The establishment and intensive management of forests for the production of timber can have significant effects on the soil carbon dynamics. The establishment of forest on organic soils under grasslands may lead to substantial losses in soil carbon, due to the site preparation for the planting of trees and other disturbances. This is gradually compensated by carbon accumulation in tree biomass as the forest grows until clearfelling at maturity may initiate another substantial carbon loss. This study had two main aims. The first was to investigate the long-term effects of forest establishment on natural grassland as well as clearfelling and re-growth of the forest during second rotation, by looking at the changes in soil carbon stocks and soil carbon balance in a Sitka spruce (Picea sitchsensis) in Harwood (N. E. England). Secondly, to investigate the short-term effects of forest clearfelling on the fluxes of soil CO2, N2O and CH4 and on the environmental factors (soil temperature, water content and water table depth) affecting them. The fluxes were initially measured in two mature stands (40-years old) during one growth season. One of the two stands was subsequently clearfelled while the other was kept intact and fluxes were measured for a further ten months after clearfelling. The relationships between these fluxes and the environmental factors were also examined. The study also investigated the spatial variability of soil CO2 emissions using geostatistical approaches. The soil CO2 fluxes were measured with two methods, a closed dynamic chamber and a closed static chamber, giving the opportunity to compare their relative performance. A performance further investigation on this discrepancy between the two methods took place in lab experiments and on a soil monolith, excavated from the 40-year old stand and kept under controlled conditions in the greenhouse.

The search for a low cost and effective technique to control and remove volatile organic chemicals (VOCs) has gathered a great attention from the adsorption process field. Advances in manufacturing technology have enabled the creation of activated carbon monoliths (ACM) as promising substitute for traditional packed beds of granular adsorbent materials. The research described in this thesis comprises an extensive experimental study of a single component adsorption process onto square and hexagonal channel Novacarb™ ACM supplied by MAST Carbon Technology Ltd. ACM characterisation methods such as nitrogen and solvent adsorption isotherms, electron microscopy, thermo-gravimetric analysis and thermal dynamic characterization have been used. High BET surface area, high total pore volume and high total solvent mass uptakes have been found. ACM were tested by obtaining column breakthrough curves mainly using dichloromethane and acetone as the adsorbates at the bench-scale. The adsorption dynamics of the ACMs studied were also compared with those of extrudates manufactured by the same process as the ACMs. The influence of humidity on the adsorption process has been studied at the bench-scale. Finally, the adsorption system was scaled-up to about 60cm length monoliths in order to study both adsorption and electrical regeneration taking advantage of the particular electrical properties held by the Novacarb™ ACM. It has been found that ACMs are able to adsorb high levels of VOCs, up to 40% by weight of DCM, good behaviour under humidity conditions and low pressure drop. In contrast, kinetics of ACMs have been found to be somewhat inferior to those of equivalent packed beds, although the ACM performance can be improved by reducing the wall thickness. Adsorption of DCM at the pilot-scale has demonstrated that the Novacarb™ ACM could easily be used in a cyclic thermal swing adsorption process with a half cycle time of less than one hour.

Carbon nanoparticles constitute a class of important materials that have uses in many different fields. This thesis focuses on the synthesis and surface modification of different carbon nanoparticles and each novel nanomaterial is demonstrated to have a specific sensing application. Carbon blacks play a significant role in the research that is presented herein. Emperor 2000, a commercial bulk-produced carbon black available from Cabot Corporation, is the starting material for many of the investigations. The surface of Emperor 2000 is shown to be susceptible to physisorption, through π-π stacking. These interactions are exploited to append pyrene-based compounds onto the surface of the carbon nanoparticles. This methodology results in carbon nanoparticles with surface boronic acid functionality that is demonstrated to be affective in the electrochemical detection of catecholic caffeic acid. Emperor 2000 carbon nanoparticles are commercially produced with phenylsulphonic acid functional groups on the surface. This functionality is subjected to synthetic methods to obtain carbon nanoparticles with extremely hydrohphobic character, which are demonstrated as important substrates for probing lipophilic redox systems and lipid character under different experimental conditions. Fluorescent carbon nanodots (C-dots) are another important form of carbon nanoparticle. Herein, the facile synthesis of C-dots that possess intrinsic pyridine functionality is described. These nanodots exhibit two-photon fluorescence that is exhibited both in solution and in HeLa cells. The nanodots are demonstrated to have the potential to be developed into nanomedicines and biocompatible scaffolds for new drug delivery mechanisms. These straightforward synthesis, modification, and application methods demonstrate the effectiveness and the versatility of carbon nanoparticles. This class of nanomaterial is generally outclassed by modern and more fashionable carbon nanotubes and graphene-based systems. However, carbon nanoparticles are more cost effective and readily available carbon-based nanomaterials that can be used for a wide range of applications.

The aim of this work is to produce a manufacturing strategy for high current (>10 mA) field emission (FE) devices for military (microwave generation) and civilian (particle accelerator electron beam) applications using carbon nanotubes (CNT) as base material. With a particular focus on the relationship of the laser time pulse duration used for cutting CNTs and how this affects the field emission performance. Material selection for this work was narrowed to CNT as they possess unique characteristics such as: high aspect ratio; high thermal conductivity; high chemical stability and high current carrying capacities up to a theoretical limit of 1,200 MA∙cm-1 making them an ideal material for FE. The CNT material studied in this work is produced in two distinct forms, fibres (∅~7-10 μm) and films (h~30 μm), using a floating catalyst chemical vapour deposition process which produces high quantities of CNT material with mixed mechanical and electrical properties. The material is difficult to handle because of its dimensions and is susceptible to environmental changes i.e. electrostatic forces. In order to reduce the variability in electrical properties, a laser purification process was developed. The process consists of locally irradiating an infra-red (IR) laser several microseconds directly at the material. A percentage is vaporised (mainly non-conductive or defective material) and the remaining CNT material shows very high crystallinity with an increase of up to ten times (G/D ratio > 100) compared to the original material and electron mean free path is increased by an order of magnitude. The production strategy is based on directly coating the CNT material with copper using an electroplating process. This allowed for CNT fibre and film to be easily handled and improved the overall electrical contact. Emitter geometry was customised by a laser cutting process to achieve increased enhancement factor geometries, in this case, triangles with 29 tips whilst reducing FE variability. FE performance was quantified by testing the devices in a continuous DC mode with a sweep up to 1,000 V until the material suffered catastrophic failure. The gap distance between the tip of the triangles and the anode was varied to increase the electric field until failure. FE results using the production strategy improved more than 400% compared to untreated material. Applications for these devices are intended to be in the creation of high energy electron beam lines and generation of high powered directed microwaves.

Soil is the largest terrestrial carbon (C) store, containing an estimated ~1500 Gt C in the upper 1 m of soil. The long term storage of soil organic C (SOC) requires that it is somehow protected from microbial decomposition – or ‘stabilised’ – in the soil matrix. Three mechanisms are commonly identified as factors controlling the stability of SOM: chemical recalcitrance, physical protection in aggregates and adsorption to soil mineral surfaces. The stability of SOC in the soil matrix can be influenced by management practices and changes in soil structure can lead to loss of SOC and increases in greenhouse gas (GHG) emissions. It is, therefore, important to understand the impact that management practices have on SOC stability and to manage soils in such a way as to optimise the volume of SOC which is locked away for climatically significant periods of time. Two methods are generally used to estimate SOC stability: indirectly by measuring CO2 fluxes as a proxy for SOC microbial decomposition, or directly through physical fractionation of soil in to pools with different levels of physical and chemical protection. Both methods were employed in this thesis. Arable and grassland soils which represent the range of soil textures and climatic conditions of the main agricultural areas in the UK were incubated at two different moisture contents and with or without inorganic fertiliser application and GHG fluxes from them were monitored. Soil texture, mineral N concentration and soil C concentration were found to be the most important measured variables controlling GHG fluxes of the UK agricultural soils in this study. The results were generally in support of those found in the literature for a wide range of soils, conditions and locations; however, N2O emissions from the two Scottish soils appeared to be more sensitive to inorganic N fertilisation at the higher moisture content than the other soils, with the N2O emissions being exceptionally high in comparison. Although incubations of whole soils are useful in measuring the impacts of soil management practices on GHG emissions under controlled conditions they do not identify the mechanisms controlling the stability of SOC. Dividing SOM into functional pools may identify different C stabilising mechanisms and improves soil C models. A large number of operationally defined separation methods have been used to fractionate SOM into biologically meaningful pools of different stability. Direct comparisons of different fractionation methods using radiocarbon (14C) dating and spectroscopic analyses has not previously been undertaken. Average 14C ages and chemical composition of SOM fractions isolated from a grassland soil using three published and frequently applied fractionation methods were compared. (1) a density separation technique isolating three fractions (2) a combined physical and chemical separation isolating five fractions (3) a hot-water extraction method isolating two fractions. The fractions from Method 1 had the most distinct average 14C ages, the fractions from Method 2 fell into two age groups, and both Method 3 fractions were dominated by modern C. The average 14C ages of the labile fractions from Method 1 and 2 were higher than the mineral bound fractions, although they made up a relatively small proportion of the total SOC. This was a surprising result, and spectroscopic analysis confirmed that these fractions had greater relative contents of aliphatic and aromatic characteristics than the mineral bound fractions. The presence of black C in a whole soil sample and one of the labile fractions from Method 2 was confirmed by hydrogen pyrolysis. The availability of archived soils from an abandoned long term tillage treatment experiment and the ability to relocate the plots provided a unique opportunity to assess the resilience of SOC stocks to land management practices several years after the conversion from arable to grassland. SOC stability was assessed by soil fractionation of archived (1975) and freshly collected (2014) soil samples. The mass corrected SOC stocks from the four different treatments (deep plough, shallow plough, chisel plough and direct drill) were higher in 2014 than 1975 across the whole profile (0 – 36 cm). Reductions were observed at some depths for some treatments but the overall effect was an evening out of SOC stocks across all plots. The fractionations (using Method 2), revealed that there was a relative increase in the mass of the sand and aggregate fraction but a decrease in the relative proportion of SOC stored in this fraction (physically protected). There was also a significant increase in the C:N ratio of the silt and clay fraction (chemical adsorption). This suggests that reduced disturbance of agricultural soils leads to preferential physical stabilisation of fresh SOM but also increased adsorption of older material to mineral surfaces. The labile fractions were sensitive to land-use change in all tillage treatment plots, but were more sensitive in the low impact tillage plots (chisel plough and direct drill) than the inversion tillage plots (deep plough and shallow plough). It is well established that tillage disrupts aggregation. However, a direct measurement of the level of SOM physical protection in the soil matrix due to aggregation has not previously been undertaken. The soil was fractionated using Method 1 (fractions with distinctly different 14C ages) and isolated soil fractions were incubated separately, recombined and mixed in to whole soil at three different temperatures. The C respiration rate of the isolated intra-aggregate fraction was generally consistently as high as the whole soil. This supports the theory that there is a labile component of soil which is protected from decomposition by physical protection within aggregates. Therefore, the lack of any priming effect with the addition of labile fractions to the whole soil, and indeed the suppression of emissions relative to the whole soil, was unusual. Fractions and whole soils incubated at 25 and 35 °C had a wider range of Q10 (temperature sensitivity) values than those incubated at 15 and 25 °C, however, median values were surprisingly similar (range from 0.7 to 1.9). Overall, the results from this thesis highlight the importance of the soil structure in stabilising C. Disrupting aggregates leaves a proportion of otherwise stable C susceptible to loss through microbial decomposition, particularly when the entire soil matrix is disrupted. It also provided some unexpected results which warrant future investigation; in particular, further direct measurement of physical stabilisation of SOM in soils of different type, from different climates and different land uses would be useful.

Dissolved organic matter (DOM) is found in all freshwaters globally, by dissolving in rainwaterduring its path through soil and on to oceans via. rivers and streams. To provide potable water fit for human consumption, selected streams and rivers are used by either direct abstraction, or by diversion into reservoirs prior to treatment. For ca.100 years, chlorine and its compounds have been used by water treatment companies to disinfect water. However, research has shown that reactions between chlorine and DOM can produce compounds (disinfection by-products, or DBPs) which may be hazardous to human health. This thesis explores the relationship between catchment character, organic matter concentration, and the potential formation of DBPs. In particular, trihalomethanes (THMs) were measured as these are currently the only regulated DBPs in the UK. To achieve this, water samples were collected quarterly over one year from two contrasting catchments, to study seasonal variations in DOM concentration and character. A third catchment was also sampled, with similar catchment characters to the first two catchments, to determine whether geographical location and land use types affected the data. Each catchment was studied to see if catchment characteristics (e.g. class of vegetation, soil type or bedrock) could be mapped using a Geographical Information Systems (GIS) approach), to observe any effects on DOM and/or the DBPs found in treated water, with the aim of producing a risk assessment map to aid the choice of future abstraction locations for drinking water. Hence, samples were chlorinated and chloraminatedin the laboratory before being analysed for DBP formation and residual chlorine concentrations were measured. Catchment specific GIS derived data were statistically analysed with water chemistry data, and detected relationships were explored statistically. Major findings include medium to strong positive correlations between the standardised THM4 (STHM4 - the concentration of THM4 formed from 1 mg L-1 dissolved organic carbon (DOC)) concentration and geology, where an increase of the area of inland rock in a catchment increases STHM4 concentration. Medium strength positive correlations were found between STHM4 and vegetation classes, where, as the area of acid grassland, and heather increase, so does the concentration of STHM4. Negative relationships were discovered showing the obverse, where, as loamy and clayey floodplain soils with naturally high groundwater increased in area, STHM4 concentration dropped (at the Hampshire Avon ii and Conwy catchments combined). The occurrence of coniferous woodland in a catchment was found to correlate with the CHCl3 formation potential of waters (Pearsons, f=0.530, p= < 0.05, n=20), supporting findings in published literature. Laboratory based chlorination and chloramination of sample waters, followed by gas chromatography provided DBP data, specifically THM4. These data show that more chloroform was formed after chlorination than chloramination, and that chloramination formed 3 times more CHBr3 (another THM4 compound) than chlorination, under laboratory formation potential conditions. Results showed that the chlorination of water prior to DOM removal could result in a THM4 concentrations 5 times greater than the current UK regulatory limit, per mg L-1 dissolved organic carbon (DOC), whereas chloramination forms ca.5 times less than the current UK regulation per 1 mg L-1 DOC. However, chlorination of water prior to DOM removal is never done in practice, so this data provides information on the composition of the organic matter and whether DOM from a specific catchment contains specific components that are responsible for an increase in a specific DBP. Data also show that increasing organic nitrogen or organic carbon does not necessarily increase nitrogenous or carbonaceousDBPs (N-DBPs or C-DBPs). However, importantly, data shows that an increase in the area of land use classed as 'urban', results in an increase in DON (likely due to human influences) in the water draining from them, posing potential issues for eutrophication in downstream water bodies and the formation of N-DBPs at water treatment works. Whilst N-DBP detection was explored from several different angles, the development of a definitive method was not possible due to very low N-DBP concentrations, time and financial constraints. However, various methods were adapted to aid in the detection of them, showing promising initial results, providing the background for future projects into the discovery of a suite of N-DBPs such as haloacetonitriles and halonitromethanes. Finally, the data in this thesis have been inputted into maps for each major catchment to present data with a high visual impact, but also to illustrate land use types that have been found to correlate with increases in DBPs and specific nutrients in the water draining from them. However, the high variation in DOM concentration and character from site to site make extrapolation of these risk assessment data, to other catchments, unsafe. Nevertheless, collection of data from a catchment (similar to the work presented here) where a new water abstraction location is desired can prove advantageous in providing information to utility companies of what difficulties they may encounter when treating the water. Though this can be done by grab sampling at each site of interest, this can prove costly and timely and involves both field and laboratory based work aspects, wheras the method presented here requires less cost and time, once the method is initialised, to derive data of similar value. Despite the fact that disinfection performance would always trump DBP minimalisation, this is likely to be a vital tool in ensuring the provision of safe and healthy water fit for the consumption of an ever increasing human population.

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Suc Chiu Ho. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 57-60). / Abstracts in English and Chinese. / TITLE PAGE --- p.i / THESIS COMMUTE --- p.ii / ABSTRACT (English) --- p.iii / ABSTRACT (Chinese) --- p.iv / ACKNOWLEDGMENTS --- p.v / TABLE OF CONTENTS --- p.vi / LIST OF FIGURES --- p.viii / LIST OF TABLES --- p.ix / Chapter CHAPTER ONE --- General introduction and methodology / Chapter 1.1 --- General introduction --- p.1 / Chapter 1.2 --- Approximation in ab initio calculation --- p.4 / Chapter 1.2.1 --- Born-Oppenheimer approximation --- p.5 / Chapter 1.2.2 --- Density function theory (DFT) --- p.6 / Chapter 1.2.3 --- Periodic supercell approach for solid reaction --- p.8 / Chapter 1.2.4 --- Pseudopotential approximation --- p.11 / Chapter CHAPTER TWO --- "Adsorption of N02 molecules on zigzag (6,0) and (8,0) single-walled carbon nanotubes (SWNTs)" / Chapter 2.1 --- Introduction --- p.15 / Chapter 2.2 --- Computational details --- p.17 / Chapter 2.3 --- Resultsand discussion --- p.19 / Chapter 2.3.1 --- "Adsorption of a single N02 on (6,0) SWNT" --- p.19 / Chapter 2.3.2 --- "Adsorption of a second N02 on (6,0) SWNT" --- p.22 / Chapter 2.3.3 --- "Comparison of NO2 adsorptions on (8,0) SWNT with different cutoff energies" --- p.25 / Chapter 2.3.4 --- "Adsorption of more N02 on a (8,0) SWNT" --- p.28 / Chapter 2.4 --- Summary --- p.34 / Chapter CHAPTER THREE --- Diameter dependence for the adsorption of N02 molecules on zigzag single-walled carbon nanotubes (SWNTs) (n=6~12) / Chapter 3.1 --- Introduction --- p.35 / Chapter 3.2 --- Computational method --- p.37 / Chapter 3.3 --- Results and discussion --- p.38 / Chapter 3.3.1 --- Adsorption of a single N02 on SWNT --- p.38 / Chapter 3.3.2 --- Adsorption of a second on N02 SWNT --- p.40 / Chapter 3.3.3 --- Electronic structures of SWNTs after NO2 adsorption --- p.42 / Chapter 3.4 --- Summary --- p.55 / References --- p.57