Comparison between Shannon and Tsallis entropies for prediction of shear stress distribution in open channels

The concept of Tsallis entropy was applied to model the probability distribution functions for the shear stress magnitudes in circular channels (with filling ratios of 0.506, 0.666, 0.826), circular with flat bed (filling ratios of 0.333, 0.666), rectangular channel (1.34, 2, 3.94, 7.37 aspect ratios) and compound channel (with relative depths of 0.324, 0.46). The equation for the shear stress distribution was obtained according to the entropy maximization principle, and is able to estimate the shear stress distribution as much on the walls as the channel bed. The approach is also compared with the predictions obtained based on the Shannon entropy concept. By comparing the two prediction models, this study highlights the application of Tsallis entropy to estimate the shear stress distribution of open channels. Although the results of the two models are similar in the circular cross-section, the differences between them are more significant in circular with flat bed and rectangular channels. For a wide range of filling ratio values, experimental data are used to illustrate the accuracy and reliability of the proposed model.     

Flow–duration curve integration into digital filtering algorithms for simulating climate variability based on river baseflow

ABSTRACT

A baseflow separation methodology combining the outcomes of the flow–duration curve and the digital filtering algorithms to cope with the restrictions of traditional procedures has been assessed. Using this methodology as well as the monitored and simulated hydro-climatological data, the baseflow annual variations due to climate change and human-induced activities were determined. The outcomes show that the long-term baseflow index at the upstream sub-basin is nearly half of that at the downstream from October to April, whereas they are close to each other for the remaining months. Some of the groundwater reacts to precipitation and an evident rise in the groundwater contribution was detected for the hydrological years 1998–2001 and 2006–2008. The contrary was recorded for1987. The water released from the reservoir in the dry periods led to distinctions in the detected baseflow index between the pre-damming and post-damming periods of the river.     

Hydrocarbon pollution of the Mediterranean coastline of Morocco

Organic geochemical study of hydrocarbon pollution of the Mediterranean coastline of Morocco (Tangier-Nador) was performed during March–April 2002. It corresponds to a preliminary work representing an initial assessment of oil contamination of Moroccan coast.Three coastal sites corresponding to Tangier, Tetouan and Nador, representing the main built-up area of this marine region, were selected for superficial sediments, water and organism sampling. Results showed high contamination levels in these three selected sites, known as the most exposed areas to urban and industrial discharges. The maximal contamination corresponding to the sum of non-aromatic (NAH) and polycyclic aromatic hydrocarbons (PAH) encountered in sediment samples was about 553 μg/g (dw). Nevertheless, even a small city agglomeration without any industrial activity showed high values reaching 370 μg/g (dw), which confirm the important hydrocarbons input coming from discharges of fishing ships and oil transporting tankers.The obtained results from this survey reflecting in part the important amounts drained via effluents toward the Moroccan Mediterranean coasts, presented to the concerned authorities drove to the realization of the project of treatment of the wastewater.They later expect to lower rates by 50%, which is still insufficient for a fragile ecosystem such as the Mediterranean and sensitive to anthropogenic effects.     

Determination of organophosphorus insecticide residues in the rice paddies

In most rice paddies in Mazandaran Province, diazinon is applied to control Chilo suppressalis. Due to the extensive application of insecticides in the rice paddies of the Caspian coasts of Iran, this investigation was carried out on the rice fields in order to obtain the necessary data and information on the concentration of insecticide residues. A total of 125 samples were taken from five areas of Amol township in 2007. Then, according to the analysis of variance procedures, the water samples were statistically analyzed after the spraying of diazinon. Results indicate that the insecticide was used frequently to control stem boring caterpillar of rice. The residuals of this toxic chemical were observed in the majority of stations from the day after the spraying until one to two months later. The greatest level of diazinon was observed in station 1 in amount of 1.14 ppm. This study revealed that the physical and chemical properties of the studied diazinon such as fumigation characteristic as well as the ecological conditions and soil type influence the reduction and eventual removal of the insecticides during the cultivation and harvest periods.     

Forced folding of the neoautochthonous Late Cretaceous–Early Tertiary sequence at the western end of the Hatta Zone, Northern Oman Mountains

At the western end of the Hatta Zone (the Jebel Rawdha area), Northern Oman Mountains, the neoautochthonous Late Cretaceous–Early Tertiary sequence (“cover”) lies with an angular unconformity on the obducted Semail ophiolite, Haybi Complex and Sumeini Group (“basement”). Structural analysis of the faults in both the basement and cover sequences has shown that they are similar in type and configuration to those that develop in a transpressional left-lateral strike-slip deformational regime (a restraining bend) that is characterised by the dominance of the dip-slip component over the strike-slip component. The WNW–ESE (P_o) faults together with the linking NW–SE (P) faults have divided the basement into elongated blocks. These blocks, in turn, are subdivided by transverse normal faults into horst and graben sub-blocks. The cover sequence is gently folded into a generally WNW–ESE-trending ‘Main’ folds and NE–SW-trending ‘Cross’ folds superimposed on them. These folds appear to be dominantly forced folds that developed as a result of repeated uplift and depression of basement blocks. Their trends correspond to the trends of the subjacent basement blocks. Hence, the Jebel Rawdha folds trend differently from other post-obduction major folds in the foreland region of the Northern Oman Mountains, such as the Hafit and Jebel Faiyah folds. Differences in stratigraphic thicknesses and lateral facies changes of the cover sequence within the blocks and sub-blocks indicate that the earliest differential movement of the blocks must have occurred during the early Maastrichtian, and the latest movement in post-mid-Eocene. Thus, pushing back the initiation of the post-obduction deformation in the Northern Oman Mountains to the early Maastrichtian.     

Spatial distribution and contamination assessment of heavy metals in surface soils of Hassi Messaoud, Algeria

An increase in heavy metal pollution in the soils of Hassi Messaoud (Algeria) due to intense industrialization and urbanization has become a serious environmental problem. There are three large industrial complexes that have been established in the region of Hassi Messaoud for petroleum extraction field and refinery. The region hosts several industrial facilities which are the main sources for hazardous wastes. Surface soil samples from 58 sampling sites (systematically sampled; 1 × 1 km regular grid), including different functional areas in Hassi Messaoud, were collected and analyzed. The results showed that the average concentrations of Cu, Ni, Mn, Pb and Zn in soil of Hassi Messaoud were up to 13.17, 35.78, 121.21, 130.97 and 61.08 mg/kg, respectively. Ni concentrations were comparable to background values, while Cu, Mn, Pb and Zn concentrations were higher than their corresponding background values. Among the functional areas, the industrial regions displayed the highest metal concentrations, while the lowest concentrations occurred in rural soil. Principal component analysis coupled with cluster analysis showed that: (1) Pb and Zn had anthropogenic sources; and (2) Ni, Cu and Mn were associated with parent materials. Contaminations in soils were classified as geoaccumulation index and enrichment factor. Pollution index values of Cu, Ni, Mn, Pb and Zn varied in the range of 0.04–5.41, 0.46–2.49, 0.01–5.73, 0.62–152.9 and 0.09–53.01, with mean values of 1.32, 1.08, 1.26, 5.64 and 3.1, respectively. The integrated pollution index (IPI) of all the analyzed samples varied from 0.42 to 31.59, with a mean of 2.48, and more than 5.45 % of samples are extremely contaminated; 18.18 % are heavily contaminated; 60 % are moderately contaminated; and others are low contaminated. The spatial distribution of IPI showed that desert and rural areas displayed relatively lower heavy metal contamination in comparison with other areas.     

Weathering and anthropogenic influences on the water and sediment chemistry of Wular Lake,Kashmir Himalaya

This paper presents a study on the Wular Lake which is the largest fresh water tectonic lake of Kashmir Valley, India. One hundred and ninety-six (196) water samples and hundred (100) sediment samples (n = 296) have been collected to assess the weathering and Anthropogenic impact on water and sediment chemistry of the lake. The results showed a significant seasonal variability in average concentration of major ions being highest in summer and spring and lower in winter and autumn seasons. The study revealed that lake water is alkaline in nature characterised by medium total dissolved solids and electrical conductivity. The concentration of the major ion towards the lake central showed a decreasing trend from the shore line. The order of major cations and anions was Ca²⁺ > Mg²⁺ > Na⁺ > K⁺ and HCO₃ ^? > SO₄ ^2? > Cl^?, respectively. The geochemical processes suggested that the chemical composition lake water is mostly influenced by the lithology of the basin (carbonates, silicates and sulphates) which had played a significant role in modifying the hydrogeochemical facies in the form of Ca–HCO₃, Mg–HCO₃ and hybrid type. Chemical index of alteration values of Wular Lake sediments reflect moderate weathering of the catchment area. Compared to upper continental crust and the post-Archean Shale, the sediments have higher Si, Ti, Mg and Ca contents and lower Al, Fe, Na, K, P, Zn, Pb, Ni, Cu content. Geoaccumulation index (Igeo) and US Environmental Protection Agency sediment quality standards indicated that there is no pollution effect of heavy metals (Zn, Mn, Pb, Ni and Co).The study also suggested that Wular Lake is characterised by both natural and anthropogenic influences.     

Rock slope stability and design in Arafat–Muzdalifa area,Saudi Arabia

The present contribution is a complete study extending before, during, and after the excavation of the mountain side that lying north of road 7. It includes slope stability analysis, rock cut design, and rockfall modeling for natural slope and rock cut face. Neoproterozoic granodiorite and biotite granite forming the slope body have medium to very high strengths. Mineral compositions and textures of these intact rocks control the strength values. These rocks are intensively dissected by fractures that are filled with montmorillonite and chlorite. The high plasticity and slippery nature of these filling materials represent the main problem that may face a rock cut designer because they damage the mechanical properties of these fractures. The problem begins with the selection of the rock mass classification that deals with the fracture fillings and extends during the stability analysis and the suggestion of mitigation and supporting measures. The rock masses building the natural slope are suffered by plane, wedge, and toppling failures. Therefore, two rock cut designs are suggested to avoid the hazards related to these failures and considering the construction cost as well. Rockfall modeling for the natural slope and rock cut designs was done to assess the hazards related to these falling of the blocks. The kinetic energy of falling blocks is represented on the roadway by the coverage distance and block rebound amplitude. Slope height has a positive effect on the values of these distance and amplitude, whereas the steepness of berm height has a negative effect on them. Coverage distance is a function to the location of rockfall barrier and to the width of road ditch, while the amplitude controls the barrier height.     

Petroleum system analysis of the Khatatba Formation in the Shoushan Basin,north Western Desert,Egypt

The Middle Jurassic Khatatba Formation is an attractive petroleum exploration target in the Shoushan Basin, north Western Desert, Egypt. However, the Khatatba petroleum system with its essential elements and processes has not been assigned yet. This study throws the lights on the complete Khatatba petroleum system in the Shoushan Basin which has been evaluated and collectively named the Khatatba-Khatatba (!) petroleum system. To evaluate the remaining hydrocarbon potential of the Khatatba system, its essential elements were studied, in order to determine the timing of hydrocarbon generation, migration and accumulation. Systematic analysis of the petroleum system of the Khatatba Formation has identified that coaly shales and organic-rich shales are the most important source rocks. These sediments are characterised by high total organic matter content and have good to excellent hydrocarbon generative potential. Kerogen is predominantly types II–III with type III kerogen. The Khatatba source rocks are mature and, at the present time, are within the peak of the oil window with vitrinite reflectance values in the range of 0.81 to 1.08 % Ro. The remaining hydrocarbon potential is anticipated to exist mainly in stratigraphic traps in the Khatatba sandstones which are characterised by fine to coarse grain size, moderate to well sorted. It has good quality reservoir with relatively high porosity and permeability values ranging from 1 to 17 % and 0.05–1,000 mD, respectively. Modelling results indicated that hydrocarbon generation from the Khatatba source rocks began in the Late Cretaceous time and peak of hydrocarbon generation occurred during the end Tertiary time (Neogene). Hydrocarbon primarily migrated from the source rock via fractured pathways created by abnormally high pore pressures resulting from hydrocarbon generation. Hydrocarbon secondarily migrated from active Khatatba source rocks to traps side via vertical migration pathways through faults resulting from Tertiary tectonics during period from end Oligocene to Middle Miocene times.     

Diagenesis in the Middle Jurassic Khatatba Formation sandstones in the Shoushan Basin,northern Western Desert,Egypt

The Middle Jurassic Khatatba Formation acts as a hydrocarbon reservoir in the subsurface in the Western Desert, Egypt. This study, which is based on core samples from two exploration boreholes, describes the lithological and diagenetic characteristics of the Khatatba Formation sandstones. The sandstones are fine‐ to coarse‐grained, moderately to well‐sorted quartz arenites, deposited in fluvial channels and in a shallow‐marine setting. Diagenetic components include mechanical and chemical compaction, cementation (calcite, clay minerals, quartz overgrowths, and a minor amount of pyrite), and dissolution of calcite cements and feldspar grains. The widespread occurrence of an early calcite cement suggests that the Khatatba sandstones lost a significant amount of primary porosity at an early stage of its diagenetic history. In addition to calcite, several different cements including kaolinite and syntaxial quartz overgrowth occur as pore‐filling and pore‐lining cements. Kaolinite (largely vermicular) fills pore spaces and causes reduction in the permeability of the reservoir. Based on framework grain–cement relationships, precipitation of the early calcite cement was either accompanied by or followed the development of part of the pore‐lining and pore‐filling cements. Secondary porosity development occurred due to partial to complete dissolution of early calcite cements and feldspar. Late kaolinite clay cement occurs due to dissolved feldspar and has an impact on the reservoir quality of the Khatatba sandstones. Open hydraulic fractures also generated significant secondary porosity in sandstone reservoirs, where both fractures and dissolution took place in multiple phases during late diagenetic stages. The diagenesis and sedimentary facies help control the reservoir quality of the Khatatba sandstones. Fluvial channel sandstones have the highest porosities and permeabilities, in part because of calcite cementation, which inhibited authigenic clays or was later dissolved, creating intergranular secondary porosity. Fluvial crevasse‐splay and marine sandstones have the lowest reservoir quality because of an abundance of depositional kaolinite matrix and pervasive, shallow‐burial calcite and quartz overgrowth cements, respectively. Copyright © 2013 John Wiley & Sons, Ltd.