Coordinated Oxygen Isotopic and Petrologic Studies of CAIS Record Varying Composition of Protosolar

Science.gov (United States)

Simon, Justin I.; Matzel, J. E. P.; Simon, S. B.; Weber, P. K.; Grossman, L.; Ross, D. K.; Hutcheon, I. D.

2012-01-01

Ca-, Al-rich inclusions (CAIs) record the O-isotope composition of Solar nebular gas from which they grew [1]. High spatial resolution O-isotope measurements afforded by ion microprobe analysis across the rims and margin of CAIs reveal systematic variations in (Delta)O-17 and suggest formation from a diversity of nebular environments [2-4]. This heterogeneity has been explained by isotopic mixing between the O-16-rich Solar reservoir [6] and a second O-16-poor reservoir (probably nebular gas) with a "planetary-like" isotopic composition [e.g., 1, 6-7], but the mechanism and location(s) where these events occur within the protoplanetary disk remain uncertain. The orientation of large and systematic variations in (Delta)O-17 reported by [3] for a compact Type A CAI from the Efremovka reduced CV3 chondrite differs dramatically from reports by [4] of a similar CAI, A37 from the Allende oxidized CV3 chondrite. Both studies conclude that CAIs were exposed to distinct, nebular O-isotope reservoirs, implying the transfer of CAIs among different settings within the protoplanetary disk [4]. To test this hypothesis further and the extent of intra-CAI O-isotopic variation, a pristine compact Type A CAI, Ef-1 from Efremovka, and a Type B2 CAI, TS4 from Allende were studied. Our new results are equally intriguing because, collectively, O-isotopic zoning patterns in the CAIs indicate a progressive and cyclic record. The results imply that CAIs were commonly exposed to multiple environments of distinct gas during their formation. Numerical models help constrain conditions and duration of these events.

Late Glacial Tropical Savannas in Sundaland Inferred From Stable Carbon Isotope Records of Cave Guano

Science.gov (United States)

Wurster, C. M.; Bird, M. I.; Bull, I.; Dungait, J.; Bryant, C. L.; Ertunç, T.; Hunt, C.; Lewis, H. A.; Paz, V.

2008-12-01

During the Last Glacial Period (LGP), reduced global sea level exposed the continental shelf south of Thailand to Sumatra, Java, and Borneo to form the contiguous continent of Sundaland. However, the type and extent of vegetation that existed on much of this exposed landmass during the LGP remains speculative. Extensive bird and bat guano deposits in caves throughout this region span beyond 40,000 yr BP, and contain a wealth of untapped stratigraphic palaeoenvironmental information. Stable carbon isotope ratios of insectivorous bird and bat guano contain a reliable record of the animal's diet and, through non-specific insect predation, reflect the relative abundance of major physiological pathways in plants. Various physiological pathways of carbon fixation in plants yield differing stable carbon isotope ratios. Stable carbon isotope values of C3 plants are lower than C4 vegetation due to different enzymatic discriminations of the heavy isotope through the carbon fixing pathways. In tropical locales, grasses nearly always follow the C4 photosynthetic pathway, whereas tropical rainforest uses C3 photosynthesis, providing a proxy for vegetation and therefore climate change in the past. Here we discuss four guano stable-isotope records, based on insect cuticle and n-alkane analysis, supplemented by pollen analysis. All sites suggest a C3 dominated ecosystem for the Holocene, consistent with the wet tropical forest vegetation present at all locations. Two sites from Palawan Island, Philippines, record stable carbon isotope values of guano that document a drastic change from C3 (forest) to C4 (savanna) dominated ecosystems during the Last Glacial Maximum (LGM). A third location, at Niah Great Cave, Malaysia, indicates C3-dominant vegetation throughout the record, but does display variation in stable carbon isotope values likely linked to humidity changes. A fourth location, Batu Caves in Peninsular Malaysia, also indicates open vegetation during the LGM. Vegetation

Lead isotopes in deep-sea coral skeletons: Ground-truthing and a first deglacial Southern Ocean record

Science.gov (United States)

Wilson, David J.; van de Flierdt, Tina; Adkins, Jess F.

2017-05-01

Past changes in seawater lead (Pb) isotopes record the temporal evolution of anthropogenic pollution, continental weathering inputs, and ocean current transport. To advance our ability to reconstruct this signature, we present methodological developments that allow us to make precise and accurate Pb isotope measurements on deep-sea coral aragonite, and apply our approach to generate the first Pb isotope record for the glacial to deglacial mid-depth Southern Ocean. Our refined methodology includes a two-step anion exchange chemistry procedure and measurement using a 207Pb-204Pb double spike on a Thermo Finnigan Triton TIMS instrument. By employing a 1012 Ω resistor (in place of a 1011 Ω resistor) to measure the low-abundance 204Pb ion beam, we improve the internal precision on 206,207,208Pb/204Pb for a 2 ng load of NIST-SRM-981 Pb from typically ∼420 ppm to ∼230 ppm (2 s.e.), and the long term external reproducibility from ∼950 ppm to ∼550 ppm (2 s.d.). Furthermore, for a typical 500 mg coral sample with low Pb concentrations (∼6-10 ppb yielding ∼3-5 ng Pb for analysis), we obtain a comparable internal precision of ∼150-250 ppm for 206,207,208Pb/204Pb, indicating a good sensitivity for tracing natural Pb sources to the oceans. Successful extraction of a seawater signal from deep-sea coral aragonite further relies on careful physical and chemical cleaning steps, which are necessary to remove anthropogenic Pb contaminants and obtain results that are consistent with ferromanganese crusts. Applying our approach to a collection of late glacial and deglacial corals (∼12-40 ka BP) from south of Tasmania at ∼1.4-1.7 km water depth, we generated the first intermediate water Pb isotope record from the Southern Ocean. That record reveals millennial timescale variability, controlled by binary mixing between two Pb sources, but no distinct glacial-interglacial Pb isotope shift. Mixing between natural endmembers is fully consistent with our data and points to

Argon isotopes as recorders of magmatic processes

Science.gov (United States)

Layer, P. W.; Gardner, J. E.; Mora Chaparro, J. C.; Arce, J. L.

2003-12-01

Argon isotopic ratios vary enough between different reservoirs (atmosphere, crust, mantle) and diffuse fast enough through most minerals at magmatic temperatures (700-1200 C) to make them ideal for looking at magma chamber dynamics. Indeed, diffusion is sufficiently fast to allow short time scales to be deciphered, setting argon apart from many other isotopic methods. A mineral's ability to retain "excess" argon (40Ar/36Ar ratios greater than the atmospheric value and apparent ages older than the known eruption age) during post-eruption cooling is key to Ar studies. Previous work shows that both phenocrysts (crystallizing in the magma chamber; e.g. Mt St. Helens; Layer and Gardner, 2001) and xenocrysts (introduced into the magma chamber; e.g Toba; Gardner et al., 2002) preserve excess argon, which enables magma chamber processes to be deciphered through the variable diffusion rates between crystal phases. Single crystal 40Ar/39Ar step-heating of biotite from the 10.5 ka eruption of Nevado de Toluca volcano, Mexico indicates that they are xenocrystic and resided for only a short (< 1 year) time in the magma before it erupted. The biotite has reaction rims of hornblende, orthopyroxene and plagioclase, and failed to grow experimentally at pressure-temperature conditions of the magma, confirming the xenocrystic nature of this phase. Single-step fusion of plagioclase phenocrysts from eruptions of El Chichon volcano, Mexico, shows evidence of excess (mantle) argon, whereas hornblende from the same eruptions contains little or none. In this case, faster diffusion of Ar in plagioclase than in hornblende allow plagioclase to incorporate excess argon during magma recharge; hornblende does not. Combining such results with other isotopic systems may in fact better determine magma chamber processes. At El Chichon, Sr isotopes suggest magma recharges ocurred (Tepley et al., 2000), whereas the argon isotopes suggest such pulses occurred just before each eruption. The fast and

Estimation of pollutant source contribution to the Pampanga River Basin using carbon and nitrogen isotopes

International Nuclear Information System (INIS)

Castaneda, Solidad S.; Sta Maria, Efren J.; Ramirez, Jennyvi D.; Collado, Mario B.; Samar, Edna D.

2013-01-01

This study assessed and estimated the percentage contribution of potential pollution sources in Pampanga River Basin using carbon and nitrogen isotopes as environmental tracers. The δ 13 C and δ 15 N values were determined in particulate organic matter, surface sediment, and plant tissue samples from point and non-point sources from several land use areas, namely domestic, croplands, livestock, fishery and forestry. Investigations were conducted in the wet and dry seasons (2012 and 2013). Some N sources do not have unique δ 15 N and there is overlapping among different N- sources type. δ 13 C data from the N sources provided an additional dimension which distinguished animal manure, human waste (septic and sewage), leaf litter, and synthetic fertilizer. Characterization of the non-point N-sources based on the isotopic fingerprints obtained from the point sources revealed that domestic, cropland, livestock, and fishery, influenced the isotopic composition of the materials but domestic and cropland land use provided the most significant influence. Livestock also contributed to a lesser extent. Isotope mixing model revealed that cropland sources generally contributed the most to pollutant loading during the wet season, from 22% to 98%, while domestic waste contributed higher in the dry season, from 55% to 65%. (author)

Use of a Bayesian isotope mixing model to estimate proportional contributions of multiple nitrate sources in surface water

International Nuclear Information System (INIS)

Xue Dongmei; De Baets, Bernard; Van Cleemput, Oswald; Hennessy, Carmel; Berglund, Michael; Boeckx, Pascal

2012-01-01

To identify different NO 3 − sources in surface water and to estimate their proportional contribution to the nitrate mixture in surface water, a dual isotope and a Bayesian isotope mixing model have been applied for six different surface waters affected by agriculture, greenhouses in an agricultural area, and households. Annual mean δ 15 N–NO 3 − were between 8.0 and 19.4‰, while annual mean δ 18 O–NO 3 − were given by 4.5–30.7‰. SIAR was used to estimate the proportional contribution of five potential NO 3 − sources (NO 3 − in precipitation, NO 3 − fertilizer, NH 4 + in fertilizer and rain, soil N, and manure and sewage). SIAR showed that “manure and sewage” contributed highest, “soil N”, “NO 3 − fertilizer” and “NH 4 + in fertilizer and rain” contributed middle, and “NO 3 − in precipitation” contributed least. The SIAR output can be considered as a “fingerprint” for the NO 3 − source contributions. However, the wide range of isotope values observed in surface water and of the NO 3 − sources limit its applicability. - Highlights: ► The dual isotope approach (δ 15 N- and δ 18 O–NO 3 − ) identify dominant nitrate sources in 6 surface waters. ► The SIAR model estimate proportional contributions for 5 nitrate sources. ► SIAR is a reliable approach to assess temporal and spatial variations of different NO 3 − sources. ► The wide range of isotope values observed in surface water and of the nitrate sources limit its applicability. - This paper successfully applied a dual isotope approach and Bayesian isotopic mixing model to identify and quantify 5 potential nitrate sources in surface water.

A 40-year record of Northern Hemisphere atmospheric carbon monoxide concentration and isotope ratios from the firn at Greenland Summit.

Science.gov (United States)

Place, P., Jr.; Petrenko, V. V.; Vimont, I.; Buizert, C.; Lang, P. M.; Edwards, J.; Harth, C. M.; Hmiel, B.; Mak, J. E.; Novelli, P. C.; Brook, E.; Weiss, R. F.; Vaughn, B. H.; White, J. W. C.

2014-12-01

Carbon Monoxide (CO) is an important atmospheric trace gas that affects the oxidative capacity of the atmosphere and contributes indirectly to climate forcing by being a major sink of tropospheric OH. A good understanding of the past atmospheric CO budget is therefore important for climate models attempting to characterize recent changes in the atmosphere. Previous work at NEEM, Greenland provided the first reconstructions of Arctic atmospheric history of CO concentration and stable isotope ratios (δC18O and δ13CO) from firn air, dating to the 1950s. In this new study, firn air was sampled from eighteen depth levels through the firn column at Summit, Greenland (in May 2013), yielding a second, independent record of Arctic CO concentration and isotopic ratios. Carbon monoxide stable isotope ratios were analyzed on replicate samples and using a newly developed system with improved precision allowing for a more robust reconstruction. The new CO concentration and stable isotope results overall confirm the earlier findings from NEEM, with a CO concentration peak around the 1970s and higher δC18O and δ13CO values associated with peak CO. Modeling and interpretation of the data are in progress.

Contribution of Isotopic Tools to the Numerical Simulation of the Mar del Plata Coastal Aquifer, Argentina

Energy Technology Data Exchange (ETDEWEB)

Bocanegra, E.; Martinez, D. E. [Instituto de Geologia de Costas y del Cuaternario, UNMDP (Argentina); Pool, M.; Carrera, J. [Instituto de Diagnostico Ambiental y Estudios del Agua, CSIC (Spain)

2013-07-15

Over-exploitation in the coastal aquifer in Mar del Plata, Argentina, led to a seawater intrusion process affecting groundwater by salinization. The aim of this paper is to show the contribution of isotopic techniques to generate the numerical flow and transport model of the Mar del Plata aquifer. On the basis of the hydrogeological conceptual model, a numerical model was constructed. It consists of a multilayer aquifer in the urban area with 2 layers separated by an aquitard and a monolayer aquifer in the rest of the basin. The isotopic difference recorded in groundwaters allow the identification of the origin of the recharge and the confirmation of the presence of the hydrogeological environments incorporated in the numerical model. Flow simulation reflects the evolution of piezometric heads. Chloride transport simulation represents the salinization process due to seawater intrusion and the subsequent backward movement of the interface due to the abandonment of salinized wells. The results of numerical simulation confirm the conceptual model and reproduce the impact of the adopted management strategies. (author)

Stable and strontium isotopic records of molluscan shells, lower jurassic, Cuenca Neuquina, southwestern Mendoza, Argentina

International Nuclear Information System (INIS)

Cagnoni, M.C.; Valencio, S.A.; Ramos, A.M; Riccardi, A.C; Panarello, H.O

2001-01-01

The strontium, carbon and oxygen isotopic signal of the past oceans is accurately recorded by authigenic marine minerals such as carbonates, sulfates and phosphates. The variation of these isotope ratios through the geological time is used as a tool in correlating and dating marine sedimentary rocks. Many works have been done concerning to the changes in carbon, oxygen and strontium isotope ratios of different marine successions in the world. These allow the construction of curves of secular variations of the isotope signals with geological time (Jones et al., 1994a, 1994b; Veizer et al., 1999; Jacobsen and Kaufman, 1999). This work presents strontium, carbon and oxygen isotope ratios of Early Jurassic biogenic marine carbonates of Cuenca Neuquina in southwestern Mendoza (au)

Kinetic control on Zn isotope signatures recorded in marine diatoms

Science.gov (United States)

Köbberich, Michael; Vance, Derek

2017-08-01

Marine diatoms dominate the oceanic cycle of the essential micronutrient zinc (Zn). The stable isotopes of zinc and other metals are increasingly used to understand trace metal micronutrient cycling in the oceans. One clear feature of the early isotope data is the heavy Zn isotope signature of the average oceanic dissolved pool relative to the inputs, potentially driven by uptake of light isotopes into phytoplankton cells and export to sediments. However, despite the fact that diatoms strip Zn from surface waters across the Antarctic polar front in the Southern Ocean, the local upper ocean is not isotopically heavy. Here we use culturing experiments to quantify the extent of Zn isotope fractionation by diatoms and to elucidate the mechanisms driving it. We have cultured two different open-ocean diatom species (T. oceanica and Chaetoceros sp.) in a series of experiments at constant medium Zn concentration but at bioavailable medium Fe ranging from limiting to replete. We find that T. oceanica can maintain high growth rates and Zn uptake rates over the full range of bioavailable iron (Fe) investigated, and that the Zn taken up has a δ66Zn that is unfractionated relative to that of the bioavailable free Zn in the medium. The studied representative of the genus Chaetoceros, on the other hand, shows more significantly reduced Zn uptake rates at low Fe and records more variable biomass δ66Zn signatures, of up to 0.85‰ heavier than the medium. We interpret the preferential uptake of heavy isotopes at extremely low Zn uptake rates as potentially due to either of the following two mechanisms. First, the release of extracellular polymeric substances (EPS), at low Fe levels, may preferentially scavenge heavy Zn isotopes. Second, the Zn uptake rate may be slow enough to establish pseudo-equilibrium conditions at the transporter site, with heavy Zn isotopes forming more stable surface complexes. Thus we find that, in our experiments, Fe-limitation exerts a key control that

Preservation of Fe Isotope Proxies in the Rock Record

Science.gov (United States)

Johnson, C.; Beard, B.; Valley, J.; Valaas, E.

2005-12-01

Iron isotope variations provide powerful constraints on redox conditions and pathways involved during biogeochemical cycling of Fe in surface and near-surface environments. The relative isotopic homogeneity of igneous rocks and most bulk weathering products contrasts with the significant isotopic variations (4 per mil in 56Fe/54Fe) that accompany oxidation of Fe(II)aq, precipitation of sulfides, and reduction by bacteria. These isotopic variations often reflect intrinsic (equilibrium) Fe isotope fractionations between minerals and aqueous species whose interactions may be directly or indirectly catalyzed by bacteria. In addition, Fe isotope exchange may be limited between reactive Fe pools in low-temperature aqueous-sediment environments, fundamentally reflecting disequilibrium effects. In the absence of significant sulfide, dissimilatory Fe(III) reduction by bacteria produces relatively low 56Fe/54Fe ratios for Fe(II)aq and associated biogenic minerals such as magnetite and siderite. In contrast, Fe(II)aq that exchanges with Fe sulfides (FeS and pyrite) is relatively enriched in 56Fe/54Fe ratios. In modern and ancient environments, anoxic diagenesis tends to produce products that have low 56Fe/54Fe ratios, whereas oxidation of Fe(II)aq from hydrothermal sources tends to produce ferric Fe products that have high 56Fe/54Fe ratios. Redox cycling by bacteria tends to produce reactive ferric Fe reservoirs that have low 56Fe/54Fe ratios. Application of Fe isotopes as a proxy for redox conditions in the ancient rock record depends upon the preservation potential during metamorphism, given the fact that most Archean sedimentary sequences have been subjected to regional greenschist- to granulite-facies metamorphism. The 1.9 Ga banded iron formations (BIFs) of the Lake Superior region that are intruded by large ~1 Ga intrusions (e.g., Duluth gabbro) provide a test of the preservation potential for primary, low-temperature Fe isotope variations in sedimentary rocks. 56Fe/54

The Pb isotopic record of historical to modern human lead exposure

International Nuclear Information System (INIS)

Kamenov, George D.; Gulson, Brian L.

2014-01-01

Human teeth and bones incorporate trace amounts of lead (Pb) from the local environment during growth and remodeling. Anthropogenic activities have caused changes in the natural Pb isotopic background since historical times and this is reflected in the Pb isotopes of historical European teeth. Lead mining and use increased exponentially during the last century and the isotopic compositions of modern human teeth reflect the modern anthropogenic Pb. USA teeth show the most radiogenic Pb and Australian teeth show the least radiogenic Pb, a result of different Pb ores used in the two regions. During the last century the Australian Pb was exported to Europe, Asia, South America, and Africa, resulting in swamping of the local environmental Pb signal by the imported Pb. As a result, the modern human teeth in Europe show a significant drop to lower isotopic values compared with historical times. Similarly, modern human teeth in other regions of the world show similar Pb isotopic ratios to modern European teeth reflecting the Pb imports. The specific pattern of human Pb exposure allows us to use the Pb isotopic signal recorded in the skeleton as a geo-referencing tool. As historical European teeth show a distinct Pb signal, we can identify early European skeletal remains in the New World and likely elsewhere. In modern forensic investigations we can discriminate to some extent Eastern Europeans from Western and Northern Europeans. Australians can be identified to some extent in any region in the world, although there is some overlap with Western European individuals. Lead isotopes can be used to easily identify foreigners in the USA, as modern USA teeth are distinct from any other region of the world. By analogy, USA individuals can be identified virtually in any other region of the world. - Highlights: • We present high-precision Pb isotope data for historical and modern human teeth. • Human teeth reflect human Pb exposure since historical times. • Modern teeth show

The Pb isotopic record of historical to modern human lead exposure

Energy Technology Data Exchange (ETDEWEB)

Kamenov, George D., E-mail: kamenov@ufl.edu [Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL 32611 (United States); Gulson, Brian L. [Graduate School of the Environment, Faculty of Science, Macquarie University, Sydney, NSW 2109 (Australia)

2014-08-15

Human teeth and bones incorporate trace amounts of lead (Pb) from the local environment during growth and remodeling. Anthropogenic activities have caused changes in the natural Pb isotopic background since historical times and this is reflected in the Pb isotopes of historical European teeth. Lead mining and use increased exponentially during the last century and the isotopic compositions of modern human teeth reflect the modern anthropogenic Pb. USA teeth show the most radiogenic Pb and Australian teeth show the least radiogenic Pb, a result of different Pb ores used in the two regions. During the last century the Australian Pb was exported to Europe, Asia, South America, and Africa, resulting in swamping of the local environmental Pb signal by the imported Pb. As a result, the modern human teeth in Europe show a significant drop to lower isotopic values compared with historical times. Similarly, modern human teeth in other regions of the world show similar Pb isotopic ratios to modern European teeth reflecting the Pb imports. The specific pattern of human Pb exposure allows us to use the Pb isotopic signal recorded in the skeleton as a geo-referencing tool. As historical European teeth show a distinct Pb signal, we can identify early European skeletal remains in the New World and likely elsewhere. In modern forensic investigations we can discriminate to some extent Eastern Europeans from Western and Northern Europeans. Australians can be identified to some extent in any region in the world, although there is some overlap with Western European individuals. Lead isotopes can be used to easily identify foreigners in the USA, as modern USA teeth are distinct from any other region of the world. By analogy, USA individuals can be identified virtually in any other region of the world. - Highlights: • We present high-precision Pb isotope data for historical and modern human teeth. • Human teeth reflect human Pb exposure since historical times. • Modern teeth show

Reconstruction of three centuries of annual accumulation rates based on the record of stable isotopes of water from Lomonosovfonna, Svalbard

NARCIS (Netherlands)

Pohjola, V.; Martma, T.; Meijer, H.A.J.; Moore, J.; Isaksson, E.; Vaikmae, R.; van de Wal, R.S.W.

2002-01-01

We use the upper 81 in of the record of stable isotopes of water from a 122 in long ice core from Lomonosovfonna, central Spitsbergen, Svalbard, to construct an ice-core chronology and the annual accumulation rates over the icefield. The isotope cycles are counted in the ice-core record using a

Paired carbon stable-isotope records for the Cenomanian Stage (100.5 -93.9 Ma): correlation tool and Late Cretaceous pCO2 record?

Science.gov (United States)

Jarvis, Ian; Gröcke, Darren; Laurin, Jiří; Selby, David; Roest-Ellis, Sascha; Miles, Andrew; Lignum, John; Gale, Andrew; Kennedy, Jim

2016-04-01

Carbon stable-isotope stratigraphy of marine carbonates (δ13Ccarb) provides remarkable insights into past variation in the global carbon cycle, and has become firmly established as a powerful global correlation tool. Continuous δ13Ccarb time series are becoming increasingly available for much of the geological record, including the Upper Cretaceous. However, our knowledge of stratigraphic variation in the carbon isotopic composition of sedimentary organic matter (δ13Corg) is much poorer, and is generally restricted to organic-rich sedimentary successions and/or key boundary intervals. Close coupling exists between the global isotopic composition of the reduced and oxidised carbon reservoirs on geological time scales, but the stratigraphic resolution of most long-term δ13Corg Mesozoic records is inadequate to identify leads and lags in the responses of the two reservoirs to carbon cycle perturbations. Cenomanian times (100.5-93.9 Ma) represent perhaps the best documented episode of eustatic rise in sea level in Earth history and the beginning of the Late Mesozoic thermal maximum, driving global expansion of epicontinental seas and the onset of widespread pelagic and hemipelagic carbonate deposition. Significant changes occurred in global stable-isotope records, including two prominent perturbations of the carbon cycle - the Mid-Cenomanian Event I (MCEI; ~96.5-96.2 Ma) and Oceanic Anoxic Event 2 (OAE2; ~94.5-93.8 Ma). OAE2, one of two truly global Cretaceous OAEs, was marked by the widespread deposition of black shales, and a global positive carbon stable-isotope excursion of 2.0 - 2.5‰ δ13Ccarb, and up to 7‰ in the sulphur-bound phytane biomarker. MCEI, by contrast, shows a English Chalk reference section at Folkestone, and correlate the carbon-isotope events between England, France, Germany and Italy. Comparison of the Vergons δ13Ccarb vs. δ13Corg profiles demonstrates similar medium-term stratigraphic variation, but significant differences in both short

Reassessing the stable water isotope record in understanding past climate

International Nuclear Information System (INIS)

Noone, D.; Simmonds, I.

1999-01-01

Full text: The impact of atmospheric circulation on the stable water isotope record has been examined using an atmospheric general circulation model to reassess the validity of using isotopes to reconstruct Earth's climate history. Global temperature changes are classically estimated from the variations in (polar) isotopic values assuming a simple linear relationship. Such a relationship can be justified from first order theoretical considerations given that the isotopic fractionation at the deposition (ice core) site is temperature dependent. However, it is found that the history of a given air mass is more important that local processes because of the net effect of condensation events active along the transport pathway from the source region. Modulations in the hemispheric flow are seen to be crucial to Antarctic precipitation and the isotopic signal. Similarly, both transient and stationary disturbances influence the pathways of the air masses associated with Antarctic precipitation. During different climate regimes, such as that of the Last Glacial Maximum, the properties of these types of disturbances may not be assumed to be the same. As such, we may not assume that the condensation histories are the same as under different climate conditions. Therefore, the veracity of the linear climate reconstructions becomes questionable. Notwithstanding this result, the types of changes to the circulation regime that are expected generally correspond to changes in the global temperature. This fortunate result does not disallow the use of regressional reconstruction, however, the uncertainties associated with these circulation changes are of the same magnitude as the differences suggested by conventional linear regression in climate reconstruction. This indicates that interpretation of ice core data must be accompanied by detailed examination of the atmospheric processes and quantification of the impacts of their changes. Copyright (1999) Geological Society of Australia

Limnological controls on stable isotope records of late-holocene palaeoenvironment change in sw greenland: A paired lake study

DEFF Research Database (Denmark)

Olsen, Jesper; John Anderson, N.; Leng, M.J.

2013-01-01

Stable isotope records are increasingly being used in palaeoenvironmental studies of Arctic lakes. Here we compare stable isotope and elemental records (δ13C, δ15N, C/N) with high resolution XRF-derived geochemical and colour data from low Arctic lakes (SS1220 and SS85) in southwest Greenland. Lake...... SS1220 sediments are laminated gyttja whereas SS85 consist of homogeneous gyttja, both records cover the last c. 5000 years. d13C and carbon content suggest that organic matter in both lakes is predominantly autochthonous. The C/N variability, ranging between 11 and 15, is interpreted...... composition of lake sediments when there is a reasonable understanding of limnological processes, and records may be lake specific....

The magnesium isotope record of cave carbonate archives

Science.gov (United States)

Riechelmann, S.; Buhl, D.; Schröder-Ritzrau, A.; Riechelmann, D. F. C.; Richter, D. K.; Vonhof, H. B.; Wassenburg, J. A.; Geske, A.; Spötl, C.; Immenhauser, A.

2012-11-01

Here we explore the potential of magnesium (δ26Mg) isotope time-series data as continental climate proxies in speleothem calcite archives. For this purpose, a total of six Pleistocene and Holocene stalagmites from caves in Germany, Morocco and Peru and two flowstones from a cave in Austria were investigated. These caves represent the semi-arid to arid (Morocco), the warm-temperate (Germany), the equatorial-humid (Peru) and the cold-humid (Austria) climate zones. Changes in the calcite magnesium isotope signature with time are compared against carbon and oxygen isotope records from these speleothems. Similar to other proxies, the non-trivial interaction of a number of environmental, equilibrium and disequilibrium processes governs the δ26Mg fractionation in continental settings. These include the different sources of magnesium isotopes such as rainwater or snow as well as soil and host rock, soil zone biogenic activity, shifts in silicate versus carbonate weathering ratios and residence time of water in the soil and karst zone. Pleistocene stalagmites from Morocco show the lowest mean δ26Mg values (GDA: -4.26 ± 0.07‰ and HK3: -4.17 ± 0.15‰), and the data are well explained in terms of changes in aridity over time. The Pleistocene to Holocene stalagmites from Peru show the highest mean value of all stalagmites (NC-A and NC-B δ26Mg: -3.96 ± 0.04‰) but only minor variations in Mg-isotope composition, which is consistent with the rather stable equatorial climate at this site. Holocene stalagmites from Germany (AH-1 mean δ26Mg: -4.01 ± 0.07‰; BU 4 mean δ26Mg: -4.20 ± 0.10‰) suggest changes in outside air temperature was the principal driver rather than rainfall amount. The alpine Pleistocene flowstones from Austria (SPA 52: -3.00 ± 0.73‰; SPA 59: -3.70 ± 0.43‰) are affected by glacial versus interglacial climate change with outside air temperature affecting soil zone activity and weathering balance. Several δ26Mg values of the Austrian and two

Subduction Contributions in the Trans-Mexican Volcanic Belt: Implications from Lava Chemistry and Hf-Nd-Pb Isotopes

Science.gov (United States)

Cai, Y.; Goldstein, S. L.; Langmuir, C. H.; Gómez-Tuena, A.; Lagatta, A.; Straub, S. M.; Martín Del Pozzo, A.

2007-05-01

Despite thick continental crust, near primitive lavas erupt throughout the Trans-Mexican Volcanic Belt (TMVB). In order to distinguish and better constrain subduction contributions and effects of crustal contamination, we analyzed samples representing subducting sediments from DSDP Site 487, and Quaternary lavas from stratovolcanoes and cinder cones, including alkaline "high-Nb" lavas from the Sierra Chichinautzin Volcanic Field (SCVF) showing negligible subduction signature in its trace element chemistry and representing melts of the mantle wedge. Our primary observations and implications are: (1) The high-Nb SCVF `intraplate' lavas define a linear trend along the "Nd-Hf mantle-crust array", defining the composition of the mantle wedge. (2) Popocatepetl and Nevado de Toluca stratovolcanoes show the highest Nd and Hf isotope ratios, higher than the `intraplate' lavas, indicating their sources are more "depleted mantle-like" than the regional mantle wedge. (3) The Popo and Toluca chemical and isotopic trends sharply contrast with Pico de Orizaba, which shows classic indications of crustal contamination (e.g. high 207Pb/204Pb, low Nd-Hf isotope ratios), consistent with contamination by local Precambrian crust. (4) Higher Nd-Hf isotopes in Popo and Toluca lavas also correlate with lower Pb isotope ratios, and lower Lu/Hf and Zr/Hf. Together, these data indicate contributions from subducted Pacific oceanic crust and hydrothermal sediment. (5) Popo and Toluca are also enriched in Th/LREE compared with `intraplate' lavas, reflecting subducted sediment contributions. (6) Nd-Hf isotope ratios of hydrothermal sediment from DSDP Site 487 lie on the "seawater array", with high Hf isotope ratios compared to the "mantle-crust array". Popo and Toluca Nd-Hf isotopes display a shallower slope than the "intraplate lava Nd-Hf array", reflecting contributions from hydrothermal sediment. Popocatepetl and Toluca lavas therefore avoid substantial crustal contamination of mantle wedge

History of Animals using Isotope Records (HAIR): a 6-year dietary history of one family of African elephants.

Science.gov (United States)

Cerling, Thure E; Wittemyer, George; Ehleringer, James R; Remien, Christopher H; Douglas-Hamilton, Iain

2009-05-19

The dietary and movement history of individual animals can be studied using stable isotope records in animal tissues, providing insight into long-term ecological dynamics and a species niche. We provide a 6-year history of elephant diet by examining tail hair collected from 4 elephants in the same social family unit in northern Kenya. Sequential measurements of carbon, nitrogen, and hydrogen isotope rations in hair provide a weekly record of diet and water resources. Carbon isotope ratios were well correlated with satellite-based measurements of the normalized difference vegetation index (NDVI) of the region occupied by the elephants as recorded by the global positioning system (GPS) movement record; the absolute amount of C(4) grass consumption is well correlated with the maximum value of NDVI during individual wet seasons. Changes in hydrogen isotope ratios coincided very closely in time with seasonal fluctuations in rainfall and NDVI whereas diet shifts to relatively high proportions of grass lagged seasonal increases in NDVI by approximately 2 weeks. The peak probability of conception in the population occurred approximately 3 weeks after peak grazing. Spatial and temporal patterns of resource use show that the only period of pure browsing by the focal elephants was located in an over-grazed, communally managed region outside the protected area. The ability to extract time-specific longitudinal records on animal diets, and therefore the ecological history of an organism and its environment, provides an avenue for understanding the impact of climate dynamics and land-use change on animal foraging behavior and habitat relations.

Oxygen-isotope wiggle maching as a tol for synchronising ice-cor and terrestrial records over Termination !

NARCIS (Netherlands)

Hoek, W.Z.; Bohncke, S.J.P.

2001-01-01

In NW Europe, the large number of terrestrial records that are now available from Termination 1 (15-10kcal yr BP) form the basis for a highly detailed picture of Lateglacial environmental change. Nevertheless, the Greenland oxygen-isotope records (GRIP/GISP2) are still regarded as the best

Assessment of diffusive isotopic fractionation in polar firn, and application to ice core trace gas records

DEFF Research Database (Denmark)

Buizert, C.; Sowers, T.; Blunier, T.

2013-01-01

During rapid variations of the atmospheric mixing ratio of a trace gas, diffusive transport in the porous firn layer atop ice sheets and glaciers alters the isotopic composition of that gas relative to the overlying atmosphere. Records of past atmospheric trace gas isotopic composition from ice...... cores and firn need to be corrected for this diffusive fractionation artifact. We present a novel, semi-empirical method to accurately estimate the magnitude of the diffusive fractionation in the ice core record. Our method (1) consists of a relatively simple analytical calculation; (2) requires only...... commonly available ice core data; (3) is not subject to the uncertainties inherent to estimating the accumulation rate, temperature, close-off depth and depth-diffusivity relationship back in time; (4) does not require knowledge of the true atmospheric variations, but uses the smoothed records obtained...

Multiple Nebular Gas Reservoirs Recorded by Oxygen Isotope Variation in a Spinel-Rich CAI in CO3 MIL 090019

Science.gov (United States)

Simon, J. I.; Simon, S. B.; Nguyen, A. N.; Ross, D. K.; Messenger, S.

2017-07-01

We conducted NanoSIMS ion imaging studies of a primitive spinel-rich CAI from the MIL 090019 CO3 chondrite. It records radial O-isotopic heterogeneity among multiple occurrences of the same mineral, reflecting distinct nebular O-isotopic reservoirs.

Climatic correlations in the stable isotope records of silver fir (Abies pindrow) trees from Kashmir, India

International Nuclear Information System (INIS)

Ramesh, R.; Bhattacharya, S.K.; Gopalan, K.

1986-01-01

A high degree of coherence in the annual stable isotopic records along different radial directions of a silver fir tree and between two members of this species from the Kashmir Valley has recently been reported by us. Since such a common pattern of isotopic variability is most likely due to the climatic fluctuations in the site, we have compared the mean δD, δ 13 C and δ 18 O records of these trees with instrumentally measured climatic parameters recorded in a nearby weather station to identify the climatic parameters predominantly influencing the isotopic record. A multiple regression analysis of the two records for the period 1903-1932 yields the following: δD is most sensitive to the amount of growing season precipitation, followed by mean maximum temperature. Tree cellulose shows an amount effect analogous to precipitation samples. The temperature coefficient for δD is in good agreement with earlier estimates based on spatial correlations. δ 13 C is significantly related to humidity and cloud amount. The signs of the regression coefficients are consistent with the recent model of Francey and Farquhar for 13 C/ 12 C fractionation in C 3 plants. δ 18 O of cellulose appears to be controlled significantly by relative humidity. δ 18 O shows less overall correlation with climatic parameters than δD and δ 13 C. δD of carbon bound hydrogen and δ 18 O of tree cellulose are linearly related with a slope of 7.9±0.3, suggesting evaporative enrichment in leaf water. (orig.)

Eocene to Oligocene benthic foraminiferal isotopic record in the Bay of Biscay

International Nuclear Information System (INIS)

Miller, K.G.; Curry, W.B.

1982-01-01

Oxygen and carbon isotopic records of Eocene to Oligocene benthic foraminifera from two Bay of Biscay Deep Sea Drilling Project sites are presented. The delta 18 O figures for benthic foraminifera are significantly higher than those previously reported from deeper North Atlantic sites, the differences arising it is believed from diagenetic alteration of the sediments in the deeper-buried sites. (U.K.)

Contribution to optimisation of Environmental Isotopes tracing in Hydrogeology. Case study of Madagascar

International Nuclear Information System (INIS)

RAJAOBELISON, J.

2003-01-01

The aim of this work is to suggest some improvements on the theory of interpretation and on the methodological approach for the optimum use of environmental isotopes tracing applied to hydrogeological investigation. A review of the theory of environmental isotopes used in hydrogeology has been made. The main constraints have been highlighted and led to some comments and proposals of improvement, in particular with regard to the continental effect on stable isotopes, to the seasonal variation of groundwater 1 4C content, and to the appropriate model for fractured crystalline aquifers. A literature survey on ten specific scientific papers, dealing with isotopic hydrology in miscellaneous types of aquifers and catchments, allowed to draw a synthesis of the hydrogeological, geochemical and isotopic constraints. A proposal of optimum methodological approach, taking into account the above mentioned constraints, have been inferred. The results of an on-going hydrogeological investigation carried out in the Southern crystalline basement and coastal sedimentary aquifers of Madagascar highlights an unusual methodological approach based on the lack of initial basic hydrogeological data. Besides, it shows to what extent the experience of the above mentioned research works can apply in the specific case of the complex aquifers of Madagascar. The lessons gained from this study contribute to enrich the synthesis of environmental isotopes constraints in hydrogeology and lead to a more realistic methodological approach proposal wich is likely to better make profitable the isotope hydrology technology

Electrochemically controlled iron isotope fractionation

Science.gov (United States)

Black, Jay R.; Young, Edward D.; Kavner, Abby

2010-02-01

Variations in the stable isotope abundances of transition metals have been observed in the geologic record and trying to understand and reconstruct the physical/environmental conditions that produced these signatures is an area of active research. It is clear that changes in oxidation state lead to large fractionations of the stable isotopes of many transition metals such as iron, suggesting that transition metal stable isotope signatures could be used as a paleo-redox proxy. However, the factors contributing to these observed stable isotope variations are poorly understood. Here we investigate how the kinetics of iron redox electrochemistry generates isotope fractionation. Through a combination of electrodeposition experiments and modeling of electrochemical processes including mass-transport, we show that electron transfer reactions are the cause of a large isotope separation, while mass transport-limited supply of reactant to the electrode attenuates the observed isotopic fractionation. Furthermore, the stable isotope composition of electroplated transition metals can be tuned in the laboratory by controlling parameters such as solution chemistry, reaction overpotential, and solution convection. These methods are potentially useful for generating isotopically-marked metal surfaces for tracking and forensic purposes. In addition, our studies will help interpret stable isotope data in terms of identifying underlying electron transfer processes in laboratory and natural samples.

Links between meteorological conditions and spatial/temporal variations in long-term isotope records from the Austrian precipitation network

International Nuclear Information System (INIS)

Kaiser, A.; Scheifinger, H.; Kralik, M.; Papesch, W.; Rank, D.; Stichler, W.

2002-01-01

The isotope records from the Austrian Network for Isotopes in Precipitation (ANIP) show significant but not uniform long-term trends. While the 10-year running means of some mountain stations exhibit a pronounced increase in δ 18 O of about 1 per mille since 1975, the change of δ 18 O at the valley stations is much lower. There are also differences in the time behaviour. The differences in the δ 18 O-values of sampling stations at similar altitudes can be explained by different origins of the air moisture (Atlantic or Mediterranean influence). Furthermore, a significant difference in the behaviour of the deuterium excess at neighbouring mountain and valley stations has been observed. There is a slight increase of the yearly mean of the deuterium excess with increasing altitude of the sampling station. But moreover, the seasonal pattern of the deuterium excess is quite different. While the valley stations exhibit the expected minimum in summer, the mountain stations show a distinct maximum between June and October. As a first step into a comprehensive analysis of the meteorological effects on the isotope patterns, the role of advection of different air masses is studied by trajectory statistics. Back trajectories, based on the three dimensional wind fields of the ECMWF model, are calculated for each hour within each precipitation event. Thus, the frequency of the origin of air masses and their contribution to the isotope patterns of the monthly precipitation samples are studied for two selected mountain stations north and south of the main ridge of the Alps. (author)

The magnesium isotope record of cave carbonate archives

Directory of Open Access Journals (Sweden)

S. Riechelmann

2012-11-01

Full Text Available Here we explore the potential of magnesium (δ²⁶Mg isotope time-series data as continental climate proxies in speleothem calcite archives. For this purpose, a total of six Pleistocene and Holocene stalagmites from caves in Germany, Morocco and Peru and two flowstones from a cave in Austria were investigated. These caves represent the semi-arid to arid (Morocco, the warm-temperate (Germany, the equatorial-humid (Peru and the cold-humid (Austria climate zones. Changes in the calcite magnesium isotope signature with time are compared against carbon and oxygen isotope records from these speleothems. Similar to other proxies, the non-trivial interaction of a number of environmental, equilibrium and disequilibrium processes governs the δ²⁶Mg fractionation in continental settings. These include the different sources of magnesium isotopes such as rainwater or snow as well as soil and host rock, soil zone biogenic activity, shifts in silicate versus carbonate weathering ratios and residence time of water in the soil and karst zone. Pleistocene stalagmites from Morocco show the lowest mean δ²⁶Mg values (GDA: −4.26 ± 0.07‰ and HK3: −4.17 ± 0.15‰, and the data are well explained in terms of changes in aridity over time. The Pleistocene to Holocene stalagmites from Peru show the highest mean value of all stalagmites (NC-A and NC-B δ²⁶Mg: −3.96 ± 0.04‰ but only minor variations in Mg-isotope composition, which is consistent with the rather stable equatorial climate at this site. Holocene stalagmites from Germany (AH-1 mean δ²⁶Mg: −4.01 ± 0.07‰; BU 4 mean δ²⁶Mg: −4.20 ± 0.10‰ suggest changes in outside air temperature was the principal driver rather than rainfall amount. The alpine Pleistocene flowstones from Austria (SPA 52: −3.00 ± 0.73‰; SPA 59: −3.70 ± 0.43‰ are affected by glacial versus interglacial climate change with outside air temperature

Dual temperature effects on oxygen isotopic ratio of shallow-water coral skeleton: Consequences on seasonal and interannual records

Science.gov (United States)

Juillet-Leclerc, A.; Reynaud, S.

2009-04-01

Oxygen isotopic ratio from coral skeleton is regarded for a long time as promising climate archives at seasonal scale. Although in isotopic disequilibrium relative to seawater, it is supposed to obey to the isotope thermometer. Indeed, coral oxygen isotopic records are strongly temperature dependent, but d18O-temperature calibrations derived from different corals are highly variable. The isotope thermometer assumption does not take into account vital effects due to biogenic origin of the mineral. Corals are animals living in symbiosis with algae (zooxanthellae). Interactions between symbiont photosynthesis and coral skeleton carbonation have been abundantly observed but they remain poorly understood and the effects of photosynthesis on coral growth and skeleton oxygen ratio are ignored. Coral cultured under two light conditions enabled to relate metabolic parameters and oxygen isotopic variability with photosynthetic activity. By examining responses provided by each colony they revealed that photosynthesis significantly affected d18O, by an opposite sense compared with the sole temperature influence. Since temperature and light changes are associated during seasonal variations, this complicates the interpretation of seasonal record. Additionally, this complexity is amplified because photosynthetic activity is also directly impacted by temperature variability. Thus, the annual isotopic amplitude due to the "physical" temperature influence is partly compensated through photosynthesis. Similar opposite effect is also shown by extension rate of the cultured colonies. First, we will examine and quantify consequences of photosynthesis on growth rate and oxygen isotopic signature, from cultured corals. Second, we will consider the consequences of this vital effect on data series, at seasonal and interannual time scales.

Constraining the cause of the end-Guadalupian extinction with coupled records of carbon and calcium isotopes

Science.gov (United States)

Jost, A. B.; Mundil, R.; He, B.; Brown, S. T.; Altiner, D.; Sun, Y.; DePaolo, D. J.; Payne, J.

2013-12-01

A negative δ13C excursion in carbonate sediments from Guadalupian (Middle Permian) and Lopingian (Late Permian) stratigraphic sections has been interpreted to result from a large carbon cycle disturbance during end-Guadalupian extinction event (ca. 260 Ma). However, the carbon isotope data alone are insufficient to uniquely determine the type and magnitude of perturbations to the global carbon cycle. The carbon and calcium cycles are coupled via CaCO3 burial, so changes in calcium isotopes can be used to constrain the cause of a carbon isotope excursion. In this study, we present coupled carbon and calcium isotope records from three Guadalupian-Lopingian (G/L) sections in China and Turkey. Isotope records among our studied sections are inconsistent in both their δ13C and δ44/40Ca records. Similar inconsistencies in δ13C among sections occur across previously published datasets. Sections with large (>3‰) changes in δ13C either show evidence for diagenetic alteration or do not show δ13C and δ44/40Ca changes consistent with severe volcanic degassing from Emeishan or methane clathrate destabilization. We conclude that the large isotopic changes are more likely the result of local burial conditions or diagenetic effects, rather than a large carbon cycle disturbance. Perturbations to the global carbon and calcium cycles appear to have been much smaller across the G/L transition than across the subsequent Permian-Triassic boundary. This finding is consistent with recent paleobiological data showing that the end-Guadalupian extinction was much less severe than previously believed, and was indistinguishable in magnitude from background intervals. However, selective extinction of marine animals with passive respiratory physiology indicates that the G/L extinction cannot simply be due to background extinction or sampling failure, and that it was triggered by some environmental event. Therefore, any environmental event must have been small enough to not generate large

Hf Isotope Evidence for Subducted Basalt and Sediment Contributions to the Eastern Trans-Mexican Volcanic Belt

Science.gov (United States)

Cai, Y.; Tuena, A. G.; Capra, L.; Straub, S. M.; Goldstein, S. L.; Langmuir, C. H.

2005-12-01

Magmas generated at thick crust continental arcs often have enriched continental crust-like trace element patterns and Pb-Sr-Nd isotope ratios that are intermediate to both upper mantle and crustal compositions. Thus it is difficult to distinguish between contributions from (a) the subducted basalt and the upper mantle wedge, and (b) subducted sediment and the continental crust. These issues have been the focus of major controversy. Here we show evidence for subduction contributions to lavas in a classic thick crust environment. In Eastern Trans-Mexican Volcanic Belt, the upper continental crust is 30 km to 45 km thick. However, primitive mafic lavas erupt on many sites across the arc. We have analyzed the subducting sediments as represented by DSDP 487, located seaward of the trench, where the lower third of the sediment column has strongly hydrothermal pelagic features and the upper two-thirds is composed of terrigenous sediments. The pelagic sediments have distinctive features that could be used to identify a subduction component in the volcanics, including high REE/Hf, negative Ce anomalies, and Nd-Hf isotopes that lie on the "seawater array" and offset from the "mantle-crust" array. We have focused on a unique series of lavas from volcano Nevado de Toluca, located southwest of Mexico City. These lavas show negative Ce anomalies coupled with low REE/Hf and Zr/Nd ratios. Hf-Nd isotope ratios show a shallow trend compared to the mantle-crust array, consistent with a pelagic component. In addition, Hf isotopes show a striking positive correlation with Ce anomalies that trend toward the pelagic sediment compositions. These and other observations provide clear evidence for a component from subducted sediment in the lavas. In addition, there is a negative correlation of Lu/Hf and Hf isotopes that requires a mixing endmember with MORB-like Hf isotope ratios but with lower than MORB Lu/Hf. This indicates a melt from eclogitic subducted basalt. Compared to other

Holocene elemental, lead isotope and charcoal record from peat in southern Poland

Directory of Open Access Journals (Sweden)

K. Tudyka

2017-03-01

Full Text Available This article presents a mid-resolution elemental, isotopic and charcoal record from 10700 BC to AD 500 in a peat core located in Żyglin (southern Poland. The objective is to give insight into the proxies with emphasis on lead (Pb sources in this minerogenic peat deposit. During the Early Holocene (10700–7550 BC the average 206Pb/207Pb quotient was around 1.196. This isotopic signature is consistent with natural dust derived from long-distance soil and rock weathering. The Mid-Holocene period (7550–3200 BC shows a significant change in the peat accumulation conditions. The growth rate is approximately 0.04 mm yr-1 and the 206Pb/207Pb quotients are shifted toward values that are found in local galena ores. This is simultaneous with a significantly increased lead flux which further confirms local sources of material in this peat deposit. In the Late Holocene period (3200 BC–AD 500 a large quantity of charcoal particles with diameters ranging from 2 mm up to 3 cm is found; also, Pb, Zn and Cu fluxes reach their highest values. This period corresponds to the Eneolithic, Bronze and Iron Ages, and human impact is recorded as charcoal.

Lake Baikal isotope records of Holocene Central Asian precipitation

Science.gov (United States)

Swann, George E. A.; Mackay, Anson W.; Vologina, Elena; Jones, Matthew D.; Panizzo, Virginia N.; Leng, Melanie J.; Sloane, Hilary J.; Snelling, Andrea M.; Sturm, Michael

2018-06-01

Climate models currently provide conflicting predictions of future climate change across Central Asia. With concern over the potential for a change in water availability to impact communities and ecosystems across the region, an understanding of historical trends in precipitation is required to aid model development and assess the vulnerability of the region to future changes in the hydroclimate. Here we present a record from Lake Baikal, located in the southern Siberian region of central Asia close to the Mongolian border, which demonstrates a relationship between the oxygen isotope composition of diatom silica (δ18Odiatom) and precipitation to the region over the 20th and 21st Century. From this, we suggest that annual rates of precipitation in recent times are at their lowest for the past 10,000 years and identify significant long-term variations in precipitation throughout the early to late Holocene interval. Based on comparisons to other regional records, these trends are suggested to reflect conditions across the wider Central Asian region around Lake Baikal and highlight the potential for further changes in precipitation with future climate change.

Multiple Nebular Gas Reservoirs Recorded by Oxygen Isotope Variation in a Spinel-rich CAI in CO3 MIL 090019

Science.gov (United States)

Simon, J. I.; Simon, S. B.; Nguyen, A. N.; Ross, D. K.; Messenger, S.

2017-01-01

We conducted NanoSIMS O-isotopic imaging of a primitive spinel-rich CAI spherule (27-2) from the MIL 090019 CO3 chondrite. Inclusions such as 27-2 are proposed to record inner nebula processes during an epoch of rapid solar nebula evolution. Mineralogical and textural analyses suggest that this CAI formed by high temperature reactions, partial melting, and condensation. This CAI exhibits radial O-isotopic heterogeneity among multiple occurrences of the same mineral, reflecting interactions with distinct nebular O-isotopic reservoirs.

Lateglacial and Holocene climatic changes in south-eastern Patagonia inferred from carbonate isotope records of Laguna Potrok Aike (Argentina)

Science.gov (United States)

Oehlerich, M.; Mayr, C.; Gussone, N.; Hahn, A.; Hölzl, S.; Lücke, A.; Ohlendorf, C.; Rummel, S.; Teichert, B. M. A.; Zolitschka, B.

2015-04-01

First results of strontium, calcium, carbon and oxygen isotope analyses of bulk carbonates from a 106 m long sediment record of Laguna Potrok Aike, located in southern Patagonia are presented. Morphological and isotopic investigations of μm-sized carbonate crystals in the sediment reveal an endogenic origin for the entire Holocene. During this time period the calcium carbonate record of Laguna Potrok Aike turned out to be most likely ikaite-derived. As ikaite precipitation in nature has only been observed in a narrow temperature window between 0 and 7 °C, the respective carbonate oxygen isotope ratios serve as a proxy of hydrological variations rather than of palaeotemperatures. We suggest that oxygen isotope ratios are sensitive to changes of the lake water balance induced by intensity variations of the Southern Hemisphere Westerlies and discuss the role of this wind belt as a driver for climate change in southern South America. In combination with other proxy records the evolution of westerly wind intensities is reconstructed. Our data suggest that weak SHW prevailed during the Lateglacial and the early Holocene, interrupted by an interval with strengthened Westerlies between 13.4 and 11.3 ka cal BP. Wind strength increased at 9.2 ka cal BP and significantly intensified until 7.0 ka cal BP. Subsequently, the wind intensity diminished and stabilised to conditions similar to present day after a period of reduced evaporation during the "Little Ice Age". Strontium isotopes (87Sr/86Sr ratio) were identified as a potential lake-level indicator and point to a lowering from overflow conditions during the Glacial (∼17 ka cal BP) to lowest lake levels around 8 ka cal BP. Thereafter the strontium isotope curve resembles the lake-level curve which is stepwise rising until the "Little Ice Age". The variability of the Ca isotope composition of the sediment reflects changes in the Ca budget of the lake, indicating higher degrees of Ca utilisation during the period with

Methane clumped isotopes: Progress and potential for a new isotopic tracer

Energy Technology Data Exchange (ETDEWEB)

Douglas, Peter M. J.; Stolper, Daniel A.; Eiler, John M.; Sessions, Alex L.; Lawson, Michael; Shuai, Yanhua; Bishop, Andrew; Podlaha, Olaf G.; Ferreira, Alexandre A.; Santos Neto, Eugenio V.; Niemann, Martin; Steen, Arne S.; Huang, Ling; Chimiak, Laura; Valentine, David L.; Fiebig, Jens; Luhmann, Andrew J.; Seyfried, William E.; Etiope, Giuseppe; Schoell, Martin; Inskeep, William P.; Moran, James J.; Kitchen, Nami

2017-11-01

The isotopic composition of methane is of longstanding geochemical interest, with important implications for understanding hydrocarbon systems, atmospheric greenhouse gas concentrations, the global carbon cycle, and life in extreme environments. Recent analytical developments focusing on multiply substituted isotopologues (‘clumped isotopes’) are opening a potentially valuable new window into methane geochemistry. When methane forms in internal isotopic equilibrium, clumped isotopes can provide a direct record of formation temperature, making this property particularly valuable for identifying different methane origins. However, it has also become clear that in certain settings methane clumped isotope measurements record kinetic rather than equilibrium isotope effects. Here we present a substantially expanded dataset of methane clumped isotope analyses, and provide a synthesis of the current interpretive framework for this parameter. We review different processes affecting methane clumped isotope compositions, describe the relationships between conventional isotope and clumped isotope data, and summarize the types of information that this measurement can provide in different Earth and planetary environments.

Glacial/interglacial wetland, biomass burning, and geologic methane emissions constrained by dual stable isotopic CH4 ice core records

Science.gov (United States)

Bock, Michael; Schmitt, Jochen; Beck, Jonas; Seth, Barbara; Chappellaz, Jérôme; Fischer, Hubertus

2017-07-01

Atmospheric methane (CH4) records reconstructed from polar ice cores represent an integrated view on processes predominantly taking place in the terrestrial biogeosphere. Here, we present dual stable isotopic methane records [δ13CH4 and δD(CH4)] from four Antarctic ice cores, which provide improved constraints on past changes in natural methane sources. Our isotope data show that tropical wetlands and seasonally inundated floodplains are most likely the controlling sources of atmospheric methane variations for the current and two older interglacials and their preceding glacial maxima. The changes in these sources are steered by variations in temperature, precipitation, and the water table as modulated by insolation, (local) sea level, and monsoon intensity. Based on our δD(CH4) constraint, it seems that geologic emissions of methane may play a steady but only minor role in atmospheric CH4 changes and that the glacial budget is not dominated by these sources. Superimposed on the glacial/interglacial variations is a marked difference in both isotope records, with systematically higher values during the last 25,000 y compared with older time periods. This shift cannot be explained by climatic changes. Rather, our isotopic methane budget points to a marked increase in fire activity, possibly caused by biome changes and accumulation of fuel related to the late Pleistocene megafauna extinction, which took place in the course of the last glacial.

Age of underground waters: isotopes contribution

International Nuclear Information System (INIS)

Chery, L.; Olive, Ph.

2006-01-01

Does water has an age? The age of underground waters can be the duration of their underground travel between their infiltration inside the ground and their captation at a spring or a drilled well. The isotopic geochemistry comes to the support of classical geochemistry to estimate these residence times. Radio-isotopes, like tritium for young waters or carbon 14 for old waters, are used as chronometers to interpret the recharge ways, the flow mechanisms and the residence times of underground waters. Their use is presented in this article with some theoretical recalls and some examples of application. (J.S.)

Modern Deep-sea Sponges as Recorders of Bottom Water Silicon Isotopes

Science.gov (United States)

Hendry, K. R.; Georg, R. B.; Rickaby, R. E.; Robinson, L. F.; Halliday, A. N.

2008-12-01

Major zones of opal accumulation in the world oceans have experienced geographical shifts during the Cenozoic coincident with times of transition in oceanic circulation and climate. The global marine silica cycle is likely to respond to various large-scale changes including the distillation of Si and other nutrients in ocean basins; weathering and continental inputs; and biological productivity in surface waters. These processes could potentially be distinguished by their impact on the isotopic composition of dissolved silica in the world oceans. Although diatoms dominate uptake of silica in surface waters, box-modelling (de la Rocha and Bickle, 2005) suggests that sponges spicules have a greater potential to reflect whole ocean changes in the silica cycle, by recording deep-water silicon isotopes. Here, we introduce a new calibration study of modern deep- sea sponges collected on a transect cruise across the Drake Passage, in the Southern Ocean, from a range of depths and seawater silicic acid concentrations. Sponges were collected by benthic trawling, and dried immediately. The spicules were later isolated from cellular material and cleaned for surface contaminants, before dissolution and analysis by NuPlasma HR MC-ICP-MS in medium resolution mode. We discuss our preliminary data, the extent to which inter and intraspecies variations reflect environmental conditions, and the implications for palaeoreconstructions of the marine silicon cycle. de la Rocha, C. and M. Bickle (2005). Sensitivity of silicon isotopes to whole-ocean changes in the silica cycle. Marine Geology 217, 267-282.

The Mt Logan Holocene-late Wisconsinan isotope record

DEFF Research Database (Denmark)

Dahl-Jensen, Dorthe; Fisher, David; Osterberg, Erich

2008-01-01

Mt Logan • stable isotopes • Holocene • ENSO • peat • N Pacific • sudden change Udgivelsesdato: August......Mt Logan • stable isotopes • Holocene • ENSO • peat • N Pacific • sudden change Udgivelsesdato: August...

Hydrothermal sediments as a potential record of seawater Nd isotope compositions: The Rainbow vent site (36°14'N, Mid-Atlantic Ridge)

Science.gov (United States)

Chavagnac, ValéRie; Palmer, Martin R.; Milton, J. Andrew; Green, Darryl R. H.; German, Christopher R.

2006-09-01

Geochemical compositions and Sr and Nd isotopes were measured in two cores collected ˜2 and 5 km from the Rainbow hydrothermal vent site on the Mid-Atlantic Ridge. Overall, the cores record enrichments in Fe and other metals from hydrothermal fallout, but sequential dissolution of the sediments allows discrimination between a leach phase (easily leachable) and a residue phase (refractory). The oxy-anion and transition metal distribution combined with rare earth element (REE) patterns suggest that (1) the leach fraction is a mixture of biogenic carbonate and hydrothermal Fe-Mn oxy-hydroxide with no significant contribution from detrital material and (2) >99.5% of the REE content of the leach fraction is of seawater origin. In addition, the leach fraction has an average 87Sr/86Sr ratio indistinguishable from modern seawater at 0.70916. Although we lack the ɛNd value of present-day deep water at the Rainbow vent site, we believe that the REE budget of the leach fraction is predominantly of seawater origin. We suggest therefore that the leach fraction provides a record of local seawater ɛNd values. Nd isotope data from these cores span the period of 4-14 ka (14C ages) and yield ɛNd values for North East Atlantic Deep Water (NEADW) that are higher (-9.3 to -11.1) than those observed in the nearby Madeira Abyssal Plain from the same depth (-12.4 ± 0.9). This observation suggests that either the Iceland-Scotland Overflow Water (ISOW) and Lower Deep Water contributions to the formation of NEADW are higher along the Mid-Atlantic Ridge than in the surrounding basins or that the relative proportion of ISOW was higher during this period than is observed today. This study indicates that hydrothermal sediments have the potential to provide a higher-resolution record of deep water ɛNd values, and hence deepwater circulation patterns in the oceans, than is possible from other types of sediments.

Stable isotope ratios in freshwater mussel shells as high resolution recorders of riverine environmental variation

Science.gov (United States)

Kukolich, S.; Kendall, C.; Dettman, D. L.

2017-12-01

The geochemical record stored in growth increments of freshwater mussel shells reveals annual to sub-annual changes in environmental conditions during the lifetime of the organism. The carbon, nitrogen, and oxygen stable isotope composition of aragonite shells responds to changes in water chemistry, temperature, streamflow, turbidity, growth rate, size, age, and reproduction. The goals of this study are to determine how stable isotopes can be used to reconstruct the conditions in which the mussels lived and to illuminate any vital effects that might obscure the isotopic record of those conditions. Previous research has suggested that annual δ13C values decrease in older freshwater mussel shells due to lower growth rates and greater incorporation of dietary carbon into the shell with increasing age. However, a high-resolution, seasonal investigation of δ13C, δ15N, and δ18O as they relate to organism age has not yet been attempted in freshwater mussels. A total of 28 Unionid mussels of three different species were collected live in 2011 in the Tennessee River near Paducah, Kentucky, USA. In this study, we analyzed the shell nacre and external organic layers for stable carbon, nitrogen, and oxygen isotope ratios, focusing on growth bands formed between 2006 and 2011. We present a time series of shell δ13C, δ18O, and δ15N values with monthly resolution. We also compare the shell-derived geochemical time series to a time series of the δ13C and δ15N of particulate organic matter, δ13C of DIC, δ18OWater, and water temperature in which the mussels lived. Results show that environmental factors such as water temperature and primary productivity dominate shell chemistry while animal age has little or no effect.

Contributions of isotopic bio-geochemistry to the analysis of water - soil - root interactions

International Nuclear Information System (INIS)

Cayet, S.

2001-07-01

The aim of this work is to study the origin of the isotopic signal of the water produced by plants transpiration. It stresses more particularly on the water movements between the soil and the plant in a context of heterogenous water availability for the root system. The use of water isotopes ( 18 O and 2 H) should allow to precise the water extraction depth of the roots and the plant strategy in front of a hydric stress of edaphic origin. The first chapter presents the place of water in the soil-plant-atmosphere continuum, the different potential sources of water accessible to the plant, the principles of water absorption and the hydric transfer in the plant in relation with the variations of water absorption and of the evaporative conditions. The isotopic method is introduced with the natural variability of the isotopic composition of the atmospheric and soil waters. Finally, the reaction of the plant in front of a hydric stress is described. The second chapter presents a series of experiments carried out in the natural environment and shows the problems encountered during the determination of water origin in heterogenous hydric availability conditions. The third chapter describes the experiments performed in controlled environment. One series of experiments is performed in homogenous hydric availability condition. The aim is to analyze the isotopic signal emitted by the plant and its significance with respect to the feeding water. The second series of experiments is performed in heterogenous hydric availability conditions and in stable or variable climatic conditions. In the last chapter, the different experiments performed in natural environment are presented, first in optimum hydric availability conditions, and second in variable hydric conditions. These experiments allow to reconstruct the isotopic signal of the soil water which is recorded by the plant and to precise the preferential areas of water extraction by the roots, and the competitive behaviour of

A contribution to the future prospect of uranium laser-isotope separation

International Nuclear Information System (INIS)

Becker, F.S.

1981-01-01

The two-frequency multiphoton-dissociation of UF 6 seems promising, using a high-power laser, which is tunable in the 16 μm spectral region due to the frequency shift of the 10 μm CO 2 -laser radiation, induced by the stimulated rotational Raman effect of para-hydrogen. In the present experiments the isotope selectivity of the multiphoton-dissociation process is studied in order to contribute to the solution of some questions, as for example the influence of high fluorine concentrations on the optical dissociation of UF 6 . (DG) [de

Could a secular increase in organic burial explain the rise of oxygen? Insights from a geological carbon cycle model constrained by the carbon isotope record

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Krissansen-Totton, J.; Kipp, M.; Catling, D. C.

2017-12-01

The stable isotopes of carbon in marine sedimentary rock provide a window into the evolution of the Earth system. Conventionally, a relatively constant carbon isotope ratio in marine sedimentary rocks has been interpreted as implying constant organic carbon burial relative to total carbon burial. Because organic carbon burial corresponds to net oxygen production from photosynthesis, it follows that secular changes in the oxygen source flux cannot explain the dramatic rise of oxygen over Earth history. Instead, secular declines in oxygen sink fluxes are often invoked as causes for the rise of oxygen. However, constant fractional organic burial is difficult to reconcile with tentative evidence for low phosphate concentrations in the Archean ocean, which would imply lower marine productivity and—all else being equal—less organic carbon burial than today. The conventional interpretation of the carbon isotope record rests on the untested assumption that the isotopic ratio of carbon inputs into the ocean reflect mantle isotopic values throughout Earth history. In practice, differing rates of carbonate and organic weathering will allow for changes in isotopic inputs, as suggested by [1] and [2]. However, these inputs can not vary freely because large changes in isotopic inputs would induce secular trends in carbon reservoirs, which are not observed in the isotope record. We apply a geological carbon cycle model to all Earth history, tracking carbon isotopes in crustal, mantle, and ocean reservoirs. Our model is constrained by the carbon isotope record such that we can determine the extent to which large changes in organic burial are permitted. We find both constant organic burial and 3-5 fold increases in organic burial since 4.0 Ga can be reconciled with the carbon isotope record. Changes in the oxygen source flux thus need to be reconsidered as a possible contributor to Earth's oxygenation. [1] L. A. Derry, Organic carbon cycling and the lithosphere, in Treatise on

Effects of ocean acidification on the marine calcium isotope record at the Paleocene-Eocene Thermal Maximum

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Griffith, Elizabeth M.; Fantle, Matthew S.; Eisenhauer, Anton; Paytan, Adina; Bullen, Thomas D.

2015-06-01

Carbonates are used extensively to reconstruct paleoclimate and paleoceanographic conditions over geologic time scales. However, these archives are susceptible to diagenetic alteration via dissolution, recrystallization and secondary precipitation, particularly during ocean acidification events when intense dissolution can occur. Despite the possible effects of diagenesis on proxy fidelity, the impacts of diagenesis on the calcium isotopic composition (δ44Ca) of carbonates are unclear. To shed light on this issue, bulk carbonate δ44Ca was measured at high resolution in two Pacific deep sea sediment cores (ODP Sites 1212 and 1221) with considerably different dissolution histories over the Paleocene-Eocene Thermal Maximum (PETM, ∼ 55 Ma). The δ44Ca of marine barite was also measured at the deeper Site 1221, which experienced severe carbonate dissolution during the PETM. Large variations (∼ 0.8 ‰) in bulk carbonate δ44Ca occur in the deeper of the two sites at depths corresponding to the peak carbon isotope excursion, which correlate with a large drop in carbonate weight percent. Such an effect is not observed in either the 1221 barite record or the bulk carbonate record at the shallower Site 1212, which is also less affected by dissolution. We contend that ocean chemical changes associated with abrupt and massive carbon release into the ocean-atmosphere system and subsequent ocean acidification at the PETM affected the bulk carbonate δ44Ca record via diagenesis in the sedimentary column. Such effects are considerable, and need to be taken into account when interpreting Ca isotope data and, potentially, other geochemical proxies over extreme climatic events that drive sediment dissolution.

Stable Isotopic signatures of Adélie penguin remains provide long-term paleodietary records in Northern Victoria Land (Ross Sea, Antarctica)

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Lorenzini, Sandra; Baroni, Carlo; Fallick, Anthony Edward; Baneschi, Ilaria; Salvatore, Maria Cristina; Zanchetta, Giovanni; Dallai, Luigi

2010-05-01

The stable isotopes geochemistry of carbon and nitrogen provides a powerful tools for investigating in animal dietary patterns and shifts during the past. The signature of C and N isotopes provide direct information about the diet of an individual and its dietary patterns, especially when the dietary sources consist of prey from different trophic levels (i.e. different C and N isotopic composition) (DeNiro and Epstein 1978, Minawaga and Wada 1984, Koch et al. 1994, Hobson 1995). By analyzing the isotopic composition of penguin remains, we present a new detailed Adélie penguin (Pygoscelis adeliae) paleodietary record for the area of Terra Nova Bay (Victoria Land, Ross Sea). Adélie penguins primarily feed on fish (mainly the silverfish Pleuragramma antarcticum) and krill (Euphausia superba, Euphausia cristallorophias) (Ainley 2002, Lorenzini et al. 2009) that belonging to two different trophic levels. Consequently, they are characterized by different isotopic signatures. Specifically, we analyzed 13C/12C and 15N/14N ratios of more than one thousand of modern and fossil Adélie penguin eggshell and guano samples collected from ornithogenic soils (penguin guano-formed) dated back to ≈7,200 years BP (Baroni and Orombelli 1994, Lambert et al. 2002, Baroni and Hall 2004, Hall et al. 2006). The expanded database of stable isotope values obtained from Adélie penguin remains define a detailed paleodietary record with an excellent temporal continuity over all the investigated time period. Our data indicate a significant dietary shift between fish and krill, with a gradual decrease from past to present time in the proportion of fish compared to krill in Adélie penguin diet. From 7200 yrs BP to 2000 yrs BP, δ13C and δ15N values indicate fish as the most eaten prey. The dietary contribution of lower-trophic prey in penguin diet started becoming evident not earlier than 2000 yrs BP, when the δ13C values reveal a mixed diet based on fish and krill consumption. Modern

A biomarker stable isotope record of late Quaternary climate and organic matter export in Southwestern Taiwan

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Chang, Q.; Hren, M. T.; Lin, A. T.; Eley, Y.; Yu, S. W.; Harris, G.

2017-12-01

We present new leaf wax n-alkane hydrogen (δD) and carbon (δ13C) isotopic data from a 36-m-long core from off-shore southwestern Taiwan to evaluate late Quaternary changes in climate and the source of organic matter exported from the landscape. The core (MD178-3291) is located on the flank of the Gaoping Submarine Canyon that connects with the Gaoping river catchment in southwestern Taiwan. The sediment deposition in this core spans the last 26 kyr, providing a unique record of glacial-interglacial changes in organic matter export from the Taiwan orogen. The δD and δ13C both show a shift in isotopic compositions at 15 kyr, that coincides with the shift in planktonic foraminifera δ18O record from the same core as well as the global sea level. We therefore interpret this dominant shift as affected by the global glacial to interglacial transition. Following by this transition and through the interglacial period, both biomarker δD and δ13C data record fluctuations that we suggest result from short timescale changes in the distribution of organic inputs to the offshore site. This change in source is most likely caused by increases in storm and landslide frequency or intensity during warmer intervals. This interpretation is supported by terrestrial records that show an increase in landslides in the Gaoping catchment and evidence for enhanced rainfall intensity and a corresponding increase in the frequency of turbidity currents.

The isotopic record of atmospheric lead fall-out on an Icelandic salt marsh since AD 50

International Nuclear Information System (INIS)

Marshall, William A.; Clough, Robert; Gehrels, W. Roland

2009-01-01

We report a record of atmospheric Pb deposition at a coastal site in western Iceland that spans the last two millennia. The elemental concentrations of Pb, Al, Li and Ti are determined using ICP-MS from a sediment monolith collected from a salt marsh. Multicollector (MC) ICP-MS analysis is used to obtain isotopic ratios of stable Pb. The Pb/Ti and Pb/Li ratios are used to separate natural Pb background concentrations from Pb derived from remote anthropogenic sources. The pollution record in western Iceland is subdued in comparison with Pb records from the European mainland, but the isotopic character, profile and timing of Pb deposition show good agreement with the atmospheric Pb fall-out reported from sites in Scandinavia and northwestern Europe. At the bottom of the sequence we isolate a low-level (0.1-0.4 mg kg -1 ) Pb enrichment signal dated to AD 50-150. The isotopic signature and timing of this signal suggest Roman metal working industries as the source. In the subsequent millennium there was no significant or very low (i.e. elemental concentrations -1 ) anthropogenic Pb deposition at the site up to, and including, the early Medieval period. Above a pumice layer, dated to AD 1226-1227, a small increase in Pb deposition is found. This trend is maintained until a more substantive and progressive increase is signalled during the late 1700s and early 1800s. This is followed by a substantial enrichment signal in the sediments (> 3.0 mg kg -1 ) that is interpreted as derived from industrial coal burning and metal working during the 19th and 20th centuries in northern Europe. During the late 20th century, significant fall-out from European fuel additives reached Iceland

A Two-year Record of Daily Rainfall Isotopes from Fiji: Implications for Reconstructing Precipitation from Speleothem δ18O

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Brett, M.; Mattey, D.; Stephens, M.

2015-12-01

Oxygen isotopes in speleothem provide opportunities to construct precisely dated records of palaeoclimate variability, underpinned by an understanding of both the regional climate and local controls on isotopes in rainfall and groundwater. For tropical islands, a potential means to reconstruct past rainfall variability is to exploit the generally high correlation between rainfall amount and δ18O: the 'amount effect'. The GNIP program provides δ18O data at monthly resolution for several tropical Pacific islands but there are few data for precipitation isotopes at daily resolution, for investigating the amount effect over different timescales in a tropical maritime setting. Timescales are important since meteoric water feeding a speleothem has undergone storage and mixing in the aquifer system and understanding how the isotope amount effect is preserved in aquifer recharge has fundamental implications on the interpretation of speleothem δ18O in terms of palaeo-precipitation. The islands of Fiji host speleothem caves. Seasonal precipitation is related to the movement of the South Pacific Convergence Zone, and interannual variations in rainfall are coupled to ENSO behaviour. Individual rainfall events are stratiform or convective, with proximal moisture sources. We have daily resolution isotope data for rainfall collected at the University of the South Pacific in Suva, covering every rain event in 2012 and 2013. δ18O varies between -18‰ and +3‰ with the annual weighted averages at -7.6‰ and -6.8‰ respectively, while total recorded rainfall amount is similar in both years. We shall present analysis of our data compared with GNIP, meteorological data and back trajectory analyses to demonstrate the nature of the relationship between rainfall amount and isotopic signatures over this short timescale. Comparison with GNIP data for 2012-13 will shed light on the origin of the amount effect at monthly and seasonal timescales in convective, maritime, tropical

Speleothem stable isotope records for east-central Europe: resampling sedimentary proxy records to obtain evenly spaced time series with spectral guidance

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Gábor Hatvani, István; Kern, Zoltán; Leél-Őssy, Szabolcs; Demény, Attila

2018-01-01

Uneven spacing is a common feature of sedimentary paleoclimate records, in many cases causing difficulties in the application of classical statistical and time series methods. Although special statistical tools do exist to assess unevenly spaced data directly, the transformation of such data into a temporally equidistant time series which may then be examined using commonly employed statistical tools remains, however, an unachieved goal. The present paper, therefore, introduces an approach to obtain evenly spaced time series (using cubic spline fitting) from unevenly spaced speleothem records with the application of a spectral guidance to avoid the spectral bias caused by interpolation and retain the original spectral characteristics of the data. The methodology was applied to stable carbon and oxygen isotope records derived from two stalagmites from the Baradla Cave (NE Hungary) dating back to the late 18th century. To show the benefit of the equally spaced records to climate studies, their coherence with climate parameters is explored using wavelet transform coherence and discussed. The obtained equally spaced time series are available at PANGAEA.875917" target="_blank">https://doi.org/10.1594/PANGAEA.875917.

Oxygen isotopes in tree rings record variation in precipitation δ18O and amount effects in the south of Mexico.

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Brienen, Roel J W; Hietz, Peter; Wanek, Wolfgang; Gloor, Manuel

2013-12-01

[1] Natural archives of oxygen isotopes in precipitation may be used to study changes in the hydrological cycle in the tropics, but their interpretation is not straightforward. We studied to which degree tree rings of Mimosa acantholoba from southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings ( δ 18 O tr ). Interannual variation in δ 18 O tr was highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations with δ 13 C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation in δ 18 O tr correlated negatively with local rainfall amount and intensity. Correlations with the amount of precipitation extended along a 1000 km long stretch of the Pacific Central American coast, probably as a result of organized storm systems uniformly affecting rainfall in the region and its isotope signal; episodic heavy precipitation events, of which some are related to cyclones, deposit strongly 18 O-depleted rain in the region and seem to have affected the δ 18 O tr signal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show that δ 18 O tr of M . acantholoba can be used as a proxy for source water δ 18 O and that interannual variation in δ 18 O prec is caused by a regional amount effect. This contrasts with δ 18 O signatures at continental sites where cumulative rainout processes dominate and thus provide a proxy for precipitation integrated over a much larger scale. Our results confirm that processes influencing climate-isotope relations differ between sites located, e.g., in the western Amazon versus coastal Mexico, and that tree ring isotope records can help in

Estimation of snow and glacier melt contribution to Liddar stream in a mountainous catchment, western Himalaya: an isotopic approach.

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Jeelani, Gh; Shah, Rouf A; Jacob, Noble; Deshpande, Rajendrakumar D

2017-03-01

Snow- and glacier-dominated catchments in the Himalayas are important sources of fresh water to more than one billion people. However, the contribution of snowmelt and glacier melt to stream flow remains largely unquantified in most parts of the Himalayas. We used environmental isotopes and geochemical tracers to determine the source water and flow paths of stream flow draining the snow- and glacier-dominated mountainous catchment of the western Himalaya. The study suggested that the stream flow in the spring season is dominated by the snowmelt released from low altitudes and becomes isotopically depleted as the melt season progressed. The tracer-based mixing models suggested that snowmelt contributed a significant proportion (5-66 %) to stream flow throughout the year with the maximum contribution in spring and summer seasons (from March to July). In 2013 a large and persistent snowpack contributed significantly (∼51 %) to stream flow in autumn (September and October) as well. The average annual contribution of glacier melt to stream flow is little (5 %). However, the monthly contribution of glacier melt to stream flow reaches up to 19 % in September during years of less persistent snow pack.

Contrasting Cu-Au and Sn-W Granite Metallogeny through the Zircon Geochemical and Isotopic Record

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Gardiner, Nicholas; Hawkesworth, Chris; Robb, Laurence; Whitehouse, Martin; Roberts, Nick; Kirkland, Chris

2017-04-01

Magmatic genesis and evolution - mediated by geodynamic setting - exert a primary control on the propensity of granites to be metal fertile. A revolution in our understanding of these petrogenetic processes has been made through a range of mineral-based tools, most notably the common accessory mineral zircon. There is consequently considerable interest in whether the geochemical and isotopic compositions of zircon can be applied to metallogenic problems. The paired magmatic belts of Myanmar have broadly contrasting metallogenic affinities (Sn-W versus Cu-Au), and are interpreted to have formed on the accretionary margin of the subducting Neo-Tethys Ocean. They therefore present the opportunity to geochemically compare and contrast the zircon compositions in two end-member types of granite-hosted mineral deposits generated in collisional settings. We present an integrated zircon isotope (U-Pb, Lu-Hf, O) and trace element dataset that fingerprint: (a) source; (b) redox conditions; and (c) degree of fractionation. These variables all impact on magma fertility, and our key question to address is whether they can be reliably traced and calibrated within the Myanmar zircon record. Granitoid-hosted zircons from the I-type copper arc have juvenile ɛHf (+7 to +12) and mantle-like δ18O (5.3 ‰), whereas zircons from the S-type tin belt have low ɛHf (-7 to -13) and heavier δ18O (6.2-7.7 ‰). Plotting Hf versus U/Yb reaffirms that the tin belt magmas contain greater crustal contributions than the copper arc rocks. Links between whole rock Rb/Sr and zircon Eu/Eu* highlights that the latter can be used to monitor magma fractionation in systems that crystallize plagioclase (low Sr/Y). Ce/Ce* and Eu/Eu* in zircon are thus sensitive to redox and fractionation respectively, and can be used to evaluate the sensitivity of zircons to the metallogenic affinity of their host rocks. Tin contents that exceed the solubility limit are required in order to make a magmatic

Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz.

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Budd, David A; Troll, Valentin R; Deegan, Frances M; Jolis, Ester M; Smith, Victoria C; Whitehouse, Martin J; Harris, Chris; Freda, Carmela; Hilton, David R; Halldórsson, Sæmundur A; Bindeman, Ilya N

2017-01-25

Quartz is a common phase in high-silica igneous rocks and is resistant to post-eruptive alteration, thus offering a reliable record of magmatic processes in silicic magma systems. Here we employ the 75 ka Toba super-eruption as a case study to show that quartz can resolve late-stage temporal changes in magmatic δ 18 O values. Overall, Toba quartz crystals exhibit comparatively high δ 18 O values, up to 10.2‰, due to magma residence within, and assimilation of, local granite basement. However, some 40% of the analysed quartz crystals display a decrease in δ 18 O values in outermost growth zones compared to their cores, with values as low as 6.7‰ (maximum ∆ core-rim  = 1.8‰). These lower values are consistent with the limited zircon record available for Toba, and the crystallisation history of Toba quartz traces an influx of a low-δ 18 O component into the magma reservoir just prior to eruption. Here we argue that this late-stage low-δ 18 O component is derived from hydrothermally-altered roof material. Our study demonstrates that quartz isotope stratigraphy can resolve magmatic events that may remain undetected by whole-rock or zircon isotope studies, and that assimilation of altered roof material may represent a viable eruption trigger in large Toba-style magmatic systems.

Compiled records of carbon isotopes in atmospheric CO2 for historical simulations in CMIP6

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H. Graven

2017-12-01

Full Text Available The isotopic composition of carbon (Δ14C and δ13C in atmospheric CO2 and in oceanic and terrestrial carbon reservoirs is influenced by anthropogenic emissions and by natural carbon exchanges, which can respond to and drive changes in climate. Simulations of 14C and 13C in the ocean and terrestrial components of Earth system models (ESMs present opportunities for model evaluation and for investigation of carbon cycling, including anthropogenic CO2 emissions and uptake. The use of carbon isotopes in novel evaluation of the ESMs' component ocean and terrestrial biosphere models and in new analyses of historical changes may improve predictions of future changes in the carbon cycle and climate system. We compile existing data to produce records of Δ14C and δ13C in atmospheric CO2 for the historical period 1850–2015. The primary motivation for this compilation is to provide the atmospheric boundary condition for historical simulations in the Coupled Model Intercomparison Project 6 (CMIP6 for models simulating carbon isotopes in the ocean or terrestrial biosphere. The data may also be useful for other carbon cycle modelling activities.

Compiled records of carbon isotopes in atmospheric CO2 for historical simulations in CMIP6

Science.gov (United States)

Graven, Heather; Allison, Colin E.; Etheridge, David M.; Hammer, Samuel; Keeling, Ralph F.; Levin, Ingeborg; Meijer, Harro A. J.; Rubino, Mauro; Tans, Pieter P.; Trudinger, Cathy M.; Vaughn, Bruce H.; White, James W. C.

2017-12-01

The isotopic composition of carbon (Δ14C and δ13C) in atmospheric CO2 and in oceanic and terrestrial carbon reservoirs is influenced by anthropogenic emissions and by natural carbon exchanges, which can respond to and drive changes in climate. Simulations of 14C and 13C in the ocean and terrestrial components of Earth system models (ESMs) present opportunities for model evaluation and for investigation of carbon cycling, including anthropogenic CO2 emissions and uptake. The use of carbon isotopes in novel evaluation of the ESMs' component ocean and terrestrial biosphere models and in new analyses of historical changes may improve predictions of future changes in the carbon cycle and climate system. We compile existing data to produce records of Δ14C and δ13C in atmospheric CO2 for the historical period 1850-2015. The primary motivation for this compilation is to provide the atmospheric boundary condition for historical simulations in the Coupled Model Intercomparison Project 6 (CMIP6) for models simulating carbon isotopes in the ocean or terrestrial biosphere. The data may also be useful for other carbon cycle modelling activities.

Direct dating of the oxygen-isotope record of the last deglaciation by 14C accelerator mass spectrometry

International Nuclear Information System (INIS)

Duplessy, J.C.; Arnold, Maurice; Maurice, Pierre; Bard, Edouard; Duprat, Josette; Moyes, Jean

1986-01-01

The authors have measured 14 C for various species of foraminifera to produce a reliable timescale for the oxygen-isotope record. The results show that, at the end of the last ice age, continental ice sheets began to melt more than 4,000 yr before the Northern Hemisphere maximum of summer calorific radiation. (author)

Spatial and temporal variation in tree-ring α-cellulose oxygen and hydrogen isotope values as a record of water availability in the Atacama Desert

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Olson, E. J.; Dodd, J. P.

2015-12-01

Previous studies have documented that tree ring oxygen and hydrogen isotopes primarily reflect source water; however, biosynthetic fractionation processes modify this signal and can have a varied response to environmental conditions. The degree to which source water contributes to δ2H and δ18O values of plant α-cellulose is species-specific and modern calibration studies are necessary. Here we present a calibration data set of P. tamarugo α-cellulose δ2H and δ18O values from the Atacama Desert in Northern Chile. P. tamarugo trees are endemic to the region and have adapted to the extremely arid environment where average annual precipitation is 2 ‰ over the past 20 years associated with a ~1.1 m lowering of the local groundwater table throughout the area. The correlation between a-cellulose isotope values and hydrologic conditions in modern times provides a baseline for interpretation of tree-ring isotope chronologies from the past 9.5 kya. A high-resolution Holocene (1.8-9.1 kya) age record of Prosopis sp. tree ring α-cellulose δ18O values provides a proxy for climatic and hydrologic conditions. During the early Holocene δ18O values range from 31 to 35‰ (2σ=0.58‰), while during the late Holocene values are much more variable (27.4 to 41‰; 2σ=2.64‰). Anthropogenic demand on local water sources is the most significant environmental factor affecting the variation in modern α-cellulose δ18O values; however, climate induced changes in regional water availability are the dominant driver of variability in the paleo-record. Increased variability in α-cellulose δ18O values in the late Holocene most likely indicates a reduction in annual recharge and an increase in episodic flood events driven by ENSO and other modes of atmospheric variability.

High-frequency paleoclimatic variability: a spectral analysis of the Vostok ice-core isotopic record

Energy Technology Data Exchange (ETDEWEB)

Yiou, P.; Genthon, C.; Jouzel, J.; Le Treut, H.; Lorius, C.; Ghil, M.; Korotkevich, Y.S.

1988-01-01

This paper uses a recently analysed isotopic record from an ice core drilled at the Soviet Antartic Station VOSTOK, representing a total time span of about 160,000 years. Results obtained show the existence of a significative climatic variability at the time scale of 10,000 years and below. The many spectral peaks appear to be approximate linear combination of a little number among them, a clear indication of the non linear nature of climate fluctuations at these ''short'' time scales.

The isotope record of short- and long-term dietary changes in sheep tooth enamel: Implications for quantitative reconstruction of paleodiets

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Zazzo, A.; Balasse, M.; Passey, B. H.; Moloney, A. P.; Monahan, F. J.; Schmidt, O.

2010-06-01

Quantitative reconstruction of paleodiet by means of sequential sampling and carbon isotope analysis in hypsodont tooth enamel requires a precise knowledge of the isotopic enrichment between dietary carbon and carbon from enamel apatite ( ɛD-E), as well as of the timing and duration of the enamel mineralization process (amelogenesis). To better constrain these parameters, we performed a series of controlled feeding experiments on sheep ranging in age from 6 to 24 months-old. Twenty-eight lambs and 14 ewes were fed isotopically distinct diets for different periods of time, and then slaughtered, allowing the timing and rate of molar growth to be determined. High resolution sampling and stable carbon isotope analysis of breath CO 2 performed on six individuals following a diet-switch showed that 70-90% of dietary carbon had turned over in less than 24 h. Sequential sampling and carbon isotopic analysis was performed on the first (M 1) and second (M 2) lower molars of four lambs as well as on the third lower molar (M 3) of 11 ewes. The changes in diet were recorded in all molars. We found that the length of enamel matrix apposition is approximately one-quarter of the final tooth length during crown extension, and that enamel maturation spans slightly less than 3 months in M 1, and 4 months in M 2 and M 3. Portions of enamel in equilibrium with dietary carbon were used to calculate ɛD-E values. Animals on grass silage diets had values similar to previous observations, whereas animal switched to pelleted corn diets had values ca. 4‰ lower, a pattern consistent with lower methane production observed for animals fed concentrate diets. The tooth enamel forward model of Passey and Cerling (2002) closely predicted the amplitude of isotope changes recorded in tooth enamel, but slightly underestimated the rate of isotope change, suggesting that the rate of accumulation of carbonate during maturation may not be constant over time. Although stable isotope profiles in tooth

Multidecadal climate variability in Brazil's Nordeste during the last 3000 years based on speleothem isotope records

Science.gov (United States)

Novello, Valdir F.; Cruz, Francisco W.; Karmann, Ivo; Burns, Stephen J.; Stríkis, Nicolás M.; Vuille, Mathias; Cheng, Hai; Lawrence Edwards, R.; Santos, Roberto V.; Frigo, Everton; Barreto, Eline A. S.

2012-12-01

We present the first high resolution, approximately ∼4 years sample spacing, precipitation record from northeastern Brazil (hereafter referred to as ‘Nordeste’) covering the last ∼3000 yrs from 230Th-dated stalagmites oxygen isotope records. Our record shows abrupt fluctuations in rainfall tied to variations in the intensity of the South American summer monsoon (SASM), including the periods corresponding to the Little Ice Age (LIA), the Medieval Climate Anomaly (MCA) and an event around 2800 yr B.P. Unlike other monsoon records in southern tropical South America, dry conditions prevailed during the LIA in the Nordeste. Our record suggests that the region is currently undergoing drought conditions that are unprecedented over the past 3 millennia, rivaled only by the LIA period. Using spectral, wavelet and cross-wavelet analyses we show that changes in SASM activity in the region are mainly associated with variations of the Atlantic Multidecadal Oscillation (AMO) and to a lesser degree caused by fluctuations in tropical Pacific SST. Our record also shows a distinct periodicity around 210 years, which has been linked to solar variability.

Evidence for Slab Melt Contributions to the Mexican Volcanic Belt and Other Young Hot Slab Arcs from Lu-Hf Isotopes

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Goldstein, S. L.; Cai, Y. M.; Langmuir, C. H.; Lagatta, A.; Straub, S. M.; Gomez-Tuena, A.; Martin Del Pozzo, A.

2007-12-01

Despite major advances in delineating the processes that govern magma generation at convergent margins, the problem persists of distinguishing slab, mantle wedge, and crustal contributions. A corrollary question is whether there is significant melting of subducted ocean crust. Especially in thick crust regions, the importance of crustal versus mantle contributions to lavas represents a long-standing fundamental issue in arc magma geochemistry. We show that frontal arc magmas from the Central Mexican Volcanic Belt (CMVB), including the large andesitic stratovolcanoes Popocatepetl and Nevado de Toluca, display negligible crustal contamination, and contain substantial contributions from melting of subducted Pacific ocean crust. Despite ca. 50 km thick continental crust, the CMVB erupts near primitive lavas including "high-Nb" alkaline basalts that show negligible "subduction signatures" in their trace element patterns. These "high-Nb" basalts define the regional mantle wedge composition in isotope-trace element space. The "normal" calcalkaline lavas form a negative correlation between Hf isotopes and Lu/Hf. One endmember is like the high Nb basalts representing the regional mantle wedge. The other endmember has higher Hf isotopes (approaching values of Pacific MORB) and very low Lu/Hf of less than 0.04 (e.g. compared to typical values of ca. 0.2 in Pacific MORB). The low Lu/Hf values require low degree partial melting of a source rich in garnet. The high Hf isotopes require a depleted mantle source with isotopes like Pacific MORB. Together the Lu-Hf data indicate a substantial component derived from melting of eclogitic Pacific ocean crust. A key feature of the data is that the stratovolcano lavas showing the largest slab melt signature also show the highest Hf isotope ratios and thus are more "depleted mantle-like" than the regional mantle wedge. Thus, the integrated data allow us to clearly distinguish between mantle and crustal sources in the CMVB and point to

Diet in pottery-making societies from Central Chile: The contribution of stable isotope analyses

International Nuclear Information System (INIS)

Falabella, Fernanda; Planella, M.Teresa; Aspillaga, Eugenio; Sanhueza, Lorena; Tykot, Robert H

2007-01-01

This is the first time that stable carbon, nitrogen and oxygen isotope analyses of human bones and teeth have been used to reconstruct subsistence and settlement patterns of prehispanic ceramic societies from Central Chile. Isotope analyses, unlike the evidence from botanical, faunal and artifactual remains from archaeological sites, and from dental and skeletal pathologies, gave information of which resources were really eaten by each individual during the last years of their life. The human data were evaluated against isotopic values of marine and terrestrial resources from central Chile. These results were interpreted taking into consideration different lines of paleodiet evidence. The main contributions are: empirical evidence of dietary differences according to cultural groups; low dependence on marine foods for most people living on the coast; indirect evidence of mobility strategies that show differences between Early and Late Intermediate societies; increased dependence on maize with time, especially among the Aconcagua people; gender differences in maize consumption for the same Aconcagua groups, men showing the greatest levels of maize intake. The results support some hypotheses, such as the difference in dietary patterns between contemporary Bato and Lolleo groups, contradict others, such as the supposed importance of marine diet for coastal inhabitants, and open new research questions for the future [es

Stable isotopes in fish eye lenses as potential recorders of trophic and geographic history.

Directory of Open Access Journals (Sweden)

Amy A Wallace

Full Text Available We evaluated eye lenses as potential recorders of stable isotope histories in fish because they consist of metabolically inert optical proteins that are deposited in successive, concentric circles (laminae much like otolith circuli and tree rings. We conducted four different tests on lenses from red snapper, red grouper, gag, and white grunt. The first test was a low-resolution screening of multiple individuals (4-5 radial groups of laminae per lens, all species except white grunt. Along the radial axis, all individuals exhibited substantial isotopic variability. Red snapper individuals separated into two groups based on δ15N and gag separated into two groups based on δ13C. Two gag with the greatest variation were chosen for high-resolution temporal analysis using individual laminae from their second eye lenses. The first-order patterns from the high-resolution analysis generally mimicked patterns from the low-resolution screening of grouped laminae, yet the high-resolution plots revealed early-life details that were not apparent in the low-resolution screenings. For the third test, left- versus right-eye variation was compared using high-resolution methods. White grunt left- and right-eye radial isotopic patterns were almost identical for both δ13C and δ15N, suggesting the variations observed among individual fish were not artifacts. The final test evaluated intra-laminar variation; multiple samples were analyzed from different parts of the same lamina. Seven laminae from three individuals of two species were analyzed in this manner; variations among laminae were found to be much higher than variations within laminae. However, nominal intra-laminar variations were comparable to nominal differences between left and right lenses, suggesting intra-laminar variation established measurement precision. Eye lens isotopes appear to be useful for reconstructing the isotopic histories of individual fish; these histories can be compared with spatially

Stable isotope records for the last 10 000 years from Okshola cave (Fauske, northern Norway and regional comparisons

Directory of Open Access Journals (Sweden)

H. Linge

2009-11-01

Full Text Available The sensitivity of terrestrial environments to past changes in heat transport is expected to be manifested in Holocene climate proxy records on millennial to seasonal timescales. Stalagmite formation in the Okshola cave near Fauske (northern Norway began at about 10.4 ka, soon after the valley was deglaciated. Past monitoring of the cave and surface has revealed stable modern conditions with uniform drip rates, relative humidity and temperature. Stable isotope records from two stalagmites provide time-series spanning from c. 10 380 yr to AD 1997; a banded, multi-coloured stalagmite (Oks82 was formed between 10 380 yr and 5050 yr, whereas a pristine, white stalagmite (FM3 covers the period from ~7500 yr to the present. The stable oxygen isotope (δ¹⁸O_c, stable carbon isotope (δ¹³C_c, and growth rate records are interpreted as showing i a negative correlation between cave/surface temperature and δ¹⁸O_c, ii a positive correlation between wetness and δ¹³C_c, and iii a positive correlation between temperature and growth rate. Following this, the data from Okshola show that the Holocene was characterised by high-variability climate in the early part, low-variability climate in the middle part, and high-variability climate and shifts between two distinct modes in the late part.

A total of nine Scandinavian stalagmite δ¹⁸O_c records of comparable dating precision are now available for parts or most of the Holocene. None of them show a clear Holocene thermal optimum, suggesting that they are influenced by annual mean temperature (cave temperature rather than seasonal temperature. For the last 1000 years, δ¹⁸O_c values display a depletion-enrichment-depletion pattern commonly interpreted as reflecting the conventional view on climate development for the last millennium. Although the δ¹⁸

Climatic signals in multiple highly resolved stable isotope records from Greenland

DEFF Research Database (Denmark)

Vinther, Bo Møllesøe; Dahl-Jensen, Dorthe; Johnsen, Sigfus Johann

2010-01-01

are found to correspond better with winter stable isotope data than with summer or annual average stable isotope data it is suggested that a strong local Greenland temperature signal can be extracted from the winter stable isotope data even on centennial to millennial time scales. Udgivelsesdato: Feb....

Trace gases and CO sub(2) isotope records from Cabo de Rama, India

Digital Repository Service at National Institute of Oceanography (India)

Bhattacharya, S.K.; Borole, D.V.; Francey, R.J.; Allison, C.E.; Steele, L.P.; Krummel, P.; Langenfelds, R.; Masarie, K.A.; Tiwari, Y.K.; Patra, P.K.

to avoid dan- gerous climate change due to GHG forced warming. Con- centrations of CO 2 , CH 4 and N 2 O have increased at alarming rates, from preindustrial values of 280 ppm, 715 ppb and 270 ppb (circa. 1750) to 379 ppm, 1732 ppb and 319 ppb... an important effect on the con- centration and isotopic composition of atmospheric CO 2 , and the concentrations of other trace gases. Air sampling at CRI contributes to the global atmospheric composition study 10,11 . Given the potential for global impacts...

Hydrogen isotopic messages in sulfate reducer lipids: a recorder of metabolic state?

Science.gov (United States)

Bradley, A. S.; Leavitt, W.; Zhou, A.; Cobban, A.; Suess, M.

2017-12-01

A significant range in microbial lipid 2H/1H ratios is observed in modern marine sediments. The magnitude of hydrogen isotope fractionation between microbial lipids and growth water (2ɛlipid-H2O) is hypothesized to relate to the central carbon and energy metabolism. These observations raise the possibility for culture independent identification of the dominant metabolic pathways operating in a given environment [Zhang et al. 2009]. One such metabolism we aim to track is microbial sulfate reduction. To-date, sulfate reducing bacteria have been observed to produce lipids that are depleted in fatty acid H-isotope composition, relative to growth water (2ɛlipid-H2O -50 to -175 ‰) [Campbell et al. 2009; Dawson et al. 2015; Osburn et al.], with recent work demonstrating a systematic relationship between lipid/water fractionation and growth rate when the electron-bifurcating NAD(P)(H) transhydrogenase (ebTH) activity was disrupted and the available electron requires the ebTH [Leavitt et al. 2016. Front Microbio]. Recent work in aerobic methylotrophs [Bradley et al. 2014. AGU] implicates non-bifurcating NAD(P)(H) transhydrogenase activity is a critical control on 2ɛlipid-H2O. This suggests a specific mechanism to control the range in fractionation is the ratio of intracellular NADPH/NADH/NADP/NAD in aerobes and perhaps the same in anaerobes with some consideration for FADH/FAD. Fundamentally this implies 2ɛlipid-H2O records intracellular redox state. In our sulfate reducer model system Desulfovibrio alaskensis strain G20 a key component of energy metabolism is the activity of ebTH. Nonetheless, this strain contains two independent copies of the genes, only one of which generates a distinctive isotopic phenotype [Leavitt et al. 2016. Front Microbio]. In this study we extend the recent work in G20 to continuous culture experiments comparing WT to nfnAB-2 transposon interruptions, where both organisms are cultivated continuously, at the rate of the slower growing mutant

McCall Glacier record of Arctic climate change: Interpreting a northern Alaska ice core with regional water isotopes

Science.gov (United States)

Klein, E. S.; Nolan, M.; McConnell, J.; Sigl, M.; Cherry, J.; Young, J.; Welker, J. M.

2016-01-01

We explored modern precipitation and ice core isotope ratios to better understand both modern and paleo climate in the Arctic. Paleoclimate reconstructions require an understanding of how modern synoptic climate influences proxies used in those reconstructions, such as water isotopes. Therefore we measured periodic precipitation samples at Toolik Lake Field Station (Toolik) in the northern foothills of the Brooks Range in the Alaskan Arctic to determine δ18O and δ2H. We applied this multi-decadal local precipitation δ18O/temperature regression to ∼65 years of McCall Glacier (also in the Brooks Range) ice core isotope measurements and found an increase in reconstructed temperatures over the late-20th and early-21st centuries. We also show that the McCall Glacier δ18O isotope record is negatively correlated with the winter bidecadal North Pacific Index (NPI) climate oscillation. McCall Glacier deuterium excess (d-excess, δ2H - 8*δ18O) values display a bidecadal periodicity coherent with the NPI and suggest shifts from more southwestern Bering Sea moisture sources with less sea ice (lower d-excess values) to more northern Arctic Ocean moisture sources with more sea ice (higher d-excess values). Northern ice covered Arctic Ocean McCall Glacier moisture sources are associated with weak Aleutian Low (AL) circulation patterns and the southern moisture sources with strong AL patterns. Ice core d-excess values significantly decrease over the record, coincident with warmer temperatures and a significant reduction in Alaska sea ice concentration, which suggests that ice free northern ocean waters are increasingly serving as terrestrial precipitation moisture sources; a concept recently proposed by modeling studies and also present in Greenland ice core d-excess values during previous transitions to warm periods. This study also shows the efficacy and importance of using ice cores from Arctic valley glaciers in paleoclimate reconstructions.

Testing Urey's carbonate-silicate cycle using the calcium isotopic composition of sedimentary carbonates

Science.gov (United States)

Blättler, Clara L.; Higgins, John A.

2017-12-01

Carbonate minerals constitute a major component of the sedimentary geological record and an archive of a fraction of the carbon and calcium cycled through the Earth's surface reservoirs for over three billion years. For calcium, carbonate minerals constitute the ultimate sink for almost all calcium liberated during continental and submarine weathering of silicate minerals. This study presents >500 stable isotope ratios of calcium in Precambrian carbonate sediments, both limestones and dolomites, in an attempt to characterize the isotope mass balance of the sedimentary carbonate reservoir through time. The mean of the dataset is indistinguishable from estimates of the calcium isotope ratio of bulk silicate Earth, consistent with the Urey cycle being the dominant mechanism exchanging calcium among surface reservoirs. The variability in bulk sediment calcium isotope ratios within each geological unit does not reflect changes in the global calcium cycle, but rather highlights the importance of local mineralogical and/or diagenetic effects in the carbonate record. This dataset demonstrates the potential for calcium isotope ratios to help assess these local effects, such as the former presence of aragonite, even in rocks with a history of neomorphism and recrystallization. Additionally, 29 calcium isotope measurements are presented from ODP (Ocean Drilling Program) Site 801 that contribute to the characterization of altered oceanic crust as an additional sink for calcium, and whose distinct isotopic signature places a limit on the importance of this subduction flux over Earth history.

Contribution of Electronic Medical Records to the Management of Rare Diseases

Directory of Open Access Journals (Sweden)

Dominique Bremond-Gignac

2015-01-01

Full Text Available Purpose. Electronic health record systems provide great opportunity to study most diseases. Objective of this study was to determine whether electronic medical records (EMR in ophthalmology contribute to management of rare eye diseases, isolated or in syndromes. Study was designed to identify and collect patients’ data with ophthalmology-specific EMR. Methods. Ophthalmology-specific EMR software (Softalmo software Corilus was used to acquire ophthalmological ocular consultation data from patients with five rare eye diseases. The rare eye diseases and data were selected and collected regarding expertise of eye center. Results. A total of 135,206 outpatient consultations were performed between 2011 and 2014 in our medical center specialized in rare eye diseases. The search software identified 29 congenital aniridia, 6 Axenfeld/Rieger syndrome, 11 BEPS, 3 Nanophthalmos, and 3 Rubinstein-Taybi syndrome. Discussion. EMR provides advantages for medical care. The use of ophthalmology-specific EMR is reliable and can contribute to a comprehensive ocular visual phenotype useful for clinical research. Conclusion. Routinely EMR acquired with specific software dedicated to ophthalmology provides sufficient detail for rare diseases. These software-collected data appear useful for creating patient cohorts and recording ocular examination, avoiding the time-consuming analysis of paper records and investigation, in a University Hospital linked to a National Reference Rare Center Disease.

Contribution of Electronic Medical Records to the Management of Rare Diseases.

Science.gov (United States)

Bremond-Gignac, Dominique; Lewandowski, Elisabeth; Copin, Henri

2015-01-01

Electronic health record systems provide great opportunity to study most diseases. Objective of this study was to determine whether electronic medical records (EMR) in ophthalmology contribute to management of rare eye diseases, isolated or in syndromes. Study was designed to identify and collect patients' data with ophthalmology-specific EMR. Ophthalmology-specific EMR software (Softalmo software Corilus) was used to acquire ophthalmological ocular consultation data from patients with five rare eye diseases. The rare eye diseases and data were selected and collected regarding expertise of eye center. A total of 135,206 outpatient consultations were performed between 2011 and 2014 in our medical center specialized in rare eye diseases. The search software identified 29 congenital aniridia, 6 Axenfeld/Rieger syndrome, 11 BEPS, 3 Nanophthalmos, and 3 Rubinstein-Taybi syndrome. EMR provides advantages for medical care. The use of ophthalmology-specific EMR is reliable and can contribute to a comprehensive ocular visual phenotype useful for clinical research. Routinely EMR acquired with specific software dedicated to ophthalmology provides sufficient detail for rare diseases. These software-collected data appear useful for creating patient cohorts and recording ocular examination, avoiding the time-consuming analysis of paper records and investigation, in a University Hospital linked to a National Reference Rare Center Disease.

What climate information is recorded in stable isotope ratios of wood lignin methoxyl groups?

Science.gov (United States)

Greule, Markus; Keppler, Frank

2010-05-01

The stable isotope composition of the bioelements C, O, H and N in plant organic matter is known to be a very powerful for various environmental impacts. Particularly tree rings are suitable for this analysis because they exhibit a "climate archive" with a yearly or even biannual resolution. One of the most determined wood compounds is cellulose which amongst others is used to reconstruct the temperature due to measurement of stable hydrogen and oxygen isotopes. Therefore cellulose is converted into cellulose nitrate to eliminate the exchangeable hydroxyl hydrogen or equilibration methods are used. However, a general problem associated with the determination of the stable hydrogen values of marker compounds for the study of climate and environmental conditions is the isolation of the pure compound for analysis by isotope ratio mass spectrometry. Exploitation of components of wood as markers, in particular, has been restricted by the very labour intensive and time consuming preparation of samples (e.g. cellulose nitrate). An alternative way to record climate information from tree rings was recently proposed by Keppler et al. (2007) who measured the stable hydrogen values of methoxyl groups in wood. Lignin methoxyl groups are considered to be stable, i.e. the hydrogen atoms of the methoxyl moiety do not exchange with those of plant water during ongoing metabolic reactions in the plant. Thus the initial deuterium content of the methoxyl groups of lignin in woody tissue at formation is retained throughout the lifetime of the tree and in preserved tissue. The methoxyl content of lignin in wood is usually determined by the Zeisel method (Zeisel, 1885) - the reaction between methyl ethers and hydroiodic acid to form methyl iodide. Exploiting this reaction for the measurement of stable hydrogen values of lignin methoxyl groups ensures that during the entire analytical procedure the isotope signal is preserved since no isotopic exchange occurs between the methyl groups and

Isotopically controlled semiconductors

Energy Technology Data Exchange (ETDEWEB)

Haller, Eugene E.

2006-06-19

The following article is an edited transcript based on the Turnbull Lecture given by Eugene E. Haller at the 2005 Materials Research Society Fall Meeting in Boston on November 29, 2005. The David Turnbull Lectureship is awarded to recognize the career of a scientist who has made outstanding contributions to understanding materials phenomena and properties through research, writing, and lecturing, as exemplified by the life work of David Turnbull. Haller was named the 2005 David Turnbull Lecturer for his 'pioneering achievements and leadership in establishing the field of isotopically engineered semiconductors; for outstanding contributions to materials growth, doping and diffusion; and for excellence in lecturing, writing, and fostering international collaborations'. The scientific interest, increased availability, and technological promise of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor crystals. This article reviews results obtained with isotopically controlled semiconductor bulk and thin-film heterostructures. Isotopic composition affects several properties such as phonon energies, band structure, and lattice constant in subtle, but, for their physical understanding, significant ways. Large isotope-related effects are observed for thermal conductivity in local vibrational modes of impurities and after neutron transmutation doping. Spectacularly sharp photoluminescence lines have been observed in ultrapure, isotopically enriched silicon crystals. Isotope multilayer structures are especially well suited for simultaneous self- and dopant-diffusion studies. The absence of any chemical, mechanical, or electrical driving forces makes possible the study of an ideal random-walk problem. Isotopically controlled semiconductors may find applications in quantum computing, nanoscience, and spintronics.

Carbon and nitrogen isotopic signatures of bat guanos as record of past environments

International Nuclear Information System (INIS)

Mizutani, Hiroshi; Kabaya, Yuko; McFarlane, D.A.

1992-01-01

Carbon and nitrogen isotope ratios were measured for various ecogeochemical samples relevant to bat guano ecosystems. In particular, ca. 800-year-old subfossil guano from Jackson's Bay Cave Compex, Jamaica, yielded ratios similar to the modern guano from other Jamaican bat caves but quite different from modern guano of the same area. Diagenetic change and differences in bat food habits were unlikely explanations for the observation. Instead, insects that feed on C 4 and CAM plants were the main prey for the bats in present Jackson's Bay area, while the ultimate source of organic matter for bats in other Jamaican caves and for the bats that deposited guano in Jackson's Bay Great Cave ca. 800 years ago were C 3 photosynthesis. We suggests that the isotopic data indicate that the surrounding environment experienced a significant mesic episode in the recent past. This mesic climate would have supported a large population of bats, which in turn would have accumulated significant quantities of guano. The subsequent return to the more xeric conditions prevailing today would have caused a drastic reduction in bat population size and effectively ended significant guano accumulation. Fossil guano from Carlsbad Caverns, New Mexico, U.S.A., suggested that native C 3 plants might have been more abundant in Wisconsinan than today. Isotope analyses of old guanos from Bat Cave in Grand Canyon National Park, Arizona, U.S.A., found a possible implication that C 4 photosynthesis might have had contributed a little more to the bats' diet in the cave before the construction of Glen Canyon Dam. (author)

Biosynthetic effects on the stable carbon isotopic compositions of agal lipids: Implications for deciphering the carbon isotopic biomarker record

NARCIS (Netherlands)

Sinninghe Damsté, J.S.; Schouten, S.; Klein Breteler, W.C.M.; Blokker, P.; Schogt, N.; Rijpstra, W.I.C.; Grice, K.; Baas, M.

1998-01-01

Thirteen species of algae covering an extensive range of classes were cultured and stable carbon isotopic compositions of their lipids were analysed in order to assess carbon isotopic fractionation effects during their biosynthesis. The fatty acids were found to have similar stable carbon isotopic

Patterns of contribution to citizen science biodiversity projects increase understanding of volunteers' recording behaviour.

Science.gov (United States)

Boakes, Elizabeth H; Gliozzo, Gianfranco; Seymour, Valentine; Harvey, Martin; Smith, Chloë; Roy, David B; Haklay, Muki

2016-09-13

The often opportunistic nature of biological recording via citizen science leads to taxonomic, spatial and temporal biases which add uncertainty to biodiversity estimates. However, such biases may also give valuable insight into volunteers' recording behaviour. Using Greater London as a case-study we examined the composition of three citizen science datasets - from Greenspace Information for Greater London CIC, iSpot and iRecord - with respect to recorder contribution and spatial and taxonomic biases, i.e. when, where and what volunteers record. We found most volunteers contributed few records and were active for just one day. Each dataset had its own taxonomic and spatial signature suggesting that volunteers' personal recording preferences may attract them towards particular schemes. There were also patterns across datasets: species' abundance and ease of identification were positively associated with number of records, as was plant height. We found clear hotspots of recording activity, the 10 most popular sites containing open water. We note that biases are accrued as part of the recording process (e.g. species' detectability) as well as from volunteer preferences. An increased understanding of volunteer behaviour gained from analysing the composition of records could thus enhance the fit between volunteers' interests and the needs of scientific projects.

Isotope angiocardiography

International Nuclear Information System (INIS)

Stepinska, J.; Ruzyllo, W.; Konieczny, W.

1979-01-01

Method of technetium isotope 99 m pass through the heart recording with the aid of radioisotope scanner connected with seriograph and computer is being presented. Preliminary tests were carried out in 26 patients with coronary disease without or with previous myocardial infarction, cardiomyopathy, ventricular septal defect and in patients with artificial mitral and aortic valves. The obtained scans were evaluated qualitatively and compared with performed later contrast X-rays of the heart. Size of the right ventricle, volume and rate of left atrial evacuation, size and contractability of left ventricle were evaluated. Similarity of direct and isotope angiocardiographs, non-invasional character and repeatability of isotope angiocardiography advocate its usefulness. (author)

Isotopes in heterogeneous catalysis

CERN Document Server

Hargreaves, Justin SJ

2006-01-01

The purpose of this book is to review the current, state-of-the-art application of isotopic methods to the field of heterogeneous catalysis. Isotopic studies are arguably the ultimate technique in in situ methods for heterogeneous catalysis. In this review volume, chapters have been contributed by experts in the field and the coverage includes both the application of specific isotopes - Deuterium, Tritium, Carbon-14, Sulfur-35 and Oxygen-18 - as well as isotopic techniques - determination of surface mobility, steady state transient isotope kinetic analysis, and positron emission profiling.

Isotopic evidence for multiple contributions to felsic magma chambers

DEFF Research Database (Denmark)

Waight, Tod Earle; Wiebe, R.A.; Krogstad, E.J.

2007-01-01

The Gouldsboro Granite forms part of the Coastal Maine Magmatic Province, a region characterized by granitic plutons that are intimately linked temporally and petrogenetically with abundant co-existing mafic magmas. The pluton is complex and preserves a felsic magma chamber underlain...... with identical isotopic compositions to more mafic dikes suggest that closed system fractionation may be occurring in deeper level chambers prior to injection to shallower levels. The granitic portion of the pluton has the highest Nd isotopic composition (eNd=+3.0) of plutons in the region whereas the mafic...

Oxygen Isotope Speleothem record of Decadal and Multidecadal Atlantic Oscillations over the last millennium in Southwestern Morocco

Science.gov (United States)

Ait Brahim, Yassine; Sha, LiJuan; Sifeddine, Abdelfettah; Cheng, Hai; Bouchaou, Lhoussaine; Da Cruz Junior, Francisco William; Khodri, Myriam; Peerbocus, Nawaaz; Mariller, Alexandre; Apaestegui, James; Guyot, Jean-Loup; Auler, Augusto; Hassane Beraaouz, El

2016-04-01

In this work, we present a stable oxygen isotope (δ18O) speleothem record from Ifoulki cave located South-West of Morocco (N 30°42'29'', W 09°19'39'' and 1267 meters above sea level). The age model, based on eighteen U-Th dates, reveals that the record covers the AD 790-1953 period with a data resolution of ~1.7 years. Stable oxygen isotope variations show substantial decadal to multi-decadal swings between dry and humid periods. The Medieval Climate Anomaly (MCA) is characterized by the longest period with δ18O values above the average, suggestive of pronounced drying possibly as a response to positive North Atlantic Oscillation (NAO) phases and increased volcanic activity during this period. However, at least two short wet phases are recognized during the MCA in Morocco, with peaks centered on the years AD 1040 and AD 1190 and seem to overlap with negative NAO phases as recorded in a recently published NAO reconstruction for the last millennium. During the next centuries, the NAO again depicts predominantly negative values and the δ18O drops below the average during the Little Ice Age (LIA). Furthermore, a striking resemblance is observed between our record and another recently published stalagmite record from the Piste cave in Northeastern Morocco, which is quite remarkable given the different type of tracers (δ18O vs. Mg and Sr) obtained from different environments (Western High Atlas vs. Northeastern Middle Atlas and ~634 km away). Comparison with regional paleorecords from other studies also reveals the replication of many characteristic climate features from the last millennium, first detected in Northern Morocco and the Iberian Peninsula. In particular, the evidence of generally dry conditions during the MCA and wetter conditions in the LIA, which is confirmed by all the paleorecords. These similarities indicate coherent climate variability in Northwest Africa and the Iberian Peninsula and suggest a strong regional control of the NAO during the last

Isotope shift studies in gadolinium spectra

International Nuclear Information System (INIS)

Ahmad, S.A.; Saksena, G.D.; Venugopalan, A.

1976-01-01

Isotope shift studies have been carried out in the gadolinium spectrum using a recording Fabry-Perot spectrometer and gadolinium samples enriched in 156 Gd and 160 Gd isotopes. Isotope shifts Δsigma(156-160) have been recorded in 134 lines in the region 3930-4140 A. Some of these lines involve the recently identified even configuration 4f 8 5d6s of Gd I and the newly classified transition 4f 8 6s-4f 8 6p of Gd II. From the isotope shift measurements of lines involving the 4f 8 6s-4f 8 6p transition in Gd II, the isotope shift, ΔT(156-160)=87 mK, has been obtained for the 4f 8 6s configuration. Electronic configurations have been suggested for a number of energy levels and configuration mixing has been pointed out in certain cases. (Auth.)

Post-Wisconsinan Chemical Weathering Rates and Trajectories From a 13,400-Year Sediment Core Record of Lead Isotopic Ratios in Maine

Science.gov (United States)

Perry, R. H.; Norton, S. A.; Koons, P. O.; Handley, M.

2008-12-01

Lead isotopic ratios recorded in a 5.3-m 13.4-ka 14C-dated lake sediment core from Sargent Mountain Pond, Maine (USA) are interpreted as an archive of post-glacial chemical weathering. Early weathering yielded highly radiogenic sediment from the preferential release of U and Th decay products (206Pb, 207Pb, and 208Pb) from accessory mineral phases in the catchment's predominantly-granitic till and bedrock relative to non-radiogenic 204Pb from the more abundant primary minerals. Values for 207Pb/206Pb in the sediment increased rapidly from 0.799 to 0.814 in the catchment's first 4,000 years of post-Wisconsinan weathering, and thereafter increased only slightly to just prior to the 19th century. Values for 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb decline over the same time-scale, as a result of decreasing radiogenic Pb being released from catchment weathering. Our results are consistent with: (1) the published interpretation of Pb isotopic variation in ferromanganese ocean crusts as a reflection of continental-scale glacial-interglacial chemical weathering cycles, (2) bench-scale whole-rock weathering experiments, and (3) soil chronosequence Pb isotope dissolution experiments and bridge the gap between short-term, mineral-scale experiments and long-term, ocean sediment records. We establish a time-scale for depletion of accessory minerals, and loss of their Pb isotopic signature at one catchment, and document the concurrent shift to slower primary mineral-controlled chemical weathering after deglaciation.

Isotopic studies of Yucca Mountain soil fluids and carbonate pedogenesis

International Nuclear Information System (INIS)

McConnaughey, T.A.; Whelan, J.F.; Wickland, K.P.; Moscati, R.J.

1994-01-01

Secondary carbonates occurring within the soils, faults, and subsurface fractures of Yucca Mountain contain some of the best available records of paleoclimate and palehydrology for the potential radioactive waste repository site. This article discusses conceptual and analytical advances being made with regard to the interpretation of stable isotope data from pedogenic carbonates, specifically related to the 13 C content of soil CO 2 , CaCO 3 , precipitation mechanisms, and isotopic fractionations between parent fluids and precipitating carbonates. The 13 C content of soil carbon dioxide from Yucca Mountain and vicinity shows most of the usual patterns expected in such contexts: Decreasing 13 C content with depth decreasing 13 C with altitude and reduced 13 C during spring. These patterns exist within the domain of a noisy data set; soil and vegetational heterogeneities, weather, and other factors apparently contribute to isotopic variability in the system. Several soil calcification mechanisms appear to be important, involving characteristic physical and chemical environments and isotopic fractionations. When CO 2 loss from thin soil solutions is an important driving factor, carbonates may contain excess heavy isotopes, compared to equilibrium precipitation with soil fluids. When root calcification serves as a proton generator for plant absorption of soil nutrients, heavy isotope deficiencies are likely. Successive cycles of dissolution and reprecipitation mix and redistribute pedogenic carbonates, and tend to isotopically homogenize and equilibrate pedogenic carbonates with soil fluids

The geochemical record of the ancient nitrogen cycle, nitrogen isotopes, and metal cofactors.

Science.gov (United States)

Godfrey, Linda V; Glass, Jennifer B

2011-01-01

The nitrogen (N) cycle is the only global biogeochemical cycle that is driven by biological functions involving the interaction of many microorganisms. The N cycle has evolved over geological time and its interaction with the oxygen cycle has had profound effects on the evolution and timing of Earth's atmosphere oxygenation (Falkowski and Godfrey, 2008). Almost every enzyme that microorganisms use to manipulate N contains redox-sensitive metals. Bioavailability of these metals has changed through time as a function of varying redox conditions, and likely influenced the biological underpinnings of the N cycle. It is possible to construct a record through geological time using N isotopes and metal concentrations in sediments to determine when the different stages of the N cycle evolved and the role metal availability played in the development of key enzymes. The same techniques are applicable to understanding the operation and changes in the N cycle through geological time. However, N and many of the redox-sensitive metals in some of their oxidation states are mobile and the isotopic composition or distribution can be altered by subsequent processes leading to erroneous conclusions. This chapter reviews the enzymology and metal cofactors of the N cycle and describes proper utilization of methods used to reconstruct evolution of the N cycle through time. Copyright © 2011 Elsevier Inc. All rights reserved.

Lithospheric Contributions to Arc Magmatism: Isotope Variations Along Strike in Volcanoes of Honshu, Japan

Science.gov (United States)

Kersting; Arculus; Gust

1996-06-07

Major chemical exchange between the crust and mantle occurs in subduction zone environments, profoundly affecting the chemical evolution of Earth. The relative contributions of the subducting slab, mantle wedge, and arc lithosphere to the generation of island arc magmas, and ultimately new continental crust, are controversial. Isotopic data for lavas from a transect of volcanoes in a single arc segment of northern Honshu, Japan, have distinct variations coincident with changes in crustal lithology. These data imply that the relatively thin crustal lithosphere is an active geochemical filter for all traversing magmas and is responsible for significant modification of primary mantle melts.

Pyrite sulfur isotopes reveal glacial-interglacial environmental changes

Science.gov (United States)

Pasquier, Virgil; Sansjofre, Pierre; Rabineau, Marina; Revillon, Sidonie; Houghton, Jennifer; Fike, David A.

2017-06-01

The sulfur biogeochemical cycle plays a key role in regulating Earth’s surface redox through diverse abiotic and biological reactions that have distinctive stable isotopic fractionations. As such, variations in the sulfur isotopic composition (δ34S) of sedimentary sulfate and sulfide phases over Earth history can be used to infer substantive changes to the Earth’s surface environment, including the rise of atmospheric oxygen. Such inferences assume that individual δ34S records reflect temporal changes in the global sulfur cycle; this assumption may be well grounded for sulfate-bearing minerals but is less well established for pyrite-based records. Here, we investigate alternative controls on the sedimentary sulfur isotopic composition of marine pyrite by examining a 300-m drill core of Mediterranean sediments deposited over the past 500,000 y and spanning the last five glacial-interglacial periods. Because this interval is far shorter than the residence time of marine sulfate, any change in the sulfur isotopic record preserved in pyrite (δ34Spyr) necessarily corresponds to local environmental changes. The stratigraphic variations (>76‰) in the isotopic data reported here are among the largest ever observed in pyrite, and are in phase with glacial-interglacial sea level and temperature changes. In this case, the dominant control appears to be glacial-interglacial variations in sedimentation rates. These results suggest that there exist important but previously overlooked depositional controls on sedimentary sulfur isotope records, especially associated with intervals of substantial sea level change. This work provides an important perspective on the origin of variability in such records and suggests meaningful paleoenvironmental information can be derived from pyrite δ34S records.

P contribution derived from phosphate solubilizing microorganism activity, rock phosphate and SP-36 determination by isotope "3"2P technique

International Nuclear Information System (INIS)

Anggi Nico Flatian; Iswandi Anas; Atang Sutandi; Ishak

2016-01-01

The "3"2P isotope technique has been used to trace P nutrients in the soil and soil-plant systems. The use of the isotope "3"2P has made it possible to differentiate the P contribution derived from phosphate solubilizing microorganism activity and the fertilizer P in the soil. The aims of the study were to obtain the quantitative data of P contribution derived from phosphate-solubilizing microorganism activity (Aspergillus niger and Burkholderia cepacia), rock phosphate and SP-36 through P uptake by the plants using isotope "3"2P technique and also to study the effects on growth and production of corn plants. The results were showed that phosphate-solubilizing microorganism, rock phosphate and SP-36 was produced specific activity ("3"2P) lower than control. The results were indicated that all treatments could contribute P for the plants. The lower specific activity was caused by supply P from rock phosphate and SP-36, and also was caused by solubilized of unavailable "3"1P from PSM activity, which decreased specific activity on labeled soil. The combination of phosphate-solubilizing microorganism and SP-36 treatments produced the highest P contribution, significantly higher than control and SP-36 only. Phosphate derived from combination of microorganism and SP-36 treatments ranging from 56.06% - 68.54% after 50 days planting, after 35 days planting, 51.96% - 59.65% on stover, 46.33% - 47.70% on grain and 53.02% - 59.87% on corn cob. In addition, the treatments could significantly support the plant growth and yield. It is expressed by increased number of leave at 35 days after planting, dry weight of leave at 35 days after planting and dry weight of grain. (author)

Investigating the hydrological significance of stalagmite geochemistry (Mg, Sr) using Sr isotope and particulate element records across the Late Glacial-to-Holocene transition

Science.gov (United States)

Belli, R.; Borsato, A.; Frisia, S.; Drysdale, R.; Maas, R.; Greig, A.

2017-02-01

The trace element and Sr isotope records in two coeval stalagmites characterized by different growth rates and flow regimes at Savi cave (Grotta Savi, NE Italy) reveal different sources and incorporation mechanisms for Mg and Sr. Mg is sourced primarily from dissolved cave host rock while particulate Mg derived from soil plays a subordinate role. The presence of particulate-borne Mg is inferred from the co-variation of Mg and particle-associated elements (Th, Al and Mn) which are preferentially concentrated in open columnar calcite layers. Variation in Mg concentrations corrected for particle-influenced components, the Mgc parameter, is controlled by water-rock interaction, with higher and lower Mgc during dry and wet phases, respectively. This is thought to reflect incongruent dissolution of Mg-rich phases. Correction of Sr concentrations for contributions from airborne exogenic Sr, based on 87Sr/86Sr ratios, yields the bedrock-only contribution (Src). Src variation in stalagmite calcite is influenced by speleothem growth rate and by variation of the calcite-water Sr partitioning in wet and dry phases, and only to a minor extent by incongruent dissolution of Mg-rich phases. Concentration profiles for Mgc and Srcg (corrected for growth rate effects) show inverse correlations and are inferred to show hydrological significance which is captured in a hydrological index, HI. We suggest HI provides robust information on water-rock interaction related to hydrological changes and can be utilized in both wet and semi-arid environments, provided the corrections for soil Mg and exogenic Sr can be applied with confidence. Application of the HI index allows correction of Grotta Savi oxygen isotope data, to yield a δ18Oc time series that shows when changes in moisture sources and atmospheric reorganization, or changes in moisture amount, were significant. This is especially evident during the Younger Dryas (YD). The Savi record supports the concept of a two-phase YD, marked by

Application of Fe Isotopes to the Search for Life and Habitable Planets

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Johnson, Clark M.; Beard, Brian L.; Nealson, Kenneth L.

2001-01-01

The relatively new field of Fe isotope geochemistry can make important contributions to tracing the geochemical cycling of Fe, which bears on issues such as metabolic processing of Fe, surface redox conditions, and development of planetary atmospheres and biospheres. It appears that Fe isotope fractionation in nature and the lab spans about 4 per mil (%) in Fe-56/Fe-54, and although this range is small, our new analytical methods produce a precision of +/- 0.05% on sample sizes as small as 100 ng (10(exp -7) g); this now provides us with a sufficient "signal-to-noise" ratio to make this isotope system useful. We review our work in three areas: 1) the terrestrial and lunar rock record, 2) experiments on inorganic fractionation, and 3) experiments involving biological processing of Fe. Additional information is contained in the original extended abstract.

Temporal diet changes recorded by stable isotopes in Asiatic black bear (Ursus thibetanus) hair.

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Mizukami, R N; Goto, M; Izumiyama, S; Yoh, M; Ogura, N; Hayashi, H

2005-03-01

Carbon and nitrogen stable isotope ratios were measured in hair samples of the Asiatic black bear (Ursus thibetanus) inhabiting the Northern Japanese Alps (NJA) (n = 20) and the periphery of Nagano City (NC) (n = 6), in Nagano Prefecture, Japan. The hair of NJA bears, which did not have access to anthropogenic foods, showed lower values of d13C and d15N than that of NC bears which had access to garbage and corn fields, especially during the summer. These results reflect somewhat differing diets between the NJA and NC bears. We attempted to assess the feeding history during the hair growth cycle using the growth section analysis method. Each hair sample had been cut into 3?mm lengths from root to tip, labeled, and analyzed along the hair growth. We measured the carbon and nitrogen stable isotope ratios of each 3?mm length of hair sample from one NC bear which had been killed while raiding a corn field. The sections showed wide ranges of isotope ratios, from -23.2% to -14.6% for delta13C, and from 0.3% to 4.6% for delta15N. It was shown that the diet of this bear shifted dramatically from principally C3 plants to more C4 plants and to foods of animal origin. An analysis of the whole hair reflects just the average feeding habit during hair growth, but the present method can trace its diet history. This method can contribute to obtain precise ecological information of wildlife.

Scale and the isotopic record of C4 plants in pedogenic carbonate: from the biome to the rhizospere.

Energy Technology Data Exchange (ETDEWEB)

Monger, Dr. H Curtis [New Mexico State University, Las Cruces; Cole, David R [ORNL; Buck, Dr. Brenda [University of Nevada, Las Vegas; Gallegos, Robert [Sant fe Water Division

2009-01-01

The 13C/12C ratio in pedogenic carbonate (i.e., CaCO3 formed in soil) is a significant tool for investigating C4 biomes of the past. However, the paleoecological meaning of d13C values in pedogenic carbonate can change with the scale at which one considers the data. We describe studies of modern soils, fossil soils, and vegetation change in the Chihuahuan Desert of North America and elsewhere that reveal four scales important for paleoecologic interpretations. (1) At the broadest scale, the biome scale (hundreds to millions of km2), an isotopic record interpreted as C3 vegetation replacing C4 grasslands may indicate invading C3 woody shrubs instead of expanding C3 forests (a common interpretation). (2) At the landscape scale (several tens of m2 to hundreds of km2), the accuracy of scaling up paleoclimatic interpretations to a regional level is affected by the landform containing the isotopic record. (3) At the soil-profile scale (cm2 to m2), soil profiles with multiple generations of carbonate mixed together have a lower-resolution paleoecologic record than soil profiles repeatedly buried. (4) At the rhizosphere scale (lm2 to cm2), carbonate formed on roots lack the 14 17 enrichment observed at broader scales, revealing different fractionation processes at different scales. A multi-scale approach in dealing with d13C in pedogenic carbonate will increase the accuracy of paleoecologic interpretations and understanding of soil geomorphic climatic interactions that affect boundaries between C4 and C3 vegetation.

Scale and the isotopic record of C4 plants in pedogenic carbonate: from the biome to the rhizosphere

Energy Technology Data Exchange (ETDEWEB)

Monger, Dr. H Curtis [New Mexico State University, Las Cruces; Cole, David [Ohio State University; Buck, Dr. Brenda [University of Nevada, Las Vegas; Gallegos, Robert [Sant fe Water Division

2009-01-01

The 13C/12C ratio in pedogenic carbonate (i.e., CaCO3 formed in soil) is a significant tool for investigating C4 biomes of the past. However, the paleoecological meaning of d13C values in pedogenic carbonate can change with the scale at which one considers the data. We describe studies of modern soils, fossil soils, and vegetation change in the Chihuahuan Desert of North America and elsewhere that reveal four scales important for paleoecologic interpretations. (1) At the broadest scale, the biome scale (hundreds to millions of km2), an isotopic record interpreted as C3 vegetation replacing C4 grasslands may indicate invading C3 woody shrubs instead of expanding C3 forests (a common interpretation). (2) At the landscape scale (several tens of m2 to hundreds of km2), the accuracy of scaling up paleoclimatic interpretations to a regional level is affected by the landform containing the isotopic record. (3) At the soil-profile scale (cm2 to m2), soil profiles with multiple generations of carbonate mixed together have a lower-resolution paleoecologic record than soil profiles repeatedly buried. (4) At the rhizosphere scale (lm2 to cm2), carbonate formed on roots lack the 14 17 enrichment observed at broader scales, revealing different fractionation processes at different scales. A multi-scale approach in dealing with d13C in pedogenic carbonate will increase the accuracy of paleoecologic interpretations and understanding of soil geomorphic climatic interactions that affect boundaries between C4 and C3 vegetation.

Sulfur isotope variability of oceanic DMSP generation and its contributions to marine biogenic sulfur emissions.

Science.gov (United States)

Oduro, Harry; Van Alstyne, Kathryn L; Farquhar, James

2012-06-05

Oceanic dimethylsulfoniopropionate (DMSP) is the precursor to dimethylsulfide (DMS), which plays a role in climate regulation through transformation to methanesulfonic acid (MSA) and non-seasalt sulfate (NSS-SO(4)(2-)) aerosols. Here, we report measurements of the abundance and sulfur isotope compositions of DMSP from one phytoplankton species (Prorocentrum minimum) and five intertidal macroalgal species (Ulva lactuca, Ulva linza, Ulvaria obscura, Ulva prolifera, and Polysiphonia hendryi) in marine waters. We show that the sulfur isotope compositions (δ(34)S) of DMSP are depleted in (34)S relative to the source seawater sulfate by ∼1-3‰ and are correlated with the observed intracellular content of methionine, suggesting a link to metabolic pathways of methionine production. We suggest that this variability of δ(34)S is transferred to atmospheric geochemical products of DMSP degradation (DMS, MSA, and NSS-SO(4)(2-)), carrying implications for the interpretation of variability in δ(34)S of MSA and NSS-SO(4)(2-) that links them to changes in growth conditions and populations of DMSP producers rather than to the contributions of DMS and non-DMS sources.

The isotopic record of Northern Hemisphere atmospheric carbon monoxide since 1950: implications for the CO budget

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Z. Wang

2012-05-01

Full Text Available We present a 60-year record of the stable isotopes of atmospheric carbon monoxide (CO from firn air samples collected under the framework of the North Greenland Eemian Ice Drilling (NEEM project. CO concentration, δ¹³C, and δ¹⁸O of CO were measured by gas chromatography/isotope ratio mass spectrometry (gc-IRMS from trapped gases in the firn. We applied LGGE-GIPSA firn air models (Witrant et al., 2011 to correlate gas age with firn air depth and then reconstructed the trend of atmospheric CO and its stable isotopic composition at high northern latitudes since 1950. The most probable firn air model scenarios show that δ¹³C decreased slightly from −25.8‰ in 1950 to −26.4‰ in 2000, then decreased more significantly to −27.2‰ in 2008. δ¹⁸O decreased more regularly from 9.8‰ in 1950 to 7.1‰ in 2008. Those same scenarios show CO concentration increased gradually from 1950 and peaked in the late 1970s, followed by a gradual decrease to present day values (Petrenko et al., 2012. Results from an isotope mass balance model indicate that a slight increase, followed by a large reduction, in CO derived from fossil fuel combustion has occurred since 1950. The reduction of CO emission from fossil fuel combustion after the mid-1970s is the most plausible mechanism for the drop of CO concentration during this time. Fossil fuel CO emissions decreased as a result of the implementation of catalytic converters and the relative growth of diesel engines, in spite of the global vehicle fleet size having grown several fold over the same time period.

Carbon 13 and oxygen 18 isotope record of the early eocene nammal formation, salt range, pakistan

International Nuclear Information System (INIS)

Ghazi, S.; Sajid, Z.

2014-01-01

The Nammal Formation is the lowermost unit of the Early Eocene succession in the Salt Range, Pakistan. It is well exposed throughout the Salt Range. The Nammal Formation having 30 to 35 meters thickness is predominantly composed of nodular limestone interbedded with marl and shale. The present study was focussed on stable carbon 13 and oxygen 18 isotopic analysis based on data from two stratigraphically important sections. The samples from the Nilawahan section provided with the delta 13C values varied between 1.34 to -1.56 (VPDB) and values of delta 18O fluctuated between -4.47 to -6.59 (VPDB). Likewise the sample analysis of BadshahPur section exhibited that the delta 13C values changes from 1.09 to -1.65 (VPDB) and delta 18O values range from -4.17 to -6.85 (VPDB). The isotopic records of carbon 13 and oxygen 18 indicated the shallow marine deposition of the Nammal Formation under tropical conditions. It highlighted the palaeo climatic and diagenetic conditions of the Nammal Formation at the time of deposition in the Salt Range region. (author)

Resetting of Mg isotopes between calcite and dolomite during burial metamorphism: Outlook of Mg isotopes as geothermometer and seawater proxy

Science.gov (United States)

Hu, Zhongya; Hu, Wenxuan; Wang, Xiaomin; Lu, Yizhou; Wang, Lichao; Liao, Zhiwei; Li, Weiqiang

2017-07-01

Magnesium isotopes are an emerging tool to study the geological processes recorded in carbonates. Calcite, due to its ubiquitous occurrence and the large Mg isotope fractionation associated with the mineral, has attracted great interests in applications of Mg isotope geochemistry. However, the fidelity of Mg isotopes in geological records of carbonate minerals (e.g., calcite and dolomite) against burial metamorphism remains poorly constrained. Here we report our investigation on the Mg isotope systematics of a dolomitized Middle Triassic Geshan carbonate section in eastern China. Magnesium isotope analysis was complemented by analyses of Sr-C-O isotopic compositions, major and trace element concentrations, and petrographic and mineralogical features. Multiple lines of evidence consistently indicated that post-depositional diagenesis of carbonate minerals occurred to the carbonate rocks. Magnesium isotope compositions of the carbonate rocks closely follow a mixing trend between a high δ26Mg dolomite end member and a low δ26Mg calcite end member, irrespective of sample positions in the section and calcite/dolomite ratio in the samples. By fitting the measured Mg isotope data using a two-end member mixing model, an inter-mineral Δ26Mgdolomite-calcite fractionation of 0.72‰ was obtained. Based on the experimentally derived Mg isotope fractionation factors for dolomite and calcite, a temperature of 150-190 °C was calculated to correspond to the 0.72‰ Δ26Mgdolomite-calcite fractionation. Such temperature range matches with the burial-thermal history of the local strata, making a successful case of Mg isotope geothermometry. Our results indicate that both calcite and dolomite had been re-equilibrated during burial metamorphism, and based on isotope mass balance of Mg, the system was buffered by dolomite in the section. Therefore, burial metamorphism may reset Mg isotope signature of calcite, and Mg isotope compositions in calcite should be dealt with caution in

The origin and evolution of chondrites recorded in the elemental and isotopic compositions of their macromolecular organic matter

Science.gov (United States)

Alexander, C. M. O.'D.; Fogel, M.; Yabuta, H.; Cody, G. D.

2007-09-01

Extraterrestrial organic matter in meteorites potentially retains a unique record of synthesis and chemical/thermal modification by parent body, nebular and even presolar processes. In a survey of the elemental and isotopic compositions of insoluble organic matter (IOM) from 75 carbonaceous, ordinary and enstatite chondrites, we find dramatic variations within and between chondrite classes. There is no evidence that these variations correlate with the time and/or location of chondrite formation, or with any primary petrologic or bulk compositional features that are associated with nebular processes (e.g., chondrule and volatile trace element abundances). Nor is there evidence for the formation of the IOM by Fischer-Tropsch-Type synthesis in the nebula or in the parent bodies. The elemental variations are consistent with thermal maturation and/or oxidation of a common precursor. For reasons that are unclear, there are large variations in isotopic composition within and between chondrite classes that do not correlate in a simple way with elemental composition or petrologic type. Nevertheless, because of the pattern of elemental variations with petrologic type and the lack of any correlation with the primary features of the chondrite classes, at present the most likely explanation is that all IOM compositional variations are the result of parent body processing of a common precursor. If correct, the range of isotopic compositions within and between chondrite classes implies that the IOM is composed of several isotopically distinct components whose relative stability varied with parent body conditions. The most primitive IOM is found in the CR chondrites and Bells (CM2). Isotopically, the IOM from these meteorites resembles the IOM in interplanetary dust particles. Chemically, their IOM resembles the CHON particles of comet Halley. Despite the large isotopic anomalies in the IOM from these meteorites, it is uncertain whether the IOM formed in the interstellar medium or

Crust-mantle contribution to Andean magmatism

International Nuclear Information System (INIS)

Ruiz, J; Hildreth, W; Chesley, J

2001-01-01

represent purely mantle-derived melts (nominally ca. 0.13). The Os-isotopic system mimics the variations recorded by the other isotopic systems but is significantly magnified, demonstrating its power for evaluating crustal contributions to arc-magma genesis. Mixing calculations suggest that the Os isotopic values of the Chilean samples represent mixing of mantle-derived magmas with 20% or more of material derived from mafic lower crust (au)

Oxygen isotope records of Globigerina bulloides across a north-south transect in the south-western Indian Ocean

Digital Repository Service at National Institute of Oceanography (India)

Khare, N.; Chaturvedi, S.K.; Saraswat, R

, Washington, D.C). Lutjeharms, J.R.E., N.M. Walters and B.R. Allanson. 1985. Oceanic frontal systems and biologicalenhancement. p.11-21. In: Antarctic Nutrient Cycles and Food Webs. ed. by W.R. Siegfried et al., Springer-Verlag, NewYork. Matsumoto, K., J...: Ocean Sci. J.: 44(2); 2009; 117-123 OXYGEN ISOTOPE RECORDS OF GLOBIGERINA BULLOIDES ACROSS A NORTH-SOUTH TRANSECT IN THE SOUTH-WESTERN INDIAN OCEAN N. Khare 1* , S. K. Chaturvedi 2 and R. Saraswat 3 1. Ministry of Earth Sciences, Block...

Using the magmatic record to constrain the growth of continental crust-The Eoarchean zircon Hf record of Greenland

Science.gov (United States)

Fisher, Christopher M.; Vervoort, Jeffrey D.

2018-04-01

Southern West Greenland contains some of the best-studied and best-preserved magmatic Eoarchean rocks on Earth, and these provide an excellent vantage point from which to view long-standing questions regarding the growth of the earliest continental crust. In order to address the questions surrounding early crustal growth and complementary mantle depletion, we present Laser Ablation Split Stream (LASS) analyses of the U-Pb and Hf isotope compositions of zircon from eleven samples of the least-altered meta-igneous rocks from the Itsaq (Amîtsoq) Gneisses of the Isukasia and Nuuk regions of southern West Greenland. This analytical technique allows a less ambiguous approach to determining the age and Hf isotope composition of complicated zircon. Results corroborate previous findings that Eoarchean zircon from the Itsaq Gneiss (∼3.85 Ga to ∼3.63 Ga) were derived from a broadly chondritic source. In contrast to the Sm-Nd whole rock isotope record for southern West Greenland, the zircon Lu-Hf isotope record provides no evidence for early mantle depletion, nor does it suggest the presence of crust older than ∼3.85 Ga in Greenland. Utilizing LASS U-Pb and Hf data from the Greenland zircons studied here, we demonstrate the importance of focusing on the magmatic (rather than detrital) zircon record to more confidently understand early crustal growth and mantle depletion. We compare the Greenland Hf isotope data with other Eoarchean magmatic complexes such as the Acasta Gneiss Complex, Nuvvuagittuq greenstone belt, and the gneissic complexes of southern Africa, and all lack zircons with suprachondritic Hf isotope compositions. In total, these data suggest only a very modest volume of crust was produced during (or survived from) the Hadean and earliest Eoarchean. There remains no record of planet-scale early Earth mantle depletion in the Hf isotope record prior to 3.8 Ga.

Stable isotopes and diet of hunters gatherers of southwest of Buenos Aires province (Argentina)

International Nuclear Information System (INIS)

Scabuzzo, Clara; Frontini, Romina; Vecchi, Rodrigo; Bayon, Cristina

2016-01-01

Results of the first stable isotopes analysis (δ""1"3C and δ"1"5N) of archaeological sites located in the southwest of the province of Buenos Aires (Argentina) are presented. Both the construction of an isotopic ecology and prehistoric human diets of the sector are explored. The isotopic ecology indicates diverse environments in which marine animals have enriched δ"1"3C col. values; while terrestrial species such as coypo, greater rhea and large-sized herbivores have the poorest values that are indistinguishable among the different taxa. Furthermore, ducks and a hairy armadillo showed intermediate values. Human isotopic values indicate a diet based on the consumption of meat. These proteins came predominantly from terrestrial animals complemented by marine resources. The local archaeological record is consistent with this information, as the main faunal resources are terrestrial species; nevertheless a scarce representation of marine fauna, mainly Otariids, is registered. In this paper we present the first isotopic values for the studied area and thus it is a preliminary contribution that must be further investigated with new samples

Estimation of different source contributions to sediment organic matter in an agricultural-forested watershed using end member mixing analyses based on stable isotope ratios and fluorescence spectroscopy.

Science.gov (United States)

Derrien, Morgane; Kim, Min-Seob; Ock, Giyoung; Hong, Seongjin; Cho, Jinwoo; Shin, Kyung-Hoon; Hur, Jin

2018-03-15

The two popular source tracing tools of stable isotope ratios (δ 13 C and δ 15 N) and fluorescence spectroscopy were used to estimate the relative source contributions to sediment organic matter (SeOM) at five different river sites in an agricultural-forested watershed (Soyang Lake watershed), and their capabilities for the source assignment were compared. Bulk sediments were used for the stable isotopes, while alkaline extractable organic matter (AEOM) from sediments was used to obtain fluorescent indices for SeOM. Several source discrimination indices were fully compiled for a range of the SeOM sources distributed in the catchments of the watershed, which included soils, forest leaves, crop (C3 and C4) and riparian plants, periphyton, and organic fertilizers. The relative source contributions to the river sediment samples were estimated via end member mixing analysis (EMMA) based on several selected discrimination indices. The EMMA based on the isotopes demonstrated that all sediments were characterized by a medium to a high contribution of periphyton ranging from ~30% to 70% except for one site heavily affected by forest and agricultural fields with relatively high contributions of terrestrial materials. The EMMA based on fluorescence parameters, however, did not show similar results with low contributions from forest leaf and periphyton. The characteristics of the studied watershed were more consistent with the source contributions determined by the isotope ratios. The discrepancy in the EMMA capability for source assignments between the two analytical tools can be explained by the limited analytical window of fluorescence spectroscopy for non-fluorescent dissolved organic matter (FDOM) and the inability of AEOM to represent original bulk particulate organic matter (POM). Copyright © 2017 Elsevier B.V. All rights reserved.

Carbon and nitrogen isotope variations in tree-rings as records of perturbations in regional carbon and nitrogen cycles.

Science.gov (United States)

Bukata, Andrew R; Kyser, T Kurtis

2007-02-15

Increasing anthropogenic pollution from urban centers and fossil fuel combustion can impact the carbon and nitrogen cycles in forests. To assess the impact of twentieth century anthropogenic pollution on forested system carbon and nitrogen cycles, variations in the carbon and nitrogen isotopic compositions of tree-rings were measured. Individual annual growth rings in trees from six sites across Ontario and one in New Brunswick, Canada were used to develop site chronologies of tree-ring delta 15N and delta 13C values. Tree-ring 615N values were approximately 0.5% per hundred higher and correlated with contemporaneous foliar samples from the same tree, but not with delta 15N values of soil samples. Temporal trends in carbon and nitrogen isotopic compositions of these tree-rings are consistent with increasing anthropogenic influence on both the carbon and nitrogen cycles since 1945. Tree-ring delta 13C values and delta 15N values are correlated at both remote and urban-proximal sites, with delta 15N values decreasing since 1945 and converging on 1% per hundred at urban-proximal sites and decreasing but not converging on a single delta 15N value in remote sites. These results indicate that temporal trends in tree-ring nitrogen and carbon isotopic compositions record the regional extent of pollution.

Dolomite clumped isotope constraints on the oxygen isotope composition of the Phanerozoic Sea

Science.gov (United States)

Ryb, U.; Eiler, J. M.

2017-12-01

The δ18O value of the Phanerozoic Sea has been debated several decades, largely motivated by an 8‰ increase in δ18O of sedimentary carbonates between the Cambrian and the present. Some previous studies have interpreted this increase to be a primary depositional signal, resulting from an increase in the 18O content of ocean water over time, or from a decrease in ocean temperature increasing the oxygen isotope fractionation between seawater and carbonates. In contrast, other studies have interpreted lower δ18O compositions as the products of diagenetic alteration at elevated burial temperatures. Here, we show that the Phanerozoic dolomite δ18O record overlaps with that of well-preserved calcite fossils, and use carbonate clumped isotope measurements of Cambrian to Pleistocene dolomites to calculate their formation temperatures and the isotopic compositions of their parent-waters. The observed variation in dolomite δ18O is largely explained by dolomite formation at burial temperatures of up to 158°C. The δ18O values of dolomite parent-waters range -2 to +12‰ and are correlated with formation temperatures. Such correlation is consistent with the modification of seawater (0±2‰, VSMOW) toward isotopically heavier compositions through water-rock reactions at elevated burial temperatures. The similarity between the dolomite and calcite δ18O records, and published clumped isotope-based calculations of water compositions, suggests that like dolomite, temporal variations of the calcite δ18O record may also be largely driven by diagenetic alteration. Finally, the relationship we observe between temperature of dolomitization and d18O of dolomite suggests platform carbonates generally undergo dolomitization through reaction with modified marine waters, and that there is no evidence those waters were ever significantly lower in d18O than the modern ocean.

Spanish Network for Isotopes in Precipitation: Isotope Spatial distribution and contribution to the knowledge of the hydrological cycle

International Nuclear Information System (INIS)

Diaz-Teijeiro, M. F.; Rodriguez-Arevalo, J.; Castano, S.

2009-01-01

The results of seven years of operation of the Spanish Network for Isotopes ( 2 H, 1 8O y 3 H) in Precipitation (REVIP) are shown. this Network is managed since 2000 by the Centro de Estudios de Tecnicas Aplicadas of the Centro de Estudios y Experimentacion de Obras Publicas (CEDEX) in collaboration with the Agencia Estatal de Meteorologia (AEMET). The results of REVIP are sent to the International Atomic Energy Agency (IAEA) in order to be integrated in the Global Network for Isotopes in Precipitation (GNIP). The spatial distribution of stable isotopes ( 1 8O h 2 H) in precipitation in Spain follows a multiple regression model, based on two geographic factors: latitude and elevation, which is strongly correlated with temperature, an important factor controlling isotope fractionation. This information on 1 8O and 2 H is useful to trace surface and ground waters and, combined with the information, about the spatial and temporal distribution of the Tritium ( 3 H) concentration in precipitation, allows to date these waters in order to estimate flow directions and velocities, and to evaluate the residence time of water resources and aquifer vulnerability. (Author)

Oxygen Isotopes Archived in Subfossil Chironomids: Advancing a Promising Proxy for Lake Water Isotopes

Science.gov (United States)

Lasher, G. E.; Axford, Y.; Blair, N. E.

2017-12-01

Oxygen isotopes measured in subfossil chironomid head capsules (aquatic insect remains) in lake sediments are beginning to offer paleoclimate insights from previously under-studied areas of the world. Since the first published pilot study demonstrated the potential of chironomid δ18O to record lake water δ18O (Wooller et al., 2004), subsequent work has refined our understanding of this proxy: confirming via lab cultures that growth water controls head capsule δ18O (Wang et al., 2009), refining laboratory pretreatment protocols, and further validating the method by demonstrating strong agreement between carbonate and chironomid-derived paleo-isotope records (Verbruggen et al., 2009, 2010, 2011). However, outstanding questions remain, including the seasonality of chironomid growth, possible species-dependent vital effects, and diagenetic effects on the protein-chitin complex that comprise chironomid cuticles. To address some of these questions, we summarize available data from paired modern chironomid-lake water δ18O values from around the world and discuss climatic and environmental factors affecting chironomid isotopic signatures. We also present new data on the resistance of these subfossils to diagenesis and degradation throughout the late Quaternary using Fourier Transform Infrared Spectroscopy (FT-IR) and Pyrolysis Gas Chromatography Mass Spectrometry (Py-GC/MS) of chironomid remains up to >100,000 years old. As chironomids are nearly ubiquitous in lakes globally and, we argue, molecularly stable through glacial and interglacial cycles, this proxy has the potential to greatly expand the spatial and temporal resolution of Quaternary paleo-isotopes and thus climate records. In addition to reviewing and presenting new methodological advances, we also present applications of chironomid δ18O from millennial- to centennial-scale Holocene Greenland lake records.

An isotopic approach to study the recharge mechanism in Haripur plain contribution to the area from Tarbela and Khanpur lakes

International Nuclear Information System (INIS)

Sajjad, M.I.; Tasneem, M.A.; Khan, I.H.; Ahmad, M.; Akram, W.

1992-01-01

Environmental isotopic investigation were carried out in Haripur plain to determine the recharge mechanism in the area. The Haripur plain is bounded by river Doar (that falls in Tarbela lake) in the north mountain ranges in the east and west, while the river Haro flows on the south eastern boundary upon which Khanpur dam has been built. Effort were made to identify the different sources which recharge the aquifer in the area. Isotopic data reveals that the major source of recharge is the rainfall on adjoining hills There is no contribution of Tarbela and Khanpur lakes. The residence time varies from a few years to more than fifty years depending upon the geology of the area. 14 figs. (author)

Development of Stable Isotope Technology

International Nuclear Information System (INIS)

Jeong, Do Young; Kim, Cheol Jung; Han, Jae Min

2009-03-01

KAERI has obtained an advanced technology with singular originality for laser stable isotope separation. Objectives for this project are to get production technology of Tl-203 stable isotope used for medical application and are to establish the foundation of the pilot system, while we are taking aim at 'Laser Isotope Separation Technology to make resistance to the nuclear proliferation'. And we will contribute to ensuring a nuclear transparency in the world society by taking part in a practical group of NSG and being collaboration with various international groups related to stable isotope separation technology

Geomorphic Drainage Capture Recorded by Oxygen Isotopes of Green River Formation Lacustrine Mudstone, Eocene, Wyoming

Science.gov (United States)

Doebbert, A. C.; Booth, A. L.; Carroll, A.; Chamberlain, C.; Rhodes, M.

2005-12-01

The isotopic composition of cement and other meteoric precipitates are increasingly being used to interpret orogenic uplift histories, based on the relationship between altitude and rainwater δ18O. However, other variables such as changing regional drainage patterns may also affect the downstream composition of surface waters, especially when multiple drainages commingle in a lake. The Green River Formation contains some of the best documented lacustrine deposits in the world, making it ideal for examining such issues. Carbonate mudstone in balanced-fill facies of the lower LaClede Bed averages 3.41‰ (PDB), and records a deep, saline to brackish lake that fluctuated near its sill. In contrast, overfilled facies of the upper LaClede Bed record a freshwater lake, and δ18O reaches values as low as -9.72‰. This transition occurred shortly after deposition of the Analcite Tuff at 48.94 ± 0.12 Ma (Smith et al., 2003), and was geologically abrupt. Based on 40Ar/39Ar-calibrated sediment accumulation rates it required no more than 200-300 ky. An almost identical transition occurs in two cores separated by about 30 km, making local diagenesis an unlikely cause. The magnitude of δ18O change is similar to that in some uplift studies, but its rapidity virtually excludes uplift as a controlling mechanism. Instead, we propose that both the change in sedimentation and the sharp decrease in δ18O are the result of a drainage capture event. The addition of a new drainage to the basin may have adjusted isotopic values in two ways: by introducing runoff with relatively low δ18O, and by decreasing residence time (and therefore evaporation) of lake water. Decreasing 87Sr/86Sr across the same transition suggests that the newly added waters may have been sourced from rising volcanic topography to the north in the Absaroka province. Although this rising topography allows for the possibility of some uplift component, the rate of change in lacustrine δ18O is consistent with

Contribution of stable isotopes to the study of pharmacokinetics of magnesium salts

International Nuclear Information System (INIS)

Benech, H.

1999-01-01

The use of stable isotopes as labels is becoming an attractive tool for the study of magnesium behavior in humans. It has been used two stable isotopes of magnesium, 25 Mg and 26 Mg, to measure the absolute bioavailability of a pharmaceutical form of magnesium. (N.C.)

2. Workshop 'Isotopes in Nature'. 1

International Nuclear Information System (INIS)

1979-11-01

The workshop was aimed at discussing in detail the following problems: (1) distribution of stable and radioactive isotopes in nature, (2) theoretical and experimental studies of isotopic effects in natural processes, (3) problems of sample preparation and sample measurement in determining the relative abundance of stable isotopes or radioactive isotopes in nature, (4) age estimations of samples from different areas of the geosphere, (5) contributions to the specification of global and regional substance cycles in nature with the aid of isotopic and geochemical studies. 75 summaries are included

Geochemistry contribution of Pb isotopes on basalts origin study from Parana basin, Brazil

International Nuclear Information System (INIS)

Marques, L.S.; Dupre, B.; Allegre, C.J.

1990-01-01

This paper presents thirty new Pb-isotope and concentration data for low- and high-tiO sub(2) continental flood basalts of the Parana Basin. The results obtained from representative samples show significant differences with respect to type and location of these basic rocks. The low- and high-TiO sub(2) basalts from the northern region of the Parana Basin exhibit very similar Pb-isotope compositions. On the other hand, the low-TiO sub(2) basalts of central and southern areas, which exhibit low Sr initial isotope ratios (less than 0,7060), show very small variation in Pb isotope compositions which are highly enriched in radiogenic Pb in comparison with the analogues of northern region. The high-TiO sub(2) basic rocks analysed from northern and central regions have the same values for Pb isotope ratios, which are slightly more radiogenic compared with high-TiO sub(2) basalts from southern region. The data obtained, combined with other geochemical (major and trace elements, including rare earths) and isotope (Sr and Nd) results support the view that the basalts from northern and southern areas of the Parana Basin originated in lithospheric mantle reservoirs with different geochemical characteristics. (author)

Constraining the redox landscape of the mid-Proterozoic oceans: new insights from the carbonate uranium isotope record

Science.gov (United States)

Gilleaudeau, G. J.; Kaufman, A. J.; Luo, G.; Romaniello, S. J.; Zhang, F.; Kah, L. C.; Azmy, K.; Bartley, J. K.; Sahoo, S. K.; Knoll, A. H.; Anbar, A. D.

2017-12-01

The redox landscape of the global oceans during the prolonged period between the Great Oxidation Event (GOE) and the Neoproterozoic Oxygenation Event (NOE) is a topic of considerable debate. Data from local redox proxies such as iron speciation suggest largely ferruginous conditions in the subsurface oceans (with the exception of one report of oxic subsurface waters) and a variable degree of euxinia in shallow shelf and epeiric sea environments. There is general consensus that anoxia was more widespread than in the modern ocean, but quantifying the degree of seafloor anoxia is challenging given that most redox proxies are inherently local and/or based on the relatively sparse black shale record. Here, we present new uranium (U) isotope data from carbonate rocks than span the mid-Proterozoic Eon. U-isotopes operate as a proxy for seafloor anoxia because the δ238U value of seawater is largely controlled by the size of the anoxic/euxinic U sink, which preferentially removes isotopically heavy 238U, leaving the oceans enriched in 235U. Our compilation of data from mid-Proterozoic successions reveals δ238U values similar to modern seawater (-0.39 ± 0.19 ‰ [1 s.d.] for the Gaoyuzhuang, Angmaat, El Mreiti, Vazante, and Turukhansk successions spanning 1.5 to 0.9 Ga). Given the potential for an isotopic offset between carbonate minerals and seawater of up to 0.3 ‰, we suggest that mid-Proterozoic seawater had a δ238U value generally between -0.4 and -0.7 ‰, which is lower than modern seawater, but higher than has been inferred for intervals of expanded anoxia elsewhere in Earth history. These results are consistent with recently published U-isotope data from the 1.36 Ga Velkerri Formation, and suggest that large portions of the seafloor may have been covered by at least weakly oxygenated waters during the mid-Proterozoic Eon. Uncertainty remains, however, because the isotopic effects of the non-euxinic anoxic sink are poorly constrained. Nonetheless, our data

The potential of elemental and isotopic analysis of tree bark for discriminating sources of airborne lead contamination in the UK.

Science.gov (United States)

Bellis, D; McLeod, C W; Satake, K

2001-02-01

Samples of tree bark, which accumulate airborne material, were collected from seven locations in the UK to provide an indication of the magnitude and source of lead pollution. Measurement of the Pb content and 206/207Pb stable isotope ratio by inductively coupled plasma mass spectrometry revealed significant differences between the sites. The concentration of Pb varied over almost four orders of magnitude from 7.2 to 9,600 micrograms g-1, the maximum values being found near a 'secondary' Pb smelter. The 206/207Pb isotope ratios varied from 1.108 +/- 0.002 to 1.169 +/- 0.001. The lowest Pb concentrations and highest isotope ratios were detected in bark samples from the Scilly Isles, reflecting the low-level of industry and road traffic. In contrast, samples obtained from a city centre (Sheffield) and near a motorway (M1) contained 25-46 micrograms g-1 Pb and recorded the lowest 206/207Pb ratios. Higher concentrations in the vicinity of a coal-fired power station recorded a 206/207Pb ratio of 1.14, suggesting a significant contribution from fly-ash. The relative contribution of lead from petrol (206/207Pb = 1.08) and other sources such as coal (206/207Pb = 1.18) were thus estimated using mass balance equations. Tree bark near the lead smelter recorded an intermediate 206/207Pb ratio of 1.13 reflecting the processing of material of mixed origin.

Study of groundwater recharge in Rechna Doab using isotope techniques

International Nuclear Information System (INIS)

Sajjad, M.I.; Tasneem, M.A.; Ahmed, M.; Hussain, S.D.; Khan, I.H.; Akram, W.

1992-04-01

Isotopic studies were performed in the Rechna Doab area to understand the recharge mechanism, investigate the relative contributions from various sources such as rainfall, rivers and canal system and to estimate the turn over times and replenishment rate of groundwater. The isotopic data suggest that the groundwater in the project area can be divided into different zones each having its own characteristic isotopic composition. The enriched isotopic values show rain recharge and depleted isotopic values are associated with river/canal system while the intermediate isotopic values show a mixing of two or more sources of water. The major contribution, however, comes from canal system. The isotopic data suggest that there is no quick movement of groundwater in the area. 18 figs. (author)

U-series dating and stable isotope records of speleothem records from the Scladina Cave (Belgium)

Science.gov (United States)

van der Lubbe, Jeroen; Bonjean, Dominique; Hellstrom, John; Verheyden, Sophie; Vonhof, Hubert

2015-04-01

The Scladina cave, situated in the village of Sclayn (Ardennes, Belgium) at the southern bank of the Meuse, is famous for its Neanderthal fossils and artefacts. The infilling of the cave consists of a succession of flowstone layers interbedded with reworked loess sediment from outside the cave. The younger flowstone layers correspond to interglacials MIS 5 and the Holocene, while the reworked loess sediments represent cooler conditions. By careful diagenetic screening, well-preserved speleothem material was selected for U-series dating and stable isotope analysis of calcite and fluid inclusions. The results provide important new constraints on the age of Neanderthal fossils and artefacts, and bracket the time periods with a hydroclimate favorable for speleothem growth. The combination of fluid inclusion and calcite isotope analysis documents climate variability in the interglacials at high temporal resolution.

Sources and Contributions of Oxygen During Microbial Pyrite Oxidation: the Triple Oxygen Isotopes of Sulfate

Science.gov (United States)

Ziegler, K.; Coleman, M. L.; Mielke, R. E.; Young, E. D.

2008-12-01

The triple isotopes of oxygen (Δ17O' = δ17O'-0.528 × δ18O' using logarithmic deltas) can trace the oxygen sources of sulfate produced during sulfide oxidation, an important biogeochemical process on Earth's surface and possibly also on Mars [1]. δ18OSO4 compositions are determined by the isotopic selectivity of the mechanism(s) responsible for their changes, and the δ18O value of the reactants (O2 vs. H2O). The relative proportional importance and contribution of each of those sources and mechanisms, as well as their associated isotopic fractionations, are not well understood. We are investigating the use of Δ 17O as a quantitative and qualitative tracer for the different processes and oxygen sources involved in sulfate production. Δ17O signatures are distinct fingerprints of these reservoirs, independent of fractionation factors that can be ambiguous. We conducted controlled abiotic and biotic (Acidithiobacillus ferrooxidans, A.f.) laboratory experiments in which water was spiked with 18O, allowing us to quantify the sources of sulfate oxygen and therefore the processes attending sulfate formation. Results of this Δ17O tracer study show that A.f. microbes initiate pyrite S-oxidation within hours of exposure, and that sulfate is produced from ~90% atmospheric oxygen. This initial lag-phase (behavior in the initial lag-phase will aid in the understanding of the ecological conditions required for microbial populations to establish and survive. An exponential phase of growth, facilitated by microbial Fe2+-oxidation, follows. The source of sulfate rapidly switches to abiotic sulfide oxidation during exponential growth and the source of oxygen switches from atmospheric O2 to nearly ~100% water. Pending acquisition of complimentary chemistry data (in progress), we interpret our isotope data to indicate that the biotic fractionation factor ɛ18OSO4-O2 of at least ~ -25 to - 35‰ is augmented by microbially induced kinetic fractionation; it is larger than

Isotopic signatures suggest important contributions from recycled gasoline, road dust and non-exhaust traffic sources for copper, zinc and lead in PM10 in London, United Kingdom

Science.gov (United States)

Dong, Shuofei; Ochoa Gonzalez, Raquel; Harrison, Roy M.; Green, David; North, Robin; Fowler, Geoff; Weiss, Dominik

2017-09-01

The aim of this study was to improve our understanding of what controls the isotope composition of Cu, Zn and Pb in particulate matter (PM) in the urban environment and to develop these isotope systems as possible source tracers. To this end, isotope ratios (Cu, Zn and Pb) and trace element concentrations (Fe, Al, Cu, Zn, Sb, Ba, Pb, Cr, Ni and V) were determined in PM10 collected at two road sites with contrasting traffic densities in central London, UK, during two weeks in summer 2010, and in potential sources, including non-combustion traffic emissions (tires and brakes), road furniture (road paint, manhole cover and road tarmac surface) and road dust. Iron, Ba and Sb were used as proxies for emissions derived from brake pads, and Ni, and V for emissions derived from fossil fuel oil. The isotopic composition of Pb (expressed using 206Pb/207Pb) ranged between 1.1137 and 1.1364. The isotope ratios of Cu and Zn expressed as δ65CuNIST976 and δ66ZnLyon ranged between -0.01‰ and +0.51‰ and between -0.21‰ and +0.33‰, respectively. We did not find significant differences in the isotope signatures in PM10 over the two weeks sampling period and between the two sites, suggesting similar sources for each metal at both sites despite their different traffic densities. The stable isotope composition of Pb suggests significant contribution from road dust resuspension and from recycled leaded gasoline. The Cu and Zn isotope signatures of tires, brakes and road dust overlap with those of PM10. The correlation between the enrichments of Sb, Cu, Ba and Fe in PM10 support the previously established hypothesis that Cu isotope ratios are controlled by non-exhaust traffic emission sources in urban environments (Ochoa Gonzalez et al., 2016). Analysis of the Zn isotope signatures in PM10 and possible sources at the two sites suggests significant contribution from tire wear. However, temporary additional sources, likely high temperature industrial emissions, need to be invoked

Oxygen isotope ratios in the shell of Mytilus edulis: archives of glacier meltwater in Greenland?

DEFF Research Database (Denmark)

Versteegh, E. A. A.; Blicher, Martin E.; Mortensen, J.

2012-01-01

Melting of the Greenland Ice Sheet (GrIS) is accelerating and will contribute significantly to global sea level rise during the 21st century. Instrumental data on GrIS melting only cover the last few decades, and proxy data extending our knowledge into the past are vital for validating models...... predicting the influence of ongoing climate change. We investigated a potential meltwater proxy in Godthåbsfjord (West Greenland), where glacier meltwater causes seasonal excursions with lower oxygen isotope water (δ18Ow) values and salinity. The blue mussel (Mytilus edulis) potentially records...... its potential as a palaeo-meltwater proxy. First, we confirmed that M. edulis shell calcite oxygen isotope (δ18Oc) values are in equilibrium with ambient water and generally reflect meltwater conditions. Subsequently we investigated if this species recorded the full range of δ18Ow values occurring...

Tertiary climate records from arid areas as indicated by isotopic signature of alunite

International Nuclear Information System (INIS)

Arehart, G.B.

1997-01-01

Alunite (ideally KAl 3 (SO 4 ) 2 (OH) 6 ] is a relatively common mineral in some hydrothermal systems as well as in the weathering environment in arid regions. Because of its composition, alunite is an ideal mineral for use in stable isotopic studies of all types. In particular, there is little or no hydrogen isotope fractionation between alunite formed at surficial temperatures and water from which it forms. Therefore, the isotopic composition (delta D) of this mineral reflect the isotopic composition of meteoric waters at the time of deposition, which can in turn be utilised to infer paleoclimatic information. In addition, the presence of K (and its decay products) allows simple and accurate determination of absolute ages for mineral deposition making alunite one of very few paleoclimate indicators that is directly datable. (author)

Filling the gap in Ca input-output budgets in base-poor forest ecosystems: The contribution of non-crystalline phases evidenced by stable isotopic dilution

Science.gov (United States)

van der Heijden, Gregory; Legout, Arnaud; Mareschal, Louis; Ranger, Jacques; Dambrine, Etienne

2017-07-01

In terrestrial ecosystems, plant-available pools of magnesium and calcium are assumed to be stored in the soil as exchangeable cations adsorbed on the surface of mineral and/or organic particles. The pools of exchangeable magnesium and calcium are measured by ion-exchange soil extractions. These pools are sustained in the long term by the weathering of primary minerals in the soil and atmospheric inputs. This conceptual model is the base of input-output budgets from which soil acidification and the sustainability of soil chemical fertility is inferred. However, this model has been questioned by data from long-term forest ecosystem monitoring sites, particularly for calcium. Quantifying the contribution of atmospheric inputs, ion exchange and weathering of both primary, secondary and non-crystalline phases to tree nutrition in the short term is challenging. In this study, we developed and applied a novel isotopic dilution technique using the stable isotopes of magnesium and calcium to study the contribution of the different soil phases to soil solution chemistry in a very acidic soil. The labile pools of Mg and Ca in the soil (pools in equilibrium with the soil solution) were isotopically labeled by spraying a solution enriched in 26Mg and 44Ca on the soil. Labeled soil columns were then percolated with a dilute acid solution during a 3-month period and the isotopic dilution of the tracers was monitored in the leaching solution, in the exchangeable (2 sequential 1 mol L-1 ammonium acetate extractions) and non-crystalline (2 sequential soil digestions: oxalic acid followed by nitric acid) phases. Significant amounts of Mg and Ca isotope tracer were recovered in the non-crystalline soil phases. These phases represented from 5% to 25% and from 24% to 50%, respectively, of the Mg and Ca labile pools during the experiment. Our results show that non-crystalline phases act as both a source and a sink of calcium and magnesium in the soil, and contribute directly to soil

Geochemical and isotopic determination of deep groundwater contributions and salinity to the shallow groundwater and surface water systems, Mesilla Basin, New Mexico, Texas, and Mexico

Science.gov (United States)

Robertson, A.; Carroll, K. C.; Kubicki, C.; Purtshert, R.

2017-12-01

The Mesilla Basin/Conejos-Médanos aquifer system, extending from southern New Mexico to Chihuahua, Mexico, is a priority transboundary aquifer under the 2006 United States­-Mexico Transboundary Aquifer Assessment Act. Declining water levels, deteriorating water quality, and increasing groundwater use by municipal, industrial, and agricultural users on both sides of the international border raise concerns about long-term aquifer sustainability. Relative contributions of present-day and "paleo" recharge to sustainable fresh groundwater yields has not been determined and evidence suggests that a large source of salinity at the distal end of the Mesilla Basin is saline discharge from deep groundwater flow. The magnitude and distribution of those deep saline flow paths are not determined. The contribution of deep groundwater to discharge and salinity in the shallow groundwater and surface water of the Mesilla Basin will be determined by collecting discrete groundwater samples and analyzing for aqueous geochemical and isotopic tracers, as well as the radioisotopes of argon and krypton. Analytes include major ions, trace elements, the stable isotopes of water, strontium and boron isotopes, uranium isotopes, the carbon isotopes of dissolved inorganic carbon, noble gas concentrations and helium isotope ratios. Dissolved gases are extracted and captured from groundwater wells using membrane contactors in a process known as ultra-trace sampling. Gas samples are analyzed for radioisotope ratios of krypton by the ATTA method and argon by low-level counting. Effectiveness of the ultra-trace sampling device and method was evaluated by comparing results of tritium concentrations to the krypton-85 content. Good agreement between the analyses, especially in samples with undetectable tritium, indicates that the ultra-trace procedure is effective and confirms that introduction of atmospheric air has not occurred. The geochemistry data indicate a complex system of geochemical

Hydrogen Isotopic Composition of Apatite in Northwest Africa 7034: A Record of the "Intermediate" H-Isotopic Reservoir in the Martian Crust?

Science.gov (United States)

McCubbin, F. M.; Barnes, J. J.; Santos, A. R.; Boyce, J. W.; Anand, M.; Franchi, I. A.; Agee, C. B.

2016-01-01

Northwest Africa (NWA) 7034 and its pairings comprise a regolith breccia with a basaltic bulk composition [1] that yields a better match than any other martian meteorite to visible-infrared reflectance spectra of the martian surface measured from orbit [2]. The composition of the fine-grained matrix within NWA 7034 bears a striking resemblance to the major element composition estimated for the martian crust, with several exceptions. The NWA 7034 matrix is depleted in Fe, Ti, and Cr and enriched in Al, Na, and P [3]. The differences in Al and Fe are the most substantial, but the Fe content of NWA 7034 matrix falls within the range reported for the southern highlands crust [6]. It was previously suggested by [4] that NWA 7034 was sourced from the southern highlands based on the ancient 4.4 Ga ages recorded in NWA 7034/7533 zircons [4, 5]. In addition, the NWA 7034 matrix material is enriched in incompatible trace elements by a factor of 1.2-1.5 [7] relative to estimates of the bulk martian crust. The La/Yb ratio of the bulk martian crust is estimated to be approximately 3 [7], and the La/Yb of the NWA 7034 matrix materials ranges from approximately 3.9 to 4.4 [3, 8], indicating a higher degree of LREE enrichment in the NWA 7034 matrix materials. This elevated La/Yb ratio and enrichment in incompatible lithophile trace elements is consistent with NWA 7034 representing a more geochemically enriched crustal terrain than is represented by the bulk martian crust, which would be expected if NWA 7034 represents the bulk crust from the southern highlands. Given the similarities between NWA 7034 and the martian crust, NWA 7034 may represent an important sample for constraining the composition of the martian crust, particularly the ancient highlands. In the present study, we seek to constrain the H isotopic composition of the martian crust using Cl-rich apatite in NWA 7034. Usui et al., [9] recently proposed that a H isotopic reservoir exists within the martian crust that has

Ca and Sr isotope records support ocean acidification during end-Permian mass extinction

Science.gov (United States)

Wang, J.; Jacobson, A. D.; Zhang, H.; Ramezani, J.; Sageman, B. B.; Hurtgen, M.; Bowring, S. A.; Shen, S.

2017-12-01

The end-Permian mass extinction represents the most devastating loss of biodiversity during the Phanerozoic. A negative carbon isotope (δ13C) excursion that accompanies the event suggests a significant perturbation to the global carbon cycle, likely induced by CO2 emissions during eruption of the Siberian Traps large igneous province. The carbon cycle is linked with the Ca and Sr cycles through chemical weathering and carbonate precipitation. Therefore, analyses of Ca (δ44/40Ca), radiogenic Sr (87Sr/86Sr), and stable Sr (δ88/86Sr) isotope abundance variations in marine carbonate rocks spanning the Permian-Triassic Boundary (PTB) can reveal key information about biogeochemical changes that occurred during this time. We report δ44/40Ca, 87Sr/86Sr, and δ88/86Sr records analyzed by TIMS for the Meishan and Dajiang sections in China. δ44/40Ca values exhibit similar patterns in both sections. The values remain unchanged across the extinction event layer (EXT) and then decrease by 0.20‰ before increasing by 0.20‰ to 0.40‰ around the PTB. In the Meishan section, 87Sr/86Sr ratios increase after the EXT and return to pre-excursion levels by the PTB. Simultaneously, δ88/86Sr values decrease by 0.12‰ across the EXT and increase by 0.08‰ by the PTB. The patterns of our data support the hypothesis that elevated atmospheric CO2 levels enhanced chemical weathering inputs and might have caused transient ocean acidification, with an "alkalinity overshoot" and increased carbonate deposition occurring after the extinction. Additional measurements and model calculations are underway to help refine and improve these preliminary interpretations.

Contribution of records management to audit opinions and accountability in government

Directory of Open Access Journals (Sweden)

Rodreck David

2017-05-01

Full Text Available Background: Auditing can support national democratic processes, national development and government good will. Supreme Audit Institutions (SAI, such as offices of Auditor General, publish consolidated reports on audit outcomes for local authorities, government departments, parastatals and related public entities. These reports identify broad areas analysed during audit exercises that often include financial management, governance, asset management, risk management, revenue collection and debt recovery. They highlight trends that were detected during audit exercises at the end of a financial year. The reports further show how records and records management affect audit exercises as well as financial management within the audited institutions. Objectives: The intention of the research was to ascertain the contribution of records management to audit opinions and accountability in financial management in Zimbabwean government entities. Method: A document analysis of Comptroller and Auditor General of Zimbabwe (CAGZ’s reports was used to identify the types of decisions and recommendations (audit opinions issued, in juxtaposition to the records management issues raised. Results and Conclusion: This study shows that there is a strong correlation between records management concerns and audit opinions raised by the CAGZ’s narrative audit reports. Inadequate records management within government entities was associated with adverse and qualified opinions and, in some cases, unqualified opinions that had emphases of matter. There was a causal loop in which lack of documentary evidence of financial activities was the source cause of poor accounting and poor audit reports. Errors resulting from incomplete or inaccurate records meant that government entities were not showing a true picture of their financial status and their financial statements could be materially misstated. As an important monitoring and control system, records management should be

Osmium isotope perturbations during the Pliensbachian-Toarcian (Early Jurassic): Relationships between volcanism, weathering, and climate change

Science.gov (United States)

Percival, Lawrence; Cohen, Anthony; Davies, Marc; Dickson, Alexander; Jenkyns, Hugh; Hesselbo, Stephen; Mather, Tamsin; Xu, Weimu; Storm, Marisa

2016-04-01

weathering, and note that both excursions coincide with negative excursions in δ13C (indicating a massive release of isotopically light carbon to the atmosphere) and positive excursions in Hg/TOC (indicating enhanced volcanic activity associated with the Karoo-Ferrar LIP). These concurrent changes suggest that carbon-emissions related to the Karoo-Ferrar may have aided climate warming, leading to the enhanced weathering and marine anoxia recorded in Toarcian strata. Additionally, we record a potential lag in the recovery of 187Os/188Os compared to δ13C; such a lag would support previous hypotheses that enhanced weathering contributed towards draw-down of excess atmospheric carbon, alleviating the Toarcian warming. Finally, our recording of a second (stratigraphically lower) excursion in Os isotopes, coincident with previously recorded excursions, indicates that major climate change during the Toarcian in fact began, albeit to a lesser degree, at the Pl-To boundary, rather than being restricted solely to the T-OAE.

Tracing the recently increasing anthropogenic Pb inputs into the East China Sea shelf sediments using Pb isotopic analysis

International Nuclear Information System (INIS)

Wang, Deli; Zhao, Zhiqi; Dai, Minhan

2014-01-01

Highlights: • Lithogenic Pb dominated in the ECS shelf sediments. • Small but increasing anthropogenic Pb occurred in the ECS shelf sediments. • HCl-leachated Pb suggested a source from “polluted” coastal sediments. • Residual Pb was mainly contributed from the “pristine” upper Yangtze watershed. - Abstract: This study examined the Pb content and Pb isotopic composition in a sediment core taken from the East China Sea (ECS) shelf, and it was observed that since 2003 the increasing anthropogenic Pb inputs have impacted as far as the ECS shelf sediments. The ECS shelf sediments were generally characterized with low bulk Pb contents (12.5–15.0 μg/g) and relatively lithogenic Pb isotopic signatures (both HCl-leached and residual fractions). However, elevated Pb records along with lighter Pb isotopic signals have occurred in the post-2003 sediments, as a result of a small but increasing anthropogenic Pb contribution from the heavily human perturbed coastal sediments due to the sharply increasing coal consumption in mainland China since 2003

What controls the stable isotope composition of precipitation in the Mekong Delta? A model-based statistical approach

Science.gov (United States)

Le Duy, Nguyen; Heidbüchel, Ingo; Meyer, Hanno; Merz, Bruno; Apel, Heiko

2018-02-01

This study analyzes the influence of local and regional climatic factors on the stable isotopic composition of rainfall in the Vietnamese Mekong Delta (VMD) as part of the Asian monsoon region. It is based on 1.5 years of weekly rainfall samples. In the first step, the isotopic composition of the samples is analyzed by local meteoric water lines (LMWLs) and single-factor linear correlations. Additionally, the contribution of several regional and local factors is quantified by multiple linear regression (MLR) of all possible factor combinations and by relative importance analysis. This approach is novel for the interpretation of isotopic records and enables an objective quantification of the explained variance in isotopic records for individual factors. In this study, the local factors are extracted from local climate records, while the regional factors are derived from atmospheric backward trajectories of water particles. The regional factors, i.e., precipitation, temperature, relative humidity and the length of backward trajectories, are combined with equivalent local climatic parameters to explain the response variables δ18O, δ2H, and d-excess of precipitation at the station of measurement. The results indicate that (i) MLR can better explain the isotopic variation in precipitation (R2 = 0.8) compared to single-factor linear regression (R2 = 0.3); (ii) the isotopic variation in precipitation is controlled dominantly by regional moisture regimes (˜ 70 %) compared to local climatic conditions (˜ 30 %); (iii) the most important climatic parameter during the rainy season is the precipitation amount along the trajectories of air mass movement; (iv) the influence of local precipitation amount and temperature is not significant during the rainy season, unlike the regional precipitation amount effect; (v) secondary fractionation processes (e.g., sub-cloud evaporation) can be identified through the d-excess and take place mainly in the dry season, either locally

The Use of Isotope Techniques to Separate of Hydrography Components. Case Study: Ankara-Guvenc Basin

International Nuclear Information System (INIS)

Tekeli, Y.I.; Sorman, A.U.; Sayin, M.

2002-01-01

In this research, a stable environmental isotope study was carried out from analysis of water samples collected from rainfall, runoff (total discharge), springs (subsurface flows), and wells (ground waters)in Ankara-Guevenc basin having a drainage area of about 16.125 km 2 between 1996-2000. The aim of the study was to investigate the rainfall-runoff relationship for the basin. Recorded total ten discharge hydrographs are separated to their components using stable isotopes (Oxygen-18, Deuterium) contents. Among these samples, unit hydrographs from two one-peak storm hydrographs were derived using both isotope and graphical methods, and the derived unit hydrographs values including peaks were compared. Peak values of 10 and 20 minutes unit hydrographs of the basin derived by using isotope method (Q p = 1322 1/s and Q p = 1327 l/s) are compared with those of graphical method (Q p = 1656 1/s, and Q p = 1250 1/s) using Barnes semi-log approach. It was found out that, the contribution of subsurface flow which is component of total discharge hydrograph and originating from various sub layers are important in the total flow of basin using isotope method of approach

Equipment for isotope diagnostics

International Nuclear Information System (INIS)

Platz, W.

1976-01-01

The invention concerns an improvement of equipment for isotope diagnostics allowing to mark special intensity ranges of the recorded measurements by means of different colors. For undisturbed operation it is of advantage to avoid electric circuits between movable and unmovable parts of the color recorder. According to the invention, long gear wheels of glass fiber-reinforced polyamide are used for these connections. (ORU) [de

Utilizing Stable Isotopes and Isotopic Anomalies to Study Early Solar System Formation Processes

Science.gov (United States)

Simon, Justin

2017-01-01

Chondritic meteorites contain a diversity of particle components, i.e., chondrules and calcium-, aluminum-rich refractory inclusions (CAIs), that have survived since the formation of the Solar System. The chemical and isotopic compositions of these materials provide a record of the conditions present in the protoplanetary disk where they formed and can aid our understanding of the processes and reservoirs in which solids formed in the solar nebula, an important step leading to the accretion of planetesimals. Isotopic anomalies associated with nucleosynthetic processes are observed in these discrete materials, and can be compared to astronomical observations and astrophysical formation models of stars and more recently proplyds. The existence and size of these isotopic anomalies are typically thought to reflect a significant state of isotopic heterogeneity in the earliest Solar System, likely left over from molecular cloud heterogeneities on the grain scale, but some could also be due to late stellar injection. The homogenization of these isotopic anomalies towards planetary values can be used to track the efficiency and timescales of disk wide mixing,

Radiometric report for a blast furnace tracing with radioactive isotopes

International Nuclear Information System (INIS)

Tanase, G.; Tanase, M.

1995-01-01

One of the methods to monitor refractory wall of blast furnace is its tracing with radioactive isotopes. The tracer isotope can be detected by two ways: the external dosimetric measurement at the armour of the blast furnace and/or the radiometric measurement of the iron sample charge by charge. Any change in radiometric situation of tracer radioisotope is recorded in a radiometric report. This paper presents an original concept of radiometric report based upon PARADOX and CORELDRAW soft kits. Their advantage are: quick and easy changes, easy recording of current radioactivity of tracer isotope, short history of changes, visual mapping of the tracer isotope and others. In this way we monitored 6 blast furnaces and more than 180 radioactive sources

Precipitation stable isotope records from the northern Hengduan Mountains in China capture signals of the winter India-Burma Trough and the Indian Summer Monsoon

Science.gov (United States)

Yu, Wusheng; Tian, Lide; Yao, Tandong; Xu, Baiqing; Wei, Feili; Ma, Yaoming; Zhu, Haifeng; Luo, Lun; Qu, Dongmei

2017-11-01

This project reports results of the first precipitation stable isotope (δ18 O and δD) time series produced for Qamdo in the northern Hengduan Mountains in the southeastern Tibetan Plateau. The data showed that the fluctuations of precipitation stable isotopes at Qamdo during the different seasons revealed various moisture sources. The westerlies and local recycling moisture dominated at the study area before the pre-monsoon and after the post-monsoon seasons, which resulted in similar trends of both precipitation stable isotopes and temperature. The marine moisture was transported to the northern Hengduan Mountains by the winter India-Burma Trough combined with convection. Consequently, stable isotopes in subsequent precipitation were occasionally observed to decrease suddenly. However, δ18 O and δD values of precipitation at Qamdo were lower during the monsoon period and the duration of those low values was longer because of the effects of the Indian Summer Monsoon and the strengthening convection. Our findings indicate that the effects of seasonal precipitation differences caused by various climate systems, including the winter India-Burma Trough and Indian Summer Monsoon, need to be considered when attempting to interpret tree-ring and ice core records for the Hengduan Mountains.

A continuous high-resolution record of western South Island environmental change over the last 31,000 years from stable isotope analyses of two north-west Nelson speleothems

International Nuclear Information System (INIS)

Hellstrom, J.; McCulloch, M.; Stone, J.

1997-01-01

Core samples were taken through large sheets of calcite flowstone growing in two cave systems, Nettlebed, and Exhaleair, in north-west Nelson, New Zealand. The sampled flowstones are at elevations of 400 m asl and 600 m asl, and are both located 200m below the surface. Ten high-precision U-series dates, measured by thermal ionisation mass spectroemtry, indicate the Nettlebed flowstone grew continuously over the last 31 ka. The Exhaleair flowstone grew continuously over the last 16 ka, following a 50 ka hiatus in deposition. The speleothems from both caves show similar records of oxygen isotope variation over the last 16 ka. The carbon isotope record from Nettlebed shows considerable variation, of almost 10 per thousand from the last glacial maximum to the early Holocene. It is anticipated that these well-dated speleothem records will enable more accurate constraints to be placed on the timing of glacial advances and vegetation changes in the western South Island than are possible using the available radiocarbon ages alone. (author)

Isotope Reanalysis for 20th century: Reproduction of isotopic time series in corals, tree-rings, and tropical ice cores

Science.gov (United States)

Yoshimura, K.

2012-04-01

In the present study, an isotope-incorporated GCM simulation for AD1871 to AD2008 nudged toward the so-called "20th Century Reanalysis (20CR)" atmospheric fields is conducted. Beforehand the long-term integration, a method to downscale ensemble mean fields is proposed, since 20CR is a product of 56-member ensemble Kalman filtering data assimilation. The method applies a correction to one of the ensemble members in such a way that the seasonal mean is equal to that of the ensemble mean, and then the corrected member is inputted into the isotope-incorporated GCM (i.e., IsoGSM) with the global spectral nudging technique. Use of the method clearly improves the skill than the cases of using only a single member and of using the ensemble means; the skill becomes equivalent to when 3-6 members are directly used. By comparing with GNIP precipitation isotope database, it is confirmed that the 20C Isotope Reanalysis's performance for latter half of the 20th century is just comparable to the other latest studies. For more comparisons for older periods, proxy records including corals, tree-rings, and tropical ice cores are used. First for corals: the 20C Isotope Reanalysis successfully reproduced the δ18O in surface sea water recorded in the corals at many sites covering large parts of global tropical oceans. The comparison suggests that coral records represent past hydrologic balance information where interannual variability in precipitation is large. Secondly for tree-rings: δ18O of cellulose extracted from the annual rings of the long-lived Bristlecone Pine from White Mountain in Southern California is well reproduced by 20C Isotope Reanalysis. Similar good performance is obtained for Cambodia, too. However, the mechanisms driving the isotopic variations are different over California and Cambodia; for California, Hadley cell's expansion and consequent meridional shift of the submerging dry zone and changes in water vapor source is the dominant control, but in Cambodia

Identification of historical lead sources in roof dust and recent lake sediments from an industrialized are: Indications from lead isotopes

International Nuclear Information System (INIS)

Chenhall, B.E.; Depers, A.M.; Jones, B.G.; Chiaradia, M.

1997-01-01

X-ray fluorescence and stable lead (Pb) isotopic analyses have been undertaken on dusts, known from microscopic investigation to contain significant quantities of industrially- and urban-derived particulate matter, present in the roof cavities of houses in the Illawarra region (N.S.W., Australia), with the objective of examining the historic record of Pb pollution. All investigated houses contained in excess of 250 μg g -1 Pb, with dwellings close to a copper smelter, in a large industrial complex including a major steelworks, containing higher (>2500 μg g -1 ) Pb concentrations. The isotopic composition in the dusts, expressed here as 206 Pb/ 204 Pb, is relatively constant at 17.0, irrespective of dwelling age or distance from the industrial complex. Contamination of the dusts by Pb sourced from paint cannot explain the isotopic uniformity of the dust samples. Isotopic modelling indicates that the dusts contain Pb derived from the copper smelter, gasoline-air Pb and a minor contribution from the steelworks. Isotopic calculations, together with records of particulate pollution emission, indicate a link between the Pb in roof dusts and Pb contamination of the near surface lagoonal sediments. Over the last five decades, atmospheric fallout of Pb-bearing particulate matter appears to have been the dominant pathway for addition of Pb to the lagoon and dwellings in the Illawarra region

Carbon dioxide effects research and assessment program. Proceedings of the International Meeting on Stable Isotopes in Tree-Ring Research, New Paltz, New York, May 22-25, 1979

Energy Technology Data Exchange (ETDEWEB)

Jacoby, G [ed.

1980-12-01

Information about the past and present concentrations of CO/sub 2/ in the atmosphere and variations in climate can be obtained from measurements of stable isotopes in tree rings; specifically carbon-13, oxygen-18 and deuterium. The analysis of these stable isotopes in tree rings is a relatively new and rapidly developing field. This proceedings volume contains most of the papers presented at the meeting. The first paper gives an overview of the status of carbon-13 research. Papers relating to carbon-13 are in section I and grouped separately from the contributions on carbon-14. Although the meeting was primarily concerned with stable isotopes, all carbon isotopic analysis may be helpful in understanding the carbon-13 record in tree rings. The papers on hydrogen and oxygen isotope studies are in sections II and III respectively. The remaining sections contain papers that consider more than one isotope at a time, general topics related to isotopes, atmospheric changes and tree growth, and methods of isotopic analysis.

Isotopic tools for protecting the seas

International Nuclear Information System (INIS)

Kinley, D. III

2006-01-01

The oceans and seas are our greatest natural resource, providing us with much of the food we eat and the air we breathe. More than US $900 billion per year of the world's economy is directly tied to ocean-based activities such as fishing, coastal tourism and shipping, and the oceans and seas contribute greatly to the broad ecological balance of our planet. Yet numerous human activities are mounting a growing threat to the health and sustainability of the marine environment. Coral reefs around the world are suffering a rapid decline. Fish stocks are increasingly overexploited, and some unsustainable commercial fish farming is destroying marine habitats. Pollution of the ocean is extensive and, in some cases, irreversible. And our greatest guarantee against global warming - the ocean's vast ability to act as a carbon sink - may be seriously undermined. Protection of the oceans and seas against further deterioration requires scientific investigation to better understand and manage the principal processes. It is here that the use of radionuclides and stable isotopes, which have been used for about 50 years as investigative tools, comes into its own. They have been used to study environmental processes, fate of contaminants in ecosystems, atmosphere-ocean interactions, surface and groundwater systems and the response of atmospheric, hydrological and marine systems to climate change. Coastal zones, supporting about 60% of the global population, require special attention because of their contribution to the world's food supply and their sensitivity to pollution. Nuclear and isotopic techniques provide tools for addressing on a quantitative basis the problems of coastal zone management, including investigation of contamination, groundwater - seawater interactions and other adverse impacts such as salt-water intrusion. One of the most important parameters in determining the climate on Earth is the temperature record of the ocean. It is believed that surface seawater

Stable isotope measurement techniques for atmospheric greenhouse gases

International Nuclear Information System (INIS)

2002-01-01

The technical requirements to perform useful measurements of atmospheric greenhouse gas concentrations and of their isotope ratios are of direct relevance for all laboratories engaged in this field. A meaningful interpretation of isotopes in global models on sources and sinks of CO 2 and other greenhouse gases depends on strict laboratory protocols and data quality control measures ensuring comparable data in time and space. Only with this precondition met, the isotope techniques can serve as a potentially powerful method for reducing uncertainties in the global CO 2 budgets and for tracing pathways and interaction of terrestrial, oceanic, and atmospheric pools of carbon. This publication provides four contributions describing methods for the determination of the isotopic composition of trace gases in atmospheric air and in ice cores. These contributions have been indexed separately

UV-laser microdissection system - A novel approach for the preparation of high-resolution stable isotope records (δ13C/δ18O) from tree rings

Science.gov (United States)

Schollaen, Karina; Helle, Gerhard

2013-04-01

Intra-annual stable isotope (δ13C and δ18O) studies of tree rings at various incremental resolutions have been attempting to extract valuable seasonal climatic and environmental information or assessing plant ecophysiological processes. For preparing high-resolution isotope samples normally wood segments or cores are mechanically divided in radial direction or cut in tangential direction. After mechanical dissection, wood samples are ground to a fine powder and either cellulose is extracted or bulk wood samples are analyzed. Here, we present a novel approach for the preparation of high-resolution stable isotope records from tree rings using an UV-laser microdissection system. Firstly, tree-ring cellulose is directly extracted from wholewood cross-sections largely leaving the wood anatomical structure intact and saving time as compared to the classical procedure. Secondly, micro-samples from cellulose cross-sections are dissected with an UV-Laser dissection microscope. Tissues of interest from cellulose cross-sections are identified and marked precisely with a screen-pen and dissected via an UV-laser beam. Dissected cellulose segments were automatically collected in capsules and are prepared for stable isotope (δ13C and δ18O) analysis. The new techniques facilitate inter- and intra-annual isotope analysis on tree-ring and open various possibilities for comparisons with wood anatomy in plant eco-physiological studies. We describe the design and the handling of this novel methodology and discuss advantages and constraints given by the example of intra-annual oxygen isotope analysis on tropical trees.

Sea-level records from the U.S. mid-Atlantic constrain Laurentide Ice Sheet extent during Marine Isotope Stage 3.

Science.gov (United States)

Pico, T; Creveling, J R; Mitrovica, J X

2017-05-30

The U.S. mid-Atlantic sea-level record is sensitive to the history of the Laurentide Ice Sheet as the coastline lies along the ice sheet's peripheral bulge. However, paleo sea-level markers on the present-day shoreline of Virginia and North Carolina dated to Marine Isotope Stage (MIS) 3, from 50 to 35 ka, are surprisingly high for this glacial interval, and remain unexplained by previous models of ice age adjustment or other local (for example, tectonic) effects. Here, we reconcile this sea-level record using a revised model of glacial isostatic adjustment characterized by a peak global mean sea level during MIS 3 of approximately -40 m, and far less ice volume within the eastern sector of the Laurentide Ice Sheet than traditional reconstructions for this interval. We conclude that the Laurentide Ice Sheet experienced a phase of very rapid growth in the 15 kyr leading into the Last Glacial Maximum, thus highlighting the potential of mid-field sea-level records to constrain areal extent of ice cover during glacial intervals with sparse geological observables.

Oxygen isotope variability in snow from western Dronning Maud Land, Antarctica and its relation to temperature

International Nuclear Information System (INIS)

Helsen, M.M.; Wal, R.S.W. van de; Broeke, M.R. van den; As, D. van; Reijmer, C.H.; Meijer, H.A.J.

2005-01-01

This paper presents (delta) 18 O records from snow pits from four locations in Dronning Maud Land, Antarctica that contain at least four annual cycles. The aim of the study was to analyse in detail these records as well as the prevailing temperatures during accumulation in order to infer to what extent isotopic composition in this area can be interpreted as temperature information. The original seasonal amplitudes of the isotope records were reconstructed by use of a simple back-diffusion model. Automatic weather station data were used to describe the accumulation history and the near-surface temperatures; the temperatures at the atmospheric level of snow formation were inferred from a regional climate model. The results show that the strongly intermittent nature of the accumulation in this area can result in the exclusion of entire seasons from the isotope records. The temperature records also reveal that the oxygen isotope records in these snow pits are biased towards higher temperatures, since snowfall conditions are associated with higher temperatures. This effect is greatest at low temperatures. A comparison between the seasonal extreme isotopic and temperature values points out that on timescales of seasons to several years, isotopic variability cannot be interpreted with confidence as temperature changes at the accumulation sites

The first steps of isotope hydrology

International Nuclear Information System (INIS)

Moser, H.

1995-01-01

The author narrated on his personal experience of the past forty years of the development of isotope hydrology as an independent scientific branch. He started with the basic research work of for example Dansgaard and Libby and went on to the recent world-wide recording and interpreting isotopic data network. The IAEA organisation has accompanied the scientific development in an exemplary manner and, thus brought forward the isotope hydrological research activities to the high standard reached presently. This is documented by the great number of publications promoted by the IAEA throughout this time. 4 figs, 24 refs

Hafnium isotope stratigraphy of ferromanganese crusts

Science.gov (United States)

Lee; Halliday; Hein; Burton; Christensen; Gunther

1999-08-13

A Cenozoic record of hafnium isotopic compositions of central Pacific deep water has been obtained from two ferromanganese crusts. The crusts are separated by more than 3000 kilometers but display similar secular variations. Significant fluctuations in hafnium isotopic composition occurred in the Eocene and Oligocene, possibly related to direct advection from the Indian and Atlantic oceans. Hafnium isotopic compositions have remained approximately uniform for the past 20 million years, probably reflecting increased isolation of the central Pacific. The mechanisms responsible for the increase in (87)Sr/(86)Sr in seawater through the Cenozoic apparently had no effect on central Pacific deep-water hafnium.

Sr-Pb-Nd isotopic evidence that both MORB and OIB sources contribute to oceanic island arc magmas in Fiji

International Nuclear Information System (INIS)

Gill, J.B.

1984-01-01

Twenty-eight new Pb, 20 Sr, and 9 Nd isotopic compositions are presented for 32 rocks and one galena from Fiji and the South Fiji (back-arc) Basin. The Fijian rocks range in age from 35 to 143 Nd/ 144 Nd and low 206 Pb/ 204 Pb). Nearly constant 207 Pb/ 204 Pb, and an OIB source component lying within the conventional Sr-Nd-Pb mantle array. In later calc-alkaline and shoshonitic series rocks, these same trace element and isotopic ratios are more like those of OIB. The change was not accompanied by an increase in 207 Pb/ 204 Pb or Cs/K, indeed, 207 Pb/ 204 Pb is closer to the mantle array in these later series. Consequently, the change indicates a greater contribution from OIB sources, rather than from recycled ocean crust. These interpretations require that both MORB and OIB sources coexist in the uppermost mantle above subducted lithosphere. (orig./WB)

Sub-annual North Pacific hydroclimate variability since 1450AD from updated St. Elias ice core isotope and accumulation rate records

Science.gov (United States)

Kreutz, K. J.; Campbell, S. W.; Winski, D.; Osterberg, E. C.; Kochtitzky, W. H.; Copland, L.; Dixon, D.; Introne, D.; Medrzycka, D.; Main, B.; Bernsen, S.; Wake, C. P.

2017-12-01

A growing array of high-resolution paleoclimate records from the terrestrial region bordering the Gulf of Alaska (GoA) continues to reveal details about ocean-atmosphere variability in the region during the Common Era. Ice core records from high-elevation ranges in proximity to the GoA provide key information on extratropical hydroclimate, and potential teleconnections to low latitude regions. In particular, stable water isotope and snow accumulation reconstructions from ice cores collected in high precipitation locations are uniquely tied to regional water cycle changes. Here we present new data collected in 2016 and 2017 from the St. Elias Mountains (Eclipse Icefield, Yukon Territories, Canada), including a range of ice core and geophysical measurements. Low- and high-frequency ice penetrating radar data enable detailed mapping of icefield bedrock topography and internal reflector stratigraphy. The 1911 Katmai eruption layer can be clearly traced across the icefield, and tied definitively to the coeval ash layer found in the 345 meter ice core drilled at Eclipse Icefield in 2002. High-resolution radar data are used to map spatial variability in 2015/16 and 2016/17 snow accumulation. Ice velocity data from repeat GPS stake measurements and remote sensing feature tracking reveal a clear divide flow regime on the icefield. Shallow firn/ice cores (20 meters in 2017 and 65 meters in 2016) are used to update the 345 meter ice core drilled at Eclipse Icefield in 2002. We use new algorithm-based layer counting software to improve and provide error estimates on the new ice core chronology, which extends from 2017 to 1450AD. 3D finite element modeling, incorporating all available geophysical data, is used to refine the reconstructed accumulation rate record and account for vertical and horizontal ice flow. Together with high-resolution stable water isotope data, the updated Eclipse record provides detailed, sub-annual resolution data on several aspects of the regional

GEOCHEMICAL AND ISOTOPIC INVESTIGATION OF LAKES IN THE TRENTO PROVINCE (ITALY

Directory of Open Access Journals (Sweden)

Marco Natale

2013-09-01

Full Text Available We present the geochemical composition and the stable isotope signature (18O/16O and 2H/1H of waters sampled from six lakes (Caldonazzo, Levico, Lases, Santa Colomba, Lamar and Santo located in the Province of Trento. The chemical compositions invariably revealed a HCO3-Ca hydrochemical facies; however slight differences were observed among the lakes, in relation to the lithologies distinguishing each lakes’drainage basin. Elemental ratios and in particular the Rb/Sr provide a discriminative tool to recognize the rocks that have been weathered; for example this ratio is high in water that interacted with volcanic ignimbrites (rhyolites, and low in rocks that interacted with carbonate rocks. Many other trace elements were analyzed, thus providing baseline data, and only arsenic displayed concentrations higher than the legislative threshold defined for drinking water (10mg/l, especially in Lake Levico (10-19 mg/l. As concerns the stable isotopes δD and δ18O, the obtained results approach the meteoric signature for waters sampled during the 2012 winter season. The waters sampled during two summers (2011 and 2012 displayed distinctive trends, reflecting the significant influence of evaporative processes. We emphasize that the annual differences recorded in the isotopic composition of distinct years are plausibly related to temperature changes and type of precipitation that recharged the lakes. In this light, the peculiar isotopic signature recorded in the year 2011 is possibly related to a significant snowy period, which greatly contributed to the lakes’ water budget. Interestingly, waters from Lake Santa Colomba were systematically different from all the other samples, possibly due to more effective evaporative processes, or to the involvement of deep underground recharge including fossil waters.

What controls the stable isotope composition of precipitation in the Mekong Delta? A model-based statistical approach

Directory of Open Access Journals (Sweden)

N. Le Duy

2018-02-01

Full Text Available This study analyzes the influence of local and regional climatic factors on the stable isotopic composition of rainfall in the Vietnamese Mekong Delta (VMD as part of the Asian monsoon region. It is based on 1.5 years of weekly rainfall samples. In the first step, the isotopic composition of the samples is analyzed by local meteoric water lines (LMWLs and single-factor linear correlations. Additionally, the contribution of several regional and local factors is quantified by multiple linear regression (MLR of all possible factor combinations and by relative importance analysis. This approach is novel for the interpretation of isotopic records and enables an objective quantification of the explained variance in isotopic records for individual factors. In this study, the local factors are extracted from local climate records, while the regional factors are derived from atmospheric backward trajectories of water particles. The regional factors, i.e., precipitation, temperature, relative humidity and the length of backward trajectories, are combined with equivalent local climatic parameters to explain the response variables δ18O, δ2H, and d-excess of precipitation at the station of measurement. The results indicate that (i MLR can better explain the isotopic variation in precipitation (R2  =  0.8 compared to single-factor linear regression (R2  =  0.3; (ii the isotopic variation in precipitation is controlled dominantly by regional moisture regimes (∼ 70 % compared to local climatic conditions (∼ 30 %; (iii the most important climatic parameter during the rainy season is the precipitation amount along the trajectories of air mass movement; (iv the influence of local precipitation amount and temperature is not significant during the rainy season, unlike the regional precipitation amount effect; (v secondary fractionation processes (e.g., sub-cloud evaporation can be identified through the d-excess and take

Water and carbon stable isotope records from natural archives: a new database and interactive online platform for data browsing, visualizing and downloading

Science.gov (United States)

Bolliet, Timothé; Brockmann, Patrick; Masson-Delmotte, Valérie; Bassinot, Franck; Daux, Valérie; Genty, Dominique; Landais, Amaelle; Lavrieux, Marlène; Michel, Elisabeth; Ortega, Pablo; Risi, Camille; Roche, Didier M.; Vimeux, Françoise; Waelbroeck, Claire

2016-08-01

Past climate is an important benchmark to assess the ability of climate models to simulate key processes and feedbacks. Numerous proxy records exist for stable isotopes of water and/or carbon, which are also implemented inside the components of a growing number of Earth system model. Model-data comparisons can help to constrain the uncertainties associated with transfer functions. This motivates the need of producing a comprehensive compilation of different proxy sources. We have put together a global database of proxy records of oxygen (δ18O), hydrogen (δD) and carbon (δ13C) stable isotopes from different archives: ocean and lake sediments, corals, ice cores, speleothems and tree-ring cellulose. Source records were obtained from the georeferenced open access PANGAEA and NOAA libraries, complemented by additional data obtained from a literature survey. About 3000 source records were screened for chronological information and temporal resolution of proxy records. Altogether, this database consists of hundreds of dated δ18O, δ13C and δD records in a standardized simple text format, complemented with a metadata Excel catalog. A quality control flag was implemented to describe age markers and inform on chronological uncertainty. This compilation effort highlights the need to homogenize and structure the format of datasets and chronological information as well as enhance the distribution of published datasets that are currently highly fragmented and scattered. We also provide an online portal based on the records included in this database with an intuitive and interactive platform (http://climateproxiesfinder.ipsl.fr/), allowing one to easily select, visualize and download subsets of the homogeneously formatted records that constitute this database, following a choice of search criteria, and to upload new datasets. In the last part, we illustrate the type of application allowed by our database by comparing several key periods highly investigated by the

Triple nitrate isotopes indicate differing nitrate source contributions to streams across a nitrogen saturation gradient

Science.gov (United States)

Lucy A. Rose; Emily M. Elliott; Mary Beth. Adams

2015-01-01

Nitrogen (N) deposition affects forest biogeochemical cycles worldwide, often contributing to N saturation. Using long-term (>30-year) records of stream nitrate (NO3-) concentrations at Fernow Experimental Forest (West Virginia, USA), we classified four watersheds into N saturation stages ranging from Stage 0 (N-...

Oxygen isotope variations in phosphate of biogenic apatites. Pt.1

International Nuclear Information System (INIS)

Kolodny, Y.; Luz, B.; Navon, O.

1983-01-01

The major advantage of the oxygen in phosphate isotope paleothermometry is that it is a system which records temperatures with great sensitivity while bone (and teeth) building organisms are alive, and the record is nearly perfectly preserved after death. Fish from seven water bodies of different temperatures (3-23 0 C) and different delta 18 O (values - 16 to + 3) of the water were analysed. The delta 18 O values of the analysed PO 4 vary from 6 to 25. The system passed the following tests: (a) the temperature deduced from isotopic analyses of the sequence of fish from Lake Baikal are in good agreement with the temperatures measured in the thermally stratified lake; (b) the isotopic composition of fish bone phosphate is not influenced by the isotopic composition of the phosphate which is fed to the fish, but only by temperature and water composition. Isotopic analysis of fossil fish in combination with analysis of mammal bones should be a useful tool in deciphering continental paleoclimates. (orig.)

Exploring the isotopic niche: isotopic variance, physiological incorporation, and the temporal dynamics of foraging

Directory of Open Access Journals (Sweden)

Justin Douglas Yeakel

2016-01-01

Full Text Available Consumer foraging behaviors are dynamic, changing in response to prey availability, seasonality, competition, and even the consumer's physiological state. The isotopic composition of a consumer is a product of these factors as well as the isotopic `landscape' of its prey, i.e. the isotopic mixing space. Stable isotope mixing models are used to back-calculate the most likely proportional contribution of a set of prey to a consumer's diet based on their respective isotopic distributions, however they are disconnected from ecological process. Here we build a mechanistic framework that links the ecological and physiological processes of an individual consumer to the isotopic distribution that describes its diet, and ultimately to the isotopic composition of its own tissues, defined as its `isotopic niche’. By coupling these processes, we systematically investigate under what conditions the isotopic niche of a consumer changes as a function of both the geometric properties of its mixing space and foraging strategies that may be static or dynamic over time. Results of our derivations reveal general insight into the conditions impacting isotopic niche width as a function of consumer specialization on prey, as well as the consumer's ability to transition between diets over time. We show analytically that moderate specialization on isotopically unique prey can serve to maximize a consumer's isotopic niche width, while temporally dynamic diets will tend to result in peak isotopic variance during dietary transitions. We demonstrate the relevance of our theoretical findings by examining a marine system composed of nine invertebrate species commonly consumed by sea otters. In general, our analytical framework highlights the complex interplay of mixing space geometry and consumer dietary behavior in driving expansion and contraction of the isotopic niche. Because this approach is established on ecological mechanism, it is well-suited for enhancing the

Environmental forcing of terrestrial carbon isotope excursion amplification across five Eocene hyperthermals

Science.gov (United States)

Bowen, G. J.; Abels, H.

2015-12-01

Abrupt changes in the isotope composition of exogenic carbon pools accompany many major episodes of global change in the geologic record. The global expression of this change in substrates that reflect multiple carbon pools provides important evidence that many events reflect persistent, global redistribution of carbon between reduced and oxidized stocks. As the diversity of records documenting any event grows, however, discrepancies in the expression of carbon isotope change among substrates are almost always revealed. These differences in magnitude, pace, and pattern of change can complicate interpretations of global carbon redistribution, but under ideal circumstances can also provide additional information on changes in specific environmental and biogeochemical systems that accompanied the global events. Here we evaluate possible environmental influences on new terrestrial records of the negative carbon isotope excursions (CIEs) associated with multiple hyperthermals of the Early Eocene, which show a common pattern of amplified carbon isotope change in terrestrial paleosol carbonate records relative to that recorded in marine substrates. Scaling relationships between climate and carbon-cycle proxies suggest that that the climatic (temperature) impact of each event scaled proportionally with the magnitude of its marine CIE, likely implying that all events involved release of reduced carbon with a similar isotopic composition. Amplification of the terrestrial CIEs, however, does not scale with event magnitude, being proportionally less for the first, largest event (the PETM). We conduct a sensitivity test of a coupled plant-soil carbon isotope model to identify conditions that could account for the observed CIE scaling. At least two possibilities consistent with independent lines of evidence emerge: first, varying effects of pCO2 change on photosynthetic carbon isotope discrimination under changing background pCO2, and second, contrasting changes in regional

An Ontology for Musical Phonographic Records: Contributing with a Representation Model

Science.gov (United States)

de Oliveira Albuquerque, Marcelo; Siqueira, Sean Wolfgand M.; de Saldanha da G. Lanzelotte, Rosana; Braz, Maria Helena L. B.

Music is a complex domain with some interesting specificities that makes it difficult to be modeled. If different types of music are considered, then the difficulties are even bigger. This paper presents some of the characteristics that makes music such a hard domain to model and proposes an ontology for representing musical phonographic records. This ontology will provide a global representation that can be used to support systems interoperability and data integration, which provides disseminating music worldwide, contributing to culture in the knowledge society.

Normalization of oxygen and hydrogen isotope data

Science.gov (United States)

Coplen, T.B.

1988-01-01

To resolve confusion due to expression of isotopic data from different laboratories on non-corresponding scales, oxygen isotope analyses of all substances can be expressed relative to VSMOW or VPDB (Vienna Peedee belemnite) on scales normalized such that the ??18O of SLAP is -55.5% relative to VSMOW. H3+ contribution in hydrogen isotope ratio analysis can be easily determined using two gaseous reference samples that differ greatly in deuterium content. ?? 1988.

Deglacial Western Equatorial Pacific pCO2 Reconstruction Using Boron Isotopes of Planktonic Foraminiferas

Science.gov (United States)

Kubota, K.; Yokoyama, Y.; Ishikawa, T.; Sagawa, T.; Ikehara, M.; Yamazaki, T.

2017-12-01

During the last deglaciation (ca. 19 - 11 ka), partial pressure of CO2 (pCO2) of the atmosphere increased by 80 μatm. Many paleoceanographers point out that the ocean had played an important role in atmospheric CO2 rise, since the ocean have 60 times larger capacity to store carbon compared to the atmosphere. However, evidence on where carbon was transferred from the ocean to the atmosphere is still lacking, hampering our understanding of global carbon cycles in glacial-interglacial timescales. Boron isotope of skeletons of marine calcifying organisms such as corals and foraminiferas can pin down where CO2 source/sink existed, because boron isotopes of marine calcium carbonates is dependent on seawater pH, from which pCO2 of the past seawater can be reconstructed. In previous studies using the boron isotope teqnique, Martinez-Boti et al. (2015, Nature) and Kubota et al. (2014, Scientific Reports) revealed that central and eastern parts of the equatorial Pacific acted as a CO2 source (i.e., CO2 emission) during the last deglaciation, suggesting the equatorial Pacific's contribution to atmospheric CO2 rise. However, some conflicting results have been confirmed in a marine sediment record from the western part of the equatorial Pacific (Palmer & Pearson, 2003, Science), making the conclusion elusive. In this presentation, we will show new results of Mg/Ca, oxygen isotope, and boron isotope measurements during the last 35 ka on two species of surface dwelling foraminiferas (Globigerinoides ruber and G. sacculifer) which was hand-picked separatedly from a well-dated marine sediment core recovered from the West Caroline Basin (KR05-15 PC01) (Yamazaki et al., 2008, GRL). From the new records, we will discuss how the equatorial Pacific behaved during the last deglaciation and how it related to the global carbon cycles.

On the Use of Biomineral Oxygen Isotope Data to Identify Human Migrants in the Archaeological Record: Intra-Sample Variation, Statistical Methods and Geographical Considerations.

Directory of Open Access Journals (Sweden)

Emma Lightfoot

Full Text Available Oxygen isotope analysis of archaeological skeletal remains is an increasingly popular tool to study past human migrations. It is based on the assumption that human body chemistry preserves the δ18O of precipitation in such a way as to be a useful technique for identifying migrants and, potentially, their homelands. In this study, the first such global survey, we draw on published human tooth enamel and bone bioapatite data to explore the validity of using oxygen isotope analyses to identify migrants in the archaeological record. We use human δ18O results to show that there are large variations in human oxygen isotope values within a population sample. This may relate to physiological factors influencing the preservation of the primary isotope signal, or due to human activities (such as brewing, boiling, stewing, differential access to water sources and so on causing variation in ingested water and food isotope values. We compare the number of outliers identified using various statistical methods. We determine that the most appropriate method for identifying migrants is dependent on the data but is likely to be the IQR or median absolute deviation from the median under most archaeological circumstances. Finally, through a spatial assessment of the dataset, we show that the degree of overlap in human isotope values from different locations across Europe is such that identifying individuals' homelands on the basis of oxygen isotope analysis alone is not possible for the regions analysed to date. Oxygen isotope analysis is a valid method for identifying first-generation migrants from an archaeological site when used appropriately, however it is difficult to identify migrants using statistical methods for a sample size of less than c. 25 individuals. In the absence of local previous analyses, each sample should be treated as an individual dataset and statistical techniques can be used to identify migrants, but in most cases pinpointing a specific

Determination of fission gas yields from isotope ratios

DEFF Research Database (Denmark)

Mogensen, Mogens Bjerg

1983-01-01

This paper describes a method of calculating the actual fission yield of Kr and Xe in nuclear fuel including the effect of neutron capture reactions and decay. The bases for this calculation are the cumulative yields (ref. 1) of Kr and Xe isotopes (or pairs of isotopes) which are unaffected...... by neutron capture reactions, and measured Kr and Xe isotope ratios. Also the burnup contribution from the different fissile heavy isotopes must be known in order to get accurate fission gas yields....

Time-resolved record of 236U and 239,240Pu isotopes from a coral growing during the nuclear testing program at Enewetak Atoll (Marshall Islands).

Science.gov (United States)

Froehlich, M B; Chan, W Y; Tims, S G; Fallon, S J; Fifield, L K

2016-12-01

A comprehensive series of nuclear tests were carried out by the United States at Enewetak Atoll in the Marshall Islands, especially between 1952 and 1958. A Porites Lutea coral that was growing in the Enewetak lagoon within a few km of all of the high-yield tests contains a continuous record of isotopes, which are of interest (e.g. 14 C, 236 U, 239,240 Pu) through the testing period. Prior to the present work, 14 C measurements at ∼2-month resolution had shown pronounced peaks in the Δ 14 C data that coincided with the times at which tests were conducted. Here we report measurements of 236 U and 239,240 Pu on the same coral using accelerator mass spectrometry, and again find prominent peaks in the concentrations of these isotopes that closely follow those in 14 C. Consistent with the 14 C data, the magnitudes of these peaks do not, however, correlate well with the explosive yields of the corresponding tests, indicating that smaller tests probably contributed disproportionately to the debris that fell in the lagoon. Additional information about the different tests can also be obtained from the 236 U/ 239 Pu and 240 Pu/ 239 Pu ratios, which are found to vary dramatically over the testing period. In particular, the first thermonuclear test, Ivy-Mike, has characteristic 236 U/ 239 Pu and 240 Pu/ 239 Pu signatures which are diagnostic of the first arrival of nuclear test material in various archives. Copyright © 2016 Elsevier Ltd. All rights reserved.

High-resolution conodont oxygen isotope record of Ordovician climate change

Science.gov (United States)

Chen, J.; Chen, Z.; Algeo, T. J.

2013-12-01

The Ordovician Period was characterized by several major events, including a prolonged 'super greenhouse' during the Early Ordovician, the 'Great Ordovician Biodiversification Event (GOBE)' of the Middle and early Late Ordovician, and the Hirnantian ice age and mass extinction of the latest Ordovician (Webby et al., 2004, The Great Ordovician Biodiversification Event, Columbia University Press). The cause of the rapid diversification of marine invertebrates during the GOBE is not clear, however, and several scenarios have been proposed including widespread development of shallow cratonic seas, strong magmatic and tectonic activity, and climate moderation. In order to investigate relationships between climate change and marine ecosystem evolution during the Ordovician, we measured the oxygen isotopic composition of single coniform conodonts using a Cameca secondary ion mass spectrometer. Our δ18O profile shows a shift at the Early/Middle Ordovician transition that is indicative of a rapid 6 to 8 °C cooling. This cooling event marks the termination of the Early Ordovician 'super greenhouse' and may have established cooler tropical seawater temperatures that were more favorable for invertebrate animals, setting the stage for the GOBE. Additional cooling episodes occurred during the early Sandbian, early Katian, and Hirnantian, the last culminating in a short-lived (extinction. Our results differ from those of Trotter et al. (2008, 'Did cooling oceans trigger Ordovician biodiversification? Evidence from conodont thermometry,' Science 321:550-554). Instead of a slow, protracted cooling through the Early and Middle Ordovician, our high-resolution record shows that cooling occurred in several discrete steps, with the largest step being at the Early/Middle Ordovician transition.

Canada's isotope crisis : what next?

International Nuclear Information System (INIS)

Nathwani, J.; Wallace, D.

2010-01-01

Canada urgently requires a rigorous debate on the strategic options for ensuring a robust, reliable, and affordable supply of radioactive isotopes. Should the debate be confined to how Canada can best develop the necessary technologies solely for our own use or should Canada abandon the idea of producing its own isotope supply and any future aspirations to serve the global market? Canada's Isotope Crisis focuses on the central policy question: do we dare to try to shape the future or do we retreat into silence because we are not prepared to make the necessary investments for the future well-being of Canadians? This volume showcases pointed essays and analysis from members of the academy and individuals who have made contributions to the development of medical isotopes and pioneered their use in medical practice. It also includes commentary from those involved in the production, manufacturing, processing, and distribution of isotopes. Canada's Isotope Crisis is a multi-disciplinary effort that addresses the global dimension of isotope supply and combines expert opinions on the present and past with knowledge of the relevant government agencies and the basis for their decisions at critical junctures.

Rare earth element and neodymium isotope tracing of element input and past ocean circulation. Study from north and south pacific seawater and sediments

Energy Technology Data Exchange (ETDEWEB)

Froellje, Henning

2016-08-09

incorporation of NADW contribute to the changes in the Nd isotope signature of CDW. The absence of such early deglacial Nd isotope changes in the northernmost core were attributed to the isolation of this core from bottom waters by South Pacific bathymetry with potential contribution from shifts in the Southern Ocean's frontal system and potential influence of increased deglacial NPDW convection. Overall the results highlight the important role of glacial deep stratification in sustaining a deep glacial carbon reservoir in the Southern Ocean and the importance of Southern Hemisphere climate to the breakdown of deep stratification and the release of sequestered CO{sub 2} through upwelling. A 140,000 year long Nd isotope record from the Southeast Pacific covering the last glacial-interglacial cycle demonstrates comparable deep water mass mixing in the South Pacific during the last two glacial maxima, but higher NADW contributions during the glacial Marine Isotope Stage (MIS) 4 (chapter 4). Likewise, the penultimate interglacial (MIS 5) was characterised by similar amounts of NADW and NPDW in CDW as the Holocene and the modern Southeast Pacific. Comparison of the last two glacial terminations thus shows high consistency and suggests similar mechanisms that controlled the deglacial change in water mass structure in the deep South Pacific, including a Southern Ocean contribution to early deglacial Nd isotope shifts. The results show weaker absolute glacial-interglacial Nd isotope changes compared to the South Atlantic due to the lack of direct NADW and slightly higher NPDW influence in the Southeast Pacific. Further, the Nd isotope record confirms the glacial-interglacial variability in NADW and NPDW mixture in CDW obtained previously from carbon isotope records.

Rare earth element and neodymium isotope tracing of element input and past ocean circulation. Study from north and south pacific seawater and sediments

International Nuclear Information System (INIS)

Froellje, Henning

2016-01-01

incorporation of NADW contribute to the changes in the Nd isotope signature of CDW. The absence of such early deglacial Nd isotope changes in the northernmost core were attributed to the isolation of this core from bottom waters by South Pacific bathymetry with potential contribution from shifts in the Southern Ocean's frontal system and potential influence of increased deglacial NPDW convection. Overall the results highlight the important role of glacial deep stratification in sustaining a deep glacial carbon reservoir in the Southern Ocean and the importance of Southern Hemisphere climate to the breakdown of deep stratification and the release of sequestered CO_2 through upwelling. A 140,000 year long Nd isotope record from the Southeast Pacific covering the last glacial-interglacial cycle demonstrates comparable deep water mass mixing in the South Pacific during the last two glacial maxima, but higher NADW contributions during the glacial Marine Isotope Stage (MIS) 4 (chapter 4). Likewise, the penultimate interglacial (MIS 5) was characterised by similar amounts of NADW and NPDW in CDW as the Holocene and the modern Southeast Pacific. Comparison of the last two glacial terminations thus shows high consistency and suggests similar mechanisms that controlled the deglacial change in water mass structure in the deep South Pacific, including a Southern Ocean contribution to early deglacial Nd isotope shifts. The results show weaker absolute glacial-interglacial Nd isotope changes compared to the South Atlantic due to the lack of direct NADW and slightly higher NPDW influence in the Southeast Pacific. Further, the Nd isotope record confirms the glacial-interglacial variability in NADW and NPDW mixture in CDW obtained previously from carbon isotope records.

Modeling the carbon isotope composition of bivalve shells (Invited)

Science.gov (United States)

Romanek, C.

2010-12-01

The stable carbon isotope composition of bivalve shells is a valuable archive of paleobiological and paleoenvironmental information. Previous work has shown that the carbon isotope composition of the shell is related to the carbon isotope composition of dissolved inorganic carbon (DIC) in the ambient water in which a bivalve lives, as well as metabolic carbon derived from bivalve respiration. The contribution of metabolic carbon varies among organisms, but it is generally thought to be relatively low (e.g., 90%) in the shells from terrestrial organisms. Because metabolic carbon contains significantly more C-12 than DIC, negative excursions from the expected environmental (DIC) signal are interpreted to reflect an increased contribution of metabolic carbon in the shell. This observation contrasts sharply with modeled carbon isotope compositions for shell layers deposited from the inner extrapallial fluid (EPF). Previous studies have shown that growth lines within the inner shell layer of bivalves are produced during periods of anaerobiosis when acidic metabolic byproducts (e.g., succinic acid) are neutralized (or buffered) by shell dissolution. This requires the pH of EPF to decrease below ambient levels (~7.5) until a state of undersaturation is achieved that promotes shell dissolution. This condition may occur when aquatic bivalves are subjected to external stressors originating from ecological (predation) or environmental (exposure to atm; low dissolved oxygen; contaminant release) pressures; normal physiological processes will restore the pH of EPF when the pressure is removed. As a consequence of this process, a temporal window should also exist in EPF at relatively low pH where shell carbonate is deposited at a reduced saturation state and precipitation rate. For example, EPF chemistry should remain slightly supersaturated with respect to aragonite given a drop of one pH unit (6.5), but under closed conditions, equilibrium carbon isotope fractionation

Contribution to the future prospects of laser separation of uranium isotopes

International Nuclear Information System (INIS)

Becker, F.S.

1981-04-01

In the past several years, the selective absorption of laser light has been considered as an alternative to the large-scale technical uranium isotope separation schemes based on the mass-dependence of the diffusion velocity or the centrifugal force. An analysis of the published results appears to show that two-frequency multiphoton dissociation is especially attractive for a technical process. To clarify the prospects of such a scheme, studies of the isotope selectivity of the multiphoton dissociation of statically cooled UF 6 with two infrared frequencies, one of which is tunable in the region of the UF 6 ν(3) band at 16 μm, are proposed. The construction and testing of a high-power laser, tunable in the 16 μm region, based on the frequency conversion of 10 μm CO 2 radiation by means of stimulated rotational Raman scattering in para-hydrogen, is described. Pulse-widths of about 80 nsec and pulse energies of about one half J are obtained which ought to permit, in combination with a CO 2 laser, the multiphoton dissociation of UF 6 without focussing. By means of UV-light experiments it is shown that optical dissociation of UF 6 can be obtained even in the presence of high F-concentrations, thus permitting a high dissociation yield without a F-scavenger which could negatively affect the isotope selectivity. (orig./HP) [de

Deep circulation changes in the South Atlantic since the Last Glacial Maximum from Nd isotope and multi-proxy records

Science.gov (United States)

Wei, R.; Abouchami, W.; Zahn, R.; Masque, P.

2016-01-01

We report down-core sedimentary Nd isotope (εNd) records from two South Atlantic sediment cores, MD02-2594 and GeoB3603-2, located on the western South African continental margin. The core sites are positioned downstream of the present-day flow path of North Atlantic Deep Water (NADW) and close to the Southern Ocean, which makes them suitable for reconstructing past variability in NADW circulation over the last glacial cycle. The Fe-Mn leachates εNd records show a coherent decreasing trend from glacial radiogenic values towards less radiogenic values during the Holocene. This trend is confirmed by εNd in fish debris and mixed planktonic foraminifera, albeit with an offset during the Holocene to lower values relative to the leachates, matching the present-day composition of NADW in the Cape Basin. We interpret the εNd changes as reflecting the glacial shoaling of Southern Ocean waters to shallower depths combined with the admixing of southward flowing Northern Component Water (NCW). A compilation of Atlantic εNd records reveals increasing radiogenic isotope signatures towards the south and with increasing depth. This signal is most prominent during the Last Glacial Maximum (LGM) and of similar amplitude across the Atlantic basin, suggesting continuous deep water production in the North Atlantic and export to the South Atlantic and the Southern Ocean. The amplitude of the εNd change from the LGM to Holocene is largest in the southernmost cores, implying a greater sensitivity to the deglacial strengthening of NADW at these sites. This signal impacted most prominently the South Atlantic deep and bottom water layers that were particularly deprived of NCW during the LGM. The εNd variations correlate with changes in 231Pa/230Th ratios and benthic δ13C across the deglacial transition. Together with the contrasting 231Pa/230Th: εNd pattern of the North and South Atlantic, this indicates a progressive reorganization of the AMOC to full strength during the Holocene.

Biomarker and stable carbon isotopic signatures for 100–200 year sediment record in the Chaihe catchment in southwest China

International Nuclear Information System (INIS)

Wang, Yanhua; Yang, Hao; Zhang, Jixiang; Xu, Meina; Wu, Changbin

2015-01-01

Natural inputs and anthropogenic influences on lakes and their catchments are reflected in the sediment record. In the present study, the extractable organic compounds from sediments in the Chaihe catchment of the Dianchi watershed were analyzed to characterize source inputs. Results show that the sediments are dominated by odd numbered n-alkanes (n-C 16 –n-C 33 ), maximizing at n-C 17 , n-C 29 and n-C 31 . Aliphatic hydrocarbon may be composed of terrestrial plants and bacteria. The values of δ 13 C 27 , δ 13 C 29 and δ 13 C 31 of n-alkanes exhibit a range from − 33.27‰ to − 25.46‰, from − 35.76‰ to − 28.47‰ and from − 33.67‰ to − 27.42‰, respectively and three records strongly covary with depth, falling within the range of C 3 plants in the study area. An isotopic model revealed C 3 plant contribution to sedimentary organic matter (OM) ranging from 40.75% to 97.22%. The values of ACL 27–33 , CPI 27–33 , OEP, Paq, Pr/Ph, (C 27 + C 29 )/2C 31 , (C 21 + C 23 + C 25 )/3C 17 and nC 26 − /nC 27 + are consistent with the C 3 plant predominance. A constant CRS model gave the accumulation rates ranging from 2.69 to 8.46 mm a −1 spanning 1885–2010. It was concluded that OM transport in the Chaihe catchment was influenced strongly by human activities resulting in enhanced eutrophication. - Highlights: • Strong predominance of odd-numbered n-alkanes maximized at n-C 17 , n-C 29 and n-C 31 • Sedimentary OM in the Chaihe catchment was deduced mainly from C 3 plants. • Human activities enhanced OM transport, resulting in worse ecosystem

Pharmaceuticals labelled with stable isotopes

International Nuclear Information System (INIS)

Krumbiegel, P.

1986-11-01

The relatively new field of pharmaceuticals labelled with stable isotopes is reviewed. Scientific, juridical, and ethical questions are discussed concerning the application of these pharmaceuticals in human medicine. 13 C, 15 N, and 2 H are the stable isotopes mainly utilized in metabolic function tests. Methodical contributions are given to the application of 2 H, 13 C, and 15 N pharmaceuticals showing new aspects and different states of development in the field under discussion. (author)

Investigating C4 Grass Contributions to N-alkane Based Paleoclimate Reconstructions

Science.gov (United States)

Doman, C. E.; Enders, S. K.; Chadwick, O.; Freeman, K. H.

2014-12-01

Plant wax n-alkanes are long-chain, saturated hydrocarbons contained within the protective waxy cuticle on leaves. These lipids are pervasive and persistent in soils and sediments and thus are ideal biomarkers of ancient terrestrial organic matter. In ecosystems dominated by C3 plants, the relationship between the carbon isotopic value of whole leaves and lipids is fairly well documented, but this relationship has not been fully investigated for plants that use C4 photosynthesis. In both cases, it is unclear if the isotopic relationships are sensitive to environmental conditions, or reflect inherited characteristics. This study used a natural climate gradient on the Kohala peninsula of Hawaii to investigate relationships between climate and the δ13C and δ2H values of n-alkanes in C3 and C4 plants. δ13C of C3 leaves and lipids decreased 5 ‰ from the driest to the wettest sites, consistent with published data. Carbon isotope values of C4 plants showed no relationship to moisture up to 1000 mm mean annual precipitation (MAP). Above this threshold, δ 13C values were around 10‰ more depleted, likely due to a combination of canopy effects and C4 grasses growing in an uncharacteristically wet and cold environment. In C3 plants, the fractionation between leaf and lipid carbon isotopes did not vary with MAP, which allows estimations of δ13C leaf to be made from alkanes preserved in ancient sediments. Along this transect, C3 plants produce around twice the quantity of n-alkanes as C4 grasses. C4 grasses produce longer carbon chains. As a result, n-alkanes in the geologic record will be biased towards C3 plants, but the presence of alkanes C33 and C35 indicate the contributions of C4 grasses. In both C3 and C4 plants, average chain length increased with mean annual precipitation, but the taxonomic differences in chain length were greater than environmental differences. Hydrogen isotopes of n-alkanes show no trends with MAP, but do show clear differences between plant

Autotrophic fixation of geogenic CO2 by microorganisms contributes to soil organic matter formation and alters isotope signatures in a wetland mofette

DEFF Research Database (Denmark)

Beulig, Felix

2015-01-01

of radiocarbon and enriched in 13C compared to atmospheric CO2. Together, these isotopic signals allow us to distinguish C fixed by plants from C fixed by autotrophic microorganisms using their differences in 13C discrimination. We can then estimate that up to 27 % of soil organic matter in the 0–10 cm layer...... geogenic CO2 was fixed by plants or by CO2 assimilating microorganisms, we first used the proportional differences in radiocarbon and δ13C values to indicate the magnitude of discrimination of the stable isotopes in living plants. Deviation from this relationship was taken to indicate the presence...... can recycle significant amounts of carbon in wetland soils and might contribute to observed radiocarbon reservoir effects influencing Δ14C signatures in peat deposits....

Isotope tracers in global water and climate studies of the past and present

International Nuclear Information System (INIS)

Edwards, T.W.D.; Birks, S.J.; Gibson, J.J.

2002-01-01

To date the global distribution of isotopes in modern precipitation has been characterized almost exclusively from the IAEA/WMO GNIP database, although patchiness of GNIP station records in both time and space has limited the potential of isotope hydrology and climate applications in some areas. Herein, we discuss the prospect of utilizing GCMs for simulating global isotope distributions as a supplementary tool for modern and paleoclimate isotope studies to bridge this gap. Such models currently generate reliable zonal isotope fields, and it is anticipated that future enhancements in finescale resolution of GCMs, and incorporation of land-surface feedbacks and topography will allow for future development of a global reanalysis data set ground-truthed by GNIP. Compilation of time-slice maps of past isotope distribution in precipitation from archival records of meteoric waters also offers significant potential to ground-truth paleoclimate simulations extending back tens to hundreds of thousands of years. (author)

Climate variability from isotope records in precipitation

International Nuclear Information System (INIS)

Grassl, H.; Latif, M.; Schotterer, U.; Gourcy, L.

2002-01-01

Selected time series from the Global Network for Isotopes in Precipitation (GNIP) revealed a close relationship to climate variability phenomena like El Nino - Southern Oscillation (ENSO) or the North Atlantic Oscillation (NAO) although the precipitation anomaly in the case studies of Manaus (Brazil) and Groningen (The Netherlands) is rather weak. For a sound understanding of this relationship especially in the case of Manaus, the data should include major events like the 1997/98 El Nino, however, the time series are interrupted frequently or important stations are even closed. Improvements are only possible if existing key stations and new ones (placed at 'hot spots' derived from model experiments) are supported continuously. A close link of GNIP to important scientific programmes like CLIVAR, the Climate Variability and Predictability Programme seems to be indispensable for a successful continuation. (author)

Isotopic tools for protecting the seas

International Nuclear Information System (INIS)

Verlini, G.; Osvath I.; Razmjoo, M.

2009-09-01

The oceans and seas are our greatest natural resource, providing us with much of the food we eat and the air we breathe. More than US $900 billion per year of the world's economy is directly tied to ocean-based activities such as fishing, coastal tourism and shipping, and the oceans and seas contribute greatly to the broad ecological balance of our planet. Yet numerous human activities are mounting a growing threat to the health and sustainability of the marine environment. Coral reefs around the world are suffering a rapid decline. Fish stocks are increasingly overexploited, and some unsustainable commercial fish farming is destroying marine habitats. Pollution of the ocean is extensive and, in many cases, irreversible. And our greatest guarantee against global warming - the ocean's vast ability to act as a carbon sink - may be seriously undermined. Protection of the oceans and seas against further deterioration requires scientific investigation to better understand and manage the principal processes. It is here that the use of radionuclides and stable isotopes, which have been used for about 50 years as investigative tools, comes into its own. They have been used to study environmental processes, the fate of contaminants in ecosystems, atmosphere-ocean interactions, surface and groundwater systems and the response of atmospheric, hydrological and marine systems to climate change. Coastal zones, supporting about 60% of the global population, require special attention because of their contribution to the world's food supply and their sensitivity to pollution. Nuclear and isotopic techniques provide tools for addressing on a quantitative basis the problems of coastal zone management, including investigation of contamination, groundwater-seawater interactions and other adverse impacts such as salt-water intrusion. One of the most important parameters in determining the climate on Earth is the temperature record of the ocean. It is believed that surface seawater

Iron isotope fractionation during pyrite formation in a sulfidic Precambrian ocean analogue

Science.gov (United States)

Rolison, John M.; Stirling, Claudine H.; Middag, Rob; Gault-Ringold, Melanie; George, Ejin; Rijkenberg, Micha J. A.

2018-04-01

The chemical response of the Precambrian oceans to rising atmospheric O2 levels remains controversial. The iron isotope signature of sedimentary pyrite is widely used to trace the microbial and redox states of the ocean, yet the iron isotope fractionation accompanying pyrite formation in nature is difficult to constrain due to the complexity of the pyrite formation process, difficulties in translating the iron isotope systematics of experimental studies to natural settings, and insufficient iron isotope datasets for natural euxinic (i.e. anoxic and sulfidic) marine basins where pyrite formation occurs. Herein we demonstrate, that a large, permil-level shift in the isotope composition of dissolved iron occurs in the Black Sea euxinic water column during syngenetic pyrite formation. Specifically, iron removal to syngenetic pyrite gives rise to an iron isotope fractionation factor between Fe(II) and FeS2 of 2.75 permil (‰), the largest yet reported for reactions under natural conditions that do not involve iron redox chemistry. These iron isotope systematics offer the potential to generate permil-level shifts in the sedimentary pyrite iron isotope record due to partial drawdown of the oceanic iron inventory. The implication is that the iron stable isotope signatures of sedimentary pyrites may record fundamental regime shifts between pyrite formation under sulfur-limited conditions and pyrite formation under iron-limited conditions. To this end, the iron isotope signatures of sedimentary pyrite may best represent the extent of euxinia in the past global ocean, rather than its oxygenation state. On this basis, the reinterpreted sedimentary pyrite Fe isotope record suggests a fundamental shift towards more sulfidic oceanic conditions coincident with the 'Great Oxidation Event' around 2.3 billion years ago. Importantly, this does not require the chemical state of the ocean to shift from mainly de-oxygenated to predominantly oxygenated in parallel with the permanent rise

Isotopes in environmental studies - Aquatic Forum 2004. Proceedings of an international conference. Unedited papers

International Nuclear Information System (INIS)

2006-01-01

A better understanding of key processes in the aquatic environment, responsible for its future development and its protection, were at the forefront of the IAEA's International Conference on Isotopes in Environmental Studies - AQUATIC FORUM 2004 convened in Monaco from 25 to 29 October 2004, which was the most important gathering of the year of isotope environmental scientists. Over 320 experts from 60 IAEA Member States and 6 international organizations delivered 185 oral presentations in 6 plenary and 31 parallel sessions and made 130 poster presentations. The conference reviewed the present state of the art isotopic methods for investigation of the aquatic environment. The main conference subjects considered were: (i) behaviour, transport and distribution of isotopes in the aquatic environment; (ii) climate change studies using isotopic records in the marine environment; (iii) groundwater dynamics, modelling and management of freshwater sources; (iv) important global projects, such as WOCE, WOMARS, SHOTS, GEOTRACES; (v) joint IAEA-UNESCO submarine groundwater investigations in the Mediterranean Sea, the Southwest Atlantic and Pacific Oceans; (vi) new trends in radioecological investigations, concentrating on the protection of marine biota against radioactive contamination; (vii) transfers in analytical technologies from bulk analyses to particle and compound specific analyses of environmental samples; (viii) development of new isotopic techniques, such as AMS and ICPMS, and their successful applications in environmental studies; and many other exciting topics which were presented and discussed during the Conference. Four workshops were held simultaneously: - ATOMS-Med Workshop - development of a project proposal for oceanographic investigations in the Eastern Mediterranean. - El Nino - Research Co-ordination Meeting of the new IAEA Coordinated Research Project investigating climate change using isotopic records in the marine environment. - CELLAR Workshop

Oxygen isotopes of marine mollusc shells record Eocene elevation change in the Pyrenees

Science.gov (United States)

Huyghe, Damien; Mouthereau, Frédéric; Emmanuel, Laurent

2012-09-01

Constraining paleoaltimetry of collisional orogens is critical to understand the dynamics of topographic evolution and climate/tectonics retroactions. Here, we use oxygen stable-isotope record on oyster shells, preserved in marine foreland deposits, to examine the past elevation of the Pyrenees during the Eocene. Our approach is based on the comparison with the Paris basin, an intracratonic basin not influenced by orogenic growth. The finding of a shift of 1.5‰ between 49 and 41 Ma, indicating more negative δ18Oc in the south Pyrenean foreland, is interpreted to reflect the inflow of river water sourced from higher elevation in the Pyrenees. To test this and provide paleoelevation estimate, we adopt a morphologic-hydrological model accounting for the hypsometry of drainage basin. Our best fitting model shows that the Pyrenees rose up to 2000 m. This indicates that the Pyrenees reached high elevation in the Eocene, thus providing new critical constraints on their long-term orogenic development. δ18O of marine mollusc shells are proved potentially attractive for paleoelevation studies, especially for mountain belts where elevated continental surfaces have not been preserved.

Reconstruction of historical atmospheric Pb using Dutch urban lake sediments: A Pb isotope study

Energy Technology Data Exchange (ETDEWEB)

Walraven, N., E-mail: n.walraven@geoconnect.nl [GeoConnect, Meester Dekkerstraat 4, 1901 PV Castricum (Netherlands); Os, B.J.H. van, E-mail: b.vanos@rce.nl [Rijksdienst voor Archeologie, Cultuurlandschap en Monumenten, P.O. Box 1600, 3800 BP Amersfoort (Netherlands); Klaver, G.Th., E-mail: g.klaver@brgm.nl [BRGM, 3 avenue Claude-Guillemin, BP 36009, 45060 Orléans Cedex 2 (France); Middelburg, J.J., E-mail: j.b.m.middelburg@uu.nl [University Utrecht, Faculty of Geosciences, P.O. Box 80021, 3508 TA Utrecht (Netherlands); Davies, G.R., E-mail: g.r.davies@vu.nl [VU University Amsterdam, Faculty of Earth and Life Sciences, Petrology, De Boelelaan 1085, 1081 HV Amsterdam (Netherlands)

2014-06-01

Lake sediments provide a record of atmospheric Pb deposition and changes in Pb isotope composition. To our knowledge, such an approach has not previously been performed in The Netherlands or linked to national air monitoring data. Results are presented for Pb content and isotope composition of {sup 137}Cs dated lake sediments from 2 Dutch urban lakes. Between 1942 and 2002 A.D. anthropogenic atmospheric Pb deposition rates in the two lakes varied from 12 ± 2 to 69 ± 16 μg cm{sup −2} year{sup −1}. The rise and fall of leaded gasoline is clearly reflected in the reconstructed atmospheric Pb deposition rates. After the ban on leaded gasoline, late 1970s/early 1980s, atmospheric Pb deposition rates decreased rapidly in the two urban lakes and the relative contributions of other anthropogenic Pb sources — incinerator ash (industrial Pb) and coal/galena — increased sharply. Atmospheric Pb deposition rates inferred from the lake record a clear relationship with nearby measured annual mean air Pb concentrations. Based on this relationship it was estimated that air Pb concentrations between 1942 and 2002 A.D. varied between 5 and 293 ng/m{sup 3}. - Highlights: • Sixty years of atmospheric Pb was reconstructed using urban lake sediments. • Stable Pb isotopes were applied to determine Pb sources in urban lakes. • The rise and fall of leaded gasoline is clearly reflected in the lake sediments. • Other dominant anthropogenic Pb sources are incinerator ash and coal/galena. • The lake Pb record shows a clear relationship with measured air Pb concentrations.

The production of cosmogenic isotopes in the earth's atmosphere and their inventories

International Nuclear Information System (INIS)

O'Brien, K.; de la Zerda Lerner, A.; Shea. M.A.; Smart, D.F.

1991-01-01

In this paper, production rates of cosmogenic isotopes in the Earth's atmosphere and their dependence on solar modulation and geomagnetic field intensity are calculated. Spallation cross sections were also obtained using the Silberberg-Tsao equations and solar modulation effects were calculated using the force-field model. The current geomagnetic field is treated in detail, and past magnetic fields are modeled based on the archeomagnetic record. Radiocarbon and radioberyllium inventories so obtained are in good agreement with current values. The neutrino-emitting radioactivity of the Earth's atmosphere is shown to add a negligible contribution to the flux from the Sun

Water stable isotopes: application to the water cycle and climate variations study

International Nuclear Information System (INIS)

Risi, C.

2009-12-01

The stable isotopic composition of water (H 2 16 , HDO, H 2 18 , H 2 17 ) is a promising tracer of the present day water cycle and past climates. While the isotopic composition recorded in polar ice core have long been used to reconstruct past temperatures, however, what controls the isotopic composition of the tropical precipitation is more complex. The goal of this thesis is thus to better understand the processes that affect the isotopic composition of tropical precipitation and atmospheric water, more particularly in the tropics. Since most of the tropical precipitation arises from atmospheric convection, and most isotopic archives are on land, we focus more particularly on the impact of convective and land surface processes. In turn, what can be learned about convection and land surface processes using isotopic measurements? Can they help constrain their representation in models? At the inter-annual to climate change scale, what information about the tropical climate variability is recorded in isotopic signals observed in archives? First, we investigate the influence of convection on water stable isotopes. We use both (1) numerical modeling, with a hierarchy of models (single column model, two-dimensional model of squall lines, general circulation model) and (2) data analysis, using isotopic data from rain collected in the Sahel during the African Monsoon Multidisciplinary Analysis campaign, at the event and intra-event scales. These studies highlight the strong impact of convection on the precipitation composition, and stress the importance of rain evaporation and convective or meso-scale subsidence in controlling the rain isotopic composition. Convection also plays an important role on isotopic profiles in the upper troposphere-lower stratosphere. Second, we study what information about climatic variability is recorded by water stable isotopes in precipitation. We analyze simulations of present day and past climates with LMDZ, and evaluate to what extent

Using lead isotopes and trace element records from two contrasting Lake Tanganyika sediment cores to assess watershed – Lake exchange

Science.gov (United States)

Odigie, Kingsley; Cohen, A.D.; Swarzenski, Peter W.; Flegal, R

2014-01-01

Lead isotopic and trace element records of two contrasting sediment cores were examined to reconstruct historic, industrial contaminant inputs to Lake Tanganyika, Africa. Observed fluxes of Co, Cu, Mn, Ni, Pb, and Zn in age-dated sediments collected from the lake varied both spatially and temporally over the past two to four centuries. The fluxes of trace elements were lower (up to 10-fold) at a mid-lake site (MC1) than at a nearshore site (LT-98-58), which is directly downstream from the Kahama and Nyasanga River watersheds and adjacent to the relatively pristine Gombe Stream National Park. Trace element fluxes at that nearshore site did not measurably change over the last two centuries (1815–1998), while the distal, mid-lake site exhibited substantial changes in the fluxes of trace elements – likely caused by changes in land use – over that period. For example, the flux of Pb increased by ∼300% from 1871 to 1991. That apparent accelerated weathering and detrital mobilization of lithogenic trace elements was further evidenced by (i) positive correlations (r = 0.77–0.99, p factors (EF operations within the lake’s watershed over the past century. The data also indicate that the mid-lake site is a much more sensitive and useful recorder of environmental changes than the nearshore site. Furthermore, the lead isotopic compositions of sediment at the sites differed spatially, indicating that the Pb (and other trace elements by association) originated from different natural sources at the two locations.

Erosion of the Alps: use of Rb-Sr isotopic data from molassic sediments to identify the ages of the metamorphism recorded by the eroded rocks

International Nuclear Information System (INIS)

Henry, P.; Deloule, E.

1994-01-01

Rb-Sr isotopic data from Oligocene and Miocene peri-alpine molassic sediments allow us to identify the different periods for which the eroded rocks have or have not recorded an alpine metamorphism. The Chattian and the Burdigalian sediments result from the erosion of rocks for which the latest metamorphic event was variscan, while the Stampian, Aquitanian and ''Helvetian'' sediments show evidence for the erosion of rocks which have recorded alpine metamorphic events. The application of this method to old detrital sediments could permit determination of the ages of the tectonic events which occurred in the sediment source regions. (authors). 18 refs., 6 figs

Seasonal Cyclicity in Trace Elements and Stable Isotopes of Modern Horse Enamel.

Science.gov (United States)

de Winter, Niels J; Snoeck, Christophe; Claeys, Philippe

2016-01-01

The study of stable isotopes in fossil bioapatite has yielded useful results and has shown that bioapatites are able to faithfully record paleo-environmental and paleo-climatic parameters from archeological to geological timescales. In an effort to establish new proxies for the study of bioapatites, intra-tooth records of enamel carbonate stable isotope ratios from a modern horse are compared with trace element profiles measured using laboratory micro X-Ray Fluorescence scanning. Using known patterns of tooth eruption and the relationship between stable oxygen isotopes and local temperature seasonality, an age model is constructed that links records from six cheek upper right teeth from the second premolar to the third molar. When plotted on this age model, the trace element ratios from horse tooth enamel show a seasonal pattern with a small shift in phase compared to stable oxygen isotope ratios. While stable oxygen and carbon isotopes in tooth enamel are forced respectively by the state of the hydrological cycle and the animal's diet, we argue that the seasonal signal in trace elements reflects seasonal changes in dust intake and diet of the animal. The latter explanation is in agreement with seasonal changes observed in carbon isotopes of the same teeth. This external forcing of trace element composition in mammal tooth enamel implies that trace element ratios may be used as proxies for seasonal changes in paleo-environment and paleo-diet.

Monitoring Isotopes in Rivers: Creation of the Global Network of Isotopes in Rivers (GNIR). Results of a Coordinated Research Project 2002-2006

International Nuclear Information System (INIS)

2012-03-01

River runoff plays a key role in human development in all societies through the provision of water for agriculture, industry and domestic use. Although the monitoring of water availability and our understanding of the main hydrological processes at the catchment scale are relatively good, many important aspects, especially those related to the interaction of runoff and groundwater, remain poorly understood. Additionally, the impact of human activities - such as the construction of large reservoirs and diversions, and the redirection of rivers to supply drinking water or water for irrigation or hydropower - are highly relevant and, together with the predicted impact of climate change, are likely to heavily impact local water cycles. The effects of such changes include: limited availability of water; changes in flood or drought frequency; changes in water quality, sediment load and groundwater recharge; and biodiversity loss in riparian environments. Additionally, political disputes may result as water resources become affected in terms of availability and/or quality. In most instances, stable isotopes and other water tracers provide a deeper insight into hydrological processes, especially in aspects related to water pathways, interconnections, transport of water and pollutants, and the transit time of water. To explore the contribution of these techniques in more detail, the IAEA has launched a monitoring programme, the Global Network of Isotopes in Rivers (GNIR), aimed at regular analysis of the isotope composition of runoff in large rivers. This isotope monitoring network complements an earlier precipitation network, the Global Network of Isotopes in Precipitation (GNIP). To prepare for GNIR, the IAEA launched a coordinated research project (CRP) called Design Criteria for a Network to Monitor Isotope Compositions of Runoff in Large Rivers. The main aim of the CRP was to develop a scientific rationale and a protocol for the operation of such a network, as well as

Proxies of Tropical Cyclone Isotope Spikes in Precipitation: Landfall Site Selection

Science.gov (United States)

Lawrence, J. R.; Maddocks, R.

2011-12-01

The human experience of climate change is not one of gradual changes in seasonal or yearly changes in temperature or rainfall. Despite that most paleoclimatic reconstructions attempt to provide just such information. Humans experience climate change on much shorter time scales. We remember hurricanes, weeks of drought or overwhelming rainy periods. Tropical cyclones produce very low isotope ratios in both rainfall and in atmospheric water vapor. Thus, climate proxies that potentially record these low isotope ratios offer the most concrete record of climate change to which humans can relate. The oxygen isotopic composition of tropical cyclone rainfall has the potential to be recorded in fresh water carbonate fossil material, cave deposits and corals. The hydrogen isotopic composition of tropical cyclone rainfall has the potential to be recorded in tree ring cellulose and organic matter in fresh water bodies. The Class of carbonate organisms known as Ostracoda form their carapaces very rapidly. Thus fresh water ephemeral ponds in the subtropics are ideal locations for isotopic studies because they commonly are totally dry when tropical cyclones make landfall. The other proxies suffer primarily from a dilution effect. The water from tropical cyclones is mixed with pre-existing water. In cave deposits tropical cyclone rains mix with soil and ground waters. In the near shore coral environment the rain mixes with seawater. For tree rings there are three sources of water: soil water, atmospheric water vapor that exchanges with leaf water and tropical cyclone rain. In lakes because of their large size rainfall runoff mixes with ground water and preexisting water in the lake. A region that shows considerable promise is Texas / Northeast Mexico. In a study of surface waters that developed from the passage of Tropical Storm Allison (2001) in SE Texas both the pond water and Ostracoda that bloomed recorded the low oxygen isotope signal of that storm (Lawrence et al, 2008). In

Upward revision of global fossil fuel methane emissions based on isotope database.

Science.gov (United States)

Schwietzke, Stefan; Sherwood, Owen A; Bruhwiler, Lori M P; Miller, John B; Etiope, Giuseppe; Dlugokencky, Edward J; Michel, Sylvia Englund; Arling, Victoria A; Vaughn, Bruce H; White, James W C; Tans, Pieter P

2016-10-06

Methane has the second-largest global radiative forcing impact of anthropogenic greenhouse gases after carbon dioxide, but our understanding of the global atmospheric methane budget is incomplete. The global fossil fuel industry (production and usage of natural gas, oil and coal) is thought to contribute 15 to 22 per cent of methane emissions to the total atmospheric methane budget. However, questions remain regarding methane emission trends as a result of fossil fuel industrial activity and the contribution to total methane emissions of sources from the fossil fuel industry and from natural geological seepage, which are often co-located. Here we re-evaluate the global methane budget and the contribution of the fossil fuel industry to methane emissions based on long-term global methane and methane carbon isotope records. We compile the largest isotopic methane source signature database so far, including fossil fuel, microbial and biomass-burning methane emission sources. We find that total fossil fuel methane emissions (fossil fuel industry plus natural geological seepage) are not increasing over time, but are 60 to 110 per cent greater than current estimates owing to large revisions in isotope source signatures. We show that this is consistent with the observed global latitudinal methane gradient. After accounting for natural geological methane seepage, we find that methane emissions from natural gas, oil and coal production and their usage are 20 to 60 per cent greater than inventories. Our findings imply a greater potential for the fossil fuel industry to mitigate anthropogenic climate forcing, but we also find that methane emissions from natural gas as a fraction of production have declined from approximately 8 per cent to approximately 2 per cent over the past three decades.

The ruthenium isotopic composition of the oceanic mantle

Science.gov (United States)

Bermingham, K. R.; Walker, R. J.

2017-09-01

The approximately chondritic relative, and comparatively high absolute mantle abundances of the highly siderophile elements (HSE), suggest that their concentrations in the bulk silicate Earth were primarily established during a final ∼0.5 to 1% of ;late accretion; to the mantle, following the cessation of core segregation. Consequently, the isotopic composition of the HSE Ru in the mantle reflects an amalgamation of the isotopic compositions of late accretionary contributions to the silicate portion of the Earth. Among cosmochemical materials, Ru is characterized by considerable mass-independent isotopic variability, making it a powerful genetic tracer of Earth's late accretionary building blocks. To define the Ru isotopic composition of the oceanic mantle, the largest portion of the accessible mantle, we report Ru isotopic data for materials from one Archean and seven Phanerozoic oceanic mantle domains. A sample from a continental lithospheric mantle domain is also examined. All samples have identical Ru isotopic compositions, within analytical uncertainties, indicating that Ru isotopes are well mixed in the oceanic mantle, defining a μ100Ru value of 1.2 ± 7.2 (2SD). The only known meteorites with the same Ru isotopic composition are enstatite chondrites and, when corrected for the effects of cosmic ray exposure, members of the Main Group and sLL subgroup of the IAB iron meteorite complex which have a collective CRE corrected μ100Ru value of 0.9 ± 3.0. This suggests that materials from the region(s) of the solar nebula sampled by these meteorites likely contributed the dominant portion of late accreted materials to Earth's mantle.

Contribution to the isotopic analysis of nitrogen using optical spectrometry; Contribution a l'analyse isotopique de l'azote par spectrometrie optique

Energy Technology Data Exchange (ETDEWEB)

Leicknam, J P [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires

1968-07-01

The possibility of analyzing a gaseous mixture of {sup 14}N{sub 2} and {sup 14}N-{sup 15}N by emission spectrometry is well known. However, for mixtures which are poor in nitrogen 15 (isotopic abundance less than 2 per cent), the methods proposed up till now do not give sufficiently accurate results rapidly. The method of isotopic analysis proposed here only requires a spectrometer of average resolving power; it is even possible, as we have done; to use a spectrograph with a slit replacing the photographic plate, and a photomultiplier; this transformation is very simple to carry out and the signals from the detector can then be received by a recorder. Under these conditions a measurement takes only from three to ten minutes, according to the accuracy required. The light sources are made up of electrode-less discharge lamps, excited by high frequency; the filling conditions are such that the lamps may be prepared in a few minutes, the impurities being sufficiently eliminated for the measurements not to be affected. The choice of the analytical band couple depends on the relative position of the isotopic bands and on the possible presence of traces of these impurities: amongst the transitions in the system C({sup 3}{pi}{sub u}) <-> B({sup 3}{pi}{sub g}), it is the 2 {yields} 0 transition which has the most favorable position for this isotopic analysis. The method is applied to samples of varying origins (ammonium salts, fertilizer and plants): the isotopic contents are determined with an accuracy of 3 per cent in the neighbourhood of the natural abundance, and of 1 per cent when the sample contains about 1.5 atoms of nitrogen-15 for 100 atoms of nitrogen-14. The accuracy is therefore quite sufficient for most of the biological research using the mass 15 as tracer. (author) [French] La possibilite d'analyser un melange gazeux des azotes {sup 14}N{sub 2} et {sup 14}N-{sup 15}N par spectrometrie d'emission est bien connue. Cependant, pour des melanges pauvres en azote

Lessons learned from oxygen isotopes in modern precipitation applied to interpretation of speleothem records of paleoclimate from eastern Asia

Science.gov (United States)

Dayem, Katherine E.; Molnar, Peter; Battisti, David S.; Roe, Gerard H.

2010-06-01

Variability in oxygen isotope ratios collected from speleothems in Chinese caves is often interpreted as a proxy for variability of precipitation, summer precipitation, seasonality of precipitation, and/or the proportion of 18O to 16O of annual total rainfall that is related to a strengthening or weakening of the East Asian monsoon and, in some cases, to the Indian monsoon. We use modern reanalysis and station data to test whether precipitation and temperature variability over China can be related to changes in climate in these distant locales. We find that annual and rainy season precipitation totals in each of central China, south China, and east India have correlation length scales of ∼ 500 km, shorter than the distance between many speleothem records that share similar long-term time variations in δ18O values. Thus the short distances of correlation do not support, though by themselves cannot refute, the idea that apparently synchronous variations in δ18O values at widely spaced (> 500 km) caves in China are due to variations in annual precipitation amounts. We also evaluate connections between climate variables and δ18O values using available instrumental measurements of δ18O values in precipitation. These data, from stations in the Global Network of Isotopes in Precipitation (GNIP), show that monthly δ18O values generally do not correlate well with either local precipitation amount or local temperature, and the degree to which monthly δ18O values do correlate with them varies from station to station. For the few locations that do show significant correlations between δ18O values and precipitation amount, we estimate the differences in precipitation amount that would be required to account for peak-to-peak differences in δ18O values in the speleothems from Hulu and Dongge caves, assuming that δ18O scales with the monthly amount of precipitation or with seasonal differences in precipitation. Insofar as the present-day relationship between δ18O

Isotope angiocardiography. Method and preliminary own studies

Energy Technology Data Exchange (ETDEWEB)

Stepinska, J; Ruzyllo, W; Konieczny, W [Centrum Medyczne Ksztalcenia Podyplomowego, Warsaw (Poland)

1979-01-01

Method of technetium isotope 99 m pass through the heart recording with the aid of radioisotope scanner connected with seriograph and computer is being presented. Preliminary tests were carried out in 26 patients with coronary disease without or with previous myocardial infarction, cardiomyopathy, ventricular septal defect and in patients with artificial mitral and aortic valves. The obtained scans were evaluated qualitatively and compared with performed later contrast X-rays of the heart. Size of the right ventricle, volume and rate of left atrial evacuation, size and contractability of left ventricle were evaluated. Similarity of direct and isotope angiocardiographs, non-invasional character and repeatability of isotope angiocardiography advocate its usefulness.

Stable isotope record in annually laminated lake sediments from Lake Żabińskie (NE Poland) for the last millennium.

Science.gov (United States)

Gabryś, Alicja; Piotrowska, Natalia; Tylmann, Wojciech; Bonk, Alicja; Filipiak, Janusz; Wacnik, Agnieszka; Hernandez-Almeida, Ivan; Grosjean, Martin

2015-04-01

Stable isotope record of carbon (13C) and oxygen (18O) has been analysed from an annually laminated sediment from Lake Zabinskie (Mazurian Lakeland, NE Poland) with high resolution (1-3 yrs). The sediment layers which were formed in each year during the last millennium contain information about environmental changes in the past. The calcite layers are formed in lake sediment in warm months of the year, therefore the reconstruction of summer climate variables in the past is potentially possible. The investigation of correlation between isotope dataset and instrumental climate data for years 1897-2008 AD confirmed that theory. The record of temperature, precipitation and SPEI (Standardised Precipitation Evaporation Index) coefficient, which is a combination of both temperature and precipitation, was tested. The strongest linear correlations were found for most samples for June, July, August (JJA) months but in some cases the correlation coefficient was stronger when also May was taken into account. For the whole 120-yrs series the correlation between δ18O and average JJA temperature is 0.007, average JJA precipitation is 0.16 and average JJA SPEI is 0.20. Analyzing the results for 1897-2008 we can distinguish period 1960-2008 with relevantly stronger correlations: R(temperature) = 0.19, R(precipitation) = 0.20 and R(SPEI) = 0.45. This period is connected with cessation of human activity close to Lake Zabinskie. Reconstruction of climate variables for the last millennium was made using transfer function obtained for calibration period (1897-2008). Reconstructions showed that known climate extremes like Medieval Warm Period, Little Ice Age with Sporer (1420-1570), Maunder (1645-1715) and Dalton (1790-1820) Minimum was recorded in sediment from Lake Zabinskie. The presented study is a part of the project "Climate of northern Poland during the last 1000 years: Constraining the future with the past (CLIMPOL)", funded within Polish-Swiss Research Programme. http://www.climpol.ug.edu.pl

Late Eocene to present isotopic (Sr-Nd-Pb) and geochemical evolution of sediments from the Lomonosov Ridge, Arctic Ocean: Implications for continental sources and linkage with the North Atlantic Ocean

Science.gov (United States)

Stevenson, Ross; Poirier, André; Véron, Alain; Carignan, Jean; Hillaire-Marcel, Claude

2015-09-01

New geochemical and isotopic (Sr, Nd, Pb) data are presented for a composite sedimentary record encompassing the past 50 Ma of history of sedimentation on the Lomonosov Ridge in the Arctic Ocean. The sampled sediments encompass the transition of the Arctic basin from an enclosed anoxic basin to an open and ventilated oxidized ocean basin. The transition from anoxic basin to open ventilated ocean is accompanied by at least three geochemical and isotopic shifts and an increase in elements (e.g., K/Al) controlled by detrital minerals highlighting significant changes in sediment types and sources. The isotopic compositions of the sediments prior to ventilation are more variable but indicate a predominance of older crustal contributions consistent with sources from the Canadian Shield. Following ventilation, the isotopic compositions are more stable and indicate an increased contribution from younger material consistent with Eurasian and Pan-African crustal sources. The waxing and waning of these sources in conjunction with the passage of water through Fram Strait underlines the importance of the exchange of water mass between the Arctic and North Atlantic Oceans.

Carbon and hydrogen isotopic effects of stomatal density in Arabidopsis thaliana

Science.gov (United States)

Lee, Hyejung; Feakins, Sarah J.; Sternberg, Leonel da S. L.

2016-04-01

Stomata are key gateways mediating carbon uptake and water loss from plants. Varied stomatal densities in fossil leaves raise the possibility that isotope effects associated with the openness of exchange may have mediated plant wax biomarker isotopic proxies for paleovegetation and paleoclimate in the geological record. Here we use Arabidopsis thaliana, a widely used model organism, to provide the first controlled tests of stomatal density on carbon and hydrogen isotopic compositions of cuticular waxes. Laboratory grown wildtype and mutants with suppressed and overexpressed stomatal densities allow us to directly test the isotope effects of stomatal densities independent of most other environmental or biological variables. Hydrogen isotope (D/H) measurements of both plant waters and plant wax n-alkanes allow us to directly constrain the isotopic effects of leaf water isotopic enrichment via transpiration and biosynthetic fractionations, which together determine the net fractionation between irrigation water and n-alkane hydrogen isotopic composition. We also measure carbon isotopic fractionations of n-alkanes and bulk leaf tissue associated with different stomatal densities. We find offsets of +15‰ for δD and -3‰ for δ13C for the overexpressed mutant compared to the suppressed mutant. Since the range of stomatal densities expressed is comparable to that found in extant plants and the Cenozoic fossil record, the results allow us to consider the magnitude of isotope effects that may be incurred by these plant adaptive responses. This study highlights the potential of genetic mutants to isolate individual isotope effects and add to our fundamental understanding of how genetics and physiology influence plant biochemicals including plant wax biomarkers.

Pyroxene Homogenization and the Isotopic Systematics of Eucrites

Science.gov (United States)

Nyquist, L. E.; Bogard, D. D.

1996-01-01

The original Mg-Fe zoning of eucritic pyroxenes has in nearly all cases been partly homogenized, an observation that has been combined with other petrographic and compositional criteria to establish a scale of thermal "metamorphism" for eucrites. To evaluate hypotheses explaining development of conditions on the HED parent body (Vesta?) leading to pyroxene homogenization against their chronological implications, it is necessary to know whether pyroxene metamorphism was recorded in the isotopic systems. However, identifying the effects of the thermal metamorphism with specific effects in the isotopic systems has been difficult, due in part to a lack of correlated isotopic and mineralogical studies of the same eucrites. Furthermore, isotopic studies often place high demands on analytical capabilities, resulting in slow growth of the isotopic database. Additionally, some isotopic systems would not respond in a direct and sensitive way to pyroxene homogenization. Nevertheless, sufficient data exist to generalize some observations, and to identify directions of potentially fruitful investigations.

Middle Pleistocene Transition (MPT) in the Eastern Indian Ocean: a 2000 kyr planktic faunal and isotope record from DSDP site 214

International Nuclear Information System (INIS)

Gupta, Anil K.; Dhingra, Hitesh

2004-01-01

Planktic foraminiferal faunal and isotope data from Deep Sea Drilling Project (DSDP) Site 214 reveal a major change in surface water properties in the eastern Indian Ocean, coinciding with the mid-Pleistocene climate transition (MPT). A comparative study of Globigerinoides sacculifer (a surface dwelling, warm water, mixed layer tropical planktic foraminifera), Globorotalia menardii Complex (a deep dwelling, tropical species group), and Orbulina universa (an intermediate depth warm-water subtropical foraminifera) with the stable isotope record of Globigerinoides ruber suggests a warm, thick mixed layer in the eastern Indian Ocean during,∼ 2000 Kyr to ∼ 900 Kyr. Since,∼ 900 Kyr the surface water mass stratification weakened, and the mixed layer as well as thermocline were shallow. A decrease in the population abundance of Gs. sacculifer, together with a decrease in δ 13 C and increase in δ 18 O values suggest a continuous cool climate and increased surface productivity over the last ∼ 900 Kyr. This coincides with an increased variance in the 400 ∼Kyr component of Earth's eccentricity cycle. (author)

Contribution of isotopic data in cerebrospinal fluid (CSF) studies

International Nuclear Information System (INIS)

Askienazy, S.; Ducassou, D.

The growing interest in isotopic CSF studies is explained by the fact that the mechanism and classification of hydrocephalus cases are based not only on anatomoclinical data but also on physiological information inaccessible by static image methods. This article shows the full importance of dynamic CSF research (ideal tracer: 111 In-DTPA); the possibilities of myeloscintigraphy to study the permeability of the medullary sub-arachnoid spaces (tracers used: sup(99m)Tc-DTPA in the liquid phase or xenon bubble technique in the gas phase); ventricular morphology; existence of meningeal gaps [fr

Atmospheric methane isotopic record favors fossil sources flat in 1980s and 1990s with recent increase

Science.gov (United States)

Rice, Andrew L.; Butenhoff, Christopher L.; Teama, Doaa G.; Röger, Florian H.; Khalil, M. Aslam K.; Rasmussen, Reinhold A.

2016-09-01

Observations of atmospheric methane (CH4) since the late 1970s and measurements of CH4 trapped in ice and snow reveal a meteoric rise in concentration during much of the twentieth century. Since 1750, levels of atmospheric CH4 have more than doubled to current globally averaged concentration near 1,800 ppb. During the late 1980s and 1990s, the CH4 growth rate slowed substantially and was near or at zero between 1999 and 2006. There is no scientific consensus on the drivers of this slowdown. Here, we report measurements of the stable isotopic composition of atmospheric CH4 (13C/12C and D/H) from a rare air archive dating from 1977 to 1998. Together with more modern records of isotopic atmospheric CH4, we performed a time-dependent retrieval of methane fluxes spanning 25 y (1984-2009) using a 3D chemical transport model. This inversion results in a 24 [18, 27] Tg y-1 CH4 increase in fugitive fossil fuel emissions since 1984 with most of this growth occurring after year 2000. This result is consistent with some bottom-up emissions inventories but not with recent estimates based on atmospheric ethane. In fact, when forced with decreasing emissions from fossil fuel sources our inversion estimates unreasonably high emissions in other sources. Further, the inversion estimates a decrease in biomass-burning emissions that could explain falling ethane abundance. A range of sensitivity tests suggests that these results are robust.

Isotope methods in hydrology

International Nuclear Information System (INIS)

Moser, H.; Rauert, W.

1980-01-01

Of the investigation methods used in hydrology, tracer methods hold a special place as they are the only ones which give direct insight into the movement and distribution processes taking place in surface and ground waters. Besides the labelling of water with salts and dyes, as in the past, in recent years the use of isotopes in hydrology, in water research and use, in ground-water protection and in hydraulic engineering has increased. This by no means replaces proven methods of hydrological investigation but tends rather to complement and expand them through inter-disciplinary cooperation. The book offers a general introduction to the application of various isotope methods to specific hydrogeological and hydrological problems. The idea is to place the hydrogeologist and the hydrologist in the position to recognize which isotope method will help him solve his particular problem or indeed, make a solution possible at all. He should also be able to recognize what the prerequisites are and what work and expenditure the use of such methods involves. May the book contribute to promoting cooperation between hydrogeologists, hydrologists, hydraulic engineers and isotope specialists, and thus supplement proven methods of investigation in hydrological research and water utilization and protection wherever the use of isotope methods proves to be of advantage. (orig./HP) [de

Seasonal Cyclicity in Trace Elements and Stable Isotopes of Modern Horse Enamel.

Directory of Open Access Journals (Sweden)

Niels J de Winter

Full Text Available The study of stable isotopes in fossil bioapatite has yielded useful results and has shown that bioapatites are able to faithfully record paleo-environmental and paleo-climatic parameters from archeological to geological timescales. In an effort to establish new proxies for the study of bioapatites, intra-tooth records of enamel carbonate stable isotope ratios from a modern horse are compared with trace element profiles measured using laboratory micro X-Ray Fluorescence scanning. Using known patterns of tooth eruption and the relationship between stable oxygen isotopes and local temperature seasonality, an age model is constructed that links records from six cheek upper right teeth from the second premolar to the third molar. When plotted on this age model, the trace element ratios from horse tooth enamel show a seasonal pattern with a small shift in phase compared to stable oxygen isotope ratios. While stable oxygen and carbon isotopes in tooth enamel are forced respectively by the state of the hydrological cycle and the animal's diet, we argue that the seasonal signal in trace elements reflects seasonal changes in dust intake and diet of the animal. The latter explanation is in agreement with seasonal changes observed in carbon isotopes of the same teeth. This external forcing of trace element composition in mammal tooth enamel implies that trace element ratios may be used as proxies for seasonal changes in paleo-environment and paleo-diet.

Isotopic abundances relevant to the identification of magma sources

International Nuclear Information System (INIS)

O'Nions, R.K.

1984-01-01

The behaviour of natural radiogenic isotope tracers in the Earth that have lithophile and atmophile geochemical affinity is reviewed. The isotope tracer signature of oceanic and continental crust may in favourable circumstances by sufficiently distinct from that of the mantle to render a contribution from these sources resolvable within the isotopic composition of the magma. Components derived from the sedimentary and altered basaltic portion of oceanic crust are recognized in some island arc magmas from their Sr, Nd and Pb isotopic signatures. The rare-gas isotope tracers (He, Ar, Xe in particular) are not readily recycled into the mantle and thus provide the basis of an approach that is complementary to that based on the lithophile tracers. In particular, a small mantle-derived helium component may be readily recognized in the presence of a predominant radiogenic component generated in the continents. The importance of assessing the mass balance of these interactions rather than merely a qualitative recognition is emphasized. The question of the relative, contribution of continental-oceanic crust and mantle to magma sources is an essential part of the problem of generation and evolution of continental crust. An approach to this problem through consideration of the isotopic composition of sediments is briefly discussed. (author)

Clumped-isotope geochemistry of carbonates: A new tool for the reconstruction of temperature and oxygen isotope composition of seawater

Energy Technology Data Exchange (ETDEWEB)

Bernasconi, Stefano M., E-mail: Stefano.bernasconi@erdw.ethz.ch [Geological Institute, ETH Zuerich, Sonneggstrasse 5, 8092 Zuerich (Switzerland); Schmid, Thomas W.; Grauel, Anna-Lena [Geological Institute, ETH Zuerich, Sonneggstrasse 5, 8092 Zuerich (Switzerland); Mutterlose, Joerg [Institut fuer Geologie, Mineralogie und Geophysik, Ruhr Universitaet Bochum, Universitaetsstr. 150, 44801 Bochum (Germany)

2011-06-15

Highlights: > Clumped-isotope thermometry of carbonates is discussed. > Clumped isotopes of Belemnites show higher sea surface temperatures than commonly assumed for the lower Cretaceous. > The potential of clumped-isotope measurement on foraminifera is discussed. - Abstract: Clumped-isotope geochemistry deals with State of ordering of rare isotopes in molecules, in particular with their tendency to form bonds with other rare isotopes rather than with the most abundant ones. Among its possible applications, carbonate clumped-isotope thermometry is the one that has gained most attention because of the wide potential of applications in many disciplines of the earth sciences. In particular, it allows reconstructing the temperature of formation of carbonate minerals without knowledge of the isotopic composition of the water from which they were formed. In addition, the O isotope composition of the waters from which they were formed can be calculated using the {delta}{sup 18}O of the same carbonate sample. This feature offers new approaches in paleoclimatology for reconstructing past global geochemical cycles. In this contribution two applications of this method are presented. First the potential of a new analytical method of measurement of clumped isotopes on small samples of foraminifera, for high-resolution SST and seawater {delta}{sup 18}O reconstructions from marine sediments is shown. Furthermore the potential of clumped isotope analysis of belemnites, for reconstructing seawater {delta}{sup 18}O and temperatures in the Cretaceous is shown.

Discriminating assimilants and decoupling deep- vs. shallow-level crystal records at Mount Adams using 238U-230Th disequilibria and Os isotopes

Science.gov (United States)

Jicha, B.R.; Johnson, C.M.; Hildreth, Wes; Beard, B.L.; Hart, G.L.; Shirey, S.B.; Singer, B.S.

2009-01-01

A suite of 23 basaltic to dacitic lavas erupted over the last 350??kyr from the Mount Adams volcanic field has been analyzed for U-Th isotope compositions to evaluate the roles of mantle versus crustal components during magma genesis. All of the lavas have (230Th/238U) > 1 and span a large range in (230Th/232Th) ratios, and most basalts have higher (230Th/232Th) ratios than andesites and dacites. Several of the lavas contain antecrysts (crystals of pre-existing material), yet internal U-Th mineral isochrons from six of seven lavas are indistinguishable from their eruption ages. This indicates a relatively brief period of time between crystal growth and eruption for most of the phenocrysts (olivine, clinopyroxene, plagioclase, magnetite) prior to eruption. One isochron gave a crystallization age that is ~ 20-25??ka older than its corresponding eruptive age, and is interpreted to reflect mixing of older and juvenile crystals or a protracted period of magma storage in the crust. Much of the eruptive volume since 350??ka consists of lavas that have small to moderate 230Th excesses (2-16%), which are likely inherited from melting of a garnet-bearing intraplate ("OIB-like") mantle source. Following melt generation and subsequent migration through the upper mantle, most Mt. Adams magmas interacted with young, mafic lower crust, as indicated by 187Os/188Os ratios that are substantially more radiogenic than the mantle or those expected via mixing of subducted material and the mantle wedge. Moreover, Os-Th isotope variations suggest that unusually large 230Th excesses (25-48%) and high 187Os/188Os ratios in some peripheral lavas reflect assimilation of small degree partial melts of pre-Quaternary basement that had residual garnet or Al-rich clinopyroxene. Despite the isotopic evidence for lower crustal assimilation, these processes are not generally recorded in the erupted phenocrysts, indicating that the crystal record of the deep-level 'cryptic' processes has been

Prospects and Challenges in tropical isotope dendroclimatology

Science.gov (United States)

Evans, M. N.; Anchukaitis, K. J.; White, S. R.; Ektvedt, T. M.; Penniston, R. C.; Rheaume, M. M.; Bowman, D. M.

2008-12-01

We review a stable isotope-based approach to the development, modeling, interpretation, and analysis of hydrometeorological estimates from tropical trees. The strategy overcomes the common problem of missing, intermittent or non-annual ring structure in tropical trees by relying instead on the observation of the annual wet-dry seasonality typical to tropical environments as mirrored in the oxygen isotopic composition of wood-derived α-cellulose. We explore regions for which forward modeling of the proxy system would expect us to resolve hydrometeorological variations associated with the El Niño-Southern Oscillation (ENSO) phenomenon, rather than being limited to regions with tree species or environments producing verifiable annual ring chronologies. A modified protocol allows for rapid, simple and non-toxic micro-extraction of pure α-cellulose, which is isotopically indistinguishable from that produced by more classical means. We describe a new reactor for the pyrolysis of α-cellulose in an induction heater, which permits isotopic analysis of α-cellulose samples as small as 30μg, and as many as 100 automated sample analyses per day. A forward model adapted for tropical environments can be used to test and refine the interpretation of the isotopic data, and to predict locales for which we should be able to maximize the paleoclimatic potential of future sample collections. We have found the modeled isotopic chronometer and raingage in agreement with independent chronological controls in a variety of environments and tree species in Costa Rica, Indonesia, Brazil, Peru and Australia. Development of long hydrometeorological records from the terrestrial tropics is underway not only by our group, but by a growing number of collaborators and colleagues. Together we should be able to build a network of paleoprecipitation records and better understand the linkages between tropical surface ocean temperatures and large-scale drought.

The 2-nd Conference on Isotopic and Molecular Processes. Abstracts

International Nuclear Information System (INIS)

Bogdan, Mircea

2001-01-01

The proceedings of the 2-nd Conference on Isotopic and Molecular Processes held on September 27 - 29, 2001 in Cluj - Napoca, Romania, contains contributions presented as: 11 plenary lectures, 24 oral presentations and 103 posters in two sections, namely, isotopic processes and molecular processes. The main topics treated in this conference were isotope production, separation and enrichment as well as stable isotope applications. Also, studies on isotope effects in different fields are reported. Besides reports on isotope effects, exchange and separation, new methods of preparation and labelling compounds used particularly in nuclear medicine are presented. Environmental studies by means of stable isotope and radon monitoring are described. Applications of radiation effects and different nuclear methods in medicine are also addressed

EVALUATION OF GLACIER MELT CONTRIBUTION TO RUNOFF IN THE NORTH CAUCASUS ALPINE CATCHMENTS USING ISOTOPIC METHODS AND ENERGY BALANCE MODELING

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E. Rets

2017-01-01

Full Text Available Frequency and intensity of river floods rise observed in the North Caucasus during last decades is considered to be driven by recent climate change. In order to predict possible future trends in extreme hydrological events in the context of climate change, it is essential to estimate the contribution of different feed sources in complicated flow-forming processes in the alpine part of the North Caucasus. A study was carried out for the Djankuat River basin, the representative for the North Caucasus system. Simultaneous measurements of electrical conductivity, isotopic and ion balance equations, and energy balance modeling of ice and snow melt were used to evaluate the contribution of different sources and processes in the Djankuat River runoff regime formation. A forecast of possible future changes in the Djankuat glacier melting regime according to the predicted climate changes was done.

Sulfur Isotope Trends in Archean Microbialite Facies Record Early Oxygen Production and Consumption

Science.gov (United States)

Zerkle, A.; Meyer, N.; Izon, G.; Poulton, S.; Farquhar, J.; Claire, M.

2014-12-01

The major and minor sulfur isotope composition (δ34S and Δ33S) of pyrites preserved in ~2.65-2.5 billion-year-old (Ga) microbialites record localized oxygen production and consumption near the mat surface. These trends are preserved in two separate drill cores (GKF01 and BH1-Sacha) transecting the Campbellrand-Malmani carbonate platform (Ghaap Group, Transvaal Supergroup, South Africa; Zerkle et al., 2012; Izon et al., in review). Microbialite pyrites possess positive Δ33S values, plotting parallel to typical Archean trends (with a Δ33S/δ34S slope of ~0.9) but enriched in 34S by ~3 to 7‰. We propose that these 34S-enriched pyrites were formed from a residual pool of sulfide that was partially oxidized via molecular oxygen produced by surface mat-dwelling cyanobacteria. Sulfide, carrying the range of Archean Δ33S values, could have been produced deeper within the microbial mat by the reduction of sulfate and elemental sulfur, then fractionated upon reaction with O2 produced by oxygenic photosynthesis. Preservation of this positive 34S offset requires that: 1) sulfide was only partially (50­­-80%) consumed by oxidation, meaning H2S was locally more abundant (or more rapidly produced) than O2, and 2) the majority of the sulfate produced via oxidation was not immediately reduced to sulfide, implying either that the sulfate pool was much larger than the sulfide pool, or that the sulfate formed near the mat surface was transported and reduced in another part of the system. Contrastingly, older microbialite facies (> 2.7 Ga; Thomazo et al., 2013) appear to lack these observed 34S enrichments. Consequently, the onset of 34S enrichments could mark a shift in mat ecology, from communities dominated by anoxygenic photosynthesizers to cyanobacteria. Here, we test these hypotheses with new spatially resolved mm-scale trends in sulfur isotope measurements from pyritized stromatolites of the Vryburg Formation, sampled in the lower part of the BH1-Sacha core. Millimeter

Bringing organic carbon isotopes and phytoliths to the table as additional constraints on paleoelevation

Science.gov (United States)

Sheldon, N. D.; Cotton, J. M.; Hren, M. T.; Hyland, E. G.; Smith, S. Y.; Strömberg, C. A. E.

2015-12-01

A commonly used tool in paleotectonic and paleoaltimetry studies is the oxygen isotopic composition of authigenic carbonates formed that formed in lakes or soils, with both spatial (e.g., shoreline to mountain top) or temporally resolved records potentially providing constraints. However, in many cases there is a substantial spread in the oxygen isotope data for a given time period, often to the point of allowing for essentially any interpretation of the data depending upon how they have been used by the investigator. One potential way of distinguishing between different potential paleotectonic or paleoaltimetric interpretations is to use carbon isotope and plant microfossil (phytolith) analyses from the same paleosols to screen the oxygen isotope data by looking for evidence of evaporative enrichment. For example, if both inorganic (carbonate) and organic carbon isotopes are measured from the same paleosol, then in it possible to determine if the two isotope record equilibrium conditions or if they record disequilibrium driven by kinetic effects. In the former case, the oxygen isotope results can be considered reliable whereas in the latter case, the oxygen isotope results can be considered unreliable and could be culled from the interpretation. Similarly, because the distribution of C4 plants varies as a function of temperature and elevation, the presence/absence or abundance of C4 plant phytoliths, or of carbon isotope compositions that require a component of C4 vegetation can also be used to constrain paleoelevation by providing a maximum elevation constraint. Worked examples will include the late Miocene-Pliocene of Catamarca, Argentina, where phytoliths and organic carbon isotopes provide a maximum elevation constraint and can be used to demonstrate that oxygen isotopes do not provide a locally useful constraint on paleoelevation, and Eocene-Miocene of southwestern Montana where organic matter and phytoliths can be used to select between different potential

Stable carbon isotope response to oceanic anoxic events

International Nuclear Information System (INIS)

Hu Xiumian; Wang Chengshan; Li Xianghui

2001-01-01

Based on discussion of isotope compositions and fractionation of marine carbonate and organic carbon, the author studies the relationship between oceanic anoxic events and changes in the carbon isotope fractionation of both carbonate and organic matter. During the oceanic anoxic events, a great number of organisms were rapidly buried, which caused a kind of anoxic conditions by their decomposition consuming dissolved oxygen. Since 12 C-rich organism preserved, atmosphere-ocean system will enrich relatively of 13 C. As a result, simultaneous marine carbonate will record the positive excursion of carbon isotope. There is a distinctive δ 13 C excursion during oceanic anoxic events in the world throughout the geological time. In the Cenomanian-Turonian anoxic event. this positive excursion arrived at ∼0.2% of marine carbonate and at ∼0.4% of organic matter, respectively. Variations in the carbon isotopic compositions of marine carbonate and organic carbon record the changes in the fraction of organic carbon buried throughout the geological time and may provide clues to the changes in rates of weathering and burial of organic carbon. This will provide a possibility of interpreting not only the changes in the global carbon cycle throughout the geological time, but also that in atmospheric p CO 2

Water Isotope Proxy-Proxy and Proxy-Model Convergence for Late Pleistocene East Asian Monsoon Rainfall Reconstructions

Science.gov (United States)

Clemens, S. C.; Holbourn, A.; Kubota, Y.; Lee, K. E.; Liu, Z.; Chen, G.

2017-12-01

Confidence in reconstruction of East Asian paleomonsoon rainfall using precipitation isotope proxies is a matter of considerable debate, largely due to the lack of correlation between precipitation amount and isotopic composition in the present climate. We present four new, very highly resolved records spanning the past 300,000 years ( 200 year sample spacing) from IODP Site U1429 in the East China Sea. We demonstrate that all the orbital- and millennial-scale variance in the onshore Yangtze River Valley speleothem δ18O record1 is also embedded in the offshore Site U1429 seawater δ18O record (derived from the planktonic foraminifer Globigerinoides ruber and sea surface temperature reconstructions). Signal replication in these two independent terrestrial and marine archives, both controlled by the same monsoon system, uniquely identifies δ18O of precipitation as the primary driver of the precession-band variance in both records. This proxy-proxy convergence also eliminates a wide array of other drivers that have been called upon as potential contaminants to the precipitation δ18O signal recorded by these proxies. We compare East Asian precipitation isotope proxy records to precipitation amount from a CCSM3 transient climate model simulation of the past 300,000 years using realistic insolation, ice volume, greenhouse gasses, and sea level boundary conditions. This model-proxy comparison suggests that both Yangtze River Valley precipitation isotope proxies (seawater and speleothem δ18O) track changes in summer-monsoon rainfall amount at orbital time scales, as do precipitation isotope records from the Pearl River Valley2 (leaf wax δ2H) and Borneo3 (speleothem δ18O). Notably, these proxy records all have significantly different spectral structure indicating strongly regional rainfall patterns that are also consistent with model results. Transient, isotope-enabled model simulations will be necessary to more thoroughly evaluate these promising results, and to

Temperature evolution and the oxygen isotope composition of Phanerozoic oceans from carbonate clumped isotope thermometry

Science.gov (United States)

Henkes, Gregory A.; Passey, Benjamin H.; Grossman, Ethan L.; Shenton, Brock J.; Yancey, Thomas E.; Pérez-Huerta, Alberto

2018-05-01

Surface temperature is among the most important parameters describing planetary climate and habitability, and yet there remains considerable debate about the temperature evolution of the Earth's oceans during the Phanerozoic Eon (541 million years ago to present), the time during which complex metazoan life radiated on Earth. Here we critically assess the emerging record of Phanerozoic ocean temperatures based on carbonate clumped isotope thermometry of fossil brachiopod and mollusk shells, and we present new data that fill important gaps in the Late Paleozoic record. We evaluate and reject the hypothesis that solid-state reordering of 13C-18O bonds has destroyed the primary clumped isotope temperature signal of most fossils during sedimentary burial at elevated temperatures. The resulting Phanerozoic record, which shows a general coupling between tropical seawater temperatures and atmospheric carbon dioxide (CO2) levels since the Paleozoic, indicates that tropical temperatures during the icehouse climate of the Carboniferous period were broadly similar to present (∼25-30 °C), and suggests that benthic metazoans were able to thrive at temperatures of 35-40 °C during intervals of the early and possibly the latest Paleozoic when CO2 levels were likely 5-10× higher than present-day values. Equally important, there is no resolvable trend in seawater oxygen isotope ratios (δ18 O) over the past ∼500 million years, indicating that the average temperature of oxygen exchange between seawater and the oceanic crust has been high (∼270 °C) since at least the early Paleozoic, which points to mid-ocean ridges as the dominant locus of water-rock interaction over the past half-billion years.

Strontium isotopic stratigraphy utilizing authigenic dolomites in hemipelagic sediments

Energy Technology Data Exchange (ETDEWEB)

Baker, P.A. (Duke Univ., Durham, NC (USA)); Kastner, M. (Scripps Institute of Oceanography, La Jolla, CA (USA)); Elderfield, H. (Univ. of Cambridge (England))

1990-05-01

Authigenic dolomites commonly occur in organic-rich, continental margin marine sediments. These dolomites play a key role in the age dating of stratigraphic sections. The dolomites often are the only lithology amenable to paleomagnetic stratigraphy; they preserve siliceous microfossils against diagenetic; recrystallization, and provide useful strontium isotopic stratigraphic ages. Several potential sources of error frequently are unique to the use of authigenic dolomites in the strontium isotope methods. (1) The dolomites occur as cements of the host lithology, hence, they are not a pure phase. Potentially important contaminants during analysis include gypsum clay minerals, feldspars, and iron and manganese oxides. Strontium may occur as a structural substituent ion in these minerals or as a surface-adsorbed ion. Various leaching techniques have been tested to isolate dolomitic strontium. Purer dolomites and strontium-enriched dolomites often can be selected to ease these problems. (2) The dolomites form after the deposition of the host sediment, therefore, they record the diagenetic age not the depositional age. The stable isotopic composition of the dolomites can aid in selection of early formed samples. (3) The dolomites record pore-water strontium isotope compositions, not seawater isotopic compositions. This problem is also minimized by choosing dolomites formed near the sediment-water interface. (4) The dolomites formed near the sediment-water interface originated as rotodolomites and undergo subsequent burial diagenesis, creating a potential for later strontium isotope exchange. This problem is minimized by selecting fresh samples from the interior of nearly impermeable beds and nodules. Results from the Miocene Monterey Formation of California and from the Eocene through Pliocene Pisco basin of Peru show that authigenic dolomites can provide useful strontium isotopic age estimates.

A new record of the Paleocene Carbon Isotope Maximum from the Mississippi Embayment

Science.gov (United States)

Platt, B. F.; Gerweck, E. D.

2017-12-01

The Paleocene-Eocene interval is well known as a time of climatic transitions, especially hyperthermals associated with disturbances in the carbon cycle that are used as proxies for impacts of projected anthropogenic global climate change. A recent roadcut in Benton County, Mississippi exposes a disconformity between the Paleocene Naheola Formation and the Eocene Meridian Sand. The disconformity is developed on a thick, kaolinitic paleosol, which we interpret as a mature Oxisol that supported tropical rainforest vegetation (as evidenced by associated well preserved leaf fossils). The nature of the paleosol at the disconformity led us to hypothesize that the strata might contain evidence of the Paleocene Eocene Thermal Maximum (PETM). We sampled two Mississippi Mineral Resources Institute (MMRI) cores from the equivalent stratigraphic interval from Benton and Tippah Counties, Mississippi, for bulk organic carbon stable isotopes at 25-cm intervals. Results showed no evidence of the negative excursion characteristic of the PETM. Instead, we found a gradual upsection enrichment that we interpret as the positive trend characteristic of the lower Paleocene Carbon Isotope Maximum (PCIM). This is reasonable based on published biostratigraphy and absolute ages from elsewhere in the Naheola Formation. Further analyses will be performed to determine whether the PCIM trend continues throughout the remainder of the core. The identification of the PCIM in Mississippi Embayment (ME) sediments is important because stable carbon isotope data may be useful for improving chronostratigraphy in the ME. Also, the PCIM is associated with a gradual warming trend as indicated by previously published stable oxygen isotopes from benthic foraminifera. Studying successive ME paleosols throughout the PCIM may yield information about the impacts of gradual atmospheric warming on soils and associated terrestrial systems.

18O, 2H and 3H isotopic composition of precipitation and shallow groundwater in Olkiluoto

International Nuclear Information System (INIS)

Hendriksson, N.; Karhu, J.; Niinikoski, P.

2014-12-01

The isotopic composition of oxygen and hydrogen in local precipitation is a key parameter in the modelling of local water circulation. This study was initiated in order to provide systematic monthly records of the isotope content of atmospheric precipitation in the Olkiluoto area and to establish the relation between local rainfall and newly formed groundwater. During January 2005 - December 2012, a total of 85 cumulative monthly rainfall samples and 68 shallow groundwater samples were collected and the isotopic composition of oxygen and hydrogen was recorded for all those samples. Tritium values are available for 79 precipitation and 65 groundwater samples. Based on the 8-year monitoring, the long-term weighted annual mean isotope values of precipitation and the mean values of shallow groundwater are -11.59 per mille and -11.27 per mille for δ 18 O, - 82.3 per mille and -80.3 per mille for δ 2 H and 9.8 and 9.1 TU for tritium, respectively. Based on these data, the mean stable isotope ratios of groundwater represent the long-term mean annual isotopic composition of local precipitation. The precipitation data were used to establish the local meteoric water line (LMWL) for the Olkiluoto area. The line is formulated as: δ 2 H = 7.45 star δ 18 O + 3.82. The isotope time series reveal a change in time. The increasing trend for the δ 18 O and δ 2 H values may be related to climatic variability while the gradual decline observed in the 3 H data is attributed to the still continuing decrease in atmospheric 3 H activity in the northern hemisphere. The systematic seasonal and long-term tritium trends suggest that any potential ground-level tritium release from the Olkiluoto nuclear power plants is insignificant. The d-excess values of Olkiluoto precipitation during the summer period indicated that a notable amount of re-cycled Baltic Sea water may have contributed to precipitation in the Finnish southern coast. Preliminary estimates of the evaporated Baltic Sea water

Reconstruction of the isotope activity content of heterogeneous nuclear waste drums.

Science.gov (United States)

Krings, Thomas; Mauerhofer, Eric

2012-07-01

Radioactive waste must be characterized in order to verify its conformance with national regulations for intermediate storage or its disposal. Segmented gamma scanning (SGS) is a most widely applied non-destructive analytical technique for the characterization of radioactive waste drums. The isotope specific activity content is generally calculated assuming a homogeneous matrix and activity distribution for each measured drum segment. However, real radioactive waste drums exhibit non-uniform isotope and density distributions most affecting the reliability and accuracy of activities reconstruction in SGS. The presence of internal shielding structures in the waste drum contributes generally to a strong underestimation of the activity and this in particular for radioactive sources emitting low energy gamma-rays independently of their spatial distribution. In this work we present an improved method to quantify the activity of spatially concentrated gamma-emitting isotopes (point sources or hot spots) in heterogeneous waste drums with internal shielding structures. The isotope activity is reconstructed by numerical simulations and fits of the angular dependent count rate distribution recorded during the drum rotation in SGS using an analytical expression derived from a geometric model. First results of the improved method and enhancements of this method are shown and are compared to each other as well as to the conventional method which assumes a homogeneous matrix and activity distribution. It is shown that the new model improves the accuracy and the reliability of the activity reconstruction in SGS and that the presented algorithm is suitable with respect to the framework requirement of industrial application. Copyright © 2011 Elsevier Ltd. All rights reserved.

A 500 year sediment lake record of anthropogenic and natural inputs to Windermere (English Lake District) using double-spike lead isotopes, radiochronology, and sediment microanalysis.

Science.gov (United States)

Miller, Helen; Croudace, Ian W; Bull, Jonathan M; Cotterill, Carol J; Dix, Justin K; Taylor, Rex N

2014-07-01

A high-resolution record of pollution is preserved in recent sediments from Windermere, the largest lake in the English Lake District. Data derived from X-ray core scanning (validated against wavelength dispersive X-ray fluorescence), radiochronological techniques ((210)Pb and (137)Cs) and ultrahigh precision, double-spike mass spectrometry for lead isotopes are combined to decipher the anthropogenic inputs to the lake. The sediment record suggests that while most element concentrations have been stable, there has been a significant increase in lead, zinc, and copper concentrations since the 1930s. Lead isotope down-core variations identify three major contributory sources of anthropogenic (industrial) lead, comprising gasoline lead, coal combustion lead (most likely source is coal-fired steam ships), and lead derived from Carboniferous Pb-Zn mineralization (mining activities). Periods of metal workings do not correlate with peaks in heavy metals due to the trapping efficiency of up-system lakes in the catchment. Heavy metal increases could be due to flood-induced metal inwash after the cessation of mining and the weathering of bedrock in the catchment. The combination of sediment analysis techniques used provides new insights into the pollutant depositional history of Windermere and could be similarly applied to other lake systems to determine the timing and scale of anthropogenic inputs.

A 560 yr summer temperature reconstruction for the Western Mediterranean basin based on stable carbon isotopes from Pinus nigra ssp. laricio (Corsica/France

Directory of Open Access Journals (Sweden)

J. Kuhlemann

2012-10-01

Full Text Available The Mediterranean is considered as an area which will be affected strongly by current climate change. However, temperature records for the past centuries which can contribute to a better understanding of future climate changes are still sparse for this region. Carbon isotope chronologies from tree-rings often mirror temperature history but their application as climate proxies is difficult due to the influence of the anthropogenic change in atmospheric CO2 on the carbon isotope fractionation during photosynthetic CO2 uptake. We tested the influence of different correction models accounting for plant response to increased atmospheric CO2 on four annually resolved long-term carbon isotope records (between 400 and 800 yr derived from Corsican pine trees (Pinus nigra ssp. laricio growing at ecologically varying mountain sites on the island of Corsica. The different correction factors have only a minor influence on the main climate signals and resulting temperature reconstructions. Carbon isotope series show strong correlations with summer temperature and precipitation. A summer temperature reconstruction (1448–2007 AD reveals that the Little Ice Age was characterised by low, but not extremely low temperatures on Corsica. Temperatures have been to modern temperatures at around 1500 AD. The reconstruction reveals warm summers during 1480–1520 and 1950–2007 AD and cool summers during 1580–1620 and 1820–1890 AD.

Radiation-related retrograde hydrogen isotope and K-Ar exchange in clay minerals

International Nuclear Information System (INIS)

Halter, C.; Pagel, M.; Sheppard, S.M.F.; Weber, F.; Clauer, N.

1987-01-01

Hydrogen and oxygen isotope studies have been widely applied to characterize the origin of fluids during ore-foaming processes. The primary isotope record, however, may be disturbed by retrograde exchange reactions, thus complicating the interpretation of the data. The susceptibility of minerals to retrograde isotope and chemical exchange is variable, reflecting differences in the mechanism and rate of isotope exchange. Results are presented on deuterium depletion, K/Ar ages and H 2 O + content of illites associated with uranium mineralization from the Athabasca basin (Canada). (author)

Biomarker and stable carbon isotopic signatures for 100–200 year sediment record in the Chaihe catchment in southwest China

Energy Technology Data Exchange (ETDEWEB)

Wang, Yanhua, E-mail: wangyanhua@njnu.edu.cn [School of Geography Science, Nanjing Normal University, 1 Wenyuan Road, Qixia, Nanjing 210023 (China); Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application (China); Yang, Hao [School of Geography Science, Nanjing Normal University, 1 Wenyuan Road, Qixia, Nanjing 210023 (China); Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application (China); Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control (China); Zhang, Jixiang [College of Economics and Management, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Baixia, Nanjing 210016 (China); Xu, Meina; Wu, Changbin [School of Geography Science, Nanjing Normal University, 1 Wenyuan Road, Qixia, Nanjing 210023 (China)

2015-01-01

Natural inputs and anthropogenic influences on lakes and their catchments are reflected in the sediment record. In the present study, the extractable organic compounds from sediments in the Chaihe catchment of the Dianchi watershed were analyzed to characterize source inputs. Results show that the sediments are dominated by odd numbered n-alkanes (n-C{sub 16}–n-C{sub 33}), maximizing at n-C{sub 17}, n-C{sub 29} and n-C{sub 31}. Aliphatic hydrocarbon may be composed of terrestrial plants and bacteria. The values of δ{sup 13}C{sub 27}, δ{sup 13}C{sub 29} and δ{sup 13}C{sub 31} of n-alkanes exhibit a range from − 33.27‰ to − 25.46‰, from − 35.76‰ to − 28.47‰ and from − 33.67‰ to − 27.42‰, respectively and three records strongly covary with depth, falling within the range of C{sub 3} plants in the study area. An isotopic model revealed C{sub 3} plant contribution to sedimentary organic matter (OM) ranging from 40.75% to 97.22%. The values of ACL{sub 27–33}, CPI{sub 27–33}, OEP, Paq, Pr/Ph, (C{sub 27} + C{sub 29})/2C{sub 31}, (C{sub 21} + C{sub 23} + C{sub 25})/3C{sub 17} and nC{sub 26}{sup −}/nC{sub 27}{sup +} are consistent with the C{sub 3} plant predominance. A constant CRS model gave the accumulation rates ranging from 2.69 to 8.46 mm a{sup −1} spanning 1885–2010. It was concluded that OM transport in the Chaihe catchment was influenced strongly by human activities resulting in enhanced eutrophication. - Highlights: • Strong predominance of odd-numbered n-alkanes maximized at n-C{sub 17}, n-C{sub 29} and n-C{sub 31} • Sedimentary OM in the Chaihe catchment was deduced mainly from C{sub 3} plants. • Human activities enhanced OM transport, resulting in worse ecosystem.

Constraining recent lead pollution sources in the North Pacific using ice core stable lead isotopes

Science.gov (United States)

Gross, B. H.; Kreutz, K. J.; Osterberg, E. C.; McConnell, J. R.; Handley, M.; Wake, C. P.; Yalcin, K.

2012-08-01

Trends and sources of lead (Pb) aerosol pollution in the North Pacific rim of North America from 1850 to 2001 are investigated using a high-resolution (subannual to annual) ice core record recovered from Eclipse Icefield (3017 masl; St. Elias Mountains, Canada). Beginning in the early 1940s, increasing Pb concentration at Eclipse Icefield occurs coevally with anthropogenic Pb deposition in central Greenland, suggesting that North American Pb pollution may have been in part or wholly responsible in both regions. Isotopic ratios (208Pb/207Pb and 206Pb/207Pb) from 1970 to 2001 confirm that a portion of the Pb deposited at Eclipse Icefield is anthropogenic, and that it represents a variable mixture of East Asian (Chinese and Japanese) emissions transported eastward across the Pacific Ocean and a North American component resulting from transient meridional atmospheric flow. Based on comparison with source material Pb isotope ratios, Chinese and North American coal combustion have likely been the primary sources of Eclipse Icefield Pb over the 1970-2001 time period. The Eclipse Icefield Pb isotope composition also implies that the North Pacific mid-troposphere is not directly impacted by transpolar atmospheric flow from Europe. Annually averaged Pb concentrations in the Eclipse Icefield ice core record show no long-term trend during 1970-2001; however, increasing208Pb/207Pb and decreasing 206Pb/207Pb ratios reflect the progressive East Asian industrialization and increase in Asian pollutant outflow. The post-1970 decrease in North American Pb emissions is likely necessary to explain the Eclipse Icefield Pb concentration time series. When compared with low (lichen) and high (Mt. Logan ice core) elevation Pb data, the Eclipse ice core record suggests a gradual increase in pollutant deposition and stronger trans-Pacific Asian contribution with rising elevation in the mountains of the North Pacific rim.

Canada's isotope crisis : what next?

Energy Technology Data Exchange (ETDEWEB)

Nathwani, J.; Wallace, D. (eds.)

2010-07-01

Canada urgently requires a rigorous debate on the strategic options for ensuring a robust, reliable, and affordable supply of radioactive isotopes. Should the debate be confined to how Canada can best develop the necessary technologies solely for our own use or should Canada abandon the idea of producing its own isotope supply and any future aspirations to serve the global market? Canada's Isotope Crisis focuses on the central policy question: do we dare to try to shape the future or do we retreat into silence because we are not prepared to make the necessary investments for the future well-being of Canadians? This volume showcases pointed essays and analysis from members of the academy and individuals who have made contributions to the development of medical isotopes and pioneered their use in medical practice. It also includes commentary from those involved in the production, manufacturing, processing, and distribution of isotopes. Canada's Isotope Crisis is a multi-disciplinary effort that addresses the global dimension of isotope supply and combines expert opinions on the present and past with knowledge of the relevant government agencies and the basis for their decisions at critical junctures.

Noncovalent Hydrogen Isotope Effects

Science.gov (United States)

Buchachenko, A. L.; Breslavskaya, N. N.

2018-02-01

Zero-point energies (ZPE) and isotope effects, induced by intermolecular, noncovalent vibrations, are computed and tested by experimental data. The ZPE differences of H- and D-complexes of water with hydrogen, methane, and water molecules are about 100-300 cal/mol; they result to isotope effects IE of 1.20-1.70. Semi-ionic bonds between metal ions and water ligands in M(H2O) 6 2+ complexes are much stronger; their ZPEs are about 12-14 kcal/mol per molecule and result to IE of 1.9-2.1 at 300 K. Protonated (deuterated) water and biwater exhibit the largest ZPE differences and isotope effects; the latter are 25-28 and 12-13 for water and biwater, respectively. Noncovalent IEs contribute markedly into the experimentally measured effects and explain many anomalous and even magic properties of the effects, such as the dependence of IE on the solvents and on the presence of the third substances, enormously large isotope effects at the mild conditions, the difference between IEs measured in the reactions of individual protiated and deuterated compounds and those measured in their mixture. Noncovalent IEs are not negligible and should be taken into account to make correct and substantiated conclusions on the reaction mechanisms. The kinetic equations are derived for the total isotope effects, which include noncovalent IEs as additive factors.

Isotopic diversity in nebular dust: The distribution of Ti isotopic anomalies in carbonaceous chondrites

International Nuclear Information System (INIS)

Niemeyer, S.

1988-01-01

Average Ti isotopic patterns are derived for each class of carbonaceous chondrite from a chemically characterized suite of whole-rock samples. There is a well-resolved excess of 50 Ti in a subset of CI meteorites. Mean values of the 50 Ti excess for the four classes span a range of only 2 ε-units, with an apparent positive correlation with Al content. Previous evidence for anomalies in chondrules is augmented here by demonstrating that: (1) the more pristine Ca-Al-rich inclusions (CAIs) in Efremovka show the same isotopic pattern as the typical Allende CAI; and, (2) CM and CV matrix carry 50 Ti excesses of about 2 ε-units. The distribution of Ti isotopic anomalies among matrix, chondrules, and CAIs suggests a model in which all three constituents formed from precursor-assemblages in which some chemical memories were still intact; the isotopic differences reflect fractionations among the carrier phases of the different isotopic components. Chondrules formed by a mostly closed-system melting of their precursors, and thus provide a recording of the extent of nebular heterogeneity on the mg-size scale. The larger anomalies in CAIs, compared to matrix and most (but not all) chondrules, are attributed primarily to an open- rather than closed-system processing of the CAI precursors. Precursors of both FUN and normal CAIs experienced an episode of intense processing, perhaps partial melting, that created the FUN characteristics, but for normal CAIs the FUN effects were erased by subsequent isotopic equilibration and exchange

Absolute isotopic abundances of Ti in meteorites

International Nuclear Information System (INIS)

Niederer, F.R.; Papanastassiou, D.A.; Wasserburg, G.J.

1985-01-01

The absolute isotope abundance of Ti has been determined in Ca-Al-rich inclusions from the Allende and Leoville meteorites and in samples of whole meteorites. The absolute Ti isotope abundances differ by a significant mass dependent isotope fractionation transformation from the previously reported abundances, which were normalized for fractionation using 46 Ti/ 48 Ti. Therefore, the absolute compositions define distinct nucleosynthetic components from those previously identified or reflect the existence of significant mass dependent isotope fractionation in nature. We provide a general formalism for determining the possible isotope compositions of the exotic Ti from the measured composition, for different values of isotope fractionation in nature and for different mixing ratios of the exotic and normal components. The absolute Ti and Ca isotopic compositions still support the correlation of 50 Ti and 48 Ca effects in the FUN inclusions and imply contributions from neutron-rich equilibrium or quasi-equilibrium nucleosynthesis. The present identification of endemic effects at 46 Ti, for the absolute composition, implies a shortfall of an explosive-oxygen component or reflects significant isotope fractionation. Additional nucleosynthetic components are required by 47 Ti and 49 Ti effects. Components are also defined in which 48 Ti is enhanced. Results are given and discussed. (author)

Isotope hydrology: applied discipline in earth sciences

International Nuclear Information System (INIS)

Froehlich, K.; Rozanski, K.; Araguas Araguas, L.

1998-01-01

The discipline 'isotope hydrology' is being reviewed from the perspective of the Isotope Hydrology Section of the International Atomic Energy Agency in Vienna. The Section was created in the late fifties and is activities involved int the scientific progress of the discipline. The role of the IAEA in the development of isotope hydrology has always been of a dual nature: on one hand, the Section has been and still is heavily engaged in supporting and coordinating further development of isotope methodologies, on the other hand, it serves as an interface between the methodological development in research institutes and the applied work using proven techniques in field projects on water resources assessment and management. The paper provides a brief overview of applications of isotope-based methodologies in hydrology, with emphasis on new trends and challenges related to man's growing impact on the water cycle. This contribution is a tribute to the memory of the former Head of the Isotope Hydrology Section, Jean-Charles Fontes, to whom we owe so much. (authors)

The Isotopologue Record of Repeat Vital Effect Offenders: Tracking (Dis)equilibrium Effects in Sea Urchins and Nannofossil Using Clumped Isotopes

Science.gov (United States)

John, C. M.; Davies, A.; Drury, A. J.

2016-12-01

Vital effects vary between species and affect various isotopic systems in unequal proportion. The magnitude of the response of different isotopic systems might thus be key in understanding biologically-mediated disequilibrium, especially in groups that show a tendency to be "repeat offenders" with regards to vital effects. Here we present carbon, oxygen, and clumped isotope data from echinoderm calcite and nannofossil ooze, both of which exhibit strong vital effects in bulk isotopes. Our study is the first to investigate the clumped isotope (dis)equilibrium of echinoids. Results from two echinoids, three marine gastropods and a bivalve mollusk from modern beach deposits of Bali, Indonesia, highlight a significant offset in clumped isotopes of a regular echinoid test from expected values, interpreted as evidence of a similar "vital effect" as observed in surface corals. This is in contrast to the test of an irregular "sand dollar" echinoid, with clumped isotope values within error of expected sea surface temperature. Furthermore, data on the inter-skeletal variability in the clumped isotopic composition of two regular echinoid species shows that the spines of the echinoids are in equilibrium with seawater with respect to clumped isotopes, but the test is not. For the nannofossil material, no clumped isotope vital effects are observed, consistent with previously published studies but at odds with strong vital effects in carbon and oxygen isotopes, often correlated with cell-size. In addition, we reveal that the <63 micron fraction of deep-sea ooze could constitute useful material for clumped isotope studies. An intriguing result of our study is that vital effects are mostly absent in clumped isotopes, even in phylums known for important isotopic effects. It remains to be explained why some parts of the echinoids show clear vital effects, notably enrichment in clumped isotopes of urchin tests. Mechanisms that could explain this include pH effects during calcification

Quaternary magnetic excursions recorded in marine sediments.

Science.gov (United States)

Channell, J. E. T.

2017-12-01

This year is the golden (50th) anniversary of the first documentation of a magnetic excursion, the Laschamp excursion in volcanics from the Chaine des Puys (Bonhommet and Babkine, 1967). The first recording of an excursion in sediments was from the Blake Outer Ridge (Smith and Foster, 1969). Magnetic excursions are directional aberrations of the geomagnetic field apparently involving short-lived reversal of the main dipole field. They have durations of a few kyrs, and are therefore rarely recorded in sediments with mean sedimentation rates Palma), and 670 ka (Osaka Bay), implying at least 11 excursions in the Brunhes Chron. For the Matuyama Chron, excursions have been recorded in marine sediments at 868 ka (Kamikatsura?), 932 ka (Santa Rosa), 1051 ka (Intra-Jaramillo), 1115 ka (Punaruu), 1255 ka (Bjorn), 1476 ka (Gardar), 1580 ka (Gilsa), and 2737 ka (Porcupine). Excursions coincide with minima in relative paleointensity (RPI) records. Ages are from correlation of excursion records to oxygen isotope records in the same cores, and ice-volume calibration of the oxygen isotope template. The marine sediment record of excursions, combined with independent documentation of excursions in lavas with Ar/Ar age control, is progressively strengthening our knowledge of the excursion inventory in the Quaternary, and enhancing the importance of excursions and RPI in Quaternary stratigraphy.

Fallout isotope chronology of the near-surface sediment record of Lake Bolătău.

Science.gov (United States)

Bihari, Árpád; Karlik, Máté; Mîndrescu, Marcel; Szalai, Zoltán; Grădinaru, Ionela; Kern, Zoltán

2018-01-01

Fallout isotope ( 210 Pb ex, 137 Cs and 241 Am) based dating has been carried out on the near-surface sediment core collected from Lake Bolătău-Feredeu (Bukovina, Romania). The motivation was to improve the chronology of this recent section in connection with significant fluctuations observed in sediment accumulation rates, particle size distribution and primordial radioisotope (i.e. 40 K and 232 Th) composition. Previously only an extrapolation of a broad-range OxCal age-depth model, which was based on 8 AMS radiocarbon dates from the deeper part of a parallel sediment sequence and tentatively validated for the upper part using the double peaks of the 137 Cs activity concentration distribution, was available for the studied section (1-24 cm). Parallel to the previous 137 Cs measurement, 210 Pb and 226 Ra (for a more detailed, 210 Pb ex -based chronology), 241 Am (for an additional time-marker), as well as 40 K and 232 Th concentrations have also been determined by gamma-spectrometry. In case of the 210 Pb ex -based chronology, due to a large deviation from a pure exponential distribution, the Constant Flux (CF) model has been used for the calculation of sediment ages and accumulation rates. Although the broad-range OxCal and the CF model were broadly similar down to 22 cm, the 210 Pb ex -based ages are clearly superior in terms of uncertainty in the uppermost 12 cm, while the broad-range model has smaller uncertainty below 20 cm (>150 years). The CF model gave an average mass accumulation rate of (0.08 ± 0.03) g cm -2 yr -1 for sections 0-11 cm, and (0.03 ± 0.01) g cm -2 yr -1 for sections 12-22 cm, respectively. Significant changes have been observed in the depth distribution of both the particle size distribution and the elemental/isotopic composition of the sediment record, most likely related to the variation observable in the intensity and volume of precipitation in the catchment. The obtained high-resolution records of Lake Bolătău, including

A manual for a Laboratory Information Management System (LIMS) for light stable isotopes

Science.gov (United States)

Coplen, Tyler B.

1998-01-01

The reliability and accuracy of isotopic data can be improved by utilizing database software to (i) store information about samples, (ii) store the results of mass spectrometric isotope-ratio analyses of samples, (iii) calculate analytical results using standardized algorithms stored in a database, (iv) normalize stable isotopic data to international scales using isotopic reference materials, and (v) generate multi-sheet paper templates for convenient sample loading of automated mass-spectrometer sample preparation manifolds. Such a database program is presented herein. Major benefits of this system include (i) an increase in laboratory efficiency, (ii) reduction in the use of paper, (iii) reduction in workload due to the elimination or reduction of retyping of data by laboratory personnel, and (iv) decreased errors in data reported to sample submitters. Such a database provides a complete record of when and how often laboratory reference materials have been analyzed and provides a record of what correction factors have been used through time. It provides an audit trail for stable isotope laboratories. Since the original publication of the manual for LIMS for Light Stable Isotopes, the isotopes 3 H, 3 He, and 14 C, and the chlorofluorocarbons (CFCs), CFC-11, CFC-12, and CFC-113, have been added to this program.

How the oxygen isotope ratio of rain water influences the isotope ratio of chicken eggshell carbonate

Science.gov (United States)

Price, Gregory; Grimes, Stephen

2015-04-01

The stable oxygen isotope ratio of chicken eggshell carbonate was analysed from chicken eggs laid under free range, and organic farming regimes from across the UK. The eggshell carbonate oxygen isotope data shows a clear depletion in delta18O distribution from the southwest to the northeast. Although consistently offset by around 1 permil, the same isotopic distribution as that seen in eggshell carbonate is observed in the delta18O ratio of rainfall and groundwater from across the UK. This distribution is related to the Rayleigh distillation of rainfall driven by westerly winds across the UK landmass. The clear relationship observed between eggshell delta18O values and that of rainwater presumably reflects the nature of free range chickens which must be drinking locally derived rainwater and supplementing their diet and water intake with locally derived food. These results suggest that the oxygen isotope value of chicken eggshells can be used as a forensic tool to identify the locality that free range and organic eggs were laid within the UK. Furthermore, if suitable material is preserved in the archaeological and geological record then such a relationship can potentially be used to establish the oxygen isotope value of rainwater from which ancient and / or ancestral birds lived.

Influences of large-scale convection and moisture source on monthly precipitation isotope ratios observed in Thailand, Southeast Asia

Science.gov (United States)

Wei, Zhongwang; Lee, Xuhui; Liu, Zhongfang; Seeboonruang, Uma; Koike, Masahiro; Yoshimura, Kei

2018-04-01

Many paleoclimatic records in Southeast Asia rely on rainfall isotope ratios as proxies for past hydroclimatic variability. However, the physical processes controlling modern rainfall isotopic behaviors in the region is poorly constrained. Here, we combined isotopic measurements at six sites across Thailand with an isotope-incorporated atmospheric circulation model (IsoGSM) and the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to investigate the factors that govern the variability of precipitation isotope ratios in this region. Results show that rainfall isotope ratios are both correlated with local rainfall amount and regional outgoing longwave radiation, suggesting that rainfall isotope ratios in this region are controlled not only by local rain amount (amount effect) but also by large-scale convection. As a transition zone between the Indian monsoon and the western North Pacific monsoon, the spatial difference of observed precipitation isotope among different sites are associated with moisture source. These results highlight the importance of regional processes in determining rainfall isotope ratios in the tropics and provide constraints on the interpretation of paleo-precipitation isotope records in the context of regional climate dynamics.

Second international conference on isotopes. Conference proceedings

International Nuclear Information System (INIS)

Hardy, C.J.

1997-10-01

The Second International Conference on Isotopes (2ICI) was hosted by the Australian Nuclear Association in Sydney, NSW, Australia. The Theme of the Second Conference: Isotopes for Industry, Health and a Better Environment recognizes that isotopes have been used in these fields successfully for many years and offer prospects for increasing use in the future. The worldwide interest in the use of research reactors and accelerators and in applications of stable and radioactive isotopes, isotopic techniques and radiation in industry, agriculture, medicine, environmental studies and research in general, was considered. Other radiation issues including radiation protection and safety were also addressed. International and national overviews and subject reviews invited from leading experts were included to introduce the program of technical sessions. The invited papers were supported by contributions accepted from participants for oral and poster presentation. A Technical Exhibition was held in association with the Conference. This volume contains the foreword, technical program, the author index and of the papers (1-60) presented at the conference

Second international conference on isotopes. Conference proceedings

Energy Technology Data Exchange (ETDEWEB)

Hardy, C J [ed.

1997-10-01

The Second International Conference on Isotopes (2ICI) was hosted by the Australian Nuclear Association in Sydney, NSW, Australia. The Theme of the Second Conference: Isotopes for Industry, Health and a Better Environment recognizes that isotopes have been used in these fields successfully for many years and offer prospects for increasing use in the future. The worldwide interest in the use of research reactors and accelerators and in applications of stable and radioactive isotopes, isotopic techniques and radiation in industry, agriculture, medicine, environmental studies and research in general, was considered. Other radiation issues including radiation protection and safety were also addressed. International and national overviews and subject reviews invited from leading experts were included to introduce the program of technical sessions. The invited papers were supported by contributions accepted from participants for oral and poster presentation. A Technical Exhibition was held in association with the Conference. This volume contains the full text or extended abstracts of papers number 61- to number 114

Second international conference on isotopes. Conference proceedings

Energy Technology Data Exchange (ETDEWEB)

Hardy, C J [ed.

1997-10-01

The Second International Conference on Isotopes (2ICI) was hosted by the Australian Nuclear Association in Sydney, NSW, Australia. The Theme of the Second Conference: Isotopes for Industry, Health and a Better Environment recognizes that isotopes have been used in these fields successfully for many years and offer prospects for increasing use in the future. The worldwide interest in the use of research reactors and accelerators and in applications of stable and radioactive isotopes, isotopic techniques and radiation in industry, agriculture, medicine, environmental studies and research in general, was considered. Other radiation issues including radiation protection and safety were also addressed. International and national overviews and subject reviews invited from leading experts were included to introduce the program of technical sessions. The invited papers were supported by contributions accepted from participants for oral and poster presentation. A Technical Exhibition was held in association with the Conference. This volume contains the foreword, technical program, the author index and of the papers (1-60) presented at the conference.

Carbon Isotope Chemostratigraphy, the Baby and the Bathwater

Science.gov (United States)

Arthur, M. A.

2008-12-01

Secular variations in the carbon isotopic values of carbonate sediments and rocks and their individual components have been applied successfully to problems of stratigraphic correlation and for interpretation of past changes in the global carbon cycle. However, this methodology is not without problems. A major tenet of stable isotope chemostratigraphy involves sampling and analyzing multiple, widely separated sequences, and, if possible, multiple carbon-bearing components (e.g., carbonate and organic carbon) in order to demonstrate a global signal. In some cases, this methodology has been short-circuited in the zeal to reveal a new event or excursion, particularly for time intervals for which adequate sequences are somewhat rare. Likewise, although most carbonate researchers are quite aware of the possible importance of diagenesis, particularly in organic-carbon rich sequences or in shoal-water carbonate sequences with longer-term subaerial exposure events, such overprints commonly go unrecognized or are considered of minor impact. Studies of stable isotope variations in carbonate sequences should always employ textural and geochemical methodologies for detecting and even quantifying diagenesis, if possible. Although some diagenetically overprinted or misinterpreted geochemical data have undoubtedly appeared in the literature, there are many excellent examples of global carbon isotope variations in records expressed in pelagic biogenic carbonate, marine organic carbon, platform carbonates, and terrestrial organic matter. Arguably, one of the best-documented examples is the Cenomanian-Turonian (ca. 93 Ma) positive carbon isotope excursion. The amplitude of the Cenomanian-Turonian carbon isotope excursion is similar among all types of records, but there are subtle pattern differences that arise from differences in sedimentation rate among and within sequences. Organic carbon and carbonate carbon isotope signals also may differ in phasing and amplitude for certain

Mass-independent isotope effects in chemical exchange reaction

International Nuclear Information System (INIS)

Nishizawa, Kazushige

2000-01-01

Isotope effects of some elements in chemical exchange reaction were investigated by use of liquid-liquid extraction, liquid membrane or chromatographic separation. Cyclic polyether was used for every method. All polyethers used in a series of the studies were made clear that they distinguished the isotopes not only by their nuclear masses but also by their nuclear sizes and shapes. Chromium isotopes, for example, were recognized to have enrichment factors being proportional to δ 2 > which is a parameter to show field shift or the nuclear size and shape of the isotope. It follows that the chromium isotopes are separated not by their masses but by their field shift effects. Nuclear spin also played a great role to separate odd mass number isotopes from even mass number isotopes in even atomic number elements. Contribution of the nuclear spin (I=3/2) of 53 Cr to total enrichment factor, ε 53/52 = -0.00028, for 53 Cr to 52 Cr was observed to be, ε spin = -0.0025. (author)

Estimates of water source contributions in a dynamic urban water supply system inferred via a Bayesian stable isotope mixing model

Science.gov (United States)

Jameel, M. Y.; Brewer, S.; Fiorella, R.; Tipple, B. J.; Bowen, G. J.; Terry, S.

2017-12-01

Public water supply systems (PWSS) are complex distribution systems and critical infrastructure, making them vulnerable to physical disruption and contamination. Exploring the susceptibility of PWSS to such perturbations requires detailed knowledge of the supply system structure and operation. Although the physical structure of supply systems (i.e., pipeline connection) is usually well documented for developed cities, the actual flow patterns of water in these systems are typically unknown or estimated based on hydrodynamic models with limited observational validation. Here, we present a novel method for mapping the flow structure of water in a large, complex PWSS, building upon recent work highlighting the potential of stable isotopes of water (SIW) to document water management practices within complex PWSS. We sampled a major water distribution system of the Salt Lake Valley, Utah, measuring SIW of water sources, treatment facilities, and numerous sites within in the supply system. We then developed a hierarchical Bayesian (HB) isotope mixing model to quantify the proportion of water supplied by different sources at sites within the supply system. Known production volumes and spatial distance effects were used to define the prior probabilities for each source; however, we did not include other physical information about the supply system. Our results were in general agreement with those obtained by hydrodynamic models and provide quantitative estimates of contributions of different water sources to a given site along with robust estimates of uncertainty. Secondary properties of the supply system, such as regions of "static" and "dynamic" source (e.g., regions supplied dominantly by one source vs. those experiencing active mixing between multiple sources), can be inferred from the results. The isotope-based HB isotope mixing model offers a new investigative technique for analyzing PWSS and documenting aspects of supply system structure and operation that are

Tracking the rise of eukaryotes to ecological dominance with zinc isotopes.

Science.gov (United States)

Isson, Terry T; Love, Gordon D; Dupont, Christopher L; Reinhard, Christopher T; Zumberge, Alex J; Asael, Dan; Gueguen, Bleuenn; McCrow, John; Gill, Ben C; Owens, Jeremy; Rainbird, Robert H; Rooney, Alan D; Zhao, Ming-Yu; Stueeken, Eva E; Konhauser, Kurt O; John, Seth G; Lyons, Timothy W; Planavsky, Noah J

2018-06-05

The biogeochemical cycling of zinc (Zn) is intimately coupled with organic carbon in the ocean. Based on an extensive new sedimentary Zn isotope record across Earth's history, we provide evidence for a fundamental shift in the marine Zn cycle ~800 million years ago. We discuss a wide range of potential drivers for this transition and propose that, within available constraints, a restructuring of marine ecosystems is the most parsimonious explanation for this shift. Using a global isotope mass balance approach, we show that a change in the organic Zn/C ratio is required to account for observed Zn isotope trends through time. Given the higher affinity of eukaryotes for Zn relative to prokaryotes, we suggest that a shift toward a more eukaryote-rich ecosystem could have provided a means of more efficiently sequestering organic-derived Zn. Despite the much earlier appearance of eukaryotes in the microfossil record (~1700 to 1600 million years ago), our data suggest a delayed rise to ecological prominence during the Neoproterozoic, consistent with the currently accepted organic biomarker records. © 2018 John Wiley & Sons Ltd.

Archival processes of the water stable isotope signal in East Antarctic ice cores

Science.gov (United States)

Casado, Mathieu; Landais, Amaelle; Picard, Ghislain; Münch, Thomas; Laepple, Thomas; Stenni, Barbara; Dreossi, Giuliano; Ekaykin, Alexey; Arnaud, Laurent; Genthon, Christophe; Touzeau, Alexandra; Masson-Delmotte, Valerie; Jouzel, Jean

2018-05-01

The oldest ice core records are obtained from the East Antarctic Plateau. Water isotopes are key proxies to reconstructing past climatic conditions over the ice sheet and at the evaporation source. The accuracy of climate reconstructions depends on knowledge of all processes affecting water vapour, precipitation and snow isotopic compositions. Fractionation processes are well understood and can be integrated in trajectory-based Rayleigh distillation and isotope-enabled climate models. However, a quantitative understanding of processes potentially altering snow isotopic composition after deposition is still missing. In low-accumulation sites, such as those found in East Antarctica, these poorly constrained processes are likely to play a significant role and limit the interpretability of an ice core's isotopic composition. By combining observations of isotopic composition in vapour, precipitation, surface snow and buried snow from Dome C, a deep ice core site on the East Antarctic Plateau, we found indications of a seasonal impact of metamorphism on the surface snow isotopic signal when compared to the initial precipitation. Particularly in summer, exchanges of water molecules between vapour and snow are driven by the diurnal sublimation-condensation cycles. Overall, we observe in between precipitation events modification of the surface snow isotopic composition. Using high-resolution water isotopic composition profiles from snow pits at five Antarctic sites with different accumulation rates, we identified common patterns which cannot be attributed to the seasonal variability of precipitation. These differences in the precipitation, surface snow and buried snow isotopic composition provide evidence of post-deposition processes affecting ice core records in low-accumulation areas.

Novel proxies for reconstructing paleohydrology from ombrotrophic peatlands: biomarker and compound-specific H and C stable isotope ratios

Science.gov (United States)

Wang, J.; Nichols, J. E.; Huang, Y.

2008-12-01

Ombrotrophic peatlands are excellent archives for paleohydrologic information because they are hydrologically isolated from their surroundings. However, quantitative proxies for deciphering peatland archives are lacking. Here, we present development and application of novel organic geochemical methods for quantitative reconstruction of paleohydrology from the ombrotrophic sediments, and comparison of organic geochemical data with conventional paleoecological proxies. Application of these methods to the sediments of several North American and European peatlands has revealed significant changes in the hydroclimate throughout the Holocene. The plant assemblage living at the surface of the peatland is tightly controlled by surface moisture. Under wet conditions, Sphagnum mosses, with no active mechanism for drawing water from below the surface of the peatland, are dominant. During dry conditions, vascular plants are more productive relative to Sphagnum. A ratio of the abundance of two biomarkers representing Sphagnum and vascular plants sensitively records changes in hydrologic balance (Nichols et al., 2006, Org. Geochem. 37, 1505-1513). We have further developed stable isotope models to compute climate parameters from compound-specific H and C isotope ratios of biomarkers to create a more comprehensive climate reconstruction. Vascular plant leaf waxes carry the D/H ratio signature of precipitation that is little affected by evaporation, whereas the Sphagnum biomarker records isotopic ratios of the water at the peatland surface, which is strongly enriched by evaporation. Evaporation amount can be calculated using the differences between D/H ratios of the two types of biomarkers. C isotope ratios of Sphagnum biomarkers can also be used to quantify surface wetness. Methanotrophic bacteria live symbiotically with Sphagnum, providing isotopically light carbon for photosynthesis. These bacteria are more active when the Sphagnum is wet, thus providing more 13C-depleted CO2

Evidence of a connection between the Atlantic and Mediterranean during the Messinian Salinity Crisis from Pb and Nd isotopes

Science.gov (United States)

Modestou, Sevasti; Gutjahr, Marcus; Fietzke, Jan; Rodés, Ángel; Frank, Martin; Bolhão Muiños, Susana; Ellam, Rob; Flecker, Rachel

2014-05-01

Prior to the opening of the Gibraltar Strait at 5.33 Ma, the Betic (southern Spain) and Rifian (northern Morocco) marine palaeocorridors linked the Mediterranean to the Atlantic. Although the central regions of these corridors have been heavily eroded due to uplift, evidence published to date indicates that both closed before the onset of the Messinian Salinity Crisis (MSC; 5.97 to 5.33 Ma [1, 2]). However, pre-MSC corridor closure presents a paradox, as the volume of halite deposited within the Mediterranean basin requires several times the volume of seawater contained in the basin itself. In this regard, radiogenic isotopes such as Sr, Pb, and Nd can provide key information about the timing of exchange through the Betic and Rifian palaeogateways. Due to the resolvable isotopic difference in Nd isotope signatures of outgoing Mediterranean and incoming Atlantic water masses, demonstrated both for the present day as well as the past environment, this isotope system can be used to identify exchange between these two water bodies. Although less well constrained to date, the Pb isotope system can be used in a similar manner due to its short residence time in seawater and interbasin variability. A high resolution Pb isotope record extracted using laser ablation from ferromanganese crust 3514-6 (recovered from the Lion Seamount, NE Atlantic, water depth 690-940 m) indicates a relatively constant Pb isotope signature before, during and after the MSC period. The previously published [3] Nd isotope record of crust 3514-6 corroborates that the crust was deposited in a current distinct from NE Atlantic Deep water or Antarctic Intermediate Water, the principal currents in the region of the Lion Seamount. The combined Pb and Nd isotope evolution suggests that Mediterranean Outflow Water (MOW) was continuously advected into the NE Atlantic during and after the MSC. Furthermore, preliminary Nd isotope records from Late Miocene sediments collected in the Sorbas Basin, Spain

Contribution of isotope techniques to evaluate water resources in the Peruvian Altiplano

International Nuclear Information System (INIS)

Araguas, L.; Arroyo, C.; Palza, G.; Rojas, R.; Romero, J.; Silar, J.

1999-01-01

Environmental isotopes H , 18 O, 13 C, 3 H, and 14 C were regularly measured in precipitation, surface, and ground water to investigate a series of problems linked with the management of water resources in the Peruvian Altiplano, a plateau located in Southern Peru

Collaborative Project: Development of an Isotope-Enabled CESM for Testing Abrupt Climate Changes

Energy Technology Data Exchange (ETDEWEB)

Liu, Zhengyu [Univ. of Wisconsin, Madison, WI (United States). Dept. of Atmospheric and Oceanic Sciences

2018-01-24

One of the most important validations for a state-of-art Earth System Model (ESM) with respect to climate changes is the simulation of the climate evolution and abrupt climate change events in the Earth’s history of the last 21,000 years. However, one great challenge for model validation is that ESMs usually do not directly simulate geochemical variables that can be compared directly with past proxy records. In this proposal, we have met this challenge by developing the simulation capability of major isotopes in a state-of-art ESM, the Community Earth System Model (CESM), enabling us to make direct model-data comparison by comparing the model directly against proxy climate records. Our isotope-enabled ESM incorporates the capability of simulating key isotopes and geotracers, notably δ¹⁸O, δD, δ¹⁴C, and δ¹³C, Nd and Pa/Th. The isotope-enabled ESM have been used to perform some simulations for the last 21000 years. The direct comparison of these simulations with proxy records has shed light on the mechanisms of important climate change events.

Some measurements of H/D polarizability isotope effects using differential refractometry

Energy Technology Data Exchange (ETDEWEB)

Foster Smith, M; Van Hook, W A [Tennessee Univ., Knoxville (USA). Dept. of Chemistry

1989-05-01

Refractive index differences between the H and D isomers of some common molecules in the liquid phase were measured between 404.7 and 690.0 nm. The data are combined with information on molar volume isotope effects to yield values for H/D isotope effects on the static polarizability, the vibrational contribution to the static and frequency dependent parts of the polarizability, and the H/D isotope effect on the second moment of the electronic charge distribution. The present results suffice to demonstrate the practicability of this technique to measure the components of the polarizability listed above. However for accurate resolution of the vibrational and second moment contributions, refractive index data of still greater precision will be required. (orig.).

Some measurements of H/D polarizability isotope effects using differential refractometry

International Nuclear Information System (INIS)

Foster Smith, M.; Van Hook, W.A.

1989-01-01

Refractive index differences between the H and D isomers of some common molecules in the liquid phase were measured between 404.7 and 690.0 nm. The data are combined with information on molar volume isotope effects to yield values for H/D isotope effects on the static polarizability, the vibrational contribution to the static and frequency dependent parts of the polarizability, and the H/D isotope effect on the second moment of the electronic charge distribution. The present results suffice to demonstrate the practicability of this technique to measure the components of the polarizability listed above. However for accurate resolution of the vibrational and second moment contributions, refractive index data of still greater precision will be required. (orig.)

Isotopes in environmental research

International Nuclear Information System (INIS)

Bowen, G.; Rozanski, K.; Vose, P.

1990-01-01

Radioactive and stable isotopes have long been considered a very efficient tool for studying physical and biological aspects of how the global ecosystem functions. Their applications in environmental research are numerous, embracing research at all levels. This article looks at only a few of the approaches to environmental problems that involve the use of isotopes. Special attention is given to studies of the Amazon Basin. Environmental isotopes are very efficient tools in water cycle studies. Tritium, a radioactive tracer, is especially useful in studying dynamics of water movement in different compartments of the hydrosphere, both on the local and global scales. Heavy stable isotopes of hydrogen and oxygen (deuterium and oxygen-18) provide information about steady-state characteristics of the water cycle. Isotope methods, some relatively new, have a major role in site-specific studies. Some indicative examples include: Studying turnover of organic matter. Changes in the carbon-13/carbon-12 isotopic ratio of organic matter were used to determine the respective contributions of organic carbon derived from forest and pasture. Studying biological nitrogen fixation. One of the ways nitrogen levels in soil can be maintained for productivity is by biological nitrogen fixation. Studying nitrogen availability and losses. The experimental use of nitrogen-15 is invaluable for defining losses of soil nitrogen to the atmosphere and to groundwater. Studies can similarly be done with stable and radioactive sulphur isotopes. This article indicates some potential uses of isotopes in environmental research. While the major problem of global climate change has not been specifically addressed here, the clearing of the Amazon forest, one focus of the IAEA's environmental programme, may have serious consequences for the global climate. These include substantial reduction of the amount of latent heat transported to the regions outside the tropics and acceleration of the greenhouse

Stable isotope analysis of Dacryoconarid carbonate microfossils: a new tool for Devonian oxygen and carbon isotope stratigraphy.

Science.gov (United States)

Frappier, Amy Benoit; Lindemann, Richard H; Frappier, Brian R

2015-04-30

Dacryoconarids are extinct marine zooplankton known from abundant, globally distributed calcite microfossils in the Devonian, but their shell stable isotope composition has not been previously explored. Devonian stable isotope stratigraphy is currently limited to less common invertebrates or bulk rock analyses of uncertain provenance. As with Cenozoic planktonic foraminifera, isotopic analysis of dacryoconarid shells could facilitate higher-resolution, geographically widespread stable isotope records of paleoenvironmental change, including marine hypoxia events, climate changes, and biocrises. We explored the use of Dacryoconarid isotope stratigraphy as a viable method in interpreting paleoenvironments. We applied an established method for determining stable isotope ratios (δ(13) C, δ(18) O values) of small carbonate microfossils to very well-preserved dacryoconarid shells. We analyzed individual calcite shells representing five common genera using a Kiel carbonate device coupled to a MAT 253 isotope ratio mass spectrometer. Calcite shell δ(13) C and δ(18) O values were compared by taxonomic group, rock unit, and locality. Single dacryoconarid calcite shells are suitable for stable isotope analysis using a Kiel-IRMS setup. The dacryoconarid shell δ(13) C values (-4.7 to 2.3‰) and δ(18) O values (-10.3 to -4.8‰) were consistent across taxa, independent of shell size or part, but varied systematically through time. Lower fossil δ(18) O values were associated with warmer water temperature and more variable δ(13) C values were associated with major bioevents. Dacryoconarid δ(13) C and δ(18) O values differed from bulk rock carbonate values. Dacryoconarid individual microfossil δ(13) C and δ(18) O values are highly sensitive to paleoenvironmental changes, thus providing a promising avenue for stable isotope chemostratigraphy to better resolve regional to global paleoceanographic changes throughout the upper Silurian to the upper Devonian. Our results

Comparison of three gamma ray isotopic determination codes: FRAM, MGA, and TRIFID

International Nuclear Information System (INIS)

Cremers, T.L.; Malcom, J.E.; Bonner, C.A.

1994-01-01

The determination of the isotopic distribution of plutonium and the americium concentration is required for the assay of nuclear material by calorimetry or neutron coincidence counting. The isotopic information is used in calorimetric assay to compute the effective specific power from the measured isotopic fractions and the known specific power of each isotope. The effective specific power is combined with the heat measurement to obtain the mass of plutonium in the assayed nuclear material. The response of neutron coincidence counters is determined by the 240 Pu isotopic fraction with contributions from the other even plutonium isotopes. The effect of the 240 Pu isotopic fraction and the other neutron contributing isotopes are combined as 240 Pu effective. This is used to calculate the mass of nuclear material from the neutron counting data in a manner analogous to the effective specific power in calorimeter. Comparisons of the precision and accuracy of calorimetric assay and neutron coincidence counting often focus only on the precision and accuracy of the heat measurement (calorimetry) compared to the precision and accuracy of the neutron coincidence counting statistics. The major source of uncertainty for both calorimetric assay and neutron coincidence counting often lies in the determination of the plutonium isotopic distribution ad determined by gamma ray spectroscopy. Thus, the selection of the appropriate isotopic distribution code is of paramount importance to good calorimetric assay and neutron coincidence counting. Three gamma ray isotopic distribution codes, FRAM, MGA, and TRIFID have been compared at the Los Alamos Plutonium Facility under carefully controlled conditions of similar count rates, count times, and 240 Pu isotopic fraction

Hydrologic inferences from strontium isotopes in pore water from the unsaturated zone at Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Marshall, B.D.; Futa, K.; Peterman, Z.E.

1997-01-01

Calcite is ubiquitous at Yucca Mountain, occurring in the soils and as fracture and cavity coatings within the volcanic tuff section. Strontium is a trace element in calcite, generally at the tens to hundreds of ppm level. Because calcite contains very little rubidium and the half-life of the 87 Rb parent is billions of years, the 87 Sr/ 86 Sr ratios of the calcite record the ratio in the water from which the calcite precipitated. Dissolution and reprecipitation does not alter these compositions so that, in the absence of other sources of strontium, one would expect the strontium ratios along a flow path to preserve variations inherited from strontium in the soil zone. Strontium isotope compositions of calcites from various settings in the Yucca Mountain region have contributed to the understanding of the unsaturated zone (UZ), especially in distinguishing unsaturated zone calcite from saturated zone calcite. Different populations of calcite have been compared, either to group them together or distinguish them from each other in terms of their strontium isotope compositions. Ground water and perched water have also been analyzed; this paper presents strontium isotope data obtained on pore water

Inverse methods for estimating primary input signals from time-averaged isotope profiles

Science.gov (United States)

Passey, Benjamin H.; Cerling, Thure E.; Schuster, Gerard T.; Robinson, Todd F.; Roeder, Beverly L.; Krueger, Stephen K.

2005-08-01

Mammalian teeth are invaluable archives of ancient seasonality because they record along their growth axes an isotopic record of temporal change in environment, plant diet, and animal behavior. A major problem with the intra-tooth method is that intra-tooth isotope profiles can be extremely time-averaged compared to the actual pattern of isotopic variation experienced by the animal during tooth formation. This time-averaging is a result of the temporal and spatial characteristics of amelogenesis (tooth enamel formation), and also results from laboratory sampling. This paper develops and evaluates an inverse method for reconstructing original input signals from time-averaged intra-tooth isotope profiles. The method requires that the temporal and spatial patterns of amelogenesis are known for the specific tooth and uses a minimum length solution of the linear system Am = d, where d is the measured isotopic profile, A is a matrix describing temporal and spatial averaging during amelogenesis and sampling, and m is the input vector that is sought. Accuracy is dependent on several factors, including the total measurement error and the isotopic structure of the measured profile. The method is shown to accurately reconstruct known input signals for synthetic tooth enamel profiles and the known input signal for a rabbit that underwent controlled dietary changes. Application to carbon isotope profiles of modern hippopotamus canines reveals detailed dietary histories that are not apparent from the measured data alone. Inverse methods show promise as an effective means of dealing with the time-averaging problem in studies of intra-tooth isotopic variation.

What can Fe stable isotopes tell us about magmas?

DEFF Research Database (Denmark)

Stausberg, Niklas

the differentiation of magmas from the perspective of Fe stable isotopes, integrated with petrology, by studying igneous rocks and their constituent phases (minerals and glasses) from the Bushveld Complex, South Africa, Thingmuli, Iceland, Pantelleria, Italy, and the Bishop Tuff, USA. The findings are interpreted......The majority of the Earth’s crust is formed by magmas, and understanding their production and differentiation is important to interpret the geologic rock record. A powerful tool to investigate magmatic processes is the distribution of the stable isotopes of the major redox-sensitive element...... in magmas, Fe. Fe isotope compositions of magmatic rocks exhibit systematic differences, where the heaviest compositions are found in rhyolites and granites. Understanding of these systematics is complicated by a lack of constraints on Fe isotope fractionation among minerals and liquids under magmatic...

Isotopic Tracing of Thallium Contamination in Soils Affected by Emissions from Coal-Fired Power Plants.

Science.gov (United States)

Vaněk, Aleš; Grösslová, Zuzana; Mihaljevič, Martin; Trubač, Jakub; Ettler, Vojtěch; Teper, Leslaw; Cabala, Jerzy; Rohovec, Jan; Zádorová, Tereza; Penížek, Vít; Pavlů, Lenka; Holubík, Ondřej; Němeček, Karel; Houška, Jakub; Drábek, Ondřej; Ash, Christopher

2016-09-20

Here, for the first time, we report the thallium (Tl) isotope record in moderately contaminated soils with contrasting land management (forest and meadow soils), which have been affected by emissions from coal-fired power plants. Our findings clearly demonstrate that Tl of anthropogenic (high-temperature) origin with light isotope composition was deposited onto the studied soils, where heavier Tl (ε(205)Tl ∼ -1) naturally occurs. The results show a positive linear relationship (R(2) = 0.71) between 1/Tl and the isotope record, as determined for all the soils and bedrocks, also indicative of binary Tl mixing between two dominant reservoirs. We also identified significant Tl isotope variations within the products from coal combustion and thermo-desorption experiments with local Tl-rich coal pyrite. Bottom ash exhibited the heaviest Tl isotope composition (ε(205)Tl ∼ 0), followed by fly ash (ε(205)Tl between -2.5 and -2.8) and volatile Tl fractions (ε(205)Tl between -6.2 and -10.3), suggesting partial Tl isotope fractionations. Despite the evident role of soil processes in the isotope redistributions, we demonstrate that Tl contamination can be traced in soils and propose that the isotope data represent a possible tool to aid our understanding of postdepositional Tl dynamics in surface environments for the future.

Isotopes in the Arctic atmospheric water cycle

Science.gov (United States)

Bonne, Jean-Louis; Werner, Martin; Meyer, Hanno; Kipfstuhl, Sepp; Rabe, Benjamin; Behrens, Melanie; Schönicke, Lutz; Steen Larsen, Hans Christian; Masson-Delmotte, Valérie

2016-04-01

measurements highlighted significant synoptic variations in summer in both sites. In Samoylov, the premises of a seasonal cycle have been observed during the summer-fall transition, with a fast humidity level and isotopic decrease. The latitudinal gradient is also highly visible on the Polarstern record. Complementing simulations of the water vapour isotopic composition by the ECHAM5-wiso model reproduce the Polarstern synoptic variability and spatial patterns with a good accuracy. In the near future, our records will be combined with simultaneous water isotope measurements in Iceland (by Hans Christian Steen-Larsen, CIC), Svalbard (by Valérie-Masson Delmotte, LSCE) and paired with complementing climate simulations enhanced by water isotope diagnostics. These data sets, covering an approx. 6,000 km transect of Northern Eurasia will allow for a quantitative assessment of the isotopic variations of the Arctic water cycle. The results of these analyses will also be of relevance for the interpretation of isotope signals found in ice cores and on terrestrial Arctic sites in terms of past climate change.

Isotope study in geothermal fields in Java Island

International Nuclear Information System (INIS)

Wandowo, Z.A.

1995-01-01

Study in two geothermal fields, Dieng and Kamojang, in Java island by utilizing isotope technique has been carried out. Isotopic data of wells, springs and other geothermal manifestations providing informations on the recharge area of precipitation contributed to geothermal resources, flow paths and origin of geothermal fluids. The data of oxygen shift has also provided information on the characteristic the fields. (author). 8 refs, 5 figs, 3 tabs

Seasonal and ENSO Influences on the Stable Isotopic Composition of Galápagos Precipitation

Science.gov (United States)

Martin, N. J.; Conroy, J. L.; Noone, D.; Cobb, K. M.; Konecky, B. L.; Rea, S.

2018-01-01

The origin of stable isotopic variability in precipitation over time and space is critical to the interpretation of stable isotope-based paleoclimate proxies. In the eastern equatorial Pacific, modern stable isotope measurements in precipitation (δ18Op and δDp) are sparse and largely unevaluated in the literature, although insights from such analyses would benefit the interpretations of several regional isotope-based paleoclimate records. Here we present a new 3.5 year record of daily-resolved δ18Op and δDp from Santa Cruz, Galápagos. With a prior 13 year record of monthly δ18Op and δDp from the island, these new data reveal controls on the stable isotopic composition of regional precipitation on event to interannual time scales. Overall, we find Galápagos δ18Op is significantly correlated with precipitation amount on daily and monthly time scales. The majority of Galápagos rain events are drizzle, or garúa, derived from local marine boundary layer vapor, with corresponding high δ18Op values due to the local source and increased evaporation and equilibration of smaller drops with boundary layer vapor. On monthly time scales, only precipitation in very strong, warm season El Niño months has substantially lower δ18Op values, as the sea surface temperature threshold for deep convection (28°C) is only surpassed at these times. The 2015/2016 El Niño event did not produce strong precipitation or δ18Op anomalies due to the short period of warm SST anomalies, which did not extend into the peak of the warm season. Eastern Pacific proxy isotope records may be biased toward periods of high rainfall during strong to very strong El Niño events.

The impact of moisture sources on the oxygen isotope composition of precipitation at a continental site in central Europe

Science.gov (United States)

Krklec, Kristina; Domínguez-Villar, David; Lojen, Sonja

2018-06-01

The stable isotope composition of precipitation records processes taking place within the hydrological cycle. Potentially, moisture sources are important controls on the stable isotope composition of precipitation, but studies focused on this topic are still scarce. We studied the moisture sources contributing to precipitation at Postojna (Slovenia) from 2009 to 2013. Back trajectory analyses were computed for the days with precipitation at Postojna. The moisture uptake locations were identified along these trajectories using standard hydrometeorological formulation. The moisture uptake locations were integrated in eight source regions to facilitate its comparison to the monthly oxygen isotope composition (δ18O values) of precipitation. Nearly half of the precipitation originated from continental sources (recycled moisture), and >40% was from central and western Mediterranean. Results show that moisture sources do not have a significant impact on the oxygen isotope composition at this site. We suggest that the large proportion of recycled moisture originated from transpiration rather than evaporation, which produced water vapour with less negative δ18O values. Thus the difference between the oceanic and local vapour source was reduced, which prevented the distinction of the moisture sources based on their oxygen isotope signature. Nevertheless, δ18O values of precipitation are partially controlled by climate parameters, which is of major importance for paleoclimate studies. We found that the main climate control on Postojna δ18O values of precipitation is the surface temperature. Amount effect was not recorded at this site, and the winter North Atlantic Oscillation (NAO) does not impact the δ18O values of precipitation. The Western Mediterranean Oscillation (WeMO) was correlated to oxygen stable isotope composition, although this atmospheric pattern was not a control. Instead we found that the link to δ18O values results from synoptic scenarios affecting We

Multiple S and O isotope constraints on O2 at 2.25 Ga

Science.gov (United States)

Killingsworth, B.; Sansjofre, P.; Philippot, P.; Thomazo, C.; Cartigny, P.; Lalonde, S.

2017-12-01

The composition of Earth's atmosphere around the time of the Great Oxidation Event (GOE) at the Archean-Proterozoic boundary is of great interest for reconstructing the redox evolution of the Earth. Sulfate has been shown to be a valuable recorder of isotopic signals of atmospheric O2 but its records are sparse around the time of the GOE. To constrain O2 around the GOE, we have measured quadruple sulfur and triple oxygen isotopes of sulfate from barite in sedimentary drill core from the Turee Creek Group, Australia from 2.25 Ga. A combined sulfur and oxygen approach for estimating the triple oxygen isotope composition of O2 at 2.25 Ga will be presented and its implications for the Paleoproterozoic atmosphere will be discussed.

Fossil isotope records of seasonal climate and ecology: Straight from the horse's mouth

Science.gov (United States)

Sharp, Z. D.; Cerling, T. E.

1998-03-01

Isotope analysis of a bulk fossil tooth gives a “snapshot” impression of paleoclimatic conditions—a single point in time. However, hypsodont teeth grow over a period of a year or more, so that stable carbon and oxygen isotope variations along their length are a “tape recorder” of short-term seasonal variations from the distant past. We have used a new in situ micro-laser sampling method to determine submillimeter carbon and oxygen isotope variations in the enamel of individual fossil horse teeth to assess ancient annual meteoric water variations and feeding patterns. The δ18O values from a 6.8 Ma fossil horse tooth (Astrohippus ansae) from Texas vary cyclically along the 6 cm length of the tooth with a smoothed amplitude of >4‰, similar to the monthly averaged amplitude measured in modern meteoric waters from the region. The seasonal δ18O values are ˜3‰ to 4‰ higher than those calculated from modern meteoric water data, suggesting either a higher local meteoric water value in the Miocene of Texas, or that the animal received a high proportion of its dietary water from plants or highly evaporated water. A Holocene horse tooth from the shores of Glacial Lake Agassiz, North Dakota (Equus sp.), also has isotopic variations with the same 35 mm periodicity, but a smoothed amplitude of only 2‰. This horse most likely had a buffered drinking supply. The calculated δ18O of the water in equilibrium with this tooth is the same as the modern measured annual average. The variations within a single tooth can be as large as those generally observed in entire stratigraphic sections of fossil teeth analyzed by bulk methods. The new method provides an important technique for evaluating fossil diagenesis; conventional bulk analyses of teeth fragments may not be representative of the whole tooth, thus explaining analytical scatter that has been previously attributed to diagenesis.

Isotope decay equations solved by means of a recursive method

International Nuclear Information System (INIS)

Grant, Carlos

2009-01-01

The isotope decay equations have been solved using forward finite differences taking small time steps, among other methods. This is the case of the cell code WIMS, where it is assumed that concentrations of all fissionable isotopes remain constant during the integration interval among other simplifications. Even when the problem could be solved running through a logical tree, all algorithms used for resolution of these equations used an iterative programming formulation. That happened because nearly all computer languages used up to a recent past by the scientific programmers did not support recursion, such as the case of the old versions of FORTRAN or BASIC. Nowadays also an integral form of the depletion equations is used in Monte Carlo simulation. In this paper we propose another programming solution using a recursive algorithm, running through all descendants of each isotope and adding their contributions to all isotopes in each generation. The only assumption made for this solution is that fluxes remain constant during the whole time step. Recursive process is interrupted when a stable isotope was attained or the calculated contributions are smaller than a given precision. These algorithms can be solved by means an exact analytic method that can have some problems when circular loops appear for isotopes with alpha decay, and a more general polynomial method. Both methods are shown. (author)

Precipitation regime influence on oxygen triple-isotope distributions in Antarctic precipitation and ice cores

Science.gov (United States)

Miller, Martin F.

2018-01-01

The relative abundance of 17O in meteoric precipitation is usually reported in terms of the 17O-excess parameter. Variations of 17O-excess in Antarctic precipitation and ice cores have hitherto been attributed to normalised relative humidity changes at the moisture source region, or to the influence of a temperature-dependent supersaturation-controlled kinetic isotope effect during in-cloud ice formation below -20 °C. Neither mechanism, however, satisfactorily explains the large range of 17O-excess values reported from measurements. A different approach, based on the regression characteristics of 103 ln (1 +δ17 O) versus 103 ln (1 +δ18 O), is applied here to previously published isotopic data sets. The analysis indicates that clear-sky precipitation ('diamond dust'), which occurs widely in inland Antarctica, is characterised by an unusual relative abundance of 17O, distinct from that associated with cloud-derived, synoptic snowfall. Furthermore, this distinction appears to be largely preserved in the ice core record. The respective mass contributions to snowfall accumulation - on both temporal and spatial scales - provides the basis of a simple, first-order explanation for the observed oxygen triple-isotope ratio variations in Antarctic precipitation, surface snow and ice cores. Using this approach, it is shown that precipitation during the last major deglaciation, both in western Antarctica at the West Antarctic Ice Sheet (WAIS) Divide and at Vostok on the eastern Antarctic plateau, consisted essentially of diamond dust only, despite a large temperature differential (and thus different water vapour supersaturation conditions) at the two locations. In contrast, synoptic snowfall events dominate the accumulation record throughout the Holocene at both sites.

Contribution of stable isotopes to the study of pharmacokinetics of magnesium salts; Apport des isotopes stables a l'etude de la pharmacocinetique de sels de magnesium

Energy Technology Data Exchange (ETDEWEB)

Benech, H

1999-05-28

The use of stable isotopes as labels is becoming an attractive tool for the study of magnesium behavior in humans. It has been used two stable isotopes of magnesium, {sup 25}Mg and {sup 26}Mg, to measure the absolute bioavailability of a pharmaceutical form of magnesium. (N.C.)

Contribution to the structure study of mercury isotopes with the (p,d) reaction

International Nuclear Information System (INIS)

Grafeuille, S.

1985-10-01

The mercury isotopes were studied by means of the two pick-up reactions (p,d) and (p,t). Enriched targets of 204 Hg, 202 Hg, 201 Hg, 200 Hg, 199 Hg, 198 Hg and 196 Hg were bombarded by a 25 MeV proton beam from the Orsay MP tandem accelerator. Emitted particles were analyzed by a split-pole magnetic spectrometer. We present all the results (nearly 150 states) of the analysis of the (p,d) reactions. Our (p,d) and (p,t) study show new discontinuities around 200 Hg in systematics of mercury isotopes. Part of the results are compared to the U(5) limits of Interacting Bosons (and Fermions) Models. The light nuclei can be considered reasonably described but this could be somewhat fortuitous. (71 refs) [fr

Carbon isotopic record from Upper Devonian carbonates at Dongcun in Guilin, southern China, supporting the world-wide pattern of carbon isotope excursions during Frasnian-Famennian transition

Institute of Scientific and Technical Information of China (English)

无

2003-01-01

Two positive δ13C excursions are presented in records from the Frasnian-Famennian (F-F) marine carbonate sediments in Europe, America, Africa, and Australia, having been considered as a worldwide pattern, and attributed to enhanced organic carbon burial during the F-F biological mass extinction. However, this worldwide pattern has not been revealed from the well-deposited Late Devonian sequences in southern China. In this paper, a detailed investigation has been made on the Late Devonian section at Dongcun, Guilin, southern China to constrain perturbations in δ13C of carbonates in the F-F deposited sequence. The result from this section also indicates two positive δ13C excursions during the F-F transition. The first excursion with an amplitude of 1.5‰ occurred at the bottom of linguiformis Zone, later than the early excursion existing in the Late rhenana Zone of the Late Devonian profiles in other continents, especially, in central Europe. This difference has been expected to be a result as conodont Palmatolepis linguiformis occurred earlier in southern China than other sites. The second excursion with an amplitude of 2.1‰ is located at the F-F boundary, same as the records from other continents. This result strongly supports the view that two carbon isotope positive excursions during the F-F transition are common in carbonate sediments, resulting from worldwide increases of organic carbon burial intensity.

New approaches for stable isotope ratio measurements. Proceedings of an advisory group meeting

International Nuclear Information System (INIS)

2001-10-01

This report includes a summary of discussions at the meeting and contributions on isotope applications in a range of specific biogeochemical fields using the new analytical techniques. It is expected to serve as a useful reference for researchers and laboratory managers who plan to develop or apply state-of-the-art stable isotope techniques. Individual contributions contained in this book have been indexed separately

New approaches for stable isotope ratio measurements. Proceedings of an advisory group meeting

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-10-01

This report includes a summary of discussions at the meeting and contributions on isotope applications in a range of specific biogeochemical fields using the new analytical techniques. It is expected to serve as a useful reference for researchers and laboratory managers who plan to develop or apply state-of-the-art stable isotope techniques. Individual contributions contained in this book have been indexed separately.

Quantifying the relative contribution of natural gas fugitive emissions to total methane emissions in Colorado, Utah, and Texas using mobile isotopic methane analysis based on Cavity Ringdown Spectroscopy

Science.gov (United States)

Rella, Chris; Winkler, Renato; Sweeney, Colm; Karion, Anna; Petron, Gabrielle; Crosson, Eric

2014-05-01

Fugitive emissions of methane into the atmosphere are a major concern facing the natural gas production industry. Because methane is more energy-rich than coal per kg of carbon dioxide emitted into the atmosphere, it represents an attractive alternative to coal for electricity generation, provided that the fugitive emissions of methane are kept under control. A key step in assessing these emissions in a given region is partitioning the observed methane emissions between natural gas fugitive emissions and other sources of methane, such as from landfills or agricultural activities. One effective method for assessing the contribution of these different sources is stable isotope analysis, using the isotopic carbon signature to distinguish between natural gas and landfills or ruminants. We present measurements of methane using a mobile spectroscopic stable isotope analyzer based on cavity ringdown spectroscopy, in three intense natural gas producing regions of the United States: the Denver-Julesburg basin in Colorado, the Uintah basin in Utah, and the Barnett Shale in Texas. Performance of the CRDS isotope analyzer is presented, including precision, calibration, stability, and the potential for measurement bias due to other atmospheric constituents. Mobile isotope measurements of individual sources and in the nocturnal boundary layer have been combined to establish the fraction of the observed methane emissions that can be attributed to natural gas activities. The fraction of total methane emissions in the Denver-Julesburg basin attributed to natural gas emissions is 78 +/- 13%. In the Uinta basin, which has no other significant sources of methane, the fraction is 96% +/- 15%. In addition, results from the Barnett shale are presented, which includes a major urban center (Dallas / Ft. Worth). Methane emissions in this region are spatially highly heterogeneous. Spatially-resolved isotope and concentration measurements are interpreted using a simple emissions model to

Individual-specific transgenerational marking of fish populations based on a barium dual-isotope procedure.

Science.gov (United States)

Huelga-Suarez, Gonzalo; Moldovan, Mariella; Garcia-Valiente, America; Garcia-Vazquez, Eva; Alonso, J Ignacio Garcia

2012-01-03

The present study focuses on the development and evaluation of an individual-specific transgenerational marking procedure using two enriched barium isotopes, (135)Ba and (137)Ba, mixed at a given and selectable molar ratio. The method is based on the deconvolution of the isotope patterns found in the sample into four molar contribution factors: natural xenon (Xe nat), natural barium (Ba nat), Ba135, and Ba137. The ratio of molar contributions between Ba137 and Ba135 is constant and independent of the contribution of natural barium in the sample. This procedure was tested in brown trout ( Salmo trutta ) kept in captivity. Trout were injected with three different Ba137/Ba135 isotopic signatures ca. 7 months and 7 days before spawning to compare the efficiency of the marking procedure at long and short term, respectively. The barium isotopic profiles were measured in the offspring by means of inductively coupled plasma mass spectrometry. Each of the three different isotopic signatures was unequivocally identified in the offspring in both whole eggs and larvae. For 9 month old offspring, the characteristic barium isotope signatures could also be detected in the otoliths even in the presence of a high and variable amount of barium of natural isotope abundance. In conclusion, it can be stated that the proposed dual-isotope marking is inheritable and can be detected after both long-term and short-term marking. Furthermore, the dual-isotope marking can be made individual-specific, so that it allows identification of offspring from a single individual or a group of individuals within a given fish group. © 2011 American Chemical Society

A novel methodology to investigate isotopic biosignatures

Science.gov (United States)

Horner, T. J.; Lee, R. B. Y.; Henderson, G. M.; Rickaby, R. E. M.

2012-04-01

An enduring goal of trace metal isotopic studies of Earth History is to find isotopic 'fingerprints' of life or of life's individual physiochemical processes. Generally, such signatures are sought by relating an isotopic effect observed in controlled laboratory conditions or a well-characterized environment to a more complex system or the geological record. However, such an approach is ultimately limited because life exerts numerous isotopic fractionations on any one element so it is hard to dissect the resultant net fractionation into its individual components. Further, different organisms, often with the same apparent cellular function, can express different isotopic fractionation factors. We have used a novel method to investigate the isotopic fractionation associated with a single physiological process-enzyme specific isotopic fractionation. We selected Cd isotopes since only one biological use of Cd is known, CdCA (a Cd/Zn carbonic anhydrase from the coastal diatom T. Weissflogii). Thus, our investigation can also inform the long standing mystery as to why this generally toxic element appears to have a nutrient-like dissolved isotopic and concentration profile in the oceans. We used the pET-15b plasmid to insert the CdCA gene into the E. coli genome. There is no known biochemical function for Cd in E. coli, making it an ideal vector for studying distinct physiological processes within a single organism. The uptake of Cd and associated isotopic fractionation was determined for both normal cells and those expressing CdCA. It was found that whole cells always exhibited a preference for the light isotopes of Cd, regardless of the expression of CdCA; adsorption of Cd to cell surfaces was not seen to cause isotopic fractionation. However, the cleaning procedure employed exerted a strong control on the observed isotopic composition of cells. Using existing protein purification techniques, we measured the Cd isotopic composition of different subcellular fractions of E

Seasonal isotope hydrology of a coffee agroforestry watershed in Costa Rica

Science.gov (United States)

Welsh Unwala, K.; Boll, J.; Roupsard, O.

2014-12-01

Improved information of seasonal variations in watershed hydrology in the tropics can strengthen models and understanding of hydrology of these areas. Seasonality in the tropics produces rainy seasons versus dry seasons, leading to different hydrologic and water quality processes throughout the year. We questioned whether stable isotopes in water can be used to trace the seasonality in this region, despite experiencing a "drier" season, such as in a Tropical Humid location. This study examines the fluctuations of stable isotope compositions (δ18O and δD) in water balance components in a small (deep groundwater system contributes significantly to baseflow, although a shallow, spring-driven system also contributes to stream water within the watershed. During storm events, precipitation contributes to stormflow in the short-term, confirming the role of superficial runoff. These results indicate that isotopes are helpful to partition the water balance even in a Tropical Humid situation where the rainfall seasonality is weak.

Contribution of bulk mass spectrometry isotopic analysis to characterization of materials in the framework of CMX-4

International Nuclear Information System (INIS)

Kuchkin, A.; Stebelkov, V.; Zhizhin, K.; Lierse von Gostomski, Ch.; Kardinal, Ch.; Loi, E.; Keegan, E.; Kristo, M.J.

2018-01-01

Seven laboratories used the results of bulk uranium isotopic analysis by either inductively coupled plasma mass spectrometry (ICP-MS) or thermal ionization mass spectrometry (TIMS) for characterization of the samples in the Nuclear Forensic International Technical Working Group fourth international collaborative material exercise, CMX-4. Comparison of the measured isotopic compositions of uranium in three exercise samples is implemented for identifying any differences or similarities between the samples. The role of isotopic analyses in the context of a real nuclear forensic investigation is discussed. Several limitations in carrying out ICP-MS or TIMS analysis in CMX-4 are noted. (author)

Deciphering human-climate interactions in an ombrotrophic peat record: REE, Nd and Pb isotope signatures of dust supplies over the last 2500 years (Misten bog, Belgium)

Science.gov (United States)

Fagel, N.; Allan, M.; Le Roux, G.; Mattielli, N.; Piotrowska, N.; Sikorski, J.

2014-06-01

A high-resolution peat record from Eastern Belgium reveals the chronology of dust deposition for the last 2500 years. REE and lithogenic elements in addition to Nd and Pb isotopes were measured in a 173 cm age-dated peat profile and provide a continuous chronology of dust source and intensity. Calculated dust flux show pronounced increases c. 300 BC, 600 AD, 1000 AD, 1200 AD and from 1700 AD, corresponding to local and regional human activities combined with climate change. The Industrial Revolution samples (1700-1950 AD) are characterised by a significant enrichment in Sc-normalised REE abundance (sum REE/Sc > 25) due to intensive coal combustion. For the pre-Industrial Revolution samples, the Sc-normalised REE abundance (10 climate. Combining REE abundance, fractionation between Light REE and Heavy REE and Nd isotope data in ombrotrophic peat allows one to distinguish between dust flux changes related to human and climate forcings.

Isotopes as tracers in a contaminated fractured chalk aquitard

Science.gov (United States)

Nativ, R.; Adar, E.

2003-04-01

Clusters of industrial plants often generate contaminant plumes with several potential sources. Prevention of further pollution and designing suitable remedial measures require identification of the contributing source among all potential ones and the sorting of currently active sources from historical ones. In the study area, an industrial complex in the Negev desert, Israel, the lateral spread of groundwater contamination combined with water level patterns and the location of wastewater storage lagoons and treatment facilities posed a serious monitoring problem. Because (1) wastewater from all plants was mixed through a central wastewater pipeline and spread in various ways and means throughout the site, and (2) a groundwater mounding area was formed upgradient of the site, the contribution of potentially contaminating individual downgradient facilities could not be inferred using site-specific contaminants and/or the increased hydraulic head. Stable isotopes of oxygen, hydrogen and sulfur, as well as tritium, proved to be an efficient monitoring tool. Isotopic characterization of the two end members, namely, the natural, uncontaminated groundwater in off-site wells, and the industrial wastewater, provided the criteria for constraining a contaminating source when several alternative sources appeared viable. The isotopic fractionation of oxygen and hydrogen isotopes could be tied to the various disposal phases of the industrial wastewater. The presented case studies illustrate the important role of isotopes as tracers at contaminated sites.

Combined electrolysis catalytic exchange (CECE) process for hydrogen isotope separation

International Nuclear Information System (INIS)

Hammerli, M.; Stevens, W.H.; Butler, J.P.

1978-01-01

Hydrogen isotopes can be separated efficiently by a process which combines an electrolysis cell with a trickle bed column packed with a hydrophobic platinum catalyst. The column effects isotopic exchange between countercurrent streams of electrolytic hydrogen and liquid water while the electrolysis cell contributes to isotope separation by virtue of the kinetic isotope effect inherent in the hydrogen evolution reaction. The main features of the CECE process for heavy water production are presented as well as a discussion of the inherent positive synergistic effects, and other advantages and disadvantages of the process. Several potential applications of the process in the nuclear power industry are discussed. 3 figures, 2 tables

Measurements of flux and isotopic composition of soil carbon dioxide

International Nuclear Information System (INIS)

Gorczyca, Z.; Rozanski, K.; Kuc, T.

2002-01-01

The flux and isotope composition of soil CO 2 has been regularly measured at three sites located in the southern Poland, during the time period: January 1998 - October 2000. They represent typical ecosystems appearing in central Europe: (i) mixed forest; (ii) cultivated agricultural field; (iii) grassland. To monitor the flux and isotopic composition of soil CO 2 , a method based on the inverted cup principle was adopted. The flux of soil CO 2 reveals distinct seasonal fluctuations, with maximum values up to ca. 25 mmol/m 2 /h during sommer months and around ten times lower values during winter time. Also significant differences among the monitored sites were detected, the flux density of this gas being highest for the mixed forest site and ca. two times lower for the cultivated grassland. Carbon-13 content of the soil CO 2 reveals little seasonal variability, with δ 13 C values essentially reflecting the isotopic composition of the soil organic matter and the vegetation type. The carbon-14 content of soil CO 2 flux also reveals slight seasonality, with lower δ 14 C values recorded during winter time. Significantly lower δ 14 C values recorded during winter time. Significantly lower δ 14 C values were recorded at depth. (author)

Contribution of environmental isotopes to the study of large aquifers in Morocco

International Nuclear Information System (INIS)

Kabbaj, A.; Zeryouhi, I.; Carlier, P.

1978-01-01

The geochemistry of environmental isotopes has been applied to several aquifers in Maroc, some of them quite large: Charf el Akab in the Tanger region, the Oum er Rbia basin and the Tadla aquifer, the free nappe of limnic limes tone in the Sais plane, and the lias limestone aquifer. The isotopic investigations on the basis of hydrogeochemical data have given more precise information on the supply conditions of these aquifers. The types of water of different origin from the Atlas or the phosphate plateau in the Sais plane and the Tadla basin have been distinguished, the supply from one aquifer to another Lias nappe which, via the flexures of the Sais plane, supplies the nappe of limic limestone has been assessed, the homogeneity or heterogeneity of these aquifers has been investigated as well as their impermeability, the Tadla aquifer and the special case of Charf el Akab compared with the marine region. The findings have proved the usefulness of these techniques and permitted a specification of the general conditions for their application. (orig.) [de

{sup 18}O, {sup 2}H and {sup 3}H isotopic composition of precipitation and shallow groundwater in Olkiluoto

Energy Technology Data Exchange (ETDEWEB)

Hendriksson, N. [Geological Survey of Finland, Espoo (Finland); Karhu, J.; Niinikoski, P. [Univ. of Helsinki (Finland)

2014-12-15

The isotopic composition of oxygen and hydrogen in local precipitation is a key parameter in the modelling of local water circulation. This study was initiated in order to provide systematic monthly records of the isotope content of atmospheric precipitation in the Olkiluoto area and to establish the relation between local rainfall and newly formed groundwater. During January 2005 - December 2012, a total of 85 cumulative monthly rainfall samples and 68 shallow groundwater samples were collected and the isotopic composition of oxygen and hydrogen was recorded for all those samples. Tritium values are available for 79 precipitation and 65 groundwater samples. Based on the 8-year monitoring, the long-term weighted annual mean isotope values of precipitation and the mean values of shallow groundwater are -11.59 per mille and -11.27 per mille for δ{sup 18}O, - 82.3 per mille and -80.3 per mille for δ{sup 2}H and 9.8 and 9.1 TU for tritium, respectively. Based on these data, the mean stable isotope ratios of groundwater represent the long-term mean annual isotopic composition of local precipitation. The precipitation data were used to establish the local meteoric water line (LMWL) for the Olkiluoto area. The line is formulated as: δ{sup 2}H = 7.45 star δ{sup 18}O + 3.82. The isotope time series reveal a change in time. The increasing trend for the δ{sup 18}O and δ{sup 2}H values may be related to climatic variability while the gradual decline observed in the {sup 3}H data is attributed to the still continuing decrease in atmospheric {sup 3}H activity in the northern hemisphere. The systematic seasonal and long-term tritium trends suggest that any potential ground-level tritium release from the Olkiluoto nuclear power plants is insignificant. The d-excess values of Olkiluoto precipitation during the summer period indicated that a notable amount of re-cycled Baltic Sea water may have contributed to precipitation in the Finnish southern coast. Preliminary estimates

A Record of the Eastern Tropical Pacific of Water Column Structure Reorganization during the Rapid Climate Changes of Marine Isotope Stage 3.

Science.gov (United States)

Hendy, I. L.

2007-05-01

Little is known about the details of paleoceanographic changes in the Eastern Tropical Pacific (ETP) during marine isotope stage 3. Here we present a high resolution record of climate change from core ME0005A 10JC (15.7°N; 95.3°E, 1040 m water depth) collected in the Gulf of Tehuantepec spanning 48 to 38 Ka. Planktonic and benthic stable isotope records have been generated alongside Corg, carbonate, δ15N and trace metal concentrations of bulk sediments. Seasonal intense wind forced upwelling produces high Corg flux in the Gulf. In winter, high atmospheric pressures in the Gulf of Mexico and low pressures in the ETP (associated with the ITCZ) create a strong pressure gradient generally blocked by high mountains along the isthmus. A gap near the Gulf of Tehuantepec allows air to spill over into the Pacific creating a hurricane force wind (the Tehuanos) that pushes water off the broad shelf, producing non-Ekman upwelling. Corg production increases from 48 to 38 Ka in association with increasing nitrate utilization as indicated by increasing δ15N values. Conservative trace metals increase relative to non-conservative between 45 and 43 Ka simultaneously with shift to more positive benthic δ13C, while non-conservative (nutrient- like) metals increase after 43 Ka. A prominent short ~1‰ negative shift in benthic δ18O occurs at 44.5 Ka with a 0.5‰ positive step occurring at 43.5 Ka. Globigerina ruber records δ18O values of ~-1‰ between 46 and 45 Ka, decreasing by ~1‰ at 45 Ka, while δ13C values vary between 0 and 1‰. Globigerina bulloides records δ18O values of ~0.5‰ and δ13C of 1‰ between 46 and 45 Ka, but records δ18O values of ~-1‰ and δ13C of -1‰ between 44 and 42 Ka. G. bulloides is associated with winter upwelling in the region, while G. ruber is a surface dweller associated with the Costa Rica Current that enters the Gulf in summer. Neogloboquadrina dutertrei and Globorotalia menardii generally record δ18O values of 0.5 to 0‰ and δ13

An isotope method for the measurement of creaming

International Nuclear Information System (INIS)

Wiechen, A.; Heine, K.

1974-01-01

The principle of a method is described which allows the course of creaming to be recorded continously and automatically by means of isotopes. Without affecting the colloidal system of milk, an isotope is added in hydrosoluble form and with only small amounts of carriers. A small detector sensitive to the respective radiation of the isotope is used to measure the decrease of counting rate on the head of the creaming cylinder, the decrease of rate being due to the effective recess of the radiation source and to the absorption of rays in the cream layer. The choice of the isotope, i.e. kind and energy of its radiation, and of the detector allows to adapt the sensitivity of the method to the rate of creaming. The method described appears to be superior to those techniques in which sedimentation balances are used; it could therefore supply useful information in research work on the process of creaming. (orig.) [de

Stable water isotope variation in a Central Andean watershed dominated by glacier and snowmelt

Directory of Open Access Journals (Sweden)

N. Ohlanders

2013-03-01

Full Text Available Central Chile is an economically important region for which water supply is dependent on snow- and ice melt. Nevertheless, the relative contribution of water supplied by each of those two sources remains largely unknown. This study represents the first attempt to estimate the region's water balance using stable isotopes of water in streamflow and its sources. Isotopic ratios of both H and O were monitored during one year in a high-altitude basin with a moderate glacier cover (11.5%. We found that the steep altitude gradient of the studied catchment caused a corresponding gradient in snowpack isotopic composition and that this spatial variation had a profound effect on the temporal evolution of streamflow isotopic composition during snowmelt. Glacier melt and snowmelt contributions to streamflow in the studied basin were determined using a quantitative analysis of the isotopic composition of streamflow and its sources, resulting in a glacier melt contribution of 50–90% for the unusually dry melt year of 2011/2012. This suggests that in (La Niña years with little precipitation, glacier melt is an important water source for central Chile. Predicted decreases in glacier melt due to global warming may therefore have a negative long-term impact on water availability in the Central Andes. The pronounced seasonal pattern in streamflow isotope composition and its close relation to the variability in snow cover and discharge presents a potentially powerful tool to relate discharge variability in mountainous, melt-dominated catchments with related factors such as contributions of sources to streamflow and snowmelt transit times.

Lead isotope ratios in six lake sediment cores from Japan Archipelago: Historical record of trans-boundary pollution sources

International Nuclear Information System (INIS)

Hosono, Takahiro; Alvarez, Kelly; Kuwae, Michinobu

2016-01-01

Sediment cores from six lakes situated from north to south on the Japanese Archipelago were collected during 2009–2010 to investigate the hypothesis that deposition of lead (Pb) was coming from East Asia (including China, South Korea and eastern part of Russia). Accumulation rates and ages of the lake sediment were estimated by the "2"1"0Pb constant rate of supply model and "1"3"7Cs inputs to reconstruct the historical trends of Pb accumulation. Cores from four lakes located in the north and central Japan, showed clear evidence of Pb pollution with a change in the "2"0"6Pb/"2"0"7Pb and "2"0"8Pb/"2"0"7Pb ratios in the recent sediment as compared to the deeper sediment. Among the six studied lakes, significant inputs of anthropogenic lead emissions were observed at Lake Mikazuki (north Hokkaido in north Japan), Lake Chokai (north of Honshu), and Lake Mikuriga (central part of Honshu). Pb isotopic comparison of collected core sediment and previously reported data for wet precipitation and aerosols from different Asian regions indicate that, before 1900, Pb accumulated in these three lakes was not affected by trans-boundary sources. Lake Mikazuki started to receive Pb emissions from Russia in early 1900s, and during the last two decades, this lake has been affected by trans-boundary Pb pollution from northern China. Lake Chokai has received Pb pollutant from northern China since early 1900s until 2009, whereas for the Lake Mikuriga the major Pb contaminant was transported from southern China during the past 100 years. The results of our study demonstrate that Japan Archipelago has received trans-boundary Pb emissions from different parts of East Asian region depending on location, and the major source region has changed historically. - Highlights: • Historical trend of Pb pollution was recorded in six Japanese Lakes. • Pb concentration and Pb isotope ratios were determined for sediment cores. • High [Pb] and less radiogenic Pb isotope ratios were observed since

Lead isotope ratios in six lake sediment cores from Japan Archipelago: Historical record of trans-boundary pollution sources

Energy Technology Data Exchange (ETDEWEB)

Hosono, Takahiro, E-mail: hosono@kumamoto-u.ac.jp [Priority Organization for Innovation and Excellence, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Alvarez, Kelly [Priority Organization for Innovation and Excellence, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Kuwae, Michinobu [Senior Research Fellow Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577 (Japan)

2016-07-15

Sediment cores from six lakes situated from north to south on the Japanese Archipelago were collected during 2009–2010 to investigate the hypothesis that deposition of lead (Pb) was coming from East Asia (including China, South Korea and eastern part of Russia). Accumulation rates and ages of the lake sediment were estimated by the {sup 210}Pb constant rate of supply model and {sup 137}Cs inputs to reconstruct the historical trends of Pb accumulation. Cores from four lakes located in the north and central Japan, showed clear evidence of Pb pollution with a change in the {sup 206}Pb/{sup 207}Pb and {sup 208}Pb/{sup 207}Pb ratios in the recent sediment as compared to the deeper sediment. Among the six studied lakes, significant inputs of anthropogenic lead emissions were observed at Lake Mikazuki (north Hokkaido in north Japan), Lake Chokai (north of Honshu), and Lake Mikuriga (central part of Honshu). Pb isotopic comparison of collected core sediment and previously reported data for wet precipitation and aerosols from different Asian regions indicate that, before 1900, Pb accumulated in these three lakes was not affected by trans-boundary sources. Lake Mikazuki started to receive Pb emissions from Russia in early 1900s, and during the last two decades, this lake has been affected by trans-boundary Pb pollution from northern China. Lake Chokai has received Pb pollutant from northern China since early 1900s until 2009, whereas for the Lake Mikuriga the major Pb contaminant was transported from southern China during the past 100 years. The results of our study demonstrate that Japan Archipelago has received trans-boundary Pb emissions from different parts of East Asian region depending on location, and the major source region has changed historically. - Highlights: • Historical trend of Pb pollution was recorded in six Japanese Lakes. • Pb concentration and Pb isotope ratios were determined for sediment cores. • High [Pb] and less radiogenic Pb isotope ratios

A Paleoevaporation Proxy Using Compound Specific Stable Isotope Measurements from Peatland Biomarkers

Science.gov (United States)

Wang, J.; Nichols, J. E.; Huang, Y.

2009-12-01

It is important to understand how evaporation from wetlands changes with climate. To do this, we have developed a paleoevaporation proxy for use in ombrotrophic peatland sediments. Using compound specific hydrogen isotopic ratios of vascular plant and Sphagnum biomarkers, we can quantitatively reconstruct past changes in evaporation. The contrast in H isotopic ratios of water available to living Sphagnum and water in the acrotelm can be used to estimate “f”—the fraction of water remaining after evaporation. Vascular plant leaf waxes record H isotopic ratios of precipitation which is little affected by evaporation, whereas the Sphagnum biomarker, C23 n-alkane, records H isotopic ratios of the water inside its cells and between its leaves, which is strongly affected by evaporation at the bog surface. Evaporation changes can then be calculated with the H-isotopic ratios of the two types of biomarkers. We calibrated the apparent fractionation of D/H ratios from source water to C23 n-alkane with lab-grown Sphagnum. We also present several reconstructions of paleoevaporation from peatlands throughout eastern North America. By comparison with overall hydrologic balance, we are able to understand the varying role of evaporation in the hydrologic system in both time and space.

61 stable isotope compositions of organic carbon and contents of ...

African Journals Online (AJOL)

Mgina

isotope record from Lake Ndutu shows a general downcore decrease in δ. 13C values ... in bulk δ13C of the terrestrial biomass in the tropics may ... CO2, temperature, moisture conditions and ... A map showing location of sampling sites of Ngorongoro Crater, Lake Ndutu and .... the Lakes Makat and Masek records cannot.

Hydrogen Isotopes Record the History of the Martian Hydrosphere and Atmosphere

Science.gov (United States)

Usui, T.; Simon, J. I.; Jones, J. H.; Kurokawa, H.; Sato, M.; Alexander, C. M. O'D; Wang, J.

2015-01-01

The surface geology and geomorphology of Mars indicates that it was once warm enough to maintain a large body of liquid water on its surface, though such a warm environment might have been transient. The transition to the present cold and dry Mars is closely linked to the history of surface water, yet the evolution of surficial water is poorly constrained. This study presents insights from hydrogen isotopes for the origin and evolution of Martian water reservoirs.

Assessing wine quality using isotopic methods

International Nuclear Information System (INIS)

Costinel, Diana; Ionete, Roxana Elena; Vremera, Raluca; Stefanescu, Ioan

2010-01-01

Full text: The analytical methods used to determine the isotope ratios of deuterium, carbon-13 and oxygen-18 in wines have gained official recognition from the Office International de la Vigne et du Vin (OIV) and National Organisation of Vine and Wine. The amount of stable isotopes in water and carbon dioxide from plant organic materials and their distribution in sugar and ethanol molecules are influenced by geo-climatic conditions of the region, grape varieties and the year of harvest. For wine characterization, to prove the botanical and geographical origin of the raw material, the isotopic analysis by continuous flow mass spectrometry CF-IRMS has made a significant contribution. This paper emphasize the results of a study concerning the assessing of water adulterated wines and non-grape alcohol and sugar additions at different concentration levels, using CF-IRMS analytical technique. (authors)

Sulfur isotopic analysis of carbonyl sulfide and its application for biogeochemical cycles

Science.gov (United States)

Hattori, Shohei; Kamezaki, Kazuki; Ogawa, Takahiro; Toyoda, Sakae; Katayama, Yoko; Yoshida, Naohiro

2016-04-01

reaction does not contribute to the MIF signatures observed in sulfate aerosol samples and/or Archaean rock records. At the presentation, we report the comparison of 34ɛ values determined using some strains and the atmospheric implications for the OCS degradation in the present atmosphere are discussed. Hattori, S., Danielache, S. O., Johnson, M. S., Schmidt, J. A., Kjaergaard, H. G., Toyoda, S., Ueno, Y., Yoshida, N. Ultraviolet absorption cross sections of carbonyl sulfide isotopologues OC32S, OC33S, OC34S and O13CS: isotopic fractionation in photolysis and atmospheric implications, Atmos. Chem. Phys., 11, 10293-10303, 2011. Schmidt, J. A., Johnson, M. S., Jung, Y., Danielache, S. O., Hattori, S., Yoshida, N., Predictions of the sulfur and carbon kinetic isotope effects in the OH + OCS reaction, Chem. Phys. Lett., 531, 64-69, 2012. Hattori, S., Schmidt J. A., Mahler D., Danielache, S. O., Johnson M. S., Yoshida N. Isotope Effect in the Carbonyl Sulfide Reaction with O(3P), J. Phys. Chem. A, 116, 3521-3526, 2012. Hattori, S., Toyoda, A., Toyoda, S., Ishino S., Ueno, Y., Yoshida, N.: Determination of the Sulfur Isotope Ratio in Carbonyl Sulfide using Gas Chromatography/Isotope Ratio Mass Spectrometry on Fragment Ions 32S+, 33S+, and 34S+, Anal. Chem., 87, 477-484, 2015. Kato, H., Saito, M., Nagahata, Y., Katayama, Y.: Degradation of ambient carbonyl sulfide by Mycobacterium spp. in soil. Microbiol., 154(1), 249-255, 2008.

Multiple stable isotope fronts during non-isothermal fluid flow

Science.gov (United States)

Fekete, Szandra; Weis, Philipp; Scott, Samuel; Driesner, Thomas

2018-02-01

develop in kinetically limited systems, which propagates with the advection speed of the incoming fluid and is, therefore, traveling fastest. The results show that oxygen isotope signatures at thermal fronts recorded in rocks and veins that experienced isotope exchange with fluids can easily be misinterpreted, namely if bulk analytical techniques are applied. However, stable isotope microanalysis on precipitated minerals may - if later isotope exchange is kinetically limited - provide a valuable archive of the transient thermal and hydrological evolution of a system.

Stable isotopic analysis of fossil chironomids as an approach to environmental reconstruction: state of development and future challenges

Directory of Open Access Journals (Sweden)

Oliver Heiri

2012-10-01

Full Text Available Remains of chironomid larvae, especially their strongly sclerotized head capsules, can be found abundantly and well preserved in most lake sediment records. These remains mainly consist of chitin and proteins and, since their chemical composition does not seem to be strongly affected by decompositional processes, they can be used to develop palaeoenvironmental reconstructions based on their stable isotopic composition. Here we review available stable isotope studies based on fossil chironomids and indicate future research necessary to further develop this still relatively new research approach. Efforts to produce stable isotope records based on fossil chironomids have mainly examined the elements H, N, C, and O. They have focussed on (1 developing the methodology for preparing samples for isotopic analysis, (2 laboratory studies cultivating chironomid larvae under controlled conditions to determine the factors affecting their stable isotopic composition, (3 ecosystem-scale studies relating stable isotopic measurements of fossil chironomid assemblages to environmental conditions, and (4 developing first down-core records describing past changes in the stable isotopic composition of chironomid assemblages. These studies have shown that chemical sample pretreatment may affect the isotopic composition for some elements. Laboratory runs suggest that the diet of the larvae influences their stable isotopic composition for H, N, C and O, whereas stable isotopes in the ambient water also strongly influence their oxygen and to a lesser extent hydrogen isotopic composition. These experiments also indicate only minor offsets between the nitrogen and carbon isotopic composition of chironomid soft tissue and the fossilizing head capsules, whereas for hydrogen and oxygen this offset remains to be explored. Though few datasets have been published, the available ecosystem studies and developed down-core sediment records indicate that stable isotopes in

Stable isotope (δ"1"3C and δ"1"5N) based interpretation of organic matter source and paleoenvironmental conditions in Al-Azraq basin, Jordan

International Nuclear Information System (INIS)

Ahmad, Khaldoun; Davies, Caroline

2017-01-01

This study examines the stable isotopes of carbon and nitrogen from cored lacustrine sediments of the Al-Azraq, an arid lake basin on the Jordan Plateau. Lacustrine sediments contain valuable records of paleoenvironmental conditions, recording local and regional responses to environmental change. Previous paleo-reconstructions on the Jordan Plateau are based on archaeology, pollen, mineralogy, and stratigraphy. The application of organic geochemistry analyses to these lake sediments identifies multiple sources of organic matter, biological production, and contributes to understanding the paleoenvironments of the Al-Azraq basin during the mid-Pleistocene period. Organic carbon concentration (Corg) provides an overview of the organic matter distribution. Carbon isotopic composition (δ13Corg) and nitrogen isotopic composition (δ15N) are indicators of organic matter sources and paleoproductivity. Magnetic susceptibility (MGSUS) measured the concentration of ferromagnetic minerals and indicated aeolian inputs. Organic geochemistry differentiated five paleoenvironmental zones with specific sources of organic matter, both aquatic and terrestrial. It identified a long period of climate wetter than the present, punctuated by a short intense period of aridity. Diagenesis plays an important role in the decomposition of organic matter and studies indicate this degradation can alter the isotopic signals of organic matter. Analyses of the isotopic signals and statistical analyses demonstrate diagenesis is not a factor in the Al-Azraq sediments in all but Zone 4 of the paleoenvironmental zones. This Zone is defined by less negative carbon isotopic composition and the presence of thick primary gypsum layers, in addition to the influx of high peaks of aeolian sediment as reflected in the magnetic susceptibility data. Stable isotope geochemistry provides detailed information on the paleoenvironments of lake sediments, and is applicable to typically challenging arid basin sediments

Ancient mantle in a modern arc: osmium isotopes in izu-bonin-mariana forearc peridotites

Science.gov (United States)

Parkinson; Hawkesworth; Cohen

1998-09-25

Mantle peridotites drilled from the Izu-Bonin-Mariana forearc have unradiogenic 187Os/188Os ratios (0.1193 to 0.1273), which give Proterozoic model ages of 820 to 1230 million years ago. If these peridotites are residues from magmatism during the initiation of subduction 40 to 48 million years ago, then the mantle that melted was much more depleted in incompatible elements than the source of mid-ocean ridge basalts (MORB). This result indicates that osmium isotopes record information about ancient melting events in the convecting upper mantle not recorded by incompatible lithophile isotope tracers. Subduction zones may be a graveyard for ancient depleted mantle material, and portions of the convecting upper mantle may be less radiogenic in osmium isotopes than previously recognized.

Water vapour source impacts on oxygen isotope variability in tropical precipitation during Heinrich events

Directory of Open Access Journals (Sweden)

S. C. Lewis

2010-06-01

Full Text Available Water isotope records such as speleothems provide extensive evidence of past tropical hydrological changes. During Heinrich events, isotopic changes in monsoon regions have been interpreted as implying a widespread drying through the Northern Hemisphere tropics and an anti-phased precipitation response in the south. Here, we examine the sources of this variability using a water isotope-enabled general circulation model, Goddard Institute for Space Studies ModelE. We incorporate a new suite of vapour source distribution tracers to help constrain the impact of precipitation source region changes on the isotopic composition of precipitation and to identify nonlocal amount effects. We simulate a collapse of the North Atlantic meridional overturning circulation with a large freshwater input to the region as an idealised analogue to iceberg discharge during Heinrich events. An increase in monsoon intensity, defined by vertical wind shear, is modelled over the South American domain, with small decreases simulated over Asia. Simulated isotopic anomalies agree well with proxy climate records, with lighter isotopic values simulated over South America and enriched values across East Asia. For this particular abrupt climate event, we identify which climatic change is most likely linked to water isotope change – changes in local precipitation amount, monsoon intensity, water vapour source distributions or precipitation seasonality. We categorise individual sites according to the climate variability that water isotope changes are most closely associated with, and find that the dominant isotopic controls are not consistent across the tropics – simple local explanations, in particular, fall short of explaining water isotope variability at all sites. Instead, the best interpretations appear to be site specific and often regional in scale.

Isotope dilution mass spectrometry: What can it contribute to accuracy in trace analysis?

International Nuclear Information System (INIS)

Bievre, P. de

1990-01-01

IDMS uses the fact that the isotopes are much better 'representatives' of an element than the average chemical atom and their numbers can be measured better in a more physical measurement than in a classicial chemical measurement where atoms are involved. (orig./EF)

CO2-dependent carbon isotope fractionation in the dinoflagellate Alexandrium tamarense

Science.gov (United States)

Wilkes, Elise B.; Carter, Susan J.; Pearson, Ann

2017-09-01

The carbon isotopic composition of marine sedimentary organic matter is used to resolve long-term histories of pCO2 based on studies indicating a CO2-dependence of photosynthetic carbon isotope fractionation (εP). It recently was proposed that the δ13C values of dinoflagellates, as recorded in fossil dinocysts, might be used as a proxy for pCO2. However, significant questions remain regarding carbon isotope fractionation in dinoflagellates and how such fractionation may impact sedimentary records throughout the Phanerozoic. Here we investigate εP as a function of CO2 concentration and growth rate in the dinoflagellate Alexandrium tamarense. Experiments were conducted in nitrate-limited chemostat cultures. Values of εP were measured on cells having growth rates (μ) of 0.14-0.35 d-1 and aqueous carbon dioxide concentrations of 10.2-63 μmol kg-1 and were found to correlate linearly with μ/[CO2(aq)] (r2 = 0.94) in accord with prior, analogous chemostat investigations with eukaryotic phytoplankton. A maximum fractionation (εf) value of 27‰ was characterized from the intercept of the experiments, representing the first value of εf determined for an algal species employing Form II RubisCO-a structurally and catalytically distinct form of the carbon-fixing enzyme. This value is larger than theoretical predictions for Form II RubisCO and not significantly different from the ∼25‰ εf values observed for taxa employing Form ID RubisCO. We also measured the carbon isotope contents of dinosterol, hexadecanoic acid, and phytol from each experiment, finding that each class of biomarker exhibits different isotopic behavior. The apparent CO2-dependence of εP values in our experiments strengthens the proposal to use dinocyst δ13C values as a pCO2 proxy. Moreover, the similarity between the εf value for A. tamarense and the consensus value of ∼25‰ indicates that the CO2-sensitivity of carbon isotope fractionation saturates at similar CO2 levels across all three

Use of a mini-computer for the processing of medical records in a radioisotope cardiac functional investigation service

International Nuclear Information System (INIS)

Belleguic, J.-C.

1978-01-01

The aim of this work is to familiarize medical users with informatics and to show what advantages can offer this technique in the handling of medical records. The field is limited here to isotopic functional explorations in cardiology, but obviously this data processing method can be applied to any isolated problem. Considering the invaluable contribution of nuclear medicine to coronary deficiency, on which 2/3 of the scintigraphic or gamma camera explorations are carried out, the study of results is centred on this branch of pathology [fr

Productivity, facies and stable-isotope records of OAE2 (Cenomanian - Turonian) in the NW European epicontinental sea: from the English Chalk to North Sea black shales

Science.gov (United States)

Jarvis, Ian; Olde, Kate; Trabucho-Alexandre, João; Gröcke, Darren

2013-04-01

The Late Cretaceous (100.5 - 66.0 Ma) provides perhaps the best example of how the Earth System may function under long-term extreme greenhouse conditions. Rapidly rising global temperatures indicate that we are heading 'back to the Cretaceous' within a few hundred years, so a better understanding of this time interval is essential. The beginning of the Late Cretaceous was characterized by a period of rapidly rising eustatic sea level, the Cenomanian transgression, which flooded continental margins and established large areas of new epicontinental sea that accumulated thick sequences of pelagic and hemipelagic carbonate (chalk). Highest global temperatures were reached during the early part of the Turonian Stage (93.9 - 89.8 Ma). This period of dramatic palaeoenvironmental change was accompanied by one the largest perturbations of the global carbon cycle in the Mesozoic: Oceanic Anoxic Event 2 (OAE2), which was characterized by a 500 kyr episode of oceanic anoxia, widespread black shale deposition, biotic turnover, and a large global positive carbon stable-isotope excursion (2 - 6 ‰ ∂13C) recorded in marine carbonates and both marine and terrestrial organic matter. The Cenomanian-Turonian boundary interval exposed at Eastbourne, southern England, has become established as a European reference section for OAE2. Here, and elsewhere in Europe, the base of the ∂13C excursion is coincident with a marked facies change from rhythmically bedded grey chalks and marls, to a >8 m thick package of dark greenish-grey marl - the Plenus Marl. The termination of OAE2 occurs 6 m above, in a package of pale-yellow-weathering nodular chalks with prominent marl seams. Sediments are organic lean (10 wt%. The onshore equivalent in eastern England (the Black Band) is similarly organic-rich, as are comparable sections in northern Germany (e.g. Wunstorf), indicating likely fully anoxic episodes within some NW European basins. The exact stratigraphic equivalence between the onshore

Contribution of stable isotopes to the study of pharmacokinetics of magnesium salts; Apport des isotopes stables a l'etude de la pharmacocinetique de sels de magnesium

Energy Technology Data Exchange (ETDEWEB)

Benech, H

1999-05-28

The use of stable isotopes as labels is becoming an attractive tool for the study of magnesium behavior in humans. It has been used two stable isotopes of magnesium, {sup 25}Mg and {sup 26}Mg, to measure the absolute bioavailability of a pharmaceutical form of magnesium. (N.C.)

Contributions of detrital subsidies to aboveground spiders during secondary succession, revealed by radiocarbon and stable isotope signatures.

Science.gov (United States)

Haraguchi, Takashi F; Uchida, Masao; Shibata, Yasuyuki; Tayasu, Ichiro

2013-04-01

Prey subsidies originating from detritus add nutrients and energy to arboreal communities. Measurement of this subsidy is required in the understanding of how food web dynamics respond to changes in surrounding environments. Shrub spiders are one of the key predators involved in food web coupling. We evaluate the effects of potential changes in prey availabilities during secondary succession on the contribution of subsidy from detrital food webs to shrub spiders and how different spider feeding guilds used the subsidy of prey from detrital food webs. We measured the relative importance of the subsidy for the spider feeding guilds, using the ratios of stable isotopes of C (δ(13)C), and N (δ(15)N) and C isotope discrimination (Δ(14)C). Diet age was calculated from Δ(14)C values, because old diet ages of spiders indicate that the spiders consume prey from detrital food sources. Dominant aerial prey (Diptera) had a distinctively old diet age compared with arboreal prey, which indicates that aerial prey were subsidized from detrital food webs. Sit-and-wait spiders tended to have an older diet age than active hunting spiders, which indicates that sit-and-wait spiders depended more on subsidies. Diet age varied only slightly for spiders in stands of different ages, indicating that rates at which spiders use grazing and detrital prey are probably determined more by foraging strategies and not by stand age. A dominance of sit-and-wait predators will lead to higher detrital subsidy inputs in shrub habitats. This study highlights the effect of shrub spider community structure (feeding guild composition) on the volume of the subsidy received from the detrital food web.

Stable Isotopic Composition of Rainfall in Western Cameroon

Energy Technology Data Exchange (ETDEWEB)

Ketchemen-Tandia, B.; Ngo Boum, S.; Ebonji Seth, C. R.; Nkoue Ndong, G. R.; Wonkam, C. [Universite de Douala, Douala (Cameroon); Huneau, F. [Universite de Bordeaux, EA Georessources and Environnement, Talence (France); Celle-Jeanton, H. [Clermont Universite, Clermont-Ferrand (France)

2013-07-15

Monthly rainfall collected at the douala station (Western cameroon) from 2006 to 2008 was analysed for oxygen-18 and deuterium content. The dataset, which is now integrated into the GNIP database, was compared to the local groundwater record in order to define the input function of regional hydrosystems. The isotope data displays a wide range of values from -0.59 to -6.14 per mille for oxygen-18 and from -7.75 to -38.8 per mille for deuterium, closely following the GMWL (global Meteoric Water line), suggesting that rain formation processes occurred under isotopic equilibrium conditions between the condensate and the corresponding vapour. No significant evaporation tendency was found. The comparison with the previous studies in the area provides a realistic pattern of isotope concentrations in both surface and groundwater throughout Cameroon. (author)

Isotope-based partitioning of streamflow in the oil sands region, northern Alberta: Towards a monitoring strategy for assessing flow sources and water quality controls

Directory of Open Access Journals (Sweden)

J.J. Gibson

2016-03-01

Full Text Available Study region: This study is based on the rapidly developing Athabasca Oil Sands region, northeastern Alberta. Study focus: Hydrograph separation using stable isotopes of water is applied to partition streamflow sources in the Athabasca River and its tributaries. Distinct isotopic labelling of snow, rain, groundwater and surface water are applied to estimate the contribution of these sources to streamflow from analysis of multi-year records of isotopes in streamflow. New hydrological insights for the region: The results provide new insight into runoff generation mechanisms operating in six tributaries and at four stations along the Athabasca River. Groundwater, found to be an important flow source at all stations, is the dominant component of the hydrograph in three tributaries (Steepbank R., Muskeg R., Firebag R., accounting for 39–50% of annual streamflow. Surface water, mainly drainage from peatlands, is also found to be widely important, and dominant in three tributaries (Clearwater R., Mackay R., Ells R., accounting for 45–81% of annual streamflow. Fairly limited contributions from direct precipitation illustrate that most snow and rain events result in indirect displacement of pre-event water by fill and spill mechanisms. Systematic shifts in regional groundwater to surface-water ratios are expected to be an important control on spatial and temporal distribution of water quality parameters and useful for evaluating the susceptibility of rivers to climate and development impacts. Keywords: Stable isotopes, Hydrograph separation, Groundwater, Surface water, Snowmelt, Oil sands

Cenozoic History of the Equatorial Indian Ocean Recorded by Nd Isotopes: The Closure of the Indonesian Gateway

Science.gov (United States)

Gourlan, A. T.; Meynadier, L.; Allegre, C. J.

2005-12-01

The northward tectonic motion of the Australian plate and the evolution of the Indonesian Island Arcs through the last 20 Ma, generate changes in the flow and the origin of the circulation between the Pacific and the Southern Indian Oceans. Indeed, the emergence of the Indonesian Archipelago and probably the rapid uplift of the island of Halmahera have dramatically reduced the Indonesian Gateway. However, the precise dating of this event is still a matter of debate. The Neodymium isotopic composition of marine sediments is an extremely good proxy to reconstruct the major changes in the past ocean circulation. The residence time of Nd is shorter than the circulation time of the global ocean. Therefore, the Nd isotopic composition varies between the different ocean basins and is function of changes in source provenances, paleocirculation, orogenic processes, and intensity of weathering on the continents as well as on the volcanic arcs. To reconstruct the evolution of the oceanic flow from the Pacific to the equatorial Indian Ocean since the Miocene, we have applied on high carbonates content sediments a leaching technique using acetic acid. The reliability of our technique has been assessed by comparison with the Hydroxylamine hydrochloride technique developed by Bayon et al (1). The Nd isotopic composition is determinated in the past seawater from the record in Fe-Mn oxides. The sedimentary sequences are accurately dated using bio and chimiostratigraphy. Three ODP Sites were chosen in the Indian Ocean with a water depth ranging from 1600 to 2800 m and mutually distant by about 3000 km. From West to East: Site 761 which is at the western edge of the Indonesian Gateway on the central northeastern part of the Wombat Plateau off NW Australia, Site 757 is located on the south of the Ninetyeast ridge and Site 707 is located in the western tropical Indian Ocean near the Seychelles Islands. Our data are compared with the first results from Site 807 located in the Pacific

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

Science.gov (United States)

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

Assessing connectivity of estuarine fishes based on stable isotope ratio analysis

Science.gov (United States)

Herzka, Sharon Z.

2005-07-01

Assessing connectivity is fundamental to understanding the population dynamics of fishes. I propose that isotopic analyses can greatly contribute to studies of connectivity in estuarine fishes due to the high diversity of isotopic signatures found among estuarine habitats and the fact that variations in isotopic composition at the base of a food web are reflected in the tissues of consumers. Isotopic analysis can be used for identifying nursery habitats and estimating their contribution to adult populations. If movement to a new habitat is accompanied by a shift to foods of distinct isotopic composition, recent immigrants and residents can be distinguished based on their isotopic ratios. Movement patterns thus can be reconstructed based on information obtained from individuals. A key consideration is the rate of isotopic turnover, which determines the length of time that an immigrant to a given habitat will be distinguishable from a longtime resident. A literature survey indicated that few studies have measured turnover rates in fishes and that these have focused on larvae and juveniles. These studies reveal that biomass gain is the primary process driving turnover rates, while metabolic turnover is either minimal or undetectable. Using a simple dilution model and biomass-specific growth rates, I estimated that young fishes with fast growth rates will reflect the isotopic composition of a new diet within days or weeks. Older or slower-growing individuals may take years or never fully equilibrate. Future studies should evaluate the factors that influence turnover rates in fishes during various stages of the life cycle and in different tissues, as well as explore the potential for combining stable isotope and otolith microstructure analyses to examine the relationship between demographic parameters, movement and connectivity.

Barium isotopes in cold-water corals

Science.gov (United States)

Hemsing, Freya; Hsieh, Yu-Te; Bridgestock, Luke; Spooner, Peter T.; Robinson, Laura F.; Frank, Norbert; Henderson, Gideon M.

2018-06-01

Recent studies have introduced stable Ba isotopes (δ 138 / 134Ba) as a novel tracer for ocean processes. Ba isotopes could potentially provide insight into the oceanic Ba cycle, the ocean's biological pump, water-mass provenance in the deep ocean, changes in activity of hydrothermal vents, and land-sea interactions including tracing riverine inputs. Here, we show that aragonite skeletons of various colonial and solitary cold-water coral (CWC) taxa record the seawater (SW) Ba isotope composition. Thirty-six corals of eight different taxa from three oceanic regions were analysed and compared to δ 138 / 134Ba measurements of co-located seawater samples. Sites were chosen to cover a wide range of temperature, salinity, Ba concentrations and Ba isotope compositions. Seawater samples at the three sites exhibit the well-established anti-correlation between Ba concentration and δ 138 / 134Ba. Furthermore, our data set suggests that Ba/Ca values in CWCs are linearly correlated with dissolved [Ba] in ambient seawater, with an average partition coefficient of DCWC/SW = 1.8 ± 0.4 (2SD). The mean isotope fractionation of Ba between seawater and CWCs Δ138/134BaCWC-SW is -0.21 ± 0.08‰ (2SD), indicating that CWC aragonite preferentially incorporates the lighter isotopes. This fractionation likely does not depend on temperature or other environmental variables, suggesting that aragonite CWCs could be used to trace the Ba isotope composition in ambient seawater. Coupled [Ba] and δ 138 / 134Ba analysis on fossil CWCs has the potential to provide new information about past changes in the local and global relationship between [Ba] and δ 138 / 134Ba and hence about the operation of the past global oceanic Ba cycle in different climate regimes.

Rapid enhancement of chemical weathering recorded by extremely light seawater lithium isotopes at the Permian-Triassic boundary

Science.gov (United States)

Sun, He; Xiao, Yilin; Gao, Yongjun; Zhang, Guijie; Casey, John F.; Shen, Yanan

2018-04-01

Lithium (Li) isotope analyses of sedimentary rocks from the Meishan section in South China reveal extremely light seawater Li isotopic signatures at the Permian–Triassic boundary (PTB), which coincide with the most severe mass extinction in the history of animal life. Using a dynamic seawater lithium box model, we show that the light seawater Li isotopic signatures can be best explained by a significant influx of riverine [Li] with light δ7Li to the ocean realm. The seawater Li isotope excursion started ≥300 Ky before and persisted up to the main extinction event, which is consistent with the eruption time of the Siberian Traps. The eruption of the Siberian Traps exposed an enormous amount of fresh basalt and triggered CO2 release, rapid global warming, and acid rains, which in turn led to a rapid enhancement of continental weathering. The enhanced continental weathering delivered excessive nutrients to the oceans that could lead to marine eutrophication, anoxia, acidification, and ecological perturbation, ultimately resulting in the end-Permian mass extinction.

Reconstruction of historical atmospheric Pb using Dutch urban lake sediments: A Pb isotope study

NARCIS (Netherlands)

Walraven, N.; van Os, B.J.H.; Klaver, G.Th.; Middelburg, J.J.; Davies, G.R.

2014-01-01

Lake sediments provide a record of atmospheric Pb deposition and changes in Pb isotope composition. To our knowledge, such an approach has not previously been performed in The Netherlands or linked to national air monitoring data. Results are presented for Pb content and isotope composition of 137Cs

A Compound-Specific Hydrogen Isotope Record at the Onset of Ocean Anoxic Event 2, Kaiparowits Plateau, Southern Utah

Science.gov (United States)

Todes, J.; Jones, M. M.; Sageman, B. B.; Osburn, M. R.

2017-12-01

Rhythmic lithologic variations (limestone-shale couplets) interpreted to reflect Milankovitch cycles occur at the onset of Ocean Anoxic Event 2 (OAE2) in deposits of the Western Interior Seaway. These couplets have been interpreted to reflect climate cycles: however, the physical mechanism(s) through which climate cycles were translated to the sedimentary record during peak greenhouse conditions remain unsettled. Although glacioeustasy has been considered, variance in surface ocean temperature, ocean circulation, or local hydrology may be more plausible options. Compound-specific hydrogen isotope ratios (δ2H) of n-alkanes and other biomarkers may provide a means to evaluate such mechanisms. Since sedimentary alkanes are direct products of plants and membrane lipid diagenesis and are resistant to secondary hydrogen exchange during thermal maturation at low (chain length distributions suggest low thermal maturity and the possible preservation of primary δ2H values. Short and long chain ­n-alkanes are potentially sourced from planktonic biomass and terrestrial plants, respectively, enabling a comparison of climatic processes between marine and terrestrial settings. Biomarkers, including both steranes and hopanes, are also preserved and reflect putative source organisms and local paleoenvironmental conditions. Facies-specific δ2H analysis will allow for evaluation of changes in the dominant source of atmospheric moisture in the Western Interior during orbitally-forced climate cycles. Organic matter deposited during periods of northerly Boreal influence would have a depleted 2H-isotope composition relative to those deposited during periods of more southerly Tethys influence. In this model, these variations are reflected by lithology - limestone deposition would occur during warm, evaporative Tethys-dominated times, while cooler, wetter Boreal periods would promote shale deposition.

Online Stable Isotope Analysis of Dissolved Organic Carbon Size Classes Using Size Exclusion Chromatography Coupled to an Isotope Ratio Mass Spectrometer

Digital Repository Service at National Institute of Oceanography (India)

Malik, A.; Scheibe, A.; LokaBharathi, P.A.; Gleixner, G.

size classes by coupling high-performance liquid chromatography (HPLC) - size exclusion chromatography (SEC) to online isotope ratio mass spectrometry (IRMS). This represents a significant methodological contribution to DOC research. The interface...

Isotopic studies of rare gases in terrestrial samples and in natural nucleosynthesis

International Nuclear Information System (INIS)

Reynolds, J.H.

1988-08-01

This project is concerned with research in rare gas mass spectrometry. The broad objective is to read the natural record that isotopes of the rare gases comprise as trace constituents of natural gases, rocks, and meteorites. In past years, these interests have led to the study of such diverse problems as the dating of rocks, the early chronology and isotopic structure of the solar system as revealed by extinct radioactivities, and the elemental and isotopic composition of trapped primordial rare gases in meteorites. In recent years, the project has focused progressively more on terrestrial problems

Isotopic studies of rare gases in terrestrial samples and in natural nucleosynthesis

International Nuclear Information System (INIS)

1987-07-01

This project is concerned with research in rare gas mass spectrometry. The broad objective is to read the natural record that isotopes of the rare gases comprise as trace constituents of natural gases, rocks, and meteorites. In past years, these interests have led to the study of such diverse problems as the dating of rocks, the early chronology and isotopic structure of the solar system as revealed by extinct radioactivities, and the elemental and isotopic composition of trapped primordial rare gases in meteorites. In recent years, the project has focused progressively more on terrestrial problems

The contribution of environmental isotopes to studies of large aquifers in Morocco

International Nuclear Information System (INIS)

Kabbaj, A.; Zeryouhi, I.; Carlier, Ph.

1979-01-01

The geochemistry of environmental isotopes has been used for the study of various aquifers in Morocco, some of which are large, such as the Charf el Akab in the Tangiers area, the Oum er Rbia basin and the Turonian aquifer of the Tadla, the free groundwater of the Quaternary lacustrine limestones of the Sais Plain and the Lias limestone aquifer. These isotope studies take hydrogeochemical data into account and have made it possible to determine the conditions of recharge of the aquifers, to distinguish waters of different origin from the Atlas Mountains or from the Phosphate Plateau in the Tadla Basin and the Sais plain, to estimate the recharge of one aquifer by another - for example groundwater of the Lias limestones passing via the folds of the Sais Plain into the lacustrine limestone aquifer - and to test the homogeneity or heterogeneity of these aquifers and their tightness (e.g. the Turonian aquifer of the Tadla and the special case of the Charf el Akab in relation to the marine environment). Altogether, these results made it possible to test the value of the techniques used and to specify the general conditions in which they can profitably be used. (author)

Combined use of isotopic and hydrometric data to conceptualize ecohydrological processes in a high-elevation tropical ecosystem

Science.gov (United States)

Mosquera, Giovanny M; Celleri, Rolando; Lazo, Patricio X; Vache, Kellie B; Perakis, Steven; Crespo, Patricio

2016-01-01

Few high-elevation tropical catchments worldwide are gauged and even fewer are studied using combined hydrometric and isotopic data. Consequently, we lack information needed to understand processes governing rainfall-runoff dynamics and to predict their influence on downstream ecosystem functioning. To address this need, we present a combination of hydrometric and water stable isotopic observations in the wet Andean páramo ecosystem of the Zhurucay Ecohydrological Observatory (7.53 km2). The catchment is located in the Andes of south Ecuador between 3400 and 3900 m a.s.l. Water samples for stable isotopic analysis were collected during 2 years (May 2011 – May 2013), while rainfall and runoff measurements were continuously recorded since late 2010. The isotopic data reveal that Andosol soils predominantly situated on hillslopes drain laterally to Histosols (Andean páramo wetlands) mainly located at the valley bottom. Histosols, in turn, feed water to creeks and small rivers throughout the year, establishing hydrologic connectivity between wetlands and the drainage network. Runoff is primarily comprised of pre-event water stored in the Histosols, which is replenished by rainfall that infiltrates through the Andosols. Contributions from the mineral horizon and the top of the fractured bedrock are small and only seem to influence discharge in small catchments during low flow generation (non-exceedance flows hydrological process and 2) (Histosols) wetlands are the major source of stream runoff. Our study highlights that detailed isotopic characterization during short time periods provides valuable information about ecohydrological processes in regions where very few basins are gauged.

Advances in primate stable isotope ecology-Achievements and future prospects.

Science.gov (United States)

Crowley, Brooke E; Reitsema, Laurie J; Oelze, Vicky M; Sponheimer, Matt

2016-10-01

Stable isotope biogeochemistry has been used to investigate foraging ecology in non-human primates for nearly 30 years. Whereas early studies focused on diet, more recently, isotopic analysis has been used to address a diversity of ecological questions ranging from niche partitioning to nutritional status to variability in life history traits. With this increasing array of applications, stable isotope analysis stands to make major contributions to our understanding of primate behavior and biology. Most notably, isotopic data provide novel insights into primate feeding behaviors that may not otherwise be detectable. This special issue brings together some of the recent advances in this relatively new field. In this introduction to the special issue, we review the state of isotopic applications in primatology and its origins and describe some developing methodological issues, including techniques for analyzing different tissue types, statistical approaches, and isotopic baselines. We then discuss the future directions we envision for the field of primate isotope ecology. Am. J. Primatol. 78:995-1003, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

ISOFORMAL: isotopic tracing of formaldehyde sources in housing. Intermediary report

International Nuclear Information System (INIS)

2011-01-01

The authors report an investigation which comprised a sampling and a chemical and isotopic analysis of emissions from the main indoor formaldehyde pollution sources in order to create a exhaustive database. Emissions which are characteristic of motorcar traffic, are also sampled in order to asses their possible contribution in the housing air. This step will be used to develop emission simulations of formaldehyde sources in a laboratory-house in order to validate the isotopic approach as tracing tool for sources of this compound. The report describes the carbon and hydrogen steady isotopes. It presents the sampling procedure, reports the determination of formaldehyde concentrations by high performance liquid chromatography with UV detectors, the use of gas source mass spectrometry, and the analytic development of the isotopic analysis of formaldehyde by gas chromatography combustion isotope ratio mass spectrometry. Outdoor and indoor pollution sources are discussed

Isotope composition and volume of Earth's early oceans.

Science.gov (United States)

Pope, Emily C; Bird, Dennis K; Rosing, Minik T

2012-03-20

Oxygen and hydrogen isotope compositions of Earth's seawater are controlled by volatile fluxes among mantle, lithospheric (oceanic and continental crust), and atmospheric reservoirs. Throughout geologic time the oxygen mass budget was likely conserved within these Earth system reservoirs, but hydrogen's was not, as it can escape to space. Isotopic properties of serpentine from the approximately 3.8 Ga Isua Supracrustal Belt in West Greenland are used to characterize hydrogen and oxygen isotope compositions of ancient seawater. Archaean oceans were depleted in deuterium [expressed as δD relative to Vienna standard mean ocean water (VSMOW)] by at most 25 ± 5‰, but oxygen isotope ratios were comparable to modern oceans. Mass balance of the global hydrogen budget constrains the contribution of continental growth and planetary hydrogen loss to the secular evolution of hydrogen isotope ratios in Earth's oceans. Our calculations predict that the oceans of early Earth were up to 26% more voluminous, and atmospheric CH(4) and CO(2) concentrations determined from limits on hydrogen escape to space are consistent with clement conditions on Archaean Earth.

Contribution of deep sourced carbon from hydrocarbon seeps to sedimentary organic carbon: Evidence from Δ14C and δ13C isotopes

Science.gov (United States)

Feng, D.; Peckmann, J.; Peng, Y.; Liang, Q.; Roberts, H. H.; Chen, D.

2017-12-01

Sulfate-driven anaerobic oxidation of methane (AOM) limits the release of methane from marine sediments and promotes the formation of carbonates close to the seafloor along continental margins. It has been established that hydrocarbon seeps are a source of dissolved inorganic and organic carbon to marine environments. However, questions remain about the contribution of deep sourced carbon from hydrocarbon seeps to the sedimentary organic carbon pool. For a number of hydrocarbon seeps from the South China Sea and the Gulf of Mexico, the portion of modern carbon was determined based on natural radiocarbon abundances (Δ14C) and stable carbon isotope (δ13Corganic carbon) compositions of the non-carbonate fractions extracted from authigenic carbonates. Samples from both areas show a mixing trend between ideal planktonic organic carbon (δ13C = -22‰ VPDB and 90% modern carbon) and the ambient methane. The δ13Corganic carbon values of non-carbonate fractions from three ancient seep deposits (northern Italy, Miocene; western Washington State, USA, Eocene to Oligocene) confirm that the proxy can be used to constrain the record of sulfate-driven AOM through most of Earth history by measuring the δ13C values of organic carbon. This study reveals the potential of using δ13C values of organic carbon to discern seep and non-seep environments. This new approach is particularly promising when authigenic carbonate is not present in ancient sedimentary environments. Acknowledgments: The authors thank BOEM and NOAA for their years' support of the deep-sea dives. Funding was provided by the NSF of China (Grants: 41422602 and 41373085).

Use of stable isotopes in human nutrition in Senegal

International Nuclear Information System (INIS)

2016-01-01

In Senegal, the Laboratory of Nutrition of the Department of Animal Biology of the Faculty of Science and Technology of UCAD has been using stable isotopic techniques for nearly twenty years. Stable isotopes were applied to different target populations to measure milk production, exclusive breastfeeding, body composition, micronutrient bioavailability and total energy expenditure.The application of stable isotopic techniques in nutrition has contributed to advocacy for exclusive breastfeeding for up to 6 months in Senegal. It enabled government decision-makers to obtain essential information on the quality of foods needed for optimal effect during pregnancy and for infant growth and the results were reflected in the national policy on micronutrient supplementation.

Latest Permian carbonate carbon isotope variability traces heterogeneous organic carbon accumulation and authigenic carbonate formation

Science.gov (United States)

Schobben, Martin; van de Velde, Sebastiaan; Gliwa, Jana; Leda, Lucyna; Korn, Dieter; Struck, Ulrich; Vinzenz Ullmann, Clemens; Hairapetian, Vachik; Ghaderi, Abbas; Korte, Christoph; Newton, Robert J.; Poulton, Simon W.; Wignall, Paul B.

2017-11-01

Bulk-carbonate carbon isotope ratios are a widely applied proxy for investigating the ancient biogeochemical carbon cycle. Temporal carbon isotope trends serve as a prime stratigraphic tool, with the inherent assumption that bulk micritic carbonate rock is a faithful geochemical recorder of the isotopic composition of seawater dissolved inorganic carbon. However, bulk-carbonate rock is also prone to incorporate diagenetic signals. The aim of the present study is to disentangle primary trends from diagenetic signals in carbon isotope records which traverse the Permian-Triassic boundary in the marine carbonate-bearing sequences of Iran and South China. By pooling newly produced and published carbon isotope data, we confirm that a global first-order trend towards depleted values exists. However, a large amount of scatter is superimposed on this geochemical record. In addition, we observe a temporal trend in the amplitude of this residual δ13C variability, which is reproducible for the two studied regions. We suggest that (sub-)sea-floor microbial communities and their control on calcite nucleation and ambient porewater dissolved inorganic carbon δ13C pose a viable mechanism to induce bulk-rock δ13C variability. Numerical model calculations highlight that early diagenetic carbonate rock stabilization and linked carbon isotope alteration can be controlled by organic matter supply and subsequent microbial remineralization. A major biotic decline among Late Permian bottom-dwelling organisms facilitated a spatial increase in heterogeneous organic carbon accumulation. Combined with low marine sulfate, this resulted in varying degrees of carbon isotope overprinting. A simulated time series suggests that a 50 % increase in the spatial scatter of organic carbon relative to the average, in addition to an imposed increase in the likelihood of sampling cements formed by microbial calcite nucleation to 1 out of 10 samples, is sufficient to induce the observed signal of carbon

Latest Permian carbonate carbon isotope variability traces heterogeneous organic carbon accumulation and authigenic carbonate formation

Directory of Open Access Journals (Sweden)

M. Schobben

2017-11-01

Full Text Available Bulk-carbonate carbon isotope ratios are a widely applied proxy for investigating the ancient biogeochemical carbon cycle. Temporal carbon isotope trends serve as a prime stratigraphic tool, with the inherent assumption that bulk micritic carbonate rock is a faithful geochemical recorder of the isotopic composition of seawater dissolved inorganic carbon. However, bulk-carbonate rock is also prone to incorporate diagenetic signals. The aim of the present study is to disentangle primary trends from diagenetic signals in carbon isotope records which traverse the Permian–Triassic boundary in the marine carbonate-bearing sequences of Iran and South China. By pooling newly produced and published carbon isotope data, we confirm that a global first-order trend towards depleted values exists. However, a large amount of scatter is superimposed on this geochemical record. In addition, we observe a temporal trend in the amplitude of this residual δ13C variability, which is reproducible for the two studied regions. We suggest that (sub-sea-floor microbial communities and their control on calcite nucleation and ambient porewater dissolved inorganic carbon δ13C pose a viable mechanism to induce bulk-rock δ13C variability. Numerical model calculations highlight that early diagenetic carbonate rock stabilization and linked carbon isotope alteration can be controlled by organic matter supply and subsequent microbial remineralization. A major biotic decline among Late Permian bottom-dwelling organisms facilitated a spatial increase in heterogeneous organic carbon accumulation. Combined with low marine sulfate, this resulted in varying degrees of carbon isotope overprinting. A simulated time series suggests that a 50 % increase in the spatial scatter of organic carbon relative to the average, in addition to an imposed increase in the likelihood of sampling cements formed by microbial calcite nucleation to 1 out of 10 samples, is sufficient to induce the

Contribution to the hydrogeological, geochemical and isotopic study of Ain El Beidha and Merguellil (Kairouan plain) aquifers: Implication for the dam-aquifer relationship

International Nuclear Information System (INIS)

Ben Ammar, Safouan

2007-01-01

karst before reaching the Kairouan plain aquifer (springs). Groundwater under flow is estimated at 9 M m3 year-1 and the karstic spring flow is evaluated at 10 M m3 year-1. The spring waters show an intermediate isotope composition between dam reservoir water and the upper catchment of Ain el Beidha basin. The contribution of dam water in mixed water (spring) varies between 21 to 66% depending on time. Values from 18O and 2H ratio are well correlated with the karstic spring flow and with the water level in the reservoir. The hydrogeological study helped to understand the hydrodynamic functioning of the Kairouan plain aquifer system and identified a decline of the water table levels (1.5 m year-1). This decrease is explained mainly by over exploitation (4.8 M m3 year-1). The hydrochemical investigation indicated that the rock-water interaction is the main process contributing to the groundwater salinization. All the samples collected in the Merguellil basin are of the main hydrochemical type: Cl-SO4-Na. Stable isotope values measured in the upstream part of plain, closer the dam, differ from other parts of the aquifer, therefore suggesting a significant input from evaporated dam waters mixed with Ain el Beidha groundwater (spring water coming from the karst). This contamination can be observed as far as 7 km downstream. However, isotopic imprint of the previous recharge process (infiltration of wadi floods) are still noticeable. The residence time of the groundwater was estimated by carbon-14 dating that shows variable values of transit velocity of the groundwater ranging from 3.36 to 0.44 m year-1 depending on the groundwater flow and on the lithological variability of the aquifer. (Author).

Enhanced forensic discrimination of pollutants by position-specific isotope analysis using isotope ratio monitoring by (13)C nuclear magnetic resonance spectrometry.

Science.gov (United States)

Julien, Maxime; Nun, Pierrick; Höhener, Patrick; Parinet, Julien; Robins, Richard J; Remaud, Gérald S

2016-01-15

In forensic environmental investigations the main issue concerns the inference of the original source of the pollutant for determining the liable party. Isotope measurements in geochemistry, combined with complimentary techniques for contaminant identification, have contributed significantly to source determination at polluted sites. In this work we have determined the intramolecular (13)C profiles of several molecules well-known as pollutants. By giving additional analytical parameters, position-specific isotope analysis performed by isotope ratio monitoring by (13)C nuclear magnetic resonance (irm-(13)C NMR) spectrometry gives new information to help in answering the major question: what is the origin of the detected contaminant? We have shown that isotope profiling of the core of a molecule reveals both the raw materials and the process used in its manufacture. It also can reveal processes occurring between the contamination site 'source' and the sampling site. Thus, irm-(13)C NMR is shown to be a very good complement to compound-specific isotope analysis currently performed by mass spectrometry for assessing polluted sites involving substantial spills of pollutant. Copyright © 2015 Elsevier B.V. All rights reserved.

Romanian wines characterization with CF-IRMS (Continuous Flow Isotope Ratio Mass Spectrometry) isotopic analysis

International Nuclear Information System (INIS)

Costinel, Diana; Ionete, Roxana Elena; Vremera, Raluca; Stanciu, Vasile

2007-01-01

Wine growing has been known for centuries long in Romania. The country has been favored by its geographical position in south-eastern Europe, by its proximity to the Black Sea, as well as by the specificity of the local soil and climate. Alongside France, Italy, Spain, Germany, countries in this area like Romania could also be called 'a vine homeland' in Europe. High quality wines produced in this region were object of trade ever since ancient times. Under current EU research projects, it is necessary to develop new methods of evidencing wine adulteration and safety. The use of mass spectrometry (MS) to determine the ratios of stable isotopes in bio-molecules now provides the means to prove the botanical and geographical origin of a wide variety of foodstuffs - and therefore, to authenticate and eliminate fraud. Isotope analysis has been officially adopted by the EU as a means of controlling adulteration of wine. Adulteration of wine can happen in many ways, e.g. addition of non-grape ethanol, addition of non-grape sugar, water or other unauthorized substances, undeclared mixing of wines from different wards, geographical areas or countries, mislabelling of variety and age. The present paper emphasize the isotopic analysis for D/H, 18 O/ 16 O, 13 C/ 12 C from wines, using a new generation Isotope Ratio MS, Finnigan Delta V Plus, coupling with a three flexible continuous flow preparation device (GasBench II, TC Elemental Analyser and GC-C/TC). Therefore authentication of wines is an important problem to which isotopic analysis has made a significant contribution. (authors)

Upper Campanian–Maastrichtian nannofossil biostratigraphy and high-resolution carbon-isotope stratigraphy of the Danish Basin

DEFF Research Database (Denmark)

Thibault, Nicolas Rudolph; Harlou, Rikke; Schovsbo, Niels

2012-01-01

High-resolution carbon isotope stratigraphy of the upper Campanian – Maastrichtian is recorded in the Boreal Realm from a total of 1968 bulk chalk samples of the Stevns-1 core, eastern Denmark. Isotopic trends are calibrated by calcareous nannofossil bio-events and are correlated with a lower...

Wide-band digital equipment for study of neutron reactions producing short-living isotopes

International Nuclear Information System (INIS)

Bonyushkin, E.K.; Boyarintsev, V.A.; Goryushkin, S.I.; Drozdov, Yu.M.; Orlov, R.A.

1976-01-01

Digital equipment designed for recording automatically curves of decay for radioactive isotopes with a half-life period of about 10 Ms is described. Detection of a signal produced by isotope-isomer radioactive radiation is performed in the integral mode. A block-diagram of the measuring channel corresponding to the current mode of recording is presented. The accuracy characteristics of such a measuring channel are determined primarily by parameters of an analog-digital converter and they do not depend upon the length of the signal cable. Principles of operation for digital equipment are based on logarithmic conversion of the d.c. voltage into a number of pulses by the oscillating contour, i.e. a number of pulses in the envelope is proportional to the logarithm of the strobbed voltage. The amplitude range of recording is higher than 10 3 . Total instrumental errors of recording are about 5 per cent

Water isotope systematics: Improving our palaeoclimate interpretations

Science.gov (United States)

Jones, M. D.; Dee, S.; Anderson, L.; Baker, A.; Bowen, G.; Noone, D.

2016-01-01

implications of advances in understanding in these areas for the interpretation of palaeo records and proxy data – climate model comparison.Here, we briefly review these areas of research, and discuss challenges for the water isotope community in improving our ability to partition climate vs. auxiliary signals in palaeoclimate data.

Fractionation of Stable Isotopes in Atmospheric Aerosol Reactions

DEFF Research Database (Denmark)

Meusinger, Carl

-independent) fractionation processes of stable isotopes of C, N, O and S in order to investigate three different systems related to aerosols: 1. Post-depositional processes of nitrate in snow that obscure nitrate ice core records 2. Formation and aging of secondary organic aerosol generated by ozonolysis of X...... reactions and undergo complex chemical and physical changes during their lifetimes. In order to assess processes that form and alter aerosols, information provided by stable isotopes can be used to help constrain estimates on the strength of aerosol sources and sinks. This thesis studies (mass...... as required. The kndings provide important results for the studies' respective felds, including a description of the isotopic fractionation and quantum yield of nitrate photolysis in snow, equilibrium fractionation in secondary organic aerosol and fractionation constants of different oxidation pathways of SO2....

Improvement of Groundwater Modeling by Using of the Environmental Isotopes with Liquid Water Isotope Analyzer

International Nuclear Information System (INIS)

Kamdee, K.; Laoharojanaphand, S.; Noipow, N.; Jaruratanab, A.; Detoup, D.; Chantarachota, W.

2011-06-01

Full text: A new analysis method of stable isotope was developed by using the absorption characteristic of pulsed laser beam concept for trace gas analysis (O'Keefe, 1989). The method provides high performance and analysis capacity but contribute less applicative compared to the traditional IRMS methods by using only pure liquids phase of water. The methods are using with environmental isotopes techniques to improve groundwater management of the Chiang Mai Basin, the biggest Cenozoic basin in the northern part of Thailand. Unconsolidated and consolidated sediments form three main aquifers, the Chao Phraya, Chiang Rai and Chiang Mai Aquifers, show clearly unconfined to confined characteristic. From chemical composition of the groundwater, most of groundwater samples are of calcium-magnesium bicarbonate and sodium-potassium bicarbonate type and few of them show the risk of fluorine content for drinking purpose. Radioactive Carbon results showed the ages of groundwater vary from 2,300 ±240 to +30,000 years. The tritium results showed low tritium content, less than 1.0 Tritium Unit (T.U.) in all groundwater samples, was compared to the surface water that arranged from 2.1-2.6 T.U. The stable isotope result of the liquid water isotope analyzer (Los Gatos Research: DLT-100) indicated the main recharge resources of groundwater in the basin was from the local rain water in terrace area and from both sides of the basin at different altitudes. Surface water from rivers and dams have no contribution to the origin of groundwater in the basin. The radioactive and stable isotope data of ground water from different aquifers did not show clear separation and was similar to the previous study of the basin in 1993 (Buapheng et al., 1993). Thus, the recent data accrue to be convinced that there was some mixing of groundwater within three aquifers and rather slow replenishment. The conceptual modeling of groundwater system in Chiang Mai Basin can be revised. The Upper part of Chiang

Holocene climate variability revealed by oxygen isotope analysis of Sphagnum cellulose from Walton Moss, northern England

Science.gov (United States)

Daley, T. J.; Barber, K. E.; Street-Perrott, F. A.; Loader, N. J.; Marshall, J. D.; Crowley, S. F.; Fisher, E. H.

2010-07-01

Stable isotope analyses of Sphagnum alpha-cellulose, precipitation and bog water from three sites across northwestern Europe (Raheenmore, Ireland, Walton Moss, northern England and Dosenmoor, northern Germany) over a total period of 26 months were used to investigate the nature of the climatic signal recorded by Sphagnum moss. The δ18O values of modern alpha-cellulose tracked precipitation more closely than bog water, with a mean isotopic fractionation factor αcellulose-precipitation of 1.0274 ± 0.001 (1 σ) (≈27‰). Sub-samples of isolated Sphagnum alpha-cellulose were subsequently analysed from core WLM22, Walton Moss, northern England yielding a Sphagnum-specific isotope record spanning the last 4300 years. The palaeo-record, calibrated using the modern data, provides evidence for large amplitude variations in the estimated oxygen isotope composition of precipitation during the mid- to late Holocene. Estimates of palaeotemperature change derived from statistical relationships between modern surface air temperatures and δ18O precipitation values for the British Isles give unrealistically large variation in comparison to proxies from other archives. We conclude that use of such relationships to calibrate mid-latitude palaeo-data must be undertaken with caution. The δ18O record from Sphagnum cellulose was highly correlated with a palaeoecologically-derived index of bog surface wetness (BSW), suggesting a common climatic driver.

Isotopic evidences of past upwelling intensity in the Arabian Sea

Digital Repository Service at National Institute of Oceanography (India)

Naidu, P.D.

and understand the history of upwelling as it is recorded in deep-sea sediments. The southwest (SW) monsoon strongly influences the climatic conditions in South and Southeast Asia and biological productivity in the Arabian Sea. ability at the ODP Site 728... climatic change and ocean history (McCrea, 1950; Epstein et al., 1953; Emiliani, 1955). The isotopic role of planktic forami- nifera expanded, it was recognized that foraminifera did not secret their shells in isotopic equilibrium with ambient water (Be...

Isotopic Analysis of Fingernails as a USGS Open House Demonstration of the Use of Stable Isotopes in Foodweb Studies

Science.gov (United States)

Silva, S. R.; Kendall, C.; Young, M. B.; Choy, D.

2011-12-01

the American Journal of Physical Anthropology (Nardoto et al., 2006). This study found that despite global trends toward dietary homogenization, regional differences in food resources and dietary preferences were recorded in the carbon and nitrogen isotopic compositions of fingernails.

Isotopic composition of Pb and Th in interplinian volcanics from Somma-Vesuvius volcano, Italy

International Nuclear Information System (INIS)

Cortini, M.; De Vivo, B.; Somma, R.; Ayuso, R.A.; Holden, P.

2004-01-01

We present a detailed isotopic study of volcanic rocks emitted from Somma-Vesuvius volcano during three periods of interplinian activity: 'Protohistoric' (3550 y B.P. to 79 A.D.), 'Ancient Historic' (79 to 472 A.D.) and 'Medieval' (472 to 1631 A.D.). Pb isotopic compositions of two acid leached fractions and whole rock residues of 37 whole rock samples (determined by Somma et al., 2001) show that each of the three interplinian periods is distinguished by small, systematic, and unique uranogenic and thorogenic Pb isotopic trends. This key and novel feature is compatible with the notion that the Pb isotopic data reflect small-scale source heterogeneity operating over relatively short periods of time. From this representative group of samples, a selected set of nine whole rocks were analyzed for Th isotopes. 232 Th/ 238 U ratios in the source can be obtained independently from Pb and from Th isotopes. Those obtained from Pb isotopes represent source ratios, time-integrated over the whole age of the earth; they range from 3.9 to 4.1. 232 Th/ 238 U obtained from Th isotopes are those of the present source. They are lower, and cluster around 3.5; this difference probably indicates recent U enrichment of the present source. The behavior of Pb, as inferred by its isotopic ratios, is quite distinct from that of Sr and Nd isotopes: Pb isotope variations are not correlated to Sr or Nd isotope variations. The isotopic contrast is compatible with the idea that the isotopes were decoupled during magmatic production, evolution, and ascent through the crust. Thus, the Pb isotopes do not reflect the effects of the same processes as in the case of the Sr and Nd isotopes, or, as we also favor, they do not necessarily reflect the same source contributions into the magmas. Moreover, the Pb isotopic evolution of the interplinian rocks chiefly reflects mixing, driven by processes that are superimposed on, and independent of, other source contributions that determine the isotopic

The correct use of Sr isotopes in river-groundwater mixing models: A ...

African Journals Online (AJOL)

2005-07-03

Jul 3, 2005 ... Stable isotopes are used extensively in hydrology as a means of establishing the contribution of different reservoirs and sources to the water budget. If the information contained in stable isotope data is to be used in a quantitative sense, appro- priate mass balance equations have to be used. Specifically ...

Preferential flow pathways revealed by field based stable isotope analysis of CO2 by mid-infrared laser spectroscopy

Science.gov (United States)

van Geldern, Robert; Nowak, Martin; Zimmer, Martin; Szizybalski, Alexandra; Myrttinen, Anssi; Barth, Johannes A. C.; Jost, Hj

2016-04-01

A newly developed and commercially available isotope ratio laser spectrometer for CO2 analyses has been tested during a 10-day field monitoring campaign at the Ketzin pilot site for CO2 storage in northern Germany. The laser instrument is based on tunable laser direct absorption in the mid-infrared. The instrument recorded a continuous 10-day carbon stable isotope data set with 30 minutes resolution directly on-site in a field-based laboratory container during a tracer experiment. To test the instruments performance and accuracy the monitoring campaign was accompanied by daily CO2 sampling for laboratory analyses with isotope ratio mass spectrometry (IRMS). The carbon stable isotope ratios measured by conventional IRMS technique and by the new mid-infrared laser spectrometer agree remarkably well within 2σ analytical precision (<0.3 ‰). This proves the capability of the new mid-infrared direct absorption technique to measure high precision and accurate real-time table isotope data directly in the field. The injected CO2 tracer had a distinct δ13C value that was largely different from the reservoir background value. The laser spectroscopy data revealed a prior to this study unknown, intensive dynamic with fast changing δ13C values. The arrival pattern of the tracer suggest that the observed fluctuations were probably caused by migration along separate and distinct preferential flow paths between injection well and observation well. The new technique might contribute to a better tracing of the migration of the underground CO2 plume and help to ensure the long-term integrity of the reservoir.

Salinity information in coral δ18O records

Science.gov (United States)

Conroy, J. L.; Thompson, D. M.; Dassié, E. P.; Stevenson, S.; Konecky, B. L.; DeLong, K. L.; Sayani, H. R.; Emile-Geay, J.; Partin, J. W.; Abram, N. J.; Martrat, B.

2017-12-01

Coral oxygen isotopic ratios (δ18O) are typically utilized to reconstruct sea surface temperature (SST), or SST-based El Niño-Southern Oscillation metrics (e.g., NIÑO3.4), despite the influence of both SST and the oxygen isotopic composition of seawater (δ18Osw) on coral δ18O. The ideal way to isolate past δ18Osw variations is to develop independent and univariate SST and δ18Osw responders, for instance, via paired coral δ18O and Sr/Ca analyses. Nonetheless, many coral δ18O records without paired Sr/Ca records already exist in the paleoclimatic literature, and these may be able to provide some insight into past δ18Osw and salinity changes due to the nature of the significant positive relationship between instrumental salinity and δ18Osw. Here we use coral δ18O records from the new PAGES Iso2k database to assess the regions in which coral δ18O has the greatest potential to provide salinity information based on the strength of the relationship between instrumental salinity and coral δ18O values. We find from annual pseudocoral similations that corals in the western tropical Pacific share a substantial fraction of their variance with δ18Osw rather than SST. In contrast, in the Indian Ocean and eastern tropical Pacific it is SST that predominantly explains coral δ18O variance. In agreement with this variance decomposition, we find that coral δ18O time series from the western tropical Pacific are significantly correlated with mid to late 20th century salinity. However, variations in the strength of the δ18Osw-salinity relationship across the western tropical Pacific will likely have a significant influence on coral δ18O-based salinity reconstructions. Additionally, in some cases a strong, negative correlation between SST and δ18Osw might not allow their influences to be adequately separated in coral δ18O records without the use of coupled Sr/Ca estimates of the temperature contribution. Overall, we find a range of modern salinity and SST

Chemical and oxygen isotope zonings in garnet from subducted continental crust record mineral replacement and metasomatism

Science.gov (United States)

Vho, Alice; Rubatto, Daniela; Regis, Daniele; Baumgartner, Lukas; Bouvier, Anne-Sophie

2017-04-01

, and variations up to 6.5‰ in Cima Bonze garnets suggest significant metasomatic replacement from external fluids. The combination of oxygen isotopes, trace element geochemistry and P-T modelling allows reconstructing the major stages of metasomatism, as well as identifying the nature of the fluid interacting with the rock at each metamorphic stage. REFERENCES Lardeaux, J. M., & Spalla, M. I. (1991). From granulites to eclogites in the Sesia zone (Italian Western Alps): A record of the opening and closure of the Piedmont ocean. Journal of Metamorphic Geology, 9, 35-59. Regis, D., Rubatto, D., Darling, J., Cenki-Tok, B., Zucali, M., & Engi, M. (2014). Multiple metamorphic stages within an eclogite-facies terrane (Sesia Zone, Western Alps) revealed by Th-U-Pb petrochronology. Journal of Petrology, 55(7), 1429-1456. Robyr, M., Darbellay, B., & Baumgartner, L. P. (2014). Matrix-dependent garnet growth in polymetamorphic rocks of the Sesia zone, Italian Alps. Journal of Metamorphic Geology, 32(1), 3-24.

Oxygen and hydrogen isotope fractionation during cellulose metabolism in Lemna gibba L

International Nuclear Information System (INIS)

Yakir, D.; DeNiro, M.J.

1990-01-01

Lemna gibba L. B3 was grown under heterotrophic, photoheterotrophic, and autotrophic conditions in water having a variety of hydrogen and oxygen isotopic compositions. The slopes of the linear regression lines between the isotopic composition of water and leaf cellulose indicated that under the three growth conditions about 40, 70, and 100% of oxygens and carbon-bound hydrogens of cellulose exchanged with those of water prior to cellulose formation. Using the equations of the linear relationships, we estimated the overall fractionation factors between water and the exchanged oxygen and carbon bound-hydrogen of cellulose. At least two very different isotope effects must determine the hydrogen isotopic composition of Lemna cellulose. One reflects the photosynthetic reduction of NADP, while the second reflects exchange reactions that occur subsequent to NADP reduction. Oxygen isotopic composition of cellulose apparently is determined by a single type of exchange reaction with water. Under different growth conditions, variations in metabolic fluxes affect the hydrogen isotopic composition of cellulose by influencing the extent to which the two isotope effects mentioned above are recorded. The oxygen isotopic composition of cellulose is not affected by such changes in growth conditions

Hydro-geochemical and isotopic composition of ground water in Helwan area

Directory of Open Access Journals (Sweden)

W.M. Salem

2015-12-01

The environmental stable isotopes oxygen and hydrogen (18O, and deuterium were studied and used to identify the sources of recharge. The studied ground waters are enriched in D and 18O and the isotopic features suggest that most of the ground water recharged indirectly after evaporation prior to infiltration from irrigation return water as well as the contribution from Nile water.

Forward Modeling of Carbonate Proxy Data from Planktonic Foraminifera using Oxygen Isotope Tracers in a Global Ocean Model

Science.gov (United States)

Schmidt, Gavin A.

1999-01-01

The distribution and variation of oxygen isotopes in seawater are calculated using the Goddard Institute for Space Studies global ocean model. Simple ecological models are used to estimate the planktonic foraminiferal abundance as a function of depth, column temperature, season, light intensity, and density stratification. These models are combined to forward model isotopic signals recorded in calcareous ocean sediment. The sensitivity of the results to the changes in foraminiferal ecology, secondary calcification, and dissolution are also examined. Simulated present-day isotopic values for ecology relevant for multiple species compare well with core-top data. Hindcasts of sea surface temperature and salinity are made from time series of the modeled carbonate isotope values as the model climate changes. Paleoclimatic inferences from these carbonate isotope records are strongly affected by erroneous assumptions concerning the covariations of temperature, salinity, and delta (sup 18)O(sub w). Habitat-imposed biases are less important, although errors due to temperature-dependent abundances can be significant.

FY 2005 annual report. 21st century COE program isotope science and engineering from basics to applications

International Nuclear Information System (INIS)

2006-09-01

The 05' activity on 21st century COE program, Nagoya University, Isotopes open the future' is reported. The contents are: Research and educational execution planning; Operational reports (research activities, educational activities, international conferences, etc.); Research activities (1. the basic research field...isotope separation, isotope production, isotope measurement, and isotope materials, 2. the composite and development field...isotopes in biology, cultural science, and environment, 3. research contributions); Educational activities (1. programs for assist of young research students, 2. lectures on English, 3. lectures for postgraduate students). (M.H.)

Seasonal radiogenic isotopic variability of the African dust outflow to the tropical Atlantic Ocean and across to the Caribbean

Science.gov (United States)

Kumar, Ashwini; Abouchami, W.; Galer, S. J. G.; Singh, Satinder Pal; Fomba, K. W.; Prospero, J. M.; Andreae, M. O.

2018-04-01

- reaching Cape Verde and Barbados during the summer, while contributions during the winter months are likely patchy and minor at most. Importantly, a short-term isotopic excursion is resolved in the Cape Verde winter record during a dust outbreak on 06-08 February 2012. This features a highly radiogenic Pb and Sr and unradiogenic Nd signature, marking a clear shift in dust provenance relative to that of normal days. As the dust storm waned, continuous gradual changes are observed, reflecting mixing and progressive dilution with dust typical of normal days. These inferences from radiogenic isotope tracers are corroborated by both satellite images (CALIPSO and MODIS) and back-trajectory analyses. The radiogenic isotope fingerprinting of these presently-active North African dust sources, and especially the Saharan Air Layer, will prove invaluable in studies of past dust emission from Northern Africa, where imagery and back trajectory analysis are unavailable.

Isotopic paleoecology of Clovis mammoths from Arizona

Science.gov (United States)

Metcalfe, Jessica Z.; Longstaffe, Fred J.; Ballenger, Jesse A. M.; Vance Haynes, C., Jr.

2011-11-01

The causes of megafaunal extinctions in North America have been widely debated but remain poorly understood. Mammoths (Mammuthus spp.) in the American Southwest were hunted by Clovis people during a period of rapid climate change, just before the regional onset of Younger Dryas cooling and mammoth extirpation. Thus, these mammoths may provide key insights into late Pleistocene extinction processes. Here we reconstruct the seasonal diet and climatic conditions experienced by mammoths in the San Pedro Valley of Arizona, using the carbon (13C/12C) and oxygen (18O/16O) isotope compositions of tooth enamel. These records suggest that Clovis mammoths experienced a warm, dry climate with sufficient summer rainfall to support seasonal C4 plant growth. Monsoon intensity may have been reduced relative to the preceding time period, but there is no isotopic evidence for severe drought. However, it is possible that the "Clovis drought", inferred from stratigraphic evidence, occurred suddenly at the end of the animals' lives and thus was not recorded in the enamel isotopic compositions. Unlike mammoths that lived before the Last Glacial Maximum, Clovis mammoths regularly increased C4 grass consumption during summer, probably seeking seasonally green grasslands farther from the river valley. This predictable seasonal behavior may have made mammoths easier to locate by Clovis hunters. Furthermore, Clovis mammoths probably had no previous experience of such sudden climatic change as is believed to have occurred at the time of their extinction.

Geology and stable isotope geochemistry of Paleoarchean sulfur. Formation, preservation and geobiology of ancient pyrite and barite

NARCIS (Netherlands)

Roerdink, D.L.|info:eu-repo/dai/nl/318834340

2013-01-01

Sulfur isotopes in ancient sulfate and sulfide minerals provide a comprehensive record of microbial processes involved in the early sulfur cycle on Earth. However, the interpretation of these isotopic signatures requires information on the geological context of such samples, because abiotic

Isotope diagnostics apparatus

International Nuclear Information System (INIS)

Herrschaft, H.

1976-01-01

The invention relates to a measuring probe for an isotope diagnostics apparatus to determine the distribution of radioactive substances in a body by measuring the radiation emanating from this body by means of a multiplicity of measuring probes directed simultaneously towards areas of measuring surfae and carried in guidances of a holding block. The measuring results of the individual probes are recorded separately, thus allowing the possibility of being evaluated separately, too. Measuring probes of this kind are used in multi-channel measuring objects and are useful particularly for determining the regional cerebral blood flow. (orig./ORU) [de

The use of carbon stable isotope ratios in drugs characterization

Energy Technology Data Exchange (ETDEWEB)

Magdas, D. A., E-mail: gabriela.cristea@itim-cj.ro; Cristea, G., E-mail: gabriela.cristea@itim-cj.ro; Bot, A., E-mail: gabriela.cristea@itim-cj.ro; Mirel, V., E-mail: gabriela.cristea@itim-cj.ro [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath Str., 400293 Cluj-Napoca (Romania)

2013-11-13

Isotopic Ratio Mass Spectrometry (IRMS) is an effective toll to be used for drug product authentication. The isotopic composition could be used to assist in the differentiation between batches of drugs and assist in the identification of counterfeit materials on the market. Only two factors affect the isotopic ratios in pharmaceutical components: the isotopic composition of the raw materials and the synthetic processes performed upon them. Counterfeiting of pharmaceutical drugs threatens consumer confidence in drug products companies' economical well-being. In this preliminary study, the analyzed samples consist in two types of commercially available analgesics, which were purchases from Romanian pharmacies. Differences in δ{sup 13}C between batches from −29.7 to −31.6% were observed, demonstrating that this method can be used to differentiate among individual drug batches and subsequently identify counterfeits on the market. On the other hand, carbon isotopic ratios differences among producers were recorded, the variations being between −31.3 to −34.9% for the same type of analgesic, but from different manufactures.

Disentangling Diagenesis From the Rock Record: An Example From the Permo-Triassic Wordie Creek Formation, East Greenland

Science.gov (United States)

Roberts, J.; Turchyn, A. V.; Wignall, P. B.; Newton, R. J.; Vane, C. H.

2018-01-01

The measurement of isotope ratios in sedimentary rocks deposited over geological time can provide key insights to past environmental change over important intervals in the past. However, it is important to be aware that secondary alteration can overprint the original isotopic records. We demonstrate this principle using high-resolution carbon, sulfur, and oxygen isotope measurements in organic carbon, pyrite, and carbonate minerals (δ13Corg, δ34Spyr, δ34SCAS, δ13Ccarb, and δ18Ocarb) and kerogen analyses (HI and OI) from the Wordie Creek Formation, East Greenland. These sediments were initially deposited across the Permo-Triassic transition, but as we will show, the carbonate record has been altered by interaction with meteoric water significantly after initial deposition. Comparison of the better preserved organic carbon and pyrite records with a proximal Permo-Triassic sequence reveals significant pyrite-sulfur isotope variability across the Permo-Triassic transition. This regional heterogeneity argues against basin-wide euxinia and instead suggests localized changes in sulfur fractionation in response to variations in organic carbon flux. This hypothesis can be used to explain seemingly inconsistent regional trends in other sulfur isotopes across the Permo-Triassic transition.

Groundwater geochemistry of nile delta-desert interface 1.isotope hydrology

International Nuclear Information System (INIS)

Hussein, M.F.; Nada, A.A.; Awad, M.A.

1995-01-01

Sustenance and environmental protection of groundwater supply is of major concern in the integral environmental development in the arid to sub-arid regions in the Nile basin. Isotope data ( 18O , 2H and 3H ) of groundwater in the west of the Nile delta indicates the contribution of palaeo groundwater component (in the range 0.1 - 0.8 with means of 0.39 and 0.52 for tahrir and khatatbah, respectively) along with sub recent recharge from the delta aquifer and recent recharge from irrigation conveyance canals in desert. Isotope mixing model (developed as Two-input table using excel TM spreads heat on apple Macintosh TM) is proposed to explain the apparent discrepancies in groundwater isotopic composition of khatatbah and tahrir areas assuming the contribution of two isotopically different palaeo-oples with two isotopically similar maind delta groundwater poles. About 0.30% 1 8 O depletion per 10 Km downstream is detected and low northward groundwater recharge is suggested along 75 Km of the western strip of rosetta Nile. Higher sub-recent recharge from the main delta aquifer is believed to take place in khatatbah than tahrir whereas the last is believed to be replenished at present from the irrigation/ drainage network and irrigated fields with higher pollution risk for groundwater system in tahrir aquifer is exposed to northern marine intrusion. Lowering of the piezo metric level is to be expected in the newly exploited desertic areas under over pumping. 9 figs

A 60,000-year record of hydrologic variability in the Central Andes from the hydrogen isotopic composition of leaf waxes in Lake Titicaca sediments

Science.gov (United States)

Fornace, Kyrstin L.; Hughen, Konrad A.; Shanahan, Timothy M.; Fritz, Sherilyn C.; Baker, Paul A.; Sylva, Sean P.

2014-12-01

A record of the hydrogen isotopic composition of terrestrial leaf waxes (δDwax) in sediment cores from Lake Titicaca provides new insight into the precipitation history of the Central Andes and controls of South American Summer Monsoon (SASM) variability since the last glacial period. Comparison of the δDwax record with a 19-kyr δD record from the nearby Illimani ice core supports the interpretation that precipitation δD is the primary control on δDwax with a lesser but significant role for local evapotranspiration and other secondary influences on δDwax. The Titicaca δDwax record confirms overall wetter conditions in the Central Andes during the last glacial period relative to a drier Holocene. During the last deglaciation, abrupt δDwax shifts correspond to millennial-scale events observed in the high-latitude North Atlantic, with dry conditions corresponding to the Bølling-Allerød and early Holocene periods and wetter conditions during late glacial and Younger Dryas intervals. We observe a trend of increasing monsoonal precipitation from the early to the late Holocene, consistent with summer insolation forcing of the SASM, but similar hydrologic variability on precessional timescales is not apparent during the last glacial period. Overall, this study demonstrates the relative importance of high-latitude versus tropical forcing as a dominant control on glacial SASM precipitation variability.

Long-term sedimentary recycling of rare sulphur isotope anomalies.

Science.gov (United States)

Reinhard, Christopher T; Planavsky, Noah J; Lyons, Timothy W

2013-05-02

The accumulation of substantial quantities of O2 in the atmosphere has come to control the chemistry and ecological structure of Earth's surface. Non-mass-dependent (NMD) sulphur isotope anomalies in the rock record are the central tool used to reconstruct the redox history of the early atmosphere. The generation and initial delivery of these anomalies to marine sediments requires low partial pressures of atmospheric O2 (p(O2); refs 2, 3), and the disappearance of NMD anomalies from the rock record 2.32 billion years ago is thought to have signalled a departure from persistently low atmospheric oxygen levels (less than about 10(-5) times the present atmospheric level) during approximately the first two billion years of Earth's history. Here we present a model study designed to describe the long-term surface recycling of crustal NMD anomalies, and show that the record of this geochemical signal is likely to display a 'crustal memory effect' following increases in atmospheric p(O2) above this threshold. Once NMD anomalies have been buried in the upper crust they are extremely resistant to removal, and can be erased only through successive cycles of weathering, dilution and burial on an oxygenated Earth surface. This recycling results in the residual incorporation of NMD anomalies into the sedimentary record long after synchronous atmospheric generation of the isotopic signal has ceased, with dynamic and measurable signals probably surviving for as long as 10-100 million years subsequent to an increase in atmospheric p(O2) to more than 10(-5) times the present atmospheric level. Our results can reconcile geochemical evidence for oxygen production and transient accumulation with the maintenance of NMD anomalies on the early Earth, and suggest that future work should investigate the notion that temporally continuous generation of new NMD sulphur isotope anomalies in the atmosphere was likely to have ceased long before their ultimate disappearance from the rock record.

Isotopic abundance of 13 C and contribution of eucalyptus biomass to soil organic matter conversion

Directory of Open Access Journals (Sweden)

Fabiane Figueiredo Severo

Full Text Available ABSTRACT: It has become possible to evaluate the conversion of soil organic matter (SOM in pastures and arboreal crops due to the difference between the photosynthetic cycles of Eucalyptus (C3 and most grasses (C4. The auto analyzer method coupled to the IRMS (Isotope Ratio Mass Spectrometer in the present study evaluated the 13C content in soil profiles of Eucalyptus plantations of different ages (2, 10 and 21 years, in natural regeneration areas and natural grazing fields, and estimated the SOM conversion of each crop type of. The initial management of all sampled areas was natural pasture. The following profile layers were evaluated: 0-5, 5-10, 10-20, 20-30, 30-40, 40-50, 50-70 and 70-90cm, and the contribution of Eucalyptus biomass over the years of farming was estimated in the SOM conversion process. After 2 years of planting Eucalyptus, the beginning of pasture carbon conversion process occurred in the surface layer (0-5cm. Ten years after planting, the process of converting organic matter by arboreal crops reached the layers up to 20cm. After 21 years of planting and in natural regeneration areas, the entire profile has already been changed by planting Eucalyptus and native tree species.

Isotopes as validation tools for global climate models

International Nuclear Information System (INIS)

Henderson-Sellers, A.

2001-01-01

Global Climate Models (GCMs) are the predominant tool with which we predict the future climate. In order that people can have confidence in such predictions, GCMs require validation. As almost every available item of meteorological data has been exploited in the construction and tuning of GCMs to date, independent validation is very difficult. This paper explores the use of isotopes as a novel and fully independent means of evaluating GCMs. The focus is the Amazon Basin which has a long history of isotope collection and analysis and also of climate modelling: both having been reported for over thirty years. Careful consideration of the results of GCM simulations of Amazonian deforestation and climate change suggests that the recent stable isotope record is more consistent with the predicted effects of greenhouse warming, possibly combined with forest removal, than with GCM predictions of the effects of deforestation alone

FY 2006 annual report. 21st century COE program isotope science and engineering from basics to applications

International Nuclear Information System (INIS)

2007-01-01

The 06' activity on 21st century COE program, Nagoya University, Isotopes open the future' is reported. The contents are: Research and educational execution planning; Operational reports (research activities, educational activities, international conferences, etc.); Research activities (1. the basic research field...isotope separation, isotope production, isotope measurement, and isotope materials, 2. the composite and development field...isotopes in biology, cultural science, and environment, 3. the young researchers unit for composite research, 4. research contributions); Educational activities (1. programs for assist of young researchers, 2. lectures on English, 3. lectures for postgraduate students). (J.P.N.)

Advanced Collimators for Verification of the Pu Isotopic Composition in Fresh Fuel by High Resolution Gamma Spectrometry

International Nuclear Information System (INIS)

Lebrun, Alain; Berlizov, Andriy

2013-06-01

IAEA verification of the nuclear material contained in fresh nuclear fuel assemblies is usually based on neutron coincidence counting (NCC). In the case of uranium fuel, active NCC provides the total content of uranium-235 per unit of length which, combined with active length verification, fully supports the verification. In the case of plutonium fuel, passive NCC provides the plutonium-240 equivalent content which needs to be associated with a measurement of the isotopic composition and active length measurement to complete the verification. Plutonium isotopic composition is verified by high resolution gamma spectrometry (HRGS) applied on fresh fuel assemblies assuming all fuel rods are fabricated from the same plutonium batch. For particular verifications when such an assumption cannot be reasonably made, there is a need to optimize the HRGS measurement so that contributions of internal rods to the recorded spectrum are maximized, thus providing equally strong verification of the internal fuel rods. This paper reports on simulation work carried out to design special collimators aimed at reducing the relative contribution of external fuel rods while enhancing the signal recorded from internal rods. Both cases of square lattices (e.g. 17x17 pressurized water reactor (PWR) fuel) and hexagonal compact lattices (e.g. BN800 fast neutron reactor (FNR) fuel) have been addressed. In the case of PWR lattices, the relatively large optical path to internal pins compensates for low plutonium concentrations and the large size of the fuel assemblies. A special collimator based on multiple, asymmetrical, vertical slots allows recording a spectrum from internal rods only when needed. In the FNR case, the triangular lattice is much more compact and the optical path to internal rods is very narrow. However, higher plutonium concentration and use of high energy ranges allow the verification of internal rods to be significantly strengthened. Encouraging results from the simulation

Integrating stomach content and stable isotope analyses to quantify the diets of pygoscelid penguins.

Directory of Open Access Journals (Sweden)

Michael J Polito

Full Text Available Stomach content analysis (SCA and more recently stable isotope analysis (SIA integrated with isotopic mixing models have become common methods for dietary studies and provide insight into the foraging ecology of seabirds. However, both methods have drawbacks and biases that may result in difficulties in quantifying inter-annual and species-specific differences in diets. We used these two methods to simultaneously quantify the chick-rearing diet of Chinstrap (Pygoscelis antarctica and Gentoo (P. papua penguins and highlight methods of integrating SCA data to increase accuracy of diet composition estimates using SIA. SCA biomass estimates were highly variable and underestimated the importance of soft-bodied prey such as fish. Two-source, isotopic mixing model predictions were less variable and identified inter-annual and species-specific differences in the relative amounts of fish and krill in penguin diets not readily apparent using SCA. In contrast, multi-source isotopic mixing models had difficulty estimating the dietary contribution of fish species occupying similar trophic levels without refinement using SCA-derived otolith data. Overall, our ability to track inter-annual and species-specific differences in penguin diets using SIA was enhanced by integrating SCA data to isotopic mixing modes in three ways: 1 selecting appropriate prey sources, 2 weighting combinations of isotopically similar prey in two-source mixing models and 3 refining predicted contributions of isotopically similar prey in multi-source models.

An eclogitic diamond from Mir pipe (Yakutia), recording two growth events from different isotopic sources

NARCIS (Netherlands)

Bulanova, G.P.; Wiggers de Vries, D.F.; Pearson, D.G.; Beard, A.; Mikhail, S.; Smelov, A.P.; Davies, G.R.

2014-01-01

An eclogitic octahedral macrodiamond from the Mir kimberlite (Yakutia) has a complex growth structure with distinctive core, intermediate and rim zones. Carbon isotope ratios change abruptly from depleted δ

High-resolution stable isotope stratigraphy of the upper Cambrian and Ordovician in the Argentine Precordillera

DEFF Research Database (Denmark)

Sial, A.N.; Peralta, S.; Gaucher, C.

2013-01-01

We report the occurrence of important carbon isotope excursions in early Paleozoic formations of the Eastern and Central Argentine Precordillera. The Steptoean positive isotope carbon excursion (SPICE) is known from North America, Kazakhstan, South China, Australia and South America, and the nega......We report the occurrence of important carbon isotope excursions in early Paleozoic formations of the Eastern and Central Argentine Precordillera. The Steptoean positive isotope carbon excursion (SPICE) is known from North America, Kazakhstan, South China, Australia and South America......, and the negative isotope carbon excursion (SNICE) has been described for the first time in South America. We report here the record of the SPICE and SNICE in a single section in the Eastern Precordillera. In the Central Precordillera, a minor middle Darriwilian positive carbon isotope excursion (MDICE) and a late...

Coral-based history of lead and lead isotopes of the surface Indian Ocean since the mid-20th century

Science.gov (United States)

Lee, Jong-Mi; Boyle, Edward A.; Suci Nurhati, Intan; Pfeiffer, Miriam; Meltzner, Aron J.; Suwargadi, Bambang

2014-07-01

Anthropogenic lead (Pb) from industrial activities has greatly altered the distribution of Pb in the present-day oceans, but no continuous temporal Pb evolution record is available for the Indian Ocean despite rapidly emerging industries around the region. Here, we present the coral-inferred annual history of Pb concentration and isotope ratios in the surface Indian Ocean since the mid-20th century (1945-2010). We analyzed Pb in corals from the Chagos Archipelago, western Sumatra and Strait of Singapore - which represent the central Indian Ocean via nearshore sites. Overall, coral Pb/Ca increased in the mid-1970s at all the sites. However, coral Pb isotope ratios evolve distinctively at each site, suggesting Pb contamination arises from different sources in each case. The major source of Pb in the Chagos coral appears to be India's Pb emission from leaded gasoline combustion and coal burning, whereas Pb in western Sumatra seems to be largely affected by Indonesia's gasoline Pb emission with additional Pb inputs from other sources. Pb in the Strait of Singapore has complex sources and its isotopic composition does not reflect Pb from leaded gasoline combustion. Higher 206Pb/207Pb and 208Pb/207Pb ratios found at this site may reflect the contribution of Pb from coals and ores from southern China, Indonesia, and Australia, and local Pb sources in the Strait of Singapore. It is also possible that the Pb isotope ratios of Singapore seawater were elevated through isotope exchange with natural fluvial particles considering its delta setting.

Carbon, nitrogen and oxygen isotope fractionation during food cooking: Implications for the interpretation of the fossil human record.

Science.gov (United States)

Royer, Aurélien; Daux, Valérie; Fourel, François; Lécuyer, Christophe

2017-08-01

Stable isotope data provide insight into the reconstruction of ancient human diet. However, cooking may alter the original stable isotope compositions of food due to losses and modifications of biochemical and water components. To address this issue, carbon, nitrogen and oxygen isotope ratios were measured on meat aliquots sampled from various animals such as pork, beef, duck and chicken, and also from the flesh of fishes such as salmon, European seabass, European pilchard, sole, gilt-head bream, and tuna. For each specimen, three pieces were cooked according to the three most commonly-known cooking practices: boiling, frying and roasting on a barbecue. Our data show that cooking produced isotopic shifts up to 1.8‰, 3.5‰, and 5.2‰ for δ 13 C, δ 15 N, and δ 18 O values, respectively. Such variations between raw and cooked food are much greater than previously estimated in the literature; they are more sensitive to the type of food rather than to the cooking process itself, except in the case of boiling. Reconstructions of paleodietary may thus suffer slight bias in cases of populations with undiversified diets that are restrained toward a specific raw or cooked product, or using a specific cooking mode. In cases of oxygen isotope compositions from skeletal remains (bones, teeth), they not only constitute a valuable proxy for reconstructing past climatic conditions, but they could also be used to improve our knowledge of past human diet. © 2017 Wiley Periodicals, Inc.

Geostatistical analysis and isoscape of ice core derived water stable isotope records in an Antarctic macro region

Science.gov (United States)

Hatvani, István Gábor; Leuenberger, Markus; Kohán, Balázs; Kern, Zoltán

2017-09-01

Water stable isotopes preserved in ice cores provide essential information about polar precipitation. In the present study, multivariate regression and variogram analyses were conducted on 22 δ2H and 53 δ18O records from 60 ice cores covering the second half of the 20th century. Taking the multicollinearity of the explanatory variables into account, as also the model's adjusted R2 and its mean absolute error, longitude, elevation and distance from the coast were found to be the main independent geographical driving factors governing the spatial δ18O variability of firn/ice in the chosen Antarctic macro region. After diminishing the effects of these factors, using variography, the weights for interpolation with kriging were obtained and the spatial autocorrelation structure of the dataset was revealed. This indicates an average area of influence with a radius of 350 km. This allows the determination of the areas which are as yet not covered by the spatial variability of the existing network of ice cores. Finally, the regional isoscape was obtained for the study area, and this may be considered the first step towards a geostatistically improved isoscape for Antarctica.

A Plant-Based Proxy for the Oxygen Isotope Ratio of Atmospheric Water Vapor

Science.gov (United States)

Helliker, B.

2007-12-01

Atmospheric water vapor is a major component of the global hydrological cycle, but the isotopic balance of vapor is largely unknown. It is shown here that the oxygen isotope ratio of leaf water in the epiphytic Crassulacean acid metabolism (CAM) plant Tillandsia usneoides (Spanish Moss) is controlled by the oxygen isotope ratio of atmospheric water vapor in both field and lab studies. Assuming that the leaf-water isotopic signature (and hence the atmospheric water vapor signature) is recorded in plant organic material, the atmospheric water vapor oxygen isotope ratios for Miami, Florida (USA) were reconstructed for several years from 1878 to 2005 using contemporary and herbarium specimens. T. usneoides ranges from Virginia, USA southwards through the tropics to Argentina, and the CAM epiphytic lifeform is widespread in other species. Therefore, epiphytes may be used to reconstruct the isotope ratio of atmospheric water for spatial scales that span over 60° of latitude and temporal scales that cover the last century of global temperature increase.

A latitudinal study of oxygen isotopes within horsehair

Science.gov (United States)

Thompson, E.; Bronk Ramsey, C.; McConnell, J. R.

2016-12-01

This study aims to explore the hypothesis that 'if oxygen isotope ratios deplete with decreasing temperature then a study of oxygen isotope ratios within horsehair from Oxfordshire to Iceland will show a latitudinal depletion gradient'. By looking at oxygen isotope values at different geographical positions, we can track the relationship with latitude and with different regional climate features. This will provide a firmer understanding of how to compare climate records from different locations. Additionally, a comparison of the horse breeds from this study to those analysed within previous studies will create an even better understanding of the intra-species variation within the δ18O values of horsehair. A total of 24 horses were sampled on the 7th March from Thordale Stud in Shetland, the Icelandic Food And Veterinary Authority in Iceland, the Exmoor Pony Centre in Exmoor and the Pigeon House Equestrian Centre in Oxfordshire. By starting the sampling process from the most recent growth at the follicle, the sampling date becomes a chronological marker, temporally fixing the first sample within a sequential set of data points extending for one year or longer, depending on the length of each individual hair. The samples were analysed for oxygen isotope values using an IRMS coupled within a Sercon HTEA. Preliminary results show a latitudinal gradient is evident on comparison between the locations, consistent with the findings of Darling and Talbot's study of fresh water isotopes in the British Isles (2003). These results support the hypothesis, showing that a study of oxygen isotope ratios within horse hair from Oxfordshire to Iceland showing a latitudinal depletion gradient, consistent with a depletion of oxygen isotope ratios due to decreasing temperatures. Darling, W. and Talbot, J. (2003). The O and H stable isotope composition of freshwaters in the British Isles. 1. Rainfall. Hydrol. Earth System Science, 7(2), pp.163-181.

Carbon isotopes in mollusk shell carbonates

Science.gov (United States)

McConnaughey, Ted A.; Gillikin, David Paul

2008-10-01

Mollusk shells contain many isotopic clues about calcification physiology and environmental conditions at the time of shell formation. In this review, we use both published and unpublished data to discuss carbon isotopes in both bivalve and gastropod shell carbonates. Land snails construct their shells mainly from respired CO2, and shell δ13C reflects the local mix of C3 and C4 plants consumed. Shell δ13C is typically >10‰ heavier than diet, probably because respiratory gas exchange discards CO2, and retains the isotopically heavier HCO3 -. Respired CO2 contributes less to the shells of aquatic mollusks, because CO2/O2 ratios are usually higher in water than in air, leading to more replacement of respired CO2 by environmental CO2. Fluid exchange with the environment also brings additional dissolved inorganic carbon (DIC) into the calcification site. Shell δ13C is typically a few ‰ lower than ambient DIC, and often decreases with age. Shell δ13C retains clues about processes such as ecosystem metabolism and estuarine mixing. Ca2+ ATPase-based models of calcification physiology developed for corals and algae likely apply to mollusks, too, but lower pH and carbonic anhydrase at the calcification site probably suppress kinetic isotope effects. Carbon isotopes in biogenic carbonates are clearly complex, but cautious interpretation can provide a wealth of information, especially after vital effects are better understood.

Isotopic tools for protecting the seas; Outils isotopiques pour la protection des mers

Energy Technology Data Exchange (ETDEWEB)

Kinley, D III [International Atomic Energy Agency, Division of Public Information, Vienna (Austria)

2006-07-01

The oceans and seas are our greatest natural resource, providing us with much of the food we eat and the air we breathe. More than US $900 billion per year of the world's economy is directly tied to ocean-based activities such as fishing, coastal tourism and shipping, and the oceans and seas contribute greatly to the broad ecological balance of our planet. Yet numerous human activities are mounting a growing threat to the health and sustainability of the marine environment. Coral reefs around the world are suffering a rapid decline. Fish stocks are increasingly overexploited, and some unsustainable commercial fish farming is destroying marine habitats. Pollution of the ocean is extensive and, in some cases, irreversible. And our greatest guarantee against global warming - the ocean's vast ability to act as a carbon sink - may be seriously undermined. Protection of the oceans and seas against further deterioration requires scientific investigation to better understand and manage the principal processes. It is here that the use of radionuclides and stable isotopes, which have been used for about 50 years as investigative tools, comes into its own. They have been used to study environmental processes, fate of contaminants in ecosystems, atmosphere-ocean interactions, surface and groundwater systems and the response of atmospheric, hydrological and marine systems to climate change. Coastal zones, supporting about 60% of the global population, require special attention because of their contribution to the world's food supply and their sensitivity to pollution. Nuclear and isotopic techniques provide tools for addressing on a quantitative basis the problems of coastal zone management, including investigation of contamination, groundwater - seawater interactions and other adverse impacts such as salt-water intrusion. One of the most important parameters in determining the climate on Earth is the temperature record of the ocean. It is believed that surface seawater

Application of the isotopic index in isotope geochemical investigation

International Nuclear Information System (INIS)

Schuetze, H.

1982-06-01

A method is described which allows to calculate approximately isotope exchange equilibria between different crystalline silicates. The algorithm uses a newly introduced isotopic index. It is defined using isotopic increments of the variant types of silicatic bonds. This isotopic index gives a quantitative measure of the ability to enrich 18 O or 30 Si, respectively. The dependence of isotopic fractionations on temperature can be calculated approximately by means of the isotopic index, too. On this theoretical base some problems of magmatism and two varieties of an isotope geochemical model of the evolution of the Earth's crust are treated. Finally, the possibility is demonstrated to give prognostic statements about the likelihood of ore bearing of different granites. (author)

Oxygen isotope variations at the margin of a CAI records circulation within the solar nebula.

Science.gov (United States)

Simon, Justin I; Hutcheon, Ian D; Simon, Steven B; Matzel, Jennifer E P; Ramon, Erick C; Weber, Peter K; Grossman, Lawrence; DePaolo, Donald J

2011-03-04

Micrometer-scale analyses of a calcium-, aluminum-rich inclusion (CAI) and the characteristic mineral bands mantling the CAI reveal that the outer parts of this primitive object have a large range of oxygen isotope compositions. The variations are systematic; the relative abundance of (16)O first decreases toward the CAI margin, approaching a planetary-like isotopic composition, then shifts to extremely (16)O-rich compositions through the surrounding rim. The variability implies that CAIs probably formed from several oxygen reservoirs. The observations support early and short-lived fluctuations of the environment in which CAIs formed, either because of transport of the CAIs themselves to distinct regions of the solar nebula or because of varying gas composition near the proto-Sun.

Application of Isotope techniques in the arid and semi-arid zone hydrology

International Nuclear Information System (INIS)

Gonfiantini, R.; Louvat, D.; Aranyossy, J.F.

1993-01-01

The paper presents a brief introduction on the scientific background of isotope hydrology,and after, explains the applications of environment isotope techniques in groundwater hydrology of the arid and semi-arid zones. It includes the study of aquifer recharge and discharge, identification of palaeorecharge, groundwater movement and age in unconfined and confined aquifers, and interconnections between aquifers. The contribution of isotopes is highlighted with many examples of field case studies, with emphasis on studies carried out with IAEA support. Finally, a short description of IAEA program on isotope hydrology is given, with a list of regional projects supported through the IAEA Technical Cooperation program, and of Coordinated Research Programs. The latter give the modern research trends in isotope application to hydrology and hydrosphere environmental studies. (author). 2 tabs., 25 figs., 69 refs

The isotopic contamination in electromagnetic isotope separators; La contagion isotopique dans les separateurs electromagnetiques d'isotopes

Energy Technology Data Exchange (ETDEWEB)

Cassignol, Ch [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

In the early years of isotope separation, and in particular electromagnetic isotope separation, needs for rapid results have conducted to empiric research. This paper describes fundamental research on the electromagnetic isotope separation to a better understanding of isotope separators as well as improving the performances. Focus has been made on the study of the principle of isotope contamination and the remedial action on the separator to improve the isotope separation ratio. In a first part, the author come back to the functioning of an electromagnetic separator and generalities on isotope contamination. Secondly, it describes the two stages separation method with two dispersive apparatus, an electromagnetic separation stage followed by an electrostatic separation stage, both separated by a diaphragm. The specifications of the electrostatic stage are given and its different settings and their consequences on isotope separation are investigated. In a third part, mechanisms and contamination factors in the isotope separation are discussed: natural isotope contamination, contamination by rebounding on the collector, contamination because of a low resolution, contamination by chromatism and diffusion effect, breakdown of condenser voltage. Analysis of experimental results shows the diffusion as the most important contamination factor in electromagnetic isotope separation. As contamination factors are dependent on geometric parameters, sector angle, radius of curvature in the magnetic field and clearance height are discussed in a fourth part. The better understanding of the mechanism of the different contamination factors and the study of influential parameters as pressure and geometric parameters lead to define a global scheme of isotope contamination and determinate optima separator design and experimental parameters. Finally, the global scheme of isotope contamination and hypothesis on optima specifications and experimental parameters has been checked during a

Isotopes in water resources management. V.1. Proceedings of a symposium

International Nuclear Information System (INIS)

1996-01-01

In recent years isotope applications in hydrology and water resources assessment have reached a level of maturity. Adequate investigations have been carried out to provide sufficient examples for practical applications in combination with other hydrological methods. The IAEA contributed to this development through field projects implemented in Member States within the framework of the Agency's Technical Co-operation programme. At present, the thrusts of the IAEA involvement are towards improved management of water resources in regions suffering from water scarcity, assessment of human impact on water resources, e.g. water pollution, and exploration and management of geothermal resources. Lately, novel isotope based techniques have been evolving from specialized laboratories. While the techniques have emerged, efforts need to be concentrated on more practical work to accomplish a visible impact on water resources management. These trends and challenges are reflected by the scientific contributions to the International Symposium on Isotopes in Water Resources Management. The main themes of the symposium were groundwater resources management, with about two thirds of the contributions addressing origin and recharge of groundwater, groundwater dynamics and pollution, modelling approaches, and geothermal and palaeowater resources. The remaining third of the contributions were concerned with surface water and sediments, unsaturated zones and methodological aspects. These proceedings contain the 43 papers presented and the extended synopses of over 100 poster presentations. Refs, figs and tabs

Isotopically modified compounds

International Nuclear Information System (INIS)

Kuruc, J.

2009-01-01

In this chapter the nomenclature of isotopically modified compounds in Slovak language is described. This chapter consists of following parts: (1) Isotopically substituted compounds; (2) Specifically isotopically labelled compounds; (3) Selectively isotopically labelled compounds; (4) Non-selectively isotopically labelled compounds; (5) Isotopically deficient compounds.

A Novel Framework for Quantifying past Methane Recycling by Sphagnum-Methanotroph Symbiosis Using Carbon and Hydrogen Isotope Ratios of Leaf Wax Biomarkers

Science.gov (United States)

Nichols, Jonathan E.; Isles, Peter D. F.; Peteet, Dorothy M.

2014-01-01

The concentration of atmospheric methane is strongly linked to variations in Earth's climate. Currently, we can directly reconstruct the total atmospheric concentration of methane, but not individual terms of the methane cycle. Northern wetlands, dominated by Sphagnum, are an important contributor of atmospheric methane, and we seek to understand the methane cycle in these systems. We present a novel method for quantifying the proportion of carbon Sphagnum assimilates from its methanotrophic symbionts using stable isotope ratios of leaf-wax biomarkers. Carbon isotope ratios of Sphagnum compounds are determined by two competing influences, water content and the isotope ratio of source carbon. We disentangled these effects using a combined hydrogen and carbon isotope approach. We constrained Sphagnum water content using the contrast between the hydrogen isotope ratios of Sphagnum and vascular plant biomarkers. We then used Sphagnum water content to calculate the carbon isotope ratio of Sphagnum's carbon pool. Using a mass balance equation, we calculated the proportion of recycled methane contributed to the Sphagnum carbon pool, 'PRM.' We quantified PRM in peat monoliths from three microhabitats in the Mer Bleue peatland complex. Modern studies have shown that water table depth and vegetation have strong influences on the peatland methane cycle on instrumental time scales. With this new approach, delta C-13 of Sphagnum compounds are now a useful tool for investigating the relationships among hydrology, vegetation, and methanotrophy in Sphagnum peatlands over the time scales of entire peatland sediment records, vital to our understanding of the global carbon cycle through the Late Glacial and Holocene.

Nuclear charge radii of light isotopes based on frequency comb measurements

International Nuclear Information System (INIS)

Zakova, Monika

2010-01-01

Optical frequency comb technology has been used in this work for the first time to investigate the nuclear structure of light radioactive isotopes. Therefore, three laser systems were stabilized with different techniques to accurately known optical frequencies and used in two specialized experiments. Absolute transition frequency measurements of lithium and beryllium isotopes were performed with accuracy on the order of 10 -10 . Such a high accuracy is required for the light elements since the nuclear volume effect has only a 10 -9 contribution to the total transition frequency. For beryllium, the isotope shift was determined with an accuracy that is sufficient to extract information about the proton distribution inside the nucleus. A Doppler-free two-photon spectroscopy on the stable lithium isotopes 6,7 Li was performed in order to determine the absolute frequency of the 2S → 3S transition. The achieved relative accuracy of 2 x 10 -10 is improved by one order of magnitude compared to previous measurements. The results provide an opportunity to determine the nuclear charge radius of the stable and short-lived isotopes in a pure optical way but this requires an improvement of the theoretical calculations by two orders of magnitude. The second experiment presented here was performed at ISOLDE/CERN, where the absolute transition frequencies of the D 1 and D 2 lines in beryllium ions for the isotopes 7,9,10,11 Be were measured with an accuracy of about 1 MHz. Therefore, an advanced collinear laser spectroscopy technique involving two counter-propagating frequency-stabilized laser beams with a known absolute frequency was developed. The extracted isotope shifts were combined with recent accurate mass shift calculations and the root-mean square nuclear charge radii of 7,10 Be and the one-neutron halo nucleus 11 Be were determined. Obtained charge radii are decreasing from 7 Be to 10 Be and increasing again for 11 Be. While the monotone decrease can be explained by a

Trace elements and Pb isotopes in soils and sediments impacted by uranium mining

Energy Technology Data Exchange (ETDEWEB)

Cuvier, A., E-mail: alicia.cuvier@hotmail.fr [ECOLAB, Université de Toulouse, CNRS, INPT, UPS, Toulouse (France); IRSN/PRP-ENV/SESURE/Laboratoire d' études radioécologiques en milieu continental et marin, BP 1, 13108 Saint Paul Lez Durance Cedex (France); Pourcelot, L. [IRSN/PRP-ENV/SESURE/Laboratoire d' études radioécologiques en milieu continental et marin, BP 1, 13108 Saint Paul Lez Durance Cedex (France); Probst, A. [ECOLAB, Université de Toulouse, CNRS, INPT, UPS, Toulouse (France); Prunier, J. [Observatoire Midi-Pyrénées, laboratoire Géosciences Environnement Toulouse, CNRS/IRD/Université Paul Sabatier, 14 avenue Edouard Belin, 31400 Toulouse (France); Le Roux, G., E-mail: gael.leroux@ensat.fr [ECOLAB, Université de Toulouse, CNRS, INPT, UPS, Toulouse (France)

2016-10-01

The purpose of this study is to evaluate the contamination in As, Ba, Co, Cu, Mn, Ni, Sr, V, Zn and REE, in a high uranium activity (up to 21,000 Bq ∙ kg{sup −1}) area, downstream of a former uranium mine. Different geochemical proxies like enrichment factor and fractions from a sequential extraction procedure are used to evaluate the level of contamination, the mobility and the availability of the potential contaminants. Pb isotope ratios are determined in the total samples and in the sequential leachates to identify the sources of the contaminants and to determine the mobility of radiogenic Pb in the context of uranium mining. In spite of the large uranium contamination measured in the soils and the sediments (EF ≫ 40), trace element contamination is low to moderate (2 < EF < 5), except for Ba (5 < EF < 15), due to the precipitation of barium sulfate resulting from mining activities. Most of the trace elements are associated with the most mobile fractions of the sediments/soils, implying an enhanced potential availability. Even if no Pb enrichment is highlighted, the Pb isotopic signature of the contaminated soils is strongly radiogenic. Measurements performed on the sequential leachates reveal inputs of radiogenic Pb in the most mobile fractions of the contaminated soil. Inputs of low-mobile radiogenic Pb from mining activities may also contribute to the Pb signature recorded in the residual phase of the contaminated samples. We demonstrate that Pb isotopes are efficient tools to trace the origin and the mobility of the contaminants in environments affected by uranium mining. - Highlights: • Contamination of soils is evidenced by a multiproxy approach. • Enrichment factors highlight a low contamination except for U, S and Ba. • Pb isotope ratios point out inputs of radiogenic Pb from the mine. • Radiogenic Pb is mainly in the acid-soluble and the reducible fractions.

Using Dual Isotopes and a Bayesian Isotope Mixing Model to Evaluate Nitrate Sources of Surface Water in a Drinking Water Source Watershed, East China

Directory of Open Access Journals (Sweden)

Meng Wang

2016-08-01

Full Text Available A high concentration of nitrate (NO3− in surface water threatens aquatic systems and human health. Revealing nitrate characteristics and identifying its sources are fundamental to making effective water management strategies. However, nitrate sources in multi-tributaries and mix land use watersheds remain unclear. In this study, based on 20 surface water sampling sites for more than two years’ monitoring from April 2012 to December 2014, water chemical and dual isotopic approaches (δ15N-NO3− and δ18O-NO3− were integrated for the first time to evaluate nitrate characteristics and sources in the Huashan watershed, Jianghuai hilly region, China. Nitrate-nitrogen concentrations (ranging from 0.02 to 8.57 mg/L were spatially heterogeneous that were influenced by hydrogeological and land use conditions. Proportional contributions of five potential nitrate sources (i.e., precipitation; manure and sewage, M & S; soil nitrogen, NS; nitrate fertilizer; nitrate derived from ammonia fertilizer and rainfall were estimated by using a Bayesian isotope mixing model. The results showed that nitrate sources contributions varied significantly among different rainfall conditions and land use types. As for the whole watershed, M & S (manure and sewage and NS (soil nitrogen were major nitrate sources in both wet and dry seasons (from 28% to 36% for manure and sewage and from 24% to 27% for soil nitrogen, respectively. Overall, combining a dual isotopes method with a Bayesian isotope mixing model offered a useful and practical way to qualitatively analyze nitrate sources and transformations as well as quantitatively estimate the contributions of potential nitrate sources in drinking water source watersheds, Jianghuai hilly region, eastern China.

Isotope effect and isotope separation. A chemist's view

International Nuclear Information System (INIS)

Ishida, Takanobu

2002-01-01

What causes the isotope effects (IE)? This presentation will be centered around the equilibrium isotope effects due to the differences in the nuclear masses. The occurrence of the equilibrium constant, K, of isotope exchange reactions which differ from the values predicted by the classical theory of statistical mechanics, K cl , is explored. The non-classical K corresponds to the unit-stage separation factor, α, that is different from unity and forms a basis of an isotope separation process involving the chemical exchange reaction. Here, the word 'chemical exchange' includes not only the isotope exchange chemical reactions between two or more chemical species but also the isotope exchanges involving the equilibria between liquid and vapor phases and liquid-gas, liquid solution-gas, liquid-liquid, and solid-liquid phases. In Section I, origins of the isotope effect phenomena will be explored and, in the process, various quantities used in discussions of isotope effect that have often caused confusions will be unambiguously defined. This Section will also correlate equilibrium constant with separation factor. In Section II, various forms of temperature-dependence of IE and separation factor will be discussed. (author)

Last glacial-Holocene temperatures and hydrology of the Sea of Galilee and Hula Valley from clumped isotopes in Melanopsis shells

Science.gov (United States)

Zaarur, Shikma; Affek, Hagit P.; Stein, Mordechai

2016-04-01

The carbonate clumped isotope (Δ47) thermometer was applied to fresh water snails (Melanopsis spp.) grown in the waters of the Sea of Galilee and Hula Valley, in the north of Israel. Modern shells, grown at known temperatures agree with the Δ47-T calibration of Zaarur et al. (2013). Fossil Melanopsis shells from 2 locations, Gesher Bnot Ya'aqov (at the southern tip of the Hula Valley) and the Sea of Galilee provide a temperature record for the region during the time interval of the past 20 kyrs. Glacial temperatures are ∼5 °C cooler than mid-Holocene and ∼3 °C cooler than modern, similar to other records in the region. These Δ47-derived temperatures are combined with δ18O of the shell carbonate to calculate the oxygen isotopic composition of the habitat waters. Contrary to global trends and other regional records, reconstructed δ18Owater values increase from the late glacial through the Holocene. This reversed signal reflects a decrease in the relative contribution of snowmelt to the watershed post-LGM and a transition to a more rain dominated inflow. A fairly constant difference in δ18Owater values between the Hula Valley and Sea of Galilee waters, suggests that the hydrological relationship of the two water bodies had remained constant, with the temperature changes playing only a minor role in the extent of evaporation of the Sea of Galilee relative to the Hula.

A stable isotope-based approach to tropical dendroclimatology

Science.gov (United States)

Evans, Michael N.; Schrag, Daniel P.

2004-08-01

We describe a strategy for development of chronological control in tropical trees lacking demonstrably annual ring formation, using high resolution δ 18O measurements in tropical wood. The approach applies existing models of the oxygen isotopic composition of alpha-cellulose (Roden et al., 2000), a rapid method for cellulose extraction from raw wood (Brendel et al., 2000), and continuous flow isotope ratio mass spectrometry (Brenna et al., 1998) to develop proxy chronological, rainfall and growth rate estimates from tropical trees lacking visible annual ring structure. Consistent with model predictions, pilot datasets from the temperate US and Costa Rica having independent chronological control suggest that observed cyclic isotopic signatures of several permil (SMOW) represent the annual cycle of local rainfall and relative humidity. Additional data from a plantation tree of known age from ENSO-sensitive northwestern coastal Peru suggests that the 1997-8 ENSO warm phase event was recorded as an 8‰ anomaly in the δ 18O of α-cellulose. The results demonstrate reproducibility of the stable isotopic chronometer over decades, two different climatic zones, and three tropical tree genera, and point to future applications in paleoclimatology.

Estimation and calibration of the water isotope differential diffusion length in ice core records

NARCIS (Netherlands)

van der Wel, G.; Fischer, H.; Oerter, H.; Meyer, H.; Meijer, H. A. J.

2015-01-01

Palaeoclimatic information can be retrieved from the diffusion of the stable water isotope signal during firnification of snow. The diffusion length, a measure for the amount of diffusion a layer has experienced, depends on the firn temperature and the accumulation rate. We show that the estimation

Isotope shift studies in gadolinium spectra

International Nuclear Information System (INIS)

Ahmad, S.A.; Saksena, G.D.; Venugopalan, A.

1975-01-01

Isotope shift studies have been carried out in the gadolinium spectrum using a recording Fabry-Perot spectrometer and gadolinium samples enriched in 156 Gd and 160 Gd isotopes. The source used is a liquid-nitrogen-cooled hollow cathode with Ne as the carrier gas and operating at about 30 mA. Isotope shifts Δsigma (156-160) have been recorded in 350 transitions of Gd I and Gd II. In the case of the Gd I spectrum, the transitions studied presently involve almost all the reported configurations assigned to the energy levels of Gd I. The odd configurations are 4f 7 5d6s 2 , 4f 7 5d 2 6s, 4f 7 5d 3 , 4f 8 6s6p, 4f 7 5d6s7s and 4f 7 6s 2 6p, and the even ones are 4f 8 6s 2 , 4f 7 5d6s6p, 4f 7 6s 2 6p, 4f 8 5d6s and 4f 7 5d 2 6p. In the case of the Gd II spectrum isotope shifts in the lines of the newly classified transition 4f 8 6s - 4f 8 6p have been studied and isotope shift ΔT (156-160) 87 mK has been obtained for the 4f 8 6s configuration. The other transitions of Gd II involve the odd configurations 4f 7 5d6s, 4f 7 6s 2 , 4f 7 5d 2 and 4f 8 6p and the even ones 4f 7 6s6p, 4f 8 5d, 4f 7 5d6p and 4f 8 6p. The ΔT (156-160) of a large number of odd and even levels of Gd I and Gd II have been evaluated. Electronic configurations have been suggested for a number of energy levels and configuration mixing has been pointed out in certain cases. A number of hitherto unreported transitions have been found and using a monoisotopic sample of Gd, that is 160 Gd, their separations from the closest listed transitions have been measured. (author)

Isotope scanning for tumor localization

Energy Technology Data Exchange (ETDEWEB)

NONE

1961-09-15

At the request of the Government of the United Arab Republic, the Agency provided the services of an expert for the establishment in the UAR of a tumor localization program using photoscanning techniques and appropriate radioactive tracers. Photoscanning is a recently developed technique whereby the differences in isotope concentrations are enhanced on the record, and this facilitates the interpretation of the record. A variety of brain tumors were located, using a suitable radioactive tracer (Hg-203 - labelled Neohydrin) obtained from the USA. In some other investigations, processes in the kidney were scanned. Further, radioactive gold was used to demonstrate the normal and pathological spleen and liver and these tests showed various types of space occupying lesions resulting from malignancy and the parasitic infections endemic to the area. While the localization of brain tumors by scanning techniques is extremely useful, it does not always establish the precise extent of the tumor which should be known at the time of surgery. Dr. Bender, therefore, thought it advisable to instruct personnel in the use of what is known as an in-vivo needle scintillation probe - a technique for the investigation of the isotope concentration in a particular tissue during operation. The necessary instrument was obtained for this purpose and demonstrations were given; one patient was examined in this way at the time of surgery at the University of Alexandria Hospital.

Oxygen isotope mass balance of atmospheric nitrate at Dome C, East Antarctica, during the OPALE campaign

Directory of Open Access Journals (Sweden)

J. Savarino

2016-03-01

Full Text Available Variations in the stable oxygen isotope composition of atmospheric nitrate act as novel tools for studying oxidative processes taking place in the troposphere. They provide both qualitative and quantitative constraints on the pathways determining the fate of atmospheric nitrogen oxides (NO + NO2 = NOx. The unique and distinctive 17O excess (Δ17O = δ17O − 0.52 × δ18O of ozone, which is transferred to NOx via oxidation, is a particularly useful isotopic fingerprint in studies of NOx transformations. Constraining the propagation of 17O excess within the NOx cycle is critical in polar areas, where there exists the possibility of extending atmospheric investigations to the glacial–interglacial timescale using deep ice core records of nitrate. Here we present measurements of the comprehensive isotopic composition of atmospheric nitrate collected at Dome C (East Antarctic Plateau during the austral summer of 2011/2012. Nitrate isotope analysis has been here combined for the first time with key precursors involved in nitrate production (NOx, O3, OH, HO2, RO2, etc. and direct observations of the transferrable Δ17O of surface ozone, which was measured at Dome C throughout 2012 using our recently developed analytical approach. Assuming that nitrate is mainly produced in Antarctica in summer through the OH + NO2 pathway and using concurrent measurements of OH and NO2, we calculated a Δ17O signature for nitrate on the order of (21–22 ± 3 ‰. These values are lower than the measured values that ranged between 27 and 31 ‰. This discrepancy between expected and observed Δ17O(NO3− values suggests the existence of an unknown process that contributes significantly to the atmospheric nitrate budget over this East Antarctic region. However, systematic errors or false isotopic balance transfer functions are not totally excluded.

Growth history of cultured pearl oysters based on stable oxygen isotope analysis

Science.gov (United States)

Nakashima, R.; Furuta, N.; Suzuki, A.; Kawahata, H.; Shikazono, N.

2007-12-01

We investigated the oxygen isotopic ratio in shells of the pearl oyster Pinctada martensii cultivated in embayments in Mie Prefecture, central Japan, to evaluate the biomineralization of shell structures of the species and its pearls in response to environmental change. Microsamples for oxygen isotope analysis were collected from the surfaces of shells (outer, middle, and inner shell layers) and pearls. Water temperature variations were estimated from the oxygen isotope values of the carbonate. Oxygen isotope profiles of the prismatic calcite of the outer shell layer reflected seasonal variations of water temperature, whereas those of nacreous aragonites of the middle and inner shell layers and pearls recorded temperatures from April to November, June to September, and July to September, respectively. Lower temperatures in autumn and winter might slow the growth of nacreous aragonites. The oxygen isotope values are controlled by both variations of water temperature and shell structures; the prismatic calcite of this species is useful for reconstructing seasonal changes of calcification temperature.

Combined oxygen- and carbon-isotope records through the Early Jurassic: multiple global events and two modes of carbon-cycle/temperature coupling

DEFF Research Database (Denmark)

Hesselbo, Stephen P.; Korte, Christoph

2010-01-01

, to the extent that meaningful comparisons between these events can begin to be made. Here we present new carbon and oxygen isotope data from mollusks (bivalves and belemnites) and brachiopods collected through the marine Early Jurassic succession of NE England, including the Sinemurian-Plienbachian boundary...... GSSP. All materials have been screened by chemical analysis and scanning electron microscopy to check for diagenetic alteration. Analysis of carbon isotopes from marine calcite is supplemented by analysis of carbon-isotope values from fossil wood collected through the same section. It is demonstrated...... that both long-term and short-term carbon-isotope shifts from the UK Early Jurassic represent global changes in carbon cycle balances. The Sinemurian-Pliensbachian boundary event is an event of global significance and shows several similarities to the Toarcian OAE (relative sea-level change, carbon-isotope...

Isotopic evidence for enhanced fossil fuel sources of aerosol ammonium in the urban atmosphere.

Science.gov (United States)

Pan, Yuepeng; Tian, Shili; Liu, Dongwei; Fang, Yunting; Zhu, Xiaying; Gao, Meng; Gao, Jian; Michalski, Greg; Wang, Yuesi

2018-04-20

The sources of aerosol ammonium (NH 4 + ) are of interest because of the potential of NH 4 + to impact the Earth's radiative balance, as well as human health and biological diversity. Isotopic source apportionment of aerosol NH 4 + is challenging in the urban atmosphere, which has excess ammonia (NH 3 ) and where nitrogen isotopic fractionation commonly occurs. Based on year-round isotopic measurements in urban Beijing, we show the source dependence of the isotopic abundance of aerosol NH 4 + , with isotopically light (-33.8‰) and heavy (0 to +12.0‰) NH 4 + associated with strong northerly winds and sustained southerly winds, respectively. On an annual basis, 37-52% of the initial NH 3 concentrations in urban Beijing arises from fossil fuel emissions, which are episodically enhanced by air mass stagnation preceding the passage of cold fronts. These results provide strong evidence for the contribution of non-agricultural sources to NH 3 in urban regions and suggest that priority should be given to controlling these emissions for haze regulation. This study presents a carefully executed application of existing stable nitrogen isotope measurement and mass-balance techniques to a very important problem: understanding source contributions to atmospheric NH 3 in Beijing. This question is crucial to informing environmental policy on reducing particulate matter concentrations, which are some of the highest in the world. However, the isotopic source attribution results presented here still involve a number of uncertain assumptions and they are limited by the incomplete set of chemical and isotopic measurements of gas NH 3 and aerosol NH 4 + . Further field work and lab experiments are required to adequately characterize endmember isotopic signatures and the subsequent isotopic fractionation process under different air pollution and meteorological conditions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Tracing source and migration of Pb during waste incineration using stable Pb isotopes

Energy Technology Data Exchange (ETDEWEB)

Li, Yang [State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Institute of Waste Treatment and Reclamation, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Zhang, Hua, E-mail: zhanghua_tj@tongji.edu.cn [State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Institute of Waste Treatment and Reclamation, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Shao, Li-Ming; He, Pin-Jing [Institute of Waste Treatment and Reclamation, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Research and Training Center on Rural Waste Management, Ministry of Housing and Urban-Rural Development of P.R. China, 1239 Siping Road, Shanghai 200092 (China)

2017-04-05

Highlights: • The migration of Pb during waste incineration was investigated using Pb isotopes. • Source tracing of Pb during incineration by isotopic technology was feasible. • Contributions of MSW components were measured to trace Pb sources quantitatively. • Isotopic technology helps understand the migration of Pb during thermal treatment. - Abstract: Emission of Pb is a significant environmental concern during solid waste incineration. To target Pb emission control strategies effectively, the major sources of Pb in the waste incineration byproducts must be traced and quantified. However, identifying the migration of Pb in each waste component is difficult because of the heterogeneity of the waste. This study used a laboratory-scale incinerator to simulate the incineration of municipal solid waste (MSW). The Pb isotope ratios of the major waste components ({sup 207}Pb/{sup 206}Pb = 0.8550–0.8627 and {sup 208}Pb/{sup 206}Pb = 2.0957–2.1131) and their incineration byproducts were measured to trace sources and quantify the Pb contribution of each component to incineration byproducts. As the proportions of food waste (FW), newspaper (NP), and polyethylene bag (PE) in the artificial MSW changed, the contribution ratios of FW and PE to Pb in fly ash changed accordingly, ranging from 31.2% to 50.6% and from 35.0% to 41.8%, respectively. The replacement of PE by PVC significantly increased the partitioning and migration ratio of Pb. The use of Pb isotope ratios as a quantitative tool for tracing Pb from raw waste to incineration byproducts is a feasible means for improving Pb pollution control.

Assessing methane oxidation under landfill covers and its contribution to the above atmospheric CO2 levels: The added value of the isotope (δ13C and δ18O CO2; δ13C and δD CH4) approach

International Nuclear Information System (INIS)

Widory, D.; Proust, E.; Bellenfant, G.; Bour, O.

2012-01-01

Highlights: ► Comparison of the isotope and mass balance approaches to evaluate the level of methane oxidation within a landfill. ► The level of methane oxidation is not homogenous under the landfill cover and is strongly correlated to the methane flux. ► Isotope tracking of the contribution of the methane oxidation to the CO 2 concentrations in the ambient air. - Abstract: We are presenting here a multi-isotope approach (δ 13 C and δ 18 O of CO 2 ; δ 13 C and δD of CH 4 ) to assess (i) the level(s) of methane oxidation during waste biodegradation and its migration through a landfill cover in Sonzay (France), and (ii) its contribution to the atmospheric CO 2 levels above the surface. The isotope approach is compared to the more conventional mass balance approach. Results from the two techniques are comparable and show that the CH 4 oxidation under the landfill cover is heterogenous, with low oxidation percentages in samples showing high biogas fluxes, which was expected in clay covers presenting fissures, through which CH 4 is rapidly transported. At shallow depth, more immobile biogas pockets show a higher level of CH 4 oxidation by the methanotrophic bacteria. δ 13 C of CO 2 samples taken at different heights (from below the cover up to 8 m above the ground level) were also used to identify and assess the relative contributions of its main sources both under the landfill cover and in the surrounding atmosphere.

Titanium Isotopes Provide Clues to Lunar Origin

Science.gov (United States)

Taylor, G. J.

2012-05-01

The idea that the Moon formed as the result of the giant impact of a Mars-sized impactor with the still-growing Earth explains two central facts about the Earth-Moon system: its total angular momentum (Earth's spin and the Moon's orbital motion), and the sizes of the metallic cores of the Earth (large) and Moon (tiny). This gives cosmochemists some confidence in the hypothesis, but they would greatly appreciate additional compositional tests. One undisputed point is the identical abundance of the three oxygen isotopes in Earth and Moon. Junjun Zhang and colleagues at the University of Chicago (USA) and the University of Bern (Switzerland) have added another isotopic system to the cosmochemical testing tool kit, titanium isotopes. They find that the ratio of titanium-50 to titanium-47 is identical in Earth and Moon to within four parts per million. In contrast, other solar system materials, such as carbonaceous chondrites, vary by considerably more than this-- up to 150 times as much. The identical oxygen and titanium isotopic compositions in Earth and Moon are surprising in light of what we think we know about planet formation and formation of the Moon after a giant impact. The variations in oxygen and titanium isotopes among meteorite types suggest that it is unlikely that the Moon-forming giant impactor would have had the same isotopic composition as the Earth. Simulations show that the Moon ends up constructed mostly (40-75%) from the impactor materials. Thus, the Moon ought to have different isotopic composition than does Earth. The isotopes might have exchanged in the complicated, messy proto-lunar disk (as has been suggested for oxygen isotopes), making them the same. However, Zhang and colleagues suggest that this exchange is unlikely for a refractory element like titanium. Could the impact simulations be greatly overestimating the contributions from the impactor? Was the mixing of building-block materials throughout the inner solar system much less than

Seasonality of bottom water temperature in the northern North Sea reconstructed from the oxygen isotope composition of the bivalve Arctica islandica

Science.gov (United States)

Trofimova, Tamara; Andersson, Carin; Bonitz, Fabian

2017-04-01

The seasonality of temperature changes is an important characteristic of climate. However, observational data for the ocean are only available for the last 150 year from a limited number of locations. Prior to 18th century information is only available from proxy reconstructions. The vast majority of such reconstructions depend on land-based archives, primarily from dendrochronology. Established marine proxy records for the ocean, especially at high latitudes, are both sparsely distributed and poorly resolved in time. Therefore, the identification and development of proxies for studying key ocean processes at sub-annual resolution that can extend the marine instrumental record is a clear priority in marine climate science. In this study, we have developed a record of early Holocene seasonal variability of bottom water temperature from the Viking Bank in the northern most North Sea. This area is of a particular interest since the hydrography is controlled by the inflow of Atlantic water. The reconstruction is based on the oxygen isotope composition of the growth increments in two sub-fossil shells of Arctica islandica (Bivalvia), dated to 9600-9335 cal. yr BP. By combining radiocarbon dating and sclerochronological techniques a floating chronology spanning over 200 years was constructed. Using the chronology as an age model, oxygen isotope measurements from 2 shells were combined into a 22-years long record. The results from this oxygen isotope record are compared with stable oxygen isotope profiles from modern shells to estimate changes in the mean state and seasonality between present and early Holocene. Shell-derived oxygen isotope values together with ice-volume corrected oxygen isotope values for the seawater were used to calculate bottom-water temperatures on a sub-annual time-scale. Preliminary results of the reconstructed early Holocene bottom water temperature indicate higher seasonality and lower minimum temperature compared to the present.

Groundwater geochemistry of nile delta-desert interface 1.isotope hydrology

Energy Technology Data Exchange (ETDEWEB)

Hussein, M F [Cairo University, Dept., of Soil and water, Giza, Gamma Street, (Egypt); Nada, A A; Awad, M A [Atomic Energy Authority, Nuclear Chemistry Dept., P.o. Box 13759, Cairo, (Egypt)

1995-10-01

Sustenance and environmental protection of groundwater supply is of major concern in the integral environmental development in the arid to sub-arid regions in the Nile basin. Isotope data ({sup 18O}, {sup 2H} and {sup 3H}) of groundwater in the west of the Nile delta indicates the contribution of palaeo groundwater component (in the range 0.1 - 0.8 with means of 0.39 and 0.52 for tahrir and khatatbah, respectively) along with sub recent recharge from the delta aquifer and recent recharge from irrigation conveyance canals in desert. Isotope mixing model (developed as Two-input table using excel{sup TM} spreads heat on apple Macintosh{sup TM)} is proposed to explain the apparent discrepancies in groundwater isotopic composition of khatatbah and tahrir areas assuming the contribution of two isotopically different palaeo-oples with two isotopically similar maind delta groundwater poles. About 0.30% {sup 1}8{sup O} depletion per 10 Km downstream is detected and low northward groundwater recharge is suggested along 75 Km of the western strip of rosetta Nile. Higher sub-recent recharge from the main delta aquifer is believed to take place in khatatbah than tahrir whereas the last is believed to be replenished at present from the irrigation/ drainage network and irrigated fields with higher pollution risk for groundwater system in tahrir aquifer is exposed to northern marine intrusion. Lowering of the piezo metric level is to be expected in the newly exploited desertic areas under over pumping. 9 figs.

An open source Bayesian Monte Carlo isotope mixing model with applications in Earth surface processes

Science.gov (United States)

Arendt, Carli A.; Aciego, Sarah M.; Hetland, Eric A.

2015-05-01

The implementation of isotopic tracers as constraints on source contributions has become increasingly relevant to understanding Earth surface processes. Interpretation of these isotopic tracers has become more accessible with the development of Bayesian Monte Carlo (BMC) mixing models, which allow uncertainty in mixing end-members and provide methodology for systems with multicomponent mixing. This study presents an open source multiple isotope BMC mixing model that is applicable to Earth surface environments with sources exhibiting distinct end-member isotopic signatures. Our model is first applied to new δ18O and δD measurements from the Athabasca Glacier, which showed expected seasonal melt evolution trends and vigorously assessed the statistical relevance of the resulting fraction estimations. To highlight the broad applicability of our model to a variety of Earth surface environments and relevant isotopic systems, we expand our model to two additional case studies: deriving melt sources from δ18O, δD, and 222Rn measurements of Greenland Ice Sheet bulk water samples and assessing nutrient sources from ɛNd and 87Sr/86Sr measurements of Hawaiian soil cores. The model produces results for the Greenland Ice Sheet and Hawaiian soil data sets that are consistent with the originally published fractional contribution estimates. The advantage of this method is that it quantifies the error induced by variability in the end-member compositions, unrealized by the models previously applied to the above case studies. Results from all three case studies demonstrate the broad applicability of this statistical BMC isotopic mixing model for estimating source contribution fractions in a variety of Earth surface systems.

Using stable isotopes to investigate individual diet specialization in California sea otters (Enhydra lutris nereis)

Science.gov (United States)

Newsome, S.D.; Tinker, M.T.; Monson, Daniel H.; Oftedal, O.T.; Ralls, K.; Staedler, M.M.; Fogel, M.L.; Estes, J.A.

2009-01-01

Differences in diet composition among conspecifics (dietary specialization) have been documented across a broad range of taxonomic groups and habitats, and such variation at the individual level is increasingly recognized as an important component of diversity in trophic interactions. Accurate identification of individual dietary specialization, however, requires longitudinal dietary records that are labor-intensive and cost-prohibitive to obtain for many species. Here we explore the use of stable isotopes (δ13C and δ15N) as a promising technique for detecting and quantifying patterns of individual dietary specialization. Southern sea otters (Enhydra lutris nereis) offer a unique opportunity for testing this approach because (1) they consume a wide variety of prey that span multiple trophic levels, habitats, and ecologically defined functional groups; and (2) individual diet specialization can be validated with existing observational data. We analyzed the isotopic composition of sea otter vibrissae (n = 31) in order to characterize inter- and intra-individual variation in sea otter diets at Monterey Bay, California, USA. At the population level, sea otters showed substantial variation in both δ13C and δ15N values, occupying nearly all of the “isotopic space” created by the diversity of isotopic signatures of potential prey taxa. Most of the variation in sea otter vibrissae was accounted for by differences between individuals, with much less contributed by within-individual variation. A majority of sea otters (∼80%) showed relatively little temporal variability in isotopic composition, suggesting that the proportional composition of most individuals' diets is relatively constant over time; a few individuals (∼20%) exhibited a high degree of intra-vibrissa isotopic variability, suggesting seasonal shifts in diet composition. These results and our interpretation of them were supported by long-term observational data on the diets of radio-tagged sea otters

Large-scale drivers of Caucasus climate variability in meteorological records and Mt El'brus ice cores

Science.gov (United States)

Kozachek, Anna; Mikhalenko, Vladimir; Masson-Delmotte, Valérie; Ekaykin, Alexey; Ginot, Patrick; Kutuzov, Stanislav; Legrand, Michel; Lipenkov, Vladimir; Preunkert, Susanne

2017-05-01

A 181.8 m ice core was recovered from a borehole drilled into bedrock on the western plateau of Mt El'brus (43°20'53.9'' N, 42°25'36.0'' E; 5115 m a.s.l.) in the Caucasus, Russia, in 2009 (Mikhalenko et al., 2015). Here, we report on the results of the water stable isotope composition from this ice core with additional data from the shallow cores. The distinct seasonal cycle of the isotopic composition allows dating by annual layer counting. Dating has been performed for the upper 126 m of the deep core combined with 20 m from the shallow cores. The whole record covers 100 years, from 2013 back to 1914. Due to the high accumulation rate (1380 mm w.e. year-1) and limited melting, we obtained isotopic composition and accumulation rate records with seasonal resolution. These values were compared with available meteorological data from 13 weather stations in the region and also with atmosphere circulation indices, back-trajectory calculations, and Global Network of Isotopes in Precipitation (GNIP) data in order to decipher the drivers of accumulation and ice core isotopic composition in the Caucasus region. In the warm season (May-October) the isotopic composition depends on local temperatures, but the correlation is not persistent over time, while in the cold season (November-April), atmospheric circulation is the predominant driver of the ice core's isotopic composition. The snow accumulation rate correlates well with the precipitation rate in the region all year round, which made it possible to reconstruct and expand the precipitation record at the Caucasus highlands from 1914 until 1966, when reliable meteorological observations of precipitation at high elevation began.

Correlating carbon and oxygen isotope events in early to middle Miocene shallow marine carbonates in the Mediterranean region using orbitally tuned chemostratigraphy and lithostratigraphy

Science.gov (United States)

Auer, Gerald; Piller, Werner E.; Reuter, Markus; Harzhauser, Mathias

2015-04-01

During the Miocene prominent oxygen isotope events (Mi-events) reflect major changes in glaciation, while carbonate isotope maxima (CM-events) reflect changes in organic carbon burial, particularly during the Monterey carbon isotope excursion. However, despite their importance to the global climate history they have never been recorded in shallow marine carbonate successions. The Decontra section on the Maiella Platform (central Apennines, Italy), however, allows to resolve them for the first time in such a setting during the early to middle Miocene. The present study improves the stratigraphic resolution of parts of the Decontra section via orbital tuning of high-resolution gamma ray (GR) and magnetic susceptibility data to the 405 kyr eccentricity metronome. The tuning allows, within the established biostratigraphic, sequence stratigraphic, and isotope stratigraphic frameworks, a precise correlation of the Decontra section with pelagic records of the Mediterranean region, as well as the global paleoclimatic record and the global sea level curve. Spectral series analyses of GR data further indicate that the 405 kyr orbital cycle is particularly well preserved during the Monterey Event. Since GR is a direct proxy for authigenic uranium precipitation during increased burial of organic carbon in the Decontra section, it follows the same long-term orbital pacing as observed in the carbon isotope records. The 405 kyr GR beat is thus correlated with the carbon isotope maxima observed during the Monterey Event. Finally, the Mi-events can now be recognized in the δ18O record and coincide with plankton-rich, siliceous, or phosphatic horizons in the lithology of the section.

Past climate changes derived from isotope measurements in polar ice cores

International Nuclear Information System (INIS)

Beer, J.; Muscheler, R.; Wagner, G.; Kubik, P.K.

2002-01-01

Measurements of stable and radioactive isotopes in polar ice cores provide a wealth of information on the climate conditions of the past. Stable isotopes (δ 18 O, δD) reflect mainly the temperature, whereas δ 18 O of oxygen in air bubbles reveals predominantly the global ice volume and the biospheric activity. Cosmic ray produced radioisotopes (cosmogenic nuclides) such as 10 Be and 36 Cl record information on the solar variability and possibly also on the solar irradiance. If the flux of a cosmogenic nuclide into the ice is known the accumulation rate can be derived from the measured concentration. The comparison of 10 Be from ice with 14 C from tree rings allows deciding whether observed 14 C variations are caused by production or system effects. Finally, isotope measurements are very useful for establishing and improving time scales. The 10 Be/ 36 Cl ratio changes with an apparent half-life of 376,000 years and is therefore well suited to date old ice. Significant abrupt changes in the records of 10 Be, 36 Cl from ice and of δ 18 O from atmospheric oxygen representing global signals can be used to synchronize ice and sediment cores. (author)

Evaporation Induced Oxygen Isotope Fractionation in Impact Ejecta

Science.gov (United States)

Macris, C. A.; Young, E. D.; Kohl, I. E.; zur Loye, T. E.

2017-12-01

Tektites are natural glasses formed as quenched impact melt ejecta. Because they experienced extreme heating while entrained in a hot impact vapor plume, tektites allow insight into the nature of these ephemeral events, which play a critical role in planetary accretion and evolution. During tektite formation, the chemical and isotopic composition of parent materials may be modified by (1) vapor/liquid fractionation at high T in the plume, (2) incorporation of meteoric water at the target site, (3) isotope exchange with atmospheric oxygen (if present), or some combination of the three. Trends from O isotope studies reveal a dichotomy: some tektite δ18O values are 4.0-4.5‰ lower than their protoliths (Luft et al. 1987; Taylor & Epstein 1962), opposite in direction to a vaporization induced fractionation; increases in δ18O with decreasing SiO2 in tektites (Taylor & Epstein 1969) is consistent with vapor fractionation. Using an aerodynamic levitation laser furnace (e.g. Macris et al. 2016), we can experimentally determine the contributions of processes (1), (2) and (3) above to tektite compositions. We conducted a series of evaporation experiments to test process (1) using powdered tektite fused into 2 mm spheres and heated to 2423-2473 K for 50-90 s while levitated in Ar in the furnace. Mass losses were from 23 to 26%, reflecting evaporation of Si and O from the melt. The starting tektite had a δ18O value of 10.06‰ (±0.01 2se) and the residues ranged from 13.136‰ (±0.006) for the least evaporated residue to 14.30‰ (±0.02) for the most evaporated (measured by laser fluorination). The increase in δ18O with increasing mass loss is consistent with Rayleigh fractionation during evaporation, supporting the idea that O isotopes are fractionated due to vaporization at high T in an impact plume. Because atmospheric O2 and water each have distinctive Δ17O values, we should be able to use departures from our measured three-isotope fractionation law to evaluate

Mid- to late Holocene climate-driven regime shifts inferred from diatom, ostracod and stable isotope records from Lake Son Kol (Central Tian Shan, Kyrgyzstan)

Science.gov (United States)

Schwarz, Anja; Turner, Falko; Lauterbach, Stefan; Plessen, Birgit; Krahn, Kim J.; Glodniok, Sven; Mischke, Steffen; Stebich, Martina; Witt, Roman; Mingram, Jens; Schwalb, Antje

2017-12-01

Arid Central Asia represents a key region for understanding climate variability and interactions in the Northern Hemisphere. Patterns and mechanisms of Holocene climate change in arid Central Asia are, however, only partially understood. Multi-proxy data combining diatom, ostracod, sedimentological, geochemical and stable isotope analyses from a ca. 6000-year-old lake sediment core from Son Kol (Central Kyrgyzstan) show distinct and repeated changes in species assemblages. Diatom- and ostracod-inferred conductivity shifts between meso-euhaline and freshwater conditions suggest water balance and regime shifts. Organism-derived data are corroborated by stable isotope, mineralogical and geochemical records, underlining that Son Kol was affected by strong lake level fluctuations of several meters. The δ13Ccarb/δ18Ocarb correlation shows repeated switchovers from a closed to an open lake system. From 6000 to 3800 and 3250 to 1950 cal. yr BP, Son Kol was a closed basin lake with higher conductivities, increased nutrient availability and a water level located below the modern outflow. Son Kol became again a hydrologically open lake at 3800 and 1950 cal. yr BP. Comparisons to other local and regional paleoclimate records indicate that these regime shifts were largely controlled by changing intensity and position of the Westerlies and the Siberian Anticyclone that triggered changes in the amount of winter precipitation. A strong influence of the Westerlies ca. 5000-4400, 3800-3250 and since 1950 cal. yr BP enhanced the amount of precipitation during spring, autumn and winter, whereas cold and dry winters prevailed during phases with a strong Siberian Anticyclone and southward shifted Westerlies at ca. 6000-5000, 4400-3800 and 3250-1950 cal. yr BP. Similarities between variations in winter precipitation at Son Kol and records of the predominant NAO-mode further suggest a teleconnection between wet (dry) winter climate in Central Asia and a positive (negative) NAO

The isotopic contamination in electromagnetic isotope separators; La contagion isotopique dans les separateurs electromagnetiques d'isotopes

Energy Technology Data Exchange (ETDEWEB)

Cassignol, Ch. [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

In the early years of isotope separation, and in particular electromagnetic isotope separation, needs for rapid results have conducted to empiric research. This paper describes fundamental research on the electromagnetic isotope separation to a better understanding of isotope separators as well as improving the performances. Focus has been made on the study of the principle of isotope contamination and the remedial action on the separator to improve the isotope separation ratio. In a first part, the author come back to the functioning of an electromagnetic separator and generalities on isotope contamination. Secondly, it describes the two stages separation method with two dispersive apparatus, an electromagnetic separation stage followed by an electrostatic separation stage, both separated by a diaphragm. The specifications of the electrostatic stage are given and its different settings and their consequences on isotope separation are investigated. In a third part, mechanisms and contamination factors in the isotope separation are discussed: natural isotope contamination, contamination by rebounding on the collector, contamination because of a low resolution, contamination by chromatism and diffusion effect, breakdown of condenser voltage. Analysis of experimental results shows the diffusion as the most important contamination factor in electromagnetic isotope separation. As contamination factors are dependent on geometric parameters, sector angle, radius of curvature in the magnetic field and clearance height are discussed in a fourth part. The better understanding of the mechanism of the different contamination factors and the study of influential parameters as pressure and geometric parameters lead to define a global scheme of isotope contamination and determinate optima separator design and experimental parameters. Finally, the global scheme of isotope contamination and hypothesis on optima specifications and experimental parameters has been checked during a

The Cadmium Isotope Record of the Great Oxidation Event from the Turee Creek Group, Hamersley Basin, Australia

Science.gov (United States)

Abouchami, W.; Busigny, V.; Philippot, P.; Galer, S. J. G.; Cheng, C.; Pecoits, E.

2016-12-01

The evolution of the ocean, atmosphere and biosphere throughout Earth's history has impacted on the biogeochemistry of some key trace metals that are of particular importance in regulating the exchange between Earth's reservoirs. Several geochemical proxies exhibit isotopic shifts that have been linked to major changes in the oxygenation levels of the ancient oceans during the Great Oxygenation Event (GOE) between 2.45 and 2.2 Ga and the Neoproterozoic Oxygenation Event at ca. 0.6 Ga. Studies of the modern marine biogeochemical cycle of the transition metal Cadmium have shown that stable Cd isotope fractionation is mainly driven by biological uptake of light Cd into marine phytoplankton in surface waters leaving behind the seawater enriched in the heavy Cd isotopes. Here we use of the potential of this novel proxy to trace ancient biological productivity which remains an enigma, particularly during the early stages of Earth history. The Turee Creek Group in the Hamersley Basin, Australia, provides a continuous stratigraphic sedimentary section covering the GOE and at least two glacial events, offering a unique opportunity to examine the changes that took place during these periods and possibly constrain the evolution, timing and onset of oxygenic photosynthesis. Stable Cd isotope data were obtained on samples from the Boolgeeda Iron Fm. (BIFs), the siliciclastic and carbonate successions of Kungara (including the Meteorite Bore Member) and the Kazputt Fm., using a double spike technique by TIMS (ThermoFisher Triton) and Cd concentrations were determined by isotope dilution. The Boolgeeda BIFs have generally low Cd concentrations varying between 8 and 50ppb, with two major excursions marked by an increase in Cd content, reaching similar levels to those in the overlying Kungarra Fm. (≥150 ppb). These variations are associated with a large range in ɛ112/110Cd values (-2 to +2), with the most negative values typically found in the organic and Cd-rich shales and

A radiogenic isotope tracer study of transatlantic dust transport from Africa to the Caribbean

Science.gov (United States)

Kumar, A.; Abouchami, W.; Galer, S.J.G.; Garrison, V.H.; Williams, E.; Andreae, M.O.

2014-01-01

Many studies have suggested that long-range transport of African desert dusts across the Atlantic Ocean occurs, delivering key nutrients and contributing to fertilization of the Amazon rainforest. Here we utilize radiogenic isotope tracers – Sr, Nd and Pb – to derive the provenance, local or remote, and pathways of dust transport from Africa to the Caribbean. Atmospheric total suspended particulate (TSP) matter was collected in 2008 on quartz fibre filters, from both sides of the Atlantic Ocean at three different locations: in Mali (12.6°N, 8.0°W; 555 m a.s.l.), Tobago (11.3°N, 60.5°W; 329 m a.s.l.) and the U.S. Virgin Islands (17.7°N, 64.6°W; 27 m a.s.l.). Both the labile phase, representative of the anthropogenic signal, and the refractory detrital silicate fraction were analysed. Dust deposits and soils from around the sampling sites were measured as well to assess the potential contribution from local sources to the mineral dust collected. The contribution from anthropogenic sources of Pb was predominant in the labile, leachate phase. The overall similarity in Pb isotope signatures found in the leachates is attributed to a common African source of anthropogenic Pb, with minor inputs from other sources, such as from Central and South America. The Pb, Sr and Nd isotopic compositions in the silicate fraction were found to be systematically more radiogenic than those in the corresponding labile phases. In contrast, Nd and Sr isotopic compositions from Mali, Tobago, and the Virgin Islands are virtually identical in both leachates and residues. Comparison with existing literature data on Saharan and Sahelian sources constrains the origin of summer dust transported to the Caribbean to mainly originate from the Sahel region, with some contribution from northern Saharan sources. The source regions derived from the isotope data are consistent with 7-day back-trajectory analyses, demonstrating the usefulness of radiogenic isotopes in tracing dust provenance and

A radiogenic isotope tracer study of transatlantic dust transport from Africa to the Caribbean

Science.gov (United States)

Kumar, A.; Abouchami, W.; Galer, S. J. G.; Garrison, V. H.; Williams, E.; Andreae, M. O.

2014-01-01

Many studies have suggested that long-range transport of African desert dusts across the Atlantic Ocean occurs, delivering key nutrients and contributing to fertilization of the Amazon rainforest. Here we utilize radiogenic isotope tracers - Sr, Nd and Pb - to derive the provenance, local or remote, and pathways of dust transport from Africa to the Caribbean. Atmospheric total suspended particulate (TSP) matter was collected in 2008 on quartz fibre filters, from both sides of the Atlantic Ocean at three different locations: in Mali (12.6°N, 8.0°W; 555 m a.s.l.), Tobago (11.3°N, 60.5°W; 329 m a.s.l.) and the U.S. Virgin Islands (17.7°N, 64.6°W; 27 m a.s.l.). Both the labile phase, representative of the anthropogenic signal, and the refractory detrital silicate fraction were analysed. Dust deposits and soils from around the sampling sites were measured as well to assess the potential contribution from local sources to the mineral dust collected. The contribution from anthropogenic sources of Pb was predominant in the labile, leachate phase. The overall similarity in Pb isotope signatures found in the leachates is attributed to a common African source of anthropogenic Pb, with minor inputs from other sources, such as from Central and South America. The Pb, Sr and Nd isotopic compositions in the silicate fraction were found to be systematically more radiogenic than those in the corresponding labile phases. In contrast, Nd and Sr isotopic compositions from Mali, Tobago, and the Virgin Islands are virtually identical in both leachates and residues. Comparison with existing literature data on Saharan and Sahelian sources constrains the origin of summer dust transported to the Caribbean to mainly originate from the Sahel region, with some contribution from northern Saharan sources. The source regions derived from the isotope data are consistent with 7-day back-trajectory analyses, demonstrating the usefulness of radiogenic isotopes in tracing dust provenance and