No description available.

No periodic patterns of temporal variations in the metal levels in U. lactuca or in other seven common seaweed species from Ping Chau were observed from 1999 to 2000. Cu levels were generally negatively correlated with other metals in seaweeds. / Spore production of U. lactuca was significantly reduced by the elevation of copper and nickel levels in the seaweed samples. The reproductive frequency of U. lactuca generally increased from January and February to the maxima in March and April. Copper, nickel and nitrate levels showed significant negative correlations with these reproductive frequencies. / The metal abundance in 24 seaweeds showed the following trend: Fe > Mn, Zn > Cu, Ni, Pb, Cr > Cd. U. lactuca and Padina australis showed relatively high mean and large range values of metal levels. Principal component analysis summarized the overall metal loadings in these 24 seaweed species. The variations in Pb, Fe, Mn and Cr levels in the seaweeds varied greatly. / There were significant spatial variations of different metal levels in the extensive study of U. lactuca from various intertidal waters in Hong Kong from 1999 to 2001. In general, metal levels in U. lactuca increased from January to March or April and then dropped in the following months. No periodic patterns or temporal trends of variations of metal levels in U. lactuca were found. Different metal levels in U. lactuca were comparatively lower than those in other studies in other countries and in past studies in Hong Kong. / There were significantly differences in various metal levels in different structures of Sargassum hemiphyllum, generally decreased in the following order: receptacles > vesicles > leaves > branches. / This thesis research involves biomonitoring levels of eight metal species (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in seaweed and the effects of these metals on the reproduction of Ulva lactuca. The study started from September 1999 and ended in June 2001, covering 40 intertidal sites in Hong Kong and 24 seaweed species. Environmental data on pH, salinity and nutrient levels (ammonia, nitrite, nitrate and phosphate) in seawater from these sites were also monitored. / Wong Tai Choi Richard. / "April 2005." / Advisers: P. C. K. Cheung; P. O. Ang, Jr. / Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0159. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 371-401). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

University of Macau / Institute of Chinese Medical Sciences

Thesis (MSc) -- University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Shrews are excellent bioindicators of environmental heavy metal pollution. This is due to their diets and the high rate of consumption at which these small mammals consume their prey. Shrews feed mostly on earthworms, and earthworms accumulate high levels of heavy metals in their bodies. Biomarkers measure responses to environmental pollution in the bodies of exposed organisms. Cellular biomarkers give an indication of responses to pollutants at levels of pollutant exposure that are not yet lethal to the organism. This study was prompted by concern that the number of shrews in the Stellenbosch region was declining. For the present study, shrews (Myosorex varius and Crocidura jlavescens) from the Stellenbosch region were sampled. The levels of Cd and Pb in their bodies were analysed in order to ascertain whether or not these two heavy metals, which occur in the environment as a result of various anthropogenic activities, are present in the food chain of the shrews. In the laboratory, shrews were fed live control and metal exposed earthworms from laboratory cultures. The earthworms had been exposed to either Cd or Pb in these cultures over a number of generations. This was performed to determine whether the presence of the metals in the body of the shrews, had resulted from metal accumulation from the earthworms which were fed to the shrews. Cellular biomarkers were used to determine the cellular response to the metals and membrane integrity and DNA integrity were investigated. This was done by exposing the cells of the shrews and ofBALB/c mice to metal salt solutions of Cd, Pb and Zn in vitro. Membrane integrity was tested by cell leaching techniques viz. the LDH assay and the trypan blue assay. DNA integrity was determined by using the comet assay as a biomarker of exposure. The results of the study show that the shrews in the immediate Stellenbosch region are exposed to lower levels of Cd and even lower levels of Pb than shrews from a site 16km out of the town of Stellenbosch. The cellular responses induced by metal exposure of laboratory mice show that the metals are indeed cytotoxic and genotoxic to the cells of small mammals. Cd and Pb were found to be more cytotoxic than Zn, while Zn was more genotoxic than either CqorPb. / AFRIKAANSE OPSOMMING: Skeerbekke is uitstekende bioindikatore van swaarmetaalbesoedeling in die omgewing. Dit is as gevolg van hul dieët en die hoë koers waarteen hierdie klein soogdiere hul prooi verorber. Skeerbekke voed meestalop erdwurms, en erdwurms akkumuleer hoë vlakke van swaarmetale in hul liggaam. Biomerkers meet response as gevolg van omgewingsbesoedeling in die liggame van blootgestelde organismes. Sellulêre biomerkers gee 'n aanduiding van response op besoedelingstowwe by vlakke wat nog nie dodelik is vir die organisme nie. Die studie is aangespoor deur die bekommernis dat die getal van skeerbekkies in Stellenbosch besig is om te daal. In die studie is skeerbekke (Myosorex varius en Crocidura flavescens) van die Stellenbosch omgewing gevang en die vlakke van Cd en Pb in hul liggame gemeet om vas te stelof die twee swaarmetale, wat in die omgewing beland as gevolg van verskeie antropogeniese aktiwiteite, teenwoordig is in die voedselketting van die skeerbekke. Die skeerbekke is in die laboratorium met lewende kontrole en metaalblootgestelde erdwurms uit kulture in die laboratorium gevoer. Die erdwurms is aan Cd en Pb oor baie generasies blootgestel in hierdie kulture. Dit is gedoen om vas te stelof die teenwoordigheid van die metale in die liggame van die skeerbekke 'n oorsaak is van metaalakkumuleering as gevolg van die erdwurms waarmee hulle gevoer is. Sellulêre biomerkers is gebruik om sellulêre respons op die metale op die membraanintegriteit en DNA-integriteit vas te stel. Dit is gedoen deur die selle van skeerbekke so wel as BALB/c muise in vitro bloot te stel aan metaalsoutoplossings van Cd, Pb en Zn. Membraanintegriteit is getoets deur selmembraan permeabiliteit tegnieke nl. die LDH en tripaan blou toetse. DNA-integriteit is getoets deur die komeettoets te gebruik. Die resultate van die studie dui daarop dat die skeerbekke van Stellenbosch aan laer vlakke van Cd, en nóg laer vlakke van Pb blootgestel is as die skeerbekke van 'n perseel 16km buite die dorp. Die sellulêre response geïndusseer deur blootstelling aan metale by die laboratoriummuise het aangetoon dat die metale inderdaad skadelik is vir die selmembraan en die DNA van die selle van die muise. Cd en Pb is meer toksies vir die selmembraan as Zn, terwyl Zn weer meer toksies is vir die DNA-integriteit as Cd en Pb.

Thesis (PhD (Botany and Zoology)) -- University of Stellenbosch, 2006. / Metals are natural elements of the earth crust usually present at low concentrations in all soils. Although many metals such as cobalt, copper, iron and zinc are essential to living organisms, at elevated concentrations most metals are toxic to organisms living in and on soils. Elevated concentrations of metals are caused either by anthropogenic deposition following remobilisation from the earth crust or are of natural origin. Ultramafic soils do not only pose unfavourable living conditions such as drought and poor organic content, these soils are also characterized by extremely high concentrations of a range of metals known to be toxic under normal circumstances. Ultramafic soils are of high ecological importance as a high proportion of endemic organisms, especially plants, live on these soils. As it is known that earthworms do occur in ultramafic soils, the aims of the present study were to investigate the abilities of earthworms to survive in these soils and the influences of elevated chromium, cobalt, copper, manganese and nickel levels. For the evaluation of the metal background conditions, soils originating from ultramafic rocks of the Barberton Greenstone Belt, Mpumalanga, South Africa were collected and different fractions representing different levels of bioavailability were analyzed for arsenic, chromium, cobalt, copper, manganese and nickel. To assess the mobile, readily available metal fraction, i.e. Ca2+- exchangeable metal cations, a 0.01 mol/L CaCl2 extraction was performed. To investigate the mobilisable metal fraction, representing the amount of easily remobilisable complexed and carbonated metal ions, a DTPA (di-ethylene-triamine-pentaacetic acid) extraction was conducted. In relation to non-ultramafic or anthropogenic contaminated soils, a far lower proportion of metals were extractable by the above mentioned extraction methods. To investigate the availability and effects of these metals on earthworms, two ecophysiologically different species were employed. Aporrectodea caliginosa and Eisenia fetida were long-term exposed to the ultramafic soils collected at the Barberton region and a control soil from a location at Stellenbosch with a known history of no anthropogenic metal contamination. The responses to the ecological stress originating in the ultramafic soils were measured on different levels of earthworm organisation. As endpoints affecting population development, cocoon production, fecundity and viability were evaluated. On individual level, growth, metal body burden and tissue distribution were investigated. As endpoints on subcellular level, the membrane integrity was assessed by the neutral red retention assay, the mitochondrial activity was measured by the MTT colorimetric assay and as a biomarker for the DNA integrity, the comet assay was performed. Focussing on manganese and nickel, the uptake by E. fetida of these metals was investigated with the exclusion of soil related properties using an artificial aqueous medium to draw comparisons to the uptake of these metals in natural soils. The possible development of resistance towards nickel was tested by exposing pre-exposed (for more than 10 generations) E. fetida specimens to ultramafic soils with concentrations of more than 4000 mg/kg nickel. The results showed that, except on the endpoint survival, which was less sensitive than all other bioassays, significant responses to the ultramafic challenge were observed in all earthworm bioassays and on all levels of organisation. The sensitivity of the responses of the earthworms towards the ultramafic conditions was not predictable by the level of organisation. The two species showed different strategies of metal elimination. In A. caliginosa, metals such as nickel, manganese and chromium were transported to the posterior section and the posterior section was subsequently pushed off by autotomization. In E. fetida, metals such as chromium and nickel were sequestered in storage compartments in the coelomic cells or fluid. Other metals, such as cobalt, were not taken up at elevated concentrations. Although an increased accumulation of nickel was observed in E. fetida specimens pre-exposed to nickel, development of resistance or cross resistance was not observed in this species. In contrast, pre-exposed specimen exposed to elevated concentrations of nickel showed a higher sensitivity in terms of survival, indicating the absence of acclimatisation or even genetic adaptation. A comparison of the two species employed indicated that A. caliginosa was less suited for the assessment of the ultramafic soils due to the high individual variation in metal body burden, the mass loss observed and the slow reproduction rate even in the control soils. This happened despite the fact that A. caliginosa was a soil dwelling species supposed to be better adapted to the soil substrate than the litter dwelling E. fetida. The toxicity of the ultramafic soils was not necessarily related to total or environmentally available amounts of the selected metals. Thus, it can be speculated that either these soils contained unidentified toxicants with resulting interactions between toxicants playing an important role or earthworms were able to remobilize metals occurring in these soils. As the singular application of an ecotoxicological endpoint did not give reliable results, especially seen over the duration of the exposures, it can be concluded that, when studying soils with such a complex composition, the utilisation of endpoints addressing different levels of organisation is necessary for the assessment of toxic stress emerging from these ultramafic soils.

Ascaris suum were exposed to a number of stressors, including heavy metals and both high (40°C) and low (18°C) temperatures. The 70kD and 90kD heat shock proteins (HSPs) in the different A. suum tissues were analyzed by Western blot and quantitated by Macintosh Image Program.

No description available.

No description available.

Water is one of the most important resources in South Africa. The increased pressure on river systems in SA as a result of human activities and industrial development is evident from the systematic deterioration of the Olifants River (Mpumalanga). While the number of water users grows daily, the river is seen as a convenient disposal site. It is necessary to continually monitor the river to be aware of its status. Regular monitoring also supplements the existing data on water quality, biotic communities and possible points of pollution. The study had the following aims: Firstly to contribute to a larger project on the effect of pollutants on the physiology of fish populations in the Olifants River. This study concentrates on the bioaccumulation of certain metals (i.e. chromium, copper, iron, manganese, nickel, lead, strontium and zinc), in the gills, liver and muscle of Labeo congoro. Standard methods were used to prepare the organs and tissues for metal analysis using atomic absorption spectrophotometry. The following conclusions were reached subsequent to statistical analysis of the results: • The highest mean concentrations of all metals were recorded in the liver of Labeo congoro. • The lowest mean metal concentrations were calculated in the muscle, except for chromium, the concentrations of which were the lowest in the gills. • The highest mean concentration of each metal was recorded in organs / tissues of fish sampled at locality 2. • None of the three localities can be singled out to indicate the lowest mean concentration of each metal. Summary iii The second aim of this study was to determine the 96-hr LC50 (lethal concentration at which 50% of the test population dies) of nickel. Oreochromis mossambicus was used as test organisms for these laboratory studies. A flow through system was used to ensure that the organisms were exposed to the same concentration of nickel for 96 hours. Subsequent to the 96-hr LC50 determination, test organisms were subjected to sublethal exposure of nickel to determine the effects of the various concentrations of the haematology and blood coagulation processes of fish. The following conclusions were drawn from the statistical data processing: • The 96-hr LC50 of nickel for Oreochromis mossambicus is 50 μg.l-1. • The exposure to sublethal concentrations of nickel did effect certain haematological variables • No statistically significant differences in the blood coagulation variables at different sublethal concentrations of nickel were confirmed The results of this study can be used to supplement the database on the water quality and general status of the Olifants River (Mpumalanga). The LC50 of nickel can be used as one of the variables in water quality studies. / Prof. Johan van Vuren

Landfills have served as the major sites for waste disposal in both developed and developing countries. Upon closure of a landfill site, the surface could be converted to a golf course, recreation park, playground, animal refuge, tennis court and industrial site. Even when closed, landfills still have the potential to contaminate the surrounding environment as a result of the migration of leachate from decomposing waste contained in the site. This study focused on assessing the impacts of a closed landfill on soils and plants at Lumberstewart closed landfill site in Bulawayo, Zimbabwe. Soil samples were collected at three different depths (0-30 cm, 30 - 60 cm and 60-90 cm) at the landfill and a control site. The soil samples were analysed for their texture, pH, electrical conductivity, organic matter content, cation exchange capacity and concentrations of Cd, Cu, Cr, Fe, Ni and Zn. Samples of jimson weed and pigweed growing at the closed landfill and the control site were collected from the same sites where soil samples were collected, and the concentrations of the same set of heavy metals in these weeds determined. Soil samples were digested using EPA method 3050B: Acid Digestion of Sediments, Sludge and soils whereas nitric acid and hydrogen peroxide was used for digestion of plant samples. Both plant and soil digests were analyzed for heavy metals concentrations using Flame Atomic Absorption Spectrometry (AAS). Soils from the landfill as well as the control site had a high content of sand with soil pH values which were alkaline. The electrical conductivity values of the soil samples were relatively low ranging from 0.39 to 1.67 dS/m, indicating low levels of salts in soils at the landfill. The concentrations of heavy metals at the closed landfill site were higher than the control site. Heavy metals concentrations in soils at the closed landfill followed the order Fe>Zn>Cu>Cr>Ni>Cd. Results indicated that Fe was exceptionally higher than the other metals with concentration values averaging 45690±17255 mg/kg. Cadmium on the other hand had the least concentration with values of 0.01±0.00 mg/kg. Values of Enrichment Factors of heavy metals around the soil at different depths indicated that the enrichment of heavy metals increased with depth at the landfill up to 30-60 cm after which a decrease was observed. Values for heavy metal Contamination Factor of soils around the landfill ranged from low concentration (CF<1) to very high concentration (CF>6). The Pollution Load Index (PLI) values for the soil at the Lumberstewart landfill indicated that all sites were polluted (PLI>1). Site 6 had significantly higher mean concentration of heavy metals in soils at the landfill whereas site 11 had the least. The concentrations of Cd and Ni in soils at the landfill were below permissible limits of South African National Norms and Standards (NNS) as prescribed by NEMA (2008) in South Africa whereas Cr, Cu and Zn in soils were above the NNS permissible limits. Heavy metal concentrations in soils at the landfill were above World Health (WHO) permissible limits except for Cd which was equal (0.01 mg/kg) to the permissible values of Cd in the soils at sites 5, 8, 9, 10, 11 and 12. Mean concentrations of heavy metals in jimson weed and pigweed were in the order Fe>Zn>Cu>Cr>Ni>Cd. The concentrations of Cd, Cr, Cu, Fe and Zn in both plants from all sites at the landfill were significantly higher than the control site. Heavy metal transfer coefficient for both plants indicated that heavy metal uptake was more species dependent than soil heavy metal concentration dependent. The results from this research indicate that though the Lumberstewart Landfill has been closed, it is still affecting the soils in the vicinity of the landfill. Plants and water around the Lumberstewart closed landfill could be at risk from heavy metal contamination. High concentrations of heavy metals observed in the soil could present a health risk to communities should they decide to use the landfill site for arable purposes. / Environmental Sciences / M. Sc. (Environmental Science)