The effects of kinetic sorting on sediment mobility on steep slopes

In poorly mobile static armour, sorting is usually considered the result of hiding/exposure effects. We called this effect ‘static sorting’ in opposition to very efficient grain‐to‐grain mechanisms produced by a mobile mixture, called ‘kinetic sorting’. We hypothesized that kinetic sorting can be an important contributor to the morphodynamics of mountain streams and attempted to demonstrate this with new flume experiments. Two long runs were produced with natural poorly sorted sediments, and with transport stages of the coarse fraction (defined by the ratio between the shear stress and the critical shear stress for transport), smaller and higher than 1, respectively. Both runs produced an efficient transfer downstream of the injected material, but with a major difference: the first run (no kinetic sorting) produced permanent armour figuring clusters, akin to what has already been observed in similar experiments; the second run (with kinetic sorting) also produced bed armouring, but this armour was periodically totally destroyed, leading to substantial bed erosion. This phenomenon was explained by kinetic sorting, the effects of which are to produce an efficient downward migration of fine materials and bed surface armouring. The consequence is that fine materials are hidden to the flow during aggradation, allowing the slope to attain values much steeper than would have been expected at equilibrium for the mixture. However, whereas the surface armouring tends to stabilize the bed, construction of a layer of fine sediments at the subsurface also contributes to making it very unstable. These two contradictory effects explain the complex bed behaviours and the existence of very large bedload and slope fluctuations. Copyright © 2014 John Wiley & Sons, Ltd.     

Risk assessment of soil erosion in semi-arid mountainous watershed in Saudi Arabia by RUSLE model coupled with remote sensing and GIS

Soil erosion is the most important factor in land degradation and influences desertification in semi-arid areas. A comprehensive methodology that integrates revised universal soil loss equation (RUSLE) model and GIS was adopted to determine the soil erosion risk (SER) in semi-arid Aseer region, Saudi Arabia. Geoenvironmental factors viz. rainfall (R), soil erodibility (K), slope (LS), cover management and practice factors were computed to determine their effects on average annual soil loss. The high potential soil erosion, resulting from high denuded slope, devoid of vegetation cover and high intensity rainfall, is located towards the north western part of the study area. The analysis is investigated that the SER over the vegetation cover including dense vegetation, sparse vegetation and bushes increases with the higher altitude and higher slope angle. The erosion maps generated with RUSLE integrated with GIS can serve as effective inputs in deriving strategies for land planning/management in the environmentally sensitive mountainous areas.     

Natural uranium and thorium isotopes in sediment cores off Malaysian ports

Ocean Science Journal - Sediment cores collected from three Malaysian marine ports, namely, Kota Kinabalu, Labuan and Klang were analyzed to determine the radioactivities of 234U, 238U, 230Th,...     

Heavy Metal Concentrations in Sediment and Intertidal Gastropod Nerita lineata from Two Opposing Sites in the Straits of Malacca

The concentrations of Cd, Cu, Pb, Zn, Ni and Fe were determined in the surface sediment and marine gastropod Nerita lineata collected in May 2005 from the intertidal zone of Dumai, Sumatera, Indonesia and Johor, Peninsular Malaysia. The results showed that metal concentrations in sediment and the soft tissue of N. lineata varied at different sampling stations. Mean heavy metal concentrations were 0. 92 μg/g(Cd) ;6.40 μg/g(Cu) ;32.77 μg/g(Pb) ;54.41μg/g(Zn) ;11.56 μg/g(Ni) and 2.97%(Fe) in sediment from Dumai and 1.15 μg(Cd) ;26.73 μg/g(Cu) ;53.45μg/g(Pb) ;130.77 μg/g(Zn) ;20.79 μg/g( Ni ) and 2.72% (Fe) in sediment from Johor. Concentrations of metals in gastropod N. lineata were 0.71 μg/g(Cd) ;15.16 μg(Cu) ;9.35 μg/g(Pb) ;94.69 μg/g(Zn) ;5.08 μg/g(Ni) and 397.97 μg/g(Fe) in samples from Dumai and 1.24 μg(Cd) ;18.02 μg/g(Cu) ;19.75 μg/g(Pb) ;95.09 μg/g(Zn) ;5.57 μg/g ( Ni ) and 473. 56 μg/g (Fe) in samples from Johor. Although they were not statistically significant (p >0.05), heavy metal concentrations in N. lineata were correlated with the concentrations of respective metals in sediment in both samples from Dumai and Johor. In general, samples of sediment and gastropod from Johor accumulated significantly higher heavy metal concentrations when compared to samples from Dumai(p < 0. 05). Higher concentrations of metals were recorded in samples collected from the stations close to the industrial and anthropogenic activities in both Dumai and Johor areas. However, most of the concentrations were still comparable to the previous reported studies from other geographical areas.     

Evolution of the REE mineralogy in HP–LT metapelites of the Sebtide complex, Rif, Morocco: Monazite stability and geochronology

REE mineralogy was characterized at the micrometer scale (using scanning electron microscopy) in the four tectono-metamorphic units of the Beni Mzala window, Sebtide Complex, Internal Rif, Morocco, which sample a HP-LT metamorphic gradient from subgreenschist to blueschist/eclogite facies. These tectonic units are composed of garnet-free metapelites (and associated synmetamorphic veins) from the same homogeneous aluminium-rich and calcium-poor protolith. In that context, mineralogical differences between units are assumed to result from contrasted pressure and temperature histories. Light REE-bearing Al-phosphates of the crandallite group with florencite-rich composition and variable goyazite content are the dominant LREE minerals in the lowest-grade units, Tizgarine (300 °C, 3 kbar as peak conditions) and Boquete de Anjera (350 °C, 10 kbar). In the latter unit, metamorphic florencite is associated with MREE-rich monazite. In the schist of the highest-grade units, Beni Mzala 2 (420–450 °C, 12 kbar) and Beni Mzala 1 (550 °C, 16 kbar), associations of allanite-rich epidote and synchisite (a LREE-fluorocarbonate) are found whereas florencite and monazite are no longer observed. At the wall of the quartz–kyanite veins, retrograde monazite-(Ce) with grain size of 20 to 50 μm is the only LREE-bearing mineral. Th–Pb and U–Pb SIMS data on some of these grains yield ages of 21.3 ± 1.7 Ma and 20.9 ± 2.1 Ma, respectively, consistent with previous K–Ar ages obtained on retrograde clay–mica mixtures in rocks from the same locality. The identification of a stability field for monazite in high-pressure aluminous metapelites with an upper thermal-limit below 450 °C as well as the derivation of meaningful U–Pb and Th–Pb SIMS ages demonstrates the monazite potential for dating HP-LT metapelites. However, since, under these conditions, monazite growth occurs below its admitted closure-temperature, these ages must be interpreted on the basis of monazite textural relationships.     

Metallothionein induction by Cu, Cd and Hg in Dicentrarchus labrax liver: assessment by RP-HPLC with fluorescence detection and spectrophotometry

Metallothionein was quantified in sea bass Dicentrarchus labrax intraperitoneally (i.p.) injected with different Cu, Cd and Hg doses (50-250 microg kg(-1) wet wt) after 48 h exposure. A distinct peak with 16.8 min retention time was obtained by reversed-phase high performance liquid chromatography coupled to fluorescence detection (RP-HPLC-FD) with the three metals. Total metallothionein levels assayed in unheated liver extracts by RP-HPLC-FD were significantly higher (1.3-1.95-fold) than those obtained by the well-established spectrophotometric method. In the RP-HPLC-FD method, metallothionein increased linearly with Cu and Hg doses, being saturated beyond 100 mug kg(-1) Cd. Maximum induction was obtained at 100 microg kg(-1) Cd (5.3-fold), and 250 microg kg(-1) Cu or Hg (8- and 5.1-fold, respectively). At low doses no metallothionein induction was shown by the less sensitive spectrophotometric assay.     

Settlement relocations in the char-lands of Padma River basin in Ganges delta, Bangladesh

Bangladesh has a unique hydro-geological setting and deltaic floodplain which is jointly formed by the deposition of the Ganges (Padma), Brahmaputra (Jamuna) and Meghna River. The physical characteristics of the geographic location, river morphology and the monsoon climate render Bangladesh highly vulnerable to natural disasters, primarily, floods and cyclones. River flooding has exerted a great impact on the culture and socioeconomic activities. The char people and their settlements in the Padma River channel are under threat due to floods and associated river bank erosion. The excess of water happens during the monsoon season because of widespread flooding that damages char-land settlements, agricultural crops, infrastructure and communication networks. Purba Khas Bandarkhola Mouza of Char-Janajat is largely affected by annual floods, and as a result the char people are displaced frequently from one place to another within and/or outside the char. The dwellers can return to the native char when new land emerges in the river channel after floods. This study has revealed that the displacement of char settlement takes place in almost every 3–5a at Purba Khas Bandarkhola Mouza of Char-Janajat. Our findings shed light on the char flood disaster management and social adaptation plan for settlement development of char livelihood in the Padma River basin in the Ganges delta of Bangladesh.     

Wavelet bicoherence analysis of wind–wave interaction

A new technique in the analysis of wind–wave interaction, wavelet bicoherence, will be applied in this article. Wavelet bicohence has the ability to detect phase coupling and nonlinear interactions of the quadratic order with time resolution. It is used in this study to analyze wind–wave interaction during wave growth in a Mistral event. A selected record of simultaneously measured wind and wave data during Mistral is divided into five segments and the computations of the wavelet bicoherence are conducted for the whole record and for all divided segments. The results show that the phase coupling occurs between wind speed and wave height over a certain range of frequencies and that the range is different from one segment to another due to the non-stationary feature of the time series.     

Groundwater condition based on geoelectrical technique and Dar Zarrouk parameters between El Alamein and El Dabaa—Egypt

El Alamein-El-Dabaa area lies in the western Mediterranean coastal zone of Egypt with about 50 km long. The aims of the present study are the shallow groundwater aquifer determination and calculate the electric parameters of the overburden to achieve the easiest way for detecting groundwater contamination and considered it during the planning of new development project(s). To attain this target, 44 vertical resistivity soundings using Schlumberger array of the maximum AB/2?=?1000 m in the form of four profiles were carried out. From the interpretation results, six geoelectrical layers have been established in the area, and iso-resistivity, depth to water, and isopach contour maps are presented. Four geoelectrical cross-sections (two geoelectrical cross-sections are parallel to the Mediterranean shoreline and the other two are normal to the Mediterranean shoreline) have been constructed. According to this work, the upper part of the Oolitic Limestone represents the shallow groundwater aquifer in this area and can be distinguished into two zones. The upper zone is brackish, whereas the lower one is saline. The geoelectrical succession reveals that the aquifer is free type. The depth to water ranges between 20 and 63 m; therefore, it is the choice as the best sites for groundwater exploitation. In the area under study, the depth to water and the thickness of the brackish increase towards the south side as well as the depth to the brackish water. The Dar-Zarrouk parameters clarified that there are some parts that may contaminate pathways and other parts are not.     

Capacity assessment of the Qattara Depression: Egypt as a sink for the global sea level rise

One of the most prominent geomorphological features in the Western Desert of Egypt is the occurrence of the Qattara Depression (20,800 km² or 2% of Egypt’s area), which has the deepest point in Africa. Topographic analysis of the depression was carried out using fine resolution digital elevation models acquired from the Advanced Spaceborne Thermal Emission and Reflection Radiometer-Global Digital Elevation Model (ASTER-GDEM) in order to assess the capacity of the depression. Results showed that the lower point in the depression occurs at ?136 m and its capacity at the sea level is 1340 billion m³, which equals 10 times the live storage capacity of the Lake Nasser behind the Aswan High Dam. Although the depression has the aptitude to be a reservoir for any augmentation in the sea level, detailed environmental impact assessment studies should be implemented to address geologic, climatic, biologic as well as socio-economic impacts.