'n Evaluering van analisetegnieke vir die bepaling van kalkbehoefte van goudmynslikdam-materiaal vir die vestiging van plantegroei

Abstract

AN EVALUATION OF ANALYSIS TECHNIQUES FOR THE DETERMINATION OF LIME REQUIREMENTS OF GOLD MINE SLIMES DAM MATERIAL FOR THE ESTABLISHMENT OF VEGETATION Owing to the potential pollution problems inherent to gold mine slimes dams, it is essential to find means to curtail the pollution. Vegetative cover has proven to be effective in this regard . However, the very low pH values of the slimes material is detrimental to plant growth. These low pH values can be ascribed to the oxidation of pyrite, a mineral which occurs in the slimes material. It therefore becomes necessary to neutralize the active acidity as well as the potential acidity due to the ongoing oxidation process. A number of analysis techniques for the determination of lime requirements were evaluated on gold mine slimes dam material. After the identification of a suitable method to determine the lime requirements, gold mine slimes dam material can be quantitatively evaluated without the administration of estimated quantities of lime on the basis of a pH value only. Slimes material of 3 gold slimes dams was incubated in pots treated respectively with 8 different levels of lime. These were layed out in an randomized block design. A similar experiment was layed out with identical lime applications in pots in which the grass Eragrostis curvula (Schrad.) Nees variety PUK 4L36 was subsequently planted. The pH of the incubated material was measured weekly during the first 4 weeks after which it was measured every month for 11 months. The electrical conductivity of the material was measured at the end of the experiment. The number of seedlings that germinated in each pot was counted on a weekly basis and the biomass of the plants was measured at the end of the experiment. At the same time various lime requirement measuring methods were evaluated on incubated gold mine slimes dam material. Samples of slime were taken at different locations on two of the slimes dams to determine homo or heterogenety of the slimes dams with regards to lime requirements.

The results show that the best correlation between pH value of the incubated material and plant biomass was found where the dubbel buffer titration (DBTM) lime requirement determination method was used. At the higher application levels of lime, the pH values of the material reached a plateau. An increase in electrical conductivity was observed after dolomitic lime had been applied. Using the DBTM to determine the lime requirements of the slimes material from the 2 slimes dams, it was found that the different horisontal layers in a slimes dam have different lime requirements. Samples taken for the determination of the lime requirements of a particular slimes dam will therefore have to be taken in such a way that the differences in lime requirements of the different horisontal layers will be taken into account.