As traditional disinfection techniques have proved to be inefficient in coping with toxic pollutants, there is a real need to create and develop alternatives such as Advanced Oxidation Processes (AOP's). As one of the most promising AOP's developed to date, heterogeneous semiconductor UV-photocatalysis has been shown to efficiently mineralise and inactivate a wide range of organic, inorganic and biological pollutants. This technique is based on the powerful redox properties of UV-illuminated semiconductors. The photocatalyst (semiconductor), which is insoluble in water, can be used in the form of a dispersion or as a thin coated film over which the pollutant can flow and interact in the liquid as well as in the gas phase. Although many pollutants have been studied, the development of more powerful analytical tools has meant that trace levels of water pollutants such as bromate, a potential carcinogenic by-product of the ozonation process and their destruction needs to be addressed. Chapters Three, Four and Five investigate the development and use of an analytical method for monitoring trace levels of bromate (ppb level or μg.dm<SUP>-3</SUP>), in studies involving the use of Granular Activated Carbon (or GAC) and platinised TiO<SUB>2</SUB> (Pt-TiO<SUB>2</SUB>) UV-photocatalysis for the removal of this inorganic pollutant. In Chapter Six, a study of TiO<SUB>2</SUB> photocatalysed oxidation of urea-based pesticides is given. Chapter Seven investigates two photoreactor designs for use in flow systems with larger volumes of pollutant which is required if the system is to be commercially viable. These flow photoreactors use thin immobilised films of TiO<SUB>2</SUB> over which the pollutant can flow. Finally, using the flow photoreactor designs studied in Chapter Seven, Chapter Eight presents a study of the photocatalysed oxidation of volatile organic pollutants (or VOC's) in the gas phase.

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A large class of xenobiotic compounds can enter the marine environment as constituents of fuel oils, synthetic dyes, foods and industrial wastes. Some of these compounds may pose long term hazards to aquatic biota because of their mutagenic and carcinogenic activities. The metabolism of such chemicals is of primary concern because these compounds may require metabolic activation and detoxification will determine the hazard posed by exposure to these chemicals. We chose to assess these processes in the edible mussel <i>Mytilus edulis</i> as a model to study the metabolism of such potential toxins. The postmitochondrial fraction from the bay mussel <i>M. edulis</i> was used as an activation system in Salmonella/microsome assay. Three protocols (plate-incorporation, pre-incubation assays and fluctuation tests) were evaluated in order to identify optimal techniques for such studies. The fluctuation tests were known to be more sensitive than the other protocols in the detection of the activity of mussel S9 against a panel of promutagens (Chapter 3). This technique was used to determine the range of metabolic capacities of mussel S9 in the activation of a variety of environmental promutagens. The other part of the thesis involved a study of the mutagenic potency of cigarette smoke particulate matter in the Salmonella/mammalian microsome assay in the presence of rat-liver S9. This work involved the study of some of the factors such as ventilation, which influence mutagenic activity in bacteria and in mammalian cell lines (V79 and XEM2). The results of the study indicate that the tobacco particulate matter (TPM) derived from ultra low tar cigarettes, induce more revertants than that from high tar cigarettes. Finally, the data demonstrate that the mutagenic potency of tobacco particulate matter (TPM) is slightly affected by the ventilation either in bacterial (Salmonella) assay or in mammalian assay (micronucleus test) in V79 and XEM2 cell lines.

A study has been made on the effect of zinc, calcium and copper on the growth and <SUP>14</SUP>C fixation of <i>Phaeodactylum tricornutum</i> and <i>Dunaliella primolecta</i>. Experiments were carried out to examine the uptake of <SUP>65</SUP>Zn by <i>Phaeodactylum</i> and <i>Dunaliella</i> in laboratory culture, to investigate the processes involved, its relationship to metabolism, and the factors affecting it. Also, experiments were carried out to investigate the effect of these metals on chlorophyll concentration and protein content of <i>Phaeodactylum</i> and <i>Dunaliella</i>. It has been found that the organisms displayed varying degrees of tolerance to the presence of the metals zinc, cadmium and copper in the growth medium. Of the three metals copper was found to be more effective upon the growth, <SUP>14</SUP>C fixation, zin-65, chlorophyll<i>a</i> concentration and protein content of <i>Phaeodactylum</i> and <i>Dunaliella</i>.

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