The thesis begins with an examination of the pattern of global mangrove clearance. In Belize unlike many other countries, mangrove clearance is being driven by the current market requirement for housing, rather than industrial or agricultural demands. There is little local demand for mangrove related products (notwithstanding that many of the fish and crustaceans that use the mangrove forest as a nursery ground or habitat are commercially exploited). Analysis of recent clearance permit applications shows that mangrove forest clearance is rapidly accelerating around Belize City. The physical process of forest clearance in Belize is then outlined emphasising its effect upon the forest environmental processes. These are conceptualised in a series of predictive hypotheses considering the expected changes in a range of soil, water and other environmental properties following forest clearance. These are grouped into four - changes stemming from alteration to the little input; changes due to a reduction in the vegetation cover; changes driven by surface water and drainage modification; and finally changes determined by the geology and physical alteration to the ground surface. The significance of such changes in these measured properties is given in a discussion of mangroves stress tolerance and avoidance strategies. Published mangrove tolerance ranges and responses to critical levels of flooding, salinity, temperature, insolation, tidal action, sedimentation, wind, soil acidity, anaerobic state and the presence or absence of soil nutrients are reviewed, summarised in a series of flow diagrams. A field site sampling strategy is devised and three sites of different ages and stages in the clearance process are selected, to provide an insight into both the spatial and temporal aspects of change. A range of soil, water and environmental properties such as ground level insolation and litter cover are measured at these sites using both areal and transect sampling schemes. The resulting data are analysed using 3D visualisation techniques, comparative statistical testing (Mann Whitney-U tests and one way ANOVA) ordination techniques and semi-variogram analysis. These show that significant differences do exist between sites located in the forest and those in the newly cleared areas, with this difference changing through time and manifested at different scales across space. For some properties a third conceptual unit can be sustained - referred to as the "transition zone" - this straddles both sides of the clearance cut-line. By showing that changes occur in the forest soil and water properties in areas next to cleared sites, this thesis concludes with a re-evaluation of Belize's existing mangrove forest clearance legislation. It asks whether the current 66' wide mangrove forest buffer is sufficient to provide a sustainable protective barrier along Belize's coasts and waterways.

The consequence of lead pollution on the metabolism of a number of moss species which had been characterized as "sensitive" to pollutants according to Black (1974) were investigated by laboratory experiments. The effects of lead pollution on the moss membrane system, on their growth, on their physiology and in particular, on their respiration, photosynthesis and photosynthetic pigments were demonstrated. An investigation was undertaken to compare lead mines (Lead Hills and Strontian - Scotland), with that of the area surrounding, but just off the strontian mine and with the lead accumulation in moss adjacent to some main thoroughfares. A two-part study to ascertain the physiological effects of experimentally induced lead pollution on uncontaminated moss samples ensued. In the first experimental section, treatments involving different concentrations of lead were carried out for a short duration (a few days) by using a percolation system In the second section, experimental samples were cultured onto lead media for a long-term exposure. The results from both experiments showed the physiological response of the mosses to lead uptake; these included low photosynthetic rates, high rates of respiration and converted chlorophyll pigment to phaeo phytin pigment. The uptake of lead in the experimental samples being percolated in lead solution was much higher than the lead uptake of the samples cultured on Pb enriched media. In accordance with these results, it was suggested that the rhizoid might take up lead more than the stem and perhaps there is a barrier between them which stops lead going throughout the stem. A further experiment was carried out to test the validity of this suggestion. Again utilizing moss samples collected from lead mines and busy roads, the results substantiated the above suggestion. The investigation involving lead pollution along main roads, both inside and outside of the city showed that the lead uptake ratio of rhizoid to stem was not the same as that of the mosses from lead mines. This could be attributed to atmospheric pollution which comes from auto-exhaust fumes.

Factors contributing to the natural reproductive performance of flowers, plants and populations of British and Mediterranean Orchidaceae are considered. Reproductive success is found to be pollinator limited, with most European orchids failing to achieve their maximum potential within the season, particularly nectarless species. There is a consistent discrepancy in gender function, with many more pollinia being removed than returned, because of pollinator foraging behaviour. Patterns of insect visitation to orchids are influenced by inflorescence and labellum characters, such as floral spurs. Spurs vary in size and shape between species, and many are nectarless. Trichomes are often present on the inner surface, and may prolong insect visits. The principal orchid pollinators are all members of the Hymenoptera, Lepioptera and Diptera, which normally visit other plants for food. Co-occurring species can act in a facilitative way to maintain a band of local pollinator, and pollination of all species examined is found to be significantly associated with the presence of 1 or 2 key foreign species or a guild of such plants. Under conditions of infrequent pollination, various features of the European Orchidaceae act to maximise their reproductive success when pollination does occur. The flowers are found to be long-lived and remain receptive to additional pollinations which may lead to increased seed quantity and diversity. Pollen maintains viability for several week which prolongs the opportunity of insect transported pollinia to effect pollination. Break up of pollinia into smaller dispersal units increases the likelihood of widespread dispersal and reduces pollen wastage. Even the smallest pollen load is found to stimulate embryogenesis, but more seeds are set with larger loads. PL:O ratios of 2-3:1 are most commonly found, which should result in both maximal seed set and increased quality of the offspring. Furthermore, seed output is significantly associated with fruit set and average levels of capsule formation are consistently higher in nectariferous orchids than in nectarless ones. Most rare British orchids are nectarless, and are particularly vulnerable to environmental alterations which influence the floral composition of their habitat, and density and distribution of supporting species.

The aim of this study is to evaluate sediment and solute dynamics of the River Don, represented by the records collected at Parkhill, and to assess the changes brought by man's intervention upon the reach between Parkhill and Seaton. The need to make an investigation of this kind became apparent, when increasing concern was expressed about the presence of excessive suspended matter in the river. It was known that water quality was being affected. The variations in concentration of suspended solids and solutes (magnesium, calcium, sodium, potassium and conductivity) were sampled three times a day in the river Don at Parkhill station (in an agricultural area, upstream of the main industrial works) and at Seaton (downstream of the industrial works, in an urbanarea) using vacuum samplers during the period March 1976 March 1977. Twice a week sampling was conduced at Seaton, during a previous period from March 1975 to March 1976. The suspended solids discharge relationships have been evaluated and there is a tendency for maximum concentration to occur during the summer storms. Suspended solids concentration were seen to increase between 20 and 200 times, downstream of Parkhill mainly as a result of industrial pollution, road works and higher transporting capacity at Seaton in particular during the winter floods when sand-size material was beeing transported. The output of suspended matter was estimated at 33,633 tonnes/year at Parkhill and 682,979 tonnes/year at Seaton. The effects of variation in discharge upon the solutes on the River Don showed that magnesium, sodium, calcium and conductivity tended to be diluted by increase in discharge. Potassium is seen to increase with rising strearflow. The response of potassium results from its tendency to be lost from solution by abscption. Concentrations of solutes were found to increase downstream of Parkhill, during spring and summer, mainly as a result of unmeasured factors such as pollution (e.g. high suspended solids, mainly organic matter, and calcium carbonate) and nutrient cycling affect the river water chemistry. An erosion rate of 26,4 tonnes/km2 was estimated for the Don catchment. The chemical denudation was estimated at 117.7 tonnes/km2 for total dissolved solids, and 2.1 tonnes/km2 for magnesium, 11.5 tonnes/km2 for calcium, 3.1 tonnes/km2 for sodium and 1.2 tonnes/km2 for potassium. These figures were compared with others from the British Isles.

In the first section of this thesis, series of tetraorganotin compounds have been synthesised for their use as calibrants in speciation studies. The preparation of these organotin species involve the combination of alkylation of organotin halides with Grignard reagents and selective cleavage of carbon-tin bonds using iodine as cleavage reagent. Some of the compounds synthesised have been used to carry out a comparative study of derivation of butyltin halides by pentylation using pentylmagnesium bromide, PeMgBr, and by ethylation with sodium tetraethylborate, NaBEt4. The determination of the resulting tetraalkyltin species was made by Gas Chromatography with Flame Photometric Detection, GC-FPD. No significant differences between both procedures were found. The capability of sodium tetraethylborate as ethylating reagent was tested for other organotin compounds such are organotin oxides, carboxylates and mercaptides. It was found that, in some cases, the success of the reaction depends on the volume of the other groups attached to the tin centre. Finally it was study the selectivity of the reaction of sodium tetraethylborate with organotin halides with alkyl chains carrying other functional groups (i.e. carboxylates, phosphines) bonded to the tin atom. In the second section, it is described the synthesis of some arsenoribosides related with the organoarsenic species that so far have been isolated and identified in marine organisms and that are considered of interest for the fully establishment of the biodegradation pathways which lead to the formation of the major organoarsenic species in marine environments, the arsenobetaine.

No description available.

Between 1830 and 1968 Glasgow was home to one of the world’s largest producers of Cr-based chemicals. Chromite ore processing residue (COPR) arising from the factory was used as infill material across large areas of SE Glasgow, resulting in widespread land contamination with Cr(VI), a known human carcinogen of significant mobility. This thesis presents the results of a research project into the bioaccessibility of Cr in Glasgow soils, using a physiologically based extraction test (PBET). 27 Samples were analysed, four of which had a Cr concentration above the residential SGV (200 mg/kg). Two samples where identified with a sizeable Cr(VI) concentration, 1485 ± 24 and 171 ± 5 mg/kg, respectively. Bioaccessible Cr was significantly less than the total concentration, being an average 5% of the total concentration. One sample had a notably high Cr bioaccessibility, at 1156 ± 32 mg/kg. This sample, from Rutherglen, was the only one to exceed assessment criteria, and as such pose a potential risk to human health. The solid phase distribution was also assessed, making it possible to identify the likely mineral sources of bioaccessible Cr within a sample. In the majority of samples Cr was associated with Fe oxide phases, resulting in a low bioaccessibility. Two samples had a sizeable amount of Cr associated with clay and carbonate phases, which have less acid stability, resulting in a higher bioaccessibility (1156 ± 32 and 116 ± 2 mg/kg). A carbonate phase, unique to samples from sites with known history of COPR disposal, was also identified. This had a large amount of associated Cr, suggesting it was derived from the COPR.

In recent years, the environmental occurrence, fate and effects of pharmaceuticals or pharmaceutically active compounds (PhACs) and their metabolites have received increased attention. PhACs have been detected in wastewater, river water, marine waters and even sewage sludge and soil. Since PhACs are developed with the intention of stimulating or inhibiting physiological responses, these findings have prompted concern over their environmental fate and potential adverse effects on nontarget ecological species. The major source of discharge of PhACs to the environment is through sewage treatment works (STWs) effluents and sludges. Although used in quantities similar to many agrochemicals and other organic micropollutants, PhACs are not required by legislation to undergo the same level of testing for possible environmental effects. Therefore, PhACs and their metabolites have been subject to many years of unrestricted emission to the environment. Typically, concentrations measured in municipal sewage treatment plant effluents are mg L'', whilst those in the surface waters range from ng L' to μg L"1. The fate of PhACs in the aquatic environment is determined by both abiotic and biotic processes. Abiotic transformations in surface waters may occur via hydrolysis and photolysis, with photolysis thought to be a significant factor in determining their environmental fate. In the present study, the anti-anxiety drug, diazepam (Valium®) along with its known human metabolites, nordiazepam, temazepam and oxazepam were selected for photodegradation studies. The photodegradability of each drug in distilled and natural waters was evaluated using a Suntest CPS Xenon are lamp, selected to reproduce the spectral distribution of solar irradiation, with emphasis on the determination of degradation rate constants and half-lives under realistic environmental conditions. Solid phase extraction (SPE) methods were developed for extraction of these compounds from natural water samples and analysis was performed using high performance liquid chromatography (I-IPLC) separation with electrospray ionisation multistage mass spectrometry (ESI-MS") detection. Results demonstrated that whilst the compounds were hydrolytically stable in aqueous solutions, photolysis significantly reduced the concentration of diazepam and its metabolites in aqueouss olutions. The measuredh alf-lives (t112o) f diazepam, nordiazepam, temazepam and oxazepam in distilled water were 100,193,36 and 32 hours respectively. Novel photoproducts including 5-chloro-2-methylaminobenzophenone (m/z 246, [M+11]+) and 2-arnino-5-chlorobenzophenone (#/z 232, [M+II]+) were detected and characterised by electrospray ionisation multistage mass spectrometry (EST-MS") and comparison with reference compounds. The identities of a range of further photoproducts observed in aqueous solutions of photodegraded PhACs were proposed based on ESI-MS" data analysis, The presence of natural organic matter (NOM), specifically humic acids at environmental levels (1 mg L'') were found to approximately double the rate of photodegradation for diazepam and nordiazepam (t1n 28 and 48 hours respectively). In contrast, results for the metabolites temazepam and oxazepam suggest that the presence of humic acids led to a reduction in the rateo f photodegradatio(nti n 72 and6 6 hoursr espectively). The direct and indirect photodegradation kinetics determined in the present study for diazepam and its human metabolites were applied to UK river catchment models using a computer model, GREAT-ER. Maximum predicted environmental concentrations (PECs) were determined for each compound and the impact of phototransformation on the removal of each compound was evaluated in two river catchments representing an urban/industrial catchment (river Aire) and a rural catchment (river Exe) respectively, under low flow (summer) and mean flow (winter) river conditions. The modelling predictions suggest that phototransformation may be an important process for removing diazepam and excreted human metabolites of diazepam from natural riverine and lacustrine environments. The overall results demonstrated that with photolysis half-lives ranging from 193-32 hours, diazepam and its human metabolites are unlikely to be persistent in natural waters.

The central theme of this thesis was the search for ecologically meaningful ways to quantify the relationships between the biota and ecosystem processes. This thesis investigated whether a "functional group" approach, that characterised the fauna according to similarities in their activities, could be successfully employed to quantifiably link species' performance to important ecosystem processes. Initially the abilities of traditional "trophic" and "bioturbatory" categories to characterise the estuarine macrobenthic fauna and discriminate between estuarine sites were examined. This thesis determined that the perceived inter-site similarity within an estuary varied according to the function being investigated and that the apparent associations between abiotic factors and biotic assemblages were also heavily influenced by the choice of functional classification. This study provided strong evidence that links between the macrobenthos and abiotic factors were most easily detected if the species were grouped according to their bioturbatory abilities. Thus, attempts to model the contribution of the estuarine macrofauna to sediment mixing throughout an estuary were pursued in preference to modelling trophic group distribution. This thesis identified limitations of existing "bioturbation" categories and hence, developed a novel classification system that incorporated species' activity rates, magnitude and location within the sediment. Strong evidence was found that estuarine macrobenthic communities should be treated as two separate assemblages: one shallow assemblage occupying surface and near surface layers, and one deep assemblage with the ability to exploit the sediment at greater depths. The two separate assemblages displayed different associations with the environmental factors examined in this study. By developing new functional groupings of species' behaviour, and treating shallow and deep assemblages as separate entities, this thesis was able to estimate the contribution of the biota to sediment mixing and successfully develop and validate generic predictive models of functional group distribution within the Tamar/Plym estuarine system. Since the functional groups themselves convey information about the magnitude of their effect and the sediment horizons impacted, this thesis represents an important advance in our ability to predict biological contribution to sediment mixing processes in estuarine ecosystems.

Air pollution in urban areas is a problem affecting many countries in the world and has important implications for health and environmental management. However, air quality prediction plays an important role in the controlling air pollution problem. Air-quality models are also extensively used in all aspects of air pollution control and to predict spatial and temporal dispersion of pollutants in the atmosphere. The main objectives of this work are to provide an overview of the pollutant levels and their trends in the study area (Rabia) and to predict the ground level concentrations of sulphur dioxide (SO2) and nitrogen oxide (NOx) mainly emitted from power generation stations by using Source Complex model for Short-term Dispersion (ISCST 4.5) for years 2001 and 2004. The hourly air pollutants concentrations were measured continuously by fixed ambient air stations located over the polyclinics in Rabia area in Capital Governorate in the State of Kuwait.