined from using mixing ratio indicated that downwelling in wet season and upwelling in dry season. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2011-0007232).

  2. Ice-wedge based permafrost chronologies and stable-water isotope records from Arctic Siberia

    NASA Astrophysics Data System (ADS)

    Wetterich, Sebastian; Opel, Thomas; Meyer, Hanno; Schwamborn, Georg; Schirrmeister, Lutz; Dereviagin, Alexander Yu.

    2016-04-01

    Late Quaternary permafrost of northern latitudes contains large proportions of ground ice, including pore ice, segregation ice, massive ice, buried glacier ice and in particular ice wedges. Fossil ice-wedges are remnants of polygonal patterned ground in former tundra areas, which evolved over several tens of thousands of years in non-glaciated Beringia. Ice wedges originate from repeated frost cracking of the ground in winter and subsequent crack filling by snowmelt and re-freezing in the ground in spring. Hence, the stable water isotope composition (δ18O, δD, d excess) of wedge ice derives from winter precipitation and is commonly interpreted as wintertime climate proxy. Paleoclimate studies based on ice-wedge isotope data cover different timescales and periods of the late Quaternary. (MIS 6 to MIS 1). In the long-term scale the temporal resolution is rather low and corresponds to mid- and late Pleistocene and Holocene stratigraphic units. Recent progress has been made in developing centennial Late Glacial and Holocene time series of ice-wedge stable isotopes by applying radiocarbon dating of organic remains in ice samples. Ice wedges exposed at both coasts of the Dmitry Laptev Strait (East Siberian Sea) were studied to deduce winter climate conditions since about 200 kyr. Ice wedges aligned to distinct late Quaternary permafrost strata were studied for their isotopic composition and dated by radiocarbon ages of organic matter within the wedge ice or by cosmogenic nuclide ratios (36Cl/Cl-) of the ice. The paleoclimate interpretation is furthermore based on geocryological and paleoecological proxy data and geochronological information (radiocarbon, luminescence, radioisotope disequilibria 230Th/U) from ice-wedge embedding frozen deposits. Coldest winter conditions are mirrored by most negative δ18O mean values of -37 ‰ and δD mean values of -290 ‰ from ice wedges of the Last Glacial Maximum (26 to 22 kyr BP) while late Holocene (since about 4 kyr BP) and in

  3. Ion exchange separation of chromium from natural water matrix for stable isotope mass spectrometric analysis

    USGS Publications Warehouse

    Ball, J.W.; Bassett, R.L.

    2000-01-01

    A method has been developed for separating the Cr dissolved in natural water from matrix elements and determination of its stable isotope ratios using solid-source thermal-ionization mass spectrometry (TIMS). The separation method takes advantage of the existence of the oxidized form of Cr as an oxyanion to separate it from interfering cations using anion-exchange chromatography, and of the reduced form of Cr as a positively charged ion to separate it from interfering anions such as sulfate. Subsequent processing of the separated sample eliminates residual organic material for application to a solid source filament. Ratios for 53Cr/52Cr for National Institute of Standards and Technology Standard Reference Material 979 can be measured using the silica gel-boric acid technique with a filament-to-filament standard deviation in the mean 53Cr/52Cr ratio for 50 replicates of 0.00005 or less. (C) 2000 Elsevier Science B.V. All rights reserved.

  4. Evaluation of soil water stable isotope analysis by H2O(liquid)-H2O(vapor) equilibration method

    NASA Astrophysics Data System (ADS)

    Gralher, Benjamin; Stumpp, Christine

    2014-05-01

    Environmental tracers like stable isotopes of water (δ18O, δ2H) have proven to be valuable tools to study water flow and transport processes in soils. Recently, a new technique for soil water isotope analysis has been developed that employs a vapor phase being in isothermal equilibrium with the liquid phase of interest. This has increased the potential application of water stable isotopes in unsaturated zone studies as it supersedes laborious extraction of soil water. However, uncertainties of analysis and influencing factors need to be considered. Therefore, the objective of this study was to evaluate different methodologies of analysing stable isotopes in soil water in order to reduce measurement uncertainty. The methodologies included different preparation procedures of soil cores for equilibration of vapor and soil water as well as raw data correction. Two different inflatable sample containers (freezer bags, bags containing a metal layer) and equilibration atmospheres (N2, dry air) were tested. The results showed that uncertainties for δ18O were higher compared to δ2H that cannot be attributed to any specific detail of the processing routine. Particularly, soil samples with high contents of organic matter showed an apparent isotope enrichment which is indicative for fractionation due to evaporation. However, comparison of water samples obtained from suction cups with the local meteoric water line indicated negligible fractionation processes in the investigated soils. Therefore, a method was developed to correct the raw data reducing the uncertainties of the analysis.. We conclude that the evaluated method is advantageous over traditional methods regarding simplicity, resource requirements and sample throughput but careful consideration needs to be made regarding sample handling and data processing. Thus, stable isotopes of water are still a good tool to determine water flow and transport processes in the unsaturated zone.

  5. Constraints on water cycling in a deep mountain valley from stable water isotope and sap flux measurements

    NASA Astrophysics Data System (ADS)

    Fiorella, R.; Poulsen, C. J.; Matheny, A. M.; Bohrer, G.

    2015-12-01

    The stable isotopes of oxygen and hydrogen in water are unequally partitioned during phase changes, with environmental conditions controlling the degree of partitioning. As a result, the isotopic composition of water reflects the thermodynamic history of water parcels in the water cycle. Recent advances in cavity ringdown spectrometry allow for the continuous measurement of water vapor isotope compositions, and provide insight into the processes influencing the concentration of near-surface water vapor at high resolution. We used stable water isotopes to investigate the processes controlling water vapor cycling in a deep mountain valley in northwestern Wyoming. A Picarro L2120-i Cavity Ring-Down spectrometer was deployed to measure the isotopic composition of atmospheric water vapor at the University of Michigan Camp Davis Field Station near Jackson, WY for three consecutive summers (2012-2014) and during winter 2013. We also constructed a network of Granier-style sap flux probes to estimate the local transpiration flux from regionally dominant tree species in July 2014. A prominent diurnal cycle was observed during the summer that was mostly absent in the winter. Summer specific humidity, δD, δ18O, and sap flux all reach daily maximum values in the mid-to-late morning that we associate with the onset of transpiration. The mountain valley is capped by an inversion, which limits atmospheric mixing during the morning. After the breakup of the inversion, the atmospheric boundary layer develops quickly and results in decreases in near-surface specific humidity and δ18O. δD appears to be less affected following the inversion breakup, resulting in a strong diurnal cycle in d-excess. Specific humidity, δD, and δ18O all return to their morning values rapidly near sunset, marking the cessation of mixing and atmospheric stratification. This absence of this diurnal cycle in the winter is consistent with reduced transpiration and atmospheric mixing anticipated for the

  6. Using Stable Water Isotopes to Differentiate Source Flows in the Santa Monica Mountains, Southern California

    NASA Astrophysics Data System (ADS)

    Hu, W.; Hibbs, B. J.

    2009-12-01

    The Santa Monica Mountains contain diverse land uses: urban, residential, commercial, agricultural, parks & recreation and natural preserves. Local precipitation, groundwater derived from local precipitation, runoff of imported tap water, and treated wastewater derived from imported tap water are all possible inputs to local streams. Historically, the semi-arid Mediterranean climate caused some local streams to flow intermittently. Recently, some of these previously intermittent streams began to flow perennially. Continuous flow has often been attributed to inputs of imported water from urban runoff or irrigation. Continuous flow is regarded as a facilitator for the spread of exotic, invasive species. If urban runoff were found to be the source of perennial flows, policy controls on urban runoff could be needed. Imported water from northern California is isotopically distinct from southern California precipitation. This distinction allows differentiation of source flows to creeks and streams. As a representative example of source flow discrimination, detailed studies were done on McCoy Creek, a stream in the Santa Monica Mountains. McCoy Creek runs through both natural areas and land developed for residential and recreational uses. In populated places, the stream flows past housing developments, parks and a golf course. These sites are all irrigated with imported water. Samples of stream water, tap water and treated wastewater were analyzed for stable water isotopes and other parameters such as nitrate and selenium. Results were used to examine the relative contribution of imported water to McCoy Creek. Sampling occurred about every 6 weeks from July 2008 through March 2009. From upstream to downstream, the sampled reach began at a housing development with relatively low impervious cover, flowed through a native riparian reach and then through a golf course, and then through an area of recreational, residential and commercial land use. In most instances, the

  7. Stable isotope estimates of evaporation: inflow and water residence time for lakes across the United States as a tool for national lake water quality assessments

    EPA Science Inventory

    Stable isotope ratios of water (delta18O and delta2H) can be very useful in large-scale monitoring programs because water samples are easy to collect and isotope ratios integrate information about basic hydrologic processes such as evaporation as a percentage of inflow (E/I) and ...

  8. Stable isotopes reveal ecotypic variation of water uptake patterns in Aleppo pine

    NASA Astrophysics Data System (ADS)

    Ferrio, Juan Pedro; Lucabaugh, Devon; Chambel, Regina; Voltas, Jordi

    2014-05-01

    Aleppo pine (Pinus halepensis Mill.) has a large natural distribution range that encompasses a multitude of thermal and moisture conditions found in the Mediterranean basin. We hypothesized that due to the recurrent incidences of drought stress and high temperatures that occur at varying degrees along its distribution range, populations of Aleppo pine have undergone ecotypic differentiation in soil water uptake patterns. This study analyzed stable isotopic compositions (δ18O and δ2H) of xylem water to identify adaptive divergence associated to the pattern of soil water consumption by roots of Aleppo pine populations originating from the Mediterranean region. The results from this study show that genetic diversity in the extraction pattern of soil water can be found among populations and ecological regions of Aleppo pine under common garden conditions. However, the ability to detect such differences depended on the period of the year examined. In particular, data collection in full summer (end of July) proved to be the most adequate in revealing genetic divergence among populations, while end of spring and, to a lesser extent, end of summer, were less successful for this purpose. Both water uptake patterns (as estimated by δ18O and δ2H) and above-ground growth, exhibited significant relationships with both climatic and geographical variables. This suggests that the underlying variation among populations can be explained by certain characteristics at origin. In addition, we used a bayesian mixing model (SIAR package for R) that incorporated isotopic signatures from xylem and soil water in order to determine the predominant soil layer of water source consumption at the aforementioned periods of the growing season, where water availably ranged from lowest to highest. This allowed us to gain some understanding of Aleppo pines' differential reaction to drought, at the intraspecific level, across the fluctuating conditions of the growing season by comparing the

  9. On the cross-sensitivity between water vapor mixing ratio and stable isotope measurements of in-situ analyzers

    NASA Astrophysics Data System (ADS)

    Parkes, Stephen; Wang, Lixin; McCabe, Matthew

    2015-04-01

    In recent years there has been an increasing amount of water vapor stable isotope data collected using in-situ instrumentation. A number of papers have characterized the performance of these in-situ analyzers and suggested methods for calibrating raw measurements. The cross-sensitivity of the isotopic measurements on the mixing ratio has been shown to be a major uncertainty and a variety of techniques have been suggested to characterize this inaccuracy. However, most of these are based on relating isotopic ratios to water vapor mixing ratios from in-situ analyzers when the mixing ratio is varied and the isotopic composition kept constant. An additional correction for the span of the isotopic ratio scale is then applied by measuring different isotopic standards. Here we argue that the water vapor cross-sensitivity arises from different instrument responses (span and offset) of the parent H2O isotope and the heavier isotopes, rather than spectral overlap that could cause a true variation in the isotopic ratio with mixing ratio. This is especially relevant for commercial laser optical instruments where absorption lines are well resolved. Thus, the cross-sensitivity determined using more conventional techniques is dependent on the isotopic ratio of the standard used for the characterization, although errors are expected to be small. Consequently, the cross-sensitivity should be determined by characterizing the span and zero offset of each isotope mixing ratio. In fact, this technique makes the span correction for the isotopic ratio redundant. In this work we model the impact of changes in the span and offset of the heavy and light isotopes and illustrate the impact on the cross-sensitivity of the isotopic ratios on water vapor. This clearly shows the importance of determining the zero offset for the two isotopes. The cross-sensitivity of the isotopic ratios on water vapor is then characterized by determining the instrument response for the individual isotopes for a

  10. A comparison of the toluene distillation and vacuum/heat methods for extracting soil water for stable isotopic analysis

    NASA Astrophysics Data System (ADS)

    Ingraham, Neil L.; Shadel, Craig

    1992-12-01

    Hanford Loam, from Richland, Washington, was used as a test soil to determine the precision, accuracy and nature of two methods to extract soil water for stable isotopic analysis: azeotropic distillation using toluene, and simple heating under vacuum. The soil was oven dried, rehydrated with water of known stable isotopic compositions, and the introduced water was then extracted. Compared with the introduced water, initial aliquots of evolved water taken during a toluene extraction were as much as 30 ‰ more depleted in D and 2.7 ‰ more depleted in 18O, whereas final aliquots were as much as 40 ‰ more enriched in D and 14.3 ‰ more enriched in 18O. Initial aliquots collected during the vacuum/heat extraction were as much as 64 ‰ more depleted in D and 8.4 ‰ more depleted in 18O than was the introduced water, whereas the final aliquots were as much as 139 ‰ more enriched in D, and 20.8 ‰ more enriched in 18O. Neither method appears quantitative; however, the difference in stable isotopic composition between the first and last aliquots of water extracted by the toluene method is less than that from the vacuum/heat method. This is attributed to the smaller fractionation factors involved with the higher average temperatures of distillation of the toluene. The average stable isotopic compositions of the extracted water varied from that of the introduced water by up to 1.4 ‰ in δD and 4.2 ‰ in δ18O with the toluene method, and by 11.0 ‰ in δD and 1.8 ‰ in δ18O for the vacuum/heat method. The lack of accuracy of the extraction methods is thought to be due to isotopic fractionation associated with water being weakly bound (not released below 110°C) in the soil. The isotopic effect of this heat-labile water is larger at low water contents (3.6 and 5.2% water by weight) as the water bound in the soil is a commensurately larger fraction of the total. With larger soilwater contents the small volume of water bound with an associated fractionation is

  11. Can stable isotopes ride out the storms? The role of convection for water isotopes in models, records, and paleoaltimetry studies in the central Andes

    NASA Astrophysics Data System (ADS)

    Rohrmann, Alexander; Strecker, Manfred R.; Bookhagen, Bodo; Mulch, Andreas; Sachse, Dirk; Pingel, Heiko; Alonso, Ricardo N.; Schilgen, Taylor F.; Montero, Carolina

    2015-04-01

    Globally, changes in stable isotope ratios of oxygen and hydrogen (δ18O and δD) in the meteoric water cycle result from distillation and evaporation processes. Isotope fractionation occurs when air masses rise in elevation, cool, and reduce their water-vapor holding capacity with decreasing temperature. As such, d18O and dD values from a variety of sedimentary archives are often used to reconstruct changes in continental paleohydrology as well as paleoaltimetry of mountain ranges. Based on 234 stream-water samples, we demonstrate that areas experiencing deep convective storms in the eastern south-central Andes (22 - 28° S) do not show the commonly observed relationship between δ18O and δD with elevation. These convective storms arise from intermontane basins, where diurnal heating forces warm air masses upward, resulting in cloudbursts and raindrop evaporation. Especially at the boundary between the tropical and extra-tropical atmospheric circulation regimes where deep-convective storms are very common (~ 26° to 32° N and S), the impact of such storms may yield non-systematic stable isotope-elevation relationships as convection dominates over adiabatic lifting of air masses. Because convective storms can reduce or mask the depletion of heavy isotopes in precipitation as a function of elevation, linking modern or past topography to patterns of stable isotope proxy records can be compromised in mountainous regions, and atmospheric circulation models attempting to predict stable isotope patterns must have sufficiently high spatial resolution to capture the fractionation dynamics of convective cells. Rohrmann, A. et al. Can stable isotopes ride out the storms? The role of convection for water isotopes in models, records, and paleoaltimetry studies in the central Andes. Earth Planet. Sci. Lett. 407, 187-195 (2014).

  12. Reconstructing Water Column Hydrography Using Individual Shell Stable Isotope Data From Multiple Planktic Foraminifera Species

    NASA Astrophysics Data System (ADS)

    Spero, H. J.; Fehrenbacher, J. S.; Davis, K. V.; Griffin, J. M.; Grimm, B. L.; Kercher, P.; Kostlan, M.; Menicucci, A. J.; Santare, L.; Starnes, J.; Vetter, L.; Wilbanks, E.; Wildgoose, M.

    2012-12-01

    , ontogeny, and the depth-dependent variation of the carbonate ion effect, water column light levels, temperature and salinity. In the context of these variables, stable isotope datasets from multiple foraminifera species may be accurately interpreted for paleoceanographic reconstructions of upper water column structure.

  13. Investigating the Persistence of a Snowpack Sublimation Stable Isotope Signal in Tree Xylem Water during the Growing Season

    NASA Astrophysics Data System (ADS)

    Schulze, E. S.; Bowling, D. R.

    2014-12-01

    Previous work identified a riparian meadow in the Rocky Mountains where streamside box elder (Acer negundo) trees did not use stream water, the most reliable and readily available source. A follow-up study showed that the water used by trees appears to be more evaporatively enriched than all available measured sources, including stream water, precipitation-derived soil water, and groundwater. While it is unlikely that there is a missing pool of water these trees are accessing, they may be tapping into a distinct subset of the bulk soil water available, possibly derived from much colder and older snowmelt. In this study, we investigated whether snowpack sublimation and subsequent melt water may impart an enriched isotopic signature that persists throughout the following growing season in less-mobile soil water pools. Profile samples of the snowpack, bulk melt water, and early season soil lysimeter water were collected throughout the winter and analyzed for hydrogen and oxygen stable isotopes. As snow began to melt in the spring, water samples for isotope analysis were taken from soil profiles, stream water, groundwater, and stems. Although sublimation likely occurred at the site, such processes did not impart an evaporative isotope enrichment on the snowpack throughout the season. Both snow pack and melt water remained closely tied to the local meteoric water line as they infiltrated soil. These findings suggest that snowpack sublimation processes preceding melt water infiltration are not the source of evaporative enrichment in tree water at our site.

  14. Use of stable lead isotopes to characterize the sources of anthropogenic lead in North Atlantic surface waters

    SciTech Connect

    Veron, A.J. Univ. of Delaware, Newark, DE ); Church, T.M. ); Patterson, C.C. ); Flegal, A.R. Univ. of California, Santa Cruz, CA )

    1994-08-01

    Stable lead isotopes are used to illustrate the impact of surface water circulation on dissolved lead distribution in North Atlantic surface waters during oligotrophic conditions. Using stable lead isotopic signatures from (1) the Sargasso Sea and (2) direct tropospheric deposition to the North Atlantic, the authors estimate that 10-40% of the lead accumulated in surface waters of the European Basin is transported from the western North Atlantic by the North Atlantic Current. South of 50[degrees]N, lead appears to be primarily distributed by the Subtropical North Atlantic Gyre that extends well beyond the western basins to 30[degrees]W in the North African Basin (at 30-40[degrees]N). There are different lead isotopic signatures between the subtropical gyre of the Guiana and western Guinea Basins, which suggests that the Inter Tropical Convergence Zone acts as an efficient barrier limiting chemical exchanges between the gyre and the equatorial currents.

  15. Stable isotope laser spectroscopy

    NASA Technical Reports Server (NTRS)

    Becker, J. F.; Yaldaei, Ramil; Mckay, Christopher P.

    1989-01-01

    Recent advances in semiconductor laser technology have produced a reliable lightweight device ideally suited for a spacecraft high resolution molecular spectrometer. Lead-salt tunable diode lasers (TDL) emit in several spectral modes, each with a very narrow linewidth of -0.0003/cm. This spectral resolution is much narrower than typical Doppler broadened molecular linewidths in the mid-IR range. Thus it is possible to detect individual rotational lines within the vibrational band and measure their intensity, which can be used to determine gas concentration. The narrow spectral lines of any impurity gas tend to lie between the narrow lines of the gas of interest. This represents a major advantage over the accepted gas chromatograph mass spectrometer (GCMS) technique for measuring gas concentrations and isotope ratios. The careful and extensive gas purification procedures required to remove impurities for reliable GCMS measurements will not be required for an IR laser gas analysis. The infrared laser gas analysis technique is being developed to measure stable isotopic ratios of gases such as CO2, CH4, N2O, and NH3. This will eventually lead to development of instruments capable of in situ istopic measurements on planets such as Mars. The carbon (C-12, C-13) isotope ratio is indicative of the type of carbon fixation mechanisms (e.g., photosynthesis, respiration) in operation on a planet, while the nitrogen (N-14, N-15) isotope ratio can probably be used to date nitrogen-bearing Martian samples. The absorbance ratio of two adjacent lines of CO2 in the 2300/cm (4.3 micron) region of the spectrum was measured. The precision of the measurement is presently better than 1 percent and significant improvement is anticipated as rapid sweep-integration techniques and computer controlled data acquistion capabilities are incorporated.

  16. Stable isotope laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Becker, J. F.; Yaldaei, Ramil; McKay, Christopher P.

    1989-03-01

    Recent advances in semiconductor laser technology have produced a reliable lightweight device ideally suited for a spacecraft high resolution molecular spectrometer. Lead-salt tunable diode lasers (TDL) emit in several spectral modes, each with a very narrow linewidth of -0.0003/cm. This spectral resolution is much narrower than typical Doppler broadened molecular linewidths in the mid-IR range. Thus it is possible to detect individual rotational lines within the vibrational band and measure their intensity, which can be used to determine gas concentration. The narrow spectral lines of any impurity gas tend to lie between the narrow lines of the gas of interest. This represents a major advantage over the accepted gas chromatograph mass spectrometer (GCMS) technique for measuring gas concentrations and isotope ratios. The careful and extensive gas purification procedures required to remove impurities for reliable GCMS measurements will not be required for an IR laser gas analysis. The infrared laser gas analysis technique is being developed to measure stable isotopic ratios of gases such as CO2, CH4, N2O, and NH3. This will eventually lead to development of instruments capable of in situ istopic measurements on planets such as Mars. The carbon (C-12, C-13) isotope ratio is indicative of the type of carbon fixation mechanisms (e.g., photosynthesis, respiration) in operation on a planet, while the nitrogen (N-14, N-15) isotope ratio can probably be used to date nitrogen-bearing Martian samples. The absorbance ratio of two adjacent lines of CO2 in the 2300/cm (4.3 micron) region of the spectrum was measured. The precision of the measurement is presently better than 1 percent and significant improvement is anticipated as rapid sweep-integration techniques and computer controlled data acquistion capabilities are incorporated.

  17. Long-term and high frequency non-destructive monitoring of water stable isotope profiles in an evaporating soil column

    NASA Astrophysics Data System (ADS)

    Rothfuss, Y.; Merz, S.; Vanderborght, J.; Hermes, N.; Weuthen, A.; Pohlmeier, A.; Vereecken, H.; Brüggemann, N.

    2015-04-01

    The stable isotope compositions of soil water (δ2H and δ18O) carry important information about the prevailing soil hydrological conditions and for constraining ecosystem water budgets. However, they are highly dynamic, especially during and after precipitation events. The classical method of determining soil water δ2H and δ18O at different depths, i.e., soil sampling and cryogenic extraction of the soil water, followed by isotope-ratio mass spectrometer analysis is destructive and laborious with limited temporal resolution. In this study, we present a new non-destructive method based on gas-permeable tubing and isotope-specific infrared laser absorption spectroscopy. We conducted a laboratory experiment with an acrylic glass column filled with medium sand equipped with gas-permeable tubing at eight different soil depths. The soil column was initially saturated from the bottom, exposed to evaporation for a period of 290 days, and finally rewatered. Soil water vapor δ2H and δ18O were measured daily, sequentially for each depth. Soil liquid water δ2H and δ18O were inferred from the isotopic values of the vapor assuming thermodynamic equilibrium between liquid and vapor phases in the soil. The experimental setup allowed following the evolution of typical exponential-shaped soil water δ2H and δ18O profiles with unprecedentedly high temporal resolution. As the soil dried out, we could also show for the first time the increasing influence of the isotopically depleted ambient water vapor on the isotopically enriched liquid water close to the soil surface (i.e., atmospheric invasion). Rewatering at the end of the experiment led to instantaneous resetting of the stable isotope profiles, which could be closely followed with the new method.

  18. Pleistocene paleo-groundwater as a pristine fresh water resource in southern Germany--evidence from stable and radiogenic isotopes.

    PubMed

    van Geldern, Robert; Baier, Alfons; Subert, Hannah L; Kowol, Sigrid; Balk, Laura; Barth, Johannes A C

    2014-10-15

    Shallow groundwater aquifers are often influenced by anthropogenic contaminants or increased nutrient levels. In contrast, deeper aquifers hold potentially pristine paleo-waters that are not influenced by modern recharge. They thus represent important water resources, but their recharge history is often unknown. In this study groundwater from two aquifers in southern Germany were analyzed for their hydrogen and oxygen stable isotope compositions. One sampling campaign targeted the upper aquifer that is actively recharged by modern precipitation, whereas the second campaign sampled the confined, deep Benkersandstein aquifer. The groundwater samples from both aquifers were compared to the local meteoric water line to investigate sources and conditions of groundwater recharge. In addition, the deep groundwater was dated by tritium and radiocarbon analyses. Stable and radiogenic isotope data indicate that the deep-aquifer groundwater was not part of the hydrological water cycle in the recent human history. The results show that the groundwater is older than ~20,000 years and most likely originates from isotopically depleted melt waters of the Pleistocene ice age. Today, the use of this aquifer is strictly regulated to preserve the pristine water. Clear identification of such non-renewable paleo-waters by means of isotope geochemistry will help local water authorities to enact and justify measures for conservation of these valuable resources for future generations in the context of a sustainable water management. PMID:25063917

  19. Using Stable Isotopes to Understand Degradation of Organic Contaminants in Ground Water

    EPA Science Inventory

    Stable isotopes are a powerful tool to understand biodegradation. However, there are two interactions that can substantially confuse the interpretation of CSIR data: heterogeneity in flow paths in the aquifer and proximity to NAPL or other source of contamination to ground wate...

  20. Sulfur speciation and stable isotope trends of water-soluble sulfates in mine tailings profiles.

    PubMed

    Dold, Bernhard; Spangenberg, Jorge E

    2005-08-01

    Sulfur speciation and the sources of water-soluble sulfate in three oxidizing sulfidic mine tailings impoundments were investigated by selective dissolution and stable isotopes. The studied tailings impoundments--Piuquenes, Cauquenes, and Salvador No. 1--formed from the exploitation of the Rio Blanco/La Andina, El Teniente, and El Salvador Chilean porphyry copper deposits, which are located in Alpine, Mediterranean, and hyperarid climates, respectively. The water-soluble sulfate may originate from dissolution of primary ore sulfates (e.g., gypsum, anhydrite, jarosite) or from oxidation of sulfide minerals exposed to aerobic conditions during mining activity. With increasing aridity and decreasing pyrite content of the tailings, the sulfur speciation in the unsaturated oxidation zones showed a trend from dominantly Fe(III) oxyhydroxide fixed sulfate (e.g., jarosite and schwertmannite) in Piuquenes toward increasing presence of water-soluble sulfate at Cauquenes and Salvador No. 1. In the saturated primary zones, sulfate is predominantly present in water-soluble form (mainly as anhydrite and/or gypsum). In the unsaturated zone at Piuquenes and Cauquenes, the delta34S(SO4)values ranged from +0.5 per thousand to +2.0 per thousand and from -0.4 per thousand to +1.4 per thousand Vienna Canyon Diablo Troilite (V-CDT), respectively, indicating a major sulfate source from pyrite oxidation (delta34S(pyrite) = -1.1 per thousand and -0.9 per thousand). In the saturated zone at Piuquenes and Cauquenes, the values ranged from -0.8 per thousand to +0.3 per thousand and from +2.2 per thousand to +3.9 per thousand, respectively. At Cauquenes the 34S enrichment in the saturated zone toward depth indicates the increasing contribution of isotopically heavy dissolved sulfate from primary anhydrite (approximately +10.9 per thousand). At El Salvador No. 1, the delta34S(SO4) average value is -0.9 per thousand, suggesting dissolution of supergene sulfate minerals (jarosite, alunite, gypsum

  1. Using stable isotopes of water and strontium to investigate the hydrology of a natural and a constructed wetland

    SciTech Connect

    Hunt, R.J.; Krabbenhoft, D.P.; Bullen, T.D.; Kendall, C.

    1998-05-01

    Wetlands cannot exist without water, but wetland hydrology is difficult to characterize. In this study, water sources and mass transfer processes in a natural and constructed wetland complex were investigated using isotopes of water and strontium. Water isotope profiles in the saturated zone revealed that the natural wetland and one site in the constructed wetland were primarily fed by ground water; profiles in another constructed wetland site showed recent rain was the predominant source of water in the root zone. Water isotopes in the capillary fringe indicated that the residence time for rain is less in the natural wetland than in the constructed wetland, thus transpiration (an important water sink) was greater in the natural wetland. Strontium isotopes showed a systematic difference between the natural and constructed wetlands that the authors attribute to the presence or absence of peat. In the peat-rich natural wetland, {delta}{sup 87}Sr in the pore water increased along the flowline due to preferential weathering of minerals containing radiogenic Sr in response to elevated Fe concentrations in the water. In the constructed wetland, where peak thickness was thin and Fe concentrations in water were negligible, {delta}{sup 87}Sr did not increase along the flowline. The source of the pea (on-site or off-site derived) applied in the constructed wetland controlled the {delta}{sup 87}Sr at the top of the profile, but the effects were restricted by strong cation exchange in the underlying fluvial sediments. Based on the results of this study, neither constructed wetland site duplicated the water source and weathering environment of the adjoining natural wetland. Moreover, stable isotopes were shown to be effective tools for investigating wetlands and gaining insight not easily obtained using non-isotopic techniques. These tools have potential widespread application to wetlands that have distinct isotopic endmember sources.

  2. Using stable isotopes of water and strontium to investigate the hydrology of a natural and a constructed wetland

    USGS Publications Warehouse

    Hunt, R.J.; Bullen, T.D.; Krabbenhoft, D.P.; Kendall, C.

    1998-01-01

    Wetlands cannot exist without water, but wetland hydrology is difficult to characterize. As a result, compensatory wetland mitigation often only assumes the proper hydrology has been created. In this study, water sources and mass transfer processes in a natural and constructed wetland complex were investigated using isotopes of water and strontium. Water isotope profiles in the saturated zone revealed that the natural wetland and one site in the constructed wetland were primarily fed by ground water; profiles in another constructed wetland site showed recent rain was the predominant source of water in the root zone. Water isotopes in the capillary fringe indicated that the residence time for rain is less in the natural wetland than in the constructed wetland, thus transpiration (an important water sink) was greater in the natural wetland. Strontium isotopes showed a systematic difference between the natural and constructed wetlands that we attribute to the presence or absence of peat. In the peat-rich natural wetland, ??87Sr in the pore water increased along the flowline due to preferential weathering of minerals containing radiogenic Sr in response to elevated Fe concentrations in the water. In the constructed wetland, where peat thickness was thin and Fe concentrations in water were negligible, ??87Sr did not increase along the flowline. The source of the peat (on-site or off-site derived) applied in the constructed wetland controlled the ??87Sr at the top of the profile, but the effects were restricted by strong cation exchange in the underlying fluvial sediments. Based on the results of this study, neither constructed wetland site duplicated the water source and weathering environment of the adjoining natural wetland. Moreover, stable isotopes were shown to be effective tools for investigating wetlands and gaining insight not easily obtained using non-isotopic techniques. These tools have potential widespread application to wetlands that have distinct isotopic

  3. Soil-water dynamics and tree water uptake in the Sacramento Mountains of New Mexico (USA): a stable isotope study

    NASA Astrophysics Data System (ADS)

    Gierke, Casey; Newton, B. Talon; Phillips, Fred M.

    2016-04-01

    In the southwestern United States, precipitation in the high mountains is a primary source of groundwater recharge. Precipitation patterns, soil properties and vegetation largely control the rate and timing of groundwater recharge. The interactions between climate, soil and mountain vegetation thus have important implications for the groundwater supply. This study took place in the Sacramento Mountains, which is the recharge area for multiple regional aquifers in southern New Mexico. The stable isotopes of oxygen and hydrogen were used to determine whether infiltration of precipitation is homogeneously distributed in the soil or whether it is partitioned among soil-water `compartments', from which trees extract water for transpiration as a function of the season. The results indicate that "immobile" or "slow" soil water, which is derived primarily from snowmelt, infiltrates soils in a relatively uniform fashion, filling small pores in the shallow soils. "Mobile" or "fast" soil water, which is mostly associated with summer thunderstorms, infiltrates very quickly through macropores and along preferential flow paths, evading evaporative loss. It was found that throughout the entire year, trees principally use immobile water derived from snowmelt mixed to differing degrees with seasonally available mobile-water sources. The replenishment of these different water pools in soils appears to depend on initial soil-water content, the manner in which the water was introduced to the soil (snowmelt versus intense thunderstorms), and the seasonal variability of the precipitation and evapotranspiration. These results have important implications for the effect of climate change on recharge mechanisms in the Sacramento Mountains.

  4. Soil-water dynamics and tree water uptake in the Sacramento Mountains of New Mexico (USA): a stable isotope study

    NASA Astrophysics Data System (ADS)

    Gierke, Casey; Newton, B. Talon; Phillips, Fred M.

    2016-06-01

    In the southwestern United States, precipitation in the high mountains is a primary source of groundwater recharge. Precipitation patterns, soil properties and vegetation largely control the rate and timing of groundwater recharge. The interactions between climate, soil and mountain vegetation thus have important implications for the groundwater supply. This study took place in the Sacramento Mountains, which is the recharge area for multiple regional aquifers in southern New Mexico. The stable isotopes of oxygen and hydrogen were used to determine whether infiltration of precipitation is homogeneously distributed in the soil or whether it is partitioned among soil-water `compartments', from which trees extract water for transpiration as a function of the season. The results indicate that "immobile" or "slow" soil water, which is derived primarily from snowmelt, infiltrates soils in a relatively uniform fashion, filling small pores in the shallow soils. "Mobile" or "fast" soil water, which is mostly associated with summer thunderstorms, infiltrates very quickly through macropores and along preferential flow paths, evading evaporative loss. It was found that throughout the entire year, trees principally use immobile water derived from snowmelt mixed to differing degrees with seasonally available mobile-water sources. The replenishment of these different water pools in soils appears to depend on initial soil-water content, the manner in which the water was introduced to the soil (snowmelt versus intense thunderstorms), and the seasonal variability of the precipitation and evapotranspiration. These results have important implications for the effect of climate change on recharge mechanisms in the Sacramento Mountains.

  5. Identifying Controls on the Stable Water Isotope Composition of Precipitation in the Southwestern Yukon Using GCMs

    NASA Astrophysics Data System (ADS)

    Field, R.; Moore, K.

    2007-12-01

    The goal of our work is to better understand what controls the stable water isotope (SWI) composition of precipitation in the southwestern Yukon, and in particular, to better-interpret the SWI signal from the Mount Logan ice core. To this end, we are conducting experiments with the GISS ModelE general circulation model, which is equipped with SWI diagnostics. One feature of interest in the Mt. Logan ice core record is a significant drop in d18O in the 1850's towards more depleted values. The current explanation for this shift is a transition in the North Pacific circulation towards a deeper Aleutian Low, with the stronger meridional flow bringing moisture from more southerly sources. Because of their greater arrival times, these air masses would have undergone a greater isotopic depletion than moisture from closer, colder sources under a more zonal flow regime. Although physically plausible, it is possible that the d18O drop caused by this proposed shift in circulation might be offset by warmer source evaporation conditions and integrated air mass trajectories, both of which would be associated with less depleted precipitation. To test the physical plausibility of the meridional hypothesis, we conducted numerical experiments with the NASA GISS ModelE isotopically-equipped general circulation model. In the Yukon, SWI variability is influenced, via the regional temperature, by the Pacific North America pattern and ENSO. We found that positive d18O anomalies in the SW Yukon region were in fact associated with a deeper Aleutian Low; it would appear that the effect of a longer transit time is offset by a warmer moisture transport pathway, in disagreement with the current moisture shift explanation. Our results are in agreement, however, with recent tree-ring reconstructions of the North Pacific Index, which suggest an 1850's shift towards a weaker Aleutian Low. We also found that the degree of Pacific control on the SW Yukon isotope signal is highly dependant on

  6. Stable water isotope simulation by current land-surface schemes: Results of iPILPS Phase 1

    NASA Astrophysics Data System (ADS)

    Henderson-Sellers, A.; Fischer, M.; Aleinov, I.; McGuffie, K.; Riley, W. J.; Schmidt, G. A.; Sturm, K.; Yoshimura, K.; Irannejad, P.

    2006-05-01

    Phase 1 of isotopes in the Project for Intercomparison of Land-surface Parameterization Schemes (iPILPS) compares the simulation of two stable water isotopologues ( 1H 218O and 1H 2H 16O) at the land-atmosphere interface. The simulations are offline, with forcing from an isotopically enabled regional model for three locations selected to offer contrasting climates and ecotypes: an evergreen tropical forest, a sclerophyll eucalypt forest and a mixed deciduous wood. Here, we report on the experimental framework, the quality control undertaken on the simulation results and the method of intercomparisons employed. The small number of available isotopically enabled land-surface schemes (ILSSs) limits the drawing of strong conclusions, but, despite this, there is shown to be benefit in undertaking this type of isotopic intercomparison. Although validation of isotopic simulations at the land surface must await more and much more complete, observational campaigns, we find that the empirically based Craig-Gordon parameterization (of isotopic fractionation during evaporation) gives adequately realistic isotopic simulations when incorporated in a wide range of land-surface codes. By introducing two new tools for understanding isotopic variability from the land surface, the isotope transfer function and the iPILPS plot, we show that different hydrological parameterizations cause very different isotopic responses. We show that ILSS-simulated isotopic equilibrium is independent of the total water and energy budget (with respect to both equilibration time and state), but interestingly the partitioning of available energy and water is a function of the models' complexity.

  7. Mesozooplankton stable isotope composition in Cyprus coastal waters and comparison with the Aegean Sea (eastern Mediterranean)

    NASA Astrophysics Data System (ADS)

    Hannides, Cecelia C. S.; Zervoudaki, Soultana; Frangoulis, Constantin; Lange, Manfred A.

    2015-03-01

    Here we use bulk and amino acid-specific stable nitrogen (N) isotope analysis (AA-CSIA) to evaluate seasonal and regional change in mesozooplankton dynamics for the first time in coastal waters of the eastern Mediterranean. Cyprus mesozooplankton δ15N values were significantly higher in late winter (2.3‰) than in summer (1.2‰), and in all cases were less than the δ15N values of mesozooplankton in the northeast Aegean Sea (NEA; 3.4‰). AA-CSIA indicates that these differences can primarily be attributed to seasonal and regional change in mesozooplankton community trophic structure, with overall trophic position increasing by 0.2-0.3 in winter as compared to summer around Cyprus, and trophic position higher in the NEA than in Cyprus by 0.3-0.6. Such differences are most likely related to the larger contribution of carnivorous mesozooplankton observed in winter around Cyprus and in the NEA. Overall, our findings indicate change in bulk mesozooplankton δ15N value in the eastern Mediterranean is primarily driven by change in community trophic position, rather than variability in δ15N value at the base of the food web.

  8. Interaction of a river with an alluvial basin aquifer: Stable isotopes, salinity and water budgets

    NASA Astrophysics Data System (ADS)

    Eastoe, Christopher J.; Hutchison, William R.; Hibbs, Barry J.; Hawley, John; Hogan, James F.

    2010-12-01

    SummaryDetailed sets of tracer data (isotopes, salinity) and the results of MODFLOW modeling of water budgets provide an unprecedented opportunity for comparing modeling with field data in the area where the Rio Grande enters the Hueco Bolson basin of Texas and Chihuahua. Water from the Rio Grande has recharged the Hueco Bolson aquifer to a depth of 300 m below the surface in the El Paso-Ciudad Juárez area, the depth of infiltration corresponding to the depth of ancestral Rio Grande fluvial sediments. Groundwater beneath the river exhibits complex isotope and salinity stratification. Post-dam (post -1916, type A) river water has infiltrated to depths up to 80 m. Pre-dam (type B) river water has infiltrated to 300 m depth near downtown El Paso, and has mixed with, or been displaced further downstream by high-salinity native Hueco Bolson groundwater (type C, present in the basin north of the river). Salinity and isotope boundaries do not correspond precisely. Isotope stratification corresponds to water residence time and (for type C) to degree of evaporation; the highest salinities are associated with the most evaporated water. Modeling of water budgets in the basin fill beneath the river predicts present-day mixing of water types B and C where changing rates of pumping have caused a reversal of groundwater flow direction between El Paso and Ciudad Juárez, and deep recharge of type B water under conditions prevailing in the 1960s.

  9. Effects of Mild Water Stress and Diurnal Changes in Temperature and Humidity on the Stable Oxygen and Hydrogen Isotopic Composition of Leaf Water in Cornus stolonifera L. 1

    PubMed Central

    Flanagan, Lawrence B.; Ehleringer, James R.

    1991-01-01

    In this paper we make comparisons between the observed stable isotopic composition of leaf water and the predictions of the Craig-Gordon model of isotopic enrichment when plants (Cornus stolonifera L.) were exposed to natural, diurnal changes in temperature and humidity in a glasshouse. In addition, we determined the effects of mild water stress on the isotopic composition of leaf water. The model predicted different patterns of diurnal change for the oxygen and hydrogen isotopic composition of leaf water. The observed leaf water isotopic composition followed qualitatively similar patterns of diurnal change to those predicted by the model. At midday, however, the model always predicted a higher degree of heavy isotope enrichment than was actually observed in leaves. There was no effect of mild water stress on the hydrogen isotopic composition of leaf water. For the oxygen isotopic composition of leaf water, there was either no significant difference between control and water-stressed plants or the stressed plants had lower δ18O values, despite the enriched stem water isotopic composition observed for the stressed plants. PMID:16668385

  10. Monitoring water stable isotope composition in soils using gas-permeable tubing and infrared laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Rothfuss, Youri; Vereecken, Harry; Brüggemann, Nicolas

    2013-04-01

    The water stable isotopologues 1H2H16O and 1H218O are powerful tracers of processes occurring in nature. Their slightly different masses as compared to the most abundant water isotopologue (1H216O) affect their thermodynamic (e.g. during chemical equilibrium reactions or physical phase transitions with equilibration) and kinetic (liquid and vapor phases transport processes and chemical reactions without equilibration) properties. This results in measurable differences of the isotopic composition of water within or between the different terrestrial ecosystem compartments (i.e. sub-soil, soil, surface waters, plant, and atmosphere). These differences can help addressing a number of issues, among them water balance closure and flux partitioning from the soil-plant-atmosphere continuum at the field to regional scales. In soils particularly, the isotopic composition of water (δ2H and δ18O) provides qualitative information about whether water has only infiltrated or already been re-evaporated since the last rainfall event or about the location of the evaporation front. From water stable isotope composition profiles measured in soils, it is also possible, under certain hypotheses, to derive quantitative information such as soil evaporation flux and the identification of root water uptake depths. In addition, water stable isotopologues have been well implemented into physically based Soil-Vegetation-Atmosphere Transfer models (e.g. SiSPAT-Isotope; Soil-Litter iso; TOUGHREACT) and have demonstrated their potential. However, the main disadvantage of the isotope methodology is that, contrary to other soil state variables that can be monitored over long time periods, δ2H and δ18O are typically analyzed following destructive sampling. Here, we present a non-destructive method for monitoring soil liquid water δ2H and δ18O over a wide range of water availability conditions and temperatures by sampling and measuring water vapor equilibrated with soil water using gas

  11. Comparison of Modeled and Observed Environmental Influences on the Stable Oxygen and Hydrogen Isotope Composition of Leaf Water in Phaseolus vulgaris L. 1

    PubMed Central

    Flanagan, Lawrence B.; Comstock, Jonathan P.; Ehleringer, James R.

    1991-01-01

    In this paper we describe how a model of stable isotope fractionation processes, originally developed by H. Craig and L. I. Gordon ([1965] in E Tongiorgi, ed, Proceedings of a Conference on Stable Isotopes in Oceanographic Studies and Paleotemperature, Spoleto, Italy, pp 9-130) for evaporation of water from the ocean, can be applied to leaf transpiration. The original model was modified to account for turbulent conditions in the leaf boundary layer. Experiments were conducted to test the factors influencing the stable isotopic composition of leaf water under controlled environment conditions. At steady state, the observed leaf water isotopic composition was enriched above that of stem water with the extent of the enrichment dependent on the leaf-air vapor pressure difference (VPD) and the isotopic composition of atmospheric water vapor (AWV). The higher the VPD, the larger was the observed heavy isotope content of leaf water. At a constant VPD, leaf water was relatively depleted in heavy isotopes when exposed to AWV with a low heavy isotope composition, and leaf water was relatively enriched in heavy isotopes when exposed to AWV with a large heavy isotope composition. However, the observed heavy isotope composition of leaf water was always less than that predicted by the model. The extent of the discrepancy between the modeled and observed leaf water isotopic composition was a strong linear function of the leaf transpiration rate. PMID:16668226

  12. Long Term and High Frequency Non-Destructive Monitoring of Soil Water Stable Isotope Compositions in the Laboratory

    NASA Astrophysics Data System (ADS)

    Rothfuss, Y.; Merz, S.; Pohlmeier, A. J.; Vereecken, H.; Brueggemann, N.

    2014-12-01

    The fate and dynamics of water stable isotopologues (1H2H16O and 1H218O) are currently well implemented into physically based Soil-Vegetation-Atmosphere Transfer (SVAT) models (e.g. Hydrus 1D, SiSPAT-I, Soil-Litter iso, TOUGHREACT). However, contrary to other state variables (e.g., water content and tension) that can be monitored over long periods (e.g., by time-domain reflectometry, capacitive sensing, tensiometry or micro-psychrometry), water stable isotope compositions (δ2H and δ18O) are analyzed following destructive sampling, and thus are available only at a given time. Thus, there are important discrepancies in time resolution between soil water and stable isotope information which greatly limit the insight potential of the latter. Recently however, a technique based on direct infrared laser absorption spectroscopy was developed that allows simultaneous and direct measurements of δ2H and δ18O in water vapor. Here, we present a non-destructive method for monitoring soil liquid δ2H and δ18O by sampling and measuring water vapor equilibrated with soil water using gas-permeable polypropylene tubing and a Cavity Ring-Down laser Spectrometer (CRDS). An acrylic glass column (d=11 cm, h=60 cm) was (i) equipped with temperature and soil water probes in addition to gas-permeable tubing sections at eight different depths, (ii) filled with pure quartz sand, (iii) saturated from the bottom, and (iv) installed on weighing balances and let dry for 250 days. Each day, soil vapor δ2H and δ18O were measured for each depth by purging the soil water vapor sampled in the tubing sections with dry air and analyzing it with a CRDS. Soil liquid water δ2H and δ18O were then inferred from the values measured in the vapor. The experimental setup allowed following the evolution of the soil water δ2H and δ18O profile, which developed as a result of isotope convective capillary rise and back-diffusion of the stable isotope excess at the soil surface due to fractionating soil

  13. Chemical and stable-radiogenic isotope compositions of Polatlı-Haymana thermal waters (Ankara, Turkey)

    NASA Astrophysics Data System (ADS)

    Akilli, Hafize; Mutlu, Halim

    2016-04-01

    Complex tectono-magmatic evolution of the Anatolian land resulted in development of numerous geothermal areas through Turkey. The Ankara region in central Anatolia is surrounded by several basins which are filled with upper Cretaceous-Tertiary sediments. Overlying Miocene volcanics and step faulting along the margins of these basins played a significant role in formation of a number of low-enthalpy thermal waters. In this study, chemical and isotopic compositions of Polatlı and Haymana geothermal waters in the Ankara region are investigated. The Polatlı-Haymana waters with a temperature range of 24 to 43 °C are represented by Ca-(Na)-HCO3 composition implying derivation from carbonate type reservoir rocks. Oxygen-hydrogen isotope values of the waters are conformable with the Global Meteoric Water Line and point to a meteoric origin. The carbon isotopic composition in dissolved inorganic carbon (DIC) of the studied waters is between -21.8 and -1.34 permil (vs. VPDB). Marine carbonates and organic rocks are the main sources of carbon. There is a high correlation between oxygen (3.7 to 15.0 permil; VSMOW) and sulfur (-9.2 to 19.5 permil; VCDT) isotope compositions of sulfate in waters. The mixing of sulfate from dissolution of marine carbonates and terrestrial evaporite units is the chief process behind the observed sulfate isotope systematics of the samples. 87Sr/86Sr ratios of waters varying from 0.705883 to 0.707827 are consistent with those of reservoir rocks. The temperatures calculated by SO4-H2O isotope geothermometry are between 81 and 138 °C nearly doubling the estimates from chemical geothermometers.

  14. Groundwater Ages and Stable Isotope Fingerprints of Contaminated Water to Examine Potential Solute Sources at a Uranium Processing Mill

    NASA Astrophysics Data System (ADS)

    Hurst, T. G.; Solomon, D. K.

    2007-12-01

    To evaluate sources of high solute concentrations in groundwater near a uranium processing facility, groundwater recharge dates are correlated to specific solute concentrations and depth in the water column. Stable isotopes are also used as potential fingerprints of water sourced from mill tailing cells. Passive diffusion samplers, to be analyzed for 3He/4He ratio, were deployed in 15 different wells with samplers at two depths in the saturated interval. Low-flow purging and sampling was then conducted to isolate sampling points at different depths in the wells, with sampling at multiple depths being completed in 4 of the 15 wells sampled. Laboratory analyses were conducted for CFC recharge age, as well as T/3He recharge age. Contract laboratories analyzed for: deuterium and oxygen-18 isotopes of water; sulfur-34 and oxygen-18 isotopes of sulfate; trace metals uranium, manganese, and selenium; and nitrate and sulfate. Analysis for 235U/238U isotope ratios will be conducted to further identify fingerprint signals of source water. Groundwater recharge ages determined using CFC analysis show some vertical stratification in ages across the water column. Upon initial data processing and analysis, measured CFC ages ranged from 30 to 40 years within the water column of one well to only several years difference in another well. Additional results for trace metal concentrations, stable isotope ratios, and T/3He recharge ages will be reported when results are received. Further post-processing of CFC laboratory analysis and noble gas analyses will provide greater clarity as to groundwater ages within the aquifer and, combined with field pumping data, will allow for a comprehensive groundwater model to be constructed. This study provides great insight to potential mine tailings leakage problems and using isotopes and groundwater age dating techniques as a means of tracing contaminated groundwater to the leakage source. Utilizing stable isotopes of water and sulfate, combined

  15. A profound meteoric water influence on genesis in the Permian Waterberg Coalfield, South Africa: Evidence from stable isotopes

    SciTech Connect

    Faure, K.; Harris, C.; Willis, J.P.

    1995-10-02

    The coal, carbonaceous mudrock, and mudrock of the Grootegeluk Formation of the Waterberg Coalfield contain calcite, ankerite, and siderite. The aim of this paper is to use the stable isotope ratios of these minerals to determine the depositional environment of the host rock and the evolution of pore water with burial. In addition, calcite lenses, which are discrete, conformable layers between mudrock and coal seams in the Grootegeluk Formation, allow estimation of the oxygen isotope ratios of ambient meteoric water during diagenesis of the Waterberg Coalfield. Limits on the maximum temperature of formation can be estimated from vitrinite reflectance data of the organic material in the coal and carbonaceous mudrock units. One of the carbonate minerals present in the Grootegeluk Formation is siderite, which does not undergo recrystallization and reequilibration under normal diagenetic conditions. For this reason, the elemental and stable isotope composition of siderite is considered to reflect the sources of carbon and the origin of water and temperature in siderite formation (Mozley 1989; Mozley and Wersin 1992). The carbonates in the Waterberg Coalfield are present in both coal and organic-poor mudrock, thus permitting a comparison of the stable isotope variations of carbonates in these two rock formations.

  16. Using stable isotopes to determine sources of evaporated water to the atmosphere in the Amazon basin

    NASA Astrophysics Data System (ADS)

    Martinelli, Luiz Antonio; Victoria, Reynaldo Luiz; Silveira Lobo Sternberg, Leonel; Ribeiro, Aristides; Zacharias Moreira, Marcelo

    1996-09-01

    The return of water in vapor form from the land to the atmosphere, via plant transpiration and evaporation, is fundamental for the maintenance of the regional water cycle in the Amazon basin. Whereas transpiration, the dominant process, has the extensive vegetation cover as a large single source, evaporation can have several sources, and their relative importance and location are poorly known. The isotopic composition (δ 18O and δD) of water from various sources was used to see whether or not specific sources of water vapor to the atmosphere could be determined. It is well established that natural waters fall on a line called the meteoric water line (MWL; the regression of δ 18O × δD), with slope equal to eight and an intercept equal to ten. When a water body loses water via evaporation the slope become smaller than eight, typically 5-6. We estimated the slope of the regression of δ 18O × δD for several potential sources. We analyzed 1273 samples: 500 of rainfall, 409 of river water, 134 of lake water, 164 of soil water, 40 of throughfall and stemflow water, and 26 of shallow ground-water. We found that large rivers and lakes are likely contributors of evaporated water to the atmosphere. However, as they cover only a small area of the basin, other sources are needed. Probably, evaporated water originates from several small sources that were not detected by the isotopic composition of our data.

  17. Intra-annual water store and stable isotope dynamics for Himalayan basins of Nepal

    NASA Astrophysics Data System (ADS)

    Hannah, D. M.; Fairchild, I. J.; Boomer, I.; Pokhrel, A.; Kansakar, S. R.

    2009-04-01

    Isotope-based hydrograph separations are applied commonly to reveal the sources, mixing-ratios and timing of river flow and so evaluate runoff generation mechanisms. In this context, rivers draining the Himalayas have received limited attention despite their high sensitivity to climate change and their importance for regional and global water budgets and biogeochemical cycles. Seasonal variation in river water isotope compositions is not well documented for this high mountain region. Hence, this research aims to determine the nature and dynamics of water store contributions to river flow for Himalayan basins of Nepal over a hydrological year by undertaking a study of ^18O and ^D variation in river water and rainfall for two sub-basins of the Trishuli river with contrasting hydrology: (a) glacierized Langtang Khola and (b) rain-fed Phalankhu Khola. Weekly water samples were taken from April 2004-March 2005 at 4 river sites (in each sub-basin and above and below their confluences) and from two aggregate rainfall collectors. Sampling locations were paired with river and precipitation gauges. Isotopic data yield tight and internally consistent arrays that facilitate interpretation in relation to rainfall amount and isotopic composition, and river discharge data, and thus quantification of changing water store contributions (i.e. rainfall including summer monsoon, snow- and ice-melt, and groundwater), over the hydrological year, and between basins. This research provides a key baseline study during the current period of Himalayan glacier recession.

  18. Spatial, seasonal, and source variability in the stable oxygen and hydrogen isotopic composition of tap waters throughout the USA

    USGS Publications Warehouse

    Landwehr, Jurate M.; Coplen, Tyler B.; Stewart, David W.

    2013-01-01

    To assess spatial, seasonal, and source variability in stable isotopic composition of human drinking waters throughout the entire USA, we have constructed a database of δ18O and δ2H of US tap waters. An additional purpose was to create a publicly available dataset useful for evaluating the forensic applicability of these isotopes for human tissue source geolocation. Samples were obtained at 349 sites, from diverse population centres, grouped by surface hydrologic units for regional comparisons. Samples were taken concurrently during two contrasting seasons, summer and winter. Source supply (surface, groundwater, mixed, and cistern) and system (public and private) types were noted. The isotopic composition of tap waters exhibits large spatial and regional variation within each season as well as significant at-site differences between seasons at many locations, consistent with patterns found in environmental (river and precipitation) waters deriving from hydrologic processes influenced by geographic factors. However, anthropogenic factors, such as the population of a tap’s surrounding community and local availability from diverse sources, also influence the isotopic composition of tap waters. Even within a locale as small as a single metropolitan area, tap waters with greatly differing isotopic compositions can be found, so that tap water within a region may not exhibit the spatial or temporal coherence predicted for environmental water. Such heterogeneities can be confounding factors when attempting forensic inference of source water location, and they underscore the necessity of measurements, not just predictions, with which to characterize the isotopic composition of regional tap waters. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

  19. High frequency sampling of stable water isotopes for assessing runoff generation processes in a mesoscale urbanized catchment

    NASA Astrophysics Data System (ADS)

    Wrede, Sebastian; Fenicia, Fabrizio; Kurtenbach, Andreas; Keßler, Sabine; Bierl, Reinhard

    2013-04-01

    Experimental hydrology critically relies on tracer techniques to decipher and uncover runoff generation processes. Although tracer measurements contributed significantly to a better understanding of catchment functioning, their potential is not yet fully exploited. The temporal resolution of tracer measurements is typically relatively coarse, and applications are confined to a few locations. Additionally, experimental hydrology has focused primarily on pristine catchments, and the influence of anthropogenic effects remains largely unexplored. High frequency sampling of multiple tracers may therefore substantially enhance our understanding of hydrological processes and the impact of anthropogenic effects and enable a better protection and management of water resources and water quality. In this preliminary study we aim to assess runoff generation processes using geochemical and isotopic tracer techniques in the mesoscale Olewiger Bach catchment (24 km²) that is located in the low mountain ranges of the city of Trier, southwest Germany. The catchment is mainly characterized by quartzite and Devonian schist, overlain by fluvial sediments. Mixed land use prevails in the southern part of the basin, while the northern lower reaches are mainly urbanized. Several waste water treatment plants, separate sewer and stormwater management systems are present in parts of the catchment and contribute to the discharge of the main river. Tracer techniques employed in this ongoing study are twofold. A long term sampling of stable water isotopes (oxygen-18 and deuterium) was initiated in order to allow inferences about mean residence times of water in different catchment compartments, while event-based sampling using a multi-tracer approach was used to identify different runoff components and associated water pathways. Special attention is given to the observation of in-channel processes by assessing the dynamics of dissolved and particulate geochemical tracers and stable water

  20. Can stable isotopes ride out the storms? The role of convection for water isotopes in models, records, and paleoaltimetry studies in the central Andes

    NASA Astrophysics Data System (ADS)

    Rohrmann, Alexander; Strecker, Manfred R.; Bookhagen, Bodo; Mulch, Andreas; Sachse, Dirk; Pingel, Heiko; Alonso, Ricardo N.; Schildgen, Taylor F.; Montero, Carolina

    2014-12-01

    Globally, changes in stable isotope ratios of oxygen and hydrogen (δ 18O and δ D ) in the meteoric water cycle result from distillation and evaporation processes. Isotope fractionation occurs when air masses rise in elevation, cool, and reduce their water-vapor holding capacity with decreasing temperature. As such, δ 18O and δ D values from a variety of sedimentary archives are often used to reconstruct changes in continental paleohydrology as well as paleoaltimetry of mountain ranges. Based on 234 stream-water samples, we demonstrate that areas experiencing deep convective storms in the eastern south-central Andes (22-28° S) do not show the commonly observed relationship between δ 18O and δ D with elevation. These convective storms arise from intermontane basins, where diurnal heating forces warm air masses upward, resulting in cloudbursts and raindrop evaporation. Especially at the boundary between the tropical and extra-tropical atmospheric circulation regimes where deep-convective storms are very common (∼26° to 32° N and S), the impact of such storms may yield non-systematic stable isotope-elevation relationships as convection dominates over adiabatic lifting of air masses. Because convective storms can reduce or mask the depletion of heavy isotopes in precipitation as a function of elevation, linking modern or past topography to patterns of stable isotope proxy records can be compromised in mountainous regions, and atmospheric circulation models attempting to predict stable isotope patterns must have sufficiently high spatial resolution to capture the fractionation dynamics of convective cells.

  1. Processes governing the stable isotope composition of water in the St. Lawrence river system, Canada.

    PubMed

    Rosa, Eric; Hillaire-Marcel, Claude; Hélie, Jean-François; Myre, Alexandre

    2016-01-01

    Linkages between δ(18)O-δ(2)H and hydrological processes have been investigated from isotopic time series recorded in the St. Lawrence River basin. Three stations were monitored from 1997 to 2008. They include the Ottawa River, the St. Lawrence River main channel at Montreal and the fluvial estuary. All sites depict seasonal isotopic cycles characterized by heavy isotope depletions during the snowmelt period and heavy isotope enrichments throughout the ice-free period. The data define δ(2)H-δ(18)O regression lines falling below the meteoric water line. In the Ottawa River, calculations suggest that approximately 8 % of the total inflow to the basin is lost through evaporation. In the St. Lawrence River main channel, seasonal isotopic fluctuations most likely reflect hydrological processes occurring within the Great Lakes and mixing with tributaries located downstream. In the St. Lawrence River fluvial estuary, isotopic data allow partitioning streamflow components and suggest that the recorded seasonal variations mainly respond to mixing processes. PMID:26963148

  2. Utilizing Present-Day Stable Water Isotopes to Improve Paleoclimate Records from the Southeast (USA)

    NASA Astrophysics Data System (ADS)

    McKay, K. K.; Lambert, W. J.

    2015-12-01

    Present-day water isotope data are used to help interpret climate (paleo-rainfall) proxies archived in the geologic record, which can then aid in the creation of General Circulation Models (GCM). The Southeast (USA) is under-represented with respect to present-day measurement of water isotopes and high-resolution paleoclimate records, thus GCMs must extrapolate data for the region. We will evaluate water isotope data (δ18O, δD) collected and analyzed at The University of Alabama (33°13'N, 87°33'W) since June 2005. The monitoring station, central to the Southeast, was established to provide long-term water isotope data needed for reconstructing paleo-rainfall records of the region. Proxy data (e.g., δ18Ocalcite) archived in speleothems have been demonstrated to provide trustworthy information about past climate conditions; however, present-day monitoring of both local rainfall and cave dripwater are crucial. The decade-long (June 2005 - May 2015) rainfall record allows for the establishment of the relationship between water isotopes (δ18O, δD) and monthly air temperature, rainfall amount, as well as the general differences between summer and winter rainfall. Dripwater from Cathedral Caverns (34°34'N, 86°13'W), located in northeastern Alabama, has been sampled at a monthly resolution since January 2015 to determine if the water chemistry in the cave represents an annual mean for the rainfall or if it is seasonally biased. The ultimate goal of this study is to better understand how atmospheric air currents (specifically the strength/position of the Polar Jet Stream, PJS), and hence rainfall in the Southeast, varied during past periods of relative warming (e.g., Dansgaard-Oeschger events) and cooling (e.g., Heinrich events) of the Northern Hemisphere atmosphere. Future GCMs will be improved if a reliable high-resolution paleo-rainfall record can be produced for the Southeast.

  3. Stable isotope composition of land snail body water and its relation to environmental waters and shell carbonate

    SciTech Connect

    Goodfriend, G.A.; Magaritz, M.; Gat, J.R. )

    1989-12-01

    Day-to-day and within-day (diel) variations in {delta}D and {delta}{sup 18}O of the body water of the land snail, Theba pisana, were studied at a site in the southern coastal plain of Israel. Three phases of variation, which relate to isotopic changes in atmospheric water vapor, were distinguished. The isotopic variations can be explained by isotopic equilibration with atmospheric water vapor and/or uptake of dew derived therefrom. During the winter, when the snails are active, there is only very minor enrichment in {sup 18}O relative to equilibrium with water vapor or dew, apparently as a result of metabolic activity. But this enrichment becomes pronounced after long periods of inactivity. Within-day variation in body water isotopic composition is minor on non-rain days. Shell carbonate is enriched in {sup 18}O by ca. 1-2% relative to equilibrium with body water. In most regions, the isotopic composition of atmospheric water vapor (or dew) is a direct function of that of rain. Because the isotopic composition of snail body water is related to that of atmospheric water vapor and the isotopic composition of shell carbonate in turn is related to that of body water, land snail shell carbonate {sup 18}O should provide a reliable indication of rainfall {sup 18}O. However, local environmental conditions and the ecological properties of the snail species must be taken into account.

  4. Investigating hydraulic connections and the origin of water in a mine tunnel using stable isotopes and hydrographs

    USGS Publications Warehouse

    Walton-Day, Katherine; Poeter, Eileen

    2009-01-01

    Turquoise Lake is a water-supply reservoir located north of the historic Sugarloaf Mining district near Leadville, Colorado, USA. Elevated water levels in the reservoir may increase flow of low-quality water from abandoned mine tunnels in the Sugarloaf District and degrade water quality downstream. The objective of this study was to understand the sources of water to Dinero mine drainage tunnel and evaluate whether or not there was a direct hydrologic connection between Dinero mine tunnel and Turquoise Lake from late 2002 to early 2008. This study utilized hydrograph data from nearby draining mine tunnels and the lake, and stable isotope (δ18O and δ2H) data from the lake, nearby draining mine tunnels, imported water, and springs to characterize water sources in the study area. Hydrograph results indicate that flow from the Dinero mine tunnel decreased 26% (2006) and 10% (2007) when lake elevation (above mean sea level) decreased below approximately 3004 m (approximately 9855 feet). Results of isotope analysis delineated two meteoric water lines in the study area. One line characterizes surface water and water imported to the study area from the western side of the Continental Divide. The other line characterizes groundwater including draining mine tunnels, springs, and seeps. Isotope mixing calculations indicate that water from Turquoise Lake or seasonal groundwater recharge from snowmelt represents approximately 10% or less of the water in Dinero mine tunnel. However, most of the water in Dinero mine tunnel is from deep groundwater having minimal isotopic variation. The asymmetric shape of the Dinero mine tunnel hydrograph may indicate that a limited mine pool exists behind a collapse in the tunnel and attenutates seasonal recharge. Alternatively, a conceptual model is presented (and supported with MODFLOW simulations) that is consistent with current and previous data collected in the study area, and illustrates how fluctuating lake levels change the local water

  5. Investigating hydraulic connections and the origin of water in a mine tunnel using stable isotopes and hydrographs

    USGS Publications Warehouse

    Walton-Day, K.; Poeter, E.

    2009-01-01

    Turquoise Lake is a water-supply reservoir located north of the historic Sugarloaf Mining district near Leadville, Colorado, USA. Elevated water levels in the reservoir may increase flow of low-quality water from abandoned mine tunnels in the Sugarloaf District and degrade water quality downstream. The objective of this study was to understand the sources of water to Dinero mine drainage tunnel and evaluate whether or not there was a direct hydrologic connection between Dinero mine tunnel and Turquoise Lake from late 2002 to early 2008. This study utilized hydrograph data from nearby draining mine tunnels and the lake, and stable isotope (??18O and ??2H) data from the lake, nearby draining mine tunnels, imported water, and springs to characterize water sources in the study area. Hydrograph results indicate that flow from the Dinero mine tunnel decreased 26% (2006) and 10% (2007) when lake elevation (above mean sea level) decreased below approximately 3004 m (approximately 9855 feet). Results of isotope analysis delineated two meteoric water lines in the study area. One line characterizes surface water and water imported to the study area from the western side of the Continental Divide. The other line characterizes groundwater including draining mine tunnels, springs, and seeps. Isotope mixing calculations indicate that water from Turquoise Lake or seasonal groundwater recharge from snowmelt represents approximately 10% or less of the water in Dinero mine tunnel. However, most of the water in Dinero mine tunnel is from deep groundwater having minimal isotopic variation. The asymmetric shape of the Dinero mine tunnel hydrograph may indicate that a limited mine pool exists behind a collapse in the tunnel and attenutates seasonal recharge. Alternatively, a conceptual model is presented (and supported with MODFLOW simulations) that is consistent with current and previous data collected in the study area, and illustrates how fluctuating lake levels change the local water

  6. Use of Stable Isotopes to Follow Intracellular Water Dynamics in Living Cells

    SciTech Connect

    Kreuzer, Helen W.; Hegg, Eric L.

    2012-01-28

    Despite the importance of water to cell structure and function, intracellular water dynamics are poorly understood. A new method based on isotope ratio measurements has revealed that a substantial portion of the O and H atoms in the intracellular water of rapidly-dividing cultured cells is derived from metabolic activity, and not from environmental water. These findings have led to a dynamic model of intracellular water composition: (1) Intracellular water is composed of water that diffuses in from the extracellular environment and water that is created as a result of metabolic activity. (2) The relative amounts of environmental and metabolic water inside a cell are a function of the cell's metabolic activity. (3) The oxygen and hydrogen isotope ratios of cellular metabolites are a function of those of intracellular water, and therefore reflect the metabolic activity of the cell at the time of biosynthesis. Data from gram-positive and gram-negative bacteria as well as cultured mammalian cells are consistent with the model.

  7. Water-Use Efficiency and Stable Carbon Isotopes: Accounting for Photosynthetic Refixation

    NASA Astrophysics Data System (ADS)

    Ubierna Lopez, N.; Marshall, J. D.

    2007-12-01

    Three processes are performed by every green plant tissue: photosynthesis, respiration and refixation. Each of these affects the ratio of stable isotopes, 12C and 13C. Refixation allows plants to fix a portion of the CO2 produced via respiration prior to releasing the remaining CO2 back into the atmosphere. The process begins with a pool of CO2 already depleted in 13C and subsequently depletes it further, resulting in two simultaneous effects: enrichment of CO2 released into the atmosphere and depletion of biomass that is formed. Recently, considerable research has concentrated on identifying processes that determine the isotopic composition of a given plant tissue. A convincing explanation for the observed enrichment of stems versus leaves has still not been derived. We advocate that refixation can explain currently inexplicable patterns. We hypothesized that leaves re-fix carbon during their entire lifespan when light intensity is below the light compensation point and above total darkness. We grew Idaho hybrid poplars under controlled conditions in a growth chamber. Light intensity was regulated to create three different treatments: (1) Light (PAR=270 μmol/m2s), (2) Shade (PAR=89 μmol/m2s) and (3) Dark (PAR=0 μmol/m2s). For each treatment we modified respiration values by regulating the light environment between total darkness and the light compensation point. For the light treatment group, leaf respired CO2 was collected at 5% (PAR=14) and 22% (PAR=59) of the light growing environment. For the shade treatment group, leaf respired CO2 was collected at 22% (PAR=20) of the light growing environment. We estimated the amount of refixation as (Ddark- Dlight)/Ddark, where Ddark represents dark respiration (μmol/gs) and Dlight respiration during light periods (μmol/gs). Light treatments plants exhibited a maximum refixation level of 53% at PAR=59, with an associated enrichment of leaf respired C isotopic composition (δ13CLR) of 3.3‰. At PAR=14, refixation rate

  8. A hydrogen gas-water equilibration method produces accurate and precise stable hydrogen isotope ratio measurements in nutrition studies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stable hydrogen isotope methodology is used in nutrition studies to measure growth, breast milk intake, and energy requirement. Isotope ratio MS is the best instrumentation to measure the stable hydrogen isotope ratios in physiological fluids. Conventional methods to convert physiological fluids to ...

  9. A soil water distillation technique using He-purging for stable isotope analysis

    NASA Astrophysics Data System (ADS)

    Ignatev, A.; Velivetckaia, T.; Sugimoto, A.; Ueta, A.

    2013-08-01

    A new method of soil water extraction for oxygen and hydrogen isotopic analysis has been developed; this method uses a helium flow system as an alternative to the conventional vacuum extraction method. The method significantly increases the efficiency of sample preparation and simplifies the extraction. During the water distillation, a helium carrier gas transfers water vaporized at 95 °C from the soil sample to a cold trap at liquid nitrogen temperature. An extraction time of 180 min is used to distill the water from the fine-grained soil completely. The proposed He-purging distillation technique makes it possible to distill approximately a dozen samples simultaneously. The method was tested using liquid water samples and clayey soil samples hydrated with water of known isotopic composition. The standard deviations for these tests were 0.08‰ for δ18O and 0.7‰ for δD. An intercomparison test was conducted for the helium and vacuum extraction methods using natural soil samples. The correlation coefficients between the methods were 0.9926 and 0.9939 for δD and δ18O, respectively. The proposed He-purging distillation method can achieve high precision for clayey soil samples with low water content and has the potential to provide adequate isotopic data in hydrological and ecological studies. The method is relatively fast, efficient, and inexpensive. We also recommend using the method to distill salt solutions (sea water, mineralized water) before determining the δD and δ18O values using a chromium or carbon reduction method to avoid “salt effects”.

  10. Study of mineral water resources from the Eastern Carpathians using stable isotopes.

    PubMed

    Magdas, Dana A; Cuna, Stela M; Berdea, Petre; Balas, Gabriela; Cuna, Cornel; Dordai, Edina; Falub, Mihaela C

    2009-08-30

    The Eastern Carpathians contain many mineral water springs that feed famous Romanian health resorts such as Borsec, Biborteni and Vatra Dornei. These waters have been used for their different therapeutic effects. In this work, mineral and spring waters from these Romanian regions were investigated by means of chemical and isotopic (deltaD and delta(18)O) analyses in order to understand the recharge mechanisms and also to determine their origins. Most of the investigated springs are of meteoric origin, having the average deuterium content of the local meteoric water. The higher (18)O content with respect to the Meteoric Water Line (MWL) indicated an exchange reaction with crystalline igneous rocks at depth and with other rocks that the water encounters on its journey back to the surface. PMID:19603457

  11. Refining Isotopic Parameterization Choices Using Stable Water Isotope Profiles In Surface Layer And Soil To Improve Modeling Of Mid-Latitude Continental Moisture Cycling

    NASA Astrophysics Data System (ADS)

    Kaushik, A.; Berkelhammer, M. B.; O'Neill, M.; Noone, D. C.

    2015-12-01

    The moisture balance of the continental boundary layer plays an important role in regulating the exchange of water and energy between the land surface and atmosphere. The surface layer moisture balance is controlled by a number of factors including precipitation, infiltration, evaporation and transpiration. Measurements of stable isotope ratios in water can be exploited to better understand the mechanisms controlling atmosphere-land surface water fluxes. We present three years of in situ tower-based measurements of stable isotope ratios of water (δD and δ18O) in vapor, precipitation, vegetation and soil from the Boulder Atmospheric Observatory, a semi-arid 300 meter tall-tower site in Erie, Colorado. Co-located meteorological and disdrometer measurements at the surface and 300m allow us to explore key aspects of continental moisture cycling in a semi-arid environment such as the important contribution of sub-surface vapor diffusion to the surface water vapor budget and its implications for partitioning in dry ecosystems, and the role of rain evaporation during precipitation events on inter-event and seasonal time scales. We use our observations to constrain a Craig-Gordon evaporation model at the land surface to weight the contributions of rainfall, surface water vapor exchange and sub-surface vapor diffusion to soil water isotope values. A multi-season in situ time series of surface vapor isotope profiles in conjunction with soil and precipitation allows us to field-validate choices for parameters such as the kinetic fractionation factor for each process. This has implications both for modeling short-term gas exchange at the land surface in modern-day climate models as well as for refining paleoclimate interpretations of stable oxygen and hydrogen isotope-based proxies. Tall-tower precipitation and vapor isotope profile data can also be analyzed in conjunction with disdrometer data on inter-event and seasonal time scales to quantify the role of rain evaporation

  12. Mesoscale Model Validation using Stable Water Isotopes: The isoWATFLOOD Model

    NASA Astrophysics Data System (ADS)

    Stadnyk, T.; Kouwen, N.; Edwards, T.; Gibson, J.; Pietroniro, A.

    2009-05-01

    A methodology to improve mesoscale model validation is developed by calibrating simulations of both water and isotope mass simultaneously. The isoWATFLOOD model simulates changes in oxygen-18 of streamflow and hydrological processes contributing to streamflow. The added constraint of simulated to measured delta oxygen-18 in streamflow lowers the models degrees of freedom and generates more physically-based model parameterizations. Modelled results are shown to effectively reduce and constrain errors associated with equifinality in streamflow generation, providing a practical new approach for the assessment of mesoscale modelling. The WATFLOOD model is a conceptually-based distributed hydrological model used for simulating streamflow on mesoscale watersheds. Given the model's intended application to mesoscale hydrology, it remains crucial to ensure conceptualizations are physically representative of the hydrologic cycle and the natural environment. Building upon the existing flowpath-separation module within WATFLOOD, the capability to simulate changes in oxygen-18 through each component of the hydrological cycle is introduced. Masses of heavy-isotope are computed for compartmental storages; compartmental flows transfer flux-weighted portions of isotope mass between storages; and mass outflows from each compartment simultaneously combine to form the resultant channel flow composition. Heavy-isotope compositions are enriched when storages undergo evaporation resulting from the loss of isotopically-depleted vapour described by the well-known Craig & Gordon isotopic fractionation model. The isoWATFLOOD model is forced by oxygen-18 in rain, oxygen-18 in snow, and relative humidity; and requires no additional parameterizations of WATFLOOD. The first mesoscale, continuous simulations of changes in oxygen-18 in streamflow are presented for the remote Fort Simpson basin in Northwest Territories, Canada and for the largely populated Grand River Basin in south western Ontario

  13. Palaeo-hydrogeology of the Cretaceous Sediments of the Williston Basin using Stable Isotopes of Water

    NASA Astrophysics Data System (ADS)

    Hendry, Michael J.; Barbour, S. Lee; Novakowski, Kent; Wassenaar, Len I.

    2013-04-01

    Hydraulic and isotopic data collected from aquifers are typically used to characterize hydrogeological conditions within sedimentary basins. Similar data from confining units are generally not collected despite their ability to provide insights into important water/solute transport controls. In this study, we characterized palaeo-groundwater flow and solute transport mechanisms across 384 m of a Cretaceous shale aquitard in the Williston Basin, Canada, using high-resolution depth profiles of water isotopes (δ18O and δ2H). Water samples were also collected from wells installed in the underlying regional aquifer (Mannville Fm; 93 m thick) and from seepage inflows into potash mine shafts (to 825 m below ground). 1-D numerical transport modeling of isotopic profiles yielded insight into large-scale/long-term solute transport in both Cretaceous sediments and the Basin. Molecular diffusion was determined to be the dominant solute transport mechanism through the aquitard. Transport model simulations suggest average vertical groundwater velocities of <0.05 m/10 ka and an average excess hydraulic head of <10 m. These values are less than anticipated by successive glaciations. The dominant palaeo-event reflected in present-day profiles is introduction during the Pleistocene of glaciogenic meteoric water to the aquifer underlying the aquitard, likely along an aquifer outcrop area east of the site or through local vertical conduits in the aquitard. Simulations suggest these recharge events occurred during one or more glacial periods. The isotopic profile over the upper 25 m of Pleistocene till and shale is consistent with glacial deposition and transport processes within these units during the Holocene (past 10 ka).

  14. Stable Carbon Isotope Evidence for Neolithic and Bronze Age Crop Water Management in the Eastern Mediterranean and Southwest Asia

    PubMed Central

    Wallace, Michael P.; Jones, Glynis; Charles, Michael; Fraser, Rebecca; Heaton, Tim H. E.; Bogaard, Amy

    2015-01-01

    In a large study on early crop water management, stable carbon isotope discrimination was determined for 275 charred grain samples from nine archaeological sites, dating primarily to the Neolithic and Bronze Age, from the Eastern Mediterranean and Western Asia. This has revealed that wheat (Triticum spp.) was regularly grown in wetter conditions than barley (Hordeum sp.), indicating systematic preferential treatment of wheat that may reflect a cultural preference for wheat over barley. Isotopic analysis of pulse crops (Lens culinaris, Pisum sativum and Vicia ervilia) indicates cultivation in highly varied water conditions at some sites, possibly as a result of opportunistic watering practices. The results have also provided evidence for local land-use and changing agricultural practices. PMID:26061494

  15. Stable Water Isotope Tracing and Model Evaluation in Large Basins: the `` Special Case'' of Semi-Arid Catchments

    NASA Astrophysics Data System (ADS)

    Henderson-Sellers, A.; Airey, P.; McGuffie, K.; Bradd, J.; Stone, D.

    2004-05-01

    The use of stable water isotopes in hydro-climate monitoring and modelling offers a new means of measuring and parameterizing critical processes. Here we review these specifically for the case of semi-arid basins where water resources are essential for potable supply and agriculture around the world. The verity and performance of existing models is examined using observations and simulations of stable water isotopes in rivers, aquifers and their precedent precipitations. Here we report on the Murray-Darling basin in Australia as one example of the `` special case'' of semi-arid catchments and use these data and results to examine evaluation and refinement of models and predictions on three time-scales: (i) minutes to months, (ii) years to decades and (iii) tens to thousands of years. We find that modelled isotopic depletions become increasingly sensitive to parameterized characteristics as the time period is decreased and/or a significant atmospheric circulation disturbance occurs. Minute to monthly isotope fluxes simulated by land surface schemes and river hydrology models allow comparison of the partition of precipitation between transpiration, run-off and open-water evaporation with isotope observations from 2002 and 2003. A range of atmospheric global circulation models (GCMs) simulations of key hydrological parameters over years to decades reveals poor results for the majority (13 in 20). We show that between 1979 and 1996 modelled groundwater is apparently being `tapped' in many of these GCMs at rates required to allow evaporation to greatly exceed precipitation (Ev>>Pr). Analysis of the `` good"'' versus the `` poor'' hydro-climate models reveals that unwitting application of `` poor'' models to current and future hydrological issues in semi-arid basins generates errors of over 100% in predictions. Isotopes demonstrate that in warm semi-arid regions, in contrast to the behaviour in cool temperate zones, groundwater recharge occurs only when rainfall

  16. The impact of snowpack decline on high elevation surface-water flow in the Willamette River: a stable isotope perspective

    NASA Astrophysics Data System (ADS)

    Brooks, J. R.; Johnson, H.; Cline, S. P.; Rugh, W.

    2015-12-01

    Much of the water that people in Western Oregon rely on comes from the snowpack in the Cascade Range, and this snowpack is expected to decrease in coming years with climate change. In fact, the past five years have shown dramatic variation in snowpack from a high of 174% of normal in 2010-11 to a low of 11% for 2014-15, one of the lowest on record. During this timeframe, we have monitored the stable isotopes of water within the Willamette River twice monthly, and mapped the spatial variation of water isotopes across the basin. Within the Willamette Basin, stable isotopes of water in precipitation vary strongly with elevation and provide a marker for determining the mean elevation from which water in the Willamette River is derived. In the winter when snow accumulates in the mountains, low elevation precipitation (primarily rain) contributes the largest proportion of water to the Willamette River. During summer when rainfall is scarce and demand for water is the greatest, water in the Willamette River is mainly derived from high elevation snowmelt. Our data indicate that the proportion of water from high elevation decreased with decreasing snowpack. We combine this information with the river flow data to estimate the volume reduction related to snow pack reduction during the dry summer. Observed reductions in the contribution of high elevation water to the Willamette River after just two years of diminished snowpack indicate that the hydrologic system responds relatively rapidly to changing snowpack volume. Reconciling the demands between human use and biological instream requirements during summer will be challenging under climatic conditions in which winter snowpack is reduced compared to historical amounts.

  17. Stable isotope composition of waters in the Great Basin, United States 1. Air-mass trajectories

    USGS Publications Warehouse

    Friedman, I.; Harris, J.M.; Smith, G.I.; Johnson, C.A.

    2002-01-01

    Isentropic trajectories, calculated using the NOAA/Climate Monitoring and Diagnostics Laboratory's isentropic transport model, were used to determine air-parcel origins and the influence of air mass trajectories on the isotopic composition of precipitation events that occurred between October 1991 and September 1993 at Cedar City, Utah, and Winnemucca, Nevada. Examination of trajectories that trace the position of air parcels backward in time for 10 days indicated five distinct regions of water vapor origin: (1) Gulf of Alaska and North Pacific, (2) central Pacific, (3) tropical Pacific, (4) Gulf of Mexico, and (5) continental land mass. Deuterium (??D) and oxygen-18 (??18O) analyses were made of precipitation representing 99% of all Cedar City events. Similar analyses were made on precipitation representing 66% of the precipitation falling at Winnemucca during the same period. The average isotopic composition of precipitation derived from each water vapor source was determined. More than half of the precipitation that fell at both sites during the study period originated in the tropical Pacific and traveled northeast to the Great Basin; only a small proportion traversed the Sierra Nevada. The isotopic composition of precipitation is determined by air-mass origin and its track to the collection station, mechanism of droplet formation, reequilibration within clouds, and evaporation during its passage from cloud to ground. The Rayleigh distillation model can explain the changes in isotopic composition of precipitation as an air mass is cooled pseudo-adiabatically during uplift. However, the complicated processes that take place in the rapidly convecting environment of cumulonimbus and other clouds that are common in the Great Basin, especially in summer, require modification of this model because raindrops that form in the lower portion of those clouds undergo isotopic change as they are elevated to upper levels of the clouds from where they eventually drop to the

  18. Stable isotope composition of waters in the Great Basin, United States 1. Air-mass trajectories

    NASA Astrophysics Data System (ADS)

    Friedman, Irving; Harris, Joyce M.; Smith, George I.; Johnson, Craig A.

    2002-10-01

    Isentropic trajectories, calculated using the NOAA/Climate Monitoring and Diagnostics Laboratory's isentropic transport model, were used to determine air-parcel origins and the influence of air mass trajectories on the isotopic composition of precipitation events that occurred between October 1991 and September 1993 at Cedar City, Utah, and Winnemucca, Nevada. Examination of trajectories that trace the position of air parcels backward in time for 10 days indicated five distinct regions of water vapor origin: (1) Gulf of Alaska and North Pacific, (2) central Pacific, (3) tropical Pacific, (4) Gulf of Mexico, and (5) continental land mass. Deuterium (δD) and oxygen-18 (δ18O) analyses were made of precipitation representing 99% of all Cedar City events. Similar analyses were made on precipitation representing 66% of the precipitation falling at Winnemucca during the same period. The average isotopic composition of precipitation derived from each water vapor source was determined. More than half of the precipitation that fell at both sites during the study period originated in the tropical Pacific and traveled northeast to the Great Basin; only a small proportion traversed the Sierra Nevada. The isotopic composition of precipitation is determined by air-mass origin and its track to the collection station, mechanism of droplet formation, reequilibration within clouds, and evaporation during its passage from cloud to ground. The Rayleigh distillation model can explain the changes in isotopic composition of precipitation as an air mass is cooled pseudo-adiabatically during uplift. However, the complicated processes that take place in the rapidly convecting environment of cumulonimbus and other clouds that are common in the Great Basin, especially in summer, require modification of this model because raindrops that form in the lower portion of those clouds undergo isotopic change as they are elevated to upper levels of the clouds from where they eventually drop to the

  19. Rapid Method for the Determination of the Stable Oxygen Isotope Ratio of Water in Alcoholic Beverages.

    PubMed

    Wang, Daobing; Zhong, Qiding; Li, Guohui; Huang, Zhanbin

    2015-10-28

    This paper demonstrates the first successful application of an online pyrolysis technique for the direct determination of oxygen isotope ratios (δ(18)O) of water in alcoholic beverages. Similar water concentrations in each sample were achieved by adjustment with absolute ethyl alcohol, and then a fixed GC split ratio can be used. All of the organic ingredients were successfully separated from the analyte on a CP-PoraBond Q column and subsequently vented out, whereas water molecules were transferred into the reaction furnace and converted to CO. With the system presented, 15-30 μL of raw sample was diluted and can be analyzed repeatedly; the analytical precision was better than 0.4‰ (n = 5) in all cases, and more than 50 injections can be made per day. No apparent memory effect was observed even if water samples were injected using the same syringe; a strong correlation (R(2) = 0.9998) was found between the water δ(18)O of measured sample and that of working standards. There was no significant difference (p > 0.05) between the mean δ(18)O value and that obtained by the traditional method (CO2-water equilibration/isotope ratio mass spectrometry) and the newly developed method in this study. The advantages of this new method are its rapidity and straightforwardness, and less test portion is required. PMID:26373434

  20. Stable isotope composition of Earth's large lakes

    NASA Astrophysics Data System (ADS)

    Jasechko, S.; Gibson, J. J.; YI, Y.; Birks, S. J.; Sharp, Z. D.

    2011-12-01

    Lakes cover about three percent of Earth's continental area. Large lakes can significantly influence lake shore and regional climates by increasing specific humidity during evaporation and by moderating air temperatures. Stable isotopes of oxygen and hydrogen can be used to quantify lake evaporation, providing a supplementary and often cost-advantageous alternative to conventional hydrologic approaches that require over lake monitoring. Further, stable isotopes in lake sediments are an established tool in paleolimnology; however, interpreting changes to a lake's past isotope composition requires a comprehensive understanding of contemporary controls. Here, δ18O and δ2H values of water in modern lakes exceeding roughly five hundred square kilometres are compiled (n > 35). Voluminous and seasonally mixed lakes - such as the North American Great Lakes - have the most homogenous stable isotope compositions, while perennially-stratified and shallow lakes show greater variability. A rudimentary stable isotope mass balance is used to assess evaporation fluxes from large lakes on Earth. The approach taken simultaneously constrains evaporation outputs for both oxygen and hydrogen stable isotopes by accounting for lake effects on the overlying atmosphere. Model development highlights important considerations such as isotopic stratification (Tanganyika), disequilibrium isotopic mass balances (Baikal), and non-steady hydrologic balances. Further, the isotope composition of Earth's continental surface water reservoir is calculated. This value - weighted to volume - is δ18O = -7.5±1.7 per mille relative to standard mean ocean water. The compiled data may be a useful tracer of continental evaporate in global atmospheric water cycle studies and could be coupled to climate models capable of incorporating oxygen-18 and deuterium tracers to improve or validate calculations of lake effects on regional water cycling.

  1. Hydrogeochemical and stable isotopic investigations on CO2-rich mineral waters from Harghita Mts. (Eastern Carpathians, Romania)

    NASA Astrophysics Data System (ADS)

    Kis, Boglárka-Mercedesz; Baciu, Călin; Kármán, Krisztina; Kékedy-Nagy, Ladislau; Francesco, Italiano

    2013-04-01

    There is a worldwide interest on geothermal, mineral and groundwater as a resource for energy, drinking water supply and therapeutic needs. The increasing trend in replacing tap water with commercial bottled mineral water for drinking purposes has become an economic, hydrogeologic and medical concern in the last decades. Several investigations have been carried out worldwide on different topics related to geothermal and mineral waters, dealing with mineral water quality assessment, origin of geothermal and mineral waters, geochemical processes that influence water chemistry and water-rock interaction In Romania, the Călimani-Gurghiu-Harghita Neogene to Quaternary volcanic chain (Eastern Carpathians) is one of the most important areas from the point of view of CO2-rich mineral waters. These mineral water springs occur within other post-volcanic phenomena like dry CO2 emissions, moffettes, bubbling pools, H2S gas emissions etc. Mineral waters from this area are used for bottling, local spas and drinking purposes for local people. The number of springs, around 2000 according to literature data, shows that there is still a significant unexploited potential for good quality drinking water in this area. Within the youngest segment of the volcanic chain, the Harghita Mts., its volcaniclastic aprons and its boundary with the Transylvanian Basin, we have carried out an investigation on 23 CO2-rich mineral water springs from a hydrogeochemical and stable isotopic point of view. The mineral waters are Ca-Mg-HCO3 to Na-Cl type. Sometimes mixing between the two types can be observed. We have detected a great influence of water-rock interaction on the stable isotopic composition of the mineral waters, shown by isotopic shifts to the heavier oxygen isotope, mixing processes between shallow and deeper aquifers and local thermal anomalies. Acknowledgements: The present work was financially supported by the Romanian National Research Council, Project PN-II-ID-PCE-2011-3-0537 and by

  2. Tracing the hydrological cycle by water stable isotopes on the Tibetan plateau

    NASA Astrophysics Data System (ADS)

    Tian, L.; Yao, T.; Yu, W.

    2013-05-01

    A network of precipitation, river, lake water, ice core and atmospheric vapor sampling was set up on the Tibetan Plateau to trance the moisture origins supplied to the plateau, the inland hydrological cycle process and land surface evaporation processes. This work shows different moisture from Indian Ocean monsoon and the westerlies dominate the precipitation δ18O in the south and north of the plateau respectively, which can cause a difference in precipitation δ18O of about 5‰ in average. Precipitation δ18O bears "temperature effect" in the northern Tibetan Plateau, whereas the seasonal precipitation δ18O shows precipitation "amount effect" in the south. This relation is also held in the ice core records on the plateau. An instance is the δ18O record from shallow ice cores in Muztagata Glacier, Dunde ice cap and Naimona'Nyi Glacier. The ice core δ18O record from monsoon region in south Tibet, such as Dasuopu glacier in Xixiabangma, shows a precipitation "amount effect" at least in the annual scale. Further isotope enrichment can be found in the land surface evaporation processes. A simple case is in the close lake system in Yamdruk-tso catchment, southern part of Tibetan Plateau. Both observation and simulation work shows the enrichment of heavy isotope in lake water can be over 10‰ for δ18O, which is much linked to the local climatic condition. Simulation work also shows that atmospheric vapor isotope is also very important to capture the lake water δD value. However, vapor isotopes data are usually less available on the plateau.

  3. Baboons, water, and the ecology of oxygen stable isotopes in an arid hybrid zone.

    PubMed

    Moritz, Gillian L; Fourie, Nicolaas; Yeakel, Justin D; Phillips-Conroy, Jane E; Jolly, Clifford J; Koch, Paul L; Dominy, Nathaniel J

    2012-01-01

    Baboons regularly drink surface waters derived from atmospheric precipitation, or meteoric water. As a result, the oxygen isotope (δ(18)O) composition of their tissues is expected to reflect that of local meteoric waters. Animal proxies of the oxygen isotope composition of meteoric water have practical applications as paleoenvironmental recorders because they can be used to infer aridity and temperature in historic and fossil systems. To explore this premise, we measured the δ(18)O values of hair from two baboon species, Papio anubis and Papio hamadryas, inhabiting Awash National Park, Ethiopia. The hybridizing taxa differ in their ranging behavior and physiological response to heat. Papio hamadryas ranges more widely in the arid thornbush and is inferred to ingest a greater proportion of leaf water that is enriched in (18)O as a result of evaporative fractionation. It is also better able to conserve body water, which reduces its dependence on meteoric waters depleted in (18)O. Taken together, these factors would predict relatively higher δ(18)O values in the hair (δ(18)O(hair)) of P. hamadryas. We found that the δ(18)O(hair) values of P. hamadryas were higher than those of P. anubis, yet the magnitude of the difference was marginal. We attribute this result to a common source of drinking water, the Awash River, and the longer drinking bouts of P. hamadryas. Our findings suggest that differences in δ(18)O values among populations of Papio (modern or ancient) reflect different sources of drinking water (which might have ecological significance) and, further, that Papio has practical value as a paleoenvironmental recorder. PMID:22902370

  4. Hydrologic Activity of Deciduous Agroforestry Tree : Observed through Monitoring of Stable Isotopes in Stem Water, Solar Radiation Attenuation, and Sapflow

    NASA Astrophysics Data System (ADS)

    Ceperley, N. C.; Mande, T.; Parlange, M. B.

    2012-12-01

    The net benefit of agroforestry trees for small scale farmers in dryland agricultural systems is debatable because while they provide significant direct and indirect services, they also consume considerable amounts of scare water resources. In this study we monitor the stable isotopes of water to improve a water budget of a Sclerocarya birrea tree in a millet field in South Eastern Burkina Faso. Data obtained from air temperature and humidity, surface temperature, solar radiation, and soil moisture sensors attached to a wireless sensor network uniquely configured around the agroforestry tree provided the initial calculation of the local water balance. Isotopic ratios were determined from water extracted from stems and sub canopy soil, and from nearby ground water, precipitation, and surface water that was sampled weekly. A linear mixing model is used to predict when the tree switched between water sources. The results from the linear mixing model coupled with a tree water balance demonstrate the extreme seasonality of the annual cycle of water use by this deciduous species.

  5. Stable isotopes as indicators of water and salinity sources in a southeast Australian coastal wetland: identifying relict marine water, and implications for future change

    NASA Astrophysics Data System (ADS)

    Currell, Matthew J.; Dahlhaus, Peter; , Hiroyuki, Ii

    2015-03-01

    The Lake Connewarre Complex is an internationally protected wetland in southeast Australia, undergoing increasing environmental change due to urbanisation. Stable isotopes of water (δ18O and δ2H) and other geochemical indicators were used to assess sources of water and salinity in the shallow groundwater and surface-water systems, and to better understand groundwater/surface-water interactions. While much of the shallow groundwater is saline (from 1.27 to 50.3 g/L TDS) with overlapping salinities across water groups, stable isotopes allow clear delineation of two distinct sources of water and salinity: marine water with δ18O between -1.4 and +1.3 ‰ and ion ratios characteristic of seawater; and meteoric water with δ18O between -6.1 and -3.6 ‰ containing cyclic salts, probably concentrated by plant transpiration. Groundwater bodies in shallow sediments beneath the wetlands have salinities and stable isotopic compositions intermediate between fresh wetland surface water and a marine water end-member. This marine-type water is likely relict seawater emplaced when the wetlands were connected to the estuary, prior to modern river regulation. Freshwater input to underlying groundwater is a recent consequence of this regulation. Future predicted changes such as increased stormwater inflow, will increase rates of freshwater leakage to shallow groundwater, favouring the proliferation of exotic reed species.

  6. Paleohydrogeology of the Cretaceous sediments of the Williston Basin using stable isotopes of water

    NASA Astrophysics Data System (ADS)

    Hendry, M. Jim; Barbour, S. L.; Novakowski, K.; Wassenaar, L. I.

    2013-08-01

    Hydraulic and isotopic data collected from aquifers are routinely used to characterize hydrogeological conditions within sedimentary basins, but similar data from confining units are generally not collected despite their ability to provide insights on important water/solute transport controls. We characterized paleogroundwater flow and solute transport mechanisms across 384 m of Cretaceous shale (aquitard) in the Williston Basin, Canada, using high-resolution depth profiles of water isotopes (δ18O, δ2H). Water samples were also collected from wells installed in the underlying regional sandy aquifer (Mannville Fm; 93 m thick) and from seepage inflows into potash mine shafts (to 825 m below ground). The 1-D numerical transport modeling of δ18O profiles provided insight into large-scale/long-term solute transport in both Cretaceous sediments and the basin. Despite the potential for significant advective migration during glaciations, molecular diffusion appears to be the dominant solute transport mechanism through the aquitard. Simulations suggest average vertical groundwater velocities of <0.05 m/10 ka and an average excess hydraulic head of <10 m; these values are much less than anticipated by successive glaciations. The dominant paleoevent reflected in present-day profiles is introduction during the Pleistocene of glaciogenic meteoric water to the aquifer underlying the shale, likely along an aquifer outcrop area east of the site or through local vertical conduits. Simulations suggest these recharge events occurred during one or more glacial periods. The isotopic profile over the upper 25 m of Pleistocene till and shale is consistent with glacial deposition and transport processes within these units over the Holocene (past 10 ka).

  7. Method for determining stable isotope ratios of dissolved organic carbon in interstitial and other natural marine waters

    NASA Technical Reports Server (NTRS)

    Bauer, J. E.; Haddad, R. I.; Des Marais, D. J.

    1991-01-01

    A procedure is described for the analysis of the stable carbon isotopic composition of dissolved organic carbon (DOC) in natural waters from marine and higher-salinity environments. Rapid (less than 5 min) and complete oxidation of DOC is achieved using a modification of previous photochemical oxidation techniques. The CO2 evolved from DOC oxidation can be collected in less than 10 min for isotopic analysis. The procedure is at present suitable for oxidation and collection of 1-5 micromoles of carbon and has an associated blank of 0.1-0.2 micromole of carbon. Complete photochemical oxidation of DOC standards was demonstrated by quantitative recovery of CO2 as measured manometrically. Isotopic analyses of standards by photochemical and high-temperature sealed-tube combustion methods agreed to within 0.3%. Photochemical oxidation of DOC in a representative sediment pore-water sample was also quantitative, as shown by the excellent agreement between the photochemical and sealed-tube methods. The delta 13C values obtained for pore-water DOC using the two methods of oxidation were identical, suggesting that the modified photochemical method is adequate for the isotopically non-fractionated oxidation of pore-water DOC. The procedure was evaluated through an analysis of DOC in pond and pore waters from a hypersaline microbial mat environment. Concentrations of DOC in the water column over the mat displayed a diel pattern, but the isotopic composition of this DOC remained relatively constant (average delta 13C = -12.4%). Pore-water DOC exhibited a distinct concentration maximum in the mat surface layer, and delta 13C of pore-water DOC was nearly 8% lighter at 1.5-2.0-cm depth than in the mat surface layer (0-0.5-cm depth). These results demonstrate the effectiveness of the method in elucidating differences in DOC concentration and delta 13C over biogeochemically relevant spatial and temporal scales. Carbon isotopic analysis of DOC in natural waters, especially pore waters

  8. Comparison of modeled and observed environmental influences on the stable oxygen and hydrogen isotope composition of leaf water in Phaseolus vulgaris L

    SciTech Connect

    Flanagan, L.B.; Comstock, J.P.; Ehleringer, J.R. )

    1991-06-01

    In this paper the authors describe how a model of stable isotope fractionation processes, originally developed by H. Craig and L.I. Gordon for evaporation of water from the ocean, can be applied to leaf transpiration. The original model was modified to account for turbulent conditions in the leaf boundary layer. Experiments were conducted to test the factors influencing the stable isotopic composition of leaf water under controlled environment conditions. At steady state, the observed leaf water isotopic composition was enriched above that of stem water with the extent of the enrichment dependent on the leaf-air vapor pressure difference (VPD) and the isotopic composition of atmospheric water vapor (AMV). The higher the VPD, the larger was the observed heavy isotope content of leaf water. At a constant VPD, leaf water was relatively enriched in heavy isotopes when exposed to AWV with a large heavy isotope composition. However, the observed heavy isotope composition of leaf water was always less than that predicted by the model. The extent of the discrepancy between the modeled and observed leaf water isotopic composition was a strong linear function of the leaf transpiration rate.

  9. Quantitative microbial ecology through stable isotope probing.

    PubMed

    Hungate, Bruce A; Mau, Rebecca L; Schwartz, Egbert; Caporaso, J Gregory; Dijkstra, Paul; van Gestel, Natasja; Koch, Benjamin J; Liu, Cindy M; McHugh, Theresa A; Marks, Jane C; Morrissey, Ember M; Price, Lance B

    2015-11-01

    Bacteria grow and transform elements at different rates, and as yet, quantifying this variation in the environment is difficult. Determining isotope enrichment with fine taxonomic resolution after exposure to isotope tracers could help, but there are few suitable techniques. We propose a modification to stable isotope probing (SIP) that enables the isotopic composition of DNA from individual bacterial taxa after exposure to isotope tracers to be determined. In our modification, after isopycnic centrifugation, DNA is collected in multiple density fractions, and each fraction is sequenced separately. Taxon-specific density curves are produced for labeled and nonlabeled treatments, from which the shift in density for each individual taxon in response to isotope labeling is calculated. Expressing each taxon's density shift relative to that taxon's density measured without isotope enrichment accounts for the influence of nucleic acid composition on density and isolates the influence of isotope tracer assimilation. The shift in density translates quantitatively to isotopic enrichment. Because this revision to SIP allows quantitative measurements of isotope enrichment, we propose to call it quantitative stable isotope probing (qSIP). We demonstrated qSIP using soil incubations, in which soil bacteria exhibited strong taxonomic variations in (18)O and (13)C composition after exposure to [(18)O]water or [(13)C]glucose. The addition of glucose increased the assimilation of (18)O into DNA from [(18)O]water. However, the increase in (18)O assimilation was greater than expected based on utilization of glucose-derived carbon alone, because the addition of glucose indirectly stimulated bacteria to utilize other substrates for growth. This example illustrates the benefit of a quantitative approach to stable isotope probing. PMID:26296731

  10. Simultaneous measurements of stable water isotopes in near-surface vapor and precipitation to constrain below-cloud processes

    NASA Astrophysics Data System (ADS)

    Graf, Pascal; Sodemann, Harald; Pfahl, Stephan; Schneebeli, Marc; Ventura, Jordi Figueras i.; Leuenberger, Andreas; Grazioli, Jacopo; Raupach, Tim; Berne, Alexis; Wernli, Heini

    2016-04-01

    Present-day observations of stable water isotopes (SWI) in precipitation on monthly time scales are abundant and the processes governing the variation of SWI on these time scales have been investigated by many studies. However, also on much shorter time scales of hours mesoscale meteorological processes lead to significant variations of SWIs, which are important to understand. There are only few studies investigating the variations of SWI on this short time scale, for which, e.g., frontal dynamics, convection and cloud microphysics play an essential role. In particular, the isotopic composition of both near-surface vapor and precipitation is significantly influenced by below-cloud processes that include precipitation evaporation and isotopic exchange between falling precipitation and surrounding vapor. In this study, simultaneous measurements of SWI in near-surface vapor and precipitation with high (sub-hourly) temporal resolution in combination with observational data from radars, disdrometers, radiosondes and standard meteorological instruments are used for a detailed analysis of the relative importance of below-cloud and in-cloud (i.e., precipitation formation) processes during the course of three rain events in Switzerland in spring 2014. Periods are identified when the isotopic composition of near-surface vapor and equilibrium vapor above liquid rain drops agree and when they differ due to either evaporation of precipitation or incomplete equilibration of precipitation with surrounding vapor. These findings are verified by the supporting observational data. In addition, calculations with a simple rain-shaft model fed with observational data are compared to the actual isotopic composition of precipitation. This combination of isotope measurements and model calculations allows us to test the sensitivity of the precipitation isotope signal to rain intensity, drop-size distribution and temperature and humidity profiles.

  11. Variability of the vertical stable water isotope composition from airborne measurements in the western Mediterranean in October 2012

    NASA Astrophysics Data System (ADS)

    Sodemann, Harald; Aemisegger, Franziska; Pfahl, Stephan; Corsmeier, Ulrich; Wieser, Andreas; Bitter, Mark; Feuerle, Thomas; Hankers, Rudolf; Schulz, Helmut; Hsiao, Gregor; Wernli, Heini

    2014-05-01

    Stable water isotopes are useful indicators of meteorological processes on a broad range of scales, reflecting for example evaporation, precipitation and airmass mixing processes. Here we present a detailed analysis of the first set of airborne spectroscopic stable water isotopes measurements in the western Mediterranean. Measurements have been acquired by a customised Picarro L2130i instrument with enhanced data acquisition rate by a dual-laser system. The instrument was deployed in cooperation with the Karlsruhe Institute of Technology (KIT) onboard the Dornier 128-6 research aircraft D-IBUF of the Institute of Flight Guidance, TU Braunschweig together with a meteorological flux measurement package during an international field campaign within the framework of HYMEX (Hydrological Cycle in Mediterranean Experiment) in Corsica, France. Vertical profiles of δD and δ18O show strong variability between flights depending on the prevailing meteorological situation, and in the vertical during individual flights. The principal factors influencing the vertical variability are shown to be advection and the temperature structure of the marine boundary layer. In particular, strong inversions at the top of the marine boundary layer can at times lead to step-like changes in δD exceeding 100 permil within 100 meters in the vertical. The isotopic information of the sampled water vapour is generally consistent with indicators of moisture source age and distance obtained from a Lagrangian method. Finally, the significance of the observed temporal and vertical variability for the representation of the atmospheric isotope composition in GCMs and remote-sensing retrievals are discussed.

  12. Rooting depth and water source flexibility of Arundo donax across a wide and topographically varied floodplain inferred from stable isotopes

    NASA Astrophysics Data System (ADS)

    Moore, G. W.; West, J. B.; Li, F.; Kui, L.

    2011-12-01

    Floodplain environments can exhibit strong gradients in soil moisture availability, from very dry to saturated, with important consequences for riparian vegetation transpiration and productivity and therefore ecohydrologic flowpaths. These gradients are often driven by geomorphic features that themselves can be affected by vegetation change over relatively short timescales. The Rio Grande has undergone substantial change in the past half century, including channel narrowing and significant expansion of non-native vegetation, often across previously unvegetated sandbars and natural levees. The objective of this study was to assess water sources for Arundo donax L. (giant reed), a now common invasive grass growing along the floodplains of the Rio Grande. Our hypotheses were: a) Arundo would switch from primarily shallow soil moisture to groundwater during periods of soil moisture deficit, but that this access would be limited by increasing groundwater depths, and b) transpiration would decline with floodplain elevation and decreasing surface soil moisture because of increasing depth to groundwater and surface soil moisture deficits. We used natural-abundance stable isotopes of oxygen (δ18O) and hydrogen (δ2H) to determine the water sources of Arundo along four approximately 100-meter transects arrayed perpendicular to the Rio Grande in southwest Texas. Surface soil water, river water, groundwater, precipitation and rhizome sections were collected every month from summer 2010 until summer 2011 to assess potential source water isotopic composition for Arundo. Mixing models were used to estimate Arundo dependence on surface soil moisture or groundwater. The isotopic compositions of groundwater and river water were similar throughout the year, indicating significant hyporheic exchange. As expected, the isotopic composition of precipitation events and a large flood event were distinct from the slowly-changing river and allowed an assessment of Arundo use of these

  13. Determining the Spatial Influence of Imported and Local Water Sources to Municipal Tap Water Systems in the Southwestern United States Using Stable Isotopes of Oxygen and Hydrogen

    NASA Astrophysics Data System (ADS)

    Stalker, J. C.; Kennedy, C. D.; Bowen, G. J.

    2010-12-01

    In arid and semi-arid parts of the southwestern USA, imported waters derived from large canal systems like the Colorado River Aqueduct, Los Angeles Aqueduct, and the California Aqueduct service a significant component of the regional water needs. These waters are sourced primarily from high altitude snowmelt runoff and have relatively low annually averaged stable isotope ratios of hydrogen and oxygen (δD, δ18O) (-99 to -127‰, -10 to -13‰,) when compared to water derived from local rainfall and surface river sources (-35 to -42 ‰, -5 to -7‰) in southern California, western Arizona, and southern Nevada. The distinct isotope signatures of these two waters can be used to differentiate the two sources in tap water from municipal systems. In this study, samples of tap water, aqueduct water, and surface water were collected throughout the Southwest to produce a series of maps of the spatial influence of imported water in municipal tap water. This data was then be used to develop mixing models to determine the relative importance of imported water regionally, and track the prominence of the movement of these imported waters after initial use and addition to a system. The use of isotopes to trace this anthropogenically introduced water is of interest to water management, resolving water rights issues and disputes, as well as environmental applications in ecological studies. Additionally these tracing methods may be applied worldwide in areas where the movement and dynamics of hydrologic systems are either unclear or unknown.

  14. Assessing site-specific spatio-temporal variations in hydrogen and oxygen stable isotopes of human drinking water

    NASA Astrophysics Data System (ADS)

    Kennedy, C. D.; Bowen, G. J.; Ehleringer, J. R.

    2008-12-01

    Stable isotope ratios of hydrogen and oxygen (δ2H and δ18O) are environmental forensic tracers that can be used to constrain the origin and movement of animals, people, and products. The fundamental assumption underlying this method is that water resources at different geographic locations have distinct and characteristic isotopic signatures that are assimilated into organic tissues. Although much is known about regional-scale spatio-temporal variability in δ2H and δ18O of water, few studies have addressed the question of how distinct these geographic and seasonal patterns are for any given site. To address this question, a 2-year survey of δ2H and δ18O in tap water from across the contiguous U.S. and Canada was conducted. The data show that seasonal variability in δ2H and δ18O of tap water is generally low (<10 ‰ for δ2H), and those with the highest variability can be classified as: a) cities or towns in areas of high climate seasonality, or b) large cities in arid or seasonally arid regions which access and switch among multiple water sources throughout the year. The data suggest that inter-annual variation in tap water isotope ratios is typically low, with a median difference for month-month pairs during the 2 sampling years of 2.7 (δ2H). The results from this study confirm the existence of temporal variability in δ2H and δ18O of tap water, but suggest that this variability in human-managed systems is highly damped and may be amenable to classification, modeling, and prediction. In all, the data provide the foundation for incorporating temporal variation in predictive models of water and organic δ2H and δ18O, leading to more robust and statistically defensible tests of geographic origin.

  15. The stable isotope composition of transpired water and the rate of change in leaf water enrichment in response to variable environments

    NASA Astrophysics Data System (ADS)

    Simonin, K. A.; Roddy, A. B.; Link, P.; Apodaca, R. L.; Tu, K. P.; Hu, J.; Dawson, T. E.; Barbour, M.

    2012-12-01

    Previous research has shown that during daylight hours the isotope composition of leaf water is generally well approximated by steady-state leaf water isotope enrichment models. However, there is little direct confirmation of isotopic steady state (ISS) transpiration. Here we use a novel method to evaluate the frequency (or infrequency) of ISS transpiration and the rate of change in leaf water enrichment when leaves are exposed to a variable environment. Specifically, our study had three goals. First, we wanted to develop a new method to measure the isotope fluxes of transpiration that relies on isotope ratio infrared spectroscopy (IRIS) and highlight how an IRIS instrument can be coupled to plant gas exchange systems. In doing so, we also developed a method for controlling the absolute humidity entering the gas exchange cuvettes across a wide range of concentrations (approximately 4000 ppmv to 22000 ppmv) without changing the isotope composition of water vapour entering the cuvette. Second, we quantified variation in the isotope composition of transpired water vapor and the rate of change in leaf water enrichment that can occur as a result of changes in relative humidity, leaf surface conductance to water vapour, leaf temperature and the isotope composition of atmospheric water vapor. Third, we examine the differences between steady state and non-steady state model predictions of leaf water enrichment at the site of evaporation. In our measurements the isotopic compositions of transpired water were neither stable nor equal to source water until leaves had been maintained at physiological steady state for at least 40 minutes. Additionally when transpiration was not at ISS, the steady state model predictions of leaf water enrichment at the site of evaporation exceeded non steady-state model predictions by up to 8 per mil. Further, the rate of change in leaf water enrichment was highly sensitive to variation in leaf water content. Our results suggest that a variable

  16. The O and H stable isotope composition of freshwaters in the British Isles. 2. Surface waters and groundwater

    NASA Astrophysics Data System (ADS)

    Darling, W. G.; Bath, A. H.; Talbot, J. C.

    The utility of stable isotopes as tracers of the water molecule has a long pedigree. The study reported here is part of an attempt to establish a comprehensive isotopic "baseline" for the British Isles as background data for a range of applications. Part 1 of this study (Darling and Talbot, 2003) considered the isotopic composition of rainfall in Britain and Ireland. The present paper is concerned with the composition of surface waters and groundwater. In isotopic terms, surface waters (other than some upland streams) are poorly characterised in the British Isles; their potential variability has yet to be widely used as an aid in hydrological research. In what may be the first study of a major British river, a monthly isotopic record of the upper River Thames during 1998 was obtained. This shows high damping of the isotopic variation compared to that in rainfall over most of the year, though significant fluctuations were seen for the autumn months. Smaller rivers such as the Stour and Darent show a more subdued response to the balance between runoff and baseflow. The relationship between the isotopic composition of rainfall and groundwater is also considered. From a limited database, it appears that whereas Chalk groundwater is a representative mixture of weighted average annual rainfall, for Triassic sandstone groundwater there is a seasonal selection of rainfall biased towards isotopically-depleted winter recharge. This may be primarily the result of physical differences between the infiltration characteristics of rock types, though other factors (vegetation, glacial history) could be involved. In the main, however, groundwaters appear to be representative of bulk rainfall within an error band of 0.5‰ δ18O. Contour maps of the δ18O and δ2H content of recent groundwaters in the British Isles show a fundamental SW-NE depletion effect modified by topography. The range of measured values, while much smaller than those for rainfall, still covers some ‰ for δ18

  17. Distal and proximal controls on the silicon stable isotope signature of North Atlantic Deep Water

    NASA Astrophysics Data System (ADS)

    de Souza, Gregory F.; Slater, Richard D.; Hain, Mathis P.; Brzezinski, Mark A.; Sarmiento, Jorge L.

    2015-12-01

    It has been suggested that the uniquely high δ30Si signature of North Atlantic Deep Water (NADW) results from the contribution of isotopically fractionated silicic acid by mode and intermediate waters that are formed in the Southern Ocean and transported to the North Atlantic within the upper limb of the meridional overturning circulation (MOC). Here, we test this hypothesis in a suite of ocean general circulation models (OGCMs) with widely varying MOCs and related pathways of nutrient supply to the upper ocean. Despite their differing MOC pathways, all models reproduce the observation of a high δ30Si signature in NADW, as well showing a major or dominant (46-62%) contribution from Southern Ocean mode/intermediate waters to its Si inventory. These models thus confirm that the δ30Si signature of NADW does indeed owe its existence primarily to the large-scale transport of a distal fractionation signal created in the surface Southern Ocean. However, we also find that more proximal fractionation of Si upwelled to the surface within the Atlantic Ocean must also play some role, contributing 20-46% of the deep Atlantic δ30Si gradient. Finally, the model suite reveals compensatory effects in the mechanisms contributing to the high δ30Si signature of NADW, whereby less export of high-δ30Si mode/intermediate waters to the North Atlantic is compensated by production of a high-δ30Si signal during transport to the NADW formation region. This trade-off decouples the δ30Si signature of NADW from the pathways of deep water upwelling associated with the MOC. Thus, whilst our study affirms the importance of cross-equatorial transport of Southern Ocean-sourced Si in producing the unique δ30Si signature of NADW, it also shows that the presence of a deep Atlantic δ30Si gradient does not uniquely constrain the pathways by which deep waters are returned to the upper ocean.

  18. Determination of groundwater travel time in a karst aquifer by stable water isotopes, Tanour and Rasoun spring (Jordan)

    NASA Astrophysics Data System (ADS)

    Hamdan, Ibraheem; Wiegand, Bettina; Sauter, Martin; Ptak, Thomas

    2016-04-01

    Key words: karst aquifers, stable isotopes, water travel time, Jordan. Tanour and Rasoun karst springs are located about 75 kilometers northwest of the city of Amman in Jordan. The aquifer is composed of Upper Cretaceous limestone that exhibits a moderate to high degree of karstification. The two springs represent the main drinking water resources for the surrounding villages. The yearly water production is about 1,135,000 m3/yr for Tanour spring and 125,350 m3/yr for Rasoun spring (MWI 2015). Due to contamination from microbiological pollution (leakage of wastewater from septic tanks) or infiltration of wastewater from local olive presses, drinking water supply from the two springs is frequently interrupted. From November 2014 through March 2015, spring water samples were collected from Tanour and Rasoun spring for the analysis of stable hydrogen and oxygen isotopes to investigate spring response to precipitation and snowmelt events. Both Tanour and Rasoun spring show a fast response to precipitation and snowmelt events, implying short water travel times. Based on the variation of δ 18O and δ 2H in spring discharge, the average maximum water travel time is in the order of 8 days for Tanour spring and 6 days for Rasoun spring. Due to fast water travel times, Tanour and Rasoun spring can be considered as highly vulnerable to pollutants. δ 18O and δ 2H values of Tanour and Rasoun springs parallel other monitored parameter like water temperature, turbidity, electrical conductivity and spring discharge. In addition, a high turbidity peak was monitored in Tanour spring during a pollution event from olive mills wastewater (Hamdan et al., 2016; Hamdan, in prep.). The fast response in both Tanour and Rasoun springs to precipitation events requires monitoring potential sources of pollution within the catchment area. References: MWI (Ministry of Water and Irrigation) (2015) Monthly Production values for Tanour and Rasoun Springs for the time period between 1996 and 2014

  19. Inconsistent relationships between major ions and water stable isotopes in Antarctic snow under different accumulation environments

    NASA Astrophysics Data System (ADS)

    Hoshina, Yu; Fujita, Koji; Iizuka, Yoshinori; Motoyama, Hideaki

    2016-03-01

    Major ions, stable oxygen isotopes (δ18O), and accumulation rates are analyzed using high temporal resolution data from shallow ice cores and snow pits from East and West Antarctica. Seasonal cycles of major ions and δ18O are well preserved at sites with an accumulation rate threshold of >100 kg m-2 a-1 and calm wind conditions. The seasonal cycle is unclear at sites with high wind speeds, even if the accumulation rate is greater than the threshold. To eliminate the influences of different source regions on major ion and δ18O signals in ice cores, we calculate correlation coefficients between annually averaged major ion concentrations and δ18O, and then compare these with accumulation rates and other geographical variables such as latitude, elevation, and distance from the coast. We find that accumulation rates are highly correlated with elevation and the 10-m snow temperature, and that major ions and δ18O are negatively correlated at low accumulation sites in inland Antarctica. Negative correlations could reflect inconsistent accumulation due to a large inter-annual variability in the accumulation rate. The results show that the relationships between major ions and δ18O may not reflect climatic signatures, and could be a result of the unique characteristics of this arid environment.

  20. Use of stable isotopes in order to clarify complex interactions among various water bodies in a coastal aquifer system

    NASA Astrophysics Data System (ADS)

    Gemitzi, Alexandra; Stefanopoulos, Kyriakos; Schmidt, Marie; Richnow, Hans H.

    2013-04-01

    Isotopes of hydrogen and oxygen are commonly applied in groundwater research in order to investigate groundwater origin, movement or interactions with other water bodies and sources of salinity. The present work deals with the elucidation of the complex interactions among various water bodies in a Mediterranean coastal aquifer system i.e., the Neon Sidirochorion aquifer in Northeastern Greece, using their stable isotope composition. The study area comprises several important water bodies and ecosystems; Ismarida lake which is protected by the Ramsar Treaty and during the last 30 years is artificially connected via a channel to the sea, Vosvozis river which discharges into Ismarida lake and the Neon Sidirochorion aquifer which is the main source of irrigation water for this agricultural area and it is subject to saltwater intrusion. Within the present work, the d18O and d2H isotopic composition of seawater, lake water, river water and groundwater in combination with hydrogeological and hydrochemical data were studied in order to reveal the interactions of surface and groundwaters and the origins of salinity within the aquifer system. Additionally, the conceptual model in the study area was determined and is presented taking into account the existing hydrogeological information. Analysis of the seasonal and spatial trends of the isotope pattern showed that all water bodies in the study area interact. It was also shown that increased salinity of the aquifer is not due to relic water from past geological periods, but it is attributed to intrusion of the lake water into the aquifer, a process which is induced because of the extensive groundwater pumping for irrigation. Additionally, direct interaction of the sea was certified only in the case of Ismarida lake which is subject to seawater intrusion during summertime and a consequent increase of the Electrical Conductivity (EC) values its waters. Progressively, brackish lake water moves towards the aquifer with a time lag

  1. Hydrogeochemistry and stable isotopes of ground and surface waters from two adjacent closed basins, Atacama Desert, northern Chile

    USGS Publications Warehouse

    Alpers, C.N.; Whittemore, D.O.

    1990-01-01

    The geochemistry and stable isotopes of groundwaters, surface waters, and precipitation indicate different sources of some dissolved constituents, but a common source of recharge and other constituents in two adjacent closed basins in the Atacama Desert region of northern Chile (24??15???-24??45???S). Waters from artesian wells, trenches, and ephemeral streams in the Punta Negra Basin are characterized by concentrations of Na>Ca>Mg and Cl ???SO4, with TDS Mg ??? Ca and SO4 > Cl, with TDS also Mg ??? Ca and SO4 > Cl, but with TDS up to 40 g/l. The deep mine waters have pH between 3.2 and 3.9, and are high in dissolved CO2 (??13 C = -4.8%PDB), indicating probable interaction with oxidizing sulfides. The deep mine waters have ??18O values of ???-1.8%.compared with values < -3.5??? for other Hamburgo Basin waters; thus the mine waters may represent a mixture of meteoric waters with deeper "metamorphic" waters, which had interacted with rocks and exchanged oxygen isotopes at elevated temperatures. Alternatively, the deep mine waters may represent fossil meteoric waters which evolved isotopically along an evaporative trend starting from values quite depleted in ??18O and ??Dd relative to either precipitation or shallow groundwaters. High I/Br ratios in the Hamburgo Basin waters and La Escondida mine waters are consistent with regionally high I in surficial deposits in the Atacama Desert region and may represent dissolution of a wind-blown evaporite component. Rain and snow collected during June 1984, indicate systematic ??18O and ??D fractionation with increasing elevation between 3150 and 4180 m a.s.l. (-0.21??.??18O and -1.7??.??D per 100 m). Excluding the deep mine waters from La Escondida, the waters from the Hamburgo and Punta Negra Basins have similar ??D and ??18O values and together show a distinct evaporative trend (??D = 5.0 ??18O - 20.2). Snowmelt from the central Andes Cordillera to the east is the most likely source of recharge to both basins. Some of the

  2. New Stable Isotope Tropical Paleoclimate Proxies

    NASA Astrophysics Data System (ADS)

    Lawrence, J. R.

    2005-05-01

    Organized tropical rain systems such as tropical cyclones (TC) and mesoscale convective systems (MCS) produce both water vapor and rainfall with distinctly low isotope ratios. This lowering is caused by recyling of water in organized systems. Therefore, fresh water carbonate organisms have considerable potential to act as proxy recorders of these systems. Ostracoda are ephemeral making them especially attractive candidates. Tropical trees offer another opportunity because the low isotopic spikes produced in both soil waters when heavy rains result and ambient water vapor surronding the trees may be recorded in the tree cellulose. Ostracoda living in the surface waters derived from Tropical Storm Allison (2001) document the passage of the storm in their oxygen isotope ratios. The stable isotopic composition of water vapor along the southwest coast of Mexico shows considerable variation in response to TC and MCS activity offshore even when no rain falls in the region. Potentially a long-term record of this activity may be found in the stable isotopic composition of trees providing low elevation trees of sufficient longevity can be found.

  3. Bayesian stable isotope mixing models

    EPA Science Inventory

    In this paper we review recent advances in Stable Isotope Mixing Models (SIMMs) and place them into an over-arching Bayesian statistical framework which allows for several useful extensions. SIMMs are used to quantify the proportional contributions of various sources to a mixtur...

  4. The Western Ghat as the water tower of the South Indian Rivers : a stable isotope investigation on the origin of water and factors affecting the water cycle.

    NASA Astrophysics Data System (ADS)

    Lambs, Luc; Tripti, Muguli; Balakrishna, Keshava

    2014-05-01

    The long stretch (1600 km) of Ghats on the western side (Western Ghats) of Peninsular India separates relatively wetter west coast from drier eastern coast. The western and eastern sides of the Ghats are having distinct isotopic signatures indicating unequal distribution of the moisture sources. South India is characterized by having moisture source for southwest monsoon from Arabian Sea and northeast monsoon from Bay of Bengal. The wetter side of Peninsular region is covered by combination of evergreen tropical forest and grass lands, termed as Shola Forests which support higher vapor recycling process. Very few isotopic studies have been undertaken in these areas, except few places, mainly along the coast lines. This study presents the stable isotope results on rivers and groundwater of the Western Ghats covering Agumbe (Karnataka) to Ooty (Tamil Nadu) and its west coast river basins as observed for the three year period. The stable isotope results on the surface, subsurface and deep water pools show that the mean d18O value range from -4 o to -2 o on the west slope, and from -5 o to -4 o on the east slope, with quite no altitude or amount effect up to 2000 m asl. The more depleted values are found only in higher elevation, like the Doddabeta in the Nilgiri (2637m), with d18O close to -9 o which is exceptional for a tropical area. The hills on the west slope of the Western Ghats as well as in the mountainous Shola forest exhibit strong water vapor recycling as evidenced by high d-excess values. On the contrary on the eastern slope, the drier condition and the numerous impoundments and river damming support strong evaporation process. Thus, the study identifies the profound effect of tropical vegetation and anthropogenic factors on the recharge functioning of river and groundwater pools in Southern India.

  5. STABLE ISOTOPES IN ECOLOGICAL STUDIES: NEW DEVELOPMENTS IN MIXING MODELS

    EPA Science Inventory

    Stable isotopes are increasingly being used as tracers in ecological studies. One application uses isotopic ratios to quantify the proportional contributions of multiple sources to a mixture. Examples include food sources for animals, water sources for plants, pollution sources...

  6. Stable isotopes and mercury in a model estuarine fish: multibasin comparisons with water quality, community structure, and available prey base.

    PubMed

    Adams, Douglas H; Paperno, Richard

    2012-01-01

    Stable-isotope ratios (δ(13)C and δ(15)N) and mercury in a model predator, and associated prey community assessments were used to make inferences regarding food web relationships and how these relationships are influenced by habitat variability and anthropogenic factors. Although interconnected, the three major basins of the Indian River Lagoon system on the Atlantic coast of Florida comprise noticeably different available habitat types with spatially distinct faunal communities and available prey for spotted seatrout, Cynoscion nebulosus, a model predatory fish species. Water quality, degree of urbanization, human population density, and levels of nitrogen enrichment clearly differ between these representative estuarine basins. The differences can influence feeding ecology and therefore result in different mercury concentrations and different stable-isotope signatures of spotted seatrout between basins. Mercury concentrations in spotted seatrout were greatest in Mosquito Lagoon (ML) and least in the Indian River Lagoon proper (IRL), although concentrations were low for all basins. Spotted seatrout from IRL were carbon-depleted and nitrogen-enriched compared with those from the other basins; this suggests either that the fish's primary source of carbon in IRL is an algae- or phytoplankton-based food web or that the pathway through the food web is shorter there. The δ(15)N values of IRL spotted seatrout were greater than those in the Banana River Lagoon or ML, suggesting slightly different trophic positioning of fish in these basins. The greater δ(15)N values in IRL spotted seatrout may also reflect the greater human population density and resultant anthropogenic inputs (e.g., observed higher total nitrogen levels) in IRL compared with the other more pristine basins examined. Understanding species' responses to broad-scale habitat heterogeneity in estuaries and knowing basin-specific differences in stable isotopes, mercury, prey communities, and comprehensive

  7. Abundant climatic information in water stable isotope record from a maritime glacier on southeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Zhao, Huabiao; Xu, Baiqing; Li, Zhen; Wang, Mo; Li, Jiule; Zhang, Xiaolong

    2016-04-01

    Climatic significance of ice core stable isotope record in the Himalayas and southern Tibetan Plateau (TP), where the climate is alternately influenced by Indian summer monsoon and mid-latitude westerlies, is still debated. A newly drilled Zuoqiupu ice core from a temperate maritime glacier on the southeastern TP covering 1942-2011 is investigated in terms of the relationships between δ18O and climate parameters. Distinct seasonal variation of δ18O is observed due to high precipitation amount in this area. Thus the monsoon (June to September) and non-monsoon (October to May) δ18O records are reconstructed, respectively. The temperature effect is identified in the annual δ18O record, which is predominantly contributed by temperature control on the non-monsoon precipitation δ18O record. Conversely, the negative correlation between annual δ18O record and precipitation amount over part of Northeast India is mostly contributed by the monsoon precipitation δ18O record. The variation of monsoon δ18O record is greatly impacted by the Indian summer monsoon strength, while that of non-monsoon δ18O record is potentially associated with the mid-latitude westerly activity. The relationship between Zuoqiupu δ18O record and Sea Surface Temperature (SST) is found to be inconsistent before and after the climate shift of 1976/1977. In summer monsoon season, the role of SST in the monsoon δ18O record is more important in eastern equatorial Pacific Ocean and tropical Indian Ocean before and after the shift, respectively. In non-monsoon season, however, the Atlantic Multidecadal Oscillation has a negative impact before but positive impact after the climate shift on the non-monsoon δ18O record.

  8. Using stable isotopes to determine seasonal variations in water uptake of summer maize under different fertilization treatments.

    PubMed

    Ma, Ying; Song, Xianfang

    2016-04-15

    Fertilization and water both affect root water uptake in the nutrient and water cycle of the Soil-Plant-Atmosphere-Continuum (SPAC). In this study, dual stable isotopes (D and (18)O) were used to determine seasonal variations in water uptake patterns of summer maize under different fertilization treatments in Beijing, China during 2013-2014. The contributions of soil water at different depths to water uptake were quantified by the MixSIAR Bayesian mixing model. Water uptake was mainly sourced from soil water in the 0-20cm depth at the seeding (67.7%), jointing (60.5%), tasseling (47.5%), dough (41.4%), and harvest (43.9%) stages, and the 20-50cm depth at the milk stage (32.8%). Different levels of fertilization application led to considerable differences in the proportional contribution of soil water at 0-20cm (6.0-58.5%) and 20-50cm (6.1-26.3%). There was little difference of contributions in the deep layers (50-200cm) among treatments in 2013, whereas differences were observed in 50-90cm at the milk stage and 50-200cm at the dough stage during 2014. The main water uptake depth was concentrated in the upper soil layers (0-50cm) during the wet season (2013), whereas a seasonal drought in 2014 promoted the contribution of soil water in deep layers. The contribution of soil water was significantly and positively correlated with the proportions of root length (r=0.753, p<0.01). The changes of soil water distribution were consistent with the seasonal variation in water uptake patterns. The present study identified water sources for summer maize under varying fertilization treatments and provided scientific implications for fertilization and irrigation management. PMID:26845183

  9. Tracing nitrogenous disinfection byproducts after medium pressure UV water treatment by stable isotope labeling and high resolution mass spectrometry.

    PubMed

    Kolkman, Annemieke; Martijn, Bram J; Vughs, Dennis; Baken, Kirsten A; van Wezel, Annemarie P

    2015-04-01

    Advanced oxidation processes are important barriers for organic micropollutants (e.g., pharmaceuticals, pesticides) in (drinking) water treatment. Studies indicate that medium pressure (MP) UV/H2O2 treatment leads to a positive response in Ames mutagenicity tests, which is then removed after granulated activated carbon (GAC) filtration. The formed potentially mutagenic substances were hitherto not identified and may result from the reaction of photolysis products of nitrate with (photolysis products of) natural organic material (NOM). In this study we present an innovative approach to trace the formation of disinfection byproducts (DBPs) of MP UV water treatment, based on stable isotope labeled nitrate combined with high resolution mass spectrometry. It was shown that after MP UV treatment of artificial water containing NOM and nitrate, multiple nitrogen containing substances were formed. In total 84 N-DBPs were detected at individual concentrations between 1 to 135 ng/L bentazon-d6 equivalents, with a summed concentration of 1.2 μg/L bentazon-d6 equivalents. The chemical structures of three byproducts were confirmed. Screening for the 84 N-DBPs in water samples from a full-scale drinking water treatment plant based on MP UV/H2O2 treatment showed that 22 of the N-DBPs found in artificial water were also detected in real water samples. PMID:25760315

  10. Water use Efficiency in a Blue oak ( Quercus douglasii) Savanna - a Combined Analysis of Stable Isotopes and Eddy Covariance Measurements

    NASA Astrophysics Data System (ADS)

    Mambelli, S.; Tu, K. P.; Knohl, A.; Ma, S.; Baldocchi, D. D.; Dawson, T. E.

    2007-12-01

    Understanding the relationship between carbon assimilation and water consumption by natural vegetation is needed to assess how changes in climate will affect plant carbon and water exchange as well as the energy fluxes of ecosystems. While climate change is expected to cause significant warming, most models also suggest changes in the timing and amount of precipitation received; thus implications of this type of change are particularly acute in Mediterranean regions of the world. Blue oak savannas are already exposed to broad variation in water availability and to severe droughts during the summer months. Our objective was to evaluate the trade-off between carbon gain and water loss (Water Use Efficiency) in this ecosystem at both the leaf and at the ecosystem scales. We monitored the ratio of the partial pressures of CO2 inside the leaf (Ci) and in the outside air (Ca) or Ci/Ca, during the summer months of three subsequent years. This ratio is determined by the balance between photosynthetic capacity and stomatal conductance to water loss. Leaf-level estimates for individual trees were based on the carbon isotope composition (δ13C) of bulk leaf tissue and of recently fixed carbohydrates (leaf soluble sugars). These leaf and individual tree based estimates were then compared with canopy-level estimates derived from continuous eddy covariance measurements of fluxes of CO2, water vapor and meteorological variables from two eddy covariance systems, one above (23m) and one below (2m) the tree canopy. We found that savanna Blue oak trees cope with severe drought through coordinated down-regulation of carbon and water fluxes, i.e. the ratio Ci/Ca remained stable over four summer months, despite decreasing soil water content and leaf water potentials. Stable C isotope composition of leaf soluble sugars is the most robust measure of Ci/Ca because it reflects the initial discrimination of photosynthetic products, without the confounding effects ascribed to storage, tissue

  11. Vegetation effects on event water dynamics - Insights from in-situ stable isotope observations and dye patterns

    NASA Astrophysics Data System (ADS)

    Volkmann, Till; Haberer, Kristine; Gessler, Arthur; Weiler, Markus

    2014-05-01

    The predicted changes of climate and land-use could have drastic effects on the water balance of ecosystems, particularly under frequent drought and subsequent rewetting conditions. Yet, inference of these effects and related consequences for the structure and functioning of ecosystems, groundwater recharge, leaching of nutrients and pollutants, drinking water availability, and the water cycle is currently impeded by gaps in our understanding of the manifold interactions between vegetation and soil water dynamics. While plants require water and nutrients, they also exert, for instance, important below-ground controls on the distribution and movement of water and chemicals in the rooted soil horizons via uptake and redistribution of water, modification of soil hydraulic properties, and formation of conduits for rapid preferential water flow. This work aims to contribute to fill existing gaps by assessing the effects of different plant types and their rooting systems on the soil water dynamics. Therefore, we conducted artificial drought and subsequent rewetting experiments using isotopically and dye (Brilliant Blue FCF) labeled water on plots of various surface cover (bare soil, grass, beech, oak, vine) established on relatively homogeneous luvisol on loess in southwestern Germany. Detailed insight into the short-term dynamics of event water infiltration and root uptake during the field experiments was facilitated by the application of novel techniques for high-frequency in-situ monitoring of stable isotope signatures in pore and transpiration water using commercial laser-based spectrometers, augmenting conventional observations of soil physicochemical states (soil water content, matric potential, electrical conductivity). The temporal point information is complemented by dye staining profiles, providing a detailed picture of spatial infiltration patterns, and by root density observations. The results of the experiments allow for a comprehensive spatiotemporal

  12. Human drinking water compared with river waters throughout the United States with respect to their stable hydrogen and oxygen isotopic composition

    NASA Astrophysics Data System (ADS)

    Landwehr, J. M.; Coplen, T. B.; Qi, H.

    2009-04-01

    The composition of stable isotopes of hydrogen (^2H) and oxygen (^18O) in animal tissues, such as hair, nail, teeth and bone, has been used to trace migrations and geographic origin of individuals. Variations of these isotopic ratios in tissue are known to show significant correlations with the isotopic composition of ingested water, as well as with diet and other oxygen sources. Drinking water in natural ecosystems is defined by what is locally available for animal consumption, primarily surface waters such as streams, ponds, lakes, seeps, springs, etc. Tap water provides the drinking water in many human ecosystems. It may derive from local sources but can also draw on more diverse sources, such as large rivers with watersheds larger than those of local creeks, deep ground waters or even imported supplies, which may be isotopically distinct from local ecosystem supplies. Because of the potentially complex hydrologic pathways of water sources available in either animal or human ecosystems, the stable isotopic composition of these supplies may differ significantly from that of the (weighted average) local precipitation which is sometimes used to represent local water supplies. For example, water samples taken from three different taps in Washington, D.C., USA, on August 15, 2007, had measured ^2H and ^18O values of -41.7 per mill and -6.13 per mill, -41.7 per mill and -6.06 per mill, and -42.2 per mill and -6.22 per mill, respectively. A water sample taken on the same day from the Potomac River, which is the source of the D.C. water supply, had ^2H and ^18O values of -41.7 per mill and -6.06 per mill, respectively, consistent with that of the urban tap water. However, precipitation samples collected locally in Reston, Virginia, USA, had ^2H and ^18O values of -16.1 per mill and -3.13 per mill, respectively, for the week ending on August 15, 2007; -17.5 per mill and -3.40 per mill, respectively, for the month preceding August 15, 2007; and -13.6 per mill and -3

  13. In situ unsaturated zone water stable isotope (2H and 18O) measurements in semi-arid environments: a soil water balance

    NASA Astrophysics Data System (ADS)

    Gaj, Marcel; Beyer, Matthias; Koeniger, Paul; Wanke, Heike; Hamutoko, Josefina; Himmelsbach, Thomas

    2016-02-01

    Stable isotopes (deuterium, 2H, and oxygen-18, 18O) of soil water were measured in the field using a liquid water isotope analyzer (tunable off-axis integrated cavity output spectroscope, OA-ICOS, LGR) and commercially available soil gas probes (BGL-30, UMS, Munich) in the semi-arid Cuvelai-Etosha Basin (CEB), Namibia. Results support the applicability of an in situ measurement system for the determination of stable isotopes in soil pore water. High spatial and temporal resolution was achieved in the study area with reasonable accuracy and measurements were in agreement with laboratory-based cryogenic vacuum extraction and subsequent cavity ring-down laser spectroscopic isotope analysis (CRDS, L2120-i, Picarro Inc.). After drift and span correction of the in situ isotope data, precision for over 140 measurements taken during two consecutive field campaigns (June and November 2014) was 1.8 and 0.48 ‰ for δ2H and δ18O, respectively. Mean measurement trueness is determined using quality check standards and was 5 and 0.3 ‰ for δ2H and δ18O, respectively. The isotope depth profiles are used quantitatively to calculate a soil water balance. The contribution of transpiration to total evapotranspiration ranged between 72 and 92 %. Shortly after a rain event, the contribution of transpiration was much lower, at 35 to 50 %. Potential limitations of such an in situ system are related to environmental conditions which could be minimized by using a temperature-controlled chamber for the laser spectrometer. Further, the applicability of the system using previously oven-dried soil material might be limited by physicochemical soil properties (i.e., clay minerals). Uncertainty in the in situ system is suggested to be reduced by improving the calibration procedure and further studying fractionation effects influencing the isotope ratios in the soil water, especially at low water contents. Furthermore, the influence of soil-respired CO2 on isotope values within the root zone

  14. Stable isotope geochemical study of Pamukkale travertines: New evidences of low-temperature non-equilibrium calcite-water fractionation

    NASA Astrophysics Data System (ADS)

    Kele, Sándor; Özkul, Mehmet; Fórizs, István; Gökgöz, Ali; Baykara, Mehmet Oruç; Alçiçek, Mehmet Cihat; Németh, Tibor

    2011-06-01

    In this paper we present the first detailed geochemical study of the world-famous actively forming Pamukkale and Karahayit travertines (Denizli Basin, SW-Turkey) and associated thermal waters. Sampling was performed along downstream sections through different depositional environments (vent, artificial channel and lake, terrace-pools and cascades of proximal slope, marshy environment of distal slope). δ 13C travertine values show significant increase (from + 6.1‰ to + 11.7‰ PDB) with increasing distance from the spring orifice, whereas the δ 18O travertine values show only slight increase downstream (from - 10.7‰ to - 9.1‰ PDB). Mainly the CO 2 outgassing caused the positive downstream shift (~ 6‰) in the δ 13C travertine values. The high δ 13C values of Pamukkale travertines located closest to the spring orifice (not affected by secondary processes) suggest the contribution of CO 2 liberated by thermometamorphic decarbonation besides magmatic sources. Based on the gradual downstream increase of the concentration of the conservative Na +, K +, Cl -, evaporation was estimated to be 2-5%, which coincides with the moderate effect of evaporation on the water isotope composition. Stable isotopic compositions of the Pamukkale thermal water springs show of meteoric origin, and indicate a Local Meteoric Water Line of Denizli Basin to be between the Global Meteoric Water Line (Craig, 1961) and Western Anatolian Meteoric Water Line (Şimşek, 2003). Detailed evaluation of several major and trace element contents measured in the water and in the precipitated travertine along the Pamukkale MM section revealed which elements are precipitated in the carbonate or concentrated in the detrital minerals. Former studies on the Hungarian Egerszalók travertine (Kele et al., 2008a, b, 2009) had shown that the isotopic equilibrium is rarely maintained under natural conditions during calcite precipitation in the temperature range between 41 and 67 °C. In this paper

  15. Deciphering Ecohydrological Interactions Using Stable Isotopes

    NASA Astrophysics Data System (ADS)

    McDonnell, J.; Evaristo, J. A.; Jasechko, S.

    2014-12-01

    Deciphering the nature of ecohydrological interconnections and scaling that knowledge gained at single points to watersheds is challenging. One tool that that has proved useful in this regard is stable isotope tracing. Single isotope studies have been used recently to quantify landuse change effects on streamflow source apportionment and ecological effects on transit time distributions of water at the catchment scale. However, most work to date has assumed that plant transpiration, groundwater recharge and streamflow are all sourced or mediated by the same well mixed reservoir—the soil. Recent work in Oregon and Mexico has shown evidence of ecohydrological separation, whereby different subsurface compartmentalized pools of water supply either plant transpiration fluxes or the combined fluxes of groundwater recharge and streamflow. However, these findings have not yet been widely tested. Here we assemble the first dual isotope database for δ2H and δ18O extracted from 47 globally-distributed stable isotopic datasets. We use these data to test the ecohydrological separation hypothesis. We combine this dual isotope dataset with global precipitation, streamwater, groundwater and soil water datasets. Our results show that precipitation, streamwater and groundwater from the 47 sites plot approximately along the δ2H/δ18O slope of eight, suggesting that local precipitation inputs supply streamwater and groundwater. Soil waters extracted from the 47 studies plot below the regression of local streamwater and groundwater with a slope of 6.6±0.05 ‰. Local plant xylem waters from our matched dataset plot on a slope 6.6±0.07 ‰ consistent with local soil waters. The tight association of soil water slopes and not that of local groundwater or streamflow suggests that plants use soil water that does not itself contribute to groundwater recharge or stream water. This ubiquity of subsurface water compartmentalization is surprising and has important implications for how we

  16. Chromium stable isotope fractionation during adsorption

    NASA Astrophysics Data System (ADS)

    Ellis, A.; Johnson, T.; Bullen, T.

    2003-04-01

    Chromium is a common anthropogenic contaminant in ground water. It is redox-active; the two common valences in natural waters are Cr(VI), which is highly soluble and toxic, and Cr(III), which is relatively insoluble. Redox reactions control Cr mobility in aqueous solutions with Cr(VI) reduction to Cr(III) controlling the attenuation of Cr in groundwater. Our previous study demonstrated that abiotic Cr(VI) reduction causes an isotope fractionation of -3.5 permil (53Cr/52Cr) and isotopes can therefore be used to calculate the extent of reduction. In the present study, experiments were conducted to measure Cr isotope fractionation during Cr(VI) sorption on Al203. Sorption of Cr(VI) could be important as a small isotope fractionation may get amplified along the edges of a Cr(VI) contaminated plume. A previous study demonstrated a similar process with Fe isotopes on anion exchange resin. Initial solutions of 200 mg/l Cr(VI) (as K2Cr2O7) and 0.1 mM KCl were made up. Sufficient solid Al203 was added to achieve 50% sorption. After equilibration, the solution was extracted by centrifuging and filtering with a 0.2 micron filter. Al203 was then added again to result in a further 50% sorption of the remaining Cr(VI). This process was repeated 10 times to amplify any isotopic fractionation between dissolved and adsorbed Cr(VI). The instantaneous stable isotope fractionation was calculated based on the δ 53Cr values of the initial and final Cr(VI) solutions. The results show that the stable isotope values measured in the solutions after the ten steps were within the uncertainty of the isotope value of the initial solution. Therefore, no significant stable isotope fractionation occurred. We are presently conducting experiments with goethite and expect similar results. Therefore, any fractionation of chromium stable isotopes observed in contaminant plumes are a result of processes other than adsorption (i.e., reduction).

  17. VeWa: Assessing Vegetation Effects on Water Flows and Mixing in Northern Mountain Environments using Stable Isotopes and Conceptual Runoff Models

    NASA Astrophysics Data System (ADS)

    Tetzlaff, D.; Buttle, J. M.; Carey, S. K.; Laudon, H.; McDonnell, J.; McNamara, J. P.; Van Huijgevoort, M.; Spence, C.; Soulsby, C.

    2015-12-01

    The lack of comprehensive tracer data sets still hinders the development of a generalized understanding of how northern headwaters function hydrologically. As part of the ERC funded "VeWa" project, we combined a conceptual rainfall-runoff model and input-output relationships of stable isotopes to understand ecohydrological influences on hydrological partitioning in in six high-latitude experimental catchments located in the UK, USA, Sweden and Canada. We used stable isotope records from precipitation and stream flow to examine the effects of soils and landcover. A meta-analysis was carried out using the HBV-model to estimate the main storage changes characterising annual water balances. Annual snowpack storage importance was ranked differently across the sites, and the subsequent rate and longevity of melt was reflected in calibrated parameters that determine partitioning of waters between more rapid and slower flowpaths and associated variations in soil and groundwater storage. Variability of stream water isotopic composition depends on: (i) rate and duration of spring snowmelt; (ii) significance of summer/autumn rainfall; (iii) relative importance of near-surface and deeper flowpaths in routing water to the stream. Flowpath partitioning also regulates influences of summer evaporation on drainage waters. Deviations of isotope data from the Global Meteoric Water Line showed subtle effects of internal catchment processes on isotopic fractionation most likely through evaporation. After accounting for climate, evaporative fractionation is strongest at sites where lakes and near-surface runoff processes in wet riparian soils can mobilize isotopically-enriched water during summer and autumn. Given close soil-vegetation coupling, this may result in spatial variability in soil water isotope pools available for plant uptake. We argue that stable isotope studies are crucial in addressing the many open questions on hydrological functioning of northern environments.

  18. Temporal variation of nitrogen balance within constructed wetlands treating slightly polluted water using a stable nitrogen isotope experiment.

    PubMed

    Zhang, Wanguang; Lei, Qiongye; Li, Zhengkui; Han, Huayang

    2016-02-01

    Slightly polluted water has become one of the main sources of nitrogen contaminants in recent years, for which constructed wetlands (CW) is a typical and efficient treatment. However, the knowledge about contribution of individual nitrogen removal pathways and nitrogen balance in constructed wetlands is still limited. In this study, a stable-isotope-addition experiment was performed in laboratory-scale constructed wetlands treating slightly polluted water to determine quantitative contribution of different pathways and temporal variation of nitrogen balance using Na(15)NO3 as tracer. Microbial conversion and substrate retention were found to be the dominant pathways in nitrogen removal contributing 24.4-79.9 and 8.9-70.7 %, respectively, while plant contributed only 4.6-11.1 % through direct assimilation but promoted the efficiency of other pathways. In addition, microbial conversion became the major way to remove N whereas nitrogen retained in substrate at first was gradually released to be utilized by microbes and plants over time. The findings indicated that N2 emission representing microbial conversion was not only the major but also permanent nitrogen removal process, thus keeping a high efficiency of microbial conversion is important for stable and efficient nitrogen removal in constructed wetlands. PMID:26438366

  19. Food sources of wintering piscivorous waterbirds in coastal waters: A triple stable isotope approach for the southeastern Baltic Sea

    NASA Astrophysics Data System (ADS)

    Morkūnė, Rasa; Lesutienė, Jūratė; Barisevičiūtė, Rūta; Morkūnas, Julius; Gasiūnaitė, Zita R.

    2016-03-01

    This study uses a triple isotope approach (δ13C, δ15N, and δ34S) to quantify the main food sources for wintering piscivorous waterbirds in the coastal zone of the southeastern Baltic Sea. Significant differences of δ15N and δ34S values among pelagic fishes, benthic fishes, and benthopelagic European smelt (Osmerus eperlanus) were detected, while δ13C was similar among these sources. Using different combinations of δ13C, δ15N, and δ34S values in mixing models, we found that common guillemot (Uria aalge) and red-throated diver (Gavia stellata) mostly foraged on pelagic prey (50-70% and 51-56%, respectively), whereas great crested grebe (Podiceps cristatus) consumed benthic prey (48-53%). European smelt comprised a substantial proportion of the diet of studied birds (19-36%). A stable isotope approach can be recommended as a non-lethal method to study avian diets in the coastal waters of the Baltic Sea.

  20. Comparison of the stable-isotopic composition of soil water collected from suction lysimeters, wick samplers, and cores in a sandy unsaturated zone

    USGS Publications Warehouse

    Landon, M.K.; Delin, G.N.; Komor, S.C.; Regan, C.P.

    1999-01-01

    Soil water collected from suction lysimeters and wick samplers buried in the unsaturated zone of a sand and gravel aquifer and extracted from soil cores were analyzed for stable oxygen and hydrogen isotope values. Soil water isotopic values differed among the three sampling methods in most cases. However, because each sampling method collected different fractions of the total soil-water reservoir, the isotopic differences indicated that the soil water at a given depth and time was isotopically heterogeneous. This heterogeneity reflects the presence of relatively more and less mobile components of soil water. Isotopic results from three field tests indicated that 95–100% of the water collected from wick samplers was mobile soil water while samples from suction lysimeters and cores were mixtures of more and less mobile soil water. Suction lysimeter samples contained a higher proportion of more mobile water (15–95%) than samples from cores (5–80%) at the same depth. The results of this study indicate that, during infiltration events, soil water collected with wick samplers is more representative of the mobile soil water that is likely to recharge ground water during or soon after the event than soil water from suction lysimeters or cores.

  1. Characterization of para-Nitrophenol-Degrading Bacterial Communities in River Water by Using Functional Markers and Stable Isotope Probing

    PubMed Central

    Eyice, Özge; Schäfer, Hendrik; Price, Oliver R.; Finnegan, Christopher J.; van Egmond, Roger A.; Shaw, Liz J.; Barrett, Glyn; Bending, Gary D.

    2015-01-01

    Microbial degradation is a major determinant of the fate of pollutants in the environment. para-Nitrophenol (PNP) is an EPA-listed priority pollutant with a wide environmental distribution, but little is known about the microorganisms that degrade it in the environment. We studied the diversity of active PNP-degrading bacterial populations in river water using a novel functional marker approach coupled with [13C6]PNP stable isotope probing (SIP). Culturing together with culture-independent terminal restriction fragment length polymorphism analysis of 16S rRNA gene amplicons identified Pseudomonas syringae to be the major driver of PNP degradation in river water microcosms. This was confirmed by SIP-pyrosequencing of amplified 16S rRNA. Similarly, functional gene analysis showed that degradation followed the Gram-negative bacterial pathway and involved pnpA from Pseudomonas spp. However, analysis of maleylacetate reductase (encoded by mar), an enzyme common to late stages of both Gram-negative and Gram-positive bacterial PNP degradation pathways, identified a diverse assemblage of bacteria associated with PNP degradation, suggesting that mar has limited use as a specific marker of PNP biodegradation. Both the pnpA and mar genes were detected in a PNP-degrading isolate, P. syringae AKHD2, which was isolated from river water. Our results suggest that PNP-degrading cultures of Pseudomonas spp. are representative of environmental PNP-degrading populations. PMID:26209677

  2. Characterization of para-Nitrophenol-Degrading Bacterial Communities in River Water by Using Functional Markers and Stable Isotope Probing.

    PubMed

    Kowalczyk, Agnieszka; Eyice, Özge; Schäfer, Hendrik; Price, Oliver R; Finnegan, Christopher J; van Egmond, Roger A; Shaw, Liz J; Barrett, Glyn; Bending, Gary D

    2015-10-01

    Microbial degradation is a major determinant of the fate of pollutants in the environment. para-Nitrophenol (PNP) is an EPA-listed priority pollutant with a wide environmental distribution, but little is known about the microorganisms that degrade it in the environment. We studied the diversity of active PNP-degrading bacterial populations in river water using a novel functional marker approach coupled with [(13)C6]PNP stable isotope probing (SIP). Culturing together with culture-independent terminal restriction fragment length polymorphism analysis of 16S rRNA gene amplicons identified Pseudomonas syringae to be the major driver of PNP degradation in river water microcosms. This was confirmed by SIP-pyrosequencing of amplified 16S rRNA. Similarly, functional gene analysis showed that degradation followed the Gram-negative bacterial pathway and involved pnpA from Pseudomonas spp. However, analysis of maleylacetate reductase (encoded by mar), an enzyme common to late stages of both Gram-negative and Gram-positive bacterial PNP degradation pathways, identified a diverse assemblage of bacteria associated with PNP degradation, suggesting that mar has limited use as a specific marker of PNP biodegradation. Both the pnpA and mar genes were detected in a PNP-degrading isolate, P. syringae AKHD2, which was isolated from river water. Our results suggest that PNP-degrading cultures of Pseudomonas spp. are representative of environmental PNP-degrading populations. PMID:26209677

  3. Using stable isotopes and integrated flow-tracer modeling to conceptualise vegetation influences on water partitioning, storage and runoff generation in high-latitude environments

    NASA Astrophysics Data System (ADS)

    Tetzlaff, Doerthe; Buttle, Jim; Carey, Sean; Laudon, Hjalmar; McDonnell, Jeff; McNamara, Jim; Spence, Chris; Sprenger, Matthias; van Huijgevoort, Marjolein; Soulsby, Chris

    2016-04-01

    Stable isotopes tracers have been widely used as a means to assess the sources and flow paths of stream flow in a wide range of geographical environments. However, the paucity of high resolution isotope data sets from high latitude northern headwaters hinders the development of a generalized understanding of boreal watershed. As part of the ERC funded "VeWa" project, we use stable isotopes of different waters (that is precipitation, soil water, groundwater, streamwater, plant xylem water) to understand the role of vegetation on the partitioning of precipitation, and the subsequent storage and release of water at six, long-term experimental sites across the wider North (in Scotland, Sweden, Canada and the US). We investigated the effects of vegetation on interception, precipitation partitioning and isotope inputs as well as evaporative losses and dynamics in soil water isotopes. We also used a tracer-aided, spatially distributed rainfall-runoff model to conceptualise and integrate flow paths, storage dynamics and mixing processes at the catchment scale. Whilst inter-site findings differ in detail, in general, vegetation canopy cover had a large influence on the quantity and distribution of interception and throughfall. However, the isotopic signature of throughfall was mainly driven by that of precipitation. Whilst temporal variability in soil water isotopes was mainly driven by throughfall or snowmelt in wet periods, the effects of soil evaporation was dominant in soils during the dry periods, with the effects of evaporative fractionation evident in in the upper 10cm of the soils. At some sites, this evaporative fractionation in the rooting zone seemed to explain the isotopic composition of xylem water. Despite these processes affecting the partitioning of isotopes in the soils, at the catchment scale modelling showed that these differences have limited influence on stream water isotopes. Using the coupled flow-tracer model, we could model stream and soil isotope

  4. Tracing coalbed natural gas-coproduced water using stable isotopes of carbon

    SciTech Connect

    Sharma, S.; Frost, C.D.

    2008-03-15

    Recovery of hydrocarbons commonly is associated with coproduction of water. This water may be put to beneficial use or may be reinjected into subsurface aquifers. In either case, it would be helpful to establish a fingerprint for that coproduced water so that it may be tracked following discharge on the surface or reintroduction to geologic reservoirs. This study explores the potential of using {delta}{sup 13}C of dissolved inorganic carbon (DIC) of coalbed natural gas (CBNG) - coproduced water as a fingerprint of its origin and to trace its fate once it is disposed on the surface. Our initial results for water samples coproduced with CBNG from the Powder River Basin show that this water has strongly positive {delta}{sup 13}C(DIC) (12 parts per thousand to 22 parts per thousand) that is readily distinguished from the negative {delta}{sup 13}C of most surface and ground water (-8 parts per thousand to -11 parts per thousand). Furthermore, the DIC concentrations in coproduced water samples are also high (more than 100 mg C/L) compared to the 20 to 50 mg C/L in ambient surface and ground water of the region. The distinctively high {delta}{sup 13}C and DIC concentrations allow us to identify surface and ground water that have incorporated CBNG-coproduced water. Accordingly, we suggest that the {delta}{sup 13}C(DIC) and DIC concentrations of water can be used for long-term monitoring of infiltration of CBNG-coproduced water into ground water and streams. Our results also show that the {delta} {sup 13}C (DIC) of CBNG-coproduced water from two different coal zones are distinct leading to the possibility of using {delta}{sup 13}C(DIC) to distinguish water produced from different coal zones.

  5. (Bio)degradation of glyphosate in water-sediment microcosms - A stable isotope co-labeling approach.

    PubMed

    Wang, Shizong; Seiwert, Bettina; Kästner, Matthias; Miltner, Anja; Schäffer, Andreas; Reemtsma, Thorsten; Yang, Qi; Nowak, Karolina M

    2016-08-01

    Glyphosate and its metabolite aminomethylphosphonic acid (AMPA) are frequently detected in water and sediments. Up to date, there are no comprehensive studies on the fate of glyphosate in water-sediment microcosms according to OECD 308 guideline. Stable isotope co-labeled (13)C3(15)N-glyphosate was used to determine the turnover mass balance, formation of metabolites, and formation of residues over a period of 80 days. In the water-sediment system, 56% of the initial (13)C3-glyphosate equivalents was ultimately mineralized, whereas the mineralization in the water system (without sediment) was low, reaching only 2% of (13)C-glyphosate equivalents. This finding demonstrates the key role of sediments in its degradation. Glyphosate was detected below detection limit in the water compartment on day 40, but could still be detected in the sediments, ultimately reaching 5% of (13)C3(15)N-glyphosate equivalents. A rapid increase in (13)C(15)N-AMPA was noted after 10 days, and these transformation products ultimately constituted 26% of the (13)C3-glyphosate equivalents and 79% of the (15)N-glyphosate equivalents. In total, 10% of the (13)C label and 12% of the (15)N label were incorporated into amino acids, indicating no risk bearing biogenic residue formation from (13)C3(15)N-glyphosate. Initially, glyphosate was biodegraded via the sarcosine pathway related to microbial growth, as shown by co-labeled (13)C(15)N-glycine and biogenic residue formation. Later, degradation via AMPA dominated under starvation conditions, as shown by the contents of (13)C-glycine. The presented data provide the first evidence of the speciation of the non-extractable residues as well as the utilization of glyphosate as a carbon and nitrogen source in the water-sediment system. This study also highlights the contribution of both the sarcosine and the AMPA degradation pathways under these conditions. PMID:27140906

  6. Influence of continental shelf processes in the water mass balance and productivity from stable isotope data on the Southeastern Brazilian coast

    NASA Astrophysics Data System (ADS)

    Venancio, Igor M.; Belem, Andre L.; dos Santos, Tarcio Henrique R.; Zucchi, Maria do R.; Azevedo, Antonio Expedito G.; Capilla, Ramsés; Albuquerque, Ana Luiza S.

    2014-11-01

    Stable isotopic composition (δ18O and δD of water, δ13CDIC) of the water column in the open ocean is related to the origin of water masses. Due to the recent increase of paleoceanographic studies on continental shelves, it is also important to understand their distribution and variability in those systems. To examine the influence of continental shelves internal processes on isotopic composition of water masses, we present data of stable isotopes and phosphate content from a western boundary upwelling system located on the Southeastern Brazilian coast and compare them with offshore observations. High mixing of the main water masses (SSW, TW and SACW) was observed in the majority of the samples collected during different seasons in 2011 and 2012. A mixing triangle approach was used to separate the water masses contribution and characterize their isotopic composition. In addition, an isotopic three end-member model was established, proposing it as a paleoceanographic tool to reconstruct relative contribution of these water masses in sediment records. Variations of δ18O values are linked to oceanographic dynamics, mixing, continental runoff and upwelling processes on the shelf. Differently the δ13CDIC variations in the middle and inner parts of the shelf are related to the productivity of the upwelling system. Seasonal variability of the δ13CDIC values may be also related to changes in the upwelling intensity.

  7. Water isotopes in desiccating lichens

    PubMed Central

    Cuntz, Matthias; Máguas, Cristina; Lakatos, Michael

    2009-01-01

    The stable isotopic composition of water is routinely used as a tracer to study water exchange processes in vascular plants and ecosystems. To date, no study has focussed on isotope processes in non-vascular, poikilohydric organisms such as lichens and bryophytes. To understand basic isotope exchange processes of non-vascular plants, thallus water isotopic composition was studied in various green-algal lichens exposed to desiccation. The study indicates that lichens equilibrate with the isotopic composition of surrounding water vapour. A model was developed as a proof of concept that accounts for the specific water relations of these poikilohydric organisms. The approach incorporates first their variable thallus water potential and second a compartmentation of the thallus water into two isotopically distinct but connected water pools. Moreover, the results represent first steps towards the development of poikilohydric organisms as a recorder of ambient vapour isotopic composition. PMID:19888598

  8. Water isotopes in desiccating lichens.

    PubMed

    Hartard, Britta; Cuntz, Matthias; Máguas, Cristina; Lakatos, Michael

    2009-12-01

    The stable isotopic composition of water is routinely used as a tracer to study water exchange processes in vascular plants and ecosystems. To date, no study has focussed on isotope processes in non-vascular, poikilohydric organisms such as lichens and bryophytes. To understand basic isotope exchange processes of non-vascular plants, thallus water isotopic composition was studied in various green-algal lichens exposed to desiccation. The study indicates that lichens equilibrate with the isotopic composition of surrounding water vapour. A model was developed as a proof of concept that accounts for the specific water relations of these poikilohydric organisms. The approach incorporates first their variable thallus water potential and second a compartmentation of the thallus water into two isotopically distinct but connected water pools. Moreover, the results represent first steps towards the development of poikilohydric organisms as a recorder of ambient vapour isotopic composition. PMID:19888598

  9. Sources, migration and transformation of antimony contamination in the water environment of Xikuangshan, China: Evidence from geochemical and stable isotope (S, Sr) signatures.

    PubMed

    Wen, Bing; Zhou, Jianwei; Zhou, Aiguo; Liu, Cunfu; Xie, Lina

    2016-11-01

    The Xikuangshan (XKS) mine in central China is the largest antimony (Sb) mine in the world. The mining activity has seriously contaminated the waters in the area. To determine the sources, migration and transformation of Sb contamination, 32 samples from groundwater (aquifer water), surface water and mine water were collected for water chemistry, trace element and SSO4 and Sr stable isotope analyses. The results showed that the groundwater and surface water were in an oxidized environment. The SSO4 and Sr isotope compositions in the water indicated that dissolved Sb and SO4(2) originated from sulfide mineral (Sb2S3) oxidation, whereas radiogenic Sr may have been sourced from silicified limestone and stibnite in the Shetianqiao aquifer. Furthermore, a positive correlation between δ(34)SSO4 and δ(87)Sr values revealed that the Sr, S and Sb in the waters had a common contamination source, i.e., silicified limestone and stibnite, whereas the Sr, S and Sb in rock and ore were sourced from Proterozoic basement clastics. The analysis also indicated that the isotope composition of dissolved SO4(2-) had been influenced by slight bacterial SO4 reduction in the Magunao aquifer. Mining or rock collapse may have caused Shetianqiao aquifer water to contaminate the Magunao aquifer water via mixing. This study has demonstrated that the stable isotopes of (34)SSO4 and (87)Sr, combined with hydrochemical methods, are effective in tracking the sources, migration and transformation of Sb contamination. PMID:27341112

  10. Residence times and age distributions of spring waters at the Semmering catchment area, Eastern Austria, as inferred from tritium, CFCs and stable isotopes.

    PubMed

    Han, Liangfeng; Hacker, Peter; Gröning, Manfred

    2007-03-01

    The groundwater system in the mountainous area of Semmering, Austria, was studied by environmental tracers in several karst springs. The tracers used included stable isotopes ((18)O, (2)H), tritium ((3)H) and chlorofluorocarbons (CFCs). The tracers provided valuable information in regard to (1) the mean altitude of the spring catchment areas; (2) the residence time and age distribution of the spring waters; and (3) the interconnection of the springs to a sinkhole. The combination of the stable isotopic data and the topography/geology provided the estimates of the mean altitudes of the catchment areas. Based on the stable isotopic data the recharge temperature of the spring waters was estimated. The smoothing of precipitation's isotopic signal in spring discharge provided information on the minimum transit time of the spring waters. Due to short observation time, (3)H data alone cannot be used for describing the mean residence time of the karst waters. CFCs, though useful in recognizing the co-existence of young (post-1993) water with old (CFC-free) water, could not be used to resolve age distribution models. It is shown in this article, however, that the combined use of tritium and CFCs can provide a better assessment of models to account for different groundwater age distributions. In Appendix A, a simplified method for collecting groundwater samples for the analysis of CFCs is described. The method provides a real facilitation for fieldwork. Test data are given for this sampling method in regard to potential contamination by atmospheric CFCs. PMID:17454271

  11. Stable carbon isotope ratios and intrinsic water-use efficiency of Miocene fossil leaves compared to modern congeners

    SciTech Connect

    Marshall, J.D.; Zhang, J.; Rember, W.C.; Jennings, D.; Larson, P. )

    1994-06-01

    Miocene fossil leaves of forest trees were extracted from the Clarkia, Idaho fossil beds and their stable carbon isotope ratios were analyzed. Fossils had higher lignin concentrations and lower cellulose concentrations that modern leaves due to diagenesis and the HF used to extract the fossils. Therefore, [delta][sup 13]C of extracted fossil lignin was compared to that of modern lignin. Fossil lignin [delta][sup 13]C was significantly different from that of congeneric modern leaves (paired t-test, P<0.0001), but was 1.9% less negative. Gymnosperms (Metasequoia, Taxodium) were less negative than angiosperms (e.g., Magnolia, Quercus, Acer, Persea), but no difference between evergreen and deciduous species was detected. Using published estimates of the concentration and [delta][sup 13]C of atmospheric CO[sub 2] during the Miocene was estimated the CO[sub 2] partial pressure gradient across the stomata (intrinsic water-use efficiency). Intrinsic water-use efficiency was at least 70% higher during this past [open quotes]greenhouse[close quotes] period than at present.

  12. Drought Impact on Water - Carbon Interaction in Soil: A Stable Isotopic Approach

    NASA Astrophysics Data System (ADS)

    Joseph, J.; Weiler, M.; Gessler, A.

    2014-12-01

    Extreme climatic conditions like drought introduce drastic changes in carbon and water dynamics in the plant - soil continuum, starting from carbon assimilation till carbon allocation in the soil, root water uptake till transpiration via leaves. Our objective was to study the drought impact on the dynamics of Carbon, and water cycles, as well as the interaction between them under extreme climatic conditions in the plant soil continuum. The first phase of the experiment involved 13CO2 pulse labeling of drought exposed and well-water beech microcosms, during which we monitored the 13C allocation to roots, and in the soil by measuring the CO2 concentration, ∂13C, and ∂18O of root derived CO2. We found that drought had a significant impact on, a) carbon assimilation, allocation, and translocation rate in the plant - soil system. The drought stressed plants not only assimilated fewer amounts of CO2, but also translocation of those assimilates belowground was extremely slow, and root respiration was low in comparison the well watered control plants. The second phase involved rewetting of the drought chambers (and the application of similar amounts of water to the controls) using D218O enriched water followed by an additional 13CO2 pulse labeling approach so as to study the effects of drought on the infiltration patterns of a precipitation event as well as the recovery of the carbon relations of previously drought stressed beech saplings.

  13. Tungsten Stable Isotope Compositions of Ferromanganese Crusts

    NASA Astrophysics Data System (ADS)

    Abraham, K.; Barling, J.; Hein, J. R.; Schauble, E. A.; Halliday, A. N.

    2014-12-01

    We report the first accurate and precise data for mass-dependent fractionation of tungsten (W) stable isotopes, using a double spike technique and MC-ICPMS. Results are expressed relative to the NIST 3136 W isotope standard as per mil deviations in 186W/184W (δ186W). Although heavy element mass-dependent fractionations are expected to be small, Tl and U both display significant low temperature isotopic fractionations. Theoretical calculations indicate that W nuclear volume isotopic effects should be smaller than mass-dependent fractionations at low temperatures. Hydrogenetic ferromanganese (Fe-Mn) crusts precipitate directly from seawater and have been used as paleoceanographic recorders of temporal changes in seawater chemistry. Crusts are strongly enriched in W and other metals, and are a promising medium for exploring W isotopic variability. Tungsten has a relatively long residence time in seawater of ~61,000 years, mainly as the tungstate ion (WO42-). Water depth profiles show conservative behaviour. During adsorption on Fe-Mn crusts, W species form inner-sphere complexes in the hexavalent (W6+) state. The major host phase is thought to be Mn oxides and the lighter W isotope is expected to be absorbed preferentially. Surface scrapings of 13 globally distributed hydrogenetic Fe-Mn crusts display δ186W from -0.08 to -0.22‰ (±0.03‰, 2sd). A trend toward lighter W isotope composition exists with increasing water depth (~1500 to ~5200m) and W concentration. One hydrothermal Mn-oxide sample is anomalously light and Mn nodules are both heavy and light relative to Fe-Mn crusts. Tungsten speciation depends on concentration, pH, and time in solution and is not well understood because of the extremely slow kinetics of the reactions. In addition, speciation of aqueous and/or adsorbed species might be sensitive to pressure, showing similar thermodynamic stability but different effective volumes. Thus, W stable isotopes might be used as a water-depth barometer in

  14. Experimental investigations of water fluxes within the soil-vegetation-atmosphere system: Stable isotope mass-balance approach to partition evaporation and transpiration

    NASA Astrophysics Data System (ADS)

    Wenninger, Jochen; Beza, Desta Tadesse; Uhlenbrook, Stefan

    Irrigated agriculture is the largest user of freshwater worldwide and the scale of irrigated agriculture can be so large that it can have dramatic effects on the water cycle and even alter regional climates. Therefore, it is vital to improve the water use efficiency of irrigated lands in order to address the sustainable use of water resources, the growing need for agricultural products, and the health of ecosystems. Environmental isotopes have unique attributes that make them particularly suitable for tracing hydrological pathways and quantifying hydrological fluxes within the soil-vegetation-atmosphere system. The stable isotopic composition of soil water is mainly controlled by precipitation or irrigation inputs and evaporative losses. Because transpiration does not fractionate soil water isotopes, it is possible to estimate the relative proportions of evaporation and transpiration using isotopic mass balance calculations. In this study experimental investigations, combining classical hydrometric measurements, tracer hydrological methods and a soil water model were applied to laboratory lysimeters to study the transpiration processes of Teff ( Eragrostis tea (Zucc.) Trotter). Teff is an annual bunch cereal and an important aliment in Ethiopia and Eritrea and it is also gaining popularity in other countries. To determine the soil water contents, sensors using a capacitance/frequency domain technology were installed at different depths and soil water samples for the isotope analysis were taken using pore water samplers. Water contents in different depths and water fluxes, such as percolation and evaporation were modeled using the HYDRUS-1D software package. By using an isotope mass balance model the total evaporation and the fractions between soil evaporation and transpiration could be determined. The water losses which were estimated using the isotope mass-balance approach are in good agreement with the measured values using classical hydrometric measurements. The

  15. Tracing ground-water movement by using the stable isotopes of oxygen and hydrogen, upper Penitencia Creek alluvial fan, Santa Clara Valley, California

    USGS Publications Warehouse

    Muir, K.S.; Coplen, Tyler B.

    1981-01-01

    Starting in 1965 the Santa Clara Valley Water District began importing about i00,000 acre-feet per year of northern California water. About one-half of this water was used to artificially recharge the Upper Penitencia Creek alluvial fan in Santa Clara Valley. In order to determine the relative amounts of local ground water and recharged imported water being pumped from the wells, stable isotopes of oxygen and hydrogen were used to trace the movement of the imported water in the alluvial fan. To trace the movement of imported water in the Upper Penitencia Creek alluvial fan, well samples were selected to give areal and depth coverage for the whole fan. The stable isotopes of oxygen-16, oxygen-18, and deuterium were measured in the water samples of imported water and from the wells and streams in the Santa Clara Valley. The d18oand dD compositions of the local runoff were about -6.00 o/oo (parts per thousand) and -40 o/oo, respectively; the average compositions for the local native ground-water samples were about -6.1 o/oo and -41 o/oo, respectively; and the average compositions of the imported water samples were -10.2 o/oo and -74 o/oo, respectively. (The oxygen isotopic composition of water samples is reported relative to Standard Mean Ocean Water, in parts per thousand.) The difference between local ground water and recharged imported water was about 4.1 o/oo in d18o and 33 o/oo in dL. The isotopic data indicate dilution of northern California water with local ground water in a downgradient direction. Two wells contain approximately 74 percent northern California water, six wells more than 50 percent. Data indicate that there may be a correlation between the percentage of northern California water and the depth or length of perforated intervals in wells.

  16. Ecological and dietary correlates of stable hydrogen isotope ratios in fur and body water of syntopic tropical bats.

    PubMed

    Voigt, Christian C; Schneeberger, Karin; Luckner, Anja

    2013-02-01

    Hydrogen stable isotope ratios of keratin (delta2H(K)) are increasingly used as endogenous markers to study animal movements, yet it is unclear what factors might influence delta2H(K) in free-ranging animals. We studied hydrogen stable isotope ratios of body water (delta2H(BW)) and fur keratin in 36 bat species (> 400 individuals) from a tropical forest assemblage to evaluate if delta2H(BW) and delta2H(K) are related to body size, trophic position, and movement ecology. We found a relatively large range of delta2H(BW) values (approximately 65 per thousand) across bat species. Our phylogenetically controlled analysis showed that delta2H(BW) was not related to body size, trophic position, or movement ecology of species. The analysis also indicated that delta2H(BW) of primary consumers (i.e., fruit-eating bats) was similar to that of fruit juice, and delta2H(BW) of secondary consumers (i.e., animalivorous bats) was similar to that of surface water. Across bat species, delta2H(K) tended to decrease with increasing delta2H(BW), suggesting that delta2H(K) is not directly linked to delta2H(BW). We further tested whether delta2H(K) varied with a species' trophic position (measured as delta15N) and movement ecology (local or regional species). In syntopic bats, delta2H(K) ranged over 73 per thousand, yet delta2H(K) was related neither to delta15N nor to the movement ecology of species. Fur keratin of secondary consumers was more enriched in 2H by 44 per thousand and in 15N by 3.7 per thousand compared with fur keratin of primary consumers. In an intraspecific analysis, we found that delta2H(K) of an insectivorous bat varied by 20 per thousand between colonies at 4 km distance. Within this species, deltaH(K) was not related to individual delta15N and body mass. Our data suggest that variation in delta2H(K) can be large in bats of tropical assemblages, both across species (range approximately 70 per thousand) and even within sedentary species (range approximately 20 per

  17. Quantifying uncertainty in stable isotope mixing models

    NASA Astrophysics Data System (ADS)

    Davis, Paul; Syme, James; Heikoop, Jeffrey; Fessenden-Rahn, Julianna; Perkins, George; Newman, Brent; Chrystal, Abbey E.; Hagerty, Shannon B.

    2015-05-01

    Mixing models are powerful tools for identifying biogeochemical sources and determining mixing fractions in a sample. However, identification of actual source contributors is often not simple, and source compositions typically vary or even overlap, significantly increasing model uncertainty in calculated mixing fractions. This study compares three probabilistic methods, Stable Isotope Analysis in R (SIAR), a pure Monte Carlo technique (PMC), and Stable Isotope Reference Source (SIRS) mixing model, a new technique that estimates mixing in systems with more than three sources and/or uncertain source compositions. In this paper, we use nitrate stable isotope examples (δ15N and δ18O) but all methods tested are applicable to other tracers. In Phase I of a three-phase blind test, we compared methods for a set of six-source nitrate problems. PMC was unable to find solutions for two of the target water samples. The Bayesian method, SIAR, experienced anchoring problems, and SIRS calculated mixing fractions that most closely approximated the known mixing fractions. For that reason, SIRS was the only approach used in the next phase of testing. In Phase II, the problem was broadened where any subset of the six sources could be a possible solution to the mixing problem. Results showed a high rate of Type I errors where solutions included sources that were not contributing to the sample. In Phase III some sources were eliminated based on assumed site knowledge and assumed nitrate concentrations, substantially reduced mixing fraction uncertainties and lowered the Type I error rate. These results demonstrate that valuable insights into stable isotope mixing problems result from probabilistic mixing model approaches like SIRS. The results also emphasize the importance of identifying a minimal set of potential sources and quantifying uncertainties in source isotopic composition as well as demonstrating the value of additional information in reducing the uncertainty in calculated

  18. Uses of stable isotopes in fish ecology

    EPA Science Inventory

    Analyses of fish tissues (other than otoliths) for stable isotope ratios can provide substantial information on fish ecology, including physiological ecology. Stable isotopes of nitrogen and carbon frequently are used to determine the mix of diet sources for consumers. Stable i...

  19. STABLE ISOTOPE ANALYSIS OF MTBE TO EVALUATE THE SOURCE OF TBA IN GROUND WATER

    EPA Science Inventory

    Although tert-butyl alcohol (TBA) has not been used as a fuel oxygenate in Orange County, California, the concentrations of TBA in ground water at gasoline spill sites are high compared those of the conventional fuel oxygenate methyl tert-butyl ether (MTBE). In the year 2002, th...

  20. Stable Isotope Spectroscopy for Diagnostic Medicine

    NASA Astrophysics Data System (ADS)

    Murnick, D. E.

    2000-06-01

    Isotopic tracers have been used in medical research for more than fifty years. Radioactive isotopes have been most used because of the high detection efficiencies possible. With increased awareness of the effects of low level radiation and radioactive waste management problems, the need for safe non radioactive tracers has become apparent. Rare stable isotopes of biologically active elements can be used for metabolic and pharmacokinetic studies provided that both sufficient detection sensitivity can be achieved and reliable cost effective instruments can be developed. High resolution optical spectroscopic methods which can determine isotopic ratios with high precision and accuracy are viable for research and clinical use. The study of 13C/12C ratios in CO2 for breath test diagnostics will be described in detail. Using the laser optogalvonic effect with isotopic lasers a specific medical diagnostic for h-pylori infection, has recently received FDA approval. Opportunities exist to study D/H ratios in water and 18O/16O ratios in CO2 and water for basic metabolism diagnostics and 15N/14N ratios in urine for liver function and related studies.

  1. A Pilot Study of Watershed Flow Using Stable Water Isotopes in Support of the Development of the Lamprey River Watershed (Southeast New Hampshire) as a Hydrologic Observatory

    NASA Astrophysics Data System (ADS)

    Frades, M.; Davis, J.; Bryce, J.; McDowell, W. H.

    2008-12-01

    The Lamprey River Watershed provides a suite of ecologic, geographic, geologic, and cultural characteristics that together provide an excellent opportunity to establish a convenient, unique, instructive, and informative natural laboratory. Researchers at the University of New Hampshire are establishing the Lamprey River Watershed, located in the seacoast region of New Hampshire, as a long term hydrologic observatory, where the instrumentation, data, and results from multi-disciplinary studies can be integrated to achieve greater understanding of the hydrologic system as a whole.One component of this proposed research is the establishment of a long term record of water isotope data. The results of a 1.5-year pilot study of stable water isotopes in the Headwaters of the Lamprey River Watershed (HLRW) are the focus of this presentation. In order to better understand groundwater flowpaths and residence times within the HLRW, we used stable water isotopes as natural tracers. For the period of June 2006 through October 2007, over 200 total water samples of groundwater, surface water, precipitation, and infiltration were collected and analyzed for stable hydrogen and oxygen isotopes. Based on analysis of isotopic and hydrometric data, the groundwater system is interpreted to be comprised of three distinct but interconnected reservoirs: a shallow groundwater reservoir which does not directly contribute to stream flow at the watershed outlet and has a mean residence time greater than 9 years; a near-surface groundwater reservoir, which is fed by the shallow system, flows through surface water bodies and wetlands with a mean residence time of approximately 1.5 months, and is the primary source of baseflow in the stream network; and a deep groundwater reservoir. The findings have significant implications for the interpretation of biogeochemical mass balance models of the Lamprey River Watershed and ongoing strontium isotope and trace element tracer studies. In a broader sense

  2. Transport of stable isotopes of water and sulphate within reclaimed oil sands saline-sodic mine overburden

    NASA Astrophysics Data System (ADS)

    Huang, Mingbin; Hilderman, Joel N.; Barbour, Lee

    2015-10-01

    The reclamation of shale overburden dumps from oil sands mining requires the placement of reclamation covers comprised of salvaged organic and mineral soils. The primary issues associated with the long-term performance of these covers are their ability to store sufficient water to meet transpiration demands and the potential threat of salt ingress into the cover from the underlying shale. The first issue has been addressed in previous studies, so the objective of this study was to evaluate controls on salt ingress through observations and modelling of the transport of the stable isotopes of water and salt within reclaimed profiles at the South Bison Hills overburden dump located north of Fort McMurray, Alberta. The water flow model was based on a dual porosity soil-vegetation-atmosphere model calibrated to observed field data. This model was then used to simulate deuterium and sulphate transport within the soil profiles. The optimized transport model for deuterium was used to estimate net percolation rates through the cover soil into the underlying shale. This model was then used to assess the controls on sulphate migration, including the rate of sulphate generation as a result of ongoing oxidation of the pyritic shale. The model results indicate that the average net percolation rate is a function of topographic location, ranging from 2.2 × 10-5 m/d at slope locations to 20.8 × 10-5 m/d at plateau locations during the unfrozen days. These rates of net percolation should have produced observable patterns of salt flushing from the cover and upper shale. However, the observed sulphate levels could only be simulated by including a production term related to pyrite oxidation of the shale. The simulated oxidation rates ranged from 0.4 to 5.65 mg/L/d, similar to those estimated from previous laboratory and field investigations.

  3. Stable isotopes in cave drip waters from the semi-arid southern Portugal: implication for paleoenvironment reconstructions

    NASA Astrophysics Data System (ADS)

    Veiga-Pires, Cristina; Hélie, Jean-François; Hillaire-Marcel, Claude

    2014-05-01

    Paleo-environmental studies rely on proxies for which present day conditions need to be documented. Here, we present results from a nearly two years sampling program of waters in precipitation, aquifers and cave drip waters in the semi arid region of Southern Portugal where a Mediterranean type climate prevails. Isotopic compositions of precipitations at Faro, from 1978 until 2001, are available through the Global Network of Isotopes in Precipitation (GNIP) database of the International Atomic Energy Agency. In addition, we measured oxygen and hydrogen isotopic compositions of water samples collected in 2011 and 2012 at one meteorological station located 20 km apart from the cave. In the cave itself, four different dripping locations were surveyed. Finally, five wells from the aquifer flowing underneath the cave were also sampled. Whereas local meteoric water line obtained from GNIP data shows an important contribution of local evaporating waters, precipitation data from this project rather points out to a drier moisture source, exhibiting a deuterium excess of close to 16.5 oȦquifer isotopic compositions show very small variations during the 2 yr sampling period, with mean values of -4.53±0.06 o (VSMOW) and 23.39±0.81 o (VSMOW) for δ18O and δ2H, respectively. On the other hand, drip waters isotopic compositions are dependent of the sampling site, although varying linearly (δ2H~13.3*δ18O + 38.1, R2=0.74, p

  4. State of radionuclides in seawater. Comparison of natural stable and artificial radioactive isotope s of mercury and zinc in natural waters of the arid zone of the USSR

    SciTech Connect

    Rakhmatov, U; Khikmatov, K; Kist, A.A.; Kulmatov, R.A.; Teshabaev, S.T.; Volkov, A.A.

    1986-09-01

    This paper studies the state of stable and artificial radioactive isotopes of merury and zinc in natural waters of the arid zone of the USSR by radioactivity and radiochemical methods. Convergent results have been obtained for the dissolved forms of mercury and zinc in natural waters of the arid zone in a comparison of the results of radioactivation analysis and laboratory simulation using the radionuclides mercury-203 and zinc-65.

  5. Quality assurance and quality control in light stable isotope laboratories: A case study of Rio Grande, Texas, water samples

    USGS Publications Warehouse

    Coplen, T.B.; Qi, H.

    2009-01-01

    New isotope laboratories can achieve the goal of reporting the same isotopic composition within analytical uncertainty for the same material analysed decades apart by (1) writing their own acceptance testing procedures and putting them into their mass spectrometric or laser-based isotope-ratio equipment procurement contract, (2) requiring a manufacturer to demonstrate acceptable performance using all sample ports provided with the instrumentation, (3) for each medium to be analysed, prepare two local reference materials substantially different in isotopic composition to encompass the range in isotopic composition expected in the laboratory and calibrated them with isotopic reference materials available from the International Atomic Energy Agency (IAEA) or the US National Institute of Standards and Technology (NIST), (4) using the optimum storage containers (for water samples, sealing in glass ampoules that are sterilised after sealing is satisfactory), (5) interspersing among sample unknowns local laboratory isotopic reference materials daily (internationally distributed isotopic reference materials can be ordered at three-year intervals, and can be used for elemental analyser analyses and other analyses that consume less than 1 mg of material) - this process applies to H, C, N, O, and S isotope ratios, (6) calculating isotopic compositions of unknowns by normalising isotopic data to that of local reference materials, which have been calibrated to internationally distributed isotopic reference materials, (7) reporting results on scales normalised to internationally distributed isotopic reference materials (where they are available) and providing to sample submitters the isotopic compositions of internationally distributed isotopic reference materials of the same substance had they been analysed with unknowns, (8) providing an audit trail in the laboratory for analytical results - this trail commonly will be in electronic format and might include a laboratory

  6. Quality assurance and quality control in light stable isotope laboratories: a case study of Rio Grande, Texas, water samples.

    PubMed

    Coplen, Tyler B; Qi, Haiping

    2009-06-01

    New isotope laboratories can achieve the goal of reporting the same isotopic composition within analytical uncertainty for the same material analysed decades apart by (1) writing their own acceptance testing procedures and putting them into their mass spectrometric or laser-based isotope-ratio equipment procurement contract, (2) requiring a manufacturer to demonstrate acceptable performance using all sample ports provided with the instrumentation, (3) for each medium to be analysed, prepare two local reference materials substantially different in isotopic composition to encompass the range in isotopic composition expected in the laboratory and calibrated them with isotopic reference materials available from the International Atomic Energy Agency (IAEA) or the US National Institute of Standards and Technology (NIST), (4) using the optimum storage containers (for water samples, sealing in glass ampoules that are sterilised after sealing is satisfactory), (5) interspersing among sample unknowns local laboratory isotopic reference materials daily (internationally distributed isotopic reference materials can be ordered at three-year intervals, and can be used for elemental analyser analyses and other analyses that consume less than 1 mg of material) - this process applies to H, C, N, O, and S isotope ratios, (6) calculating isotopic compositions of unknowns by normalising isotopic data to that of local reference materials, which have been calibrated to internationally distributed isotopic reference materials, (7) reporting results on scales normalised to internationally distributed isotopic reference materials (where they are available) and providing to sample submitters the isotopic compositions of internationally distributed isotopic reference materials of the same substance had they been analysed with unknowns, (8) providing an audit trail in the laboratory for analytical results - this trail commonly will be in electronic format and might include a laboratory

  7. Understanding the role of fog in forest hydrology: Stable isotopes as tools for determining input and partitioning of cloud water in montane forests

    USGS Publications Warehouse

    Scholl, M.; Eugster, W.; Burkard, R.

    2011-01-01

    Understanding the hydrology of tropical montane cloud forests (TMCF) has become essential as deforestation of mountain areas proceeds at an increased rate worldwide. Passive and active cloud-water collectors, throughfall and stemflow collectors, visibility or droplet size measurements, and micrometeorological sensors are typically used to measure the fog water inputs to ecosystems. In addition, stable isotopes may be used as a natural tracer for fog and rain. Previous studies have shown that the isotopic signature of fog tends to be more enriched in the heavier isotopes 2H and 18O than that of rain, due to differences in condensation temperature and history. Differences between fog and rain isotopes are largest when rain is from synoptic-scale storms, and fog or orographic cloud water is generated locally. Smaller isotopic differences have been observed between rain and fog on mountains with orographic clouds, but only a few studies have been conducted. Quantifying fog deposition using isotope methods is more difficult in forests receiving mixed precipitation, because of limitations in the ability of sampling equipment to separate fog from rain, and because fog and rain may, under some conditions, have similar isotopic composition. This article describes the various types of fog most relevant to montane cloud forests and the importance of fog water deposition in the hydrologic budget. A brief overview of isotope hydrology provides the background needed to understand isotope applications in cloud forests. A summary of previous work explains isotopic differences between rain and fog in different environments, and how monitoring the isotopic signature of surface water, soil water and tree xylem water can yield estimates of the contribution of fog water to streamflow, groundwater recharge and transpiration. Next, instrumentation to measure fog and rain, and methods to determine isotopic concentrations in plant and soil water are discussed. The article concludes with

  8. Stable isotopic analyses in paleoclimatic reconstruction

    SciTech Connect

    Wigand, P.E.

    1995-09-01

    Most traditional paleoclimatic proxy data have inherent time lags between climatic input and system response that constrain their use in accurate reconstruction of paleoclimate chronology, scaling of its variability, and the elucidation of the processes that determine its impact on the biotic and abiotic environment. With the exception of dendroclimatology, and studies of short-lived organisms and pollen recovered from annually varved lacustrine sediments, significant periods of time ranging from years, to centuries, to millennia may intervene between climate change and its first manifestation in paleoclimatic proxy data records. Reconstruction of past climate through changes in plant community composition derived from pollen sequences and plant remains from ancient woodrat middens, wet environments and dry caves all suffer from these lags. However, stable isotopic analyses can provide more immediate indication of biotic response to climate change. Evidence of past physiological response of organisms to changes in effective precipitation as climate varies can be provided by analyses of the stable isotopic content of plant macrofossils from various contexts. These analyses consider variation in the stable isotopic (hydrogen, oxygen and carbon) content of plant tissues as it reflects (1) past global or local temperature through changes in meteoric (rainfall) water chemistry in the case of the first two isotopes, and (2) plant stress through changes in plant respiration/transpiration processes under differing water availability, and varying atmospheric CO, composition (which itself may actually be a net result of biotic response to climate change). Studies currently being conducted in the Intermountain West indicate both long- and short-term responses that when calibrated with modem analogue studies have the potential of revealing not only the timing of climate events, but their direction, magnitude and rapidity.

  9. The stable isotopic composition of Daphnia ephippia reflects changes in δ13C and δ18O values of food and water

    NASA Astrophysics Data System (ADS)

    Schilder, J.; Tellenbach, C.; Möst, M.; Spaak, P.; van Hardenbroek, M.; Wooller, M. J.; Heiri, O.

    2015-06-01

    The stable isotopic composition of fossil resting eggs (ephippia) of Daphnia spp. is being used to reconstruct past environmental conditions in lake ecosystems. However, the underlying assumption that the stable isotopic composition of the ephippia reflects the stable isotopic composition of the parent Daphnia, of their diet and of the environmental water have yet to be confirmed in a controlled experimental setting. We performed experiments with Daphnia pulicaria cultures, which included a control treatment conducted at 12 °C in filtered lake water and with a diet of fresh algae and three treatments in which we manipulated the stable carbon isotopic composition (δ13C value) of the algae, stable oxygen isotopic composition (δ18O value) of the water and the water temperature, respectively. The stable nitrogen isotopic composition (δ15N value) of the algae was similar for all treatments. At 12 °C, differences in algal δ13C values and in δ18O values of water were reflected in those of Daphnia. The differences between ephippia and Daphnia stable isotope ratios were similar in the different treatments (δ13C: +0.2 ± 0.4 ‰ (standard deviation); δ15N: -1.6 ± 0.4 ‰; δ18O: -0.9 ± 0.4 ‰), indicating that changes in dietary δ13C values and in δ18O values of water are passed on to these fossilizing structures. A higher water temperature (20 °C) resulted in lower δ13C values in Daphnia and ephippia than in the other treatments with the same food source and in a minor change in the difference between δ13C values of ephippia and Daphnia (to -1.3 ± 0.3 ‰). This may have been due to microbial processes or increased algal respiration rates in the experimental containers, which may not affect Daphnia in natural environments. There was no significant difference in the offset between δ18O and δ15N values of ephippia and Daphnia between the 12 and 20 °C treatments, but the δ18O values of Daphnia and ephippia were on average 1.2 ‰ lower at 20 °C than at

  10. A comprehensive theory for the coupling between terrestrial carbon and water cycles, supported by stable carbon isotope measurements from leaves

    NASA Astrophysics Data System (ADS)

    Wang, H.; Cornwell, W.; Wright, I. J.; Prentice, I. C.

    2014-12-01

    Stomata actively regulate the CO2 concentration inside plant leaves, which co-determines the biochemical rate of photosynthesis. Stomatal behaviour thus controls leaf-level water-use efficiency and the 'exchange rate' between the terrestrial carbon and hydrological cycles. Least-cost theory (based on the hypothesis that plants minimize the combined unit costs of maintaining the capacities for water transport and carbon uptake) predicts that (a) long-term mean values of the ci/ca ratio, i.e. the ratio of leaf-internal to ambient CO2 concentration, should be independent of both photon flux density and ca; and (b) these values should vary systematically with growing-season vapour pressure deficit, growth temperature, and atmospheric pressure. Stable carbon isotope (δ13C) measurements provide an integrated measure of the ci/ca in C3 plants. A number of previous studies have focused on the aridity dependence of δ13C. The temperature dependence seems to have been overlooked, but the elevation dependence has been known for a long time: plants at high elevations have systematically lowered ci/ca, and correspondingly increased photosynthetic capacity (Vcmax). Why this should be is a long-standing puzzle: there are various speculative explanations in the literature, and a certain amount of controversy. By contrast, least-cost theory provides quantitative predictions of all three environmental effects. We have analysed a large (3652) set of δ13C measurements from C3 plants, spanning all latitudes and biomes, and shown that these predictions are quantitatively consistent with environmental dependences that can be shown in the measurements using a generalized linear model. This analysis implies the ability to predict ci/ca ratios for large-scale terrestrial ecosystem modelling. Combined with the long-standing 'co-ordination hypothesis' for the control of photosynthetic capacity, least-cost theory provides a basis for a remarkably simple global model for gross primary

  11. Stable sulfur and carbon isotope investigations of pore-water and solid-phase compounds in sediments of the Chapopote Asphalt Volcano, southern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Wilhelm, T.; Bruechert, V.; Pape, T.; Schubotz, F.; Kasten, S.

    2007-05-01

    During R/V Meteor cruise M67 2a/b (March-April 2006) to the Asphalt Volcanoes of the southern Gulf of Mexico two gravity cores were retrieved from the central depression of the Chapopote Knoll which contained viscous oil/asphalt a few meters below the sediment surface. Also several push cores were taken with the remotely operated vehicle (ROV) QUEST at sites where oil/asphalt reached closely below the sediment surface. From these cores solid-phase and pore-water samples were taken for on-board and subsequent shore-based analyses. Together with a core taken from a background site which is not influenced by asphalt/oil seepage these sediment and pore water samples are currently subject to detailed analyses of (1) the stable sulfur isotopic composition of both dissolved (sulfate and sulfide) and solid-phase (iron monosulfides, pyrite) sulfur compounds, and (2) the composition and stable carbon isotopic signatures of hydrocarbon gases. The major aims of these investigations are to identify whether and to which extent the upward migration of oil, asphalt and gas (1) stimulates biogeochemical processes and turn-over rates, and (2) influences the stable sulfur isotopic signatures of both dissolved and solid phase sulfur compounds. Furthermore, we seek to determine the potential of these - possibly unusual - stable sulfur isotopic signals of solid-phase sulfides to reconstruct hydrocarbon seepage in older geological records and to elucidate how the composition and the stable carbon isotopic signatures of the hydrocarbon gases are altered by the action of typical chemosynthetic communities thriving at these sites.

  12. Stable isotopes of soil water are affected by clay minerals: A post correction approach for dry soils based on physicochemical soil properties

    NASA Astrophysics Data System (ADS)

    Gaj, Marcel; Kaufhold, Stephan; Koeniger, Paul; Matthias, Beyer; Himmelsbach, Thomas

    2016-04-01

    The cryogenic vacuum extraction is commonly used to access soil water that will be subsequently analyzed for stable isotopes (18O and 2H). However, the analytical error associated with this method is high compared to that of stable isotopes measured directly from water samples. Additionally, the accuracy of data derived from soil water extractions decreases with the increasing presence of fine compounds such as silt and clay. To overcome these limitations an extended applicability of the cryogenic vacuum extraction method is demonstrated. This study proposes two new methods to improve isotope values using the cryogenic vacuum extraction method. First, by showing that the extraction temperature of 205 ° C improves the precision and the accuracy for all tested soil types. Secondly, that the post correction of data based on physicochemical soil properties and common extraction temperature will reduce errors. Results show a reduction in error of d-values of soil water derived from soils with clay content between 0.1 to 48 %. The analytical error could be significantly reduced compared to previous studies by increasing the extraction temperature even for soils with high clay content. Soil water extractions from sandy soils are improved by halving the analytical error. If soil material is available, the proposed correction scheme can be applied to past isotope data and will improve comparability between studies and heterogeneous soils. It is recommended to conduct spike experiments prior to unsaturated zone isotope studies. We encourage future experiments with extraction temperatures above 205 ° C. If previously oven dried substrate is used for standard preparation old water might remain in soil with a fine texture (i.e., high clay content) after oven drying at 105 ° C and that this old water will enrich any added calibration water resulting in the enrichment of all samples normalized using it.

  13. What can one sample tell us? Stable isotopes can assess complex processes in national assessments of lakes, rivers and streams.

    EPA Science Inventory

    Stable isotopes can be very useful in large-scale monitoring programs because samples for isotopic analysis are easy to collect, and isotopes integrate information about complex processes such as evaporation from water isotopes and denitrification from nitrogen isotopes. Traditi...

  14. Substitution of stable isotopes in Chlorella

    NASA Technical Reports Server (NTRS)

    Flaumenhaft, E.; Katz, J. J.; Uphaus, R. A.

    1969-01-01

    Replacement of biologically important isotopes in the alga Chlorella by corresponding heavier stable isotopes produces increasingly greater deviations from the normal cell size and changes the quality and distribution of certain cellular components. The usefulness of isotopically altered organisms increases interest in the study of such permuted organisms.

  15. Stable Isotope Signatures for Microbial Forensics

    SciTech Connect

    Kreuzer, Helen W.

    2012-01-03

    The isotopic distribution of the atoms composing the molecules of microorganisms is a function of the substrates used by the organisms. The stable isotope content of an organism is fixed so long as no further substrate consumption and biosynthesis occurs, while the radioactive isotopic content decays over time. The distribution of stable isotopes of C, N, O and H in heterotrophic microorganisms is a direct function of the culture medium, and therefore the stable isotope composition can be used to associate samples with potential culture media and also with one another. The 14C content depends upon the 14C content, and therefore the age, of the organic components of the culture medium, as well as on the age of the culture itself. Stable isotope signatures can thus be used for sample matching, to associate cultures with specific growth media, and to predict characteristics of growth media.

  16. Stable isotope (δ18O and δ2H) data for precipitation, stream water, and groundwater in Puerto Rico

    USGS Publications Warehouse

    Scholl, Martha A.; Torres-Sanchez, Angel; Rosario-Torres, Manuel

    2014-01-01

    Puerto Rico is located in the northeastern Caribbean Sea (18.2 °N, 66.3 °W), with the Atlantic Ocean on its northern coast. The U.S. Geological Survey’s Water, Energy, and Biogeochemical Budgets (WEBB) program study area in which most of these data were collected comprises the El Yunque National Forest and surrounding area of eastern Puerto Rico. Samples were collected in two forested watersheds, the Rio Mameyes and the Rio Icacos/Rio Blanco, on opposite sides of a ridge in the Luquillo Mountains on the eastern end of the island (fig. 1). Elevation in both watersheds ranges from sea level to approximately 1,000 meters (m). Near sea level, land use is mixed pasture, moist forest, and residential, grading to completely forested within the boundaries of El Yunque National Forest. Forest type changes with elevation from tabonuco to palo colorado to sierra palm to cloud forest above approximately 950 m (Murphy and others, 2012). The Rio Mameyes watershed is oriented north-northeast, and the basin is underlain by volcaniclastic bedrock (basaltic to andesitic volcanic sandstone/mudstone/conglomerate/breccia). The Rio Icacos/Rio Blanco watershed is oriented south-southeast. The Rio Icacos is one of the headwaters of the Rio Blanco and is underlain by quartz diorite. The lower Rio Blanco basin is underlain by andesitic volcaniclastic bedrock. This report also contains a long-term rain isotope dataset from the San Agustin site, in north-central Puerto Rico (fig. 1). Puerto Rico has a tropical climate dominated by easterly trade winds, and seasonal climate patterns affect the hydrology of the study area. The summer wet season is characterized by convective precipitation from tropical easterly waves, troughs, and cyclonic low-pressure systems, including tropical storms and hurricanes; in contrast, the drier winter season is characterized by trade-wind showers and frontal systems. The highest single-event rainfall totals tend to be associated with tropical storms

  17. Hydrogeochemistry and quality of surface water and groundwater in the vicinity of Lake Monoun, West Cameroon: approach from multivariate statistical analysis and stable isotopic characterization.

    PubMed

    Kamtchueng, Brice T; Fantong, Wilson Y; Wirmvem, Mengnjo J; Tiodjio, Rosine E; Takounjou, Alain F; Ndam Ngoupayou, Jules R; Kusakabe, Minoru; Zhang, Jing; Ohba, Takeshi; Tanyileke, Gregory; Hell, Joseph V; Ueda, Akira

    2016-09-01

    With the use of conventional hydrogeochemical techniques, multivariate statistical analysis, and stable isotope approaches, this paper investigates for the first time surface water and groundwater from the surrounding areas of Lake Monoun (LM), West Cameroon. The results reveal that waters are generally slightly acidic to neutral. The relative abundance of major dissolved species are Ca(2+) > Mg(2+) > Na(+) > K(+) for cations and HCO3 (-) ≫ NO3 (-) > Cl(-) > SO4 (2-) for anions. The main water type is Ca-Mg-HCO3. Observed salinity is related to water-rock interaction, ion exchange process, and anthropogenic activities. Nitrate and chloride have been identified as the most common pollutants. These pollutants are attributed to the chlorination of wells and leaching from pit latrines and refuse dumps. The stable isotopic compositions in the investigated water sources suggest evidence of evaporation before recharge. Four major groups of waters were identified by salinity and NO3 concentrations using the Q-mode hierarchical cluster analysis (HCA). Consistent with the isotopic results, group 1 represents fresh unpolluted water occurring near the recharge zone in the general flow regime; groups 2 and 3 are mixed water whose composition is controlled by both weathering of rock-forming minerals and anthropogenic activities; group 4 represents water under high vulnerability of anthropogenic pollution. Moreover, the isotopic results and the HCA showed that the CO2-rich bottom water of LM belongs to an isolated hydrological system within the Foumbot plain. Except for some springs, groundwater water in the area is inappropriate for drinking and domestic purposes but good to excellent for irrigation. PMID:27535404

  18. Evaluating the Historical Importance of Impact Induced Hydrothermal Systems on Mars Using the Stable Isotopic Composition of Martian Water

    NASA Technical Reports Server (NTRS)

    Niles, Paul B.

    2010-01-01

    The importance of impact events during the early history of Mars is obvious through a simple examination of the character of the martian surface. This ancient, heavily cratered terrain has been shown to be associated with extensive phyllosilicate deposits. This geologic link could suggest that the extensive phyllosilicate-forming alteration may have occurred during early martian history through impact-induced hydrothermal alteration. However, examination of the oxygen isotopic composition of water on Mars suggests that the extensive phyllosilicate deposits were formed primarily through low temperature (<30 C) interactions, and that high temperature weathering in impact-induced hydrothermal systems have not been a dominant process on Mars. The average oxygen isotopic composition of water on Earth is dictated by the nature of water-rock interactions. If these interactions occur at higher temperatures then the water will contain a higher proportion of 18O, while lower temperature interactions will result in water with a lower proportion of 18O. Water on Earth today contains a higher proportion of 18O because of plate tectonics and hydrothermal interaction at mid-ocean ridges. The oxygen isotopic composition of water on early earth, however, may have been quite different, containing a smaller proportion of 18O suggesting much less hydrothermal interaction. Because there are not yet any direct measurements of the oxygen isotopic composition of water on Mars, it needs to be inferred through examination of carbonates preserved in martian meteorites and the isotopic composition of atmospheric CO2. This can be done because the oxygen incorporated into carbonates and CO2 is easily exchanged with liquid water if it is present. Independently, both measurements provide an estimate for the (Sigma)18O of water on Mars to be near -16%. This composition is consistent with low temperature weathering of the silicate crust, and indicates that impact hydrothermal systems did not play

  19. Quantifying uncertainty in stable isotope mixing models

    SciTech Connect

    Davis, Paul; Syme, James; Heikoop, Jeffrey; Fessenden-Rahn, Julianna; Perkins, George; Newman, Brent; Chrystal, Abbey E.; Hagerty, Shannon B.

    2015-05-19

    Mixing models are powerful tools for identifying biogeochemical sources and determining mixing fractions in a sample. However, identification of actual source contributors is often not simple, and source compositions typically vary or even overlap, significantly increasing model uncertainty in calculated mixing fractions. This study compares three probabilistic methods, SIAR [Parnell et al., 2010] a pure Monte Carlo technique (PMC), and Stable Isotope Reference Source (SIRS) mixing model, a new technique that estimates mixing in systems with more than three sources and/or uncertain source compositions. In this paper, we use nitrate stable isotope examples (δ15N and δ18O) but all methods tested are applicable to other tracers. In Phase I of a three-phase blind test, we compared methods for a set of six-source nitrate problems. PMC was unable to find solutions for two of the target water samples. The Bayesian method, SIAR, experienced anchoring problems, and SIRS calculated mixing fractions that most closely approximated the known mixing fractions. For that reason, SIRS was the only approach used in the next phase of testing. In Phase II, the problem was broadened where any subset of the six sources could be a possible solution to the mixing problem. Results showed a high rate of Type I errors where solutions included sources that were not contributing to the sample. In Phase III some sources were eliminated based on assumed site knowledge and assumed nitrate concentrations, substantially reduced mixing fraction uncertainties and lowered the Type I error rate. These results demonstrate that valuable insights into stable isotope mixing problems result from probabilistic mixing model approaches like SIRS. The results also emphasize the importance of identifying a minimal set of potential sources and quantifying uncertainties in source isotopic composition as well as demonstrating the value of additional information in reducing the

  20. Quantifying uncertainty in stable isotope mixing models

    DOE PAGESBeta

    Davis, Paul; Syme, James; Heikoop, Jeffrey; Fessenden-Rahn, Julianna; Perkins, George; Newman, Brent; Chrystal, Abbey E.; Hagerty, Shannon B.

    2015-05-19

    Mixing models are powerful tools for identifying biogeochemical sources and determining mixing fractions in a sample. However, identification of actual source contributors is often not simple, and source compositions typically vary or even overlap, significantly increasing model uncertainty in calculated mixing fractions. This study compares three probabilistic methods, SIAR [Parnell et al., 2010] a pure Monte Carlo technique (PMC), and Stable Isotope Reference Source (SIRS) mixing model, a new technique that estimates mixing in systems with more than three sources and/or uncertain source compositions. In this paper, we use nitrate stable isotope examples (δ15N and δ18O) but all methods testedmore » are applicable to other tracers. In Phase I of a three-phase blind test, we compared methods for a set of six-source nitrate problems. PMC was unable to find solutions for two of the target water samples. The Bayesian method, SIAR, experienced anchoring problems, and SIRS calculated mixing fractions that most closely approximated the known mixing fractions. For that reason, SIRS was the only approach used in the next phase of testing. In Phase II, the problem was broadened where any subset of the six sources could be a possible solution to the mixing problem. Results showed a high rate of Type I errors where solutions included sources that were not contributing to the sample. In Phase III some sources were eliminated based on assumed site knowledge and assumed nitrate concentrations, substantially reduced mixing fraction uncertainties and lowered the Type I error rate. These results demonstrate that valuable insights into stable isotope mixing problems result from probabilistic mixing model approaches like SIRS. The results also emphasize the importance of identifying a minimal set of potential sources and quantifying uncertainties in source isotopic composition as well as demonstrating the value of additional information in reducing the uncertainty in calculated

  1. Patterns of local and nonlocal water resource use across the western U.S. determined via stable isotope intercomparisons

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this paper we develop an isotope-based statistical framework to evaluate the dynamics of the relationship between water supplies used for human consumption and several hydrological factors, including the spatiotemporal distribution of precipitation and snowmelt as well as the timing and rates of ...

  2. Long-term and high-frequency non-destructive monitoring of water stable isotope profiles in an evaporating soil column

    NASA Astrophysics Data System (ADS)

    Rothfuss, Y.; Merz, S.; Vanderborght, J.; Hermes, N.; Weuthen, A.; Pohlmeier, A.; Vereecken, H.; Brüggemann, N.

    2015-10-01

    The stable isotope compositions of soil water (δ2H and δ18O) carry important information about the prevailing soil hydrological conditions and for constraining ecosystem water budgets. However, they are highly dynamic, especially during and after precipitation events. In this study, we present an application of a method based on gas-permeable tubing and isotope-specific infrared laser absorption spectroscopy for in situ determination of soil water δ2H and δ18O. We conducted a laboratory experiment where a sand column was initially saturated, exposed to evaporation for a period of 290 days, and finally rewatered. Soil water vapor δ2H and δ18O were measured daily at each of eight available depths. Soil liquid water δ2H and δ18O were inferred from those of the vapor considering thermodynamic equilibrium between liquid and vapor phases in the soil. The experimental setup allowed for following the evolution of soil water δ2H and δ18O profiles with a daily temporal resolution. As the soil dried, we could also show for the first time the increasing influence of the isotopically depleted ambient water vapor on the isotopically enriched liquid water close to the soil surface (i.e., atmospheric invasion). Rewatering at the end of the experiment led to instantaneous resetting of the stable isotope profiles, which could be closely followed with the new method. From simple soil δ2H and δ18O gradients calculations, we showed that the gathered data allowed one to determinate the depth of the evaporation front (EF) and how it receded into the soil over time. It was inferred that after 290 days under the prevailing experimental conditions, the EF had moved down to an approximate depth of -0.06 m. Finally, data were used to calculate the slopes of the evaporation lines and test the formulation for kinetic isotope effects. A very good agreement was found between measured and simulated values (Nash and Sutcliffe efficiency, NSE = 0.92) during the first half of the

  3. Stable oxygen isotope analysis reveal vegetation influence on soil water movement and ecosystem water fluxes in a semi-arid oak woodland

    NASA Astrophysics Data System (ADS)

    Piayda, Arndt; Dubbert, Maren; Werner, Christiane; Cuntz, Matthias

    2015-04-01

    Mechanistically disentangling the role and function of vegetation within the hydrological cycle is one of the key questions in the interdisciplinary field of ecohydrology. The presence of vegetation can have various impacts on soil water relations: transpiration of active vegetation causes great water losses, rainfall is intercepted, soil evaporation can be reduced and infiltration, hydraulic redistribution and translatory flow might be altered. In drylands, covering around 40% of the global land surface, the carbon cycle is closely coupled to water availability due to (seasonal) droughts. Specifically savannah type ecosystems, which cover large areas worldwide, are, due to their bi-layered structure, very suitable to study the effects of distinct vegetation types on the ecosystem water cycle. Oxygen isotope signatures (δ18O) have been used to partition ecosystem evapotranspiration (ET ) because of the distinct isotopic compositions of water transpired by leaves relative to soil evaporated vapor. Recent developments in laser spectroscopy enable measurements of δ18O in the vapor phase with high temporal resolution in the field and bear a novel opportunity to trace water movement within the ecosystem. In the present study, the effects of distinct vegetation layers (i.e. trees and herbaceous vegetation) on soil water infiltration and redistribution as well as ecosystem water fluxes in a Mediterranean cork-oak woodland are disentangled. An irrigation experiment was carried out using δ18O labeled water to quantify the distinct effects of trees and herbaceous vegetation on 1) infiltration and redistribution of water in the soil profile and 2) to disentangle the effects of tree cover on the contribution of unproductive soil evaporation and understory transpiration to total ET . First results proof that stable δ18O isotopes measured onsite with laser spectroscopy is a valuable tool to trace water movement in the soil showing a much higher sensitivity than common TDR

  4. VeWa: Investigating effects of Vegetation on Water flows and mixing in northern ecosystems using stable isotopes and conceptual models

    NASA Astrophysics Data System (ADS)

    Tetzlaff, Doerthe

    2015-04-01

    The lack of comprehensive tracer data sets still hinders the development of a generalized understanding of how northern catchments function hydrologically. Here, we use stable isotope records from precipitation and stream flow to examine the effects of soils and landcover along representative landscape transects in six high-latitude experimental catchments located in the UK, USA, Sweden and Canada. Precipitation and stream flow at each site occupies space on the meteoric water line that broadly reflects latitude. The annual variability of stream water isotopes at each site reflects both the nature (rate and duration) of the spring snowmelt and the relative importance of near-surface and deeper flow paths. This hydrological partitioning also acts a fundamental control on the influence of summer evaporation on stream waters. After accounting for differences in radiation inputs, strongest fractionation is most evident at sites where wet riparian soils with near-surface runoff processes can mobilize evaporated soil water during summer and autumn storms.

  5. Stable isotope views on ecosystem function: challenging or challenged?

    PubMed Central

    Resco, Víctor; Querejeta, José I.; Ogle, Kiona; Voltas, Jordi; Sebastià, Maria-Teresa; Serrano-Ortiz, Penélope; Linares, Juan C.; Moreno-Gutiérrez, Cristina; Herrero, Asier; Carreira, José A.; Torres-Cañabate, Patricia; Valladares, Fernando

    2010-01-01

    Stable isotopes and their potential for detecting various and complex ecosystem processes are attracting an increasing number of scientists. Progress is challenging, particularly under global change scenarios, but some established views have been challenged. The IX meeting of the Spanish Association of Terrestrial Ecology (AAET, Úbeda, 18–22 October 2009) hosted a symposium on the ecology of stable isotopes where the linear mixing model approach of partitioning sinks and sources of carbon and water fluxes within an ecosystem was challenged, and new applications of stable isotopes for the study of plant interactions were evaluated. Discussion was also centred on the need for networks that monitor ecological processes using stable isotopes and key ideas for fostering future research with isotopes. PMID:20015858

  6. Stable Isotope Enrichment Capabilities at ORNL

    SciTech Connect

    Egle, Brian; Aaron, W Scott; Hart, Kevin J

    2013-01-01

    The Oak Ridge National Laboratory (ORNL) and the US Department of Energy Nuclear Physics Program have built a high-resolution Electromagnetic Isotope Separator (EMIS) as a prototype for reestablishing a US based enrichment capability for stable isotopes. ORNL has over 60 years of experience providing enriched stable isotopes and related technical services to the international accelerator target community, as well as medical, research, industrial, national security, and other communities. ORNL is investigating the combined use of electromagnetic and gas centrifuge isotope separation technologies to provide research quantities (milligram to several kilograms) of enriched stable isotopes. In preparation for implementing a larger scale production facility, a 10 mA high-resolution EMIS prototype has been built and tested. Initial testing of the device has simultaneously collected greater than 98% enriched samples of all the molybdenum isotopes from natural abundance feedstock.

  7. Chemical and light-stable isotope characteristics of waters from the raft river geothermal area and environs, cassia county, idaho; box elder county, Utah

    USGS Publications Warehouse

    Nathenson, M.; Nehring, N.L.; Crosthwaite, E.G.; Harmon, R.S.; Janik, C.; Borthwick, J.

    1982-01-01

    Chemical and light-stable isotope data are presented for water samples from the Raft River geothermal area and environs. On the basis of chemical character, as defined by a trilinear plot of per cent milliequivalents, and light-stable isotope data, the waters in the geothermal area can be divided into waters that have and have not mixed with cold water. The non-mixed waters have essentially a constant value of light-stable isotopes but show a large variation in chloride content. The variation of chloride composition is not the usual pattern for deep geothermal waters, where it is normally assumed that the deep water has a single chloride composition. Different mixed waters also have hot-water sources of varying chloride composition. Plots of chloride values on cross-sections show that water circulation patterns are confused, with non-mixed waters having different chloride concentrations located in close proximity. Three models can explain the characteristics of the deep geothermal water: (1) in addition to near-surface mixing of cold and hot water, there is deep mixing of two hot waters with the same enthalpy and isotopic composition but differing chloride concentrations to produce the range of chloride concentrations found in the deep geothermal water; (2) there is a single deep hot water, and the range of chloride concentrations is produced by the water passing through a zone of highly soluble materials (most likely in the sedimentary section above the basement) in which waters have different residence times or slightly different circulation paths; (3) the varying chloride concentrations in space have been caused by varying chloride concentrations in the deep feed water through time. Some of this older water has not been flushed from the system by the natural discharge. Although one model may seem more plausible than the others, the available data do not rule out any of them. Data for water samples from the Raft River and Jim Sage Mountains show that water from

  8. The effect of forced ventilation through snow on the stable water isotope content of the vapor and the snow - an experiment

    NASA Astrophysics Data System (ADS)

    Berben, Sarah; Steen-Larsen, Hans Christian; Johnsen, Sigfus

    2010-05-01

    The stable water isotope signal throughout an ice core is a well known and often used proxy for past temperature reconstructions and is important in our understanding of the climate system. The knowledge about the post depositional processes influencing the isotope signal within the snowpack is therefore important. As wind blow across the snow surface micro high and low pressure areas arise because of sastrugies. These pressure differences create forced ventilation through the snowpack which then affect the interstitial mass exchange between water vapor and snow crystals and therefore the climatic signal stored in the snow. In order of understanding the physics behind this ongoing exchange, a combination of modeling and a controlled experiment has been set up. The process of forced ventilation -as it is believed to occur on Greenland and Antarctica- has then been simulated. The snow within this experiment is collected in Greenland during the new deep drilling project in NW Greenland (NEEM). Within this experiment, air with a known amount of moisture is pulled through a snow sample of different thicknesses. This sample has a known isotopic content and is kept at different sub-zero temperatures. The flow rate of the air has been controlled between 0,01 and 0,5 cm/s. After the interaction between the water vapor and the ice crystals the changes in both humidity and isotope signal are been studied. New in this research are the measurements of the isotope content with a Picarro WS-CRDS analyzer of the water vapour before and after the snow sample. Eventually, to estimate the magnitude of the effect of ventilation through snow on the stable isotope content of the water vapor, the results of the experiment are compared with the output from the computer model. This research will quantify the effect of forced ventilation on the mean isotope signal in the snow and its implications for the derived temperature signal from the water isotope ratio of the ice core as well as

  9. Stable isotope labeling methods for DNA.

    PubMed

    Nelissen, Frank H T; Tessari, Marco; Wijmenga, Sybren S; Heus, Hans A

    2016-08-01

    NMR is a powerful method for studying proteins and nucleic acids in solution. The study of nucleic acids by NMR is far more challenging than for proteins, which is mainly due to the limited number of building blocks and unfavorable spectral properties. For NMR studies of DNA molecules, (site specific) isotope enrichment is required to facilitate specific NMR experiments and applications. Here, we provide a comprehensive review of isotope-labeling strategies for obtaining stable isotope labeled DNA as well as specifically stable isotope labeled building blocks required for enzymatic DNA synthesis. PMID:27573183

  10. In-situ unsaturated zone stable water isotope (2H and 18O) measurements in semi-arid environments using tunable off-axis integrated cavity output spectroscopy

    NASA Astrophysics Data System (ADS)

    Gaj, M.; Beyer, M.; Koeniger, P.; Wanke, H.; Hamutoko, J.; Himmelsbach, T.

    2015-06-01

    Stable isotopes (deuterium, 2H, and oxygen-18, 18O) of soil pore water were measured directly in the field using tunable off-axis integrated cavity output spectroscopy (OA-ICOS) and commercially available soil gas probes in a semi-arid region of the Cuvelai-Etosha-Basin, Namibia. High spatial and temporal resolution was achieved in the study area with reasonable accuracy and measurements were in agreement with laboratory-based cryogenic vacuum extraction and subsequent cavity ring down laser spectroscopic isotope analysis (CRDS). After drift correction of the isotope data, mean precision for over 140 measurements of two consecutive field campaigns in June and November 2014 were 1.8 and 0.46 ‰ for δ2H and 18O, respectively. Mean Accuracy using quality check standards was 5 and 0.3 ‰ for δ2H and δ18O, respectively. Results support the applicability of an in-situ measurement system for the determination of stable isotopes in soil pore water. Spatio-temporal variability could be deduced with the observed data in an extremely dry evaporation dominated environment which was sporadically affected by intermittent rainfall.