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Volatile C<SUB>1</SUB> and C<SUB>2</SUB> chlorinated hydrocarbons and their oxidative degradation products are possible contributors to forest decline in Europe and north America. These species originate from both natural and anthropogenic sources, the latter including use as solvents and degreasers within the chemical, dry-cleaning and nuclear industries. Concentrations have been reported in central European forest air, soil and foliage, but no measurements have been made in the UK. This study presents the temporal and spatial distribution of 1,1,1-trichloroethane (C<SUB>2</SUB>H<SUB>3</SUB>Cl<SUB>3</SUB>), tetrachloromethane (CCl<SUB>4</SUB>), trichloroethene (C<SUB>2</SUB>HCl<SUB>3</SUB>) and tetrachloroethene (C<SUB>2</SUB>Cl<SUB>4</SUB>) in air and foliage of three northern UK forests over a 15 month period. Potential sources were identified as petrochemical industry at Grangemouth (Central Region, Scotland) and the nuclear reprocessing complex at BNFL plc. Sellafield (Cumbria, England). A 'clean' site (Grampian, Scotland) was included for comparison. The tree species monitored was <I>Pinus sylvestris</I> (L.). Air measurements were made using novel passive diffusion samplers containing an extract of <I>Pinus sylvestris</I> (L.) wax exposed to the atmosphere for approximately one month. Analysis of the tubes and composite needle samples used solvent extraction and quantitative capillary gas chromatography with electron capture detection. Complementary GC-MSMS was used qualitatively. The needle concentrations found were similar to those of central Europe, and were log-normally distributed. Geometric mean concentrations (ng/g dry weight) were C<SUB>2</SUB>H<SUB>3</SUB>Cl<SUB>3</SUB> 20; CCl<SUB>4</SUB> 5; C<SUB>2</SUB>HCl<SUB>3</SUB> 130; C<SUB>2</SUB>Cl<SUB>4</SUB> 30. There was no statistically significant difference at the 95% level between median concentrations at the three sites, or between the 1992 and 1993 needle year classes. The geometric standard deviation of 2-3 was typical of other gaseous pollutants, and the vertical profile through the canopy at Devilla forest suggested an atmospheric source.

Loch Leven is a largest, eutrophic loch in Scotland, and has historically suffered from eutrophication problems as a result of large phosphorus (P) inputs from point and diffuse P sources. Since the major reduction in point source phosphorus through more efficient sewage treatment and a reduction of industrial effluent, this research project has provided evidence that diffuse sources now contribute a much greater proportion of the loch’s annual P load, compared to a decade ago. High-flow events have been recognised as being one of the major mobilisation and transport drivers of diffuse pollutants in rural catchments. The purpose of this research was to investigate aspects of P transport and delivery during high-flow events in the Loch Leven catchment. Such research will be important in planning effective diffuse pollution management plans in order to further reduce P loads and improve Loch Levens water quality.

The nature of high altitude precipitation and its effect on Scots pine (Pinus sylvestris L.) and Sitka spruce (Picea sitchensis (Bong.) Carr.) was investigated. Scots pine and Sitka spruce are important British forestry species and the effect of acidic cloud on these has been inadequately investigated. At a field site in the Scottish Southern Uplands, impacted cloudwater was either collected from, or measured with a microelectrode in situ on, artificial polypropylene snoots which closely mimicked live shoots. Temporal variation of pH within cloud deposition events was strong and the potential for damage by acid clouds was seen to be high. Impacted cloudwater was also collected from, or measured in situ on, live shoots and the interchange of ions between shoots and cloudwater investigated. Leaching of basic cations was considerable but not sufficient to neutralize cloudwater acidity. Dry deposition on live shoots appeared to increase the acidity of impacted cloudwater on shoots. The change in pH of evaporating droplets was measured in situ with the microelectrode. Droplet acidity increased dramatically as a result of evaporation. The potential for damage by snow was investigated by collecting and analysing snowmelt. Ground snowpack showed an initial flush of ions (including H+) on melting, followed by a steep decline to very low ion concentrations. Meltwater from live shoots did not show this flush/decline but did exhibit higher acidity levels which were also related to the pathway of the snowmelt through the snowpack. A series of four glasshouse experiments were undertaken in which a system for applying simulated acid cloud (SAC) was developed. Six to eight-year-old Scots pine and Sitka spruce were subjected to SAC at pH 5.6, 3.0 and 2.5. Considerable leaching of Ca, Mg, K, NO~-N and PO~-P occurred and showed an increasing response to increasing acidity of SAC. Both extension growth and needle area declined with increasing acidity but the decline was statistically insignificant. Visible injury on Scots pine needles was limited to those subjected to SAC at pH 2.0. Sitka spruce damage occurred to a very small extent at pH 2.5 but was again largely restricted to pH 2.0. Artificial abrasion of needles did not increase susceptibility to acid damage. Acid damage generally progressed from tip to base and at the junction of the brown and green tissue a darker brown band formed. Tissue underlying brown areas was subject to cell collapse and underneath the dark bown band the extracellular spaces were filled with an unknown material and the cells had not collapsed. The structure of the epicuticular wax was not affected by SAC acidity and even over necrotic areas the crystalline wax remained intact. The functional integrity of the cuticle, investigated by measuring cuticular conductance and contact angles, was unaffected by SAC. Controlled experiments on the changing acidity of evaporating droplets took place with three-year-old Scots pine and Sitka spruce in a large wind-tunnel, again with the use of the microelectrode. Droplet acidity again increased dramatically evaporation and there was also a close relationship between the increase of acidity of the droplet and that predicted by a direct relationship to the amount of water evaporated. Scots pine and Sitka spruce thus appear to be resistant to direct effects of acid cloud at pH 3.0 which is the lowest generally encountered in the Scottish Southern Uplands. However acidity enhancement through evaporation, extreme pH values at the start or finish of cloud events and high acidity flushes at the start of snowmelt may all expose trees to pH levels approaching those causing direct damage. In addition, the nutrient budgeting of trees may be adversely affected and lead to long term reductions in growth.

With the increasing need for the re-development of contaminated urban areas, the establishment of rapid and reliable analytical tools to support risk assessment and remediation, has become an important issue in recent years. In order to account for the different factors contributing to the bioavailability and ecotoxicity of pollutants, a complete ecotoxicity screening should use a combination of chemical and biological analyses. Chemical analyses cannot provide by themselves ecotoxicological information, and microorganisms, despite having proved to be good indicators of the toxicity of aquatic and terrestrial systems, usually cannot describe their composition. In this work the (eco)toxicity of Cr in soil contaminated with Cr salts or Chromite Ore Processing Residue (COPR) was studied and compared, using chemical analysis and bioassays. Chemical analyses were used to characterise Cr-contaminated soils to determine Cr and its chemical forms in a series of extracts. The bioassays were used to determine the (eco)toxicity of the extracts and soils characterised. The bioassays used included a single species bioassay (the luminescent bacteria <i>Escherichia coli</i> pUCD607), soil community assays (measurement of soil microorganisms respiration and phopholipid fatty acids) and plant assays (studying the growth of <i>Hordeum vulgare</i> in Cr-contaminated soils). The possible interactions between chemical composition and the (eco)toxicity observed in the bioassays was studied and compared by a range of statistical analysis. The results of this work as well as the feasibility and usefulness of this combined approach are presented and discussed.

This thesis is concerned with the development of qualitative modelling approaches that can be used in educational contexts for simulation and explanation about ecological systems. Students have to learn about complex systems, and computers have great potential for providing tools to support ecology teaching. Most of the simulation models created so far for this purpose are based on mathematical equations. However, quantitative data is often missing. Moreover, mathematical models hardly can support explanations because they lack explicit representation of concepts about the system being modelled and of the causal relations between the modelling components. Qualitative Reasoning has the potential for handling these problems, as it provides ontologies and techniques for building models with qualitative and incomplete knowledge. Accordingly, different modelling formalisms are explored and compared in this thesis. The specific domain chosen is the ecology of the effect of fire on the vegetation of the Brazilian cerrado. Recurrent issues in scientific research and teaching are the effects of fire on flowering, germination, establishment, mortality of the cerrado plants, and on the succession of cerrado communities. The qualitative knowledge involved in these issues is represented in a domain theory of plant population dynamics. To implement this domain theory, a framework is proposed in which the structure of the system being modelled is represented as a combination of the conceptual, the causal and the mathematical components. The conceptual structure includes knowledge about the objects, their quantities, quantity relations, typical scenarios, and the mechanisms causing changes in the system. The causal structure is a representation of how changes start and propagate within the system. The mathematical structure is a description of the constraints between the quantities and the procedures for calculating their values.

In this study an alternative ‘top-down’ approach was used to provide direct measurement of the net UK flux of greenhouse gas emissions at the UK scale, using aircraft sampling of the entire plume of GHG emissions downwind of the UK. An atmospheric mass budget over the country was established for each experimental flight and a direct calculation of the UK budget made from concentration measurements upwind and downwind of the UK. The measurements reveal annual UK emissions of CO of 2400 kT yr^-1 and CO₂ of 514 MT yr^-1, within 10% of the NAEI emissions of 2400 kT yr^-1 for CO and 555 MT yr^-1 for CO₂. However, estimates of N₂O (330 kT yr^-1) and CH₄ (3300 kT yr^-1) emissions are significantly larger than inventory estimates of 130 kT yr^-1 and 2400 kT yr^-1 respectively. This suggests that there are potentially important sources of N₂O and CH₄ not currently included in the inventory, that the strength of some sources is underestimated or a combination of the two. The inverse modelling approach further validated the NAEI CO and CO₂ emissions while providing further evidence that the NAEI emissions underestimate the UK emissions for N₂O and CH₄. The mapped Halocarbon emissions produced source locations consistent with localised industrial sources. The oxidation analysis showed oxidation rates tend to be consistent for individual plumes between flights with greater variation between different plumes reflecting the differing nature of the plume sources. The average oxidation rate for NO_x for a power station plume is 1.4 ± 0.66% N hr^-1 compared to 4.4 ± 3.95% N hr^-1 for an urban plume and the average oxidation rate for SO₂ for a power station plume is 4.8 ± 0.76% S hr^-1 compared to 6.5 ± 5.71% S hr^-1 for an urban plume. The average oxidation rate for the whole UK was estimated as 3.2 ± 2.38% N hr^-1 for NO_x and 5.3 ± 1.80% S hr^-1 for SO₂. Uncertainties in the method of measurement are small relative to the magnitude of the differences between the inventory and measurements for individual flights, but extrapolation from the 14 flights to provide annual budgets is an important source of uncertainty for N₂O emissions, which show considerable temporal variability in emissions. These new data provide a viable approach to estimate annual country scale UK emissions to test the quality of the existing inventory and to verify the progress of the emission reductions with time.

The biotransformation of heavy oils in soil microcosms was studied over a period of 9 months. Over this time, a medium-to-heavy boiling ballast oil and a crude oil exhibited a total reduction in total solvent extractable material (TSEM) of approximately 80%<SUP>w</SUP>/<SUB>w</SUB> and 60%<SUP>w</SUP>/<SUB>w</SUB> respectively. No.6 fuel oil was found to be largely recalcitrant to biotransformation. Abiotic controls indicated that up to 60% of the ballast oil was lost due to microbial activity, and that its microbial half-life was approximately 120 days. Over the 9 months, the %<SUP>w</SUP>/<SUB>w</SUB> of saturates within the ballast oil TSEM decreased from 74.6 to 23.2; the %<SUP>w</SUP>/<SUB>w</SUB> of aromatics increased from 12.5 to 23.0, the %<SUP>w</SUP>/<SUB>w</SUB> of polars increased from 8.6 to 31.3 and the %<SUP>w</SUP>/<SUB>w</SUB> of asphaltenes increased from 4.3 to 22.5. Similar changes were observed for the crude oil. The reliability of several oil biomarker source correlation indices was determined. The most reliable were those comprising ratios of individual hopane isomer pairs, which remained almost constant in both oils even after extensive constant at 0.7 for both oils over the 9 month biotransformation period. Methods of monitoring oil biotransformation through biomarker analysis were also assessed. The most sensitive indicator of oil biotransformation was the ratio of total n-alkanes to 17α(H),21β(H)-hopane. For the ballast oil, this ratio decreased from 748.0 to 8.5 over 9 months. The carbon isotopic composition of individual compounds did not vary significantly with oil biotransformation. However, isotopic characterisation of authentic oil-contaminated groundwater samples showed shifts of 1 - 2‰ in favour of C<SUB>13</SUB> in some progressively weathered samples, although it is not established whether this shift is due to microbial activity. These results are of considerable use to researchers and practitioners in the field of contaminated land assessment elucidating the source terms, weathering characteristics and bioremediation potential of complex heavy oil waste matrices.

This project was set up to test the hypothesis that treatment with wind will alter pathways for pollutants into the needles of Norway spruce, and will render them more susceptible to air pollution. To test this hypothesis two year old seedlings were treated with either acid mist or ozone in open-top chambers, combined with treatments in a controlled environment wind tunnel. Acid mist was applied at pH = 2.5 and pH = 5.0 as a control. The ozone treatment was designed to fumigate the plants with air containing on average 140 nmol and mol<SUP>-1</SUP> of ozone, and was compared with a charcoal-filtered control. The wind treatments were applied in a controlled environment wind tunnel, at various times during the year, usually for 48 hours at 16 m s<SUP>-1</SUP>, which were compared with a 'no-wind' control. The main measurements made on the Norway spruce seedlings in this project were of gas exchange and frost hardiness. In 1990 two series of gas exchange measurements were made, shortly before and immediately after the wind treatments, during August and September. In 1991 the plants from the acid mist experiment were measured during August, while the plants from the ozone experiment were measured in November, both after the wind treatments. Frost hardiness was assessed from both pollution experiments in November 1990, while in 1991 only the frost hardiness of the seedlings from the ozone experiment was determined, in early October, immediately after the last wind treatment. Measurements of visible injury, whole plant transpiration rates, chlorophyll concentrations and a destructive harvest, were also carried out, to support the findings of the main experiments. This study on Norway spruce showed that synergistic interactions, which would have proved the main hypothesis of this study, were only found for a few of the variables measured, probably a consequence of the tough cuticle on this species. The ozone and wind treatments did not interact significantly to produce effects on any of the parameters measured in this study, and therefore the working hypothesis was not substantiated. This study did suggest that the nutritional status of trees can strongly modify the effects of air pollution. The capacity of trees to absorb and neutralize pollutants is higher when all elements are available in sufficient amounts, compared to deficient growth conditions. This study also demonstrated that high speeds may reduce the effects of pollutants on tree foliage, but this depends on the timing of the high winds.

The work described in this thesis is primarily concerned with (i) the development of analytical methods for the determination of inorganic elements in peat, (ii) the production and analysis of a certified peat reference material, and (iii) the application of methods and procedures to the generation and interpretation of elemental profiles in cores from the largest ombrotrophic peat bog in Scotland. The effects of sample preparation on the determination of inorganic elements in peak samples were thoroughly investigated. The analytical methods and quality assurance procedures developed using the certified reference material were applied to the analysis of two Flanders Moss peat cores that had been collected by different coring techniques. An offset between the elemental profiles of the two cores was attributed to loss of surface material in the case of one, confirmed by stable (²⁰⁶Pb/²⁰⁷Pb) and radioactive (²¹⁰Pb) isotopic analysis. The depth profiles of the various elements were interpreted in terms of influences such as nutrient uptake and recycling, anthropogenic inputs from industry, energy generation and transport, soil dust, and post-depositional remobilisation and redistribution. For Pb, for which a record for atmospheric deposition was retained, the relative contributions of different sources (e.g. smelting, coal combustion, car-exhaust emissions) during the industrial era were assessed using Pb concentration and ²⁰⁶Pb/²⁰⁷Pb ratio variations in ²¹⁰Pb-dated peat. The importance of atmospheric Pb deposition prior to the introduction of leaded petrol was confirmed and, in the more distant past, a small Pb peak at a depth of ~1 m was tentatively attributed to Pb mining and smelting activities during the period of the Roman Empire.