Preferential exchange rate effect of isotopic fractionation in a melting snowpack

Stable isotope exchange processes between solid and liquid phases of a natural melting snowpack are investigated in detail by separating the liquid water from snow grains at different depths of the snowpack and collecting the bottom discharge using a lysimeter. In the melting–freezing mass exchange process between the two phases, the theoretical slope of the δD? δ¹⁸O line for newly refrozen ice is calculated to be nearly that of pore water. However, based on observations of the isotopic evolution and snow grain coarsening of the snowpack, it is demonstrated that the slope of the δD? δ¹⁸O line for newly refrozen ice is equal to that of the original ice. This is proved to be due to preferential water flow in the snowpack, which leads to relatively more deuterium and less oxygen‐18 in the mobile water than the immobile water because of the kinetic effect. Higher mass exchange rate in the mobile water region results in excess deuterium in the bulk refrozen ice, compared with the fractionation of uniform fractionation factors and exchange rate. This effect, which is termed the ‘preferential exchange rate effect of isotopic fractionation’, is shown to be larger in the lower part than the upper part of the snowpack. Copyright © 2008 John Wiley & Sons, Ltd.     

Underplating of mélange evidenced by the depositional ages: U–Pb dating of zircons from the Shimanto accretionary complex, southwest Japan

Abstract   Growth of an accretionary prism is effected by frontal accretion and deep subsurface underplating at the base of the prism. A systematic oceanward and structurally downward younging of underplated sequences is expected as the prism thickens and grows. To test this hypothesis and explore the processes of underplating, the U–Pb ages of zircon grains contained in underplated mélange sequences or packages of the Late Cretaceous and early Paleogene accretionary complex of the Shimanto Belt, southwest Japan, were determined using LA–ICP–MS laser technology. The results document systematic but intermittent younging ages within a single underplated mélange package. This finding suggests that underplating took place episodically during a period of several million years and that between episodes of underplating, a large amount of sediment was subducted to depths much greater than where underplating was occurring.     

Selective release of D and 13C from insoluble organic matter of the Murchison meteorite by impact shock

Abstract— We performed shock‐recovery experiments on insoluble organic matter (IOM) purified from the Murchison meteorite, and determined the abundances and isotope ratios of hydrogen and carbon in the shocked IOM sample. We also performed shock experiments on type III kerogen and compared the results of these experiments with the experimental results regarding IOM. The shock selectively released D and ¹³C from the IOM, while it preferably released H and ¹²C from the kerogen. The release of these elements from IOM cannot be explained in terms of the isotope effect, whereas their release from kerogen can be explained by this effect. The selective release of heavier isotopes from IOM would be due to its structure, in which D and ¹³C‐enriched parts are present as an inhomogeneity and are weakly attached to the main network. Shock gave rise to a high release of D even at a lower degree of dehydrogenation compared with the stepwise heating of IOM. This effective release of D is probably an inherent result of shock, in which a dynamic high‐pressure and high‐temperature condition prevails. Thus, shock would effectively control the hydrogen isotope behavior of extraterrestrial organic matter during the evolution of the solar nebula.     

Sylvite and halite on particles recovered from 25143 Itokawa: A preliminary report

We observed cross sectional ultra‐thin sections near the surface of 12 particles recovered from the S‐type asteroid Itokawa by the Hayabusa spacecraft in 2010, using spherical aberration–corrected STEM and conventional TEM. Although their mineralogy is almost identical to the equilibrated LL chondrites and therefore basically anhydrous, micrometer‐to‐submicrometer‐sized sylvite was identified on the surface of Itokawa particle RA‐QD02‐0034. Separately, micrometer‐sized halite was also identified on the surface of Itokawa particle RA‐QD02‐0129. Detailed inspection of the sample processing procedures at the JAXA's Planetary Materials Sample Curation Facility and textural observation of the sylvite and halite indicate that they were clearly present on two Itokawa particles before they were removed from Clean Chamber #2 at JAXA. However, there is no direct evidence for their extraterrestrial origin at present. If the sylvite and halite are extraterrestrial, their presence suggests that they may be more abundant on the surface of S‐type asteroids than previously thought.     

Analysis of suspended sediment yields after low impact forest harvesting

Disturbances to forest catchments have profound effects on the environment of headwater streams and have an impact on suspended sediment (SS) management. Forest harvesting is a dominant factor in increasing SS yields. Road construction, skidder activity and ploughing associated with harvesting cause serious soil disturbance that results in SS increases. However, few studies have shown whether harvesting itself increases SS yields. This study examined how harvesting influenced SS yields in a steep forested area. During harvesting, soil surface disturbance was prevented as much as possible by using skyline logging treatments and piling branches and leaves at selected locations in the watershed. Using these methods, the representative SS rating curve did not change significantly after harvesting. The results also show that the characteristics of SS transport were related to the SS source area, and reveal that the riparian zone/stream bank was a dominant SS source area at the study site. Annual SS yields did not increase despite increasing annual water yields after harvesting. The limited water capacity of the soil at the study site likely led to only slight differences in pre‐ and post‐harvest water discharge from heavy rainfall events. Most SS was transported during heavy rainfall events, and increases in SS yields were not detected after harvesting. We concluded that it is possible to prevent post‐harvest SS increases by performing careful, low‐impact harvesting procedures. Copyright © 2007 John Wiley & Sons, Ltd.     

The Hinode (Solar-B) Mission: An Overview

The Hinode satellite (formerly Solar-B) of the Japan Aerospace Exploration Agency’s Institute of Space and Astronautical Science (ISAS/JAXA) was successfully launched in September 2006. As the successor to the Yohkoh mission, it aims to understand how magnetic energy gets transferred from the photosphere to the upper atmosphere and results in explosive energy releases. Hinode is an observatory style mission, with all the instruments being designed and built to work together to address the science aims. There are three instruments onboard: the Solar Optical Telescope (SOT), the EUV Imaging Spectrometer (EIS), and the X-Ray Telescope (XRT). This paper provides an overview of the mission, detailing the satellite, the scientific payload, and operations. It will conclude with discussions on how the international science community can participate in the analysis of the mission data. T. Kosugi deceased 26 November 2006.     

Densification and grain coarsening of melting snow

1　IntroductionSnowdensificationiscriticalforcalculationsinengineering glaciology,snowavalancheforecasting ,springflooding,andotherpracticalaspects.Itisalsoimportantforinterpretingicecoredataincludingthosetakenfromratherwarmsiteswheresurfacelay ersexperiencemelting ,sinceitwouldaffectthechangeofannuallayerthicknesswithtime.Whileextensivestudies(e.g .AndersonandBenson 1 963 ;Bader1 960 ,1 962 ;Koji ma 1 95 4,1 95 5 ,1 95 6,1 95 7,1 95 8,1 95 9,1 964;Keeler 1 967;Gow 1 975 ;MaenoandE binuma 1…     

Formation of stars by implosion of a gas cloud

In the standard Friedmann cosmology the black-body radiation spectrum is usually taken (without explicit proof as far as we know) to have the same familiarT ⁴-form that it has in a flat space. With explicit use of the equation of motion of a quantized massless field propagating in a curved background Robertson-Walker metric we show (for the readily tractable scalar field case) that the assumption is in fact true for an open Universe. For a closed Universe, we find that there is an in principle modification to theT ⁴-law. Unfortunately, the correction turns out to be too small to be experimentally detectable. In passing, we also obtain a simple derivation for the cosmological red shift of frequencies.     

Effects of Lime‐Based Waste Materials on Immobilization and Phytoavailability of Cadmium and Lead in Contaminated Soil

Low cost lime‐based waste materials have recently been used to immobilize metals in contaminated soils. This study was conducted to evaluate the effects of oyster shells and eggshells as lime‐based waste materials on immobilization of cadmium (Cd) and lead (Pb) in contaminated soil, as well as their effects on metal availability to maize plants (Zea mays L.). Oyster shells and eggshells were applied to soils at 1 and 5% w/w, after which they were subject to 420 days of incubation. The toxicity characteristic leaching procedure (TCLP) test was employed to determine the mobility of Cd and Pb in soils. The results showed that the addition of waste materials effectively reduced the metal mobility as indicated by the decrease in the concentration of TCLP‐extractable Cd and Pb, and this was mainly due to significant increases in soil pH (from 6.74 in untreated soil to 7.85–8.13 in treated soil). A sequential extraction indicated that the addition of such alkaline wastes induced a significant decline in the concentration of Cd in the exchangeable fraction (from 23.64% in untreated soil to 1.90–3.81% in treated soil), but it increased the concentration of Cd in the carbonate fraction (from 19.59% in untreated soil to 36.66–46.36% in treated soil). In the case of Pb, the exchangeable fraction was also reduced (from 0.67% in untreated soil to 0.00–0.01% in treated soil), and the fraction of Pb bound to carbonate was slightly increased (from 16.61% in untreated soil to 16.41–18.25% in treated soil). Phytoavailability tests indicated that the metal concentrations in the shoots of maize plant were reduced by 63.39–77.29% for Cd and by 47.34–75.95% for Pb in the amended soils, with no significant differences being observed for the amendment types and the application rates. Overall, these results indicate that oyster shells and eggshells can be used as low cost lime‐based amendments for immobilizing Cd and Pb in contaminated soils.