A controlled field pilot has been developed in Bozeman, Montana, USA, to study near surface CO2 transport and detection technologies. A slotted horizontal well divided into six zones was installed in the shallow subsurface. The scale and CO2 release rates were chosen to be relevant to developing monitoring strategies for geological carbon storage. The field site was characterized before injection, and CO2 transport and concentrations in saturated soil and the vadose zone were modeled. Controlled releases of CO2 from the horizontal well were performed in the summers of 2007 and 2008, and collaborators from six national labs, three universities, and the U.S. Geological Survey investigated movement of CO2 through the soil, water, plants, and air with a wide range of near surface detection techniques. An overview of these results will be presented. 相似文献
We examine the magnitude, frequency, and precipitation threshold of the extreme flood hazard on 37 low-order streams in the lower Stehekin River Valley on the arid eastern slope of the North Cascades. Key morphometric variables identify the magnitude of the hazard by differentiating debris flood from debris flow systems. Thirty-two debris flow systems are fed by basins?<?6 km2 and deposited debris cones with slopes?>?10°. Five debris flood systems have larger drainage areas and debris fans with slopes 7–10°. The debris flood systems have Melton ruggedness ratios from 0.42–0.64 compared to 0.78–3.80 for debris flow basins. We record stratigraphy at seven sites where soil surfaces buried by successive debris flows limit the age of events spanning 6000 years. Eighteen radiocarbon ages from the soils are the basis for estimates of a 200 to1500-year range in recurrence interval for larger debris flows and a 450?±?50-year average. Smaller events occur approximately every 100 years. Fifteen debris flows occurred in nine drainage systems in the last 15 years, including multiple flows on three streams. Summer storms in 2010 and 2013 with peak rainfall intensities of 7–9 mm/h sustained for 8–11 h triggered all but one flow; the fall 2015 event on Canyon Creek occurred after 170 mm of rain in 78 h. A direct link between fires and debris flows is unclear because several recent debris flows occurred in basins that did not burn or burned at low intensity, and basins that burned at high intensity did not carry debris flows. All but one of the recent flows and fires occurred on the valley’s southwest-facing wall. We conclude that fires and debris flows are linked by aspect at the landscape scale, where the sunny valley wall has flashy runoff due to sparse vegetation from frequent fires.
The sections penetrated on Leg 58 of the Deep Sea Drilling Project represent periods of geologic time during which depositional conditions apparently remained quite constant, thus offering an unusual opportunity to study the effects of diagenesis on organic material.Organic carbon and nitrogen contents decrease monotonically with increasing depth of burial before levelling off at minimum values of about 0.05-0.10 and 0.01%, respectively. The depths at which minima are reached vary from site to site, but the ages of the sediments at the minima are all about 2–5 Myr.These data indicate that diagenetic transformations are responsible for the gradual depletion of organic carbon and nitrogen. If diagenesis is at least partly the result of microbial activity, then the role of bacterial ecosystems in deep water sediments is much greater than has previously been thought. 相似文献
British Rail was privatised by the Conservative government of 1992-1997. This privatisation was driven primarily by political ideology and there is little to suggest the policy was implemented as part of an integrated transport strategy designed to encourage modal shift from road to rail. Since privatisation, however, passenger numbers and freight shipments have risen in absolute and relative terms and the current Labour administration has stated that its transport strategy offers the potential for a ‘railway renaissance’. In this paper, we question whether, four years on from the publication of the new strategy, such a renaissance--that is, a 50% increase in passenger kilometres and an 80% increase in freight kilometres by 2010, along with a degree of modal shift to rail from car and lorry--can be achieved given recent developments both within the rail industry and in government transport policy. 相似文献
Flow-parallel linear ridge–runnel (R–R) bedforms composed of mainly cohesive sediments have been investigated at an intertidal site located at Hills Flats in the Severn Estuary, UK. It is argued that the sequences of sand–mud laminae in the ridge sediments indicate strongly that R–R are depositional bedforms. Faint R–R topography scoured in the underlying soft bedrock and parallel rows of coarser particle now found at the base of ridges are evidence of secondary vortices that may have provided a catalyst for mud ridge growth. Bed shear stress remains below the erosion threshold for all but the most recent and weak surficial mud deposits which are removed by evorsion [mechanical erosion by turbulent flows that may also carry sand and/or gravel] during Spring tidal flow ca. 60 cm/s. Differences in flow characteristics between ridges and runnel are minor. Corrasion [to erode or be eroded by abrasion] by sparse coarse sediment largely prevents net deposition in the runnels. Over time a slight imbalance between mud deposition and erosion rates allows slow growth of the ridges suggesting that these mudflats may be especially sensitive to slight changes in the local hydrodynamic regime and/or sediment supply. 相似文献
This paper analyses the complexity and attempted pragmatism of current practices surrounding the management of current local government policy reform in England. In particular, it focuses on the tensions and contradictions between a national policy dynamic which seeks to encourage locally contingent solutions to be developed for localised problems, and the centralising tendencies of the national state which result in ‘blueprints’ and ‘models’ being developed for local policy delivery and a requirement to meet centrally derived targets. These assumptions are explored through the experiences of local government attempts to introduce innovative and experimental praxis in line with the complex cultural and political changes of ‘modernisation’ agendas advanced by the UK government. This is being rolled out by an overarching project of ‘new localism’ - an attempt to devolve power and resources from the central state to front line local managers, sub-local structures and partnerships and to deliver ‘what works’. It is argued that new attempts at subsidiarity should be more flexible to local conditions rather than directed by national policy and that greater discretion and freedom should be given to local managers to achieve this task. Using the concept of ‘pragmatic localism’ and grounded examples from a recent initiative - Local Area Agreements - it is highlighted that there are signs that local state management of national policy could be becoming increasingly adaptable, enabling managers to deal with the fluid nature of ongoing public policy reform, although this is far from a completed project with many factors still constraining this change process. 相似文献