A study on chemical modification of mbberwood (Hevea brasiliensis Muell. Arg) with acetic or hexanoic anhydride was carried out. Dimensional stability (DS) testing was carried out based on water-saturation (WS) and oven-drying (OD) cycles. DS property of acylated mbberwood was improved where a reduction in volumetric swelling coefficient (S) and increment in anti shrink efficiency (ASE) were observed. An ultimate ASE value for acetylated and hexanoylated rubberwood of 80 % and 95 % was recorded. It was found that the DS afforded to acylated rubberwood was due to bulking rather than hydroxyl (OH) substitution. Analysis of volumetric change of acylated rubberwood _showed that there is no differences between helium pyc!10meter and microcaliper data,' suggesting that the lumen volume does not change substantially, therefore microcalipers can be used to measure volume increase of the cell wall in this case. It was found that the measured molar volume (MV) is slightly lower than theoretically predicted for acylated rubberwood. Therefore based on all analyses, it was concluded that bulking is equal to the amount of bonded adducts added. Biological decay of modified rubberwood was also studied. Mass loss (ML) was reduced with increasing WPG after exposure to Coniophora puteana, Phanerochaefe chrysosporiurn and Trarnetes versicolor. The threshold (WPG) of acetylated rubberwood exposed to these fungi was 10 %, 6 % and 8 % respectively, whereas the threshold of hexanoylated rubberwood exposed to these fungi was 26 %, 17 % and 35 % respectively. Hydroxyl (OH) groups substitution is proposed as the decay protection mechanism of acylated rubberwood exposed to C. puteana, P. chrysosporiurn and T. versicolor rather than bulking. Hydroxyl (OH) groups substitution is thought to chemically and sterically supress the lower molecular weight diffusible agent (LMWDAs) activity. It is suggested that data on EMC, fibre saturation point (FSP) and size of voids of each modified sample is required to study the decay protection mechanisms of acylated rubberwood. Decay ML is reduced as the ASE increases suggesting that bulking has reduced the fungal activity to some extent.

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The contents of this thesis describes the design, modification and testing of a differential absorption laser lidar system for the determination of ambient levels of sulphur dioxide in suburban land agricultural environments. Chapter 1 discusses the origins of atmospheric sulphur dioxide pollution and its determination by conventional techniques. The principles of the differential absorption technique are presented in Chapter 2. Chapter 3 presents an extensive error analysis while Chapter 4 describes the instrumental design and the system modifications. The computer programs (both control and data processing) are discussed in Chapter 5. The results of preliminary testing and the performance of the system as a tool for measuring atmospheric S02 are presented in Chapters 6 and 7 respectively. Suggestions for the future and conclusions are presented in Chapter 8. Appendices I - V contain the electronic circuit descriptions and the computer program flow charts.

The Prospect Theory proposes to assess outcomes relative to a reference point (or benchmark). Although the literature recognises the relevance of dynamic benchmarks, most of the applications of Prospect Theory employ static reference points (or a status quo). This paper aims to develop a Prospect Theory framework for investment under uncertainty subject to a dynamic reference point, within the context of environmental policy making, where the distinction between a dynamic and a static frameworks is crucial. I evince that, in contrast to the static framework, in a dynamic framework the investor measures not only the absolute but also the relative risk premium (Sharpe ratio) of the investment opportunity, incorporating the risks and returns of a reference portfolio. I propose that there exists a relation between static and dynamic frameworks. Using the dynamic framework, I argue that in the environmental context international co-operation is the key to a successful environmental policy

Pour résoudre les problèmes environnementaux mondiaux, la formation d'accords multilatéraux est une solution privilégiéee. Dans cette approche, des objectifs en matière de protection de l'environnement sont définis au cours d'un cycle de négociations internationales. Une fois ces objectifs définis, une étape cruciale est de recueillir l'engagement des pays au respect de cesobjectifs. Dans la première partie de cette thèse, nous nous intéressons à deux déterminants importants de l'engagement des pays: l'influence des pairs, à travers le chapitre 3, et la tenue d'élections dans le pays, à travers le chapitre 4. Néanmoins, le relatif échec de cette approche descendante à résoudre les problèmes environnementaux globaux a poussé à s'intéresser au rôle de l'approche ascendante. En effet, alors qu'une approche descendante consiste à définir, lors de néegociations internationales, des objectifs qui vont s'imposer à chaque pays, une approche ascendante consiste à partir d'initiatives unilatérales pour aller vers des actions au niveau international.La protection de la biodiversité est un domaine où l'approche ascendante occupe une place prépondérante. Nous avons choisi de nous intéresser à une initiative innovante, l'ICMS-Ecologico. Nous présentons ce mécanisme de transfert fiscal mis en place au Brésil depuis le début des années 1990 dans le chapitre 5, et testons une condition de son efficience dans le chapitre 6. Un résumé des contributions analytiques et méthodologiques, ainsi qu'une discussion des possibles extensions de cette thèse, sont fournis au chapitre 7. / The primary approach to dealing with global environmental problems is to conclude international environmental agreements. In this top-down approach, a crucial step is to obtain the participation of countries. This thesis attempts to examine two prominent drivers/obstacles to participation : countries' interactions, in Chapter 3, and national elections, in Chapter 4.Yet, the relative failure of the top-down approach to solve environmental challenges has pushed interest toward bottom-up approaches. While a top-down approach consists in defining targets during multilateral negotiations and in obtaining the agreement of countries to respect these targets, a bottom-up approach begins with a unilateral initiative and moves toward globalsolutions. An environmental issue for which the bottom-up approach plays a crucial role is biodiversity conservation. In Chapter 5, we present the ICMS-Ecologico, an innovative conservation instrument that has been considered to be an interesting tool for the implementation of commitments in international environmental agreements, and, in Chapter 6, we test one condition for its efficiency. We synthesize the analytical and methodological contributions of this thesis and discuss their potential extensions in Chapter 7.

The use of an area for informal recreation will have long-term environmental effects, particularly on the vegetation. Changes associated with large numbers of visitors may be plain to see, but less noticeable changes induced in areas of lower use may be just as important to the preservation of the natural habitat; such changes may be difficult to detect without expensive and time-consuming research. The degree of change permissible will vary according to the type of site, the value of the habitat, and the insistence of the demand for access. Control of vegetation change requires an understanding of the background environment and the ecology of the site, as well as an anticipation of the probable effects of recreation use and some means of influencing visitor activity and distribution. Identification of indicator species for general application has so far proved inconclusive. The uncertainties surrounding the chances induced by recreation use are further complicated by the fact that many of our informal sites occupy areas of semi-natural sub-climax vegetation. Such vegetation say be worthy of preservation in its own right, but management of seral communities requires careful monitoring and control, and may not lend itself to a recreation programme. The desire to protect certain habitats from destruction and extinction has led to the development of a system of protective designations, such as Nature Reserves and Sites of Special Scientific Interest. Vegetation not so designated may still be valuable wildlife refuges, as well as providing attractive settings for informal recreation. The problem is to control the distribution of visitors so that their very numbers do not destroy the countryside they come to see. The contemporary solution lies in various schemes for zoning; the basic idea being an hierarchy of sites, divided according to attractiveness, vulnerability and capacity. Such a scheme will only be successful if the sites can consistently attract visitors within the prescribed numbers and uses. This study will concentrate on two sites within such a scheme in Lancashire. The major landscape attraction of the areas is the Forest of Bowland Area of Outstanding Natural Beauty. The sites investigated represent the two extremes of management: an informal, uncontrolled site within the designated area of AONB (the Trough of Bowland), and a formally planned site managed for countryside recreation, located on the fringe of the designated area (Beacon Fell Country Park). The importance of preserving certain habitats and the relevance of theoretical studies of vegetation change is considered. An attempt is made to devise a means of objectively relating vegetation disturbance and trampling pressure, with a view to predicting likely changes in areas of new use. An assessment of contemporary changes on the heavily used recreation site led to a consideration of the importance of the vegetation community in the perception of landscape, and of the importance of landscape in the recreation experience. It became clear that the reaction of visitors to the site was related to the general form of the vegetation, but apparently not to the specific detail of species or structure. A comparative study involving the two contrasting sites is made in an attempt to elucidate this point. The function and use of the two sites is examined by a detailed visitor survey, involving observation of distribution and activity, and an investigation of opinions and attitudes by questionnaire. The pattern of use of two picnic sites is analysed in an attempt to evaluate the landscape features influencing site choice, and specific location in relation to fixed features and other groups already present. The sites chosen demonstrate how such features may be used to modify the perceptual capacity of a site, thus allowing an increase in density where necessary, without loss of visitor satisfaction. An analysis of the characteristics of the visitors and their activities is linked to an interpretation of site perception and use. It would sees that Beacon Fell Country Park is a very successful site. In spite of being partly landscaped plantation, it is fulfilling the desire of many visitors for a natural countryside setting. However, evidence suggests that it is not fulfilling its official planing aim; that is, to act as a filter for Bowland AONB. The implications of this finding are discussed.