Storage of carbon dioxide in geological reservoirs has the potential to greatly reduce the amount of CO₂ being released into the atmosphere and slow global warming until more sustainable power sources can be implemented. However, it is vital before CO₂ is sequestered on a global scale, that tools are developed to both understand how CO₂ behaves in the geologic environment and/or monitor site leakage. Noble gases have been shown to be a powerful tracer of subsurface fluid systems. While there have been many studies addressing natural gas and oil systems, few have dealt directly with CO₂ sequestration.

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Explosive volcanic eruptions perturb the atmosphere, and their main impact arises from the large quantities of 802 emitted. Within this thesis this effect is characterised from a modelling perspective and the detection and measure- ment of 802 by a satellite are improved. A stratospheric aerosol box model is developed that parameterises the aerosol evolution from an emitted mass of volcanic 802. Using aerosol optical depth measurements and a simple energy balance model, the 802 mass is directly related to a global average tempera- ture change. Combining this model with historical eruption records yields a measure of the significance of eruptions based on frequency and magnitude. The model predicts that eruptions of 0.1-1 Mt of 802 are the most significant for perturbing the climate. This is consistent with recent satellite observations of stratospheric optical depth. The model establishes that the radiative forcing from a large volcanic eruption is determined by the mass of 802 erupted, sug- gesting accurate measurement of volcanic 802 is paramount for quantitative monitoring of its atmospheric impact. The brightness temperature difference method developed by Prata et al. (2003) demonstrated the potential for mon- itoring volcanic 802 using the High Resolution Infrared Radiation Sounder 2 (HIR8/2) instruments on the NOAA and MetOp platforms. The Prata method is fast but of limited accuracy. This thesis improves upon this by using an optimal estimation retrieval approach yielding increased accuracy for only moderate computational cost. This is principally achieved by fitting the column water vapour and accounting for its interference in the retrieval of 802. A cloud and aerosol model is used to evaluate the sensitivity of the scheme to the presence of ash and water/ice cloud. This identifies that the cloud or ash above 6 km limits the accuracy of the water vapour fit, increasing the error in the 802 estimate. Cloud top height is also retrieved and this finding quantifies a cloud screening limit that can be imposed. The scheme is applied to a case study event, the 1991 eruption of Cerro Hudson in Chile. A new total erupted mass estimate was found to be 2200 kT ± 600 kT. This fit method yields a minimum mass per unit area detection limit of 3 DU, which is comparable with that for the Total Ozone Mapping 8pectrometer (TOM8), the only other instrument capable of monitoring 802 from 1979-1996. v.

Waste materials are hazardous if they display toxic, corrosive or other characteristics which have the potential to cause danger to health or the environment. New regulations to meet the requirements of the Landfill Directive contain controls on hazardous waste including the requirement to pre-treat hazardous waste prior to disposal and to ensure these wastes meet stringent waste acceptance criteria (WAC) on leachability. Waste from the cleaning of combustion gases produced from municipal solid waste (MSW) incineration is classed as hazardous by virtue of their corrosive properties. The majority of these air pollution control (APC) residues which contain dioxins, heavy metals and high levels of chloride are currently sent to landfill. To meet the new controls, pretreatment will be required to improve the handling properties and reduce the release of chloride ions into the environment. Ordinary Portland cement (OPC) is used to treat hazardous wastes. The solid form produced with the addition of OPC is however susceptible to degradation from aggressive leaching fluids and may release contaminants over time. Additives with high silica content can be used to interact with free lime produced during OPC hydration to improve the physical and chemical properties of the solid waste form. The treatment of MSW APC residues with sodium silicate and cement produces a solid waste form with a reduced structural integrity and a tendency to breakdown under attack from aggressive fluids. Silica 'gels' are formed during initial setting reactions which 'depolymerise' with fluid ingress to form new calcium rich silica 'gels' within cracks and voids of the solid waste form. Expansion due to water absorption and continual 'gel' formation causes structural failure. The addition of sodium silicate to sludges produced from a current treatment by mixing MSW APC residues with other mixed hazardous waste improves strength development by 'encapsulating' the waste sludge inside a calcium/silica 'gel'. This stops components of the sludge from interfering with normal OPC hydration. The treatment of MSW APC residues with sodium silicate will not produce a solid form to meet the new waste acceptance criteria. However, sodium silicate has the potential to improve handling and structural integrity of the sludge produced from the current treatment process.

In order to protect the environment and human health from being harmed by air pollution, governments and organisations have been publishing standards and guideline values for pollutant emissions and ambient concentrations, as well as acts and regulations for enforcement. Consequently, various techniques have been developed for sampling and analysing ambient air, to ensure that the set standards and regulations are complied with. New legislation increasingly requires investment in environmental monitoring and pollution control that will deliver the greatest added value to regulatory bodies, by reducing costs and targeting the most culpable sources. The work described in this thesis was therefore to explore and develop suitable methods and techniques to help with cost-effective air quality monitoring. An approach which may add to the range of tools available is directional passive air sampling. A new flow-through directional passive air sampler (DPAS) was designed and tested to facilitate both enhanced sampling rates and pollution source locating and apportionment. Different from performing directional analysis on historical air monitoring data acquired by automatic monitors, the new sampler designs should be able to directly obtain direction-resolved air samples for source-concerning studies. Desirable features of such a device are discussed, and a possible design for sampling gaseous pollutants was conceived, and tested. Preliminary wind tunnel tests showed that it started to turn into the wind direction at fairly low wind velocity, and was successful in generating an identifiable directional result after short exposure in a pilot chemical test. Based on the first findings, the first prototype for gas directional sampling was re-designed and further characterised in the wind tunnel. Nitrogen dioxide (N02) was the test analyte. Uptake rates were derived, and linearity between the internal and external wind velocities established.

Increasing evidence suggests that exposures to air pollutants present in indoor environments are contributing factors to the recently observed increase in respiratory symptoms among young children. The SchoolAir pilot study aimed to assess the hypothesis that poor indoor and outdoor air quality in schools is associated with increased prevalence of asthma, respiratory and allergic symptoms among primary school children, and assess the feasibility of a bigger full-scale research project in the future. The main aim of this MPhil project was to develop and test a methodology for exposure assessment of indoor and outdoor pollutants in primary schools. A secondary aim was to assess the prevalence rate or respiratory symptoms and their relationship to air pollutant exposure in different schools. The following pollutants were measured indoors and outdoors: carbon monoxide (CO), carbon dioxide (C02), nitrogen dioxide (N02), total volatile organic compounds (TVOC) formaldehyde (HCHO), and particulate matter of 0.5-5.0 micrometers in diameter (PM0.5-5.0). A questionnaire was used to assess respiratory health effects in children. Air quality monitoring was conducted in three rounds in four primary schools in England. Real time measurements were performed simultaneously in three indoor locations and one outdoor location within each school, for one week during usual school hours. Personal exposure (PE) to each pollutant was estimated combining time-activity patterns of children and measured concentrations. Findings showed important temporal and spatial variations in concentrations of certain air components. The most prominent variability was observed for PM0.5-5.0 and CO2. Weekly means for PE to PM0.5-5.0, N02 and TVOC were higher than concentrations measured in classrooms (ME) in the majority of cases, whereas for CO, HCHO and CO2 the opposite effect was observed. The calculated coefficients of variations for ME and PE revealed that variability of modelled PE was higher than that of relevant ME. Thus modelled PE seems to reflect more of the actual variability of exposures that children had during their days at school than exposures measured by fixed monitors in a classroom. The results of linear regression of PE to ME showed that for the three of the six investigated indoor air components - PMO.5-5.0, N02, and CO2 - less than 50% of the variation of PE could be explained by the variation of relevant ME. For the other three pollutants - CO, HCHO and TVOC the results of linear regression were inconclusive, as half of the calculated coefficients of determinations (R2) were above 0.5 and the other half were below 0.5. Preliminary analysis of the health survey results revealed variations of respiratory and allergic symptoms prevalence between the investigated schools. It was shown that the children in one of the suburban schools, where the modelled yearly mean PEs were in the upper end of the inter-school yearly means range had the highest proportion of respiratory and allergic symptoms, whereas in the rural school the modelled yearly mean PEs were overall in the lower end of the inter-school yearly means range, and the children of the rural school had the lowest prevalence of symptoms. The methodology used in this study for the assessment of children's personal exposure to air pollutants during a school day employed a combination of measurements by stationary monitors in school microenvironments and children's time-activity-location patterns. This study revealed important differences between concentrations measured with fixed monitors and estimated personal exposures for all measured pollutants. This methodology is efficient and potentially less expensive than individual personal monitoring.

Perfluorocarbon tracer experiments have been undertaken to study atmospheric dispersion mechanisms on urban and regional scales. Urban experiments have been undertaken in central London and central Manchester, United Kingdom, in order to investigate flow and dispersion patterns in street networks with source-receptor distances ranging from >100 m up to 1300 m. Substantial data sets have been produced.

Complaints regarding environmental odours are common. Such complaints may be reported as a nuisance or related to health effects. Odour complaints are difficult to manage and resolve. One of the reasons for this is that odours are complex entities and difficult to characterise. In addition, there is uncertainty regarding the impact odours can have on health. The objectives of this research were to create a knowledge-base on the subject of odours, to examine the relationship between odours and health effects and to develop tools and guidance to improve the assessment and management of odour related incidents. The research was generated by the investigation of a series of odour incidents where the Health Protection Agency has been asked for advice on the health protection impacts of odours. In addition, an experimental study investigating exposure patterns in different environmental settings was carried out. A model of olfactory response was applied to the experimental data in order to gain insights into that process and the potential for odour complaints. The research has developed improved methods for the determination and estimation of population exposure to chemicals involved in, or associated with, odour complaints to aid the assessment of health effects. The knowledge leads to new approaches to community level hazard assessment for odour and is beneficial for health professionals and regulators of environmental odours. The results of this project have important implications for the way in which odour incidents are managed and with respect to the regulation of odorous emissions. In addition to investigating exposure assessment, a toolkit was developed to assist dealing with odour related issues. This toolkit improves the public health response to odour incidents, helping to ensure that odours pose a minimal risk to public health.

In recent years roadside concentrations of the European regulated pollutant N02 have been leveling, or in some cases increasing, throughout Europe and in the UK. The roadside concentration behavior was unexpected, and was not predicted by air quality modeling due to a poor understanding of typical or 'real-world' f-N02. Various estimations have been made but there are few measurements of real-world f-N02 due to the inherent difficulty of measurement afforded by the ambient reactivity of NOx. In answer to the need for determining real-world f-N02 both a detailed and comprehensive measurement campaign was undertaken in a road tunnel. The Westgate Tunnel, the tunnel in which the research was conducted provided an environment where measurement of primary emissions of NOx could be made, due to the restricted dispersion environment and the removal of the impact of secondary chemistry. Further to this aim, the research employed the modified tunnel rationale where simultaneous measurements from two positions in the bore are made. The net difference between the measurements was considered as primary NOx, and used to quantify f-N02. To improve upon previous research a detailed characterisation of the tunnel was made, to ensure a full understanding of the environment. Consequently, a 23 week measurement campaign was undertaken between January and September 2010. The results exhibited a high degree of statistical reproducibility and all weekdays were combined into a single overall dataset from which real-world f-N02 was quantified. This provided f-N02 ranging between O.10~~:~~ and 0.21 ~~:~~, with a mean value of O.17~~:~~. Our observed f-N02 compared favourably with estimated f-N02 values derived from chassis-dynamometer studies, that are currently used and recommended for use in air quality modelling.