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The harmful effects of air pollutants on human beings and environment have been the major reason for efforts in sampling, analysis and control of their sources. The major pollutants emitted to atmosphere from stationary combustion processes are nitrogen oxides, inorganic acids, carbon dioxide, carbon monoxide, hydrocarbon and soot. In the current work two methods are developed for sampling and analysis of volatile chlorinated aromatic hydrocarbons and semi-volatile chlorinated aromatic hydrocarbons for example 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) by using solid sorbent, thermal desorption and high resolution GC-MS. The capacity of several solid sorbents is compared by breakthrough value and percentage recovery ofthe analyte from the sorbent. The thermal stability of polyvinyl chloride (PVC) and PVC in the presence of metals is studied because PVC is a polymer commonly found in solid waste derived from medical waste, car recycling and electrical cable. Harmful pollutant emissions from combustion and pyrolysis of PVC are measured using the novel method developed in this work. The main inorganic volatile is HCl while benzene is the major volatile organic formed under pyrolysis and combustion conditions. The thermal degradation of PVC produces a large number of chlorinated aromatic hydrocarbon, aromatic hydrocarbon and short chain linear gases. A study is designed for control of harmful pollutants from combustion of PVC including HCl, aromatic hydrocarbon, chlorinated aromatic hydrocarbons and soot. It is reported that the presence of metal oxides have the ability to control the level of harmful emissions by facilitating the producing of more short chain linear gases. A study is designed for control of harmful pollutants from combustion of PVC including HCl, aromatic hydrocarbon, chlorinated aromatic hydrocarbons and soot. It is reported that the presence of metal oxides have the ability to control the level of harmful emissions by facilitating the producing of more short chain linear gases. Two methods are developed for the control of soot from liquid and gas combustion process by using applied fields, Magnetic and electric fields. In this study, it is shown that an increase in applied field strength leads to an increase in flame temperature but a decrease in the length of flame. The level of soot emission was decreased in presence of an applied field. A discussion of the effect of applied fields on the combustion process is given.

An understanding of the dispersion of contaminants in turbulent flows is important in many fields ranging from air pollution to chemical engineering, and random walk models provide one approach to understanding and calculating aspects of dispersion. Two types of random walk model are investigated in this thesis. The first type, so-called "one-particle models", are capable of predicting only mean concentrations while the second type, "two-particle models", are able to give some information on the fluctuations in concentration as well. Many different one-particle random walk models have been proposed previously and several criteria have emerged to distinguish good models from bad. In this thesis, the relationships between the various criteria are examined and it is shown that most of the criteria are equivalent. It is also shown how a model can be designed to (i) satisfy the criteria exactly and (ii) be consistent with inertial subrange theory. Some examples of models which obey the criteria are described. The theory developed for one-particle models is then extended to the two-particle case and used to design a two-particle model suitable for modelling dispersion in high Reynolds number isotropic turbulence. The properties of this model are investigated in detail and compared with previous models. In contrast to most previous models, the new model is three-dimensional and leads to a prediction for the particle separation probability density function which is in agreement with inertial subrange theory. The values of concentration variance from the new model are compared with experimental data and show encouraging agreement.

We have developed novel experiments aimed at understanding whether and how quickly organic aerosols (OA) mix using single-particle mass spectrometry, as different treatments of mixing in regional models significantly affect predicted mass and composition. First, we designed experiments that separate OA formation chemistry from thermodynamics to test whether two populations of particles equilibrate with eachother through the gas phase on experimental timescales. Single-particle mass spectrometry measurements from the aerosol mass spectrometer (AMS) allowed us to quantify the extent of mixing that had occurred. We calibrated this technique using pure-component aerosols with known vapor pressure and phase state, the results of which agreed with a condensation-evaporation model. We then applied these techniques to three atmospherically-relevant situations to determine that: 1) anthropogenic secondary OA (aSOA) does not mix with a surrogate for hydrophobic primary OA (POA), 2) biogenic SOA (bSOA) does not mix with hydophobic POA, and 3) bSOA shows significant mixing with aSOA. The sum of these experiments show that these complex interactions can be measured for atmospherically important systems, a first step towards quantifying activity coefficients for complex OA mixtures. We also investigated mixing within individual particles, using mixed-particles of squalane (a surrogate for hydrophobic POA) and SOA from ↵+pinene + O3 that we determined to contain two separate phases. In these experiments, after formation of the mixed-particles, we perturbed smog chamber with a heat ramp. These data revealed that squalane is able to quickly evaporate from the mixed-particles, and that almost all of the SOA is comprised of material lower in volatility than squalane (a low-volatility constituent of pump oil). For this latter “comparative volatility analysis,” we had to correct for the highly variable collection efficiency (CE) of the mixed particles to correctly calculate the mass fraction of SOA remaining. One of the larger implications of this work is highly dependent on the particle morphology, which we were not able to determine definitively: if indeed the particles are coreshell with squalane inside a thick layer of SOA, our results show that diffusivity within SOA is not ultra-low. Lastly, we present work that furthers our understanding of single-particle CE in the AMS, a quantity especially important for experiments where particle phase is dynamic or there are two separate populations of particles. We report the particle CE of SOA, ammonium sulfate, ammonium nitrate, and squalane. We also determine that half of SOA particles that give meaningful signal, do so at a time later than would be predicted based on their optically-measured flight time through the instrument. We present convincing evidence that the nature of this delay is due to particles ricocheting around the ionization region of the instrument before vaporizing on an auxillary surface near the the vaporizer. This process affects how much mass signal comes from a particle, the particle mass spectrum, and the bulk mass distribution derived from particle time-of-flight mode. Our results also show that while there is no size dependence to CE for SOA, particles that have passed through a thermodenuder have lower CE, implicating oxidation state and/or volatility as a controller of particle bounce.

Emission limits for diesel engine exhaust pollutants are being continually reduced in line with increasingly stringent emissions legislation. Essential to the task of reducing diesel exhaust emissions is an understanding of the origin of the exhaust pollutants. This research has investigated the origin of a group of compounds, polycyclic aromatic hydrocarbons (PAH), in diesel exhaust emissions using 14C-radiotracer techniques developed specifically to investigate the origin of the organic components in diesel emissions. The use of radiotracers in this research has enabled both the extent to which individual PAH survive combustion and the extent to which PAH are pyrosynthesized during combustion to be measured accurately. No other diesel emissions research technique has yielded information which is so unequivocal. Radio-chromatographic techniques were developed specifically for the identification and quantification of radioactive species present in diesel emissions resulting from the combustion of a single 14C-radiolabelled precursor. Radio-high performance liquid chromatography (radio-HPLC) was the main technique used and was applicable as both a tool for sample fractionation and for analytical measurement. Radio-gas chromatographic techniques (radio-GC) were also developed and applied to the identification of radioactive species in the exhaust emissions. Diesel exhaust samples were collected from a 2L direct injection Perkins Prima diesel engine using a novel exhaust sampling device, the Total Exhaust Solvent Stripping Apparatus (TESSA) devised previously to sample organic species from automobile exhausts. Diesel combustion experiments were performed on three 14C-radiolabelled PAH, fluorene, pyrene and benzo[α]pyrene (B[α]P), and 14C-n-hexadecane. These were spiked into the diesel fuel and were combusted in the Prima Engine. The extent of survival was 0.04% for B[α]P, 0.17% for pyrene and 0.87% for fluorene. The amount of each PAH in the exhaust emissions derived from pyrosynthetic sources ranged from <20% for B[α]P, to 26.5% for fluorene and 71% for pyrene. The extent to which individual PAH survive the diesel combustion process was correlated with the molecular orbital distribution of the molecule, and especially the energy levels of the lowest unoccupied molecular orbital (LUMO). It is concluded that the relationship between PAH survival and PAH molecular orbitals (MOs) is owing to the kinetics of combustion reactions and the chemical reactivity of the P AH. The extent to which individual PAH molecules are formed during combustion varies considerably. From the limited number of experiments performed in the current research it has not been possible to determine the mechanisms responsible for the formation of these PAH during combustion. Mass balance calculations have demonstrated that the degree of pyrosynthesis of the parent PAH molecules investigated in this research may be accounted for by comparatively low rates of dealkylation of alkyl-substituted derivatives present in diesel fuel. The importance of dealkylation reactions during diesel combustion, was investigated by combusting a low aromatic fuel spiked with a non-radiolabelled alkyl-PAH, 2- and 3-ethylphenanthrene (2- and 3-EtPa), which were synthesized for this purpose. The 2 and 3-EtPa isomers were recovered in yields of 0.35% and 0.3% respectively. No dealkylation of the EtPa was detected. A statistically significant increase in the emissions of 3-methylphenanthrene (3-MePa) was detected and was equivalent to a conversion rate of 0.0004% of the EtPa spike. It is proposed that the ease with which individual alkyl-PAH isomers are dealkylated varies for specific isomers, and is dependent on the position of the alkyl-substituent on the aromatic nucleus. The major product from the combustion of the EtPa was vinylphenanthrene (ViPa) which produced in a yield equivalent to a conversion of 0.01% of the EtPa spike. Radiotracer experiments with 14C-n-hexadecane were performed to investigate the origin of the aliphatic component of diesel emissions. The extent of hexadecane survival was 0.35%. Approximately two thirds of the hexadecane in the emissions was derived from pyrosynthetic sources. The most probable source of the pyrosynthesized hexadecane in the emissions was 'thermal cracking of higher molecular weight aliphatic species in diesel fuel during the combustion process. This process may account for a significant proportion of lower molecular weight n-alkanes emitted in diesel emissions.

A capillary flow gas viscometer has been used to measure the shear viscosities of the hydrofluoroalkanes HFC 134a, HCFC 123, HCFC 124 and the ternary blend MP 39, at pressures up to 0.1 MPa relative to a nitrogen standard. Having applied small correction factors to the measured flow time data, the resultant viscosities are compared to those obtained by other workers (where possible) using alternative techniques. We calculate self diffusion coefficients and hard sphere collision diameters for the molecules within the rigorous Chapman-Enskog kinetic theory of gases, and calculate optimum well depths of the intermolecular interactions using the Extended Law of Corresponding States. The use of a Stockmayer potential energy function by other workers is discussed and within this, the Mason-Monchick approximation is applied to calculate the percentage effect of the dipole moment on the collision integral. In order to assess the affect to the atmospheric chlorine loading of the hydrochlorofluorocarbons measured above (HCFC 123. HCFC 124 and HCFC 22 in MP 39) as well as other halocarbons currentiy in use, two globally averaged mass balance models have been developed on a workstation spreadsheet to assess the future chlorine and bromine levels in the atmosphere and the sensitivity of those loadings to possible forcing factors. These models use production, growth, lifetime and concentration data for fourteen chlorocarbons and three bromocarbons and allow for characteristic emission profiles according to the use to which the halocarbon is applied. Current international agreement, ie. Montreal Protocol 3, is used as a reference level (in most cases), and the models have been used to assess tiiose scenarios which most influence the peak level of chlorine and bromine attained, when that peak occurs and the period of time before 'safe' levels are reached.

Diesel engines account for a large percentage of the particulates in urban city environments. Polycyclic aromatic compounds (PAC), some proven carcinogens, have been found on diesel particulates. The trace level nitro-PAC emissions, such as 1-nitropyrene and dinitropyrenes, contribute a large proportion of the mutagenicity in the particulates; in the case of 1-nitropyrene between 10 to 40% of the total mutagenicity of the particulate has been claimed. The potential health hazards of PAC require the levels and sources of such emissions to be evaluated over a range of speeds and loads. PAC emissions are dependant on the engine specification, such as normally aspirated compared with turbocharged, and the operating conditions (speed and load). The effect of such variables can be determined using emission profiling, in which profiles of the exhaust are compared at varying engine powers. In this way the effect of speed and load on the combustion efficiency can be established. Identification of PAC sources may be further complicated when engine sampling systems, such as the conventional dilution tunnel/filter system, are prone to artefact formation. This is especially relevant to secondary nitro-PAC emissions, which are prone to forming as artefacts of the filter installed in the dilution tunnel. In this study, organic emission maps were constructed using the unique total exhaust solvent-stripping apparatus (TESSA) developed at the University of Plymouth. TESSA allowed rapid sampling with a minimum potential for artefact formation. The close proximity of TESSA to the engine allowed the role of the combustion chamber in the formation of emissions to be evaluated. Primary organic emissions, such as pyrene, are derived from survival of compounds in the fuel/oil and by combustion generation. Establishment of emission maps for the primary emissions are vital to resolving the formation of secondary emissions, such as 1-nitropyrene. Profiling of primary emissions sampled 26 different speeds and loads using TESSA (sampling times as low as IS seconds). Following simple work-up, quantification of the o-alkanes was by gas chromatography with flame ionisation detection and PAH by gas chromatography/mass spectrometry operated in electron impact mode. Emissions were expressed as a recovery of the compound emitted as a percentage of the same compound entering the chamber in the fuel. The o-alkane and PAH emission maps correlated with the gaseous unburnt hydrocarbon emissions, indicating that fuel survival was an important source of emissions, whereas lubricating oil contributions were minimal. Fuel survival contributions decreased with load; at 1000 rpm the average PAH survival of 0.95% at idling decreased to 0.2% at full load. High survivals under idling was a consequence of the low chamber temperatures and air:fuel ratios mixed beyond the lean flammability limits, whereas at full load, the high temperatures resulted in the greatest combustion efficiency. The o-alkane emission trends replicated those of PAH; at 1000 rpm the average o-alkane survival was 0.48% at idle compared with 0.084% at full load. Correlations between the distribution of the emissions and fuel at high load, suggested fuel survival unchanged was responsible. At low loads the exhaust/fuel PAH ratios were more varied, with the range of percentage recoveries at low loads increasing with speed (difference between percentage recovery of fluorene and phenanthrene at idling for 1000 rpm and 3000 rpm was 0.05 and 0.18 respectively). At high load, the combustion environment can be envisaged as producing areas under which complete combustion and survival unchanged occur. In between the complete combustion and unburnt fuel zones, a narrow range of temperatures and time for combustion reduce the opportunity for combustion generation reactions and/or preferential survival. Low load at 3000 rpm may increase the intermediate zone, allowing preferential survival and/or combustion generation reactions to evolve. Possible pyrolytic cracking of o-alkanes and demethylation of PAH at low loads and 3000 rpm was evident. The optimum time, swirl, and temperature for efficient combustion at low loads was generated at 2000 rpm to 2500 rpm, whereas at the higher temperatures corresponding to high loads, the effect of speed was much smaller. The primary emissions map show engineering improvements, particularly at low loads, could be implemented to lower the PAH emissions. The correlation between the emissions and fuel input suggest modifications to the PAH content of fuels may lower emissions. The formation of secondary nitro- and oxy-PAC emissions is by transformation of primary emissions. In the case of nitro-PAC, nitration has been proposed to occur by free radical processes between PAH and oxides of nitrogen, NO,, within the chamber and by electrophilic substitution of PAH surviving combustion by nitrogen dioxide and nitric acid, via the nitronium ion. The combustion contribution to nitro-PAC emissions was investigated using an upgraded TESSA system, and 3 speeds at low, mid, and high NO, for each speed were sampled. Following initial extraction, concentration and clean-up of the samples, the nitro-PAC fractions of interest were isolated by normal phase high performance liquid chromatography. The nitro-PAC were identified and quantified by gas chromatography with electron capture detection, and gas chromatography/mass spectrometry operated in the negative ion chemical ionisation mode (the detection limits for both analytical systems was of the order of 40-50 pg of nitro-PAC standards injected). The profiling indicated that a proportion of the fuel underwent nitration within the combustion chamber across a range of speeds and loads. The extract concentrations (average of 5.3 ppm) found in this study were much lower than those previous found (ranging from 55 to 2280 ppm). The majority of the previous studies relied on sampling using dilution tunnel/filter systems, for which post combustion contributions are simulated; suggesting that a major source of nitro-PAC is derived from post-combustion nitration of PAH surviving combustion, some of which may be artefacts of the filter. Different speeds produced different trends for nitro-PAC emissions with respect to engine load. It was not until the high temperature speed of 3500 rpm was reached that both NO, and nitro-PAC increased with load (R-sq= 0.989 &amp; p=0.067 for 1-nitronaphthalene &amp; NO,). Nitro-PAC emissions at 3500 rpm were primarily the result of combustion chamber nitration of PAH at high NO. In the case of 1-nitropyrene, there was strong evidence to support pyrosynthetic contributions to the pyrene mass, which in turn became nitrated. The nitro-PAC emissions at low loads were the result of post-combustion nitration of PAH surviving combustion with the nitronium ion. The correlation of the PAH precursors to nitro-PAC in the fuel and nitro-PAC emissions suggest fuel modifications may to some extent lower the nitro-PAC emissions. The combustion generation of nitro-PAC at high engine powers may require post-combustion after treatment.

The ceramic glazing techniques of vapour glazing, reduction lustre, Raku and fuming all require specialised firing conditions with the use of potentially hazardous kiln atmospheres and specialist kiln designs for their successful execution. The technique of reduction lustre is an ancient, highly decorative technique in which pigments or glazes containing reducible metal oxides such as copper, silver and bismuth are subjected to a reducing atmosphere which results in the formation of stable iridescent lustrous colour effects. Conventionally hydrocarbons are used to produce a reducing atmosphere, the combustion of which can lead to potentially high levels of CO. This research has concentrated on the technique of reduction lustre with the aim of producing a safe, environmentally friendly firing system. Reduction lustre effects were reproduced using a 100 litre down draft gas kiln designed and constructed for the purpose. A 40 litre electric kiln was modified for use with reducing atmospheres and a laboratory muffle kiln was also adapted to provide closely controlled firing conditions. Alternative reducing atmospheres were assessed, consisting of either 5% H2 in N2 or hydrocarbon vapour in N2 The former is reliable, safe, environmentally friendly and is recommended for studio pottery use. A theoretical design for a reduction lustre kiln incorporating a gas control system based on the use of a 5% H2 in N2 gas mixture and a gas tight outer casing was developed. Thermoanalytical methods were used to investigate the reduction behaviour of raw materials, glazes and frits under different atmospheric conditions. Diffusional and topochemical models of reduction reactions occurring in a typical lustre glaze have been evaluated. In-glaze lustres reduce with thecharacteristics of diffusion processes. Water diffusion out of the glaze may be rate determining. Studies carried out using energy dispersive x-ray analysis andphoto electron spectroscopy show that lustres are associated with the presence of metallic copper, the actual colour being dependent on the surface concentration of the metal. The aesthetic results of the various firing methods developed were assessed using a perceptual study based on the use of a semantic differential test developed from a multiple sorting survey carried out using lustred tiles. The survey used both lustred tiles to represent a 2-dimensional surface and lustred vases which represented a 3-dimensional lustre glazed surface. The survey showed that statistically significant differences were observed between lustred ceramics fired in different systems, allowing comparisons to be made in an objective manner.

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