Browsing by Author "Orren, Michael J"

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    Baseline surveys and metal binding proteins as metal pollution indicators
    (1985) Hennig, Helmke Friedrich-Karl Otto; Orren, Michael J; Branch, George M; Brandt, Wolf F
    The field of metal determination as a part of pollution studies, has been critically examined and metal pollution may be defined in one simple statement: The presence of metal binding proteins confirms toxic metal pollution. It has been shown that current methods of metal determination in biological systems are of little use. This has been illustrated by both a review of metal concentration in Southern African coastal water, sediments and biotopes, and by a comparative baseline study of organisms from Gough Island and Mar ion Island. These showed that extrapolation of results from one geographical area to another are invalid and that this interpretation is made difficult by factors such as age, sex, size life stage of the organisms. Furthermore, it was shown that many reports on metal pollution do not even mention fundamental information such as the size or the sex of the animals. Metal pollution could be linked to metal binding protein through an independent pollution er i ter ia, for example, the out of season moulting of crayfish. The new definition of metal pollution has then been tested by application to five different organisms (crayfish, Jasus lalandii; hermit crab, Diogenes brevirostris; shrimp, Palaemon pacificus; black mussel, Choromytilus meridionalis and limpet, Patella granularis) kept under identical conditions and it was shown that a much more meaningful interpretation of the results could be made. The new definition was al so tested with two naturally occurring metal accumulating organisms (whelk, Bullia digitalis and "kikuyu" grass) and it was shown that dramatic increases in metal may not necessarily be toxic. It was concluded that less effort and time should be spent on metal analysis in determination of metal pollution and attention should rather be directed to the presence or absence of metal-binding proteins.
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    Hydrogeochemical exploration at Tsumeb
    (1980) Marchant, James William; Orren, Michael J; Erlank, A J
    The Precambrian Otavi dolomites in the district of Tsumeb in Namibia are host to base metal mineralization but large tracts of these rocks occupy a mature pediplain and are deeply buried by transported overburden of Kalahari age. This sandy material makes exploration for minerals very difficult. Hydrogeochemistry was considered as a possible answer to the problem of prospecting in this region but a major obstacle was the lack of an undisturbed site for orientation studies. The Tsumeb mine was therefore used as a "surrogate" orientation target and water samples collected there were analyzed for about forty elements or ions. The data were plotted on long-sections through the orebody and examined with the aid of simple statistical calculations. The Na/Cl⁻ ratio proved to be a powerful index for identifying groups of waters with a common origin. It appeared that the most important of these groups of waters were not natural groundwaters but were being recycled. Millions of litres of water are pumped from the mine daily and a significant proportion finds its way back into the workings through seepage. This conclusion was supported by chemical data and by calculations in which the rates of pumping and recharge were balanced. Over the years the process of recycling has caused a rise in the concentrations of sodium, chloride and sulphate in the water arriving at the sumps in the mine. The other major components of these waters - Ca, Mg and HCO₃⁻ - are not affected to the same extent by recycling because of controls imposed by the carbonic system. It was not generally possible to establish rational links between the distributions of the trace elements, the major groups of related waters and the proximity of ore. Although some trace elements tended to be more abundant in samples from the upper parts of the mine, where exposure to broken, weathered ore is greatest, the value of this association was diminished by the fact that these waters are recycled effluents that cannot be equated with the natural groundwaters that would be in contact with any undiscovered ore-bodies similar to the Tsumeb lode. This conclusion was reinforced by the fact that some of the trace elements were relatively abundant in waters that were comparatively saline but which had not been exposed to oxidized ore. It was concluded that it would not be possible to interpret the trace element data from the mine waters unambiguously. Nevertheless it was clear that sulphate, Cu, Pb, Zn, Hg, Cd, Se, Te and perhaps U were being mobilized from the ore and that these were therefore all good "candidate'' pathfinders. Less probable candidates were Mo, Ge, As, Na and chloride. A second orientation study was then undertaken, using normal groundwaters from boreholes and springs on surface. Sampling was concentrated around the Tsumeb and Kombat mines as targets and waters were also obtained from background areas where dolomites were exposed. The chemical data were plotted on maps by computer and were examined with the aid of simple statistical calculations such as the cumulative frequency distribution. Although anthropogenic effects were apparent at both mines they were not severe and it was possible to be more confident about the prospective roles of the various chemical species in hydrogeochemical exploration for ores in the Otavi dolomites. These prospective roles may be summarized as follows: undetectable or of virtually no interest: pH, temperature, phosphate, K, Ti, Fe, li, Rb, Cs, V, Cr, Mo, Ag, Au, Cd, Hg, Tl, Ge, As, Sb, Bi, Se and Te; useful as iridicators of regional hydrogeochemical features not directly related to mineralization: Si, F⁻, Sr and Al; weak regional pathfinders: Ni and Co; probably good regional pathfinders: sulphate, Cu, Pb and Zn. Bicarbonate, Cl⁻, Na, Ca and Mg are not pathfinders but it is useful to have these data when considering the nature and significance of the samples and the abundances in them of the trace elements. Despite the identification of a suite of pathfinders it was not feasible to establish orientation criteria such as contrast ratios. An attempt was made to apply the findings of this orientation survey in an area to the northeast of Tsumeb, where dolomites are buried under thick sand and calcrete. An area of five thousand square kilometres was selected and all usable sources of groundwater within it were sampled. The following data were collected: total dissolved solids, pH, Ca, Mg, Na, bicarbonated chloride, sulphate, Cu, Pb and Zn. Hydrological data suggested that the regional movement of groundwater was from the exposed dolomites into the pediplain. The hydrogeochemical data showed that during this migration the major element composition of the groundwater changed ("metamorphosed") radically. Because of this metamorphism, very severe difficulties stood in the way of applying in the sandy pediplain what had been learned in the areas of well-exposed dolomite. An attempt was therefore made to provide tighter control between the lithology of the geological profile and the hydrogeochemistry of the associated formational waters in the pediplain. This work consisted of (a) a sampling program to try to ''fingerprint" specific formational waters. This proved to be impossible. (b) drilling four diamond drill holes near selected anomalies and studying the cores in detail. These revealed that the Kalahari beds were very thick (46 to >103m). In all cases the base of the overburden was far below the present water table and in some cases the overburden was underlain by unmineralized rocks other than dolomite. These results indicated that the hydrogeochemical anomalies were probably spurious and it was concluded that hydrogeochemical exploration in this kind of Kalahari terrane was not practicable.
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    A precolumn derivatization procedure for the analysis of marine amino acids with 9-fluorenylmethyl chloroformate and high performance liquid chromatography
    (1986) Garside, Daniel Mark; Orren, Michael J
    The separation of 20 amino acids has been achieved by gradient elution and reversed phase high performance liquid chromatography employing 9-fluorenylmethyl chloroformate as the precolumn derivatizing reagent. The application of this technique to assess the extent of marine bacterial uptake of amino acids released from kelp has also been determined. The problem of excess reagent reacting with water to form a hydrolysis product has largely been overcome. Pentane extraction of the reagent after amino acid reaction caused the loss of less polar amino acid derivatives. Other factors such as the formation of dilabelled products and the pH dependance of the derivatization reaction have been investigated. The reproducibility between-analyses had a percentage error of 2 - 6%. The stability of the derivatives is about 2 weeks at room temperature. The application to physiological samples and seawater has been demonstrated. The method was applied to the study of kelp release and bacterial uptake of marine amino acids. Other chemical profiles of ammonia, nitrate, total N, particulate C, together with bacterial activity and bacterial density (biomass) were determined to provide correlative profiles to the amino acid values. The experiment was set up with kelp fronds in buckets, some containing antibiotics to halt bacterial activity, and a control bucket with untreated seawater. Alanine is the most dominant amino acid (concentration between 5 and 100 nmol.dm⁻³). Values of glycine, aspartic acid, glutamic acid and arginine have much lower levels. Traces, of histidine, asparagine, cystine, serine and tyrosine appeared near the end of the experiment. It was found that the amino acid concentrations were low compared with the inorganic nitrogen species. The flux of these species was found to be too low to create a substantial response, as the activities are also low compared with normal in-shore regions. In order to infer more from the processes occurring in this study, we would have to increase the experimental time to the order of days.
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    Separation, preconcentration and determination of rare earth elements by inductively coupled plasma emission spectroscopy
    (1988) Cracknell, R H; Orren, Michael J
    Rare earth elements, (REE), at ug g⁻¹ levels are used for studies of petrogenisis of different geological materials. For these studies, the REE must be determined precisely. An analytical program was established using an IL 200 Inductively Coupled Plasma, (ICP), spectrometer for the determination of the REE in various matrices, taking into consideration both matrix and spectral interferences, which were found to be severe in some cases. Dissolution of the sample, (0.4-1.0 g), was carried out using two methods; a microwave heated dissolution using a modified commercial microwave oven and a conventional oven heated closed pressure digestion vessel method. The results of these two methods were compared to determine the viability of using the more rapid microwave heated method. Separation of the REE from matrix elements was investigated using three cation exchange resins; Amber lite IR 120 (H), Zeocarb 225 and Dowex 50-WXS. A gradient acid elution method was established using a 15 cm by 20 mm Zeocarb 225 column. The sample was eluted with 140 ml of a 1.5 M H⁺ solution containing 0.75 M Cl⁻ and 0.75 M NO₃⁻, this fraction containing all the matrix elements. The REE were then eluted from the resin with 100 ml of 3 M HNO₃. The REE containing fraction was then reduced to 5 ml, diluted to 10 ml, and analysed for REE content. Liquid-liquid extraction methods for the separation of REE from matrix elements were investigated. It was found that the REE could be extracted synergistically from various buffered aqueous acidic media into chloroform, (CHCl₃), by hexafluoroacetylacetone, (HHFA), and quinoline. Acetylacetone, ( AcAc), was found to react with hexamethylenetetramine, (hexamine), when hexamine was used to buffer the aqueous phase during extraction procedures. The product of this reaction, 3.5-diacetyl-1.4-dihydro-2.6-dimethyl pyridine, was identified using X-ray crystallography.