scholarly journals Climatic variations during the Holocene inferred from radiocarbon and stable carbon isotopes in a high-alpine cave

2021 ◽  
Author(s):  
Caroline Welte ◽  
Jens Fohlmeister ◽  
Melina Wertnik ◽  
Lukas Wacker ◽  
Bodo Hattendorf ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Stable Carbon Isotopes ◽  
Stable Carbon Isotope ◽  
Climatic Conditions ◽  
Stable Carbon ◽  
Novel Technique ◽  
Climatic Variations ◽  
Spatially Resolved ◽  
Exchange Processes ◽  
Carbon Reservoir

<div> <p>Laser ablation coupled online to accelerator mass spectrometry [1] allows analyzing the radiocarbon (<sup>14</sup>C) concentration in carbonate samples in a fast and spatially resolved manner. This novel technique can provide <sup>14</sup>C data at a spatial resolution comparable to that of stable carbon isotope measurements and, thus, can help to interpret δ<sup>13</sup>C signatures. In this work, we analyzed δ<sup>13</sup>C and <sup>14</sup>C of a Holocene stalagmite from the high-alpine Spannagel Cave (Austria). Combined δ<sup>13</sup>C and <sup>14</sup>C profiles allow identifying three growth periods : (i) the period > 8 ka BP exhibits relatively low δ<sup>13</sup>C values with small variability combined with a comparably high dead carbon fraction (dcf) of around 60%. This points towards C contributions of an old organic carbon reservoir in the karst potentially mobilized due to the warm climatic conditions of the early Holocene. (ii) Between 3.8 and 8 ka BP, a strong variability in δ<sup>13</sup>C with values from -8 to +1‰ and a generally lower dcf was observed. The δ<sup>13</sup>C variability was most likely caused by changes in gas exchange processes in the cave, which are induced by reduced drip rates as derived from lower stalagmite growth rates. Additionally, the lower dcf indicates that the OM reservoir contributed less to stalagmite growth in this period possibly as a result of reduced precipitation or because the OM reservoir became exhausted. (iii) In the youngest section between 2.4 and 3.8 ka BP, comparably stable and low δ<sup>13</sup>C values combined with an increasing dcf reaching up to 50% are again hinting towards a contribution of an aged organic carbon reservoir in the karst.</p> </div><p>[1] C. Welte, et al., (2016). Anal. Chem., 88, 8570– 8576.</p>

scholarly journals Climatic variations during the Holocene inferred from radiocarbon and stable carbon isotopes in a high-alpine cave

2020 ◽  
Author(s):  
Caroline Welte ◽  
Jens Fohlmeister ◽  
Melina Wertnik ◽  
Lukas Wacker ◽  
Bodo Hattendorf ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Spatial Resolution ◽  
Stable Carbon Isotopes ◽  
Isotope Ratio Mass Spectrometry ◽  
Climatic Conditions ◽  
Stable Carbon ◽  
Δ13c Values ◽  
The Holocene ◽  
Exchange Processes ◽  
Radiocarbon Data

Abstract. A novel technique making use of laser ablation coupled online to accelerator mass spectrometry (LA-AMS) allows analyzing the radiocarbon (14C) concentration in carbonate samples continuously at high spatial resolution within very short analysis times. This new technique can provide radiocarbon data similar to the spatial resolution of stable carbon (C) isotope measurements by isotope-ratio mass spectrometry (IRMS) and, thus, can help to interpret δ13C signatures, which otherwise are difficult to understand due to numerous processes contributing to changes in C-isotope changes ratios. In this work we analyzed δ13C and 14C on the Holocene stalagmite SPA 127 from the high-alpine Spannagel Cave (Austria). Combined stable carbon and radiocarbon profiles allow to identify three growth periods characterized by different δ13C signatures: (i) the period > 8 ka BP is characterized by relatively low δ13C values with small variability combined with a comparably high radiocarbon reservoir effect (expressed as dead carbon fraction, dcf) of around 60 %. This points towards C contributions of host rock dissolution and/or from an old organic matter (OM) reservoir in the karst potentially mobilized due to the warm climatic conditions of the early Holocene. (ii) Between 3.8–8 ka BP a strong variability in δ13C reaching values from −8 to +1 ‰ with a generally lower dcf was observed. The δ13C variability is most likely caused by changes in gas exchange processes in the cave, which are induced by reduced drip rates as derived from reduced stalagmite growth rates. Additionally, the lower dcf indicates that the OM reservoir is contributing less to stalagmite growth in this period possibly as a result of reduced precipitation or because it is exhausted. (iii) In the youngest section between 2.4–3.8 ka BP, comparably stable and low δ13C values combined with an increasing dcf reaching up to 50 % are again hinting towards a contribution of an aged OM reservoir in the karst.

Radiocarbon and Stable Carbon Isotopes of Labile and Inert Organic Carbon in the Critical Zone Observatory in Illinois, USA

Radiocarbon ◽  
2018 ◽  
Vol 60 (3) ◽  
pp. 989-999 ◽  
Author(s):  
Hong Wang ◽  
Andrew J. Stumpf ◽  
Praveen Kumar
Keyword(s):  
Organic Carbon ◽  
Stable Carbon Isotopes ◽  
Stable Carbon Isotope ◽  
Critical Zone ◽  
Carbon Pools ◽  
Stable Carbon ◽  
Labile Carbon ◽  
Carbonate Carbon ◽  
Critical Zone Observatory ◽  
Bt Horizon

ABSTRACTWe applied the high temperature pyrolysis-combustion technique to partition the total soil organic carbon (SOC) into labile and inert carbon pools for accelerator mass spectrometry radiocarbon (AMS 14C) dating and stable carbon isotope (δ13C), SOC, and carbonate carbon (CC) content analyses to examine SOC variability at a Critical Zone Observatory site in Illinois, USA. The AMS 14C dates of labile and inert carbon in the top 1.55 m overlap except in the Bt horizon. Below 1.55 m the labile carbon is younger by 8000–14,800 years. The SOC content decreases from 3.61% to 0.12% and CC content increases from 0% to 19.16% at this depth. Results indicate that SOC production exceeds its loss in the weathering zone causing a continuous turnover of both SOC pools. A small amount of modern SOC infiltrates into deeper sediment below 1.55 m, making the labile carbon pool much younger. Their difference of AMS 14C contents, ΔF14C, reveals 3−5% more modern carbon in the labile SOC pools except in the Bt horizon, further quantifying that <3−5% modern carbon with potential pollutants is translocated into the unweathered sediments. The δ13C reveals the sources for SOC cycling dynamics in both carbon pools at this site.

scholarly journals Past climate variations recorded in needle-like aragonites correlate with organic carbon burial efficiency as revealed by lake sediments in Croatia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ivan Razum ◽  
Petra Bajo ◽  
Dea Brunović ◽  
Nikolina Ilijanić ◽  
Ozren Hasan ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Stable Carbon Isotope ◽  
Climate Variations ◽  
Before Present ◽  
Stable Carbon ◽  
Climate Trends ◽  
Geochemical Proxies ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Burial Efficiency

AbstractThe drivers of organic carbon (OC) burial efficiency are still poorly understood despite their key role in reliable projections of future climate trends. Here, we provide insights on this issue by presenting a paleoclimate time series of sediments, including the OC contents, from Lake Veliko jezero, Croatia. The Sr/Ca ratios of the bulk sediment are mainly derived from the strontium (Sr) and calcium (Ca) concentrations of needle-like aragonite in Core M1-A and used as paleotemperature and paleohydrology indicators. Four major and six minor cold and dry events were detected in the interval from 8.3 to 2.6 calibrated kilo anno before present (cal ka BP). The combined assessment of Sr/Ca ratios, OC content, carbon/nitrogen (C/N) ratios, stable carbon isotope (δ13C) ratios, and modeled geochemical proxies for paleoredox conditions and aeolian input revealed that cold and dry climate states promoted anoxic conditions in the lake, thereby enhancing organic matter preservation and increasing the OC burial efficiency. Our study shows that the projected future increase in temperature might play an important role in the OC burial efficiency of meromictic lakes.

Drought signals inferred from ring-width and stable carbon isotope chronologies from Thuja occidentalis trees growing at their northwestern distribution limit, central Canada

2012 ◽  
Vol 42 (3) ◽  
pp. 517-531 ◽  
Author(s):  
Robert Au ◽  
Jacques C. Tardif
Keyword(s):  
Tree Ring ◽  
Tree Rings ◽  
Stable Carbon Isotopes ◽  
Stable Carbon Isotope ◽  
Ring Width ◽  
Ring Formation ◽  
Moisture Regime ◽  
Stable Carbon ◽  
Thuja Occidentalis ◽  
Central Canada

Stable carbon isotopes (δ13C) fixed in tree rings are dependent upon environmental conditions. Old northern white-cedar ( Thuja occidentalis L.) trees were sampled at their northwestern limit of distribution in central Canada. The objectives of the study were (i) to investigate the association between tree-ring δ13C values and radial growth in addition to the response of these variables to climate, (ii) to assess site differences between two sites varying in moisture regime, and (iii) to compare tree-ring δ13C of T. occidentalis with that of other boreal tree species growing at the northern limit of their distribution in central Canada. Over 2500 tree rings comprised of 15 T. occidentalis trees were analyzed for δ13C. Annually resolved δ13C (1650–2006) and ring-width (1542–2006) chronologies were developed. During the year of ring formation, ring width was associated with spring and early-summer conditions, whereas δ13C was more indicative of overall summer conditions. However, compared with δ13C values, ring width was more often associated with climate conditions in the year prior to ring formation. Conditions conducive to moisture stress were important for both parameters. Although ring width and δ13C corresponded to the drought intervals of the 1790s, 1840s, 1890s, 1930s, and 1960–1970, ring width may be more responsive to prolonged drought than δ13C. Tree-ring δ13C could, however, provide important information regarding physiological adaptations to drought.

Increase in soil stable carbon isotope ratio relates to loss of organic carbon: results from five long-term bare fallow experiments

Oecologia ◽  
2014 ◽  
Vol 177 (3) ◽  
pp. 811-821 ◽  
Author(s):  
Lorenzo Menichetti ◽  
Sabine Houot ◽  
Folkert van Oort ◽  
Thomas Kätterer ◽  
Bent T. Christensen ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Isotope ◽  
Isotope Ratio ◽  
Stable Carbon Isotope ◽  
Carbon Isotope Ratio ◽  
Stable Carbon ◽  
Stable Carbon Isotope Ratio ◽  
Bare Fallow

scholarly journals Characterizing the origins of dissolved organic carbon in coastal seawater using stable carbon isotope and light absorption characteristics

2021 ◽  
Vol 18 (5) ◽  
pp. 1793-1801
Author(s):  
Heejun Han ◽  
Jeomshik Hwang ◽  
Guebuem Kim
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Carbon Isotope ◽  
Stable Carbon Isotope ◽  
The Yellow Sea ◽  
Bacterial Degradation ◽  
Western Coast ◽  
Stable Carbon ◽  
Δ13c Values ◽  
Lower Salinity

Abstract. In order to determine the origins of dissolved organic matter (DOM) occurring in the seawater of Sihwa Lake, we measured the stable carbon isotope ratios of dissolved organic carbon (DOC-δ13C) and the optical properties (absorbance and fluorescence) of DOM in two different seasons (March 2017 and September 2018). Sihwa Lake is enclosed by a dike along the western coast of South Korea, and the water is exchanged with the Yellow Sea twice a day through the sluice gates. The DOC concentrations were generally higher in lower-salinity waters in both periods, and excess of DOC was also observed in 2017 in high-salinity waters. Here, the excess DOC represents any DOC concentrations higher than those in the incoming open-ocean seawater. The excess DOC occurring in the lower-salinity waters originated mainly from marine sediments of tidal flats, based on the DOC-δ13C values (-20.7±1.2 ‰) and good correlations among the DOC, humic-like fluorescent DOM (FDOMH), and NH4+ concentrations. However, the origins of the excess DOC observed in 2017 appear to be from two different sources: one mainly from marine sources such as biological production based on the DOC-δ13C values (−19.1 ‰ to −20.5 ‰) and the other mainly from terrestrial sources by land–seawater interactions based on its depleted DOC-δ13C values (−21.5 ‰ to −27.8 ‰). This terrestrial DOM source observed in 2017 was likely associated with DOM on the reclaimed land, which experienced extended exposure to light and bacterial degradation as indicated by the higher spectral slope ratio (SR) of light absorbance and no concurrent increases in the FDOMH and NH4+ concentrations. Our study demonstrates that the combination of these biogeochemical tools can be a powerful tracer of DOM sources and characteristics in coastal environments.

scholarly journals Characterizing the origin of excess dissolved organic carbon in coastal seawater using stable carbon isotope and light absorption characteristics

2020 ◽  
Author(s):  
Heejun Han ◽  
Jeomshik Hwang ◽  
Guebuem Kim
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Isotopic Ratio ◽  
Stable Carbon Isotope ◽  
Bacterial Degradation ◽  
Salinity Range ◽  
Stable Carbon ◽  
Reclaimed Land ◽  
Δ13c Values ◽  
Coastal Seawater

Abstract. In order to determine the origins of dissolved organic matter (DOM) occurring in coastal seawater of the Sihwa Lake, South Korea, which is semi-enclosed by a dyke, we measured the stable carbon isotopic ratio of dissolved organic carbon (DOC-δ13C) and optical properties (absorbance and fluorescence) of the DOM in two different seasons (March 2017 and September 2018). The concentrations of DOC were generally higher in lower-salinity waters in both periods, while a significant excess of DOC was observed in 2017 in the same salinity range. The main source of DOC, dependent on salinity, was found to be from marine sediments in the freshwater-seawater mixing zone rather than from terrestrial sources based on the DOC-δ13C values (−20.7±1.2 ‰) and good correlations among DOC, humic-like fluorescent DOM (FDOMH), and NH4+ concentrations. However, the excess DOC observed in 2017 seems to originate from terrestrial sources by direct land-seawater interactions rather than from in-situ biological production, considering the lower DOC-δ13C values (−27.8 ‰ to −22.6 ‰) and higher spectral slope ratio (SR) of light absorbance, without increases in FDOMH and NH4+ concentrations. This terrestrial DOM source could have been exposed to light and bacterial degradation for a long time, resulting in nonfluorescent and low-molecular-weight DOM, as this study area is surrounded by the reclaimed land. Our results suggest that the combination of these biogeochemical tools can be a powerful tracer of coastal DOM sources.

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