The continuing need for improved assessment of risk from heavy metal contamination of the environment has prompted scientific interest in quantifying and predicting metal solubility, ‘lability’ and bioavailability. This has led to the development of new techniques to fractionate and speciate trace metals in soils. The objectives of the current study were to increase understanding of the effects of (i) soil properties, (ii) contaminant source and (iii) contact time on metal lability and solubility in soils. Multi-stable isotope dilution (ID) methods were used to determine the lability (E-values) of Ni, Cu, Zn, Cd and Pb in soils, alongside more traditional approaches employed for metal fractionation including single and sequential extraction procedures. Most of the work was undertaken using (i) archived soils amended by metal salts (MA soils; n=23) and (ii) topsoils collected from Nottingham, Wolverhampton and London (Urban soils; n=100). The resulting data was used first to quantify the factors affecting trace metal lability in the MA soils using a logistic (S-shape) model which described metal E-value primarily as a function of soil pH with secondary influences from other soil properties. It was apparent that mineral oxides were important fixation phases for Ni, Zn and Cd while Pb was strongly affected by organic matter in soils. This model, parameterised on soils contaminated originally by metal nitrate solution, was then applied to the Urban soils to reveal the extent to which contaminant source still controlled metal lability. A further investigation of the long-term effect of metal source on metal lability was pursued through a third dataset of rural roadside soils (n=42) which had received Pb mainly from petrol-derived and geogenic sources, defined by their isotopic signature. It was demonstrated that petrol-derived Pb remained more labile than Pb from the parent material, despite decades of contact, although both petrol-derived and geogenic Pb contributed to both the labile and non-labile fractions. In a fourth dataset, soils that had received Pb from sewage sludge amendment (n=16), the co-existence of high phosphate concentration from sewage sludge limited the magnitude and range of Pb lability, probably through formation of Pb-phosphate minerals. No consistent agreement was found between labile fraction of Pb and any single sequential extraction (SEP) fraction in all soils contaminated by Pb from multiple sources. Both empirical equations (extended Freundlich) and mechanistic models (WHAM-VII) were used to predict metal solubility in the MA and Urban soils. The advantage of using E-values (ME) over metal extractable by dilute nitric acid (MExt) to represent the reactive metal fraction in predictions of solubility was very clear for WHAM-VII, but not for the ‘locally parameterised’ Freundlich model. This was almost certainly due to the strong links between pH and E-value becoming subsumed into the coefficient nominally describing the direct influence of pH on metal solubility in the extended Freundlich equation. However, overestimation of the solution concentration from WHAM-VII was observed for all five metals, and strongly correlated with soil pH. Fractionation information from WHAM suggested that the source of the model’s underestimation of metal binding most likely lay with errors in the description of metal binding by Fe and Mn oxides for Ni, Zn and Cd and humic acid (HA) for Cu. An additional factor is the absence of potential binding phases in the WHAM model, such as particulate CaCO3, and the greater diversity of active adsorbents in soils at high pH values. WHAM is based on the assumption that all metal bound to HA is labile. However, in the current study, ‘non-labile’ Cu, Zn and Pb fractions were observed in suspensions of HA extracted from grassland and peat soils. These were quantified by measuring metal E-values and EDTA-extraction of HA-bound metal using size-exclusion chromatography (SEC) coupled to ICP-MS to separate free and HA-complexed metal forms. Evidence of time-dependent metal fixation by HA was found for all three metals during the course of a 40 and 160 day incubation study. The proportion of non-labile Cu held by HA could be 40-50%. The presence of a non-labile metal fraction held by HA may substantially invalidate the assumption of reversible equilibrium which is central to all current geochemical models of metal binding to humic substances.

Climate change is a consequence of changing in climate on environment over the worldwide. The increase in developmental activities and Greenhouse Gases (GHGS) put a strain on environment, resulting in increased use of fuel resources. The consequence of such an emission to the atmosphere exacerbates climate pattern. There are numerous Climate Change Downscaling studies in coarse resolution, which have largely centred on employing the dynamic approaches, and in most of these investigations, the Regional Climate Model (RCM) has been reported to numerically predict the local climatic variables. The majority of previous investigations have failed to account for the spatial watershed scale, which could generate an average value of downscaled variables over the watershed scale. To address shortcomings of previous investigations, the work undertaken in this project has two main objectives. The study first aims to implement a spatially distributed Statistical Downscaling Model (SDSM) to downscale the predictands, and second to evaluate the impact of climate changes on the future discharge and peak flow. It is conducted based on the IPCC Scenarios A2 (Medium–High Emission scenario) and B2 (Medium–Low Emission scenario). The main objectives of the study are as follows: • To generate fine resolution climate change scenarios using Statistical Downscaling Model in the watershed scale, • To project the variability in temperature, precipitation and evaporation for the three time slices, 2020s (2010 to 2039), 2050s (2040 to 2069) and 2080s (2070 to 2099), based on A2 and B2 scenarios, • To calibrate and validate hydrological model using historical observed flow data to verify the performance of the hydrological model, • To evaluate the impact of climate changes on the future discharge and future peak flow for three timeslices: 2020s (2010 to 2039), 2050s (2040 to 2069) and 2080s (2070 to 2099). Thus, to meet the objectives of the study, projection of the future climate based on climate change scenarios from IPCC is carried out as the most important component in the research. The results of this research are presented as follows: • The study indicates that there will be an increase of mean monthly precipitation but with an intensified decrease in the number of consecutive wet-days and can be concluded as a possibility of more precipitation amount in fewer days. • The watershed is found to experience increased rainfall towards the end of the century. However, the analysis indicates that there will likely be a negative trend of mean precipitation in 2020s and with no difference in 2050s. The precipitation experiences a mean annual decrease by 7.9%, 0.6% in 2020s and 2050s and an increase by 12.4% in 2080s corresponding A2 scenario. • The maximum and minimum temperatures are likely to be increased toward the end of the century by 2.7oC and 0.8oC respectively when compared to the current observed temperature (1975-2001) at the Subang temperature station. • The average annual mean discharge is predicted to be decreasing by 9.4%, 4.9% and an increase of 3.4% for the A2 and a decrease of 17.3%, 13.6% and 5.1% for the B2 scenario, respectively in the 2020s, 2050s and 2080s. • The average annual maximum discharge is projected to decrease by 7.7% in 2020s and an increase by 4.2% and 29% in A2 scenario for 2050s and 2080s, respectively. But there will most likely be a decrease in the maximum discharge for all the future under B2 scenario. It is projected a decrease of 32.3%, 19.5% and 2.3% for 2020s, 2050s and 2080s, respectively. • The projected mean discharge indicates a decline in the months from January to April and also from July to August in all the three future periods for A2 and B2 scenarios. There is an increasing trend in the discharge of September and October in the 2020s according to the A2 and B2 scenarios. • The highest increase in precipitation frequency occurs in 2080s under A2 scenario in which the increase in the magnitude of 100 Return Year is found to be 88% greater than the one of the maximum observed. • The highest increase in flood frequency at Sulaiman streamflow station occurs in 2080s under A2 scenario. The increase in the magnitude of 100 Return Year is found to be 26.5% greater than the one of the maximum observed.

No description available.

Dust from mining activities is produced from several unit operations and is often a serious problem to the industry, due to the influence it can have on human health and the safety record and productivity of a mine. So far, legislative parties and the industry have approached dust as an issue that needs to be controlled, only when a mining operation or process generates undesirable particulates. Nevertheless, new legislation and standards, such as the EU IPPC directive (Integrated Pollution Prevention and Control) and air quality strategies aim to drive mining companies to incorporate dust assessment planning that will be implemented through the whole life cycle of the mine. Mitigation and monitoring practices as well as health surveillance programs will need to be clearly defined. This project’s purpose is to understand how mining processes and in particular how the mechanisms inherent within common unit operations (i.e transfer processes using haulage roads or conveyor belts, the tipping, loading and stockpiling process, the screening process etc) result in the generation of dust. If the operation of unit operations could by optimized to produce less dust, then a “fit-for-purpose” strategy for dust minimisation could be developed to follow exploitation, processing and production demand. The literature on dust from mining operations identified that generation of fines/dust occurs due to the presence of the mechanisms of abrasion and impact. Based on this logic, an experimental methodology was developed, which aimed to assess how dust was generated for each different mechanism and for a variety of ores of different mineralogy. Five different ores were tested, a limestone, talc, an iron ore, a lamproite and a copper ore and the same experimental methodology was followed for each. Experimentation using the HSE-WSL tumbling mill test determined that under the effect of abrasion, ores yielded higher dustiness values during longer tumbling times, whilst parameters such as the sample mass and the particle size distribution of the feed sample could also influence the dust generation patterns. The findings of the computational modelling (discreet element modelling) and experimentation (high speed video recording) suggested that control and optimisation of operational parameters (e.g mill velocity, or tumbling time) within processes that involve abrasion, such as the use of conveyor belts, mills, and screens could minimise the potential of dust generation by this mechanism. The use of a novel impact test determined a positive relationship between the energy input and the particle size distributions of the broken particles, as well as the accumulation of fine particulates in the range of dust (<75μm). Also an increase in the bulk volume of ores resulted in larger quantities of fine particulates. These observations suggest that it is possible to reduce dust in processes that involve drop from heights and impaction (i.e transfer points in conveyor belts, tipping, loading) by adjusting the energy input and the bulk volume of ore at impact to as low a level possible. Particle size analysis of the produced dust fractions were found to be material dependent and varied considerably for the different ores. Almost all materials produced significant amounts of ultra fine particles below 10μm and 2.5μm, both under impact and abrasion, which reveals the potential adverse impacts to the environment and human health. Quantitative mineralogical analysis using the mineral liberation analyser determined that the dust fraction presents a different composition to that of the ore. Comparison of the results collected for the five different ores using the HSE-WSL mill and the impact test identified that certain materials yielded high dust levels under abrasion and low under impact. Therefore it would be expected that dust control approaches for such materials would differ according to the mechanisms of the involved process and the mineralogy of the sample. According to the findings of this study a reduction in dust produced from mining unit operations could be possible by optimising the involved processes either by altering their operating parameters (drop height during tipping, velocity of conveyor belt) or by optimising the design of processes so as to reduce abrasion or impact. New legislation such as the EU IPPC directive has already started considering such an approach as important, and newly developed Best Available Techniques documents refer to this as the primary step companies should follow to minimise dust. Additional advantages of this approach are that it can reduce cost for dust control by making use of less conventional mitigation practices, and in the long term it could also minimise the utilization of energy and water going to suppression, extraction and dust collection systems. In certain cases the proposed route could also optimise the production chain, especially where the generation of fines is undesirable (e.g iron ore processing or aggregates production).

Results are presented from sets of field and laboratory experiments conducted to measure and quantify the Hydraulic Residence Time Distribution in treatment ponds containing vegetation. The field measurements were taken in the Lyby field pond (Sweden) with complementary experiments on a distorted, laboratory scale model pond designed and built in the University of Warwick’s engineering laboratory. Rhodamine WT Dye tracer experiments were used in both the Lyby field pond and the distorted physical scale model to investigate vegetation and discharge affects on HRTD characteristics and the technique of PIV (Particle Image Velocimetry) was used in the distorted physical scale model to investigate how surface flow profiles were affected by different vegetation and discharge configurations. The results show that the distorted physical scale pond did not reflect the HRTD characteristics of the field site, with the actual residence time, (tm), for the distorted physical scale pond ranging from 85 % to 125% of its nominal residence time. For the distorted scale model, pond vegetation and discharge did not affect the relative HRTD centroid, em, or the actual residence time, tm. This finding is attributed to the unique pond geography and associated aspect ratios However, flow rates did have a significant effect on the HRTD e0 (time of first dye arrival at the outlet) and ep (time of peak dye concentration). Changes in vegetation were found to have little effect on e0 and ep. For the laboratory pond, vegetation had a significant control on the surface flow field whereas, flow rates did not – the latter suggests that surface flow fields are not representative of the internal flow field in different layers of the pond. The experiments demonstrate that the specific shape of the distorted physical scale pond in this study enables optimal actual resident times to be achieved over a wide range of vegetation and flow rate configurations. If full scale field ponds based upon this design give the same stable centroid results, then this would be a substantial breakthrough in pond design, which would aid the design and management of pond treatment and allow more robust optimisation of treatment efficiency.

The performance and sustainability of ground source heat systems is dependent on the thermal behaviour of neighbouring ground. This thesis describes a comprehensive experimental and numerical investigation into the ground behaviour in response to horizontal ground source heat systems. Experimental investigations comprised of a field-scale monitoring scheme, designed and implemented in a horizontal ground source heat system providing space heating to a domestic property located in Mid-Wales, UK. A high resolution ground temperature data-set has been compiled over a 13 month period via 112 thermistors buried in the ground. Further data-sets representing the climatic variables and heat pump behaviour were also compiled over the same period, facilitating a thorough investigation of the ground behaviour in response to heat extraction at the site. Soil properties were also measured at the site as part of a larger site investigation undertaken. The numerical model applied is a coupled thermal-hydraulic (TH) model previously developed at the Geoenvironmental Research Centre (GRC). The GRC’s current model was extended to include developed boundary conditions for the TH simulation of horizontal ground source heat systems, describing the soil’s interaction with the ground-loop and atmosphere. Developments were subject to rigorous validation including comparisons with ground-data collected at the experimental site. The validated model was applied to investigate the long-term ground behaviour at the monitoring site and the effects of different surface materials on the ground behaviour including the recharge process. Finally, the model was applied to investigate the validity of an existing design code for ground source heat system design. The resolution and duration of the collated data-set facilitated extensive analysis, including a thorough investigation of the ground thermal distributions resulting from heat extraction and recharge. Findings indicated unsymmetrical distributions, highlighting potential avenues for system optimisation. Further to this it can be said that the data-set, in its own right, is a significant contribution to the scientific community and is able to provide a means of validation for future models. Results from the numerical investigation indicated that the ground thermal behaviour exhibits an annual cyclic pattern after approximately 3 years. From a holistic perspective, the results demonstrate that horizontal ground source heat systems can provide a sustainable means of providing space heating. Further long-term studies investigating the effects of surface materials show that more thermal energy can be sustainably extracted from systems with urban surface types (i.e. asphalt and brick). Investigations into an existing design code revealed that a ground-loop designed to meet the loads of the monitoring site resulted in unsustainable heat extraction, in doing so demonstrating the simplification of ground-loop burial depth within the current design process. Knowledge regarding the ground response to horizontal ground source heat systems has been furthered through the collection and analysis of field-scale data within this study. Further to this, the boundary developments and validation undertaken have allowed for a more thorough investigation of the long-term ground behaviour than previous studies.

The destruction of Direct-Red #79 textile dye in dilute aqueous solution was demonstrated by heterogeneous solar photocatalysis over suspended titanium dioxide. Dye oxidation and adsorption mechanisms, TiO2 photocatalysis, and external oxidant (H2O2) addition are discussed. Experimental data are presented which support previous studies reporting first order destruction of organic contaminants using recirculating batch reactor systems. The observance of optimum catalyst concentration, and reaction rate conformance to the Langmuir-Hinshelwood kinetic model were similar to results obtained by others. Dye destruction by free radicals was investigated. Evidence suggesting involvement of these processes is proposed by relating the rate of dye destruction to solution pH and alkalinity levels. Enhancement of dye destruction rate upon hydrogen peroxide addition was examined. Results of total organic carbon analyses, spectrophotometric absorbance measurements, and molecular weight estimations suggested the formation of reaction intermediates and indicated the extent of dye oxidation.

To investigate the effect of fluid shear on uptake rates of low diffusivity macromolecular substrates by suspended cultures, I measured the radiolabel and oxygen uptake of two model compounds, bovine serum albumin and dextran, in pure cultures of Zoogloea ramigera and E. coli, respectively. Oxygen utilization rates of stirred samples grown on BSA and dextran were 2.3 and 2.9 times higher, respectively, than undisturbed (still) samples. Uptake rates of (3H) BSA and (3H) dextran by stirred samples were 12.6 and 6.2 times higher, respectively, than still samples. These experimentally obtained increases are larger than increases predicted using a mass transfer model. The mass transfer model predicts uptake rate will increase by a factor of 1.6 and 1.8 for BSA and dextran, respectively, as a result of stirring. Uptake rates of low-molecular-weight substrates with high diffusivities, such as leucine and glucose, were only slightly affected by fluid shear. Since macromolecules can comprise a major portion of bacterial substrate in engineered, laboratory, and natural systems, the demonstrated effect of fluid shear has wide implications for the evaluation of engineered bioreactors used for wastewater treatment as well as for kinetic studies performed in basic metabolic research.

Disposable diapers are a possible source of infectious enteric viruses that are disposed of in landfills. A total of 210 disposable diapers were collected from seven sites and ten depths at three landfills. Of these total, 110 diapers were processed with a 1.5% beef-extract-elution organic-flocculation-concentration method to recover viruses. The concentrated samples were assayed on BGM cell cultures for the detection of enteroviruses and with cDNA probes specific for poliovirus, hepatitis A virus and rotavirus. Enteroviruses were not detected in any sample assayed using cell culture techniques. Three samples were positive using nucleic acid probes for poliovirus. These results suggest that poliovirus RNA was present in some diapers but that the viruses were not viable after two years or longer in a landfill.

Landfill emissions are the major environmental impact associated with the landfilling of / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2007