Analysis Of Carbon Isotope Composition Research Articles

Using isotope-geochemical criteria for Olympiadinskoye gold deposit gas system genesis diagnosis

   The authors studied modern gas manifestations spatially associated with the ore deposits in the Kaitbinskaya lithological-facies zone of the Yenisei Ridge.   The purpose of the research is to obtain scientifically based data on the genesis of gaseous and vaporous fluids in various sampling environments of the Vostochny open-pit mine of the Olympiadinskoye gold deposit: rocks, natural waters, free-flowing gases from blastholes and air of the surface atmosphere.   It has been conducted a complex of field and analytical works including degassing, gas chromatography, pyrolysis of the organic substance of lithified and metamorphosed deposits, analysis of carbon isotopic composition in carbon dioxide and methane in fluidal systems. In order to study normal gas-geochemical field (natural background) of the work area an atmospheric geochemical survey was carried out at the reference site – an “environmentally friendly” site with the minimal influence of technogenic factors. It has been determined that the surface atmosphere of the site had been formed due to the landscape and geomorphological conditions of the Kaitbinskaya lithological-facies zone as well as fluidal systems of deep horizons. The latter, due to the presence of an extensive network of disruptive disturbances and diffusion-filtration processes of mass transfer reached the zone of exploratory geochemical sounding. The conducted pyrolytic studies of rocks have proved that within the open section of the Vostochny open-pit mine the organic substance of the Kordinskaya series of the lower Riphean deposits has implemented its oil and gas generation potential and cannot serve the formation source of abnormal gas fields of the Olympiadinskoye gold deposit. The studied gas systems are polygenic in nature and, being allochthonous to the host sediments, are formed without the participation of gases from the upper generating (bio) zone. According to isotope-geochemical criteria, these are mainly endogenous and naphthidogenic fluids identical to the gas condensate accumulations of the Yurubcheno-Tokhomskaya oil and gas accumulation zone.

High-precision analysis of carbon isotopic composition for individual CO2 inclusions via Raman spectroscopy: Addressing issues arising from the laser-heating effects

The carbon isotopic composition of carbon dioxide fluid inclusions trapped within minerals reflects the origin and evolution of the CO2-bearing fluids and melts. Recently, we developed a highly accurate method using Raman spectroscopy to determine the carbon isotopic composition of CO2 fluid inclusions, by simultaneously collecting 13CO2 and hot bands at a controlled temperature, and using the peak height ratio of 13CO2 and one of hot bands near 1410 cm−1 (HR) to determine δ13C value. This microanalytical technique enables precise measurements of the δ13C values of different CO2 fluid inclusions within zoned mineral crystals to reveal the multiple-stages evolution of CO2-bearing fluids and melts. However, when studying fluid inclusions hosted within high laser heating coefficient minerals such as olivine and pyroxene in mantle xenoliths, local temperature near the inclusions will be higher than the temperature controlled by heating-cooling stage. To address this issue, we examined the effects of laser heating on CO2 isotopic standard samples sealed in the silica capillary, and developed a novel procedure to determine the δ13C values of natural fluid inclusions by using two CO2 standard samples with known carbon isotopic compositions. The proposed workflow successfully determines the δ13C values of natural CO2 inclusions, with an average deviation of 0.58 ‰ between the measurements and the model.

High-precision analysis of carbon isotopic composition for individual CO2 inclusions via Raman spectroscopy to reveal the multiple-stages evolution of CO2- bearing fluids and melts

The carbon isotopic composition of CO2 inclusions trapped in minerals reflects the origin and evolution of CO2-bearing fluids and melts, and records the multiple-stages carbon geodynamic cycle, as CO2 took part in various geological processes widely. However, the practical method for determination isotope composition of individual CO2 inclusion is still lacking. Developing a microanalytical technique with spatial resolution in micrometers to precisely determinate the δ13C value of individual CO2 inclusion, will make it possible to analyze a tiny portion of a zoning mineral crystal, distinguish the differences in micro-scale, and possible to find many useful information that could not be obtained with the bulk extraction and analysis techniques. In this study, we systematically collected Raman spectra of CO2 standards with different δ13C values (−34.9 ‰ to 3.58 ‰) at 32.0 °C and from ∼7.0 MPa to 120.0 MPa, and developed a new procedure to precisely determinate the δ13C value of individual CO2 inclusion. We investigated the relationship among the Raman peak intensity ratio, δ13C value, and CO2 density, and established a calibration model with high accuracy (0.5 ‰−1.5 ‰), sufficient for geological application to distinguish different source of CO2 with varying δ13CO2. As a demonstration, we measured the δ13C values and the density of CO2 inclusions in the growth zones of alkali basalt-hosted corundum megacrysts from Changle, Shandong Province. We found the significant differences of density and δ13C between the CO2 inclusions in the core of corundum and those inclusions in the outer growth zones, the δ13C value decreases from core to rim with decreasing density: δ13C values are from −7.5 ‰ to −9.2 ‰ for the inclusions in the core, indicating the corundum core was crystallized from mantle-derived magmas; from −13.5 ‰ to −18.5 ‰ for CO2 inclusions in zone 1 and from −16.5 ‰ to –22.0 ‰ for inclusions in zone 2, indicating the outer zones of corundum grew in a low δ13C value environment, resulted from an infilling of low δ13C value fluid and/or degassing of the ascending basaltic magma.

Leaf and tree water-use efficiencies of Populus deltoides × P. nigra in mixed forest and agroforestry plantations.

In a global context where water will become a scarce resource under temperate latitudes, managing tree plantations with species associations, i.e., forest mixture or agroforestry, could play a major role in optimizing the sustainable use of this resource. Conceptual frameworks in community ecology suggest that, in mixed plantations, environmental resources such as water may be more efficiently used for carbon acquisition and tree growth thanks to niche complementarity among species. To test the hypotheses behind these conceptual frameworks, we estimated water-use efficiency (WUE) for poplar trees grown in a monoculture, in association with alder trees (forest mixture) and in association with clover leys (agroforestry) in an experimental plantation located in northeastern France. Water-use efficiency was estimated (i) at leaf level through gas exchange measurements and analysis of carbon isotope composition, (ii) at wood level through carbon isotope composition and (iii) at tree level with sap flow sensors and growth increment data. We hypothesized that species interactions would increase WUE of poplars in mixtures due to a reduction in competition and/or facilitation effects due to the presence of the N2-fixing species in mixtures. Poplar trees in both mixture types showed higher WUE than those in the monoculture. The differences we found in WUE between the monoculture and the agroforestry treatment were associated to differences in stomatal conductance and light-saturated net CO2 assimilation rate (at the leaf level) and transpiration (at the tree level), while the differences between the monoculture and the forest mixture were more likely due to differences in stomatal conductance at the leaf level and both transpiration and biomass accumulation at the tree level. Moreover, the more WUE was integrated in time (instantaneous gas exchanges < leaf life span < seasonal wood core < whole tree), the more the differences among treatments were marked.

Isotope composition of carbon dioxide and methane in a tropical urban atmosphere

ABSTRACT This work presents a weekly carbon isotope composition analysis (June 2017–January 2018) of carbon dioxide (CO2) and methane (CH4) in a tropical urban atmosphere (Central Valley, Costa Rica). δ13C values of CO2 and CH4 ranged from –12.2 to –5.9 ‰, and from –51.6 to –46.3 ‰, respectively. Mixing ratios of CO2 and CH4 varied from 384.2 to 528.5 ppmv, and from 1.860 to 2.613 ppmv, respectively. δ13C spatial variation and mixing ratios of CO2 and CH4 were influenced by the atmospheric stability and air circulation patterns in the metropolitan area. Low δ13C values and large mixing ratios were observed in the southwestern area of the valley during the rainiest period (September–November). Preliminary linear relationships between reciprocal CO2 mixing ratios and δ13C values indicate that CO2 emissions in the Central Valley are probably related to respiration processes and fossil fuel combustion, although CO2 enriched in 13C from volcanic degassing was also detected. Under stable atmospheric conditions, CH4 data seems to reflect the influence of emissions near the sampling sites. These preliminary results based on the carbon isotope technique demonstrate potential for carrying out atmospheric studies at tropical urban locations with different terrain characteristics and atmospheric mixing conditions.

A new method for determination of the photosynthetic pathway in grasses

An easy and inexpensive method of determining the photosynthetic pathway in grasses using a dye widely used in microscopy. To evaluate the efficiency of a new histochemical test for determination of the photosynthetic pathway in grasses (Poacea). Leaves of 58 grass species were sectioned transversally, and the sections treated with a 2% sodium hypochlorite solution to clarify the tissue. After discoloration, sections were washed with distilled water and double-stained with astra blue and safranin (1% each in 50% ethanol) for 1 min. Sections were then mounted between microscopy glass slides and coverslips using water. Grass species showing red staining of the bundle sheath cells were considered C4, and species with translucent bundle sheath were considered C3. The results of the histochemical test were then compared with results from carbon isotope composition analysis and the relevant scientific literature. Observations from the histochemical test were congruent with results from δ13C isotope composition analysis, and with data previously presented in the scientific literature. The proposed histochemical test proved efficient for characterization of the photosynthetic pathway in the tested grasses; however, the method should be further tested in a greater number of grass species, encompassing, preferably, all Poacea subfamilies. Future studies may elucidate if the proposed method can effectively be used in other botanical families. Furthermore, additional investigations may determine whether the phenolic compounds indicated by the histochemical test are exclusive to the bundle sheath of C4 grasses and if possible relations exist between these phenolic compounds and the C4 photosynthetic pathway in grasses.

Riverine discharges impact physiological traits and carbon sources for shell carbonate in the marine intertidal mussel Perumytilus purpuratus

AbstractAnthropogenic modification watersheds and climate change have altered export from fluvial systems causing changes to the carbonate chemistry of river‐influenced near shore environments. To determine the possible effects of riverine discharges on the mussel Perumytilus purpuratus, we performed in situ transplant experiments between river‐influenced and open coastal habitats with contrasting seawater carbonate chemistries (i.e., pCO2, pH, Ωar) across four regions covering a wide latitudinal range (32°55′S–40°10′S). The river‐influenced habitats selected for transplant experiments were different than open coastal habitats; with higher pCO2 (354–1313 μatm), lower pH (7.6–7.9) and Ωar values (0.4–1.4) than in open coastal area. Growth, calcification, metabolism were measured in a reciprocal transplant experiment to determine physiological responses associated with river‐influenced sites and non‐influenced control sites. Growth and calcification rates were higher in river‐influenced habitats; however the organisms in this area also had lower metabolic rates, possibly due to enhanced food supply from river systems. Further analysis of carbon isotopic composition (δ13C) indicated that the relative contribution of seawater dissolved inorganic carbon (DIC) to the carbonate shells of P. purpuratus was much higher than respiratory carbon. Nevertheless, P. purpuratus incorporated between 7% and 26% of metabolic carbon in the shell depending on season. There was a strong, significant relationship between δ13CPOC and δ13CTissue, which likely influenced the isotopic composition of the shell carbon.

Assessment of a degree of geochemical maturation and activity of a closed landfill site in Poland

The study was conducted around a reclaimed municipal landfill site, located in the suburbs of Otwock, about 25 km south-west of Warsaw (Poland). The research was carried out about 15 years after the landfill site ceased operation. According to the regulations on landfills sites in Poland (J. of Laws of 2002 No. 220 item 1858, Regulation of the Minister of Environment of 9 December 2002 on the scope, time, manner and conditions of landfill monitoring; J. of Laws of 2010 No. 238 item 1588, Regulation of the Minister of Environment of 8 December 2010 amending the regulation on the scope, time, manner and conditions of landfill monitoring), the monitoring period will end in 2021. Despite reclamation, the landfill site still affects the environment. The aim of this study was to assess the geochemical maturation of the stored waste and the landfill site activity by determining the current phase of the landfill site lifetime. This was achieved by means of non-standard application of carbon stable isotopes for the assessment of the landfill activity combined with conventional methods for measuring COD, BOD, DOC, BOD/COD ratio, and H2S and O2 content in biogas. An analysis of carbon isotopic composition and COD, BOD, DOC of the leachate-contaminated groundwater and O2 concentration in biogas indicated that the landfill site was between the methanogenic phase and air intrusion phase. However, BOD/COD ratio and H2S concentration in the biogas suggested that the landfill site is still active and the wastes contain readily biodegradable organic matter. The impact of the landfill site on the environment seems quite significant. In this case, and in other situations when the impact of a landfill site on the environment is high after the post-closure stage, the monitoring period should be extended.

Preparation of starch and soluble sugars of plant material for the analysis of carbon isotope composition: a comparison of methods

Starch and soluble sugars are the major photosynthetic products, and their carbon isotope signatures reflect external versus internal limitations of CO(2) fixation. There has been recent renewed interest in the isotope composition of carbohydrates, mainly for use in CO(2) flux partitioning studies at the ecosystem level. The major obstacle to the use of carbohydrates in such studies has been the lack of an acknowledged method to isolate starch and soluble sugars for isotopic measurements. We here report on the comparison and evaluation of existing methods (acid and enzymatic hydrolysis for starch; ion-exchange purification and compound-specific analysis for sugars). The selectivity and reproducibility of the methods were tested using three approaches: (i) an artificial leaf composed of a mixture of isotopically defined compounds, (ii) a C(4) leaf spiked with C(3) starch, and (iii) two natural plant samples (root, leaf). Starch preparation methods based on enzymatic or acid hydrolysis did not yield similar results and exhibited contaminations by non-starch compounds. The specificity of the acidic hydrolysis method was especially low, and we therefore suggest terming these preparations as HCl-hydrolysable carbon, rather than starch. Despite being more specific, enzyme-based methods to isolate starch also need to be further optimized to increase specificity. The analysis of sugars by ion-exchange methods (bulk preparations) was fast but produced more variable isotope compositions than compound-specific methods. Compound-specific approaches did not in all cases correctly reproduce the target values, mainly due to unsatisfactory separation of sugars and background contamination. Our study demonstrates that, despite their wide application, methods for the preparation of starch and soluble sugars for the analysis of carbon isotope composition are not (yet) reliable enough to be routinely applied and further research is urgently needed to resolve the identified problems.

Carbon isotope composition of fossil charcoal reveals aridity changes in the NW Mediterranean Basin

AbstractAlthough several proxies for the inference of precipitation have been proposed, evidence of changes in aridity during the Holocene is scarce, and most is only qualitative. Moreover, precipitation regimes show relatively poor spatial correlations and can exhibit contrasting responses to global climate trends in different areas. Thus, there is a need to concentrate efforts at the local scale in order to increase the spatial resolution of palaeoclimate records, especially regarding water availability in semiarid zones. We propose the analysis of carbon isotope composition (δ13C) in fossil charcoal (routinely recovered from archaeological sites) to quantify changes in water availability in the past. We applied this approach to reconstruct variations in aridity during the last four millennia in the Ebro Depression (NE Iberian Peninsula). First, we studied the effect of carbonization over a range of temperatures (300–500°C) on the δ13C of Aleppo pine (Pinus halepensis Mill.) wood cores, collected from nine locations in NE Iberian Peninsula with distinct water availability. Despite significant changes in δ13C caused by carbonization, the original climatic signal of wood δ13C was well preserved. Moreover, δ13C shifts induced by this process were successfully corrected by accounting for variation in charcoal carbon concentration (%C). After removing the effect of carbonization, we estimated annual precipitation (P) and the ratio between annual precipitation and evapotranspiration (P/E) from the δ13C of fossil charcoal. In general, estimated water availability in the past was higher than present values, indicating that latter‐day (semiarid) conditions are mostly due to recent climate changes. The good agreement between our findings and other evidence indicates that the analysis of δ13C in charcoal may be useful to expand current palaeoclimate records as it provides a complementary (and quantitative) source of information to assess climate dynamics.

Investigating the record of Permian climate change from argillaceous sedimentary rocks, Oman

A standard method for the analysis of carbon isotope composition of bulk organic matter (δ 13 C bulk ) in palaeoenvironmental and stratigraphic studies of sedimentary basins associated with hydrocarbons is suggested. This method includes the removal of interstitial hydrocarbon within the sediments, which is shown to have a negative effect on δ 13 C. Using the method, a δ 13 C bulk trend ( c . −21 to −24‰) was found within the Lower Permian Al Khlata and lower Gharif formations of Thuleilat-16 and -42 well sections, south Oman. Palaeontological and sedimentological evidence indicates considerable palaeoenvironmental change, from a cold climate lowland fern flora and upland primitive conifer flora low in the sequence, to a lowland cycad-like and upland glossopterid or other gymnospermous flora higher in the sequence. The lithologies range from glacial diamictite at the base to calcrete horizons and redbeds at the top. It is therefore likely that the δ 13 C bulk trend is related to palaeoenvironmental change.

Development of biochemical specialization and organelle partitioning in the single‐cell C4 system in leaves of Borszczowia aralocaspica (Chenopodiaceae)

The terrestrial plant Borszczowia aralocaspica (Chenopodiaceae) has recently been shown to contain the entire C(4) photosynthesis mechanism within individual, structurally and biochemically polarized chlorenchyma cells rather than in a dual cell system, as has been the paradigm for this type of carbon fixation (Nature 414: 543-546, 2001). Analysis of carbon isotope composition and (14)CO(2) fixation shows that photosynthesis and growth of B. aralocaspica occurs through carbon acquired by C(4) photosynthesis. The development of this unique single-cell C(4) system in chlorenchyma cells was studied by analysis of young (0.2-0.3 cm length), intermediate (ca. 0.5-0.6 cm length), and mature leaves (ca. 3 cm length). The length of chlorenchyma cells approximately doubles from young to intermediate and again from intermediate to the mature leaf stage. In young chlorenchyma cells, there is a single type of chloroplast; the chloroplasts are evenly distributed throughout the cytosol, and all contain starch and rubisco. During leaf development, the activities of phosphoenolpyruvate carboxylase (PEPC; which is cytosolic), rubisco, and pyruvate,Pi dikinase (PPDK) increase on a chlorophyll basis. As leaves mature, chloroplasts differentiate into two distinct structural and biochemical types that are spatially separated into the proximal and distal parts of the cell (the proximal end being closest to the center of the leaf). The early stages of this polarization are observed in intermediate leaves, and the polarization is fully developed in mature leaves. The chloroplasts in the distal ends of the cell have reduced grana and little starch, while those at the proximal ends have well-developed grana and abundant starch. In mature leaves, PPDK is expressed in chloroplasts at the distal end of the cells, while rubisco and adenosine diphosphate glucose (ADPG) pyrophosphorylase are selectively expressed in chloroplasts at the proximal end of the cell. Mitochondrial polarization also occurs during development as nicotinamide-adenine dinucleotide phosphate-malic enzyme (NAD-ME) and the photorespiratory enzyme glycine decarboxylase are expressed in mature but not young leaves and are localized in mitochondria at the proximal end of the cells. The data show that single-cell C(4) develops from a single pool of identical organelles that develop differential biochemical functions and spatial partitioning in the cell during maturation.

Features of major greenhouse gases in loess, Shanxi Province, China

According to the investigations of five loess sections in Shanxi Province, China, it was found that the concentrations of the major greenhouse gases CO2, CH4 and N2O in loess-paleosol sequences are generally high, even sometimes may be several times or scores of times higher than their atmospheric concentrations respectively. Although the CO2 concentration in the same loess section shows poor regularity among different layers, it increases slowly from north to south in space. The CH4 concentration in the layers under Malan Loess is much higher than that in the atmosphere, although it is not high in Malan Loess. Most of the δ13C values of CO2 in loess are −11.14‰–−15.48‰ (relative to PDB standard). Analysis of carbon isotopic compositions of CO2 indicates that the main source of CO2 in loess section is decomposition of ‘stable’ organic matters by microbes. The δ13Cg of CO2 is a little heavier than organic source for exchanging carbon isotope with carbonate in loess. The abundant carbonate in loess not only makes the loess a huge carbon reservior but also adjusts atmospheric CO2 during the formation of deuterogenic carbonate.

Correlation between the Carbon Isotope Discrimination in Leaf Starch and Sugars of C3 Plants and the Ratio of Intercellular and Atmospheric Partial Pressures of Carbon Dioxide

Carbon isotope discrimination (Delta) was analyzed in leaf starch and soluble sugars, which represent most of the recently fixed carbon. Plants of three C(3) species (Populus nigra L. x P. deltoides Marsh., Gossypium hirsutum L. and Phaseolus vulgaris L.) were kept in the dark for 24 hours to decrease contents of starch and sugar in leaves. Then gas exchange measurements were made with constant conditions for 8 hours, and subsequently starch and soluble sugars were extracted for analysis of carbon isotope composition. The ratio of intercellular, p(i), and atmospheric, p(a), partial pressures of CO(2), was calculated from gas exchange measurements, integrated over time and weighted by assimilation rate, for comparison with the carbon isotope ratios in soluble sugars and starch. Carbon isotope discrimination in soluble sugars correlated strongly (r = 0.93) with p(i)/p(a) in all species, as did Delta in leaf starch (r = 0.84). Starch was found to contain significantly more (13)C than soluble sugar, and possible explanations are discussed. The strong correlation found between Delta and p(i)/p(a) suggests that carbon isotope analysis in leaf starch and soluble sugars may be used for monitoring, indirectly, the average of p(i)/p(a) weighted by CO(2) assimilation rate, over a day. Because p(i)/p(a) has a negative correlation with transpiration efficiency (mol CO(2)/mol H(2)O) of isolated plants, Delta in starch and sugars may be used to predict differences in this efficiency. This new method may be useful in ecophysiological studies and in selection for improved transpiration efficiency in breeding programs for C(3) species.