Paleomagnetism of the Late Cretaceous ignimbrite from the Okhotsk-Chukotka Volcanic Belt,Kolyma-Omolon Composite Terrane: Tectonic implications

New Late Cretaceous paleomagnetic results from the Okhotsk-Chukotka Volcanic Belt in the Kolyma-Omolon Composite Terrane yield stable and consistent remanent directions. The Late Cretaceous (86–81 Ma) ignimbrites from the Kholchan and Ola suites were sampled at 19 sites in the Magadan area (60.4° N, 151.0° E). We isolated the characteristic paleomagnetic directions from 16 sampled sites using an alternating field demagnetization procedure. The primary nature of these directions is ascertained by dual polarities and positive fold tests. A tilt-corrected mean direction (D = 42.8°, I = 84.7°, k = 46.0, α₉₅ = 10.0°) yields a paleomagnetic pole of 66.7° N, 168.5° E (A₉₅ = 18.8°) which appears almost identical to the 90–67 Ma pole reported from the Lake El’gygytgyn area of the Okhotsk-Chukotka Volcanic Belt (Chukotka Terrane). This consistency suggests that the Kolyma-Omolon Composite Terrane and Chukotka Terrane has acted as a single tectonic unit since 80 Ma without any significant internal deformation. Accordingly, we calculate a combined 80 Ma characteristic paleomagnetic pole (Long. = 164.7° E, Lat. = 68.0°, A₉₅ = 10.9°, N = 12) for the Kolyma-Omolon-Chukotka Block which falls 16.5–17.5° south of the same age poles from Europe and East Asia. We ascribe this discrepancy in pole positions to tectonic activity in the area and infer a southward displacement of 1640 ± 1380 km for the Kolyma-Omolon-Chukotka Block with respect to the North American and Eurasian blocks since 80 Ma; more than 260 km of it is attributed to tectonic displacement in the Arctic Ocean due to the opening of the Canadian Basin.     

Age estimation of the deposition of the cretaceous Upper Sandstones and a later remagnetization event,from Hirna area,SE Ethiopia

Outcrops of the Cretaceous Upper sandstone formation some 375 km to the East of Addis Ababa on the motor Highway to Harar was paleomagnetically investigated. About seventy core samples were collected at various stratigraphic levels from 250–300 meters thick sedimentary formation. After standard sample preparations in the laboratory the resulting specimens were subjected to routine paleomagnetic demagnetization protocol. In the first steps of demagnetizations process the recent and viscous magnetizations were removed by heating until a temperature of level of 300 °C. Further demagnetization of the samples resulted in the isolation of the final magnetization with stable line segments that is directed towards the origin, which is interpreted as Characteristic Remanent Magnetization (ChRM). Rock – magnetic experiments have identified goethite (αFeOOH), hematite (αFe₂O₃), detritial hematite, and magnetite as the magnetic mineral phases carrying the remanence. The ChRM identified resulted in an average value of (D_s = 0.5°, I_s = ?0.7°, α₉₅ = 4.3°, N = 34) for the red sandstones while an average value of (D_s = 335.8°, I_s = ?31.8°, α₉₅ = 4.7°, N = 14) for the limestone intercalations. The former ChRM in the red sandstone is determined to be secondary while the latter ChRM is known to be primary. Comparison of these directional results and their pole equivalents with the African plate Apparent Polar Wander Path curve established by Besse and Courtillot (2003) give ages of between 115–130 Million years for the limestone intercalation and ages of 30 million years for red sandstone unit. These are interpreted respectively as estimates of the age of deposition and a later remagnetization respectively.     

H2O and CO2 in kimberlitic fluid as recorded by diamonds and olivines in several Ekati Diamond Mine kimberlites,Northwest Territories,Canada

Surface dissolution features on diamonds and Fourier Transform Infra Red spectroscopy (FTIR) of phenocrystal and xenocrystal olivines from kimberlites contain a record of magmatic fluid in kimberlite magmas. We investigated composition and behavior of kimberlitic fluid and the effect of volatiles on the eruption style and geology of kimberlites using microdiamonds and olivine concentrates from six kimberlite pipes with different lithologies and the character of diamond resorption (Ekati Diamond Mine, Northwest Territories, Canada). The study showed a clear correlation between the resorption style of diamond population of the kimberlites and the type of infrared (IR) spectra of their olivines. Four kimberlites have high quality diamonds with smooth regular surface features and high H₂O content of the olivines indicating the presence of H₂O-rich fluid during the emplacement. Fast ascent rates of fluid-rich magma can explain explosive eruption and filling the pipes with volcaniclastic kimberlite facies. Conversely, Grizzly and Leslie kimberlites have diamonds with complex sharp features diminishing diamond quality and indicating loss of the fluid. The slower ascent rates and less explosive eruption of the fluid-free magmas produced kimberlite pipes filled with magmatic facies kimberlite. Distinctive peaks in olivine IR spectra at 3356 and 3327 cm^? 1 were found to correlate with the presence of hydrous magmatic fluid. Character of diamond morphology suggests that during the whole ascent of all six kimberlites, the magmatic fluid when present had a high H₂O:CO₂ ratio.     

Importance of reversible attachment in predicting E. coli transport in saturated aquifers from column experiments

Drinking water wells indiscriminatingly placed adjacent to fecal contaminated surface water represents a significant but difficult to quantify health risk. Here we seek to understand mechanisms that limit the contamination extent by scaling up bacterial transport results from the laboratory to the field in a well constrained setting. Three pulses of Escherichia coli originating during the early monsoon from a freshly excavated pond receiving latrine effluent in Bangladesh were monitored in 6 wells and modeled with a two-dimensional (2-D) flow and transport model conditioned with measured hydraulic heads. The modeling was performed assuming three different modes of interaction of E. coli with aquifer sands: (1) irreversible attachment only (best-fit k_i = 7.6 day⁻¹); (2) reversible attachment only (k_a = 10.5 and k_d = 0.2 day⁻¹); and (3) a combination of reversible and irreversible modes of attachment (k_a = 60, k_d = 7.6, k_i = 5.2 day⁻¹). Only the third approach adequately reproduced the observed temporal and spatial distribution of E. coli, including a 4-log₁₀ lateral removal distance of ∼9 m. In saturated column experiments, carried out using aquifer sand from the field site, a combination of reversible and irreversible attachment was also required to reproduce the observed breakthrough curves and E. coli retention profiles within the laboratory columns. Applying the laboratory-measured kinetic parameters to the 2-D calibrated flow model of the field site underestimates the observed 4-log₁₀ lateral removal distance by less than a factor of two. This is promising for predicting field scale transport from laboratory experiments.     

Immune responses to combined effect of hypoxia and high temperature in the green-lipped mussel Perna viridis

Flow cytometry was used to examine immune responses in haemocytes of the green-lipped mussel Perna viridis under six combinations of oxygen level (1.5 mg O₂ l⁻¹, 6.0 mg O₂ l⁻¹) and temperature (20 °C, 25 °C and 30 °C) at 24 h, 48 h, 96 h and 168 h. The mussels were then transferred to normoxic condition (6.0 mg O₂ l⁻¹) at 20 °C for further 24 h to study their recovery from the combined hypoxic and temperature stress. Esterase (Est), reactive oxygen species (ROS), lysosome content (Lyso) and phagocytosis (Pha) were reduced at high temperatures, whereas hypoxia resulted in higher haemocyte mortality (HM) and reduced phagocytosis. For HM and Pha, changes were observed after being exposed to the stresses for 96 h, whereas only a 24 h period was required for ROS and Lyso, and a 48 h one for Est. Recovery from the stresses was observed for HM and Pha but not other immune responses.     

Evapotranspiration in the Pampean Region using field measurements and satellite data

Evapotranspiration (LE) is an important factor for monitoring crops, water requirements, and water consumption at local and regional scale. In this paper, we applied the semi-empirical model to estimate the daily latent heat flux (LE_d = Rn_d + A − B(Ts − Ta)). LE_d has been estimated using satellite images (Thematic Mapper sensor) and a local dataset (incoming and outgoing short- and long-wave radiation) measured during three years. We first estimated the daily net Radiation (Rn_d) from a linear equation derived from the instantaneous net Radiation (Rn_d = CRn_i + D). Subsequently, coefficients A and B have been estimated for two different cover vegetations (pasture and soybean). For each vegetation cover, an error analysis combining Rn_d, A, B, and surface and air temperatures has been calculated. Results showed that Rn_d had good performance (nonbias and low RMSE). LE_d errors for pasture and soybean were ±28 W m⁻² and ±40 W m⁻² respectively.     

Aluminum incorporation in α-PbO2 type TiO2 at pressures up to 20 GPa

Aluminum incorporation into the high pressure polymorph of TiO₂ with the structure of α-PbO₂ has been studied from 10 to 20 GPa and 1300 °C by XRD, high-resolution ²⁷Al MAS-NMR and TEM. Al-doped α-PbO₂ type TiO₂ can be recovered at atmospheric pressure. Al₂O₃ solubility in α-PbO₂ type TiO₂ increases with increasing the synthesis pressure. The α-PbO₂ type TiO₂ polymorph is able to incorporate up to 35 wt.% Al₂O₃ at 13.6 GPa and 1300 °C, being the substitution of Ti⁴⁺ by Al³⁺ on normal octahedral sites the mechanism of solubility. The transition to the higher pressure TiO₂ polymorph with the ZrO₂ baddeleyite structure, Akaogiite, has not been observed in the quenched samples at room pressure. The microstructure of the recovered sample synthesized at 16 GPa and 1300 °C points to the existence of a non-quenchable aluminum titanium oxide phase at these conditions.     

Multiple extreme environmental conditions of intermittent soda pans in the Carpathian Basin (Central Europe)

Soda lakes and pans represent saline ecosystems with unique chemical composition, occurring on all continents. The purpose of this study was to identify and characterise the main environmental gradients and trophic state that prevail in the soda pans (n = 84) of the Carpathian Basin in Central Europe. Underwater light conditions, dissolved organic matter, phosphorus and chlorophyll a were investigated in 84 pans during 2009–2010. Besides, water temperature was measured hourly with an automatic sensor throughout one year in a selected pan. The pans were very shallow (median depth: 15 cm), and their extremely high turbidity (Secchi depth median: 3 cm, min: 0.5 cm) was caused by high concentrations of inorganic suspended solids (median: 0.4 g L⁻¹, max: 16 g L⁻¹), which was the dominant (>50%) contributing factor to the vertical attenuation coefficient in 67 pans (80%). All pans were polyhumic (median DOC: 47 mg L⁻¹), and total phosphorus concentration was also extremely high (median: 2 mg L⁻¹, max: 32 mg L⁻¹). The daily water temperature maximum (44 °C) and fluctuation maximum (28 °C) were extremely high during summertime. The combination of environmental boundaries: shallowness, daily water temperature fluctuation, intermittent hydroperiod, high turbidity, polyhumic organic carbon concentration, high alkalinity and hypertrophy represent a unique extreme aquatic ecosystem.     

Oxfordian magnetostratigraphy of Britain and its correlation to Tethyan regions and Pacific marine magnetic anomalies

A suite of 11 sections through the Oxfordian (Upper Jurassic) strata in the Dorset and Yorkshire regions of England and the Isle of Skye in Scotland yielded magnetic polarity patterns directly calibrated to the ammonite biostratigraphy of the Boreal and the Subboreal faunal provinces. The sections include the leading candidate for the global stratotype (GSSP) for the Callovian–Oxfordian stage boundary. The mean Oxfordian paleomagnetic pole derived from the Dorset and Yorkshire sections is 71.3°N, 172.6°E (δp = 4.2°, δm = 6.1°). The integrated magneto-biostratigraphic scale is consistent with results from the Sub-Mediterranean faunal province and extends the polarity pattern to the base of the Oxfordian. After adjusting for the estimated durations of ammonite subzones from cycle stratigraphy, the magnetostratigraphy confirms models for marine magnetic anomalies M30 through to M37, including some of the short-duration features recorded by deep-tow magnetic surveys in the western Pacific. The Callovian–Oxfordian boundary (base of Quenstedtoceras mariae Zone) occurs in a normal-polarity zone that is correlated to the youngest part of polarity chron M37n of this extension to the M-sequence.     

Age and nature of eclogites in the Huwan shear zone,and the multi-stage evolution of the Qinling-Dabie-Sulu orogen,central China

In situ LA-ICPMS U-Pb, trace element, and Hf isotope data in zircon demonstrate a Carboniferous age for eclogite-facies metamorphism in Siluro-Devonian protoliths in the Huwan shear zone, Dabie Mountains, Central China. This age contrasts with the more prevailing Triassic age for high- to ultrahigh pressure (HP to UHP) metamorphism in the Qinling-Dabie-Sulu orogen. Metamorphic zircon in two eclogite samples from Sujiahe is characterized by low Th/U ratios, small negative Eu anomalies, flat HREE patterns, and low ¹⁷⁶Lu/¹⁷⁷Hf ratios. These geochemical signatures suggest that the zircon crystallized in the presence of garnet and in the absence of plagioclase feldspar. Furthermore, temperatures of ~ 655 and ~ 638 °C, calculated using the Ti content of zircon, are consistent with their formation during eclogite-facies metamorphism. The weighted mean ²⁰⁶Pb/²³⁸U age of 309 ± 4 Ma (2δ) for this zircon improves previous age estimates for eclogite-facies metamorphism in the Huwan shear zone, ranging from 420 to 220 Ma. Metamorphic zircon from one eclogite sample from Hujiawan, most likely formed during prograde metamorphism, yields an equivalent age estimate of 312 ± 11 Ma. Magmatic zircon cores in the three samples yield ages for the magmatic protoliths of the eclogites ranging from 420 ± 7 to 406 ± 5 Ma, and post-dating the middle Paleozoic collision of the North China and the Qinling terrain. The zircon crystals in the three eclogite samples display a large variation of ε_Hf (t) values of ? 4.9 to 21.3. The metamorphic zircon overgrowths show the same range of ε_Hf (t) values as those of the inherited magmatic crystal interiors. This suggests that the metamorphic zircon overgrowths may have formed by dissolution-reprecipitation of pre-existing magmatic zircon thereby preserving their original Hf isotopic composition. The high ε_Hf (t) values suggest that the protoliths were derived from depleted mantle sources, most likely Paleotethyan oceanic crust; while the low ε_Hf (t) values are attributed to crustal contamination. Some eclogites in the Huwan shear zone have a distinctive signature of continental crust most probably derived from the Yangtze Craton. The coexistence of Paleozoic oceanic crust and Neoproterozoic continental crust with similar metamorphic ages in the Huwan shear zone implies that Paleozoic Paleotethyan oceanic crust was produced within a marginal basin of the northern Yangtze Craton. The opening of the Paleo-Tethyan ocean was slightly younger than the collision of the North China Craton and the Qinling terrain during the Late Paleozoic in the Qinling-Dabie-Sulu orogen. Subduction of the Paleo-Tethyan oceanic crust and associated continental basement resulted in the 309 ± 2 Ma (2σ) eclogite-facies metamorphism in the Huwan shear zone. The subsequent Triassic continent-continent collision led to the final coalescence of the Yangtze and Sino-Korean cratons. Amalgamation of the Yangtze and North China cratons was, therefore, a multistage process extending over at least 200 Ma.     

Recycling of harbor sediment as lightweight aggregate

Sediment sampled from Taichung Harbor was mixed with local reservoir sediment at different weight ratios to prepare lightweight aggregate at 1050, 1100, and 1150 °C. A pressure of 3000 or 5000 psi was used to shape the powder mixtures into pellets before the heating processes. The results indicate that the leaching levels of trace metals from the lightweight aggregate samples are considerably reduced to levels less than Taiwan Environmental Protection Administration regulatory limits. Increasing final process temperature tends to reduce the bulk density and crushing intensity of lightweight aggregate with a concomitant increase in water sorption capability. Lightweight aggregate with the lowest bulk density, 0.49 g cm⁻³ for the 5000 psi sample, was obtained with the heating process to 1150 °C. Based on the X-ray absorption near edge structure results, FeSO₄ decomposition with a concomitant release of SO_x (x = 2, 3) is suggested to play an important role for the bloating process in present study.     

High-precision 40Ar/39Ar age of the Jänisjärvi impact structure (Russia)

The ～ 14 km diameter Jänisjärvi impact structure is located in Svecofennian Proterozoic terrain in the southeastern part of the Baltic shield, Karelia, Russia. Previous radioisotopic dating attempts gave K/Ar and ⁴⁰Ar/³⁹Ar ages of 700 ± 5 Ma and 698 ± 22 Ma, respectively, with both results being difficult to interpret. Recent paleomagnetic results have challenged these ages and proposed instead ages of either 500 Ma or 850–900 Ma. In order to better constrain the age of the Jänisjärvi impact structure, we present new ⁴⁰Ar/³⁹Ar data for the Jänisjärvi impact melt rock. We obtained five concordant isochron ages that yield a combined isochron age of 682 ± 4 Ma (2σ) with a MSWD of 1.2, P = 0.14, and ⁴⁰Ar/³⁶Ar intercept of 475 ± 3. We suggest that this date indicates the age of the impact and therefore can be used in conjunction with existing paleomagnetic results to define the position of the Baltica paleocontinent at that time. Argon isotopic results imply that melt homogenization was achieved at the hundred-micrometer scale certainly, because of the low-silica content of the molten target rock that allows fast ⁴⁰Ar^? diffusion in the melt. However, the large range of F(⁴⁰Ar^?_inherited) (4.1% to 11.0%) observed for seven grains shows that complete isotopic homogenization was not reached at the centimeter and perhaps the millimeter scale. The F(⁴⁰Ar^?_inherited) results are also in good agreement with previous Rb and Sr isotopic data.     

Magnetic susceptibility and Cs-137 inventory variability as influenced by land use change and slope positions in a hilly,semiarid region of west-central Iran

The objective of this study was to explore the slope position and land use change effects on the variability in magnetic susceptibility and ¹³⁷Cs inventory as the soil redistribution indicators in a hilly semiarid calcareous area in Iran. The selected study area is located in a hilly region with pasture and cultivation land use of Fereydunshahr, Isfahan Province in west-central Iran. In the two mentioned dominant ecosystems, four slope positions including summit, shoulder, backslope and footslope were identified and in each land use and slope position, three cores were selected to collect 72 soil samples from three depths (0–10, 10–20, 20–30 cm) in an area of 15 × 15 cm. Additional 28 soil samples were collected from the reference site for soil loss and deposition calculations by using the Cs-137 measurement. The results of the study with the use of the Cs-137 technique showed that the average soil loss in the pasture land (46.4 t ha^− 1 yr^− 1) was significantly (p < 0.05) lower than the average soil loss in the cultivated land (80.4 t ha^− 1 yr^− 1). The highest soil loss in both land uses was obtained in the shoulder position, 60.1 and 84.4 t ha^− 1 yr^− 1, respectively, for the pasture and cultivated lands. Moreover, the highest rates of soil deposition was observed in a footslope position in both land uses and they were 34 and 32.4 t ha^− 1 yr^− 1 for the pasture and cultivated lands, respectively. Magnetic susceptibility was significantly (p < 0.05) greater in pasture (χ_lf = 41.51 × 10^− 8 m³/kg) than in the cultivated land (χ_lf = 34.90 × 10^− 8 m³/kg). The pasture land with a lower soil loss rate, indicated significantly higher magnetic susceptibility in all landform positions as compared to that in the cultivated land. The results of the correlation analysis showed that among the studied soil physico-chemical properties, χ_lf (r = 0.83, p < 0.01) in the pasture land had the highest correlation with the Cs-137 inventory. Throughout the non-linear regression analysis, χ_lf was introduced for relating soil parameters and the cesium inventory explained 68% and 79% of the total variability of ¹³⁷Cs in the pasture and cultivated lands, respectively. The results implied that the variability in the magnetic susceptibility within the hillslope is consistent with the variation of the Cs-inventory; and the results thus demonstrate the slope and land use effects on soil redistribution.     

Inorganic carbon and nutrient fluxes on the Arctic Shelf

Historic data from the Russian-American Hydrochemical Atlas of Arctic Ocean together with data from the TRANSDRIFT II 1994 and TUNDRA 1994 cruises have been used to assess the spatial and inter-annual variability of carbon and nutrient fluxes, as well as air–sea CO₂ exchange in the Laptev and western East Siberian Seas during the summer season. Budget computations using summer data of dissolved inorganic phosphate (DIP), dissolved inorganic nitrogen (DIN) and dissolved inorganic carbon (DIC) gives that the Laptev Sea shelf is a net sink of DIP and DIN of 2.5×10⁶, 23.2×10⁶ mol d⁻¹, respectively, while it is a net source of DIC (excluding air–sea exchange) of 1249×10⁶ mol d⁻¹. In the East Siberian Seas the budget computations give 0.5×10⁶, −11.4×10⁶ and −173×10⁶ mol d⁻¹ (minus being a sink) for DIP, DIN, and DIC, respectively. In summers, the Laptev Sea Shelf is net autotrophic while the East-Siberian Sea Shelf is net heterotrophic, and both systems are weak net denitrifying. The Laptev Sea Shelf takes up 2.1 mmol CO₂ m⁻² d⁻¹ from atmosphere, whereas the western part of the East-Siberian Sea Shelf loose 0.3 mmol CO₂ m⁻² d⁻¹ to the atmosphere. The variability of DIP, DIN and DIC fluxes during summer in the different regions of the Laptev and East Siberian Seas depends on bottom topography, river runoff, exchange with surrounding seas and wind field.     

The oxidation state of sulfur in magmatic fluids

Sulfur compounds in volcanic gases are responsible for the global cooling after explosive eruptions and they probably controlled the early evolution of the Earth's atmosphere. We have therefore studied the oxidation state of sulfur in aqueous fluids under the pressure and temperature conditions and oxygen fugacities typical for magma chambers (0.5–3 kbar, 650–950 °C, Ni–NiO to Re–ReO₂ buffer conditions). Sulfur speciation was determined by Raman spectroscopy of quenched fluids trapped as inclusions in quartz. Our results show that sulfur in hydrothermal fluids and volcanic gases is much more oxidized than previously thought and in particular, some explosive eruptions may release a significant fraction of sulfur as SO₃ or its hydrated forms. In the pressure range from 500 to 2000 bar, the equilibrium constant K₁ of the reaction 2H₂S + 3O₂ = 2SO₂ + 2H₂O in aqueous fluids can be described by lnK₁ = ?(57.1 ± 7.1) + (173,480 ± 7592)T^? 1, where T is temperature in Kelvin. The equilibrium constant K₂ for the reaction SO₂ + ½O₂ = SO₃ in aqueous fluids, where SO₃ may include hydrated forms, such as H₂SO₄, was found to be strongly pressure dependent, with lnK₂ = ?(5.2 ± 5.7) + (19,243 ± 5993)T^? 1 at 1500 bar; lnK₂ = ?(11.1 ± 1.3) + (25,383 ± 1371)T^? 1 at 2000 bar and lnK₂ = ?(22.1 ± 2.2) + (37,082 ± 2248)T^? 1 at 2500 bar. Our data imply that volcanoes may directly inject hexavalent sulfur in the form of H₂SO₄ into the atmosphere, not only on Earth, but possibly also on Venus and on Mars, when it was still tectonically active. Remote measurements from satellites may have underestimated the sulfur yield of some recent eruptions. Moreover, the mechanisms of the interaction of volcanic gases with the stratosphere need to be reconsidered.     

Mercury emissions and stable isotopic compositions at Vulcano Island (Italy)

Sampling and analyses methods for determining the stable isotopic compositions of Hg in an active volcanic system were tested and optimized at the volcanic complex of Vulcano (Aeolian Islands, Italy). Condensed gaseous fumarole Hg_(fum)^T, plume gaseous elemental Hg_(g)⁰ and plume particulate Hg_(p)^II were obtained at fumaroles F0, F5, F11, and FA. The average total Hg emissions, based on Hg^T/SO₂ in condensed fumarolic gases and plumes, range from 2.5 to 10.1 kg y^? 1, in agreement with published values [Ferrara, R., Mazzolai, B., Lanzillotta, E., Nucaro, E., Pirrone, N., 2000. Volcanoes as emission sources of atmospheric mercury in the Mediterranean Basin. Sci. Total Environ. 259(1–3), 115–121; Aiuppa, A., Bagnato, E., Witt, M.L.I., Mather, T.A., Parello, F., Pyle, D.M., Martin, R.S., 2007. Real-time simultaneous detection of volcanic Hg and SO₂ at La Fossa Crater, Vulcano (Aeolian Islands, Sicily). Geophys. Res. Lett. 34(L21307).]. Plume Hg_(p)^II increases with distance from the fumarole vent, at the expense of Hg_(g)⁰ and indicates significant in-plume oxidation and condensation of fumarole Hg_(fum)^T.Relative to the NIST SRM 3133 Hg standard, the stable isotopic compositions of Hg are δ²⁰²Hg_(fum)^T = ? 0.74‰ ± 0.18 (2SD, n = 4) for condensed gaseous fumarole Hg_(fum)^T, δ²⁰²Hg_(g)⁰ = ? 1.74‰ ± 0.36 (2SD, n = 1) for plume gaseous elemental Hg_(g)⁰ at the F0 fumarole, and δ²⁰²Hg_(p)^II = ? 0.11‰ ± 0.18 (2SD, n = 4) for plume particulate Hg_(p)^II. The enrichment of Hg_(p)^II in the heavy isotopes and Hg_(g)⁰ in the light isotopes relative to the total condensed fumarolic Hg_(fum)^T gas complements the speciation data and demonstrates a gas-particle fractionation occurring after the gas expulsion in ambient T° atmosphere. A first order Rayleigh equilibrium condensation isotope fractionation model yields a fractionation factor α_cond-gas of 1.00135 ± 0.00058.     

Variability of the dissolved nutrient (N,P, Si) concentrations in the Bay of Annaba in relation to the inputs of the Seybouse and Mafragh estuaries

Dissolved inorganic nitrogen (DIN), phosphate (PO₄) and silicic acid (Si(OH)₄) loads from the Seybouse and the Mafragh estuaries into the Bay of Annaba, Algeria, were assessed at three stations of the Bay over three years. The Seybouse inputs had high levels of DIN and PO₄, in contrast to the Mafragh estuary’s near-pristine inputs; Si(OH)₄ levels were low in both estuaries. The DIN:PO₄ molar ratios were over 30 in most samples and the Si(OH)₄:DIN ratio was less than 0.5 in the Seybouse waters, but nearly balanced in the Mafragh. The specific fluxes of Si–Si(OH)₄ (400–540 kg Si km⁻² yr⁻¹) were comparable in the two catchments, but those of DIN were several-fold higher in the Seybouse (373 kg N km⁻² yr⁻¹). The inner Bay affected by the Seybouse inputs had high levels of all nutrients, while the Mafragh plume and the outer marine station were less enriched.     

Whistlers observed at low-latitude ground-based VLF facility in Fiji

The propagation features of nighttime whistlers to low-latitude station, Suva (−18.2°, 178.3°, geomag. lat. −22.1°, geomag. long. 253.5°, L=1.15), Fiji, from preliminary observations made during the period from September 2003–2005, are reported. The observations of ELF–VLF signals commenced in September 2003 using the VLF set-up of World Wide Lightning Location Network at our station. The whistlers were observed during the severe magnetic storm of 20–22 November 2003 and moderate magnetic storm of 17–19 July 2005. A whistler with dispersion D=12.7 s^1/2 occurred on 22 November at 00:11 h LT. On 20 July at 01:00 h LT, a short whistler with dispersion D=20.9 s^1/2 and two whistler events having two-component whistlers with D=15.8, 16.7 s^1/2 and 16.7, 17.3 s^1/2 were observed. Non-ducted pro-longitudinal mode of the whistler propagation supported by negative latitudinal electron density gradients in the ionosphere that are enhanced by magnetic storms, seems most likely mode of propagation for the whistlers with dispersion of 12.7–17.3 s^1/2 to this low-latitude station.     

Adsorption studies of aqueous Pb(II) onto a sugarcane bagasse/multi-walled carbon nanotube composite

Adsorption of Pb²⁺ from aqueous solution onto a sugarcane bagasse/multi-walled carbon nanotube (MWCNT) composite was investigated by using a series of batch adsorption experiments and compared with the metal uptake ability of sugarcane bagasse. The efficiency of the adsorption processes was studied experimentally at various pH values, contact times, adsorbent masses, temperatures and initial Pb²⁺ concentrations. A pH of 4.5 was found to be the optimum pH to obtain a maximum adsorption percentage in 120 min of equilibration time. The composite showed a much enhanced adsorption capacity for Pb²⁺ of 56.6 mg g⁻¹ compared with 23.8 mg g⁻¹ for bagasse at 28 °C. The Langmuir adsorption isotherm provided the best fit to the equilibrium adsorption data. The pseudo first-order, pseudo second-order, intraparticle diffusion and Elovich kinetics models were used to analyse the rate of lead adsorption and the results show that the Elovich model is more suitable. The thermodynamic parameters of adsorption, namely ΔG°, ΔH° and ΔS°, were determined over the temperature range of 20–45 °C. The adsorption of Pb²⁺ onto both bagasse and the sugarcane bagasse/MWCNT composite was found to be spontaneous but for the former adsorbent it was enthalpy-driven whereas for the latter it was entropy-driven. Desorption of the lead-loaded adsorbents was fairly efficient with 0.1 mol dm⁻³ HCl. Overall this composite has the potential to be a good adsorbent for the removal of Pb²⁺ from wastewaters.     

Potential application of activated carbon from maize tassel for the removal of heavy metals in water

Water-pollution problems worldwide have led to an acute shortage of clean and pure water for both domestic and human consumption. Various technologies and techniques are available for water treatment which includes the use of activated carbon. In this study activated carbons used for the removal of lead (II) ions from water samples were prepared from maize tassels (an agricultural waste residue) which were modified using physical and chemical activation. In the physical activation CO₂ was used as the activating agent, while in chemical activation H₃PO₄ with an impregnation ratio ranging from 1 to 4 was employed. The maize tassel was pyrolysed at different temperatures ranging from 300 °C to 700 °C in an inert atmosphere for a period of 60 min and activated at 700 °C for 30 min. The effects of activation temperature, impregnation ratio and duration were examined. The resultant modified tassels were characterised by measuring their particle-size distribution, porosities, pore volume, and pore-size distribution using scanning electron microscopy (SEM). The activated carbon produced by chemical activation had the highest BET surface area ranging from 623 m² g⁻¹ to 1 262 m² g⁻¹. The surface chemistry characteristics of the modified tassels were determined by FT–IR spectroscopy and Boehm’s titration method. The experimental data proved that properties of activated carbon depend on final temperature of the process, impregnation ratio and duration of the treatment at final temperature. The adsorption studies showed that chemically prepared activated carbon performed better than physically prepared activated carbon.