Mineralogical and porosity characterisation of potential aquifer and seal units for carbon capture and storage methodologies for the CASSEM Project

This report describes the methods used and data collected in mineralogical and petrological characterisation of potential carbon capture and storage (CCS) aquifer and seal units in Yorkshire-Lincolnshire-Nottinghamshire and the Forth area of eastern central Scotland. It forms part of CASSEM work package 1 (WP1)

Understanding the controls on sediment-P interactions and dynamics along a non-tidal river system in a rural–urban catchment: the River Nene

The release of Phosphorus (P) from river sediments has been identified as a contributing factor to waters failing the criteria for ‘Good Ecological Status’ under the EU Water Framework Directive (WFD). To identify the contribution of sediment-P to river systems, an understanding of the factors that influence its distribution within the entire non-tidal system is required. Thus the aims of this work were to examine the (i) total (PTotal) and labile (PLabile) concentrations in sediment, (ii) the sequestration processes and (iii) the interactions between sediment P and the river water in the six non-tidal water bodies of the River Nene, U.K. Collection of sediments followed a long period of flooding and high stream flow. In each water body, five cores were extracted and homogenised for analysis with an additional core being taken and sampled by depth increments. Comparing the distribution of sediment particle size and PTotal data with soil catchment geochemical survey data, large increases in PTotal were identified in sediments from water body 4–6, where median concentrations of PTotal in the sediment (3603 mg kg−1) were up to double those of the catchment soils. A large proportion of this increase may be related to in-stream sorption of P, particularly from sewage treatment facilities where the catchment becomes more urbanised after water body 3. A linear correlation (r = 0.8) between soluble reactive phosphate (SRP) and Boron in the sampled river waters was found suggesting increased STW input in water bodies 4–6. PLabile concentrations in homogenised cores were up to 100 mg kg−1 PO4–P (generally < 2% of PTotal) and showed a general increase with distance from the headwaters. A general increase in Equilibrium Phosphate Concentrations (EPC0) from an average of 0.9–∼1.7 μm L−1 was found between water bodies 1–3 and 4–6. Fixation within oxalate extractable phases (Al, Fe and Mn) accounted for ∼90% of P binding in water bodies 4–6, but only between 31 and 74% in water bodies 1–3. Statistical models predicting PTotal (R2 = 0.78), oxalate extractable P (R2 = 0.78) and Olsen P (R2 = 0.73) concentrations in river sediments identified Mn oxy-hydroxides (MnOx) as a strong predictive variable along with the location within the river system. It is suggested that MnOx within model predictions is identifying a pool of mixed Fe–Mn oxy-hydroxides (MnOx–FeOOH) or Fe oxy-hydroxide (FeOOH) from the wider FeOxalate pool that are particularly effective at sorbing and fixing P. The findings demonstrate how sediment and P may accumulate along a 100 km non-tidal river system, the extent to which a range of processes can fix P within mineral phases and how natural flooding processes may flush sediment from the river channel. The processes identified in this study are likely to be applicable to similar river systems over their non-tidal water bodies in eastern England

How the composition of sandstone matrices affects rates of soil formation

Soils deliver multiple ecosystem services and their long-term sustainability is fundamentally controlled by the rates at which they form and erode. Our knowledge and understanding of soil formation is not commensurate with that of soil erosion, in part due to the difficulty of measuring the former. However, developments in cosmogenic radionuclide accumulation models have enabled soil scientists to more accurately constrain the rates at which soils form from bedrock. To date, all three major rock types – igneous, sedimentary and metamorphic lithologies – have been examined in such work. Soil formation rates have been measured and compared between these rock types, but the impact of rock characteristics on soil formation rates, such as rock matrices and mineralogy, have seldom been explored. In this UK-based study, we used cosmogenic radionuclide analysis to investigate whether the lithological variability of sandstone governs pedogenesis. Soil formation rates were measured on two arable hillslopes at Woburn and Hilton, which are underlain by different types of arenite sandstone. Rates were faster at Woburn, and we suggest that this is due to the fact that the Woburn sandstone formation is less cemented that that at Hilton. Similarly, rates at Woburn and Hilton were found to be faster than those measured at two other sandstone-based sites in the UK, and faster than those compiled in a global inventory of cosmogenic studies on sandstone-based soils. We suggest that the cementing agents present in matrix-abundant wackes studied previously may afford these sandstones greater structural integrity and resistance to weathering. This work points to the importance of factoring bedrock matrices into our understanding of soil formation rates, and the biogeochemical cycles these underpi

Microbial impacts of CO2 transport in Sherwood Sandstone

Work carried out by BGS and the Japan Atomic Energy Authority (JAEA) has shown that microbial processes can have profound effects on the transport properties of host rock (i.e. the movement of fluids and contaminants through the host material) relevant to radioactive waste disposal. Recent research, performed as part of the BGS Radtran project, has examined Sherwood Sandstone samples in the context of radioactive waste disposal; this particular formation is also a potential reservoir for carbon dioxide storage in the UK. As part of the BGS opportunities fund programme, this project has, for the first time, evaluated interactions between fluids saturated with carbon dioxide/Sherwood Sandstone/microbes (Pseudomonas aeruginosa) in transport experiments, using BGS developed apparatus under pressurised subsurface conditions. This pilot study has highlighted the impacts of differences in the physical characteristics of core Sherwood Sandstone samples collected adjacent to each other in a core sample, and the ability of P. aeruginosa to survive in CO2 saturated artificial groundwater and the potential to form a biofilm in an environment suitable likely to be found at a carbon capture and storage location. These results demonstrate that in this short study, the injection of P. aeruginosa into the biotic experiment does not appear to impact on the physical transport properties of the Sherwood Sandstone, although the presence of CO2 appears to enhance the mobilisation of a number of chemical species. However, in other work which utilised the same organism and rock type but without introduction of CO2 saturated fluid, post-inoculation injection changes were observed. These included short but rapid saw-tooth like changes in the pressure profile (Wragg et al, 2012). These impacts were not observed in the current study which suggests that the CO2 saturated fluid was impacting on the ability of the microbes to alter permeability. This short study has, however, indicated the need to carry out longer term investigations to reproduce these initial findings

Immobilisation of chromium in magnesium carbonate minerals

Hexavalent chromium (Cr6+) is a toxic carcinogenic pollutant that might be released by the mining and processing of ultramafic rocks and nickel laterites and which requires permanent removal from the contaminated biosphere. Ultramafic material can also serve as a feedstock for the sequestration of CO2 resulting from the growth of new minerals, raising the intriguing proposition of integrated sequestration of both pollutants, CO2 and chromium, into magnesium carbonates. Such a synergistic process downstream of ore recovery and mineral processing could be an elegant proposition for more sustainable utilisation and management of the Earth's resources. We have therefore carried out an experimental and microanalytical study to investigate potentially suitable carbonate minerals. Uptake of chromium in carbonate phases was determined, followed by identification of the crystalline phases and characterisation of the local structural environment around the incorporated chromium centres. The results suggest that neither nesquehonite nor hydromagnesite have the structural capacity to incorporate Cr6+ or Cr3+ significantly at room temperature. We therefore propose that further research into this technology should focus on laboratory assessments of other phases, such as layered double hyroxides, that have a natural structural capacity to uptake both chromium and CO2

Life path analysis: scaling indicates priming effects of social and habitat factors on dispersal distances

1. Movements of many animals along a life-path can be separated into repetitive ones within home ranges and transitions between home ranges. We sought relationships of social and environmental factors with initiation and distance of transition movements in 114 buzzards Buteo buteo that were marked as nestlings with long-life radio tags. 2. Ex-natal dispersal movements of 51 buzzards in autumn were longer than for 30 later in their first year and than 35 extra-natal movements between home ranges after leaving nest areas. In the second and third springs, distances moved from winter focal points by birds that paired were the same or less than for unpaired birds. No post-nuptial movement exceeded 2 km. 3. Initiation of early ex-natal dispersal was enhanced by presence of many sibs, but also by lack of worm-rich loam soils. Distances travelled were greatest for birds from small broods and with relatively little short grass-feeding habitat near the nest. Later movements were generally enhanced by the absence of loam soils and short grassland, especially with abundance of other buzzards and probable poor feeding habitats (heathland, long grass). 4. Buzzards tended to persist in their first autumn where arable land was abundant, but subsequently showed a strong tendency to move from this habitat. 5. Factors that acted most strongly in ½-km buffers round nests, or round subsequent focal points, usually promoted movement compared with factors acting at a larger scale. Strong relationships between movement distances and environmental characteristics in ½-km buffers, especially during early ex-natal dispersal, suggested that buzzards became primed by these factors to travel far. 6. Movements were also farthest for buzzards that had already moved far from their natal nests, perhaps reflecting genetic predisposition, long-term priming or poor habitat beyond the study area

Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks, 1990-2015: A systematic analysis for the Global Burden of Disease Study 2015

Background: The Global Burden of Diseases, Injuries, and Risk Factors Study 2015 provides an up-to-date synthesis of the evidence for risk factor exposure and the attributable burden of disease. By providing national and subnational assessments spanning the past 25 years, this study can inform debates on the importance of addressing risks in context. Methods: We used the comparative risk assessment framework developed for previous iterations of the Global Burden of Disease Study to estimate attributable deaths, disability-adjusted life-years (DALYs), and trends in exposure by age group, sex, year, and geography for 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks from 1990 to 2015. This study included 388 risk-outcome pairs that met World Cancer Research Fund-defined criteria for convincing or probable evidence. We extracted relative risk and exposure estimates from randomised controlled trials, cohorts, pooled cohorts, household surveys, census data, satellite data, and other sources. We used statistical models to pool data, adjust for bias, and incorporate covariates. We developed a metric that allows comparisons of exposure across risk factors—the summary exposure value. Using the counterfactual scenario of theoretical minimum risk level, we estimated the portion of deaths and DALYs that could be attributed to a given risk. We decomposed trends in attributable burden into contributions from population growth, population age structure, risk exposure, and risk-deleted cause-specific DALY rates. We characterised risk exposure in relation to a Socio-demographic Index (SDI). Findings: Between 1990 and 2015, global exposure to unsafe sanitation, household air pollution, childhood underweight, childhood stunting, and smoking each decreased by more than 25%. Global exposure for several occupational risks, high body-mass index (BMI), and drug use increased by more than 25% over the same period. All risks jointly evaluated in 2015 accounted for 57·8% (95% CI 56·6–58·8) of global deaths and 41·2% (39·8–42·8) of DALYs. In 2015, the ten largest contributors to global DALYs among Level 3 risks were high systolic blood pressure (211·8 million [192·7 million to 231·1 million] global DALYs), smoking (148·6 million [134·2 million to 163·1 million]), high fasting plasma glucose (143·1 million [125·1 million to 163·5 million]), high BMI (120·1 million [83·8 million to 158·4 million]), childhood undernutrition (113·3 million [103·9 million to 123·4 million]), ambient particulate matter (103·1 million [90·8 million to 115·1 million]), high total cholesterol (88·7 million [74·6 million to 105·7 million]), household air pollution (85·6 million [66·7 million to 106·1 million]), alcohol use (85·0 million [77·2 million to 93·0 million]), and diets high in sodium (83·0 million [49·3 million to 127·5 million]). From 1990 to 2015, attributable DALYs declined for micronutrient deficiencies, childhood undernutrition, unsafe sanitation and water, and household air pollution; reductions in risk-deleted DALY rates rather than reductions in exposure drove these declines. Rising exposure contributed to notable increases in attributable DALYs from high BMI, high fasting plasma glucose, occupational carcinogens, and drug use. Environmental risks and childhood undernutrition declined steadily with SDI; low physical activity, high BMI, and high fasting plasma glucose increased with SDI. In 119 countries, metabolic risks, such as high BMI and fasting plasma glucose, contributed the most attributable DALYs in 2015. Regionally, smoking still ranked among the leading five risk factors for attributable DALYs in 109 countries; childhood underweight and unsafe sex remained primary drivers of early death and disability in much of sub-Saharan Africa. Interpretation: Declines in some key environmental risks have contributed to declines in critical infectious diseases. Some risks appear to be invariant to SDI. Increasing risks, including high BMI, high fasting plasma glucose, drug use, and some occupational exposures, contribute to rising burden from some conditions, but also provide opportunities for intervention. Some highly preventable risks, such as smoking, remain major causes of attributable DALYs, even as exposure is declining. Public policy makers need to pay attention to the risks that are increasingly major contributors to global burden. Funding: Bill & Melinda Gates Foundation

Reaction of bentonite in low alkali cement leachates : preliminary results from the Cyprus Natural Analogue Project (CNAP)

Bentonite is a key component in many designs for radioactive waste repositories. The plasticity, swelling capacity, colloid filtration, low hydraulic conductivity, high retardation of key radionuclides and stability in relevant geological environments all make bentonite an ideal barrier/buffer material. However, bentonite is chemically unstable under\ud higher pH conditions and this is a potential problem for repository designs which mix cement and concrete with bentonite barriers. The hyperalkaline (pH~13) leachates from the cement are expected to cause alteration of the bentonite. Low alkali cements produce lower pH (around 10-11) leachates and it is expected that this will slow bentonite reaction (or even stop it altogether) over the timespan of relevance to repository safety. Unfortunately, it has proven extremely difficult to study these very slow reactions in the laboratory so an alternative approach, that of studying natural analogues of the reaction process, has begun in Cyprus. In this paper, preliminary details of this new investigation of long-term bentonite reaction in the natural hyperalkaline groundwaters of the Troodos ophiolite in Cyprus are presented. Here, groundwater pH values of 10.0 to 11.9 have been reported, falling into the range typical of lowalkali cements that are presently being developed for use in radioactive waste disposal. The aims of this stage of the project were to identify likely sites of hyperalkaline groundwater/bentonite reaction and assess the relevance of the current site conceptual model. Preliminary groundwater and petrographic data for one group of related sites where hyperalkaline groundwaters are present are also discussed

Evidence for gas-induced pathways in clay using a nanoparticle injection technique

Corrosion, water radiolysis and microbial degradation will result in the generation of gas within repositories designed for the geological disposal of high-level radioactive waste. It is therefore crucial in the design of such facilities that the relevant mechanisms allowing gas migration through repository materials, both engineered barriers and clay-based candidate host rocks, are correctly identified. In Belgium, the Boom Clay represents a candidate host material for which the advective gas breakthrough characteristics and transport properties have been extensively tested and are well defined by numerous studies. The Boom Clay displays a significant capacity for self-sealing and both laboratory and field tests indicate that advective gas transport occurs not by visco-capillary flow, but instead through the formation of pressure-induced dilatant pathways. In this study, we present results from a gas injection test designed to demonstrate the presence of these features by injecting nanoparticulate tracers with helium gas into a sample of Boom Clay. The results provide conclusive evidence for the formation of transient, dilatant gas pathways within a candidate clay-based host rock. This technique provides a novel diagnostic tool for the identification of processes governing multi-phase flow, supporting robust long-term assessments of repository performance