Release of phosphorus (P) from bed sediments to overlying waters (internal P-loading) can detrimentally alter ecological structure and function in shallow lakes. The theory of regime shifts states that shallow lakes can exist in alternative states and that shifts between states can occur as a result of disturbance. The main hypothesis of this study was that the use of a P-capping agent (Phoslock®) in shallow lakes (i.e. a controlled disturbance) will break down the internal P-loading feedback mechanism resulting in a regime shift. Experiments, ranging in scale from mesocosm to whole-lake, showed that Phoslock® significantly reduced internal P-loading by increasing the mass of P stored in more refractory sediment P-fractions relative to potentially release-sensitive P-fractions. Intact sediment core experiments highlighted that the application of high areal loads of Phoslock® can, at least temporarily, significantly alter the vertical distribution of sediment dissolved oxygen concentrations and cycling of nutrients other than P, suggesting that the application of high areal loads of Phoslock® to lakes should be avoided. Disruption of internal P-loading in Loch Flemington (Inverness, UK) caused a significant reduction of in-lake P concentrations, a decrease of phytoplankton biomass and an increase in water clarity. The observed changes were generally comparable to those observed in long-term multi-lake studies investigating the recovery of shallow lakes following external P-load control, but occurred over a shorter time scale (1 year compared to decades). Alterations in ecological structure and function indicated that a change in state from a ‘phytoplankton dominated turbid state’ to a ‘macrophyte dominated clear water state’ was achieved in Loch Flemington. This study confirms that it is possible to force a state change in shallow lakes by disturbing feedback mechanisms and documents further work required to improve the efficacy of the Pcapping approach in lake remediation.

This project compares palaeo-oxygenation related features of lower Cretaceous rocks from the shallow sea muds of the Gault Clay (south east England) and Niveau Pacquier and Briestroffer sequences (south east France), and the Tarfaya Basin upwelling-zone Amma Fatma sediments (Morocco). The palaeo-oxygenation indicators investigated include: sedimentological proxies, including ichnology, sedimentology, taphonomy and pyrite framboid size distribution; faunal proxies including macrofaunal properties, and biofacies models; and geochemical proxies, including trace-element abundances [Mo, V, Ni, Mn], element ratios and parameters [U/Th, authigenic U (Ua), V/Cr, Ni/Co, Ni/V, (Cu+Mo)/Zn, V/Sc and V/(V+Ni)] and Fe-S-C systematics [Total Organic Carbon (TOC), Total Sulphur/TOC ratio, Degree of Pyritisation and the Indicator of Anoxia]. The presence of lamination is a key sedimentological indicator of restricted bottom water oxygenation conditions. New descriptive categories of pyrite morphology are proposed. Interpretation of faunal proxies can be limited by poor preservation, but taphonomy-related indicators correlate well with proposed palaeo-oxygenation conditions. Molybdenum is the most reliable of the trace-metal enrichment proxies studied and altered numerical boundaries are proposed for Ua, U/Th, V/Cr and Ni/Co. Of the Fe-S-C systematics indicators, Total Organic Carbon and the Indicator of Anoxia to provide the greatest definition between palaeo-oxygenation data sets. Combinations of trace metal and Fe-S-C indicators such as [Molybdenum Enrichment Factor x Indicator of Anoxia], and plots of Ua against TOC provide the strongest palaeo-oxygenation proxies and distinguish between oxic/dysoxic, anoxic and euxinic conditions.

Oceanic barium has many potential proxy applications, from the quantification of export productivity using sedimentary barite, to the tracing of freshwater inputs or the circulation of deep water masses. Using these proxies to reconstruct past oceanic conditions is of particular importance in the Southern Ocean, where the ventilation of deep water masses and the biological drawdown of CO2 are thought to play a significant role in climate regulation. However, the distribution of particulate and dissolved barium in this region is not solely controlled large scale water mass circulation and predictable biological associations, but by an additional combination of spatially and temporally variable local and coastal processes. In this thesis I have found that stronger near-surface gradients are observed in Antarctic waters than in other ocean basins, with a significant association between Bad and silicic acid in surface waters at the WAP. As no direct link was observed between Bad and biological productivity, these observations can be explained by an association between Bad and siliceous detrital material, either by adsorption mechanisms or through barite precipitation in surface waters. Greater levels of Bad release and inferred barite precipitation production are observed from the decay of diatom-dominated detrital material. The accumulation of particulate barium phases in WAP shelf sediments appears to produce a benthic Bad flux that acts as a significant source of Bad to coastal waters. Sea ice is found to be a further, little studied, control on Antarctic coastal Bad distributions, with non-conservative distributions of Bad observed in sea ice cores that may be due to abiotic barite precipitation, and large fluxes of sea ice melt associated with unusually low surface Bad concentrations.

The routine monitoring of workers exposed to uranium and plutonium traditionally uses urine samples. Conventionally this analysis, typically using ≥1 L urine samples, is carried out by alpha spectrometry. A method for the rapid, simultaneous determination of plutonium and uranium in urine has been developed. It significantly improves on traditional methods by exploiting the increased sensitivity achievable using SF-ICP-MS, and uses much smaller (40 mL) sample volumes. The ultimate aim for detection limits is 1 μBq/L (0.4 fg/L) for Pu, and <0.2 mBq/L (8 ng/L) for U, measuring both the concentration and isotope ratios. Isolation of the uranium and plutonium is achieved through a calcium phosphate precipitation followed by separation using a single UTEVA column. A rapid clean up of the plutonium fraction, using TEVA resin is required to ensure high uranium decontamination. The samples are measured using an Element XR ICP-MS and the Aridus sample introduction system. The procedural blank contribution is paramount to the success of the method because of the combined demands of low detection limits, and the need to control the uranium hydride interference (238U+ on 239Pu). Sub boiled acids are used throughout ultra-pure reagents and MilliQ water, and all work is carried out in a class 100 clean laboratory. Instrumental detection limits (calculated as 3 ◊ SD of blank) achieved are ≥1 ppq for uranium, and ≥0.1 ppq for plutonium. As part of this work, the retention of material by the ICP-MS has been explored. As samples are ‘consumed’ by the instrument, any activity contained within the sample will be retained by the components of the instrument. Retention of material by the ICPMS raises questions of a potential radiation dose to instrument operators. The cones and sample introduction system retain the most material. The potential radiation dose for an instrument used for low level radioactive material has been calculated and demonstrated to be less than the public radiation dose limit in the UK.

In the first part of this study are presented the synthesis and results of structural investigations of mixed metal sulfosalts. Included are the structures of five new lead, bismuth and antimony sulfosalts; phase GZ1 (Bi4.39 Pb1.4 Sb3.21 S13), phase GZ2 (Bi1.74 Pb2.62 Sb2.15 S8), phase GZ3 (Bi0.87 Pb1.22 Sb0.42 S3), phase GZ4 (Sb4.66 Pb3.97 Bi1.37 S13) and phase GZ5 (Sb6 Pb14 S23), and the revaluation of the known phases zinckenite (Pb1.49 Sb3.64 S7), stibnite (Sb2 S3), lillianite (Pb3 Bi2 S6) and galenobismutite (Pb Bi2 S4). With the exception of stibnite and galenobismutite these phases are characterised by mixed occupancies, and the site populations were assigned via a combination of microprobe analyses, polyhedral distortion and bond valence analysis results. To this end two FORTRAN programs were written, OCCGEN96 and VOLUME96, the former to calculate the occupancy of a site based on the bond valence contributions of its constituents, and the latter to calculate its polyhedral volume. Phase GZ1 exhibits a monoclinic structure with a central region reminiscent of stibnite, and its distribution of occupancies indicate the presence of a supercell produced by ordering. Phases GZ2 and GZ3 are hexagonal with features in common with zinckenite. GZ3 possesses the smallest hexagonal cell yet found for a sulfosalt and its structure contains three-fold metallic columns, in addition it displays a metal coordination environment not previously seen in this type of structure. The positional disorder, and partial occupancies (manifest as poorly defined hexagonal channels) exhibited by zinckenite and the other hexagonal sulfosalts are here explained for the first time in terms of alternately occupied configurations arranged on a superlattice. Phase GZ5 resulted from an attempt to crystallise the mineral semseyite whose structure is unknown, but possibly closely related to that of GZ5. The poorly defined phases from the literature have all been refined with better discrepancy indices and in the case of lillianite the results differ significantly from those previously reported. Additional investigations of phase GZ1 were carried out using transmission electron microscopy, and these lead to the identification of a number of related phases and also revealed the presence of disordered and composite structures. In the second part of the study diamond inclusions of lower mantle origin are investigated. In common with the sulfosalts they are characterised by mixed occupancies, however the distribution of metal species within mineral silicates is better understood than in sulfosalts, and they provided a good base from which to study the latter. The presented results include the crystal structure of the new mineral TAPP (Mg0.76 Fe0.15) (Al1.76 Cr0.16 Mn0.06) (Mg1.88 Fe0.08) Si1 (Si1.92 Al0.08) O12, which is of great significance in lower mantle genesis theory; the structures of two novel pyroxenes (Mg0.46 Al0.43 Fe0.06 Cr0.05) (Mg0.39 Na0.31 Ca0.16 Fe0.06 Mn0.04) (Si1.91 Al0.09) O6 and (Mg0.73 Al0.23 Cr0.03) (Mg0.70 Na0.06 Ca0.03 Fe0.16 Mn0.04) (Si0.83 Al0.17) SiO6 and the only sapphire (Al1.98Fe0.01Si0.01O3) to be found as a diamond inclusion. The structure of TAPP is particularly interesting as it has a garnet composition but is tetragonal not cubic. In the past the only non cubic garnets have been so only by a few angstroms at the most, while the cell of TAPP has a c parameter nearly three times that of a.

Studies of adsorption of several surfactants from aqueous solution onto kaolin have been made, such as might be employed in an enhanced oil recovery process. Investigations of the surfactants were carried out with regard to pH, ionic strength, temperature, the addition of short chain aliphatic alcohols, the addition of sacrificial complexing agents and various ion-exchanged forms of kaolin. The various forms of kaolin were synthesised to simulate the effect of clay contact with sea water and/or formation water. To try and understand the surfactant solution more fully an attempt was made to determine the number of bound Ca2+ ions and A13+ ions using an ion-selective electrode and atomic adsorption spectroscopy techniques. The results of the adsorption experiments show that monolayer coverage of the kaolin takes place, and the minimum adsorption is favoured by the following conditions: high pH, low ionic strength and elevated temperatures. The presence of butan-l-ol and sodiwn citrate are also beneficial. In the presence of high ionic strength solutions, the anionic surfactant may also be lost due to salt formation with the metal ion present and hence be precipitated from solution. In the absence of the short chain alcohols the adsorption isotherms of the anionic surfactants can be said! at low concentrations « 10-3 mol dm-3), to be due to electrostatic interactions between the edge of the clay particles and the charged surfactant. At higher concentrations the adsorption becomes limited due to the formation of micelles. At concentrations> 10-2 mol dm-3 the surfactants appear to desorb into solution. This is due to the resolubilisation of the adsorbed surfactant-metal ion species by the excess micelles which exist at these surfactant concentrations. The determination of bound counter ions has been investigated and found to give acceptable results comparable to those that would be expected, However, slight reservations are made as to the total accuracy of the test method. This study has been able to define the conditions which will allow various anionic surfactants to be used in conjooction with other chemical species in enhanced oil recovery processes for both land or sea based wells.

Heinrich events involve the massive release of icebergs from continental ice sheets into the sub-polar North Atlantic, which travel as far south as 40°N and deposit large quantities of Ice Rafted Debris (IRD) in marine sediments. Determining the distribution of IRD sources across the Atlantic during Heinrich events is a vital step in ascertaining the sequence of iceberg rafting, and the relative involvement of circum-North Atlantic ice sheets in this release of freshwater to the North Atlantic. This study examines evidence from multiple radiogenic isotope (Nd, Sr and Pb) analyses on the detrital clay size fraction (<2μm), and stable isotopes in the detrital <63 μm fraction of a Hudson Strait (HS) source (δ18O of <-2.5 and εNd of <-19) in the clay and fine fraction deposited at the IRD belt site during Heinrich events. At the north-eastern British margin changes in detrital δ18O and εd are related to small inputs of HS derived material during H4, however during H2 there is no discernible HS source to the fine fraction this is contrary to previous coarse fraction studies at the site. It is proposed that the dominance of the British and Irish Ice Sheet (BIIS) source at the site during H2 is due to the increasing size of the British Ice sheet over the course of the last glacial. Endmember modelling of particle size distributions demonstrate a coarsening of the silt fraction over the Heinrich events at the IRD belt site. At the margin of the BIIS there is a correspondence between millennial scale IRD events and coarse particle size distributions which is superimposed on increases in the finest endmember over the last glacial in response to the BIIS reaching the shelf edge. Changes in stable isotopes of surface dwelling foraminifera demonstrate that the surface waters were fresher during H2 and H4 coinciding with fine fraction IRD inputs. At the British ice sheet margin, increasing surface water stratification after 27 ka BP coincides with increases in fine particle size endmember and δ18O of the fine fraction further indicating the consistent presence of the BIIS at the shelf edge after 27 ka BP.

Sustainable urban Drainage Systems (SuDS) have become an important approach for protection of natural watercourses from non-point sources of pollution. In particular, filtration based SuDS build on the concept of simple, low-cost technology that has been utilized in water treatment for over a century. While it is widely studied and acknowledged that filtration of polluted water through granular material is extremely effective, the inherent geochemical and biogeochemical mechanisms are complex and difficult to ascertain. This is especially true for SuDS filter drains as they have been less well studied. Therefore, this thesis set out to quantify heavy metal removal in gravel filter drains and investigate (bio)geochemical mechanisms responsible for metal immobilization. Determining specific mechanisms responsible for pollutant removal within SuDS provides data that can be used to enhance SuDS design and performance. First, the impact of engineered iron-oxide coatings on heavy metal removal rates were investigated. It was determined that unamended microgabbro gravel immobilized similar quantities of heavy metals to the engineered iron oxide coated gravel. Consequently, engineered iron-oxide coatings were not recommended for future research or use in SuDS systems. Analysis of the surface of microgabbro gravel revealed the surface minerals are weathering to clays, enhancing the gravels affinity for heavy metals naturally. Comparison of microgabbro with other lithologies demonstrated microgabbro displayed enhanced removal by 3-80%. Comparison of microgabbro gravels with and without weathered surfaces demonstrated the weathered surface enhanced metal removal by 20%. From this, it is recommended weathered microgabbro gravel be used in filtration based SuDS where immobilization of incoming heavy metals typical in surface water runoff is important. Following this, the contribution to metal immobilization due to biofilm growth in a gravel filter was examined. Through heavy metal breakthrough curves obtained from experimental flow cells with and without biofilm growth, it was determined that biofilm enhances heavy metal removal between 8-29%. Breakthrough curves were modelled with an advection diffusion equation. The model demonstrated heavy metal removal mechanisms within the column could be described effectively by a permanent loss term. Further, the typical microbial community found within biofilms collected from an urban filter drain was determined to be composed of over 70% cyanobacteria. However, when inoculated into two different lithologies of gravel, the biofilm community composition changed and was influenced by gravel lithology. Dolomite gravel retained 47% cyanobacteria dominance while microgabbro demonstrated 54% proteobacteria dominance. Despite variations in biofilm composition, heavy metal removal capacity and mechanisms were broadly similar between different biofilm types. An additional approach to determine effects of biofilm growth on porosity and flow patterns through a horizontal gravel flow cell was assessed with non-invasive magnetic resonance imaging (MRI). While a copper (Cu) tracer could be imaged within the gravel flow cell, the transport pathways were too complicated to model as the Cu does not follow a plug flow. Processing of 3D high resolution images determined the porosity of the gravel filter to be between 32-34%, in line with literature values for coarse grained dolomite gravel. Further post-processing allowed for localized biofouling to be analyzed. Highest concentration of biofilm growth in columns resulted from longer growth periods and exposure to light. Moreover, biofilms tended to grow closer to the inlet which typically offers a higher nutrient dose and in pore space regions close to the light source (both of which would be representative of the surface of a filter drain). Thus, MRI analysis of biofouling has important implications for filter drain design and efficiency through assessment of pore space blockage. Finally, the possibility of enhancing heavy metal removal in sand (another filter material common in SuDS) with nano zero-valent iron (nZVI) particles was considered. Metal breakthrough curves for column experiments indicate that use of 10% nZVI enhanced sand improved metal immobilization between 12-30% and successfully removed > 98% Cu and Pb. It is therefore believed that nZVI enhanced sand is a promising avenue of future research for areas prone to high heavy metal loads.

Information on the concentration and distribution of dissolved methane (CH4), together with other geochemical tracers, in real time is of great value in detecting, monitoring, and understanding the functioning of hydrothermal plumes. Water column anomalies of light transmission, dissolved CH4, manganese (Mn), and iron (Fe) were located over segments 15 and 16 of the Central Indian Ridge (CIR 20ºS), in December 2006. Along segment 15, a hydrothermal plume was present at 19°33’S/65°50’E. The source might be located north of that position and dispersed along the western flank by NW-SE currents. Methane to manganese ratios suggest that methane is produced by magmatic processes. On Segment 16, evidence for 1 or 2 hydrothermal plumes were detected over a lava plain (18°20’S/65°18’E). These data suffered from uncertainties due to sampling issues, which demonstrate the need for a reliable in-situ methane sensing technology. Current in-situ methane sensing technology is based on gas partitioning across gas permeable membranes, which are poorly characterised and variable in terms of permeability and environmental pressures. Two optical techniques were laboratory tested for the measurement of dissolved methane; Near Infrared Fibre-optic Evanescent Wave Spectroscopy (FEWS) and Surface Plasmon Resonance (SPR). No detection (at the µM level) was possible with FEWS, but the second technique using SPR sensors associated with a methane specific binding chemically showed great promise. A limit of detection of 0.2 nM and a linear concentration range from 1 to 300 nM was demonstrated, under a range of temperature and salinity. In-situ deployments confirmed the suitability of the method for in-situ measurements. Values given by the sensor correlated well with the concentrations measured by traditional techniques. Future work is needed to decrease instrumental noise and to reduce the response time, and associated hysteresis effect.

This study investigates the preserved fluid contents of different generations of mineralised and unmineralised vein minerals from multiple different deposits across the Zambian Copperbelt to define the fluid physicochemical characteristics of the fluids and investigate the importance of fluid processes through the basin history. An investigation into REE and trace element and sulphur isotope signatures of sulphides was conducted to investigate sulphide formation mechanisms. Re-Os dating of sulphides from the Domes Region to provide temporal constraints on mineralisation processes in this area. A textural study on uranium mineralisation at the Lumwana deposit was undertaken to understand the relationships between uranium and sulphide mineralisation. Variable Cl/Br of fluids indicates they were derived from evaporation of seawater, deposition of evaporite sequences and the subsequent dissolution of these evaporite sequences, with bittern brines dominant earlier in the basin history, and dissolution of halite more important during compression and orogenesis. Cation contents of fluids record the development of alteration assemblages caused by the movement of these brines at temperatures typically >200C and salinities >30 wt% NaCl equiv. Stable isotope data records the role of organic reductants and fluid-host rock equilibration through basin history. Rare earth element signatures of sulphides further record the importance of the development of the alteration assemblage on the changing chemistry of the hydrothermal fluids, whilst trace element concentrations suggest the metal budget in the fluids reflects source rock variation. Sulphur isotope data suggests the main mechanism of sulphide formation was thermochemical sulphate reduction of seawater sulphate, consistent with the temperatures of the fluids reported here. Re-Os dating records the importance of orogenesis on the timing of mineralisation in the Domes Region, and are consistent with published Re-Os dating of sulphides and U-Pb dating of uranium minerals. Textural relationships indicate initial uranium mineralisation at the Lumwana deposit pre dates sulphide mineralisation, and final movement on the shear zone, but has undergone a remobilisation event later in the deposit history.