Tracking mobility using human hair: What can we learn from lead and strontium isotopes?

Strontium isotopes track female dispersal in Taï chimpanzees

OBJECTIVES

Chimpanzees (Pan troglodytes) are patrilocal, with males remaining in their natal community and females dispersing when they reach sexual maturity. However, the details of female chimpanzee dispersal, such as their possible origin, are difficult to assess, even in habituated communities. This study investigates the utility of 87Sr/86Sr analysis for (1) assessing Sr baseline differences between chimpanzee territories and (2) identifying the status (immigrant or natal) of females of unknown origin within the territories of five neighboring communities in Taï National Park (Côte d'Ivoire).

MATERIALS AND METHODS

To create a local Sr isoscape for the Taï Chimpanzee Project (TCP) study area, we sampled environmental samples from TCP-established territories (n = 35). To assess dispersal patterns, 34 tooth enamel samples (one per individual) were selected from the Taï chimpanzee skeletal collection. 87Sr/86Sr analysis was performed on all 69 samples at the W.M. Keck Lab. The theoretical density and overlap of chimpanzee communities as well as generalized linear mixed models (GLMMs) were used to test each question.

RESULTS

87Sr/86Sr ratios for natal male chimpanzees ranged from 0.71662 to 0.72187, which is well within the corresponding environmental baseline range of 0.70774-0.73460. The local Sr isoscapes fit was estimated with the root-mean-square error value, which was 0.0048 (22% of the whole 87Sr/86Sr data range). GLMMs identified significant differences in 87Sr/86Sr ratios between natal and unknown North community origin groups, suggesting that after 1980, females of unknown origin could be immigrants to North community (n = 7, z-ratio = -4.08, p = 0.0001, power = 0.94).

DISCUSSION

This study indicates that 87Sr/86This study indicates that 87Sr/86Sr analysis can successfully identify immigrant females in skeletal collections obtained from wild chimpanzee communities, enabling the tracking of female dispersal patterns historically. There are, however, significant limitations within the scope of this study, such as (1) the absence of reliable maps for the TCP study area, (2) limited capacity for environmental sampling, (3) small sample sizes, and (4) tooth formation in wild chimpanzees.

A reanalysis of strontium isotope ratios as indicators of dispersal in South African hominins

Dispersal patterns in primates have major implications for behavior and sociality but are difficult to reconstruct for fossil species. This study applies novel strontium isotope methodologies that have reliably predicted philopatry and dispersal patterns in chimpanzees and other modern primates to previously published strontium isotope ratios (87Sr/86Sr) of two South African hominins, Australopithecus africanus and Australopithecus robustus. In this study, the difference or 'offset' was calculated between the 87Sr/86Sr of each fossil tooth compared to local bioavailable 87Sr/86Sr as defined by cluster analysis of modern plant isotope ratios. Large teeth (presumably belonging to males) have low offsets from local 87Sr/86Sr proxies, while small teeth (presumably from females) have greater offsets from local 87Sr/86Sr proxies. This supports previous conclusions of male philopatry and female dispersal in both A. africanus and A. robustus. Furthermore, A. robustus shows more extreme differences between presumed males and females compared to A. africanus. This is analogous to differences seen in modern olive baboons compared to chimpanzees and suggests that A. africanus may have had a larger home range than A. robustus. Neither hominin species has 87Sr/86Sr consistent with riparian habitat preferences despite the demonstrated presence of riparian habitats in South Africa at the time.

Machine learning-based Sr isoscape of southern Sardinia: A tool for bio-geographic studies at the Phoenician-Punic site of Nora

Since prehistoric times, the island of Sardinia-in the western Mediterranean-has played a leading role in the dynamics of human population and mobility, in the circulation of raw materials and artefacts, idioms and customs, of technologies and ideas that have enriched the biological, linguistic and cultural heritage of local groups. For the Phoenician and Punic periods (from the 9th to the 3rd centuries BCE), the ancient site of Nora-in southern Sardinia-represents an emblematic case in the study of migratory phenomena that occurred on the Island from the Iron Age until the Roman conquest. Despite the importance of exploring (and characterising) such movements from a wider bio-cultural perspective, the application of bio-geochemical tools for geographical provenance to the ancient skeletal populations of Sardinia is yet scarce. The present work is the first step towards filling this gap with the development of the first isoscape of southern Sardinia using new bioavailable Sr isotope data and a machine-learning approach. From a geolithological point of view, Sardinia is rather heterogeneous and requires detailed studies to correctly assess the distribution of the isotopic signature of bioavailable Sr. The random forest model employed here to construct the Sr isoscape uses several external environmental and geological variables. The most important predictors are related to age and bedrock type, with additional input from local soil properties. A 10-fold cross-validation gives a mean square error of 0.0008 and an R-squared of 0.81, so the model correctly predicts the 87Sr/86Sr ratio of unknown areas. By using a Bayesian provenance assignment workflow, we tested the isoscape here produced to determine the geographic origin and the mobility of archaeological and modern fauna collected from the Phoenician-Punic site of Nora and the surrounding Pula Plain. Our results indicate that archaeological sheep and goats (87Sr/86Sr < 0.7090) are compatible with areas close to Nora and Pula Plain, in agreement with archaeological evidence of pastoralism in those areas. Modern wild and domesticated fauna (87Sr/86Sr > 0.7090) show compatibility with several natural and anthropogenic locations in southern Sardinia, as expected based on modern species distribution data. Finally, we discuss the large Sr isotopic variability of the Nora baseline, where human mobility studies of human cremated and inhumed individuals are currently underway.

Multi-isotopes in human hair: A tool to initiate cross-border collaboration in international cold-cases

Unidentified human remains have historically been investigated nationally by law enforcement authorities. However, this approach is outdated in a globalized world with rapid transportation means, where humans easily move long distances across borders. Cross-border cooperation in solving cold-cases is rare due to political, administrative or technical challenges. It is fundamental to develop new tools to provide rapid and cost-effective leads for international cooperation. In this work, we demonstrate that isotopic measurements are effective screening tools to help identify cold-cases with potential international ramifications. We first complete existing databases of hydrogen and sulfur isotopes in human hair from residents across North America by compiling or analyzing hair from Canada, the United States (US) and Mexico. Using these databases, we develop maps predicting isotope variations in human hair across North America. We demonstrate that both δ2H and δ34S values of human hair are highly predictable and display strong spatial patterns. Multi-isotope analysis combined with dual δ2H and δ34S geographic probability maps provide evidence for international travel in two case studies. In the first, we demonstrate that multi-isotope analysis in bulk hair of deceased border crossers found in the US, close to the Mexico-US border, help trace their last place of residence or travel back to specific regions of Mexico. These findings were validated by the subsequent identification of these individuals through the Pima County Office of the Medical Examiner in Tucson, Arizona. In the second case study, we demonstrate that sequential multi-isotope analysis along the hair strands of an unidentified individual found in Canada provides detailed insights into the international mobility of this individual during the last year of life. In both cases, isotope data provide strong leads towards international travel.

Use of strontium isotope ratios in geolocation of Guatemalan population: Potential role in identification of remains

Within post‐conflict communities, attempts to identify and repatriate unidentified and missing individuals poses a difficult task. As current forensic strategies commonly lack the capacity to provide region of origin assessments, forensic anthropologists/investigators are often unable to identify sources of DNA for kinship analysis. Using Thermal Ionization Mass Spectrometry (TIMS), hair samples from 10 volunteers were used to assess the variation in strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) between extant people in Guatemala City and Coban; with a leach (external) and digest (dietary) signal analyzed for each sample. A two‐way anova demonstrated that the difference between ⁸⁷Sr/⁸⁶Sr of Guatemala City and Coban was statistically significant (F [1, 16] = 259.839, p < 0.05), with no statistically significant differences observed between leach and digest ⁸⁷Sr/⁸⁶Sr (F [1,16] = 4.319, p = 0.054). Overall, individuals from Coban demonstrate ⁸⁷Sr/⁸⁶Sr comparable to previously recorded baseline values, demonstrating a minimal change in diet which is reflected in associated surveys. Volunteers from Guatemala City, however, show a marked shift in ⁸⁷Sr/⁸⁶Sr away from predicted values highlighting the potential influence of imported goods. The results here highlight the applicability of ⁸⁷Sr/⁸⁶Sr in hair to serve as a potential tool to support the identification of unknown individuals in Guatemala in a forensic context.

Longitudinal isotope ratio variations in human hair and nails

Due to the straightforward and non-invasive sampling, ease of transport and long-term storage and access to time-resolved information, determination of element concentrations and isotope ratios in hair and nails finds increasing use. Multi-isotopic information preserved in keratinous tissues allows one to reveal dietary, physiological and environmental influences, but progress in this area is still limited by complicated and time-consuming analytical procedures and challenges in accuracy assessment. In this study, longitudinal distributions of δ³⁴S, ⁸⁷Sr/⁸⁶Sr, ^207,208Pb/²⁰⁶Pb, δ⁶⁶Zn, δ⁵⁶Fe, δ⁶⁵Cu, δ²⁶Mg, and δ¹¹⁴Cd were obtained for hair and nails collected from nine subjects with different age, biological sex, diet and/or place of residence. For S and Zn, the distribution along hair strands revealed a trend towards a heavier isotopic signature from the proximal to the distal end, with a maximum difference within the hair of a single subject of 1.2‰ (Δ³⁴S) and 0.4‰ (Δ⁶⁶Zn). For Fe, Cu, Mg and Cd, a shift towards either a lighter (Cu) or heavier (Fe, Mg and Cd) isotopic composition is accompanied by increasing concentration towards the distal hair end, indicating possible isotope fractionation during deposition or external contamination with a different isotopic composition. Pb and Sr isotope ratios are relatively stable throughout the hair strands despite notable concentration increases towards the distal end, likely reflecting external contamination. The isotopic composition of Sr points to tap water as a probable main source, explaining the relative stability of the ratio for individuals from the same geographical location. For Pb, isotopic compositions suggest tap water and/or indoor dust as possible sources. Similar δ³⁴S, ⁸⁷Sr/⁸⁶Sr, ^207,208Pb/²⁰⁶Pb, δ⁶⁶Zn, δ⁵⁶Fe, and δ⁶⁵Cu observed for hair, fingernails and toenails sampled from the same individual suggest that keratinous tissues are conservative receivers of internal and external inputs and can be used complementary. Seasonal variation in δ³⁴S, ^207,208Pb/²⁰⁶Pb, and δ⁶⁵Cu was observed for fingernails.

Spatial distributions of strontium isotope ratios in human hair and tap water from South Korea

Natural variations of ⁸⁷Sr/⁸⁶Sr ratios in biological samples, such as human hair, provide a biological record of provenance. Spatial distribution maps reflecting heterogeneity in isotopic signatures across large geographical regions are helpful for discerning the provenance and mobility of organisms. In this national-scale study conducted across South Korea, we investigated the spatial distribution patterns of ⁸⁷Sr/⁸⁶Sr ratios in human hair and tap water samples to determine their spatial variabilities and the relationships of isotopic signatures between hair and tap water. The strontium isoscapes of tap water and hair showed similar spatial distribution patterns. Non-parametric comparison indicated no significant differences in isotopic ratios between the two sample types. The ⁸⁷Sr/⁸⁶Sr ratios in human hair showed a significant and strong correlation with the ratios in tap water in eastern Korea, suggesting potential use of ⁸⁷Sr/⁸⁶Sr ratios in provenance studies. However, tap water and hair samples from western Korea did not show significant correlation between them, overall reducing the predictive power of the hair ⁸⁷Sr/⁸⁶Sr ratios for provenance studies. The deviation between ⁸⁷Sr/⁸⁶Sr_{tap water} and ⁸⁷Sr/⁸⁶Sr_hair was much larger in western coastal areas than in eastern Korea. Relatively high utilization of groundwater or exogenous materials, such as Asian dust, may have been responsible for this pattern. To fully utilize the potential of the strontium isotope signature as a biorecorder in provenance studies, it is essential to evaluate the effects of groundwater and other exogenous materials on the isotope signatures of hair and other biological samples. In this study, only hair samples from males were used to develop ⁸⁷Sr/⁸⁶Sr isoscapes. Therefore, further studies are required to examine the applicability of ⁸⁷Sr/⁸⁶Sr hair isoscapes based solely on human hair samples from males to forensic and provenance studies of human hair samples from females.

The Use of Intrinsic Markers for Studying the Migratory Movements of Bats

Mortality of migratory bat species at wind energy facilities is a well-documented phenomenon, and mitigation and management are partially constrained by the current limited knowledge of bat migratory movements. Analyses of biochemical signatures in bat tissues ("intrinsic markers") can provide information about the migratory origins of individual bats. Many tissue samples for intrinsic marker analysis may be collected from living and dead bats, including carcasses collected at wind energy facilities. In this paper, we review the full suite of available intrinsic marker analysis techniques that may be used to study bat migration, with the goal of summarizing the current literature and highlighting knowledge gaps and opportunities. We discuss applications of the stable isotopes of hydrogen, oxygen, nitrogen, carbon, sulfur; radiogenic strontium isotopes; trace elements and contaminants; and the combination of these markers with each other and with other extrinsic markers. We further discuss the tissue types that may be analyzed for each and provide a synthesis of the generalized workflow required to link bats to origins using intrinsic markers. While stable hydrogen isotope techniques have clearly been the leading approach to infer migratory bat movement patterns across the landscape, here we emphasize a variety of lesser used intrinsic markers (i.e., strontium, trace elements, contaminants) that may address new study areas or answer novel research questions.

Comparison of strontium isotope ratios in Mexican human hair and tap water as provenance indicators

Deceased undocumented border crossers are some of the most difficult individuals to identify due to the inability to narrow down the region of origin and therefore to obtain family reference samples for DNA comparison. The isotopic compositions of various body tissues have been demonstrated to be useful biomarkers for tracking locations and movements to aid in the identification of human remains. This study closes the large spatial gap of available ⁸⁷Sr/⁸⁶Sr ratios from North America in tap water and presents the first ⁸⁷Sr/⁸⁶Sr human tissue-based ratios from Mexico. The 101 hair samples from 32 locations in Mexico range in ⁸⁷Sr/⁸⁶Sr ratios from 0.70424 to 0.71613 (ΔSr_max-min=0.01189). Furthermore, 151 tap water samples from 51 locations range between 0.70404 to 0.71385 (ΔSr_max-min=0.00981). Overall, small variations in the hair and tap water samples collected from individual locations were recorded (ΔSr_max-min=0.00041 and 0.00034 respectively). Despite the fact that Mexico is one of the largest bottled water consumers in the world, the ⁸⁷Sr/⁸⁶Sr ratios of human hair and tap water correlated strongly (R²=0.87 for location averages and R²=0.80 when using individual data points). These data represent a valuable resource for identifying the provenance of human remains.

A comprehensive review of biogeochemical distribution and fractionation of lead isotopes for source tracing in distinct interactive environmental compartments

Lead (Pb) is a non-essential and extremely noxious metallic-element whose biogeochemical cycle has been influenced predominantly by increasing human activities to a great extent. The introduction and enrichment of this ubiquitous contaminant in the terrestrial-environment has a long history and getting more attention due to its adverse health effects to living organisms even at very low exposure levels. Its lethal-effects can vary widely depending on the atmospheric-depositions, fates and distribution of Pb isotopes (i.e., ²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb &²⁰⁸Pb) in the terrestrial-environment. Thus, it is essential to understand the depositional behavior and transformation mechanism of Pb and the factors affecting Pb isotopes composition in the terrestrial-compartments. Owing to the persistence nature of Pb-isotopic fractions, regardless of ongoing biogeochemical-processes taking place in soils and in other interlinked terrestrial-compartments of the biosphere makes Pb isotope ratios (Pb-IRs) more recognizable as a powerful and an efficient-tool for tracing the source(s) and helped uncover pertinent migration and transformation processes. This review discusses the ongoing developments in tracing migration pathway and distribution of lead in various terrestrial-compartments and investigates the processes regulating the Pb isotope geochemistry taking into account the source identification of lead, its transformation among miscellaneous terrestrial-compartments and detoxification mechanism in soil-plant system. Additionally, this compendium reveals that Pb-pools in various terrestrial-compartments differ in Pb isotopic fractionations. In order to improve understanding of partition behaviors and biogeochemical pathways of Pb isotope in the terrestrial environment, future works should involve investigation of changes in Pb isotopic compositions during weathering processes and atmospheric-biological sub-cycles.

Fast exchange of strontium between hair and ambient water: Implication for isotopic analysis in provenance and forensic studies

Trace elements in hair originate from intake (e.g., diet, inhalation, skin absorption), are transported in the bloodstream, and then incorporated during hair formation. However, the trace element abundance and isotopic compositions may be altered by post-eruption environmental processes. Such alterations must be addressed to obtain a meaningful interpretation of hair analysis for biomonitoring. In this study, we used strontium (Sr) isotopic analysis together with sorption kinetics of ionic Sr to quantify the rate and extent of replacement of endogenous Sr in hair by exogenous Sr from ambient water. We found that with only 10 minutes of exposure at room temperature (22°C), more than 30% of original endogenous Sr in hair was replaced with exogenous Sr from the solution. After 16 days of exposure to the solution, more than 90% of endogenous Sr was replaced, with a warmer temperature (60°C) accelerating the exchange substantially. We also found that acid leaching of exposed hair did not remove or isolate the exogenous Sr; therefore, neither the original endogenous nor the exogenous 87Sr/86Sr signal could be separated. Nonetheless, these findings illustrated that the quantitative correlation between the fraction of exogenous Sr and the soaking time, if established, could be used to estimate the length of water contact time for hair in forensic studies. Even if such time since initial contact cannot be established, the combination of acid leaching and 87Sr/86Sr analysis of hair samples may still be valuable in provenance studies to identify recent changes in the exogenous Sr pool, including movements or changes in water source.

Strontium, oxygen, and carbon isotope variation in modern human dental enamel

OBJECTIVES

Isotopic analyses using human dental enamel provide information on the mobility and diet of individuals in forensic and archeological studies. Thus far, no study has systematically examined intraindividual coupled strontium (Sr), oxygen (O), and carbon (C) isotope variation in human enamel or the effect that caries have on the isotopic integrity of the enamel. The inadequate quantification of isotopic variation affects interpretations and may constrain sample selection of elements affected by caries. This study aims to quantify the intraindividual isotopic variation and provides recommendations for enamel sampling methods.

MATERIAL AND METHODS

This study presents the first systematic results on intraindividual variation in Sr-O-C isotope composition and Sr concentration in modern human dental enamel of third molars (affected and unaffected by caries). A multiloci sampling approach (n = 6-20) was used to analyze surface and inner enamel, employing thermal ionization mass spectrometry (TIMS) and isotope ratio mass spectrometry (IRMS). Third molars were analyzed from 47 individuals from the Netherlands, Iceland, the United States, the Caribbean, Colombia, Somalia, and South Africa.

RESULTS

Intradental isotopic variation in modern Dutch dental elements was recorded for Sr, O, and C and exceeded the variation introduced by the analytical error. Single loci and bulk sampling approaches of third molars established that a single analysis is only representative of the bulk Sr isotope composition in 60% of the elements analyzed. Dental elements affected by caries showed twice the variation seen in unaffected dental elements. Caries did not consistently incorporate the isotopic composition of the geographical environment in which they developed.

DISCUSSION

The isotopic variability recorded in unaffected inner enamel indicates that variations greater than 0.000200 for ⁸⁷ Sr/⁸⁶ Sr and larger than 2‰ for δ¹⁸ O and δ¹³ C are required to demonstrate changes in modern Dutch human diet or geographic location.

Evaluation of neodymium isotope analysis of human dental enamel as a provenance indicator using 1013 Ω amplifiers (TIMS)

Human provenance studies employing isotopic analysis have become an essential tool in forensic and archaeological sciences, with multi-isotope approaches providing more specific location estimates compared to single isotope studies. This study reports on the human provenancing capability of neodymium isotopes (¹⁴³Nd/¹⁴⁴Nd), a relatively conservative tracer in the environment. Neodymium isotope ratios have only recently been determined on human remains due to low concentrations in human dental enamel (ppb range), requiring thermal ionisation mass spectrometry (TIMS) using 10¹³ Ω resistors. Dental elements (third molars) from 20 individuals born and raised in the Netherlands were analysed for Nd concentration (n = 12) and Nd isotope ratios (n = 15). The geological control on Nd isotope composition was examined using coupled Nd-Sr isotope analysis of the same third molar. Teeth from different geological environments were also analysed (Caribbean, Columbian, and Icelandic, n = 5). Neodymium elemental concentrations in dental elements ranged between 0.1 and 7.9 ppb (median 0.5 ppb). The Dutch ¹⁴³Nd/¹⁴⁴Nd ratios of the provinces of Limburg and Friesland were between 0.5118 and 0.5121, with Dutch ⁸⁷Sr/⁸⁶Sr ratios in agreement with the previously established local range (0.708–0.710). The current findings were compared to previously published results on Nd concentration and composition from Dutch individuals. The concentration of Nd and ¹⁴³Nd/¹⁴⁴Nd ratios were weakly correlated (R² = 0.47, n = 17) in Dutch human dental enamel. The majority (n = 25, 83.3%) of individuals had Nd and Sr isotope values isotopically indistinguishable from the geological environment in which their third molars formed and mineralised. However, the Nd isotope ratios of the Icelandic individual and several Dutch individuals (n = 4) suggested that Nd in enamel is not solely influenced by geological environment. In order for neodymium isotopes to be quantitatively applied in forensic and archaeological settings further analyses of individuals from various geographical regions with well-defined dietary Nd isotope data are required.

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First evaluation of the potential of neodymium isotopes for human provenancing

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Provides insight in Nd concentration and isotope ratios in human dental enamel

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First study presenting Nd isotope ratios from multiple geological settings

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First study combining ¹⁴³Nd/¹⁴⁴Nd and ⁸⁷Sr/⁸⁶Sr ratios of the same dental element

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The use of 10¹³ Ω resistors allows for greater precision analysis of small samples

Strontium isotope ratios of human hair from the United States: Patterns and aberrations

RATIONALE

Strontium isotope ratios (⁸⁷ Sr/⁸⁶ Sr) of hair may be a valuable tool to estimate human provenance. However, the systematics and mechanisms controlling spatial variation in ⁸⁷ Sr/⁸⁶ Sr of modern human hair remain unclear. Here, we measure ⁸⁷ Sr/⁸⁶ Sr of hair specimens from across the USA to assess the presence of geospatial relationships.

METHODS

Ninety-eight human hair specimens were collected from salon/barbershop floors in 48 municipalities throughout the conterminous USA. [Sr] and ⁸⁷ Sr/⁸⁶ Sr ratios were measured from hair using quadrupole and multi-collector inductively coupled plasma mass spectrometers, respectively. The [Sr] and ⁸⁷ Sr/⁸⁶ Sr ratios of hair were compared with the measured [Sr] and ⁸⁷ Sr/⁸⁶ Sr ratios of tap waters from the collection locations. In addition, the ⁸⁷ Sr/⁸⁶ Sr ratio of hair was compared with the modeled ratios of bedrock and surface waters.

RESULTS

Hair color was independent of the ⁸⁷ Sr/⁸⁶ Sr ratio, but related to [Sr]. The ⁸⁷ Sr/⁸⁶ Sr ratios of hair and leachate were not statistically different and were positively correlated; however, in several hair-leachate pairs, the ratios were conspicuously different. The ⁸⁷ Sr/⁸⁶ Sr ratios of both hair and leachate were linearly correlated with tap water. The ⁸⁷ Sr/⁸⁶ Sr ratio of hair was also significantly correlated with the modeled ratio of bedrock and surface waters, although the ⁸⁷ Sr/⁸⁶ Sr ratio of hair was most strongly correlated with the measured ratio of tap water.

CONCLUSIONS

The ⁸⁷ Sr/⁸⁶ Sr ratio of hair is related to the ratio of tap water, which varied geographically. The ratio of hair provided geographic information about an individual's recent residence. Differences in the ⁸⁷ Sr/⁸⁶ Sr ratios of hair and hair leachate may be concomitant with travel and could potentially be used as a screening tool to identify recent movements.

Strontium isotope ratios (87 Sr/86 Sr) of human fingernail clippings reveal multiple location signals

RATIONALE

Strontium isotope ratios (⁸⁷ Sr/⁸⁶ Sr) in human fingernail keratin tissues have been underexplored for region of origin and travel history reconstruction studies. Here we investigated ⁸⁷ Sr/⁸⁶ Sr ratios in fingernail keratin to establish baseline measurements in a resident group and to examine how ⁸⁷ Sr/⁸⁶ Sr ratios changed with relocation.

METHODS

Fingernail clippings were collected from resident (n = 10) and non-resident/traveler groups (n = 4 and n = 4) that were part of a larger study in Salt Lake City (UT, USA) from 2015 to 2016. Strontium abundance and ⁸⁷ Sr/⁸⁶ Sr ratios were determined via multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS). ⁸⁷ Sr/⁸⁶ Sr and oxygen (δ¹⁸ O) isotope ratios from the traveler participants were compared to examine temporal patterns.

RESULTS

Strontium abundance and ⁸⁷ Sr/⁸⁶ Sr ratios in fingernails from the resident group established a baseline against which we could evaluate potential differences in non-resident/traveler groups. Resident ⁸⁷ Sr/⁸⁶ Sr ratios remained constant over the study period and were consistent with previously measured tap waters for the area. ⁸⁷ Sr/⁸⁶ Sr ratio changes in non-resident/traveler groups were rapid and reflected the current location of the individual within 4-5 weeks of arrival. Lastly, δ¹⁸ O and ⁸⁷ Sr/⁸⁶ Sr ratios of the same fingernail clippings did not exhibit similar temporal patterns, since fingernail δ¹⁸ O ratios required more time to attain values characteristic of the new environment.

CONCLUSIONS

Our findings suggest that strontium is incorporated into fingernail tissues differently from hair and this could be advantageous to forensic investigations. We found that ⁸⁷ Sr/⁸⁶ Sr and δ¹⁸ O ratios of the same fingernail clippings revealed two different time points reflecting an individual's residence over short- (4-5 weeks, ⁸⁷ Sr/⁸⁶ Sr ratios) and long-term (3-5 months, δ¹⁸ O values) time scales. It is likely that the ⁸⁷ Sr/⁸⁶ Sr ratios of fingernail clippings reflect exogenous signals that are incorporated through bathing waters and that these signals change rapidly with movement to a new location. Our results may aid future forensic studies in the determination of region of origin in unidentified remains.

Transhumance pastoralism of Roccapelago (Modena, Italy) early-modern individuals: Inferences from Sr isotopes of hair strands

OBJECTIVES

In this work, we use Sr isotopes to analyze human hair and determine short-term movements of a contemporary human traveler and of early-modern individuals from an archaeological site (Roccapelago, Modena, Italy, 16th-18th century).

MATERIALS AND METHODS

Analyses were performed using a Neptune MC-ICP-MS. We first set up and tested the procedure on scalp hair of a contemporary human, who spent some time between Brazil and Italy. We then analyzed the ⁸⁷ Sr/⁸⁶ Sr ratios of eight exceptionally well-preserved archaeological hair specimens associated with human mummies from Roccapelago. Trace elements were analyzed by LA-ICP-MS on single-hair specimens to check the preservation of the archaeological samples.

RESULTS

The strontium isotope composition of modern human hair varies from 0.7087 to 0.7093. The ⁸⁷ Sr/⁸⁶ Sr ratios of the Roccapelago hair strands range from 0.7082 to 0.7137, with an average of 0.7093 ± 0.0031 (2σ), revealing also intra-individual differences in isotopic composition along the length of the hair shaft. Data were compared with local archaeological rodent bones and teeth and with published isotopic values of water and outcropping rocks. Trace element abundances of archaeological and modern human hair are similarly low in terms of Rare Earth Element (REE) and metal contents, in particular after HNO₃ leaching.

DISCUSSION

The variable modern human hair ⁸⁷ Sr/⁸⁶ Sr ratios show that high-resolution hair sampling tracks the movements of this individual between the two continents. The Sr isotope composition of the mummy hair is consistent with sub-annual human movements from Roccapelago to an area with different ⁸⁷ Sr/⁸⁶ Sr ratios. Historical sources indicate that individuals from Roccapelago travelled with their herds to Tuscany for transhumance pastoralism practices. The high radiogenic ⁸⁷ Sr/⁸⁶ Sr ratios (>0.71) found in some of the hair are possibly consistent with the Tuscan Magmatic Province and the Tuscan Metamorphic Complex isotope signature. To our knowledge, this is the first study in an archaeological context where the Sr isotope evidence of mobility is corroborated by historical documents.

Applying the principles of isotope analysis in plant and animal ecology to forensic science in the Americas

The heart of forensic science is application of the scientific method and analytical approaches to answer questions central to solving a crime: Who, What, When, Where, and How. Forensic practitioners use fundamentals of chemistry and physics to examine evidence and infer its origin. In this regard, ecological researchers have had a significant impact on forensic science through the development and application of a specialized measurement technique-isotope analysis-for examining evidence. Here, we review the utility of isotope analysis in forensic settings from an ecological perspective, concentrating on work from the Americas completed within the last three decades. Our primary focus is on combining plant and animal physiological models with isotope analyses for source inference. Examples of the forensic application of isotopes-including stable isotopes, radiogenic isotopes, and radioisotopes-span from cotton used in counterfeit bills to anthrax shipped through the U.S. Postal Service and from beer adulterated with cheap adjuncts to human remains discovered in shallow graves. Recent methodological developments and the generation of isotope landscapes, or isoscapes, for data interpretation promise that isotope analysis will be a useful tool in ecological and forensic studies for decades to come.

Strontium isotope ratios of human hair record intra-city variations in tap water source

The oxygen (¹⁸O/¹⁶O) isotope analysis of hair is commonly applied to reconstruct an individual’s residence history. However, region-of-origin as determined from oxygen isotope values (δ¹⁸O) alone is often spatially indistinct. Adding additional geochemical recorders can refine region-of-origin estimates. In this capacity, strontium (⁸⁷Sr/⁸⁶Sr) isotope analysis has attracted increased interest. While ⁸⁷Sr/⁸⁶Sr reflects the influences of local geology, ⁸⁷Sr/⁸⁶Sr of hair includes both external environmental signals as well as the internal dietary indicators. To better understand the impact of these contributions to the spatial signal encoded within ⁸⁷Sr/⁸⁶Sr of hair, human hair was collected from three locations within Salt Lake City, Utah along with the donor’s sex. The ⁸⁷Sr/⁸⁶Sr and δ¹⁸O of hair and local tap water were measured. There were no significant relationships between sex and either δ¹⁸O or ⁸⁷Sr/⁸⁶Sr of hair, nor between collection location and the δ¹⁸O of hair. However, we found significant associations between collection location and ⁸⁷Sr/⁸⁶Sr of hair. These findings suggest that interactions with local water may be an important source of Sr to human hair and that the ⁸⁷Sr/⁸⁶Sr of hair may have the capacity to record differences in ⁸⁷Sr/⁸⁶Sr of tap waters on small spatial scales.

Lead isotopic fingerprint in human scalp hair: The case study of Iglesias mining district (Sardinia, Italy)

The Sulcis-Iglesiente district (SW Sardinia, Italy) has been, until recently, one of the most important Italian polymetallic mining areas for the extraction of lead. Epidemiological studies conducted over several decades have indicated this site at high risk of environmental crisis with possible adverse effects on the public health. In the present paper we discuss Pb isotope signatures in human scalp hair and road dust collected from the Sulcis-Iglesiente area in order to trace the exposure of populations to potential Pb sources. A total of 23 determinations (20 on hair samples and 3 on road dust samples) of lead isotope ratios (²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb) were carried out. The obtained results were integrate with literature data regarding the total content of Pb in hair samples from the same study area. Hair from children living in Sant'Antioco exhibited lead isotope ratios in the ranges 1.152-1.165 for ²⁰⁶Pb/²⁰⁷Pb and 2.101-2.108 for ²⁰⁸Pb/²⁰⁶Pb, while hair samples from Iglesias resulted less radiogenic: ²⁰⁶Pb/²⁰⁷Pb~1.147-1.154 and ²⁰⁸Pb/²⁰⁶Pb~2.106-2.118. These values pointed to a multi-source mixing between the less radiogenic sources, corresponding to the Pb ore deposits, and the more radiogenic sources identified in local background.

Deuterium- and Tritium-Labelled Compounds: Applications in the Life Sciences

Hydrogen isotopes are unique tools for identifying and understanding biological and chemical processes. Hydrogen isotope labelling allows for the traceless and direct incorporation of an additional mass or radioactive tag into an organic molecule with almost no changes in its chemical structure, physical properties, or biological activity. Using deuterium-labelled isotopologues to study the unique mass-spectrometric patterns generated from mixtures of biologically relevant molecules drastically simplifies analysis. Such methods are now providing unprecedented levels of insight in a wide and continuously growing range of applications in the life sciences and beyond. Tritium (³ H), in particular, has seen an increase in utilization, especially in pharmaceutical drug discovery. The efforts and costs associated with the synthesis of labelled compounds are more than compensated for by the enhanced molecular sensitivity during analysis and the high reliability of the data obtained. In this Review, advances in the application of hydrogen isotopes in the life sciences are described.

Reconstruction of travel history using coupled δ18 O and 87 Sr/86 Sr measurements of hair

RATIONALE

Oxygen isotope ratios (δ¹⁸ O values) of hair largely reflect features of regional hydrology while strontium isotope ratios (⁸⁷ Sr/⁸⁶ Sr) are thought to reflect bedrock geology; combination of both isotope signatures may provide greater capacity for determining provenance and reconstructing travel history of an organism. To test this hypothesis, we compared the O-Sr isotope profiles of hair from domestic horses with known residency histories.

METHODS

Tail hairs were collected from a pair of horses pastured together for a period of 16 months, one of which lived in a different location for the 8 months prior. Hair samples were washed with solvents to remove external contaminants prior to sequential sampling for δ¹⁸ O and ⁸⁷ Sr/⁸⁶ Sr analysis via TC/EA-IRMS and MC-ICP-MS, respectively. Hair digests were concentrated and analyzed employing low-flow natural aspiration to measure ⁸⁷ Sr/⁸⁶ Sr.

RESULTS

Tail hair from the control and transported horses had mean δ¹⁸ O values of 11.25 ± 1.62 ‰ and 10.96 ± 1.53 ‰, and mean ⁸⁷ Sr/⁸⁶ Sr of 0.7101 ± 0.0006 and 0.7109 ± 0.0020, respectively. The δ¹⁸ O and ⁸⁷ Sr/⁸⁶ Sr profiles for the control and transported horses were indistinguishable when they were pastured together. The ⁸⁷ Sr/⁸⁶ Sr profiles were significantly different during the period that the horses were living apart, while the δ¹⁸ O values were indistinguishable during that period.

CONCLUSIONS

By comparing the O-Sr isotope profiles of a control and transported horse, we investigated isotopic signal(s) potentially useful for reconstructing travel histories via high-resolution sequential sampling along single strands of tail hair. Improved analytical capabilities allowed for extremely low Sr abundance samples to be analyzed for ⁸⁷ Sr/⁸⁶ Sr and proved capable of resolving a horse's movement between distinct regions. Copyright © 2017 John Wiley & Sons, Ltd.