Tesi sul tema "Environmental geochemistry"
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1
Krishnamurthy, Prabakaran. "Environmental Geochemistry of the Lower Baram River, Borneo". Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/59727.
Testo completoAbstract (sommario):
In order to understand the environmental geochemistry of the Lower Baram River, seasonal surface water and sediment samples, core sediments, and root, bark and leaves from mangrove trees were collected and examined for major, trace and rare earth elements. The provenance and prevailing geochemical processes which govern the characteristics of water and sediments were revealed. Further, risk assessment and bioaccumulation of trace elements as well as the mechanism of element uptake in mangroves were discussed.
2
Dredge, Jonathan. "Aerosol contributions to speleothem geochemistry". Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5136/.
Testo completoAbstract (sommario):
There is developing interest in cave aerosols due to the increasing awareness of their impacts on the cave environment and speleothems. This study presents the first multidisciplinary investigation into cave aerosols and their contribution to speleothem geochemistry. Modern monitoring of suspended aerosol concentrations, CO2 and temperature in Gough’s Cave, Cheddar Gorge have presented a strong relationship with cave ventilation processes. Temporal variations of aerosol levels have demonstrated the ability of aerosol monitoring to record seasonal ventilation shifts, beyond anthropogenic influences. When used in combination with more established monitoring methods, suspended aerosol monitoring is a beneficial addition to cave environmental studies Theoretical modelling and calculations based on modern aerosol monitoring have established that aerosol contributions are highly variable. Aerosol contributions are of greatest significance under slow growth or hiatus scenarios and high aerosol deposition scenarios. Marine and terrestrial aerosol contributions have been quantified in a flowstone core from New St Michaels Cave, Gibraltar. Additionally, bio-aerosol deposits and bacterial colonisation have been identified as a potential source of trace element bioaccumulation and flowstone coloration in Yarrangobilly Caves, Australia.
3
Harraway, Trevor John. "Chemical characterisation of landfill leachate and its potential mobility through the Cape Flats sand". Thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/26218.
Testo completo
4
Miller, Sarah Jane. "Geochemistry of ferruginous clogging of Karoo wells". Master's thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/4213.
Testo completoAbstract (sommario):
Summary in English.Includes bibliographical references.
The main source of potable water in the Karoo is groundwater and thus any problems resulting from the abstraction of water or from diffifulties in abstractions of water are important. The iron clogging of screens, pumps and filter packs in supply wells is a worldwide problem and the consequences can be severe, leading to costly and harsh rehabilitation measures or even loss of the well. A study was undertaken in order to determine the chemistry and morphology of the precipitates found in relation to the water chemistry, in several wells in the Albertinia-Oudtshoorn-Calitzdorp area of South Africa.
5
Chowdhury, Md Abu Raihan. "Removal of Select Chlorinated Hydrocarbons by Nanoscale Zero-valent Iron Supported on Powdered Activated Charcoal". Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1496150130687849.
Testo completo
6
Smith, Jason Alistair Christian. "The marine environmental geochemistry of the southern Baltic Sea". Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/16931.
Testo completoAbstract (sommario):
The initial focus of this research sought to investigate the marine geochemistry of radium and barium in order to elucidate upon the processes governing circulation patterns and residence times in the southern Baltic Sea. The project has since developed and transformed into a detailed study of the spatial and temporal distribution of a select group of metals, and in some respects pollutants, in the region north of the river Oder where it discharges into the Baltic Sea. A transect of progressively deepening water depths, thought to trace the major outflow of the river Oder into a depositional basin, were investigated over a period of 15 months. Four cruises during this time were undertaken to coincide with each season in order to investigate any broad scale seasonalities. This thesis looks at the main compartments and integrated processes associated with the sediment, nepheloid layer and the water column of this marine environment. This has been achieved by the use of coupled radionuclide and trace metal data followed by the calculation of fluxes and inventories for a select group of elements. Major and trace metals were analysed via ICPMS and XRF and radionuclides were measured by gamma ray spectrometry. Supporting data in the form of grain size analysis, XRD and carbon and nitrogen measurements were also made. Radium measurements were attempted using the Photo-Electron Rejecting Alpha Liquid Scintillation (PERALS) spectrometer system. Of particular interest Pb, Zn, and Sn and their enrichment over average shale in the Arkona Basin. Coupled with this, stable lead isotope data details a historical picture of increased pollution associated with the rise of the automobile and subsequent decline of lead with the advent of unleaded petrol in the mid eighties. In addition the significance of the mobile nepheloid layer is investigated as a primary transport and modification route for the elements of interest. This thesis challenges the traditional role and concept of the Arkona basin as a depositional site for the pollutants discharged from the river Oder and instead evaluates the depositional role of the Arkona Basin as being primarily a sink for the atmospheric input rather than that associated with riverine discharge.
7
Lax, Kaj. "Environmental applications of biogeochemical data from Geological Survey of Sweden". Licentiate thesis, Luleå : Luleå University of Technology, 2005. http://epubl.luth.se/1402-1757/2005/95.
Testo completo
8
Zhao, Linduo. "Iron redox process in clay minerals and its environmental significance". Miami University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=miami1438388284.
Testo completo
9
Huebner, Ralf. "Sediment geochemistry : a case study approach". Thesis, Bournemouth University, 2009. http://eprints.bournemouth.ac.uk/13139/.
Testo completoAbstract (sommario):
The geochemistry of sediments is a very wide field and several important aspects must be taken into account, including, but not limited to, various methodological questions, the analysis of distribution patterns, determination of origins and the assessment of risks. Therefore, this research project adapted a case study approach and analysed several important aspects of contamination in sediments at a time. In case study 1, the distribution of metals in the sediments was analysed in Bigge and Olpe, two small and fast running watercourses in Germany. The metal/metalloid concentrations showed very different distribution patterns. Mobile elements like zinc showed a very homogenous and predictable pattern, while elements with low mobility stick to the sediment and do not migrate much, leading to areas with different concentrations. In addition, it was found that the local monitoring tools in force, which are largely based on analyses of the water, are not sufficient for a reliable assessment of the environmental quality. Case study 2 aimed both to investigate the contamination profile caused by a closed landfill within the Christchurch Harbour nature reserve and the strengths/weaknesses of a partial extraction scheme based on the industrial standardised process DIN 19730. It was found that this procedure can predict the actual migration in the homogenous marshland structure rather well. In the vicinity of a linear channel, however, no correlation between the mobility and dispersion could be detected; the channel acts as an effective drainage system for both the landfill itself and the intertidal marshland in its sphere of influence. Partial extractions are only limited in their ability to predict the migration of contaminants in the ground directly affected by the channel. The main objective of case study 3 was the determination of metal distribution within the Poole Harbour estuary, both in regard to total and mobile metal concentrations. In addition, it was tested if the chosen methodology is an efficient protocol (fast, yet scientifically defendable) for the assessment of the environmental quality of an area of that size. The concentrations and mobilities of all analysed contaminants in Poole Harbour were greatest in the heavily industrialised secondary embayment Holes Bay. Although Wareham Channel typically showed higher concentrations in the total content analyses compared to Southern Bights, the potential risk associated with metals, calculated based on both total concentrations and mobile fractions, was comparable in both areas. In case study 4 a simplified grain-size based normalisation scheme was tested. The efficiency of this approach, together several other normalisation schemes was evaluated in Wareham Channel, located in the west of Poole Harbour. In such fine-grained environments, neither geochemical analyses based on aluminium, nor granulometric normalisation schemes yielded a substantial improvement. Normalisations based on the much simpler iron-ratio reduced the variance considerably. This approach was then applied to the sediments close to a former weapons facility. Case study 5 investigated the interactions between the die-back of the cord grass Spartina anglica in Poole Harbour and the metal contamination in the sediments. Despite having several evolutionary advantages over other plants in this environment, S. anglica is dying back in the estuary since 1925 and the reasons for this process are insufficiently understood. No obvious impact of the metal contamination on S. anglica growth/ die-back could be detected, although the die-back has influenced, in turn, the metal concentrations in the estuary. The overall cadmium concentrations and potential risk of adverse effects have risen since 1925, but in the zones affected by die-back, cadmium stored in the sediment by S. anglica appears to have been washed out rapidly. Existing patches still retain elevated concentrations and are potentially at risk of further cadmium release, especially if sea level rise, caused by climate change, would accelerate the die-back.
10
Hartland, Adam. "Colloidal geochemistry of speleothem-forming groundwaters". Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1659/.
Testo completoAbstract (sommario):
Natural aquatic colloids (solids with dimensions between 1 nm and 1 micron) were studied in cave waters that feed secondary carbonates [speleothems]. Results show that during hydrologically quiescent periods, trace metal (Tr) binding (e.g. Cu, Ni, Co) is dominated by humic-like, natural organic matter (NOM), with the smallest NOM-Tr complexes (≤1 to ca. 4 nm diameter) being the least labile at high pH (>pH 10). Partitioning of NOM:Tr between solution and crystal occurs minimally for the strongest complexes, providing a measure of NOM adsorption. Rapid fluxes of coarse (>100 nm) soil organic matter (SOM) and Tr in dripwaters often follow peak infiltration events, the coarse fraction of NOM quenching fluorescence in finer fractions (<100 nm). Termed ‘high-flux’ (HF), this mode of NOM-metal transport contrasts with the humic-like or ‘low-flux’ (LF) mode both hydrologically and chemically, resulting in shifts in trace metal ratios (e.g. Cu:Ni) which are characteristic of changes in the competitive binding of metals for suitable sites in NOM, and diagnostic of qualitative shifts in NOM composition (i.e. relatively more aromatic/hydrophobic). This process becomes manifest in speleothems, resulting in high- and low-flux trace metal end-members and providing information on NOM aromaticity. Changes in HF:LF metal ratios in speleothems are linked to processes in soils which are ultimately mediated by climate (i.e. ambient temperature and infiltrating precipitation); they may provide information on infiltrating precipitation, on the occurrence of surface disturbances (e.g. deforestation) and NOM composition. HF:LF indices complement the existing array of speleothem climate proxies, but each specific system and setting must be understood to ensure their proper interpretation.
11
Lanyon, Ruth. "Arsenic dispersion associated with the Barbrook gold mine in the Mpumalanga Province of South Africa". Master's thesis, University of Cape Town, 1997. http://hdl.handle.net/11427/22169.
Testo completoAbstract (sommario):
Bibliography: pages 123-137.Arseniferous sulphide-hosted gold deposits associated with the Barberton greenstone belt, located in the Mpumalanga province of South Africa, have been mined on various scales since late last century. The Barbrook mine is located close to the Swaziland border in an area of the Barberton mountainlands which forms part of the Kaap subcatchment of the Crocodile River. Scattered small communities depend on local streams and boreholes in the area for drinking and irrigation water. Hence, the prime motivation for this study was the potential risk to human health associated with enhanced As mobility as a result of the sulphide mineral weathering which accompanies gold mining and processing. Sampling of local waters, soils and sediments, as well as the ore and waste rock at Barbrook was undertaken during a week of fieldwork in August 1996. A range of chemical analyses were performed on the various samples, including As analysis by hydride generation-atomic absorption spectroscopy and inductively coupled plasma - mass spectrometry. The Barbrook ore bodies are structurally controlled and hosted by banded iron formation, carbonaceous shales and carbonate-bearing schists. Within these ore bodies, As is mainly associated with auriferous arsenopyrite (FeAsS), although minor amounts also occur within pyrite (FeS₂) and ullmannite (NiSbS). Of the streams which flow through the mining lease, those at most risk of As contamination are Barbrook Creek, Low's Creek and Crystal Stream. Low's Creek flows through the main mine area, adjacent to the level 1O mine adit entrance, and past the processing plant before converging with Barbrook Creek. The latter receives water from the Shiyalongubo Dam which is the main water source for the area. Immediately downstream of the level 10 mine adit entrance, the steep eastern bank of Low's Creek is lined for several hundred metres with waste rock containing low grade ore. Tailings material from the processing plant is pumped to two tailings dams located about 5 km to the northwest of the plant and close to Crystal Stream.
12
Ceruti, Portia Odessyl. "Crushed rock and clay amelioration of a nutrient decifient, sandy soil of Maputaland". Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/9881.
Testo completoAbstract (sommario):
Bibliography: leaves 57-62.Various studies have suggested the possibility that food derived through subsistence agriculture in the Mseleni region of Maputaland contributes to malnutrition within the local community, particularfy within the high proportion of the population which suffers from a severe, disabling form of osteoarthritis. This study was conducted to determine if the application of local crushed rock or black clay to these nutrient deficient, sandy soils would increase available nutrient concentrations and improve the growth of plants in the ameliorated soil.
13
Schwegler, Frank Rudolf. "Assessment of the suitability of composted sewage sludge as an adsorbent for the treatment of heavy-metal contaminated wastewater, with special reference to cadmium". Master's thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/17468.
Testo completoAbstract (sommario):
Includes bibliography.A large proportion of sewage sludge in South Africa contains heavy metal concentrations which are deemed to be above threshold limits for its use as a fertiliser. Furthermore, sewage sludge has a high affinity for heavy metals. Until the sources of heavy metal contamination of municipal sewage sludge are considerably reduced the contaminated sewage sludge must either be disposed of or used for some other purpose. The use of contaminated sewage sludge as an adsorbent for treating heavy metal-contaminated wastewaters may provide an alternative and practical use for this material. The objective of this study was to assess the potential of composted sewage sludge (which is more stable and has a higher permeability than ordinary sewage sludge), produced from municipal sewage sludge in Milnerton, as an adsorbent for the extraction of heavy metals from contaminated wastewaters. The study was conducted with specific reference to cadmium since it is one of the most toxic of the heavy metals and occurs in many types of wastewaters.
14
McCormick, Dean William. "An investigation into in situ biodegradtion under sulphate-reducing conditions in a petroleum contaminated shallow aquifer". Master's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/4212.
Testo completo
15
Petersen, Jacques R. "A geochemical investigation of ground water and soils affected by evaporation pond seepage, at the Namakwa Sands Mineral Seperation Plant(MSP)". Master's thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/4218.
Testo completoAbstract (sommario):
Bibliography: leaves 78-81.Evaporation ponds are used for treating wastewaters in arid regions worldwide. Namakwa Sands an Anglo American plc operation, mines heavy minerals along the semi arid West Coast of South Africa. An acid effluent is generated during treatment of these heavy minerals. The effluent is neutralized and disposed of into unlined evaporation ponds. Seepage from the ponds affects the surrounding environment as well as the subsurface waters. The main objective of this study was to investigate the effects of the seepage on the groundwater resources and potential implications for contaminant migration in the subsurface environment.
16
Soderberg, Keir. "Geochemistry of the fynbos ecosystem in a Table Mountain Group sub catchment of the Olifants River, Western Cape, South Africa". Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/4225.
Testo completoAbstract (sommario):
Bibliography: leaves 104-118.This study gives a first-order estimation of the chemical composition of the recharge, discharge, and ground waters, along with the bedrock, soil, and vegetation of the Olifants River Valley around Citrusdal. The valley occurs in a synclinal fold with the main aquifers, the Table Mountain Group (MG) sandstones of the Peninsula Formation and the Nardouw Subgroup, folded beneath the central valley.
17
Sugarman, David R. "Soil chemical properties in pine plantations of different ages in the Eastern Escarpement region of South Africa". Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/9880.
Testo completoAbstract (sommario):
Bibliography: leaves 71-78.It is widely accepted that afforestation adversely affects soil chemical properties. A significant decrease in pH, base cation status and acid neutralising capacity (ANC), coupled with increasing acidity have been observed to occur in acid coniferous forest soils both in the Northern and Southern Hemispheres. International and local studies in Southern Africa have observed declining productivity over successive rotations in pine plantations. Increasing acidity loads in the Northern Hemisphere and their adverse effects on forest health have generated a search for chemical indices that would assist in pursuing thresholds beyond which forest vitality is damaged. A common and widely used chemical index is the Ca/Al ratio. The most common parameter adopted is the Ca/Al molar ratio in soil solutions. Recent studies in Southern Africa (Swaziland. Kwazulu-Natal) and in the Sabie area (Eastern Escarpment) have indicated that some forest compartments (Pinus sp.) may experience Ca/Al molar ratios dropping below unity. The value of unity is widely used and proposed as a threshold beyond which tree vitality may be adversely affected. This study was conducted to determine the state of surface (0-20cm) soils underlying pine plantations of different ages in the Sabie area on the Eastern Escarpment of Southern Africa. The pine plantations were selected in areas overlying a uniform bedrock (shale), high attitude, high rainfall, north facing aspect and confined to 3 pine species (P. elliottii, P. patuia and P. taeda). A composite sample was taken from each of 22 forest compartments varying in age (between 22 and 67 years) and rotation (first, second and third). In addition, the results of previous investigations of forest soils in the Eastern Escarpment region were considered in order to expand the array of forest compartment ages and the size of the overall data set used for statistical analysis, so that comparisons could be made.
18
Abanda, Peter Azah. "Impact on soil chemistry of atmospheric sulfur fallout near Arnot coal-fired power station, in the Eastern Transvaal highveld region, South Africa". Master's thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/4184.
Testo completoAbstract (sommario):
Includes bibliographical references.The objective of the study was to evaluate the potential impact of atmospheric sulfur deposition on the soils surrounding Arnot power station. In particular, the study focused on the relationship between sulfur and organic carbon (OC) and on the various pools of sulfur in the soil. A representative selection of collected soil samples was characterized both physically and chemically in the laboratory. In addition to the representative soils sampled in 2000, archived soils sampled in 1996 and 1999 from the same area were included in some of the chemical analyses.
19
Dodds, Heather Anne. "An investigation into vanadium contamination of soil and its effects on plants". Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/17002.
Testo completoAbstract (sommario):
Bibliography: pages 64-67.This study constitutes a preliminary assessment of the behaviour of effluent-associated vanadium, and its possible effects on the biotic components of land treatment sites, used for the disposal of liquid industrial wastes from a chemical plant in the eastern Transvaal. A review of the literature showed that although the emission of vanadium into the environment is on the increase, very little information is available regarding its behaviour and impact as an environmental pollutant. This study is therefore important not only in the context of the land treatment operation in question, but clearly in a more universal context as well. The study involved a three-phase approach to the problem. Firstly, vanadium sorption was considered in four soils encountered on the sites in question. Secondly, an investigation was conducted into the potential toxicity of vanadium to relevant plant species. Finally, the potential inhibition of soil biological activity at increasing levels of vanadium was examined, although the results of this experiment were inconclusive.
20
Echeverría, Marietta Elena. "Impact of pine plantations on the form and mobility of nitrogen in soils of the eastern escarpment region of South Africa". Master's thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/7680.
Testo completoAbstract (sommario):
Bibliography: leaves 96-101.Recent research in the eastern escarpment area of South Africa has documented enhanced NO₃- concentrations in soil solution and stream water resulting from afforestation. There has been much research in the Northern Hemisphere regarding the qualitative and quantitative causes and consequences of N saturation in forest ecosystems. In order to assess the significance of local observations of afforestation-induced NO₃- enhancement in a global context, a study was conducted to evaluate the influence of forest plantations (Pinus spp.) on N form and mobility in soils in the eastern escarpment area of South Africa. Twenty soil samples were taken, half in grassland and half in forest, in the Graskop and Kaapsehoop areas of the eastern escarpment. Forest samples were taken as composites of approximately five individual samples in each stand from the top 20-25 em of soil, combining partially decomposed organic litter layer with the subjacent upper mineral soil horizon. Grassland samples were taken, again as composites, consisting of the upper mineral soil horizon (an organic litter layer was for the most part absent). Approximately three-quarters of each sample was air-dried, and crushed to pass through a 2-mm sieve and stored for analysis. The remaining quarter of each sample was passed through a 2-mm sieve and refrigerated at about 4°C in order to maintain field-moist conditions and to inhibit microbial transfornlations. Refrigerated samples were used for KCI-extractable NO₃- and NH₄+ analyses and N mineralisation experiments. The remaining analyses were performed on the air-dried samples. This study included two facets: physical and chemical characterisation of soil samples; and a series of laboratory experiments. The solid phase of the soils was analysed for organic carbon, total nitrogen and particle size distribution. The soil solution was investigated by making saturated paste extracts which were analysed for major ions, trace elements, electrical conductivity (EC) and pH. Extractable base cations, acidity and inorganic nitrogen (NH₄+ and NO₃-) were also analysed after extraction with NH₄OAc or KCl solutions. The laboratory experiments, intended to investigate the apparent differences in soil N transformations and mobility resulting from vegetation, consisted of both aerobic and anaerobic incubation to assess N mineralisation, a NO₃- sorption experiment and a soil to extract ratio dilution experiment.
21
Lanz, Johann. "A geochemical investigation of the waters and sediments of De Hoop Vlei, Bredasdorp district, South Africa". Master's thesis, University of Cape Town, 1997. http://hdl.handle.net/11427/20190.
Testo completoAbstract (sommario):
Bibliography: pages 117-121.De Hoop Vlei is a saline coastal lake situated 53 kilometres north-east of Cape Agulhas in the Western Cape Province of South Africa. It is probably of estuarine origin but is now separated from the sea by mobile sand dunes and, therefore, has no surface outflow. Inflow to the vlei is from a catchment area of approximately 1200 km2 in which intensive grain farming is practised. The vlei is situated within the De. Hoop Nature Reserve and its ecological value, particularly as a breeding ground for water birds, has been recognised in its designation as an international RAMSAR conservation site. Agricultural practices in the catchment have been identified as a potential threat to the ecology of the vlei. The overall objective of this study was to provide a geochemical characterisation of De Hoop Vlei. It focused on identifying the geochemical factors and processes which control the water chemistry of the vlei and attempted to identify any influence of agricultural activities on water quality. This was achieved through a geochemical interpretation of the results obtained from analyses of water and sediment samples collected during the study. Use was also made of Department of Water Affairs and Forestry monitoring data in order to examine long term behaviour of the system, particularly with respect to the effect of evaporative concentration on water composition. Furthermore, chemical equilibrium was modelled, using the geochemical model MINTEQA2, in order to give an indication of processes likely to occur in the water as well as the behaviour of certain possible pollutants in the vlei. Water and sediment core samples, collected during two separate sampling trips, were taken along the entire length of the vlei and some water samples were taken in the catchment. Interstitial waters were obtained by suction from sediment cores. Samples of secondary precipitates, found along the edge of the vlei, were also taken. The following laboratory analyses were performed on water samples: pH, EC, alkalinity, major cations and anions, dissolved P, fluoride, and the trace metals Fe, Mn, Al, Ni, Cu, Zn, and Pb. The following laboratory analyses were performed on sediment samples: pH of wet and dried sediments, organic C content, carbonate content, total elemental concentrations of major and trace elements, mineralogy, clay percentage and extractable P, Zn and K. Scanning electron microscopy and mineralogical analyses were performed on samples of secondary precipitates.
22
Gassner, Anja. "Geochemical and limnological aspects of phosphorous contamination in the Noordhoek Valley, Cape Peninsula". Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/9705.
Testo completoAbstract (sommario):
Includes bibliography.The Noordhoek Valley is situated on the Atlantic coast of the Cape Peninsula, South Africa (34°07'S, 18°22'E). Towards the east, the valley hosts numerous townships, while to the west it opens into a lowland marsh area, bordered by a five-kilometre beach. The wetland is subjected to various forms of anthropogenic pollution; the two most important being the discharge of urban runoff and treated effluent from the local sewage works. During the period of the study (Jan-Oct 1998), the occurrence of toxic cyanobacteria of the species Microcystis aeruginosa was reported for the two main water bodies within the wetland. The objective of this study was to conduct an investigation of geochemical and limnological aspects of phosphorus contamination within the wetland. The investigation concentrated on the two main water bodies of the wetland: The Lake and Wildevoëlvlei.
23
Whyte, Stewart Rodney. "A geochemical investigation of the Lake Sibiya system, Northern Zululand". Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/21695.
Testo completoAbstract (sommario):
Lake Sibaya (27°15'-21'25'S; 32°32'-32°44'E) is situated in the northern region of the Zululand coastal plain, and is remarkable in that it embodies a near-pristine· freshwater coastal lake preserving clear residual signs of its former estuarine origin. Despite the· fact that the lake constitutes perhaps the most intensively studied of all freshwater bodies in South Africa, little is known .of its geochemical character. The objective of this study was therefore to conduct an investigation of the waters and sediments of the lake system, which might then provide a chemical baseline against which the future environmental quality of the system could be gauged, and in terms of which the current functioning of the ecosystem can be better understood. In line with this rationale, water and sediment samples were collected from each of fourteen sampling sites located along three transects running, variously, S-N, SW-NE and W-E across peripheral arms of the lake. Waters in direct contact with the sediments were thoroughly agitated with the sediments and thereafter decanted for analysis. Since the lake is purported to be fed almost exclusively by groundwater flow, water samples were collected from three groundwater . . wells located north-west of the lake. The Department of Water Affairs (DW AF) databases for groundwater chemistry, and for lake level and chemistry over the period 1980 to 1998, were used to supplement this data, and to provide an indication of any medium-term parameter changes. A water sample was also· collected from the non-perennial Mseleni River, although the river is known to contribute minimally to the lake volume. The majority of laboratory analyses were conducted within the Department of Geological Sciences at the University of Cape Town, adhering to standard analytical methods wherever possible.
24
Merrett, Greg Lee. "Groundwater redox conditions at a petroleum contaminated site, Kuils River, South Africa : pathways for BTEX biodegradation". Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/8588.
Testo completoAbstract (sommario):
Includes bibliographical references (leaves 84-88).A shallow sandy aquifer, contaminated by petrol from an underground storage tank, was studied to determine if intrinsic bioremediation of the hydrocarbons is taking place. Groundwater samples taken from 32 monitoring wells were analysed for NO₃-,NH₄+, Mn²+, Fe²+, SO₄²-, and ΣH₂S. Portable electrodes were used to make field measurements of electrical conductivity, redox potential, and pH. The variation and distribution of these redox-sensitive groundwater constituents show that bioremediation via NO₃- reduction, Fe³+ reduction, and SO₄²- reduction (and possibly methanogenesis in the most reduced part of the plume) is occurring. In some cases redox processes are taking place simultaneously resulting in redox zones that overlap. Iron and sulphate reduction are the dominant processes taking place.
25
Huntsman, Philippa Rose. "An investigation into the use of smectitic clay soil for the containment and treatment of petrochemical waste". Master's thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/19708.
Testo completoAbstract (sommario):
The manufacture, transport, use and disposal of organic chemicals may result in the release of significant quantities of organic substances into soil, from which they are subject to possible transport into underlying groundwater. Many of these organic chemicals are potentially toxic (Wilson et al., 1981). Information is required concerning the chemical and physical behaviour of organic chemicals in the soil environment in order to implement measures that will protect groundwater but also permit reasonable usage of soil for waste containment. This study deals with the interactions of a smectitic clay soil of the Rensburg form and two petrochemical wastes, which were sampled from storage dams, adjacent to a petrochemical plant at Secunda, South Africa. There is growing interest at the plant in utilizing soil for cost-effective waste containment and treatment. The objectives of this study were twofold: firstly, to determine the permeability of the Rensburg soil with respect to the two waste liquids (BPlO- aqueous and phenolic, and BP2- non-aqueous); and, secondly, to investigate the sorptive capacity of the clay fraction of the soil for two common groundwater contaminants, benzene and phenol, in the context of the potential for using treated clays for decontaminating BP10 and other organic wastes. The Rensburg soil was compared with a commercial bentonite for containing and treating petrochemical waste.
26
Webster, Glen Robert. "Experimental improvement of flyash as a growth medium for plants through addition of selected solid wastes". Master's thesis, University of Cape Town, 1997. http://hdl.handle.net/11427/22551.
Testo completoAbstract (sommario):
Large quantities of coal are consumed in South Africa as a result of the generation of electricity and the manufacture of automotive fuel. A consequence of this was the production of more than 15 Mt of ash and associated coal combustion by-products in 1987 alone. This poses a large scale waste-disposal problem. Flyash, the major waste product is from South African coal sources, an alkaline, saline material the pozzolanic nature of which results in the formation of massive, compacted and cemented ash deposits which have significant environmental impacts. Efforts made to limit this impact by revegetation, in many locations throughout the world, have had limited success due to the mobility of phytotoxic concentrations of some elements, including As, B, Cr, Cu, Mo, Ni, S and Se. Flyash also has limited quantities of bioavailable Fe, Mn, P and Zn and these elemental limitations are associated with the alkaline nature of the flyash. Another element that is deficient, is N, it is unavailable in flyash as it is lost from coal during combustion. Aside from the chemical limitations to plant growth, the compacted nature results in low porosity which can limit plant available moisture. Plant root penetration is also impeded which limits nutrient uptake. The basis of this study was to incorporate other selected waste materials into the flyash to produce, by co-disposal, a combined waste material that is geochemically inert and a satisfactory plant growth medium. The ameliorants selected for inclusion in this study included interphase sulphur, a Vcontaminated waste sulphur product from the sulphur recovery plant at the SASOL' s Secunda petrochemical production facility and Catpoly, a spent catalyst consisting of phosphoric acidimpregnated diatomaceous earth, also obtained from SASOL's Secunda operation.
27
Weber, Stephen John. "An investigation of the primary sources of the Cape Town brown haze". Master's thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/4229.
Testo completoAbstract (sommario):
Includes bibliographical references.The term atmospheric haze is a condition of reduced visibility, caused by the presence of fine particulate matter in the atmosphere, which can originate from natural or anthropogenic sources. The "Brown Haze" is a phenomenon that is associated with Cape Town and can be described as brown coloured smog. It occurs over the winter months, mainly May to September, due to the strong temperature inversions and windless conditions that can occur during these months. These conditions lead to the build-up of pollutants emitted into the atmosphere. The Cape Town Brown Haze Phase Two study was used to obtain a detailed analysis of the atmosphere in a programme of lateral and vertical profiles through the Brown Haze. The field campaign took place from the 29th July 2003 to the 26th August 2003 around the Cape Town metropolitan region.
28
Campbell, Ross. "The chemical response of deep, leached and weathered soils of the Mpumalanga Highveld, South Africa, to irrigation with saline mine water". Master's thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/4189.
Testo completoAbstract (sommario):
Includes bibliographical references.Coal mining in the Highveld region of Mpumalanga Province, South Africa generates between 14 and 30 million litres of waste water per day. Much of the water is saline (TDS> 2500 mg/I) and has high concentrations of dissolved SO₄²⁻, Ca²⁺ and Mg²⁺. Crop irrigation has been proposed as a useful way to dispose of saline mine water and enhance agricultural productivity in this low rainfall (˂800 mm/year) region. In order to avoid undesirable salinization of the regional groundwater, it is necessary that soils immobilize, at least partially, the dissolved salt load of irrigation water.
29
Lopes, Lidia Velazquez. "Sorption of the platinum-group elements in selected solid matrices". Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/4210.
Testo completoAbstract (sommario):
Summary in English.Bibliography: leaves 70-75.
Recent research on the platinum-group elements (PGE) has shown increased concentrations in environmental samples, probably as a result of the widespread use of PGE (Pt, Pd and Rh in particular) as catalysts in the chemical and car industry. Most of the recent research on PGE focuses on the analysis of concentrations in environmental samples exposed to anthropogenic sources of PGE, but there are very few studies that have investigated sorption behaviour of PGE in soils.
30
Mehlomakulu, Mandla. "The Influence of urban development on the water chemistry of the Cape Flats aquifer". Master's thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/10832.
Testo completoAbstract (sommario):
Includes bibliographical references.Large quantities of water are available in the Cape Flats sandy aquifer in the Western Cape. Local industrial, agricultural, domestic and urban development activities are known to be potential polluters of this water through infiltration of wastewater, because of the unconfined nature of the aquifer. In order to determine the potential of the water in the aquifer, fifteen water samples from the Cape Flats were analysed and geochemically assessed prior to their qualify being evaluated in terms of future use in domestic, irrigation and industrial activities.
31
Mitchell, Ruth. "An investigation into the lithological source of iron in the Kammanassie Mountain aquifer". Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/6074.
Testo completoAbstract (sommario):
Includes bibliographical references.The precipitation of iron from aquifer water in boreholes is a problem in the Klein Karoo region of South Africa. The precipitation causes boreholes to clog and limits full use of well fields in the area. The iron is naturally occurring and this project sets out to identify the lithological source of the iron and in what form the iron is presented. The Table Mountain Group (TMG) aquifer is a fractured rock aquifer situated in the TMG and rock samples were taken from the various lithologies in the area.
32
Taylor, Arthur. "A trace element study of sediments from the Olifants River estuary, the Berg River estuary, and the off-shore Mud Belt". Master's thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/9027.
Testo completoAbstract (sommario):
Includes bibliographical references (leaves 99-105).Trace elements have received increased attention since the mid-1900's. Although some studies have investigated trace element accumulation as a result of urban expansion in the Western Cape, South Africa, few have catalogued the accumulation and behavior of trace elements resulting from agricultural practices. This study investigates the distribution and behavior of trace elements for the Olifants and Berg river catchments by focusing on the sediments of the estuaries. The dominant industry in both catchments is agriculture and there exists relatively little urban sprawl. Two sediment samples taken from the offshore mud belt in the vicinity of the two river mouths were also analyzed. The sediments were analyzed for trace elements using inductively coupled plasma mass spectrometry (ICP-MS), major elements using X-ray fluorescent spectroscopy (XRF), total sulfur using XRF, total and organic carbon using a C:H:N analyzer, and grain size analysis was performed (>62 μm, 38-63 μm, 2-38 μm, <2μm). The mud belt cores were dated using 14C dating. Estuarine surface waters were analyzed for trace elements, pH, dissolved oxygen (DO), electrical conductivity (EC), and temperature. The trace elements arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) were focused on. The trace element concentrations in the sediments were compared with those of soils that occur in the study area, as well as their parent materials, to determine background concentrations. The concentration profiles of elements with respect to depth are compared with natural deposition rates to recognize signs of recent enrichment of individual trace elements. Inter-element comparisons are made in an attempt to determine speciation. Comparison between the estuarine and mud belt sediments were made to assess the estuaries ability to filter fluvial trace elements, as well as to determine the sediment contributions of the Olifants and Berg rivers to the mud belt. Statistical analysis was performed to"group sediment populations Trace element and organic matter concentrations showed strong positive correlations with fine-sized particles. The mud belt sediments displayed considerably more OC than the estuarine sediments. The trace elements appear to associate predominantly with clay minerals (alumino-silicates), Fe/Mn oxides, and organic matter. Trace element correlations with S and carbonate carbon were also observed. Comparison with estimates of natural deposition rates and compositions of soils occurring in the catchments did not suggest an anthropogenic pollution input. From the data available the estuarine and Mud Belt sediments appear enriched in Cd, Cu and Zn in comparison to the background soils. The estuaries seem to effectively trap Zn and Pb, but do not capture As well. Statistical analysis suggest that, of the rock types considered, the sediments of the Olifants and Berg river estuaries and those of the off shore mud belt are most similar to sediments derived from the Malmesbury and Ecca Groups. The Olifants and Berg rivers are important sources of water for the farming community, as well as for municipal use in the Western Cape. Based on this investigation of the estuarine waters and sediments the rivers appear to be in good health in regards to trace element concentrations.
33
Makhathini, S. C. "Environmental consequences associated with ash-stabilisation of organic sludges from the synthol process". Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/7403.
Testo completoAbstract (sommario):
Includes bibliographical references.Worldwide increases in environmental awareness have led to the development of new innovative technologies aimed at site remediation and hazardous waste treatment. Solidification/Stabilisation (S/S) is one of such technologies and it has emerged as an environmentally acceptable treatment option for hazardous waste. Initially applied to inorganic wastes, S/S is now being investigated for the treatment of organic wastes and sludges. Challenges facing this venture into the SIS of organic wastes include the lack of technical information on waste-binder interactions, the uncertainty regarding an appropriate method to evaluate the performance of CPS systems, as well as evaluation of the long-term stability of stabilised material. This paper attempts to expand the understanding of chemical and micro-structural waste-binder interactions. Also addressed is the weathering behaviour of stabilised/ solidified organic waste when exposed to two different leaching media, distilled water and the US EPA's Toxicity Characteristic Leaching Procedure (TCLP) solution. Addressed to a minor extent is the effect of stabilised/solidified organic waste on biomass production of sweetcorn maize. The focus in this study was the stabilisation of the synthol sludge (synthol gunk) using a pozzolan system. This was done by preparing stabilised waste forms from synthol gunk and fine ash (ash obtained from the slimes dams, hence has hydrated to some extent). A particle size fraction less than 2 mm of these waste forms were leached with the two leaching solutions. Some of the material was pressed into pellets, which were subsequently leached in the same leaching solutions. The pellets were analysed under SEM-EDS for micro-structural analysis. In a separate set of experiments fine ash, synthol gunk and the stabilised waste forms were mixed with soil in the range 0% to 30% waste addition, after which sweetcorn maize was planted to study the effects on biomass production. Other instrumental techniques used in this study include WDXRF, ICP-MS, FTIR, IC as well as the analysis of dissolved organic carbon (DOC). The study showed that the trace metal speciation of the pozzolanic binder is affected by the presence of the organic waste, with a possible threat of turning the binder into a hazardous material. Elements that were leachable by TCLP on the stabilised product include B, Mn, Ni, Fe, and Br. The addition of lime in the system appears to lower the leachability of B, Mn, and Br while worsening the leachability of Fe, Ba, and Zn. However, addition of lime increases the leachability of B, Cr, Mn, Fe and Br in distilled water. The most likely source of B, Fe, Br and Ba is fine ash. Plant growth studies showed that the toxicity threshold of synthol gunk in the stabilised material on biomass production appears to be lowered from about 2.5% in unstabilised synthol gunk to about 1.2% either due to synergy or the additive effect of ash and synthol gunk. Furthermore, it is likely that some of the toxicity of synthol gunk is due to the hydrophobic coating of roots resulting in inadequate water intake by the plant.
34
Folefoc, Asongbecap Daniel. "Geochemical study of soil salinity in a toposequence near Riebeeck West, South Africa". Master's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/10448.
Testo completoAbstract (sommario):
Bibliography: leaves 84-91.A geochemical investigation of salt distribution in soils of the semi-arid of Western Cape, South Africa, was carried out following a pilot study which revealed widespread soil salinity in the Berg River catchment. The present study looks at the distribution of the salts along a toposequence in a subcatchment of the Berg River underlain by Malmesbury Group shale. The objectives were: to investigate salt distribution in relation to landscape topography; to identify potentially harmful trace elements associated with the salinity; and to determine the processes responsible for salt distribution. Ten soil profiles were dug to a depth of 200 cm at points along a slope of angle 10.20 along and 367 m long. The profiles at the crest of the toposequence are underlain by silcrete and alluvium while Malmesbury shale parent material underlies the rest of the profiles. Contour drains disrupt the natural shape of the slope. The soil texture is loamy sand to clay loam at the crest and loamy to sandy-clay loam in the midslope. Mineralogy at the crest is quartz dominated and kaolinite occurs in the mid and lower slope.
35
Gumede, Nyawo Basirio Simbi. "Economic structural adjustment programmes in the Southern African development community : an analysis of impact and policy considerations with special reference to Zambia and Zimbabwe". Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/9748.
Testo completoAbstract (sommario):
Bibliography: leaves 183-189.This study is primarily aimed at examining the impact of World Bank / IMF, structural adjustment programmes in the SADC region. However, the main focus of the study was on Zimbabwe and Zambia. These World Bank / IMF-influenced perestroikas, are believed to be viable panacea, for the state of economic malaise prevalent in the SADC region. In undertaking this research, various methods were utilised to acquire data. A case study approach was used. However, the main method of data collection which was heavily relied upon was document study. The collected data was analysed and presented in both graphical and tabular form. This study, inter alia, established that the implementation of IMF / WB structural adjustment programmes in the SADC region has precipitated a plethora of insurmountable socio-economic problems for the citizenry of both Zimbabwe and Zambia. Furthermore, the research has revealed that IMF / WB influenced structural adjustment programmes have culminated in large-scale unemployment, retrenchments, an acute decline in educational and health standards, ever-skyrocketing food prices, rents, taxes, mass exodus of qualified human resources to greener pastures, big debts, inflation and labour strikes in Zimbabwe and Zambia.
36
Yafa, Charun. "Accurate analysis and environmental geochemistry of inorganic elements in peat bogs". Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/11632.
Testo completoAbstract (sommario):
The work described in this thesis is primarily concerned with (i) the development of analytical methods for the determination of inorganic elements in peat, (ii) the production and analysis of a certified peat reference material, and (iii) the application of methods and procedures to the generation and interpretation of elemental profiles in cores from the largest ombrotrophic peat bog in Scotland. The effects of sample preparation on the determination of inorganic elements in peak samples were thoroughly investigated. The analytical methods and quality assurance procedures developed using the certified reference material were applied to the analysis of two Flanders Moss peat cores that had been collected by different coring techniques. An offset between the elemental profiles of the two cores was attributed to loss of surface material in the case of one, confirmed by stable (206Pb/207Pb) and radioactive (210Pb) isotopic analysis. The depth profiles of the various elements were interpreted in terms of influences such as nutrient uptake and recycling, anthropogenic inputs from industry, energy generation and transport, soil dust, and post-depositional remobilisation and redistribution. For Pb, for which a record for atmospheric deposition was retained, the relative contributions of different sources (e.g. smelting, coal combustion, car-exhaust emissions) during the industrial era were assessed using Pb concentration and 206Pb/207Pb ratio variations in 210Pb-dated peat. The importance of atmospheric Pb deposition prior to the introduction of leaded petrol was confirmed and, in the more distant past, a small Pb peak at a depth of ~1 m was tentatively attributed to Pb mining and smelting activities during the period of the Roman Empire.
37
Van, der Spuy David. "The chemical characterisation of authigenic carbonates from the Witbank no. 2 coal seam : environmental and diagenetic implications". Master's thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/22154.
Testo completoAbstract (sommario):
Six different types of authigenic carbonate were identified associated with the no.2 coal seam in the Witbank basin. These are: l) cell-filling carbonate, 2) early formed spberulites, 3) massive carbonates, 4) cleat-filling carbonate, 5) fracture-filling carbonates and 6) carbonate cement of associated sands. The textural relationships, depth of burial and chemical evolution of these carbonates were studied with the aid of X-ray diffraction, total organic carbon analysis, vitrinite reflectance, reflected and transmitted light microscopy, scanning electron microscopy and electron microprobe analysis. Comparison with the studies of Matsumoto and Iijima (1981), Curtis and Coleman (1986) and other literature showed the Witbank carbonates to have followed a fairly complex path in terms of chemical evolution. The chemistry of the earliest cell-filling carbonates is indicative of an early brackish, alkaline environment with high sulphate levels, with occasional local oxidising conditions prevailing during precipitation. Spherulite chemistry is largely representative of the continuation of alkaline conditions with high sulphate supply. Those forming closer to palaeohighs are sideritic and possibly reflect the input of fresher run-off water, allowing more acidic conditions locally. Compositional zonation of some examples indicates initial acidic conditions and later alkaline conditions. Massive carbonates are considered to have formed, at least in some cases, from amalgamations of these earlier spherulites. They are high-Ca carbonates, siderite or dolomite. A number of the high-Ca massive carbonates were found to be aragonite. These are considered to have precipitated from water with high ionic strength, in the presence of humic acids. The chemistries of these massive carbonates are representative of the continuation of relatively, alkaline conditions, or, in some cases, represent a strong brackish or marine imprint over the earlier fresh water chemistries. Chemical trends and isotope data suggest continued formation with burial. Later formed carbonates filling cleats and fractures show more diverse compositions and are interpreted as the results of mixing of pore waters at depth, primary silicate dissolution and later percolation of groundwaters after uplift. The overall evolution of the authigenic carbonates in the Witbank no.2 seam leads to the interpretation that the early swamp was only locally "fresh", and provides strong evidence for a marine influence at both early and late stages of deposition and diagenesis.
38
Pallavicini, Nicola. "Method development for isotope analysis of trace and ultra-trace elements in environmental matrices". Doctoral thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-59705.
Testo completoAbstract (sommario):
The increasing load of toxic elements entering the ecosystems, as a consequence of anthropogenic processes, has grown public awareness in the last decades, resulting in a great number of studies focusing on pollution sources, transport, distribution, interactions with living organisms and remediation. Physical/chemical processes that drive the uptake, assimilation, compartmentation and translocation of heavy metals in biota has received a great deal of attention recently, since elemental concentrations and isotopic composition in biological matrices can be used as probes of both natural and anthropogenic sources. Further they can help to evaluate fate of contaminants and to assess bioavailability of such elements in nature. While poorly defined isotopic pools, multiple sources and fractionating processes add complexity to source identification studies, tracing is hindered mainly by poorly known or unidentified fractionating factors. High precision isotope ratio measurements have found increasing application in various branches of science, from classical isotope geochronology to complex multi-tracer experiments in environmental studies. Instrumental development and refining separation schemes have allowed higher quality data to be obtained and played a major role in the recent progress of the field. The use of modern techniques such as inductively coupled plasma sector field mass spectrometry (ICP-SFMS) and multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for trace and ultra-trace element concentrations and isotope ratio measurements have given new opportunities. However, sources of errors must be accurately evaluated and avoided at every procedural step. Moreover, even with the utilization of sound analytical measurement protocols, source and process tracing in natural systems can be complicated further by spatial and temporal variability. The work described in the present thesis has been focused primarily on analytical method development, optimization and evaluation (including sample preparation, matrix separation, instrumental analysis and data evaluation stages) for isotopic and multi-elemental analyses in environmental samples at trace and ultra-trace levels. Special attention was paid to evaluate strengths and limitations of the methods as applied to complex natural environments, aiming at correct interpretation of isotopic results in environmental forensics. The analytical protocols covered several isotope systems of both stable (Cd, B, Cr, Cu, Fe, Tl and Zn) and radiogenic (Os, Pb and Sr) elements. Paper I was dedicated to the optimization and testing of a rapid and high sample throughput method for Os concentrations and isotope measurements by ICP-SFMS. If microwave (MW) digestion followed by sample introduction to ICP-SFMS by traditional solution nebulization (SN) offered unparalleled throughput important for processing large number of samples, high-pressure ashing (HPA) combined with gas-phase introduction (GPI) proved to be advantageous for samples with low (below 500 pg) analyte content. The method was applied to a large scale bio-monitoring case, confirming accumulation of anthropogenic Os in animals from an area affected by emissions from a stainless steel foundry. The method for Cr concentrations and isotope ratios in different environmental matrices was optimized in Paper II. A coupling between a high pressure/temperature acid digestion and a one pass, single column matrix separation allowed the analysis of chromites, soils, and biological matrices (first Cr isotope study in lichens and mosses) by ICP-SFMS and MC-ICP-MS. With an overall reproducibility of 0.11‰ (2σ), the results suggested a uniform isotope composition in soil depth profiles. On the other hand a strong negative correlation found between δ53Cr and Cr concentrations in lichens and mosses indicates that airborne Cr from local anthropogenic source(s) is depleted in heavy isotopes, therefore highlighting the possibility of utilization of Cr isotopes to trace local airborne pollution source from steel foundries. Paper III describes development of high-precision Cd isotope ratio measurement by MC-ICP-MS in a variety of environmental matrices. Several digestion methods (HPA, MW, ultrawave and ashing) were tested for sample preparation, followed by analyte separation from matrix using ion-exchange chromatography. The reproducibility of the method (2σ for δ114Cd/110Cd) was found to be better than 0.1‰. The method was applied to a large number of birch leaves (n>80) collected at different locations and growth stages. Cd in birch leaves is enriched in heavier isotopes relative to the NIST SRM 3108 Cd standard with a mean δ114Cd/110Cd of 0.7‰. The fractionation is assumed to stem from sample uptake through the root system and element translocation in the plant and it exhibits profound between-tree as well as seasonal variations. The latter were compared with seasonal isotopic variations for other isotopic systems (Zn, Os, Pb) in the same trees to aid a better understanding of underlying processes. In Paper IV the number of isotope systems studied was extended to include B, Cd, Cu, Fe, Pb, Sr, Tl and Zn. The analytical procedure utilized a high pressure acid digestion (UltraCLAVE), which provides complete oxidation of the organic material in biological samples, and a two-column ion-exchange separation which represents further development of the separation scheme described in Paper III. Such sample preparation ensures low blank levels, efficient separation of matrix elements, sufficiently high analyte recoveries and reasonably high sample throughput. The method was applied to a large number of biological samples (n>240) and the data obtained represent the first combined characterization of variability in isotopic composition for eight elements in leaves, needles, lichens and mushrooms collected from a geographically confined area. To further explore the reason of variability observed, soil profiles from the same area were analyzed for both concentrations and isotopic compositions of B, Cd, Cr, Cu, Fe, Pb, Sr, Tl and Zn in Paper V. Results of this study suggest that the observed high variability can be dependent on operationally-defined fractions (assessed by applying a modified SEP to process soil samples) and on the typology of the individual matrix analyzed (assessed through the coupling of soil profile results to those obtained for other matrices: lysimetric waters, mushrooms, litter, needles, leaves and lichens). The method development conducted in this work highlights the importance of considering all possible sources of biases/errors as well as possibility to use overlapping sample preparation schemes for multi-isotope studies. The results obtained for different environmental matrices represent a starting point for discussing the role of natural isotopic variability in isotope applications and forensics, and the importance of in-depth knowledge of the multiple parameters affecting the variability observed.
39
Murphy, Samantha E. M. "Characterization of a TCE-contaminated aquifer using tritium-helium dating and geochemical tracers, Valcartier, Quebec, Canada". Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28386.
Testo completoAbstract (sommario):
The groundwater supply in the Valcartier area of Quebec is contaminated with trichloroethylene (TCE) from multiple sources, and hydrogeologic characterization is being carried out to understand its origin and migration patterns. A geochemical investigation was undertaken to independently verify groundwater flow and TCE transport in Valcartier groundwater to improve a numerical model that is currently being developed.
3H-3He ages were obtained along flow paths stemming from two main source zones and compared with advective model ages produced at corresponding locations. Ages obtained above and below a prodeltaic silty aquitard in the eastern part of the study area were used to calculate an average vertical hydraulic conductivity (Kv) of 1.3-3.1x10-8 m/s. 3H-3He ages were compared with modelled ages at different values of porosity (n) and recharge; the bestcorrespondence was found to be at 0.35 and 300 mm/yr, respectively. Anomalously high concentrations of terrigenic He and unexpectedly old 3H-3He ages in some areas indicate areas where groundwater in the underlying proglacial aquifer may flow upward into the deltaic sand aquifer.
Geochemical parameters measured in groundwater along the flow paths as well as in Shannon and in the proglacial aquifer were examined for patterns. Multivariate statistics (Principal components analysis and cluster analyses) were applied to the data to distinguish different types of groundwater; the geochemistry of each group reflects recharge origin and lithology encountered. The groups verify flow paths delineated by the groundwater model, and help distinguish groundwater of different origins downgradient of source zones. One facies in particular is associated with high TCE concentrations and occurs where groundwater upflow from the proglacial aquifer in Shannon inferred from the 3H-3He data. This appears to be TCE coming from a previously unrecognized source in the south part of the study area, possibly an old bedrock dump.
This study demonstrates the value of integrating geochemical information in groundwater characterization programs with existing information to refine the understanding of groundwater flow, especially in the development of numerical models.
40
Grabb, Kalina C. "Stable Isotope Systematics of Abiotic Nitrate and Nitrite Reduction Coupled With Anaerobic Iron Oxidation: the Role of Reduced Clays and Fe-Bearing Minerals". Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17417576.
Testo completoAbstract (sommario):
Under anaerobic conditions, it is widely assumed that nitrate (NO3-) and nitrite (NO2-) reduction is primarily the result of microbial respiration (Burgin and Hamilton, 2007; Granger et al., 2008). However, it is also proven that the abiotic reduction of nitrate and nitrite by reduced iron(II) (Fe(II)), whether mineral-bound or surface-associated, may also occur under certain environmentally relevant conditions (Chao and Kroontje, 1966; Straub et al., 1996; Picardal, 2012,). With a range of experimental conditions, nitrogen and oxygen stable isotope systematics of abiotic nitrite reduction by Fe(II) were investigated in an effort to characterize the biotic and abiotic processes in the environment. While homogenous reactions between NO2- and Fe(II) in artificial seawater (ASW) showed little reduction, heterogeneous reactions involving Fe-containing minerals showed considerable nitrite loss. Specifically, rapid nitrite reduction was observed in experiments that included reduced nontronite clay and an Fe(II)-Fe(III) hydroxide mineral, termed green rust. These iron oxides and clay minerals offer both a source of reduced iron in the mineral matrix as well as a surface for Fe(II) activation. Additional control experiments with corundum as a non-Fe containing mineral surface showed little NO2- loss, implicating a more dominant role of structural iron in the clays during nitrite reduction. In experiments with nontronite and green rust the isotope effects (15ε and 18ε) ranged from 3 to 16‰ for 15ε and 2 to 6‰ for 18ε. Nitrite reduction rates and 15ε values within an experimental condition were directly correlated with slower reactions having higher isotopic fractionation. The apparent 18ε was affected by oxygen atom exchange with water, which lowered the isotope effect. Although little data exist for comparison with the dual isotopes of microbial NO2- reduction, these data serve as a benchmark for evaluating the role of abiotic processes in nitrogen (N) reduction, particularly in sediment systems low in organic carbon and high in reduced iron.Engineering Sciences
41
Maharaj, Serena P. A. "Factors contributing to elevated levels of methyl and total mercury related to alteration in wetland conditions and agricultural activity (the Raisin River watershed)". Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/27884.
Testo completoAbstract (sommario):
Seasonal and spatial patterns of methyl and total mercury and nutrient concentrations were measured during 2005--2007 in the Raisin River, North-west of Cornwall, Ontario, Canada (75°44' W, 45°08' S) to determine if inputs from farming activities or altered wetlands (Newington Bog and Monkland Drain) are contributing to the contamination of the River. Water samples were analyzed using atomic fluorescence gas chromatography for methyl mercury; a Tekran 2600 mercury analyzer for total mercury; and a Lachat Nutrient Analyzer 8000 QuikChem for nitrate, ammonia, sulphate, and total phosphorus. Land features from the Ontario Ministry of Natural Resources and local precipitation data from the City of Cornwall were used. Kruskal-Wallis and Spearman statistical analyses were applied. MeHg and THg concentrations in the 5 Divisions of the Raisin River ranged from 0.03--1.02 ng L -1 and 0--7.57 ng L-1 respectively. MeHg concentrations in the peatlands were in the range of ∼0.10 to 2.29 ng L-1, with the highest observed at the Newington Bog in May 2007. Nutrient concentrations in the Raisin River were high with ammonia ranging to 263 mug L-1, nitrate to 2575 mug L -1, and total phosphorus to 162 mug L-1. The statistical analyses support a seasonal variation of MeHg and THg in the Raisin River, but not a spatial trend for MeHg, for % of THg as MeHg, THg and for the Peatland sites. Significantly positive correlations of MeHg and THg with nutrients exist. Yield data identifies the drained peatland in the headwater regions as the major source of mercury to the river with little, if any, influence of the elevated nutrient levels found along the river. Considerations of the yield data and land features suggest that agricultural activities, including runoffs and inputs from residential/community activities in upstream towns can influence nutrients and mercury levels in water systems.
42
McDonald, Lauren. "Wipe Sampling Methodologies to Assess Exposures to Metals in Urban Canadian Homes: 1 Cadmium, Lead, Yttrium 2 Antimony, Arsenic, Chromium, Copper, Nickel". Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28588.
Testo completoAbstract (sommario):
Wipe sampling is a means of monitoring exposures to contaminants which has been used extensively for assessment of lead (Pb) in housedust in the U.S. This thesis reports the first baseline wipe dataset for urban Canadian homes, for Pb and other metal(loid)s including: arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), and antimony (Sb). The literature review covers sampling methods, health effects, and sources. The digestion procedure ASTM 1644 is the accepted HNO3 hotplate protocol for determination of Pb in wipes. However in this study, HF was added to enhance extraction efficiencies for a wide range of elements. The first paper identifies baseline and elevated subpopulations for Cd and Pb using normality plots, and investigates the use of yttrium(Y) as a soil tracer. The second paper investigates application of the wipe methodology for monitoring As, Cr, Cu, Ni, Sb, and Zn. This is the first multi-element wipe sampling dataset in the literature, and will assist risk assessors and risk managers in providing guidance to Canadians about ways to reduce exposures to metals.
43
Suchy, Martin. "Nitrate and Ammonium Transformation and Fate in Groundwater of an Agricultural Watershed: An Isotope and Geochemistry Approach". Thesis, University of Ottawa (Canada), 2011. http://hdl.handle.net/10393/28922.
Testo completoAbstract (sommario):
The purpose of this study was to characterize the groundwater recharge environment and evaluate the fate and processes affecting agricultural nutrients in groundwater. This consisted of three agricultural sites and one naturally vegetated background site.
Naturally occurring stable isotopes (delta18O and delta 2H), which are sensitive to seasonality of recharge, were used in groundwater and precipitation to provide an estimate of recharge and mass loading to the aquifer. The significance of direct infiltration through cultivated corridors where corn is grown (C4 vegetation), versus naturally forested C3 vegetation, which is predominant in the headwater environment, delta 13C analysis of DIC and DOC were conducted. To assess geochemical reactions, isotopes of nitrate and ammonium (delta15N NO3, delta18ONO3 and delta15N NH4), were used to provide insights into the transformation and attenuation processes in the nitrogen cycle.
Groundwater delta18O and delta2H results indicate that recharge occurs predominantly in late fall as photosynthetic transpiration declines and in late spring following spring thaw, when vegetation is inactive. The abundance of wormholes observed in an excavated test pit, suggests macro-porosity in the sediments aids the infiltration and contributes to the rapid transmission of the meteoric signal to the water table and thus accounting for the rapid shift in trends observed in the temporal monitoring in the overburden material.
Observations of shallow groundwater suggest the presence and concentrations of NO3 and NH4 may be dependent on the type of fertilizer application. The presence and attenuation of nitrate and ammonium varied between the three agricultural sites. There was no one dominant attenuation process throughout, nor were nitrate and ammonium consistent in the unsaturated zone and groundwater. Findings indicate the urea only site has possibly longer retention of NH 4 in soil water, low concentrations of NH4 but the presence of moderately higher NO3 concentrations (up to 20 ppm-N) in shallow groundwater. The infiltration of nitrified NO3 appears to be followed by some level of denitrification, resulting in bedrock aquifer NO3 concentrations below 5 ppm-N. Observations from the agricultural site where liquid manure was the dominant fertilization method, suggest the chronic loading of NH4 in the subsurface. There is possibly less retention of NH 4 in soil water (> 20 ppm-N), resulting in the infiltration of NH 4 (2 ppm-N in piezometers), while NO3 concentrations in shallow groundwater are below detection. Lastly, the mixed application site shows the presence of both NO3 and NH4 at similar concentration in shallow groundwater, with nitrogen attenuation by dilution, denitrification and potentially anammox.
Overall, irrespective of the type of fertilization, findings suggest that reactive losses of nitrogen together with crop uptake, greatly limit the total nitrogen flux that is reaching the underlying bedrock aquifer, indicating that agricultural activities do not have an excessive adverse impact on the aquifer. While total nitrate and ammonium concentrations of nitrogen in the unsaturated zone, as sampled in the lysimeters and tile drains reached over 30 ppm-N, concentrations in groundwater were typically <10 ppm-N, and most often <0.5 ppm-N in the bedrock aquifer. The attenuation of high ammonium concentrations in soil water was attributed to plant uptake prior to recharge to the water table, with minor loss by volatilization as groundwater 15N values exhibited slight enrichment.
Geochemical and isotopic results from a couple domestic wells exhibited signs of leaking well casings/seals, thus permitting potentially contaminated surface and/or shallow groundwater to enter the well, thereby potentially impacting the groundwater resource. If the proportion of such wells is significant throughout the region, this represents a principle threat to water quality. (Abstract shortened by UMI.)
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Saulnier, Isabelle. "Trace metal remobilization following the resuspension of Saguenay Fjord sediments". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37163.pdf.
Testo completo
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Warby, Richard Ashley Frank. "The chemical response of surface waters and organic soils across the northeastern United States, following reduced inputs of acidic deposition 1984-2001 /". Related electronic resource:, 2007. http://proquest.umi.com/pqdweb?did=1342747271&sid=1&Fmt=2&clientId=3739&RQT=309&VName=PQD.
Testo completo
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Miserendino, Rebecca Adler. "Tracing mercury pollution in aquatic ecosystems| Implications for public health". Thesis, The Johns Hopkins University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3571745.
Testo completoAbstract (sommario):
This dissertation addressed questions pertaining to mercury (Hg) fate and transport in aquatic ecosystems by applying stable Hg isotopes as a tracer. Mercury poses a public health burden worldwide. In parts of the developing world, Hg-use during artisanal and small-scale gold mining (ASGM) is pointed at as the source of elevated Hg in the environment. However, Hg from other sources including soil erosion associated with land cover and land-use change (LCLUC) may also contribute to local Hg pollution.
Stable Hg isotope profiles of sediment cores, surface sediments, and soils from two aquatic ecosystems in Amapá, Brazil, one downstream artisanal gold mining (AGM) and one isolated from AGM were assessed. Although previous studies attributed elevated environmental Hg levels in this area to AGM, stable Hg isotopic evidence suggests elevated Hg downstream of AGM sites is dominantly from erosion of soils due to LCLUC.
In contrast, the impact of Hg-use during small-scale gold mining (SGM) in the Southern Andean Region of Portovelo-Zaruma, Ecuador on Hg in the trans-boundary Puyango-Tumbes River was also investigated. By comparing preliminary isotopic Hg signatures from river sediment along the Puyango-Tumbes to soil and sediment from upstream locations along the Puyango tributaries, we suggest Hg-use during SGM in this region is likely responsible for elevated Hg downstream and into Peru. Technical and policy challenges in measuring and responding to gold mining-related cumulative impacts were also reviewed in the context of Portovelo-Ecuador.
Together, the findings not only answer questions of critical importance to preventing Hg pollution in two of the world's most vulnerable ecosystems but also provide information that can be used to better target interventions to reduce environmental Hg levels and subsequent human exposures. Furthermore, the validation and application of the stable Hg isotope method to trace Hg pollution from ASGM in different aquatic ecosystems represents a critical step to the application of stable Hg isotopes to trace pollution in other complex natural environments and to address public health-related questions.
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Nowosielski, B. E. (Bogdan E. ). "Experimental study of octanol-water partition coefficients for 2,4,6-trichlorophenol and pentachlorophenol : derivation of an empirical model of chlorophenol partitioning behaviour". Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20601.
Testo completoAbstract (sommario):
The octanol-water partition coefficients (log Kow) of 2,4,6-trichlorophenol and pentachlorophenol were determined as functions of pH, ionic strength, and aqueous metal content. For both chlorophenols, the log Kow exhibits pH dependence in the range pKa-1 < pH < pK a+2. At lower and higher pH values, the Kow behaviour of the chlorophenols is independent of pH. Our data, in conjunction with those of Westall et al. (1985), indicate that a linear relationship exists Our data, in conjunction with those of Westall et al. (1985), indicate that a linear relationship exists between log Kow and log ionic strength of the aqueous solution for pentachlorophenol. Our results r results also suggest that aqueous metal-chlorophenol ate complexation can significantly alter the also suggest that aqueous metal-chlorophenolate complexation can significantly alter the partitioning behaviour.We use our data to develop an empirical model of the partitioning behaviour based on speciation of the aqueous chlorophenol. The model requires knowledge of the low pH partitioning behaviour, as well as the acidity constant (pK a) of the chlorophenol of interest. Although Kow values have been measured as a function of pH and/or ionic strength for only pentachlorophenol, the input parameters for the empirical model are readily available in the literature for many chlorophenols. The model greatly expands our ability to quantify the hydrophobicity of chlorophenols, facilitating accurate estimations of the pH and ionic strength dependencies of the partitioning behaviour over a wide range of pH and ionic strength values of environmental interest.
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Bono, Andrew B. "The partitioning of mercury among the solid components of sediments of the Saguenay Fjord, Québec /". Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27287.
Testo completoAbstract (sommario):
An estimated 60 tonnes of mercury, released from a chlor-alkali plant between 1947 and 1976, are buried in the sediments of the Saguenay Fjord. Despite rapid sedimentation rates, concentrations of Hg in surficial sediments remain well above preindustrial levels. The partitioning of Hg among sedimentary solids was investigated to elucidate the fate of buried mercury and determine the source of contamination in surficial sediments.Box cores from two stations along the axis of the Saguenay Fjord (SAG-6B, SAG-30B) and one from the Laurentian Trough (CL-1B) were collected in June, 1992. A sequential extraction protocol modified from existing techniques was tailored to evaluate the distribution of mercury among four operationally defined chemical fractions in Saguenay Fjord sediments: organic matter (C$ sb{ rm org}$), iron and manganese (hydr)oxides, acid-volatile-sulphides (AVS), and pyrite.
This study provides new insight into the chemical pathways and fate of mercury within the Saguenay system, and contributes to a greater understanding of the geochemical behaviour of inorganic mercury in natural systems. Additionally, modifications made to the sequential extraction protocol may be applied and facilitate future studies of mercury partitioning in other systems. (Abstract shortened by UMI.)
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Boiridy, Mia Ingrid. "Potential chemical remediation of mercury in recently impounded reservoirs". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27286.
Testo completoAbstract (sommario):
Several mitigation procedures have been proposed to limit the transfer of Hg and MeHg to aquatic organisms but most cannot be applied to large reservoirs such as those of northern Quebec for practical, economical, and environmental reasons. A better understanding of the diagenetic behaviour of Hg and methylmercury in aquatic environments has lead us to consider methods of enhancing natural processes which would either limit the mobility of Hg in flooded soils or its methylation. Different concentrations of iron oxide, iron shavings and ferrous ammonium sulphate were added to soil slurries in the presence or absence of calcite and gypsum. Mercury released to the supenatent solutions and methylmercury adsorbed to the slurry solids were monitored with time to determine the trapping efficiency of the different chemical additives under both reducing and oxygenated conditions. Whereas all three reagents limited the release of Hg(2+) to the supernatent solution when reducing conditions were allowed to develop in the slurries, ferrous ammonium sulphate appeared to be the most effective at limiting Hg methylation. (Abstract shortened by UMI.)
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Mohajerin, Haug Tahmineh Jade. "Tungsten speciation, mobilization, and sequestration|Thiotungstate stability constants and examination of (thio)tungstate geochemistry in estuarine waters and sediments". Thesis, Tulane University School of Science and Engineering, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3680830.
Testo completoAbstract (sommario):
This dissertation combines laboratory experiments and analysis of field samples to examine tungsten (W) geochemistry. Data from low ionic strength experimental solutions at room temperature containing between 0.01 M to 0.0002 M total sulfide and 0.0027 M - 0.0001 M tungstate were analyzed using UV/VIS spectrophotometry. Stability constants have been determined for the formation of mono-thiotungstate log K01= 3.43 ± 0.61, di-thiotungstate log K12 = 3.02 ± 0.61, tri-thiotungstate log K23 = 2.82 ± 0.02, and we estimated the tetra-thiotungstate log K34 ~ 2.34. Analysis of W, Mo, Mn, and Fe concentrations in estuarine surface and pore waters and sediments captured environmental samples from oxic and sulfidic conditions. Both surface waters and sediments demonstrated a positive correlation between W and Fe. Unlike Mo, which was depleted in sulfidic salt marsh pore waters, W was enriched in all pore waters in comparison to overlying waters. Thermodynamic modeling of W and Mo thioanion species in sulfidic pore water samples predicts ≤ 50% of tungstate (WO4 2-) forms thiotungstate species and complete conversion of molybdate (MoO42-) to tetrathiomolybdate (oO4 2-). Unlike tetrathiomolydate that is known to be more particle reactive than molybdate, increases in dissolved W coincide with increases in dissolved sulfide in pore waters, suggesting thiotungstates are less particle reactive than thiomolybdates at circum-neutral pH. Finally, sediment analysis suggests sequestration of W is dependent on surface water salinity in the intermediate marsh sediments, and long-term W entrapment occurs in sulfidic salt marsh sediments.