Made available in DSpace on 2014-06-11T19:29:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-01-15Bitstream added on 2014-06-13T20:39:15Z : No. of bitstreams: 1 santos_aa_me_ilha.pdf: 676511 bytes, checksum: f49f6d1a9f6dfba6539f793f9e93426c (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O solo é um meio que engloba diferentes substâncias químicas e colóides e uma alta diversidade biológica. Estes componentes apresentam íntima relação funcional para sustentabilidade dos ecossistemas e, sua degradação, geralmente causada pela ação antrópica, acarreta um grande prejuízos ambientais e socioeconômicos para as gerações atuais e um enorme risco para as gerações futuras. Para reverter um processo como este, são necessárias intervenções por meio de estratégias como a revegetação. O objetivo do trabalho foi avaliar crescimento e colonização micorrízica do pinhão manso em solo decaptado que recebeu inoculo de fungos micorrizicos arbusculares, hidrogel e materiais orgânicos. O experimento foi conduzido de maio de 2008 a maio 2009, na Fazenda de Ensino, Pesquisa e Extensão (FEPE) da UNESP – Universidade Estadual Paulista, Campus de Ilha Solteira, no município de Selvíria-MS. O delineamento experimental foi o em blocos casualizado, em esquema fatorial 4x2x2, ou seja, 3 tratamentos com material orgânico (aguapé, composto e aguapé+composto), 2 tratamentos com hidrogel (com e sem adição) e 2 tratamentos de inoculação (com e sem inoculação) empregando solo proveniente de uma área preservada de cerrado como fonte de microrganimos, incluíndo fungos micorrízicos arbusculares, com 4 repetições e 5 plantas por tratamentos. O composto foi preparado com materiais de poda e esterco de bovino. Avaliou-se: o crescimento das plantas em 7 épocas diferentes, a caracterização química e número de esporos em 4 épocas, além da porcentagem de colonização micorrízica, presença de flores, número de ramos e de folhas e peso fresco e seco da parte aérea. O tratamento com hidrogel não mostrou interferência no crescimento de plantas, mas, assim como o solo-inóculo, aumentou a esporulação, a colonização micorrízica e a produção de matéria seca... / The soil is a medium that contain different chemical substances and colloids and a high biological diversity. These components have functional relationship on the sustainability of ecosystems and their degradation, usually caused by human action, which causes great socio-economic damage to the present generations and an enormous risk for the future generations. To reverse such process, action is needed using strategies, such as, revegetation. The objective of this study was to evaluate the growth and mycorrhiza colonization of Jatropha on decapitated soil that received organic materials and hydrogel. The experiment was conducted from May 2008 to May 2009, the Farm Education, Research and Extension (FEPE), UNESP - Univ. Estadual Paulista, Ilha Solteira Campus, located at Selvíria city-MS, Brazil. The experimental design was randomized blocks in factorial scheme 3x2x2, i.e., 3 treatments with organic materials (water hyacinth, compost and water hyacinth + compost), 2 hydrogel treatments (with and without addition) and 2 inoculations treatments (with and without inoculation) using natural soil from a preserved ‘cerrado’ area as a source of microorganisms, including mycorrhizal fungi, with 4 replications and 5 plants per each. The compound was prepared with materials pruning and cow dung. The growth of plants in 7 different times, the chemical characterization and number of spores in 4 times, and the percentage of mycorrhizal colonization, presence of flowers, branches and leaves and fresh and dry weight of air part was evaluated. Treatment with hydrogel showed no interference with the growth of plants; however, as well as the soilinoculum, they increased sporulation, root colonization and production of dry matter. The organic materials treatments positively altered the condition of the ground, plant growth, mycorrhizal colonization and sporulation; the improved performances... (Complete abstract click electronic access below)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Water hyacinth (Eichhornia crassipes) is an invasive aquatic weed whose main characteristic is its high growth rate. The methods applied to control this plant have high cost and waste generation. Using the water hyacinth as an adsorbent for remediation of metals is a viable and eco-friendly application. In this work, a magnetic hybrid adsorbent matrix (AGMG) was synthesized utilizing water hyacinth (Eichhornia crassipes) biomass to compose an organic phase, and its adsorption efficiency was compared to the adsorption efficiency of in natura (AGIN) water hyacinth and its biochar (BIO) in the remediation of metals in water. The adsorbents were characterized by infrared spectroscopy, confirming the presence of hydroxyl groups and carboxylates, with bands that are typical of cellulose, hemicellulose and lignin, structures found in AGIN and BIO. The AGMG spectrum presented the bands previously described and new bands in the region of 513 cm-1, characteristic of the Fe-O bond of CoFeO4, confirming the formation of a magnetic hybrid. The essays on the influence of pH on the remediation of copper, zinc, nickel and cobalt presented higher percentages of removal in the range of pH 4-5 for all adsorbents, and the following crescent order of removal efficiency AGIN<AGMG<BIO for all metals. The kinetic studies showed fast kinetics for the three adsorbents and the metals under study with a removal rate of more than 50% in the first 5 minutes. The kinetic data were adjusted to the pseudo-second order model, with correlation coefficients higher than 0,99 for the three materials. The AGMG was prominent among the other adsorbents because its adsorption capacity is high and its separation from the aqueous medium is more feasible. The isotherm data for the AGMG were adjusted to the Langmuir model, showing a good linear correlation in the concentration range studied (5-250 mg g-1), with correlation coefficient r2 between 0,9973-0,9999. The values of the calculated maximum capacity of AGMG (qmax) were 18,3 mg g-1 Cu (II), 10,1 mg g-1 Zn (II) and 7,33 mg-1 Ni (II). The percentage of removal in the different mixed solutions by the adsorbent AGMG followed this order of selectivity, Cu>Zn>Ni, copper as a highlight, > 84% removal in all evaluated mixed solutions. The AGMG was reused in four cycles of adsorption in mixed solution, without using a desorption process, and the efficiency varied according to the metal. The adsorption of copper remained high in all cycles, with 77% removal in the first cycle and 72% in the fourth cycle. For zinc and nickel, the removal decreased with each cycle, and in the third cycle there was no more nickel removal. The saturated with metals AGMG residues (AGMG-sat) showed high catalytic activities in the reduction of 4- nitrophenol to 4-aminophenol. The residues were reused in ten reduction cycles and the conversion rate in the cycles ranged from 88,9 to 100%, with short periods of time (21-26 s). / Aguapé (Eichhornia crassipes) é uma planta daninha aquática invasora cuja principal característica é sua alta taxa de crescimento. Os métodos aplicados para o controle dessas plantas possuem alto custo e geração de resíduos. Uma aplicação viável e eco-amigável é utilizá-la como adsorvente para a remediação de metais. Neste trabalho foi efetuada a síntese de uma matriz adsorvente híbrida magnética (AGMG) utilizando a biomassa aguapé (Eichhornia crassipes), para compor a fase orgânica, e comparou sua eficiência adsortiva com a aguapé in natura (AGIN) e seu biocarvão (BIO), na remediação de metais em água. Os adsorventes foram caracterizados por espectroscopia de infravermelho, que confirmou a presença de grupos hidroxilas e carboxilatos, com bandas típicas da celulose, hemicelulose e lignina, estruturas essas encontradas no AGIN e BIO. O espectro do AGMG apresentou as bandas descritas anteriormente e novas bandas na região de 513 cm-1, característica da ligação Fe-O da CoFeO4, confirmando a formação do híbrido magnético. Os ensaios da influência do pH na remediação do cobre, zinco, níquel e cobalto mostraram maiores porcentagens de remoção na faixa de pH 4-5, para todos os adsorventes, podendo estabelecer a seguinte ordem crescente de eficiência de remoção AGIN<AGMG<BIO para todos os metais. O estudo cinético evidenciou uma cinética rápida para os três adsorventes e os metais em estudo com uma taxa de remoção superior a 50% nos primeiros 5 minutos. Os dados cinéticos ajustaram-se ao modelo de pseudo-segunda ordem, com coeficientes de correlação superiores a 0,99 para os três materiais. O AGMG destacou-se entre os demais adsorventes devido sua alta capacidade de adsorção e de ser mais viável sua separação do meio aquoso. Os dados das isotermas para o AGMG ajustaram-se ao modelo de Langmuir, apresentando boa correlação linear na faixa de concentração estudada (5-250 mg g-1), com coeficiente de correlação r2 entre 0,9973-0,9999. Os valores de capacidade máxima do AGMG calculada (qmax) foram de 18,3 mg g-1 Cu(II), 10,1 mg g-1 Zn(II) e 7,33 mg -1 Ni(II). A porcentagem de remoção nas diferentes soluções mistas pelo adsorvente AGMG seguiu a ordem de seletividade, Cu>Zn>Ni, com destaque para o cobre >84% de remoção em todas as soluções mistas avaliadas. O AGMG foi reutilizado em quatro ciclos de adsorção em solução mista, sem utilização de processo de dessorção, e a eficiência variou de acordo com o metal. A adsorção para o cobre permaneceu elevada em todos os ciclos, com 77% de remoção no primeiro ciclo e 72% no quarto ciclo. Para o zinco e níquel, a remoção diminuiu a cada ciclo, sendo que no terceiro ciclo não houve mais remoção de níquel. Os resíduos do AGMG saturados com metais (AGMG-sat) apresentaram altas atividades catalíticas na redução do 4-nitrofenol a 4-aminofenol. Os resíduos foram reutilizados em dez ciclos de redução e a taxa de conversão nos ciclos variou de 88,9-100%, com curtos tempos (21-26 s). / São Cristóvão, SE

Made available in DSpace on 2016-08-19T12:56:46Z (GMT). No. of bitstreams: 1 Dissertacao JULIO EVANGELISTA DE LUCENA.pdf: 1411452 bytes, checksum: b8994e2b79faae23cab57fbe95b70fb9 (MD5) Previous issue date: 2014-05-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Activated carbon produced from water hyacinth (CAA) was used for the adsorption of textile dye Remazol Turquoise and Violet Remazol aqueous solutions. ZnCl₂ was used as the activating agent in the impregnation ratio (2:1) and pyrolysis was at 700 ° C under N₂ flow, resulting in a surface area with CAA 640 m² gˉ¹. The adsorbent was characterized, and analysis of the surface area by the BET method, by elemental analysis, vibrational spectroscopy in the infrared region, Boehm titration method, which quantified the phenolic, carboxylic and lactonic groups groups on the carbon surface, thermogravimetric analysis, diffraction the x rays and point of zero charge (PZC). Factors affecting adsorption, such as pH, equilibration time, concentration of adsorbate and temperature were estudied in batch system. The activated carbon showed better adsorption rate at pH's in the acidic range. The kinetic data were fitted to models Elovich, pseudo first order and pseudo-second order, which the Elovich model showed better fit. Adsorption isotherms were measured and fitted to Langmuir and Freundlich models, where the latter provided better fit to the experimental data. The thermodynamic data obtained by evaluation of the isotherms at temperatures of 10, 25, 35, 45 and 55 ° C, indicated that the adsorptive process is endothermic, spontaneous and favorable. The CAA proved ultimately to be a good alternative in the adsorption of the dyes studied, it showed a low production cost and a high rate of removal. / Carvão ativado produzido a partir do aguapé (CAA) foi utilizado para a adsorção dos corantes textêis Turquesa Remazol (TR) e Violeta Remazol (VR) em meio aquoso. Foi ultilizado o ZnCl₂ como agente ativante por impregnação na proporção (2:1) e a pirólise ocorreu em 700° C, sob fluxo de N₂, resultando em um CAA com área superficial de 640 m² gˉ¹. O adsorvente foi caracterizado, além de análise da área superficial pelo método BET, por análise elementar, espectroscopia vibracional na região do infravermelho, titulação pelo método de Boehm, que quantificou os grupos fenólicos, lactônicos e carboxílicos na superfície do carvão, análise termogravimétrica, difratometria de raios x e ponto de carga zero (pcz). Fatores que afetam a adsorção, como pH, tempo de equilíbrio, concentração do adsorvato e temperatura foram estudados em sistema de batelada. O carvão ativado apresentou uma boa taxa de adsorção em pH s na faixa ácida. Os dados cinéticos foram ajustados aos modelos de Elovich, pseudo-primeira ordem e pseudo-segunda ordem, apresentando melhor ajuste o modelo de Elovich. Isotermas de adsorção foram determinadas e ajustadas aos modelos de Langmuir e Freundlich, onde o último forneceu melhor ajuste aos dados experimentais. Os dados termodinâmicos, obtidos pela avaliação das isotermas nas temperaturas de 10, 25, 35, 45 e 55° C, indicaram que o processo adsortivo é endotérmico, espontâneo, e favorável. O CAA mostrou, por fim, ser uma boa alternativa na adsorção dos corantes estudados, pois apresentou um baixo custo de produção e um alto índice de remoção.

Water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach (Pontederiaceae), a free floating aquatic plant was discovered by C. von Martius in 1823 in Brazil. It is believed to have been introduced into South Africa, as an ornamental plant, in 1908 to the Cape Province and Natal. Since its introduction, water hyacinth has spread throughout South Africa to the detriment of all aquatic systems that it has been introduced to directly or indirectly. The weed was first positively identified on the Nseleni and Mposa rivers on the Nseleni Nature Reserve which is a protected area near Richards Bay in KwaZulu- Natal in 1982 and formed a 100% cover of the river by 1983. An integrated management plan was implemented in 1995 and resulted in a reduction of the weed from a 100% cover to less than 20% cover in 5 years. The keys to success of the water hyacinth integrated management plan, presented here, were finding the source of the weed, mapping the extent of the water hyacinth infestation, identifying sources of nutrient pollution, appointing a champion to drive the programme, dividing the river into management units, consultation with interested and affected parties, judicious use of herbicides and biological control and a commitment to follow-up. This study further showed that water hyacinth on the Nseleni and Mposa river systems had a negative impact on the biodiversity of the protected area and the control of water hyacinth resulted in the recovery of the benthic invertebrate, amphibian, reptile, fish and avian fauna. The implementation of this integrated management plan was very cost-effective and serves as a model approach to the control of water hyacinth in both South Africa and the rest of the world.

Aquatic weeds transform and degrade the ecosystems which they invade, impacting various aspects of their surroundings ranging from the community level to disrupting important processes affecting ecosystem services. All of the major aquatic weeds of South Africa are found in the Cape Town Metropolitan Area. Landowners, whether private or public, are legally obliged to manage the listed invasive species through applying environmentally acceptable methodologies. This thesis provides an overview of the strategic management options, prevention, early detection, rapid response and eradication of new invasions, and containment and control species of established species. It discusses the different control methods available for managing aquatic weeds, namely mechanical, manual, chemical and biological, and the integration of different methods to improve their effectiveness. Although various studies have shown that biological control is the most cost–effective, environmentally-friendly and sustainable method, it is not yet fully integrated into weed management programmes in South Africa. In addition, the successes achieved in other parts of the world with the control of water hyacinth through biological control have not been repeated in the urban environment, despite the fact that South Africa has the highest number of biological control agents available for the weed. Urbanisation puts pressure on the natural environment and ecosystem functioning. Nutrient-enriched waters support aquatic weed growth and pose a challenge to the management thereof, in particular with regard to integrating biological control into management programmes. The aims of this study were to determine the reasons for the lack of integration of biological control into weed management programmes in South Africa, to determine the feasibility of integrating biological control in aquatic weed management programmes in a complex urban environmental and socio-political landscape by means of three case studies in the Cape Town Metropolitan Area, which showed that biological control is feasible in urban environments and should be considered. Two surveys were conducted to determine the reasons for the lack of integration of biological control into weed management programmes. The surveys showed that there is a gap between research and implementation as a result of poor communication, non-supporting institutional arrangements and a lack of appropriate capacity and skills at the implementation level. Recommendations were offered to address these issues.

Resumo: A região de Ilha Solteira apresenta em sua maior extensão, como cobertura vegetal, o cerrado. No final da década de 60, com a construção da Usina Hidrelétrica de Ilha Solteira, algumas áreas foram desmatadas e serviram como .área de empréstimo. Os solos pertencentes a estas localidades foram subtraídos e estas áreas ficaram com suas características químicas e biológicas distantes das ideais. O desenvolvimento da vegetação depende das condições do substrato; melhorias de alguns dos atributos do subsolo destas áreas poderiam ser obtidos com a adição de resíduos orgânicos e/ou adubos químicos. O trabalho teve como objetivo avaliar o uso de resíduos orgânicos no crescimento do Stryphnodendron polyphyllum e como recondicionantes de subsolo degradado. A área utilizada para o experimento faz parte da Fazenda Experimental de Pesquisa e Extensão - FEPE, UNESP - Ilha Solteira, em Selvíria . MS. O subsolo continua a apresentar caráter ácido e pobre em nutrientes, após um ano de avaliação. O diâmetro do colo e altura de planta apresentam resultados crescentes ao longo do período, com os maiores valores para os tratamentos que receberam calagem, N + P e resíduos orgânicos. O carbono da biomassa, ao longo do experimento, apresentou tendências à estabilização enquanto que o quociente metabólico diminuiu no mesmo período. A colonização micorrízica e número de esporos foram influenciados positivamente pela presença de resíduos orgânicos, os quais apresentaram os maiores valores. / Abstract: Ilha Solteira region is covered for the most by cerrado as vegetation. In the late 60s as a result of the building of Hydroelectric Power Station of Ilha Solteira, some areas have been deforested and were used as loan areas. Thus, the soils belonging to these locations were subtracted and these areas became chemically poor soils with both physical and biological properties far from the ideal ones. The vegetation development depends on the substrate conditions; the improvement of some subsoil features in these areas could be obtained by adding organic residues and/or chemical fertilizers. This work aimed at evaluating the use of organic residues in the growth of Stryphnodendron polyphyllum and as a reconditioner of degraded subsoil. The area taken for the experiment is part of the Experimental Farm of Teaching and Research, FEPE, UNESP - Ilha Solteira, in Selvíria . MS. However, the subsoil keeps presenting the same acid characteristic and poor nutrient levels after a year of assessment. The column diameter and the height of the plant presented increasing results during the period; the highest values were for the treatments which received liming, N + P and organic residues. During the experiment, the carbon of the microbe biomass presented tendencies to the stabilization while the metabolic quotient decreased in the same period. The mycorrhization and the number of the spores were positively influenced by the presence of organic residues, showing the highest values. / Orientador: Ana Maria Rodrigues Cassiolato / Coorientador: Kátia Luciene Maltoni / Banca: Luiz Antonio Graciolli / Banca: Miguel Luiz Menezes de Freitas / Mestre

The characteristics of anaerobic batch co-digestion of water hyacinth (WH) with pig manure (PM) under seven mixing ratio 100%WH; 80%WH : 20%PM; 60%WH : 40%PM; 50%WH : 50%PM; 40%WH : 60%PM; 20%WH : 80%PM and 100%PM were investigated, each treatment was conducted in five replications with daily loading rate at 1 gVS.L-1.day-1. During the anaerobic digestion process of 60 days, maximum biogas production occurred in two periods, the first stage from 12- 22 days and second stage from 30 - 35 days. The maximum daily biogas productions from each stage were 17.2 L.day-1 and 15.1 L.day-1, respectively. The cumulative biogas production varied between 60 L (100%PM) and 360 L (60%WH : 40%PM). The results showed that the biogas yields of co-digestion 40- 80%WH were higher from 34.6 to 56.1% in comparison with 100%PM and from 109 to 143% in comparison with 100%WH. When mixing with WH, treatments were received more methane and the methane contents were higher than 45% (v/v) that good for energy using purposes. / Nghiên cứu được thực hiện nhằm khảo sát khả năng gia tăng lượng khí sinh học khi tiến hành đồng phân hủy yếm khí lục bình (WH) và phân heo (PM) ở các tỉ lệ phối trộn khác nhau gồm 100%WH; 80%WH : 20%PM; 60%WH : 40%PM; 50%WH : 50%PM; 40%WH : 60%PM; 20%WH : 80%PM và 100%PM. Các nghiệm thức được nạp lượng nguyên liệu là 1 gVS.L-1.ngày-1 và bố trí lặp lại 5 lần. Theo dõi quá trình phân hủy của các nghiệm thức trong 60 ngày ghi nhận có 2 khoảng thời gian lượng khí sản sinh nhiều nhất - giai đoạn 1 từ ngày 12 đến 22, giai đoạn 2 từ ngày 30 đến 35. Lượng khí sản sinh cao nhất tương ứng trong mỗi giai đoạn là 17.2 L.ngày-1 và 15.1 L.ngày-1. Lượng khí tích lũy trong suốt thời gian thí nghiệm ghi nhận thấp nhất ở nghiệm thức 100%PM đạt 60 L, và cao nhất ở nghiệm thức 60%WH : 40%PM đạt 360 L. Năng suất khí sinh ra của các nghiệm thức phối trộn lục bình từ 40 đến 80% cao hơn từ 34,6 đến 56,1% so với nghiệm thức 100%PM và cao hơn từ 109% đến 143% so với nghiệm thức 100%WH. Hàm lượng mê-tan sinh ra từ các nghiệm thức có phối trộn lục bình ổn định trong khoảng > 45% đảm bảo nhiệt lượng cho nhu cầu sử dụng năng lượng.

Domestic wastewater is one of the most interested environmental issues in Vietnam, especially in big cities and suburban residential areas. Most of the wastewater was not treated in the right way before discharging to environment. In this research, the author used water hyacinth as a main aquatic plant in aquatic pond model to treat wastewater. The experiment was operated continuously in 1 year with hydraulic retention time (HRT) is 11 and 18 days. Hydraulic loading rate (HRL) is 300 and 500 m3/ha/day, respectively. Treatment efficiency of the model for TSS is 90% (remaining 6 -12mg/l); COD, BOD5 is 63 - 81% (remaining 10 - 48mg/l); TP is 48 – 50% (remaining 3.5 - 9.8mg/l); TKN is 63 - 75% (remaining 8 - 17mg/l). Polluted parameters in effluent were lower than A and B levels of Vietnam standard QCVN 14: 2008/BTNMT and QCVN 40: 2011/BTNMT. The doubling time of water hyacinth in summer is 18days, and in autumn and winter is 28.5 days. Experiment results showed that we can use water hyacinth in aquatic pond to treat domestic wastewater with medium scale. We can apply this natural treatment method for residential areas by utilizing existing natural ponds and abandoned agricultural land with capacity up to 500m3/ha day. However, to get better efficiency we should combine with other aquatic plant species to treat wastewater and improve environmental landscape. / Nước thải – xử lý nước thải sinh hoạt hiện đang là một trong những vấn đề môi trường được quan tâm tại Việt Nam nhất là tại các thành phố lớn và các khu dân cư. Hầu hết lượng nước thải chưa được xử lý đúng cách trước khi thải ra môi trường. Trong nghiên cứu này, tác giả sử dụng mô hình hồ thủy sinh và sử dụng cây Bèo lục bình để xử lý nước thải sinh hoạt của một khu dân thuộc huyện Từ Liêm, tại khu vực này nước thải bị thải trực tiếp vào sông Nhuệ. Thực nghiệm đã được tiến hành trong khoảng thời gian một năm, trải qua các mùa của khu vực miền Bắc với hai chế độ vận hành HRT là 18 và 11 ngày, tương ứng với tải trọng thủy lực HRL là 300 và 500 m3/ha/ngày. Kết quả cho thấy mô hình thủy sinh sử dụng cây bèo lục bình cho kết quả tốt, hiệu suất xử lý với các chất ô nhiễm đạt được như sau: chất rắn lơ lửng đạt 90%, COD, BOD5 đạt 63 - 81%, Phốt pho tổng giảm tới 48 -50%, Nitơ tổng giảm tới 63 - 75%. Hàm lượng các chất ô nhiễm trong nước thải đầu ra của mô hình đều thấp hơn ngưỡng A và B của các tiêu chuẩn QCVN 14: 2008/BTNMT và QCVN 40: 2011/BTNMT. Bên cạnh đó tác giả cũng đã xác định định được tốc độ sinh trưởng của cây bèo tại khu vực miền Bắc là 18 ngày vào mùa hè và 28.5 ngày vào mùa thu đông. Kết quả nghiên cứu cho thấy có thể sử dụng bèo lục bình để xử lý nước thải sinh hoạt, với qui mô vừa và nhỏ và nên áp dụng cho các khu vực ven đô, nông thôn nơi có diện tích đất rộng hoặc tại các hồ sinh thái của các khu đô thị. Tuy nhiên, để hiệu quả tốt hơn ta cần kết hợp với nhiều loại thực vật thủy sinh khác để ngoài tác dụng xử lý nước thải mà còn tạo cảnh quan môi trường xung quanh.

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)

Water hyacinth (Eichhornia crassipes) is an aquatic macrophyte originating from the Amazon basin. Due to its beautiful appearance it has been introduced into numerous countries across the world as an ornamental pond plant. It was introduced into South Africa in the early 1900s and has since reached pest proportions in many of the country’s fresh water bodies, causing significant economic and ecological losses. It is now considered to be the worst aquatic weed in South Africa. Efforts to control the spread of the weed began in the early 1970s and there have been some successes. Biological control has been used widely as an alternative to mechanical and chemical controls because it is cost-effective, self-sustaining and environmentally friendly. To date, six biological control agents have been introduced onto water hyacinth in South Africa. However, due to factors such as cold winter temperatures and interference from chemical control, the agent populations are occasionally knocked-down and thus the impact of biological control on the weed population is variable. In addition, many South African water systems are highly eutrophic, and in these systems the plant growth may be accelerated to such an extent that the negative impact of the agents’ herbivory is mitigated. One of the agents established on the weed is the galumnid mite Orthogalumna terebrantis, which originates from Uruguay. In South Africa, the mite was initially discovered on two water hyacinth infestations in the Mpumalanga Province in 1989 and it is now established at 17 sites across the country. Many biological control researchers believe that the mite is a good biological control agent but, prior to this thesis, little quantitative data existed to confirm the belief. Thus, this thesis is a post-release evaluation of O. terebrantis in which various aspects of the mite-plant relationship were investigated to determine the efficacy of the mite and thus better understand the role of the mite in the biological control programme of water hyacinth in South Africa. From laboratory experiments, in which mite densities were lower than densities occurring in the field, it was found that water hyacinth growth is largely unaffected by mite herbivory, except possibly at very high mite densities. When grown in high nutrient conditions the growth of the plant is so great that any affect the mite has is nullified. Plant growth is thus more affected by nutrients than by mite herbivory. However, mite feeding was also influenced by water nutrient levels and mite herbivory was greatest on plants grown in high nutrient conditions. The presence of the mite had a positive effect on the performance of the mirid Eccritotarsus catarinensis, such that the interactions of the two agents together had a greater negative impact on the plant’s growth than the individual agents had alone. Furthermore, water hyacinth physiological parameters, such as the plant’s photosynthetic ability, were negatively impacted by the mite, even at the very low mite densities used in the study. Plant growth rate is dependent on photosynthetic ability i.e. the rate of photosynthesis, and thus a decrease in the plant’s photosynthetic ability will eventually be translated into decreased plant growth rates which would ultimately result in the overall reduction of water hyacinth populations. In addition, temperature tolerance studies showed that the mite was tolerant of low temperatures. The mite already occurs at some of the coldest sites in South Africa. Therefore, the mite should be able to establish at all of the water hyacinth infestations in the country, but because it is a poor disperser it is unlikely to establish at new sites without human intervention. It is suggested that the mite be used as an additional biological control agent at sites where it does not yet occur, specifically at cold sites where some of the other, less cold-tolerant, agents have failed to establish. Finally, conditions of where, how many and how often the mite should be distributed to water hyacinth infestation in South Africa are discussed.