Determination of Zirconium, Niobium, Hafnium and Tantalum at ng g-1 Levels in Geological Materials by Direct Nebulisation of Sample HF Solution into FI-ICP-MS

We have developed a rapid and accurate method to determine Zr, Nb, Hf and Ta (denoted as HFSE) in geological samples by inductively coupled plasma-mass spectrometry fitted with a flow injection system (FI-ICP-MS). The method involves sample decomposition by HF followed by HF dissolution of HFSE coprecipitated with insoluble M and Ca fluoride residues formed during the initial HF attack. This HF solution was directly nebulized into an ICP mass spectrometer. An external calibration curve method and an isotope dilution method (ID) were applied for the determination of Nb and Ta, and of Zr and Hf, respectively. Recovery yields of HFSE were > 96% for peridotite, basalt and andesite compositions, apart from Zr and Hf for peridotite (> 85%). No matrix effects for either signal intensities of HFSE or isotope ratios of Zr and Hf were observed in basalt, andesite and peridotite solutions down to a dilution factor of 100. Detection limits in silicate rocks were 40, 2, 1 and 0.1 ng g-1 for Zr, Nb, Hf and Ta, respectively. This technique required only 0.1 ml of sample solution, and thus is suitable for analysing small and/or precious samples such as meteorites, mantle peridotites and their mineral separates. We also present newly determined data for the Zr, Nb, Hf and Ta concentrations in USGS silicate reference materials DTS-1, PCC-1, BCR-1, BHVO-1 and AGV-1, GSJ reference materials JB-1, -2, -3, JA-1, -2 and -3, and the Smithsonian reference Allende powder.     

Litterfall of three subtropical mangrove species in the family Rhizophoraceae

This study was conducted to evaluate and compare the litterfall dynamics of three mangrove species in the family Rhizophoraceae: Rhizophora stylosa, Kandelia obovata, and Bruguiera gymnorrhiza, in Manko Wetland, Okinawa Island, Japan. Over 3?years, these species showed highest litterfall of leaves and stipules in summer and the lowest litterfall in winter. Litterfall of flowers and fruits peaked in July for R. stylosa, and in August and again in October?CNovember for K. obovata. Litterfall of flower buds, flowers, and propagules occurred throughout the year for B. gymnorrhiza, but was highest in summer. Litterfall of propagules was highest in September and May for R. stylosa and K. obovata, respectively. Kendall??s coefficient of concordance revealed that the monthly changes for leaf, stipule, flower, and fruit litterfalls of all the species were strongly and significantly concordant among the years. The conversion rate of flowers to propagules was 2.3?% in R. stylosa, 5.9?% in K. obovata, and 10.3?% in B. gymnorrhiza. Total annual litterfall in R. stylosa was significantly different from K. obovata and B. gymnorrhiza; however, the latter two species showed no significant differences. Leaves contributed the most to the total litterfall of all three species, and represented 58.4, 54.0, and 50.4?% of the total litterfall for R. stylosa, K. obovata, and B. gymnorrhiza, respectively. Except for branches and flower bud primordia, all other components of litterfall had clear annual cycles for all three species. Rhizophora stylosa and K. obovata showed a negative correlation between leaf production and reproductive organ production, but B. gymnorrhiza tended to increase leaf production with increasing reproductive organ production.     

The 11 March 2011 Tohoku Tsunami Survey in Rikuzentakata and Comparison with Historical Events

On 11 March 2011, a moment magnitude M _w = 9.0 earthquake occurred off the Japan Tohoku coast causing catastrophic damage and loss of human lives. In the immediate aftermath of the earthquake, we conducted the reconnaissance survey in the city of Rikuzentakata, Japan. In comparison with three previous historical tsunamis impacting the same region, the 2011 event presented the largest values with respect to the tsunami height, the inundation area and the inundation distance. A representative tsunami height of 15 m was recorded in Rikuzentakata, with increased heights of 20 m around rocky headlands. In terms of the inundation area, the 2011 Tohoku tsunami exceeded by almost 2.6 times the area flooded by the 1960 Chilean tsunami, which ranks second among the four events compared. The maximum tsunami inundation distance was 8.1 km along the Kesen River, exceeding the 1933 Showa and 1960 Chilean tsunami inundations by factors of 6.2 and 2.7, respectively. The overland tsunami inundation distance was less than 2 km. The tsunami inundation height linearly decreased along the Kesen River at a rate of approximately 1 m/km. Nevertheless, the measured inland tsunami heights exhibit significant variations on local and regional scales. A designated “tsunami control forest” planted with a cross-shore width of about 200 m along a 2 km stretch of Rikuzentakata coastline was completely overrun and failed to protect the local community during this extreme event. Similarly, many designated tsunami shelters were too low and were overwashed by tsunami waves, thereby failing to provide shelter for evacuees—a risk that had been underestimated.     

Diagnostic metrics for evaluation of annual and diurnal cycles

Two sets of diagnostic metrics are proposed for evaluation of global models?? simulation of annual and diurnal cycles of precipitation. The metrics for the annual variation include the annual mean, the solstice and equinoctial asymmetric modes of the annual cycle (AC), and the global monsoon precipitation domain and intensity. The metrics for the diurnal variation include the diurnal range, the land?Csea contrast and transition modes of the diurnal cycle (DC), and the diurnal peak propagation in coastal regions. The proposed modes for the AC and DC represent faithfully the first two leading empirical orthogonal functions and explain, respectively, 82% of the total annual variance and 87% of the total diurnal variance over the globe between 45°S and 45°N. The simulated AC and DC by the 20-km-mesh MRI/JMA atmospheric general circulation model (AGCM) are in a wide-ranging agreement with observations; the model considerably outperforms any individual AMIP II GCMs and has comparable performance to 12-AMIP II model ensemble simulation measured by Pearson??s pattern correlation coefficient. Comparison of four versions of the MRI/JMA AGCM with increasing resolution (180, 120, 60, and 20?km) reveals that the 20-km version reproduces the most realistic annual and diurnal cycles. However, the improved performance is not a linear function of the resolution. Marked improvement of the simulated DC (AC) occurs at the resolution of 60?km (20?km). The results suggest that better represented parameterizations that are adequately tuned to increased resolutions may improve models?? simulation on the forced responses. The common deficiency in representing the monsoon domains suggests the models having difficulty in replicating annual march of the Subtropical Highs that is largely driven by prominent east-west land?Cocean thermal contrast. Note that the 20-km model reproduces realistic diurnal cycle, but fails to capture realistic Madden-Julian Oscillation.     

Pressure and temperature dependence of the viscosity of a NaAlSi<Subscript>2</Subscript>O<Subscript>6</Subscript> melt

The viscosity of a silicate melt of composition NaAlSi₂O₆ was measured at pressures from 1.6 to 5.5 GPa and at temperatures from 1,350 to 1,880°C. We employed in situ falling sphere viscometry using X-ray radiography. We found that the viscosity of the NaAlSi₂O₆ melt decreased with increasing pressure up to 2 GPa. The pressure dependence of viscosity is diminished above 2 GPa. By using the relationship between the logarithm of viscosity and the reciprocal temperature, the activation energies for viscous flow were calculated to be 3.7 ± 0.4 × 10² and 3.7 ± 0.5 × 10² kJ/mol at 2.2 and 2.9 GPa, respectively.     

Variability of surface characteristics and energy flux patterns of sunn hemp (Crotalaria juncea L.) under well-watered conditions

There is not much information in the literature about the energy partitioning and micrometeorological features of sunn hemp. Therefore, in this study, the variations in the energy-balance components and plant characteristics such as aerodynamic and surface conductance, crop coefficient, albedo, short- and long wave down- and upward radiation have been measured and estimated for the time period from August to October 2004 over an irrigated sand field at the Arid Land Research Center in Tottori, Japan. The Bowen ratio energy-balance method was used to calculate the partitioning of heat fluxes of sunn hemp. The Bowen ratio values at the first growing stages in August were found to be higher than the Bowen ratio values at the latest growing stages in September and October because of the heavy rain and high soil-water content. The daytime averaged Bowen ratio was 0.19. During the measurement period, the daytime average net radiation, and soil, latent and sensible heat fluxes were approximately 231, 28, 164, and 39 W m^–2, respectively. The net radiation and soil heat flux showed decreasing trends from the beginning to the end of the experiment period due to the atmospheric and crop growth conditions. The daytime averages of aerodynamic and surface conductance for sunn hemp were around 31 and 17 mm s^–1, respectively. Also, the daytime average albedo of sunn hemp was around 19%. Finally, the high precipitation amount due to typhoons, high soil-water content, low available energy and low vapor-pressure deficit lead to decreasing trend of the energy fluxes during the generative phase of sunn hemp.     

The distribution of manganese and iron between ilmenite and granitic magma in the Ôsumi Peninsula,Japan

Manganoan ilmenite with a variable manganese content occurs as an early accessory constituent of granitic rocks in the Ôsumi Peninsula, southern Kyushu. Electron probe micro-analysis of a grain containing highest manganese gives the structural formula (Fe _1.23 ²⁺ Mn _0.81 ²⁺ ) (Ti_1.97) O₆, if all of the manganese and iron are in the divalent state. The manganese content of manganoan ilmenite increases with an increase of the differentiation index of host rocks, however, the amount of ilmenite tends to decrease with the increase of the same index. The mode of occurrence of the ilmenite suggests that it is the first mafic mineral to precipitate from the magma. The average value of the distribution coefficient of manganese and ferrous iron between ilmenite and granitic magma is 5.5, if the Mn/Fe ratio of the granitic rocks represents that of granitic magma. The variation in the FeO and MnO contents against the differentiation index for granitic rocks of the Ôsumi Peninsula, and the value of the distribution coefficient, show that high manganoan ilmenite is stable in the most differentiated granitic rock of the Ôsumi Peninsula.     

Determination of Ge, As, Se and Te in Silicate Samples Using Isotope Dilution-Internal Standardisation Octopole Reaction Cell ICP-QMS by Normal Sample Nebulisation

A method for the determination of Ge, As, Se and Te in silicate samples using isotope dilution-internal standardisation (ID-IS) octopole reaction cell (ORC) ICP-QMS by normal sample nebulisation was developed. The method does not involve either hydride generation or ion exchange. Germanium, Se and Te were determined by isotope dilution (ID), and As was determined by ID-IS. A silicate sample with an added Ge-Se-Te spike was digested with an HF-HNO₃-HBr mixture, dried, re-dissolved with HF and the supernatant liquid was directly aspirated into an ORC-ICP-QMS instrument with He or H₂ gas. No matrix effects were observed down to a dilution factor (DF) of ∼ 70 for Ge, Se and Te and DF of ∼ 1000 for As, which resulted in 3s detection limits in silicates of 2, 1, 0.1 and 4 ng g⁻¹, respectively. Advantages of the method are the simple sample introduction as well as a capability of determining S, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta by ID-IS-ICP-QMS/SFMS from the same solution. Furthermore, the total sample solution consumption was only 0.253 ml with DF = 2000. Therefore, only a 0.13 mg test portion was required. To demonstrate the applicability of this technique, Ge, As, Se and Te in eight silicate reference materials were determined, as well as S, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta in four carbonaceous chondrites.     

ENSO modulation by mountain uplift

How climate changes will modify the behavior of El Niño/Southern Oscillation (ENSO) is one of the important questions in future climate projections. An investigation under different climate forcing gives us a good insight on the mechanism of ENSO variability and its changes. In this paper, sensitivity on ENSO by progressive mountain uplift is investigated with an atmosphere–ocean coupled general circulation model. We used eight different mountain heights: 0% (no mountain), 20, 40, 60, 80, 100 (control run), 120, and 140%. Land–sea distribution is the same for all experiments and all mountains in the world are uniformly varied. Systematic changes in precipitation and circulation fields as well as SST are obtained with progressive mountain uplift. In the summertime, the precipitation area moved inland of the Asian continent with mountain uplift, while the Pacific subtropical anticyclone and associated trade winds became stronger. The western Pacific warm pool and ENSO also systematically changed. When the mountain height is low, a warm pool is located over the central Pacific due to weak trade winds in the Pacific. The model ENSO is strongest, its frequency longest, and is most periodic in the no mountain run. The model ENSO becomes weaker, shorter and less periodic when the mountain height increases. Strengthening the mean state trade winds and narrowing meridional extent of equatorial wind and ocean response by mountain uplift would be responsible for ENSO modulation.     

Upper Mantle Velocity Structure Estimated From Ps-Converted Wave Beneath the North-Eastern Japan Arc

Summary. The upper boundary of the descending oceanic plate is located by using PS -waves (converted from P to S at the boundary) in the Tohoku District, the north-eastern part of Honshu, Japan. the observed PS-P time data are well explained by a two-layered oceanic plate model composed of a thin low-velocity upper layer whose thickness is less than 10 km and a thick high-velocity lower layer; the upper and lower layers respectively have 6 per cent lower and 6 per cent higher velocity than the overriding mantle. the estimated location of the upper boundary is just above the upper seismic plane of the double-planed deep seismic zone. This result indicates that events in the upper seismic plane, at least in the depth range from 60 to 150 km, occur within the thin low-velocity layer on the surface of the oceanic plate.