Innovative methods of ground improvement for railway embankment Peat Fens foundation soil

The aim of this research was to assess the feasibility of biocementing a problematic foundation soil of railway embankments from Peat Fens in East Anglia, UK. Biocementation of soil is an emerging, novel ground improvement technique. It has recently attracted the interest of researchers worldwide because it has been proposed as potentially environmentally superior to chemical grouts and other common soil stabilisers e.g. cement or lime (linked to high CO2 11 emissions). In this study we screened and isolated non-pathogenic indigenous ureolytic microbial candidates with potential for biocementation from samples originating from Peat Fens in East Anglia, UK. Four strains were selected as the most suitable candidates, based on their growth rate and their viability in a wide range of temperatures, pH and soil moisture contents corresponding to typical seasonal field conditions. After a number of Unconfined Compressive Strength (UCS) tests, one strain (Bacillus licheniformis) was selected as the most promising for this soil treatment and used for further study. Two different methods of implementation of the treatments were considered, namely pressure flow soil column and electrokinetic injection. The UCS results supported by CaCO3 measurements as well as microstructural SEM-EDS analysis proved that biocementation did occur for both implementation methods and for a number of treatment combinations. Ongoing work on optimisation of treatments and implementation methods is carried out towards the upscaling of the techniques for in situ implementation which is planned for the next stage of the research

Biocementation of an organic soil using indigenous ureolytic bacteria

This paper describes research aiming at assessing the potential for biocementation of an unsuitable organic foundation soil encountered in the UK railway network. As opposed to the majority of previous studies it focuses on isolation and use of non-pathogenic, indigenous ureolytic bacterial strains from the in situ soil, which are capable of inducing calcite precipitation. The paper describes the procedures for indigenous bacteria isolation and screening, their growth and urease activity and shows results from soil strength and calcite precipitation testing proving biocementation for this type of soil using indigenous bacteria

Deep ROSAT Surveys & the contribution of AGNs to the soft X-ray background

The ROSAT Deep Surveys in the Lockman Hole have revealed that AGNs are the main contributors (~75%) to the soft X-ray background in the 1–2 keV band. Using new optical/infrared and radio observations we have obtained a nearly complete identification (93%) of the 91 X-ray sources down to a limiting flux of 1.2·10^(–15) erg cm^(–2) s^(–1) in the 0.5–2.0 keV band. We present the optical colors and the emission line properties of our AGNs in comparison with other X-ray selected AGN samples. Furthermore we discuss the fraction of red AGNs found in the ROSAT Deep Surveys. From the ROSAT Deep Surveys we see no evidence for a new class of X-ray bright galaxies, which significantly contributes to the soft X-ray background

Implementation of biocementation for a partially saturated problematic soil of the UK railway network

This paper refers to biocementation of a problematic soil of the UK railway network as a potential stabilisation technique of this soil using indigenous ureolytic bacteria. The soil is peat, a soft foundation soil also subject to oxidation wastage. As the peat is under existing embankments, electrokinetics (EK) is proposed as a promising technique to implement treatments. In the context of unsaturated soils the paper thus focuses on two particular aspects relevant for the implementation of treatments and the stability of this soil, namely: a) the effect of degree of saturation of the peat on the bio-electrokinetic treatment ; b) the soil water retention curve of the soil affecting flow and transport; these are relevant as we focus on understanding and modelling the implementation of treatments through electrokinetics; moreover for the peat it is of importance to understand moisture exchange in the vadose zone and control groundwater table levels (e.g. during electrokinetics) in order to prevent further oxidation. After isolation and screening of indigenous microorgansisms Bacillus licheniformis was selected for further testing. The results in terms of unconfined compressive strength, CaCO3 content, swelling and compression behaviour and water retention proved the feasibility of biocementation using this indigenous microorganism. Ongoing work is assessing the required treated soil characteristics and related required biocementation degree to solve UK rail's peat foundation problems. Upscaling of the techniques towards in situ implementation is also planned in the next stage of the research

Developing a sentinel monitoring network for Scotland's rivers and lochs

• The Scottish Environment Protection Agency’s (SEPA) surveillance monitoring networks for rivers and lochs were established over a decade ago to help assess the state of Scotland’s freshwater environment and detect environmental change. This long-term monitoring is integral in formulating evidence-based policy and evaluating whether land and water management aimed at improving environmental quality is effective. • SEPA and Scottish Government have commissioned this review of the surveillance networks to better understand their national representativeness, optimal size and sampling intensities. • The review also considered new and innovative monitoring technologies, and assessed where these may help SEPA to more cost-effectively assess long-term trends in the environment. • The specific aims of this report are: (1) to assess how well the SEPA river surveillance network represents Scotland’s environment; (2) to identify possible changes in the river surveillance network to improve its representativeness; (3) to estimate the ability of the existing river and loch surveillance networks to detect long-term environmental change, and investigate how this might be affected by changes in sampling regimes; (4) to analyse environmental changes detectable since the inception of the surveillance networks; and (5) to analyse the benefits of adopting new sampling methods

Towards the Development of Sustainable Ground Improvement Techniques —Biocementation Study of an Organic Soil

Ongoing research effort is dedicated to the development of innovative, superior and cost-effective ground improvement techniques to mitigate natural and man-made hazards while minimising waste and other environmental impacts. In this context, the nature-based process of biocementation of soils has been proposed as a potentially more sustainable technique than conventional chemical ground improvement practices. This paper focuses on the biocementation of an organic soil of the UK railway network. Having recently proven the feasibility of biocementing this soil using indigenous ureolytic bacteria, in this paper, the authors perform a parametric study to identify treatments successful in increasing the strength of the soil. Selected treatments are then applied to the soil to assess its volume change during consolidation, secondary compression and shrinkage upon drying. The results show that, depending on the treatments used, biocementation has increased the unconfined compressive strength by up to 81% compared to that of the control samples. For selected treatments and the range of water contents tested (55–33%), shrinkage upon drying reduced by 16%, while the volumetric strains of the soil upon 1-D compression reduced by 32–47%. This was reflected in the values of the coefficient of volume compressibility and the coefficient of secondary compression (the latter either reduced by up to an order of magnitude or secondary compression was not observed altogether in the testing period). Overall, the results proved that biocementation improved considerably the mechanical properties of the organic soil, which gives promise for addressing the settlement problems of this soil

Estimating fixed-frame galaxy magnitudes in the Sloan Digital Sky Survey

Broadband measurements of flux for galaxies at different redshifts measure different regions of the rest-frame galaxy spectrum. Certain astronomical questions, such as the evolution of the luminosity function of galaxies, require transforming these inherently redshift-dependent magnitudes into redshift-independent quantities. To prepare to address these astronomical questions, investigated in detail in subsequent papers, we fit spectral energy distributions (SEDs) to broadband photometric observations in the context of the optical observations of the Sloan Digital Sky Survey (SDSS). Linear combinations of four spectral templates can reproduce the five SDSS magnitudes of all galaxies to the precision of the photometry. Expressed in the appropriate coordinate system, the locus of the coefficients multiplying the templates is planar and, in fact, nearly linear. The resulting reconstructed SEDs can be used to recover fixed-frame magnitudes over a range of redshifts. This process yields consistent results in the sense that, within each sample, the intrinsic colors of similar type galaxies are nearly constant with redshift. We compare our results with simpler interpolation methods and galaxy spectrophotometry from the SDSS. The software that generates these results is publicly available and easily adapted to handle a wide range of galaxy observations