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941.
The concentrations of six heavy metals (Fe, Mn, Ni, Cu, Pb and Zn) were studied in 11 hard and 4 soft common coral species
collected from Hurghada, Wadi Al-Gemal and Gola’an along the Red Sea coast to assess the differential abilities of corals
to concentrate and assimilate the heavy metals inside soft coral tissues and hard coral skeletons. These results reveal the
order of Fe > Zn > Ni > Pb ≥ Mn > Cu. Fe recorded significant high concentrations in mushroom (funnel) forms of the soft corals
at the different sites; 125.19, 101.71 and 90.44 ppm at Gola’an, Hurghada and Wadi Al-Gemal, respectively. The soft coral
species recorded the highest average concentration of Mn, Ni, Cu and Zn than the hard corals, which were 13.22, 16.05, 13.08
and 148.17 ppm, respectively. Generally, soft corals show higher metal concentrations than the hard ones; moreover, Hurghada
recorded a higher trend of metal concentrations in soft and hard corals than the other sites. The study concluded that many
biological and local environmental factors influenced the metal occurrences and uptakes in both coral forms such as, the exposed
surface area for metal uptake, turbidity, overlying mucus thickness and the ability of metals to substitute inside the crystal
lattice of the hard corals. 相似文献
942.
Fatma Aloulou Monem Kallel Mohamed Dammak Boubaker Elleuch Alain Saliot 《Environmental Earth Sciences》2010,61(1):1-10
We investigated the mineral composition and trace element contents of dustfall with different deposited phases at the Minqin
Oasis, in China’s Hexi Corridor. The contents of elements such as Pb, Cd, Cu, As, Sb, Se, Rb, Cs, and Ba (believed to be of
anthropogenic origin) indicated that the significance of human impacts on dust emissions increased from 1970s to the early
2000s. However, variations in the content of elements including Sc, Mn, Na, Cr, V, Eu, Ce, Nb, Zr, La, and Ce (believed to
originate from natural processes such as physical and chemical weathering) show no obvious changes in the major potential
dust source areas (PSAs) in this region. In addition, analysis of the assemblage of trace elements in dustfall indicated that
the elements assumed to originate from anthropogenic and natural processes appear to be intertwined, leading to difficulties
and uncertainties in identifying the PSAs and evaluating the significance of human impacts on dust emissions. Comparisons
of the element contents of dustfall collected in Beijing and Minqin with similar data for Beijing show that under different
conditions some differences in ranges are permitted; the contents of most trace elements were similar even though the dustfall
in the two areas came from different sources. These results suggest that before attempting to identify major PSAs, researchers
should perform an integrated analysis that includes the mineral, elemental, geomorphological, vegetation cover, climatic conditions,
and other characteristics of the regions being studied. 相似文献
943.
Modeling in situ benzene bioremediation in the contaminated Liwa aquifer (UAE) using the slow-release oxygen source technique 总被引:5,自引:4,他引:1
Mohamed Mostafa Ahmed Mohamed Nawal E. Saleh Mohsen M. Sherif 《Environmental Earth Sciences》2010,61(7):1385-1399
Dissolved benzene was detected in the shallow unconfined Liwa aquifer, UAE, which represents the main freshwater source for
the nearby residence Bu Hasa camp area. The main source of this contamination is believed to be the rejected water released
from Bu Hasa liquid recovery plant. In this paper, a finite element model (METABIOTRANS) is used to simulate the fate and
transport of the dissolved benzene plume in Liwa aquifer. Different remediation scenarios were simulated in which the slow-release
oxygen source (SOS) technique is utilized to minimize benzene concentrations at the nearest camp supply wells downstream of
the contamination zone. Results of the remediation scenarios show that the highest biodegradation rates occur when the oxygen
source is placed near the plume center; where higher benzene concentrations exist. The nearest oxygen release source to the
contamination zone caused higher stimulation to bacterial growth than further down-gradient oxygen sources. It also exhibited
longer resident time of oxygen in the aquifer; and therefore, yielded higher reductions in benzene concentrations. However,
using one central SOS proved to be insufficient as contaminant escaped laterally. Additional four transverse oxygen sources
were necessary to capture benzene that laterally spread away from the contamination zone. These lateral SOSs were essential
to reduce benzene concentrations at the supply wells that are located at the plume fringes. Finally, it was found that increasing
oxygen release from one source did not always improve remediation; and that using several SOSs with lower release rates could
be a more practical approach to enhance benzene biodegradation in the aquifer. 相似文献
944.
Ahmed A. Melegy Veronika Cvečková Katarína Krčmová Stanislav Rapant 《Environmental Earth Sciences》2010,61(2):429-439
As much as 24 soil samples and 6 stream sediments from the River Nile were studied in El-Tabbin region (Great Cairo, Egypt). Twelve chemicals, potentially toxic elements posing potential environmental risk, were the object of concern in this study. Mean contents of analysed elements (in mg kg?1) in soils and the River Nile stream sediments were the following: Ass 3.6/Asss 1.5, Cds 0.33/Cdss 0.12, Crs 87.7/Crss 141.5, Cus 40.3/Cuss 43.8, Hgs 0.03/Hgss 0.13, Pbs 33.3/Pbss 20.2, Zns 150/Znss 109, Ses 0.24/Sess 0.05, Nis 37.2/Niss 48, Sbs 1.25/Sbss 1, Bas 892/Bass 431, Vs 103.3/Vss 167.8. Furthermore, geochemical background values were derived for soil and stream sediment samples. The values are as follows (in mg kg?1): Ass 1.33/Asss 1, Cds 0.48/Cdss 0.05, Crs 54.7/Crss 106.5, Cus 23.8/Cuss 23, Hgs 0.025/Hgss 0.095, Pbs 15.3/Pbss 13.5, Zns 70/Znss 55, Ses 0.13/Sess 0.05, Nis 19.5/Niss 32.5, Sbs 1/Sbss 1, Bas 266/Bass 275, Vs 50.7/Vss 119. More than two-thirds of soil and sediment samples exceeded established (based on literature data) risk limit values for non-polluted environment. Based on environmental risk assessment for potentially toxic elements in soils and sediments in more than 45% of total area disturbed environment (I ER = 1–3) was documented and more than 13% of territory was characterised with highly disturbed environment (I ER > 3). 相似文献
945.
Induced recharge at new dam sites—Sana’a Basin, Yemen 总被引:2,自引:0,他引:2
Ahmed Mohamed Alderwish 《Arabian Journal of Geosciences》2010,3(3):283-293
In approaching the task of developing recharge estimates for dam sites, several constraints are apparent, including the scarcity of site-specific data for the selected new sites and the availability of simple yet robust analysis techniques. Combined, these constraints require an approach which involves best use of available data, adoption of relatively simple analytical approximations of reality, and the adoption of several key assumptions. In arid country with limited resources, two simple techniques have been used for recharge estimation: (1) a simple water balance model in spreadsheet and (2) a more refined Darcian approach involving an analytical approximation of a flow-net solution. By applying the two models at three new dam sites, the amount of recharge rates calculated over the period 2007–2026 was close. This is because, despite Darcian approach that should have affected the recharge rate as other parameters were introduced in the calculation of q t , e.g., groundwater table mound, reservoir water height, etc., the results show general agreement between the two methods which seem to validate the assumptions made in both methods. A general conclusion of this comparison is that the hydraulic conductivity (K) is the main determining factor in recharge calculations in these situations. The water balance model was used to estimate recharge at Wadi Bahaman, under gravity and cascade dams’ scenarios. Using gravity dam at Wadi Bahaman for groundwater recharge proved not suitable based on the relatively small predicted runoff from a small catchment area and geological concerns in the abutment areas. Instead, a series of three low check dams (2 to 4 m high) was proposed. These check dams will slow down the runoff flow, form small reservoirs, and enhance recharge along the valley, without requiring expensive foundations. Estimated groundwater recharge under cascade dams (141,407 m3/year) is greater than recharge estimated for gravity dam (103,853 m3/year) by at least 36%. 相似文献
946.
Manifestation of remote sensing data and GIS on landslide hazard analysis using spatial-based statistical models 总被引:15,自引:10,他引:5
This paper presents landslide hazard analysis at Cameron area, Malaysia, using a geographic information system (GIS) and remote sensing data. Landslide locations were identified from interpretation of aerial photographs and field surveys. Topographical and geological data and satellite images were collected, processed, and constructed into a spatial database using GIS and image processing. The factors chosen that influence landslide occurrence are topographic slope, topographic aspect, topographic curvature, and distance to rivers, all from the topographic database; lithology and distance to faults were taken from the geologic database; land cover from TM satellite image; the vegetation index value was taken from Landsat images; and precipitation distribution from meteorological data. Landslide hazard area was analyzed and mapped using the landslide occurrence factors by frequency ratio and bivariate logistic regression models. The results of the analysis were verified using the landslide location data and compared with the probabilistic models. The validation results showed that the frequency ratio model (accuracy is 89.25%) is better in prediction of landslide than bivariate logistic regression (accuracy is 85.73%) model. 相似文献
947.
Ahmed I. Rushdi Khalid F. Al-Mutlaq Bernd R. T. Simoneit Adnan Al-Azri Ali A. Z. DouAbul Sheikha Al-Zarban Faiza Al-Yamani 《Arabian Journal of Geosciences》2010,3(2):113-131
River runoff and atmospheric fallout (dust and air particulate matter) are major input sources of natural and anthropogenic
terrestrial organic and inorganic components to the Arabian seas. In this study, we report on the various lipid tracer compounds
that might be transported to the Arabian Gulf by rivers, dust, and air particulate matter. These are based on geochemical
analysis of sediment, dust, and particulate samples collected from Iraq, Kuwait, and Saudi Arabia. The samples were extracted
with a dichloromethane/methanol mixture and analyzed by gas chromatography-mass spectrometry. The extractable organic compounds
(lipids) in the samples include n-alkanes, n-alkanoic acids, n-alkanols, methyl n-alkanoates, steroids, triterpenoids, carbohydrates, and petroleum hydrocarbons. The steroids and triterpenoids were major
components in river and wetland samples. The major sources of these lipids were from natural vegetation, microbial (plankton
and bacteria) residues in the sediments, sand, and soils, with some contribution from anthropogenic sources. Accordingly,
these sources could be major inputs to the Arabian seas besides the autochthonous marine products. Future studies of the organic
and inorganic biogeochemistry on river, dust, and coastal areas are needed to characterize the various regional sources, transformation,
and diagenetic processes of the organic matter en route to the marine environment. 相似文献
948.
Ismail Chenini Abdallah Ben Mammou Mohamed Moncef Turki Eric Mercier 《Arabian Journal of Geosciences》2010,3(1):41-47
The knowledge of piezometric data is of vast interest in many applications, such as assessing groundwater flow direction and identifying recharge zone of the aquifer. In this paper, a methodology is presented as a complementary approach to characterize multilayered aquifer system structure and functioning using piezometric data and the cartography of the hydraulic charge difference. The methodology is presented to gradually discriminate the aquifer system levels and to evaluate the spatial distribution of hydraulic heads. The hydraulic charge difference mapping permits to track spatial evolution of the impermeable levels. The methodology has been applied over the Maknassy basin aquifer system, located in central Tunisia. The obtained results, showing the multilayered aquifer structure, are validated using hydrochemical approach and piezometric data not considered in the reasoning. 相似文献
949.
Smail MOSTEFAOUI Ernst ZINNER Peter HOPPE Frank J. STADERMANN Ahmed El GORESY 《Meteoritics & planetary science》2005,40(5):721-743
Abstract— We performed in situ morphological and isotopic studies of graphite in the primitive chondrites Khohar (L3), Mezö‐Madaras (L3), Inman (L3), Grady (H3), Acfer 182 (CH3), Acfer 207 (CH3), Acfer 214 (CH3), and St. Marks (EH5). Various graphite morphologies were identified, including book, veins, fibrous, fine‐grained, spherulitic, and granular graphite, and cliftonite. SIMS measurements of H, C, N, and O isotopic compositions of the graphites revealed large variations in the isotopic ratios of these four elements. The δ15N and δ13C values show significant variations among the different graphite types without displaying any strict correlation between the isotopic composition and morphology. In the Khohar vein graphites, large 15N excesses are found, with δ15Nmax ~+955‰, confirming previous results. Excesses in 15N are also detected in fine‐grained graphites in chondrites of the CH clan, Acfer 182, Acfer 207, and Acfer 214, with δ15N ranging up to +440‰. The 15N excesses are attributed to ion‐molecule reactions at low temperatures in the interstellar molecular cloud (IMC) from which the solar system formed, though the largest excesses seem to be incompatible with the results of some recent calculation. Significant variations in the carbon isotopic ratios are detected between graphite from different chondrite groups, with a tendency for a systematic increase in δ13C from ordinary to enstatite to carbonaceous chondrites. These variations are interpreted as being due to small‐ and large‐scale carbon isotopic variations in the solar nebula. 相似文献
950.
Ashraf Hamdy Mostafa K. Ahmed Mohamad Radwan Fawzy Ahmed Abd El-Salam 《Earth, Moon, and Planets》2003,93(4):261-273
The objective of the present work is to develope explicit analytical expressions for the small amplitude orbits of the infinitesimal
mass about the equilibrium points in the elliptic restricted three body problem. To handle this dynamical problem, the Hamiltonian
for the elliptic problem is formed with the true anomaly and then with the eccentric anomaly as independent variables. The
origin is then transformed to a fixed point and the Hamiltonian is developed up to O(4) in the eccentricity, e, (which plays the role of the small parameter of the problem) of the primaries. The integration of the model problem under
consideration is undertaken by means of a perturbation technique based on Lie series developments, which leads to the solution
of the canonical equations of motion. 相似文献