The significance of the potential impacts of microbial activity on the transport properties of host rocks for geological repositories is an area of active research. Most recent work has focussed on granitic environments. This paper describes pilot studies investigating changes in transport properties that are because of microbial activity in sedimentary rock environments in northern Japan. For the first time, these short experiments (39 days maximum) have shown that the denitrifying bacteria, Pseudomonas denitrificans, can survive and thrive when injected into flowthrough column experiments containing fractured diatomaceous mudstone material and synthetic groundwater under pressurised conditions. Although there were few significant changes in the fluid chemistry, changes in the Microbiological impacts -mudstone 2 permeability of the biotic column were quantitatively monitored. These same methodologies could also be adapted to obtain information from cores originating from a variety of geological environments including oil reservoirs, aquifers and toxic waste disposal sites to provide an understanding of the impact of microbial activity on the transport of a range of solutes, such as groundwater contaminants and gases (e.g. injected carbon dioxide).

Traditionally, potash mineral deposits have been characterized using downhole geophysical logging in tandem with geochemical analysis of core samples to establish the critical potassium (% K2O) content. These techniques have been employed in a recent exploration study of the Permian evaporite succession of North Yorkshire, United Kingdom, but the characterization of these complex deposits has been led by mineralogical analysis, using quantitative X-ray diffraction (QXRD). The novel QXRD approach provides data on K content with the level of confidence needed for reliable reporting of resources and also identifies and quantifies more precisely the nature of the K-bearing minerals. Errors have also been identified when employing traditional geochemical approaches for this deposit, which would have resulted in underestimated potash grades.QXRD analysis has consistently identified polyhalite (K2Ca2Mg(SO4)4⋅2(H2O) in the Fordon (Evaporite) Formation and sylvite (KCl) in the Boulby Potash and Sneaton Potash members as the principal K-bearing host minerals in North Yorkshire. However, other K hosts, including kalistrontite (K2Sr(SO4)2) a first recorded occurrence in the UK, and a range of boron-bearing minerals have also been detected.Application of the QXRD-led characterization program across the evaporitic basin has helped to produce a descriptive, empirical model for the deposits, including the polyhalite-bearing Shelf and Basin seams and two, newly discovered sylvite-bearing bittern salt horizons, the Pasture Beck and Gough seams. The characterization program has enabled a polyhalite mineral inventory in excess of 2.5 billion metric tons (Bt) to be identified, suggesting that this region possesses the world's largest known resource of polyhalite.

Serpentine minerals serve as a Mg donor in carbon capture and storage by mineralisation (CCSM).The acid-treatment of nine comprehensively-examined serpentine polymorphs and polytypes, and the subsequent microanalysis of their post-test residues highlighted several aspects of great importance to the choice of the optimal feed material for CCSM. Compelling evidence for the nonuniformity of serpentine mineral performance was revealed, and the following order of increasing Mg extraction efficiency after three hours of acid-leaching was established: Al-bearing polygonal serpentine (<5%) ≤ Al-bearing lizardite 1T (≈5%) < antigorite (24-29%) < well-ordered lizardite 2H 1 (≈65%) ≤ Al-poor lizardite 1T (≈68%) < chrysotile (≈70%) < poorly-ordered lizardite 2H 1 (≈80%) < nanotubular chrysotile (≈85%).It was recognised that the Mg extraction efficiency of the minerals depended greatly on the intrinsic properties of crystal structure, chemistry and rock microtexture. On this basis, antigorite and Albearing well-ordered lizardite were rejected as potential feedstock material whereas any chrysotile, non-aluminous, widely spaced lizardite and/or disordered serpentine were recommended.The formation of peripheral siliceous layers, tens of microns thick, was not universal and depended greatly upon the intrinsic microtexture of the leached particles. This study provides the first comprehensive investigation of nine, carefully-selected serpentine minerals, covering most varieties and polytypes, under the same experimental conditions. We focused on material characterisation and the identification of the intrinsic properties of the minerals that affect particle's reactivity. It can therefore serve as a generic basis for any acid-based CCSM pre-treatment.

General assessments of orebody types and associated mine wastes with regards to their environmental signature and human health hazards are needed to help managing present and historical mine waste facilities.Bioaccessibility tests and mineralogical analysis were carried out on mine waste from a systematic sampling of mine sites from the Central Wales orefield, UK.The bioaccessible Pb widely ranged from 270 to 20300 mg/kg (mean 7250 mg/kg; median 4890 mg/kg) and the bioaccessible fraction from 4.53 % to >100 % (mean 33.2 %; median 32.2 %), with significant (p=0.001) differences among the mine sites. This implies sensitivity of bioaccessibility to site-specific conditions and suggests caution in the use of models to assess human health impacts generalised on the basis of the mineral deposit type. Mineralogical similarities of the oxidation products of primary galena provided a better control over the observed Pb bioaccessibility range. The higher Pb bioaccessibility (%) was related to samples containing cerussite, irrespective of the presence of other Pb minerals in the mineral assemblage; lower Pb bioaccessibility resulted where anglesite was the main Pb mineral phase and cerussite was absent.

Landfill and radioactive waste disposal risk assessments focus on contaminant transport and are principally concerned with understanding the movement of gas, water and solutes through engineered barriers and natural groundwater systems. However, microbiological activity can impact on transport processes changing the chemical and physical characteristics of the subsurface environment. Such effects are generally caused by biofilms attached to rock surfaces. This paper will present the results of an experimental study of the significance of biofilm growth on groundwater flow and the transport of contaminants in intergranular and fracture porosity flow systems.Risk assessments for landfills and geological repositories for radioactive waste are primarily based on the precepts of contaminant transport; and are concerned with understanding the movement of gas, water and solutes through engineered barriers and natural groundwater systems, within the concept of 'Source', 'Pathway' and 'Receptor'. The emphasis on solute migration for landfill investigations is reflected in the theoretical development used during numerical simulation. However, microbes living in such environments can have an impact on transport processes (Chapelle 2000;Cunningham et al. 1997; Fredrickson et al. 1989; Keith-Loach & Livens 2002;West & Chilton 1997;West et al. 2006). Microbial activity in any environment is generally located on chemical or physical interfaces, usually within biofilms, and the impacts can be both physical (e.g. altering porosity) and/or chemical (e.g. changing pH, redox conditions) and may result in intracellular or extracellular mineral formation or degradation (Beveridge et al. 1997;Ehrlich 1999;Konhauser et al. 1998;Milodowski et al. 1990;Tuck et al. 2006). Where biofilm growth in a crystalline host rock promotes mineral precipitation it can reduce water inflow and this can be a positive effect for limiting the transport of contaminants. Recent experimental work has investigated some of these chemical and physical effects in more detail in the context of the geological containment of radioactive waste. This paper will examine some of these studies and will indicate the significance of biofilms in influencing both granular and fracture flow. 2 BiofilmsA biofilm is an agglomeration of microbial cells and their excreted organic and inorganic products that is attached to, or coats, mineral surfaces or other substrates (Taylor & Jaffe 1990a). Biofilms are very common in the geosphere and biosphere, forming in diverse environments including the surfaces of human teeth (Marsh 2004), wall murals and stone monuments (Dornieden et al. 2000), stream sediments (Konhauser et al. 1998), cave and mine walls (Plate 1) and the subsurface (Tuck 2006). In such natural systems, they often comprise a mixture of interacting microbial species forming complex ecosystems. Biofilm thickness is extremely variable ranging from a single cell monolayer, to thick mucous microcolonies of microbes held together by Extracellular Polymeric Substances...