Accurately measuring CO<SUB>2</SUB> efflux from the soil surface and adequately simulating the processes of CO<SUB>2</SUB> production and transport in the soil are crucial to enhance our understanding of carbon cycling in an ecosystem and at the global scale. However, significant uncertainty remains in both measurement and simulation of the efflux. An open-top, dynamic chamber technique was developed for <I>in situ</I> CO<SUB>2</SUB> efflux measurement. The pressure difference between inside and outside the chamber was found to be a dominant factor controlling the measured CO<SUB>2</SUB> efflux from the soil surface with dynamics chamber methods as a change of a few tenths of a Pa in the pressure difference will cause a several fold variation in the measured CO<SUB>2</SUB> efflux. This influence is negligible in this new open-top chamber. A flow rate up to 8 dm<SUP>3</SUP> min<SUP>-1</SUP> has no influence on the measured CO<SUB>2</SUB> efflux. The mean carbon dioxide efflux, measured in a mature Florida slash pine (<I>Pinus elliottii </I>Engelm. var. <I>elliottii</I>) plantation in 1995-1996, was 0.217 mg CO<SUB>2</SUB> m<SUP>-2</SUP> s<SUP>-1</SUP> (varying from 0.179 to 0.253) in October 1995 and 0.087 mg CO<SUB>2</SUB> m<SUP>-2</SUP> s<SUP>-1</SUP> (varying from 0.031 to 0.146) in January 1996. Soil temperature, which accounts for about 90% of the variability in CO<SUB>2</SUB> efflux, is by far the most influential factor controlling the CO<SUB>2</SUB> efflux from the soil surface. The Q<SUB>10</SUB> value for total soil CO<SUB>2</SUB> efflux in relation to soil temperature measured at 5 cm is 2.5 and the activation energy of soil respiration has a value of 56.9 kJ mol<SUP>-1</SUP>. Soil respiration in the slash pine plantation is highly and spatially variable, and generally increases with increase in fine root biomass, litter and humus amount on the forest floor but is inversely related to the amount of organic matter in the mineral soil. The spatial heterogeneity of CO<SUB>2</SUB> efflux in the plantation is mainly caused by the uneven distribution of palmetto plants and can be well explained by a simple model incorporating live and dead biomass and soil total porosity as predictor variables. CO<SUB>2</SUB> concentration in the soil gas increases with depth, with ranges of 0.25% to 1% by volume at a depth of 60cm and 600-760 cm<SUP>3</SUP> m<SUP>-3</SUP> at 2 cm depth during October and January in the slash pine plantation.

Global temperatures are predicted to rise by 2- 2.5°C by 2065, profoundly affecting the Earth's environment. The response of ecosystems to past climate fluctuations can inform on how systems will respond in the future. This thesis focuses on Quaternary environmental changes in West Africa, a region important because of its high ecological value and role in the global carbon cycle. In 2004, the International Continental Drilling Program recovered c. 291 m of sediments spanning the last c. 1 Myr from Lake Bosumtwi (Ghana). Pollen, charcoal and nitrogen isotopes (815N) were analysed from the most recent c. 150m (c. 520 kyr). The latitudinal position and long duration of this core makes it unique for understanding West African monsoon dynamics and vegetation change. To aid characterisation of the Bosumtwi pollen succession, an atlas of present-day pollen was constructed for 364 pollen and spore taxa. The pollen record from Bosumtwi reveals dynamic vegetation change over the last c. 520 kyr, characterized by eleven biome shifts between savannah and forest. Savannah vegetation is dominated by Poaceae (>55%) associated with Cyperaceae, Chenopodiaceae-Amaranthaceae and Caryophyllaceae. Forest vegetation is palynologically diverse, but broadly characterised by Moraceae, Geltis, Uapaca, Macaranga and Trema. Low 815N values correspond to forest expansion and these are driven by high lake levels. The timescale indicates that the six periods of forest expansion correspond to global interglacial periods. The record indicates that the wettest climate occurred during the Holocene, and the driest during Marine Isotope Stage 7. The vegetation and 815N records show a strong response to glacial-interglacial variability between 520- 320 kyr and 130- 0 kyr. Between 320- 130 kyr there is a weaker response to glacial-interglacial cycles probably related to high eccentricity during the peak of the 400-kyr component of eccentricity, with high eccentricity resulting in greater seasonality and ultimately drier conditions.

If the response to climate change is to include a transition to a low carbon economy, then the role of small businesses will be vital. As employers, innovators, polluters and carbon users, small businesses have significant combined impacts and opportunities. Within the framework of ecological modernisation, government policy has taken a largely voluntary approach to engaging small businesses with pro-environmental behaviour. Research has consistently found small businesses to be resistant to business greening and taken a predominantly positivist approach to identifying the barriers and drivers to behaviour and to measuring the effectiveness of different policy measures. In this study, the Schwartz Value System (SVS) is used within a qualitative research design to contribute new insight into how managers make sense of climate change. The thesis demonstrates the role of values in sensemaking and the need to engage with individuals within small businesses through the value-based frames they hold. In particular, this research shows that the win-win approach aimed at encouraging SMEs to save money, save the planet through voluntary engagement strategies over-simplifies managerial motivation. The managers in this study drawing on the self-enhancing value of Power most clearly reflected win-win ideas, except that they encapsulated the save money but not the save the planet message. Environmental protection, found within Universalism values, was only demonstrated by managers drawing on Achievement. In making sense of climate change, managers constructed their ideas using a mix of self enhancing, self-transcending, open and conservation values. To fully engage SME managers with climate change, policy makers need to take a more sophisticated approach to explicitly engaging individual with values.

Modem commercial agricultural practices involving chemical inputs such as fertilisers and pesticides have been associated with huge increases in food production never witnessed before, and in the case of cereal production (especially wheat) under Green Revolution technology, recorded spectacular growth. As statistics show, production and productivity have increased. However, the high chemical usage of fertilizers and pesticides used to bring about these increases in food production are not without problems. A visible parallel correlation between higher productivity, high artificial input use and environmental degradation and human health effects is evident in many countries where commercial agriculture is widespread. The high usage of these chemical inputs has caused numerous pollution problems impacting on human health, agricultural land, other production processes, wildlife and the environment in general. The private and external costs are very high. Such a production path is clearly unsustainable. This Ph.D. study lays its focus on estimating the private costs of illnesses arising from direct exposure to pesticides during handling and spraying by farmers on their farms in Sri Lanka. For this purpose three valuation techniques are used. They are the contingent valuation, cost of illness and the aversive behaviour approaches. Multiple regression analyses are also carried out to establish several relationships involving pesticide handling/spraying and direct exposure to pesticides. Policy implications of the regression analyses are then discussed. A health production model showing the relationships between the three approaches used for estimating the private costs of ill health and thereby inferring the willingness to pay for pollution control is presented. The theoretical background to agricultural pollution, drawing examples mostly from Asia, is also dealt within this thesis. Data for this Ph.D. study were obtained from a field survey carried out in the summer of 1996. During this survey, 227 subsistence farmers handling and spraying pesticides on a regular basis were interviewed to gather the necessary data. For the analysis of data, only 203 samples are used.

The resuspension of road dust has been recognised as a source of airborne particulate matter, but little information exists as to the strength of this source or to the factors affecting it, particularly in relation .to the United Kingdom This study has focused on determining emission rates for wind-induced road dust resuspension from a tarmac surface for a range of wind speeds, including an unsteady 'gusty' flow. A wind tunnel has been used to generate a boundary-layer flow above a tarmac surface. The flow generated has been compared to that occurring close to a tarmac airport runway and the two are found to be comparable. This has enabled realistic measurements of the resuspension of a tracer dust from the tarmac surface in the wind tunnel for a range of wind speeds. Full-scale measurements have also been made of the flow occurring very close to a tarmac surface during the passage a vehicle. Qualitatively similar gusts to those generated by a vehicle have been generated in a small wind tunnel and these gusts have been shown to significantly increase resuspension. The spatial and temporal variability of the road dust loading for a number of roads in Birmingham has been investigated throughout an entire year. The dust loading at all sites is found to be very stable suggesting that road dust resuspension is in equilibrium with dust deposition to the road surface. The average road dust loading for the roads studied was found to be O.16g m-2 • Using the results of this study a rough estimate of the annual wind-induced UK road dust emissions has been found as 1.9 kilotonnes. This figure does not include the considerable contribution to road dust emissions made by vehicle-induced resuspension.

No description available.

An urban street canyon represents an environment where pollutants such as particulate matter accumulate to high levels. Regulatory guidelines of particulate matter based on the mass metric have led to the development of clean engine technologies that emit smaller particles (ultrafine «IOOnm) and fine «1 urn) which are believed to have greater health implications upon exposure. The modelling of the transport and transformation of fine and ultrafine aerosols will grant insight into the nature of dispersion within urban canyons and inform future studies. This investigation was done using a Computational Fluid Dynamics platform coupled with the Modal Method. Considering an idealized 2-D framework, using the l" order eddy viscosity turbulence model and treating aerosol particles as an inert scalar, the model is able to account for the dispersion structure of aerosol particle number concentration. Consistent with previous measurement results, modelling studies show that the vertical concentration structure at the leeward side of the canyon is such that there is an increase in aerosol concentration up to approximately 2 m in height, followed by a decrease along the height of the canyon and an even sharper decrease within the turbulent shear layer. The gradient of the structure vary at different locations in the canyon and canyon geometries due to differing extents of advection and turbulent diffusion. It is found that the escape of aerosol particles from canyons (when driven by forced convection from the roof level wind) is dominated by turbulent flux, although natural convection could modify the relative importance of turbulent and advective flux, such that advective flux may be equally important. Assuming a constant exhaust emission within the canyon, a parameterization is developed to relate particulate matter flux (from canyons) with inflow wind speed and turbulent intensity. This parameterization is also able to predict aerosol flux within neighbourhood scales fairly well; suggesting that flux measured within the inertial sublayer is an aggregation of fluxes from individual street canyons in the vicinity. The inert scalar treatment of aerosol particles needs to be evaluated by relating lifetimes of aerosol processes in relation to the residence times of particles within the canyon. For the canyon scale considered, it is found that the inert scalar assumption may be used to describe aerosol number dispersion as effects of coagulation on aerosol properties is found to be insignificant. Condensation is found to be significant only at unrealistically high levels of in-volatile species in the vapour phase and in the abundance of soot. If the content of semivolatile compound within the aerosol population is high, then effects of partitioning on aerosol properties may be important, rendering the inert scalar assumption inadequate to characterize aerosol mass concentration dispersion. In addition, partitioning is found to be sensitive to accommodation coefficient and molecular mass of the in-volatile core within the aerosol particle, pointing towards the need for a more accurate characterisation of these parameters.

As pollution control measures have reduced the loadings from continuous discharges to receiving waters, episodic pollution has become increasingly detectable and important. A pollution episode involves a toxicant discharge to rivers (or other surface waters) of short duration and high concentration which is attenuated by physicochemical processes. After an episode has passed downstream, the timeconcentration profile of exposure to pollution and previous ecological status of the river are difficult to determine. After an episode, and over the course of time, recolonisation and succession will occur. This contrasts with the response of rivers to continuous discharges of pollution where recovery is spatial through the dilution and degradation of pollutants. Such spatial recovery has led to the description of recovery zones (e. g. Kolkwitz and Marsson, 1908). Pollution from farm waste accounted for almost 20% of all reported pollution incidents in 1988 (NRA 1989), so the investigation focussed on those aspects of pollution closely associated with strong organic wastes. A range of responses of freshwater macroinvertebrates and fish was investigated during simulated episodes of reduced dissolved oxygen (D. 0. ), increased ammonia and increased sulphide concentrations. These episodes were achieved by dosing streams after acertaining their biological condition, monitoring the impact upon captive animals and invertebrate drift during events, and by describing patterns of recovery. Catastrophic increases in drift occurred under conditions of reduced D. O. and mortalities in caged animals occurred, species exhibiting a range of sensitivities. Invertebrate responses to increased ammonia and sulphide concentrations (drift and mortality) were less dramatic, however, behavioural changes in captive animals were observed during episodes. With captive Gammarus pulex (L. ), the addition of substrate (sand and stones) to the container reduced mortality and a positive correlation was found between toxicity and ambient water velocity. Parasitised individuals of G. pulex were more susceptible to the simulated episodes than unparasitised ones. Seasonal differences occurred in the response of benthic invertebrates to low D. O. In November the response of drift density to low D. O. was about 1/50th of that in July despite broadly comparable benthic abundances. The recovery of benthic invertebrates following pollution events was rapid (2-3 months). In one series of experiments, which assessed the recolonisation route, 45% came from upstream as drift. Within substrate migration (from deep to surface layers of sediments), upstream movements and aerial sources contributed 31.5%, 15.6% and 7.9% respectively. From the measurements of pollutant concentrations within sediments during episodes and from tracer studies using sodium chloride, the penetration of pollutants into stream substrates was spatially patchy. In consequence some organisms survived in the deeper layers of sediments and were available for local recolonisation. Laboratory investigations showed that it is for possible animals to migrate downwards within a substrate in response to pollution episodes.

No description available.

No description available.