Application Of Stable Isotope Analysis Research Articles

A protocol for distilling animal body water from biological samples and measuring oxygen and hydrogen stable isotopes via cavity ring-down spectroscopy

ABSTRACT The application of stable isotope analysis (SIA) to the fields of ecology and animal biology has rapidly expanded over the past three decades, particularly with regards to water analysis. SIA now provides the opportunity to monitor migration patterns, examine food webs, and assess habitat changes in current and past study systems. While carbon and nitrogen SIA of biological samples have become common, analyses of oxygen or hydrogen are used more sparingly despite their promising utility for tracing water sources and animal metabolism. Common ecological applications of oxygen or hydrogen SIA require injecting enriched isotope tracers. As such, methods for processing and analyzing biological samples are tailored for enriched tracer techniques, which require lower precision than other techniques given the large signal-to-noise ratio of the data. However, instrumentation advancements are creating new opportunities to expand the applications of high-throughput oxygen and hydrogen SIA. To support these applications, we update methods to distill and measure water derived from biological samples with consistent precision equal to, or better than, ± 0.1 ‰ for δ 17O, ± 0.3 ‰ for δ 18O, ± 1 ‰ for δ 2H, ± 2 ‰ for d-excess, and ± 15 per meg for Δ 17O.

Assessing the diet of modern and archaeological guanacos from the Great Chaco in Córdoba, Argentina, through stable isotope analysis (δ13C, δ15N) of bone and dentin collagen: Implications for paleoenvironmental and zooarchaeological studies

The application of stable isotope analyses allows a diachronic characterisation of species habitat and feeding behaviour, information of utmost importance for zooarchaeological research. In South America, the former distribution of the guanaco ( Lama guanicoe) encompassed a much larger territory than the current one. Within the Argentinean Great Chaco, only a small native population persists in Northwestern Córdoba province, Central Argentina, where it was once widely distributed. In this paper, we present the first set of dentin and collagen δ13C and δ15N values for this relict population ( N = 18) along with archaeological data of guanaco specimens ( N = 19) dated to the Middle and Late Holocene from the nearby Ongamira valley. Neither deciduous and permanent teeth nor males and females show marked differences within the modern samples. Both modern and archaeological guanaco δ13C values indicate a mixed diet of C3 and, to a lesser extent, C4 plants. Conversely, the δ15N values exhibit distinct signals between the Arid and the Mountain Chaco subregions. The diet breadth of the archaeological guanacos suggests the use of transitional or ecotonal environments, also reflected in the size of their isotopic niche as opposed to modern guanacos. Regarding the timing of the species retraction in the region, there is no evidence of a shift in its habitat during the period between ~4700 and 190014C years BP. We suggest their retraction probably occurred later than previously proposed in regional zooarchaeological models.

The diet of the human groups buried in a late- and post-Medieval rural parish cemetery in Libkovice (Czech Republic)

Libkovice is a village in the northwestern Czech Republic that was demolished at the end of the last century due to the expansion of a nearby mine. The former church cemetery has been a subject to bioarchaeological excavation and research, where some 850 burials from the 13th to the 19th Century have been discovered so far. With the application of stable isotope analysis, it has also been possible to uncover the dietary patterns of this exemplary rural Central European community, which was the aim of this study. The materials analysed here consist of samples from long bones of 56 burials and 18 animal bones discovered in Libkovice during the 2019/21 excavations. It has been employed stable carbon (δ13C) isotope analysis to determine the average contributions of foods derived from the C3 plants. Statistically significant differences were found between the analyzed fauna and human samples for nitrogen (F=47.4 p<0.05) and carbon (F=19.18 p<0.05). There were no statistically significant differences in the analyzed animal and human samples between the specify centuries. When considering the ages of various human individuals, the results indicated statistically significant differences in nitrogen isotopes (F= 7.71 p<0.05) between children from the infants I group and older children together with adults from the Middle Ages, as well as between children from the infants I group and adults (F= 3.3, p<0.05) from the modern times. The proportion of food from C3 plants that made up the diets of the studied population was on average 89%, and the potential proportion of freshwater fish in the diet could be higher than 80%. The similarity between the chronologically diverse groups may indicate similar strategies for food acquisition. The results obtained for the population of Libkovice are very similar to the diets of the populations living in Central Europe broadly during the two periods.

How to use live sampling tissues and archived specimens in cetacean stable isotope research

Cetaceans are unique ecological engineers, and their restoration may have a crucial impact on the future structure of aquatic ecosystems, which calls for more investigations into their trophic ecology. Among current techniques, stable isotope analysis (SIA) has the advantages of non-invasive sampling and long timescales. However, the full benefits of SIA in cetacean research may not be achieved due to issues like different types of tissue between sampling methods and use of chemical preservation solutions in historical specimens. To address these challenges, we conducted a study on Narrow-ridged Finless Porpoises (Neophocaena asiaeorientalis). Multiple tissues from freshwater and marine subspecies, as well as tissues preserved using different solutions such as ethanol and formalin were collected for SIA. Linear mixed effects models were used for data analysis. Our results showed that, except for blubber, kidney, and stomach, differences between other tissues were correctable. In tissues from live sampling, we found no significant difference between blood and muscle, and skin could also be used for isotope analysis after proper correction. Ethanol preservation caused significant positive changes in δ13C and δ15N values of muscle, while formalin preservation caused negative changes in δ13C and δ15N. Our findings provide valuable insight into unifying data from stranded carcasses and live sampling, as well as correcting for the effect of chemical preservation on museum specimens. Findings from this research support further application of stable isotope analysis in the conservation of endangered finless porpoises, offer a reference for other similar cetaceans, and also provide guidance for chemical preservation when freezing conditions are not available.

Application of Stable Isotope Analysis for Detecting the Geographical Origin of the Greek Currants "Vostizza": A Preliminary Study.

There is a plethora of food products with geographical indications registered in the European Union without any study about their discrimination from other similar products. This is also the case for Greek currants. This paper aims to analyze if stable isotope analysis of C, N, and S could discriminate the Greek currants "Vositzza", registered as a product of Protected Designation of Origin, from two other currants registered as products of Protected Geographical Indication coming from neighboring areas. The first results show that the stable isotope ratio of sulfur is not detectable due to the very low sulfur content in the samples, and the analysis should be based on the stable isotope ratios of carbon and nitrogen to discriminate these products. The mean value of δ15N (1.38‱) of PDO "Vostizza" currants is lower than that of currants grown outside the PDO zone (2.01‱), while the mean value of δ13C of PDO "Vostizza" currants is higher (-23.93‱) in comparison to that of currants grown outside the PDO zone (-24.83‱). Nevertheless, the results indicate that with only two isotopic ratios, discrimination could not be achieved, and further analysis is required.

Where are you from? Isotopic tracing of juvenile Olrog’s Gulls from Mar Chiquita during the wintering season

ABSTRACT Individual traits such as age-class can have profound effects on space utilisation by individual birds, with juvenile birds more often exhibiting dispersive movements. We studied the origin of juvenile Olrog’s Gulls Larus atlanticus, a threatened species, using stable isotopes ratios of carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S). We analysed feathers from individuals captured in the wintering season at Mar Chiquita Coastal Lagoon, Argentina, and the potential trophic sources of their breeding sites at Bahía Blanca and San Blas. Mean δ13C was similar for trophic sources and mean δ15N was higher for Bahía Blanca. The δ34S showed a greater variation among prey species than among sites. The mean contributions of the main colonies resulted in assigning 37.5% individuals as from Bahía Blanca, 16.7% from San Blas, and 45.8% undetermined. Results indicate that Mar Chiquita coastal lagoon attracts juvenile Olrog’s Gulls dispersing from the two main breeding grounds of the species. This work is one of the first approaches to study the origin of dispersive juvenile larids through the application of stable isotope analysis. This isotopic approach allows obtaining trophic and movement information when it is not possible to use other tools.

Stable isotope analyses of amino acids reveal the importance of aquatic resources to Mediterranean coastal hunter-gatherers.

Determining the degree to which humans relied on coastal resources in the past is key for understanding long-term social and economic development, as well as for assessing human health and anthropogenic impacts on the environment. Prehistoric hunter-gatherers are often assumed to have heavily exploited aquatic resources, especially those living in regions of high marine productivity. For the Mediterranean, this view has been challenged, partly by the application of stable isotope analysis of skeletal remains which has shown more varied coastal hunter-gatherer diets than in other regions, perhaps due to its lower productivity. By undertaking a more specific analysis of amino acids from bone collagen of 11 individuals from one of the oldest and best-known Mesolithic cemeteries in the Mediterranean, at El Collado, Valencia, we show that high levels of aquatic protein consumption were achieved. By measuring both carbon and nitrogen in amino acids, we conclude that some of the El Collado humans relied heavily on local lagoonal fish and possibly shellfish, rather than open marine species. By contrast to previous suggestions, this study demonstrates that the north-western coast of the Mediterranean basin could support maritime-oriented economies during the Early Holocene.

Application of stable isotope analysis to evaluate the assimilation of protein sources in juvenile slipper lobsters (Thenus australiensis)

Stable carbon and nitrogen isotope analyses were used to evaluate the contribution of five protein sources to the growth of juvenile slipper lobster Thenus australiensis. Protein sources tested were fish meal, krill meal, lupin meal, soybean meal and a squid by-product meal. A commercial in confidence basal mix was utilised to produce five experimental feeds containing 30% of each protein source. Juvenile lobsters were fed daily at 5% of their body weight for 12 weeks. Lobster performance was assessed by survival, feed intake and growth performance, and the effects of protein source on nutrient assimilation and discrimination factor were determined. The squid by-product meal, soybean meal, and krill meal produced better growth performance and survival. The specific growth rate on lupin meal was significantly (p < 0.05) lower than all the other protein sources. Apparent feed intake was significantly (p < 0.001) higher in squid by-product meal than lupin meal but with no significant differences in feed efficiency ratio. Protein source assimilation proportion in lobster ranged from 7% for soybean meal to 32% for squid by-product meal, whereby squid by-product meal and fish meal (29%) were the only protein sources assimilated at approximately their dietary inclusion level (30%). Overall, squid by-product meal had the best growth performance, high survival, and the highest assimilation into growth. This study demonstrated the potential of stable isotopic analysis to screen protein sources, evaluate the nutritional performance of the experimental feeds, and provide a deeper insight into ingredient utilisation. This study also provides the first whole-body isotopic discrimination factors for juvenile lobster, which can determine ingredient contribution to growth in future studies.

Pesticide degradation in an integrated constructed wetland: Insights from compound-specific isotope analysis and 16S rDNA sequencing

Carbon isotope analysis and the 16S rDNA sequencing were adopted to investigate the degradation process of chlorpyrifos during its transport in the integrated constructed wetland (ICW). Firstly, the extent of concentration decrease of chlorpyrifos was examined, and the removal efficiency in the first 36 h was found to be the highest. The removal rate reached 96.83 % after 96 h, and this process fit to the first-order kinetic model, with a kinetic constant (k) of 0.066 h−1. A significant carbon isotope fractionation was observed, with a change of the δ13C values from −26.54 ± 0.07 ‰ to −25.41 ± 0.08 ‰. The average chlorpyrifos biodegradation proportion reached 71.23 % (60.42 %–85.04 %), and it was predicted that about 11.79 %–36.41 % of chlorpyrifos removal in the ICW was attributed to abiotic factors. The outlet of the subsurface flow constructed wetland saw the highest D∗/B∗ value (1.38–3.88), indicating that the remaining fraction of dilution was much more significant than that of degradation in this period. The top 20 phyla of microbial community were identified in the ICW. Proteobacteria was the most dominant phylum, accounting for >40 % of the bacterial communities in all sampling locations. Acidobacteria and Bacteroidetes were the second and third dominant phyla. At the genus level, the microbial community composition differed more greatly in every stage of the ICW, and the spatial distribution difference was quite significant in the ICW. This study is important to figure out the migration and transformation of chlorpyrifos when the ICW was adopted as a removal tool for organic micro-pollutants, and more similar studies could be carried out in the future to promote the evaluation of pollutant removal capacity of the ICWs, and to further develop the application of stable isotope analysis of compounds in the natural environment.

A Multi-Tissue, Multi-Species Assessment of Lipid and Urea Stable Isotope Biases in Mesopredator Elasmobranchs

The application of stable isotope analysis (SIA) is increasing in elasmobranch trophic ecology, but inconsistency remains in terms of the tissue pre-treatment methods chosen to remove biases introduced by lipids and urea. SIA of a range of non-lethally extracted tissues from a diverse group of elasmobranchs, including mesopredators, is increasing, yet most studies assume that isotope biases from lipid and urea are the same across tissues and species. To determine tissue- and species-specific isotope biases across treatment methods, three tissues and their components [muscle, fin, and blood separated into plasma and red blood cells (RBC)] were non-lethally extracted from three species of mesopredatory elasmobranchs and subjected to one of three treatment methods: (1) deionized water rinse [DW], (2) chloroform/methanol lipid extraction [LE], or (3) deionized water followed by chloroform/methanol [DW+LE]. In muscle δ13C, all treatments displayed minimal variation (∼ 0‰) but large increases in δ15N (∼ 1‰) indicated urea removal. Fin δ13C values decreased with DW but increased with LE and DW+LE, whilst all treatments increased fin δ15N (∼ 0.5‰), suggesting removal of both lipid and urea. Plasma δ13C and δ15N displayed high individual variation; large decreases in δ13C (∼−0.8‰) across all treatments, but particularly DW, suggested the removal of13C-enriched compounds while a small increase in δ15N (∼ 0.2‰) suggested minimal urea removal. In RBC, all treatments showed small δ13C declines (∼−0.5‰), with no difference in δ15N, suggesting minimal removal of13C-enriched compounds and urea. For muscle and fin, DW+LE is the most appropriate treatment to standardize δ13C and δ15N consistently across individuals and tissues. The large individual variation in treatment effects on plasma suggests it is unsuitable for current treatment methods. Consistent treatment effects for RBC allow for DW+LE standardization, however, broader species-specific effects are unknown. The importance of treatment choice for accurately estimating prey contributions to elasmobranch diet was highlighted using Bayesian stable isotope mixing model comparisons, with prey contributions varying significantly among treatments. This variability suggests that ecological inferences from elasmobranch tissue SIA are not robust to different treatment methods. It is recommended that studies employ standardized corrections using a combined DW+LE treatment where applicable.

Application of Compound-Specific Isotope Analysis in Environmental Forensic and Strategic Management Avenue for Pesticide Residues

Unintended pesticide pollution in soil, crops, and adjacent environments has caused several issues for both pesticide users and consumers. For users, pesticides utilized should provide higher yield and lower persistence while considering both the environment and agricultural products. Most people are concerned that agricultural products expose humans to pesticides accumulating in vegetation. Thus, many countries have guidelines for assessing and managing pesticide pollution, for farming in diverse environments, as all life forms in soil are untargeted to these pesticides. The stable isotope approach has been a useful technique to find the source of organic matter in studies relating to aquatic ecology and environmental sciences since the 1980s. In this study, we discuss commonly used analytical methods using liquid and gas chromatography coupled with isotopic ratio mass spectrometry, as well as the advanced compound-specific isotope analysis (CSIA). CSIA applications are discussed for tracing organic pollutants and understanding chemical reactions (mechanisms) in natural environments. It shows great applicability for the issues on unintended pesticide pollution in several environments with the progress history of isotope application in agricultural and environmental studies. We also suggest future study directions based on the forensic applications of stable isotope analysis to trace pesticides in the environment and crops.

Recent advances in stable isotope ratio analysis of common explosives

炸药的深度比对与溯源对于爆炸案事件的侦破具有重大意义,以不同地域来源的原料或不同生产工艺生产的炸药,其组成元素的稳定同位素比值具有差异,因而稳定同位素比值可作为炸药深度比对与溯源的重要指标。稳定同位素比值质谱法(IRMS)作为一种高精度的稳定同位素比值测量手段,已逐渐发展成熟,与元素分析仪、气相色谱仪、液相色谱仪等仪器联用,在食品安全、环境保护、法庭科学等领域应用广泛。IRMS在炸药比对与溯源上亦发挥了重要作用,自1975年IRMS被应用于区分不同国家生产的三硝基甲苯(TNT)以来,IRMS已成功用于多种炸药的分析。但目前尚未见有文献系统地总结常见炸药的稳定同位素比值分析研究进展。该文介绍了稳定同位素比值分析的相关原理、仪器组成及特点,分别总结了硝酸铵、黑火药、TNT、太恩、黑索金等常见炸药的稳定同位素比值分析方法,汇总了文献报道的不同国家生产的硝酸铵、黑火药、TNT等炸药的稳定同位素比值。文章就不同炸药的稳定同位素比值差异、炸药生产、存储过程中相关因素对同位素比值的影响,爆炸前后稳定同位素比值的变化情况等内容进行了分析。本文还指出了目前炸药的稳定同位素比值分析研究中存在的问题,对可能的解决办法进行了讨论,对未来的发展方向提出了建议。

Isotopic Analysis of Sugarcane/Petroleum Polyethylene Blends: A Perspective on the Application of Stable Isotope Method (δ13C)

In the present work, we propose the application of stable isotope analysis (δ13C) as an auxiliary tool for the inspection of sugarcane/petroleum polyethylene blends. Our results are supported from the analysis of selected samples by accelerator mass spectrometry (14C-AMS). From the results, it was concluded that the δ13C method is suitable to discriminate samples derived from sugarcane, petroleum, or its blends. It was also noted that both regression models (δ13C method and the δ13C vs 14C-AMS regression) presents potential to estimate the bio-based content; however, future work should focus on validating these models. From the screening model, developed with δ13C data, 33.33% of the samples were highlighted as suspected of being out of specification. Thus, the screening method can identify samples most likely to be out of specification and reduce the demand for inspection of biogenic content following the ASTM D6866 standard (14C-AMS).

Top-down suppression of arthropod herbivory in intercropped maize and organic farms evidenced from δ13C and δ15N stable isotope analyses

Maize is a globally important cereal crop and a staple in sub-Saharan Africa, where it is predominantly grown by small-scale farmers. Its production, however, is undermined by numerous herbivorous arthropods, and agrochemicals used for controlling such pests are increasingly unaffordable. Farmers therefore require cheaper, effective and environmentally sustainable pest management alternatives. This study explored the hypothesis that boosting habitat heterogeneity through organic farming and intercropping enhances arthropod predator-herbivore feeding linkages that naturally suppress herbivory across non-Bt maize fields. To test this, δ13C and δ15N stable isotope analyses were conducted to establish feeding pathways from maize, legume intercrops, and marginal vegetation, through arthropod herbivores and predators across 15 small-scale maize fields in western Kenya. Farming and cropping systems’ roles in trophic linkages were also assessed. Feeding connections and plant food source contributions to arthropod consumer diets were subsequently determined using Bayesian mixing models, and predator relative efficiencies also evaluated. The results showed significantly stronger predator-herbivore trophic linkages within intercropped than monoculture fields, while farming system showed no effect. Herbivores showed stronger connections to crops than to noncrops, suggesting higher vulnerability for crops. For predators, earwigs derived most basal carbon from maize; wasps and predatory beetles, from legumes; ants, from both maize and legumes; and spiders, from both crops and noncrops. Ants and earwigs are important in maize herbivore regulation, particularly for intercropping; wasps and predatory beetles for regulating legume herbivores; and spiders for whole-field herbivore regulation. Most studies have focused on single species at single-trophic levels, but here we demonstrate, for the first time in sub-Saharan Africa, application of stable isotope analyses to characterize multitrophic feeding interactions that indicate effective agronomic practices for fostering top-down arthropod herbivore suppression in non-Bt maize fields. The results are useful in prescribing field practices with low-impact habitat management for sustainable small-scale agriculture rather than pesticide-based arthropod herbivore control.

Application of Stable Isotope Analyses to Primate Ecology: A Review

Application of Stable Isotope Analyses to Primate Ecology: A Review

You are what you eat: Examining the effects of provisioning tourism on shark diets

Wildlife tourism is a growing industry, with significant conservation and socio-economic benefits. Concerns have however been raised about the possible impacts of this industry on the long-term behaviour, health and fitness of the animal species tourists come to see (the target species), particularly when those species are regularly fed to improve the tourism experience. Information on the contribution of food rewards to the diet of the target species at feeding sites is critical to assess the dependency on handouts and to identify possible health/fitness problems that might be associated, if handouts become the main part of animals' diets. Here, we use stable isotopes (δ13C and δ15N) to evaluate the importance of handouts for a marine predator, the bull shark (Carcharhinus leucas), at a feeding site (Fiji) where shark feeds occur 5 days/week and sharks (up to 75 individuals/dive) are fed ~200 kg of tuna heads/day. There was no evidence of incorporation of food provided, even for individuals that regularly consume food rewards. Results, when combined with those from previous studies on bull shark movements and feeding rates at our study site, show that current levels of provisioning likely have no long-term impacts on bull shark diet or behaviour. This study also demonstrates the applicability of stable isotope analysis to assess and monitor the contribution of food rewards to wildlife, and highlights the benefits of using multi-sources of information to gain a holistic understanding of the effects of provisioning predators.

Modelling silicon supply during the Last Interglacial (MIS 5e) at Lake Baikal

Limnological reconstructions of primary productivity have demonstrated its response over Quaternary timescales to drivers such as climate change, landscape evolution and lake ontogeny. In particular, sediments from Lake Baikal, Siberia, provide a valuable uninterrupted and continuous sequence of biogenic silica (BSi) records, which document orbital and sub-orbital frequencies of regional climate change. We here extend these records via the application of stable isotope analysis of silica in diatom opal (δ30Sidiatom) from sediments covering the Last Interglacial cycle (Marine Isotope Stage [MIS] 5e; c. 130 to 115 ka BP) as a means to test the hypothesis that it was more productive than the Holocene. δ30Sidiatom data for the Last Interglacial range between +1.29 and +1.78‰, with highest values between c. 127 to 124 ka BP (+1.57 to +1.78‰). Results show that diatom dissolved silicon (DSi) utilisation, was significantly higher (p = 0.001) during MIS 5e than the current interglacial, which reflects increased diatom productivity over this time (concomitant with high diatom biovolume accumulation rates [BVAR] and warmer pollen-inferred vegetation reconstructions). Diatom BVAR are used, in tandem with δ30Sidiatom data, to model DSi supply to Lake Baikal surface waters, which shows that highest delivery was between c. 123 to 120 ka BP (reaching peak supply at c. 120 ka BP). When constrained by sedimentary mineralogical archives of catchment weathering indices (e.g. the Hydrolysis Index), data highlight the small degree of weathering intensity and therefore representation that catchment-weathering DSi sources had, over the duration of MIS 5e. Changes to DSi supply are therefore attributed to variations in within-lake conditions (e.g. turbulent mixing) over the period, where periods of both high productivity and modelled-DSi supply (e.g. strong convective mixing) account for the decreasing trend in δ30Sidiatom compositions (after c. 124 ka BP).

Assessing the applicability of stable isotope analysis to determine the contribution of landfills to vultures' diet.

Human activities cause changes to occur in the environment that affect resource availability for wildlife. The increase in the human population of cities has led to a rise in the amount of waste deposited in landfills, installations that have become a new food resource for both pest and threatened species such as vultures. In this study we used stable isotope analysis (SIA) and conventional identification of food remains from Egyptian Vultures (Neophron percnopterus) to assess the applicability of SIA as a new tool for determining the composition of the diets of vultures, a group of avian scavengers that is threatened worldwide. We focused on an expanding Egyptian Vulture population in NE Iberian Peninsula to determine the part played by landfills and livestock in the diet of these species, and aimed to reduce the biases associated with conventional ways of identifying food remains. We compared proportions of diet composition obtained with isotope mixing models and conventional analysis for five main prey. The greatest agreement between the two methods was in the categories ‘landfills’ and ‘birds’ and the greatest differences between the results from the two methods were in the categories ‘livestock’, ‘carnivores’ and ‘wild herbivores’. Despite uncertainty associated to SIA, our results showed that stable isotope analysis can help to distinguish between animals that rely on waste and so present enriched levels of δ 13C than those that feed on the countryside. Indeed, a high proportion of food derived from landfills (nearly 50%) was detected in some breeding pairs. Furthermore we performed GLMM analyses that showed that high values of δ 13C in Egyptian Vulture feathers (a proxy of feeding in landfills) are related with high levels of humanization of territories. This method has the potential to be applied to other threatened vulture species for which there is a lack of information regarding resources they are consuming, being especially important as the main causes of vultures decline worldwide are related to the consumption and availability of food resources.

TATP isotope ratios as influenced by worldwide acetone variation

Isotope ratio analysis has been shown to discriminate samples of forensic interest and to link many synthesized and natural materials to their precursors when traditional chemical and physical analyses cannot. Successful application of stable isotope analysis to chemicals of interest requires a background of likely variations in stable isotope ratios; often, this background population can be generated from analysis of possible precursors and the relationships of stable isotopes of precursor(s) to product(s), which may depend on synthesis techniques. Here we measured the carbon (13C/12C) and hydrogen (2H/1H) isotope ratios of the oft-illicitly manufactured explosive triacetone triperoxide, TATP, and one of its precursors, acetone. As acetone is the sole source of carbon and hydrogen to TATP, a survey of acetone from 12 countries was conducted to explore the breadth of 13C/12C and 2H/1H variation in the precursor, and therefore, its product. Carbon and hydrogen isotope ratios were measured using continuous flow isotope ratio mass spectrometry (IRMS) techniques. We observed greater ranges in both C and H isotope ratios of acetone than previously published; we also found that country-of-purchase was a large contributing factor to the observed variation, larger than acetone grade and brand. Following clandestine production methods, we observed that the stable isotope ratios of TATP retained the stable isotope signatures of acetone used in synthesis. We confirmed the robustness of TATP carbon isotope ratios to both recrystallization and time-dependent sublimation, important considerations when faced with the task of practical sampling of potential unexploded TATP from a crime scene.

Stable isotope discrimination factors and between-tissue isotope comparisons for bone and skin from captive and wild green sea turtles (Chelonia mydas).

The ecological application of stable isotope analysis (SIA) relies on taxa- and tissue-specific stable carbon (Δ13 C) and nitrogen (Δ15 N) isotope discrimination factors, determined with captive animals reared on known diets for sufficient time to reflect dietary isotope ratios. However, captive studies often prohibit lethal sampling, are difficult with endangered species, and reflect conditions not experienced in the wild. We overcame these constraints and determined the Δ13 C and Δ15 N values for skin and cortical bone from green sea turtles (Chelonia mydas) that died in captivity and evaluated the utility of a mathematical approach to predict discrimination factors. Using stable carbon (δ13 C values) and nitrogen (δ15 N values) isotope ratios from captive and wild turtles, we established relationships between bone stable isotope (SI) ratios and those from skin, a non-lethally sampled tissue, to facilitate comparisons of SI ratios among studies using multiple tissues. The mean (±SD) Δ13 C and Δ15 N values (‰) between skin and bone from captive turtles and their diet (non-lipid-extracted) were 2.3 ± 0.3 and 4.1 ± 0.4 and 2.1 ± 0.6 and 5.1 ± 1.1, respectively. The mathematically predicted Δ13 C and Δ15 N values were similar (to within 1‰) to the experimentally derived values. The mean δ15 N values from bone were higher than those from skin for captive (+1.0 ± 0.9‰) and wild (+0.8 ± 1.0‰) turtles; the mean δ13 C values from bone were lower than those from skin for wild turtles (-0.6 ± 0.9‰), but the same as for captive turtles. We used linear regression equations to describe bone vs skin relationships and create bone-to-skin isotope conversion equations. For sea turtles, we provide the first (a) bone-diet SI discrimination factors, (b) comparison of SI ratios from individual-specific bone and skin, and (c) evaluation of the application of a mathematical approach to predict stable isotope discrimination factors. Our approach opens the door for future studies comparing different tissues, and relating SI ratios of captive to wild animals.