Accelerated carbonation technology (ACT) could be used for the stabilisation of hazardous wastes, remediation of contaminated soils and re-use/recycling of various waste streams. ACT has also potential for storing anthropogenic CO2 emissions into mineral silicates and alkaline waste residues via mineral or waste carbonation. Compared to ocean and geological storage, mineral and waste carbonation offer several advantages such as long-term storage and low monitoring requirements. Currently, the biggest challenge of mineral carbonation is the low conversion rate of calcium and magnesium-based minerals into thermodynamically stable carbonates under ambient temperature and pressure. Also, literature offers little information about physical techniques or chemical substances that could enhance the efficacy of accelerated carbonation of alkaline wastes. In this study, various carbonation techniques were applied for increasing the carbonation reactivity of magnesium hydroxide. The experiments were conducted under low temperature and pressure, while the maximum reaction time was 24 hours. Under these conditions the associated costs are kept to a minimum. The possibility of producing monolithic products with value-added was investigated by using blended mixtures of magnesium and calcium hydroxide. These mixtures were cured in carbon dioxide for 7 and 28 days and their physical properties were measured and compared with the properties for normal and lightweight concrete. Moreover, several alkaline residues were carbonated with the aid of ultrasound and four candidate catalysts (acetic acid, ethanol, sodium hypochlorite and sodium nitrite) and their CO2 uptake was measured. During sonication the variables: ultrasonic frequency, water content and treatment time were examined, while the applied chemicals were added at three different molarities (0.1 M, 0.5M and 2.5M). Throughout this work a number of analytical techniques were used for the characterisation of the raw and carbonated materials. These techniques included XRay fluorescence, X-ray diffraction, wet laser analysis, total organic carbon analysis and scanning electron microscopy. The results showed that the CO2-reactivity of Mg(OH)2 was low due to thermodynamic constraints that inhibited the rapid diffusion of CO2 into the system. The mixtures composed of pure Mg showed improved compressive strength and bulk density. In addition, sonication at low water content was weak, as there was lack of enough water to facilitate cavitation. On the other hand, at high water content the achieved CO2 uptake of the products increased by up to four times, as the wet conditions enhanced the cavitation of the solid particles. Finally, it was found that ethanol and acetic acid promoted the hydration rate of CO2 during accelerated carbonation, while minerals phase analysis did not reveal the formation of toxic by-products. In conclusion, the findings of this study proved that sonication depends highly on water content and is favoured at wet conditions. Furthermore, acetic acid and ethanol are two chemicals with potential to ameliorate the accelerated carbonation of various industrial wastes without the formation of un-desired or toxic compounds.

The rapid development of palm oil industry in Malaysia has generated significant amount of solid and liquid wastes, contributing to major environmental issues in the past five decades. Palm oil residues such as palm kernel shell (PKS), empty fruit bunch (EFB) and palm oil sludge (POS) are difficult to be disposed of. Thus, the potential application of the oil palm wastes for synthesis of value added products such as adsorbents for heavy metals removal and solid biochars for fuel generation, are presented in this thesis. In the past three decades, industrialisation and urbanisation in Malaysia have led to an increase of heavy metals, such as copper, cadmium, lead, zinc, chromium and nickel, in the rivers and lakes. The presence of the heavy metals is causing harmful effects on the aquatic environment and human health, hence it is necessary to control the discharge of industrial effluent into the environment. Among various heavy metals abatement technologies, adsorption is by far the most promising technique due to its relatively easy operation and high efficiency. However, adsorption is associated with costly adsorbent, such as activated carbon which is usually made from non-renewable resource. This has motivated many researchers to investigate and develop cost effective adsorbents for the removal of heavy metals. In this research, biosorbent was prepared from palm oil sludge. The preparation steps were relatively simple and low cost, involving mechanical treatments such as drying, milling and sieving. The POS biosorbent was tested on removal of copper (Cu2+) and cadmium (Cd2+), followed by process optimisation using response surface methodology (RSM), based on central composite design (CCD). Comparing between one-factor-at-a-time (OFAT) and RSM-CCD methods, both studies produced results which were in good agreement. The investigation was carried out to evaluate the effects of adsorbent dosage (W), initial pH, initial concentration (C0) and contact time (t), on the heavy metals removal. From optimisation study using RSM-CCD, the optimum adsorption parameters for Cu2+ removal were as follows: W = 0.3 g; pH 4.56; C0 = 200 mg L-1; t = 60 min, with maximum adsorption capacity (q) of 15.84 mg g-1, and for Cd2+ removal were as follows: W = 0.3 g; pH 5.8; C0 = 200 mg L-1; t = 60 min, with maximum q of 18.49 mg g-1. The adsorption equilibrium of Cu2+ and Cd2+ were best described by Langmuir and Freundlich models, respectively, based on the lowest sum of normalised error (SNE). The adsorption kinetic of Cu2+ and Cd2+ were best fitted with pseudo-second-order kinetic model. Thermodynamically, the adsorption processes were spontaneous, exothermic and feasible. Regeneration of POS biosorbent was carried out using hydrochloric acid (HCl) as the eluent, and the results indicated the high desorption efficiency for Cu2+ (up to 0.98) and Cd2+ (0.95) from the biosorbent, respectively. The POS biomass was also converted to POS-char by slow pyrolysis which was subsequently used in lead (Pb2+) adsorption study. The synthesis of POS-char was optimised by RSM-CCD based on simultaneous maximisation of biochar yield and q of Pb2+. The interactive effects of nitrogen flowrate (FN2), heating rate (HR), pyrolysis temperature (Tpyro) and pyrolysis time (tpyro) on the responses were investigated. It was determined that the maximum biochar yield was 80.35 % and q was 4.11 mg g-1, formed at the following slow pyrolysis conditions: FN2 = 30 mL min-1; HR = 10 °C min-1; Tpyro = 500 °C; tpyro = 30 min. In Pb2+ adsorption study, the optimum parameters determined by RSM-CCD optimisation were as follows: W = 0.3 g, pH 3.2, C0 = 200 mg L-1 and t = 60 min, with a maximum q of 21.76 mg g-1. The adsorption equilibrium of Pb2+ was best represented by Freundlich model. This finding indicated that the sorption sites in POS-char were heterogeneous. The kinetic study revealed that at low concentrations, the kinetic of adsorption complied with pseudo-first-order model, while at high concentrations, it obeyed pseudo-second-order model. Regeneration of POS-char was successfully conducted using HCl and the adsorbent exhibited reusability up to 5 adsorption-desorption cycles, with the desorption efficiencies between 0.58 and 0.99. Beyond 3 cycles, the adsorbent showed noticeable structural damage. Overall, the adsorption of Pb2+ onto POS-char was spontaneous, exothermic and feasible. The slow pyrolysis of PKS and EFB to biochars was investigated by simultaneously varying factors such as FN2, HR, Tpyro and tpyro. The synthesis parameters were optimised by RSM-CCD with respect to multiple responses, including biochar yield, higher heating value (HHV) and energy yield. The interactive effects of FN2, HR, Tpyro and tpyro on the three responses were in good agreement with literature data. The determined optimum conditions for PKS-char and EFB-char production by slow pyrolysis were as follows: FN2 = 30 mL min-1, HR = 18.9 – 20.0 °C min-1, Tpyro = 500.0 – 504.3 °C and tpyro = 30 min. The combustion kinetic on the optimised PKS-char and EFB-char were found to possess favourable combustion characteristics such as low activation energy (Ea), high energy yield and HHV. Overall, the combustion of PKS-char and EFB-char occurred in multi-step kinetics behaviour until burnout. The cost analysis on synthesis of PKS-char, EFB-char, POS-char and POS biosorbent was performed based on independent case studies which considered the capital and operating costs. The results revealed that addition of the thermochemical conversion plant to existing oil palm mill was highly feasible. The unit cost for production of PKS-char, EFB-char, POS-char and POS were USD$ 3.94 kg-1, USD$ 1.21 kg-1, USD$ 2.17 kg-1 and USD$ 0.19 kg-1 ̧ respectively.

Biomass-burning haze (BBH) is an environmental concern which has a tremendous impact on human health and the economy in Southeast Asia (SEA). One of the worst haze events to ever hit Peninsular Malaysia occurred in June 2013 due to smoke from Riau, Central Sumatra. While biomass-burning in the region is common, the early occurrence of a haze episode of this magnitude is uncharacteristic of the seasonality of extreme fire events which usually occur between August and October in the Maritime Continent (MC). Previous studies on the June 2013 event mostly include statistical studies of the impacts of haze on air quality and health. Therefore, this study aims to investigate the phenomenology of this peculiar haze event and its underlying meteorological forcing agents. The aerosol and meteorological environment during the event is examined using the Moderate Resolution Imaging Spectroradiometer (MODIS) active fire hotspot detections and aerosol optical thickness (AOT) retrievals, satellite based precipitation retrievals and meteorological indices. Particular attention is given to El Niño Southern Oscillation (ENSO) and Madden-Julian Oscillation (MJO) conditions since these phenomena influence inter-annual and intra-seasonal fire-activity, respectively, as well as the influence of tropical cyclones (TC) over the South China Sea. The above datasets are then supported by a WRF-Chem nested simulation to provide a comprehensive picture of the event’s meteorology and aerosol transport phenomenology. Indeed, while the use of weather models to study BBH has become more popular, more modelling efforts need to be put into studying the June 2013 haze event to identify the mechanisms of long range transport of haze. A set of 13 sensitivity simulations are run to determine the physics settings which best represent the meteorology over the model domain during the June 2013 haze episode. The physics options used in the sensitivity simulations are selected based on previous WRF physics sensitivity studies and work which include WRF simulations with domains over Asia and SEA. In particular, the microphysics, cumulus parameterisation and planetary boundary layer (PBL) schemes are looked into to obtain the best agreement to observation data. The output from the sensitivity simulations are evaluated with satellite based precipitation retrievals and ground station data over Malaysia. The simulations run with the Lin microphysics scheme, Betts-Miller-Janjić (BMJ) cumulus parameterisation scheme and Mellor-Yamada-Janjić (MYJ) planetary boundary layer scheme performed best overall. These best settings, based on the sensitivity studies, are then used in the numerical simulations which are evaluated with satellite and ground station data. The evaluation shows that model produces similar patterns and magnitudes of AOT and successfully captures the variations in smoke plume height when compared to MODIS AOD and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) aerosol extinction profile datasets. The analysis of the time series ENSO conditions and MODIS fire count show that while extreme fire events are more characteristic of El Niño years, the MODIS fire count over the MC in June for the years 2001–2015 was highest in 2013 when neutral conditions prevailed. Although, the mean daily precipitation for June 2013 was below average for June for the years 2003–2015. In addition, the highest ratio of 0.89 of fire count for SPM to MC for any month for the period 2001–2015 was recorded in June 2013. An early and active TC season, which could have been the result of a strong transiting MJO, occurred in June 2013. The results show that the combined induced subsidence and flow enhancement due to TC Bebinca and the dry phases of the strong MJO event contributed to the event. The simulations further show that downward vertical motion of at least 6 cm s-1 prevailed over Sumatra on 22 June when TC Bebinca was most intense, while upward vertical motion reaching at least 9 cm s-1 prevailed over the same region before TC Bebinca on 17 June. Indeed, smoke sources were concentrated under this particular region of subsidence, where surface PM2.5 concentrations reached at least 1000 μg m-3 on 22 June. Vertical cross-sections across the model domain also show that subsidence during phase 6 of the MJO prevailed over Sumatra. Intense and early TC seasons over the Western North Pacific can therefore be an indication of the occurrence of early and extreme haze events over the MC. The numerical simulations are also used to study the convective mechanisms which are responsible for uplifting biomass-burning haze in the troposphere. These mechanisms over Sumatra and Peninsular Malaysia are under-studied and their physical mechanisms remain unclear. The PM2.5 mass concentration, vertical wind speed plots at different levels and vertical cross-sections of major smoke plumes are analysed and the corresponding convective mechanisms identified. Three main convective mechanisms are identified, namely, orographic motion over the Barisan Mountains of Indonesia, morning convergence over the strait of Malacca and orographic motion over Peninsular Malaysia. Results show that smoke is lifted to heights of at least 10 km in the atmosphere due to orographic lifting over Peninsular Malaysia while the average plume height increased to higher than 2 km as TC Bebinca subsided, due to the resulting decrease in subsidence. The identified mechanisms are able to uplift the biomass-burning emissions to the upper troposphere and this could have significant long-range transport and global climatic effects.

Yangtze River Delta (YRD) region experiences severe haze pollution as a result of rapid economy growth and urbanization during recent decades. Its annual average PM2.5 (particulate matter with aerodynamic diameter ≤ 2.5μm) concentration often exceeded the National Ambient Air Quality Standards of China–Grade II (35 μg m-3) and this occurs not only in urban areas but also in suburban and rural areas as well. One of the major contributors to the decreasing air quality in this region is biomass burning. Hence, this research aims to study biomass burning impact on the air quality in YRD through the investigation of atmospheric fine aerosols. An intensive field sampling campaign was conducted at four representative sampling sites in urban, suburban and rural areas of this region from December 2014 to November 2015. The characteristics of PM2.5 samples that collected in this region were investigated through a comprehensive analysis of major components of aerosol samples, including major water soluble inorganic ions (WSII), trace metals, organic carbon (OC), elemental carbon (EC), polycyclic aromatic hydrocarbons (PAHs), biomass burning tracers and fungal spore tracers. The investigation of above mentioned components can provide a very comprehensive profile of PM2.5-related pollutants in YRD. In addition, air mass backward trajectory analysis and fire-spots analysis were also carried out in this study to identify air mass origins, pathways and fire events in this region. Positive matrix factorization (PMF) was also applied to estimate the contribution from biomass burning to fine aerosols in YRD. Both temporal and spatial trends of above pollutants were studied accordingly to set up seasonal and geographical profiles. In total, more than 240 PM2.5 samples were being analysed in this study. The annual average PM2.5 concentration in this region was 66.2 ± 37.7 μg m-3, and urban sites were observed with higher PM2.5 concentrations than the other two suburban and rural sites. The annual average concentration of total 12 WSII in YRD was 29.1 ± 19.9 μg m-3, dominated by SO42-, NO3-, NH4+, Cl-, and K+. The annual averaged concentration of total 20 metals in YRD was 2.8 ± 0.4 μg m-3, dominated by K, Al, Fe, Mg, Zn and V (> 100 ng m-3). The carcinogenic risk of Cr and As via ingestion is higher than the acceptable level for all residences in YRD. The annual average level of PM2.5-associated total carbon (TC) at YRD region was 14.3 ± 4.1 μg m-3, accounted for 26.2 (± 6.5) % of annual mean PM2.5 concentration. The annual averaged concentration of total 17 PAHs in YRD was 35.5 ± 12.3 ng m-3, dominated by retene, BkF, BbF, Ind, Bpe, Flt and Chr (> 2 ng m-3). The annual lifetime cancer risk of PAHs through inhalation exposure in YRD was 3.57 × 10-4. The annual average concentrations of levoglucosan and arabitol were 81.3 ± 18.2 ng m-3 and 5.6 ± 0.7 ng m-3 respectively. These compounds above exhibited similar seasonal patterns as PM2.5 with elevated level in winter and lower level in summer, except fungal spore tracers which showed the highest concentration in summer. In total, WSII, trace metals, TC, PAHs and organic tracers explained more than 69.8 % of total PM2.5 in YRD. The contribution from biomass burning to fine aerosols in YRD was 18.2%-37.4%. The concentration of biomass burning emitted PM2.5 ranged from 10.07 μg m-3 in spring to 27.60 μg m-3 in winter. Fine aerosols in southern YRD were contributed remarkably by fuel combustion such as coal and biomass burning, with less contributions from traffic emissions and soil origins, minor from sea salts. The contribution from coal combustion and biomass burning was more significant in winter and autumn than in spring and summer. The contribution from biomass burning decreased within the provincial capital municipality and the influence from biomass burning was more significant in rural area during autumn. In addition, the air mass backward trajectory analysis also showed that the contribution from transboundary transport of aerosols from highly polluted north China cannot be neglected.

Thesis (Professional Degree)--University of Missouri, School of Mines and Metallurgy, 1928. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed September 16, 2009) Includes index (p. 67-69).

Smart meters measure aggregate energy consumption for an entire building. Recent literature suggests that disaggregated information describing appliance-by-appliance electricity consumption is more effective than aggregate information (Kelly et al. 2016, Fisher 2008). The thesis therefore investigates the potential for aggregated and disaggregated energy metering data but takes a different angle by trying to understand how newly established student households use energy in their daily lives and whether this can be changed with smart electricity display meters. The interdisciplinary methodology involved video recorded guided tours, focus groups, semi-structured interviews, photographs, video diaries and metered energy data. The data was collected in three phases. Initially, a video recorded guided tour was carried out in each student household to find out how students are sensing their environments as they move inside the house and how they are maintaining these environments through the sensory aesthetic of the home. This was followed by focus group sessions and semi-structured interviews in each household to find out how electricity was implicated in everyday practices. Next, students received three different types of smart electricity display monitors, aimed at assessing the implication of disrupting practices by real-time metering feedback. The central finding of this work is that practices-that-consume energy cannot be reduced to attitudes or intentions. This finding is nuanced by an extended discussion on the relationship between practices and the temporal structuring of practices. The research identifies other types of feedback (such as social, material and sensory) that influence the energy use in practices or substitute practices for other non-energy using practices, suggesting that there are no simple technological or behavioural fixes. More profoundly, this thesis suggests that policy should focus on connection between practices, rather than technological performance or what consumers think about electricity display monitors. The thesis concludes by discussing a re-framing of policy expectations; identifying the ways in which smart metering data could target domestic practices and its influencing elements potentially constrain or catalyse a transition towards a more sustainable way of living.

Since the usage of chemical flocculants especially polyacrylamides is closely related with environmental pollution and health hazards, synthesis of environmental friendly and economic viable bio-flocculants that exhibit high flocculating efficiency is highly desirable. The production of natural bio-flocculants extracted from plant is urgently needed as an alternative to chemical flocculants due to their inherent low toxicity, biodegradability and low environmental footprint. In this study, a plant-based bio-flocculant was extracted from Hibiscus/Abelmoschus esculentus (okra) with conventional hydrothermal extraction (CHE) and microwave assisted extraction (MAE) processes by using water as solvent. The aims of this work were to produce the bio-flocculant through environmentally friendly and economically feasible process, optimise its extraction yield, optimise its flocculating and sludge dewatering properties, and also minimise its production cost in order to be comparable to chemical flocculants (polyacrylamides) from perspectives of quality and cost. The extraction efficiencies of bio-flocculants were justified by the optimised yields, the flocculating abilities were evaluated by the removal of suspended solids (SS) and turbidity after flocculation process and sludge volume index (SVI) whereas the sludge dewatering abilities were assessed by SS removal after filtration and water recovery. Single factor experimental design was employed to study the effects of extraction temperature, time, solvent loading, and agitation speed and particle size on yield, flocculating and dewatering properties of bio-flocculants. The influence of extraction parameters to yield and the reliability of the experimental data were verified by analysing the single factor experimental results with response surface methodology. Results showed that extraction yields were significantly affected by extraction temperature and time and solvent loading. Prolonged extraction (few hours) at high temperature (60-90 ˚C) decreased the yields of bio-flocculants extracted with CHE method. Conversely, extraction at high temperature was favourable for MAE method to raise the yield due to short extraction time in minutes. Flocculating abilities of bio-flocculants were not significantly affected by the extraction conditions whilst the sludge dewatering abilities were mainly influenced by the temperature and particle size. High extraction temperature at ≥ 70 ˚C and the smallest okra particle size at 1mm were the crucial conditions for extraction of bio-flocculants with high dewatering abilities which showed > 95% of SS removal after filtration and ≥75% of water recovery. The optimised yield of CHE at 25.9% was obtained at 50 ˚C, 2 hours, solvent loading of 2.5 w/w and agitation at 200 rpm. On the other hand, microwave-extracted bio-flocculants were best extracted at 90 ˚C, 10 minutes, and solvent loading of 3.5 w/w and okra particle size at 1mm to get the optimised yield at 48.7%. These results revealed that the extraction yield has been enhanced by 87.8% by using MAE method and the extraction time was markedly reduced from hours to minutes. This study uses a combination of empirical observations and an analysis of mass transfer behaviour to yield new insights into the mechanism of MAE. Enhancements in extraction rate and yield achieved by microwave extraction were observed experimentally compared with hydrothermal extraction at temperatures in excess of 50 ˚C, however at lower temperatures there was no observable difference between the two processes. A step-change in extraction yield between microwave and hydrothermal processes was shown to be caused by selective heating. A temperature gradient of the order of 1 ˚C is sufficient to reduce the water chemical potential within the plant cell structure, which causes diffusion of water solvent into plant cell such that internal plant cell pressures can increase to the point where disruption occurs. These findings demonstrate the need to operate microwave extraction processes at a temperature that enables selective heating, and a newly-proposed mass transfer phenomenon that could have wider positive implications for extraction and leaching processes. The bio-flocculants extracted with both methods were applied in flocculation and sludge dewatering without pH alteration and addition of coagulant. Efficient flocculating abilities were attained with >99% of SS and turbidity removal and < 10 mg/L of SVI. However, microwave extracted bio-flocculants were shown to exhibit higher dewatering abilities than hydrothermal extracted bio-flocculants. The bio-flocculants displayed the results of >95% SS removal after filtration and 75% water recovery during sludge dewatering at dosage of 30 mg/L, and was shown to be comparable to or even better than polyacrylamides due to achievement of higher water recovery at the same dosage. Dried bio-flocculants were found to have higher dewatering abilities than aqueous bio-flocculants, probably because drying at low temperature (40 ˚C) has minimised the moisture content and extended the shelf life of bio-flocculants. Biopolymer bridging was preliminary predicted as the plausible bio-flocculation mechanism. The economic feasibility of production of industrial scale bio-flocculant was investigated and the production process was modelled by using SuperPro Designer v9.0 simulation software. The MAE process in continuous mode was verified to be more economically viable than CHE process either in batch or continuous mode if the production scale was beyond 15 tonne/year. Sensitivity analysis for continuous microwave process was conducted and the results indicated the strong influences of annual production and extraction yield followed by raw material okra price on the unit production cost. Continuous microwave process with extraction conditions at 90 ˚C, 10 minutes and solvent loading of 3.5 w/w was identified as the optimised scheme for production of industrial scale bio-flocculant at the lowest production cost. The estimated selling price of aqueous and dried bio-flocculants for an annual production of 220 tonne/year were 41 and 52 $/kg respectively, and was shown to be lower than food grade bio-flocculants but higher than polyacrylamides. This work has clearly showed that okra bio-flocculant could offer a feasible and sustainable alternative to synthetic flocculants for water treatment and sludge dewatering applications due to its high efficiency in flocculating and dewatering, and can be extracted using only water as a solvent, minimising the environmental footprint of the extraction process.

This study focused on the long-term cycling of radiocaesium in pine forests at Boundary Plantation (Sherwood Forest, England), Chernobyl (Ukraine) and Wat Ban Chan in northern Thailand, each of which received markedly different levels of contamination due to radiocaesium deposition from the atmosphere under different circumstances. Systematic studies were made of stable and radiocaesium, potassium and rubidium in soil horizons, tree stems, needles and throughfall (the latter only at Boundary Plantation). Measurements of total concentrations were complemented with determinations of exchangeable fractions as well as the isotopic exchangeability of radio- and stable caesium. Data from Boundary Plantation and Wat Ban Chan were used to test, validate and calibrate the RIFE (Radionuclides in Forest Ecosystems) model for long-term forecasts of radiocaesium behaviour in forest ecosystems. Finally, modelling of 137Cs migration in forest soils was carried out to describe the relationship between the depth of the forest soil profile and the year of litterfall, to better understand the migration of fallout 137Cs. Boundary Plantation, a forest of semi-natural Corsican pine (Pinus nigra), receives chronic atmospheric fallout from nuclear weapons tests in the 1960s. Forest samples were collected every three months from June 2014 to March 2015 at a 24 randomly located sampling sites. The forest soil has a well-developed surface organic horizon while the mineral soil is composed almost entirely of quartz with no identifiable clay minerals. About 65% of nuclear-weapons fallout 137Cs is distributed within the organic layer (upper 9 cm) and maximum of vertical distribution is 12.9% at 8 cm depth. The accumulation of well-decomposed organic matter in the middle of the organic layer is strongly related to the migration of 137Cs in the soil; modelling describes the relationship between the depth of organic matter accumulating in the upper part of the forest soil profile and the year of litterfall indicates that fallout 137Cs deposited in 1963 has migrated in tandem with organic matter at the same rate of migration from the surface. Soil pH also appears to play a key role in controlling the mobility of Cs isotopes, with the most acidic layers within the soil organic horizons holding the highest 137Cs activity concentrations and having the highest exchangeable 133Cs concentrations. Wat Ban Chan in Thailand is a native tropical forest of Pinus kesiya (or Three-needled pine) which received chronic distribution of atmospheric fallout from nuclear weapons tests in the 1960s. Samples were taken from this site in late February 2016 at six randomly located co-ordinates. The forest soil is typical of similar forest soils in the tropical zone. The organic matter, even at the surface, is much less abundant than in temperate forest soils while the mineral soil is composed almost entirely of quartz with no identifiable clay minerals. About 84% of nuclear weapons fallout 137Cs is distributed within the upper 3 cm and the maximal distribution is 37.6% at 2 cm depth. Even though the organic matter content in the upper 2 – 3 cm of the soil profile is low it probably still plays an important role in the vertical distribution of 137Cs. The variation of soil pH throughout the upper 13 cm of the soil profile is less than 1 pH unit and thus is unlikely to influence the vertical distributions of 137Cs and 133Cs in the soil. K and Rb are strong competitors of Cs during cycling within the forest ecosystems at Boundary Plantation and Wat Ban Chan. K is present in the exchangeable fraction in soil at much higher concentration than Rb and especially Cs. The overall degree of translocation from soil to needles is in the order of 39K > 85Rb > 133Cs. Forest sites surrounding the Chernobyl nuclear power plant in Ukraine received acute and localised deposition of nuclear fallout during the Chernobyl reactor accident in April and May 1986. Samples were taken from four Scots pine (Pinus sylvestris L.) plantations close to Chernobyl in early September 2015. Tree cores were taken at all four sites (Red Forest, North Trace, Kopachi and Bourakovka). Soil cores were also collected at Kopachi where 137Cs behaviour appears similar to 133Cs as indicated by Tag values of 133Cs and 137Cs. Scots pine at the Red Forest and the North Trace sites were exposed to extremely high and acute radiation doses (more than 5.0 mGy/h) in the very early stages of the Chernobyl accident. The surviving Scots pine trees sampled in 2015 show a transient decrease in growth rate for several years after 1986, and then show signs of accelerated growth possibly due to a reduction in competition from surrounding trees (an effect known to foresters as ‘growth release’). Calculations of present day 137Cs distributions using the RIFE model for Boundary Plantation and Wat Ban Chan calibrated with inter-compartmental half-times from seven European (‘SEMINAT’) forest sites proved surprisingly accurate, although the model consistently under- and over-predicted the percentage of the total 137Cs inventories retained in the organic and mineral soil layers, respectively. Site-specific calibrations of the RIFE model were made using newly acquired data for nuclear weapons 137Cs deposited in 1963 at Boundary Plantation and Wat Ban Chan. It is considered that these calibrations are more applicable for long-term predictions of radiocaesium cycling in forests than the SEMINAT calibrations which were based on measurements made less than 10 years after the Chernobyl accident in 1986. Finally, measured unsupported 210Pb activities in forest soil profiles were modelled to describe the relationship between the accumulating depth of organic matter in the forest soil profile and the year of litterfall, to improve understanding of the migration of fallout 137Cs at Boundary Plantation (Sherwood Forest, UK) and in the relatively organic-poor soil at Wat Ban Chan in Thailand.

Conventional dust dispersion models which employ Gaussian concentration distributions are routinely applied to predict the dispersion and deposition of fugitive dust arising from quarrying activity. However, these models are known to over-predict the long range transport of particulates beyond the confines of the quarry pit, because their complex terrain algorithms are unable to accommodate the steep gradients which are typically encountered in quarry excavations. They therefore cannot account for the internal flow regimes which contribute to the removal of suspended particulates from the air stream. Consequently, a need arises within the extractive industries, for improved dust dispersion models that are not constrained by quarry topography. This research project attempts to address this deficiency in the modelling of dust emissions from quarry blast events, by presenting an optimized RANS k−ε approach which can adequately simulate the flow-field in which particulates are entrained under a range of meteorological conditions. The stages involved in the incremental development of the numerical model are documented in the thesis, and commence with characterization of the atmospheric boundary layer. In particular, the Monin-Obukhuv Similarity Theory is applied to parametrize the atmospheric surface layer, which exerts the most influence on the dispersion and deposition of near-ground particulate emissions. Modifications to the standard k − ε model coefficients and the inclusion of buoyancy source terms have been adopted in this work, in accordance with previous studies by Alinot and Masson (2005). These modifications ensure that the turbulence closure equations are compatible with Monin-Obukhuv Similarity scaling of the atmospheric surface layer. The Businger-Dyer flux profile functions have been employed to introduce stability modifications to the logarithmic velocity, temperature and turbulence profiles which have been defined at the inlet boundaries of the computational domain to enable numerical representation of both adiabatic and diabatic atmospheric conditions. Furthermore, the Lagrangian Discrete Phase Model has been coupled with Eulerian solution of the flow field to provide a robust means of replicating fugitive dust dispersion through the stochastic tracking of injected particulates. The project also presents a consolidated post-processing methodology to incorporate wind direction variability due to mesoscale atmospheric effects into the CFD model. This methodology use the Moore (1976) equation to parametrize the standard deviation of wind direction variability and proposes a novel, Gaussian probability weighted averaging procedure to arrive at a resultant plume which accounts for the influence of mesoscale wind variability on particulate trajectory and improves the k −ε predictions of lateral spreading of the dust plume. Simulations of flow and dispersion over a series of idealized cosine depressions of varying aspect ratio have been used to assess model predictions of the flow regime and the corresponding plume attenuation within artificial valleys. To allow the model to accommodate negative terrain elevations and to produce profiles of the flow variables which conform to wall topography, a wall-distance scalar has been introduced to ensure consistency of the inlet profile with the flow solution within the domain. These simulations have demonstrated that the proposed model surpasses UK-ADMS in terms of its ability to resolve strong recirculation regimes in deep depressions. The project culminates in a case study of the Old Moor Quarry in Buxton, Derbyshire. This case study tests the viability of the proposed k−ε model and validates the model predictions of dust dispersion with field measurements obtained over the course of a monitoring campaign of approximately one month duration. Meteorological pre-processing steps in accordance with the findings of Holtslag and Van Ulden (1983) have been employed to derive atmospheric surface layer input parameters from routine meteorological data measured at the quarry site, eliminating the need for sophisticated meteorological measurements. Dust dispersion predictions obtained using the conventional dust dispersion model UK-ADMS, have been compared to the CFD model results to demonstrate the improved prediction accuracy of the proposed k −ε approach. Notably, the CFD model is shown to account for the various flow regimes which arise due to the combined effects of the site meteorology and the complex terrain of the quarry excavation. Importantly, the statistical Performance metrics, FAC2, MG, FB and NMSE recommended by Hanna et al. (2004) for the evaluation of dispersion model performance, have been used to assess the accuracy of fugitive dust deposition predictions obtained from the proposed model. The performance evaluation exercise indicates that the buoyancy modified k − ε model outperforms UK-ADMS for all of the metric tests. The incorporation of the wind variability weighted averaging procedure in the case study simulations is seen to reduce uncertainty due to random error, quantified by NMSE. This due to the fact that the wind variability averaging procedure evens out outlying predictions which may be due to the inherent stochasticity of the DPM model.

Please read the abstract in the section 00front of this document / Dissertation (M Eng (Water Resources Engineering))--University of Pretoria, 2007. / Civil Engineering / unrestricted