Thesis (MTech (Environmental Health))--Cape Peninsula University of Technology, 2009. / In the last two centuries, the natural state of the environment has changed significantly due to anthropogenic activities. With an estimated half-life of 15 - 1100 years for cadmium in soils, the metal remains a threat to the ecosystem. In general, most soils contain <1 mg/kg, except those contaminated from discrete sources or developed on parent materials with very high cadmium contents. Anthropogenic lead in soil has several well recognized major sources, namely, lead based paint, mining and smelting activities, manures, sewage sludge usage in agriculture and contamination from vehicle exhausts. Since lead is a heavy metal, over time it will settle down and build up in soil. The main aim of this study was to determine the degree of cadmium and lead contamination of soil, in and around selected pre-school facilities in the City of Cape Town (CCT). A number of pre-school facilities, particularly those nearby heavy traffic, were selected in the CeT. Natural soil and sand pit soil samples were collected and analysed for cadmium and lead. Low soil moisture is normally associated with high pH, as found in the present study. High pH values are in turn associated with low toxicity of metal contaminants. Most urban populations rely heavily on motor vehicles and vehicle-related pollution has been an increasing concern in recent years (before 2006). Air pollution in the CCT is trapped by inversion layers. In this study it has been found that cadmium is not a significant contaminant in the soils of pre-school facilities in the CCT. The Cape Town administration area was found to be the most contaminated with this metal. This study showed that the Cape Town administration area also had the highest lead concentrations in pre-school soils in the CCT. This can be attributed to the higher density of industry and traffic activities (study conducted pre-2006) in this area. There is a need for further research to determine the relationship between soil metal concentrations and blood metal levels, especially in children.

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published_or_final_version / Radioisotope / Master / Master of Philosophy

There are two main components to the research: the theoretical and the experimental. Chapter 2 contains an analysis of the state of soil quality guidelines and the scientific methods used to determine them. A number of recommendations to improve soil quality criteria for trace metals are offered including the importance of considering bioavailability and the need to use realistic conditions, trace metal sources and organisms. / A critical review of the literature dealing with predicting the availability of trace metals to plants is presented in Chapter 3. We found little agreement among hundreds of similar studies which relate plant metal uptake to the amount of metal extracted by selective chemical dissolution procedures. An extensive summary of the data shows clearly that the extraction methods are not widely applicable. Differences between individual soils, their metal retention capacities, as well as plant factors and environmental conditions contribute to the variability of the results. Alternative ways of assessing bioavailability are suggested. / The experimental component of the thesis focuses on the availability of trace metals to plants. In Chapter 4 the uptake of Cu from different soil pools was examined and the free metal ion (Cu2+) was found to be the best predictor of uptake by lettuce (Latuca sativa cv. Buttercrunch), ryegrass (Lolium perenne cv. Barmultra) and radish (Raphanus sativus cv. Cherry Belle). / In Chapters 5 and 6 we examined the effect of low-cost in-situ treatments on the availability of metals to plants in greenhouse and field experiments. Synthetic zeolites, P amendments, organic matter and clean soil were used and their effect on the bioavailability of Cd, Cu, Pb, Ni and Zn evaluated. The plants for the experimental work were lettuce and perennial ryegrass. Only the clean soil treatment was consistently effective in reducing the concentration of metals in the plant. We also wanted to determine whether the trace metals in the plant tissue came from the soil or from direct deposition of pollutants on the leaf surfaces. We found little evidence that metals in plants were a result of atmospheric fallout. / A method for the accurate analysis of total metal concentrations in a range of contaminated soils including those containing oil and grease was developed (Chapter 7). For this research the trace metals of concern are Cd, Cu, Ni, Pb and Zn---all commonly found in urban/industrial soils. The proposed method using HNO3/HClO4 has several advantages over the common HNO3/H2O2 procedure. We were able to digest larger soil samples and hence the final concentration of trace metals was usually in the range for analysis by inductively coupled plasma atomic absorption spectrometry or flame atomic absorption spectrometry.

Bioavailability of trace metals in urban contaminated soils was investigated to relate chemical extraction efficiencies with biological effects. / Results from a Collembola reproduction bioassay showed minimal toxicity suggesting limited bioavailability. Chemical extractions were carried out on these urban soils. The sodium acetate extraction was the best predictor of the biological effects of Cd while the biological effects of Zn were best explained by a water extraction. / An earthworm uptake bioassay was done to quantify the bioavailable fractions. Cadmium, Cu, Pb and Zn accumulated in Lumbricus terrestris L. The sodium acetate extraction was the best predictor of Cd uptake while calcium chloride extraction best predicted Zn uptake by earthworms. / Treatments were made to urban soils to immobilize the metals and reduce their bioavailability. The metal concentrations were so low in the soils that the effects of the treatments could not be measured. / Collembola and earthworms are good indicators of trace metal bioavailability and should be included in the evaluation of contaminated soils.

The efficacies ofsoil extraction methods, namely, Soxhlet, sonication, agitation, alkaline digestion and the ethyl acetate micro-method, for monitoring soil bioremediation were evaluated using three soil types, Swartland, Rensburg and Hutton, encompassing the mineralogical range prevalent in Kwa Zulu Natal. Phenol, atrazine and the BTEX component of petrol were the molecules used in this study and were extracted under different spiking concentrations, after prolonged ageing times up to 21 days and after changing the composition of the spiking solution. It was concluded that extraction methods must be validated for the specific conditions under which they would be used, taking into consideration, soil type, spiking solutions, moisture content, weathering times and the analyte(s) in question. A preliminary appraisal of atrazine degradation in a Hutton soil was then made under the conditions of sterilized, fertilized/non-fertilized and non-sterilized, fertilized/nonfertilized soils. The predominant pathway of atrazine degradation was deemed to be chemically/abiotically mediated due to the soil pH and the presence of iron and aluminium oxides as well as the high levels of manganese in the soil. The results obtained prompted further study into atrazinecatabolism using soil-slurry reactors, under the conditions of carbon-limitation, nitrogen limitation, carbon/nitrogen non-limitation and carbon/nitrogen limitation. A comparison was made between inoculated and non-inoculated bioreactors. The ability of the indigenous microbial population to return the Hutton soil to its original pristine state was confirmed. The expense of inoculation and culture maintenance could be avoided since carbon and nitrogen supplementation would be as equally effective as inoculation. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2002.

Most natural products and xenobiotic molecules, irrespective of their molecular or structural complexity, are degradable by some microbial species/associations within particular environments. Atrazine- and selected petroleum hydrocarbon (benzene, toluen~ and 0-, m- and p-xylene (BTX))-degrading associations were enriched and isolated"trom atrazine- and petroleum hydrocarbon (PHC)-contaminated KwaZuluNatal loamy and sandy soils, respectively. In total, eight pesticide- and forty BTXcatabolizing associations were isolated. Electron microscopy revealed that, numerically, rods constituted the majority of the populations responsible for both atrazine and PHC catabolism. Cocci and, possibly, spores or fungal reproductive bodies were observed also. For the BTX-catabolizing associations, the population profiles appeared to be dependent on the enrichment pH and the molecule concentration. After combining selected associations, to ensure that all the isolated species were present, batch cultures were made to determine the optimum pH and temperature for growth; With an atrazine concentration of 30 mgr1, the highest specific growth rates, as determined by biomass (OD) changes, were recorded at 30DC and pH 4 although the rate§ at 25DC and pH 5 were comparable. For the BTX (50 mgr1)-catabolizing associations, the highest growth rates were recorded at pH 4 for the four temperatures (15, 20, 25 and 30DC) examined. The sole exception was p-xylene with the highest specific growth rate recorded at pH 5 and 30De. Batch and continuous (retentostat) cultivations in the presence/absence of methanol and under C- and N-limited conditions were used to investigate the impacts of the solvent and the catabolic potentials of a combined atrazine-catabolizing culture (KRA30). In general, different degradation rates were recorded for the culture in response to element limitation. Addition of citrate as the primary carbon source / effected atrazine (100 mg!"l) degradation rates comparable to that of Pseudomonas sp. strain ADP while succinate addition effected herbicide co-metabolism. Carbon supplementation may, therefore, be considered for site amelioration practices. To complement conventional culture-based microbiological procedures, molecular techniques were employed to explore the diversities and analyze the structures of the microbial communities. In parallel, anaerobic microbial associations which targeted atrazine were also characterized. The soil DNA isolation/characterization protocol adopted consisted of a clean-up step followed by the polymerase chain reaction (peR) and 16S rDNA fingerprinting by denaturing-gradient gel electrophoresis (DGGE). The preliminary results suggested that despite different, but chemically similar, petroleum hydrocarbon molecules, the common selection pressures of the primary enrichments effected the isolation of similar and complex aerobic microbial associations. Some similar numerically-dominant bands characterized the aerobic and anaerobic atrazine-catabolizing associations although distinct differences were also recorded on the basis of the enrichment/isolation pH value and the concentration of the herbicide. Cloning and sequencing were then used to identify some of the numerically-dominant and non-dominant association members. Community-level physiological profiling (CLPP) for physiological fingerprinting was made with Biolog EcoPlates and highlighted the differences in the isolated aerobic atrazine-catabolizing associations depending on the enrichment pH and molecule concentration. Logarithmic-phase cultures of the combined atrazine- and BTX-catabolizing associations were used to explore the association profiles following pH and temperaiure optImIzation. Although some common numerically-dominant components were maintained, differences in numerical and, possibly, activity dominance were observed in the 16S rDNA profiles in response to changes in pH and temperature. This indicated that environmental parameter optimization and characterization of catabolic association structure must precede bioaugmentation so that control of key variables will facilitate maintenance of the dominant site-specific species. Following KRA30 cultivation in the presence/absence of methanol and under carbon and nitrogen-limited conditions, the population fingerprints showed that the presence of methanol effected shifts in species numerical dominance and, possibly, changes in atrazine catabolic capacity. Also, Coulter counter results, optical density readings and 16S rDNA characterization by DGGE indicated that degradation rate changes were accompanied by shifts in species numerical/activity dominance within the association. Although N-limitation effected the highest rates of herbicide catabolism, a potential versatility of the combined association for bioaugmented and/or biosupplemented remediation with acceptable rates regardless of any elemental limitation was recorded. To determine if the contaminated and pristine source soils contained comparable catabolic populations and, thus, offered potential for intrinsic bioremediation, PCRDGGE was used to characterize the populations in comparison with the enriched/isolated associations. Some similar dominant bands characterized the contaminated soils and the enriched/isolated associations. The significance of this, in relation to a possible correlation between numerical and activity dominance in the component species, is discussed with respect to the use of PCR-DGGE to identify natural attenuation potential and monitor sustained intrinsic and enhanced (bioaugmented and biosupplemented) bioremediation. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2001.

Microorganisms are increasingly used in toxicological studies to determine potential environmental impacts of xenobiotic compounds. A multi-stage laboratory model was developed to facilitate the examination of environmental impacts of selected pollutants on fundamental cycling processes inherent to aquatic ecosystems, namely, the degradation of organic substances and nitrogen transformations under aerobic conditions. A microbial association representative of riverine ecosystems was enriched for, isolated and cultured within the model. Characterisation of the microbial association were undertaken. Scanning electron microscopy and bright field microscopy revealed that a diverse heterogenous community of microorganisms had established within the model. Successional metabolic events, namely organic carbon catabolism, ammonification of organic nitrogen and the process of nitrification were differentiated in time and space with the microbial association integrity still being retained. The establishment of a microbial association within the model was primarily dependent on: dilution rates, specific growth rates and interactions between microorganisms and the prevailing environmental conditions. Growth-rate independent populations of microorganisms established within the model and were thought to contribute significantly to the metabolic processes within the model. Nitrifying activity was identified as a rate-limiting process within the model. Following separation of metabolic events, the ecotoxicological impacts of phenol and 2,4-dichlorophenol on the association were assessed. The biological oxidation of ammonia through to nitrate (nitrification) was found to be a sensitive indicator of perturbation. The model was found to be suitable for testing both acute and chronic intoxication by pollutant compounds as well as for biodegradation testing and the possible evaluation of ecotoxicological impacts of wastewater treatment plants. The main disadvantages of the model arose from its operational complexity, its empirical nature and its impracticality for screening large numbers of compounds. A bioassay based on the inhibition of ammonium oxidation was developed in order to fulfil the requirements for a simple and rapid test protocol for the initial screening of perturbant compounds. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1996.

The basic theme of this study is that determination of the economic value of water resources is a necessary condition for rational decision-making and management of these environmental assets, and their associated public goods, in developing countries. The research particularly evaluates the contingent valuation (CV) method as a technique for evaluating increments and decrements in environmental and natural resource service flows, and estimates households' evaluations for improvements in river water quality and connections to piped water supply for domestic uses. The study objectives were to (a) estimate the economic value of piped water supply and improved water quality in the Nzoia River Basin, Kenya, (b) evaluate the feasibility of using the CV technique to value an environmental amenity and its related quasi-public service in rural settings where respondents have limited education and monetary resources, (c) examine the role of temporal dimensions of bid payments (i e, frequency of payments) in contingent values for environmental commodities, (d) empirically investigate embedding effect bias in contingent valuation of improvements in river water quality improvement in a less developed economy, and (e) evaluate the role of water connection charges in households' willingness to hook onto piped water supply in Webuye Division, Kenya. Empirical analysis and estimates of the non-market value which local people assign to water quality in the Nzoia River and a private household water connection is based on a detailed survey of a representative sample of 311 households in Webuye Division of Bungoma District, Kenya. In an on-site survey carried out in May through September 1995, contingent markets were developed for the two goods, (1) improved river water quality, and, (2) provision of a private connection to water supply. The corresponding willingness to pay (WTP) values are explained using Ordinary Least Square regression models. Whatever the good, the WTP is seen to increase with income. However, the effects of other factors are more specific to the contingent good. In order of strength, the other determinants of WTP &quot;quality&quot; are sex, age, household ranking of status of domestic water source, distance from river to household residence, the other factors affecting WTP &quot;connections&quot; are existing source of water supply, household size, ranking of river water quality, and age of household head. On the whole, residents accepted the exercise of contingent valuation and were willing to pay important amounts (Ksh 459 and Ksh 386 on average per household per year, respectively, for goods 1 and 2). Discussion issues include policy significance of the resulting WTPs in terms of the demand for river pollution control and individual household water connections, the effect of the goods upon the CV evaluation process, the &quot;Third World&quot; impacts of frequency of payments in contingent valuation, including perceived-frequency and income-smoothing routes, the embedding effect in WTP values for water pollution abatement in the Nzoia River basin, the importance of pricing influences, specially payment profiles for initial connection charges, on household decisions to connect to piped water systems, and limitations of the study.

Several biologically important arsenic compounds including methylarsonate, trimethylarsine oxide, tetramethylarsonium ion, arsenobetaine and arsenocholine were prepared, in good yields, from sodium arsenite, or dimethylarsinic acid. These organoarsenic compounds together with arsenite, arsenate and dimethylarsinic acid were used as standards for the development of analytical methods for determining the levels of individual arsenic compounds (arsenic speciation) present in natural matrices. / Arsenobetaine, arsenocholine and tetramethylarsonium ion were separated by high performance liquid chromatography (HPLC) with on-line detection by thermochemical hydride generation (THG)-AAS. The analytes were eluted from the cyanopropyl bonded phase HPLC column with a 1% acetic acid methanolic mobile phase which also contained diethyl ether triethylamine, and trimethylsulfonium iodide or picrylsulfonic acid. A surface response methodology and a univariate optimization procedure were used to determine the optimum concentration of solvent modifiers in the methanolic mobile phase. Limits of detection in the range 4-5 ng (as As) were obtained for the arsonium analytes under optimum chromatographic conditions. / A simple phenol extraction procedure was developed to isolate arsonium analytes from edible marine tissues (lobster tail muscle, peeled and deveined shrimp, and cod fillet), cod liver oil and human urine. The crude extracts were separated on the cyanopropyl column using a methanolic mobile phase and detected on-line by THG-AAS. Recoveries from tissues or from urine which had been spiked at 0.1-3.4 $ mu$g of As cation/g of fresh weight were 80% or greater for each of five sample types. / An improved HPLC-AAS interface which was compatible with either aqueous or organic mobile phases was also developed. The interface provided approximately equivalent responses to different arsenic oxidation states which resulted in low to subnanogram chromatographic limits of detection for arsenic oxyanions and arsonium cations in an aqueous or methanolic mobile phase. Nascent As anions and As cations were conveniently coextracted from aqueous solution or from fish muscle by phenol extraction and quantified in the same chromatographic run. This method has been applied to a standard reference sample of dogfish muscle (DORM-1), a marine reference sediment sample (PACS-1) and to sediment porewaters (SAG-15) from the Saguenay Fjord.