The impact of biochar or activated carbon (AC) amendments on the biodegradation of a mixture of 12 volatile petroleum hydrocarbons ( VP Hs) in an aerobic sandy soil was investigated in batch microcosms and column experiments. The impacts of biochar amendments on nutrient availability and biogenic gases activity were also studied by batch microcosms. The maximum nutrient amount adsorbed by biochar (9 max) was very high. Therefore, biochar amendments decreased the readily available nitrogen with increasing biochar application rate and contact period. Biogenic gas activities in biochar amended soils had varied responses because these activities were dependent on soil properties. The effects of sorbent amendment significantly depended on the compound chemical structure and type of sorbent material. In the batch microcosms, the AC and biochar amendments resulted in a large increase in the K values. The biodegradation of the water-dissolved OC fraction of most compounds was as fast or faster in the soil amended with activated carbon compared to the soil with or without biochar, but the strong sorption capacity of activated carbon, in particular, greatly reduced water-dissolved concentrations. The nutrient amendments accelerated the biodegradation of VPHs in the batch microcosms and nutrient availability was the main factor controlling the biodegradation rates of total petroleum hydrocarbons in sandy soil; whereas sorption was a secondary factor influencing the biodegradation of total petroleum hydrocarbons in biochar and activated carbon amended sandy soil. The biodegrada tion in sorbent amended columns was difficult to predict. The sorbent amendments decreased the availability of both VP Hs and nutrients. Therefore, the biodegradation rate was reduced. However, the petroleum hydrocarbon vapour migration and volatilization was also reduced, which increased the residence time of contaminants in the sorbent amended column. This means there was more time available to degrade the pollutants before they emanated from soil, and therefore the sorbent amendments may result in a greater amount of biodegradation, if considered over a certain distance and over a long time period. It is concluded that b iochar and activated carbon amendments are potentially a sustainable remediation strategy for dealing with volatile petroleum hydrocarbons pollution. These sorbents are able to reduce the risk of VPHs to biota and the also surrounding environments without using large scale, energy intensive and treatment processes.

There is currently a considerable interest in characterising extreme environments, since they offer the opportunity to envision practical applications and to understand microbial diversity as an adaptive response that reflects environmental diversity. It is now well recognized that microorganisms thrive in extreme conditions such as contaminated soils/sediments and the pressurised depth of the Earth. Morphological, physiological, biochemical and genetic adaptations to extreme environments by these microorganisms have generated immense interest amongst scientists who continuously discover new occurrences and modes of microbial life on Earth. In this thesis, biogeochemical processes are investigated in two different extreme environments. (i) The deep biosphere, with a focus on shale gas basin and coal-bed methane (CBM). These environments are currently gaining momentum across the scientific community for the production of gaseous fuel. (i) [sic] Coal tar-contaminated soil and concentrated organic-phase coal tar, which was studied for bioremediation purposes. The core of this thesis consists of three articles dedicated to combination of different molecular and chromatographic methods of experimentation, analysis and interpretation. These include molecular tools such as DNA extraction techniques, PCR, 454-pyrosequencing and culturing-based approaches. The chemical experiments were metabolomic and isotopic chromatographic analyses. This study presented an extensive review of the biogeochemistry of unconventional gas systems, which provide an improved level of information of such environments. A robust culture-independent methodology was developed for the characterisation of microbial life in extreme environments, which was applied to describe, for the first time, the presence of bacteria in concentrated organic-phase coal tar. The deep sequencing methods were then used in combination with multidimensional compound specific isotope analysis (CSIA) to investigate community structure. The combined approach of deep sequencing methods with multidimensional CSIA was confirmed by statistics. Thus, high-throughput 16S rRNA gene sequencing and multidimentional CSIA, can be applied to investigate microbial community structure in extreme environments.

This thesis presents the results of a character study of the soils of Upper Weardale, Co; Durham. Part 1 presents relevant material on the soil environment of the area, emphasising the important characteristics of parent materials, relief, climate and ecology. The results of the field and laboratory investigations are summarised in the form of assoil map of the area on a scale of 2(^1)/(_2)" to one mile and in the Appendix, which presents the results of detailed field and laboratory analyses of specific profiles. The bulk of Part 2 is concerned, with discussions on the origin and properties of the different types of soil. Field and analytical characteristics are use' to assess as far as is possible with existing information, the dynamics of past and present pedogenic processes in the soil profiles. Throughout the discussions, problems of classification and interpretation are highlighted, and avenues for future research emphasised.

Demand for livestock products are expected to rise due to increasing global population, urbanisation and affluence. Sustainably managing livestock excreta will be central to achieving an expansion in production whilst minimising environmental damage. The deposition of excreta to soil by livestock accounts for ca. 21% of the UK agricultural N2O emissions. Accurate quantification of N2O and assessments of the efficacy of mitigation technologies are key research areas for progressing toward enhanced sustainability and productivity in grazed grasslands. The overall thesis aims are to enhance understanding of N cycling and losses in sheep urine patches, as ‘hot-spots’ and ‘hot-moments’ for rapid nutrient cycling. Objectives were (i) to determine how sheep urine patch and environmental parameters influence N2O emissions, (ii) to determine the optimal way to accurately measure N2O emissions from sheep urine patches via the static chamber technique, and (iii) to assess the efficacy of synthetic nitrification inhibitors as a mitigation strategy for urine patch N2O emissions. Sheep-grazed grasslands were selected for study, based on the lack of current available evidence for these agroecosystems. N2O emissions were monitored from sheep urine-influenced soil in small incubation vessels, or by the static chamber technique in the field (manual and automated campaigns). The use of 14C-labelled inhibitors were also employed in laboratory studies, to trace the fate of nitrification inhibitors in the plant-soil-microbe system and provide a better understanding of the factors that affect the efficacy of inhibitors to reduce N2O emissions. Urine patch size and N concentration were found to be important parameters influencing emissions of N2O from sheep urine patches. Emissions of N2O were generally lower than the IPCC default of 1% of the N applied in sheep excreta, where peaks in emissions occurred alongside rainfall events. Total extractable N, oxidation reduction potential and soil water-filled pore space were determined to be key drivers of N2O emissions from sheep urine under controlled conditions. The urine patch diffusional area was shown to be important for accurate quantification of N2O emissions when using the chamber technique; the importance of daily sampling of emissions, an assessment of the diurnal nature of N2O emissions and having a high number of replicate chambers to adequately represent the large spatial variability in N2O emissions was also confirmed. The nitrification inhibitors DCD and DMPP had contrasting behaviours in differing soil types. DCD had a greater sorption in comparison to DMPP and microbial uptake and degradation were concluded to be important parameters influencing their effective period in the soil. A graminaceous plant was shown to be able to acquire DCD intact through its roots and translocate the compound to shoots which raises concerns about contamination of food products. A liquid application of DMPP was not effective in reducing cumulative N2O emissions from sheep urine patches in the field. The efficacy of nitrification inhibitors to reduce N2O appears to vary widely, nevertheless they are a mitigation strategy that could be implemented in the short term. Achieving enhanced sustainability and productivity in grazed grasslands is a complex problem, requiring an interdisciplinary approach and the involvement of policy-makers and farmers to resolve. There are several mitigation strategies available or being developed, and some which require more research before being practicable. Advances in technologies to measure and mitigate N2O emissions will greatly enhance our knowledge of N cycling and losses, and the potential to alleviate such losses from the urine patch environment in the near future.

No description available.

The degradation of soil quality due to anthropogenic causes is globally important, both in terms of ecosystem services and ecological biodiversity. Soil quality reduction is stated to be detrimental for population densities and species diversity of soil invertebrates, including the mesofauna (Acari and Collembola). Within the soil food web, mesofauna occupy several trophic levels and as such facilitate nutrient turnover, fulfilling vital ecosystem functions and services. Understanding soil invertebrate population dynamics not only during degradation, but equally upon ecosystem restoration, is vital to identify possible losses or benefits to healthy ecosystem functioning. Prior to this investigation the Highfield site, Rothamsted Research, had been divided and maintained as grassland, arable cropping or bare fallow for 50 years. The latter resulted in a soil that had low soil organic matter levels, poor structure, low bacterial biomass and virtually no invertebrate population. Investigations into the invertebrate population changes, within both the experimental plots and surrounding land, upon alteration of the existing management strategies was completed over a two year period. Changes to mesofaunal populations were detected across all treatments following conversion. Generally, new fallow and arable management strategies produced low density fluctuating populations affected by the physical disturbance of ploughing and lack of soil organic matter as a basal food resource. Grassland management produced increased species diversity and abundance within a more stable soil food web. Each of the new management strategies developed towards its equivalent management strategy within the control treatments. Although it was apparent that the mesofaunal populations were re-establishing under more favourable environmental conditions, there was no definitive conclusion as to the source of the population increases. An attempt to identify the physical mode of invertebrate movement was completed, utilising a prototype mesocosm to act as a physical barrier, this showed promise for future use in such studies.

The cellular slime moulds or dictyostelids, are a major group of edaphic (soil-dwelling) unicellular eukaryotic micro-organisms which feed on bacteria in the humus layer of tropical and temperate soils. The extraordinary behaviour of dictyostelids where solitary, predatory amoebae become social, forming a multi-cellular spore-producing ‘organism’ when their food supply becomes limited has fascinated generations of researchers. Since their discovery the taxonomy of the cellular slime moulds has been largely based on morphological features, revised many times, but still remains unresolved and controversial. One focus of discussion is the controversial relationship between the two principal genera of Dictyostelium and Polysphondylium, which by virtue of a common amoeba type are placed in the same family - Dictyosteliaceae. Despite the current distinction between Dictyostelium and Polysphondylium it is impossible to definitively resolve these genera, or indeed the broader classification of cellular slime moulds, using only morphological features. Given that dictyostelids are both of major ecological importance and often used as a model eukaryotic system, it has become imperative to resolve these taxonomic uncertainties and to finally establish the validity of one or two genera. This study used two PCR based techniques: (1) direct sequencing of the ITS 1 and ITS 2 regions of the rDNA complex together with (2) ISSR-PCR, a standard molecular technique but rarely applied to the dictyostelids. The latter requiring the development of a working protocol before it could be implemented. The sequence data from 51 different dictyostelid species and isolates was aligned with CLUSTAL and analysed via PAUP. This study clearly demonstrates that molecular markers cannot distinguish Dictyostelium (sensu stricto) from Polysphondylium (sensu stricto): indeed it presents evidence to support the existence of a single genus. The implications of these results are unequivocal: the current systematics of cellular slime moulds, based on morphological characters, must be revised.