This thesis investigated the impacts of different forms of black carbon (BC) on the bioavailability and bioaccessibility of phenanthrene in soil for remediation. BC is a general term used to describe various forms of natural and engineered carbonaceous geosorbents, such as activated carbon (AC), biochar and soot. Carbon nanomaterials (CNMs) are generally agreed to be engineered structures with at least one dimension of less than 100 nanometres in length. CNMs are of interest because of their specific physicochemical properties that can be attributed to their small size, chemical composition, surface structure, solubility, shape and aggregation. CNMs could be released into water and soil not only by inadvertent discharge, but also because NPs have applications for groundwater purification and pollutant remediation. Unfortunately, very little is known about the transport of these materials in soil or the resulting ecotoxicity, and only a small number of studies have been carried out in this area. Phenanthrene, a ubiquitous, persistent and hydrophobic contaminant found in all ecosystems worldwide, was used as the target contaminant for the studies carried out in this thesis. Powdered activated carbons (PACs) with different pore volumes and particle size distributions were amended to soil, and used to assess bioaccessibility of phenanthrene to soil. Biochar from the same feedstock was also used, but prepared under different conditions. At low concentrations (0.01 %), the addition of AC to soil did not affect microbial activity, measured by the rates of respiration and overall extents of mineralisation of 14C-phenanthrene. However, the presence of AC at 0.1 and 1 %, respectively, resulted in significant reductions (P < 0.05) in the bioavailability and bioaccessibility of 14C_ phenanthrene. For CNM-amended soils, the addition of>0.01% (w/w) significantly reduced the development of phenanthrene catabolism; the only exception to this was C60, which did not show any significant difference from the control, at all concentrations. Results from this thesis suggest that soils amended with AC provide a potential strategy for in situ environmental remediation, and appropriate selection of adsorbents is a key to realising this remediation potential. The different kinds of BC described in this thesis provide a wide choice; therefore it is reasonable to regard them as a promising amendment technology.

Soil is a non-renewable natural resource at risk from degradation worldwide by human activities, mainly intensive agriculture. Soil erosion as a result of agriculture is a global problem, not only leading to loss of a growing medium, but increased pollution of fresh water systems. The soil losses from arable farmland by water erosion in excess of 1 ton ha-1 y(l has increased since the adoption of winter cereals in the UK, but exacerbated by soil compaction by heavy farm traffic. Heavy traffic impairs infiltration of rainfall, leading to infiltration excess overland flow, taking sediment and nutrients, namely phosphorus, off sloping arable fields. Tramlines, temporary lanes used for heavy farm traffic, effectively channel rainfall overland flow during the wet winters in the UK, focusing sediment and phosphorus transportation from arable land. This thesis covers the work carried out at Lancaster University from November 2009 to May 2012 in conjunction with a consortium of researchers and agricultural industry bodies, headed by ADAS UK Limited, to investigate cost-effective measures for reducing sediment and phosphorus losses from arable land. The full project: 'Reducing the risks associated with autumn wheeling of combinable crops to mitigate runoff and diffuse pollution: a field and catchment scale evaluation', was funded by the Sustainable Arable Link Project of the UK's Department for Environment, Food and Rural Affairs (DEFRA) through the Home Grown Cereals Authority. Field trials of low ground-pressure tyres compared to standard agricultural tyres, cropping within tramlines, and soil surface disruption were conducted over three growing seasons of winter wheat. The soil textures ranged from sandy loam to clays for three locations in England, and a sandy loam for one location in Scotland.1 This study focussed on investigating the physical parameters of the compaction caused by the heavy farm traffic and the effectiveness of low ground-pressure tyres in reducing soil compaction at the three field locations in England: Gatley in Herefordshire; Hattons in Staffordshire; and Loddington in Leicestershire. Tramlines, not monitored for overland runoff, but adjacent to those which were, was provided for this study. The soils of the tramlines, both wheeled and non-wheeled, were investigated with innovative approaches with radiographic, photographic and geophysical techniques to improve our understanding of physical changes to soil structure under heavy farm traffic. The aim of the study was to apply the above techniques as tools for assessing soil compaction and to help conclude with the project consortium that In November 2009, during the first trials of low ground-pressure tyres, soil was removed in intact cores from the sites. The cores were measured for saturated hydraulic conductivity by constant head method, bulk electrical conductivity, and bulk density using radiographic imaging. The results show that hydraulic conductivity measurements were inconclusive in revealing reduced compaction under low ground-pressure tyre treatments. The bulk electrical conductivity measurements provided key information on the electrical formation factor of the cores, a measure of the effective porosity conducting electrical current, revealing higher porosity of the soils treated with low ground-pressure tyres. The results of the radiography measurements provided grey-scale images, showing increased bulk density with darker shades. These shades were converted into a range of soil bulk densities for each soil texture. The results revealed that significant impacts to prevailing soil bulk density by the heavy traffic treatments was limited to 0.5-0.8 m from the surface, highlighting a zone of reduced porosity. The radiographs also provided fine spatial resolution of the change in soil bulk density with depth, difficult to achieve with traditional core techniques, revealing that under the low ground-pressure treatments significantly lower soil bulk densities can be maintained. In autumn 2010, during the second trial season of low-ground pressure tyres, the tramline wheelings were photographed and measured for electrical conductivity in-situ. The photographs were taken with a commercial digital SLR camera at three locations along the lengths of the tram line treatments. In pairs, overlapping by 60- 80%, the digital photographs showed a single tramline wheeling, with also ground referencing coordinates. These photographs formed the basis of photogrammetry, the measurement of photographs, and 3-D models of the tramline wheelings (digital terrain models) were generated with Erdas eATE imaging software. The results were of DTMs with a mean RMSE of 0.003 m in the horizontal and vertical plane, with the cleat depressions of the tyres and individual aggregates >0.005 m defined. As a tool to measure soil surface deformation, photogrammetry has increased precision over traditional pin-meter and chain techniques, though requires considerable skill and time to process the photographs.

Agriculture in Ireland is the main source of ammonia (NH3) and contributes 30% of greenhouse gas emissions (GHG), with the majority of these emissions associated with livestock production. As a result, strategies promoting reductions in NH3 and GHG emissions are required. The aim of this work was: (i) to assess the impact of various NH3 abatement techniques on GHG release from a grassland soil; (ii) to investigate the consequences of organic nitrogen (N) applications in terms of carbon (C) sequestration in soils. The effects of slurry dry-matter content, application technique and timing of application were studied in a fifteen month field-plot experiment where gaseous emissions (CO2, N2O, CH4 and NH3) post-application were monitored. The natural abundance 13C tracer technique was also used to investigate the short-term dynamic of slurry-derived C and its consequences on soil CO2 efflux. Finally, 15N labelled slurries, supplemented or not with an additional C substrate, were used in a lysimeter study, under controlled conditions, to characterise the interactions between soil C and N processes post-organic fertilisation. Trailing-shoe application technique was shown to be and efficient way to lower NH3 volatilisation from land spread slurry. However, such benefice could be easily offset by an increase in direct N2O emissions and ecosystem respiration. Conversely, adjusting the timing of slurry spreading to get favourable soil and weather conditions, and to better meet herbage N requirements, had a positive effect on field N balance through a simultaneous reduction of both NH3 and N2O emissions. Emission factors (EF) calculated for slurry-induced N2O emissions were significantly lower than those calculated for mineral fertiliser and were greatly affected by weather and soil conditions. Such results support the widely spread idea of an inappropriate use of a single default EF value of 1% for both fertiliser types, under the IPCC Tier 1 methodology for national GHG inventories, and calls for the development of region-specific emission factors based on local soil types and climatic conditions.About 60% of slurry-derived C was shown to remain in the soil, even after 6 months, thus contributing to an increase of SOC pools. However, such incorporation of slurry-derived C may be offset by a positive priming effect of slurry on the degradation of the SOM. Such short-term priming of soil CO2 efflux may be, under certain conditions, compensated by a subsequent negative PE, thus minimising the impact of such phenomenon on the long-term sequestration of added slurry C. The long-term impact of these priming effects on nutrient and GHG balances remains to be further investigated, as these phenomena may occur on a regular basis in grassland ecosystems.

In the game of cricket good ball-surface interactions are essential and require a hard, flat surface. To achieve this the clay loam soil comprising the pitch is compressed and compacted using a smooth wheeled roller, which when combined with the drying action of the grass plant roots, causing the clay minerals within the soil to shrink, creates a high bulk density, hard surface on which to play. High bulk density soils present difficult growing conditions for plants due to high mechanical resistance, reduced hydraulic conductivity and gas exchange capability. The hydraulic properties and gas exchange capability are linked to the connectivity and tortuosity of the pore network as well as pore size; all of which are diminished by compaction of the soil. Aeration is currently utilised as a tool to ameliorate the negative effects of compaction on the growing environment of the plant roots. Little research exists that describes the actions of aeration in clay loam soils. The current guidelines for aeration and the proof for its efficacy in cricket are based almost entirely on anecdotal evidence. A diverse methodology was used to meet the project objectives. This diversity reflects the broad nature of the expectations of the cricket groundsmen from aeration of pitches as reflected in a survey of current practise undertaken during the project. Novel experimental methods were used to examine the effect of aeration on soil atmospheres in the laboratory and under field conditions. The laboratory experiment revealed that vertically-operated solid tines did significantly increase the rate of diffusion through the soil, however in the field, this rate increase was only apparent after significant rainfall. New methods utilising time-lapse photography and automated image analysis quantified the magnitude of swelling in a range of soils in response to increasing water content over time to a high degree of accuracy. A similar method was employed to examine the shrinkage of the same soils as the water content was reduced, examining not only the magnitude but also the cracking patterns formed. These experiments aimed to examine the soils natural ability to recover from compaction over time. The soils natural ability to recover from compaction through shrink-swell and freeze-thaw was evident in the field trials. These field trials examined five diverse aeration treatments to examine the physical and biological effects they have on the soil. The field trials showed generally small and inconsistent effects on the physical properties of the soil from aeration treatments when compared to the natural processes of shrink-swell and freeze-thaw. One consistent effect from aeration was a 2% reduction in moisture content in one particular soil type. Aeration was found to have no effect on soil microbial biomass nor on soil organic matter content. In a pot experiment examining the effect of aeration in a range of soil densities the total root mass was not diminished by increasing soil density but became increasingly concentrated upwards in the profile. Aeration was found to slightly increase the root mass but only in the highest bulk density treatment (1.90 g cm-3) at depths below 75 mm. A set of guidelines were developed based on the evidence garnered from the experiments with a clearly defined decision process for choosing the most suitable equipment for the treatment aim. It is hoped that these guidelines will provide an informative reference for current and future groundsmen to ensure the optimum use of often scarce and valuable resources when choosing an aeration treatment.

Microbial reduction of nitrate in the top layer of irrigated soils during laboratory incubations was studied using acetylene inhibition and ¹⁵Nrecovery methods. The soils used were from two sites in the Thessaloniki plain in northern Greece. One site was the Galicos River Wastewater Treatment Experiment, where soil cores of clay loam and sandy silt loam were obtained from two areas, each irrigated either with wastewater or fresh water (well water), supplied by furrow for four years. The second site was the Axios Delta, irrigated by flooding, from which clay, clay loam and sandy loam soil cores were obtained. The maximum and minimum denitrification rates in soil cores from the Galicos River Wastewater Treatment Experiment were 2152 and 1.42 µg N kg ^-1dry soil day^-1respectively in the presence of 81 µg carbon g^-1dry soil. The maximum and minimum rates observed from soil cores from the Axios Delta were 33,000 and 1.15 µg N kg^-1 dry soil day^-1 respectively in the presence of natural carbon concentrations at field capacity. A crust layer induced on the surface of repacked and intact soil cores from the Galicos River Wastewater Treatment experiment had no significant effect on denitrification rates. The average losses of nitrogen from the nitrogen fertiliser applied to these cores, and recovered as denitrified N₂Ogas, after irrigation with wastewater and well water were 42 and 33%, respectively. The corresponding loss of N from the topsoil cores from the Axios Delta was 21%. In addition, ¹⁵N recovery indicated that an average of 43 and 51% of the nitrogen fertiliser applied to the Galicos River cores was unaccounted for at the end of incubation. An average of 18% of the nitrogen fertiliser applied to the soil cores from the Axios Delta was unaccounted for at the end of incubation.

Seabirds are known to be important sources of allochthonous nutrients on islands which they use for breeding colonies, as evidenced by their effects on aboveground secondary consumers. Grazing is also known to be a potentially strong ecological driver of below ground food web composition. The overall aim of this thesis was to determine the impacts of these two natural forces on the structure and function of the soil food web in a model island system: the Isle of May, Scotland. The results obtained have shown that both nitrogen inputs firom seabird breeding colonies and grazing by rabbits have important effects on the components of the soil food web, including the island vegetation.

No description available.

No description available.

No description available.

No description available.