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121.
122.
Turbulent velocity profile in fully-developed open channel flows 总被引:2,自引:0,他引:2
Hossein Bonakdari Frédérique Larrarte Laurent Lassabatere Claude Joannis 《Environmental Fluid Mechanics》2008,8(1):1-17
The determination of velocity profile in turbulent narrow open channels is a difficult task due to the significant effects
of the anisotropic turbulence that involve the Prandtl’s second type of secondary flow occurring in the cross section. With
these currents the maximum velocity appears below the free surface that is called dip phenomenon. The well-known logarithmic
law describes the velocity distribution in the inner region of the turbulent boundary layer but it is not adapted to define
the velocity profile in the outer region of narrow channels. This paper relies on an analysis of the Navier–Stokes equations
and yields a new formulation of the vertical velocity profile in the center region of steady, fully developed turbulent flows
in open channels. This formulation is able to predict time averaged primary velocity in the outer region of the turbulent
boundary layer for both narrow and wide open channels. The proposed law is based on the knowledge of the aspect ratio and
involves a parameter CAr depending on the position of the maximum velocity (ξdip). ξdip may be derived, either from measurements or from an empirical equation given in this paper. A wide range of longitudinal
velocity profile data for narrow open channels has been used for validating the model. The agreement between the measured
and the computed velocities is rather good, despite the simplification used. 相似文献
123.
Ali Mohammad Latifi Seyed Mohammad Nabavi Morteza Mirzaei Mahmood Tavalaei Hossein Ghafurian Claire Hellio 《毒物与环境化学》2013,95(9):1670-1677
Cesium and mercury are two mono-valent elements which can be found in toxic industrial, medical, and nuclear wastes. Their presence in the environment has deleterious effects on the ecosystem, living organisms including humans. Due to the chemical nature of these metals, bioremediation by conventional methods is more difficult to achieve compared to other metals. In this study, we used three biosorbents (oak powder, gall nut, and bacterial exopolymer) for the bioremediation of Hg and Cs. Bio-polymer was produced in the GMS mineral broth. Synthetic wastes of Hg(NO3)2 and isotope Cs-133 as the single-metal solutions were used. The biorefining process was carried out in glass columns, made of Pyrex, with dimensions 20?×?7/2?cm2 with a V-shaped bottom. The samples were analyzed using atomic absorption. The experimental results showed that eliminated metal percent by oak powder, gall nut, and bacterial exopolymer were, respectively, of 94.8%, 96%, and 13.8% for Hg and 7.8%, 4.4%, and 69.4% for Cs. The tests revealed that Ca++, when used as flocculant, played a key role in both biosorption and bio-precipitation rates. Consequently, it was concluded that the investigated biosorbents could be use as an integrated biosorption system for the refinement of mixed wastes. 相似文献
124.
Zahra Bahri-Kazempour Khosro Abdi Mojtaba Shakibaie Hamid Forootanfar Hossein Attar 《毒物与环境化学》2013,95(1):118-126
In this investigation, Fe3O4 magnetic nanoparticles (MNPs) were prepared by the alkalinization of an aqueous medium containing ferrous sulfate and ferric chloride. In the next step, a Fe3O4–AgCl magnetic nanocomposite was fabricated by the drop-by-drop addition of silver nitrate solution into a NaCl solution containing Fe3O4 MNPs. All prepared nanoparticles were characterized by transition electron microscopy (TEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). Both particle types varied in size from 2.5 to 20?nm, with an average size of 7.5?nm for Fe3O4 MNPs and 12.5?nm for Fe3O4–AgCl nanocomposites. The antibacterial effect of the Fe3O4 MNPs and fabricated Fe3O4–AgCl nanocomposites against Escherichia coli (ATCC 35218) were investigated by conventional serial agar dilution method using the Müller–Hinton Agar medium. The minimum inhibitory concentration was 4?mg?mL?1 for Fe3O4 MNPs and 2?mg?mL?1 for the Fe3O4–AgCl magnetic nanocomposites. Time-kill course assays showed that the Fe3O4–AgCl magnetic nanocomposites successfully killed all inoculated bacterial cells during an exposure time of 60?min. The antibacterial activity of recycled Fe3O4–AgCl magnetic nanocomposites over four 60?min cycles of antibacterial treatment was further tested against E. coli by the colony-forming unit (CFU) method. The antibacterial efficiency of the nanocomposites was constant over two cycles of antibacterial testing. 相似文献
125.
Hossein Nikakhtari Pardeep Kumar Mehdi Nemati Gordon A. Hill 《Process Safety and Environmental Protection》2008,86(4):252
A non-aqueous phase liquid (NAPL) containing dissolved naphthalene or phenol was used to simulate water insoluble contaminants which are produced during the processing of oil sands. Mass transfer and biodegradation of organic contaminants in the aqueous phase were studied in a baffled roller bioreactor. Mass transfer of both naphthalene and phenol from NAPL into the aqueous phase was completed in less than 60 min, by which time naphthalene reached its saturation concentration in the aqueous phase and phenol was completely transferred into the aqueous phase. Pseudomonas putida (ATCC 17484) was subsequently used in biodegradation experiments in the baffled bioreactor containing the model NAPL contaminant. The optimum loading of NAPL for biodegradation of naphthalene at 500 mg/L was found to be 40%. High biodegradation rates (136.4 mg/L h for naphthalene and 13.2 mg/L h for phenol based on the working volume of the bioreactor) were achieved. In the case of simultaneous biodegradation of naphthalene and phenol, the highest total biodegradation rate of 102.6 mg/L h was achieved. 相似文献
126.
Dadashpoor Hashem Panahi Hossein 《Environment, Development and Sustainability》2021,23(9):13628-13649
Environment, Development and Sustainability - Spatial simulation of land-use change scenarios in metropolitan areas is essential for analyzing both the causes and consequences of various future... 相似文献
127.
128.
Characterization of ionic composition of TSP and PM10 during the Middle Eastern Dust (MED) storms in Ahvaz, Iran 总被引:1,自引:0,他引:1
Shahsavani A Naddafi K Jaafarzadeh Haghighifard N Mesdaghinia A Yunesian M Nabizadeh R Arhami M Yarahmadi M Sowlat MH Ghani M Jonidi Jafari A Alimohamadi M Motevalian SA Soleimani Z 《Environmental monitoring and assessment》2012,184(11):6683-6692
Because of the recent frequent observations of major dust storms in southwestern cities in Iran such as Ahvaz, and the importance of the ionic composition of particulate matters regarding their health effects, source apportionment, etc., the present work was conducted aiming at characterizing the ionic composition of total suspended particles (TSP) and particles on the order of ~10?μm or less (PM(10)) during dust storms in Ahvaz in April-September 2010. TSP and PM(10) samples were collected and their ionic compositions were determined using an ion chromatography. Mean concentrations of TSP and PM(10) were 1,481.5 and 1,072.9?μg/m(3), respectively. Particle concentrations during the Middle Eastern Dust (MED) days were up to four times higher than those in normal days. Ionic components contributed to only 9.5% and 11.3% of the total mass of TSP and PM(10), respectively. Crustal ions were most abundant during dust days, while secondary ions were dominant during non-dust days. Ca(2+)/Na(+) and Cl(-)/Na(+) ratios can be considered as the indicators for identification of the MED occurrence. It was found that possible chemical forms of NaCl, (NH(4))(2)SO(4), KCl, K(2)SO(4), CaCl(2), Ca(NO(3))(2), and CaSO(4) may exist in TSP. Correlation between the anionic and cationic components suggests slight anion and cation deficiencies in TSP and PM(10) samples, though the deficiencies were negligible. 相似文献
129.
Effect of fertilizer application on soil heavy metal concentration 总被引:22,自引:0,他引:22
Zahra Atafar Alireza Mesdaghinia Jafar Nouri Mehdi Homaee Masoud Yunesian Mehdi Ahmadimoghaddam Amir Hossein Mahvi 《Environmental monitoring and assessment》2010,160(1-4):83-89
A large amount of chemicals is annually applied at the agricultural soils as fertilizers and pesticides. Such applications may result in the increase of heavy metals particularly Cd, Pb, and As. The objective of this study was to investigate the variability of chemical applications on Cd, Pb, and As concentrations of wheat-cultivated soils. Consequently, a study area was designed and was divided into four subareas (A, B, C, and D). The soil sampling was carried out in 40 points of cultivated durum wheat during the 2006–2007 periods. The samples were taken to the laboratory to measure their heavy metal concentration, soil texture, pH, electrical conductivity, cationic exchange capacity, organic matter, and carbonate contents. The result indicated that Cd, Pb, and As concentrations were increased in the cultivated soils due to fertilizer application. Although the statistical analysis indicates that these heavy metals increased significantly (P value < 0.05), the lead and arsenic concentrations were increased dramatically compared to Cd concentration. This can be related to overapplication of fertilizers as well as the pesticides that are used to replant plant pests, herbs, and rats. 相似文献
130.
Hossein Bayat Sabit Ersahin Estela N. Hepper 《Environmental Modeling and Assessment》2013,18(5):605-614
Specific surface area (SSA) is one of the principal soil properties used in modeling soil processes. In this study, artificial neural network (ANN) ensembles were evaluated to predict SSA. Complete soil particle-size distribution was estimated from sand, silt, and clay fractions using the model by Skaggs et al. and then the particle-size distribution curve parameters (PSDCPs) and fractal parameters were calculated. The PSDCPs were used to predict 20 particle-size classes for a soil sample’s particle size distribution. Fractal parameters were calculated by the model of Bird et al. In addition, total soil-specific surface area (TSS) was calculated using the above 20 size classes. Pedotransfer functions were developed for SSA and TSS using ANN ensembles from 63 pieces of SSA data taken from the literature. Fractal parameters, PSDCPs, and some other soil properties were used to predict SSA and TSS. Introducing fractal parameters and PSDCPs improved the SSA estimations by 12.5 and 11.1 %, respectively. The improvements were even better for TSS estimations (27.7 and 27.0 %, respectively). The use of fractal parameters as estimators described 44 and 92.8 % of the variation in SSA and TSS, respectively, while PSDCPs explained 42 and 6.6 % of the variation in SSA and TSS, respectively. The results suggested that fractal parameters and PSDCPs could be successfully used as predictors in ANN ensembles to predict SSA and TSS. 相似文献