Distribution and characteristics of PAHs in sediments from the Mediterranean coastal environment of Egypt   总被引：3，自引：0，他引：3  

Assem O. Barakat  Alaa Mostafa  Stephen T. Sweet 《Marine pollution bulletin》2011,62(9):1969-1978

To assess the contamination of polycyclic aromatic hydrocarbons (PAHs) in the Mediterranean coastal environment of Egypt, 26 sediment samples from the coastline, harbours, estuaries and coastal lakes were collected and analyzed. The sediment PAH concentrations of thirty-nine 2-6 ring PAHs ranged from 13.5 to 22,600 ng/g. PAH profiles varied according to the nature of the site and its proximity to sources. Industrialized and urbanized region showed high level of PAHs contamination. In general, the contamination levels of PAHs were similar to those observed in contaminated and slightly contaminated sediments of the Mediterranean Sea. Molecular indices based on ratios of selected PAH concentrations were used to differentiate PAHs from pyrogenic and petrogenic and mixed origins. Good correlations were observed between the petrogenic index, MP/P, A-PAHs/P-PAHs and HMW/LMW. Finally, PAH levels in sediments were compared with Sediments Quality Guidelines (ERM-ERL) for evaluation of probable toxic effects on organism.  相似文献   

Efficiency of standardized image processing in the fragmentation prediction in the case of Sungun open-pit mine     

Mostafa Badroddin  Ezzeddin Bakhtavar  Hasan Khoshrou  Bahram Rezaei 《Arabian Journal of Geosciences》2013,6(9):3319-3329

The paper proposes a standardized image-processing procedure with the use of sieve analysis results for calibration which is utilized to measure the size distribution of fragmentation at Sungun mine. Through this procedure, a number of 19 bench blasting in various levels have been initially selected as the target of the study for each, multiple photos were taken immediately after blast from suitable perspectives and locations of the muckpiles surfaces. The number of image sampling was chosen adequately high to achieve further reliability of the whole photography procedure. Then fragments of each muckpile were separately mixed by a loader, where another image sampling from these new muckpiles, bucket of loaders, and haulage trucks was performed. For the purpose of sieve analysis, seven sieves with the mesh sizes between 1.27 cm (0.5 in) and 25.4 cm (10 in) were designed, manufactured, and then installed at Sungun semi-industrial laboratory. Additionally, three mass samples of the mixed fragments were randomly chosen among the 19 muckpiles for sieving. During image analysis stage, “sieve shift” and “mass power” factors, required to obtain standardized size distribution, were precisely assigned when the results obtained by the image analysis software was in accordance with the sieving results. In order to validate the reliability of the image processing, a comparative analysis of the achieved results was made with the results of the original Kuz–Ram model [Cunningham (1983) The Kuz–Ram model for prediction of fragmentation from blasting. In: Proceedings of the first international symposium on rock fragmentation by blasting, Lulea, Sweden, pp 439–454]. Finally, the image-processing procedure was found to be more efficient, with results close-matched to the real results of the sieve analysis.  相似文献   

Robust reconstruction of aliased data using autoregressive spectral estimates     

Mostafa Naghizadeh  Mauricio D. Sacchi 《Geophysical Prospecting》2010,58(6):1049-1062

Autoregressive modeling is used to estimate the spectrum of aliased data. A region of spectral support is determined by identifying the location of peaks in the estimated spatial spectrum of the data. This information is used to pose a Fourier reconstruction problem that inverts for a few dominant wavenumbers that are required to model the data. Synthetic and real data examples are used to illustrate the method. In particular, we show that the proposed method can accurately reconstruct aliased data and data with gaps.  相似文献   

Assessment of persistent organochlorine pollutants in sediments from Lake Manzala, Egypt   总被引：2，自引：0，他引：2  

Barakat AO  Mostafa A  Wade TL  Sweet ST  El Sayed NB 《Marine pollution bulletin》2012,64(8):1713-1720

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were determined in surface and core sediment samples collected from Manzala Lake, the largest of the Egyptian coastal lakes. Total concentrations of OCPs and ∑7 PCBs (ICES) in sediments ranged from 0.63 to 31.31 ng/g and 0.26 to 31.27 ng/g, respectively. Geographical distribution indicates that levels of contaminants were significantly higher in areas which are mainly influenced by municipal discharge, indicating significant sources of these compounds in urbanised areas. The composition of DDT and its metabolites suggest old input of DDT. The levels of contaminants in Manzala Lake were similar or lower than those observed in comparable areas worldwide. The profiles of ∑OCPs and ∑PCBs in a core from a site heavily impacted by sewage discharge have highest concentrations in the surface core section indicating recent inputs. Assessment of ecotoxicological risk indicated that sediments in two sites were likely to pose potential biological adverse impact.  相似文献   

A roughness-corrected index of relative bed stability for regional stream surveys   总被引：2，自引：1，他引：1  

Philip R. Kaufmann  John M. Faustini  David P. Larsen  Mostafa A. Shirazi   《Geomorphology》2008,99(1-4):150-170

Quantitative regional assessments of streambed sedimentation and its likely causes are hampered because field investigations typically lack the requisite sample size, measurements, or precision for sound geomorphic and statistical interpretation. We adapted an index of relative bed stability (RBS) for data calculated from a national stream survey field protocol to enable general evaluation of bed stability and anthropogenic sedimentation in synoptic ecological surveys. RBS is the ratio of bed surface geometric mean particle diameter (D_gm) divided by estimated critical diameter (D_cbf) at bankfull flow, based on a modified Shield's criterion for incipient motion. Application of RBS to adequately depict bed stability in complex natural streams, however, has been limited because typical calculations of RBS do not explicitly account for reductions in bed shear stress that result from channel form roughness. We modified the index (RBS) to incorporate the reduction in bed shear stress available for sediment transport that results from the hydraulic resistance of large wood and longitudinal irregularities in channel dimensions (“form roughness”). Based on dimensional analysis, we derived an adjustment to bankfull shear stress by multiplying the bankfull hydraulic radius (R_bf) by the one-third power of the ratio of particle-derived resistance to total hydraulic resistance (C_p/C_t)^1/3, where both resistances are empirically based calculations. We computed C_p using a Keulegan equation relating resistance to relative submergence of bed particles. We then derived an empirical equation to predict reach-scale hydraulic resistance C_t from thalweg mean depth, thalweg mean residual depth, and large wood volume based on field dye transit studies, in which total hydraulic resistance C_t was measured over a wide range of natural stream channel complexity, including manipulation of large wood volumes. We tested our estimates of C_t and RBS by applying them to data from a summer low flow probability sample of 104 wadeable stream reaches in the Coastal Ecoregion of Oregon and Washington, USA. Stream discharges calculated using these C_t estimates compared favorably with velocity–area measurements of discharge during summer low flow, and with the range of 1 to 2-year recurrence floods (scaled by drainage area) at U.S.Geological Survey gauged sites in the same region. Log [RBS] ranged from − 4.2 to + 0.98 in the survey region. D_gm ranged from silt to boulders, while estimated bankfull critical diameter, D_cbf, ranged from very fine gravel to large boulders. The median value of D_cbf (adjusted for form roughness influences) averaged 40% (inter quartile range 28 to 59%) of the unadjusted estimate D_cbf. Log[RBS] was consistently negatively related to human disturbances likely to produce excess sediment inputs or hydrologic alteration. Log [RBS] ranged from − 1.9 to + 0.5 in the streams within the lower quartile of human disturbance in their basin and riparian areas and was substantially lower (− 4.2 to − 1.1) in streams within the upper quartile of human disturbance. The synoptic survey methods and designs we used appear adequate to evaluate regional patterns in bed stability and sedimentation and their general relationship to human disturbances. Although the RBS concept also shows promise for evaluating sediment and bed stability in individual streams, our approach is relatively coarse, so site-specific assessments using these rapid field methods might prudently be confined to identifying severe cases of sedimentation or channel alteration. Greater confidence to discern subtle differences in site-specific assessments could be gained by calculating RBS using more precise field measurements of channel slope, bed particle size and bankfull dimensions, and by refining our adjustments for energy loss from channel form roughness.  相似文献   

Using Na/K Ratios to Identify the Potential Impacts of Sewage Effluent on Groundwater Quality in Sohag,Egypt          下载免费PDF全文

Mostafa Redwan  Ahmed A. Abdel Moneim 《Ground Water Monitoring & Remediation》2016,36(4):62-70

Improper disposal of wastewater is an important source of groundwater contamination, as it poses serious threats to the environment and human health. In this case study, 18 groundwater and 3 sewage effluent samples were collected from the area adjacent to a wastewater treatment plant in Sohag, Egypt. These samples were subjected to detailed chemical and bacteriological analyses to quantify the potential impact of sewage effluent on the groundwater quality using geochemical indicators. The groundwater aquifer in the study area is represented by the highly permeable Qena Sands that are composed of sands and gravels. The bacteriological analyses indicated the presence of fecal coliform in groundwater at wells nearby the wastewater ponds and farm lands. NH₄ concentration of the contaminated groundwater samples ranged from 0.36 to 5.70 mg/L (78% of the samples > 1.20 mg/L) and the NH₄ in the non‐impacted samples ranged from 0.40 to 2.23 mg/L (22% > 1.20 mg/L). Variations in NH₄ concentrations are due to the transformation processes occurring in the aquifer. The groundwater samples were categorized based on the Na/K ratio into two classes. The first class shows the Na/K ratios vary from 2.52 to 12.19 for sewage effluent and contaminated samples, while in the second class they range from 12.85 to 31.60 for non‐impacted samples. As a result, the Na/K ratio in combination with other chemical and microbiological indicators is a useful screening tool for assessing possible sewage influence on shallow groundwater from shallow wells.  相似文献   

Discovery of a broad iron line in the black hole candidate Swift J1753.5−0127, and the disc emission in the low/hard state revisited     

Beike Hiemstra  Paolo Soleri  Mariano Méndez  Tomaso Belloni  Reham Mostafa  Rudy Wijnands 《Monthly notices of the Royal Astronomical Society》2009,394(4):2080-2088

We analysed simultaneous archival XMM–Newton and Rossi X-ray Timing Explorer observations of the X-ray binary and black hole candidate Swift J  1753.5−0127  . In a previous analysis of the same data, a soft thermal component was found in the X-ray spectrum, and the presence of an accretion disc extending close to the innermost stable circular orbit was proposed. This is in contrast with the standard picture in which the accretion disc is truncated at large radii in the low/hard state. We tested a number of spectral models and found that several of them fit the observed spectra without the need of a soft disc-like component. This result implies that the classical paradigm of a truncated accretion disc in the low/hard state cannot be ruled out by these data. We further discovered a broad iron emission line between 6 and 7 keV in these data. From fits to the line profile we found an inner disc radius that ranges between ∼6 and 16 gravitational radii, which can be in fact much larger, up to ∼250 gravitational radii, depending on the model used to fit the continuum and the line. We discuss the implications of these results in the context of a fully or partially truncated accretion disc.  相似文献   

A new method for processing of low-grade monazite concentrates     

E. H. Borai  Mostafa M. Hamed  A. M. Shahr El-Din 《Journal of the Geological Society of India》2017,89(5):600-604

It is very tedious to separate thorium and rare earth elements from their accompanying constituents in low-grade monazite (concentrate 50%) containing large amount of phosphorus species, illiminite, silica and zircon. Therefore, trials have been suggested to develop a new procedure to enhance the separation process of the light lanthanides from low-grade Egyptian monazite concentrates. The first point is focused on the removal of phosphorus species from the digested low-grade monazite with sulfuric acid in order to get more convenient separation. The removal was accomplished by extractive washing of sulfate paste with different alcohols. The results showed that the extractive removal of phosphorus species was not effective due to the complex nature of low-grade monazite concentrate. The second point is focused on the enhancement of separation process of uranium, thorium and rare earth elements by new ratio of sulfuric acid and develops the classical separation process. By this modified procedure, the overall results obtained revealed that the unleached residue contains mainly Si, Fe, Zr, and Ti while the elements of main consideration such as uranium, thorium and light rare earth elements were completely leached. Thorium and light rare earth elements (LREEs) were directly separated as white precipitate while the uranium was moved to the green acid solution with most of phosphorus species. This throws light on the possibility of separation of thorium and light rare earth elements from uranium, which represents a novel method.  相似文献   

A stochastic model of soil erosion     

Mostafa E. Mossaad  Tien H. Wu 《国际地质力学数值与分析法杂志》1984,8(3):201-224

The erosion model computes the rill and inter-rill flow over a surface with random roughness, and the erosion caused by this flow. The measured roughness of a surface is analysed and used to generate random surfaces for the simulation process. Computations are carried out over a number of time intervals; the steady state condition is assumed for each interval. Changes in the surface geometry due to erosion during an interval are used to revise the surface for the subsequent interval. The model includes simplified mechanisms to simulate ponding, deposition and failure of side slopes of rills.  相似文献   

Monitoring and analysing the Emirate of Dubai’s land use/land cover changes: an integrated,low-cost remote sensing approach     

Samy Ismail Elmahdy  Mohamed Mostafa Mohamed 《International Journal of Digital Earth》2018,11(11):1132-1150

This study presents a modified low-cost approach, which integrates the spectral angle mapper and image difference algorithms in order to enhance classification maps for the purpose of monitoring and analysing land use/land cover change between 2000 and 2015 for the Emirate of Dubai. The approach was modified by collecting 320 training samples from QuickBird images with a spatial resolution of 0.6 m, as well as carrying out field observations, followed by the application of a 3?×?3 Soble filter, sieving classes, majority/minority analysis, and clump classes of the obtained classification maps. The accuracy assessment showed that the targeted 2000, 2005, 2010 and 2015 classification maps have 88.1252%, 89.0699%, 90.1225% and 96.0965% accuracy, respectively. The results showed that the built-up area increased by 233.721?km² (5.81%) between 2000 and 2005 and continues to increase even up and till the present time. The assessment of changes in the periods 2000–2005 and 2010–2015 confirmed that net vegetation area losses were more pronounced from 2000 to 2005 than from 2010 to 2015, dropping from 47,618 to 40,820?km², respectively. This study is aimed to assist urban planners and decision-makers, as well as research institutes.  相似文献