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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Quantitative risk assessment of groundwater quality utilizing GIS technology and coupled groundwater models

Oladeji, Olayinka January 2012 (has links)
The thesis presents a two-dimensional Risk Assessment Method (RAM) where the assessment of risk to the groundwater resources incorporates both the quantification of the probability of the occurrence of contaminant source terms, as well as the assessment of the resultant impacts. The approach emphasizes the need for a greater dependency on the potential pollution sources, rather than the traditional approach where assessment is based mainly on the intrinsic geo-hydrologic parameters. The risk is calculated using Monte Carlo simulation methods whereby random pollution events were generated to the same distribution as historically occurring events or a priori potential probability distribution. Integrated mathematical models then simulate contaminant concentrations at the predefined monitoring points within the aquifer. The spatial and temporal distributions of the concentrations were calculated from repeated realisations, and the number of times when a user defined concentration magnitude was exceeded is quantified as a risk. The method was setup by integrating MODFLOW-2000, MT3DMS and a FORTRAN coded risk model, and automated, using a DOS batch processing file. GIS software was employed in producing the input files and for the presentation of the results. The functionalities of the method, as well as its sensitivities to the model grid sizes, contaminant loading rates, length of stress periods, and the historical frequencies of occurrence of pollution events were evaluated using hypothetical scenarios and a case study. Chloride-related pollution sources were compiled and used as indicative potential contaminant sources for the case study. At any active model cell, if a random generated number is less than the probability of pollution occurrence, then the risk model will generate synthetic contaminant source term as an input into the transport model. The results of the applications of the method are presented in the form of tables, graphs and spatial maps. Varying the model grid sizes indicates no significant effects on the simulated groundwater head. The simulated frequency of daily occurrence of pollution incidents is also independent of the model dimensions. However, the simulated total contaminant mass generated within the aquifer, and the associated volumetric numerical error appear to increase with the increasing grid sizes. Also, the migration of contaminant plume advances faster with the coarse grid sizes as compared to the finer grid sizes. The number of daily contaminant source terms generated and consequently the total mass of contaminant within the aquifer increases in a non linear proportion to the increasing frequency of occurrence of pollution events. The risk of pollution from a number of sources all occurring by chance together was evaluated, and quantitatively presented as risk maps. This capability to combine the risk to a groundwater feature from numerous potential sources of pollution proved to be a great asset to the method, and a large benefit over the contemporary risk and vulnerability methods.
12

The characterisation of dissolved organic carbon and its influence on tri-halomethane formation potential

Hughes, David Davenport January 2013 (has links)
Dissolved organic matter is best described as a mixture of soluble organic molecular structures derived principally from the degradation of plant matter by natural processes that occur in mineral and organic soils. The water industry currently utilise water catchments that are predominantly lowland or upland wetlands. These generally consist of bogs and fens that are currently under threat from changes in the global weather systems which pose a threat to the natural carbon cycling of these eco-systems. Dissolved organic carbon (DOC) when disinfected during water processing reacts to fOlm a series of disinfectant by products (DBPs) which have been repOlied to be detrimental to human health. With the threatened destabilisation of the water industry's water catchments, this thesis examines the character of the DOC being received into four lakes/reservoirs and attempts to establish what aspects or DOC characteristic relates to its reactivity when it is chlorinated with HOC!. The series of samples were collected on a 30 day cycle for 24 months with every third month's samples being fractioned using DAX 8 and XAD 4 resins and an in-house designed and built instrument. The samples were characterised using a number of established literature methods and the tri-halomethane potential (THMFP) was determined by Gas Chromatography/Electron Capture Detection and Solid Phase Micro Extraction. Analysis of the samples highlighted differences in the DOC concentrations of the lakes over the seasons and the influences of dry, wet and cold periods upon the characteristics and concentration of the DOe. The results identified the lowland Cefni lake as the most responsive to environmental influences, but it had the lowest THMFP. The highest was exhibited by the upland Conwy lake DOC which also demonstrated the least response to external environmental influences. The dry/wet event investigated illustrated the differences between mineral and peat catchments, demonstrating rapid increases and decreases in DOC concentrations in the Mineral streams with relatively slower responses in the Peat stream. Although the upland Peat DOC peak concentration was higher than that of the upland Mineral, it was the upland Mineral that demonstrated the highest THMFP/mg ofDOC. Overall the results have indicated that the THMFP is independent of DOC concentration and that there is no single inference that controls their formation, but is a combination of a number of factors with ring substitution being the foremost influence.
13

The sonochemical remediation of phthalate esters : an investigation into products and kinetics

VandenBurg, Daniel Martin January 2012 (has links)
Phthalate esters or phthalates have become ubiquitous water pollutants. They are used as plasticisers in several plastics. Due to them not being bound to the plastic material they leach out over time. Thus phthalate esters have entered the planet’s aquasphere. Phthalates are stable in the environment and also recalcitrant to most standard water processing methods. Due to their being linked to endocrine disruption and cancer they have been classed as a pollutant of concern by the EU and the American EPA. Previous work had shown that ultrasound of frequency between 20 kHz and 500 kHz can be used to remove phthalate esters from aqueous solutions as an advanced oxidation process. These works studied the effects of various parameters on the sonolysis. They however, did not perform a satisfactory analysis of the degradation products of the esters studied. These too may be biologically active and need to be ascertained for ultrasound to be considered for their removal from water in industrial and municipal processing centres. Therefore this work describes the study of additional parameters known to be pertinent to ultrasound science, namely the acoustic power, the type of gas dissolved in the solution and the initial concentration of phthalate on the sonolysis of DBP as a model for the family of phthalate esters. Work was performed using 20 kHz and 515 kHz ultrasound. The performance of these two systems is compared and contrasted throughout. A detailed analysis of the products of the degradation of DBP was then performed using LC-MS based methods. Finally the degradation of other alkyl phthalates was examined as well as the effect of DBP on the quenching of aqueous sonoluminescence. This last topic was performed hoping it would give some insight into the way DBP partitions in the bubble-water interface.
14

Determination of tributyltin environmental contamination and Kd partition coefficients in sediments using a HPLC analytical method

Doherty, David January 2009 (has links)
Tributyltin (TBT) was used as an anti-fouling paint and applied to the hulls of ships in order to prevent buildup of organisms. Major shipping routes are now contaminated with TBT due to the chemical's persistence In the environment. The use of TBT as an anti-fouling paint was banned in the 1980's due to scientific findings that the chemical causes toxic effects in aquatic life. TBT is widely known as a gender-bending chemical due to its endocrine disrupting properties. There are concerns that TBT may also present health problems for humans, and is classed as a Persistent Organic Pollutant (POP). The disposal of sediments contaminated with TBT presents a problem, as disposal to sea will cause unacceptable pollution of the environment. An Integrated pollution control strategy is needed for disposing of dredged sediments in a manner which is cost-effective and sustainable.
15

Prediction of element speciation in sediments from Sulaibikhat bay, Kuwait

Alshemmari, Hassan January 2009 (has links)
Surface sediment samples were collected from 35 locations in Sulaibikhat Bay, Kuwait. Eleven core samples were also taken. As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn concentrations were determined and, with the exceptions of As and Hg, element speciation was studied, using the BCR sequential extraction procedure. This allows the fractionation of trace elements into four phases, namely; exchangeable, reducible, oxidizable and residual. Grain sizes, TOC, carbonate, mineralogical and environmental data were also determined. The abundance of the elements, their geographical distribution, and their relationships with each other and with sediment and environmental parameters are described with reference to sediment quality guidelines and the index of geoaccumulation (Igeo). Multivariate statistical analyses have allowed the most important factors in retaining trace elements in sediments to be identified and quantified.
16

Marine environmental monitoring of a ship-based seawater scrubber system

Swift, Clare January 2009 (has links)
The shipping industry is becoming increasingly visible on the global environmental agenda as air emissions from vessels make an increasingly conspicuous contribution to air quality. With the forecast expansion of world trade; scientists are estimating global emissions to increase by 30% to 1.45 billion tonnes in the next decade. This would make shipping responsible for 6% of global emissions by 2020. The International Marine Organisation (IMO) Annex VI entered into force in 2005 and is currently the most important international treaty governing emissions to air from ocean going vessels. It has set strict limits on sulphur dioxide (SO2) and nitrogen oxide (NOx) emissions from ship exhausts, prohibits the deliberate emissions of ozone depleting substances, and places a global cap on the sulphur content of marine fiiel. As an alternative to using low sulphur fliel oils, ships have the option to fit an exhaust gas cleaning system such as a seawater scrubber (SWS) or to use any other feasible technology to limit SO2 emissions. SWS transfers SOx (ca. 95%) and partly NOx (ca. 20%) into aqueous solution, producing acidic solutions which are then buffered with seawater and finally discharged into the sea.
17

Nutrient and dissolved organic matter biogeochemistry in three UK estuaries : the Tyne, Tamar and the Humber

Anestis, Anastasios K. January 2008 (has links)
The distribution and cycling of dissolved organic carbon and nitrogen (DOC and DON), inorganic nitrogen and PO₄³- was investigated in the water column and in sediment porewaters of three UK estuaries; the Tyne (9 transect) and Humber (I transect).
18

Biomonitoring of pollution in harbours when multiple pollutants are present

Selley, Hazel A. January 2006 (has links)
This study compared the use of biomarkers to assess sub-lethal effects of pollutants alongside a standard toxicity test and sediment analysis within a harbour environment predominantly affected by TBT and PAHs, in Aberdeen, NE Scotland. Analysis of sediment sampled twice yearly showed few clear trends for metals, TBT or PAHs over a 8 year period from 1997-2005. At one sample site, (29) PAHs were seen to increase during the study period. This could potentially be linked to the Denburn storm overflow, which can release untreated waste water during periods of prolonged heavy rain. Levels of contamination were highest at sample sites located within the inner harbour, sites where sediment would accumulate and tidal flushing would be less effective at redistributing contaminants. The Corophium bioassay was used to assess temporal and spatial variation in the toxicity of harbour sediment. Significant differences were seen between sample sites located in the inner harbour areas and control sediment. In most cases, mortality did not correlate to any one individual contaminant, however when mortality was relatively low, correlations were seen with heavy metals such as Pb, Cd and Cr. A seasonal fluctuation in toxicity was evident at sample site 29, which could relate to seasonal fluctuations in water quality due to the Denburn overflow, since metals such as zinc also followed a seasonal fluctuation. By 2005, no sample sites showed a significant increase in mortality when compared to controls. At 7 sample sites, a significant improvement in Corophium survival was seen during the study period, which strongly suggests that bioavailable levels of contaminants are decreasing. Intersex in <i>L. littorea</i> was assessed on an annual basis to monitor the effects of TBT within the harbour. Again, a significant difference was found between the inner harbour and a control site, whilst intersex levels in the outer harbour area were comparable to the control site. At the inner harbour site, levels of intersex were sufficient to reduce reproductive capability individual periwinkles, but would not affect reproduction rates at the population level. Intersex ISI values suggest that water within Aberdeen harbour does not yet meet the UK EOS of 2 ngl<sup>-1</sup>. Again, a decrease in the degree of intersex was seen during the study period, this was not statistically significant, yet may indicate that the level of bioavailability pollutants is decreasing.
19

Aquatic toxicity and environmental impact of landfill leachate

Langler, Glenn J. January 2004 (has links)
No description available.
20

Responses of the decapod crustacean, Carcinus maenas, following exposure to environmental contaminants : development and application of multiple biomarkers

Watson, Giles Marcus January 2004 (has links)
Marine, coastal and estuarine ecosystems continue to be contaminated by anthropogenic chemicals. Improving our mechanistic understanding of the toxicity of environmental pollutants to aquatic organisms is therefore an important priority. This work is focussed on detecting and measuring the molecular, cellular and physiological responses of the shore crab Carcimis maenas following exposure to environmental chemicals, and uses biomarkers to do so. To better understand the response of C.maenas to polycyclic aromatic hydrocarbons (PAHs) a novel biomarker of exposure to this class of compounds was developed. Direct fluorimetric techniques revealed that the shore crab C.maenas eliminated metabolites of pyrene in the urine following waterbome exposure to this PAH in the laboratory. The levels of excreted metabolites were exposure concentration and time dependent. Levels of pyrene metabolites were also detected in the haemolymph and their levels were exposure concentration dependent. HPLC/F analysis of urine samples revealed metabolites were conjugates of 1-OH pyrene. Levels in urine determined by fluorimetry correlated well with HPLC/F and ELISA methods of analysis. Levels in haemolymph did not correlate well with the ELISA, due to sample matrix interference with the assay. Detection of urinary PAH metabolites following laboratory exposure is evidence that the parent PAH has been taken up, metabolised by the enzymatic machinery of the organism and eliminated. Whilst this is an important finding and illustrates the response of Cmaenas when faced with PAH exposure, confirmation of this phenomenon in the field is also required. Field trials revealed that comparable metabolites were eliminated in the urine following exposure to pyrogenic PAH discharges from a Norwegian aluminium smelter. The assay also provided evidence of exposure to petrogenic PAH in crabs from petroleum contaminated field sites and crabs exposed to crude oil. Both laboratory and field studies illustrated the potential for this exposure biomarker to be used for environmental monitoring. The responses of C.maenas following exposure to combinations of PAH, metal and pesticide were measured using biomarkers of exposure and effect. Increasing the number of contaminants did not affect the responses of certain biomarkers (metallothionein, micronucleus, antioxidant activity), which were not induced or remained largely unchanged. These biomarkers also showed no significant differences between exposed and control groups. Specific biomarkers of exposure (urinary PAH assay) and effect (carboxylesterase activity) responded in a concentration dependent manner when exposed to PAH and pesticide, but the level of their response was not altered upon addition of further contaminants at each concentration. The lack of induction or alterations in biomarker responses unfortunately provides little additional information on the complex mechanisms of toxicity in organisms following exposure to these contaminants. Shnilarly, investigations into the effects of environmental chemicals on endocrine mediated processes in C.maenas did not provide conclusive information on mechanisms of endocrine toxicity. Exposure to 20-hydroxyecdysone and its insecticidal analogue tebufenozide had no gross effects on the processes investigated in C.maenas (moulting, vitellogensis and locomotor activity) and consequently, no suitable endpoints were established as markers of endocrine disruption in this species. The quantitative Vg ELISA proved to be applicable for monitoring potential endocrine disruption in female C.maenas, but only after the temporal progression of vitellogenesis is understood. The present work has investigated and measured the responses of C.maenas following exposure to exogenous chemicals. This has resulted in a better understanding of PAH disposition, a field applicable PAH exposure biomarker and evidence for robust responses following exposure to multiple contaminants. It has also highlighted the need for greater understanding of endocrine mediated processes before endocrine disruption can be confirmed as a realistic mechanism of toxicity in this species.

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