Carbon catalysed hydrogen exchange in petroleum source rocks     

Robert Alexander  Daniel Dawson  Kieran Pierce  Andrew Murray 《Organic Geochemistry》2009,40(9):951-955

Exchange of carbon bound hydrogen has been observed when alkenes, saturated and aromatic hydrocarbons are heated at moderate temperatures on carbonaceous surfaces (activated carbon and coal). Isomerisation of alkenes and the formation of hydrogenated/dehydrogenated products from the saturated and aromatic reactants resulted. A suite of crude oils from the Carnarvon Basin (Western Australia) have been analysed with a view to comparing their relative abundances of structurally similar hydrocarbons. The consistent relationships between hydrocarbons in crude oils that are chemically related via hydrogenation/dehydrogenation reactions suggest that a hydrogen exchange process similar to that demonstrated in laboratory experiments occurs during crude oil formation in sedimentary rocks.  相似文献   

Evolution of the Nyiragongo Magma     

SAHAMA  TH. G. 《Journal of Petrology》1973,14(1):33-48

This paper deals with the rocks, mainly foiditic in composition,of the Nyiragongo volcano and compares them with the mainlytephritic to phonolitic rocks of the neighbouring Nyamuragiravolcano and with the South Kivu basaltic rocks. All these rocksoccur in the Lake Kivu area of the Western Rift Valley of CentralAfrica. Two hundred and sixty-four chemical analyses consideredrepresentative were selected of these rock groups and were subjectedto statistical evaluation. The Nyiragongo magma is considered to be of mantle origin withoutsignificant crustal admixture. The Nyamuragira magma and theNyiragongo magma are both potassic in character and, despitebeing geographically closely related, display pronounced differencesin chemistry. The fairly extreme composition of the Nyiragongomagma is interpreted as a result of a locally strong transferand enrichment of mainly alkalis with a passive depletion ofsilica.  相似文献   

An interdisciplinary study of weathering effects in ordinary chondrites from the Acfer region,Algeria     

TH. STELZNER  K. HEIDE  A. BISCHOFF  D. WEBER  P. SCHERER  L. SCHULTZ  M. HAPPEL  W. SCHR N  U. NEUPERT  R. MICHEL  R. N. CLAYTON  T. K. MAYEDA  G. BONANI  I. HAIDAS  S. IVY-OCHS  M. SUTER 《Meteoritics & planetary science》1999,34(5):787-794

Abstract— Weathering effects on meteorite finds from the Acfer region were studied by various analytical techniques and in dependence on the depth of sampling. In thin sections of weathered meteorites, weathering effects usually decrease from the outside to the interior of the meteorite. The results of evolved gas analysis indicate that variation in weathering between surface and core is not significant in respect to the formation of Fe-oxyhydroxides. The secondary alteration effects in the noble gases are distributed unevenly throughout the specimens, as seen in the nonsystematic differences observed for the heavy noble gases. Chemical analyses show significant enrichment of Ba and Sr in the outer parts of the weathered samples due to element contamination through aqueous solution. Iron, Ni, and Co are partly flushed from the system as the metal oxidation proceeds. Oxygen isotopes show increases in δ¹⁸O and δ¹⁷O with increasing terrestrial age. For a set of H3 chondrites, the degree of weathering determined from the water content was correlated with terrestrial ages and is discussed with respect to possible weathering mechanisms.  相似文献   

Evaluating river morphology change with a geomorphic form variation approach     

Corey Dawson  Peter Ashmore  Robert Corry 《地球表面变化过程与地形》2024,49(2):855-874

Geomorphic river design strives for natural resilience by encouraging geomorphic form complexity and morphological processes linked to greater habitat diversity. Increasing availability of high-resolution topographic data and spatial feature mapping methods provide advantages for morphological analysis and river restoration planning. We propose and evaluate an approach to quantifying topographic variability of geomorphic form and pixel-level surface roughness resulting from channel planform geometry differences using spatially continuous variety computation applied to component metrics including flow direction, aspect and planform curvature. We define this as the geomorphic form variation (GFV) approach and found it scalable, repeatable and a multi-stage analytical metric for quantifying physical aspects of river-bed topographic variability. GFV may complement process-based morphological feature mapping applications, hydraulic assessment indices and spatial habitat heterogeneity metrics commonly used for ecological quality evaluation and river restoration. The GFV was tested on controlled synthetic channels derived from River Builder software and quasi-controlled sinuous planform flume experiment channels. Component variety metrics respond independently to specific geometric surface changes and are sensitive to multi-scaled morphology change, including coarser-grained sediment distributions of pixel-level surface roughness. GFV showed systematic patterns of change related to the effects of channel geometry, vertical bed feature (pool-bar) frequency and amplitude, and bar size, shape and orientation. Hotspot analysis found that bar margins were major components of topographic complexity, whereas grain-scale variety class maps further supported the multi-stage analytical capability and scalability of the GFV approach. The GFV can provide an overall variety value that may support river restoration decision-making and planning, particularly when geomorphic complexity enhancement is a design objective. Analysing metric variety values with statistically significant hotspot cluster maps and complementary process-based software and mapping applications allows variety correspondence to systematic feature changes to be assessed, providing an analytical approach for river morphology change comparison, channel design and geomorphic process restoration.  相似文献   

Faunal relationships between the New Zealand plateau and the New Zealand sector of Antarctica based on echinoderm distribution     

Elliot W. Dawson 《新西兰海洋与淡水研究杂志》2013,47(2):126-140

The problem of New Zealand‐Antarctic faunal relationships is discussed on the basis of echinoderm distribution. The limitations of the data upon which past zoogeographical speculations have been based are pointed out.

Macquarie Island (occupying an intermediate geographical position between the New Zealand Plateau and the Antarctic) shows definite relationships with New Zealand, and the submarine Macquarie Ridge may have provided a connecting migration route. However, only four species of echinoderms are shared between the Ross Sea‐Balleny Islands area (the New Zealand sector of the Antarctic Region) and the New Zealand Pliateau‐Macquarie Island area (the New Zealand Region). Although the as yet unsampled part of the Macquarie‐Balleny Ridge may reveal other faunal similarities, the present systematic sampling has made possible a sounder understanding of the zoogeographical affinities of the two regions.  相似文献   

F) Organisations Nationales National Organizations     

J. TÓTH 《水文科学杂志》2013,58(2):165-168

ABSTRACT

The present study is based on field exploration and production records. The producing formation consists of consolidated continental sediments which are overlain by clays, sands and gravels. No areally extensive aquifers can be distinguished. The only zone of consistently high permeability is associated with a buried channel in the bedrock and is interrupted by a hydraulic barrier. Salt concentrations in the groundwater range from less than 500 ppm to over 2000 ppm. Groundwater temperatures range form 38 °F (3·3 °C) to 41 °F (5·0 °C).

The sustainable yields of individual wells of the three-well field range from 60 igpm to 150 igpm with a combined maximum of 350 igpm. Pumping creates an elongated hydraulic depression which is interrupted by the barrier in one direction and causes major changes in water levels 2 miles distant in the other direction. Short and long-term water-level fluctuations suggest two sources of recharge: direct infiltration and lateral flow.

Significantly different values of transmissivity (T) are computed from production tests of different lengths. Tests of duration of 10 to 500 min, 70 to 130 h, and several months yield values for T, in igpd/ft, of 10,000 to 50,000, 2000 to 6000, and 1300, respectively. From the three methods of attempted yield evaluation the one based on empirical relations between operating pumping rates and drawdowns yields the most satisfactory results.  相似文献   

Assessing the effectiveness of non-structural flood management measures in the Thames Estuary under conditions of socio-economic and environmental change   总被引：1，自引：0，他引：1  

Richard J. Dawson  Tom Ball 《Global Environmental Change》2011,21(2):628-646

Risk analysis and appraisal of the benefits of structural flood risk management measures such as embankments is well established. Here, a method to quantify, over extended timescales, the effectiveness of non-structural measures such as land use spatial planning, insurance and flood resilient construction is presented. The integrated approach couples socio-economic and climate change scenarios with long term land use modelling and flood risk analysis to generate maps and time series of expected annual damages. The analysis has been applied on a case study in the Thames Estuary in the UK. Stakeholders helped develop a number of scenarios that might lead to substantial changes in existing planning and insurance policies in the UK. The effectiveness of these changes was analysed and showed the substantial benefits in terms of reduction of future flood risks that are achievable with changes in planning policy, financial incentives and resilient property construction in the floodplain. Moreover, the reward can be increased through earlier action. Subsequently, the benefits of a range of policies are explored under the UK Foresight socio-economic scenarios. Different structural and non structural flood management interventions are tested and the results demonstrate that despite the potential for large increases in flood risk in the Thames Estuary, in all scenarios substantial flood risk reductions are possible. The effectiveness of non-structural measures is however sensitive to socio-economic changes and governance arrangements. The analysis described here will help to identify portfolios of non-structural and structural options that are robust to uncertainties.  相似文献   

Dynamic p-enrichment schemes for multicomponent reactive flows     

C. Michoski  C. MirabitoC. Dawson  D. WirasaetE.J. Kubatko  J.J. Westerink 《Advances in water resources》2011,34(12):1666-1680

We present a family of p-enrichment schemes. These schemes may be separated into two basic classes: the first, called fixed tolerance schemes, rely on setting global scalar tolerances on the local regularity of the solution, and the second, called dioristic schemes, rely on time-evolving bounds on the local variation in the solution. Each class of p-enrichment scheme is further divided into two basic types. The first type (the Type I schemes) enrich along lines of maximal variation, striving to enhance stable solutions in “areas of highest interest.” The second type (the Type II schemes) enrich along lines of maximal regularity in order to maximize the stability of the enrichment process. Each of these schemes are tested on three model systems. The first is an academic exact system where basic analysis is easily performed. Then we discuss a pair of application model problems arising in coastal hydrology. The first being a contaminant transport model, which addresses a declinature problem for a contaminant plume with respect to a bay inlet setting. And the second, a multicomponent chemically reactive flow model of estuary eutrophication arising in the Gulf of Mexico.  相似文献   

Discontinuous Galerkin methods for modeling Hurricane storm surge   总被引：1，自引：0，他引：1  

Clint Dawson  Ethan J. KubatkoChristopher Mirabito  Craig MichoskiNishant Panda 《Advances in water resources》2011,34(9):1165-1176

Storm surge due to hurricanes and tropical storms can result in significant loss of life, property damage, and long-term damage to coastal ecosystems and landscapes. Computer modeling of storm surge can be used for two primary purposes: forecasting of surge as storms approach land for emergency planning and evacuation of coastal populations, and hindcasting of storms for determining risk, development of mitigation strategies, coastal restoration and sustainability.Storm surge is modeled using the shallow water equations, coupled with wind forcing and in some events, models of wave energy. In this paper, we will describe a depth-averaged (2D) model of circulation in spherical coordinates. Tides, riverine forcing, atmospheric pressure, bottom friction, the Coriolis effect and wind stress are all important for characterizing the inundation due to surge. The problem is inherently multi-scale, both in space and time. To model these problems accurately requires significant investments in acquiring high-fidelity input (bathymetry, bottom friction characteristics, land cover data, river flow rates, levees, raised roads and railways, etc.), accurate discretization of the computational domain using unstructured finite element meshes, and numerical methods capable of capturing highly advective flows, wetting and drying, and multi-scale features of the solution.The discontinuous Galerkin (DG) method appears to allow for many of the features necessary to accurately capture storm surge physics. The DG method was developed for modeling shocks and advection-dominated flows on unstructured finite element meshes. It easily allows for adaptivity in both mesh (h) and polynomial order (p) for capturing multi-scale spatial events. Mass conservative wetting and drying algorithms can be formulated within the DG method.In this paper, we will describe the application of the DG method to hurricane storm surge. We discuss the general formulation, and new features which have been added to the model to better capture surge in complex coastal environments. These features include modifications to the method to handle spherical coordinates and maintain still flows, improvements in the stability post-processing (i.e. slope-limiting), and the modeling of internal barriers for capturing overtopping of levees and other structures. We will focus on applications of the model to recent events in the Gulf of Mexico, including Hurricane Ike.  相似文献   

An agent-based model for risk-based flood incident management   总被引：3，自引：1，他引：2  

Richard J. Dawson  Roger Peppe  Miao Wang 《Natural Hazards》2011,59(1):167-189

Effective flood incident management (FIM) requires successful operation of complex, interacting human and technological systems. A dynamic agent-based model of FIM processes has been developed to provide new insights which can be used for policy analysis and other practical applications. The model integrates remotely sensed information on topography, buildings and road networks with empirical survey data to fit characteristics of specific communities. The multiagent simulation has been coupled with a hydrodynamic model to estimate the vulnerability of individuals to flooding under different storm surge conditions, defence breach scenarios, flood warning times and evacuation strategies. A case study in the coastal town of Towyn in the United Kingdom has demonstrated the capacity of the model to analyse the risks of flooding to people, support flood emergency planning and appraise the benefits of flood incident management measures.  相似文献