Natural radiation and its hazard in copper ore mines in Poland

The doses of gamma radiation, concentrations of radium isotopes in water and sediments, radon concentration and concentration of alpha potential energy of radon decay products in the copper ore mine and in the mining region in the vicinity of Lubin town in Poland are presented. These data served as a basis for the assessment of radiological hazard to the mine workers and general public. The results of this assessment indicate that radiological hazard in the region does not differ substantially from typical values associated with natural radiation background. The calculated average annual effective dose for copper miners is 1.48 mSv. In general, copper ore mines can be regarded as radiologically safe workplaces.     

Suspended sediment fluxes at an intertidal flat: The shifting influence of wave,wind, tidal,and freshwater forcing

Using in situ, continuous, high frequency (8–16 Hz) measurements of velocity, suspended sediment concentration (SSC), and salinity, we investigate the factors affecting near-bed sediment flux during and after a meteorological event (cold front) on an intertidal flat in central San Francisco Bay. Hydrodynamic forcing occurs over many frequency bands including wind wave, ocean swell, seiching (500–1000 s), tidal, and infra-tidal frequencies, and varies greatly over the time scale of hours and days. Sediment fluxes occur primarily due to variations in flow and SSC at three different scales: residual (tidally averaged), tidal, and seiching. During the meteorological event, sediment fluxes are dominated by increases in tidally averaged SSC and flow. Runoff and wind-induced circulation contribute to an order of magnitude increase in tidally averaged offshore flow, while waves and seiching motions from wind forcing cause an order of magnitude increase in tidally averaged SSC. Sediment fluxes during calm periods are dominated by asymmetries in SSC over a tidal cycle. Freshwater forcing produces sharp salinity fronts which trap sediment and sweep by the sensors over short (∼30 min) time scales, and occur primarily during the flood. The resulting flood dominance in SSC is magnified or reversed by variations in wind forcing between the flood and ebb. Long-term records show that more than half of wind events (sustained speeds of greater than 5 m/s) occur for 3 h or less, suggesting that asymmetric wind forcing over a tidal cycle commonly occurs. Seiching associated with wind and its variation produces onshore sediment transport. Overall, the changing hydrodynamic and meteorological forcing influence sediment flux at both short (minutes) and long (days) time scales.     

A framework for spatio-temporal scales and concepts from different disciplines: the ‘vulnerability cube’

The concept of vulnerability is increasingly used in the fields of disaster risk reduction and climate change adaptation, as well as socioeconomic studies. This paper reviews research inputs into the concept of vulnerability and highlights the challenges of resolving its spatial and temporal variability with building resilience and adaptation. We hypothesise that a clear understanding of scale is key to integrating these related issues, by differentiating three dimensions of scale when analysing relationships between the observed and the intrinsic scale of a given phenomenon, namely space, time and dimensional level. The paper analyses 20 vulnerability assessment approaches, ranging from the global down to the local scale, and positions them with regard to their integration of the spatial component. We then develop a vulnerability cube as a framework to position existing approaches and to map them in a three-dimensional space. The three axes represent space, time and dimension and provide a structure for the different notions of scales and ultimately for a spatial analysis workflow. The vulnerability cube framework helps us to position different vulnerability assessments and to identify overlaps, differences and specific characteristics. Additionally, this three-dimensional conceptualisation allows the identification and discussion of appropriate scaling issues.     

Three-phase measurements of oil and gas trapping in sand packs

We measure the trapped saturations of oil and gas as a function of initial saturation in water-wet sand packs. We start with a water-saturated column and inject octane (oil), while water and oil are produced from the bottom. Once water production has ceased, air (gas) then enters from the top, allowing oil and gas to drain under gravity for different times. Finally water is then injected from the bottom to trap both oil and gas. The columns are sliced and the fluids analyzed using gas chromatography. We find that for high initial gas saturations more gas can be trapped in the presence of oil than in a two-phase (gas/water) system. The residual gas saturation can be over 20% compared to 14% in two-phase flow [Al Mansoori SK, Iglauer S, Pentland CH, Bijeljic B, Blunt MJ. Measurements of non-wetting phase trapping applied to carbon dioxide storage. Energy Procedia 2009;1(1):3173–80]. This is unlike previous measurements on consolidated media, where the trapped gas saturation is either similar or lower to that reached in an equivalent two-phase experiment. For lower initial gas saturation, the amount of trapping follows the initial-residual trend seen in two-phase experiments. The amount of oil trapped is insensitive to initial gas saturation or the amount of gas that is trapped, again in contrast to measurements on consolidated media. More oil is trapped than would be predicted from an equivalent two-phase (oil/water) system, although the trapped saturation is never larger than the maximum reached in two-phase flow (around 11%) [Pentland CH, Al Mansoori SK, Iglauer S, Bijeljic B, Blunt MJ. Measurement of non-wetting phase trapping in sand packs. In: SPE 115697, proceedings of the SPE annual technical conference and exhibition, Denver, Colorado, USA; 21–24 September 2008]. These initially surprising results are explained in the context of oil layer stability and the competition between snap-off and piston-like advance. In two-phase systems, displacement is principally by cooperative piston-like advance with relatively little trapping, whereas in consolidated media snap-off is generally more significant. However, oil layer collapse events during three-phase waterflooding rapidly trap the oil which acts as a barrier to direct water/gas displacement, except by snap-off, leading to enhanced gas trapping.     

Novel basin modelling concept for simulating deformation from mechanical compaction using level sets

As sedimentation progresses in the formation and evolution of a depositional geologic basin, the rock strata are subject to various stresses. With increasing lithostatic pressure, compressional forces act to compact the porous rock matrix, leading to overpressure buildup, changes in the fluid pore pressure and fluid flow. In the context of petroleum systems modelling, the present study concerns the geometry changes that a compacting basin experiences subject to deposition. The purpose is to track the positions of the rock layer interfaces as compaction occurs. To handle the challenge of potentially large geometry deformations, a new modelling concept is proposed that couples the pore pressure equation with a level set method to determine the movement of lithostratigraphic interfaces. The level set method propagates an interface according to a prescribed speed. The coupling term for the pore pressure and level-set equations consists of this speed function, which is dependent on the compaction law. The two primary features of this approach are the simplicity of the grid and the flexibility of the speed function. A first evaluation of the model concept is presented based on an implementation for one spatial dimension accounting for vertical effective stress. Isothermal conditions with a constant fluid density and viscosity were assumed. The accuracy of the implemented numerical solution for the case of a single stratigraphic unit with a linear compaction law was compared to the available analytical solution [38]. The multi-layer setup and the nonlinear case were tested for plausibility.     

The effects of boreal forest expansion on the summer Arctic frontal zone

Over the last 100?years, Arctic warming has resulted in a longer growing season in boreal and tundra ecosystems. This has contributed to a slow northward expansion of the boreal forest and a decrease in the surface albedo. Corresponding changes to the surface and atmospheric energy budgets have contributed to a broad region of warming over areas of boreal forest expansion. In addition, mesoscale and synoptic scale patterns have changed as a result of the excess energy at and near the surface. Previous studies have identified a relationship between the positioning of the boreal forest-tundra ecotone and the Arctic frontal zone in summer. This study examines the climate response to hypothetical boreal forest expansion and its influence on the summer Arctic frontal zone. Using the Weather Research and Forecasting model over the Northern Hemisphere, an experiment was performed to evaluate the atmospheric response to expansion of evergreen and deciduous boreal needleleaf forests into open shrubland along the northern boundary of the existing forest. Results show that the lower surface albedo with forest expansion leads to a local increase in net radiation and an average hemispheric warming of 0.6°C at and near the surface during June with some locations warming by 1–2°C. This warming contributes to changes in the meridional temperature gradient that enhances the Arctic frontal zone and strengthens the summertime jet. This experiment suggests that continued Northern Hemisphere high-latitude warming and boreal forest expansion might contribute to additional climate changes during the summer.     

Towards the representation of groundwater in the Joint UK Land Environment Simulator

Groundwater is an important component of the hydrological cycle with significant interactions with soil hydrological processes. Recent studies have demonstrated that incorporating groundwater hydrology in land surface models (LSMs) considerably improves the prediction of the partitioning of water components (e.g., runoff and evapotranspiration) at the land surface. However, the Joint UK Land Environment Simulator (JULES), an LSM developed in the United Kingdom, does not yet have an explicit representation of groundwater. We propose an implementation of a simplified groundwater flow boundary parameterization (JULES-GFB), which replaces the original free drainage assumption in the default model (JULES-FD). We tested the two approaches under a controlled environment for various soil types using two synthetic experiments: (1) single-column and (2) tilted-V catchment, using a three-dimensional (3-D) hydrological model (ParFlow) as a benchmark for JULES’ performance. In addition, we applied our new JULES-GFB model to a regional domain in the UK, where groundwater is the key element for runoff generation. In the single-column infiltration experiment, JULES-GFB showed improved soil moisture dynamics in comparison with JULES-FD, for almost all soil types (except coarse soils) under a variety of initial water table depths. In the tilted-V catchment experiment, JULES-GFB successfully represented the dynamics and the magnitude of saturated and unsaturated storage against the benchmark. The lateral water flow produced by JULES-GFB was about 50% of what was produced by the benchmark, while JULES-FD completely ignores this process. In the regional domain application, the Kling-Gupta efficiency (KGE) for the total runoff simulation showed an average improvement from 0.25 for JULES-FD to 0.75 for JULES-GFB. The mean bias of actual evapotranspiration relative to the Global Land Evaporation Amsterdam Model (GLEAM) product was improved from −0.22 to −0.01 mm day⁻¹. Our new JULES-GFB implementation provides an opportunity to better understand the interactions between the subsurface and land surface processes that are dominated by groundwater hydrology.     

Anaerobic ammonium oxidation by nitrite (anammox): Implications for N2 production in coastal marine sediments

The respiratory reduction of nitrate (denitrification) is acknowledged as the most important process that converts biologically available nitrogen to gaseous dinitrogen (N₂) in marine ecosystems. Recent findings, however, indicate that anaerobic ammonium oxidation by nitrite (anammox) may be an important pathway for N₂ formation and N removal in coastal marine sediments and in anoxic water columns of the oceans. In the present study, we explored this novel mechanism during N mineralization by ¹⁵N amendments (single and coupled additions of ¹⁵NH₄⁺, ¹⁴NO₃⁻ and ¹⁵NO₃⁻) to surface sediments with a wide range of characteristics and overall reactivity. Patterns of ^29/30N₂ production in the pore water during closed sediment incubations demonstrated anammox at all 7 of the investigated sites. Stoichiometric calculations revealed that 4% to 79% of total N₂ production was due to this novel route. The relative importance of anammox for N₂ release was inversely correlated with remineralized solute production, benthic O₂ consumption, and surface sediment Chl a. The observed correlations indicate competition between reductants for pore water nitrite during early diagenesis and that additional factors (e.g. availability of Mn-oxides), superimposed on overall patterns of diagenetic activity, are important for determining absolute and relative rates of anammox in coastal marine sediments.     

New insights into the origin and migration of brines in deep Devonian aquifers, Alberta, Canada

Analysis of hydraulic heads and chemical compositions of Devonian formation waters in the west central part of the Alberta Basin, Canada, characterizes the origin of formation waters and migration of brines. The Devonian succession in the study area lies 2000–5000 m below the ground surface, and has an approximate total thickness of 1000 m and an average slope of 15 m/km. Four Devonian aquifers are present in the study area, which form two aquifer systems [i.e., a Middle–Upper Devonian aquifer system (MUDAS) consisting of the Elk Point and Woodbend–Beaverhill Lake aquifers, and an Upper Devonian aquifer system (UDAS) consisting of the Winterburn and Wabamun aquifers]. The Ireton is an effective aquitard between these two systems in the eastern parts of the study area. The entire Devonian succession is confined below by efficient aquitards of the underlying Cambrian shales and/or the Precambrian basement, and above by overlying Carboniferous shales of the Exshaw and Lower Banff Formations.The formation water chemistry shows that the Devonian succession contains two distinct brine types: a ‘heavy brine,’ located updip, defined approximately by TDS >200 g/l, and a ‘light brine’ with TDS <200 g/l. Hydraulic head distributions suggest that, presently, the ‘light brine’ attempts to flow updip, thereby pushing the ‘heavy brine’ ahead. The interface between the two brines is lobate and forms large-scale tongues that are due to channeled flow along high-permeability pathways. Geological and hydrogeochemical data suggest that the following processes determined the present composition of the ‘light’ and ‘heavy’ brines: original seawater, evaporation beyond gypsum but below halite saturation, dolomitization, clay dehydration, gypsum dewatering, thermochemical sulfate reduction (TSR), and halite dissolution. The influx of meteoric (from the south) and metamorphic (from the west) waters can be recognized only in the ‘light brine.’ Albitization can be unequivocally identified only in the ‘heavy brine.’ The ‘heavy brine’ may be residual Middle Devonian evaporitic brine from the Williston Basin or the Elk Point Basin, or it may have originated from partial dissolution of thick, laterally extensive Middle Devonian evaporite deposits to the east of the study area. The ‘light brine’ most probably originated from dilution of ‘heavy brine’ in post-Laramide times.     

The reflectivity spectrum and opposition effect of Titan's surface observed by Huygens' DISR spectrometers

We determined Titan's reflectivity spectrum near the Huygens' landing site from observations taken with the Descent Imager/Spectral Radiometer below 500 m altitude, in particular the downward-looking photometer and spectrometers. We distinguish signal coming from illumination by sunlight and the lamp onboard Huygens based on their different spectral signatures. For the sunlight data before landing, we find that spatial variations of Titan's reflectivity were only ～0.8%, aside from the phase angle dependence, indicating that the probed area within ～100 m of the landing site was very homogeneous. Only the very last spectrum taken before landing gave a 3% brighter reflectivity, which probably was caused by one bright cobble inside its footprint. The contrast of the cobble was higher at 900 nm wavelength than at 600 nm.For the data from lamp illumination, we confirm that the phase function of Titan's surface displays a strong opposition effect as found by Schröder and Keller (2009. Planetary and Space Science 57, 1963–1974). We extend the phase function to even smaller phase angles (0.02°), which are among the smallest phase angles observed in the solar system. We also confirm the reflectivity spectrum of the dark terrain near the Huygens' landing site between 900 and 1600 nm wavelength by Schröder and Keller (2008. Planetary and Space Science 56, 753–769), but extend the spectrum down to 435 nm wavelength. The reflectivity at zero phase angle peaks at 0.45±0.06 around 750 nm wavelength and drops down to roughly 0.2 at both spectral ends. Our reflectivity of 0.45 is much higher than all previously reported values because our observations probe lower phase angles than others. The spectrum is very smooth except for a known absorption feature longward of 1350 nm. We did not detect any significant variation of the spectral shape along the slit for exposures after landing, probing a 25×4 cm² area. However, the recorded spectral shape was slightly different for exposures before and after landing. This difference is similar to the spectral differences seen on scales of kilometers (Keller et al., 2008. Planetary and Space Science 56, 728–752), indicating that most observations may probe spatially variable contributions from two basic materials, such as a dark soil partially covered by bright cobbles.We used the methane absorption features to constrain the methane mixing ratio near the surface to 5.0±0.3%, in agreement with the 4.92±0.24% value measured in situ by Niemann et al. (2005. Nature 438, 779–784), but smaller than their revised value of 5.65±0.18% (Niemann et al., 2010. Journal of Geophysical Research 115, E12006). Our results were made possible by an in depth review of the calibration of the spectroscopic and photometric data.