The road to deforestation: An assessment of forest loss and its causes in Basho Valley, Northern Pakistan   总被引：1，自引：0，他引：1  

Jawad Ali  Tor A. Benjaminsen  Ahmed A. Hammad   ystein B. Dick 《Global Environmental Change》2005,15(4):209-380

Deforestation in the Himalayas is generally seen as caused primarily by population growth. Based on interviews and the analysis of satellite images, we critically examine this view using Basho Valley in the Western Himalayas of Pakistan as a case study. Our findings indicate that the forest of Basho has been reduced by at least 50% after the valley was opened up through the construction of a link road in 1968. Large-scale legal and illegal commercial harvesting was carried out after the construction of the road. While legal commercial harvesting was stopped in 1987, illegal harvesting has since continued with the involvement of the Forest Department. The findings of this study do not support theories in which deforestation is attributed to rapid population growth. Instead, mismanagement and illegal commercial harvesting endorsed by the Forest Department have been the main causes of deforestation in Basho Valley.  相似文献   

Heterogeneity preserving upscaling for heat transport in fractured geothermal reservoirs     

Anna Nissen  Eirik Keilegavlen  Tor Harald Sandve  Inga Berre  Jan Martin Nordbotten 《Computational Geosciences》2018,22(2):451-467

In simulation of fluid injection in fractured geothermal reservoirs, the characteristics of the physical processes are severely affected by the local occurence of connected fractures. To resolve these structurally dominated processes, there is a need to develop discretization strategies that also limit computational effort. In this paper, we present an upscaling methodology for geothermal heat transport with fractures represented explicitly in the computational grid. The heat transport is modeled by an advection-conduction equation for the temperature, and solved on a highly irregular coarse grid that preserves the fracture heterogeneity. The upscaling is based on different strategies for the advective term and the conductive term. The coarse scale advective term is constructed from sums of fine scale fluxes, whereas the coarse scale conductive term is constructed based on numerically computed basis functions. The method naturally incorporates the coupling between solution variables in the matrix and in the fractures, respectively, via the discretization. In this way, explicit transfer terms that couple fracture and matrix solution variables are avoided. Numerical results show that the upscaling methodology performs well, in particular for large upscaling ratios, and that it is applicable also to highly complex fracture networks.  相似文献   

Consistent joint elastic‐electrical differential effective‐medium modelling of compacting reservoir sandstones     

Erling Hugo Jensen  Leiv‐J. Gelius  Tor Arne Johansen  Zhong Wang 《Geophysical Prospecting》2013,61(4):788-802

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Synthesis of Calix[4]arene‐grafted Magnetite Nanoparticles and Evaluation of Their Arsenate as Well as Dichromate Removal Efficiency     

Serkan Sayin  Fatih Ozcan  Mustafa Yilmaz  Ali Tor  Shahabuddin Memon  Yunus Cengeloglu 《洁净——土壤、空气、水》2010,38(7):639-648

In this study, 5,17‐bis‐[(4‐benzylpiperidine)methyl]‐25,26,27,28‐tetrahydroxy‐calix[4]arene ( 3 ) has been prepared by the treatment of calix[4]arene with a secondary amine (4‐benzylpiperidine) and formaldehyde by means of Mannich reaction. The prepared Mannich base ( 3 ) has been grafted onto [3‐(2,3‐epoxypropoxy)‐propyl]‐trimethoxysilane‐modified Fe₃O₄ magnetite nanoparticles (EPPTMS‐MN) in order to obtain 5,17‐bis‐[(4‐benzylpiperidine)methyl]‐25,26,27,28‐tetrahydroxy calix[4]arene‐grafted EPPTMS‐MN (BP‐calix[4]arene‐grafted Fe₃O₄). All new compounds were characterized by a combination of FTIR and ¹H‐NMR analyses. The morphology of the magnetic nanoparticles was examined by transmission electron microscopy. Moreover, the studies regarding the removal of arsenate and dichromate ions from the aqueous solutions were also carried out by using 5,17‐bis‐[(4‐benzylpiperidine)methyl]‐25,26,27,28‐tetrahydroxy‐calix[4]arene in liquid–liquid extraction and BP‐calix[4]arene‐grafted Fe₃O₄ ( 4 ) in solid–liquid extraction experiments. The extraction results indicated that 3 is protonated at proton‐switchable binding sites in acidic conditions. Hence, facilitating binding of arsenate and dichromate is resulted from both electrostatic interactions and hydrogen bonding. To understand the selectivity of 3 , the retention of dichromate anions in the presence of Cl⁻, NO, and SO anions at pH 1.5 was also examined.  相似文献   

Trench-fill submarine-fan facies associations of the Upper Cretaceous Chugach terrane, southern Alaska     

Tor H. Nilsen 《Geo-Marine Letters》1984,3(2-4):179-185

Turbidites of the Upper Cretaceous Chugach terrane of southern Alaska were deposited in a trench during northward-directed subduction. The fault-bounded outcrop belt of the Chugach terrane is about 2000-km long and 100-km wide and was accreted to Alaska during the Cenozoic. Turbidites are at least 5000 m thick, are extensively deformed, have been regionally metamorphosed, and have been intruded by anatectic granites. Facies associations indicate an east-to-west progression from inner-fan to middle-fan, outer-fan, fan-fringe, and basin-plain deposits. To the north is a marginal trench-slope facies association and a basin. Margin setting represents fan and/or source area  相似文献   

Fish behaviour and orientation-dependent backscatter in acoustic Doppler profiler data     

Zedel  Len; Patro  Ranjan; Knutsen  Tor 《ICES Journal of Marine Science》2005,62(6):1191-1201

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Boamah,Festus. 2015. Biofuels and Land Politics: Connecting the Disconnects in the Debate about Livelihood Impacts of Jatropha Biofuel Land Deals in Ghana     

Tor A. Benjaminsen  Joseph Awetori Yaro 《Norsk geografisk tidsskrift. Norwegian journal of geography》2016,70(2):125-126

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A generalized cubic equation of state with application to pure CO<Subscript>2</Subscript> injection in aquifers     

Ivar Aavatsmark  Bawfeh Kingsley Kometa  Sarah E. Gasda  Tor Harald Sandve  Halvor Møll Nilsen 《Computational Geosciences》2016,20(3):623-635

A generalized cubic equation of state is given. The Peng-Robinson and the Soave-Redlich-Kwong equations are special cases of this equation. The generalized equation of state is precisely as simple and computationally efficient as these classical equations. Through comparison with the Span-Wagner equation for CO ₂, we obtain an improved density accuracy in predefined temperature-pressure domains. The generalized equation is then verified through two relevant examples of CO ₂ injection and migration. Comparisons are made with other standard cubic EOS in order to show the range of solutions obtained with less accurate EOS.  相似文献   

Element contents in mountain birch leaves,bark and wood under different anthropogenic and geogenic conditions     

Clemens Reimann  Arnold Arnoldussen  Tor Erik Finne  Friedrich Koller  Øystein Nordgulen  Peter Englmaier 《Applied Geochemistry》2007

Forty samples each of leaves, bark and wood of mountain birch (Betula pubescens EHRH.) were collected along a 120 km long south–north transect running through Norway’s largest city, Oslo. Concentrations of 26 chemical elements (Ag, As, Au, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, La, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Sr, Ti and Zn) as well as loss on ignition for the three sample materials are reported. By far the highest concentrations of most elements appear in the leaves. Prominent exceptions are Au and Pb, both of which are enriched in wood, indicating the importance of root-uptake, and As which is enriched in bark. Bedrock lithology, ore occurrences, soil pH and urban contamination all have a visible influence on the element concentrations in mountain birch leaves, bark and wood. It is often impossible to differentiate between all the factors that can influence element concentrations in the three sample materials. Mountain birch bark shows the strongest anthropogenic impact of the city of Oslo for dust-related elements (Fe, La, Ti) and Sb. Even in mountain birch bark the influence of the city on element concentrations is no longer discernible from the background variation at a distance of less than 20 km from Oslo centre. Compared to terrestrial moss, mountain birch appears to be of little value as a biomonitor for urban contamination.  相似文献   

Determination of Polycyclic Aromatic Hydrocarbons in Soil by Miniaturized Ultrasonic Extraction and Gas Chromatography‐Mass Selective Detection     

Senar Ozcan  Ali Tor  Mehmet Emin Aydin 《洁净——土壤、空气、水》2009,37(10):811-817

A miniaturized ultrasonic extraction procedure was developed for the determination of polycyclic aromatic hydrocarbons (PAHs) in soil by gas chromatography‐mass spectrometry. After determination of the most suitable extraction solvent with 5 min sonication time, several other parameters (sample amount, solvent volume and number of extraction times) were optimized using a 2³ factorial experimental design. Recoveries of PAHs from spiked soil samples were over 90% for three different fortification levels between 50 and 300 μg/kg, and relative standard deviations of the recoveries were in the range of < 1–15%. The limits of detection ranged from 0.002 to 1.87 μg/kg. The performance of the developed procedure was also compared with other traditional Soxhlet, shake flask and large scale ultrasonic extraction procedures on real soil samples, and extraction methods showed comparable efficiencies. The proposed procedure required small volumes of solvent and sample. It was practicable, rapid and easy to use for analysis of PAHs in soils.  相似文献