• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 497
  • 97
  • 97
  • 31
  • 31
  • 31
  • 31
  • 31
  • 31
  • 13
  • 12
  • 9
  • 9
  • 5
  • 5
  • Tagged with
  • 1254
  • 1254
  • 317
  • 247
  • 241
  • 238
  • 230
  • 198
  • 192
  • 172
  • 165
  • 149
  • 95
  • 94
  • 90
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
461

A critical analysis of the water legislation of the province of British Columbia

Shelley, Melvin Jack January 1957 (has links)
Water is a key natural resource in our way of life. Without water such miracles of human achievement as the building of great cities and the spanning of the continent with railroads and automobile highways would not have been possible. Such a key natural resource must be protected and controlled by adequate legislation which will prevent its waste, undue consumption, misuse or contamination. With this view in mind the writer has critically analysed the legislation governing water distribution and sewage-disposal control in British Columbia by comparing it with that in other provinces, the United States of America, and Italy. To achieve this critical analysis, the writer has used two excellent references on which to base his recommendations in the form of desirable principles for the existing British Columbia water legislation. These two references are entitled, "Desirable Principles of State Water Legislation," and "Suggested State Water Pollution Control Act," and are published by the National Reclamation Association and the United States Public Health Service, respectively. As a result of the critical analysis of the existing British Columbia water supply and distribution legislation, it is felt that the British Columbia Act Respecting the Diversion and Use of Water has both sound legislative foundations and administrative procedure, and is far superior to any of the similar pieces of legislation of the other provinces in Canada. The writer also feels that the Act ranks high in comparison with the water acts of comparable western states in the United States. However, there are certain recommendations for improvement that have been made for the British Columbia water supply and distribution legislation. Briefly, these are as follows: 1. That some provision be made for the acquiring, controlling, and exercising of rights to the use of ground waters, including both definite underground streams and percolating waters. 2. That some provision be made for an appropriator to have the opportunity of recapturing and re-using return water which results from his development when he is diligent and uses foresight in his attempt not to infringe upon preexisting rights. 3. That some provision be made for the appropriation of salvaged water and developed water in preparation for any foreseeable shortage of our natural water resources. 4. That some provision be made for the rotation in use of water in the event of an unexpected shortage of water for domestic or other purposes. 5. That some provision be made for the exchange of water so that appropriators may exchange water with one another so long as the rights of others are not impaired with respect to either quantity or quality of the water, and so bring about a more effective utilization of water by appropriators who are already entitled to divert under terms of their separate appropriative rights. 6. That some provision be made for the appropriation of interprovincial waters with the use of a doctrine of reciprocity. As a result of the critical analysis of the existing British Columbia water-pollution control legislation, it is felt that, in the past, the authority has been divided among several agencies, a situation which gave rise to lax control and a lack of coordination. However, the recently-passed Act (March 1956) to Control the Pollution of Waters of the Province is an excellent beginning of effective, coordinated control. It is difficult to compare this Act with those in other provinces or in the United States because of its recent enactment. Briefly, the writer would suggest the following recommendations: 1. That some definite and exact classification be adopted in setting the quality standards of beneficial uses for receiving waters, and that these standards be inserted in the Pollution-control Act. 2. That the beneficial uses of the receiving water be evaluated, and that discharges into the receiving water be controlled so as to protect as many of the benefits as possible. 3. That some provision be made for setting up regional boards, in whose hands will be the primary control. 4. That the Provincial Pollution-control Board be given power to hold an inquiry, and for that purpose it be given all the powers and jurisdiction of a Justice of the Peace under the "Summary Convictions Act." 5. That the Board be given the power to require the keeping of records and making of reports, and to enter on property at reasonable times for purposes of inspection and investigation. 6. That one member of the Board be experienced in the field of municipal government and one be experienced in the field of industrial activities. / Business, Sauder School of / Graduate
462

Lower Fraser River/Estuary dissolved oxygen dynamics

Koch, Frederic A. January 1976 (has links)
This investigation into the nature of dissolved oxygen dynamics in the lower Fraser River/Estuary has made use of the application of two mathematical water quality models - a tidally averaged dissolved oxygen model and a tidally varying dissolved oxygen model. The tidally averaged model analyzes the inter-tidal behaviour of the river/ estuary, giving estimates of steady-state dissolved oxygen response. The tidally varying model, on the other hand, analyzes conditions within the tidal cycle, thereby describing the "real-time", intra-tidal behaviour of the river/estuary. Both dissolved oxygen models are one-dimensional and make the assumption that the only operative dissolved oxygen source/sink processes are deoxygenation due to the oxidation of discharged organics and reoxygenation due to atmospheric reaeration. The present high dissolved oxygen levels in the lower Fraser preclude the accurate calibration of the dissolved oxygen models. However, an analysis of model sensitivities is presented, in lieu of verification, to document model responses. Dissolved oxygen predictions made using the unverified models indicate that the assimilative capacity of the lower Fraser River/ Estuary is considerable, mainly because of the large freshwater inflows which afford extensive dilution as well as rapid flushing. The "critical period" is likely to be in late summer when the combined effects of water temperature and freshwater flows result in the lowest dissolved oxygen levels. Future water quality impairment in the main channels of the lower Fraser, at least insofar as dissolved oxygen is concerned, is considered by this study to be unlikely, providing that existing pollution control policies are adhered to. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate
463

Evaluation of selected enzymes and osmotic ions as biomarkers for detecting pollution in the aquatic environment

Vorster, Amelia 27 August 2012 (has links)
M.Sc. / Biomarkers are responses in living organisms that signify exposure to harmful substances. The use of biomarkers enables researchers to detect toxicity at suborganismal level. It can thus be used as an early warning of chronic pollution. This project employs biomarkers in preliminary field research to assess aquatic ecosystem health. The indigenous freshwater fish Oreochromis mossambicus and Labeo umbratus are used as test organisms. Mature fish are collected at polluted and unpolluted sites. Blood, brain- and liver tissue is removed and analysed. Laboratory evaluation involves the exposure of juvenile Oreochromis mossambicus to a variety of toxic chemicals in a static system to determine biomarker responses. The biomarkers investigated include acetylcholinesterase, which is inhibited by organophosphate and carbamate pesticides and pyruvate kinase, which is a ratelimiting enzyme of glycolysis. Lactate dehydrogenase is used as biomarker for muscle tissue damage and glucose-6-phosphate dehydrogenase is a key regulatory enzyme of the pentose-phosphate shunt. Osmotic anion and cation concentrations are measured to determine stress on the regulation of water- and osmotic balance. Although results from the field study is variable, some biomarkers show potential to be included in a suite of biomarkers for biomonitoring, together with other biological, physical and chemical measures. Applying techniques to assess a suite of biomarkers in key organisms, produces a more accurate reflection of ecosystem health. Exposure studies with juvenile fish produced extremely variable and unreliable results. Many repetitions of each exposure will be necessary to determine significant deviations in biomarker responses from the normal range.
464

Bio-akkumulering van metale in organe en weefsels van die platanna Xenopus laevis in myn- en nywerheidsbesoedelde varswaterekosisteme

Fleischer, Cecilie Louisa 14 April 2014 (has links)
M.Sc. (Zoology) / An investigation was made into the presence and uptake of seven selected metals by the organs and tissues of the various developmental stages of the African clawed frog Xenopus laevis from industrial, mine and sewerage polluted aquatic environments on the Witwatersrand. These results were compared with conditions in two relatively unpolluted localities where the clawed frog also occurs. Attention was given to the physical and chemical conditions including the concentration of the metals at various localities. Gut content analyses of the frog stages of the plataona was made to identify the particular food items ingested by the animal but also to correlate this with the incidence of the macro invertebrate organisms present. Metal concentrations were determined for both the gut contents as well as the macro invertebrates as a group at two selected localities. The presence and concentration of various metals were determined in specific organs and tissues of the frog and compared with each other. According to the data the spleen, gallbladder, middle & Hind gut as well as the testes were identified as the target organs containing the highest concentrations of the various metals. Shortcomings in the work is pointed out and recommendations made on possible further research.
465

An assessment of the health-related microbiological water quality of the Blesbok Spruit

Swanepoel, Cheryl Lynne 29 May 2012 (has links)
M.Tech. / South Africa is a water scarce country. The characteristic water pollution problems associated with both developing and developed economies are evident. Indicator organisms have been enumerated from samples collected from the Blesbok Spruit (Gauteng Province) over one year. Standard membrane filtration techniques were used followed by cultivation of E. coli and enterococcus on selective agars. Rainfall data was collected to enable a determination of differences, between “wet” and “dry” sampling runs. Descriptive statistics applied to the data include the calculation of the geometric mean for each sampling run and the geometric mean per sampling site in both wet and dry conditions. The Mann- Whitney Rank Sum Test and Kruskal-Wallis One way Analysis of Variance (ANOVA) were used to compare data sets. The capacity of the Blesbok Spruit, containing wetland areas, to assimilate the microbiological load was more effective than that of the Renoster Spruit (Free State Province) which does not contain distinctive wetland areas. The risk of infection has been determined by comparing the levels of E. coli and enterococcus to a set of site-specific guidelines. The water is not suitable for drinking or domestic purposes and full contact recreation will pose a risk of infection to users. The lower Blesbok Spruit has the poorest water quality and this water is unsuitable for livestock watering being only suitable for the irrigation of crops. The effects of diffuse pollution on the health related microbiological water quality need to be considered in the management of this sub-catchment.
466

Die effek van atrasien, sink en yster op die hematologie en suurstofverbruik van Tilapia sparrmanii (Cichlidae)

Grobler, Eurika 26 May 2014 (has links)
M.Sc. (Zoology) / Tilapia sparrmanii (Smith) obtained from the Provincial Fishery in Lydenburg was used for toxicological studies. The haematology of T. sparrmanii was investigated after exposure to sub-lethal doses of atrazine, zinc and iron for 72 hours in a continuous flow and static system, as well as prolonged (4 weeks) exposure in the continuous flow system. After exposure the blood of the experimental fish were sampled. Mean values and standard errors were obtained for several haematological parameters such as number of red and white blood cells, haematocrit, haemoglobin, mean corpuscular volume, pH, plasma glucose-, protein-, lipid- and lactate concentrations, as well as plasma Na+, K+, eland Ca+. Statistically significant differences were found between the values of haematological parameters of experimental and control fish. A tendency towards haemoconcentration was observed when fish were exposed to the low pollutant concentrations, while signs of haemodilution was found at higher concentrations. The results in this study demonstrate that, after prolonged exposure, T. sparrmanii develops a tolerance and partially recovers from the stress condition. The bioconcentration of atrazine in the blood of T. sparrmanii after exposure were determined by liquid chromatography and zinc and iron by atomic absorption spectrophotometry. During this study it was found that atrazine, zinc and iron concentrated in the blood of T. sparrmanii after short- and prolonged exposure to the pollutants. The routine oxygen consumption of "!'. sparrmanii exposed to atrazine, zinc and iron were determined in a continuous flow apparatus over 72 hours. The oxygen consumption of the experimental fish fluctuated for the first 8-12 hours during the acclimation period. The influence of atrazine on the routine oxygen consumption was not so drastic as that of zinc and iron. Zinc caused a decrease in the routine oxygen consumption of the experimental fish over 72 hours, while iron increased the routine oxygen consumption...
467

Die effek van swaarmetale by veriërende pH op lewerensieme en bloedstolling by Tilapia sparrmanii (Cichlidae)

Gey van Pittius, Marina 23 July 2014 (has links)
M.Sc. (Zoology) / Tilapia sparrmanii (Smith) was exposed to sub-lethal doses of chromium, manganese, zinc and iron for 96 hours at an acidic pH (5), a physiological pH (7,4) and an alkaline pH (9), as well as a prolonged exposure (2 - 4 weeks) at an uncontrolled pH. In the laboratory fish were kept in aquaria which were supplied with continuously flowing borehole water. Controlled laboratory conditions existed during experimentation. Blood and liver samples of the experimental fish were sampled after exposure. The bioconcentration and the effect of the selected metals at the mentioned conditions, were thereby determined on bloodcoagulation, total and differential leucocyte counts, and liver enzYmes to investigate the possible damage to the liver. As metals have the ability to enter and concentrate in the body, the bioconcentration of each metal was determined by atomic absorption sPectrophotometry in the blood and liver. Chromium showed an increase in concentration in both the blood and liver, with an increase in pH after short term (96h) exposure. The statistical significant increases of manganese concentration in the blood over a short term were not reflected in the liver. It may be indicative of homeostatic control. A similar phenomenon was found with .zd.nc , The concentration of zinc in the liver did not reflect the progressive decrease in the blood wi th a increase in pH. Iron revealed a statistical significant increase in bioconcentration in the liver with, an increase in pH, which is indicative of the activity of the liver. The long term exposure of fish to chromium and manganese caused a significant increase in the concentration of the metals in the blood and liver. The only significant increase in concentration after exposure to iron, occured . in the Iiver. Exposure to zinc however caused a statistical significant decrease in concentration in both the blood and liver. Differential leucocyte counts reflected lymphocytosis, eosinophilia, monocytopenia and neutropenia, after short term exposure. These conditions nearly always resulted in leucopenia. Long term exposure to manganese and zinc reflected both eosinophilia and neutropenia. Chromium reflected eosinophilia, and iron, neutropenia. The only statistically significant change in the number of leucocytes after long term exposure, was caused by zinc and resulted in leucopenia. According to the photokymographic observation of blood coagulation by the thrombelastograph, exposure to the selected heavy metals lead to a prolonged clotting time and thrombocytopenia. Long term exposure (4 weeks) to manganese caused another bleeding disease, called hemophilia. It was thus evident that the exposure to heavy metals led to clotting defects, which caused bleeding.
468

Ephippia Production, Activation, and Use of Ex-Ephippio Neonates of Ceriodaphnia Dubia as Toxicity Test Organisms

Poage, Duane W. 08 1900 (has links)
Ceriodaphnia dubia is widely used as a test organism in monitoring water quality. At the present time, cultures must be continuously maintained in the laboratory. In an attempt to avoid continuous culture and maintenance, the hatching of ephippial eggs of C. dubia would provide test organisms when needed. In order to determine the parameters required for maximum hatching, approximately ninety-four thousand ephippia were exposed to a variety of conditions ranging from light and temperature regimes to drying and freezing. A low hatching yield occurred which is believed to be caused by diminished ephippia viability and/or fertility. To evaluate factors influencing the viability and fertility rate, stains of embryos were examined as were male to female ratios and mating experiments.
469

Essays in Energy and Environmental Economics

Atal Chomali, Raimundo January 2021 (has links)
This dissertation represents an effort to advance interdisciplinary research in issues relevant for energy and environmental policy, combining economics with applied engineering and ecology. It includes work that is informed by theoretical and empirical studies, and is conceptually centered in the notion that competitive markets lead to inefficient combinations of risk and yield. In the first two chapters of the dissertation, I study this in the context of wind energy capacity investments, where profit-maximizing developers choose the location and timing of the construction of wind farms. The final chapter of the dissertation is an empirical study on the effects of intensive aquaculture on water pollution.
470

Cell culture biomarkers for monitoring of wastewater pollutants

Makene, Vedastus Wilfred January 2021 (has links)
Philosophiae Doctor - PhD / Wastewater is normally composed of a mixture of pollutants. The type and composition of pollutants in a particular wastewater depend on the source of origin. The source and characteristics of a particular wastewater determine the ideal method of sewage treatment. Specific treatment techniques are effective in the removal of certain types of pollutants and may have no impact on the levels of other types of pollutants. Therefore, a combination of treatments and assessment of the quality of effluent before release into the environment is normally recommended. The assessment of effluent can be achieved by various techniques including chemical analysis and biological assays. Chemical analyses are commonly employed; however, they often pose detection problems and are considered to be uneconomical.

Page generated in 0.1172 seconds