The invasion of ecosystems by alien species is a growing threat to the delivery of ecosystem services. This study explored the spatial distribution of water hyacinth in the Benoni Lakes and made analysis of its impact on water availability and usability in order to understand the evolution and its propagation rates. The study used satellite imagery for lake level modelling using Remote Sensing and Geographical Information Systems for calculations of area covered by weeds in each lake from 2002 to 2012.The modelling approach illustrates the potential usefulness in projecting invasive plants under climate change and enabled the quantification of long term changes in aquatic weeds. The results showed that aquatic infestations in lakes may be used as powerful predictors of correlations between plant abundance and climate change. The study therefore informs decision makers to identify areas where invasion is likely to occur and increase surveillance for early invaders. / Environmental Sciences / M. Sc. (Environmental Management)

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Doctor of Philosophy School of Animal, Plant and Environmental Sciences, Johannesburg, 2014 / Water hyacinth (Eichhornia crassipes) is one of the most notorious aquatic weeds in the world. Its management, despite the release of seven biocontrol agents since 1974, remains a problem in South Africa. This is often attributed to the high level of eutrophication. However, information on the effect of heavy metals or AMD on Neochetina eichhorniae and N. bruchi, which are the common and most widely established biocontrol agents in the country, is limited. In addition integrated management, which combines herbicides with biological control methods, is the current water hyacinth control method, and requires regular monitoring of the weed’s health status. This can be assessed via the canopy chlorophyll and water content, and can facilitate the decision when to intervene and what intervention measures are appropriate and timely. Hyperspectral Remote sensing (HRS) has the potential to be that monitoring tool. This thesis investigates the physiological status of water hyacinth grown with eight different heavy metals in a single-metal tub trial, three different simulated acid mine drainage (AMD) treatments in a pool trial under the influence of biocontrol agent from Neochetina spp., and in the Vaal River at the inlets of its tributaries, the Koekemoerspruit and the Schoonspruit. A hand-held spectrometer, the analytic spectral device (ASD), was used to measure reflectance. The hypothesis that HRS can detect the response of the plant to both the heavy metals and the biocontrol-induced stresses and their interactions was tested. Different spectral indices associated with the canopy chlorophyll and water content of water hyacinth were evaluated. Among these the modified normalized difference vegetation index (mNDVI) and those associated with the red edge position (the linear extrapolation and the maximum first derivative indices) were able to detect the metal, or AMD or weevil-induced plant health stresses and showed a strong positive correlation with the actual leaf chlorophyll content, measured by a SPAD-502 chlorophyll meter. Among the contaminants Cu, Hg, and Zn treatments from the single-metal tub trial and sulphate concentrations exceeding 700 mg/L in the AMD pool trial were detected by the RS as stressful to the plants. The RS also indicated that the water contamination level was greater downstream at the inlet of the Schoonspruit into the Vaal River, compared to the other sites after rainfall. These results were also consistent with actual measurements of the different plant growth parameters in all the trials and the weevils’ feeding and reproductive activities in the tub and pool trials. Thus, the results of this study indicated that the HRS has potential as a tool to assess the physiological status of water hyacinth from a remote position, which could be helpful in management of a serious national problem. The acquisition of spectral reflectance data at a larger scale, from aerial platforms, involves a complex data set with additional atmospheric interference that can mask the reflectance and which demands more complicated image analysis and interpretation. Thus, further such studies in future are recommended.

No description available.

Studies were carried out from July 1988 to August 1989 to assess the growth and winter survival of water hyacinth, Eichhornia crassipes (Mart.) Solms, in treatment of secondary domestic wastewater in Tucson, Arizona. Percent of surviving overwintered plants for the following frost protection treatments from November 1988 to March 1989 was: 25 (control), 48 (plastic tarps), 70 (sprinklers), 34 (fog) and 76 (greenhouse). Both control plants and protected plants had longer roots at the effluent end of the ponds than the influent ends during winter months. Greenhouse-protected plants had greater root and entire plant lengths, and greater fresh and dry weights. Dry weight per unit area (kg m⁻²) was higher for greenhouse plants though all protected plants showed decline in dry weight per unit area with temperatures below 10 C. Qualitative observations indicated that protected plants showed less chlorosis and necrosis from low temperatures than control plants, however, plants in all frost protected treatments experienced low temperature stress. Aphids were seen in some of the ponds throughout the study and contributed to severe lamina and petiole damage.

In a survey conducted in Zimbabwe in 1993, waterhyacinth was present in seven out of the eight provinces. No control measures were imposed on 35% of the infested dams and 61% of the infested rivers, while in 47% of the infested dams and 11% of the infested rivers control of waterhyacinth was being attempted with a combination of 2,4-D and mechanical control methods. The population of Neochetina eichhorniae and N. bruchi declined during the period 1993 to 1995 in the Hunyani River system. Several fungi were isolated from diseased waterhyacinth, and Fusarium moniliforme (isolate 2ex 12), F. solani (isolates 5a ex25 and 2a3), and F. pallidoroseum (isolate 3ex1) were found to be the most pathogenic. Large numbers of viable conidia were produced in shake-flask liquid fermentation with modified Richard's medium and in solid fermentation with food grains. Conidia production in straw was poor with the exception of waterhyacinth straw. Host range studies conducted in pots and in the field indicated that Commelina benghalensis was moderately susceptible to both isolates of F. solani in the field, while Setaria verticilata grown in pots was moderately susceptible to isolate 2a3. Brassica rapa and Crotalaria juncea grown in pots were moderately susceptible to F. moniliforme but they showed no infection in the field. Fifty-nine additional plant species of ecological and agricultural importance were not susceptible to the Fusarium species. When F. solani, F. pallidoroseum and Neochetina spp. were used individually in ponds, they did not control waterhyacinth. When the fungi were combined with Neochetina spp., the area covered by waterhyacinth and the volume of waterhyacinth were significantly reduced.

Floating macrophyte pond systems, with the ability to produce nutrient enriched plants simultaneously with wastewater treatment, are a sustainable solution to contribute to environmental protection and safe nutrient recovery from domestic wastewater. However, to meet the requirements for reuse with high strength wastewater containing high levels of metal pollution generated in developing countries, an adequate combination of water hyacinth and duckweed ponds is proposed in order to take advantage of the best characteristics of each of these macrophyte ponds. This research focused on the advancing of the understanding of the effectiveness of treatment and resource recovery under the effect of changing operational parameters such as pH, light intensity, influent metal content and fluctuating pollutants loading rate on pond performance and recycling ability in order to fill the noticed gap of knowledge. Experiments conducted in water hyacinth ponds (WHP), under batch and tropical natural weather conditions, revealed that pH between 6.4 and 7.1, full sunlight and seven days hydraulic retention time were optimum for plant biomass production and pollutant removal in WHP. WHP was able to regulate pH when the initial pH values moved outside this interval with a drop in biomass production as a side effect. These ponds showed a first order kinetic for the removal of iron, zinc and copper from aqueous solution and their accumulation in plants biomass with a preferential sequence Fe > Zn > Cu. However the presence of metals in water hyacinth biomass led to the reduction in ponds performances and a risk of re-pollution of the effluent through the release of metals into water. A comparative study carried out over sixty-two weeks in a pilot scale combined water hyacinth and duckweed ponds (DWP) channel and waste stabilization ponds channel working under fluctuating loading rates showed different environmental conditions occurred these ponds. The fluctuating loading rate was also found to have a reduced effect on the combined WHP/DWP channel performance and effluent quality stability with the effluents meeting the entire reuse requirement at high hydraulic flow rate (retention time greater than 20 days). Fish was able to grow in the WHP/DWP channel. Results suggested some guidelines on WHP/DWP system design, operation and maintenance. The overall outcome of this research is a significant contribution to the development of integrated combined WHP/DWP technology for treatment of wastewater and resource recovery on site.

nÃo hà / In this work was carried out an extensive investigation of the adsorption properties of synthetic dyes on different parts (rhizome, root, stolon and petiole) of Eichhornia crassipes (water hyacinth) and a comparison with the adsorption capacity of the biopolymer alginate beads doped with water hyacinth biomass. The biomasses and spheres were structurally characterized by infrared spectroscopy, scanning electron microscopy - SEM and thermal analysis (thermogravimetric analysis - TGA and Differential Scanning Calorimetry - DSC). The kinetics of adsorption processes were monitored by UV and visible spectroscopy - UV / VIS and the data applied to the models of Freundlich and Languimir. Synthetic anionic dyes (methyl orange), cationic (methylene blue) and azo (indigo carmine) were used in the investigation. Adsorption studies was obtained, under controlled agitation of 70 rpm and temperature ranging between 25ÂC and 45ÂC at concentrations of dye in the range 10-250 mg/L and pH 2-12. The best results were achieved with a dye initial concentration of 100 mg/g, an initial quantity of 60 mg biosorbent, at temperature of 45 ÂC and at basic pH. Among the tested dyes, methylene blue exhibited the best adsorption capacity. The study of adsorption kinetics showed a better fit to the model of pseudo-second order and intraparticle diffusion is involved in the mechanism of adsorption. In the study of the isotherms, the result shows best fit to data by the Langmuir and Freundlich equations, with a maximum capacity of adsorption of methylene blue dye from 819.7 mg/g at 25 ÂC, to the root. A temperature increase caused an increase in system adsorption capacity and also led to an increase in time to the system reach equilibrium. The values of the rate constant for pseudo-second order increased with increasing temperature. An increase in initial dye concentration caused an increase in the amount of dye adsorbed. The activation energy for all biosorbents are in the range 20-40 kJ.mol-1 demonstrated that the adsorption processes are physical. The thermodynamic parameters ∆HÂ, ∆S and ΔGÂ, for most biosorbents indicate that the process is exothermic in nature, spontaneous and favorable, except for the sphere of ALG/GC/Biomass where values obtained showed endothermic nature. The desorption study showed that the biosorbents can be reused. / Neste trabalho foi realizada uma investigaÃÃo extensiva das propriedades de adsorÃÃo do corante azul de metileno em diferentes partes (rizoma, raiz, estolÃo e pecÃolo) de Eichhornia Crassipes (aguapÃ), bem como uma comparaÃÃo com a adsorÃÃo em esferas do biopolÃmero alginato dopadas com biomassa de aguapÃ. As biomassas e esferas foram caracterizadas estruturalmente atravÃs de tÃcnicas de espectroscopia de infravermelho, microscopia eletrÃnica de varredura â MEV e anÃlises tÃrmicas (anÃlise termogravimÃtrica â TGA e Calorimetria Diferencial de Varredura â DSC). As cinÃticas dos processos de adsorÃÃo foram monitoradas por espectroscopia de ultravioleta e visÃvel â UV/VIS e os dados obtidos aplicados nos modelos de Languimir, Freundlich, Temkin e BET. Foram utilizados corantes sintÃticos aniÃnico (alaranjado de metila), catiÃnico (azul de metileno) e azo (Ãndigo carmin). Os estudos de adsorÃÃo foram obtidos, sob agitaÃÃo controlada de 70 rpm e temperatura variando entre 25ÂC e 45ÂC, e concentraÃÃes de corante na faixa de 10 a 250 mg/L, em pH de 2 a 12. Os melhores resultados foram alcanÃados utilizando uma concentraÃÃo inicial de corante de 100 mg/g, uma massa inicial de biosorvente de 60 mg a temperatura de 45 ÂC e em pH bÃsico. Dentre os corantes testados o azul de metileno foi o que apresentou melhores resultados de adsorÃÃo. O estudo da cinÃtica de adsorÃÃo apresentou um melhor ajuste ao modelo de pseudo-segunda ordem e a difusÃo intrapartÃcula està envolvida no mecanismo de adsorÃÃo. No estudo das isotermas de equilÃbrio, o resultado mostra melhor ajuste das equaÃÃes de Langmuir e Freundlich pelos dados, com capacidade mÃxima de adsorÃÃo do corante azul de metileno de 819,7 mg/g a 25 ÂC, para a raiz do aguapÃ. A elevaÃÃo na temperatura do sistema provocou aumento na capacidade mÃxima adsorvida e tambÃm provocou um aumento no tempo para o sistema atingir o equilÃbrio. Os valores da constante de velocidade de pseudo-segunda ordem aumentaram com o aumento da temperatura. Um aumento na concentraÃÃo inicial do corante provocou um aumento na quantidade de corante adsorvida. A energia de ativaÃÃo para todos os biosorventes, da ordem de 20 â 40 kJ.mol-1, demonstrou que o processo à de natureza fÃsica. Os parÃmetros termodinÃmicos ∆HÂ, ∆S e ∆GÂ, para a maioria dos biosorventes indicam que o processo à de natureza exotÃrmica, espontÃnea e favorÃvel, com exceÃÃo da esfera de ALG/GC/Biomassa que mostrou valores de natureza endotÃrmica. O estudo de dessorÃÃo demonstrou que os biosorventes podem ser reutilizados.

The biomass of the submersed macrophytic vegetation in four hydrilla (Hydrilla verticillata Royle) infested lakes in central Florida was monitored for one year. Lake Orienta and Little Lake Fairview received 2,320 and 960 grass carp, respectively, while Clear Lake and Lake Mann did not receive grass carp. Hydrilla was eliminated in Lake Orienta within six months of stocking; the lake was stocked at 19 grass carp/mt hydrilla (45 fish/ha). Hydrilla was not eliminated from Little Lake Fairview which contained 9 grass carp/mt hydrilla (30 fish/ha). The growth of hydrilla was restricted in Little Lake Fairview which produced 0.380 mt hydrilla, dry organic wt., in contrast to Clear Lake and Lake Mann in which annual net primary production was 0.728 and 0.880 mt organic matter/ha, respectively. The rate of hydrilla growth was greater in the two unstocked lakes. Clear Lake produced 0.31 g/m2/day, dry organic wt., while the net primary productivity of hydrilla in Lake Mann averaged 0.38 g/m2/day. The net primary productivity of hydrilla in Little Lake Fairview was 0.14 g organic matter/m2/day. Three species (in addition to hydrilla) were common to Little Lake Fairview and Lake Mann and provided the only data upon non-target species. Pondweed (Potamogeton illinoensis Morong.) and stonewort (Nitella sp.) were more abundant and more widely distributed in Little Lake Fairview than in Lake Mann. The poor representation of pondweed and stonewort in Lake Mann was attributed to competitive pressure exerted by hydrilla which comprised 83%, by weight, of the annual mean biomass of submersed macrophytic vegetation. In comparison, hydrilla comprised 74% of the annual mean biomass in Little Lake Fairview. The effect of the grass carp in Little Lake Fairview may have been to ease the competitive pressure exerted by hydrilla, allowing pondweed and stonewort to remain well established. The percentage frequency of occurrence was concluded to be a poor criterion for measuring changes in the hydrilla population. Changes in biomass as great as 900% resulted in no change in the percentage frequency of occurrence of hydrilla in Lake Mann.

A series of experiments provided data to parameterize and validate a coupled herbicide fate and target plant species effects model. This simulation model is currently designed to predict responses of water hyacinth populations to treatments of the dimethylamine formulation of 2,4- dichloro-phenoxy acetic acid (2,4-D -DMA). Experiments investigated 1) the response of water hyacinth to varying exposures of 2,4-D (DMA); 2) the role of water hyacinth density and herbicide interception in treatment effectiveness using 2,4-D (DMA); and 3) the importance of root exposure to obtain control of water hyacinth using 2,4- D (DMA). Results demonstrated the importance of leaf or canopy interception of 2,4-D (DMA) sprays in obtaining control of water hyacinth populations. The critical threshold plant tissue concentration of 2,4-D (DMA) required to elicit maximum mortality (98%) was estimated to be approximately 12 mg 2,4-D per kg water hyacinth tissue (wet weight). Root uptake apparently plays little or no role in the effectiveness of this herbicide for controlling water hyacinth growth. Validation trials illustrated the efficacy of the current model. The model was validated with data from a field operation. This research has provided considerable insight into optimal use of this auxin-type herbicide for control of water hyacinth, a monocotyledon.

Gold tailings contained in Tailing Storage Facilities (TSFs) contain pyrite which on exposure to air and water becomes a source of acid mine drainage (AMD). AMD has high salinity, elevated levels of heavy metals and low pH, which presents serious threats to surface and groundwater systems. These characteristics in tailings present a hostile environment for plant establishment and growth (Witkowski and Weiersbye 1998a). Therefore, it was hypothesized that organic mulch sourced from sewage sludge and water hyacinth could improve tailings fertility on TSFs in the Highveld gold mines of South Africa. The aim of this study was to develop a greenhouse study to understand how four indigenous plants (Asparagus laricinus Burch. (Asparagaceae), Eragrostis curvula (Schrad.) Nees. (Poaceae), Hyparrhenia hirta (L.) Stapf (Poaceae) and Sutherlandia frutescens (L.) R.Br. (Fabaceae) naturally colonizing the Highveld gold TSFs would survive, grow and accumulate metals from tailings amended using different percentages of water hyacinth and/or sewage sludge, and the susceptibility of the amended tailings to metal leaching. Tailings amended with WH: SS-1.0% proved to be the overall best amendment from the 19 treatments based on the variable tested (e.g. plant growth, plant metal uptake and metal leaching). Amending gold tailings with water hyacinth and/or sewage sludge improved seedling survival, plant survival and growth as compared to non-amended tailings. Tailings amended with dry water hyacinth (WH) created the most favourable plant growing conditions especially at 0.5% of amendment, while those amended only with sewage sludge (SS) presented the most challenging plant growth conditions for all four study species. Amending tailings with water hyacinth and/or sewage sludge showed no significant difference in tailings fertility. However, C (%) and total N decrease significantly after plant growth in all treatments. Hyparrhenia plants grown in tailings amended with WH: SS-1.0% accumulated significantly higher concentrations of Al, Cr, Ni and Zn, while those growing in tailings amended with WH-0.5% accumulated significantly lower concentration of Al, Co, Cr, Fe and Zn as compared to other treatments. Tailings amended with WH-1.0% leached significantly higher concentrations of Mn, while those amended with WH: SS-0.5% and WL-2.0% leached significantly higher concentrations of S as compared to other treatments. All four species accumulated significantly higher concentrations of Al, Co, Cr, Cu, Fe and Ni in the roots than the shoots, except for A. laricinus which accumulated significantly higher concentrations of S, Co, Cr, Mn, Ni and Zn in the shoots than the roots. Sutherlandia frutescens retained all the elements tested in its root biomass. Future field studies in the use of water hyacinth and sewage sludge as organic tailings amendments will be required to get a better understanding of these two potential tailings amendment treatment.