Farmed calcite δ18O, δ13C, and Δ47 at Ascunsă cave, Romania

2021 ◽  
Author(s):  
Virgil Dragusin ◽  
Vasile Ersek ◽  
Alvaro Fernandez ◽  
Roxana Ionete ◽  
Andreea Iordache ◽  
...  
Keyword(s):  
Air Temperature ◽  
Saturation Index ◽  
Isotope Effects ◽  
Monitoring Program ◽  
Drip Water ◽  
Water Ph ◽  
Calcite Saturation ◽  
Calcite Deposition ◽  
Clumped Isotope ◽  
Kinetic Fractionation

<p>Ascunsă cave (Romania) is the subject of a monitoring program since 2012. While the cave air temperature was very stable around 7°C for most of the time, it experienced in 2019 a 3°C rise, and remained high until the present.</p><p>We present here δ<sup>18</sup>O, δ<sup>13</sup>C, and clumped isotope results from calcite farmed at two drip points inside the cave (POM X and POM 2). POM X has a slower drip rate than POM 2 and deposits calcite more continuously. Calcite deposition has been shown to depend on cave air CO<sub>2</sub> concentration, which controls the drip water pH and, further, the calcite saturation index.</p><p>In 2019, δ<sup>18</sup>O values at both sites quickly shifted to lower values as a response to the increase in temperature. At POM X, values were situated between approximately -7.2‰ and -7.6‰ before this transition, whereas in 2019 they shifted to -7.8‰ - -8.0‰. At POM 2, where values were generally lower, they shifted from -7.5‰ to -7.8‰ to -8.0‰.</p><p>Clumped isotope temperature estimates mostly agree, within measurement error, with measured cave temperature. This agreement is notable given that strong offsets are commonly observed in mid-latitude caves, reflecting kinetic fractionation effects. However, intervals with deviations from cave temperature are also observed, suggesting variations in isotopic disequilibrium conditions with time.</p><p>Here we will discuss these isotope changes in relation to cave air temperature and CO<sub>2</sub> concentration, drip water isotope values and elemental chemistry, as well as in relation to drip rates, in order to improve our understanding of calcite precipitation and isotope effects in caves.</p>

scholarly journals Reconstruction of drip-water δ<sup>18</sup>O based on calcite oxygen and clumped isotopes of speleothems from Bunker Cave (Germany)

2013 ◽  
Vol 9 (1) ◽  
pp. 377-391 ◽  
Author(s):  
T. Kluge ◽  
H. P. Affek ◽  
T. Marx ◽  
W. Aeschbach-Hertig ◽  
D. F. C. Riechelmann ◽  
...  
Keyword(s):  
Variation Method ◽  
Clumped Isotopes ◽  
New Approach ◽  
Drip Water ◽  
The Holocene ◽  
Water Composition ◽  
Kinetic Isotope ◽  
Cave Drip Water ◽  
Clumped Isotope ◽  
Kinetic Fractionation

Abstract. The geochemical signature of many speleothems used for reconstruction of past continental climates is affected by kinetic isotope fractionation. This limits quantitative paleoclimate reconstruction and, in cases where the kinetic fractionation varies with time, also affects relative paleoclimate interpretations. In carbonate archive research, clumped isotope thermometry is typically used as proxy for absolute temperatures. In the case of speleothems, however, clumped isotopes provide a sensitive indicator for disequilibrium effects. The extent of kinetic fractionation co-varies in Δ47 and δ18O so that it can be used to account for disequilibrium in δ18O and to extract the past drip-water composition. Here we apply this approach to stalagmites from Bunker Cave (Germany) and calculate drip-water δ18Ow values for the Eemian, MIS3, and the Holocene, relying on independent temperature estimates and accounting for disequilibrium. Applying the co-variation method to modern calcite precipitates yields drip-water δ18Ow values in agreement with modern cave drip-water δ18Ow of −7.9 ± 0.3‰, despite large and variable disequilibrium effects in both calcite δ18Oc and Δ47. Reconstructed paleo-drip-water δ18Ow values are lower during colder periods (e.g., MIS3: −8.6 ± 0.4‰ and the early Holocene at 11 ka: −9.7 ± 0.2‰) and show higher values during warmer climatic periods (e.g., the Eemian: −7.6 ± 0.2‰ and the Holocene Climatic Optimum: −7.2 ± 0.3‰). This new approach offers a unique possibility for quantitative climate reconstruction including the assessment of past hydrological conditions while accounting for disequilibrium effects.

scholarly journals Reconstruction of drip-water δ<sup>18</sup>O based on calcite oxygen and clumped isotopes of speleothems from Bunker Cave (Germany)

2012 ◽  
Vol 8 (4) ◽  
pp. 2853-2892 ◽  
Author(s):  
T. Kluge ◽  
H. P. Affek ◽  
T. Marx ◽  
W. Aeschbach-Hertig ◽  
D. F. C. Riechelmann ◽  
...  
Keyword(s):  
Variation Method ◽  
Clumped Isotopes ◽  
Drip Water ◽  
The Holocene ◽  
Mis 3 ◽  
Water Composition ◽  
Kinetic Isotope ◽  
Cave Drip Water ◽  
Clumped Isotope ◽  
Kinetic Fractionation

Abstract. The geochemical signature of many speleothems used for reconstruction of past continental climates is affected by kinetic isotope fractionation. This limits quantitative paleoclimate reconstruction and, in cases where the kinetic fractionation varies with time, also affects relative paleoclimate interpretations. In carbonate archive research, clumped isotope thermometry is typically used as proxy for absolute temperatures. In the case of speleothems, however, clumped isotopes provide a sensitive indicator for disequilibrium effects. The extent of kinetic fractionation co-varies in Δ47 and δ18O so that it can be used to account for disequilibrium in δ18O and to extract the past drip-water composition. Here we apply this approach to stalagmites from Bunker Cave (Germany) and calculate drip-water δ18Ow values for the Eemian, Marine Isotope Stage (MIS) 3, and the Holocene, relying on independent temperature estimates and accounting for disequilibrium. Applying the co-variation method to modern calcite precipitates yields drip-water δ18Ow values in agreement with modern cave drip-water δ18Ow of −7.9 ± 0.3‰, despite large and variable disequilibrium effects in both calcite δ18Oc and Δ47. Reconstructed paleo-drip-water δ18Ow values are lower during colder periods (e.g., MIS 3: −8.5 ± 0.4‰ and the early Holocene at 11 kyr: −9.3 ± 0.1‰) and show higher values during warmer climatic periods (e.g., the Eemian: −7.5 ± 0.2‰ and the Holocene Climatic Optimum: −7.2 ± 0.3‰). This new approach offers a unique possibility for quantitative climate reconstruction including the assessment of past hydrological conditions while accounting for disequilibrium effects.

scholarly journals Clumped isotope effects during OH and Cl oxidation of methane

2017 ◽  
Vol 196 ◽  
pp. 307-325 ◽  
Author(s):  
Andrew R. Whitehill ◽  
Lars Magnus T. Joelsson ◽  
Johan A. Schmidt ◽  
David T. Wang ◽  
Matthew S. Johnson ◽  
...  
Keyword(s):  
Isotope Effects ◽  
Oxidation Of Methane ◽  
Clumped Isotope

scholarly journals Clumped isotope effects of thermogenic methane formation: insights from pyrolysis of hydrocarbons

2021 ◽  
Author(s):  
Guannan Dong ◽  
Hao Xie ◽  
Michael Formolo ◽  
Michael Lawson ◽  
Alex Sessions ◽  
...  
Keyword(s):  
Isotope Effects ◽  
Methane Formation ◽  
Clumped Isotope ◽  
Thermogenic Methane

scholarly journals Monitoring of a fast-growing speleothem site from the Han-sur-Lesse cave, Belgium, indicates equilibrium deposition of the seasonal δ<sup>18</sup>O and δ<sup>13</sup>C signals in the calcite

2014 ◽  
Vol 10 (5) ◽  
pp. 1871-1885 ◽  
Author(s):  
M. Van Rampelbergh ◽  
S. Verheyden ◽  
M Allan ◽  
Y. Quinif ◽  
E. Keppens ◽  
...  
Keyword(s):  
Water Temperature ◽  
Single Layer ◽  
Δ13c Values ◽  
Drip Water ◽  
Fast Growing ◽  
Cave System ◽  
Water Recharge ◽  
Opposite Behavior ◽  
Calcite Saturation ◽  
Δ18o And Δ13c

Abstract. Speleothems provide paleoclimate information on multimillennial to decadal scales in the Holocene. However, seasonal or even monthly resolved records remain scarce. Such records require fast-growing stalagmites and a good understanding of the proxy system on very short timescales. The Proserpine stalagmite from the Han-sur-Less cave (Belgium) displays well-defined/clearly visible darker and lighter seasonal layers of 0.5 to 2 mm thickness per single layer, which allows a measuring resolution at a monthly scale. Through a regular cave monitoring, we acquired a good understanding of how δ18O and δ13C signals in modern calcite reflect climate variations on the seasonal scale. From December to June, outside temperatures are cold, inducing low cave air and water temperature, and bio-productivity in the soil is limited, leading to lower pCO2 and higher δ13C values of the CO2 in the cave air. From June to December, the measured factors display an opposite behavior. The absence of epikarst water recharge between May and October increases prior calcite precipitation (PCP) in the vadose zone, causing drip water to display increasing pH and δ13C values over the summer months. Water recharge of the epikarst in winter diminishes the effect of PCP and as a result the pH and δ13C of the drip water gradually decrease. The δ18O and δ13C signals of fresh calcite precipitated on glass slabs also vary seasonally and are both reflecting equilibrium conditions. Lowest δ18O values occur during the summer, when the δ13C values are high. The δ18O values of the calcite display seasonal variations due to changes in the cave air and water temperature. The δ13C values reflect the seasonal variation of the δ13CDIC of the drip water, which is affected by the intensity of PCP. This same anticorrelation of the δ18O versus the δ13C signals is seen in the monthly resolved speleothem record that covers the period between 1976 and 1985 AD. Dark layers display lower δ18O and higher δ13C values. The cave system varies seasonally in response to the activity of the vegetation cover and outside air temperature between a "summer mode" lasting from June to December and a "winter mode" from December to June. The low δ18O and high δ13C values of the darker speleothem layers indicate that they are formed during summer, while light layers are formed during winter. The darker the color of a layer, the more compact its calcite structure is, and the more negative its δ18O signal and the more positive its δ13C signal are. Darker layers deposited from summer drip water affected by PCP are suggested to contain lower Ca2+ concentration. If indeed the calcite saturation represents the main factor driving the Proserpine growth rate, the dark layers should grow slower than the white layers.

Investigating cave responses to regional climate change: an approach to calibrate speleothem proxies in Madagascar

2021 ◽  
Author(s):  
Ny Riavo G. Voarintsoa ◽  
Antsa Lal’Aina J. Ratovonanahary ◽  
Avotriniaina Z. M. Rakotovao ◽  
Steven Bouillon
Keyword(s):  
Environmental Changes ◽  
Regional Climate ◽  
Winter Season ◽  
Regional Climate Change ◽  
Environmental Signals ◽  
Drip Water ◽  
Internal Parameters ◽  
Monitoring Study ◽  
Water Ph ◽  
Specific Factors

&lt;p&gt;Caves are an excellent natural laboratory for understanding the transfer processes of the region&amp;#8217;s environmental signals to speleothems. At least eight speleothems have produced high resolution paleoclimate and paleoenvironment records from Anjohibe Cave, NW Madagascar. However, due to the remote and difficult access to many caves in Madagascar, no studies have yet been done to understand the transfer of climate and environmental changes of the region to the cave. This is the first monitoring study to understand the linkage between regional climatology and various responses in Anjohibe Cave. We monitored (1) the drip water pH, TDS, EC, temperature, &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;DIC&lt;/sub&gt;, &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;w&lt;/sub&gt;, &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H&lt;sub&gt;w&lt;/sub&gt;, and elemental (Ca, Mg, Sr) composition, and (2) the cave atmosphere &lt;em&gt;p&lt;/em&gt;CO&lt;sub&gt;2&lt;/sub&gt;, relative humidity and temperature. Results show that air-to-air transfer is fast, and the internal parameters closely vary with the regional climatology. In contrast, rainfall to drip signal transfer is not immediate, and it can take few months to one season for the signals to be detected in the drip water due to the &amp;#8220;epikarst storage effect&amp;#8221;. The deposition of CaCO&lt;sub&gt;3&lt;/sub&gt; is inferred to occur late in the dry austral winter season, during which prior carbonate precipitation was also detected. Since the growth of speleothems is influenced by numerous cave-specific factors, this study, although preliminary, indicates that Anjohibe Cave drip waters are capable of registering changes in its surrounding environment. A longer monitoring study is expected in the future to constrain the timing and the mode of transfer.&lt;/p&gt;

scholarly journals A Forty-Year Karstic Critical Zone Survey (Baget Catchment, Pyrenees-France): Lithologic and Hydroclimatic Controls on Seasonal and Inter-Annual Variations of Stream Water Chemical Composition, pCO2, and Carbonate Equilibrium

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1227
Author(s):  
Francesco Ulloa-Cedamanos ◽  
Jean-Luc Probst ◽  
Stephane Binet ◽  
Thierry Camboulive ◽  
Virginie Payre-Suc ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Stream Water ◽  
Saturation Index ◽  
Hydrological Regime ◽  
Mineral Dissolution ◽  
Annual Variations ◽  
Water Chemical Composition ◽  
Calcite Saturation ◽  
Karst Catchment

The long-term trends and seasonal patterns of stream water chemical composition in a small remote forested karst catchment, were investigated from 1978 to 2018. Calcium, magnesium, and bicarbonates, the dominant ions, increased over the period together with temperature, while sulfates decreased. Carbonate and sulfate mineral dissolution was the main source of these elements. These trends and the seasonal opposite patterns of discharge vs. temperature, calcite saturation index vs. pCO2 and bicarbonate vs. sulfates, suggested the influence of discharge, of reduced long-range atmospheric pollution, and of increasing air temperature on biological activity and carbonate dissolution. Furthermore, the hydrological regime controlled the seasonal stream water chemical composition and fluxes by: (i) a dilution during the high discharge period, (ii) a change in the contribution rate of the waters draining different lithological areas in the catchment, e.g., the increased sulfates to bicarbonates ratio during summer low flows, with a maximum alkalinity decrease of 24%, and (iii) a “piston” and a “flushing” effects of dissolved elements stored in soils and epikarst with the first autumn heavy rains. Long-term stream water hydrochemical surveys of karst system have proved to be powerful indicators of biogeochemical processes, water sources and pathways under variable natural and anthropogenic environmental pressure conditions.

scholarly journals Equilibrium clumped-isotope effects in doubly substituted isotopologues of ethane

2017 ◽  
Vol 197 ◽  
pp. 14-26 ◽  
Author(s):  
Michael A. Webb ◽  
Yimin Wang ◽  
Bastiaan J. Braams ◽  
Joel M. Bowman ◽  
Thomas F. Miller
Keyword(s):  
Isotope Effects ◽  
Clumped Isotope

scholarly journals Kinetic isotope effects of <sup>12</sup>CH<sub>3</sub>D  + OH and <sup>13</sup>CH<sub>3</sub>D  + OH from 278 to 313 K

2016 ◽  
Vol 16 (7) ◽  
pp. 4439-4449 ◽  
Author(s):  
L. M. T. Joelsson ◽  
J. A. Schmidt ◽  
E. J. K. Nilsson ◽  
T. Blunier ◽  
D. W. T. Griffith ◽  
...  
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
State Theory ◽  
Atmospheric Methane ◽  
Isotopic Signatures ◽  
Budget Analysis ◽  
Kinetic Isotope ◽  
Methane Budget ◽  
Source Signal ◽  
Clumped Isotope

Abstract. Methane is the second most important long-lived greenhouse gas and plays a central role in the chemistry of the Earth's atmosphere. Nonetheless there are significant uncertainties in its source budget. Analysis of the isotopic composition of atmospheric methane, including the doubly substituted species 13CH3D, offers new insight into the methane budget as the sources and sinks have distinct isotopic signatures. The most important sink of atmospheric methane is oxidation by OH in the troposphere, which accounts for around 84 % of all methane removal. Here we present experimentally derived methane + OH kinetic isotope effects and their temperature dependence over the range of 278 to 313 K for CH3D and 13CH3D; the latter is reported here for the first time. We find kCH4/kCH3D = 1.31 ± 0.01 and kCH4/k13CH3D = 1.34 ± 0.03 at room temperature, implying that the methane + OH kinetic isotope effect is multiplicative such that (kCH4/k13CH4)(kCH4/kCH3D) = kCH4/k13CH3D, within the experimental uncertainty, given the literature value of kCH4/k13CH4 = 1.0039 ± 0.0002. In addition, the kinetic isotope effects were characterized using transition state theory with tunneling corrections. Good agreement between the experimental, quantum chemical, and available literature values was obtained. Based on the results we conclude that the OH reaction (the main sink of methane) at steady state can produce an atmospheric clumped isotope signal (Δ(13CH3D) = ln([CH4][13CH3D]/[13CH4][CH3D])) of 0.02 ± 0.02. This implies that the bulk tropospheric Δ(13CH3D) reflects the source signal with relatively small adjustment due to the sink signal (i.e., mainly OH oxidation).

scholarly journals The isotopic composition of methane in the stratosphere: high-altitude balloon sample measurements

2011 ◽  
Vol 11 (24) ◽  
pp. 13287-13304 ◽  
Author(s):  
T. Röckmann ◽  
M. Brass ◽  
R. Borchers ◽  
A. Engel
Keyword(s):  
Isotopic Composition ◽  
Isotope Effects ◽  
Mixing Ratio ◽  
Kinetic Isotope ◽  
Time Period ◽  
Order Of Magnitude ◽  
Stratospheric Balloon ◽  
Single Balloon ◽  
Kinetic Fractionation ◽  
The Individual

Abstract. The isotopic composition of stratospheric methane has been determined on a large suite of air samples from stratospheric balloon flights covering subtropical to polar latitudes and a time period of 16 yr. 154 samples were analyzed for δ13C and 119 samples for δD, increasing the previously published dataset for balloon borne samples by an order of magnitude, and more than doubling the total available stratospheric data (including aircraft samples) published to date. The samples also cover a large range in mixing ratio from tropospheric values near 1800 ppb down to only 250 ppb, and the strong isotope fractionation processes accordingly increase the isotopic composition up to δ13C = −14‰ and δD = +190‰, the largest enrichments observed for atmospheric CH4 so far. When analyzing and comparing kinetic isotope effects (KIEs) derived from single balloon profiles, it is necessary to take into account the residence time in the stratosphere in combination with the observed mixing ratio and isotope trends in the troposphere, and the range of isotope values covered by the individual profile. The isotopic composition of CH4 in the stratosphere is affected by both chemical and dynamical processes. This severely hampers interpretation of the data in terms of the relative fractions of the three important sink mechanisms (reaction with OH, O(1D) and Cl). It is shown that a formal sink partitioning using the measured data severely underestimates the fraction removed by OH, which is likely due to the insensitivity of the measurements to the kinetic fractionation in the lower stratosphere. Full quantitative interpretation of the CH4 isotope data in terms of the three sink reactions requires a global model.

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