排序方式： 共有30条查询结果，搜索用时 31 毫秒
21.
Prioritization of potential regions that are severely threatened by soil erosion is a prerequisite for formulating and implementing conservation measures and management practices, particularly in fragile semiarid regions. The present study prioritized eight delineated Nagmati sub-watersheds located in the Kutch District of Gujarat State, India, based on three approaches, namely principal component analysis (PCA), integrated PCA with weighted sum (I-PCWS), and analytical hierarchy process (AHP), and on 10 morphometric erosion risk parameters (ERPs). Sub-watersheds were categorized into three priority classes, namely high, medium, and low. PCA retrieved the three most significant ERPs (i.e., length of overland flow, Lo; drainage texture, Dt; and compactness coefficient, Cc) explaining 86.876% of the variance and exhibiting the highest correlation, i.e., r?=?0.961, 0.986, and 0.934 for the first three principal components. Sub-watersheds SW2 and SW7 were rated high priority, SW1 was rated low priority, and the rest were rated medium priority. The I-PCWS approach revealed that sub-watersheds SW2, SW6, and SW7 were in high-priority zone, followed by SW3, SW4, and SW8 in medium-priority zone and SW1 and SW5 in the low-priority zone. The AHP assigned the highest and lowest ranks to “Lo” and “Cc,” respectively, with consistency ratio of 8.1% and principal eigenvalue of 11.075. Results from AHP revealed sub-watershed SW2 to be the highest priority and sub-watersheds SW1 and SW5 to be the lowest priority. Out of eight prioritized sub-watersheds from three approaches, five were found to be the common priority classes, with SW2, SW6, and SW7 demanding urgent implementation of efficient soil conservation measures to prevent further degradation of the identified regions. Results from I-PCWS approach closely complied with the existing landforms within the study area, and this approach was considered more reliable and robust than the other two approaches. The methodology adopted in this study can be applied to different vulnerable, data-scarce regions to sustainably manage and conserve soil erosion through efficiently framed strategies.
相似文献22.
Saif Salim Al-Qaydi 《GeoJournal》1999,47(4):583-586
Within universities there has developed a clear theoretical convergence between Geographical Information Systems (GIS) and
geography (Antenuccl, 1991). Studies have revealed that one of the qualified departments to teach GIS within universities
is the geography department. This study focuses on: the importance of establishing GIS as a major curriculum element within
universities. In geography departments, economic geography students require a strong statistical/mathematical background to
allow them to work with major databases. They should know how to design a specific database for economic activities, such
as agriculture and manufacturing, and tertiary industry and how to relate this database to a map, so that changes can be monitored
more accurately. In any aspect of geography spatial location is a key factor and GIS allows spatial patterns to be interpreted
with great facility. Therefore it is important that students have a good knowledge not only of computers and related software
on economic geography, but also on GIS systems (Burrough, 1993). The work of geography students from the United Arab Emirates
(UAE) and other Gulf Co-operation Council (GCC) geography departments is examined to evaluate the importance of training in
GIS technology. This paper evaluates the effects of implementing GIS as a tool in teaching economic geography. At present
there are 15 geography departments in the GCC which offer economic geography. Of those 15 departments, only 3 provide GIS
courses within their curriculum, and 4 have basic equipment, although 6 additional departments are to introduce GIS in the
near future.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
23.
Danish KHAN LIANG Chao QIU Longwei Kamran MIRZA WANG Yelei Muhammad KASHIF Saif Ur REHMAN WANG Yuzhe TENG Jianbin 《《地质学报》英文版》2023,97(2):589-609
The effect of various depositional parameters including paleoclimate, paleosalinity and provenance, on the depositional mechanism of lacustrine shale is very important in reconstructing the depositional environment. The classification of shale lithofacies and the interpretation of shale depositional environment are key features used in shale oil and gas exploration and development activity. The lower 3rd member of the Eocene Shahejie Formation(Es3x shale) was sel... 相似文献
24.
Al-Bahry SN Mahmoud IY Al-Zadjali M Elshafie A Al-Harthy A Al-Alawi W 《Marine environmental research》2011,71(2):139-144
Antibiotic resistant bacteria were studied as bio-indicators of marine polluted effluents during egg-laying in green turtles. A non-invasive procedure for sampling oviductal fluid was used to test for exposure of turtles to pollution in Ras Al-Hadd, Oman, which is one of the most important nesting beaches in the world. Each sample was obtained by inserting a 15 cm sterile swab gently into the cloacal vent as the sphincter muscle is relaxed and the cloacal lining is unfolded to the outside. Forty turtles were sampled. A hundred and thirty-two species of bacteria from 7 genera were isolated. The dominant isolate was Citrobacter. Among the isolates 60.6% were multiple resistant to 15 tested antibiotics. The dominant resistance to antibiotics was ampicillin followed by streptomycin and sulphamethoxazole. Sampling oviductal fluid for resistant bacteria to antibiotics is valuable way to assess exposure to polluted effluents during feeding and migratory in turtles. Polluted effluents using bacteria as bio-indicator may influence reproductive potential in this endangered species. 相似文献
25.
Ahmed Saif Al-Mikhlafi 《Environmental Geology》2008,54(6):1145-1153
The concentration rare earth elements and Yttrium (REE + Y) were determined in coral sands from Kavaratti Island, Arabian
Sea, India. Chondrite-normalized REE + Y patterns show: (1) high REE concentration particularly light REE (LREE) enrichment;
(2) consistent negative Ce anomaly; (3) nearly chondritic Y/Ho ratios. All these features are consistent with the geochemistry
of well oxygenated seawater with significant terrestrial contribution. The seawater composition of Nd/Yb ratio inferred from
the coral record point to the dominance of LREE more than the heavy REE (HREE). The high terrestrial input rich in LREE and
property of adsorption/scavenging processes of LREE than that of HREE may be the cause. Terrigenous contributions were detected
on the basis of co-occurring trace element concentrations (Sc, Hf and Th) and Y/Ho ratio. Except for La, the REE distribution
coefficients, KD(REE)s, are between 100 and 300. KDs are high comparing to the other elements in biogenic calcite which is
attributed to detrital contamination during elemental incorporation. This study may not reflect original seawater chemistry
but it can be a good proxy to indicate proximity of corals to terrigenous input sources. 相似文献
26.
Ahmed Saif Al-Mikhlafi 《Arabian Journal of Geosciences》2010,3(2):193-205
One hundred thirty boreholes of volcanic aquifers in rural Yemen Highland Groundwaters (YHGs) were chemically investigated to assess the suitability of water for drinking. Focus is to identify inorganic constituents of significant risk to health that occur in groundwaters of this area. Results showed that a number of boreholes contain, apart from fluoride, levels of nitrate, some heavy metals, total dissolved solids, and sulfates that could pose a health risk for consumers. The lateral variations of major ions with depth varied within the same aquifer based on the dynamic equilibrium of groundwater and hydrogeological conditions. The main inorganic groundwater contaminant in volcanic YHG is fluoride which is attributed to groundwater lithology and water type. Fluoride appears high in Ca-poor groundwater and where cation exchanges of Ca for Na are dominant. High F concentration in YHG is an extension of East African fluoride-rich groundwater. Majority of tube wells show that Fe concentration exceeds WHO guideline many folds. Much of the iron and manganese in groundwaters are naturally occurring, since the source rocks are enriched in ferromagnesian minerals. NO 3 ? and Cl? concentrations that have been detected in some wells may indicate sewage and/or agricultural runoff. Elevated concentration of chemical constituents in groundwater is a sign of groundwater degradation. 相似文献
27.
Iqbaluddin Saif Ud Din Akram Javed 《Journal of the Indian Society of Remote Sensing》1997,25(3):177-186
The morphometric analysis of the surface drainage has been carried out for the four micro-watersheds of Bharatpur district, Rajasthan to quantify the drainage morphometry of the district. The morphochronology of landseape evolution has been described. Banaganga represents anomalous drainage, which causes large scale inundation during rainy season. The strain of post-collision Himalayan tectonics resulted in slope mulation in Bharatpur district which changed slope from westerly to easterly. The landform characteristics of Bharatpur district have been arehieved at the National Informatics Center, District Data Base, Bharatpur is alpha numeric mode. 相似文献
28.
29.
Saif Al-Bahry Ibrahim Mahmoud Asila Al-Harthy Issa Al-Amri 《Marine pollution bulletin》2009,58(5):720-725
Sea turtles migrate to various habitats where they can be exposed to different pollutants. Bacteria were collected from turtle eggs and their resistance to antibiotics was used as pollutant bio-indicators of contaminated effluents. Eggs were collected randomly from turtles when they were laying their eggs. A total of 90 eggs were collected and placed into sterile plastic bags (3 eggs/turtle) during June-December of 2003. The bacteria located in the eggshell, albumen and yolk were examined, and 42% of the eggs were contaminated with 10 genera of bacteria. Pseudomonas spp. were the most frequent isolates. The albumen was found to be the part of the egg to be the least contaminated by bacterial infection. Bacterial isolates tested with 14 antibiotics showed variations in resistance. Resistance to ampicillin was the highest. The presence of antibiotic resistant bacteria in eggs indicates that the green turtle populations were subjected to polluted effluents during some of their migratory routes and feeding habitats. Scanning electron microscopy revealed that Salmonella typhimurium penetrated all eggshell layers. 相似文献
30.
Alessandro Ielpi Martin R. Gibling Arden R. Bashforth Corinne Lally Michael C. Rygel Saif Al‐Silwadi 《Sedimentology》2014,61(6):1659-1700
Vegetation is a major driver of fluvial dynamics in modern rivers, but few facies models incorporate its influence. This article partially fills that gap by documenting the stratigraphy, architecture and palaeobotany of the Lower Pennsylvanian Boss Point Formation of Atlantic Canada, which contains some of the Earth's earliest accumulations of large woody debris. Braided‐fluvial systems occupied channel belts of varied scale within valleys several tens of metres deep and more than 12 km wide, and their deposits predominantly consist of sandy and gravelly bedforms with subordinate accretionary macroforms, high flow‐strength sand sheets and rippled abandonment facies. Discrete accumulations of clastic detritus and woody debris are up to 6 m thick and constitute at least 18% of the in‐channel deposits; they represent lags at the base of large and small channels, fills of minor channels and sandy macroforms that developed in central positions in the upper parts of channel fills. Sandstones with roots and other remnants of in situ vegetation demonstrate that vegetated islands were present, and the abundance of discrete channel fills suggests that the formation represents an anabranching, island‐braided sandbed river, the earliest example documented to date. Although some sphenopsid and lycopsid remains are present, most woody fragments are derived from cordaitalean trees, and the evolution of this group late in the Mississippian is inferred to have exerted a significant influence on fluvial morphodynamic patterns. The formation records a landscape in which active channel belts alternated with well‐drained floodplains colonized by dense, mature forests and local patches of pioneering, disturbance‐tolerant vegetation. Lakes and poorly drained floodplains dominated by carbonate and organic deposition, respectively, were also present. A large supply of woody debris triggered channel blockage and avulsion, and active channel margins and islands within the channel belts were initially colonized by pioneer vegetation and subsequently stabilized by large trees. A similar alternation of stable and unstable conditions is observed in modern braided rivers actively influenced by vegetation. 相似文献