Optimizing the Environmental Performance of In Situ Thermal Remediation Technologies Using Life Cycle Assessment

In situ thermal remediation technologies provide efficient and reliable cleanup of contaminated soil and groundwater, but at a high cost of environmental impacts and resource depletion due to the large amounts of energy and materials consumed. This study provides a detailed investigation of four in situ thermal remediation technologies (steam enhanced extraction, thermal conduction heating, electrical resistance heating, and radio frequency heating) in order to (1) compare the life‐cycle environmental impacts and resource consumption associated with each thermal technology, and (2) identify options to reduce these adverse effects. The study identifies a number of options for environmental optimization of in situ thermal remediation. In general, environmental optimization can be achieved by increasing the percentage of heating supplied in off peak electricity demand periods as this reduces the pressure on coal‐based electricity and thereby reduces the environmental impacts due to electricity production by up to 10%. Furthermore, reducing the amount of concrete in the vapor cap by using a concrete sandwich construction can potentially reduce the environmental impacts due to the vapor cap by up to 75%. Moreover, a number of technology‐specific improvements were identified, for instance by the substitution of stainless steel types in wells, heaters, and liners used in thermal conduction heating, thus reducing the nickel consumption by 45%. The combined effect of introducing all the suggested improvements is a 10 to 21% decrease in environmental impacts and an 8 to 20% decrease in resource depletion depending on the thermal remediation technology considered. The energy consumption was found to be the main contributor to most types of environmental impacts; this will, however, depend on the electricity production mix in the studied region. The combined improvement potential is therefore to a large extent controlled by the reduction/improvement of energy consumption.     

A diatom‐based reconstruction of summer sea‐surface salinity in the Southern Okinawa Trough,East China Sea,over the last millennium

A high‐resolution diatom record from site MD05‐2908 in the Southern Okinawa Trough, East China Sea, reveals pronounced multidecadal‐ to centennial‐scale palaeoceanographic changes throughout the last millennium. Summer sea‐surface salinity (SSS) was reconstructed using a weighted averaging partial least squares diatom‐based training set. The reconstructed SSS shows slightly decreasing values during the period AD 905–1930 with considerable fluctuations superimposed on this general trend. Relatively high‐salinity conditions during the interval AD 905–1450 probably suggest a low flood frequency in north‐eastern Taiwan. Furthermore, the high SSS values are associated with a strong and stable influence of the Kuroshio Current on the Southern Okinawa Trough during the Medieval Climate Anomaly. The period AD 1450–1930 is characterized by three low‐salinity intervals (AD 1450–1500, AD 1625–1725 and AD 1770–1880) separated by periods of relatively high salinity. The low SSS intervals indicate increased freshwater discharge into the Southern Okinawa Trough during the Little Ice Age, probably as a result of higher flood frequencies in north‐eastern Taiwan. Spectral and wavelet analyses suggest that this pattern was linked to multidecadal variations in summer SSS, presumably associated with the Pacific Decadal Oscillation. Copyright © 2012 John Wiley & Sons, Ltd.     

A credible compliance enforcement system for the climate regime

The compliance enforcement system of the Kyoto Protocol provides only weak incentives for Parties to comply with their commitments. For example, the penalties for non-compliant countries are not legally binding, and moreover, there is no second-order punishment for those countries that fail to implement them. Thus, a Party can simply refuse to comply without consequence. The alternative compliance enforcement systems that have been proposed in the literature also face substantial problems. A simple, flexible, potent, and credible compliance enforcement system for a post-Kyoto climate agreement, based on deposits, is proposed here: at ratification, each country deposits a significant amount of money, and continues to do so in the preparation stage each year until the start of the commitment period. At the end of this period, those countries that meet their emissions limitation targets receive a full refund of their deposit, while those that fail to do so forfeit part or all of it. A simplified two-country model of the deposit system and a numerical example of an agreement involving the US, Japan, Russia, and Europe is also provided. If each country's deposit is no less than its abatement costs, there is a strong incentive for participating countries to avoid non-compliance.     

A morphometric analysis of tunnel valleys in the eastern North Sea based on 3D seismic data

A 1250 km² 3D seismic volume is used to provide a detailed spatial and geometrical analysis of fifteen Pleistocene tunnel valleys in the Danish North Sea. All the valleys are buried; they are up to 39 km long, 3–4 km wide and up to 350 m deep. The valleys are part of a vast tunnel valley province covering an area of some 0.5 million km² of the formerly glaciated lowland areas of North West Europe. The valleys consist of non‐branching, non‐anastomosing troughs; they exhibit strongly undulating bottom profiles with numerous sub‐basins and thresholds, and are characterised by adverse end slopes. Cross‐cutting relationships and theoretical considerations suggest the occurrence of seven major episodes of valley incision attributed to ice marginal oscillations within a few glacials. Calculations considering the valley end gradients and theoretical ice‐surface profiles suggest that the valleys were formed by pressurised subglacial meltwater erosion. Given a range of theoretical ice‐surface profiles, the adverse end slopes are well beyond the supercooling threshold, which suggests that the water was not in thermal equilibrium with the basal ice and that flow was concentrated in substantial conduits with sufficient mass and flux to maintain water temperature well above the freezing point. Copyright © 2007 John Wiley & Sons, Ltd.     

Analysis of limestone micromechanical properties by optical microscopy

Four dense Scandinavian limestones were analyzed to determine their mechanical properties. The generation of dust (? 10 μm) and fines (? 90 μm) during a closed circuit vertical roller mill comminution process was correlated with the calcite crystal size distributions of each limestone. Thin sections were analyzed and by means of stereology the calcite crystal size distributions for each limestone was measured. The dust generation of limestones is governed by a surface abrasive mechanism (R² = 0.99) and the production of fines is governed by the mechanical strength of limestones (R² = 0.99). The overall limestone degradation mechanism is predominantly controlled by the calcite cleavage planes which reduce the power consumption during the comminution process. This study is the first step in determining the influence of limestone texture on the wear rates in heterogenous raw mixes used in closed circuit comminution equipment.     

A giant (5.3 × 10 m) middle Miocene (c. 15 Ma) sediment mound (M1) above the Siri Canyon, Norwegian–Danish Basin: Origin and significance

A large-scale enigmatic mound structure (M1) has been discovered in middle Miocene strata of the Norwegian–Danish Basin, c. 10 km east and updip of the Central Graben. It is located about 1 km beneath the seabed and clearly resolved by a 3D seismic data set focused on the deeper, remobilised, sand-filled Siri Canyon. M1 comprises two culminations, up to 80 m high and up to 1400 m long, constituting a sediment volume of some 5.3 × 10⁷ m³. It is characterized by a hard reflection at the top, a soft reflection at the base, differential compaction relative to the surrounding sediments, and 10 ms TWT velocity pull up of underlying reflections, indicating a relatively fast mound fill, attributed to the presence of sand within the mound. Internal seismic reflections are arranged in an asymmetric concentric pattern, suggesting a progressive aggradation to the NW, downstream to a mid-Miocene contour current system. Numerous elongated pockmarks occur in the upper Miocene succession close to the mound and indicate that the study area was influenced by gas expulsion in the mid- and late Miocene.The reflection configuration, velocity, dimensions, regional setting, and isolated location can best be explained by interpreting the mound as a giant sand volcano extruded >1 km upward from the Siri Canyon during the middle Miocene (c. 15 Ma). The likely causes of this remarkable structure include gas charge and lateral pressure transfer from the Central Graben along the Siri Canyon reservoir. While this is the first such structure described from this part of the North Sea, similar-aged sand extrudites have recently been inferred from seismic observations in the North Viking Graben, thus suggesting that the mid-Miocene was a time of widespread and intense sediment remobilization and fluid expulsion in the North Sea.     

Automated rainfall simulator for variable rainfall on urban green areas

Rainfall simulators can enhance our understanding of the hydrologic processes affecting the total runoff to urban drainage systems. This knowledge can be used to improve urban drainage designs. In this study, a rainfall simulator is developed to simulate rainfall on urban green surfaces. The rainfall simulator is controlled by a microcomputer programmed to replicate the temporal variations in rainfall intensity of both historical and synthetic rainfall events with constant rainfall intensity on an area of 1 m². The performance of the rainfall simulator is tested under laboratory conditions with regard to spatial uniformity of the rainfall, the kinetic energy of the raindrops, and the ability to replicate historical and synthetic rainfall events with temporally varying intensity. The rainfall simulator is applied in the field to evaluate its functionality under field conditions and the influence of wind on simulated rainfall. Finally, a field study is carried out on the relationship between runoff, soil volumetric water content, and surface slope. Performance and field tests show that the simulated rainfall has a uniform spatial distribution, whereas the kinetic energy of the raindrops is slightly higher than that of other comparable rainfall simulators. The rainfall simulator performs best in low wind speed conditions. The simulator performs well in replicating historical and synthetic rainfall events by matching both intensity variations and accumulated rainfall depth. The field study shows good correlation between rainfall, runoff, infiltration, soil water content, and surface slope.     

Silica diagenesis in Cenozoic mudstones of the North Viking Graben: physical properties and basin modelling

Silica diagenesis can significantly change physical properties of the host strata and release large volumes of water. Predicting these changes and their timing is essential to understanding compaction, fluid flow and rock deformation in sedimentary basins. In this paper, the influence of silica diagenesis (opal‐A/CT transformation) on physical properties is determined, the sediment volume affected by these changes is mapped, and a new technique to model silica diagenesis is introduced. A petrophysical analysis of 16 exploration wells shows that the opal‐A/CT transformation leads to a porosity reduction of c.20% (from 49 to 29%) in Cenozoic mudstones of the North Viking Graben. Using three‐dimensional seismic reflection data, it is shown that the c.50 m thick opal‐A/CT transformation zone covers an area of >1500 km², equating to a minimum volume of 75 km³. The spatial and temporal evolution of opal‐A/CT transformation is simulated using an innovative basin modelling approach, the results of which indicate that the transformation started around Middle‐to‐Late Eocene times and then migrated upwards until it gradually fossilised between the Miocene and present. These findings are important, as they help understanding how these sediments compact and when fluids are released by diagenesis.     

The role of shelf morphology on storm‐bed variability and stratigraphic architecture,Lower Cretaceous,Svalbard

The dominance of isotropic hummocky cross‐stratification, recording deposition solely by oscillatory flows, in many ancient storm‐dominated shoreface–shelf successions is enigmatic. Based on conventional sedimentological investigations, this study shows that storm deposits in three different and stratigraphically separated siliciclastic sediment wedges within the Lower Cretaceous succession in Svalbard record various depositional processes and principally contrasting sequence stratigraphic architectures. The lower wedge is characterized by low, but comparatively steeper, depositional dips than the middle and upper wedges, and records a change from storm‐dominated offshore transition – lower shoreface to storm‐dominated prodelta – distal delta front deposits. The occurrence of anisotropic hummocky cross‐stratification sandstone beds, scour‐and‐fill features of possible hyperpycnal‐flow origin, and wave‐modified turbidites within this part of the wedge suggests that the proximity to a fluvio‐deltaic system influenced the observed storm‐bed variability. The mudstone‐dominated part of the lower wedge records offshore shelf deposition below storm‐wave base. In the middle wedge, scours, gutter casts and anisotropic hummocky cross‐stratified storm beds occur in inferred distal settings in association with bathymetric steps situated across the platform break of retrogradationally stacked parasequences. These steps gave rise to localized, steeper‐gradient depositional dips which promoted the generation of basinward‐directed flows that occasionally scoured into the underlying seafloor. Storm‐wave and tidal current interaction promoted the development and migration of large‐scale, compound bedforms and smaller‐scale hummocky bedforms preserved as anisotropic hummocky cross‐stratification. The upper wedge consists of thick, seaward‐stepping successions of isotropic hummocky cross‐stratification‐bearing sandstone beds attributed to progradation across a shallow, gently dipping ramp‐type shelf. The associated distal facies are characterized by abundant lenticular, wave ripple cross‐laminated sandstone, suggesting that the basin floor was predominantly positioned above, but near, storm‐wave base. Consequently, shelf morphology and physiography, and the nature of the feeder system (for example, proximity to deltaic systems) are inferred to exert some control on storm‐bed variability and the resulting stratigraphic architecture.     

Mid-Palaeocene palaeogeography of the eastern North Sea basin: integrating geological evidence and 3D geodynamic modelling

The Mid‐Palaeocene palaeogeography of Denmark and the surrounding areas have been reconstructed on the basis of published geological data integrated with 3D geodynamic modelling. The use of numerical modelling enables quantitative testing of scenarios based on geological input alone and thus helps constrain likely palaeo‐water depths in areas where the geological data are inconclusive or incomplete. The interpretation of large‐scale erosional valleys and small‐scale circular depressions at the Mid‐Palaeocene Top Chalk surface in the Norwegian–Danish basin as either submarine or subaerial features is enigmatic and has strong implications for palaeogeographical reconstructions of the eastern North Sea basin. A 3D thermo‐mechanical model is employed in order to constrain the likely palaeo‐water depths of the eastern North Sea basin during the Palaeocene. The model treats the lithosphere as an elasto‐visco‐plastic continuum and models the lithospheric response to the regional stress field and thermal structure. The model includes the effects of sea‐level change, sedimentation and erosion, from the Mid Cretaceous to the present. Modelling results reproduce to first order geological data such as present sediment isopachs and palaeo‐water depths. It is concluded that the Mid Palaeocene water depths in the Norwegian–Danish basin were about 250 m. The erosional valleys and circular depressions at the top of the Upper Cretaceous‐Danian Chalk Group are thus interpreted to have formed in relatively deep water rather than due to subaerial exposure. Likely interpretations of the structures are therefore submarine valleys and pockmarks.