Radioactive isotope analyses of skeletal materials in forensic science: a review of uses and potential uses

A review of information that can be provided from measurements made on natural and anthropogenic radionuclide activities in human skeletal remains has been undertaken to establish what reliable information of forensic anthropological use can be obtained regarding years of birth and death (and hence post-mortem interval (PMI)). Of the anthropogenic radionuclides that have entered the environment, radiocarbon (14C) can currently be used to generate the most useful and reliable information. Measurements on single bones can indicate whether or not the person died during the nuclear era, while recent research suggests that measurements on trabecular bone may, depending on the chronological age of the remains, provide estimates of year of death and hence PMI. Additionally, 14C measurements made on different components of single teeth or on teeth formed at different times can provide estimates of year of birth to within 1–2 years of the true year. Of the other anthropogenic radionuclides, 90Sr shows some promise but there are problems of (1) variations in activities between individuals, (2) relatively large analytical uncertainties and (3) diagenetic contamination. With respect to natural series radionuclides, it is concluded that there is no convincing evidence that 210Pb dating can be used in a rigorous, quantitative fashion to establish a PMI. Similarly, for daughter/parent pairs such as 210Po/210Pb (from the 238U decay series) and 228Th/228Ra (from the 232Th decay series), the combination of analytical uncertainty and uncertainty in activity ratios at the point of death inevitably results in major uncertainty in any estimate of PMI. However, observation of the disequilibrium between these two daughter/parent pairs could potentially be used in a qualitative way to support other forensic evidence

Why do we need 14C inter-comparisons?: The Glasgow 14C inter-comparison series, a reflection over 30 years

Radiocarbon measurement is a well-established, routinely used, yet complex series of inter-linked procedures. The degree of sample pre-treatment varies considerably depending on the material, the methods of processing pre-treated material vary across laboratories and the detection of 14C at low levels remains challenging. As in any complex measurement process, the questions of quality assurance and quality control become paramount, both internally, i.e. within a laboratory and externally, across laboratories. The issue of comparability of measurements (and thus bias, accuracy and precision of measurement) from the diverse laboratories is one that has been the focus of considerable attention for some time, both within the 14C community and the wider user communities. In the early years of the technique when there was only a small number of laboratories in existence, inter-comparisons would function on an ad hoc basis, usually involving small numbers of laboratories (e.g.Otlet et al, 1980). However, as more laboratories were set-up and the detection methods were further developed (e.g. new AMS facilities), the need for more systematic work was recognised. The international efforts to create a global calibration curve also requires the use of data generated by different laboratories at different times, so that evidence of laboratory offsets is needed to inform curve formation. As a result of these factors, but also as part of general good laboratory practice, including laboratory benchmarking and quality assurance, the 14C community has undertaken a wide-scale, far-reaching and evolving programme of global inter-comparisons, to the benefit of laboratories and users alike. This paper looks at some of that history and considers what has been achieved in the past 30 years

A new database program installed at the SUERC radiocarbon laboratory

The SUERC Radiocarbon Dating Laboratory has recently replaced its spreadsheet-based record keeping with a new database program, custom designed to help laboratory staff manage the high throughput of nearly 5000 cathodes in the past year. The system can accept data from a variety of sources in addition to manual entry; experimental results can be uploaded from spreadsheets, while integration with graphitisation lines means that graphite yields are automatically recorded. The system is able to pass radiocarbon results directly to OxCal 4 for calibration, with the resulting plots incorporated into the dating certificates issued to submitters. There are also benefits to submitters, with electronic sample submission both eliminating transcription errors and speeding up the logging-in process which keeps turnaround times down. For bone samples, data on collagen yields are now stored electronically and are more readily obtainable from the laboratory. The new SUERC Radiocarbon Dating Laboratory database will make a significant contribution to maintaining the high quality of results produced by the laboratory, aiding staff in tracking sample progress and monitoring quality assurance (QA) samples going through the laboratory, eliminating transcription errors and making communication easier between laboratory staff and sample submitters

Studies in the Foliar Uptake and Translocation of Pesticides

This thesis is principally an investigation of the factors affecting the foliar uptake and translocation of pesticides with particular emphasis on the influence of additives on the herbicide aminotriazole. The work was subdivided as follows 1. A discussion of the various classes of additives which may influence foliar penetration and/or translocation with reference to their mode of action. 2. An investigation of the influence of adjuvants and humidity on the uptake of aminotriazole. The findings can be summarised as follows Penetration of bean leaves (Phaseolus vulgaris var. Canadian Wonder) was greatly enhanced under high humidity conditions (10% penetration in 17h at the low humidity level (LHL) compared with 100% at the high humidity level (HHL) ). The addition of polyoxyethylene 20 sorbitan monolaurate (polysorbate 20) to the spray fluid increased penetration on all occasions at the LHL. The increase obtained was found to be dependent on the concentration of polysorbate 20. Indeed, the w/w ratio of aminotriazole/polysorbate 20 seemed to be of primary importance. A 1/2 ratio appeared to bring about optimum penetration. The polysorbate 20 itself was not found to be taken up by the leaf to any great extent (5.4% penetration in 5h compared with 77.4% of the aminotriazole). The inclusion of polysorbate 20 at the HHL resulted in an increase in aminotriazole penetration at low polysorbate 20 concentrations (0.2-12.8g/litre) and a non-significant decrease over the aqueous control at a concentration of 40g/litre. Although aminotriazole penetration in the presence of polysorbate 20 (6.4g/litre) was increased at the HHL compared with the LHL, polysorbate 20 penetration was reduced. The addition of glycerol to the spray solution increased aminotriazole penetration on all occasions at the LHL while at the HHL none of the concentrations tested enhanced penetration. A polysorbate 20 plus glycerol combination (6.4g + 0.6ml/litre) gave the same order of penetration (98. 4 and 94. 0%) at the HHL and LHL respectively. In both cases, penetration exceeded that obtained with the corresponding polysorbate 20 and glycerol controls. 3. An investigation of the uptake by bean leaves (P. vulgaris var. Canadian Wonder) of aminotriazole from humectant-surfactant combinations and the influence of humidity on their effects. The findings can be summarised as follows Aminotriazole penetration was not greatly influenced by the addition to the spray solution of dimethyformamide (DMF), dimethyl sulphoxide (DMSO), ethylene glycol and polypropylene glycol 400 (PPG 400). However, the addition of polysorbate 20 (0.2 - 1.0g/litre) to spray solutions of the above additives and glycerol (5. 0ml/litre, except for DMF, 50.0ml/litre) substantially increased uptake to 80-100% in all cases at 50+10% relative humidity (r.h.). Similar trends were found when a range of polysorbate surfactants (0.2g/litre) were applied to solutions containing either DMSO or glycerol (5.0ml/litre). Humidity was found to have a critical effect upon such humectant-surfactant combinations. With DMSO-polysorbate 20 the following uptake figures were recorded: <30% r.h. - 3.1%; 45+/-10% r.h. - 86.8%; 55-65% r.h. - 48.2% and 100% r.h. - 0.3%. Similar trends were recorded with other combinations. Further studies revealed that the adverse effect of humidity on DMSO-polysorbate 20 mixtures could be at least partially overcome by regulating the DMSO concentration. 4. An investigation of the mode of action of thiocyanate and iodide in aminotriazole formulations. The findings are summarised as follows Ammonium thiocyanate (NH4SCN) was shown to inhibit aminotriazole oxidation in two free radical generating systems, namely (a) riboflavin photo sensitised oxidation, (b) oxidation by hydroxyl radicals. Evidence from in vitro studies is presented to show that NH4SCN could enhance aminotriazole performance by being preferentially oxidised within the leaf, thereby preventing aminotriazole free radical formation and subsequent conjugation with amino acids and other plant constituents. This opens up the possibility of a whole new range of additives which could enhance translocation by inhibiting free radical reactions. A comparison of possible inhibitors revealed that iodide and perhaps bromide and cyanide could be of use in this respect, Asulam was also found to be oxidised by the two free radical generating systems mentioned above. Again, the degree of oxidation was decreased by thiocyanate, iodide and also by ferrocyanide. This would suggest that additives such as NH4SCN may be of wider use than is at present recognised. In addition to inhibiting free radical reactions, NH4SCN, KSCN, NaSCN, Nal and KI were shown to have a considerable effect on aminotriazole uptake by bean leaves (P. vulgaris var. Canadian Wonder). Mgl2, Cal2 and Ca(SCN)2 had little effect on uptake. (Abstract shortened by ProQuest.)

A preliminary assessment of age at death determination using the nuclear weapons testing 14C activity of dentine and enamel

Calibration (using CALIBomb) of radiocarbon measurements made on the enamel of human teeth from people born during the nuclear era typically produce 2 possible age ranges that potentially reflect the period of tooth formation. These ranges correspond to periods before and after the 1963 atmospheric 14C maximum. Further measurements made on the collagen component of the combined dentine and cementum from the roots of the same teeth enable the appropriate age range to be selected. Using this range and the formation times for individual teeth, we estimated the year of birth of the individuals and compared these to the known dates of birth. The results were relatively accurate and confirmed those of a previous study by another research group. The present study demonstrates that it is possible to produce a good estimate of the year of birth from a single tooth

A period of calm in Scottish seas: a comprehensive study of ΔR values for the northern British Isles coast and the consequent implications for archaeology and oceanography

The Marine Radiocarbon Reservoir Effect (MRE) is a 14C age offset between contemporaneous marine- and terrestrially-derived carbon. In Northern Hemisphere surface waters it is of the order of 400 years but temporal and spatial deviations, known as ΔR, occur. This study provides a comprehensive dataset of 21 ΔR and MRE values for the east coast of Scotland and 21 recalculated values for the west coast of Scotland and Ireland, for the period c. 3500 BC to 1450 AD. They are presented as mean, site-specific ΔR and MRE values, together with their associated uncertainties, calculated as standard errors for predicted values. The ΔR values range from -320 ± 35 to +150 ± 28 14C years and show no spatial or temporal trends. The MRE values range from 59 ± 40 to 531 ± 26, show an almost identical distribution pattern to the ΔR values and again show no spatial or temporal trends. Results show that ΔR values calculated for a single site using statistically indistinguishable groups of terrestrial and marine radiocarbon age measurements can produce variability of up to 225 14C years. ΔR is an important factor in the accurate calibration of samples containing marine-derived carbon for archaeological interpretation but is often also used as an indicator of changes in 14C specific activity of the oceans, and therefore a proxy for changes in ocean circulation and/or climate. Using the methods outlined in this paper, it is apparent that ΔR values for the northern part of the British Isles have been relatively stable, within our ability to quantify non-random variation in the data. The fact that significant climatic shifts have been recorded during this time, yet these are not visible in the ΔR data, presents a cautionary tale regarding the use of ΔR to infer large-scale oceanographic or climatic changes. Upon the exclusion of 5 outliers from the 42 values, the remaining ΔR values are statistically indistinguishable from one another and range from -142 ± 61 to +40 ± 47 14C years. 34 of these values are from Scottish archaeological sites and can be combined to produce a mean value for Scotland of -47 ± 52 14C years for the period 3500 BC to 1450 AD, to be used only in the absence of site- and period-specific data

A marine reservoir effect ΔR value for Kitandach, in Prince Rupert Harbour, British Columbia, Canada

Prince Rupert Harbour (PRH), on the north Pacific Coast of British Columbia, contains at least 157 shell middens, of which 66 are known villages, in an area of approximately 180 km. These sites span the last 9500 yr and in some cases are immense, exceeding 20,000 m surface area and several meters in depth. Recent archaeological research in PRH has become increasingly reliant on radiocarbon dates from marine shell for developing chronologies. However, this is problematic as the local marine reservoir effect (MRE) remains poorly understood in the region. To account for the MRE and to better date the Harbour’s sites, we propose a ΔR of 273 ± 38 for the PRH area, based on our work at the site of Kitandach (GbTo-34), a massive shell midden-village centrally located within the Harbour. We followed the multiple paired sample approach for samples from speci fic contexts and ensured contemporaneity within the groups of marine and terrestrial materials by statistically assessing for outliers using the χ2 test. Taking together, the results for this and previous studies, it appears the MRE was fairly constant over the past 5000 yr