Measuring δ(13)C values of atmospheric acetaldehyde via sodium bisulfite adsorption and cysteamine derivatisation

δ(13)C values of gaseous acetaldehyde were measured by gas chromatograph-combustion-isotope ratio mass spectrometer (GC-C-IRMS) via sodium bisulfite (NaHSO(3)) adsorption and cysteamine derivatisation. Gaseous acetaldehyde was collected via NaHSO(3)-coated Sep-Pak(?) silica gel cartridge, then derivatised with cysteamine, and then the δ(13)C value of the acetaldehyde-cysteamine derivative was measured by GC-C-IRMS. Using two acetaldehydes with different δ(13)C values, derivatisation experiments were carried out to cover concentrations between 0.009×10(-3) and 1.96×10(-3)?mg·l(-1)) of atmospheric acetaldehyde, and then δ(13)C fractionation was evaluated in the derivatisation of acetaldehyde based on stoichiometric mass balance after measuring the δ(13)C values of acetaldehyde, cysteamine and the acetaldehyde-cysteamine derivative. δ(13)C measurements in the derivertisation process showed good reproducibility (<0.5?‰) for gaseous acetaldehyde. The differences between predicted and measured δ(13)C values were 0.04-0.31?‰ for acetaldehyde-cysteamine derivative, indicating that the derivatisation introduces no isotope fractionation for gaseous acetaldehyde, and obtained δ(13)C values of acetaldehyde in ambient air at the two sites were distinct (-34.00?‰ at an urban site versus-31.00?‰ at a forest site), implying potential application of the method to study atmospheric acetaldehyde.     

Measuring δ13C of atmospheric air with non-dispersive infrared spectroscopy

The potential use of non-dispersive infrared spectroscopy for measuring δ¹³C in air is demonstrated. This technique has already been successfully established for breath test analyses in medical diagnostics, where the CO₂ concentration ranges from 1 to 5 vol.% in the exhaled breath of vertebrates. For breath tests, the sensitivity and accuracy has been improved to reach a standard deviation of 0.2 ‰ (delta-value). Further adjustments were necessary to improve the sensitivity of the instrument at concentration levels typical of atmospheric air. The long-term stability is given by a standard deviation of 0.35 ‰ for CO₂ concentrations of about 400 ppm with signal averaging over 60 s.     

Diurnal variability of δ13C and δ18O of atmospheric CO2 in the urban atmosphere of Kraków,Poland

This article presents the results of measurements of the isotopic composition and concentration of atmospheric carbon dioxide, performed on air samples from Kraków (Southern Poland) in different seasons of the year. A simple isotope mass balance model has been applied to determine the contributions of different sources of CO₂ to the urban atmosphere of Kraków city: the latitudinal/regional background, biospheric contributions and anthropogenic emissions. The calculations show that during the summer and early autumn the dominant contribution to local CO₂ peaks is the biosphere, making up to 20% of atmospheric CO₂ during the nocturnal temperature inversion in the lower troposphere. During early spring and winter, anthropogenic emissions are the main local source.     

Field-deployable measurements of free-living individuals to determine energy balance: fuel substrate usage through δ13C in breath CO2 and diet through hair δ13C and δ15N values

Carbon isotopes of breath CO₂ vary depending on diet and fuel substrate used. This study examined if exercise-induced δ¹³C-CO₂ changes in substrate utilization were distinguishable from baseline δ¹³C-CO₂ variations in a population with uncontrolled diet, and compared hair isotope values and food logs to develop an isotope model of diet. Study participants included nine women with diverse Body Mass Index (BMI), age, ancestry, exercise history, and diet. Breath samples were collected prior to and up to 12?h after a 5- or 10?K walk/run. Indirect calorimetry was measured with a smartphone-enabled mobile colorimetric device, and a field-deployable isotope analyzer measured breath δ¹³C-CO₂ values. Diet was assessed by food logs and δ¹³C, δ¹⁵N of hair samples. Post-exercise δ¹³C-CO₂ values increased by 0.54?±?1.09‰ (1 sd, n?=?9), implying enhanced carbohydrate burning, while early morning δ¹³C-CO₂ values were lower than daily averages (p?=?0.0043), indicating lipid burning during overnight fasting. Although diurnal δ¹³C-CO₂ variation (1.90?±?0.77‰) and participant baseline range (3.06‰) exceeded exercise-induced variation, temporal patterns distinguished exercise from dietary isotope effects. Hair δ¹³C and δ¹⁵N values were consistent with a new dietary isotope model. Notwithstanding the small number of participants, this study introduces a novel combination of techniques to directly monitor energy balance in free-living individuals.     

The impact of solar and atmospheric parameter uncertainties * on the measurement of θ13 and δ

We present in this paper the analysis of the measurement of the unknown PMNS parameters θ₁₃ and δ at future LBL facilities performing complete three parameters fits, each time fully including in the fit one of the atmospheric and solar oscillation parameters within its present (future) error. We show that, due to the presence of degeneracies, present uncertainties on θ₂₃ and worsen significantly the precision on (θ₁₃,δ) at future LBL experiments. Only if a precision on the atmospheric parameters at least similar to what expected at T2K-I is reached, then the sensitivities to θ₁₃ and δ that have been presented in the literature for many facilities (where θ₂₃ and are generally considered as fixed external inputs) can indeed be almost recovered. On the other hand, the impact on this measurement of the uncertainties on the solar parameters, θ₁₂ and is already negligible. Our analysis has been performed using three reference setups: the SPL Super-Beam and the standard low-γ β-Beam, both aiming toward a Mton Water Čerenkov detector located at L = 130 km; the 50 GeV Neutrino Factory with a 40 kton Magnetized Iron Detector to look for the "golden channel" ν_e → ν_μ with baseline L = 3000 km and a 4 kton Emulsion Cloud Chamber to look for the "silver channel" ν_e → ν_τ with baseline L = 732 km. Received: 19 July 2005, Revised: 30 September 2005, Published online: 11 November 2005 PACS: 14.60.Pq, 14.60.Lm     

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.     

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.     

A robust and fast method of sampling and analysis of δ13C of dissolved inorganic carbon in ground waters

The stable carbon isotopic composition of dissolved inorganic carbon (δ¹³C_DIC) is traditionally determined using either direct precipitation or gas evolution methods in conjunction with offline gas preparation and measurement in a dual-inlet isotope ratio mass spectrometer. A gas evolution method based on continuous-flow technology is described here, which is easy to use and robust. Water samples (100–1500 μl depending on the carbonate alkalinity) are injected into He-filled autosampler vials in the field and analysed on an automated continuous-flow gas preparation system interfaced to an isotope ratio mass spectrometer. Sample analysis time including online preparation is 10 min and overall precision is 0.1 ‰. This method is thus fast and can easily be automated for handling large sample batches.     

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.     

Determination of δ13 CV−PDB and δ15NAIR values of cocaine from a big seizure in Germany by stable isotope ratio mass spectrometry†

In this study, δ¹³C_{V? PDB} and δ¹⁵N_AIR values of 132 cocaine samples from a big seizure in Germany in 2002 were determined using elemental analyser isotope ratio mass spectrometry. The 1.2 tons of cocaine were packed in 1 kg packages and the cocaine bricks inside these packages showed certain logos. Twenty different logos could be identified. Results show a large variability among some samples, for δ¹⁵N_AIR values ranging from?17 to ?2 ‰. Furthermore, the possibility of linking samples with the same logo was checked. The results show that, in general, there is no relationship between the determined isotope ratio and a certain logo.     

Effect of different lipid extraction methods on δ13C of lipid and lipid-free fractions of fish and different fish feeds

For many ecological applications of stable carbon isotope techniques, it is necessary to separate the lipid and lipid-free fractions. The effect of different lipid extraction methods on the isotope signature of the remaining lipid-free matter as well as the lipid fraction was tested. A hot extraction form of the Soxhlet method using petrol-ether was compared with two liquid-liquid extraction methods for lipid determination described by Bligh and Dyer and Smedes. Solid samples of fish and different natural food items were subjected to extraction and the carbon isotope ratios in lipid and lipid-free matter determined by IRMS. All methods were suitable for lipid extraction from all samples analysed here and did not cause biologically relevant differences (>1) in carbon isotopic ratios, except the Bligh and Dyer extraction method using chloroform which caused systematic errors for δ ¹³C when applied to diatoms.     

Adsorption of sodium ions and hydrated sodium ions on a hydrophobic graphite surface via cation-π interactions

Using density functional theory computation, we show that sodium ions and hydrated sodium ions can be strongly adsorbed onto a hydrophobic graphite surface via cation-π interactions. The key to this cation-π interaction is the coupling of the delocalized π states of graphite and the empty orbitals of sodium ions. This finding implies that the property of the graphite surface is extremely dependent on the existence of the ions on the surface, suggesting that the hydrophobic property of the graphite surface may be affected by the existence of the sodium ions.     

The effect of different fish feed compositions on δ13C and δ15N signatures of sea bass and its potential value for tracking mariculture-derived nutrients

Increasing demand for fish and seafood calls for an expansion of aquaculture production. At the same time, the status of the marine environment must not be jeopardised. Stable isotopes are potential markers for tracking feed-based nutrient flows from aquaculture into marine biota. Here, we demonstrate how four experimental diets (main protein components: fishmeal, soya protein concentrate, wheat gluten, and Jatropha kernel meal) and a commercial diet induce characteristic δ¹³C and δ¹⁵N signals in sea bass (Dicentrarchus labrax) during nine weeks of laboratory feeding under replicate conditions. The plant-protein-based diets containing wheat gluten and soya, and the commercial feed consistently induced the largest isotopic differentiation of the fish, both from the feed source and from the pre-experimental condition. The large difference of the fish on plant-protein-based diets compared to the range of natural isotopic variation in the macrozoobenthos of the North Sea lends support to the idea that plant-based feeds are suitable for tracing mariculture-derived organic matter under practical conditions. The commercial feed had a similar effect as the experimental feeds and would be a cost-effective option for an offshore aquaculture experiment.     

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).     

Characterisation of spatial variability and patterns in tree and soil δ13C at forested sites in eastern Canada

Wholistic isotopic studies provide a necessary foundation on which to build conceptual understanding of ecosystem development processes and provide the basis for further isotopic studies at a site or within an ecophysiological region. This study seeks to broadly characterise δ¹³C spatial variability and spatial patterns within soils and canopy tissues at five forest research sites in eastern Canada. We observe consistent and predictable patterns of leaf δ¹³C variation within trees and a consistent offset between woody and leafy tree tissues. Patterns are similar for both hardwoods and softwoods, but overall hardwoods had canopies that were more depleted in ¹³C. Soil carbon δ¹³C enrichment occurred with depth and appeared to vary according to site soil texture. Upper soil δ¹³C was intermediate between leaves and woody tissues, whereas deeper soil values suggested important contributions from more enriched tree tissues, such as persistent woody debris and possibly roots. The relationship between aboveground and belowground signatures suggests functional or developmental differences between study sites.     

Wild Rabbit Host and Some Parasites Show Trophic-Level Relationships for δ13C and δ15N: A First Report

Abstract

We report the first isotopic study of an animal host-parasite system. Parasitic, intestinal nematodes, Graphidium strigosum and Passalurus ambiguus, were ¹⁵N-enriched relative to their host, the European rabbit Oryctolagus cuniculus, while parasitic cestodes, Cittataenia denticulata and Mosgovoyia pectinata, were ¹⁵N-depleted, suggesting different trophic relationships. Host embryos were more similar in their δ¹³C and δ¹⁵N values to maternal muscle than were any of the parasites. Coprophagy, the direct recycling of food by the rabbit eating its own faeces, did not lead to isotopic differences between stomach contents and faeces, suggesting that the major point for isotopic discrimination in lagomorph nitrogen metabolism is in the animal rather than in the gut. We conclude that bulk δ¹³C and δ¹⁵N can reveal valuable new information about host-parasite relationships, and these could be explored further at the biochemical level using compound-specific isotopic analyses.     

The Effect of Diet Quality on δ(13)C and δ(15)N in the Tissues of Locusts, Locusta migratoria L

Abstract Locust nymphs were raised from hatching to adult locusts on either seedling wheat (C(3)) or maize (C(4)), to determine whether relative enrichments/depletions of (15)N and (13)C 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 δ(15)N 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 δ(15)N and δ(13)C suggest that substrate recycling was occurring on the low quality maize diet. Therefore diet quality determines the enrichment/depletion in δ(15)N and δ(13)C within organisms.     

First field-based observations of δ2H and δ18O values of event-based precipitation,rivers and other water bodies in the Dzungarian Gobi,SW Mongolia

For certain remote areas like Mongolia, field-based precipitation, surface and ground water isotopic data are scarce. So far no such data exist for the Mongolian Gobi desert, which hinders the understanding of isotopic fractionation processes in this extreme, arid region. We collected 26 event-based precipitation samples, 39 Bij river samples, and 75 samples from other water bodies in the Dzungarian Gobi in SW Mongolia over a period of 16 months for hydrogen and oxygen stable isotope analysis. δ²H and δ¹⁸O values in precipitation show high seasonal variation and cover an extreme range: 175?‰ for δ²H and 24?‰ for δ¹⁸O values. The calculated local meteoric water line (LMWL) shows the isotopic characteristics of precipitation in an arid region. Individual water samples fall into one of three groups: within, above or below the 95?% confidence interval of LMWL. Data presented provide a basis for future studies in this region.