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    Development of methods for the determination of bismuth and thallium in geological materials and their significance for the Cretaceous-Tertiary boundary event : a thesis presented in partial fulfilment for the degree of Master of Science, Department of Chemistry and Biochemistry, Massey University, New Zealand
    (Massey University, 1988) Hoashi, Maki
    Solvent extraction methods have been developed for the determination of thallium and bismuth in rocks. The method for thallium is based on the extraction of the chlorocomplex into methylisobutyl ketone followed by removal of the interfering chloride ion as insoluble silver chloride. The method for bismuth is based on the extraction of a stable metal complex with ammonium pyrrolidine dithiocarbamate into methylisobutyl ketone. Both elements are analysed on a electrothermal graphite furnace atomic absorption spectrometer. Tests on the efficiencies of the methods showed a good precision and accuracy with limits of detection of 9.5 ng/ml (ppb) for thallium and 20 ng/ml (ppb) for bismuth. Recovery studies on synthetic samples showed recoveries of >99.9% for both elements. A geochemical study was performed on a Cretaceous-Tertiary boundary site located near Flaxbourne River, Ward, New Zealand. Investigations were carried out to determine the enrichment of thallium and bismuth in the stratigraphic column. The results show a good correlation between the iridium and thallium content throughout the rock sequence, but the samples have very low bismuth contents. This is indicative of the different geochemical behavior of bismuth to other chalcophiles. These findings do not contradict the impact theory initially hypothesized by Alvarez et al. (1980), and instead suggest that bismuth's mobility and solubility are far greater than those of thallium and the other chalcophile elements enriched in the Flaxbourne River sequence. This results in the leaching of bismuth from the stratigraphic column by sea water after deposition.
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    Thallium phytoextraction and its economic significance: a thesis presented in partial fulfilment of the requirements for the degree of Master of Science at Massey University
    (Massey University, 2000) LaCoste, Cher
    Thallium is a volatile toxic metal which has many industrial uses. The sources of thallium include natural geochemical sources and by-products of industrial processes. One of the problems in assessing thallium pollution potential is the lack of an accurate method of quantification of this element. Flame atomic absorption spectrometry (FAAS) is a good method of analysis but only down to the 1.0 mg/kg (ppm) level. For lower concentrations, analytical techniques have been difficult and inaccurate. A newly described method using graphite furnace atomic absorption spectrometry (GFAAS) has been found useful for low T1 concentrations. A method was designed to detect low concentrations of thallium in plant and soil samples. The graphite furnace technique worked well for the data presented in this paper. However, samples of different origin could have more severe matrix effects such as high iron contents. Thallium has been found to be readily available for plant uptake. The extractability of thallium was significantly higher then other metals such as cadmium and zinc. This property is ideal when considering a possible phytoextraction operation. Two plant species were found to accumulate thallium to levels up to 411 mg/kg in Iberis intermedia and 504mg/kg in Biscutella laevigata. These high values indicate potential for phytoremediation and phytomining in areas of sufficient contamination. The properties of which make thallium an ideal candidate for phytoremediation also make the metal a high risk for biota. Experiments were also conducted to determine the partitioning and sequestration of thallium within plant organelles. This work was limited to the two hyperaccumulating species but future work could compare non-tolerant species. Evidence from this research might give a better understanding to the mechanism involved in plant uptake and storage of thallium. Agricultural crops used for human consumption or animal grazing may cause deleterious health effects. Thallium is extremely toxic, effecting the nervous system and impairing heart function at low levels. Higher concentrations will cause death. It is possible that some of the illness symptoms observed in humans may be derived from low levels of thallium in foodstuffs. Aside from a few economic mineral deposits, there is no information of a world-wide distribution of thallium, so health effects can not be accurately assessed. This thesis describes experiments carried out on common vegetable and their uptake of thallium to determine safe levels of this element within the soil. This information will also be useful to farmers growing crops on contaminated soil will advise them on which plants would uptake less thallium. Thallium has not been studied as extensively as many other heavy metals that are more common in the environment. Although the crustal abundance of thallium is low (0.49-0.7 mg/kg average range), the toxicity of this element is very high, and it is readily available for plant uptake. The toxic effects on animals and plants should be monitored closely.
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    Quantification of gallium, indium and thallium in meteorites and other geological materials by graphite furnace atomic absorption spectrometry : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1993) Guo, Xun
    Methods of solvent extraction have been developed for the determination of gallium, indium, and thallium in meteorites and other geological materials. The extraction of gallium is based on forming a chloro complex in HCl solution and extraction into MIBK. Indium was extracted into the same solvent as an iodo complex in an HBr + KI medium to which KOH had been added. Thallium was also extracted as an iodo complex from a H2SO4 + KI medium with addition of K2HPO4 as a salting out agent. Serious interference from iron(III) was eliminated by adding KI to reduce this element to its divalent state that was not extractable into the organic phase. Graphite furnace atomic absorption spectrometric techniques were employed to determine these three elements in the MIBK phase after extraction from the aqueous phase. Very low limits of detection (l.o.d.) were obtained with these methods. It was possible to lower the l.o.d for these elements either by increasing the aqueous/organic phase ratio before extraction, or by multiple loading injections. Using the developed methodology, gallium, indium, and thallium were quantified in iron and chondritic meteorites as well as in Cretaceous/Tertiary boundary clays, and some volcanic emissions. The data for thallium abundances in 49 iron meteorites were the first ever recorded for this type of meteorite and allowed for taxonomic separation of the various groups of irons. Indium abundances were only recorded in six chondrites because of the very low concentrations in iron meteorites. My data for thallium and other elements were used to classify the previously non-studied Manitouwabing iron meteorite. All three Group IIIA elements were determined in Cretaceous/Tertiary boundary clays and it was shown that these and other chalcophile elements have an abundance greater than that which would have been expected from either a volcanic or impact-derived source. Possible sources of this enrichment are discussed.