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M. E. M. Walton I. Al-Maslamani N. Haddaway H. Kennedy A. Castillo E. S. Al-Ansari I. Al-Shaikh M. Abdel-Moati M. A. A. Al-Yafei L. Le Vay 《Estuaries and Coasts》2016,39(6):1709-1723
Seagrass beds form an important part of the coastal ecosystem in many parts of the world but are very sensitive to anthropogenic nutrient increases. In the last decades, stable isotopes have been used as tracers of anthropogenic nutrient sources and to distinguish these impacts from natural environmental change, as well as in the identification of food sources in isotopic food web reconstruction. Thus, it is important to establish the extent of natural variations on the stable isotope composition of seagrass, validating their ability to act as both tracers of nutrients and food sources. Around the world, depending on the seagrass species and ecosystem, values of seagrass N normally vary from 0 to 8?‰ δ15N. In this study, highly unusual seagrass N isotope values were observed on the east coast of Qatar, with significant spatial variation over a scale of a few metres, and with δ15N values ranging from +2.95 to ?12.39?‰ within a single bay during March 2012. This pattern of variation was consistent over a period of a year although there was a seasonal effect on the seagrass δ15N values. Seagrass, water column and sediment nutrient profiles were not correlated with seagrass δ15N values and neither were longer-term indicators of nutrient limitation such as seagrass biomass and height. Sediment δ15N values were correlated with Halodule uninervis δ15N values and this, together with the small spatial scale of variation, suggest that localised sediment processes may be responsible for the extreme isotopic values. Consistent differences in sediment to plant 15N discrimination between seagrass species also suggest that species-specific nutrient uptake mechanisms contribute to the observed δ15N values. This study reports some of the most extreme, negative δ15N values ever noted for seagrass (as low as ?12.4?‰) and some of the most highly spatially variable (values varied over 15.4?‰ in a relatively small area of only 655 ha). These results are widely relevant, as they demonstrate the need for adequate spatial and temporal sampling when working with N stable isotopes to identify food sources in food web studies or as tracers of anthropogenic nutrients. 相似文献
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Ali Al Maliki Ahmed Kadhim Al-lami H. M. Hussain Nadhir Al-Ansari 《Environmental Earth Sciences》2017,76(12):433
Comparison of two conventional analytical techniques such as X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS) for measuring Pb concentrations in soil samples was achieved using field and laboratory work. Seventy-three samples were collected from urban areas surrounding the large lead smelter at South Australia, as an indicator of the environment impact of smelter activity. Soil Pb concentrations were determined using hand-held XRF analyser under laboratory conditions. ICP-MS analysis on digested soils (using a microwave-assisted nitric acid digestion-extraction) was applied to validate p-XRF data. The analysis showed that Pb concentrations determined by XRF correlated with high linearity with Pb concentrations determined by ICP-MS measurements (R 2 = 0.89). Statistical test (t test) was applied to the data of both methods applied without any significant difference between the two techniques. These results indicated that ICP-MS corroborated XRF for Pb soil measurements and suggests that XRF was a reliable and quick alternative to traditional analytical methods in studies of environmental health risk assessment, allowing for much larger sampling regimes in relatively shorter times and could be applied in the field. 相似文献
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Geotectonics - Iraq is located in the northeastern part of the Arabian Plate, which is colliding with the Iranian Plate. The collision between the two plates has developed the tectonic framework of... 相似文献
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Geotectonics - The Mesopotamian Plain is part of the Mesopotamia which extends for vast area bigger than the plain. The plain is almost flat and vast lowland, which has clearly defined... 相似文献
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Geotectonics - Majority of the Iraqi Kurdistan Region is a mountainous area with relief differences that attain up to 1000 m, and locally more. The presence of dense net of rivers, streams and... 相似文献
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Mohamadi Sedigheh Sammen Saad Sh. Panahi Fatemeh Ehteram Mohammad Kisi Ozgur Mosavi Amir Ahmed Ali Najah El-Shafie Ahmed Al-Ansari Nadhir 《Natural Hazards》2020,104(1):537-579
Natural Hazards - The modelling of drought is of utmost importance for the efficient management of water resources. This article used the adaptive neuro-fuzzy interface system (ANFIS), multilayer... 相似文献
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Geotectonics - The Low Folded Zone in Iraq is an active tectonic area witnessing different evidences for Neotectonic activities, among them are the lateral growth of Jambour, Pulkhana, and Qumar... 相似文献
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Dibs Hayder Hasab Hashim Ali Mahmoud Ammar Shaker Al-Ansari Nadhir 《Geotechnical and Geological Engineering》2021,39(8):5825-5842
Geotechnical and Geological Engineering - Adopting a low spatial resolution remote sensing imagery to get an accurate estimation of Land Use Land Cover is a difficult task to perform. Image fusion... 相似文献
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Souhir Ellouze Zeineb Bensalem Mohamed Nadhir Znaidi 《Geomechanics and Geoengineering》2017,12(2):73-85
This paper addresses the installation effects of stone columns in soft soils. Focus is made on the lateral expansion of stone material using the vibro displacement and substitution techniques by means of numerical simulations. The behaviour of reinforced soil after stone column installation is investigated to show how the properties of soft soils can be improved prior to final loading. The effect of such an improvement on the prediction of reinforced soil settlement is evaluated. The axisymmetric unit cell model (UCM) served for the comparison between numerical predictions made by the Mohr-Coulomb and hardening soil constitutive laws adopted for the soft soil. An equivalent group of end bearing columns model was investigated in the axisymmetric condition to predict the settlement of reinforced soil by adopting the Mohr-Coulomb constitutive model for soft clay. The reduction of settlements predicted by the unit cell and group of columns models, due the improvement of the Young’s modulus of soft clay, were compared. It is concluded that a significant reduction of settlement is expected when the group of columns model is considered. 相似文献
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The storage capacity of reservoirs is gradually reduced due to sediment accumulation that causes changes in the area-storage capacity (ASC) curves.Establishing these curves and predicting their future change is an important issue for planners,designers and operators of dams.Many empirical and semiempirical approaches have been suggested for establishing and predicting the future changes for these curves.In this study four empirical and semi-empirical methods were evaluated and three of them were modified to be used for the prediction of changes in the ASC curves due to sedimentation,based on the existing sedimentation survey data for 11 reservoirs in the USK For evaluation,these approaches were reviewed and used to determine sedimentation depth and establishing the ASC curves for the Mosul dam reservoir (MDR),which is the biggest hydraulic structure on the River Tigris in northern Iraq.MDR started operating in 1986 with a storage capacity of 11.11 km3 and a water surface area 380 km2 at normal operation stage (330 m a.s.l.).The results obtained from these methods were evaluated using observed bathymetric survey data that had been collected in 2011 after 25 years of the operation of the dam.The evaluation results showed three methods had presented more accurate results for estimating water depth or sedimentation depth at dam site with percentage error about 1.06-3.30％.Whilst for establishing ASC curves,one method presented good agreement result with survey data.Furthermore,ASC and sedimentation depths at dam site of MDR for periods 50,75,100 and 125 years were estimated using the modified approaches and the area reduction method.The results of the modified methods provided reasonable agreement when compared with the area reduction method proposed by the U.S.Bureau of Reclamation and the agreement became better with an increase in time period. 相似文献
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