Occupying a disjointed and vulnerable habitat, specialist Coleoptera associated with Exposed Riverine Sediments (ERS) are shown to exhibit high levels of adaptation. An assessment of the English and Welsh habitat resource confirms the presence of strong geographical and physical restraints on its distribution which partially explain the rarity of some of the associated Coleoptera. Assemblage studies reveal the presence of multiple adaptive strategies that enable specialists to utilise the resource in spite of perceived environmental pressures, and the strength of these morphological and behavioural adaptations can be used to predict abundance and distribution at alpha, beta and gamma levels. Furthermore, adaptations enforce varying nutrient acquisition strategies which spatially define communities. This study demonstrates the need specialist invertebrates have for a complex and highly connected ERS habitat with English and Welsh rivers, that exhibits structural variation along a longitudinal gradient. Reliant on riverine processes and subsidies the habitat and its associated invertebrates are symptomatic of a healthy and naturally structured lotic system operating laterally and across reach scales.

Herbivory is a globally important ecosystem function, occurring in all major biome types; including benthic freshwater habitats. Algal biofilms and their herbivore consumers are therefore important components of stream food webs. However there is relatively little empirical data quantifying the strength of these algal-herbivore interactions, or how these vary with herbivore identity, size, and biofilm physiognomy. Interactions across a diverse herbivore guild were investigated in a chalk stream, using mesocosms to determine the distribution of algal-herbivore interaction strengths. A series of experiments were used to assess: herbivore link strength distribution; context-dependency of interaction strength; the relationship of body size with interaction strength; and the effects of competing grazer species on algal resources. The algal-herbivore sub-web was dominated by weak interactions which concurred with empirical and theoretical evidence, and further supporting web stability theory. Interactions were highly context-dependent, with interaction magnitude and species identity both affected by algal biofilm type. Grazer species identity was important for determining body size relationships. Although competitive effects were apparent, they were not statistically detectable. This research builds on previous investigations of algal grazer interactions and food web structure by emphasizing; the importance of grazing as an ecosystem function, and the diversity of interactions occurring in model systems. The use of experimental mesocosms may be limited in terms of 'real' systems, but does provide a valid response of model systems that are both useful and valid tools for assessing community ecology.

Although the direct health impact of temperature has been studied extensively, the impact of Urban Heat Island (UHI) on mortality has received relatively little attention. This PhD thesis assesses the combined impacts to distinguish the differential responses between urban and rural residents in the West Midlands and Greater London. On the basis of comparison between MIDAS air temperature and MODIS land surface temperature, air UHI intensity (aUHII) and surface UHI intensity (sUHII) are compared during cloudless anticyclonic nights. The results identify the UHI ‘hotspots’ and stronger summer night-time UHI; Greater London possesses stronger aUHII-sUHII correlation (r~0.7) than the West Midlands (r~0.4). U-shaped temperature-mortality relationships using fractional polynomial regression model demonstrate that the decreased winter mortality may outweigh the increased summer mortality for the West Midlands, whereas London's increased summer mortality is more significant, particularly among the vulnerable 75+ people. This research has identified for the first time the quantitative relationships between aUHII and mortality. Overall increasing trends imply the increased impact of urban heating on mortality. These research findings could form the basis for a better understanding of temperature (UHI)-related impacts on human health that will aid policy development to maximise health benefits and minimise the negative consequences.

The studies on physical and chemical properties of airborne particulate matter were carried out in the UK atmosphere. Aerosol samples were collected at the Elm Road Observatory Site and Harwell representing urban background and rural area, respectively. The chemical components of both PM\(_2\)\(_.\)\(_5\) and PM\(_2\)\(_.\)\(_5\)\(_-\)\(_1\)\(_0\) were mainly analysed for carbonaceous compounds, sulphate, nitrate, chloride and oxalate. Size distributions of aerosol components were investigated in conjunction with the study of ammonia gas to stabilise the semivolatile species in atmospheric particles. Concentration composition of carbonaceous compounds (organic and elemental carbon - OC and EC) in particulate matter clearly observed higher value at urban background than those at rural area. The OC/EC minimum ratio of 0.35 was used to distinguish between primary and secondary OC as EC was a good indicator of primary sources. Sulphate and nitrate showed the good relationship, indicating that two species undergo similar formation and removal processes in atmosphere. Chloride was commonly originated from marine aerosol with the weak correlation observed with other major species. Oxalate is highly focused specie in this study as there is rarely available data in the UK. The good correlation and the similar pattern of size distribution between oxalate and sulphate suggest that their formation pathway formed from the same atmospheric processes. The excess ammonia gas supplied during the air sampling could be stablilsed and yielded the higher concentrations of nitrate and chloride which were expected in the forms of ammonium salts. In contrast, oxalate in ambient air was exhibited the discordant behaviour in this experiment. Our trajectory analysis suggests the important precursor sources of oxalate were from continental area associated with the high atmospheric pollutants.

A street canyon is a typical urban configuration with surrounding buildings along the street, where emissions from vehicles are normally released. Buildings are the artificial obstacles to the urban atmospheric flow and give rise to limited ventilation, especially for deep street canyons. This study implements a large-eddy simulation (LES) coupled with a reduced chemical scheme (the LES-chemistry model) to investigate the processing, dispersion and transport of reactive pollutants in a deep street canyon. Spatial variation of reactive pollutants are significant due to the existence of unsteady multiple vortices and pollutant concentrations exhibit significant contrasts within each vortex. In practical applications of using one-box model, the hypothesis of a well-mixed deep street canyon is shown to be inappropriate. A simplified two-box model (vertically segregated) is developed and evaluated against the LES-chemistry model to represent key photochemical processes with timescales similar to and smaller than the turbulent mixing timescale. The two-box model provides the capability of efficiently running a series of emission scenarios under a set of meteorological conditions. In addition, a box model with grid-averaged emissions of street canyons is compared with a two-box model considering each street canyon independently (horizontally segregated) to evaluate uncertainties when grid-averaged emissions are adopted in a grid-based urban air quality model. This study could potentially support traffic management, urban planning strategies and personal exposure assessment.

Research described in this thesis was conducted in the United Kingdom and India, and although the overall subject was source apportionment of traffic emissions, specific objectives as well as research design were different in each case. In the UK, composite PM\(_{2.5}\) traffic profiles were derived from ambient data including tunnel and twin-site measurements, and sensitivity of a CMB model to various traffic profiles was tested. The two composite profiles were found to be similar, although lower uncertainties were observed for the tunnel profile. The UK-based traffic profile was found to quantify the traffic contribution consistently, and independent estimates of traffic contribution were found to correlate well with the CMB output. PM10 road dust was chemically characterized in Birmingham and New Delhi, and detailed chemical source profiles were prepared for both cities. Source contributions from dust and non-exhaust emissions were estimated for both cities. In New Delhi, ambient PM\(_{2.5}\) and size-segregated PM data were collected at a high-traffic location. Ambient PM\(_{2.5}\) concentrations were found to be very high, especially in the winter. Source inferences were derived based on mass closure and traffic emissions were found to contribute between 15 and 25% across seasons.

A stochastic backscatter (SB) approach to subgrid-scale (SGS) modelling for large-eddy simulation (LES) of the neutral atmospheric boundary layer (ABL) has previously been shown to reduce excessive velocity shear, as seen with the popular Smagorinsky SGS model, in the under-resolved surface layer. However, previous SB models exhibit unwanted grid-dependency issues, and the range of atmospheric flows tested remains limited. Here, a new SB model is proposed that uses a grid-adaptive filter to control the length-scale, anisotropy and momentum flux of the backscatter fluctuations, independently of the model grid. Model performance is confirmed to be grid-independent in simulations of the neutral ABL, in which an 80% reduction in excessive near-surface velocity shear is achieved. The model is also applied to street canyon flow, where the shear layer that separates the recirculating vortex within the canyon from the external flow is again typically under-resolved in most LES set-ups. The backscatter acts to increase momentum transfer across the shear layer, bringing the simulated vortex intensity significantly closer towards wind-tunnel observations. A passive tracer is also released to model traffic emissions, and the pollutant exchange velocity between the canyon and the external flow is again found in better agreement with wind-tunnel data. This information can be used to improve operational urban dispersion models.

Water samples taken from nine English freshwater lakes from a mix of urban, rural, and remote locations on 13 occasions between April 2008 and February 2012 were analysed for selected non-dioxin like-PCBs, tri- through hexa-PBDEs, and the three main HBCD diastereomers (\(\alpha\)-, \(\beta\)-, and \(\gamma\)-HBCD). Concentrations of PCBs and HBCDs declined over the sampling period with half-lives of 3.8 and 5.1 years, respectively. In addition, concentrations of PCBs, HBCDs, tri- through deca-BDEs, and 32 selected NBFRs were measured in radiometrically-dated sediment core slices taken in summer 2011/2 from seven of the same English lakes. Temporal trends in contamination with “legacy” POPs generally accord with historical trends in UK manufacture and use, with PCB contamination at all lakes increasing from ~1950, peaking generally between the late-1960s and mid-1980s, before declining steadily thereafter. In contrast, at most sites, BDE-209 displayed generally smooth increases following its initial emergence, and showed no obvious levelling off trend. Contamination with some NBFRs displayed significantly increasing trends. Spatial variation in POPs contamination of the lakes studied was evident; with regression analysis suggesting concentrations are higher in lakes with surface areas that are small relative to their catchment area, and that are closer to areas of high population density. The estimated PCB burden in the British environment is 521 tons, with TBPH (281 tons) and BDE-209 (147 tons) following not far behind. Estimated UK burdens of the remaining target compounds were significantly lower.

This study aims to identify key sources that contribute to fine particulate matter (PM2.5) mass concentrations in Doha city, Qatar. Specifically, to determine the increase in PM2.5 mass caused by dust events, by comparing abundance and composition between the dust events season ‘the summer season’ and non-dust event season ‘the winter season’. Knowing PM2.5 sources in Doha will help to 1) identify the predominant (natural or anthropogenic) sources responsible for particulate matter (PM) exceedances of the daily and annual air quality standards, 2) ensure an appropriate focus on controlling major anthropogenic sources, and 3) evaluate the current air quality standards and potential improvements to the allowable margin of tolerance for PM limit and the number of allowed exceedances to take appropriate account of natural sources. Two parallel sampling campaigns at two urban sites in Doha, namely Al-Corniche (AC) and Qatar University (QU) were conducted during the winter of 2014/2015 and the summer of 2015 using low volume samplers. Chemical analysis of minerals, trace metals, soluble inorganic ions, organic and elemental carbon was carried out on PM2.5 samples. Subsequently, a mass closure analysis, and a source apportionment by means of positive matrix factorisation (PMF-5) were performed. The mass closure solution found a good closure between the samples’ gravimetric mass and the reconstructed mass of the chemical constituents determined on those samples. However, mass discrepancies ranged between -5 and +12% were found between reconstructed mass and gravimetric measured mass as a result of using different filters substances (Teflon & Quartz) to collect PM2.5 samples with contradictory behavior in retaining and releasing organic carbon and ammonium nitrate. Then comparing the sum of chemical constituents from both filters to the mass collected on the Teflon filters.

The late Palaeozoic marked the beginnings of fully established, global terrestrial ecosystems as we know them today. Large-scale provinciality of vascular plants had developed by this time, and four global phytogeographic provinces were named, superimposed on the converging Pangaean landmass: Angara (mid-high latitude north), Gondwana (mid-high latitude south), Euramerica (low latitude west) and Cathaysia (low latitude east). The low latitude provinces supported vast swathes of the famous ‘coal swamp’ wetland flora at this time. Delineation of these provinces has never been formally ratified due to most palaeobotanical work being on a local to regional scale, and results of this work being presumed as representative of a wide area. This thesis examines the wetland flora of the most contentious, low latitude provinces, and aims to assess the widely cited proposal of linkage and substantial interchange between Euramerica and Cathaysia. The proposal is upheld, specifically during the Stephanian (~305-300 Ma), when the well established flora in Euramerica migrated along a pathway through the tectonically complex Angara region and quickly colonised North Cathaysia,where it flourished and diversified after the extirpation of the source flora in Euramerica. Connections between the regions at other times are also found to be highly likely,although the complexity of the tectonic backdrop, and difficulties with characterisation of highly dynamic wetland floras, lead to ultimate recommendations to analyse the floras as fully and in as wide a context as possible, and to utilise all avenues of evidence, in order to progress in uncovering their full histories.