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1
Musich, О., A. Zubko e О. Demyanуuk. "Isotopic effect of macro- and microelements in ecosystems". Balanced nature using, n. 4 (18 agosto 2020): 132–38. http://dx.doi.org/10.33730/2310-4678.4.2020.226644.
Testo completoAbstract (sommario):
Isotopic effects occurring in living organisms due to metabolism are analyzed. The phenomenon of metabolism is considered in the classical sense as a combination of biochemical reactions (mainly enzymatic) that take place in the cells of living beings and provide the cleavage, synthesis and interconversion of complex compounds. The scope of use of natural isotopes is wide and diverse. Isotopes are carriers of information about the birth and transformation of molecules, and isotope fractionation is a chemical characteristic of a substance. Isotope metabolism consists in the intermolecular fractionation of isotopes at separate stages of biochemical reactions, namely the cleavage, synthesis and interconversion of complex compounds caused by differences in the structure and fundamental properties of isotope nuclei. It is proved that the fractionation of isotopes in chemical and biochemical reactions due to isotopic effects is based on two fundamental properties of atomic nuclei — mass and magnetic moment. The kinetic (mass-depen dent) isotopic effect distributes the isotopic nuclei by their masses, and the magnetic one fractionates the nuclei by their magnetic moments. The kinetic isotopic effect depends on the magnitude of the difference in the masses of isotopic molecules, temperature and the difference in the activation energies of isotopic forms. The magnetic isotope effect depends on the reaction rate in a single cell, its projection, magnetic moment and energy of electron-nuclear interaction. It is determined that the fractionation of isotopes in living organisms is that the relative content of one of the isotopes in this compound increases by reducing its content in the other. As a result, there is a fractionation of isotopes within one biological object.
2
Li, Xiangnan, Baisha Weng, Denghua Yan, Tianling Qin, Kun Wang, Wuxia Bi, Zhilei Yu e Batsuren Dorjsuren. "Anthropogenic Effects on Hydrogen and Oxygen Isotopes of River Water in Cities". International Journal of Environmental Research and Public Health 16, n. 22 (12 novembre 2019): 4429. http://dx.doi.org/10.3390/ijerph16224429.
Testo completoAbstract (sommario):
Stable hydrogen and oxygen isotopes are important indicators for studying water cycles. The isotopes are not only affected by climate, but are also disturbed by human activities. Urban construction has changed the natural attributes and underlying surface characteristics of river basins, thus affecting the isotopic composition of river water. We collected urban river water isotope data from the Global Network for Isotopes in Rivers (GNIR) database and the literature, and collected river water samples from the Naqu basin and Huangshui River basin on the Tibetan Plateau to measure hydrogen and oxygen isotopes. Based on 13 pairs of urban area and non-urban area water samples from these data, the relationship between the isotopic values of river water and the artificial surface area of cities around rivers was analyzed. The results have shown that the hydrogen and oxygen isotope (δD and δ18O) values of river water in urban areas were significantly higher than those in non-urban areas. The isotopic variability of urban and non-urban water was positively correlated with the artificial surface area around the rivers. In addition, based on the analysis of isotope data from 21 rivers, we found that the cumulative effects of cities on hydrogen and oxygen isotopes have led to differences in surface water line equations for cities with different levels of development. The combined effects of climate and human factors were the important reasons for the variation of isotope characteristics in river water in cities. Stable isotopes can not only be used to study the effects of climate on water cycles, but also serve as an important indicator for studying the degree of river development and utilization.
3
Pollard, A. M. "Isotopes and impact: a cautionary tale". Antiquity 85, n. 328 (maggio 2011): 631–38. http://dx.doi.org/10.1017/s0003598x00068034.
Testo completoAbstract (sommario):
There can be no doubt that isotopic studies have made a huge contribution to archaeology in recent years, so much so that isotope archaeology is now seen as an essential subdiscipline of archaeology in much the same way as isotope geochemistry is a key subdiscipline of geochemistry. Ignoring for current purposes the contribution made by the measurement of a particular radioactive isotope of carbon (14C) since 1950, we can date the beginnings of isotope archaeology to the mid 1960s with the first measurements of lead isotopes in archaeological metals and slags by Brill and Wampler (1965, 1967). This was followed by carbon stable isotopes in human bone collagen in the late 1970s, building on previous work measuring σ13C in archaeological bone for radiocarbon determinations (Vogel & Van der Merwe 1977; Van der Merwe & Vogel 1978). Other isotopes followed rapidly, such as nitrogen, oxygen, sulphur and hydrogen for archaeological, palaeoecological or palaeoclimatological purposes and, more recently, the heavier radiogenic isotopes of strontium and neodymium for determining the provenance of organic and inorganic materials (Pollard & Heron 2008).
4
Miljević, Nada, e Dušan Golobočanin. "Potential Use of Environmental Isotopes in Pollutant Migration Studies". Archives of Industrial Hygiene and Toxicology 58, n. 2 (1 giugno 2007): 251–62. http://dx.doi.org/10.2478/v10004-007-0015-5.
Testo completoAbstract (sommario):
Potential Use of Environmental Isotopes in Pollutant Migration StudiesThis article presents the use of natural abundance stable isotope (hydrogen, carbon, nitrogen, oxygen, chlorine) analysis data as a tool for providing important information about the origin of contaminants, the contribution of different sources to a multi-source plume, characterisation of their complex transport (rate and mechanisms) and for evaluating the success of contaminated site remediation. Isotopic signatures of contaminants are useful tracers of their sources, while isotopic fractionation can be used to quantitatively assess the progress of an environmental process such as biodegradation. This new isotopic approach is reliable and can offer more information than traditional techniques in pollutant migration studies, particularly after waste disposal. During biological degradation of any organic compound, molecules containing lighter isotopes are degraded, and the portion of heavier isotopes in the substrate is increased, identifying specific microbial roles in biogeochemical cycling. Since isotopic fractionation is proportional to degradation, depending on the type of contamination, a microbial degradation of 50% to 99% of the initial concentration can be quantified using isotope ratio measurements.
5
Emmanuel, S., J. A. Schuessler, J. Vinther, A. Matthews e F. von Blanckenburg. "A preliminary study of iron isotope fractionation in marine invertebrates (chitons, Mollusca) in near-shore environments". Biogeosciences 11, n. 19 (8 ottobre 2014): 5493–502. http://dx.doi.org/10.5194/bg-11-5493-2014.
Testo completoAbstract (sommario):
Abstract. Chitons (Mollusca) are marine invertebrates that produce radulae (teeth or rasping tongues) containing high concentrations of biomineralized magnetite and other iron-bearing minerals. As Fe isotope signatures are influenced by redox processes and biological fractionation, Fe isotopes in chiton radulae might be expected to provide an effective tracer of ambient oceanic conditions and biogeochemical cycling. Here, in a pilot study to measure Fe isotopes in marine invertebrates, we examine Fe isotopes in modern marine chiton radulae collected from different locations in the Atlantic and Pacific oceans to assess the range of isotopic values, and to test whether or not the isotopic signatures reflect seawater values. Values of δ56Fe (relative to IRMM-014) in chiton teeth range from −1.90 to 0.00 ‰ (±0.05‰ (2σ) uncertainty in δ56Fe), probably reflecting a combination of geographical control and biological fractionation processes. Comparison with published local surface seawater Fe isotope data shows a consistent negative offset of chiton teeth Fe isotope compositions relative to seawater. Strikingly, two different species from the same locality in the North Pacific (Puget Sound, Washington, USA) have distinct isotopic signatures. Tonicella lineata, which feeds on red algae in the sublittoral zone, has a mean δ56Fe of −0.65 ± 0.26‰ (2σ, 3 specimens), while Mopalia muscosa, which feeds on both green and red algae in the eulittoral zone, shows lighter isotopic values with a mean δ56Fe of −1.47 ± 0.98‰ (2σ, 5 specimens). Three possible pathways are proposed to account for the different isotopic signatures: (i) physiologically controlled processes within the chitons that lead to species-dependent fractionation; (ii) diet-controlled variability due to different Fe isotope fractionation in the red and green algal food sources; and (iii) environmentally controlled fractionation that causes variation in the isotopic signatures of bioavailable Fe in the different tidal regions. Our preliminary results suggest that while chitons are not simple recorders of the ambient seawater Fe isotopic signature, Fe isotopes provide valuable information concerning Fe biogeochemical cycling in near-shore environments, and may potentially be used to probe sources of Fe recorded in different organisms.
6
Jensen, Alexandria, William Ford, James Fox e Admin Husic. "Improving In-Stream Nutrient Routines in Water Quality Models Using Stable Isotope Tracers: A Review and Synthesis". Transactions of the ASABE 61, n. 1 (2018): 139–57. http://dx.doi.org/10.13031/trans.12545.
Testo completoAbstract (sommario):
Abstract. Water quality models serve as an economically feasible alternative to quantify fluxes of nutrient pollution and to simulate effective mitigation strategies; however, their applicability is often questioned due to broad uncertainties in model structure and parameterization, leading to uncertain outputs. We argue that reduction of uncertainty is partially achieved by integrating stable isotope data streams within the water quality model architecture. This article outlines the use of stable isotopes as a response variable within water quality models to improve the model boundary conditions associated with nutrient source provenance, constrain model parameterization, and elucidate shortcomings in the model structure. To assist researchers in future modeling efforts, we provide an overview of stable isotope theory; review isotopic signatures and applications for relevant carbon, nitrogen, and phosphorus pools; identify biotic and abiotic processes that impact isotope transfer between pools; review existing models that have incorporated stable isotope signatures; and highlight recommendations based on synthesis of existing knowledge. Broadly, we find existing applications that use isotopes have high efficacy for reducing water quality model uncertainty. We make recommendations toward the future use of sediment stable isotope signatures, given their integrative capacity and practical analytical process. We also detail a method to incorporate stable isotopes into multi-objective modeling frameworks. Finally, we encourage watershed modelers to work closely with isotope geochemists to ensure proper integration of stable isotopes into in-stream nutrient fate and transport routines in water quality models. Keywords: Isotopes, Nutrients, Uncertainty analysis, Water quality modeling, Watershed.
7
Orlowski, N., P. Kraft e L. Breuer. "Exploring water cycle dynamics through sampling multitude stable water isotope pools in a small developed landscape of Germany". Hydrology and Earth System Sciences Discussions 12, n. 2 (6 febbraio 2015): 1809–53. http://dx.doi.org/10.5194/hessd-12-1809-2015.
Testo completoAbstract (sommario):
Abstract. Conducting a dual stable water isotope (δ2H and δ18O) study in the developed landscape of the Schwingbach catchment (Germany) helped to unravel connectivity and disconnectivity between the different water cycle components. The two-year weekly to biweekly measurements of precipitation, stream, and groundwater isotopes revealed that surface and groundwater are decoupled from the annual precipitation cycle but showed bidirectional interactions between each other. Seasonal variations based on temperature effects were observed in the precipitation signal but neither reflected in stream nor in groundwater isotopic signatures. Apparently, snowmelt played a fundamental role for groundwater recharge explaining the observed differences to precipitation δ-values. A spatially distributed snapshot sampling of soil water isotopes in two soil depths at 52 sampling points across different land uses (arable land, forest, and grassland) revealed that top soil isotopic signatures were similar to the precipitation input signal. Preferential water flow paths occurred under forested soils explaining the isotopic similarities between top and subsoil isotopic signatures. Due to human-impacted agricultural land use (tilling and compression) of arable and grassland soils, water delivery to the deeper soil layers was reduced, resulting in significant different isotopic signatures. However, the land use influence smoothed out with depth and soil water approached groundwater δ-values. Seasonally tracing stable water isotopes through soil profiles showed that the influence of new percolating soil water decreased with depth as no remarkable seasonality in soil isotopic signatures was obvious at depth > 0.9 m and constant values were observed through space and time. Little variation in individual isotope time series of stream and groundwater restricted the use of classical isotope hydrology techniques e.g. mean transit time estimation or hydrograph separation. Still, tracing stable water isotopes through the water cycle was valuable for determining interactions between different water cycle components and gaining catchment specific process understanding in a developed, human-impacted landscape.
8
Emmanuel, S., J. A. Schuessler, J. Vinther, A. Matthews e F. von Blanckenburg. "Iron isotope fractionation in marine invertebrates in near shore environments". Biogeosciences Discussions 11, n. 4 (11 aprile 2014): 5533–55. http://dx.doi.org/10.5194/bgd-11-5533-2014.
Testo completoAbstract (sommario):
Abstract. Chitons (Mollusca) are marine invertebrates that produce radula (teeth or rasping tongue) containing high concentrations of biomineralized magnetite and other iron bearing minerals. As Fe isotope signatures are influenced by redox processes and biological fractionation, Fe isotopes in chiton radula might be expected to provide an effective tracer of ambient oceanic conditions and biogeochemical cycling. Here, in a pilot study to measure Fe isotopes in marine invertebrates, we examine Fe isotopes in modern marine chiton radula collected from different locations in the Atlantic and Pacific oceans to assess the range of isotopic values, and to test whether or not the isotopic signatures reflect seawater values. Furthermore, by comparing two species that have very different feeding habits but collected from the same location, we infer a possible link between diet and Fe isotopic signatures. Values of δ56Fe (relative to IRMM-014) in chiton teeth range from −1.90 to 0.00‰ (±0.05‰ (2σ) uncertainty in δ56Fe), probably reflecting a combination of geographical control and biological fractionation processes. Comparison with published local surface seawater Fe isotope data shows a consistent negative offset of chiton teeth Fe isotope compositions relative to seawater. Strikingly, two different species from the same locality in the North Pacific (Puget Sound, Washington, USA) have distinct isotopic signatures. Tonicella lineata, which feeds on red algae, has a mean δ56Fe of −0.65 ± 0.26‰ (2σ, 3 specimens), while Mopalia muscosa, which feeds primarily on green algae, shows lighter isotopic values with a mean δ56Fe of −1.47 ± 0.98‰ (2σ, 5 specimens). Although chitons are not simple recorders of the ambient seawater Fe isotopic signature, these preliminary results suggest that Fe isotopes provide information concerning Fe biogeochemical cycling in near shore environments, and might be used to probe sources of Fe in the diets of different organisms.
9
Fujii, T., F. Moynier, A. Agranier, E. Ponzevera e M. Abe. "Isotope fractionation of palladium in chemical exchange reaction". Proceedings in Radiochemistry 1, n. 1 (1 settembre 2011): 339–44. http://dx.doi.org/10.1524/rcpr.2011.0060.
Testo completoAbstract (sommario):
Abstract Palladium isotopes were fractionated by the solvent extraction technique with a crown ether. After purification by ion-exchange chemistry, the isotopic ratios of 105Pd/106Pd, 108Pd/106Pd, and 110Pd/106Pd were determined by multiple-collector inductively coupled plasma mass spectrometry. Isotope fractionations between the two phases were found to be larger than 0.1‰. The isotope fractionation of the odd atomic mass isotope (105Pd) showed a deviation from that estimated from the even atomic mass isotopes (106Pd, 108Pd, and 110Pd). The mass-independent isotope fractionation found was attributable to the nuclear field shift effect. The quantum chemical calculations for the different Pd species supported the validity of the isotope fractionation factors obtained.
10
Passey, Benjamin H. "Reconstructing Terrestrial Environments Using Stable Isotopes in Fossil Teeth and Paleosol Carbonates". Paleontological Society Papers 18 (novembre 2012): 167–94. http://dx.doi.org/10.1017/s1089332600002606.
Testo completoAbstract (sommario):
Carbon isotopes in Neogene-age fossil teeth and paleosol carbonates are commonly interpreted in the context of past distributions of C3 and C4 vegetation. These two plant types have very different distributions in relation to climate and ecology, and provide a robust basis for reconstructing terrestrial paleoclimates and paleoenvironments during the Neogene. Carbon isotopes in pre-Neogene fossil teeth are usually interpreted in the context of changes in the δ13C value of atmospheric CO2, and variable climate-dependent carbon-isotope discrimination in C3 plants. Carbon isotopes in pre-Neogene soil carbonates can be used to estimate past levels of atmospheric CO2. Oxygen isotopes in fossil teeth and paleosol carbonates primarily are influenced by the oxygen isotopic compositions of ancient rainfall and surface waters. The oxygen isotopic composition of rainfall is has a complex, but tractable, relationship with climate, and variably relates to temperature, elevation, precipitation amount, and other factors. Mammal species that rely on moisture in dietary plant tissues to satisfy their water requirements (rather than surface drinking water) may have oxygen isotopic compositions that track aridity. Thus, oxygen isotopes of fossil mammals can place broad constraints on paleoaridity. Carbonate clumped isotope thermometry allows for reconstruction of soil temperatures at the time of pedogenic carbonate mineralization. The method is unique because it is the only thermodynamically based isotopic paleothermometer that does not require assumptions about the isotopic composition of the fluid in which the archive mineral formed. Soil temperature reflects a complex interplay of air temperature, solar radiative heating, latent heat effects, soil thermal diffusivity, and seasonal variations of these parameters. Because plants and most animals live in and/or near the soil, soil temperature is an important aspect of terrestrial (paleo)climate.
11
Jackisch, Dominik, Bi Xuan Yeo, Adam D. Switzer, Shaoneng He, Danica Linda M. Cantarero, Fernando P. Siringan e Nathalie F. Goodkin. "Precipitation stable isotopic signatures of tropical cyclones in Metropolitan Manila, Philippines, show significant negative isotopic excursions". Natural Hazards and Earth System Sciences 22, n. 1 (28 gennaio 2022): 213–26. http://dx.doi.org/10.5194/nhess-22-213-2022.
Testo completoAbstract (sommario):
Abstract. Tropical cyclones have devastating impacts on the environment, economies, and societies and may intensify in the coming decades due to climate change. Stable water isotopes serve as tracers of the hydrological cycle, as isotope fractionation processes leave distinct precipitation isotopic signatures. Here we present a record of daily precipitation isotope measurements from March 2014 to October 2015 for Metropolitan Manila, a first-of-a-kind dataset for the Philippines and Southeast Asia. We show that precipitation isotopic variation at our study site is closely related to tropical cyclones. The most negative shift in δ18O values (−13.84 ‰) leading to a clear isotopic signal was caused by Typhoon Rammasun, which directly hit Metropolitan Manila. The average δ18O value of precipitation associated with tropical cyclones is −10.24 ‰, whereas the mean isotopic value for rainfall associated with non-cyclone events is −5.29 ‰. Further, the closer the storm track is to the sampling site, the more negative the isotopic values are, indicating that in situ isotope measurements can provide a direct linkage between isotopes and typhoon activities in the Philippines.
12
Sare, David T. J., John S. Millar e Frederick J. Longstaffe. "Tracing dietary protein in red-backed voles (Clethrionomys gapperi) using stable isotopes of nitrogen and carbon". Canadian Journal of Zoology 83, n. 5 (1 maggio 2005): 717–25. http://dx.doi.org/10.1139/z05-064.
Testo completoAbstract (sommario):
We examined the stable isotopes of nitrogen and carbon in a small mammal, the red-backed vole (Clethroinomys gapperi (Vigors, 1830)), to determine if isotope signatures reflect diet composition. Nitrogen- and carbon-isotope ratios in tissues from voles maintained on different protein levels in the laboratory were compared with wild-trapped voles. The isotopic fractionation of dietary nitrogen and carbon was also examined as food was digested in the stomach, incorporated into bone collagen, bioapatite, and hair, and excreted as feces. Nitrogen and carbon isotopes were fractionated differently depending on the isotopic composition and protein content of the diet. δ15N and δ13C values appear to be influenced by factors in addition to diet, such as macronutrients metabolized for respiration, metabolic rate, and periods of protein shortage.
13
Hughes, Abigail G., Sonja Wahl, Tyler R. Jones, Alexandra Zuhr, Maria Hörhold, James W. C. White e Hans Christian Steen-Larsen. "The role of sublimation as a driver of climate signals in the water isotope content of surface snow: laboratory and field experimental results". Cryosphere 15, n. 10 (25 ottobre 2021): 4949–74. http://dx.doi.org/10.5194/tc-15-4949-2021.
Testo completoAbstract (sommario):
Abstract. Ice core water isotope records from Greenland and Antarctica are a valuable proxy for paleoclimate reconstruction, yet the processes influencing the climate signal stored in the isotopic composition of the snow are being challenged and revisited. Apart from precipitation input, post-depositional processes such as wind-driven redistribution and vapor–snow exchange processes at and below the surface are hypothesized to contribute to the isotope climate signal subsequently stored in the ice. Recent field studies have shown that surface snow isotopes vary between precipitation events and co-vary with vapor isotopes, which demonstrates that vapor–snow exchange is an important driving mechanism. Here we investigate how vapor–snow exchange processes influence the isotopic composition of the snowpack. Controlled laboratory experiments under forced sublimation show an increase in snow isotopic composition of up to 8 ‰ δ18O in the uppermost layer due to sublimation, with an attenuated signal down to 3 cm snow depth over the course of 4–6 d. This enrichment is accompanied by a decrease in the second-order parameter d-excess, indicating kinetic fractionation processes. Our observations confirm that sublimation alone can lead to a strong enrichment of stable water isotopes in surface snow and subsequent enrichment in the layers below. To compare laboratory experiments with realistic polar conditions, we completed four 2–3 d field experiments at the East Greenland Ice Core Project site (northeast Greenland) in summer 2019. High-resolution temporal sampling of both natural and isolated snow was conducted under clear-sky conditions and demonstrated that the snow isotopic composition changes on hourly timescales. A change of snow isotope content associated with sublimation is currently not implemented in isotope-enabled climate models and is not taken into account when interpreting ice core isotopic records. However, our results demonstrate that post-depositional processes such as sublimation contribute to the climate signal recorded in the water isotopes in surface snow, in both laboratory and field settings. This suggests that the ice core water isotope signal may effectively integrate across multiple parameters, and the ice core climate record should be interpreted as such, particularly in regions of low accumulation.
14
Ibañez-Mejia, Mauricio, e François L. H. Tissot. "Reading the Isotopic Code of Heavy Elements". Elements 17, n. 6 (1 dicembre 2021): 379–82. http://dx.doi.org/10.2138/gselements.17.6.379.
Testo completoAbstract (sommario):
The isotopic variability of the elements in our planet and Solar System is the end result of a complex mixture of processes, including variable production of isotopes in stars, ingrowth of daughter nuclides due to decay of radioactive parents, and selective incorporation of isotopes into solids, liquids, or gases as a function of their mass and/or nuclear volume. Interpreting the isotopic imprints that planetary formation and evolution have left in the rock and mineral record requires not only precise and accurate measurements but also an understanding of the drivers behind isotopic variability. Here, we introduce fundamental concepts needed to “read” the isotopic code, with particular emphasis on heavy stable isotope systems.
15
Datye, Amey, Supriyo Chakraborty, Rajib Chattopadhyay, MohammadArzoo Ansari, Archana Deodhar e PM Mohan. "Precipitation isotopes’ response to the atmospheric processes over the mainland and the island region in the northern Indian Ocean: Implications to the paleo-monsoon study". MAUSAM 74, n. 2 (29 marzo 2023): 503–12. http://dx.doi.org/10.54302/mausam.v74i2.5998.
Testo completoAbstract (sommario):
The isotopic composition of precipitation was studied over a terrestrial environment in western India and an island region in the Bay of Bengal. We have examined the precipitation isotopes’ response to the surface temperature and the tropospheric warming during the monsoon season. We observed that tropospheric temperature and surface temperature are positively correlated over the ocean while they are negatively correlated over the land. As a result, the precipitation isotopes in these environments show the opposite behavior to surface temperature variability. Despite this difference, precipitation isotopes in both environments respond positively to the tropospheric temperature variability, though the relationship is weaker in the terrestrial environment. The precipitation isotopic response to tropospheric temperature may provide an alternative to the precipitation and precipitation isotope relation widely used in past monsoon reconstruction.
16
Bühler, Janica C., Josefine Axelsson, Franziska A. Lechleitner, Jens Fohlmeister, Allegra N. LeGrande, Madhavan Midhun, Jesper Sjolte, Martin Werner, Kei Yoshimura e Kira Rehfeld. "Investigating stable oxygen and carbon isotopic variability in speleothem records over the last millennium using multiple isotope-enabled climate models". Climate of the Past 18, n. 7 (13 luglio 2022): 1625–54. http://dx.doi.org/10.5194/cp-18-1625-2022.
Testo completoAbstract (sommario):
Abstract. The incorporation of water isotopologues into the hydrology of general circulation models (GCMs) facilitates the comparison between modeled and measured proxy data in paleoclimate archives. However, the variability and drivers of measured and modeled water isotopologues, as well as the diversity of their representation in different models, are not well constrained. Improving our understanding of this variability in past and present climates will help to better constrain future climate change projections and decrease their range of uncertainty. Speleothems are a precisely datable terrestrial paleoclimate archives and provide well-preserved (semi-)continuous multivariate isotope time series in the lower latitudes and mid-latitudes and are therefore well suited to assess climate and isotope variability on decadal and longer timescales. However, the relationships of speleothem oxygen and carbon isotopes to climate variables are influenced by site-specific parameters, and their comparison to GCMs is not always straightforward. Here we compare speleothem oxygen and carbon isotopic signatures from the Speleothem Isotopes Synthesis and Analysis database version 2 (SISALv2) to the output of five different water-isotope-enabled GCMs (ECHAM5-wiso, GISS-E2-R, iCESM, iHadCM3, and isoGSM) over the last millennium (850–1850 CE). We systematically evaluate differences and commonalities between the standardized model simulation outputs. The goal is to distinguish climatic drivers of variability for modeled isotopes and compare them to those of measured isotopes. We find strong regional differences in the oxygen isotope signatures between models that can partly be attributed to differences in modeled surface temperature. At low latitudes, precipitation amount is the dominant driver for stable water isotope variability; however, at cave locations the agreement between modeled temperature variability is higher than for precipitation variability. While modeled isotopic signatures at cave locations exhibited extreme events coinciding with changes in volcanic and solar forcing, such fingerprints are not apparent in the speleothem isotopes. This may be attributed to the lower temporal resolution of speleothem records compared to the events that are to be detected. Using spectral analysis, we can show that all models underestimate decadal and longer variability compared to speleothems (albeit to varying extents). We found that no model excels in all analyzed comparisons, although some perform better than the others in either mean or variability. Therefore, we advise a multi-model approach whenever comparing proxy data to modeled data. Considering karst and cave internal processes, e.g., through isotope-enabled karst models, may alter the variability in speleothem isotopes and play an important role in determining the most appropriate model. By exploring new ways of analyzing the relationship between the oxygen and carbon isotopes, their variability, and co-variability across timescales, we provide methods that may serve as a baseline for future studies with different models using, e.g., different isotopes, different climate archives, or different time periods.
17
Tea, Illa, Arnaud De Luca, Anne-Marie Schiphorst, Mathilde Grand, Sophie Barillé-Nion, Eric Mirallié, Delphine Drui, Michel Krempf, Régis Hankard e Guillaume Tcherkez. "Stable Isotope Abundance and Fractionation in Human Diseases". Metabolites 11, n. 6 (9 giugno 2021): 370. http://dx.doi.org/10.3390/metabo11060370.
Testo completoAbstract (sommario):
The natural abundance of heavy stable isotopes (13C, 15N, 18O, etc.) is now of considerable importance in many research fields, including human physiology. In fact, it varies between tissues and metabolites due to isotope effects in biological processes, that is, isotope discriminations between heavy and light isotopic forms during enzyme or transporter activity. The metabolic deregulation associated with many diseases leads to alterations in metabolic fluxes, resulting in changes in isotope abundance that can be identified easily with current isotope ratio technologies. In this review, we summarize the current knowledge on changes in natural isotope composition in samples (including various tissues, hair, plasma, saliva) found in patients compared to controls, caused by human diseases. We discuss the metabolic origin of such isotope fractionations and highlight the potential of using isotopes at natural abundance for medical diagnosis and/or prognostic.
18
Hu, Yue, Guo-dong Liu e Cheng-cheng Xia. "Multi-time scale analysis of hydrogen and oxygen isotope characteristics and influence factors in precipitation in Vienna". MATEC Web of Conferences 246 (2018): 02011. http://dx.doi.org/10.1051/matecconf/201824602011.
Testo completoAbstract (sommario):
Based on isotope and meteorology data at Vienna station from 1972 to 2014 provided by GNIP, the average monthly and annual hydrogen and oxygen stable isotopic compositions and main factors were analyzed by using various trend analysis, periodic analysis and correlation analysis methods. The monthly mean isotopic compositions change slightly, reflecting the fact that although Vienna is affected by the maritime climate and the continental climate, the former impact is more significant. The slope and intercept of the LMWL in Vienna changed significantly from October to March, indicating that it was affected by alternating effects of the two climates. The annual mean isotopes show a trend of enrichment, and it has an obvious temperature effect, but the rainfall amount effect does not exist, and no simple linear relationship was found between isotopes and vapor pressure. The annual mean isotopes also show the periodic variation characteristics with scales such as 9-16 years and 18~29 years, and it is concluded that the isotope values will be enriched after 2011 at the scale 22 years. The multivariate regression relationship established by δD and δ18O with three climate parameters of temperature, precipitation and vapor pressure can quantitatively estimate the missing value in isotopic data.
19
Kurita, N., Y. Fujiyoshi, T. Nakayama, Y. Matsumi e H. Kitagawa. "Atmospheric circulation controls on the inter-annual variability in precipitation isotope ratio in Japan". Climate of the Past Discussions 10, n. 5 (2 ottobre 2014): 3989–4032. http://dx.doi.org/10.5194/cpd-10-3989-2014.
Testo completoAbstract (sommario):
Abstract. This study explored the primary driver of variations of precipitation isotopes at multiple temporal scales (event, seasonal and inter-annual scales) to provide a greater depth of interpretation for isotope proxy records in Japan. A one-year record of the isotopic composition of event-based precipitation at Nagoya in central Japan showed less seasonal variation, but there is large isotopic variability on a storm-to-storm basis. In the summer, southerly flows transport isotopically enriched moisture from subtropical marine regions with the result that the rainfall produced by the subtropical air, or warm rainfall, was relatively enriched in heavy isotopes in comparison with the other rainfall events. In the winter, storm tracks are the dominant driver of storm-to-storm isotopic variation, and relatively lower isotopic values occurred when northerly winds in association with extratropical cyclones passing off the south coast of Japan (Nangan cyclone) brings cold precipitation. Using the historical 17 year record of monthly isotopes in precipitation at Tokyo station, we explored if the factors controlling event-scale isotopic variability can account for inter-annual isotopic variability. The relatively higher isotopes in summer precipitation were attributed to the higher contribution of the warm rainfall to the total summer precipitation. On the other hand, year-to-year variation of isotopic values in winter precipitation was negatively correlated with the relative ratio of the Nangan cyclone rainfall to the total winter precipitation. The 17 year precipitation history demonstrates that event-scale isotopic variability related to changes in meridional moisture transport is the primary driver of inter-annual isotopic variability in winter and summer precipitation. The meridional moisture transport to central Japan is likely linked to the activity of the western North Pacific subtropical high in summer and the intensity of the East Asian winter monsoon in winter. Therefore, isotope-based proxy records archived in central Japan may enable us to examine past atmospheric circulation changes in East Asia in response to climate variability.
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Doucet, Luc S., Oscar Laurent, Dmitri A. Ionov, Nadine Mattielli, Vinciane Debaille e Wendy Debouge. "Archean lithospheric differentiation: Insights from Fe and Zn isotopes". Geology 48, n. 10 (19 giugno 2020): 1028–32. http://dx.doi.org/10.1130/g47647.1.
Testo completoAbstract (sommario):
Abstract The Archean continental lithosphere consists of a dominantly felsic continental crust, made of tonalite-trondhjemite-granodiorite (TTG) and subordinate granitoids, and a cratonic lithospheric mantle, made of highly refractory peridotites. Whether they stemmed from the same process of differentiation from the primitive mantle, or were two distinct components that were physically juxtaposed, remains debated. Metal stable isotope ratios are sensitive to magmatic and metamorphic processes and do not evolve with time. Therefore, stable isotope ratios are complementary to radiogenic isotope ratios, and they allow direct comparisons to be made between different terrestrial components without age corrections. Isotopes of iron and zinc, metals ubiquitous in Earth’s lithosphere, can be tracers of lithospheric formation and evolution because they are affected by partial melting (Fe, Zn), redox state (Fe), and the presence of sulfides (Fe, Zn). Here, using stable Fe and Zn isotopic data from Archean samples of the lithospheric mantle and the continental crust, we show that Fe and Zn isotopes define a linear array, best explained by their coupled fractionation behavior during magmatic processes. Our data show that high degrees of partial melting (>30%) during the formation of the cratonic mantle and mafic protocrust, and reworking of the early crust significantly fractionate Fe and Zn isotopes. Conversely, Fe and Zn isotope ratios in the TTG are similar to those in Archean mafic rocks, suggesting an origin by fractional crystallization of basalt, and implying limited Fe and Zn isotopic fractionation, instead of partial melting of mafic crust. Moreover, the absence of Fe and Zn isotope decoupling due to redox effects, melt (fluid)–rock or sediment-rock interaction, and decarbonation indicates that subduction, at least as we understand it now, is not required to explain the Fe and Zn isotope composition of the Archean lithosphere.
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Meister, Patrick, e Carolina Reyes. "The Carbon-Isotope Record of the Sub-Seafloor Biosphere". Geosciences 9, n. 12 (5 dicembre 2019): 507. http://dx.doi.org/10.3390/geosciences9120507.
Testo completoAbstract (sommario):
Sub-seafloor microbial environments exhibit large carbon-isotope fractionation effects as a result of microbial enzymatic reactions. Isotopically light, dissolved inorganic carbon (DIC) derived from organic carbon is commonly released into the interstitial water due to microbial dissimilatory processes prevailing in the sub-surface biosphere. Much stronger carbon-isotope fractionation occurs, however, during methanogenesis, whereby methane is depleted in 13C and, by mass balance, DIC is enriched in 13C, such that isotopic distributions are predominantly influenced by microbial metabolisms involving methane. Methane metabolisms are essentially mediated through a single enzymatic pathway in both Archaea and Bacteria, the Wood–Ljungdahl (WL) pathway, but it remains unclear where in the pathway carbon-isotope fractionation occurs. While it is generally assumed that fractionation arises from kinetic effects of enzymatic reactions, it has recently been suggested that partial carbon-isotope equilibration occurs within the pathway of anaerobic methane oxidation. Equilibrium fractionation might also occur during methanogenesis, as the isotopic difference between DIC and methane is commonly on the order of 75‰, which is near the thermodynamic equilibrium. The isotopic signature in DIC and methane highly varies in marine porewaters, reflecting the distribution of different microbial metabolisms contributing to DIC. If carbon isotopes are preserved in diagenetic carbonates, they may provide a powerful biosignature for the conditions in the deep biosphere, specifically in proximity to the sulphate–methane transition zone. Large variations in isotopic signatures in diagenetic archives have been found that document dramatic changes in sub-seafloor biosphere activity over geological time scales. We present a brief overview on carbon isotopes, including microbial fractionation mechanisms, transport effects, preservation in diagenetic carbonate archives, and their implications for the past sub-seafloor biosphere and its role in the global carbon cycle. We discuss open questions and future potentials of carbon isotopes as archives to trace the deep biosphere through time.
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Carter, Wales A., Ulf Bauchinger e Scott R. McWilliams. "The Importance of Isotopic Turnover for Understanding Key Aspects of Animal Ecology and Nutrition". Diversity 11, n. 5 (26 maggio 2019): 84. http://dx.doi.org/10.3390/d11050084.
Testo completoAbstract (sommario):
Stable isotope-based methods have proved to be immensely valuable for ecological studies ranging in focus from animal movements to species interactions and community structure. Nevertheless, the use of these methods is dependent on assumptions about the incorporation and turnover of isotopes within animal tissues, which are oftentimes not explicitly acknowledged and vetted. Thus, the purpose of this review is to provide an overview of the estimation of stable isotope turnover rates in animals, and to highlight the importance of these estimates for ecological studies in terrestrial, freshwater, and marine systems that may use a wide range of stable isotopes. Specifically, we discuss 1) the factors that contribute to variation in turnover among individuals and across species, which influences the use of stable isotopes for diet reconstructions, 2) the differences in turnover among tissues that underlie so-called ‘isotopic clocks’, which are used to estimate the timing of dietary shifts, and 3) the use of turnover rates to estimate nutritional requirements and reconstruct histories of nutritional stress from tissue isotope signatures. As we discuss these topics, we highlight recent works that have effectively used estimates of turnover to design and execute informative ecological studies. Our concluding remarks suggest several steps that will improve our understanding of isotopic turnover and support its integration into a wider range of ecological studies.
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Sedaghatpour, Fatemeh, e Stein B. Jacobsen. "Magnesium stable isotopes support the lunar magma ocean cumulate remelting model for mare basalts". Proceedings of the National Academy of Sciences 116, n. 1 (17 dicembre 2018): 73–78. http://dx.doi.org/10.1073/pnas.1811377115.
Testo completoAbstract (sommario):
We report high-precision Mg isotopic analyses of different types of lunar samples including two pristine Mg-suite rocks (72415 and 76535), basalts, anorthosites, breccias, mineral separates, and lunar meteorites. The Mg isotopic composition of the dunite 72415 (δ25Mg = −0.140 ± 0.010‰, δ26Mg = −0.291 ± 0.018‰), the most Mg-rich and possibly the oldest lunar sample, may provide the best estimate of the Mg isotopic composition of the bulk silicate Moon (BSM). This δ26Mg value of the Moon is similar to those of the Earth and chondrites and reflects both the relative homogeneity of Mg isotopes in the solar system and the lack of Mg isotope fractionation by the Moon-forming giant impact. In contrast to the behavior of Mg isotopes in terrestrial basalts and mantle rocks, Mg isotopic data on lunar samples show isotopic variations among the basalts and pristine anorthositic rocks reflecting isotopic fractionation during the early lunar magma ocean (LMO) differentiation. Calculated evolutions of δ26Mg values during the LMO differentiation are consistent with the observed δ26Mg variations in lunar samples, implying that Mg isotope variations in lunar basalts are consistent with their origin by remelting of distinct LMO cumulates.
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Kim, Songyi, Yeongcheol Han, Soon Do Hur, Kei Yoshimura e Jeonghoon Lee. "Relating Moisture Transport to Stable Water Vapor Isotopic Variations of Ambient Wintertime along the Western Coast of Korea". Atmosphere 10, n. 12 (12 dicembre 2019): 806. http://dx.doi.org/10.3390/atmos10120806.
Testo completoAbstract (sommario):
Atmospheric water vapor transfers energy, causes meteorological phenomena and can be modified by climate change in the western coast region of Korea. In Korea, previous studies have utilized precipitation isotopic compositions in the water cycle for correlations with climate variables, but there are few studies using water vapor isotopes. In this study, water vapor was directly collected by a cryogenic method, analyzed for its isotopic compositions, and used to trace the origin and history of water vapor in the western coastal region of Korea during the winter of 2015/2016. Our analysis of paired mixing ratios with water vapor isotopes can explain the mechanism of water vapor isotopic fractionation and the extent of the mixing of two different air masses. We confirm the correlation between water vapor isotopes and meteorological parameters such as temperature, relative humidity, and specific humidity. The main water vapor in winter was derived from the continental polar region of northern Asia and showed an enrichment of 10 per mil (δ18O) through the evaporation of the Yellow Sea. Our results demonstrate the utility of using ground-based isotope observations as a complementary resource for constraining isotope-enabled Global Circulation Model in future investigations of atmospheric water cycles. These measurements are expected to support climate studies (speleothem) in the west coast region of Korea.
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Wang, Yan, Zhongwei Wu, Yi Huang, Xiaoming Sun, Jinhui Yan, Fan Yang, Zhengxin Yin e Li Xu. "Fe-Cu-Zn Isotopic Compositions in Polymetallic Sulfides from Hydrothermal Fields in the Ultraslow-Spreading Southwest Indian Ridge and Geological Inferences". Minerals 13, n. 7 (22 giugno 2023): 843. http://dx.doi.org/10.3390/min13070843.
Testo completoAbstract (sommario):
Submarine hydrothermal sulfides from the ultraslow-spreading Southwest Indian Ridge (SWIR) were sampled from three hydrothermal fields, and the Fe-Cu-Zn isotopic compositions were analyzed in this study. The Fe isotopes ranged from −0.011‰ to −1.333‰. We believe the processes controlling the Fe isotope variability in the hydrothermal systems include the sulfide precipitation process, the initial isotopic composition of the hydrothermal fluid, and the temperature during precipitation. Among these factors, the sulfide precipitation process is the dominant one. The Cu isotope compositions of the sulfides varied from −0.364‰ to 0.892‰, indicating that the hydrothermal fluid preferentially leached 65Cu in the early stages and that hydrothermal reworking led to decreases in the Cu isotopes in the later stages. In addition, because mass fractionation occurred during sulfide precipitation, the Zn isotope variations ranged from −0.060‰ to 0.422‰. Combined with the S isotopic compositions, these results also implied that different Fe-Cu-Zn isotopic fractionation mechanisms prevailed for the different sample types. Based on these results, we are sure that the metallic elements, including Fe, Cu, and Zn, were derived from the mantle in the SWIR hydrothermal field, and the Fe-Cu isotope results indicated that these metallic elements were provided by fluid leaching processes. Using the isotopic fractionation and sulfide results, we calculated that the Fe-Cu-Zn isotopic compositions of the hydrothermal fluid in this field were δ56Fe(fluid): −0.8~0.0‰; δ65Cu(fluid): 0.3~1.3‰; and δ66Zn(fluid): 0~0.48‰.
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Prichko, T. G., U. F. Yakuba e M. V. Karpushina. "Study of the possibility of using data on the content of stable isotopes of magnesium to predict the region of apple production". Agrarian science, n. 2 (5 marzo 2023): 95–99. http://dx.doi.org/10.32634/0869-8155-2023-367-2-95-99.
Testo completoAbstract (sommario):
Relevance. Reliable criteria for determining the region of origin of fruit products attract the constant attention of researchers in various countries. A number of approaches aimed at solving this problem are already known, and some progress has been made in interpreting experimental data for fruits on the content of stable isotopes of hydrogen, carbon, oxygen, nitrogen, and sulfur. It is possible that information about the fractionation of stable isotopes of magnesium will allow us to obtain equally important and reliable information to achieve the same goals.Methods. A mass spectrometer with inductively coupled plasma, standard samples of stable isotopes of magnesium produced in Russia were used to perform the work. The total concentration of magnesium cations was determined by atomic absorption in the flame and on the capillary electrophoresis system.Results. During the research, the mass and percentage ratio of three stable isotopes (24Mg, 25Mg, 26Mg) in the studied samples of apples grown in different soil and climatic zones was established. The data obtained reflect the relative prevalence of isotopes of this element, expressed in the ratio of the least common isotope to the most common. The deviation of the isotopic composition of Mg prototypes from the conventional standard was determined, significant deviations were obtained for the magnetic isotope 25Mg and non-magnetic 26Mg. The initial data on the fractionation of stable isotopes of magnesium in raw materials growing in different regions were obtained, with the aim of possible subsequent use as indicators in biochemical and physiological studies. A combination of the obtained information on Mg isotopes is assumed, taking into account the content of isotopes of other metals, which will make it possible to specify the region of growth of raw materials with greater reliability.
27
Sturm, C., Q. Zhang e D. Noone. "An introduction to stable water isotopes in climate models: benefits of forward proxy modelling for paleoclimatology". Climate of the Past Discussions 5, n. 3 (30 giugno 2009): 1697–729. http://dx.doi.org/10.5194/cpd-5-1697-2009.
Testo completoAbstract (sommario):
Abstract. Stable water isotopes have been measured in a wide range of climate archives, with the purpose of reconstructing regional climate variations. Yet the common assumption that the isotopic signal is a direct indicator of temperature proves to be misleading under certain circumstances, since its relationship with temperature also depends on e.g. atmospheric circulation and precipitation seasonality. The present article introduces the principles, benefits and caveats of using climate models with embedded water isotopes as a support for the interpretation of isotopic climate archives. A short overview of the limitations of empirical calibrations of isotopic proxy records is presented, with emphasis on the physical processes that infirm its underlying hypotheses. The simulation of climate and its associated isotopic signal, despite difficulties related to downscaling and intrinsic atmospheric variability, can provide a "transfer function" between the isotopic signal and the considered climate variable. The multi-proxy data can then be combined with model output to produce a physically consistent climate reconstruction and its confidence interval. A sensitivity study with the isotope-enabled global circulation model CAM3iso under idealised present-day, pre-industrial and mid-Holocene is presented to illustrate the impact of a changing climate on the isotope-temperature relationship.
28
Ivanova, Elena Sergeevna, Olga Yurievna Rumiantseva, Anastasia Sergeevna Zavertkina, Anastasia Evgenievna Bueva e Anna Sergeevna Elizarova. "The isotopic composition of hair among the population in the Vologda Region depending on the conditions of living and nutrition". Samara Journal of Science 10, n. 4 (1 dicembre 2021): 46–50. http://dx.doi.org/10.17816/snv2021104107.
Testo completoAbstract (sommario):
Isotope mass spectrometry methods are used to study changes in the isotopic composition of organisms in the food chain called trophic fractionation. In particular, with the help of isotope analysis of tissues, it is possible to determine the type of nutrition and possible place of residence of a person, which helps in solving the tasks of forensic examination. In this study, the isotopic composition C and ⁵N in the hair of residents of the industrial city of Cherepovets and the Kirillovsky District of the Vologda Region, remote from industrial sources of pollution, was determined. The determination of the isotopic composition of hair was carried out on an isotope mass spectrometer Thermo-Finnigan Delta V Plus in the Ecological and Analytical Laboratory of Cherepovets State University. The average values of isotopes in the hair of the study participants are 20,86 (C) and 9,98 (⁵N). There are differences in the ratio of carbon and nitrogen isotopes in the hair of residents of Cherepovets and Kirillovsky District. There are not statistically significant differences in the isotopic composition of C and ⁵N in the hair of female and male. There are differences of ⁵N in the hair of people who consume different amounts of fish (people who consume fish more often have a higher ratio of ⁵N).
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Reyes-García, Casandra, e José Luis Andrade. "Los isótopos estables del hidrógeno y el oxígeno en los estudios ecofisiológicos de plantas". Botanical Sciences, n. 80 (3 giugno 2017): 19. http://dx.doi.org/10.17129/botsci.1742.
Testo completoAbstract (sommario):
Stable isotope studies of elements in biological organisms have become a useful tool to assess the exchange of molecules in the biosphere. Since water is one of the most abundant molecules in such an exchange, studies on stable isotopes of hydrogen and oxygen have become a fundamental component of many plant ecophysiological studies, from the leaf level to the reconstruction of past climates. In this review, we mention the most common methodologies, general notation and the most relevant research on hydrogen and oxygen stable isotopes. Also, we discuss studies on plant water sources, leaf isotopic enrichment due to transpiration, the relationship between environment and oxygen stable isotopes in organic matter, and present studies that propose some plant species as environmental indicators in a globally changing world.
30
Xu, Yingkui, Dan Zhu, Xiongyao Li e Jianzhong Liu. "Why magnesium isotope fractionation is absent from basaltic melts under thermal gradients in natural settings". Geological Magazine 157, n. 7 (25 novembre 2019): 1144–48. http://dx.doi.org/10.1017/s0016756819001304.
Testo completoAbstract (sommario):
AbstractLaboratory experiments have shown that thermal gradients in silicate melts can lead to isotopic fractionation; this is known as the Richter effect. However, it is perplexing that the Richter effect has not been documented in natural samples as thermal gradients commonly exist within natural igneous systems. To resolve this discrepancy, theoretical analysis and calculations were undertaken. We found that the Richter effect, commonly seen in experiments with wholly molten silicates, cannot be applied to natural systems because natural igneous samples are more likely to be formed out of partially molten magma and the presence of minerals adds complexity to the behaviour of the isotope. In this study, we consider two related diffusion-rate kinetic isotope effects that originate from chemical diffusion, which are absent from experiments with wholly molten samples. We performed detailed calculations for magnesium isotopes, and the results indicated that the Richter effect for magnesium isotopes is buffered by kinetic isotope effects and the total value of magnesium isotope fractionation can be zero or even undetectable. Our study provides a new understanding of isotopic behaviour during the processes of cooling and solidification in natural magmatic systems.
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Quirt, David, e Antonio Benedicto. "Lead Isotopes in Exploration for Basement-Hosted Structurally Controlled Unconformity-Related Uranium Deposits: Kiggavik Project (Nunavut, Canada)". Minerals 10, n. 6 (31 maggio 2020): 512. http://dx.doi.org/10.3390/min10060512.
Testo completoAbstract (sommario):
Pb-isotopes have been proposed as pathfinders for sandstone-hosted unconformity-related U deposits, with isotope ratios providing information on mineralization timing and element remobilization and migration. Pb-isotopes proximal to mineralization display radiogenic signatures, often with ‘excess Pb’ suggestive of derivation from greater U concentrations than are currently present. The U deposits in the Kiggavik project area (west of Baker Lake, NU, Canada) are basement-hosted, contain several generations of pitchblende mineralization, display a strong structural control, and are located in fault-related fracture systems and foliation-parallel veinlets. Drill core samples were analysed by Inductively-Coupled Plasma-Mass Spectrometer (ICP-MS) for Pb isotopes following multi-acid total-digestion, reverse Aqua Regia partial-digestion, and weak-acid-leach attacks, to evaluate the utility of the respective dissolution methods in Pb-isotope pathfinder geochemistry. Partial-digestion results are similar to weak-acid-leach results, indicating that interpretation of Pb-isotope signatures can be carried out from partial-digestion data if weak-acid-leach data are unavailable. Application of this pathfinder method at Kiggavik shows that Pb-isotope ratios display systematic trends useful for exploration vectoring. Uranium-content-adjusted 206Pb/204Pb ratios and 206Pb/204Pb ‘excess-lead’ data highlight anomalous isotopic values. 207Pb/206Pb ratios display downhole trends complementary to location of mineralization. Three-dimensional (3D) distributions of Pb-isotope data at the Contact U prospect show systematic trends and form halos around the mineralization. Isotopic footprints are limited to <50 m from the mineralization outline, reflecting host-rock and structural control, but indicate areas with elevated potential for U mineralization and provide vectoring information within basement lithologies.
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Orlowski, Natalie, Philipp Kraft, Jakob Pferdmenges e Lutz Breuer. "Exploring water cycle dynamics by sampling multiple stable water isotope pools in a developed landscape in Germany". Hydrology and Earth System Sciences 20, n. 9 (20 settembre 2016): 3873–94. http://dx.doi.org/10.5194/hess-20-3873-2016.
Testo completoAbstract (sommario):
Abstract. A dual stable water isotope (δ2H and δ18O) study was conducted in the developed (managed) landscape of the Schwingbach catchment (Germany). The 2-year weekly to biweekly measurements of precipitation, stream, and groundwater isotopes revealed that surface and groundwater are isotopically disconnected from the annual precipitation cycle but showed bidirectional interactions between each other. Apparently, snowmelt played a fundamental role for groundwater recharge explaining the observed differences to precipitation δ values. A spatially distributed snapshot sampling of soil water isotopes at two soil depths at 52 sampling points across different land uses (arable land, forest, and grassland) revealed that topsoil isotopic signatures were similar to the precipitation input signal. Preferential water flow paths occurred under forested soils, explaining the isotopic similarities between top- and subsoil isotopic signatures. Due to human-impacted agricultural land use (tilling and compression) of arable and grassland soils, water delivery to the deeper soil layers was reduced, resulting in significant different isotopic signatures. However, the land use influence became less pronounced with depth and soil water approached groundwater δ values. Seasonally tracing stable water isotopes through soil profiles showed that the influence of new percolating soil water decreased with depth as no remarkable seasonality in soil isotopic signatures was obvious at depths > 0.9 m and constant values were observed through space and time. Since classic isotope evaluation methods such as transfer-function-based mean transit time calculations did not provide a good fit between the observed and calculated data, we established a hydrological model to estimate spatially distributed groundwater ages and flow directions within the Vollnkirchener Bach subcatchment. Our model revealed that complex age dynamics exist within the subcatchment and that much of the runoff must has been stored for much longer than event water (average water age is 16 years). Tracing stable water isotopes through the water cycle in combination with our hydrological model was valuable for determining interactions between different water cycle components and unravelling age dynamics within the study area. This knowledge can further improve catchment-specific process understanding of developed, human-impacted landscapes.
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Kakareka, S. V., T. I. Kukharchyk, A. A. Ekaykin e Yu G. Giginyak. "Stable isotopes in the snow of the coastal areas of Antarctica". Doklady of the National Academy of Sciences of Belarus 65, n. 4 (2 settembre 2021): 495–502. http://dx.doi.org/10.29235/1561-8323-2021-65-4-495-502.
Testo completoAbstract (sommario):
The first results of study of stable isotopes of oxygen (δ18O) and hydrogen (δD) in the snow samples taken on the islands of Marguerite Bay (Antarctic Peninsula), in the Vecherny Oasis (Enderby Land), and Larsemann Hills (Princess Elizabeth Land) by the participants of the 12th Belarusian Antarctic Expedition (January–March 2020) are presented. The concentration of water isotopes: deuterium (D) and oxygen-18 (18O) in the samples was determined using a laser isotope composition analyzer Picarro L2130. A total of 32 snow samples were analyzed. The statistical parameters of the isotopic composition of snow were estimated, and the main differences in the content of δ18O and δD between the study areas were shown. A decrease in the content of heavy oxygen and hydrogen isotopes in the newly fallen snow to the old snow of the surface horizons is shown. The maximum values of δ18O and δD are typical for the Maritime Antarctica, decreasing towards the coastal zone and further – towards its continental part. The possible factors affecting the isotope content are described. It is shown that the monitoring of the isotope composition can be an integral part of the monitoring of climatic changes within the area of operation of the Belarusian Antarctic Expedition. The study of the isotopic composition of surface snow is important for the reconstruction of the paleoclimate of the marginal zone of the Antarctic ice sheet based on the ice cores study.
34
Larner, Fiona, Catriona A. McLean, Alex N. Halliday e Blaine R. Roberts. "Copper Isotope Compositions of Superoxide Dismutase and Metallothionein from Post-Mortem Human Frontal Cortex". Inorganics 7, n. 7 (7 luglio 2019): 86. http://dx.doi.org/10.3390/inorganics7070086.
Testo completoAbstract (sommario):
The natural copper isotopic compositions of superoxide dismutase and metallothionein from six post-mortem human frontal cortices were determined using a combination of size exclusion protein liquid chromatography, followed by anion exchange chromatography and multiple collector inductively-coupled plasma mass spectrometry. Superoxide dismutase was enriched in the heavier 65Cu relative to the metallothionein fraction in all specimen pairs. The isotopic compositions were independent of copper content. This finding provides evidence that nitrogen ligands in protein copper binding sites will be enriched in heavy metal isotopes, and sulphur ligands will preferentially incorporate lighter isotopes in vivo. This in turn has implications for understanding isotopic distributions within different components in the body and the dominant ligands in different tissues. Differences in Cu isotope distributions between the two proteins were seen between Alzheimer’s disease and healthy control samples, when normalised for sex.
35
Halder, J., S. Terzer, L. I. Wassenaar, L. J. Araguás-Araguás e P. K. Aggarwal. "The Global Network of Isotopes in Rivers (GNIR): integration of water isotopes in watershed observation and riverine research". Hydrology and Earth System Sciences 19, n. 8 (5 agosto 2015): 3419–31. http://dx.doi.org/10.5194/hess-19-3419-2015.
Testo completoAbstract (sommario):
Abstract. We introduce a new online global database of riverine water stable isotopes (Global Network of Isotopes in Rivers, GNIR) and evaluate its longer-term data holdings. Overall, 218 GNIR river stations were clustered into three different groups based on the seasonal variation in their isotopic composition, which was closely coupled to precipitation and snowmelt water runoff regimes. Sinusoidal fit functions revealed phases within each grouping and deviations from the sinusoidal functions revealed important river alterations or hydrological processes in these watersheds. The seasonal isotopic amplitude of δ18O in rivers averaged 2.5 ‰, and did not increase as a function of latitude, like it does for global precipitation. Low seasonal isotopic amplitudes in rivers suggest the prevalence of mixing and storage such as occurs via lakes, reservoirs, and groundwater. The application of a catchment-constrained regionalized cluster-based water isotope prediction model (CC-RCWIP) allowed for direct comparison between the expected isotopic compositions for the upstream catchment precipitation with the measured isotopic composition of river discharge at observation stations. The catchment-constrained model revealed a strong global isotopic correlation between average rainfall and river discharge (R2 = 0.88) and the study demonstrated that the seasonal isotopic composition and variation of river water can be predicted. Deviations in data from model-predicted values suggest there are important natural or anthropogenic catchment processes like evaporation, damming, and water storage in the upstream catchment.
36
Halder, J., S. Terzer, L. I. Wassenaar, L. J. Araguás-Araguás e P. K. Aggarwal. "The Global Network of Isotopes in Rivers (GNIR): integration of water isotopes in watershed observation and riverine research". Hydrology and Earth System Sciences Discussions 12, n. 4 (22 aprile 2015): 4047–79. http://dx.doi.org/10.5194/hessd-12-4047-2015.
Testo completoAbstract (sommario):
Abstract. We introduce a new online global database of riverine water stable isotopes (Global Network of Isotopes in Rivers) and evaluate its longer-term data holdings. Overall, 218 GNIR river stations were clustered into 3 different groups based on the seasonal variation in their isotopic composition, which was closely coupled to precipitation and snow-melt water run-off regimes. Sinusoidal fit functions revealed periodic phases within each grouping and deviations from the sinusoidal functions revealed important river alterations or hydrological processes in these watersheds. The seasonal isotopic amplitude of δ18O in rivers averaged 2.5 ‰, and did not increase as a function of latitude, as it does for global precipitation. Low seasonal isotopic amplitudes in rivers suggest the prevalence of mixing and storage such as occurs via lakes, reservoirs, and groundwater. The application of a catchment-constrained regionalized cluster-based water isotope prediction model (CC-RCWIP) allowed direct comparison between the expected isotopic composition for the upstream catchment precipitation with the measured isotopic composition of river discharge at observation stations. The catchment-constrained model revealed a strong global isotopic correlation between average rainfall and river discharge (R2 = 0.88) and the study demonstrated that the seasonal isotopic composition and variation of river water can be predicted. Deviations in data from model predicted values suggest there are important natural or anthropogenic catchment processes, like evaporation, damming, and water storage in the upstream catchment.
37
Araújo, Daniel, Geraldo Boaventura, Daniel Mulholland, Jeremie Garnier, Wilson Machado, Marly Babinski e Elton Dantas. "Determining sedimentary material sources in a Brazilian urban lake using Zn stable isotope compositions of bottom sediments: a preliminary study". Geochimica Brasiliensis 34, n. 2 (21 dicembre 2020): 130–37. http://dx.doi.org/10.21715/gb2358-2812.2020342130.
Testo completoAbstract (sommario):
Zinc isotopes ratios provide qualitative and quantitative information about contributions from different Zn sources in the environment. Here we present the results of a preliminary study to identify the main sources controlling Zn isotope signatures of sediments from Lake Paranoá (Brazil), an urban water reservoir. The Zn isotope ratios were measured by MC-ICP-MS and expressed as δ66/64Zn notation relative to the JMC 3-0749-L solution. The studied sediments showed a narrow isotopic range (+0.00 to +0.13 ‰; n = 10) similar to that reported for intensely weathered soils worldwide (from -0.4 to +0.2‰). The geoaccumulation index (Igeo) also suggests low or negligible influence of Zn anthropogenic source. This research provides a baseline assessment of the Zn isotopes signatures in lake sedimentary environments under the influence of these weathered soils.
38
Badea, Silviu-Laurentiu, Violeta-Carolina Niculescu e Andreea-Maria Iordache. "New Trends in Separation Techniques of Lithium Isotopes: A Review of Chemical Separation Methods". Materials 16, n. 10 (18 maggio 2023): 3817. http://dx.doi.org/10.3390/ma16103817.
Testo completoAbstract (sommario):
In terms of isotopic technologies, it is essential to be able to produce materials with an enriched isotopic abundance (i.e., a compound isotopic labelled with 2H, 13C, 6Li, 18O or 37Cl), which is one that differs from natural abundance. The isotopic-labelled compounds can be used to study different natural processes (like compounds labelled with 2H, 13C, or 18O), or they can be used to produce other isotopes as in the case of 6Li, which can be used to produce 3H, or to produce LiH that acts like a protection shield against fast neutrons. At the same time, 7Li isotope can be used as a pH controller in nuclear reactors. The COLEX process, which is currently the only technology available to produce 6Li at industrial scale, has environmental drawbacks due to generation of Hg waste and vapours. Therefore, there is a need for new eco-friendly technologies for separation of 6Li. The separation factor of 6Li/7Li with chemical extraction methods in two liquid phases using crown ethers is comparable to that of COLEX method, but has the disadvantages of low distribution coefficient of Li and the loss of crown ethers during the extraction. Electrochemical separation of lithium isotopes through the difference in migration rates between 6Li and 7Li is one of the green and promising alternatives for the separation of lithium isotopes, but this methodology requires complicated experimental setup and optimisation. Displacement chromatography methods like ion exchange in different experimental configurations have been also applied to enrich 6Li with promising results. Besides separation methods, there is also a need for development of new analysis methods (ICP-MS, MC-ICP-MS, TIMS) for reliable determination of Li isotope ratios upon enrichment. Considering all the above-mentioned facts, this paper will try to emphasize the current trends in separation techniques of lithium isotopes by exposing all the chemical separation and spectrometric analysis methods, and highlighting their advantages and disadvantages.
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Kurita, N., Y. Fujiyoshi, T. Nakayama, Y. Matsumi e H. Kitagawa. "East Asian Monsoon controls on the inter-annual variability in precipitation isotope ratio in Japan". Climate of the Past 11, n. 2 (25 febbraio 2015): 339–53. http://dx.doi.org/10.5194/cp-11-339-2015.
Testo completoAbstract (sommario):
Abstract. To elucidate the mechanism for how the East Asian Monsoon (EAM) variability have influenced the isotope proxy records in Japan, we explore the primary driver of variations of precipitation isotopes at multiple temporal scales (event, seasonal and inter-annual scales). Using a new 1-year record of the isotopic composition of event-based precipitation and continuous near-surface water vapor at Nagoya in central Japan, we identify the key atmospheric processes controlling the storm-to-storm isotopic variations through an analysis of air mass sources and rainout history during the transport of moisture to the site, and then apply the identified processes to explain the inter-annual isotopic variability related to the EAM variability in the historical 17-year long Tokyo station record in the Global Network of Isotopes in Precipitation (GNIP). In the summer, southerly flows transport moisture with higher isotopic values from subtropical marine regions and bring warm rainfall enriched with heavy isotopes. The weak monsoon summer corresponds to enriched isotopic values in precipitation, reflecting higher contribution of warm rainfall to the total summer precipitation. In the strong monsoon summer, the sustaining Baiu rainband along the southern coast of Japan prevents moisture transport across Japan, so that the contribution of warm rainfall is reduced. In the winter, storm tracks are the dominant driver of storm-to-storm isotopic variation and relatively low isotopic values occur when a cold frontal rainband associated with extratropical cyclones passes off to the south of the Japan coast. The weak monsoon winter is characterized by lower isotopes in precipitation, due to the distribution of the cyclone tracks away from the southern coast of Japan. In contrast, the northward shift of the cyclone tracks and stronger development of cyclones during the strong monsoon winters decrease the contribution of cold frontal precipitation, resulting in higher isotopic values in winter precipitation. Therefore, year-to-year isotopic variability in summer and winter Japanese precipitation correlates significantly with changes in the East Asian summer and winter monsoon intensity (R=-0.47 for summer, R=0.42 for winter), and thus we conclude that the isotope proxy records in Japan should reflect past changes in the East Asian Monsoon. Since our study identifies the climate drivers controlling isotopic variations in summer and winter precipitation, we highlight the retrieval of a record with seasonal resolution from paleoarchives as an important priority.
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Wagner, D. S., C. J. Markworth, C. D. Wagner, F. J. Schoenen, C. E. Rewerts, B. K. Kay e H. M. Geysen. "Ratio encoding combinatorial libraries with stable isotopes and their utility in pharmaceutical research". Combinatorial Chemistry & High Throughput Screening 1, n. 3 (ottobre 1998): 143–53. http://dx.doi.org/10.2174/138620730103220120142733.
Testo completoAbstract (sommario):
Combinatorial libraries are an important tool for lead discovery in the pharmaceutical industry. Advances in high throughput screening coupled with combinatorial chemistry can significantly reduce the time to find lead compounds. A major difficulty in developing large combinatorial libraries is the ability to identify active compounds. This paper describes a rapid and sensitive encoding/decoding methodology that utilizes stable isotopes and mass spectrometry. The ability of mass spectrometry to precisely determine the intensity of isotopic abundances provides a unique encoding strategy employing synthetically generated ratios of stable isotopes in a compound as the code. The application of ratio encoding is demonstrated using peptoid and imidazole chemistries. Supporting data demonstrate that the incorporation of one or more stable isotopes using unique-predetermined ratios can encode chemical libraries. In addition, the presence of a unique isotopic pattern in a ligand can facilitate the pharmacokinetic analysis. Isotope incorporation into a compound and subsequently into its metabolites reliably distinguishes products from other molecules in the mass spectrum. This is illustrated by metabolic analyses of peptoid and imidazole compounds.
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Hachikubo, Akihiro, Taichi Nezu, Kaede Takizawa e Satoshi Takeya. "Effect of Pressure on Hydrogen Isotope Fractionation in Methane during Methane Hydrate Formation at Temperatures Below the Freezing Point of Water". Methane 2, n. 2 (12 aprile 2023): 129–36. http://dx.doi.org/10.3390/methane2020010.
Testo completoAbstract (sommario):
Isotopic fractionation of methane between gas and solid hydrate phases provides data regarding hydrate-forming environments, but the effect of pressure on isotopic fractionation is not well understood. In this study, methane hydrates were synthesized in a pressure cell, and the hydrogen isotope compositions of the residual and hydrate-bound gases were determined. The δ2H of hydrate-bound methane formed below the freezing point of water was 5.7–10.3‰ lower than that of residual methane, indicating that methane hydrate generally encapsulates lighter molecules (CH4) instead of CH32H. The fractionation factors αH-V of the gas and hydrate phases were in the range 0.9881–0.9932 at a temperature and pressure of 223.3–268.2 K and 1.7–19.5 MPa, respectively. Furthermore, αH-V increased with increasing formation pressure, suggesting that the difference in the hydrogen isotopes of the hydrate-bound methane and surrounding methane yields data regarding the formation pressure. Although the differences in the hydrogen isotopes observed in this study are insignificant, precise analyses of the isotopes of natural hydrates in the same area enable the determination of the pressure during hydrate formation.
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Arneson, Lynne S., Stephen MacAvoy e Ethan Basset. "Metabolic protein replacement drives tissue turnover in adult mice". Canadian Journal of Zoology 84, n. 7 (1 luglio 2006): 992–1002. http://dx.doi.org/10.1139/z06-081.
Testo completoAbstract (sommario):
Stable isotopes are increasingly being used to examine ecological and physiological questions, such as dietary choices, migration routes and timing, and physiological condition. To address these questions in the field, laboratory experiments must be done to determine diet–tissue discrimination values and turnover rates for stable isotopes in tissues. In this study, we examined the carbon and nitrogen turnover rates of whole blood, skeletal muscle, liver, kidney, heart, and brain, as well as the sulfur turnover rate of whole blood, skeletal muscle, and liver in Mus musculus L., 1758 following a diet change. By examining tissue isotope change in two groups of mice fed different diets, we found that tissues turnover at different rates (in order of fastest to slowest — liver, kidney, heart, brain, whole blood, skeletal muscle), but that carbon, nitrogen, and sulfur isotopes turned over with similar half-lives within a single tissue. By using a diet with different nutrient isotopic values, we also calculated that up to approximately 90%–95% of carbon in newly synthesized tissue was contributed by dietary protein. These results will provide field researchers with additional tissue isotopic half-lives to elucidate dietary history with a greater degree of certainty. The tissue sulfur half-lives provide an extra stable isotope that may be used in situations where carbon and nitrogen values do not differ between old and new nutrient sources.
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Böhlke, J. K. "Variation in the terrestrial isotopic composition and atomic weight of argon (IUPAC Technical Report)". Pure and Applied Chemistry 86, n. 9 (19 settembre 2014): 1421–32. http://dx.doi.org/10.1515/pac-2013-0918.
Testo completoAbstract (sommario):
AbstractThe isotopic composition and atomic weight of argon (Ar) are variable in terrestrial materials. Those variations are a source of uncertainty in the assignment of standard properties for Ar, but they provide useful information in many areas of science. Variations in the stable isotopic composition and atomic weight of Ar are caused by several different processes, including (1) isotope production from other elements by radioactive decay (radiogenic isotopes) or other nuclear transformations (e.g., nucleogenic isotopes), and (2) isotopic fractionation by physical-chemical processes such as diffusion or phase equilibria. Physical-chemical processes cause correlated mass-dependent variations in the Ar isotope-amount ratios (40Ar/36Ar, 38Ar/36Ar), whereas nuclear transformation processes cause non-mass-dependent variations. While atmospheric Ar can serve as an abundant and homogeneous isotopic reference, deviations from the atmospheric isotopic ratios in other Ar occurrences limit the precision with which a standard atomic weight can be given for Ar. Published data indicate variation of Ar atomic weights in normal terrestrial materials between about 39.7931 and 39.9624. The upper bound of this interval is given by the atomic mass of 40Ar, as some samples contain almost pure radiogenic 40Ar. The lower bound is derived from analyses of pitchblende (uranium mineral) containing large amounts of nucleogenic 36Ar and 38Ar. Within this interval, measurements of different isotope ratios (40Ar/36Ar or 38Ar/36Ar) at various levels of precision are widely used for studies in geochronology, water–rock interaction, atmospheric evolution, and other fields.
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Benbow, Timothy J., Alan R. Hayman, Robert Van Hale e Russell Frew. "Preparation of aqueous fatty acids for hydrogen and carbon stable isotope analysis by solid phase extraction". Marine and Freshwater Research 64, n. 4 (2013): 294. http://dx.doi.org/10.1071/mf12192.
Testo completoAbstract (sommario):
Stable isotope analyses of fatty acids in environmental waters provides important information as to their source(s). Analysis is often confounded due to low concentrations of fatty acids and/or a complex sample matrix requiring separation of the target analyte. The purpose of this study was to validate a method to extract fatty acids from natural waters using solid phase extraction (SPE) before compound specific isotope analysis (CSIA). Three SPE cartridges and multiple eluting solvents were tested to determine the efficiency, isotopic fractionation, and reproducibility of each extraction technique. Our results indicated that surface-modified styrene divinylbenzene cartridges, when eluted with methanol, caused negligible fractionation of the hydrogen isotopes and minimal fractionation of the carbon isotopes, but that isotopic fractionation occurred when compounds were only partially eluted from SPE cartridges. Compounds were also extracted from landfill leachate using both SPE and liquid–liquid extraction (LLE). The hydrogen isotope composition (δ2H) of compounds extracted from water using either method were within experimental precision and the carbon isotope composition (δ13C) of all but one fatty acid were within experimental precision. Therefore, these experiments prove the aforementioned SPE methods to be a convenient and precise method to extract fatty acids from natural waters before CSIA.
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Wang, Jiaxin, Mingjun Zhang, Athanassios A. Argiriou, Shengjie Wang, Deye Qu, Yu Zhang e Pengyan Su. "Recharge and Infiltration Mechanisms of Soil Water in the Floodplain Revealed by Water-Stable Isotopes in the Upper Yellow River". Sustainability 13, n. 16 (20 agosto 2021): 9369. http://dx.doi.org/10.3390/su13169369.
Testo completoAbstract (sommario):
The stable isotopes (δD and δ18O) in soil water allow tracing of the flow and transportation of water in the soil. However, there are few studies on the use of soil water stable isotopes to explore the soil water in the floodplain, especially in determining the soil water source and infiltration mechanism. The Bayesian mixing model (MixSIAR) was integrated with the line conditioned excess (lc-excess) of stable isotopes (δD and δ18O) in precipitation, soil water (0–150 cm), river water, and groundwater to determinate the source and recharge mechanisms of two different soil profile types in the floodplain of the upper Yellow River in Lanzhou, China. The results showed that soil water below 80 cm was affected by river water recharge, affecting soil water content and stable isotopic composition at S1 sampling points (profile parallel to river water); this effect was not observed at S2 (profile is higher than the river water) sampling points. The isotopic compositions of the soil water sources at the two sampling points (S1: δD = −77.41‰, δ18O = −11.01‰; S2: δD = −74.02‰, δ18O = −10.56‰) were depleted more than those in the long-term amount-weighted precipitation isotopes (δD = −56.30‰, δ18O = −8.17‰). The isotope signatures of soil water sources are similar to the isotope characteristics of some high-intensity precipitation events (≥30 mm/day), indicating that soil water originates from a fraction of the total precipitation. The piston flow (60%) and the preferential flow (40%) coexist, but soil moisture and rainfall intensity will affect the sequence of the two infiltration methods. This study provides insights for understanding the hydrological process of the upper Yellow River and evaluating groundwater quality and protecting the floodplain environment.
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Vezinet, Adrien, Emilie Thomassot, Yan Luo, Chiranjeeb Sarkar e D. Graham Pearson. "Diachronous Redistribution of Hf and Nd Isotopes at the Crystal Scale—Consequences for the Isotopic Evolution of a Poly-Metamorphic Crustal Terrane". Geosciences 12, n. 1 (12 gennaio 2022): 36. http://dx.doi.org/10.3390/geosciences12010036.
Testo completoAbstract (sommario):
In metamorphic rocks, mineral species react over a range of pressure–temperature conditions that do not necessarily overlap. Mineral equilibration can occur at varied points along the metamorphic pressure–temperature (PT) path, and thus at different times. The sole or dominant use of zircon isotopic compositions to constrain the evolution of metamorphic rocks might then inadvertently skew geological interpretations towards one aspect or one moment of a rock’s history. Here, we present in-situ U–Pb/Sm–Nd isotope analyses of the apatite crystals extracted from two meta-igneous rocks exposed in the Saglek Block (North Atlantic craton, Canada), an Archean metamorphic terrane, with the aim of examining the various signatures and events that they record. The data are combined with published U–Pb/Hf/O isotope compositions of zircon extracted from the same hand-specimens. We found an offset of nearly ca. 1.5 Gyr between U-Pb ages derived from the oldest zircon cores and apatite U–Pb/Sm–Nd isotopic ages, and an offset of ca. 200 Ma between the youngest zircon metamorphic overgrowths and apatite. These differences in metamorphic ages recorded by zircon and apatite mean that the redistribution of Hf isotopes (largely hosted in zircon) and Nd isotopes (largely hosted in apatite within these rocks), were not synchronous at the hand-specimen scale (≤~0.001 m3). We propose that the diachronous redistribution of Hf and Nd isotopes and their parent isotopes was caused by the different PT conditions of growth equilibration between zircon and apatite during metamorphism. These findings document the latest metamorphic evolution of the Saglek Block, highlighting the role played by intra-crustal reworking during the late-Archean regional metamorphic event.
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Holden, Norman E., Tyler B. Coplen, John K. Böhlke, Lauren V. Tarbox, Jacqueline Benefield, John R. de Laeter, Peter G. Mahaffy et al. "IUPAC Periodic Table of the Elements and Isotopes (IPTEI) for the Education Community (IUPAC Technical Report)". Pure and Applied Chemistry 90, n. 12 (19 dicembre 2018): 1833–2092. http://dx.doi.org/10.1515/pac-2015-0703.
Testo completoAbstract (sommario):
AbstractThe IUPAC (International Union of Pure and Applied Chemistry) Periodic Table of the Elements and Isotopes (IPTEI) was created to familiarize students, teachers, and non-professionals with the existence and importance of isotopes of the chemical elements. The IPTEI is modeled on the familiar Periodic Table of the Chemical Elements. The IPTEI is intended to hang on the walls of chemistry laboratories and classrooms. Each cell of the IPTEI provides the chemical name, symbol, atomic number, and standard atomic weight of an element. Color-coded pie charts in each element cell display the stable isotopes and the relatively long-lived radioactive isotopes having characteristic terrestrial isotopic compositions that determine the standard atomic weight of each element. The background color scheme of cells categorizes the 118 elements into four groups: (1) white indicates the element has no standard atomic weight, (2) blue indicates the element has only one isotope that is used to determine its standard atomic weight, which is given as a single value with an uncertainty, (3) yellow indicates the element has two or more isotopes that are used to determine its standard atomic weight, which is given as a single value with an uncertainty, and (4) pink indicates the element has a well-documented variation in its atomic weight, and the standard atomic weight is expressed as an interval. An element-by-element review accompanies the IPTEI and includes a chart of all known stable and radioactive isotopes for each element. Practical applications of isotopic measurements and technologies are included for the following fields: forensic science, geochronology, Earth-system sciences, environmental science, and human health sciences, including medical diagnosis and treatment.
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Carrizo, Daniel, Maria Unger, Henry Holmstrand, Per Andersson, Örjan Gustafsson, Sean P. Sylva e Christopher M. Reddy. "Compound-specific bromine isotope compositions of one natural and six industrially synthesised organobromine substances". Environmental Chemistry 8, n. 2 (2011): 127. http://dx.doi.org/10.1071/en10090.
Testo completoAbstract (sommario):
Environmental contextBrominated organic compounds of both natural and anthropogenic origin are commonly found in the environment. Bromine has two stable isotopes and the isotopic composition of brominated compounds may vary depending on production pathways and degradation processes. These variations are a result of isotope fractionation effects, when heavy isotopes react slower than lighter isotopes. We apply compound-specific bromine isotope analysis to industrial brominated organic compounds, and one naturally produced analogue, to test the feasibility of the technique to investigate the source and environmental fate of these compounds. AbstractThe stable bromine isotopic composition (δ81Br) was determined for six industrially synthesised brominated organic compounds (BOCs) and one natural BOC by gas-chromatography multi-collector inductively coupled plasma mass spectrometry (GC-mcICP-MS). The δ81Br compositions of brominated benzenes, phenols (both natural and industrial), anisoles, and naphthalenes were constrained with the standard differential measurement approach using as reference a monobromobenzene sample with an independently determined δ81Br value (–0.39‰ v. Standard Mean Ocean Bromide, SMOB). The δ81Br values for the industrial BOCs ranged from –4.3 to –0.4‰. The average δ81Br value for the natural compound (2,4-dibromophenol) was 0.2 ± 1.6‰ (1 s.d.), and for the identical industrial compound (2,4-dibromophenol) –1.1 ± 0.9‰ (1 s.d.), with a statistically significant difference of ~1.4 (P < 0.05). The δ81Br of four out of six industrial compounds was found to be significantly different from that of the natural sample. These novel results establish the bromine isotopic variability among the industrially produced BOCs in relation to a natural sample.
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Li, Xiaohu, Jianqiang Wang e Hao Wang. "Fe Isotopic Compositions of Modern Seafloor Hydrothermal Systems and Their Influence Factors". Journal of Chemistry 2017 (2017): 1–11. http://dx.doi.org/10.1155/2017/1417302.
Testo completoAbstract (sommario):
Based on previous research on the Fe isotope compositions of various components and systems of the Earth, this study focused on the Fe isotope compositions of hydrothermal systems, including the Fe isotope variations in chalcopyrite, pyrite, and sphalerite, and their possible controlling factors. The main findings are as follows: (1) The range of Fe isotopes in hydrothermal systems at mid-ocean ridge is very large. The δ56Fe values of hydrothermal fluids are characterized by significant enrichment in light Fe isotopes. (2) The δ56Fe values of sulfides also exhibit lighter Fe isotope characteristics than those of hydrothermal fluids from hydrothermal vent fields at mid-ocean ridge. The vent temperature, fluid properties, and mineral deposition processes significantly affect the δ56Fe values of hydrothermal sulfides. (3) Chalcopyrite is preferentially enriched in heavy Fe isotopes, whereas sphalerite and pyrite are enriched in light Fe isotopes. In addition, the δ56Fe values of pyrite/marcasite display a larger range than those of chalcopyrite. This pattern is directly related to equilibrium fractionation or kinetic fractionation of Fe isotopes during the deposition of sulfides. To better understand the Fe isotope compositions of modern seafloor hydrothermal systems, the geochemical behavior and fractionation mechanisms of Fe isotopes require further in situ study.
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Zhang, Wen, Zhaochu Hu, Lanping Feng, Zaicong Wang, Yongsheng Liu, Yantong Feng e Hong Liu. "Accurate Determination of Zr Isotopic Ratio in Zircons by Femtosecond Laser Ablation MC-ICP-MS with “Wet” Plasma Technique". Journal of Earth Science 33, n. 1 (febbraio 2022): 67–75. http://dx.doi.org/10.1007/s12583-021-1535-7.
Testo completoAbstract (sommario):
AbstractThis work evaluates the use of femtosecond laser ablation multiple collector inductively coupled plasma mass spectrometry (fs-LA-MC-ICP-MS) for Zr isotopic analysis in zircons. The mass fractionation caused by instrumental mass discrimination was corrected by a combination of internal correction using Sr as an internal standard (coming from a NIST SRM 987 standard solution) and external correction using a matrix-matched standard. Several important instrument parameters were investigated, such as the effect of the addition of N2 and “wet” plasma condition, the mass fractionation behaviors between Zr isotopes and Sr isotopes, the position effect in laser ablation cell and the effect of laser ablation parameters (laser spot size and energy density). The Zr isotope compositions of seven zircons (GJ-1, 91500, Plešovice, Rak-17, Paki, Aus and Mala) were determined by the developed fs-LA-MC-ICP-MS and thermal ionization mass spectrometry (TIMS). Our fs-LA-MC-ICP-MS results for Zr isotope compositions agreed with TIMS analyses within analytical uncertainties, indicating the presented method is a suitable tool to resolve isotopic zoning in natural zircons. The results also suggest that GJ-1, 91500, Plešovice, Paki, Aus and Mala had the homogenous Zr isotope composition and could be considered as the potential candidates for the Zr isotope analysis in zircons, except Rak-17 which presented the large Zr isotope variation.