Untersuchungen zur Isotopensignatur von Methan und Kohlendioxid aus biogenen Gasen unterschiedlicher Quellen

Abstract

The isotopic compositions of biogenic carbon dioxide and methane from different sites were investigated. The δ¹³C values of methane vary mainly between ?55‰ and ?75‰ whereas δ¹³C values of carbon dioxide were found from about + 11‰ to ?23‰. Especially the latter ones are not so typical for microbial gases. The different sites don't vary over the whole scales but form certain groups. Secondary effects like diffusion change the δ values of both components in an even more negative direction, while oxidation processes near the surface result in more positive δ¹³C values for methane and very negative δ¹³C values for carbon dioxide.     

Preparation of Naturally 13C-Rich Free Fatty Acids (FFA) from Corn Oil and their Application in Metabolic Studies of Lactating Cows

Abstract

When the ¹³C/¹²C ratios in lactose and milk fat of normally fed healthy cows are compared to ¹³C/¹²C in feed a metabolic depletion of ¹³C in the milk constituents becomes obvious.

Due to a carbon isotope effect in the decarboxylation step of pyruvate to Acetyl-Co-A resulting in a ¹³C depleted acetate, depot fat and milk fat are especially reduced in ¹³C relative to ¹²C.

Under pathophysiological conditions after longer fasting periods or in ketosis, long chain fatty acids from depot fat are metabolized and their ¹³C depleted carbon atoms enter the citric acid cycle via Acetyl-Co-A. Then the intermediary products of this cycle become ¹³C depleted too and with a drain on the oxalacetate pool by gluconeogenesis ¹³C depleted carbon atoms are channeled into lactose.

This hypothesis is apt to explain a ¹³C/¹²C decrease in lactose of ketotic cows relative to healthy controls. It is supported by the observation that ¹³C-rich fatty acids from corn oil dosed orally to a ketotic cow increase the ¹³C/¹²C ratios in lactose. So a crossing-over of carbon atoms from long chain fatty acids into glucose and lactose seems highly probable.     

Measurement of δ13C values of soil amino acids by GC–C–IRMS using trimethylsilylation: a critical assessment

In this study, we evaluated trimethylsilyl (TMS) derivatives as derivatization reagents for the compound-specific stable carbon isotope analysis of soil amino acids by gas chromatography–combustion–isotope ratio mass spectrometry (GC–C–IRMS). We used non-proteinogenic amino acids to show that the extraction–derivatization–analysis procedure provides a reliable method to measure δ¹³C values of amino acids extracted from soil. However, we found a number of drawbacks that significantly increase the final total uncertainty. These include the following:

• production of multiple peaks for each amino acid, identified as di-, tri- and tetra-TMS derivatives;

• a number of TMS-carbon (TMS-C) atoms added lower than the stoichiometric one, possibly due to incomplete combustion;

• different TMS-C δ¹³C for di-, tri- and tetra-TMS derivatives.

For soil samples, only four amino acids (leucine, valine, threonine and serine) provide reliable δ¹³C values with a total average uncertainty of 1.3?‰. We conclude that trimethylsilyl derivatives are only suitable for determining the ¹³C incorporation in amino acids within experiments using ¹³C-labelled tracers but cannot be applied for amino acids with natural carbon isotope abundance until the drawbacks described here are overcome and the measured total uncertainty significantly decreased.     

Influence of Nitrogen,Water and Competition on Carbon Isotope Ratios (δ13C) in a CAM Plant (Crassula argentea)

Abstract

Leaf carbon isotope ratios (δ¹³C), an indicator of long-term intercellular carbon dioxide concentration, and also stem and root carbon isotope ratios were measured on the obligate CAM species Crassula argentea cultivated in pure and mixed cultures with the succulent C₃ Peperomia obtusifolia in open-air conditions under two different levels of nitrogen and water supply.

As expected, a diminished water supply and a relatively dry and hot summer climate cause a shift of δ¹³C values to a less strong ¹³C discrimination (less negative δ¹³C values). A diminished nitrogen supply causes a shift of the δ¹³C values in direction of a higher ¹³C discrimination (more negative δ¹³C values), particularly in the leaves. Competition causes also an increased ¹³C discrimination, especially valid for shoot axes.

The shift of ¹³C/¹²C isotope ratios in case of nitrogen deficiency is discussed to be a result of a decreased PEPCase activity in the night.     

Precise δ13C-determination in the Range of Natural Abundance on Amino Acids from Protein Hydrolysates by Gas Chromatography - Isotope Ratio Mass Spectrometry

Abstract

Routine on-line ¹³C-analysis by coupled gas chromatography - combustion – isotope ratio - mass spectrometry of individual amino acids out of mixtures in the natural abundance range demands their strictly standardized derivatization. For the N-acetyl-propylesters of amino acids from protein hydrolysates and blood serum a mean precision of 0.5% ° (1 SD) for derivatization, separation and measurement could be attained. From δ¹³C-values of derivatives δ¹³C-values of amino acids could be calculated by a carbon balance equation, implying an isotope effect on the C-1 of acetate of about 1.04 for nine amino acids. The global δ¹³C-value of casein calculated from the individual amino acids differed by less than 1.5%° from the directly determined value. The δ¹³C-values of amino acids from plant protein hydrolysates analyzed by the on-line method were in agreement with results obtained by classical procedures. The method permits the δ-value determination of up to nine amino acids from 200 μg of a mixture in less than one hour. By this means the detection of ¹³C-labeled amino acids in nmole amounts diluted by the 5000-fold amount of carrier becomes possible.     

The Effect of Diet Quality on δ13C and δ15N in the Tissues of Locusts,Locusta migratoria L

Abstract

Locust nymphs were raised from hatching to adult locusts on either seedling wheat (C₃) or maize (C₄), to determine whether relative enrichments/depletions of ¹⁵N and ¹³C within body tissues are influenced by diet. The maize contained less hexose sugars and protein per gram than wheat.

The isotopic spacing between the food and the whole insect was found to differ between the two diets. The lower quality maize diet showed an overall +5.1‰ enrichment in δ¹⁵N compared to + 2.8‰ for wheat, possibly due to increased fractionation due to protein recycling.

The maize diet resulted in increased depletion in lipid and trehalose and depletion in chitin relative to diet. The results for both δ¹⁵N and δ¹³C suggest that substrate recycling was occurring on the low quality maize diet. Therefore diet quality determines the enrichment/depletion in δ¹⁵N and δ¹³C within organisms.     

Stable Carbon Isotope Fractionation in Lower Plants from the Schirmacher and Untersee Oases (Central Dronning Maud Land,East Antarctica)

Abstract

Lower plants (algae, lichens, mosses) from the Antarctic continent have been analysed for their stable carbon isotope composition. In contrast to lichens and mosses which exhibit quite normal δ¹³C-values the studied microbial benthos is characterized by an extremely low carbon isotope fractionation (δ¹³C-values up to ?1.4‰. vs. PDB). Limited CO₂ availability and bicarbonate uptake are probably the main factors responsible for this phenomenon.     

Kohlenstoffisotopendaten von tertiären Hölzern der Niederrheinischen Bucht (Carbon Isotope Data of Tertiary Wood Samples from the Lower Rhine Valley)

Abstract

Eight fossil tree trunks taken from various levels in the Tertiary deposits (Middle Miocene to Late Pliocene) of the Lower Rhine Valley were determined taxonomically and their annual rings measured. In addition, the carbon content of annual ring samples was examined by titration, cellulose was extracted and the carbon isotope ratio (¹³C/¹²C) was identified. Coalification experiments carried out in the laboratory showed that with degradation of the cellulose no notable differences could be observed in the δ¹³C values of wood or cellulose. Thus, the isotopic data from fossil wood in refer to those of recent ones are similar as long as the same taxa are considered. Within the strata, the δ¹³C values of the fossil tree trunks decreased considerably. This corresponds to the general course of temperature and eventual changes in atmospheric carbon dioxide content during the Neogene.     

Ecophysiological Studies on the Vegetation of Madagascar: A δ13C and δD Survey for Incidence of Crassulacean Acid Metabolism (Cam) Among Orchids From Montane Forests and Succulents from the Xerophytic Thorn-Bush

Abstract

The incidence of Crassulacean acid metabolism (CAM) in plants collected at various habitats in Madagascar was investigated by survey of carbon and hydrogen isotope ratios ((δ¹³C and δD values). In about 50% of the epiphytic orchids from evergreen higher and lower montane forests the δ¹³C values were indicative for CAM. The remainder of the species are presumably C₃ plants. In all samples of malagasy epiphytic leafless orchids comprising 9 species, the δ¹³C values suggest extreme CAM with CO₂ uptake proceeding entirely during the night. All terrestrial orchids collected in the lower montane forests obviously acquire external carbon by C₃-photosynthesis, whereas Lissochilus decaryi, a terrestrial orchid from the semi-arid south of Madagascar and various other species of this genus are CAM plants. This is the first report of CAM occurrence in sympodial terrestrial orchids.

Judged by the δ¹³C values, all succulents (mainly Didiereaceae, Euphorbiaceae, Crassulaceae and Asclepiadaceae) collected at the xerophytic thorn-bush of the semi-arid south perform pronounced CAM. Where it applies, our δ¹³C measurements in the thorn-bush succulents revealed values being practically identical with those found by K. Winter in samples of the same species collected at the same site nearly 10 years earlier. This shows extreme constancy over long duration of time in the mode of CAM performed by the succulents of the malagasy thorn-bush vegetation. Since the δ¹³C survey now comprises all 11 known species of the Didiereaceae, it is unequivocally clear that all members of this family are CAM plants. Most of the individuals of the species of the Didiereaceae grown in a glass-house had slightly more negative δ¹³C values compared with those grown at the natural stands suggesting some contribution of C₃-photosynthesis to carbon acquisition under the evaporatively less demanding glass-house conditions (and perhaps higher CO₂ concentrations in the gas phase).

Despite of the fact that the hydrogen isotope composition of meteoric waters depends to a large extent on the altitude and temperature-climate of the site where the concerned plants grow, it was found that in samples obtained in the cooler higher evergreen montane forest as well as in the warmer lower evergreen montane forest and the lowland thorn-bush of the hot, semiarid south of Madagascar the δ values found in the organic matter (δD^org) were in the same range (between about - 10‰ to about - 90‰). This suggests that in our case the hydrogen isotope compositions of the meteoric waters were of minor importance in bringing about the δD^org values found in the plants.     

Stable Isotope Ratios and Uric Acid Preservation in Termites Belonging to Three Feeding Habits in Thailand

Abstract

Nitrogen and carbon stable isotope ratios and uric acid concentrations in termites sampled from a dry evergreen forest in Thailand, were determined across three kinds of feeding habits. Feeding habits of Microcerotermes crassus, which is an abundant woodfeeder, and Dicuspiditermes makhamensis, a common soil-feeding termite, were confirmed by isotopic signatures. Lichen feeding termites (Hospitalitermes birmanicus, H. bicolor and H. ataramensis) were characterized by low δ¹⁵N values, suggesting that they assimilated nitrogen deposited from the atmosphere. There was also a significant difference in uric acid concentrations between termites representing different feeding habits. No significant relationships were found between uric acid concentrations and δ¹⁵N or δ¹³C in Hospitalitermes. However, δ¹⁵N values were correlated with C/N ratios in H. birmanicus, except in one colony of H. ataramensis. δ¹³C values in both species were negatively correlated with C/N ratios.     

Estimating Spatial and Seasonal Phytoplankton δ13C Variations in an Estuarine Mangrove Ecosystem

Abstract

In estuarine ecosystems, large spatial and seasonal variations in δ¹³C values of primary producers can occur, and knowledge of these variations may be crucial when interpreting stable isotope data of higher trophic levels. Obtaining clean phytoplankton samples for isotope analysis is usually impossible in such systems, and analysis of total suspended matter is not a simple proxy for phytoplankton δ¹³C variations. Based on a few simple assumptions regarding the C and N content of the two end-members (terrestrial detritus and phytoplankton) and the δ¹³C of the terrestrial component, we here present a simple model to estimate the phytoplankton δ¹³C variations using an existing dataset on the δ¹³C and elemental (C:N) composition of suspended organic matter from an estuarine mangrove ecosystem in southeast India.

These variations are related to the monthly rainfall pattern during the sampling period. It is stressed that this method estimates approximate phytoplankton δ¹³C values, which should not be used in e.g., mixing models. However, we propose that in cases where sufficiently large datasets are available, the described procedure could provide a valuable method to semi-quantitatively estimate the seasonal or spatial variations of the phytoplankton δ¹³C signal.     

13C NMR Chemical Shifts of Heterocycles: 3∗. Empirical Substituent Effects in 2-Halomethyl-2-hydroxy-tetrahydrofurans and -5,6-tetrahydro-4H-pyrans

Abstract

Evaluation by empirically derived equations for the Substituent effect (α, β, γ, δ) on the ¹³C NMR chemical shifts for C-2, C-3, C-4, C-5, C-6, the halomethyl-substituted carbon (C-7) and the cyano or oxymic carbon (C-8) in 2-halomethyl-2-hydroxy-tetrahydrofurans 1a-c, 2, 3a, b, 4a and -5,6-tetrahydro-4H-pyrans 5a-c, 6a [with C-2-substituents (R²): CF₃, CCl₃ or CHCl₂, C-3-substituents (R³): CN, C(Me)=NOH, CH=NOMe, C(Me)=NOMe or CH=NOH], taking as reference the 2-trifluoromethyl-2-hydroxy-tetrahydrofuran (la), is reported. From the additivity properties of the α-, β-, γ-, δ-and ?-effects for each Substituent it is possible to predict the chemical shift of each carbon of the compounds 1–6.

     

13C and 15N Abundances in the Sediment Core (VER 92/1-St-10-GC2) from Northern Lake Baikal

Abstract

Carbon and nitrogen stable isotope compositions of organic matter, TOC/TN ratio, and manganese concentration in a sediment core that was collected in northern part of Lake Baikal (VER92ST10-GC2, water depth at 922 m, about 3 m long) were investigated to elucidate the origin of the sedimentary organic matter and its associated environmental factors.

The sediment core was composed of mainly two parts: turbidite sections and other sections. Constant δ¹³C and δ¹⁵N values of the turbidite sections were observed (- 26.8 ±0.2 ‰ for δ¹³C and 3.2 ± 0.1 ‰ for δ¹⁵N) throughout the core. The higher δ¹³C in turbidite sections (about - 27 ‰) than that of the other sections (- 31 to - 29 ‰) was clearly observed, and δ¹⁵N was different between turbidite sections (about 3‰) and other sections (3 to 5 ‰). δ¹³C of other sections was close to that of pelagic phytoplankton, indicating that sediment other than turbidite sections is composed of autochthonous components. The variation of stable isotopes in other sections may be possibly caused by the changes in either phytoplankton growth rate or contribution ratios of terrestrial to aquatic plants for δ¹³C. Either denitrification or fluctuation of δ¹⁵N in pelagic phytoplankton can be the cause of variable δ¹⁵N in other sections.     

Field-based cavity ring-down spectrometry of δ13C in soil-respired CO2

Measurement of soil-respired CO₂ at high temporal resolution and sample density is necessary to accurately identify sources and quantify effluxes of soil-respired CO₂. A portable sampling device for the analysis of δ¹³C values in the field is described herein.

CO₂ accumulated in a soil chamber was batch sampled sequentially in four gas bags and analysed by Wavelength-Scanned Cavity Ring-down Spectrometry (WS-CRDS). A Keeling plot (1/[CO₂] versus δ¹³C) was used to derive δ¹³C values of soil-respired CO₂. Calibration to the δ¹³C Vienna Peedee Belemnite scale was by analysis of cylinder CO₂ and CO₂ derived from dissolved carbonate standards. The performance of gas-bag analysis was compared to continuous analysis where the WS-CRDS analyser was connected directly to the soil chamber.

Although there are inherent difficulties in obtaining absolute accuracy data for δ¹³C values in soil-respired CO₂, the similarity of δ¹³C values obtained for the same test soil with different analytical configurations indicated that an acceptable accuracy of the δ¹³C data were obtained by the WS-CRDS techniques presented here. Field testing of a variety of tropical soil/vegetation types, using the batch sampling technique yielded δ¹³C values for soil-respired CO₂ related to the dominance of either C₃ (tree, δ¹³C=?27.8 to?31.9 ‰) or C₄ (tropical grass, δ¹³C=?9.8 to?13.6 ‰) photosynthetic pathways in vegetation at the sampling sites. Standard errors of the Keeling plot intercept δ¹³C values of soil-respired CO₂ were typically<0.4 ‰ for analysis of soils with high CO₂ efflux (>7–9 μmol m^?2 s^?1).     

Anthropogenic and solar forcing in δ13C time pattern of coralline sponges

We present the results of a re-analysis of a previously published carbon isotope data-set related to coralline sponges in the Caribbean Sea. The original interpretation led to the discrimination between a pre-industrial period, with a signal controlled by solar-induced climatic variations, followed by the industrial era, characterized by a progressive δ¹³C negative shift due to the massive anthropogenic carbon emissions. Our re-analysis allowed to extract from the raw isotopic data evidence of a solar forcing still visible during the industrial era, with a particular reference to the 88-year Gleissberg periods. These signals are related to slope changes in both the δ¹³C versus time and the δ¹³C versus carbon emission curves.     

Evaluation of the effect of the 2011 Tsunami on coastal forests by means of multiple isotopic analyses of tree-rings

The March 2011 Mega-Tsunami in eastern Japan damaged at different degrees the black pine (Pinus thunbergii) forests along the coast. In order to evaluate the recovery of black pine four years later, tree-ring samples from 9 trees for the period 2002–2014 were analyzed for ring growth and stable isotopes (δ¹³C, δ¹⁵N and δ¹⁸O). The results showed that annual tree-ring width decreased approximately 70?% from the year 2011 to 2014 compared to the period previous to the tsunami (2002–2010). The multiple isotopic analyses showed that the reduction in growth was caused by soil salinity that prompted stomatal closure and an abrupt increase of tree-ring δ¹³C. Sea water deposition in the soil did not affect tree-ring δ¹⁸O values. Two years after the tsunami, decreasing tree-ring δ¹³C values caused by apparently photosynthetic recovery did not translate into radial tree-growth, indicating a possible shift in carbon allocation to foliage and mainly roots as a defense mechanism to sodium toxicity. The dual δ¹³C-δ¹⁸O model explains neither the limited growth nor the subsequent recovery in δ¹³C. Similarly tree-ring δ¹⁵N indicated that there was no difference in nitrogen availability before and after the tsunami, suggesting that nutrients were not a limitation but rather soil salinity.     

Estimation of microbial methane generation and oxidation rates in the municipal solid waste landfill of Kaluga city,Russia

Using a theoretical model and mass isotopic balance, biogas (methane and CO₂) released from buried products at their microbial degradation was analysed in the landfill of municipal and non-toxic industrial solid organic waste near Kaluga city, Russia. The landfill contains about 1.34×10⁶ tons of waste buried using a ‘sandwich technique’ (successive application of sand–clay and waste layers). The δ¹³C values of biogenic methane with respect to CO₂ were?56.8 (±2.5) ‰, whereas the δ¹³C of CO₂ peaked at+9.12‰ (+1.4±2.3‰ on average), reflecting a virtual fractionation of carbon isotopes in the course of bacterial CO₂ reduction at the landfill body. After passing through the aerated soil layers, methane was partially oxidised and characterised by δ¹³C in the range of?50.6 to?38.2‰, evidencing enrichment in ¹³C, while the released carbon dioxide had δ¹³C of?23.3 to?4.04‰, respectively. On the mass isotopic balance for the δ¹³C values, the methane production in the landfill anaerobic zone and the methane emitted through the aerated landfill surface to the atmosphere, the portion of methane oxidised by methanotrophic bacteria was calculated to be from 10 to 40% (averaged about 25%). According to the theoretical estimation and field measurements, the annual rate of methane production in the landfill reached about 2.9(±1.4)×10⁹ g C CH₄ yr^?1 or 5.3(±2.6)×10⁶ m³ CH₄ yr^?1. The average rates of methane production in the landfill and methane emission from landfill to the atmosphere are estimated as about 53 (±26) g C CH₄ m^?2 d^?1 (or 4 (±2) mol CH₄ m^?2 d^?1) and 33 (±12) g C CH₄ m^?2 d^?1 (or 2.7 (±1) mol CH₄ m^?2 d^?1), respectively. The calculated part of methane consumed by methanotrophic bacteria in the aerated part of the landfill was 13(±7) g C CH₄ m^?2 d^?1 (or 1.1(±0.6) mol CH₄ m^?2 d^?1) on average.     

Stable carbon isotopic composition of tree rings from a pine tree from Augustów Wilderness,Poland, as a temperature and local environment conditions indicator

Tree rings can be used as archives of climatic and environmental data with annual resolution. Tree rings widths, maximum late wood density and other parameters as stable composition in tree rings can be used for the reconstruction of past climatic and environmental changes. Stable carbon isotope ratios in tree rings may provide valuable information on past climatic conditions. ¹³C/¹²C ratios of plant organic matter can reflect corresponding ¹³C/¹²C ratio of atmospheric CO₂ during formation of the rings. Investigations of isotopic carbon composition in tree rings from in the ecologically clean the Augustów Wilderness region in the north-eastern part of Poland (22°58′E, 53°51′N) (nowadays a sanctuary) were undertaken. Series of δ¹³C in α-cellulose and in wholewood were acquired. Those measurements constituted a part of more complex investigations of carbon isotope composition in tree rings including the measurements of radiocarbon concentration and tree ring widths. This article presents preliminary results. It is argued that contrary to the tree ring widths and δ¹³C in wholewood that do not reveal significant correlation with temperature, the variation of δ¹³C in the latewood α-cellulose is correlated with combined July and August temperatures.     

Environmental Isotopes as a Useful Tool for Studies at Mixed Uranium Mill Tailings Sites

Abstract

Groundwaters in the area of a mixed landfill (domestic waste above uranium mill tailings) in Dresden (Saxony, Germany) were investigated for their isotope signatures to distinguish between different groundwater types. To determine between the two contamination sources (waste and uranium mill tailings) a multi parameter interpretation was done using both, the main hydrochemical parameters the radionuclides ²³⁴U, ²³⁸U, ²²⁶Ra and ²²²Rn as well as the environmental isotopes of the elements hydrogen, oxygen, sulphur and carbon.

The seepage water from the landfill shows higher δ³⁴S, δ¹⁸O and tritium values as the inflow. The tritium values give an idea about water movement in the dump and mean residence time of the groundwater. The water in the dump shows varying δ¹³C values which indicate different processes occurring in the dump.     

Solar Radiation Affects Modern Tree-Ring δ13C: Observations at a Cool-Temperate Forest in Japan

Abstract

Tree-ring δ¹³C of shoots in two deciduous tree species (Acer rufinerve and Clerodendrum trichotomum) at the cool-temperate forest in Japan showed similar trends with time for four years. The variation of tree-ring δ¹³C positively correlated with the total solar radiation during the growing season, although it did not always correlate with other climatic parameters. Tree-ring δ¹³C of a tree-core from 1982 to 1993 in A. rufinerve also correlated strongly with the total solar radiation. We conclude that solar radiation most probably affected the tree-ring δ¹³C in this moist cool temperate forest, because increasing solar radiation can cause Ci (intercellular CO₂ partial pressure) to decrease, consequently increasing δ¹³C.