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    The determination of gold in vegetation and its application to specific problems in biogeochemistry : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Chemistry in the Dept. of Chemistry and Biochemistry at Massey University
    (Massey University, 1985) Naidu, Shamila Devi
    Studies were carried out to devise a method for determining nanogram quantities of gold in vegetation. The samples (0.5g) were digested with fuming nitric acid over a water bath. After addition of hydrochloric acid, the gold was extracted into a small volume (1 ml) of methylisobutyl ketone (MIBK). The organic layer was back-extracted with distilled water to remove iron interference and gold in the MIBK was determined by an electro­ thermal atomization technique with graphite furnace atomic absorption spectrometry. The optimum instrumental conditions for drying, ashing and atomization of gold were as follows: drying, 4.5V, 20 secs; ashing 6V, 20 secs; atomization 8V, 4 secs. A furnace cooling time of 50 sec. was allowed to attain high precision of signal heights. Tests on the efficiency of the method developed, showed high precision, good accuracy with the limit of detection of 1 ng/g. Recovery studies on the known amounts of gold added to vegetation, showed an average recovery of 99.4%. On the basis of these results, the method developed and outlined can be used on a routine basis for analysis of vegetation, soils and rocks. Biogeochemical and geochemical studies were carried out at 4 areas having different geological, topographical and climatic conditions. These were: Waihi, New Zealand, Seruwila in Sri Lanka, the Serbomaced­onian massif in Northern Greece, and Yathkyed Lake in Arctic Canada. At each of these study areas, different plant species were collected and analyzed together with the soil for biogeochemical studies. Investigations were carried out to determine whether the concent­ration of gold in plants could be used to predict the concentration of this element in the soil and also whether any other elements present could be used as a pathfinder for gold. The results of biogeochemistry showed good correlation existing between gold in plant and gold in soil provided the gold concentration in the substrate was sufficiently high. Arsenic was found to be a possible pathfinder element for gold, particularly when the latter is present with chalcophile elements. The range of plant species analyzed in this study suggest that gold uptake is not restricted to any particular plant species or to plants with deep rooting system provided the substrate is auriferous.
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    Biogeochemical studies of nickel and copper in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1971) Timperley, Michael Horace
    The accumulations of various metals by some indigenous trees growing on the Riwaka Basic Complex, North-west Nelson, New Zealand, were investigated by the application of statistical techniques to biogeochemical data. Particular reference was given to nickel and copper to evaluate the usefulness of plant analysis as a prospecting tool. Preliminary investigations showed that serious errors could result from the methods of sampling plants and soils and sampling procedures were adopted to minimise these errors. In addition, errors arising from atomic absorption analysis were found to be significant for some metals. Leaves and twigs from three Nothofagus species, W.racemosa and Q.acutifolia as well as their associated soils, were collected and analysed for nickel, cobalt, copper, zinc, chromium, calcium, magnesium, manganese and potassium. The plants were also analysed for iron. These results showed that each species accumulated different, but related, amounts of various metals and that they distributed these metals in different ways between their leaves and twigs. N.truncata and N.fusca which are closely related genetically, accumulated metals to similar degrees, while N.menziesii which is not closely related to the other Nothofagus species accumulated metals to differing degrees. Relationships between the metal concentrations in the plants and in the soils were evaluated by computing correlation coefficients. The best correlations for nickel were obtained for the Nothofagus genus although the other species also showed highly significant correlations. The Nothofagus genus also showed the best correlation for copper. In view of the above results, a more extensive study of the Nothofagus genus was carried out. A second survey was undertaken in the same area in which leaf samples of this genus as well as their associated soils were collected. While the metal concentrations in the soils collected in this survey compared well to those collected previously, the metal concentrations in the plants, in general, did not show good agreement. Trend analysis was used to compare in detail the nickel and copper contents in the leaves of the Nothofagus genus with the concentrations of those metals in the soils. It was shown by comparison of the trend surfaces and residuals that the accumulation of nickel was determined primarily by the concentration of nickel in the soil, whereas for copper the accumulation by the plant was a function primarily of the specific requirement of the plant for this metal. Multiple regression analysis was used to improve the prediction of the copper and nickel concentrations in the soil from the concentrations of these metals in the leaves of the Nothofagus species, by making quantitative allowance for the processes influencing the accumulation of these metals by the plants. Improvements of between 25% and 35% were obtained at the 90% confidence level. Inter-metal ratios in the leaves were considered as possible indicators of nickel and copper concentrations in the soil but the results were discouraging. Studies were made of the locations and chemical forms of nickel, copper, zinc and iron in both freeze-dried and fresh leaves from some trees growing on the Complex. Atomic absorption spectrophotometry was used to measure the concentrations of these metals in both plant extracts and on the electrophoresis and chromatography papers used to separate the metal complexes in the extracts. Results indicated that the major part of the nickel present in the leaves was not contained in cell organelles nor was it bound to cell walls, but existed as a positively charged complex in either the cytoplasm and/ or the vacuole. Copper, zinc and iron were distributed differently with varying fractions, depending on the metal, existing predominately as anionic complexes. It was concluded that the research embodied in this thesis had illustrated the application of statistical techniques to biogeochemical studies, showed that biogeochemical prospecting for nickel in New Zealand was feasible and that methods of total analysis for metals could be applied to the study of microgram amounts of metals in biological systems.
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    Analytical, geochemical and biogeochemical studies of tungsten and molybdenum : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1974) Quin, Bertram Francis
    Section I : studies were carried out which significantly improved the sensitivity of the colorimetric method for the determination of tungsten in geochemical and plant samples with dithiol. Proton-induced x-ray fluorescence was also investigated to determine its suitability for the detection of nanogram quantities of tungsten. However although it showed considerable potential, the sensitivity of the method could not be developed sufficiently to compare favourably with colorimetry. A rapid method for the determination of tungsten in ores and concentrates by atomic absorption spectrometry was developed which, through the use of an alkaline sample solution, was free of interference and instability problems. Following a careful study of the parameters involved in the colorimetric method for the determination of molybdenum with dithiol, a simple procedure was developed which could be used for the analysis of a wide range of materials. The use of the nitric/hydrofluoric acid mixture for the digestion of soils and rocks was investigated. It was found that the tendency for calcium and magnesium to precipitate as their fluorides could be avoided by the addition of a small quantity of perchloric acid. Section II : Scheelites from several localities in New Zealand were analysed for their trace element content. They were found to contain very low amounts of impurities. Their Sr/Ba ratio was found to be useful for distinguishing between lodes. Section III : An investigation was carried out to compare the relative efficacy of geochemical and biogeochemical exploration for tungsten under a wide range of geological, vegetational, climatic and topographical conditions. It was found that, under most conditions, both soil and plant sampling could be used equally successfully to pinpoint scheelite bearing veins. In areas of high rainfall and rugged topography, soil sampling did not always reveal the presence of reefs and, in these cases, trunk-sampling of trees could provide additional information. It was found that, for the purposes of biogeochemical prospecting, all tree species could be grouped together. Following this investigation, a more intensive study was carried out at Barrytown to test the suitability of trend surface analysis of biogeochemical data for locating rich pockets of scheelite with veins, with promising results. A brief comparison of geochemical and biogeochemical prospecting for molybdenum was carried out at Canaan, Nelson. It was found that plant sampling gave more information where the low soil pH prevented movement of molybdenum into the upper soil. Section IV : Following the results of the biogeochemical exploration in Section IV, which showed the existence of differences in the distribution of tungsten between tree organs from Barrytown and Canaan, the affect of soil sodium and potassium was investigated and was found to be responsible for these differences. As considerable areas containing scheelite mineralisation support pasture, an investigation was carried out to study the effects of applied tungsten on clover growth. Tungsten, applied as tungstate, was found to slightly decrease growth where fixation was the sole nitrogen source. In the presence of combined nitrogen, however, increases were recorded. A comparison of the elemental composition of native tree species was carried out to investigate the effects of substrate composition. It was found that, whereas vegetation analysis can in general be used to indicate the presence of mineralisation within a rock type, it is not a reliable indicator of the composition of different rock types.