Biodegradation of cyanide and evaluation of kinetic models by immobilized cells of <Emphasis Type="Italic">Serratia marcescens</Emphasis> strain AQ07

Immobilized form of Serratia marcescens strain AQ07 was experimented for cyanide biodegradation. Cyanide degradation (200 ppm) was achieved after 24-h incubation. Three parameters were optimized which included gellan gum concentration, beads size, and number of beads. In accordance with one-factor-at-a-time method, cyanide removal was optimum at 0.6% w/v gellan gum gel, 0.3-cm-diameter beads, and 50 beads number. It was able to withstand cyanide toxicity of 800 ppm, which makes it very suitable candidate in cyanide remediation. Beads reusability indicates one-cycle ability. The first cycle removed 96.3%, while the second removed 78.5%. Effects of heavy metals at 1.0 ppm demonstrated that mercury has a considerable effect on bacteria, inhibiting degradation to 61.6%, while other heavy metals have less effect, removing 97–98%. Maximum specific degradation rate of 0.9997 h^?1 was observed at 200 ppm cyanide concentration. Gellan gum was used as the encapsulation matrix. ?-picoline-barbituric acid spectrophotometric analytical method was used to optimize the condition in buffer medium integrated with potassium cyanide via one-factor-at-a-time and response surface method. The range of cyanide concentrations used in this research, specific biodegradation rate was obtained to model the substrate inhibition kinetics. This rate fits to the kinetic models of Teisser, Aiba and Yano, which are utilized to elucidate substrate inhibition on degradation. One-factor-at-a-time approach parameters were adopted because it removes more cyanide compared to response surface methodology modules. The predicted biokinetic constant from this model suggests suitability of the bacteria for use in cyanide treatment of industrial waste effluents.     

Litter pollution on the Jordanian shores of the Gulf of Aqaba (Red Sea)

Litter was assessed on three beaches along the Jordanian coast of the Gulf of Aqaba, south of the town Aqaba, monthly during 1994 and 1995, in order to determine its nature, extent and possible sources. The overall mean was about 5 and 3 items/m(2) in 1994 and 1995, respectively. Approximately a total of 14,000 m(2) were examined and a total of 101,000 items were noted, 67,000 during 1994 and 34,000 in 1995. More than 50% of the litter was plastic and the remainder wood, glass, cardboard, Styrofoam, metal and other materials. Most litter appears to be from local land-based or near shore sources, although there are some regional influences as well. The main local sources are the passenger port, the cargo port and the beach goers. The findings are compared with other regions of the world. The amount of litter is related to distance of the beach from the main sources, and shape, physiography and orientation of the beach. Spatial and seasonal variations are examined and discussed, and actions and measures to combat the problem on local and regional levels are suggested.     

Un « point chaud » sous le système du Rift syrien : données pétrologiques complémentaires sur les enclaves du volcanisme récent

Ultrabasic xenoliths (pyroxenites, lherzolites, harzburgites) in recent (Neogene–Quaternary) volcanoes have been studied in three localities within Syria: Jubates (North), Mhailbeh (Center), Tel Thannoun (South). P–T conditions of mineral equilibration have been estimated by pyroxene thermometry (temperature) and maximum CO₂ density in primary inclusions (minimum pressure). Pyroxenites equilibrate at significantly higher conditions (T about 1200 °C, P>15 kbar) than lherzolites and harzburgites (900<T<1100 °C, P between 10 and 15 kbar). All are within the spinel lherzolite field, whereas Cretaceous xenoliths originate within the garnet lherzolite field. To cite this article: A. Bilal, F. Sheleh, C. R. Geoscience 336 (2004).     

Relative contributions of silicate and carbonate rocks to riverine Sr fluxes in the headwaters of the Ganges

Exhumation of the Himalayan-Tibetan orogen is implicated in the marked rise in seawater ⁸⁷Sr/⁸⁶Sr ratios since 40 Ma. However both silicate and carbonate rocks in the Himalaya have elevated ⁸⁷Sr/⁸⁶Sr ratios and there is disagreement as to how much of the ⁸⁷Sr flux is derived from silicate weathering. Most previous studies have used element ratios from bedrock to constrain the proportions of silicate- and carbonate-derived Sr in river waters. Here we use arrays of water compositions sampled from the head waters of the Ganges in the Indian and Nepalese Himalaya to constrain the end-member element ratios. The compositions of tributaries draining catchments restricted to a limited range of geological units can be described by two-component mixing of silicate and carbonate-derived components and lie on a plane in multicomponent composition space. Key elemental ratios of the carbonate and silicate components are determined by the intersection of the tributary mixing plane with the planes Na = 0 for carbonate and constant Ca/Na for silicate. The fractions of Sr derived from silicate and carbonate sources are then calculated by mass-balance in Sr-Ca-Mg-Na composition space. Comparison of end-member compositions with bedrock implies that secondary calcite deposition may be important in some catchments and that dissolution of low-Mg trace calcite in silicate rocks may explain discrepancies in Sr-Ca-Na-Mg covariation. Alternatively, composition-dependent precipitation or incongruent dissolution reactions may rotate mixing trends on cation-ratio diagrams. However the calculations are not sensitive to transformations of the compositions by incongruent dissolution or precipitation processes provided that the transformed silicate and carbonate component vectors are constrained. Silicates are calculated to provide ∼50% of the dissolved Sr flux from the head waters of the Ganges assuming that discrepancies between Ca-Mg-Na covariation and the silicate rock compositions arise from addition of trace calcite. If the Ca-Mg-Na mixing plane is rotated by composition-dependent secondary calcite deposition, this estimate would be increased. Moreover, when ⁸⁷Sr/⁸⁶Sr ratios of the Sr inputs are considered, silicate Sr is responsible for 70 ± 16% (1σ) of the ⁸⁷Sr flux forcing changes in seawater Sr-isotopic composition. Since earlier studies predict that silicate weathering generates as little as 20% of the total Sr flux in Himalayan river systems, this study demonstrates that the significance of silicate weathering can be greatly underestimated if the processes that decouple the water cation ratios from those of the source rocks are not properly evaluated.     

Vibration analysis of damaged and undamaged steel structure systems: cantilever column and frame

This paper presents the experimental and numerical studies conducted on a steel column and a steel frame structure using free vibration analysis. The effects of damages on structures were investigated, which were simulated by introducing multiple cracks at different locations in the experimental and numerical models. The acceleration responses of the test models, were recorded through an accelerometer, and were used to calibrate the numerical models developed in finite element based software. Modal frequencies of damaged and undamaged structures were compared and analyzed, to derive relationships for damaged and undamaged structures' frequencies in terms of crack depth. It was found that, due to the presence of cracks, the mechanical properties of a structure changes, whereby, the modal frequencies decrease. An approximately linear trend was observed for the frequency decrease with the increase in crack depth, which was also confirmed by the numerical models. The derived relationships were extended to further develop a mechanics-based damage scale for steel structures, to help facilitate structural health monitoring and screening of vulnerable structures.     

Phosphate pollution in the Jordan Gulf of Aqaba

In order to assess the magnitude of phosphate pollution in the Jordanian sector of the Gulf of Aqaba, the distribution of total phosphorus, fluoride, calcium and calcium carbonate and their association with each other were determined in sediments collected from seven stations north and south of Aqaba Port. Abnormally high values were found near the phosphate loading berth which decrease with increasing distance from the berth. The results indicate that phosphate pollution is mainly localized in the vicinity of the loading berth although its influence may be detected in other areas along the coast. The level of pollution had increased by at least an order of magnitude since 1978.     

Relationships between magnetic susceptibility and heavy metals in urban topsoils in the arid region of Isfahan, central Iran

Electromagnetic induction (EMI) method results are shown for vertical magnetic dipole (VMD) configuration by using the EM38 equipment. Performance in the location of metallic pipes and electrical cables is compared as a function of instrumental drift correction by linear and quadratic adjusting under controlled conditions. Metallic pipes and electrical cables are buried at the IAG/USP shallow geophysical test site in São Paulo City, Brazil. Results show that apparent electrical conductivity and magnetic susceptibility data were affected by ambient temperature variation. In order to obtain better contrast between background and metallic targets it was necessary to correct the drift. This correction was accomplished by using linear and quadratic relation between conductivity/susceptibility and temperature intending comparative studies. The correction of temperature drift by using a quadratic relation was effective, showing that all metallic targets were located as well deeper targets were also improved.     

Frontal recession of Parkachik Glacier between 1971-2015, Zanskar Himalaya using remote sensing and field data

Parkachik Glacier is located in the Suru sub-basin of the Upper Indus River, Zanskar Himalaya. The Glacier has been analysed using Corona KH-4B (1971), Landsat-TM (1999), field survey (2015), Google Earth^TM (2015) and ASTER GDEM (2015) for frontal recession and area changes. Overall, from 1971 to 2015, the Glacier has retreated by 127 ± 0.09 m i.e. (0.75 ± 0.07%) at a rate of 2.9 ± 0.004 ma^?1 with a simultaneous decrease in area from 49.5 to 48.8 km² i.e. 740 ± 0.7 m² (1.5 ± 0.09%) at a rate of 74 ± 0.7 m²a^?1. However, during recent decade (1999–2015), the rate of glacier recession of 3.9 ± 0.004 ma^?1 with a corresponding area loss of 500 ± 0.74m² (1 ± 0.1%) was higher than the retreat rate of 2.3 ± 0.001 ma^?1 and an area loss of 240 ± 0.02m² (0.48 ± 0.08%) during 1971–1999. In the field, the evidences of glacier recession are present in the form of separated dead ice blocks from the main Glacier, recessional dumps/moraines, active ice calving activity and a small proglacial pond/lake at the terminus/snout of the Glacier. However, the recession over the studied period has been very slow and is controlled by its topographic configuration, particularly the large altitudinal range (6030–3620 m), almost northerly aspect and steep slope (average ~ 30°).