Characterising the vertical separation of shale-gas source rocks and aquifers across England and Wales (UK).

Shale gas is considered by many to have the potential to provide the UK with greater energy security, economic growth and jobs. However, development of a shale gas industry is highly contentious due to environmental concerns including the risk of groundwater pollution. Evidence suggests that the vertical separation between exploited shale units and aquifers is an important factor in the risk to groundwater from shale gas exploitation. A methodology is presented to assess the vertical separation between different pairs of aquifers and shales that are present across England and Wales. The application of the method is then demonstrated for two of these pairs-the Cretaceous Chalk Group aquifer and the Upper Jurassic Kimmeridge Clay Formation, and the Triassic sandstone aquifer and the Carboniferous Bowland Shale Formation. Challenges in defining what might be considered criteria for 'safe separation' between a shale gas formation and an overlying aquifer are discussed, in particular with respect to uncertainties in geological properties, aquifer extents and determination of socially acceptable risk levels. Modelled vertical separations suggest that the risk of aquifer contamination from shale exploration will vary greatly between shale-aquifer pairs and between regions and this will need to be considered carefully as part of the risk assessment and management for any shale gas development.

Le gaz de schiste est considéré par beaucoup comme ayant le potentiel de procurer au Royaume Uni une plus grande sécurité énergétique, une croissance économique et des emplois. Cependant, le développement de l'industrie du gaz de schiste est fortement contesté en raison des problèmes environnementaux, qui comprennent le risque de pollution des eaux souterraines. Des données probantes suggèrent que l'isolation verticale entre les unités de schistes exploitées et les aquifères est un facteur important vis-à-vis du risque de contamination des eaux souterraines associé à l'exploitation du gaz de schiste. Une méthodologie est proposée pour évaluer la séparation verticale entre différents couples aquifères­schistes présents en Angleterre et Pays de Galle. L'application de la méthode est ensuite décrite pour deux de ces couples, d'une part l'aquifère du Groupe de la Craie du Crétacé et la formation des Argiles du Kimméridgien (Jurassique supérieur), et l'aquifère des Grés du Trias et la formation carbonifère des schistes du Bowland. Les enjeux de la définition de ce qui pourrait être considéré comme critère d'une « isolation sécuritaire ¼ entre une formation à gaz de schiste et l'aquifère sus-jacent sont discutées, en particulier au regard des incertitudes sur les propriétés géologiques, l'extension des aquifères et la définition des niveaux de risques socialement acceptables. Les isolations verticales modélisées suggèrent que le risque de contamination d'un aquifère lié à une exploration du schiste variera grandement d'un couple schiste­aquifère à l'autre et d'une région à l'autre et que cela devra être examiné avec soin dans le cadre de l'évaluation du risque et de la gestion de tout développement du gaz de schiste.

Muchos consideran que el shale gas tiene el potencial de proporcionar al Reino Unido una mayor seguridad energética, crecimiento económico y empleos. Sin embargo, el desarrollo de una industria del shale gas es muy polémico debido a las preocupaciones ambientales, incluido el riesgo de contaminación del agua subterránea. La evidencia sugiere que la separación vertical entre las unidades de shale explotadas y los acuíferos es un factor importante en el riesgo para las aguas subterráneas en la explotación del shale. Se presenta una metodología para evaluar la separación vertical entre los diferentes pares de acuíferos y los shales que están presentes en Inglaterra y Gales. La aplicación del método se demuestra para dos de estos pares­el acuífero Chalk Group del Cretácico y la Kimmeridge Clay Formation del Jurásico Superior, y el acuífero de arenisca del Triásico y la Bowland Shale Formation del Carbonífero. Se discuten los desafíos para definir los que podrían considerarse criterios para una "separación segura" entre una formación de shale gas y un acuífero superpuesto, en particular con respecto a incertidumbres en las propiedades geológicas, extensiones de acuíferos y la determinación de niveles de riesgo socialmente aceptables. Las separaciones verticales modeladas sugieren que el riesgo de contaminación del acuífero por la exploración del shale variará mucho entre los pares de shale­acuífero y entre regiones, y esto deberá considerarse cuidadosamente como parte de la evaluación y gestión de riesgos para cualquier desarrollo de shale gas.

O gás de xisto é considerado um potencial fornecedor de maior segurança energética, crescimento econômico e empregos ao Reino Unido. Porém, o desenvolvimento de uma indústria de gás de xisto é altamente controverso devido a preocupações ambientais, como o risco de poluição das águas subterrâneas. Evidências sugerem que a separação vertical entre unidades de xisto exploradas e aquíferos é um fator importante de risco para as águas subterrâneas na exploração de gás de xisto. Uma metodologia é apresentada para avaliar a separação vertical entre diferentes pares de aquíferos e blocos de xisto presentes em toda a Inglaterra e País de Gales. A aplicação do método é feita em dois pares­o Aquífero do Grupo Cretáceo Chalk com a Formação Argilosa do Jurássico Superior Kimmeridge, e o Aquífero de Arenito Triássico com a Formação Xistosa do Carbonífero Bowland. Os desafios para definir o que pode ser considerado critérios de "separação segura" entre uma formação de gás de xisto e um aquífero sobrejacente são discutidos, em particular no que diz respeito a incertezas em propriedades geológicas, extensões de aquíferos e determinação de níveis de risco socialmente aceitáveis. As separações verticais modeladas sugerem que o risco de contaminação do aquífero por exploração de xisto variará muito entre os pares de xisto­aquífero e suas regiões, devendo assim serem consideradas cuidadosamente como parte da avaliação e gerenciamento de risco para qualquer desenvolvimento de gás de xisto.

The air quality impacts of pre-operational hydraulic fracturing activities.

Hydraulic fracturing (fracking) is a short phase in unconventional oil and natural gas (O&G) development. Before fracking there is a lengthy period of preparation, which can represent a significant proportion of the well lifecycle. Extensive infrastructure is delivered onto site, leading to increased volumes of heavy traffic, energy generation and construction work on site. Termed the "pre-operational" period, this is rarely investigated as air quality evaluations typically focus on the extraction phase. In this work we quantify the change in air pollution during pre-operational activities at a shale gas exploration site near Kirby Misperton, North Yorkshire, England. Baseline air quality measurements were made two years prior to any shale gas activity and were used as a training dataset for random forest (RF) machine learning models. The models allowed for a comparison between observed air quality during the pre-operational phase and a counterfactual business as usual (BAU) prediction. During the pre-operational phase a significant deviation from the BAU scenario was observed. This was characterised by significant enhancements in NOx and a concurrent reduction in O3, caused by extensive additional vehicle movements and the presence of combustion sources such as generators on the well pad. During the pre-operational period NOx increased by 274 % and O3 decreased by 29 % when compared to BAU model values. There was also an increase in primary emissions of NO2 during the pre-operational phase which may have implications for the attainment of ambient air quality standards in the local surroundings. Unconventional O&G development remains under discussion as a potential option for improving the security of supply of domestic energy, tensioned however against significant environmental impacts. Here we demonstrate that the preparative work needed to begin fracking elevates air pollution in its own right, a further potential disbenefit that should be considered.

Environmental baseline monitoring for shale gas development in the UK: Identification and geochemical characterisation of local source emissions of methane to atmosphere.

Baseline mobile surveys of methane sources using vehicle-mounted instruments have been performed in the Fylde and Ryedale regions of Northern England over the 2016-19 period around proposed unconventional (shale) gas extraction sites. The aim was to identify and characterise methane sources ahead of hydraulically fractured shale gas extraction in the area around drilling sites. This allows a potential additional source of emissions to atmosphere to be readily distinguished from adjacent sources, should gas production take place. The surveys have used ethane:methane (C2:C1) ratios to separate combustion, thermogenic gas and biogenic sources. Sample collection of source plumes followed by high precision δ13C analysis of methane, to separate and isotopically characterise sources, adds additional biogenic source distinction between active and closed landfills, and ruminant eructations from manure. The surveys show that both drill sites and adjacent fixed monitoring sites have cow barns and gas network pipeline leaks as sources of methane within a 1 km range. These two sources are readily separated by isotopes (δ13C of -67 to -58‰ for barns, compared to -43 to -39‰ for gas leaks), and ethane:methane ratios (<0.001 for barns, compared to >0.05 for gas leaks). Under a well-mixed daytime atmospheric boundary layer these sources are generally detectable as above baseline elevations up to 100 m downwind for gas leaks and up to 500 m downwind for populated cow barns. It is considered that careful analysis of these proxies for unconventional production gas, if and when available, will allow any fugitive emissions from operations to be distinguished from surrounding sources.

Methane flux from flowback operations at a shale gas site.

We report measurements of methane (CH4) mixing ratios and emission fluxes derived from sampling at a monitoring station at an exploratory shale gas extraction facility in Lancashire, England. Elevated ambient CH4 mixing ratios were recorded in January 2019 during a period of cold-venting associated with a nitrogen lift process at the facility. These processes are used to clear the well to stimulate flow of natural gas from the target shale. Estimates of CH4 flux during the emission event were made using three independent modeling approaches: Gaussian plume dispersion (following both a simple Gaussian plume inversion and the US EPA OTM 33-A method), and a Lagrangian stochastic transport model (WindTrax). The three methods yielded an estimated peak CH4 flux during January 2019 of approximately 70 g s-1. The total mass of CH4 emitted during the six-day venting period was calculated to be 2.9, 4.2 ± 1.4(1σ) and 7.1 ± 2.1(1σ) tonnes CH4 using the simple Gaussian plume model, WindTrax, and OTM-33A methods, respectively. Whilst the flux approaches all agreed within 1σ uncertainty, an estimate of 4.2 (± 1.4) tonnes CH4 represents the most confident assessment due to the explicit modeling of advection and meteorological stability permitted using the WindTrax model. This mass is consistent with fluxes calculated by the Environment Agency (in the range 2.7 to 6.8 tonnes CH4), using emission data provided by the shale site operator to the regulator. This study provides the first CH4 emission estimate for a nitrogen lift process and the first-reported flux monitoring of a UK shale gas site, and contributes to the evaluation of the environmental impacts of shale gas operations worldwide. This study also provides forward guidance on future monitoring applications and flux calculation in transient emission events. Implications: This manuscript discusses atmospheric measurements near to the UK's first hydraulic fracturing facility, which has very high UK public, media, and policy interest. The focus of this manuscript is on a single week of data in which a large venting event at the shale gas site saw emissions of ~4 tonnes of methane to atmosphere, in breach of environmental permits. These results are likely to beresults are likely to be reported by the media and may influence future policy decisions concerning the UK hydraulic fracturing industry.

Effects of 'pre-fracking' operations on ambient air quality at a shale gas exploration site in rural North Yorkshire, England.

Rural observations of air quality and meteorological parameters (NOx, O3, NMHCs, SO2, PM) were made over a 2.5-year period (2016-2018) before, during and after preparations for hydraulic fracturing (fracking) at a shale gas exploration site near Kirby Misperton, North Yorkshire, England. As one of the first sites to apply for permits to carry out hydraulic fracturing, it has been subject to extensive regulatory and public scrutiny, as well as the focus for a major programme of long-term environmental monitoring. A baseline period of air quality monitoring (starting 2016) established the annual climatology of atmospheric composition against which a 20-week period of intensive activity on the site in preparation for hydraulic fracturing could be compared. During this 'pre-operational phase' of work in late 2017, the most significant effect was an increase in ambient NO (3-fold) and NOx (2-fold), arising from a combination of increased vehicle activity and operation of equipment on site. Although ambient NOx increased, air quality limit values for NO2 were not exceeded, even close to the well-site. Local ozone concentrations during the pre-operational period were slightly lower than the baseline phase due to titration with primary emitted NO. The activity on site did not lead to significant changes in airborne particulate matter or non-methane hydrocarbons. Hydraulic fracturing of the well did not subsequently take place and the on-site equipment was decommissioned and removed. Air quality parameters then returned to the original (baseline) climatological conditions. This work highlights the need to characterise the full annual climatology of air quality parameters against which short-term local activity changes can be compared. Based on this study, changes to ambient NOx appear to be the most significant air quality ahead of hydraulic fracturing. However, in rural locations, concentrations at individual sites are expected to be below ambient air quality limit thresholds.

A baseline of atmospheric greenhouse gases for prospective UK shale gas sites.

We report a 24-month statistical baseline climatology for continuously-measured atmospheric carbon dioxide (CO2) and methane (CH4) mixing ratios linked to surface meteorology as part of a wider environmental baselining project tasked with understanding pre-existing local environmental conditions prior to shale gas exploration in the United Kingdom. The baseline was designed to statistically characterise high-precision measurements of atmospheric composition gathered over two full years (between February 1st 2016 and January 31st 2018) at fixed ground-based measurement stations on, or near to, two UK sites being developed for shale gas exploration involving hydraulic fracturing. The sites, near Blackpool (Lancashire) and Kirby Misperton (North Yorkshire), were the first sites approved in the UK for shale gas exploration since a moratorium was lifted in England. The sites are operated by Cuadrilla Resources Ltd. and Third Energy Ltd., respectively. A statistical climatology of greenhouse gas mixing ratios linked to prevailing local surface meteorology is presented. This study diagnoses and interprets diurnal, day-of-week, and seasonal trends in measured mixing ratios and the contributory role of local, regional and long-range emission sources. The baseline provides a set of contextual statistical quantities against which the incremental impacts of new activities (in this case, future shale gas exploration) can be quantitatively assessed. The dataset may also serve to inform the design of future case studies, as well as direct baseline monitoring design at other potential shale gas and industrial sites. In addition, it provides a quantitative reference for future analyses of the impact, and efficacy, of specific policy interventions or mitigating practices. For example, statistically significant excursions in measured concentrations from this baseline (e.g. >99th percentile) observed during phases of operational extraction may be used to trigger further examination in order to diagnose the source(s) of emission and links to on-site activities at the time, which may be of importance to regulators, site operators and public health stakeholders. A guideline algorithm for identifying these statistically significant excursions, or "baseline deviation events", from the expected baseline conditions is presented and tested. Gaussian plume modelling is used to further these analyses, by simulating approximate upper-limits of CH4 fluxes which could be expected to give observable enhancements at the monitoring stations under defined meteorological conditions.

A new optical parametric amplifier based on lithium thioindate used for sum frequency generation vibrational spectroscopic studies of the amide I mode of an interfacial model peptide.

We describe a new optical parametric amplifier (OPA) that employs lithium thioindate, LiInS2 (LIS), to create tunable infrared light between 1500 cm(-1) and 2000 cm(-1). The OPA based on LIS described within provides intense infrared light with a good beam profile relative to similar OPAs built on silver gallium sulfide, AgGaS2 (AGS), or silver gallium selenide, AgGaSe2 (AGSe). We have used the new LIS OPA to perform surface-specific sum frequency generation (SFG) vibrational spectroscopy of the amide I vibrational mode of a model peptide at the hydrophobic deuterated polystyrene (d8-PS)-phosphate buffered saline interface. This model polypeptide (which is known to be an alpha-helix in the bulk solution under the high ionic strength conditions employed here) contains hydrophobic leucyl (L) residues and hydrophilic lysyl (K) residues, with sequence Ac-LKKLLKLLKKLLKL-NH2. The amide I mode at the d8-PS-buffer interface was found to be centered around 1655 cm(-1). This can be interpreted as the peptide having maintained its alpha-helical structure when adsorbed on the hydrophobic surface, although other interpretations are discussed.

New horizons for biomedical polymers.

Surface chemistry determines biological interactions at the interface of a medical device. Novel technology is described here that allows engineers to build into the polymer the type of surface that is required for a particular device application. How the technology operates and its possibilities for use in disposables, implantables and prostheses are examined.

Mains water leakage: Implications for phosphorus source apportionment and policy responses in catchments.

Effective strategies to reduce phosphorus (P)-enrichment of aquatic ecosystems require accurate quantification of the absolute and relative importance of individual sources of P. In this paper, we quantify the potential significance of a source of P that has been neglected to date. Phosphate dosing of raw water supplies to reduce lead and copper concentrations in drinking water is a common practice globally. However, mains water leakage (MWL) potentially leads to a direct input of P into the environment, bypassing wastewater treatment. We develop a new approach to estimate the spatial distribution and time-variant flux of MWL-P, demonstrating this approach for a 30-year period within the exemplar of the River Thames catchment in the UK. Our analyses suggest that MWL-P could be equivalent to up to c.24% of the P load entering the River Thames from sewage treatment works and up to c.16% of the riverine P load derived from agricultural non-point sources. We consider a range of policy responses that could reduce MWL-P loads to the environment, including incorporating the environmental damage costs associated with P in setting targets for MWL reduction, alongside inclusion of MWL-P within catchment-wide P permits.

Applications of immobilised artificial membrane chromatography to quaternary alkylammonium sulfobetaines and comparison of chromatographic methods for estimating the octanol-water partition coefficient.

The chromatographic behaviour of a series of quaternary alkylammonium sulfobetaines of general formula RN-(CH3)2(CH2)nSO3-, where n = 2-4, has been examined using an immobilised artificial membrane column. The k values have been correlated both with experimentally determined values for the octanol-water partition coefficient (P) and with aquatic toxicity measurements. Other indirect chromatographic methods for measuring log P for these compounds using reversed-phase columns and octanol-coated columns have also been investigated.

Quantitative structure-activity relationship modeling of acute toxicity of quaternary alkylammonium sulfobetaines to Daphnia magna.

The logarithm of the octanol/water partition coefficient has been widely used as the sole physicochemical property to define various types of biological activity, such as aquatic toxicity. In the present study, we derive a quantitative structure-activity relationship (QSAR) equation for the prediction of acute aquatic toxicity (48-h median effective concentration) of quaternary alkylammonium sulfobetaines to the aquatic invertebrate Daphnia magna Straus. The single-parameter approach described is also based on the hydrophobicity parameter, log P. The 17 zwitterionic compounds were considered for QSAR development. They have the general formula RN+(CH3)2(CH2)nSO3-, where n = 2 to 4, and were synthesized by reacting the corresponding N,N-dimethylamines with either sodium-2-chloroethanesulfonate (n = 2), 1,3-propanesultone (n = 3), or 1,4-butanesultone (n = 4). The R group was either a C6 to C12 alkyl chain, a phenylalkyl unit bearing a C1 to C4 chain, or a phenylpropyl unit with a C4 to C6 para-substituted alkyl group. Octanol/water partition coefficients were experimentally determined via a conventional stir-flask procedure, which was quantified using a reverse-phase, high-performance liquid chromatographic technique coupled with either an ultraviolet or an electrospray ionization mass spectrometry detection system. Median effective concentration values were also determined experimentally via a standard acute immobilization test recommended by Organisation for Economic Cooperation and Development (Paris, France) Guideline 202. The established QSAR equation for such zwitterionic compounds is consistent with the standard equation that normally defines the polar narcosis mode of toxic action.

Assembly and structure of alpha-helical peptide films on hydrophobic fluorocarbon surfaces.

The structure, orientation, and formation of amphiphilic alpha-helix model peptide films on fluorocarbon surfaces has been monitored with sum frequency generation (SFG) vibrational spectroscopy, near-edge x-ray absorption fine structure (NEXAFS) spectroscopy, and x-ray photoelectron spectroscopy (XPS). The alpha-helix peptide is a 14-mer of hydrophilic lysine and hydrophobic leucine residues with a hydrophobic periodicity of 3.5. This periodicity yields a rigid amphiphilic peptide with leucine and lysine side chains located on opposite sides. XPS composition analysis confirms the formation of a peptide film that covers about 75% of the surface. NEXAFS data are consistent with chemically intact adsorption of the peptides. A weak linear dichroism of the amide pi( *) is likely due to the broad distribution of amide bond orientations inherent to the alpha-helical secondary structure. SFG spectra exhibit strong peaks near 2865 and 2935 cm(-1) related to aligned leucine side chains interacting with the hydrophobic surface. Water modes near 3200 and 3400 cm(-1) indicate ordering of water molecules in the adsorbed-peptide fluorocarbon surface interfacial region. Amide I peaks observed near 1655 cm(-1) confirm that the secondary structure is preserved in the adsorbed peptide. A kinetic study of the film formation process using XPS and SFG showed rapid adsorption of the peptides followed by a longer assembly process. Peptide SFG spectra taken at the air-buffer interface showed features related to well-ordered peptide films. Moving samples through the buffer surface led to the transfer of ordered peptide films onto the substrates.

In situ adsorption studies of a 14-amino acid leucine-lysine peptide onto hydrophobic polystyrene and hydrophilic silica surfaces using quartz crystal microbalance, atomic force microscopy, and sum frequency generation vibrational spectroscopy.

The adsorption of a 14-amino acid amphiphilic peptide, LK14, which is composed of leucine (L, nonpolar) and lysine (K, charged), on hydrophobic polystyrene (PS) and hydrophilic silica (SiO2) was investigated in situ by quartz crystal microbalance (QCM), atomic force microscopy (AFM), and sum frequency generation (SFG) vibrational spectroscopy. The LK14 peptide, adsorbed from a pH 7.4 phosphate-buffered saline (PBS) solution, displayed very different coverage, surface roughness and friction, topography, and surface-induced orientation when adsorbed onto PS versus SiO2 surfaces. Real-time QCM adsorption data revealed that the peptide adsorbed onto hydrophobic PS through a fast (t < 2 min) process, while a much slower (t > 30 min) multistep adsorption and rearrangement occurred on the hydrophilic SiO2. AFM measurements showed different surface morphologies and friction coefficients for LK14 adsorbed on the two surfaces. Surface-specific SFG spectra indicate very different ordering of the adsorbed peptide on hydrophobic PS as compared to hydrophilic SiO2. At the LK14 solution/PS interface, CH resonances corresponding to the hydrophobic leucine side chains are evident. Conversely, only NH modes are observed at the peptide solution/SiO2 interface, indicating a different average molecular orientation on this hydrophilic surface. The surface-dependent difference in the molecular-scale peptide interaction at the solution/hydrophobic solid versus solution/hydrophilic solid interfaces (measured by SFG) is manifested as significantly different macromolecular-level adsorption properties on the two surfaces (determined via AFM and QCM experiments).

Macrophage behavior on surface-modified polyurethanes.

Adherent macrophages and foreign body giant cells (FBGCs) are known to release degradative molecules that can be detrimental to the long-term biostability of polyurethanes. The modification of polyurethanes using surface modifying endgroups (SMEs) and/or the incorporation of silicone into the polyurethane soft segments may alter macrophage adhesion, fusion and apoptosis resulting in improved long-term biostability. An in vitro study of macrophage adhesion, fusion and apoptosis was performed on polyurethanes modified with fluorocarbon SMEs, polyethylene oxide (PEO) SMEs, or poly(dimethylsiloxane) (PDMS) co-soft segment and SMEs. The fluorocarbon SME and PEO SME modifications were shown to have no effect on macrophage adhesion and activity, while silicone modification had varied effects. Macrophages were capable of adapting to the surface and adhering in a similar manner to the silicone-modified and unmodified polyurethanes. In the absence of IL-4, macrophage fusion was comparable on the modified and unmodified polyurethanes, while macrophage apoptosis was promoted on the silicone modified surfaces. In contrast, when exposed to IL-4, a cytokine known to induce FBGC formation, silicone modification resulted in more macrophage fusion to form foreign body giant cells. In conclusion, fluorocarbon SME and PEO SME modification does not affect macrophage adhesion, fusion and apoptosis, while silicone modification is capable of mediating macrophage fusion and apoptosis. Silicone modification may be utilized to direct the fate of adherent macrophages towards FBGC formation or cell death through apoptosis.