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Browsing by Author "Coulthard, Ian"

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    Element localization in archaeological bone using synchrotron radiation X-ray fluorescence: identification of biogenic uptake
    (2012) Swanston, Treena; Varney, Tamara L.; Coulthard, Ian; Feng, Renfei; Bewer, Brian; Murphy, Reg; Hennig, Cheryl; Cooper, David M. L.
    Trace element analysis related to archaeological bone is viewed as one way to determine levels of element exposure in past populations. This area of research is complex because there is the potential for the incorporation of trace elements from the burial environment into archaeological bone. We tested the hypothesis that matching the spatial distribution of trace elements within cortical bone with the biological structures would provide evidence of biogenic uptake. We examined samples from a non-segregated Royal British Naval cemetery (1793–1822) in Antigua, West Indies. A key historical question related to this population was the extent of exposure to lead and the resulting health effects. Images from conventional light microscopy (histological) analysis of the bone samples were matched with elemental maps of calcium, strontium, and lead that were created through the use of synchrotron radiation X-ray fluorescence (SR-XRF). Biogenic uptake of both strontium and lead was indicated based on the localization of these trace elements within discreet microstructural elements. The successful integration of histological information with XRF data is a powerful technique for the interpretation of past biological events through trace elements.
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    Franklin expedition lead exposure: New insights from high resolution confocal x-ray fluorescence imaging of skeletal microstructure
    (2018) Swanston, Treena; Varney, Tamara L.; Kozachuk, Madalena; Choudhury, Sanjukta; Bewer, Brian; Coulthard, Ian
    In the summer of 1845, under the command of Sir John Franklin, 128 officers and men aboard Royal Navy ships HMS Erebus and HMS Terror sailed into Lancaster Sound and entered the waters of Arctic North America. The goal of this expedition was to complete the discovery of a northwest passage by navigating the uncharted area between Barrow Strait and Simpson Strait. Franklin and his crew spent the first winter at Beechey Island, where three crewmen died and were buried. In September 1846, the ships became stranded in ice off the northwest coast of King William Island, where they remained until April 1848. At that time, the crew, reduced to 105, deserted the ships and retreated south along the island’s western and southern shores in a desperate attempt to reach the mainland and via the Back River, to obtain aid at a Hudson’s Bay Company Post. Sadly, not one individual survived. Previous analyses of bone, hair, and soft tissue samples from expedition remains found that crewmembers’ tissues contained elevated lead (Pb) levels, suggesting that Pb poisoning may have contributed to their demise; however, questions remain regarding the timing and degree of exposure and, ultimately, the extent to which the crewmembers may have been impacted. To address this historical question, we investigated three hypotheses. First, if elevated Pb exposure was experienced by the crew during the expedition, we hypothesized that those sailors who survived longer (King William Island vs. Beechey Island) would exhibit more extensive uptake of Pb in their bones and vice versa. Second, we hypothesized that Pb would be elevated in bone microstructural features forming at or near the time of death compared with older tissue. Finally, if Pb exposure played a significant role in the failure of the expedition we hypothesized that bone samples would exhibit evidence of higher and more sustained uptake of Pb than that of a contemporary comparator naval population from the 19th century. To test these hypotheses, we analyzed bone and dental remains of crew members and compared them against samples derived from the Royal Navy cemetery in Antigua. Synchrotron-based high resolution confocal X-ray fluorescence imaging was employed to visualize Pb distribution within bone and tooth microstructures at the micro scale. The data did not support our first hypothesis as Pb distribution within the samples from the two different sites was similar. Evidence of Pb within skeletal microstructural features formed near the time of death lent support to our second hypothesis but consistent evidence of a marked elevation in Pb levels was lacking. Finally, the comparative analysis with the Antigua samples did not support the hypothesis that the Franklin sailors were exposed to an unusually high level of Pb for the time period. Taken all together our skeletal microstructural results do not support the conclusion that Pb played a pivotal role in the loss of Franklin and his crew.
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    Historical overview and new directions in bioarchaeological trace element analysis: a review
    (2021) Simpson, Rachel; Cooper, David M. L.; Swanston, Treena; Coulthard, Ian; Varney, Tamara L.
    Given their strong affinity for the skeleton, trace elements are often stored in bones and teeth long term. Diet, geography, health, disease, social status, activity, and occupation are some factors which may cause differential exposure to, and uptake of, trace elements, theoretically introducing variability in their concentrations and/or ratios in the skeleton. Trace element analysis of bioarchaeological remains has the potential, therefore, to provide rich insights into past human lifeways. This review provides a historical overview of bioarchaeological trace element analysis and comments on the current state of the discipline by highlighting approaches with growing momentum. Popularity for the discipline surged following preliminary studies in the 1960s to 1970s that demonstrated the utility of strontium (Sr) as a dietary indicator. During the 1980s, Sr/Ca ratio and multi-element studies were commonplace in bioarchaeology, linking trace elements with dietary phenomena. Interest in using trace elements for bioarchaeological inferences waned following a period of critiques in the late 1980s to 1990s that argued the discipline failed to account for diagenesis, simplified complex element uptake and regulation processes, and used several unsuitable elements for palaeodietary reconstruction (e.g. those under homeostatic regulation, those without a strong affinity for the skeleton). In the twenty-first century, trace element analyses have been primarily restricted to Sr and lead (Pb) isotope analysis and the study of toxic trace elements, though small pockets of bioarchaeology have continued to analyse multiple elements. Techniques such as micro-sampling, element mapping, and non-traditional stable isotope analysis have provided novel insights which hold the promise of helping to overcome limitations faced by the discipline.
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    Insights into biogenic and diagenetic lead exposure in experimentally altered modern and archaeological bone: synchrotron radiation x-ray fluorescence imaging
    (2021) Simpson, Rachel; Varney, Tamara L.; Coulthard, Ian; Swanston, Treena; Grimes, Vaughan; Munkittrick, T. Jessica A.; Jankauskas, Rimantas; Cooper, David M. L.
    Bones represent a valuable biological archive of environmental lead (Pb) exposure for modern and archaeological populations. Synchrotron radiation X-ray fluorescence imaging (SR-XFI) generates maps of Pb in bone on a microstructural scale, potentially providing insights into an individual's history of Pb exposure and, in the context of archaeological bone, the biogenic or diagenetic nature of its uptake. The aims of this study were to (1) examine biogenic spatial patterns for Pb from bone samples of modern cadavers compared with patterns observed archaeologically, and (2) test the hypothesis that there are spatial differences in the distribution of Pb for diagenetic and biogenic modes of uptake in bone. To address these aims, this study used inductively coupled plasma-mass spectrometry (ICP-MS) and SR-XFI on unaltered and experimentally altered cadaveric bone samples (University of Saskatchewan, Saskatoon, SK) and archaeological bone samples from 18th to 19th century archaeological sites from Antigua and Lithuania. Bone concentrations of modern individuals are relatively low compared to those of archaeological individuals. SR-XFI results provide insights into modern Saskatchewan Pb exposure with some samples demonstrating a pattern of relatively low Pb exposure with higher levels of Pb exposure occurring in bone structures of a relatively older age that formed earlier in life, likely during the era of leaded gasoline (pre1980s), and other samples demonstrating a pattern of fairly consistent, low-level exposure. Results support hypotheses for the spatial distribution of Pb corresponding to biogenic vs. diagenetic uptake. Diagenetic Pb is mainly confined to the periosteal surface of each sample with some enrichment of cracks and sub-periosteal canals. This may be useful in the future for differentiating diagenetic from biogenic Pb accumulation, analyzing environmental contamination, and informing sampling strategies in archaeological or fossil bone.
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    Investigating past lead exposure in bioarchaeological remains with synchrotron X-ray fluorescence and absorption spectroscopy
    (2019) Simpson, Rachel; Varney, Tamara L.; Swanston, Treena; Coulthard, Ian; Cooper, David M. L.
    Bioarchaeology, the sub-discipline of archaeology concentrating on human remains, involves the study of skeletal tissues to make inferences about lifeways in the past. Trace metals such as lead (Pb), strontium (Sr), mercury (Hg), and barium (Ba) have a strong affinity for bones and teeth and consequently accumulate in these tissues during different timeframes of an individual's life. Bones, which constantly undergo the process of remodeling, reflect an individual's relatively recent exposure (years to decades) to trace elements [1], whereas dental tissues, which do not remodel, reflect trace element exposure during their formation during childhood. Trace element analysis of archaeological bones and teeth has the potential to provide the bioarchaeologist with insights into past human diet, health, environment, mobility, occupation, social activities, and burial conditions [2]. Lead is historically significant, given the breadth of its use throughout the human past, as well as its toxic health impacts on populations. First exploited by humans as early as the sixth millennium BCE [3], lead has been widely used by humans in paint, ammunition, cosmetics, plumbing, and as a food additive [4] with prominent peaks in lead use occurring in antiquity, the Middle Ages, and following the European Industrial Revolution [4, 5]. As such, lead has been the focus of several previous bioarchaeological studies [6–9]. Methods conventionally used to assess lead in skeletal remains are limited in their ability to discern the nature and timing of lead uptake into bone. This article will review the strides that synchrotron X-ray microbeam techniques have made regarding the analysis of lead in bioarchaeological remains by summarizing key studies and methodological advancements, such as the addition of confocal optics.
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    A preliminary investigation of lead poisoning in a Napoleonic era naval cemetery in Antigua, W.I.
    (2012) Varney, Tamara L.; Swanston, Treena; Coulthard, Ian; Cooper, David M. L.; George, Graham N.; Pickering, Ingrid J.; Murphy, A. Reginald
    Lead poisoning has been suggested as being partially responsible for the ‘demise’ of the British military in the West Indies during the colonial era. Lead was pervasive in the colonial environment, being employed in items such as eating and cooking utensils, water catchments and alcohol distillation equipment. This preliminary study represents the first attempt to determine whether this suggestion has any validity. A bone sample taken from an individual excavated from a cemetery associated with a Royal Naval Hospital cemetery (c. 1793-1822 C.E.) in Antigua was used for initial testing. A control sample from an individual from a pre-contact site provided baseline/control data. Lead levels and distribution in the samples were mapped by synchrotron microprobe X-ray fluorescence (XRF) at the Stanford Synchrotron Radiation Lightsource (SSRL). Preliminary results revealed that the precontact sample had little to no detectable lead, while that from the historic period did indeed contain lead. Further, within the historic sample, discreet biological structures were found to contain a high level of lead relative to the surrounding bone. This result strongly suggests a biogenic rather than diagenetic origin for the heavy metal. This study marks the first successful application of this technology to archaeological bone samples from this region, and represents an exciting new potential tool for bioarchaeology.
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    Synchrotron X-ray fluorescence imaging evidence of biogenic mercury identified in a burial in colonial Antigua
    (2015) Swanston, Treena; Varney, Tamara L.; Coulthard, Ian; George, Graham N.; Pickering, Ingrid J.; Murphy, Reg; Cooper, David M. L.
    A mass spectroscopic analysis of bone samples from 17 individuals once buried in a Royal Naval Hospital cemetery (1793–1822) in Antigua revealed a high level of mercury (Hg) in one individual. While the toxic properties of Hg are now recognized, this metal was used for centuries to treat ailments such as syphilis and yellow fever. Synchrotron radiation X-ray fluorescence imaging (XFI) was employed to determine whether the Hg was present in the bone as a result of environmental contamination or due to biogenic uptake. The XFI study revealed that only a localized subset of the osteons within a 2.5 mm by 1.5 mm scan contained Hg – a finding consistent with biogenic uptake. The near-edge portion of the X-ray absorption spectrum was used to determine that the Hg was present in the bone tissue as an inorganic mercuric sulfide.