Isotope analysis

Isotope analysis is the identification of isotopic signature, the abundance of certain stable isotopes and chemical elements within organic and inorganic compounds. Isotopic analysis can be used to understand the flow of energy through a food web, to reconstruct past environmental and climatic conditions, to investigate human and animal diets in the past, for food authentification, and a variety of other physical, geological, palaeontological and chemical processes. Stable isotope ratios are measured using mass spectrometry, which separates the different isotopes of an element on the basis of their mass-to-charge ratio.

Thermal ionization mass spectrometer
Magnetic sector mass spectrometer used in isotope ratio analysis, through thermal ionization

Tissue affected

Isotopic oxygen is incorporated into the body primarily through ingestion at which point it is used in the formation of, for archaeological purposes, bones and teeth. The oxygen is incorporated into the hydroxylcarbonic apatite of bone and tooth enamel.

Bone is continually remodelled throughout the lifetime of an individual. Although the rate of turnover of isotopic oxygen in hydroxyapatite is not fully known, it is assumed to be similar to that of collagen; approximately 10 years. Consequently, should an individual remain in a region for 10 years or longer, the isotopic oxygen ratios in the bone hydroxyapatite would reflect the oxygen ratios present in that region.

Teeth are not subject to continual remodelling and so their isotopic oxygen ratios remain constant from the time of formation. The isotopic oxygen ratios, then, of teeth represent the ratios of the region in which the individual was born and raised. Where deciduous teeth are present, it is also possible to determine the age at which a child was weaned. Breast milk production draws upon the body water of the mother, which has higher levels of 18O due to the preferential loss of 16O through sweat, urine, and expired water vapour.

While teeth are more resistant to chemical and physical changes over time, both are subject to post-depositional diagenesis. As such, isotopic analysis makes use of the more resistant phosphate groups, rather than the less abundant hydroxyl group or the more likely diagenetic carbonate groups present.

Applications

Isotope analysis has widespread applicability in the natural sciences. These include numerous applications in the biological, earth and environmental sciences.

Archaeology

Reconstructing ancient diets

Archaeological materials, such as bone, organic residues, hair, or sea shells, can serve as substrates for isotopic analysis. Carbon, nitrogen and zinc isotope ratios are used to investigate the diets of past people; These isotopic systems can be used with others, such as strontium or oxygen, to answer questions about population movements and cultural interactions, such as trade.[1]

Carbon isotopes are analysed in archaeology to determine the source of carbon at the base of the foodchain. Examining the 12C/13C isotope ratio, it is possible to determine whether animals and humans ate predominantly C3 or C4 plants.[2] Potential C3 food sources include wheat, rice, tubers, fruits, nuts and many vegetables, while C4 food sources include millet and sugar cane.[3] Carbon isotope ratios can also be used to distinguish between marine, freshwater, and terrestrial food sources.[4][5]

Carbon isotope ratios can be measured in bone collagen or bone mineral (hydroxylapatite), and each of these fractions of bone can be analysed to shed light on different components of diet. The carbon in bone collagen is predominantly sourced from dietary protein, while the carbon found in bone mineral is sourced from all consumed dietary carbon, included carbohydrates, lipids, and protein.[6]

To obtain an accurate picture of palaeodiets, it is important to understand processes of diagenesis that may affect the original isotopic signal. It is also important for the researcher to know the variations of isotopes within individuals, between individuals, and over time.[1]

Sourcing archaeological materials

Isotope analysis has been particularly useful in archaeology as a means of characterization. Characterization of artifacts involves determining the isotopic composition of possible source materials such as metal ore bodies and comparing these data to the isotopic composition of analyzed artifacts. A wide range of archaeological materials such as metals, glass and lead-based pigments have been sourced using isotopic characterization.[7] Particularly in the Bronze Age Mediterranean, lead isotope analysis has been a useful tool for determining the sources of metals and an important indicator of trade patterns. Interpretation of lead isotope data is, however, often contentious and faces numerous instrumental and methodological challenges.[8] Problems such as the mixing and re-using of metals from different sources, limited reliable data and contamination of samples can be difficult problems in interpretation.

Ecology

All biologically active elements exist in a number of different isotopic forms, of which two or more are stable. For example, most carbon is present as 12C, with approximately 1% being 13C. The ratio of the two isotopes may be altered by biological and geophysical processes, and these differences can be utilized in a number of ways by ecologists. The main elements used in isotope ecology are carbon, nitrogen, oxygen, hydrogen and sulfur, but also include silicon, iron, and strontium.[9]

Stable isotope analysis in aquatic ecosystems

Stable isotopes have become a popular method for understanding aquatic ecosystems because they can help scientists in understanding source links and process information in marine food webs. These analyses can also be used to a certain degree in terrestrial systems. Certain isotopes can signify distinct primary producers forming the bases of food webs and trophic level positioning. The stable isotope compositions are expressed in terms of delta values (δ) in permil (‰), i.e. parts per thousand differences from a standard. They express the proportion of an isotope that is in a sample. The values are expressed as:

δX = [(Rsample / Rstandard) – 1] × 103

where X represents the isotope of interest (e.g., 13C) and R represents the ratio of the isotope of interest and its natural form (e.g., 13C/12C).[10] Higher (or less negative) delta values indicate increases in a sample's isotope of interest, relative to the standard, and lower (or more negative) values indicate decreases. The standard reference materials for carbon, nitrogen, and sulfur are Pee Dee Belamnite limestone, nitrogen gas in the atmosphere, and Cañon Diablo meteorite respectively. Analysis is usually done using a mass spectrometer, detecting small differences between gaseous elements. Analysis of a sample can cost anywhere from $30 to $100.[10] Stable isotopes assist scientists in analyzing animal diets and food webs by examining the animal tissues that bear a fixed isotopic enrichment or depletion vs. the diet. Muscle or protein fractions have become the most common animal tissue used to examine the isotopes because they represent the assimilated nutrients in their diet. The main advantage to using stable isotope analysis as opposed to stomach content observations is that no matter what the status is of the animal's stomach (empty or not), the isotope tracers in the tissues will give us an understanding of its trophic position and food source.[11] The three major isotopes used in aquatic ecosystem food web analysis are 13C, 15N and 34S. While all three indicate information on trophic dynamics, it is common to perform analysis on at least two of the previously mentioned 3 isotopes for better understanding of marine trophic interactions and for stronger results.

Carbon isotopes aid us in determining the primary production source responsible for the energy flow in an ecosystem. The transfer of 13C through trophic levels remains relatively the same, except for a small increase (an enrichment < 1 ‰). Large differences of δ13C between animals indicate that they have different food sources or that their food webs are based on different primary producers (i.e. different species of phytoplankton, marsh grasses.) Because δ13C indicates the original source of primary producers, the isotopes can also help us determine shifts in diets, both short term, long term or permanent. These shifts may even correlate to seasonal changes, reflecting phytoplankton abundance.[11] Scientists have found that there can be wide ranges of δ13C values in phytoplankton populations over a geographic region. While it is not quite certain as to why this may be, there are several hypotheses for this occurrence. These include isotopes within dissolved inorganic carbon pools (DIC) may vary with temperature and location and that growth rates of phytoplankton may affect their uptake of the isotopes. δ13C has been used in determining migration of juvenile animals from sheltered inshore areas to offshore locations by examining the changes in their diets. A study by Fry (1983) studied the isotopic compositions in juvenile shrimp of south Texas grass flats. Fry found that at the beginning of the study the shrimp had isotopic values of δ13C = -11 to -14‰ and 6-8‰ for δ15N and δ34S. As the shrimp matured and migrated offshore, the isotopic values changed to those resembling offshore organisms (δ13C= -15‰ and δ15N = 11.5‰ and δ34S = 16‰).[12]

While there is no enrichment of 34S between trophic levels, the stable isotope can be useful in distinguishing benthic vs. pelagic producers and marsh vs. phytoplankton producers.[11] Similar to 13C, it can also help distinguish between different phytoplankton as the key primary producers in food webs. The differences between seawater sulfates and sulfides (c. 21‰ vs -10‰) aid scientists in the discriminations. Sulfur tends to be more plentiful in less aerobic areas, such as benthic systems and marsh plants, than the pelagic and more aerobic systems. Thus, in the benthic systems, there are smaller δ34S values.[11]

Nitrogen isotopes indicate the trophic level position of organisms (reflective of the time the tissue samples were taken). There is a larger enrichment component with δ15N because its retention is higher than that of 14N. This can be seen by analyzing the waste of organisms.[11] Cattle urine has shown that there is a depletion of 15N relative to the diet.[13] As organisms eat each other, the 15N isotopes are transferred to the predators. Thus, organisms higher in the trophic pyramid have accumulated higher levels of 15N ( and higher δ15N values) relative to their prey and others before them in the food web. Numerous studies on marine ecosystems have shown that on average there is a 3.2‰ enrichment of 15N vs. diet between different trophic level species in ecosystems.[11] In the Baltic sea, Hansson et al. (1997) found that when analyzing a variety of creatures (such as particulate organic matter (phytoplankton), zooplankton, mysids, sprat, smelt and herring,) there was an apparent fractionation of 2.4‰ between consumers and their apparent prey.[14]

In addition to trophic positioning of organisms, δ15N values have become commonly used in distinguishing between land derived and natural sources of nutrients. As water travels from septic tanks to aquifers, the nitrogen rich water is delivered into coastal areas. Waste-water nitrate has higher concentrations of 15N than the nitrate that is found in natural soils in near shore zones.[15] For bacteria, it is more convenient for them to uptake 14N as opposed to 15N because it is a lighter element and easier to metabolize. Thus, due to bacteria's preference when performing biogeochemical processes such as denitrification and volatilization of ammonia, 14N is removed from the water at a faster rate than 15N, resulting in more 15N entering the aquifer. 15N is roughly 10-20‰ as opposed to the natural 15N values of 2-8‰.[15] The inorganic nitrogen that is emitted from septic tanks and other human-derived sewage is usually in the form of . Once the nitrogen enters the estuaries via groundwater, it is thought that because there is more 15N entering, that there will also be more 15N in the inorganic nitrogen pool delivered and that it is picked up more by producers taking up N. Even though 14N is easier to take up, because there is much more 15N, there will still be higher amounts assimilated than normal. These levels of δ15N can be examined in creatures that live in the area and are non migratory (such as macrophytes, clams and even some fish).[14][16][17] This method of identifying high levels of nitrogen input is becoming a more and more popular method in attempting to monitor nutrient input into estuaries and coastal ecosystems. Environmental managers have become more and more concerned about measuring anthropogenic nutrient inputs into estuaries because excess in nutrients can lead to eutrophication and hypoxic events, eliminating organisms from an area entirely.[18]

Analysis of the ratio of 18O to 16O in the shells of the Colorado Delta clam was used to assess the historical extent of the estuary in the Colorado River Delta prior to construction of upstream dams.[19]

The ratio of 2H, also known as Deuterium, to 1H has been studied in both plant and animal tissue. Hydrogen isotopes in plant tissue are correlated with local water values but vary based on fractionation during photosynthesis, transpiration, and other processes in the formation of cellulose. A study on the isotope ratios of tissues from plants growing within a small area in Texas found tissues from CAM plants were enriched in deuterium relative to C4 plants.[20] Hydrogen isotope ratios in animal tissue reflect diet, including drinking water, and have been used to study bird migration[21] and aquatic food webs.[22][23]

Forensic science

A recent development in forensic science is the isotopic analysis of hair strands. Hair has a recognisable growth rate of 9-11mm[24] per month or 15 cm per year.[25] Human hair growth is primarily a function of diet, especially drinking water intake. The stable isotopic ratios of drinking water are a function of location, and the geology that the water percolates through. 87Sr, 88Sr and oxygen isotope variations are different all over the world. These differences in isotopic ratio are then biologically 'set' in our hair as it grows and it has therefore become possible to identify recent geographic histories by the analysis of hair strands. For example, it could be possible to identify whether a terrorist suspect had recently been to a particular location from hair analysis. This hair analysis is a non-invasive method which is becoming very popular in cases that DNA or other traditional means are bringing no answers.

Isotope analysis can be used by forensic investigators to determine whether two or more samples of explosives are of a common origin. Most high explosives contain carbon, hydrogen, nitrogen and oxygen atoms and thus comparing their relative abundances of isotopes can reveal the existence of a common origin. Researchers have also shown that analysis of the 12C/13C ratios can locate the country of origin for a given explosive.

Stable isotopic analysis has also been used in the identification of drug trafficking routes. Isotopic abundances are different in morphine grown from poppies in south-east Asia versus poppies grown in south-west Asia. The same is applied to cocaine that is derived from Bolivia and that from Colombia.[26]

Traceability

Stable isotopic analysis has also been used for tracing the geographical origin of food[27] and timber.[28]

Hydrology

In isotope hydrology, stable isotopes of water (2H and 18O) are used to estimate the source, age, and flow paths of water flowing through ecosystems. The main effects that change the stable isotope composition of water are evaporation and condensation.[29] Variability in water isotopes is used to study sources of water to streams and rivers, evaporation rates, groundwater recharge, and other hydrological processes.[30][31]

Paleoclimatology

The ratio of 18O to 16O in ice and deep sea cores is temperature dependent, and can be used as a proxy measure for reconstructing climate change. During colder periods of the Earth's history (glacials) such as during the ice ages, 16O is preferentially evaporated from the colder oceans, leaving the slightly heavier and more sluggish 18O behind. Organisms such as foraminifera which combine oxygen dissolved in the surrounding water with carbon and calcium to build their shells therefore incorporate the temperature-dependent 18O to 16O ratio. When these organisms die, they settle out on the sea bed, preserving a long and invaluable record of global climate change through much of the Quaternary.[32] Similarly, ice cores on land are enriched in the heavier 18O relative to 16O during warmer climatic phases (interglacials) as more energy is available for the evaporation of the heavier 18O isotope. The oxygen isotope record preserved in the ice cores is therefore a "mirror" of the record contained in ocean sediments.

Oxygen isotopes preserve a record of the effects of the Milankovitch cycles on climate change during the Quaternary, revealing an approximately 100,000-year cyclicity in the Earth's climate.

References

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External links

Ancient iron production

Ancient iron production refers to iron working in times from prehistory to the early Middle Ages where knowledge of production processes is derived from archaeological investigation. Slag, the byproduct of iron-working processes such as smelting or smithing, is left at the iron-working site rather than being moved away with the product. It also weathers well and hence it is readily available for study. The size, shape, chemical composition and microstructure of slag are determined by features of the iron-working processes used at the time of its formation.

Animal migration tracking

Animal migration tracking is used in wildlife biology, conservation biology, ecology, and wildlife management to study animals' behavior in the wild. One of the first techniques was bird banding, placing passive ID tags on birds legs, to identify the bird in a future catch-and-release. Radio tracking involves attaching a small radio transmitter to the animal and following the signal with a RDF receiver. Sophisticated modern techniques use satellites to track tagged animals, and GPS tags which keep a log of the animal's location. One of the many goals of animal migration research has been to determine where the animals are going; however, researchers also want to know why they are going "there". Researchers not only look at the animals' migration but also what is between the migration endpoints to determine if a species is moving to new locations based on food density, a change in water temperature, or other stimulus, and the animal's ability to adapt to these changes. Migration tracking is a vital tool in efforts to control the impact of human civilization on populations of wild animals, and prevent or mitigate the ongoing extinction of endangered species.

Bioarchaeology

The term bioarchaeology was first coined by British archaeologist Grahame Clark in 1972 as a reference to zooarchaeology, or the study of animal bones from archaeological sites. Redefined in 1977 by Jane Buikstra, bioarchaeology in the US now refers to the scientific study of human remains from archaeological sites, a discipline known in other countries as osteoarchaeology or palaeo-osteology. In England and other European countries, the term 'bioarchaeology' is borrowed to cover all biological remains from sites.

Bioarchaeology was largely born from the practices of New Archaeology, which developed in the US in the 1970s as a reaction to a mainly cultural-historical approach to understanding the past. Proponents of New Archaeology advocated using processual methods to test hypotheses about the interaction between culture and biology, or a biocultural approach. Some archaeologists advocate a more holistic approach to bioarchaeology that incorporates critical theory and is more relevant to modern descent populations.If possible, human remains from archaeological sites are analyzed to determine sex, age, and health.

Bromine pentafluoride

Bromine pentafluoride, BrF5, is an interhalogen compound and a fluoride of bromine. It is a strong fluorination reagent.

BrF5 finds use in oxygen isotope analysis. Laser ablation of solid silicates in the presence of bromine pentafluoride releases O2 for subsequent analysis. It has also been tested as an oxidizer in liquid rocket propellants and is used as a fluorinating agent in the processing of uranium.

Canadian Reference Materials

Canadian Reference Materials (CRM) are certified reference materials of high-quality and reliability produced by the National Metrology Institute of Canada – the National Research Council Canada. The NRC Certified Reference Materials program is operated by the Measurement Science and Standards portfolio and provides CRMs for environmental, biotoxin, food, nutritional supplement, and stable isotope analysis. The program was established in 1976 to produce CRMs for inorganic and organic marine environmental analysis and remains internationally recognized producer of CRMs.

Eastern Settlement

The Eastern Settlement (Old Norse: Eystribygð) was the first and by far the largest of the two main areas of Norse Greenland, settled c. AD 985 by Norsemen from Iceland. At its peak, it contained approximately 4,000 inhabitants. The last written record from the Eastern Settlement is of a wedding solemnized in 1408, placing it about 50–100 years later than the end of the more northern Western Settlement.Despite its name, the Eastern Settlement was more south than east of its companion and, like the Western Settlement, was located on the southwestern tip of Greenland at the head of long fjords such as Tunulliarfik Fjord or Eiriksfjord, Igaliku or Einarsfjord, and Sermilik Fjord (see map at right).

Approximately 500 groups of ruins of Norse farms are found in the area, including 16 church ruins, including Brattahlíð, Dyrnæs, Garðar, Hvalsey and Herjolfsnes. The Vatnahverfi district to the southeast of Einarsfjord had some of the best pastoral land in the colony, and boasted 10% of all the known farm sites in the Eastern Settlement.

The economy of the medieval Norse settlements was based on livestock farming - mainly sheep and cattle, with significant supplement from seal hunting. A climate deterioration in the 14th century may have increased the demand for winter fodder and at the same time decreased productivity of hay meadows. Isotope analysis of bones excavated at archaeological investigations in the Norse settlements has found that fishing played an increasing economic role towards the end of the settlement's life. While the diet of the first settlers consisted of 80% agricultural products and 20% marine food, from the 14th century the Greenland Norsemen had 50–80% of their diet from the sea.In the Greenlandic Inuit tradition, there is a legend about Hvalsey. According to this legend, there was open war between the Norse chief Ungortoq and the Inuit leader K'aissape. The Inuit made a massive attack on Hvalsey and burned down the Norse inside their houses, but Ungortoq escaped with his family. K'aissape conquered him after a long pursuit, which ended near Cape Farewell. However, according to archaeological studies, there is no sign of a conflagration. Other explanations have also been offered including soil erosion due to overgrazing and the effects of the Black Death.

Isotope-ratio mass spectrometry

Isotope-ratio mass spectrometry (IRMS) is a specialization of mass spectrometry, in which mass spectrometric methods are used to measure the relative abundance of isotopes in a given sample.This technique has two different applications in the earth and environmental sciences. The analysis of 'stable isotopes' is normally concerned with measuring isotopic variations arising from mass-dependent isotopic fractionation in natural systems. On the other hand, radiogenic isotope analysis involves measuring the abundances of decay-products of natural radioactivity, and is used in most long-lived radiometric dating methods.

Isotope fractionation

Isotope fractionation describes processes that affect the relative abundance of isotopes, often used in isotope geochemistry. Normally, the focus is on stable isotopes of the same element. Isotopic fractionation in the natural environment can be measured by isotope analysis, using isotope-ratio mass spectrometry, to separate different element isotopes on the basis of their mass-to-charge ratio, an important tool to understand natural systems. For example, in biochemistry processes cause a fluctuation in the amount of isotopes of carbon ratios incorporated into a biological being. The difference between the true amount of carbon and the amount in the plant is known as isotope fractionation.

Isotopic signature

An isotopic signature (also isotopic fingerprint) is a ratio of non-radiogenic 'stable isotopes', stable radiogenic isotopes, or unstable radioactive isotopes of particular elements in an investigated material. The ratios of isotopes in a sample material are measured by isotope-ratio mass spectrometry against an isotopic reference material. This process is called isotope analysis.

Kʼinich Yax Kʼukʼ Moʼ

Kʼinich Yax Kʼukʼ Moʼ (Mayan pronunciation: [jaʃ kʼukʼ moʔ] "Great Sun, Quetzal Macaw the First", ruled 426 – c. 437) is named in Maya inscriptions as the founder and first ruler, kʼul ajaw (also rendered kʼul ahau and kʼul ahaw - meaning holy lord), of the pre-Columbian Maya civilization polity centered at Copán, a major Maya site located in the southeastern Maya lowlands region in present-day Honduras. The motifs associated with his depiction on Copán monuments have a distinct resemblance to imagery associated with the height of the Classic-era center of Teotihuacan in the distant northern central Mexican region, and have been interpreted as intending to suggest his origins and association with that prestigious civilization. One of the most commonly cited motifs for this interpretation is the "goggle-eyed" headdress with which Yax Kʼukʼ Moʼ is commonly depicted; this is seemingly an allusion to the northern central Mexican rain deity known as Tlaloc by later peoples, such as the Aztecs. However, modern strontium isotope analysis of the human remains recovered from the tomb attributed to him indicate that Kʼinich Yax Kʼukʼ Moʼ spent his formative years much closer to Copán, at Tikal, and had not himself lived at Teotihuacan.

Medieval bioarchaeology

Medieval bioarchaeology is the study of human remains recovered from medieval archaeological sites. Bioarchaeology aims to understand populations through the analysis of human skeletal remains and this application of bioarchaeology specifically aims to understand medieval populations.

Per meg

Per meg equals 0.001 permil or 0.0001 percent or parts per million ppm. The unit is typically used in isotope analysis by multiplying an isotope ratio in delta annotation, for example δ18O, by 1000000.

This annotation is typically used in studies of atmospheric trace gases, where a high precision is needed for a significant interpretation of results.

Position-specific isotope analysis

Position-specific isotope analysis (PSIA), also called site-specific isotope analysis, is a branch of isotope analysis aimed at determining the isotopic composition of a particular atom position in a molecule. It can be described as the determination of the relative concentration of isotopomers at natural abundance. The first evidence for a deviation from a stochastic distribution was found in 1961 on amino acids whose carboxyl groups were 13C-enriched compared to the rest of the molecule. Since then, several studies have shown that PSIA can give insights into the origin of a given molecule: biosynthetic pathway, mechanism and temperature of formation.

Reference materials for stable isotope analysis

Isotopic reference materials are compounds (solids, liquids, gasses) with well-defined isotopic compositions and are the ultimate sources of accuracy in mass spectrometric measurements of isotope ratios. Isotopic references are used because mass spectrometers are highly fractionating. As a result, the isotopic ratio that the instrument measures can be very different from that in the sample's measurement. Moreover, the degree of instrument fractionation changes during measurement, often on a timescale shorter than the measurement's duration, and can depend on the characteristics of the sample itself. By measuring a material of known isotopic composition, fractionation within the mass spectrometer can be removed during post-measurement data processing. Without isotope references, measurements by mass spectrometry would be much less accurate and could not be used in comparisons across different analytical facilities. Due to their critical role in measuring isotope ratios, and in part, due to historical legacy, isotopic reference materials define the scales on which isotope ratios are reported in the peer-reviewed scientific literature.

Isotope reference materials are generated, maintained, and sold by the International Atomic Energy Agency (IAEA), the National Institute of Standards and Technology (NIST), the United States Geologic Survey (USGS), the Institute for Reference Materials and Measurements (IRMM), and a variety of universities and scientific supply companies. Each of the major stable isotope systems (hydrogen, carbon, oxygen, nitrogen, and sulfur) has a wide variety of references encompassing distinct molecular structures. For example, nitrogen isotope reference materials include N-bearing molecules such ammonia (NH3), atmospheric dinitrogen (N2), and nitrate (NO3). Isotopic abundances are commonly reported using the δ notation, which is the ratio of two isotopes (R) in a sample relative to the same ratio in a reference material, often reported in per mille (‰) (equation below). Reference material span a wide range of isotopic compositions, including enrichments (positive δ) and depletions (negative δ). While the δ values of references are widely available, estimates of the absolute isotope ratios (R) in these materials are seldom reported. This article aggregates the δ and R values of common and non-traditional stable isotope reference materials.

Robert H. Brill

Dr Robert Brill is in the field of archaeological science, best known for his work on the chemical analysis of ancient glass. Born in the United States of America in 1929, Brill attended West Side High School in Newark, New Jersey, before going on to study for his B.S. degree at Upsala College, also New Jersey (Brill 1993a, Brill 2006, Getty Conservation Institute 2009). Having completed his Ph.D in Physical Chemistry at Rutgers University in 1954, Brill was to return to Upsala College to teach chemistry himself until 1960 when he joined the staff of the Corning Museum of Glass as their second research scientist (Corning Museum of Glass, 2009)

Throughout his lengthy career at Corning, where a four-year directorship punctuated his time as a research scientist, Brill was a forerunner in the scientific investigation of glass, glazes and colorants, developing and challenging the usefulness of emerging techniques. His pioneering work with the application of lead and oxygen isotope analysis in archaeology led him occasionally to add the investigation of metal objects to his portfolio so that, together, his published works number more than 160 (Brill and Wampler 1967). Perhaps the most famous of these is his Chemical Analyses of Early Glass, a sum of his 39 years of work and now a seminal reference guide in the field (Brill 1999).

Brill is a strong proponent of interdisciplinary cooperation as well as the collaboration between scientists across the world, and has served since 1982 on the International Commission on Glass. Within this he founded TC17, the technical committee for the Archaeometry of Glass, which lists among its aims the ‘promotion of collaboration among glass specialists in widely separated countries’ and the stimulation and encouragement of glass scientists ‘in developing countries’ (Archaeometry of Glass 2005). His internationalism is aptly demonstrated by his study of glasses from around the world, with his attentions most recently being focused on those from the Silk Road. Here, as with other areas of Brill's remarkable career, it seems he was attracted by the lack of previous study and the need for further development in the field. Seeing a disparity between contemporary knowledge of glasses from the western world and those from East Asia, Brill was keen to add insight to a hitherto unexploited field and, as such, has gone on to contribute a great deal to Silk Road studies (Brill 1993b).

The broad span of Brill's career allows this paper to provide only an abridged synopsis of his métier and published works to date. Focusing on Brill's achievements during the decades after he joined the Corning Museum in February 1960, it aims to highlight areas in which Brill pioneered new techniques and improved existing ones, offering summaries of major publications and proposing sources the interested reader may turn to for more information (Brill 1999).

Stable isotope ratio

The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundance of such stable isotopes can be measured experimentally (isotope analysis), yielding an isotope ratio that can be used as a research tool. Theoretically, such stable isotopes could include the radiogenic daughter products of radioactive decay, used in radiometric dating. However, the expression stable-isotope ratio is preferably used to refer to isotopes whose relative abundances are affected by isotope fractionation in nature. This field is termed stable isotope geochemistry.

Tianyuan man

Tianyuan man (Chinese: t 田園洞人, s 田园洞人, p Tiányuándòng Rén) are the remains of one of the earliest modern humans to inhabit East Asia. In 2007, researchers found 34 bone fragments belonging to a single individual at the Tianyuan Cave near Beijing, China. Radiocarbon dating shows the bones to be between 42,000 and 39,000 years old, which may be slightly younger than the only other finds of bones of a similar age at the Niah Caves in Sarawak on Borneo.

Isotope analysis suggests that a substantial part of the diet of these individuals came from freshwater fish.TianYuan man is considered an early modern human. It lack several mandibular features common among with western Eurasian late archaic human showing its divergence. Based on the rate of dental occlusal attrition, it is estimated he died in his 40's or 50's.DNA tests published in 2013 revealed that Tianyuan man is related "to many present-day Asians and Native Americans". He had also clearly diverged genetically from the ancestors of modern Europeans. He belonged to mitochondrial DNA haplogroup B.

Tianyuan man exhibits a unique genetic affinity for GoyetQ116-1 from Goyet Caves that is not found in any other ancient individual from West Eurasia. He shares more allele with to today's people from Surui and Karitiana tribes in Brazil than other Native American populations. Suggesting a population that is related to Tianyuan man and Papuan and Andamanese Onge was once widespread in eastern Asia.

Wolfram Meier-Augenstein

Wolfram Meier-Augenstein is a Professor at Robert Gordon University, Aberdeen, a registered forensic expert advisor with the British National Crime Agency and a member of the Advisory Board of the journal Rapid Communications in Mass Spectrometry. He holds a doctorate in natural sciences awarded by the Ruprechts-Karl University Heidelberg (Germany) in 1989. The subject of PhD thesis was the structure/activity relationship of stereo-isomers of the Periodic Leaf Movement Factor 1 that triggers the nastic leaf movement of Mimosa pudica L. As Feodor-Lynen-Fellow of the Alexander-von-Humboldt Foundation and PD Fellow of the South African Research Foundation he spent 1.5 years as post-doctoral fellow with Prof. B.V. Burger at the University of Stellenbosch. Here he synthesised and studied cyclodextrine derivatives used as chiral selectors for enantioselective gas chromatography. From there, his career took him to the University Children’s Hospital Heidelberg, the University of California San Diego, the University of Dundee, the Queen’s University Belfast and back to Scotland, first to the James Hutton Institute (Dundee) and finally the Robert Gordon University (Aberdeen). From 2010 to 2014 he served as Director of the Forensic Isotope Ratio Mass Spectrometry Network (FIRMS). while from 2009 to 2013 he was a Council member of the British Association for Human Identification (BAHID). Dr Meier-Augenstein was one of the scientists consulted by An Garda Síochána investigating the case of the dismembered torso found in the Dublin Royal Canal. This case has gained some notoriety under the name Scissor Sisters (convicted killers). He was also one of the scientists consulted by the police investigating the Norfolk headless body case. Most recently, Dr Meier-Augenstein was involved with the case dubbed "The Lady of the Hills" or the "Thai Bride". His interpretation of stable isotope signatures obtained from remains of the murder victim corroborated one line of investigation that the victim might have grown up in Thailand . A subsequently launched public appeal received a response from a Thai family who believed the victim could be their daughter . DNA tests finally confirmed the identity of the victim as Lamduan Armitage, nee Seekanya, originally from Thailand who had moved to the UK in 1991 .

Dr Meier-Augenstein is the author of the book "Stable Isotope Forensics", the first textbook dedicated to principles and forensic applications of stable isotope analytical techniques..

Δ15N

In geochemistry, hydrology, paleoclimatology and paleoceanography δ15N (pronounced "delta fifteen n") or delta-N-15 is a measure of the ratio of the two stable isotopes of nitrogen, 15N:14N.

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