Magister Scientiae - MSc (Botany)

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Browsing by Author "Aalbers, J"

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    Biomonitoring as a means to determine the pollution level in Stellenbosch
    (University of the Western Cape, 1991) Davis, Shaun Andre; Raitt, L M; Aalbers, J
    A pollution survey was done in Stellenbosch, along two transects. One was south-east and the north-east of the Oorrobrick brickfield the focal point of this study. Pine and Oak trees, chasman the leaves and lichens were used as bio-indicators for this survey. The levels of fluoride and sulphur decreased with distance from the main pollution source. Exceptionally high levels were recorded in the pine and oak trees within 1.5. km from the brickworks. The availability of calcium and magnesium in the leaves of pine and oak trees appeared to be negatively affected due to their binding with F- to form insoluble compounds. The brickfield proved to be a major source of especially copper and iron, as their levels in the bark material decreased with increasing distance. Lead levels were found to be correlated with vehicular traffic in the area. There was some evidence that the iron levels were also linked to the lead concentrations in the bark.
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    a comparative study of the influence of different copper concentrations on the growth, chemical composition and activities of certain copper containing enzymes in atriplex nummularia lindl. and a. vestita (thunb.) Aell.
    (University of the Western Cape, 1990) Green, D H; Aalbers, J
    The total amount of native copper in soil depends on the amount of copper in the parent material (Tisdale .et .al.1968). It is usually in greater concentration in the soil than in parent rock because of weathering of the parent rock and the concentration of the element in the upper soil horizons by growing plants. Copper in parent rock exhibits typical chalcopyrite behaviour in that its abundant and stable minerals are sulfides rather than silicates or oxides (Mordtveldt .et .a.J. . 1972). B the most abundant of the copper minerals is which is common in igneous and sedementary rocks. The average ooppe r cxmte e s between 2 to lOOg.m- 3 soil solutions contain about 0.0-lg.m copper ( Devlin 1983). Concentrations higher than this are often regarded as toxic to plants. Two valences of copper are found in naturally occuring compounds i.e. cu+ and cu2 +. The cu 2 + ion is more commonly found in soils, adsorbed to clay minerals or tied up with organic matter.
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    Effect of simulated acid rain on seed germination and on growth and mineral nutrition of Lycopersicon esculentum var. Red kaki
    (University of the Western Cape, 1993) Marsh, Frans A; Raitt, L.M; Aalbers, J
    The phenomenon of acid rain is not new. It has been active for more than a billion years (Abelson, 1983). The term "acid rain" was introduced as early as 1872 by Robert Angus Smith, the world's first air pollution control inspector, who measured pH values of precipitation considerably lower than 5,6 (the pH of distilled water in equilibrium with atmospheric CO2) in and around northern English industrial cities. At this time relatively little interest was shown in the topic (Anon, 1984;BeI1, 1988). Widespread interest in the topic began in the mid - 1970's, when Scandinavian studies identified a downward trend in pH of precipitation in southern Norway and Sweden accompanied by an increase in acidity of lakes and rivers (Bell, 1988). At the same time' predictions were made that Swedish soils would become progressively acidified, with a concommitant fall in timber production. Initially there appeared to be little evidence to support the latter contention and research concentrated on the causes of the loss of fish, untill the early L980's when a serious forest decline was observed in Central Europe, which has been popularly ascribed to acid rain (Bell, 1988)'