A paleoclimatic perspective of triple oxygen isotopes from gypsum in Holocene Thar Desert playa lakes

2020 ◽  
Author(s):  
Alena Giesche ◽  
Yama Dixit ◽  
Fernando Gázquez ◽  
Thomas Bauska ◽  
Matthew Brady ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Isotopic Composition ◽  
Oxygen Isotopes ◽  
Hydration Water ◽  
Thar Desert ◽  
Night Time ◽  
Playa Lakes ◽  
Sedimentary Deposits ◽  
Gypsum Formation ◽  
Evaporite Minerals

<p><span>The Thar Desert (NW India) has numerous evaporative saline playa lakes. Some are still active and others are dry and preserve up to several meters of sedimentary deposits. These deposits feature a variety of evaporite minerals, including the hydrated mineral gypsum (CaSO<sub>4</sub> 2H<sub>2</sub>O). Assuming no secondary exchange, the isotopic composition of the gypsum hydration water preserves the δ<sup>18</sup>O, δ<sup>17</sup>O and δ D of palaeolake water at the time of gypsum formation. This method provides a way to understand the hydrologic balance in a part of the world where it is typically very difficult to obtain palaeoclimate records. Our 36-hour pan evaporation experiment on site shows that triple oxygen isotopes track changes in evaporative conditions, which vary diurnally due to fluctuating temperature and relative humidity, and appear to reflect night-time condensation. We present new palaeohydrological records from two dry playas (Karsandi, Khajuwala) and one active playa (Lunkaransar) in the Thar Desert using the triple oxygen and hydrogen isotopic composition of gypsum hydration water. Results show that a source of water maintained active playa lake basins in the central Thar Desert for much of the Holocene, either by enhanced direct precipitation and/or fluvial sources. The derived <sup>17</sup>O-excess and d-excess data potentially enable modelling of past changes in relative humidity, once other parameters (windiness, evaporation/inflow, etc.) are set. </span></p>

Changes of Ionic and Oxygen Isotopic Composition of the Snowpack at the Glacier Austre Okstindbreen, Norway, 1995

1998 ◽  
Vol 29 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Peter Raben ◽  
Wilfred H. Theakstone
Keyword(s):  
Isotopic Composition ◽  
Sea Level ◽  
Oxygen Isotopes ◽  
Oxygen Isotopic Composition ◽  
Isotopic Ratios ◽  
Vertical Variations ◽  
Oxygen Isotopic ◽  
The Difference ◽  
Liquid Precipitation ◽  
Different Altitudes

Marked vertical variations of ions and oxygen isotopes were present in the snowpack at the glacier Austre Okstindbreen during the pre-melting phase in 1995 at sites between 825 m and 1,470 m above sea level. As the first meltwater percolated from the top of the pack, ions were moved to a greater depth, but the isotopic composition remained relatively unchanged. Ions continued to move downwards through the pack during the melting phase, even when there was little surface melting and no addition of liquid precipitation. The at-a-depth correlation between ionic concentrations and isotopic ratios, strong in the pre-melting phase, weakened during melting. In August, concentrations of Na+ and Mg2+ ions in the residual pack were low and vertical variations were slight; 18O enrichment had occurred. The difference of the time at which melting of the snowpack starts at different altitudes influences the input of ions and isotopes to the underlying glacier.

Reconstructing Terrestrial Environments Using Stable Isotopes in Fossil Teeth and Paleosol Carbonates

2012 ◽  
Vol 18 ◽  
pp. 167-194 ◽  
Author(s):  
Benjamin H. Passey
Keyword(s):  
Isotopic Composition ◽  
Soil Temperature ◽  
Carbon Isotopes ◽  
Oxygen Isotopes ◽  
Precipitation Amount ◽  
Radiative Heating ◽  
Mammal Species ◽  
Isotopic Compositions ◽  
Heat Effects ◽  
Oxygen Isotopic

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.

scholarly journals Tropospheric water vapour and relative humidity profiles from lidar and microwave radiometry

2014 ◽  
Vol 7 (5) ◽  
pp. 1201-1211 ◽  
Author(s):  
F. Navas-Guzmán ◽  
J. Fernández-Gálvez ◽  
M. J. Granados-Muñoz ◽  
J. L. Guerrero-Rascado ◽  
J. A. Bravo-Aranda ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Water Vapour ◽  
Microwave Radiometer ◽  
Radiosonde Data ◽  
Mixing Ratio ◽  
Raman Lidar ◽  
Night Time ◽  
New Approach ◽  
Lidar Measurements ◽  
Humidity Profiles

Abstract. In this paper, we outline an iterative method to calibrate the water vapour mixing ratio profiles retrieved from Raman lidar measurements. Simultaneous and co-located radiosonde data are used for this purpose and the calibration results obtained during a radiosonde campaign in summer and autumn 2011 are presented. The water vapour profiles measured during night-time by the Raman lidar and radiosondes are compared and the differences between the methodologies are discussed. Then, a new approach to obtain relative humidity profiles by combination of simultaneous profiles of temperature (retrieved from a microwave radiometer) and water vapour mixing ratio (from a Raman lidar) is addressed. In the last part of this work, a statistical analysis of water vapour mixing ratio and relative humidity profiles obtained during 1 year of simultaneous measurements is presented.

Sauerstoffisotopieeffekte und Hydratstruktur von Alkalihalogenid-Lösungen in H2O und D2O / Oxygen Isotope Effects and Hydrate Structure of Alkali Halide Solutions in H2O and D2O

1973 ◽  
Vol 28 (2) ◽  
pp. 137-141 ◽  
Author(s):  
D. Götz ◽  
K. Heinzinger
Keyword(s):  
Oxygen Isotope ◽  
Oxygen Isotopes ◽  
Alkali Halide ◽  
Isotope Effects ◽  
Bulk Water ◽  
Hydration Water ◽  
Solvent Isotope Effect ◽  
Anion Effect ◽  
Solvent Isotope ◽  
Fractionation Factors

The fractionation of the oxygen isotopes in solutions of LiCl, NaCl. KCl, KBr, KJ and CsCl with H2O and D2O as solvent has been measured at 25 °C by means of the CO2-equilibration technique. As opposed to earlier measurements a slight anion dependence for the potassium halides has been found in H2O. This anion effect is much more pronounced in D2O. It even leads to a change in the directions of the 180 enrichment between cationic hydration water and bulk water for KCl and KBr. The absolute values of the fractionation factors for LiCl and CsCl, which differ in sign in H2O in agreement with positive and negative cationic hydration, respectively, as known from other kinds of measurements, is increased for LiCl and decreased for CsCl in D2O. There is no fractionation of the oxygen isotopes between hydration water and bulk water in both solvents for NaCl.The solvent isotope effect is explained by the stronger anion influence on the structure of the bulk water in D2O as compared with H2O. This stronger influence is expected because of the higher structural order in D2O than in H2O at the same temperature.

Isotopic Determination of Growth and Longevity in Fossil and Modern Invertebrates

1998 ◽  
Vol 4 ◽  
pp. 37-67 ◽  
Author(s):  
Douglas S. Jones
Keyword(s):  
Isotopic Composition ◽  
Oxygen Isotope ◽  
Oxygen Isotopes ◽  
Marine Organisms ◽  
Physical And Chemical

The isotopic composition of fossil invertebrates contains a wealth of information about the physical and chemical environments of the ancient past. The exploitation of this biogeochemical archive by paleontologists began about 50 years ago with the realization that the ratios of oxygen isotopes in the shells and skeletons of marine organisms offered the potential to accurately reconstruct paleoenvironmental conditions, particularly temperature (Urey, 1947; Urey et al., 1951). With the introduction of the oxygen isotope paleotemperature methodology (Epstein et al., 1951, 1953; Epstein and Lowenstam, 1953), the field of “isotope paleontology” was born (Wefer and Berger, 1991).

scholarly journals Attribution of N<sub>2</sub>O sources in a grassland soil with laser spectroscopy based isotopocule analysis

2019 ◽  
Vol 16 (16) ◽  
pp. 3247-3266 ◽  
Author(s):  
Erkan Ibraim ◽  
Benjamin Wolf ◽  
Eliza Harris ◽  
Rainer Gasche ◽  
Jing Wei ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Radiative Forcing ◽  
Dispersion Model ◽  
Stratospheric Ozone ◽  
Particle Dispersion ◽  
N2o Emissions ◽  
Specific Information ◽  
N2o Reduction ◽  
Night Time ◽  
Nitrifier Denitrification

Abstract. Nitrous oxide (N2O) is the primary atmospheric constituent involved in stratospheric ozone depletion and contributes strongly to changes in the climate system through a positive radiative forcing mechanism. The atmospheric abundance of N2O has increased from 270 ppb (parts per billion, 10−9 mole mole−1) during the pre-industrial era to approx. 330 ppb in 2018. Even though it is well known that microbial processes in agricultural and natural soils are the major N2O source, the contribution of specific soil processes is still uncertain. The relative abundance of N2O isotopocules (14N14N16N, 14N15N16O, 15N14N16O, and 14N14N18O) carries process-specific information and thus can be used to trace production and consumption pathways. While isotope ratio mass spectroscopy (IRMS) was traditionally used for high-precision measurement of the isotopic composition of N2O, quantum cascade laser absorption spectroscopy (QCLAS) has been put forward as a complementary technique with the potential for on-site analysis. In recent years, pre-concentration combined with QCLAS has been presented as a technique to resolve subtle changes in ambient N2O isotopic composition. From the end of May until the beginning of August 2016, we investigated N2O emissions from an intensively managed grassland at the study site Fendt in southern Germany. In total, 612 measurements of ambient N2O were taken by combining pre-concentration with QCLAS analyses, yielding δ15Nα, δ15Nβ, δ18O, and N2O concentration with a temporal resolution of approximately 1 h and precisions of 0.46 ‰, 0.36 ‰, 0.59 ‰, and 1.24 ppb, respectively. Soil δ15N-NO3- values and concentrations of NO3- and NH4+ were measured to further constrain possible N2O-emitting source processes. Furthermore, the concentration footprint area of measured N2O was determined with a Lagrangian particle dispersion model (FLEXPART-COSMO) using local wind and turbulence observations. These simulations indicated that night-time concentration observations were largely sensitive to local fluxes. While bacterial denitrification and nitrifier denitrification were identified as the primary N2O-emitting processes, N2O reduction to N2 largely dictated the isotopic composition of measured N2O. Fungal denitrification and nitrification-derived N2O accounted for 34 %–42 % of total N2O emissions and had a clear effect on the measured isotopic source signatures. This study presents the suitability of on-site N2O isotopocule analysis for disentangling source and sink processes in situ and found that at the Fendt site bacterial denitrification or nitrifier denitrification is the major source for N2O, while N2O reduction acted as a major sink for soil-produced N2O.

scholarly journals Effects of the solar eclipse on 15 January 2010 on the surface O<sub>3</sub>, NO, NO<sub>2</sub>, NH<sub>3</sub>, CO mixing ratio and the meteorological parameters at Thiruvanathapuram, India

2010 ◽  
Vol 28 (6) ◽  
pp. 1199-1205 ◽  
Author(s):  
S. K. Sharma ◽  
T. K. Mandal ◽  
B. C. Arya ◽  
M. Saxena ◽  
D. K. Shukla ◽  
...  
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Solar Eclipse ◽  
Meteorological Parameters ◽  
Total Solar Eclipse ◽  
Ozone Formation ◽  
Mixing Ratio ◽  
Night Time ◽  
Photochemical Ozone ◽  
Surface O3

Abstract. In this paper, we present the effect of total solar eclipse on surface O3, NO, NO2, NH3, CO mixing ratio and the meteorological parameters on 15 January 2010 at Thiruvanathapuram, India. On the day of total solar eclipse (i.e., 15 January 2010), the decrease in mixing ratio of surface O3 and NO2 is observed after the beginning of the solar eclipse events (11:15 to 15:30). Decrease in surface O3 may be due to decreased efficiency of the photochemical ozone formation, whereas, mixing ratio of NO and NH3 have been changed following the night time chemistry. Surface O3 reduced to 20.3 ppb after 22 min of full phase of the eclipse. During the solar eclipse period, the ambient temperature and wind speed have decreased, whereas, relative humidity has increased as expected.

Root exudate induced microbial activities and phosphorus cycling in soil: An application of phosphate oxygen isotopes

2020 ◽  
Author(s):  
Sunendra R Joshi ◽  
David H McNear
Keyword(s):  
Microbial Community ◽  
Isotopic Composition ◽  
Oxygen Isotope ◽  
Microbial Activity ◽  
Oxygen Isotopes ◽  
Root Exudate ◽  
Rhizosphere Soil ◽  
Microbial Activities ◽  
Oxygen Isotope Ratios ◽  
P Cycling

&lt;p&gt;Rhizosphere is the most biologically active region between the plant and the surrounding soil where plant release their fixed carbon into the soils. Depending on the availability and types of carbon compounds released from the plant, they can directly solubilize nutrient or indirectly influence nutrient cycling by promoting increased microbial activity in the rhizosphere. In this study we applied phosphate oxygen isotope ratios (d&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;P&lt;/sub&gt;) to determine how root exudate influences temporal variation in microbial activities and P cycling in the rhizosphere. Rhizoboxes were filled with soils, watered to 75% water holding capacity and equilibrated for 10 days. After equilibration labeled phosphate isotopes synthesized using &lt;sup&gt;18&lt;/sup&gt;O labeled water was applied. Then a mixed exudate (i.e., glucose, alanine, and oxalate in the ratio of 1:1:1) was introduced into the soil for 4, 10, and 20 days via an artificial root. We used a sequential extraction technique (i.e., resin-Pi, NaHCO&lt;sub&gt;3&lt;/sub&gt;-P, NaOH-P, and HCl-P) to track the fate of applied P in bulk and rhizosphere soils. The root exudate effects on the rate of P cycling and microbial activity were investigated using phosphate oxygen isotope ratios in the resin-Pi pool. Microbial community structures was determined using phospholipid fatty acids (PLFA) profiles. After supplying root exudate for 4, 10, and 20 days, the results showed that bioavailable P (i.e., resin-Pi) concentration was always higher in the bulk soil compared to rhizosphere soil and originally bioavailable P transformed gradually into unavailable P (i.e., NaOH-P and HCl-P). After supplying exudate compound for 4 days, the applied PO&lt;sub&gt;4&lt;/sub&gt; was mostly in the resin-Pi pool and its isotopic composition was heavier than the equilibrium isotopic composition suggesting that this Pi pool was not completely cycled by the microorganisms. As we continue supplying exudate compounds, the concentration of resin-Pi gradually decreased and as microbial activities increased, its isotopic composition got closer to the equilibrium isotopic composition. Further the microbial community structure in the rhizosphere soil after supply of root exudate were distinctly different then the bulk soil. Using phosphate oxygen isotopes this study shows the influence of root exudates on the rate of P cycling in rhizosphere soils.&lt;/p&gt;

scholarly journals Nitrogen and oxygen isotopic constraints on the origin of atmospheric nitrate in coastal Antarctica

2007 ◽  
Vol 7 (8) ◽  
pp. 1925-1945 ◽  
Author(s):  
J. Savarino ◽  
J. Kaiser ◽  
S. Morin ◽  
D. M. Sigman ◽  
M. H. Thiemens
Keyword(s):  
Isotopic Composition ◽  
Oxygen Isotope ◽  
Transition Period ◽  
Isotope Effects ◽  
Isotope Ratios ◽  
Background Concentration ◽  
Night Time ◽  
Oxygen Isotope Ratios ◽  
Period 2 ◽  
Oxygen Isotopic

Abstract. Throughout the year 2001, aerosol samples were collected continuously for 10 to 15 days at the French Antarctic Station Dumont d'Urville (DDU) (66°40' S, l40°0' E, 40 m above mean sea level). The nitrogen and oxygen isotopic ratios of particulate nitrate at DDU exhibit seasonal variations that are among the most extreme observed for nitrate on Earth. In association with concentration measurements, the isotope ratios delineate four distinct periods, broadly consistent with previous studies on Antarctic coastal areas. During austral autumn and early winter (March to mid-July), nitrate concentrations attain a minimum between 10 and 30 ng m−3 (referred to as Period 2). Two local maxima in August (55 ng m−3) and November/December (165 ng m−3) are used to assign Period 3 (mid-July to September) and Period 4 (October to December). Period 1 (January to March) is a transition period between the maximum concentration of Period 4 and the background concentration of Period 2. These seasonal changes are reflected in changes of the nitrogen and oxygen isotope ratios. During Period 2, which is characterized by background concentrations, the isotope ratios are in the range of previous measurements at mid-latitudes: δ18Ovsmow=(77.2±8.6)‰; Δ17O=(29.8±4.4)‰; δ15Nair=(−4.4±5.4)‰ (mean ± one standard deviation). Period 3 is accompanied by a significant increase of the oxygen isotope ratios and a small increase of the nitrogen isotope ratio to δ18Ovsmow=(98.8±13.9)‰; Δ17O=(38.8±4.7)‰ and δ15Nair=(4.3±8.20‰). Period 4 is characterized by a minimum 15N/14N ratio, only matched by one prior study of Antarctic aerosols, and oxygen isotope ratios similar to Period 2: δ18Ovsmow=(77.2±7.7)‰; Δ17O=(31.1±3.2)‰; δ15Nair=(−32.7±8.4)‰. Finally, during Period 1, isotope ratios reach minimum values for oxygen and intermediate values for nitrogen: δ18Ovsmow=63.2±2.5‰; Δ17O=24.0±1.1‰; δ15Nair=−17.9±4.0‰). Based on the measured isotopic composition, known atmospheric transport patterns and the current understanding of kinetics and isotope effects of relevant atmospheric chemical processes, we suggest that elevated tropospheric nitrate levels during Period 3 are most likely the result of nitrate sedimentation from polar stratospheric clouds (PSCs), whereas elevated nitrate levels during Period 4 are likely to result from snow re-emission of nitrogen oxide species. We are unable to attribute the source of the nitrate during periods 1 and 2 to local production or long-range transport, but note that the oxygen isotopic composition is in agreement with day and night time nitrate chemistry driven by the diurnal solar cycle. A precise quantification is difficult, due to our insufficient knowledge of isotope fractionation during the reactions leading to nitrate formation, among other reasons.

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