Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2016. / Radiostrontium (90Sr and 89Sr) has been released to the environment by global fall-out following atmospheric nuclear explosions, by waste discharges and fall-out from the Chernobyl. 89Sr, with a half-life of 50.5 days, quickly decays to undetectable levels, while 90Sr is radiobiologically more important because of its longer half-life of 28.78 years, and because it behaves chemically similar to Ca, and accumulates in bones and teeth. Cost effective and relatively simple procedures for determination of radiostrontium are desirable. An accurate determination of radionuclides from various sources in the environment is essential for assessment of the potential hazards and suitable countermeasures both in case of accidents, authorised releases and routine surveillances. Reliable radiochemical separation and detection techniques are needed for accurate determination of alpha and beta emitters. Rapid analytical methods are needed in case of an accident for early decision-making. At the Koeberg Nuclear Power Station (KNPS), 90Sr analysis are performed on liquid effluent samples making use of the traditional fuming nitric acid method, and subsequent counting of particulate samples on an alpha/beta proportional counter. This method is often at times very time – consuming, and involves many precipitation steps. The use of fuming nitric acid is also very dangerous and could lead to severe personnel injuries in the event of an accident. This project focussed on the application of Sr-Spec resin in the analysis of 90Sr. This work presents the methods for 90Sr analysis for both effluent samples as well as environmental samples. This research also focussed on the calibration of the different radiometric instruments, which are the Liquid Scintillation Counter, the Alpha/Beta Counter as well as the Gamma Detector.

Forensic anthropologists increasingly use chemical isotope analysis in the investigation of unidentified human remains, as biochemical georeferencing continually improves with the development of modern reference data of known origins. Isotope variations in trace elements such as strontium (Sr) and lead (Pb) in human teeth are some of the most useful indicators of past domicile in archaeological research and thus have high potential for modern, forensic applications. In this study, high-precision lead isotope analysis was conducted on 63 modern human teeth, which were previously analyzed for strontium isotopes. The results present new lead isotope data for the following countries: United States (n=34), Colombia (n=9), Haiti (n=5), Cape Verde (n=3), Morocco (n=2), El Salvador (n=2), Guatemala (n=2), Honduras (n=2), Jamaica (n=1), Dominican Republic (n=1), Albania (n=1), and United Kingdom (n=1). In addition, the lead and strontium isotope data of 23 modern human teeth from individuals born in Holland, eight teeth from individuals born in Bulgaria, and 26 teeth from individuals born in the U.S. are extracted from the literature to supplement the data analysis. Exploratory data analysis, nonparametric Kruskal-Wallis tests, and one-way analysis of variance (Scheffe post hoc) are conducted using IBM SPSS® Statistics 24 to test for regional variation. Several trends are observed in the lead isotope data that may be relevant to modern forensic contexts involving unidentified human remains: Individuals from the northeast U.S. have relatively distinct 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb ratios when compared to individuals from the rest of the U.S. European and American individuals can be easily distinguished from each other using 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb ratios. Central American individuals have significantly lower 87Sr/86Sr ratios than North American individuals, and these groups can be easily distinguished using lead versus strontium scatterplots. Colombian individuals have significantly lower 87Sr/86Sr ratios than North American individuals, and these groups can be easily distinguished using lead versus strontium scatterplots. Caribbean individuals have significantly lower 87Sr/86Sr isotope ratios than individuals from the northeast U.S., and these groups can be easily distinguished using lead versus strontium scatterplots.

This study is the geochemical examination of mineral weathering and its path from hinterland, through sediment deposition and pedogenesis, to its dissolution and eventual uptake into plants or precipitation as carbonate minerals. The three papers examine the rate and character of carbonate and silicate mineral weathering over a wide range of climatic and tectonic regimes, time periods, and lithologies, and focus on very different questions. Examination of the 87Sr/86Sr ratios of architectural ponderosa pine in Chaco Canyon, New Mexico confirms a societally complex style of timber procurement from the 10th to the 12th centuries. In El Malpais National Monument, New Mexico, we measured the 87Sr/86Sr ratios in local bedrock and soils and compared them to the leaf/wood cellulose of four conifers (Pinus ponderosa, Pinus edulis, Juniperus monosperma, Juniperus scopulorum), a deciduous tree (Populus tremuloides), three shrubs (Chrysothamus nauseosus, Fallugia paradoxa, Rhus trilobata), and an annual grass (Bouteloua gracilis) and a lichen (Xanthoparmelia lineola). We found that plant 87Sr/86Sr ratios covaried with variations in plant physiognomy, life history, and rooting depth. In addition, the proportion of atmospheric dust and bedrock mineral contributions to soil water 87Sr/86Sr ratios varied predictably with landscape age and bedrock lithology. On the Himalayan floodplain, soils and paleosol silicate weathering intensities were measured along a climatic transect and through time. Overall, carbonate weathering dominates floodplain weathering. But, periods of more intense silicate weathering between 9 - 2 Ma, identified in soil profile and in the 87Sr/86Sr ratios of pedogenic carbonates, appear to be driven by changes in tectonic, rather than climatic, regime. All three papers are good examples of how 87Sr/86Sr isotopic tracer studies can shed light on pedogenic formation rates and internal processes. The complexity of each system warns against generalizations based on just one locale, one species or lithology, or a few isotopic ratios.

No description available.

The collection and analysis of a large number of belemnites and oysters with excellent biostratigraphic and diagenetic control has resulted in a highly detailed determination of the seawater Sr-isotope curve through the Jurassic and Early Cretaceous. The new data confirm the broad trends established by previous work, but the much sharper resolution of the new data allows the application of Sr-isotope stratigraphy with an optimal stratigraphic resolution of ± 1 to 4 ammonite subzones (± 0.5 to 2 Ma). The data show a general decline from the Hettangian (Early Jurassic) to a minimum in the Callovian and Oxfordian (Middle/Late Jurassic). This is followed by an increase through the Kimmeridgian (Late Jurassic) to a plateau reached in the Barremian (Early Cretaceous). In addition, there are major negative excursions in the Pliensbachian/Toarcian (Early Jurassic) and Aptian/Albian (Early Cretaceous). Stable isotope data collected from belemnites and oysters have resulted in the most extensive Jurassic δ¹³C and δ¹⁸O database to date. While both the carbon and oxygen data appear to give reasonable marine signals, the scatter in the data suggests that future research must document possible biological fractionation effects and develop better indicators for the diagenetic alteration of 613C and 6i 8O. The final chapter documents an unexpected correlation between sudden shifts in the Sr-isotope curve, the occurrence of positive 513C excursions, and the eruption of flood basalts. In the Jurassic and Cretaceous there is a correlation in time between sudden downward shifts in the Sr-isotope curve (Pliensbachian, Aptian, Cenomanian/Turonian), the occurance of positive 613C excursions, and the eruption of flood basalts. Each of these major downward shifts in the Sr-isotope curve is followed by a sudden upward shift, which although associated with a positive 613C excursion is not associated with an episode of flood basalt volcanism. In the Cenozoic the Sr-isotope curve no longer displays downward shifts, but the correlation continues between the occurrence of flood basalts and positive 513C excursions. Several lines of evidence suggest that the eruption of flood basalts is associated with pulses of hydrothermal activity, and that this hydrothermal activity brings about the conditions necessary for the genesis of carbon-burial events.

Lead and strontium isotopes are two powerful tracers that can be used to identify or constrain the provenance of a wide range of archaeological materials, but these two isotopic tracers have been rarely employed to infer the sources of artifacts in the southwestern USA. This dissertation contains four studies that demonstrate how these isotopic systems can address questions about the sources of three types of archaeological materials found in this region: turquoise, lead-based glaze-paints, and metals. The analysis of 116 samples of turquoise from 17 deposits in the southwestern USA reveals that lead and strontium isotopes are robust and sensitive tracers of turquoise at multiple scales. Isotopic variation among turquoise deposits correlates with broad regional differences in the geologic and tectonic setting of the rocks and mineral deposits which host turquoise mineralization. Many turquoise deposits also have unique isotopic signatures that will enable insights into ancient patterns of turquoise acquisition at regional and local levels. To show the utility of these tracers when applied to archaeological turquoise, I use lead and strontium isotopic measurements to establish that the Silver Bell Mountains are the likely source turquoise found at the Redtail site in the Tucson Basin, Arizona, USA. This dissertation also contains new, high-precision isotopic ratios of lead ores (galena and cerrusite) from four mining districts in New Mexico, including the Cerrillos Hills. All districts studied are possible sources of lead used by Pueblo IV communities to produce glaze paints. These new measurements, made by multiple-collector ICP-MS, define the isotopic composition of the ore deposits with greater precision and accuracy than achieved in previous studies, indicating an opportunity to improve interpretations about the provenance of lead in glaze paints. Lead isotopes are also found to be useful tools for identifying lead and copper metal associated with the 1540-1542 Vázquez de Coronado expedition. Lead shot and copper crossbow boltheads from two sites with archaeological evidence for the expedition's presence were determined to share similar or identical lead isotopic ratios. I propose this specific isotopic "fingerprint" can be used to identify other artifacts belonging to the expedition in the Southwest.

Stream chemistry changes in response to snowmelt, but does not typically reflect thechemistry of the snowpack. This suggests that flow processes between snowmelt and streamsystem, such as interactions with the soil and bedrock, have an important control on waterchemistry and highlight the complex flow pathways from the snowpack to stream. To investigateflow processes in the upper Provo River watershed, northern Utah, we sampled three sites on theriver ~20 times per year during 2016 and 2017. The sites, from highest elevations to lowest wereSoapstone, Woodland, and Hailstone, corresponding to locations of active stream gauges. Toidentify possible water sources to the stream during snowmelt, water samples were taken forsnow, ephemeral streams, soil water, lake, and spring water. To investigate potential impacts ofmineralogy, samples were taken for dust, soil and bedrock. The upper Provo River showeddistinct temporal variation in filtered (<0.45 microns) stream water for 87Sr/86Sr, dissolvedorganic carbon (DOC), silica (Si), and Lead (Pb) during the snowmelt season. The watershed hasdistinct 87Sr/86Sr ratios for bedrock (0.7449)

This analysis of faunal bones from Wolf Village focuses on large game and its utility, as evidenced by what is known as the modified general utility index (MGUI). The MGUI proposes that bones at sites reflect transportation and butchering choices made by hunters at kill-butchering sites. According to the assumptions associated with the MGUI, hunters should select animal portions with high food value. The MGUI has been used in Fremont archaeology to provide a rough measure of site function. The expectation is that faunal bones would accompany the prized cuts of large game meat at habitation sites – and the animal parts with little food value would remain at kill-butchering sites because they are not worth the cost to carry them to the village. My analysis of large game animal bones found in excavations at Wolf Village counter these expectations. Fremont hunters at Wolf Village were returning to the site with low-caloric portions of large game, at least part of the time. Results from strontium isotope analysis suggest that many of the large game individuals hunted by the Fremont were not local to the immediate area. This suggests that hunters saw utility in low-caloric elements not related only to food value. Some low-caloric skeletal elements were used by the Fremont to construct bone tools and other objects, and as possible symbolic objects used in abandonment rituals. The results of this research suggests that the MGUI is not appropriate for measuring the utility of animal portions to the Fremont. Only when considering the social and non-caloric economic reasons for transporting low caloric elements, can archaeologists discover the true utility of large game animal parts to Fremont hunters.

Regions of surface water and groundwater exchange are major sites for the transfer and transformation of solutes and nutrients between stream and subsurface environments. Conventional stream and groundwater exchange investigations are limited by methodologies that require intensive field investigations and/or the set-up of expensive infrastructure. These difficulties are exacerbated where hydraulic gradients are very low and stream discharge highly variable. This thesis uses a suite of environmental tracers (Cl-, Rn-222, H-2 & O-18, Sr-87/Sr-86) to characterise the extent of stream and groundwater exchange between a sand bed stream and adjacent alluvial aquifer in a subtropical catchment (the Wollombi Brook) of eastern Australia. The aims were to identify sources and relative contributions of different sources of groundwater to stream discharge and specifically to improve the methodology of using Rn-222 to obtain quantitative estimate of groundwater fluxes. The sensitivity of the Rn-222 technique for identifying groundwater discharge based on the Rn-222 concentration in stream water was improved via an iterative numerical approach to account for Rn-222 loss from stream water via turbulent gas exchange and radioactive decay. Optimal distances between stream sampling points for defining the magnitude of groundwater discharge to stream flow based on Rn-222 concentrations in stream water is a function of average stream velocity and water depth. The maximum allowable distance between sampling points for determining the magnitude of groundwater discharge to the Wollombi Brook was 2 km. This work showed that groundwater discharged to all reaches of the Wollombi Brook during baseflow and flood recession conditions. Alluvial groundwater contributed less than 30% of water to stream flow in the mid Wollombi Brook catchment. Dilution of steady-state Rn-222 concentrations measured in transects from the stream to the alluvial sediments showed that significant surface water and groundwater exchange occurs even when gradients between surface water and groundwater are low. Lateral stream water influx to the adjacent alluvial aquifer was more extensive in the lowland areas of the Wollombi Catchment during low flow than flood recession conditions. Extensive stream water influx to the adjacent alluvial aquifer occurs contrary to the net direction of surface water and groundwater flux (as indicated by hydraulic gradients toward the stream channel). The rate of stream and groundwater exchange within the adjacent alluvial aquifer appears to be greatest during baseflow conditions. Fresh alluvial groundwater appeared to provide a buffer against higher salinity regional groundwater discharge to the alluvial aquifer in some reaches of the Wollombi Brook catchment. Pumping of the alluvial aquifer and diversions of surface water may jeopardise the water quality and volume of the alluvial aquifer and induce water flow from the regional aquifer toward the stream, potentially salinising the fresh alluvial aquifer and subsequently the stream. The change in the Cl- concentration and the variation in slope of the deuterium � oxygen-18 line between consecutive stream sampling points could be used to differentiate between regional and alluvial groundwater discharge to stream flow. Incorporating this information with three-component end-member mixing using [Sr2+] and Sr-87/Sr-86 showed that stream and alluvial groundwater exchange within the stream channel was highest in the lowland floodplains during low flow conditions. The least stream and alluvial groundwater exchange occurred in the low streambed gradient mid reaches of the Wollombi Brook regardless of stream stage. The greatest difference in the degree of stream and alluvial groundwater exchange between high and low stream stages occurred in the lowland floodplains of the Wollombi Brook.