No description available.

This thesis addresses the response of the atmosphere to past and possible future anthropogenic CO₂ emissions on timescales of up to a million years. Deep marine sediments and weathering were added to an efficient global carbon cycle model. The effect of enhanced weathering on atmosphere CO₂ response to fossil fuel CO₂ release was investigated for a range of emissions scenarios. 11 parameters in the ocean and sediment system were allowed to vary and the model was calibrated with atmospheric CO₂ data using a Bayesian methodology. This model was then used to assess the uncertainty in atmospheric CO₂ response with and without biotic feedbacks on carbonate and silicate weathering. The enhancement of weathering due to increases in CO₂ and temperature is found to significantly accelerate the drawdown of CO₂ on timescales of 10⁴-10⁵ years, although it will till take > 10⁶ years for the CO₂ level to stabilise. Enhanced weathering has most effect when all sediments in the ocean are dissolved. Timescale of response in the atmosphere depends on the weathering formulation used. Silicate weathering is required to return CO₂ to pre-industrial levels. Calibrating with data improved the model response as mean peak CO₂ levels were ~235ppmv lower than results from previous studies. Uncertainty in CO₂ response due to parameter uncertainty is >500ppmv in some cases, this uncertainty peaks on the millennial timescale and decreases thereafter. The range of uncertainty in CO₂ response for a single emissions scenario encompasses the range of uncertainty due to varying emissions from 300 to 5000GtC in other studies. The time for the atmosphere to return to current levels of CO₂ is also greatly uncertain, with the earliest possibility occurring at ~ year 10,000 but most likely occurrence at ~ year 100,000.

The initial focus of this research sought to investigate the marine geochemistry of radium and barium in order to elucidate upon the processes governing circulation patterns and residence times in the southern Baltic Sea. The project has since developed and transformed into a detailed study of the spatial and temporal distribution of a select group of metals, and in some respects pollutants, in the region north of the river Oder where it discharges into the Baltic Sea. A transect of progressively deepening water depths, thought to trace the major outflow of the river Oder into a depositional basin, were investigated over a period of 15 months. Four cruises during this time were undertaken to coincide with each season in order to investigate any broad scale seasonalities. This thesis looks at the main compartments and integrated processes associated with the sediment, nepheloid layer and the water column of this marine environment. This has been achieved by the use of coupled radionuclide and trace metal data followed by the calculation of fluxes and inventories for a select group of elements. Major and trace metals were analysed via ICPMS and XRF and radionuclides were measured by gamma ray spectrometry. Supporting data in the form of grain size analysis, XRD and carbon and nitrogen measurements were also made. Radium measurements were attempted using the Photo-Electron Rejecting Alpha Liquid Scintillation (PERALS) spectrometer system. Of particular interest Pb, Zn, and Sn and their enrichment over average shale in the Arkona Basin. Coupled with this, stable lead isotope data details a historical picture of increased pollution associated with the rise of the automobile and subsequent decline of lead with the advent of unleaded petrol in the mid eighties. In addition the significance of the mobile nepheloid layer is investigated as a primary transport and modification route for the elements of interest. This thesis challenges the traditional role and concept of the Arkona basin as a depositional site for the pollutants discharged from the river Oder and instead evaluates the depositional role of the Arkona Basin as being primarily a sink for the atmospheric input rather than that associated with riverine discharge.

Upland peat is the world's largest store of soil carbon and one of the most climatically sensitive. Concerns have been raised about the stability of the carbon within these stores and how upland peat will respond to climate change. Climate change is predicted to increase average, ~axirnum and minimum temperatures and also reduce summer rainfall in the UK. This predicted change in climate is hypothesised to reduce water table depth and increase soil respiration in upland peat causing upland peat to, potentially, turn from a net sink of carbon into a carbon net source. A range of management practises have been and are being carried out in the UK uplands, often with the view to increase grazing density or increase other commercial animal species such as grouse. This qualifies peat as grazed land under the ratified Kyoto protocol, and any demonstrated increase in carbon storage potential can be used to offset carbon emissions from the UK. Therefore, questions have been raised as to the best management practises for carbon storage potential. By demonstrating that restoration of water table depths in upland peat will reduce CO2 emissions sufficiently above the corresponding increase in CHt emissions associated with water table rise, .carbon stores can be stabilised and the carbon storage rate potentially increased. This thesis reports the results from a study of C02, both gaseous and dissolved, and CHt fluxes across a differential water table, allowing the results to .be analysed both spatially and temporally. From these results a model was constructed from literature and observations, considering dissolved and gaseous CO2as being produced by a single mechanism from within soil processes, where hydrological functions, such as rainfall to determine the endpoint for CO2. The model was used to analyse for the lowest level of monitoring that still gives a good estimate of the carbon budget for the field site by using mass balance equations from hydrological literature. To determine whether the model was valid for higher temperatures and lower water table depths, as predicted for climate change, a series of deep peat cores were sampled from the same site as the spatial and temporal study of CO2flux and moved to a warmer and drier site. When C02 data, measured from the peat cores, was compared to the spatial and temporal CO2fluxes a visual correlation was found between gross C02 flux for the two data sets, however upon statistical analysis it was shown that the data sets were incomparable for gross, net and primary productivity fluxes. Closed chamber measurements of CO2 flux from the spatial and temporal study were compared to eddy covariance measures of CO2flux. It was found that short term (hourly/daily) were poorly correlated whilst longer term (weekly - monthly) fluxes were better correlated. By studying a peatland on the boundary of peats temperature tolerance, this study can be applied to other peatlands to proved a model of expected responses to climate change for peat both in the UK and around the world.

No description available.

The osmium isotopic composition of seawater (187Os/188Os) reflects a balance between radiogenic continental sources and unradiogenic mantle and extraterrestrial derived sources. Reconstruction of this value has allowed us to unlock vital information about a series of Earth system processes, both today and in Earth’s geological past. This body of work looks to reconstruct the 187Os/188Os of seawater for past and present oceans using the 187Os/188Os composition of shales and macroalgae (seaweed) respectively. The 187Os/188Os composition of Icelandic (0.16 to 0.99) and Japanese (0.16 to 1.09) macroalgae are highly variable, and reflect the mixing between multiple sources. The 187Os/188Os of Icelandic coastal waters is dominated by seawater and local river catchments, and has been utilised to trace the influence of basaltic weathering on the global Os cycle. The 187Os/188Os of Japanese coastal waters is dominated by seawater and river catchments draining Miocene-Holocene continental rocks or anthropogenic sources, and has been utilised to trace mankind’s impact on the global Os cycle. The 187Os/188Os profiles of shales from the Silurian Ireviken, Mulde, Lau and Klonk biovents are similar to those previously recorded for the Hirnantian glaciation. This data suggests the Silurian has been punctuated by several glaciations associated with fluctuations in global temperatures, sea-level and the carbon cycle. When combined with the Li isotopic (δ7Li) composition of carbonates, this study suggests glacial processes caused large changes in oxidative and silicate weathering. This study has successfully utilised macroalgae as a proxy for the 187Os/188Os of seawater and proven it can become a powerful tracer of Earth system processes and human activity. This study has also redefined the Silurian as an icehouse, and suggests the long term decline in atmospheric CO2, due to orogeny, land-plant diversification, volcanic- arc degassing and/or paleogeography, was reversed by periodic glaciations which acted to enhance oxidative weathering whilst suppressing silicate weathering.

Rusal Aughinish operates an alumina refinery situated on Aughinish Island on the south side of the Shannon estuary. The company submitted an application to extend the Bauxite Residue Disposal Area (B.R.D.A.) by another 80 hectares in 2006. Space to store residue was estimated to run out in 2011, thus requiring the construction of the extra 80 hectares which needed planning permission and an extension of the licence. It was vital to get planning permission and licence extension. There is a large volume of residual alkalinity, held in a soluble and solid phase, retained in the bauxite. The E.P.A. has requested a Residuals Management Plan which included, as a minimum, a scope statement for the plan. The criteria, which defines the successful decommissioning of the activity or part thereof, ensures minimum impact to the environment. However, this is subject to: the provision of a sustainable vegetation cover; and demonstration of leachate attenuation to below pH 9.0 within 5 years. Residue neutralisation methods were also investigated. Rusal Aughinish has determined that the restoration of the B.R.D.A. surface will support a “nature conservation” end-use (AAL, 2005d). Therefore, sustainable re-vegetation of the B.R.D.A. was required to support this goal. Small plot trials (2m x1m) and larger plot trials (10m x 2m) were established, which were amended with gypsum, process sand, and spent mushroom compost which lowered the pH, exchangeable sodium percentage (ESP) and the availability of Al and Fe in the residue. The newly created soil (bauxite residue mixed with process sand, gypsum and organic waste) was seeded. Results show that the establishment of vegetation was achievable. Additionally, investigations were carried out into the use of machinery on the residue. Two Demonstration Cells were constructed within the confines of the B.R.D.A. (0.6ha). The sides and floor of the cells were lined and a leachate collection system was installed on the floor of the cells. Monitoring of pH, electrical conductivity, and soda was conducted in run-off and leachate before and after vegetation growth on the residue in the cell. No reduction was noted in leachate or run-off pH since monitoring commenced in 2007. Following research into neutralization methods the use of sulphuric acid was the best option, but only partial neutralization was achieved, due to the large volume of acid required for full neutralization. There was also the likelihood of creating pH conditions that would lead to H2S odour problems. Carbonation would also be possible, but would require the construction of a plant or the importation of liquid CO2. Seawater neutralisation using water from the Shannon estuary is prohibited by costs. An initial modelling project looked at groundwater flow within the B.R.D.A. in two dimensions and assumptions were made as to the physical stratification and structure of the B.R.D.A. Mud-farming commenced and was evaluated. In conclusion, direct vegetation was found to be feasible, and so avoiding the high cost of topsoil. Soil construction and plant establishment was demonstrated. Demonstration Cells were constructed as per design and monitoring for pH, conductivity and soda of the leachate and run-off was conducted before and after vegetation growth. This monitoring is still ongoing. Filling of the cell with residue was determined by the stacking angle of the residue. Controlling percentage solids of the residue is very important in order to achieve proper stacking of the residue, Leachate pH may take years to drop from 13 to 9.0 or below. Recommendations to the company include further monitoring of Demonstration Cell leachate, run-off, and the vegetation cover on the residue. Finally, it is recommended to continue investigation into residue neutralisation methods.

The results of geochemical reconnaissance in areas totalling over 3500 square miles in England and Wales have been related to the incidence of known or suspected agricultural problems. Soil and herbage studies have been carried out to investigate the interpretation of stream sediment data for trace metals of agricultural significance under varying conditions of bedrock geology and secondary environment. Anomalous patterns of Mo in streams draining black shales of different ages in some cases correlate with the known incidence of molybdenosis or molybdenum induced hypocuprosis and in others indicate areas in which molybdeniferous soils are found and in which the subclinical problem may occur. In North Staffordshire and Derbyshire molybdenum drainage anomalies extend over some 60 sq. miles while hypocuprosis was previously only recognised in 15 sq. miles. A survey of blood copper levels in 350 cattle showed 77 per cent to be copper deficient in the anomalous areas compared to 37 per cent in nearby control areas. Subsequent Cu supplementation to animals with the subclinical deficiency showed encouraging response in live weight gain. The low Cu content of sediments on the Bagshot Beds reflected low levels in soils and Cu deficiency in both seedling spruce and in cattle, though in no area was there a correlation between Cu and swayback incidence. Cobalt in drainage has been correlated with pine in sheep on granite in Devon and on alluvium in North Wales, and associated patterns of low Mn with livestock infertility and unthriftiness. Seleniferous stream sediments, rocks and soils have been found for the first time in England and Wales but do not give rise to toxic vegetation. Interpretation of drainage reconnaissance data may be complicated by sediment dilution with CaCO3 in calcareous areas, and by sediment enrichment with Mn or Fe ad associated metals under certain conditions of Eh and pH. The method is neither applicable in regions of heterogeneous geology nor where the density of surface drainage is inadequate. The application of geochemical reconnaissance in agriculture provides both rapidly and cheaply patterns of metal distribution on a regional basis and delineates areas wherein to concentrate more conventional studies.

Problems of the geochemical dispersion of tin in the marine sediments are dominantly approached from a sedimentological point of view. Section 1 - The transport of Marazion River was studied with the help of fluorescent tracers. Rainfall and stream velocity were high during the period of observations. All material was transported, but only particles of medium and smaller sizes reached the beach. River characteristics did not greatly influence the nature of the transport. Heavy minerals were transported, provided their particle size was equal to or smaller than fine sand. Section 2 - The current pattern in Mounts Bay was studied using bottom drifters. There are two currents in the Bay; the main one is a clockwise current, increasing in strength towards the east. The second current is a smaller clockwise eddy current in the western part of the Bay. No information has been obtained on current velocity. Transport of heavy minerals in the marine environment was studied by using irradiated tantalite/columbite (sp. gr. 6,95) of minus 200-mesh size. Transport occurred in four directions related to the main tidal current, the eddy current, currents induced by the ebbing tide and currents induced by ground swell. A small proportion of the total material only was affected by transport, and overall dispersion did not exceed 1 mile during the period of observation. Section 3 - Groups of samples forming traverses have been collected in western Mounts Bay. Grainsize distribution and tin content were studied and indicated a uniform sand body with the maximum tin content confined to the smallest sizes. Interpretation of the data on the Rubey and Rittenhouse application of Stokes law, indicate that the majority of the tin content of the sediments is related to terrestrial sources. In addition, primary mineralisation is postulated for persistant anomalies south of St. Michaels Mount. Furthermore, there is an additional source of tin in composite grains, whose dispersion is restricted to the eddy current. Discussion is given on the distribution of material and the dispersion of tin in wave action, subsurface samples and fossil beaches. Finally, the copper content of selected surface samples indicate that maxima in tin and copper content coincide.

The research in this thesis is presented in paper format with each of four chapters representing one complete study. Chapter two presents Re–Os and geochemical fingerprint data for UK Atlantic margin oils. organic and δ13C geochemical data demonstrate that the oil is sourced from Upper Jurassic marine shales and the Re–Os data yields an age of 68 ± 13 Ma. Comparison of this date with published basin histories and Ar-Ar geochronology demonstrate that Re–Os ages correspond with the timing of oil generation. Furthermore the similarities between oil and source rock 187Os/188Os at the time of oil generation (Osg) indicates that Osg can be used to identify oil source units. Chapter three demonstrates, through the analysis of Kimmeridge Clay Fm. core and North Sea oil, that unradiogenic mantle like values within oils from wells in the Viking Graben and East Shetland Basin cannot be inherited from source. It is hypothesised that they are caused by contamination by a hydrothermal fluid sourced from either Cenozoic intrusive units or the mantle. Strain localisation is suggested to have caused the main basin bounding faults within the Viking Graben and East Shetland Basin to be of sufficient depth to act as conduits for hydrothermal fluid to propagate through and contaminate oils within reservoirs. Chapter four investigates how Osi values across the Ordovician/Silurian boundary GSSP at Dob’s Linn, Scotland, tracks the Hirnantian glaciation within a globally important source unit: the Ordovician/Silurian “Hot” Shales. During the Late Katian, Osi values increase from 0.28 – 1.08, providing evidence for increased silicate weathering of radiogenic continental crust. A decrease to less radiogenic Osi (~0.60) occurs at the base Hirnantian and marks the onset of the Hirnantian Glaciation. This is ascribed to Hirnantian ice cover and reduced chemical weathering rates cutting the supply of radiogenic material. In the Late Hirnantian an abrupt increase in Osi values to ~1.1 over 19 cm of stratigraphy, is attributed to the leaching of exposed radiogenic glacial deposits and increased weathering of silicate terrane during deglaciation. Chapter five applies the Platinum Group Elements, specifically Pt/Pd ratios, to identify oil source units. It is demonstrated that asphaltenes from the well constrained UK Atlantic margin petroleum system contain similar Pt/Pd and Osg values to the known source unit. A further study of the poorly constrained West Canadian Tar Sands demonstrates that Pt/Pd ratios in source rocks are not affected by hydrocarbon maturation and are distinct between differing potential source units. Comparison of the Tar Sands with potential source units demonstrates that the Tar Sands are mainly sourced from the Lower Jurassic Gordondale Fm., with minor input from the Devonian/Mississippian Exshaw Fm.