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排序方式: 共有111条查询结果,搜索用时 31 毫秒
31.
Mohammed A. Khairy Marit Kolb Christiane Schmidt Dieter W. Zachmann Alaa R. Mostafa Anwar A. EL‐Fiky Müfit Bahadir 《洁净——土壤、空气、水》2010,38(12):1184-1193
Sediment samples were collected from 30 different locations in Abu Qir Bay (Mediterranean Sea), East Alexandria, Egypt and analyzed for trace elements. The highest concentrations of most of the elements were observed in the nearshore stations in the vicinity of the major anthropogenic activities as industrial settlements, wastewater discharges, and agricultural drainage. In addition, mussel samples of Mactra corallina and Tapes decussata were collected corresponding to the sediment samples. Concentrations of As, Cd, Cr, Mn, and Zn in the mussel tissues were higher than concentrations in sediments, thus indicating their relatively high bioavailability. Sequential extraction procedure was performed on selected sediment samples. Significant correlations were observed between the concentrations of Cu, Mn, Pb, and Zn in the exchangeable fraction of the sediments and the corresponding tissues of M. corallina. The output of the risk assessment applied on the sediments revealed that adverse ecological effects to benthic species could occur and that a higher level of risk is expected from the exposure to Cd, Cr, Hg, and Zn. No adverse carcinogenic or non‐carcinogenic human health effects are expected from the consumption of the two mussel species from Abu Qir Bay. 相似文献
32.
天然气水合物形成条件及其含量的研究是天然气水合物调查研究中最为关心的两个问题.从天然气水合物形成过程的热动力学理论模型出发,半定量地探讨了不同因素(温度、压力、气体组成、孔隙水盐度、沉积物孔隙大小等)对天然气水合物形成作用及含量的影响程度.结果显示,气体组成特别是丙烷的加入对天然气水合物形成的温度和压力条件影响最大,孔隙水盐度也会对天然气水合物形成的温度和压力条件产生重要影响,沉积物孔隙在一定范围内(1×10-6m~4×10-8m)对天然气水合物形成的温度和压力条件影响有限.天然气水合物含量受孔隙大小和盐度影响较小,主要只与气体的供应大小有关. 相似文献
33.
Nabil S. Awadalla 《Astrophysics and Space Science》1989,162(2):211-234
Photoelectric observations of the eclipsing variable TZ Bootis, obtained in 1983 and 1986, in the two coloursB andV are presented: They are compared with the previous light curves of the system. The light curve changes show that the system TZ Bootis has a solar-like activity cycle with a period of 1500 days. The primary shows a transit, whereas the secondary shows an occultation minima. The maxima exhibit a large difference suggesting a large complication in the system. The (O-C) trend indicates that the period did not remain constant; a satisfactory representation of all the observed time of minimum light was obtaiend assuming a linear trend in the (O-C)s. The star may be classified to A-type W UMa systems. 相似文献
34.
The purpose of this study was to investigate the concentration levels of heavy metals in different species of the main three
marine algal divisions from the Gulf of Aden coastal waters, Yemen. The divisions included Chlorophyta—green plants (Halimeda tuna, Rhizoclonium kochiamum, Caldophora koiei, Enteromorpha compressa, and Caulerpa racemosa species), Phaeophyta—brown seaweeds (Padina boryana, Turbinaria elatensis, Sargassum binderi, Cystoseira myrica, and Sargassum boveanum species), and Rhodophyta—red seaweeds (Hypnea cornuta, Champia parvula, Galaxaura marginate, Laurencia paniculata, Gracilaria foliifere, and species). The heavy metals, which included cadmium (Cd), cobalt (Co), copper (Cu), chromium (Cr), Iron (Fe), manganese
(Mn), nickel (Ni), lead (Pb), zinc (Zn), and vanadium (V) were measured by Atomic Absorption Spectrophotometer (AAs). The
concentrations of heavy metals in all algal species are in the order of Fe >> Cu > Mn > Cr > Zn > Ni > Pb > Cd > V > Co. The
results also showed that the uptake of heavy metals by different marine algal divisions was in the order of Chlorophyta > Phaeophyta > Rhodophyta.
These heavy metals were several order of magnitude higher than the concentrations of the same metals in seawater. This indicates
that marine alga progressively uptake heavy metals from seawater. 相似文献
35.
36.
The Aqra Formation represents a succession that was deposited over most of Northern Iraq and adjacent regions. In north Iraq, in the core of NW–SE trending Aqra anticline, a 438-m-thick section of the Aqra Formation crops out at Geli Zanta corge. The base of the Aqra Formation is not exposed here. The upper contact is unconformably overlain by Paleocene–Lower Eocene formations (Kolosh and Khurmala formations). A hundred and one samples were collected from the section and used for biostratigraphic and microfacies analysis. According to the occurrence of larger Foraminifera (Orbitoides media and Orbitoides apiculata) and planktonic Foraminifera (Abathomphalus mayaroensis), Late Upper Campanian–Maastrichtian age was determined for Aqra Formation. Fifteen facies were distinguishable throughout the formation, representing tidal flat (supratidal), restricted marine shelf (lagoon) and shelf margin rudist reef, and its related debris. These environments were used to interpret three depositional sequences which correlate with those of Aruma Formation (KSA), Simsima Formation (UAE) in Arabian Plate, and with Iraqi formation sequences. Three maximum flooding surfaces were recognized as MFS 175, MFS 180, and MFS 190. 相似文献
37.
38.
Matthieu Dumont Said Taibi Jean-Marie Fleureau Nabil Abou Bekr Abdelghani Saouab 《Comptes Rendus Geoscience》2010,342(12):892-900
A simple thermohydromechanical (THM) constitutive model for unsaturated soils is described. The effective stress concept is extended to unsaturated soils with the introduction of a capillary stress. This capillary stress is based on a microstructural model and calculated from attraction forces due to water menisci. The effect of desaturation and the thermal softening phenomenon are modelled with a minimal number of material parameters and based on existing models. THM process is qualitatively and quantitatively modelled by using experimental data and previous work to show the application of the model, including a drying path under mechanical stress with transition between saturated and unsaturated states, a heating path under constant suction and a deviatoric path with imposed suction and temperature. The results show that the present model can simulate the THM behaviour in unsaturated soils in a satisfactory way. 相似文献
39.
40.
Predicting soil erosion hazard in Lattakia Governorate(W Syria) 总被引:1,自引:0,他引:1
Mohammed Safwan Khallouf Alaa Alshiehabi Omran Bao Pham Quoc Thi Thuy Linh Nguyen Nam Thai Van Tran Anh Duong Harsányi Endre 《国际泥沙研究》2021,36(2):207-220
The main objective of this study is to predict soil erosion in the Lattakia Governorate(WSyria)using the Water Erosion Prediction Project model(WEPP)and to compare the result with that of the RUSLE.Field survey and data collection were carried out,and 44 soil samples were analyzed.In addition,all the necessary input files were prepared for use in the WEPP model and RUSLE.Results show that more than of 80%of the locations studied experience slight to moderate erosion(less than 5 t/ha/y),whereas the rest of the locations experience severe soil erosion hazard.Moreover,the volume of runoff estimated by the WEPP model is in the range of 51e321 mm,and the R^2 between the simulated soil erosion and the predicted runoff reached 0.68.Interestingly,the R^2 between the WEPP model and RUSLE is 0.56,which indicates a good correlation between the two models. 相似文献