Use of sediment quality indicators for heavy metals contamination and ecological risk assessment in urbanized coastal zones

The urbanized coastal zones are frequently faced to various pollutant discharges mainly in the shoreline. The quantification of the pollution level was mainly based on sea-water analysis. However, in this environment, the sediment characterization, using quality indicators, may constitute an accurate approach. The latter can be particularly appropriate to define heavy metals pollution degree. Chemical analyses of Cd, Cu, Zn, and Fe were undertaken for a total of 45 surface marine sediment samples of Gabes city coast. There is a significant extension of pollution, strongly influenced by the dominant longshore current. The studied sediments were found usually enriched with Cu, Cd, and Zn. These anthropogenic heavy metals have identical behavior and similar distribution. These metals did not show any correlations with Fe chosen as natural tracer. The multi-element indices used permitted to conclude that 70% of sampling sites are highly affected by heavy metal contamination and associated with very high ecological risk. These indices use a simple contamination factor, which, however, would not take account of the sedimentary inputs and the complex sediment behavior. Consequently, modified indices, employing enrichment factor, were used and demonstrated better to assess pollution and ecological risk.     

Effect of Strain Rate on the Strength Characteristics of Soil–Lime Mixture

The effects of rate of strain on strength and deformation characteristics of soil–lime were investigated. Five strain rates (0.1, 0.8, 2.0, 4.0 and 7.0 %/min), five lime contents (0, 3, 6, 9 and 12 %) by dry soil weight and three cell pressures (100, 200 and 340 kN/m²) were carried. Triaxial tests, under unconsolidated condition, were used to study the effect of strain rate on strength and initial modulus of elasticity of soil and soil–lime mixture after two curing periods 7 and 21 days, respectively. A total of 405 triaxial specimens have been tested, where 225 specimens have been tested with first curing period (7 days). The testing program includes nine specimens for each strain rate, and each lime content was carried out, including natural soil with zero lime content. Another set of triaxial tests with a total of 180 specimens for the second curing period (21 days) was prepared at optimum moisture content, and the corresponding maximum dry density was also tested. The effects of strain rate and curing period on each of stress–strain behavior, type of failure, deviator stress at failure, cohesion and angle of internal friction and initial modulus of elasticity were studied thoroughly for the natural soil as well as soil–lime mixtures. For natural soil, the test results showed that the undrained shear strength, the initial modulus of elasticity and the cohesion increase significantly as the strain rate increase, while for soil–lime mixture at different curing periods, the undrained shear strength, initial modulus of elasticity and the cohesion increases to a maximum and then decreases as the strain rate and lime content increase. Also, the same variables and angle of internal friction increase with increasing curing period.     

Assessment of hot groundwater in an arid area in Tunisia using geochemical and fuzzy logic approaches

In this study, thermal groundwater from arid area in southeastern Tunisia was assessed for irrigation use. For this purpose, thirty-one water samples were collected and physiochemical parameters (EC, pH, TDS, major ions) were measured and analyzed. A fuzzy logic model was developed in which six parameters were integrated: electrical conductivity, sodium adsorption ratio, sodium percentage, Kelly ratio, permeability index and temperature. The membership functions for a fuzzy logic model were developed using linguistic terms and trapezoidal shapes. The fuzzy logic model developed was validated with a dataset of chemical analyses from groundwater sampled in the study area. The assessment indicated that 26% of the samples were in the “good” class, 10% in the “good to permissible” class, 55% are in the “permissible” class, 6% are in the “permissible to harmful” class and 3% were considered to be harmful and therefore unsuitable for use in irrigation. The effectiveness, simplicity and robustness of the fuzzy model assessment make this approach a more consistent and reliable way of assessing water quality than conventional methods of assessing water quality data.     

Facies analysis of the Semanggol Formation,South Kedah,Malaysia: A possible Permian–Triassic boundary section

Although the Permian–Triassic Semanggol Formation is widely distributed in northwestern Peninsula Malaysia and is made of various lithofacies, its sedimentology and possible relation with the Permian–Triassic boundary (PTB) were not considered before. In this study, detailed facies analysis was conducted for two sections of the Semanggol Formation at the Bukit Kukus and Baling areas, South Kedah to clarify its sedimentology and relation to the PTB. Four facies from the Permian part of the Semanggol Formation that were identified at the Bukit Kukus section include laminated black mudstone, interbedded mudstone and sandstone, volcanogenic sediments, and bedded chert. In Baling area, the Triassic part of the formation is classified into three members. The lower member comprises of claystone and bedded chert facies, while the middle member is composed of sandstone and claystone interbeds (rhythmite). On the other hand, the upper member is grouped into two main units. The lower unit is mainly claystone and includes two facies: the varve-like laminated silt and clay and massive black claystone. The upper unit is composed of various sandstone lithofacies ranging from hummocky cross stratified (HCS) sandstone to thinly laminated sandstone to burrowed sandstone facies. The HCS sandstones occur as two units of fine-grained poorly sorted sandstone with clay lenses as flaser structure and are separated by a hard iron crust. They also show coarse grains of lag deposits at their bases. The laminated black mudstone at the lowermost part of the Semanggol Formation represents a reducing and quite conditions, which is most probably below the fairweather wave base in offshore environment that changed upwards into a fining upward sequence of tide environment. Abundance of chert beds in the volcanogenic sediments suggests the deposition of tuffs and volcanic ashes in deep marine setting which continues to form the Permian pelagic bedded chert and claystone. The bedded chert in the lower member of the Triassic section suggests its formation in deep marine conditions. The rhythmic sandstone and claystone interbeds of the middle member are suggestive for its formation as a distal fan of a turbidite sequence. Lithology and primary sedimentary structure of the upper member suggest its deposition in environments range from deep marine represented by the varve-like laminated silt and clay to subtidal environment corresponds to the massive black claystone to coastal environment represented by the hummocky sandstone units and reaches the maximum regression at the hiatus surface. Another cycle of transgression can be indicated from the second hummocky unit with transgressive lag deposits that develops to relatively deeper conditions as indicated from the formation of relatively thick laminated sandstone and bioturbated massive sandstone facies that represent tidal and subtidal environment, respectively. Late Permian lithological variation from the radiolarian chert into early Triassic claystone probably resulted from a decrease in productivity of radiolarians and might represent a PTB in the Semanggol Formation. Volcanogenic sediments in the studied section can be used as an evidence for volcanic activities at the end of the Permian, which is probably connected to the nearby volcanic ash layers in the eastern China, the ultimate cause of the PTB in this area. Black mudstone in the Permian part of the studied section may be interrelated to the Latest Permian Anoxia that started to build in the deep ocean well before the event on shallow shelves.     

An Upper Cretaceous (Campanian-Maastrichtian) actinopterygian fish assemblage from the marginal marine Adaffa Formation of Saudi Arabia

Actinopterygian remains have been recovered from Upper Cretaceous (lower Campanian to lower Maastrichtian) marginal marine deposits of the Adaffa Formation in northwestern Saudi Arabia. The fossils comprise gars (Lepisosteidae), pachycormids (cf. Protosphyraena sp.), indeterminate pycnodontiforms, enchodontid teleosts (cf. Enchodus sp.) and other indeterminate Teleostei. This assemblage is significant because it includes a novel occurrence for the Middle East (Pachycormidae) together with taxa (Lepisosteidae, Pycnodontiformes, Enchodontidae) that have been previously recorded from Late Cretaceous faunas elsewhere in the Mediterranean Tethyan region.     

Within versus between-lake variability of sedimentary diatoms: the role of sampling effort in capturing assemblage composition in environmentally heterogeneous shallow lakes

The effect of within-lake diatom assemblages variability on sample representativity and its subsequent impact on between-lake comparisons were addressed in three environmentally heterogeneous shallow lakes from the Argentinean Pampas. Surface sediment samples were collected from the open waters and the highly vegetated littoral areas on a seasonal basis and analyzed for diatom assemblages composition. Within-lake variability was assessed by comparing the Bray Curtis distances between original data and the Monte Carlo-simulated average assemblages composition through non-metric multidimensional scaling (NMDS). Diatom assemblages showed a high variability in composition, evidencing large dispersions of samples around the centroid in NMDS plots. Permutational multivariate analysis of variance tests signaled significant differences in average composition between the three lakes, related mainly to their differences in conductivity and depth. Representativity of original samples was assessed through principal coordinates analyses ordinations of the three lakes, being samples lying in the overlapping areas of the plot classified as poor representatives of between-lake differences. Several samples, both from littoral and open waters, were classified as poor representatives through this method. Simulation allowed us to evaluate the effect of sample replication on improving between-lake comparisons, and showed that collecting two littoral and two open-water samples allowed us to faithfully capture differences in average composition among the three lakes. Hence, the results suggest that using a single sample to estimate diatom assemblages composition in these lakes should be avoided, as it fails to capture between-lake differences, leading to biases in compositional comparisons among lakes and regions. Consequently, including multiple samples from each lake when constructing calibration sets would be the best option to obtain reliable paleoenvironmental reconstructions from single sediment cores in these environmentally heterogeneous shallow lakes.     

Expansion theory for the elliptic motion of arbitrary eccentricity and semi-major axis

In this paper of the series, the time transform and the explicit exact forms of the time will be established in terms of the sectorial variables _j ⁽ⁱ⁾ introduced in Paper IV (Sharaf, 1982) to regularize the highly oscillating perturbation force. Simple recurrence formulae are given to facilitate the computations. The formulations are general in the sense that they are valid whatever the types and the number of sectors forming the divisions situation of the elliptic orbit may be. Moreover, the constants of integration for the explicit forms of the time are determined in a way that it gives for these forms its generality during any revolution of the body in its Keplerian orbit.     

General integral transform of the exponential integrals

General integral transform of the exponential integralsE _n is considered and will be denoted asB _(k) ⁿ (). Different expressions and the equations satisfied byB _(k) ⁿ are developed. Two-term recurrence formula forB _(k) ⁿ (0) and three-term recurrence formula forB _(k) ⁿ (); 0 will be established for a givenk1 andn=2,3, ...,N. The computational algorithms based on these formulae are also constructed for the casesk=1,2,3, andn2. Finally the numerical results fork=2,3 andn=2(1)25 are presented to 15-digit accuracy