As the demand for motor vehicles has soared dramatically with the emergence of rapidly developing countries, the need for regulating vehicle emissions and pollutants is increasingly more important. With the newest regulations for diesel particulate emissions soon to be enforced, there is a great need to catalytically convert soot particles from the exhaust into relatively less polluting carbon dioxide. Here a supported silver catalyst is reported for the soot oxidation reaction. The silver catalyst is protected and supported using various capping agents and metal oxides, and modified using various synthetic methods. The catalysts are then tested with soot using thermogravimetric analysis (TGA) at a reaction temperature up to 700oC. In order for a better design and modification of the silver catalyst, an improved understanding of the interaction between silver nanoclusters and the metal oxide support must be established. XPS and UV/VIS spectroscopy are amongst the techniques used to probe the metal/metal oxide interaction. It is shown that the surface plasmon resonance of silver can be perturbed by the metal oxide support, modifying its band structure. It is also extremely important for the catalyst to be thermally stable up to 600°C for it to be employable in an exhaust system. In-situ XRD can be used to investigate the thermal stability of both the silver and metal oxide species in an oxidising environment. The phase changes, if any, of either species under heating can also provide a better understanding of the metal/metal oxide interaction and ultimately the soot combustion mechanism. It has been demonstrated that different catalyst surfaces can have different catalytic performances. By altering the morphology of the support, preferential growth of one surface can be achieved, thereby modifying the catalytic performance for soot combustion.

A compost-bioremediation approach was adopted in this study to explore more sustainable and economically viable methods of degrading pollutant hydrocarbons in oil-field drill cuttings and coal tar impacted soils (CTIS). The compost amendments used were agricultural waste products including grass cuttings, spent mushroom compost and straw. Laboratory-scale compost experiments were conducted to test the performance of different compost blends comprised of each contaminated medium and organic amendments in different mix ratios for 53 days. The compost mix type which produced the greatest reduction in pollutant hydrocarbon concentrations was further scaled-up and tested in an outdoor pilot scale compost treatment for 56 days. At the end of the lab-scale treatments, degradations in total petroleum hydrocarbon (TPH) concentrations of 85.1% and 90.6% were recorded for the drill cuttings and CTIS, compared to 36.7% and 28.4% that was achieved in the control experiments, respectively. The concentrations of total n-alkanes and polycyclic aromatic hydrocarbons (PAHs) were significantly decreased in the best performing compost mix types, however most of the 5 and 6-ring PAH compounds in the CTIS treatment compost mix exhibited recalcitrance to degradation and some even appeared to increase in concentration which is ascribed to increased PAH availability to solvent extraction and reduction in the compost mass during the composting-biodegradation process. The best performing compost mix type for treatment of CTIS was subsequently tested in outdoor tumbler compost bins after being scaled-up by a factor of 600; this was found to produce 78% degradation of TPH concentration at the end of the treatment period. Concentrations of total nalkanes and PAHs were also significantly lowered by biodegradation. Low molecular weight (2 and 3-ring) PAHs were almost completely removed and 4-ring PAHs from the coal tar, including fluoranthene, pyrene, benzo[a]anthracene and chrysene were significantly degraded but not the 5 and 6-ring PAH compounds. Phytotoxicity assays showed that the seed germination in the treated matrix was 70% and 20% more, for corn and pea, respectively, 5 days after planting and 78% more for mustard 3 days after planting. Phosphatase enzyme activity was found to decrease in the treated matrices possibly due to the short time between end of composting and testing. The results generated from the chemical and toxicity assays of this study showed the efficacy of the composting treatment for hydrocarbon removal from these contaminated matrices and identified the best performing compost mix types (DGMSt3 and SGSt3) which can be further tested in field scale trials.

Soil pollution is a global problem, resulting in a major international research effort using bioremediation technology to exploit plant and microorganism in the removal of contaminants. Phenolic compounds are major pollutants from industrial effluents and consequently are present in many soil and water systems throughout the world. Phytoremediation studies in soil contaminated with phenolic compounds are a challenge. The rhizosphere is an extremely dynamic zone, both spatially and temporally. In order to understand the complex rhizoremediation processes (including root-microbe reactions), there is a need to study the biophysical interactions at the root/soil interface. However, this is limited by sampling and analysis techniques. A modified (SiCSA) Single Cell Sampling and Analysis technique using fine glass microcapillaries was used in an attempt to overcome this issue. This micro-scale technique was used to quantify the polar phenolic compounds such as syringic acid. Phenols of lower polarity offer different technical challenges as they rapidly dissolve in paraffin oil, which was used to prevent the evaporation of micro samples. As a result, a conventional ‘macro’ approach was also used. A microcosm system for plant growth was used to facilitate access to soil and roots. The phenolic compounds were analysis using Capillary Zone Electrophoresis (CZE). The two selected plants, rye and wheat, have the ability to speed up the removal of two selected phenolic compounds from soil after their addition. The pathways through the plant of phenol (an artificial compound) and syringic acid (a biological compound) are different. Different strategies of phytoremediation of these phenolic compounds in soil was demonstrated in wheat. Phenol was absorbed into the root and transported to the leaf. Phenol seemed to be partially accumulated in the leaf, while some amount evaporated through stomata to the atmosphere. Syringic acid was taken up by the root and seemed to be metabolized there within less 2 hours. No evidence was found that this compound is rapidly transported to the leaf. Phytoremediation occurs in ways previously reported, such as metabolism, accumulation and evaporation. In conclusion, although microbial processes probably dominate the removal from soil of phenolics studied, both rye and wheat behaviour contributed to the removal of phenolic compounds. This indicates the potential of using them in phytoremediation.

Constructed wetland technology is gaining increasing attention as a low cost-efficient alternative to high-tech treatment systems for treating municipal and industrial wastewaters especially in small communities. However, its application for grey water reuse has been rarely investigated whilst performance for nutrients (N and P) still remains relatively poor. Pilot scale study was conducted in which three differently configured subsurface constructed wetlands: a horizontal flow reed bed (HFRB), vertical flow reed bed (VFRB) and a novel system - Green Roof Water Recycling System (GROW) were investigated for their suitability and robustness in treating grey water for reuse across a range of influent strengths to represent the limiting conditions observed in the literature. The HFRB and the GROW systems were found to be generally limited to comply with reuse standards especially at high strength. The release of iron from the HFRB media and particulates from the GROW system contributed to the poor turbidity of the final effluent from these systems. Overall, all wetland configurations were able to effectively treat low strength greywater but only the vertical flow system maintained its robustness when high strength greywater was treated. Analysis of the systems reveals this was due to the fact that aerobic metabolism is a more suitable treatment pathway for greywater. Ultimately, the performance of the vertical system was slightly lower but comparable to that of a membrane bioreactor making constructed wetlands a suitable technology for greywater recycling. Also, Bauxol, Red mud, Bayoxide, Ochre, Filtralite-P, Steel slag, concrete, Zeolite and various form of limestones were investigated for potential removal of soluble reactive phosphorous (SRP) and metals (Cu and Ni) in final sewage effluent for post Constructed Wetland System. P capacities exhibited by the different adsorbents correlated with type of metal (e.g. Fe, Al, Ca) and their cation exchange capacities. Ochre exhibited the best P removal ability with a P capacity of 26 g Kg-1 based on a Freundlich isotherm model. The equilibrium sorption capacity of BauxolTM and Ochre based on a Dubinin-Radushkevich model was found to be 4.1 and 4.9 mg g-1 for Cu and Ni unto BauxolTM respectively and 2.6 and 10.2 mg g-1 for Cu and Ni onto Ochre respectively. Kinetic and thermodynamic study revealed a spontaneous and efficient adsorption process via a pseudo-second order mechanism where intraparticle diffusion was shown to be the rate limiting step. An aerobic post constructed wetland system using Ochre as the bed media for large scale applications is suggested.

The storage of waste carbon dioxide (CO2) from fossil fuel combustion in deep geological formations is a strategy component for mitigating harmfully increasing atmospheric concentrations to within safe limits. This is to help prolong the security of fossil fuel based energy systems while cleaner and more sustainable technologies are developed. The work of this thesis is carried out as part of a multi-disciplinary project advancing knowledge on the modelling and monitoring of geological carbon storage/sequestration (GCS). The underlying principles for mathematically describing the multi-physics of multiphase multicomponent behaviour in porous media are reviewed with particular interest on their application to modelling GCS. A fully coupled non-isothermal multiphase Biot-type double-porosity formulation is derived, where emphasis during derivation is on capturing the coupled hydro-thermomechanical (HTM) processes for the purposes of study. The formulated system of governing field equations is discretised in space by considering the standard Galerkin finite element procedure and its spatial refinement in the context of capturing coupled HTM processes within a GCS system. This presents a coupled set of nonlinear first-order ordinary differential equations in time. The system is discretised temporally and solved using an embedded finite difference method which is schemed with control theoretical techniques and an accelerated fixed-point-type procedure. The developed numerical model is employed to solve a sequence of benchmark problems of increasing complexity in order to comprehensively study and highlight important coupled processes within potential GCS systems. This includes fracture/matrix fluid displacement, formation deformation and Joule-Thomson cooling effects. The computational framework is also extended to allow for the simulation of cosmic-ray muon radiography (muography) in order to assess the extent to which detected changes in subsurface muon flux due to CO2 storage can be used to monitor GCS. This study demonstrates promise for muography as a novel passive-continuous monitoring aid for GCS.

Particulate matter suspended in the atmosphere is a major contaminant and is prevalent in urban environs, reducing the quality of air in the places that the majority of humans reside. Medical research has labelled PM2.5 as a potential risk to human health. To combat this issue, new legislation regarding PM2.5 has been passed. Electrostatic precipitators exhibit a drop in efficiency at ~(0.1-1) μm PM diameter. Therefore, the present work is focused on an investigation of microelectrostatic precipitation technology, for improvement of indoor air quality. Initial work included investigation of impulsive positive energisation, in a specially designed single stage, coaxial reactor, utilizing 250 ns impulses superimposed on dc voltage. Precipitation efficiency for coarse and fine powders has been investigated for various levels of superimposed impulsive and dc energisation in order to identify optimal energisation conditions. Further steps were taken to decouple charging from collection stages in order to optimize the air cleaning process to a greater extent. Precipitation experiments were conducted using ambient air and cigarette smoke. Maximum precipitation efficiency was achieved when both stages were energised, under impulsive and dc energisation in each stage respectively. Analytical work regarding PM charging has also been conducted. Lastly, the coaxial precipitator reactor was scaled-up for possible indoor air cleaning applications. Similarly, impulsive energisation combined with dc voltage at the different stages has been used and proved to increase precipitation efficiency. Test fluids used were beeswax candle fumes and ambient air. Simulations have also been conducted to optimize the ESP process. In conclusion, it has been shown that impulsive energisation of ESPs is highly efficient,100% for particles greater than 250 nm, for PM2.5 in concentrations found in indoor environments. This could potentially help in increasing indoor air quality, with all the corresponding health, working efficiency and ultimately state economic benefits it could achieve.

Natural aerosols are a key component of many biogeochemical cycles, they define the baseline from which the pre‒industrial to present‒day anthropogenic aerosol radiative forcing is calculated, and they dominate the net effect of all aerosols on the incoming solar radiation. However, their impacts on climate are complex, often nonlinear, and poorly understood; leading to large uncertainties. Global model simulations are used in this thesis to define aerosol regions unperturbed by anthropogenic pollution. On a global annual mean, unperturbed aerosol regions cover 12% of the Earth (16% of the ocean surface and 2% of the land surface) with about 90% of unperturbed regions occurring in the Southern Hemisphere. In cloudy regions with a radiative forcing relative to 1750, results suggest that unperturbed aerosol conditions could still occur on a small number of days per month. However, these environments are mostly in the Southern Hemisphere, potentially limiting the usefulness in reducing Northern Hemisphere forcing uncertainty. Clustering techniques were used to identify natural emissions regimes in the pre-industrial and present-day where biomass burning, biogenic volatile organic compounds, dimethyl sulphide, volcanic sulphur dioxide and sea spray emissions dominate the variance in cloud condensation nuclei concentrations. Regimes are generally located in regions close to each emission source, before significant mixing occurs within the atmosphere with other emission types. These regimes are ideal “natural laboratory” locations for field study of the impacts of each natural emission on aerosol behaviour. When pre-industrial fire emissions from two global fire models are implemented in a global aerosol model, pre-industrial global mean cloud condensation nuclei concentrations increase by a factor 1.6-2.7 relative to the widely used AeroCom dataset. Higher pre-industrial aerosol concentrations cause a substantial reduction in the calculated global mean cloud albedo forcing of between 40 and 88 percent and a reduction in the direct radiative forcing of between 5 and 10 percent. When compared to twenty-eight other sources of uncertainty in our model, pre-industrial fire emissions are by far the single largest source of uncertainty in pre-industrial cloud condensation nuclei concentrations, and hence in our understanding of the magnitude of the historical radiative forcing due to anthropogenic aerosol emissions.

The preferred route to treatment of the vast majority of intermediate level nuclear waste (ILW) within the UK is via encapsulation within a composite cement system. The integrity of these conditioned waste packages must be maintained for hundreds to thousands of years since they will eventually be stored deep below ground in a geological disposal facility (GDF), with this expected to be a permanent route to disposal. A thorough and clear understanding of the hydration, microstructural development, and hence performance, of grouting materials is essential in providing confidence in the suitability of the technology and ensuring that structural integrity is maintained. This project comes at a time of significant uncertainty for the cement industry, as well as the steel industry which has significant ramifications on the availability of blastfurnace slag (BFS, hereafter referred to as slag). Through quantifying the ramifications of changes to supply of either of these materials it will be possible to determine the resilience of the technique to chemical and physical variations, in an effort to futureproof supply. Within this study, grouts prepared with slag and ordinary Portland cement (OPC), at a ratio of 3:1 slag: OPC at a water to binder ratio (w/b) of 0.35, were analysed at 20°C. The impact of OPC composition, slag composition and slag fineness on rate and degree of hydration were assessed. Microstructural development was followed by a number of techniques in 2 and 3 dimensions, with the engineering performance of samples also quantified via a range of testing protocols. Resilience to potential fire scenarios was also investigated through simulated heat-testing of samples and subsequent analysis. Slag fineness is the most significant factor in controlling rate and degree of its hydration within both young and mature pastes at these high replacement levels. Availability of pore space into which hydrates may grow appears to the limiting factor in continued hydration; significant quantities of CH remain after 1 year of hydration, intermixed with C-S-H in a densely filled microstructure.

Volatile organic compounds (VOCs) are released into the atmosphere from numerous anthropogenic and biogenic sources. Traditionally VOCs have been measured using offline techniques such as Gas Chromatography-Mass Spectrometry (GC-MS). The development of the proton transfer reaction mass spectrometer (PTR-MS) has enabled the online analysis of VOC’s from both biogenic and anthropogenic sources. This instrument, however, provides little structural information making it impossible to distinguish between isomeric compounds. Here a range of New-PsychoactiveSubstances (NPS) are analysed using the recently developed Selective Reagent IonTime of Flight-Mass Spectrometer (SRI-ToF-MS) demonstrating its ability to distinguish between isomeric compounds. This instrument is then applied to the analysis of biogenic VOCs (bVOCs). Plants emit a wide variety of VOCs into that atmosphere. These compounds play an important role in plant communication and defence, with predatory insects making use of VOC emissions from plants following biotic stress to identify and locate their prey. This process is termed tritrophic signalling. Ozone will readily react with any bVOCs containing an alkene functional group, and as many alkenes (primarily monoterpenes and sesquiterpenes) have been shown to play a significant role in tritrophic signalling it was hypothesised that ozone may disrupt this signalling. This thesis investigates the effect of ozone on tritrophic signalling using a Brassica napus – Myzus persicae – Adalia bipunctata larvae (rapeseed – green peach aphid – two-spotted ladybird larvae) model system. Plant volatile emission was monitored using a PTR-MS and SRI-ToF-MS which enabled the better detection and identification of bVOCs than is possible using a traditional PTR-MS. Following ozone fumigation of B. napus it was shown that a large number of oxygenated compounds are emitted by the plant and that the emission of monoterpenes and sesquiterpenes from a plant chamber is reduced. However, ozone fumigation of the plant leaves was shown to have no impact on the emission of bVOCs below ground. Using a Y-tube olfactometer it was shown that ozone at environmentally-realistic mixing ratios (ca. 100 ppbv) disrupts the ability of M. persicae to locate a host plant. Ozone was also shown to disrupt tritrophic signalling by inhibiting the location of prey by A. bipunctata larvae. This disruption in tritrophic signalling was shown to be caused by degradation of bVOCs via ozonolysis and not changes to bVOC emission from the plant. Finally fluxes of VOCs above a temperate forest canopy were recorded using PTRMS and a Proton Transfer Reaction-Time of Flight-Mass Spectrometer (PTR-ToFMS) enabling a direct comparison to be made between these instruments during field scale measurements.

Volatile organic compounds (VOCs) from biogenic and anthropogenic sources are important constituents of the atmosphere with effects on air quality and climate. Current uncertainties in measurements and models relate to their roles in tropospheric ozone and secondary organic aerosol formation, yet there have been few measurements of their fluxes from contrasting chemical environments. Additional measurements with greater spatial and temporal resolutions are required to constrain uncertainties in atmospheric chemistry and climate models. This thesis presents long-term measurements of VOC fluxes and concentrations in two contrasting environments: central London and the Brazilian Amazon. VOC concentrations were quantified by proton transfer reaction-mass spectrometry and fluxes were calculated using the virtual disjunct eddy covariance method over a period of several months at sites in central London and the Amazon rainforest. In central London, traffic was found to be the main source of aromatic compounds. Oxygenated compounds and isoprene showed strong correlations with light and temperature, suggesting biogenic, evaporative, or secondary atmospheric origins. The seven VOCs measured in central London had a five-month average total emission rate of 1.4 mg m-2 h-1. Comparisons with local and national emission inventories showed that modelled emissions were largely underestimated. Measurements of isoprene and monoterpenes at the remote ZF2 site in the Amazon rainforest showed an 11-month average total emission rate of 2.7 mg m-2 h-1 with considerable seasonal variation, which could not be accurately reproduced using the light and temperature based MEGAN algorithms. This thesis presents the first long-term VOC flux measurements providing information at high temporal resolutions on seasonal variability at an urban site and a pristine tropical forest site. They confirm that the Amazon rainforest is an extremely strong source of reactive carbon to the Earth’s atmosphere exceeding emissions from a developed megacity, such as London, per unit area.