Exploiting available data sources: location/allocation modeling for health service planning in rural Ghana     

Lasse Møller-Jensen  Richard Y. Kofie 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):145-153

The preconditions for applying GIS-based location-allocation analysis for health service planning in rural Ghana are examined in terms of data availability and quality. A population map is established from the latest available census using geo-coding methods and digital topographic sheets. A vector-based transport model of the region is established by merging data from several sources including GPS. It is suggested that a hybrid transport model is required. This model combines the possibilities for all-direction transportation inherent in the raster-based approach with the possibilities for road/path transportation inherent in the vector-based approach. All-direction movements are expected to take place close to the villages in order to reach a suitable linear transport corridor represented by a vector. Several scenarios for improving the accessibility aspects of the health service provision are examined in light of Ghana's current health service policy. Location-allocation modelling tools are used to select optimal locations and provide statistics on average distance to health centres and percentage of population covered.  相似文献   

Coarse clast ridge sequences as suitable archives for past storm events? Case study on the Houtman Abrolhos,Western Australia     

Anja M. Scheffers  Sander R. Scheffers  Dieter H. Kelletat  Peter Squire  Lindsay Collins  Yuexing Feng  Jian‐Xin Zhao  Renaud Joannes‐Boyau  Simon Matthias May  Gerhard Schellmann  Heather Freeman 《第四纪科学杂志》2012,27(7):713-724

Prehistoric storm records are relatively scarce in most parts of the world. This article presents storm records derived from coral rubble‐based geological archives of the Houtman Abrolhos Archipelago located off the west coast of Australia, where the southernmost coral reefs of the Indian Ocean are found. Winter storm swell from the circum‐Antarctic ‘Brave Westerlies’, as well as tropical cyclone waves, have left numerous ridge systems on dozens of islands of the archipelago, all composed of coral rubble from adjacent reefs. At three islands, seven ridge systems were dated by three different methods: U‐series (68 dates), radiocarbon (64 dates), electron spin resonance (7 dates); 139 radiometric dates span the last 5500 years of the Holocene. In contrast to the geomorphological interpretation, the age sequences show ‘inversions’, hiatuses and different ages for the same ridge, all pointing to complicated ridge formation processes. Time gaps, some exceeding 1000 years, are interpreted as phases of erosion and not as phases without storm activity. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

A late Pleistocene record of aeolian sedimentation in Blanche Cave, Naracoorte, South Australia     

Nicolas Darrnougu  Patrick De Deckker  Kathryn E. Fitzsimmons  Marc D. Norman  Liz Reed  Sander van der Kaars  Stewart Fallon 《Quaternary Science Reviews》2009,28(25-26):2600-2615

We provide geochemical analyses and grain size data for a clearly layered, 80 cm thick sedimentary deposit close to a roof collapse in Blanche Cave near Naracoorte in SE South Australia. This deposit contains aeolian material deposited between 40 ka and 14 ka cal BP and which yields airborne sediments spanning the Last Glacial Maximum, a period of time with little information for the Australian continent. The deposit also contains abundant vertebrate fossil material derived from owl pellets, accumulation and pitfall entrapment. Below the studied profile, large vertebrate remains are found but are not discussed here. No Holocene sedimentation occurred at the site examined in the cave, and the top of the sequence is capped with a layer that has been anthropologically disturbed and contains exotic Pinus pollen. Chronologies of the deposit were obtained using two dating techniques: single stage accelerator mass spectrometer (SSAMS) ¹⁴C analysis of 23 charcoal samples and optically stimulated luminescence (OSL) dating of quartz from 6 sediment samples. The ¹⁴C chronology is preferred to describe the history of the deposits since the OSL chronology, which consistently overestimates the associated radiocarbon dates, may be inaccurate due to complexities in calculating dose rates, and may in addition represent the timing of sediment deposition through the cave opening rather than sediment transport to the deposit site. Morphological analysis of single quartz grains and grain size analysis indicate different provenance that is confirmed through the geochemical analyses of bulk sediment. Major elements were measured by X-ray Fluorescence (XRF), trace and rare earth elements by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA ICP-MS), and Neodymium isotopic ratios were obtained using a Thermal Ionisation Mass Spectrometer (TIMS).Our results indicate that the aeolian material deposited in Blanche Cave over the 40–14 ka cal BP period originated from different sources across South Australia, although Nd isotopes clearly indicate a close association with sediments of the Kanmantoo Group outcropping along the eastern portion of the Mount Lofty Ranges and the Padthaway Ridge further south, both being located to the NW and NNW of the cave. During the latter part of Marine Isotope Stage 3, conditions were wetter and windblown sediment came from the coastal region just north and south of the Coorong Lagoon, with winds originating from the north-northwest. At that time, woody taxa appear to have vegetated the landscape. During the drier phases, especially the Last Glacial Maximum, sediment came from further inland, thus suggesting a different predominant wind direction, more from the northwest. The deglaciation saw material originating from a more northerly direction.  相似文献   

The land cover and carbon cycle consequences of large-scale utilizations of biomass as an energy source   总被引：1，自引：0，他引：1  

Rik Leemans  André van Amstel  Coos Battjes  Eric Kreileman  Sander Toet 《Global Environmental Change》1996,6(4):335-357

The use of modern biomass for energy generation has been considered in many studies as a possible measure for reducing or stabilizing global carbon dioxide (CO₂) emissions. In this paper we assess the impacts of large-scale global utilization of biomass on regional and grid scale land cover, greenhouse gas emissions, and carbon cycle. We have implemented in the global environmental change model IMAGE the LESS biomass intensive scenario, which was developed for the Second Assessment Report of IPCC. This scenario illustrates the potential for reducing energy related emission by different sets of fuel mixes and a higher energy efficiency. Our analysis especially covers different consequences involved with such modern biomass scenarios. We emphasize influences of CO₂ concentrations and climate change on biomass crop yield, land use, competition between food and biomass crops, and the different interregional trade patterns for modern biomass based energy. Our simulations show that the original LESS scenario is rather optimistic on the land requirements for large-scale biomass plantations. Our simulations show that 797 Mha is required while the original LESS scenario is based on 550 Mha. Such expansion of agricultural land will influence deforestation patterns and have significant consequenses for environmental issues, such as biodiversity. Altering modern biomass requirements and the locations where they are grown in the scenario shows that the outcome is sensitive for regional emissions and feedbacks in the C cycle and that competition between food and modern biomass can be significant. We conclude that the cultivation of large quantities of modern biomass is feasible, but that its effectiveness to reduce emissions of greenhouse gases has to be evaluated in combination with many other environmental land use and socio-economic factors.  相似文献   

Soil erosion due to rainfall impact with no inflow: a numerical solution with spatial and temporal effects of sediment settling velocity characteristics     

W.L Hogarth  C.W Rose  G.C Sander 《Journal of Hydrology》2004,294(4):229-240

Dynamic changes take place in the nature of sediment eroded from bare soil at low slopes by rainfall impact when there is no inflow of water at the top of the eroding slope. This relates initially to fine soil sediment not settling back onto the soil after the rainfall impact. Coupled partial differential equations describing such dynamic changes have been solved numerically for a bed of soil, bounded at its upper end, and subject to a constant rainfall rate. This solution allows prediction of the change with time and downslope distance in the concentration and settling velocity (or size) characteristics of eroding sediment, allowing critical evaluation of the assumption of space-independent sediment characteristics made in prior approximate analytical solutions of the equations involved. Following the determination of as yet unpredictable soil-related parameters in the equations, the solution was tested by comparison with experimented data on two soils of contrasting structural stability, namely a vertosol [The Australian Soil Classification (1996)] and a aridisol. Investigations included the determination of a minimum number of sediment size classes required to adequately describe the settling velocity characteristics, based on the shape of the underlying basic settling velocity characteristic, which is used to predict the dynamics of sediment deposition. The effect on the solution of observed structural breakdown in soil aggregation due to rainfall impact was investigated, leading to more accurate predictions of the settling velocity characteristics of eroded sediment. Other sources of discrepancy between theory and observation remain to be determined.  相似文献   

Non-iterative multiple-attenuation methods: linear inverse solutions to non-linear inverse problems – II. BMG approximation     

Luc T. Ikelle  Are Osen  Lasse Amundsen  Yunqing Shen 《Geophysical Journal International》2004,159(3):923-930

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Selection of prior distributions and multiscale analysis in Bayesian temperature reconstructions based on fossil assemblages     

Panu Erästö  Lasse Holmström 《Journal of Paleolimnology》2006,36(1):69-80

It is possible to reconstruct the past variation of an environmental variable from measured historical indicators when the modern values of the variable and the indicators are known. In a Bayesian statistical approach, the selection of a prior probability distribution for the past values of the environmental variable can then be crucial and the selection therefore should be made carefully. This is particularly the case when the data are noisy and the statistical model used is complex since the influence of the prior on the results can then be especially strong. It can be difficult to elicit the prior probability distribution from the available information, since usually there are no measured data on the past values of the variable one wants to reconstruct and different reconstructions are typically consistent with each other only at a coarse level. To overcome these difficulties we propose to use a non-informative smoothing prior, possibly in combination with an informative prior, that simply penalizes for roughness of the reconstruction as measured by the variability of its values. We believe that it can sometimes be easier to set an overall prior distribution on the roughness than to agree on a prior for the actual values of the reconstructed variable. Note that by using a smoothing prior one incorporates into the model itself the smoothing step usually done before or after the actual numerical reconstruction. Another idea proposed in this paper is to integrate the reconstruction model with a multiscale feature analysis technique known as SiZer. Multiscale analysis of the posterior distribution of the reconstructed variable makes it possible to infer its statistically significant features such as trends, maxima and minima at several different time scales. While only temperature is considered in this paper, the technique can be applied to other environmental variables.  相似文献   

Mercury mobilization by oxidative dissolution of cinnabar (α-HgS) and metacinnabar (β-HgS)     

Elizabeth A. Holley  A. James McQuillan  Dave Craw  Jonathan P. Kim  Sylvia G. Sander 《Chemical Geology》2007,240(3-4):313-325

Cinnabar (α-HgS) and metacinnabar (β-HgS) dissolved at environmentally significant rates in oxygenated slurry experiments simulating a low-flow fluvial system. Based on SO₄²⁻ production, cinnabar dissolution rates were 2.64 to 6.16 μmol (SO₄²⁻) m^− 2 day^− 1, and metacinnabar dissolution rates were 1.20 to 1.90 μmol (SO₄²⁻) m^− 2 day^− 1. Monodentate-bound thiosulfate (S₂O₃²⁻) was identified as an oxidation product on the HgS surface by ATR-IR spectroscopy based on strong infrared absorption bands in the 1140–1145 cm^− 1 and 1006–1014 cm^− 1 regions. The presence of sulfide oxidation intermediates on the HgS surface indicates that SO₄²⁻ concentration underestimates α-HgS and β-HgS dissolution in this setting. Mercury release rates during dissolution were more than two orders of magnitude less than SO₄²⁻ production, but were significant: 0.47 mg (Hg) m^− 2 y^− 1 from cinnabar [6.45 nmol (Hg) m^− 2 day^− 1], and 0.17 mg (Hg) m^− 2 y^− 1 from metacinnabar [2.29 nmol (Hg) m^− 2 day^− 1]. The Hg mobilized during α-HgS and β-HgS dissolution is sufficient to form natural Au–Hg amalgam in downstream placer settings. The proportion of mercury that is not remobilized during α-HgS and β-HgS dissolution likely adsorbs to the dissolving mercuric sulfide. Adsorption of Hg²⁺ to cinnabar was detected in situ by anodic stripping voltammetry using a cinnabar-modified carbon paste electrode following accumulation of Hg²⁺ on the electrode at open circuit potential.  相似文献   

Remote sensing and GIS in hydrogeology   总被引：1，自引：0，他引：1  

Jörn Hoffmann  Per Sander 《Hydrogeology Journal》2007,15(1):1-3

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Communicating uncertainty in the IPCC’s greenhouse gas emissions scenarios     

Niels J. Schenk  Sander M. Lensink 《Climatic change》2007,82(3-4):293-308

The issue of climate change required the development of the Special Report on Emission Scenarios (SRES) by the IPCC. The complexity of the subject and the unique science-policy relation resulted in confusion and discussions appeared in popular media like The Economist. This paper reviews scenario literature and SRES, identifies the most vulnerable elements in the communication of SRES. In the communication of GHG emission scenarios through SRES, the weaknesses that have been identified by the authors of this paper are the normative character of climate change assessment, the plausibility of the scenarios, and the risk of simplification of complex messages. The causes of these communicative issues have been identified as the intrinsic difficulties of interdisciplinary science, the uniqueness of the science-policy relation, and the need for a high degree of transparency. This paper suggests improving future communication of complex messages from scientists to their audience by means of clear reasoning when communicating with non-scientists, explicitly normative emission scenarios, and increased stakeholder participation in scenario development. Based on a presentation at the “IIASA-YSSP uncertainty seminars,” 22 July 2004, and the discussions thereafter.  相似文献