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101.
James Marcus Bishop Weizhong Chen Adel Hasan Alsaffar Hussain Mahmoud Al-Foudari 《Estuaries and Coasts》2011,34(6):1246-1254
Discharge of the Shatt Al-Arab is believed to be a dominating component of the northern Arabian Gulf’s ecology and largely
responsible for productivity of Kuwait’s fisheries. With major construction of dams on the Tigris and Euphrates Rivers in
Turkey, river discharge has been substantially reduced, and flooding essentially eliminated. We attempted to relate river
flow and shrimp landings indirectly by correlating 19 years of salinity and temperature data from Kuwait’s waters with corresponding
annual shrimp landings. For green tiger prawns (Penaeus semisulcatus), the combination of October salinities and January temperatures provided the best correlation (r = 0.67) with landings in the following shrimping season. For the combined landings of jinga and kiddi shrimps (Metapenaeus affinis and Parapenaeopsis stylifera, respectively), December salinity during season and May temperature prior to season resulted in the best correlation (r = 0.87). Landings of these two species also correlated well with spring and summer temperatures. Under normal conditions,
late winter or early spring temperatures prior to fishing season influence recruitment of the green tiger prawn, whereas December
salinities during harvest season influence the abundance of jinga–kiddi shrimps. With further reductions in the Shatt Al-Arab
discharge and the elimination of flood events, Kuwait’s shrimp landings will most likely decrease over time. 相似文献
102.
Juan Pablo Corella Adel El Amrani Javier Sigró Mario Morellón Eugenio Rico Blas Lorenzo Valero-Garcés 《Journal of Paleolimnology》2011,46(3):469-485
We present a high-resolution, multiproxy reconstruction of the depositional history of Lake Arreo, northern Spain, for the
last 60 years. We conducted sedimentological, geochemical and diatom analyses in short cores and made a detailed comparison
with regional instrumental climate data (1952–2007), limnological monitoring of the lake (1992–2008) and recent land use changes
that affect the lake catchment. Chronology is based on “floating” discontinuous varve counts and 137Cs and 14C dates. Four periods were identified in the Lake Arreo recent history: (1) prior to 1963, varved facies intercalated with
fine turbidite deposits, and diatom assemblages dominated by Cyclotella taxa indicate predominantly meromictic conditions, (2) from 1964 to 1978, permanent anoxia persisted in bottom waters, as shown
by similar facies and diatom assemblages as before, though detrital layers were coarser, (3) from 1979 to 1994, sediment delivery
to the lake increased and laminated, clastic facies were deposited, and (4) from 1995 to 2008, dominance of massive facies
and an increase in Fragilaria tenera and Achnanthes minutissima reflect relatively lower lake levels, less frequent bottom anoxia with more frequent water column mixing, similar to modern
conditions. The period 1952–1979 was a time of meromixis and varved facies deposition, and was characterized by higher rainfall
and less intense agricultural pressure in the watershed. There were two short humid periods (1992–1993 and 1996–1998) when
monitoring data show more anoxic weeks per year and relatively higher lake levels. Increased cultivation of small landholdings
in 1963, and particularly after 1979, caused a large increase in sediment delivery to the lake. The inferred lake evolution
is in agreement with monitoring data that suggest a transition from dominantly meromictic conditions prior to 1993–1994 to
a predominantly monomictic pattern of circulation since then, particularly after 2000. The synergistic effects of intensive
water extraction for irrigation and lower rainfall since 1979, and particularly since 1994, brought the long period of meromictic
conditions in Lake Arreo to an end. Water balance and sediment delivery to the lake are dominant factors that control the
limnological and mixing conditions in Lake Arreo and they must be considered in management and restoration plans. 相似文献
103.
A. I. Arbab Saadia E. Salih Sultan H. Hassan Ahmed El Agali Husam Abubaker 《Astrophysics and Space Science》2013,348(1):57-63
Using a new approach, we have obtained a formula for calculating the rotation period and radius of planets. In the ordinary gravitomagnetism the gravitational spin (S) orbit (L) coupling, $\vec{L}\cdot\vec{S}\propto L^{2}$ , while our model predicts that $\vec{L}\cdot\vec{S}\propto\frac{m}{M}L^{2}$ , where M and m are the central and orbiting masses, respectively. Hence, planets during their evolution exchange L and S until they reach a final stability at which MS∝mL, or $S\propto\frac{m^{2}}{v}$ , where v is the orbital velocity of the planet. Rotational properties of our planetary system and exoplanets are in agreement with our predictions. The radius (R) and rotational period (D) of tidally locked planet at a distance a from its star, are related by, $D^{2}\propto\sqrt{\frac{M}{m^{3}}}R^{3}$ and that $R\propto\sqrt{\frac {m}{M}}a$ . 相似文献
104.
Riaz Hossain Khan Muhammad Qumrul Hassan Mohammad Saiful Islam 《Environmental Earth Sciences》2013,69(8):2499-2512
Water quality and hydrochemistry of Shariatpur district were evaluated in terms of hydrochemical composition and some important physico-chemical parameters. The groundwater of the study area is good for drinking, domestic as well as for irrigation purposes. Among the major ions, shallow tube well waters give higher concentration of Ca2+ which ranges from 24 to 260 mg/L. The deep tubewell waters show higher concentration of Na+ which varies from 74 to 582 mg/L during dry season. Among the trace elements most of the shallow aquifer samples show higher concentration of Fe2+, Mn2+ and As. Concentration of Fe2+ varies from 0.655 to 18.8 mg/L, and Mn2+ from trace to 0.868 mg/L during dry period. Hydrochemical analyses reveal significant seasonal variation in water quality of shallow aquifer. Both the shallow aquifer and the surface water of the study area are predominantly of Ca–Mg–HCO3 type, while the deep aquifer water is mainly of Na–K–Cl–SO4 type with slight inclination to Ca–Mg–HCO3 type. The study area is suitable for groundwater development if comprehensive and holistic approaches towards water resource management are taken into consideration. 相似文献
105.
Eslam A. Al-Hogaraty Hassan K. Garamoon Farouk El-Baz Reinhard Zölitz-Möller Mohamed A. Abdel Moati 《Arabian Journal of Geosciences》2013,6(11):4093-4107
Wadi Wurayah area is one of the major wadis originating and running on the Oman Mountains and drains into the Oman Gulf. These wadis in general and Wadi Wurayah in particular are characterized with a rich diversity of rare and mountainous and freshwater habitats and species. These wadis contain unequal, representative, and sensitive areas of the dry lands ecosystem with natural, outstanding landscapes and cultural heritage, while the socioeconomic situation indicates that it has enough socioeconomic infrastructures to develop new alternatives ecologically and economically sustainable. As most of the United Arab Emirates and the region, the study area is undergoing dramatic changes linked to economic diversification and promotion of tourism. Established under the UNESCO’s Man and the Biosphere Program, Wurayah Biosphere Reserve represents protected areas intended to demonstrate well-balanced relationship between conservation of biodiversity and an appropriate local development. The main objectives of this study are to develop an environmental information system to understand the dynamics of human activities associated to land use in the study area, highlight the threats to the environment, educate people about the basic environmental issues and positive traditional practices, and promote tourism. Based on the gained results, the concept of biosphere reserve as a model is to implement ideas of sustainable land use in practice. 相似文献
106.
Hassan Eltom Mohammed Makkawi Osman Abdullatif Khalid Alramadan 《Arabian Journal of Geosciences》2013,6(11):4323-4335
Subsurface models of hydrocarbon reservoirs are coarse and of low resolution when compared with the actual geologic characteristics. Therefore, the understanding of the three-dimensional architecture of reservoir units is often incomplete. Outcrop analogues are commonly used to understand the spatial continuity of reservoir units. In this study, a Late Jurassic outcrop analogue for the Arab-D reservoir of central Saudi Arabia was used to build a high-resolution model that captures fine geologic details. Subsurface reservoir lithofacies were matched with those from the studied outcrop, and porosity values derived from published core and well log data from the Ain Dar, Uthmanyah, and Shudgum areas of the Ghawar Field, eastern Saudi Arabia, were then applied to the equivalent lithofacies in the outcrop. Maximum, minimum, and average subsurface porosity for each lithofacies were distributed in the facies model using a geostatistical algorithm to produce nine porosity models for the field data. Several realisations were run to visualise the variability in each model and to quantitatively measure the uncertainty associated with the models. The results indicated that potential reservoir zones were associated with grainstone, packstone, and some wackestone layers. Semivariogram analysis of the lithofacies showed good continuity in the N-S direction and less continuity in the E-W direction. The high-resolution lithofacies models detected permeability barriers and isolated low porosity bodies within the potential reservoir zones. This model revealed the porosity distribution in areas smaller than one cell in the subsurface model and highlighted the uncertainty associated with several aspects of the model. 相似文献
107.
Jaloul Bejaoui Mohamed Samaali Souad Baccouche Nafaa Regugui Mohamed Fethi Ben Hamouda Zohra Azzouz Adel Trabelsi Salah Bouhlel Boulamia Salim 《Arabian Journal of Geosciences》2013,6(7):2685-2689
In this study we investigate the radiological hazard of naturally occurring radioactive material in Tunisian and Algerian phosphorite deposits. Eight samples of phosphorite were collected from the phosphorite mines. The Tunisian and Algerian phosphorites occur in the Late Paleocene and Lower Eocene (Ypresian-Lutetian) in age (Béji Sassi 1984 and Zaïer 1999). Activity concentrations in all the samples were measured by alpha spectrometry and gamma spectrometry. Alpha spectrometry analyses show that the specific activity values of 238U, 234U and 235U in the samples of Tunisian phosphorite were 327?±?7 (321–327), 326?±?6 (325–331) and 14.50?±?0.72 (13.90–15.57) Bq kg?1, respectively. Specific activity measured by gamma spectrometry in the samples of the Tunisian and Algerian phosphorite shows a small difference. Specific activity levels of 40K, 226Ra, 232Th, 235U and 238U in the phosphorite samples from Tunisia were, respectively, 71.10?±?3.80, 391.54?±?9.39, 60.38?±?3.74, 12.72?±?0.54 and 527.42?±?49.57 Bq kg?1 and Algeria were 15.72?±?1.73, 989.65?±?12.52, 12.08?±?1.20, 47.50?±?1.52 and 1,148.78?±?7.30 Bq kg?1, respectively. The measured value of specific activity of 232Th and 40K in the Tunisian phosphorite samples is relatively higher than that found in the samples of Algerian phosphorite. The measured activity of uranium (238U) in the Tunisian phosphorite (527?±?49) Bq kg?1 is lower than in Algerian phosphorite. The measured activity of 238U in the Tunisian phosphorite samples was (527–1,315?±?65) 238U Bq kg?1 which is higher than its maximum background value of 110 Bq kg?1 in soils of the various countries of the world (Tufail et al. Radiat Meas 41:443–451, 2006). Different geological origins of phosphorites deposits are the main reason for the large spread in worldwide specific activities. The obtained results of uranium concentrations in phosphorites of different types (Algerian and Tunisian) demonstrate that the uranium concentrations are mainly governed by the phosphatic material. The present study reveals that phosphorite deposits contain natural radioactivity higher than background level. 相似文献
108.
One hundred forty-eight groundwater samples were collected from the lower part of Wadi Siham catchment area for hydrogeochemical investigations to understand the hydrogeochemical processes affecting groundwater chemistry and their relation with groundwater quality. Groundwater in the study area is abstracted from different aquifers. The study area is characterized by arid climate and extremely high relative humidity. The results indicate that groundwater in the study area is fresh to brackish in nature. The abundance of the major ions is as follows: Na+1?>?Ca+2?>?Mg+2?≥?K+1 and Cl?1?>?HCO 3 ?1 ?>?SO 4 ?2 ?>?NO 3 ?1 . Various graphical and ionic ration plots, statistical analyses, and saturation indices calculations have been carried out using chemical data to deduce a hydrochemical evaluation of the study area. The prevailing hydrogeochemical processes operating in the study area are dissolution, mixing, evaporation, ion exchange, and weathering of silicate minerals in the eastern part (recharge areas). The reverse ion exchange and seawater intrusion control the groundwater chemistry along the Red Sea coast areas and few parts of the study area. Deterioration in groundwater quality from anthropogenic activities has resulted from saltwater intrusion along the coastal areas due to groundwater overpumping and extensive use of fertilizers and infiltration of sewage water. Salinity and nitrate contamination are the two major problems in the area, which is alarming considering the use of this water for drinking. 相似文献
109.
Muhammad Irfan Aziz Akbar Mubashir Aziz Ammad Hassan Khan 《Geotechnical and Geological Engineering》2013,31(2):729-738
Rapid urbanization and expansion of metropolitans in the developing world is pressing the need of tall structures with multiple basements. In several such projects, open land is available around excavation site and unsupported deep excavations by maintaining appropriate side slopes offer economical solution. In this research, subsoil stratigraphy of Lahore district was established to be comprising of a top clay stratum 1.5–8 m thick, followed by a sand layer. Considering subsoil data from several geotechnical investigation reports, the effect of four key parameters viz., cohesion of clay layer, friction angle of sand layer, thickness of clay layer at the top and slope inclination of underlying sand layer on safety factor of open excavations was studied. Six hundred twenty-five slope stability analyses were conducted by considering different geometries and soil properties. Based on the results of these analyses, a regression model was suggested to estimate safety factor of open excavations in similar stratigraphy which would be useful in feasibility studies and preliminary design of deep excavations. It was established that the clay layer cohesion was the most dominant contributor to safety factor. 相似文献
110.
This paper presents a new family of interior solutions of Einstein–Maxwell field equations in general relativity for a static spherically symmetric distribution of a charged perfect fluid with a particular form of charge distribution. This solution gives us wide range of parameter, K, for which the solution is well behaved hence, suitable for modeling of superdense star. For this solution the gravitational mass of a star is maximized with all degree of suitability by assuming the surface density equal to normal nuclear density, ρ nm=2.5×1017 kg?m?3. By this model we obtain the mass of the Crab pulsar, M Crab, 1.36M ⊙ and radius 13.21 km, constraining the moment of inertia >?1.61×1038 kg?m2 for the conservative estimate of Crab nebula mass 2M ⊙. And M Crab=1.96M ⊙ with radius R Crab=14.38 km constraining the moment of inertia >?3.04×1038 kg?m2 for the newest estimate of Crab nebula mass, 4.6M ⊙. These results are quite well in agreement with the possible values of mass and radius of Crab pulsar. Besides this, our model yields moments of inertia for PSR J0737-3039A and PSR J0737-3039B, I A =1.4285×1038 kg?m2 and I B =1.3647×1038 kg?m2 respectively. It has been observed that under well behaved conditions this class of solutions gives us the overall maximum gravitational mass of super dense object, M G(max)=4.7487M ⊙ with radius $R_{M_{\max}}=15.24~\mathrm{km}$ , surface redshift 0.9878, charge 7.47×1020 C, and central density 4.31ρ nm. 相似文献