Septoria ampelina causes a disease of grapes known as septoria leaf spot. This study was done to determined which of the fungicides currently used to control the various diseases of grapes, plus one experimental fungicide, is the most effective in controlling septoria leaf spot. Both in vitro and in vivo methods were used. In vivo studies examined the systemic and/or protectant activities of the fungicides. The systemic and protectant fungicides included Bayleton, Benlate, Elite (an experimental fungicide), Nova, Rovral and Rubigan. The protectant only fungicides included Captan, Dithane and Kocide. In vitro tests to determine the minimum inhibitory concentration (MIC) for each fungicide (e.g., the concentration of the fungicide that prevents the fungus from forming colonies on the PEA-fungicide medium), indicate that Benlate (MIC = 0.1 ppm) and Elite (MIC = 1.0 ppm) have the greatest potential'to control septoria leaf spot of grape. These are followed by Dithane, Nova and Rubigan (MIC = 2.0), which in turn are followed by Bayleton and Captan (MIC = 50.0 ppm). Kocide and Rovral did not inhibit fungal growth at concentrations up through 100 ppm. Although all the fungicides tested significantly reduced the incidence of septoria leaf spot in vivo, Benlate and Elite were the most effective fungicides (both in systemic and protectant application). / Department of Biology

Thesis (Ph.D)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Copper oxychloride is a fungicide that is extensively used in vineyards in the Western Cape to treat and prevent fungal diseases. It is however not clear what the effects are on soil organisms, which play an important role in soil fertility, in South African soils. There is paucity of data linking results obtained in the laboratory to effects observed in the field, which will only become useful if a clear relation can be demonstrated. The aims of this study were to: ~ Determine the effects of copper oxychloride on field populations of earthworms and simultaneously monitor lysosomal membrane stability, measured as neutral red retention time (NRRT). ~ Validate experimental field studies by doing inventories of earthworm populations in long-term sprayed vineyards. ~ Determine the LC50 of copper oxychloride and simultaneously measuring NRRT, and linking them to the experimental field studies. ~ Conduct bioassays, burrowing activity- and soil-avoidance experiments to investigate their relations to earthworm population responses in the experimental field studies. Earthworms were sampled by hand-sorting in the field tests on treated and untreated field plots in the Western- (October 1998 - July 1999) and Northern Cape (April 1998 - October 1999). Soil samples and worms were analysed for copper contents and coelomocytes of live earthworms were used to conduct the neutral red retention assays. Acute toxicity tests were conducted over a period of 28 days during which the earthworms (Eisenia fetiday were exposed to different concentrations of copper oxychloride. Change in biomass and mortality were measured as endpoints, as well as NRRT. Bioassays, burrowing activity and soil-avoidance were conducted by exposing Aporrectodea caliginosa to grassland- and vineyard soil as well as grassland soil spiked with 60 J.1g.g-1copper in the form of copper oxychloride. Growth and mortality were recorded in the bioassays as well as copper concentrations In earthworm body tissues and substrates used over a period of28 days. Burrowing activity and soil-avoidance were determined by measuring the length of tunnels burrowed by A. caliginosa in soil profiles over a period of 4 days under different exposure regimes. Results from the field tests showed that spraying of copper oxychloride had a negative effect on earthworm populations at the prescribed application rates. NRR T in earthworms from the exposure plots was significantly (p<0.05) lower after just one spraying application. It was concluded that spraying copper oxychloride at prescribed application rates caused a decrease in field populations of earthworms and that NRRT was an early and reliable biomarker since it was indicative of later effects observed at the population level. Results obtained from the field inventory of earthworms in vineyards at Nietvoorbij, Robertson end Worcester confirmed data from the two field studies. The calculated LC50 of 882.78 I1g.g-1 for copper oxychloride and 519.40 I1g.g-1 for copper was ecologically relevant if a safety factor of 10 was applied. NRRT which manifested earlier than effects on biomass change in the acute toxicity tests, were significant when viewed against the background of responses of field populations of earthworms. From the bioassay experiments it was found that A. caliginosa exposed to copper oxychloride spiked soil had significantly (p<0.05) higher weight loss and mortality than those in grassland- and vineyard soil. This indicated that changes in biomass and mortality were indicative of population responses in the field and can be considered as ecologically relevant. Burrowing activity of A. caliginosa was significantly (p<0.05) lower in vineyard and copper oxychloride spiked soil than in grassland soil. Similarly in the soil avoidance experiments it was found that A. caliginosa avoided vineyard- and copper oxychloride contaminated soil. It is therefore concluded that burrowing activity and soil avoidance were ecologically relevant endpoints since they corresponded with population responses in the field. The study thus revealed that the long-term usage of copper oxychloride could have negative effects on earthworm populations. The spraying of copper oxychloride can have important implications on the sustainable use of agricultural soils since earthworms and other soil organisms play such an important role in soil fertility. The use of biomarkers and other ecotoxicological indicators can provide an early warning that soil organisms are under environmental stress. / AFRIKAANSE OPSOMMING: Die fungisied koperoksichloried word wyd gebruik in die Wes-Kaap om swamsiektes in wingerde te beheer en te voorkom. Dit is egter nie bekend wat die effek daarvan op Suid Afrikaanse grondbiota, wat 'n belangrike rol speel in grondvrugbaarheid, is nie. Daar is ook 'n tekort aan inligting wat die resultate van laboratoriumondersoeke in verband bring met veldstudies. Die doelstellings van die studie was om: ~ Die effek van koperoksichloried op erdwurmpopulasies in die veld te ondersoek en terselfdertyd membraanstabiliteit, as moontlike biomerker, gemeet as neutraal rooi retensietye (NRRT), te monitor. ~ Die geldigheid van eksperimentele veldstudies te toets deur ook grondanalises te doen in wingerde wat oor langtermyn met koperoksichloried bespuit is. ~ Die LC50 van koperoksichloried vir erdwurms te bepaal en terselfdertyd NRR T te meet asook om dié gegewens in verband te bring met die resultate van seisoenale veldstudies oor die uitwerking op erdwurmpopulasies. ~ Bio-evaluerings ("bioassays"), tonnelaktiwiteit- en vermydingseksperimente te onderneem en die verband tussen die toksiteitstoetse en populasieresponse, soos waargeneem in die veld, te ondersoek. Erdwurms is versamel deur handsortering tydens die veldtoetse in die Wes- (Oktober 1998 - Julie 1999) en Noord-Kaap (April 1998 - Oktober 1999) op kontrole en bespuite persele. Grondmonsters en erdwurms is spektrofotometries geanaliseer om koperinhoude te bepaal. Die selomosiete van lewende wurms is gebruik om NRR T te bepaal. Akute toksisiteitstoetse is uitgevoer oor 'n tydperk van 28 dae waartydens Eisenia fetida blootgestel is aan verskillende koperoksichloried konsentrasies. Veranderinge in biomassa en mortaliteit is bepaal asook NRRT. Bioevaluerings ("bioassays"), tonnelaktiwiteit- en vermydingseksperimente IS uitgevoer deur Aporrectodea caliginosa bloot te stel aan grasveld- en wingerdgrond asook grasveldgrond wat met koperoksichloried gekontamineer is. Groei en mortalitiet is bepaal in die "bioassays" asook koperkonsentrasies in die grond en erdwurm liggaamsweefsels oor 'n tydperk van 28 dae. Tonnelaktiwiteit en grondvermyding is bepaal deur die lengte van tonnels wat deur A. caliginosa gegrawe is te meet oor 'n tydperk van vier dae vir die verskillende blootgestelde groepe. Die resultate het aangedui dat koperoksichloriedbespuiting 'n negatiewe invloed het op erdwurmpopulasies teen die voorgeskrewe toedieningsprogram. NRRT in erdwurms van die blootstellingperseel, was beduidend (p<0.05) laer na 'n enkele bespuiting. Daar is verder bevind dat NRR T 'n betroubare en vroeë biomerker is, aangesien dit 'n aanduiding gegee het van latere effekte wat op populasievlak na vore getree het. Veldopnames in Nietvoorbij, Robertson en Worcester het die geldigheid van data verkry uit die veldstudies ondersteun. Die berekende LC50 van 882.78 ug.g" vir koperoksichloried en 519.40 ug.g" VIr koper was ekologies relevant indien 'n veiligheidsfaktor van 10 toegepas is. NRRT se ekologiese relevansie is bevestig deur dit te vergelyk met response wat in die veldtoetse waargeneem is. Deur bioevalueringseksperimente is bevind dat gewigsverlies en mortaliteit van A. caliginosa beduidend hoër was in koperoksichloried gekontamineerde grond as in die grasveld- (kontrole) en wingerdgronde. Veranderinge in biomassa en mortalitiet was aanduidend van populasieresponse soos waargeneem in die veldstudies en kan dus as ekologies relevante eindpunte beskou word. Tonnelaktiwiteit van A. caliginosa was beduidend (p<0.05) laer in wingerd- en koperoksichloried gekontamineerde grond as in grasveldgrond. Dieselfde is gevind in die grondvermydingstoetse waar A. caliginosa wingerd- en koperoksichloried gekontamineerde grond vermy het. Dit kan dus afgelei dat tonnelaktiwiteit en grondvermyding ook ekologies bruikbare eindpunte is aangesien dit verband hou met populasieresponse soos waargeneem in die veldstudies. Hierdie studie het getoon dat die herhaalde gebruik van koperoksichloried 'n nadelige invloed kan hê op erdwurmbevolkings. In die lig van die belangrike rol wat erdwurms en ander grondorganismes speel in grondvrugbaarheid kan die oormatige gebruik van hierdie fungisied ernstige implikasies inhou vir volhoubare benutting van landbougronde. Die gebruik van biomerkers en ander ekotoksikologiese eindpunte kan egter as vroeë waarskuwingsmetode dien dat die grondorganismes onder omgewingstres verkeer.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Thesis (MSc (Genetics))--University of Stellenbosch, 2009. / Worldwide, the rust diseases cause significant annual wheat yield losses (Wallwork 1992; Chrispeels & Sadava 1994). The utilization of host plant resistance to reduce such losses is of great importance particularly because biological control avoids the negative environmental impact of agricultural chemicals (Dedryver et al. 1996). The wild relatives of wheat are a ready source of genes for resistance to disease and insect pests. A large degree of gene synteny still exists among wheat and its wild relatives (Newbury & Paterson 2003). It is therefore possible to transfer a chromosome segment containing useful genes to a homologous region in the recipient genome without serious disruption of genetic information. Special cytogenetic techniques are employed to transfer genes from the wild relatives to the wheat genomes (Knott 1989). Unfortunately the transfer of useful genes may be accompanied by the simultaneous transfer of undesirable genes or redundant species chromatin which has to be mapped and removed (Feuillet et al. 2007). DNA markers are extremely useful for the characterisation and shortening of introgressed regions containing genes of interest (Ranade et al. 2001), and may also be used for marker aided selection of the resistance when the genes are employed commercially. Eight wheat lines containing translocations/introgressions of wild species-derived resistance genes were developed by the Department of Genetics (SU). These lines are presently being characterized and mapped and attempts are also being made to shorten the respective translocations. This study aimed to find DNA markers for the various translocations and to convert these into more reliable SCAR markers that can be used in continued attempts to characterize and improve the respective resistance sources. A total of 260 RAPD and 21 RGAP primers were used to screen the eight translocations and, with the exception of Lr19, it was possible to identify polymorpic bands associated with each translocation. However, it was not possible to convert all of these into more reliable SCAR markers. The primary reason for this was the low repeatability of most of the bands. Certain marker fragments turned out to be repeatable but could not be converted successfully. Some of the latter can, however, be used directly (in RAPD or RGAP reactions) as markers. The Lr19 translocation used in the study (Lr19-149-299) is a significantly reduced version of the original translocation and failure to identify polymorphisms associated with it can probably be ascribed to its small size. The following numbers of markers (direct and converted into SCARs) were Worldwide, the rust diseases cause significant annual wheat yield losses (Wallwork 1992; Chrispeels & Sadava 1994). The utilization of host plant resistance to reduce such losses is of great importance particularly because biological control avoids the negative environmental impact of agricultural chemicals (Dedryver et al. 1996). The wild relatives of wheat are a ready source of genes for resistance to disease and insect pests. A large degree of gene synteny still exists among wheat and its wild relatives (Newbury & Paterson 2003). It is therefore possible to transfer a chromosome segment containing useful genes to a homologous region in the recipient genome without serious disruption of genetic information. Special cytogenetic techniques are employed to transfer genes from the wild relatives to the wheat genomes (Knott 1989). Unfortunately the transfer of useful genes may be accompanied by the simultaneous transfer of undesirable genes or redundant species chromatin which has to be mapped and removed (Feuillet et al. 2007). DNA markers are extremely useful for the characterisation and shortening of introgressed regions containing genes of interest (Ranade et al. 2001), and may also be used for marker aided selection of the resistance when the genes are employed commercially. Eight wheat lines containing translocations/introgressions of wild species-derived resistance genes were developed by the Department of Genetics (SU). These lines are presently being characterized and mapped and attempts are also being made to shorten the respective translocations. This study aimed to find DNA markers for the various translocations and to convert these into more reliable SCAR markers that can be used in continued attempts to characterize and improve the respective resistance sources. A total of 260 RAPD and 21 RGAP primers were used to screen the eight translocations and, with the exception of Lr19, it was possible to identify polymorpic bands associated with each translocation. However, it was not possible to convert all of these into more reliable SCAR markers. The primary reason for this was the low repeatability of most of the bands. Certain marker fragments turned out to be repeatable but could not be converted successfully. Some of the latter can, however, be used directly (in RAPD or RGAP reactions) as markers. The Lr19 translocation used in the study (Lr19-149-299) is a significantly reduced version of the original translocation and failure to identify polymorphisms associated with it can probably be ascribed to its small size. The following numbers of markers (direct and converted into SCARs) were v identified: S8-introgression (Triticum dicoccoides) = one RAPD and two SCARs; S13-translocation (Aegilops speltoides) = four RAPDs, three RGAPs and five SCARs; S15-translocation (Ae. peregrina) = one RAPD and two SCARs; S20-translocation (Ae. neglecta) = two RAPDs, two RGAPs and one SCAR. The markers are already being employed in current projects aiming to map and shorten these translocations. Some of the markers can be combined in multiplex reactions for more effective mass screening. No repeatable markers could be identified for the four remaining translocations (S12 from Ae. sharonensis; S14 from Ae. kotschyi; Smac from Ae. biuncialis and Lr19-149-299 from Thinopyrum ponticum).

The challenges faced by the agricultural sector especially around improving production yields using environmentally friendly solutions have received market attention. Biological intervention can range from application of biological products to enhance the nutritional value of crops or to control plant pathogens. Biostart, a biological product that demonstrated growth enhancement when applied in lettuce crops is currently in the market. The product is comprised of a consortium of bacterial isolates (Bacillus licheniformis, Brevibacillus laterosporus and Bacillus laterosporus) but the contribution of the individual isolates to growth enhancement had not been elucidated. Green house experiments on lettuce seedlings with individual and mixed treatments were commissioned to determine such contribution. There was either no or marginal growth enhancement observed in the experiments. The results showed that the product was effective as a consortium and not as individual isolates. Further isolation and screening for potential Bacilli with antifungal properties was undertaken. An isolate identified as Bacillus subtilis that demonstrated inhibition against a wide spectrum of fungi, and especially the phytopathogenic Verticillium dahliae and Fusarium oxysporum, was successfully identified. The isolate was cryo-preserved and cultivated to significant levels at bench scale. A characterized comparison of different putative products with known systematic fungicide showed potential application even of heat treated products. The product showed control V. dahliae when tested in green houses with potatoes and tomatoes as test crops. This isolate has been targeted for further development as a biological control product.

Thesis (M. Tech) --Central University of Technology, Free State, 2008 / Aphids (Hemiptera: Aphididae) are amongst the most destructive insects in agricultural crop production systems. This reputation stems from their complex life cycles which are mostly linked to a parthenogenetic mode of reproduction, allowing them to reach immense population sizes within a short period of time. They are also notorious as important and efficient vectors of several plant viral diseases. Their short fecund life cycles allow them to be pests on crops with a short growth period, e.g. lettuce (Lactuca sativa L.). It is common practice to provide this crop with some degree of protection from environmental extremes on the South African Highveld. Shadehouses are popular in this regard, but aphids are small enough to find their way into these structures, and their presence on lettuce is discouraged due to phytosanitary issues. In addition, the excessive use of insecticides is criticized due to the negative influence on human health, and because aphids can rapidly develop resistance. This necessitates the use of alternative control options in order to suppress aphid numbers. Biological control is popular in this regard and the use of predatory ladybirds (Coleoptera: Coccinellidae) is a popular choice. This study investigated the aphid and coccinellid species complex encountered under varying shadehouse conditions on cultivated head lettuce in the central Free State Province (South Africa). Their seasonality was also examined, along with variations in their population size throughout a one-year period. Finally, the impact of varying aphid populations on some physical characteristics of head lettuce was examined, and recommendations for aphid control (using naturally occurring coccinellid predators) were made. Two shadehouse structures were evaluated during this study. One was fully covered with shade netting and designed to exclude the pugnacious ant, Anoplolepis custodiens (Hymenoptera: Formicidae), while the other was partially covered with shade netting (on the roof area) allowing access to the ants. Six cycles of head lettuce were planted and sampled four times during each cycle. These were scheduled to monitor the seedling, vegetative and heading stage of lettuce. Four important aphid species were recorded on the lettuce, namely Acyrthosiphon lactucae, Nasonovia ribisnigri, Myzus persicae and Macrosiphum euphorbiae. Both structures harboured similar aphid and coccinellid species, but their population dynamics differed. A. lactucae dominated in the absence of A. custodiens in the fully covered structure (whole study), while N. ribisnigri dominated in the partially covered structure in the presence of these ants during the warmer months (December – January). M. euphorbiae replaced this species as the dominant species in the absence of A. custodiens (April – September). M. persicae occured during the winter (May – August) in the fully covered structure. Promising coccinellid predators were Hippodamia variegata and Scymnus sp. 1, and to a lesser extent, Exochomus flavipes and Cheilomenes lunata. However, the fully covered structure hampered the entrance of the larger adult coccinellid species, resulting in their lower occurrence. Aphid and coccinellid activity peaked during the summer months (October – January), and the fully covered structure attained the highest aphid infestation levels and coccinellid larval numbers during this time. On the other hand, aphid numbers were higher in the partially covered structure during the cooler months of the year (April – July) and this structure also harboured more adult coccinellids. In most cases, aphid infestation levels did not affect the amount of leaves formed. However, symptomatic damage in terms of head weight reduction did occur under severe infestation levels. Specific environmental conditions within a shadehouse structure concurrently contributed to this reduction, with less favourable conditions accelerating this condition. Results from this study have shown that even though the type of shadehouse structure does not influence the insect species complex found on lettuce, it does have an influence on detrimental and beneficial insect population dynamics. Aphid species infesting lettuce have been identified, along with coccinellid predators that could potentially be used in their control. Both types of structures had advantages and disadvantages, and therefore, decisions concerning shadehouses should not be focused on which type of structure to use, but rather which type of structure to use during different seasons of the year.

Thesis (MSc)--Stellenbosch University, 1997. / ENGLISH ABSTRACT: The activity of iron-oxidizing bacteria, for example, Thiobacillut. ferrooxidans, in the outer layers of coal waste dumps results in the oxidation of pyrite with the formation of large volumes of acid mine drainage. The process requires atmospheric oxygen and moisture. Acid mine drainage may possibly be controlled by creating unfavourable environmental conditions in dumps for the iron-oxidizing bacteria. The present research investigated the possibility of inhibiting these bacteria and consequently acid formation in coal waste dumps by means of different dump construction techniques. Physical and chemical conditions, acid formation and populations of four groups of bacteria which might produce acid were studied in the outer layers of ten differently constructed pilot scale coal waste dumps at the Kilbarchan Mine near Newcastle, Kwazulu-Natal, from September 1993 to July 1995. Dump covers consisting of a 30-cm or 70-cm layer of Estcourt soil of low permeability covered with 70 cm or 30 cm, respectively, of more permeable Avalon soil produced anaerobic conditions in the dumps throughout most of the 22 months of the test period, as did a cover of 70 cm compacted plus 30 cm uncompacted Avalon soil alone. An uncoMpacted 30-cm or compacted 50- cm Avalon soil cover proved ineffective in causing prolonged anaerobic conditions. Uncovered dumps showed only slight reduction of oxygen in the coal waste after heavy rains. Pockets of acidity were detected on several occasions in the coal waste below the 50-cm Avalon soil layer from the time of construction and progressively increasing acidity in the uncovered dumps and the waste below the 30-cm Avalon soil cover. Iron-oxidizing bacterial populations of the T. ferrooxidans type have tended to be higher in the uncovered dumps and Avalon soil-covered dumps showing acidification than in the non-acidified dumps covered with 1 m of Avalon soil or Avalon and Estcourt soil. Associated populations of iron-oxidizing bacteria of the Metallogenium type, acidophilic and non-acidophilic thiosulphate-oxidizing bacteria were generally low in the coal waste of the dumps. Thus, five of the soil covers, all with a thickness of 1 m, but not covers with a thickness of 0.5 m or less, proved effective for almost 2 years in inhibiting the diffusion of oxygen to the underlying coal waste in the pilot scale dumps and also appeared to suppress the populations of iron-oxidizing bacteria believed to be implicated in acid formation in the coal waste. These results suggest that coal waste dumps in South Africa should be covered with soil layers of 0.5-1.0 m thick to prevent the generation of acid mine drainage. / AFRIKAANSE OPSOMMING: Die aktiwiteit van ysteroksiderende bakteriee soos Thiobacillus ferrooxidans, in die buitenste lae van steenkoolafvalhope, veroorsaak die oksidasie van piriet met die gevolg dat groot volumes suur mynafloopwater gevorm word. Hierdie proses benodig suurstof en vog. Suur mynafloopwater kan moontlik beheer word deur 'n situasie te skep waar die toestande in die hope ongunstig is vir die ysteroksiderende bakteriee. Die huidige navorsing het die moontlikheid ondersoek om hierdie bakteriee te inhibeer deur verskillende afvalhoopontwerpe op die proef te stel en sodoende suurvorming in steenkoolmynhope te beperk. Die fisiese en chemies kondisies, suurvorming en populasies van vier verskillende bakterie-groepe wat dalk by suurvorming betrokke is, is vanaf September 1993 tot Julie 1995 bestudeer in die buitenste lae van tien verskillend gekonstrueerde loodsskaalafvalhope by die Kilbarchan myn naby Newcastle in KwaZulu-Natal. Afvalhoopbedekkings bestaande uit 'n 30-cm of 70-cm Estcourt grond met 'n lae permeabiliteit bedek met'n 70-cm of 30-cm laag van meer deurlaatbare Avalon grond het anaerobe kondisies veroorsaak. Ongekompakteerde 30-cm en gekompakteerde 50-cm Avalon grondlae het egter nie bestendige anaerobe kondisies in die hope veroorsaak nie. Die onbedekte hope het aerobics gebly met slegs effense dalings van suurstofkonsentrasies gedurende en na swaar reens. Geisoleerde monsters uit die steenkoolafval onder die 50-cm Avalon grondlaag het vanaf die begin van die toetsperiode tekens van suurvorming getoon. Die onbedekte steenkoolafval en die van die sel met 'n 30-cm Avalon grondlaag het met verloop van tyd al hoe meer suur geword. Die ysteroksiderende bakterie-populasies van die T. ferrooxidans tipe het geblyk om in die onbedekte en Avalon grondbedekte hope wat tekens van suurvorming getoon het hoer te wees as in die hope wat met 'n 1-m laag Avalon grond of Avalon en Estcourt grond bedek is en geen tekens van suurvorming getoon het nie. Ysteroksiderende bakteriepopulasies van die Metallogenium tipe, nieasidofiele en asidofiele tiosulfaatoksiderende populasies was oor die algemeen laag in die steenkoolafvalhope. Vyf van die grondlae wat alma! 1 m dik was het dus geblyk om effektief te wees in die bekamping van die infiltrasie van suurstof na die onderliggende steenkoolafval in die loodskaalhope. Dit lyk asof daardie lae die ysteroksiderende populasies betrokke by suurvorming onderdruk het. Die 0.5-m grondbedekking het egter nie so 'n sterk onderdrukkende effek op die suurstofinfiltrasie of die bakteriepopulasie gehad nie. Na aanleiding van hierdie resultate blyk dit dat steenkoolafvalhope in Suid-Afrika met minstens 0.5 tot 1..0 m grond bedek moet word om effektief die probleem van suur mynafloopwater te bekamp.

Thesis (MSc)--Stellenbosch University, 1998. / One copy microfiche. / ENGLISH ABSTRACT: The biologically catalysed oxidation of pyrite in the outer layers of coal waste dumps leads to the formation of acid mine drainage. The oxidation of pyrite to ferric iron and sulphate is a complex process involving various abiotic and biologically catalysed reactions. Pyrite is abiotically oxidized by ferric iron, with the formation of thiosulphate and ferrous iron. Thiosulphate decomposes to form various inorganic sulphur compounds. Bacterial catalysis of pyrite oxidation is achieved by iron-oxidizing bacteria oxidizing ferrous iron to ferric iron. Bacteria that oxidize sulphur compounds assist the catalysis by oxidizing thiosulphate and its decomposition products. Heterotrophic organisms may play a role by consuming organic substances inhibitory to the lithotrophic bacteria. Abiotic ecological factors, acid formation and populations of iron-oxidizing bacterial groups were studied in 10 differently constructed pilot scale coal waste dumps, as the second phase of a study which started in September 1993. Gas samples were withdrawn weekly from coal waste through permanently buried stainless steel probes, for analysis in the field using a portable oxygen/carbon dioxide meter. Samples of coal waste were extracted by auger for analysis of moisture, pH and microbial populations. The analyses of oxygen and pH can be recommended for the routine monitoring of rehabilitated waste dumps. Covers of Avalon soil 0.3 or 0.5 m thick, were not adequate to prevent acidification. Coal waste covered with 0.7 m compacted beneath 0.3 m uncompacted Avalon soil, showed a slow pH decline, but reached approximately pH 3 in 1997. Covers of compacted Estcourt soil beneath tmcompacted Avalon soil to a cover depth of 1 m were effective in preventing acidification and generally kept the coal waste anaerobic. However, all covers developed cracks during drought conditions in 1995, allowing aeration. Low pH of some samples from these dumps during 1995/1996 may have indicated the start of acidification. Bacteria oxidizing high concentrations of ferrous iron and considered to be Thiobacillus ferrooxidans, were monitored routinely, but may not have been the dominant iron-oxidizer, as population counts using media with a lower ferrous iron concentration were higher. The majority of the latter organisms could also not oxidize sulphur, hence were not T. ferrooxidans. The populations of the high ferrous iron-oxidizing bacteria were affected by pH, tending to be high in acidified and low in non-acidified coal waste. Investigations of microbial populations forming iron-oxidizing consortia in enrichment cultures from coal waste and acid drainage samples showed the presence of T. ferrooxidans, the heterotrophic bacterial genus Acidiphilium, fungi of the genus Penicillium, unidentified filamentous fungi, including Cladophialophora-like morphological types, and a yeast of the genus Dipodascus. In interaction studies, the Penicillium isolate had an inhibitory effect on T. ferrooxidans (subjected to organic compound stress), but the Cladophialophora-like fungi reduced inhibition by organics. Fungi have not previously been studied in detail as components of iron-oxidizing consortia, but the bacterial isolations agree with those elsewhere, indicating that appropriate conclusions from acid mine drainage research in other parts of the world can be applied in KwaZulu-Natal. / AFRIKAANSE OPSOMMING: Die biologies gekataliseerde oksidasie van piriet in die buitenste lae van steenkoolafvalhope lei tot die vorming van suur mynafloopwater. Die oksidasie van piriet tot ferri-yster en sulfaat is 'n komplekse proses wat abiotiese en biologies gekataliseerde reaksies insluit. Piriet word abioties deur ferri-yster geoksideer, met die vrystelling van tiosulfaat en ferro-yster. Tiosulfaat verval om verskeie anorganiese swawelverbindings te vorm. Bakteriese katalise van pirietoksidasie word deur ysteroksiderende bakteriee wat ferro-yster na ferri-yster oksideer, bewerkstellig. Bakteriee wat swawelverbindings oksideer maak 'n bydrae tot die katalise deur tiosulfaat en vervalprodukte daarvan te oksideer. Heterotrofe organismes mag ook 'n rol speel deur organiese verbindings wat die litotrofe bakteriee mag inhibeer, te verbruik. Abiotiese ekologiese faktore, suurvorming en bevolkings ysteroksiderende bakteriee is in 10 verskillend gekonstrueerde loodsskaal steenkoolafvalhope bestudeer, as die tweede fase van 'n studie wat in September 1993 begin het. Gas monsters is weekliks uit die steenkoolafval onttrek deur vlekvrye staal peilers wat permanent daarin begrawe is, en met behulp van 'n draagbare suurstoflkoolstofdioksiedanaliseerder in die veld ontleed. Monsters van die steenkoolafval is met behulp van 'n kleiboor vir die analise van vog, pH en mikrobepopulasies geneem. Die analise van suurstof en pH kan aanbeveel word vir die roetiene monitering van gerehabiliteerde afvalhope. Bedekkings van 0.3 of 0.5 m Avalongrond was nie voldoende om suurvorming te verhoed nie. Steenkoolafval wat met 0.7 m gekompakteerde en 0.3 m ongekompakteerde Avalongrond bedek is, het 'n stadige pH-daling getoon, maar het in 1997 ongeveer pH 3 bereik. Bedekkings van gekompakteerde Estcourtgrond onder ongekompakteerde A valongrond met 'n totale dikte van 1 m, was effektief in die voorkoming van suurvorming. Hulle het oor die algemeen die steenkoolafval anaerobies gehou, maar aile bedekings het tydens die droogte in 1995 krake ontwikkel, wat suurstof laat binnedring het. 'n Lae pH gedurende 1995/1996 by sommige monsters uit hierdie hope mag die begin van suurvorming aangedui het. Bakteriee wat hoe konsentrasies ferro-yster oksideer en wat as Thiobacillus ferrooxidans beskou is, was moontlik nie die dominante ysteroksideerder nie, aangesien bevolkingstellings waar 'n medium met 'n laer konsentrasie ferro-yster gebruik is, hoer bevolkings getoon het. Die meerderheid van laasgenoemde organismes kon ook nie swawel benut nie en dus nie T. ferrooxidans was nie. Die bevolkings van die hoe ferro-ysteroksiderende bakteriee is deur pH beInvloed, met 'n geneigdheid tot hoe bevolkings in suur en lae bevolkings in minder suur steenkoolafval. Ondersoeke na die rnilcrobebevollcings wat in ysteroksiderende konsortia in verryldngslculture vanaf steenkoolafval- en suur mynafloopwatermonsters voorgekom het, het die teenwoordigheid van 7'. ferrooxidans, die heterotrofe balcteriegenus Acidiphilium, fungi van die genus Penicillium, ongeIdentifiseerde fungi, insluitend Cladophialophora-agtige tipes en 'n gis van die genus Dipodascus aangetoon. By interaksiestudies het die Penicillium-isolaat 'n inhiberende effek op T ferrooxidans (onderworpe aan organiese verbindingstres) gehad, maar die Cladophialophora-agtige fungi het die inhibisie deur organiese verbindings verminder. Fungi is nog the in detail as komponente van ysteroksiderende konsortia bestudeer the, maar die isolasies van bakteried stem saam met die van elders wat aandui dat toepaslike gevolgtreldcings ten opsigte van suur mynafloopwatemavorsing vanaf ander dele van die wereld ook in KwaZulu-Natal toegepas kan word.