Speciation of Chromium in Artificially Contaminated Soil Reference Material GSJ JSO-2 Using XANES and Chemical Extraction Methods

The oxidation states of chromium in GSJ JSO-2 (artificially contaminated soil) and three other geochemical reference materials (GSJ JSO-1, JLS-1 and JMS-1) were observed using X-ray near edge structure (XANES). For comparison, other artificially contaminated soil materials (mimic-JSO-2) were prepared by adding Cr(VI) into JSO-1. Their oxidation states of chromium were determined using XANES. The chromium contents were 1118 μg g^-1 for JSO-2, 1352 μg g^-1 for mimic-JSO-2 and 69-113 μg g^-1 for the other reference materials. Most chromium was present as hexavalent in mimic-JSO-2. No hexavalent species were detected in other samples. These results for chromium oxidation state in JSO-2 and mimic-JSO-2 obtained with XANES resembled those obtained from a chemical extraction method. The present JSO-2 has no trace of Cr(VI), although Cr(VI) was added as a major species during preparation. On the other hand, the content of Cr(VI) obtained in mimic-JSO-2 agreed with the original Cr(VI) content. A time-elapse study showed that Cr(VI) contents in mimic-JSO-2 decreased gradually to 70% of the original abundance during 240-day preservation in dry conditions. Moreover, the abundance of Cr(VI) decreased markedly to 15% after 240 days in the wet mimic-JSO-2 containing 20% m/m of water. These experiments suggested that soil humidity enhanced the reduction of Cr(VI) and that Cr(VI) was reduced even in dry conditions. Consequently, it is reasonable to infer that Cr(VI) doped into JSO-2 was completely reduced to Cr(III) during the preservation period of 5 years. The certification of the long-term stability of the chemical form in reference materials will be much more important in future.     

K-Ar dating studies of Ashigawa and Tokuwa granodiorite bodies and plutonic geochronology in the South Fossa Magna, central Japan

Abstract K-Ar age studies in the Ashigawa and the southern part of the Tokuwa granodioritic bodies, which consist of the southern part of the Kofu plutonic complex, revealed that they formed between 12 and 9 Ma. Quite a narrow range of ages obtained from the Ashigawa southernmost part of the Tokuwa pluton implies that they cooled rapidly. The southern part of the Tokuwa pluton, as a whole, shows a systematic age distribution with a decrease in age to the north. Compilation of currently available plutonic ages in the South Fossa Magna suggests that the plutonic activities occurred three times in this region. Episodic activity like this could be argued in relation to the tectonic development of this region.     

Tectonothermal chronology within a blueschist-eclogite complex, west-central Spitsbergen, Svalbard: Evidence from Ar/Ar and Rb---Sr mineral ages

A high-pressure, relatively low-temperature metamorphic complex is exposed at Motalafjella, Spitsbergen. White mica concentrates from the complex record variably discordant ⁴⁰Ar/³⁹Ar age spectra in which apparent ages systematically increase throughout low-temperature portions of the analyses and define intermediate- and high-temperature plateaux. Phengitic concentrates record plateau ages of c. 470 Ma whereas paragonitic concentrates yield c. 460 Ma plateaux. These ages are interpreted to date diachronous cooling through different argon closure temperatures following the high-pressure metamorphism. The slight discordance displayed in low-temperature portions of the experiments is interpreted to reflect a partial rejuvenation of intracrystalline argon systems during an c. 400–425 Ma thermal overprint associated with late Caledonian tectonothermal activity. White mica concentrates and associated whole-rocks yield Rb---Sr mineral + whole-rock ages from 457 ± 11 Ma to 474 ± 11 Ma. These are interpreted to date post-metamorphic cooling through Sr blocking temperatures. Because similar ages are recorded by both K---Ar and Rb---Sr isotopic systems, relatively rapid post-metamorphic cooling is implied. This and relatively rapid depressurization during uplift indicate that the ⁴⁰Ar/³⁹Ar and Rb---Sr mineral ages likely closely date the peak metamorphism.

The high pressure complex is unconformably overlain by variably cleaved, Upper Ordovician-Lower Silurian flysch which was deformed into regional recumbent folds prior to deposition of unconformably overlying Early Devonian molasse. Two penetratively cleaved slate samples display internally discordant ⁴⁰Ar/³⁹Ar whole-rock age spectra with ages increasing from c. 100 Ma to c. 470 Ma. The spectral discordance is interpreted to reflect the combined effects of: (1) a polymineralic character: (2) a detrital source similar in age to the Motalafjella complex; and (3) a partial, post-Paleozoic thermal rejuvenation of the detrital mica argon systems. No thermal overprint associated with Late Silurian cleavage formation appears to be recorded. This agrees with textural characteristics which suggest that the cleavage largely developed through pressure-solution assisted, grain-boundary sliding.     

Long-term patterns in the diets of Japanese temperate bassLateolabrax japonicus larvae and juveniles in Chikugo estuarine nursery ground in Ariake Bay, Japan

Larval and juvenile Japanese temperate bass (Lateolabrax japonicus) samples were collected from a wide range of spatial gradients (covering a distance of approximately 30 km) in Chikugo estuary, Ariake Bay, Japan over a period of 8 yr (1997–2004) in order to observe changes in diet. Gut contents were studied by separating, identifying, counting, and estimating the dry weight of prey organisms. Copepod samples were collected during each cruise to observe the numerical composition, abundance, and biomass in the estuary. Considerable spatial and temporal variations were observed in copepod distributions in ambient water and the diets of the fish. Two distinctly different copepod assemblages were identified in the estuary: One in the upper estuarine turbidity maximum (ETM), dominated by a single speciesSinocalanus sinensis and the other in the lower estuary consisting of a multispecies assemblage, dominated byOithona davisae, Acartia omorii, Paracalanus parvus, andCalanus sinicus. The gut content composition of the fish in the upper estuary was dominated byS. sinensis, while in the lower estuary, it consisted ofP. parvus, O. davisae, andA. omorii. Within the size group analyzed (13.0–27.0 mm SL), the smaller individuals were found to feed on a mixed diet composed of smaller prey. The diets gradually shifted to bigger prey composed predominantly ofS. sinensis for larger size groups. Greater proportions of empty guts were recorded in the smaller individuals and dropped with increasing fish size. Higher dry biomass of copepods in the environment, as well as higher dry weights of gut contents, were recorded in the upper estuary, indicating that the upper estuarine ETM areas are important nursery grounds for the early life stages of the Japanese temperate bass. The early life stages of the Japanese temperate bass are adapted to use the upstream nursery grounds and ascending to the nursery areas to useS. sinensis is one of the key survival strategies of the Japanese temperate bass in the Chikugo estuary.     

Diamond-bearing and diamond-free metacarbonate rocks from Kumdy–Kol in the Kokchetav Massif, northern Kazakhstan

Abstract Dolomite marble from the Kumdy–Kol area of the Kokchetav Massif contains abundant microdiamond, mainly in garnet and a few in diopside. The mineral assemblage at peak metamorphic condition consists of dolomite + diopside + garnet (+ aragonite) ± diamond. Inclusions of very low MgCO₃ calcite and almost pure calcite occur in diopside and are interpreted as aragonite and/or aragonite + dolomite. Single-phase Mg–calcite in diopside with a very high MgCO₃ component (up to 21.7 mol%) was also found in diamond-free dolomitic marble, and is interpreted as a retrograde product from aragonite + dolomite to Mg–calcite. The dolomite stability constrains the maximum pressure (P) at < 7 GPa using previous experimental data, whereas the occurrence of diamond yields the minimum peak pressure–temperature (P–T) condition at 4.2 GPa and 980 °C at X co ₂ = 0.1. The highest MgCO₃ in Mg–calcite constrains the minimum P–T condition higher than 2.5 GPa and 800 °C for the exhumation stage. As these marbles were subjected to nearly identical P–T metamorphic conditions, the appearance of diamond in some carbonate rocks was explained by high X co ₂. A low X co ₂ condition refers to high oxidized conditions and diamond (and/or graphite) becomes unstable. Difference in X co ₂ for marble from the same area suggests local heterogeneity of fluid compositions during ultrahigh-pressure metamorphism.     

Geotechnical evaluation of slope and ground failures during the 8 October 2005 Muzaffarabad earthquake, Pakistan

A large devastating earthquake with a magnitude of 7.6 struck in Kashmir on Oct. 8, 2005. The largest city influenced by the earthquake was Muzaffarabad. Balakot town was the nearest settlement to the epicenter, and it was the most heavily damaged. The earthquake caused extensive damage to housing and structures founded on loose deposits or weathered/sheared rock masses. Furthermore, extensive slope failures occurred along Neelum and Jhelum valleys, which obstructed both river flow and roadways. In this article, failures of natural and cut slopes as well as other ground failures induced by the earthquake and their geotechnical evaluation are presented, and their implications on civil infrastructures and site selection for reconstruction and rehabilitation are discussed. It is suggested that if housing and constructions on soil slopes containing boulders as observed in Balakot and Muzaffarabad are allowed, there should be a safety zone between the slope crest and allowable construction boundary.     

Modelling for prediction of global deforestation based on the growth of human population

Deforestation due to ever-increasing activities of the growing human population has been an issue of major concern for the global environment. It has been especially serious in the last several decades in the developing countries. A population-deforestation model has been developed by the authors to relate the population density with the cumulative forest loss, which is defined and computed as the total forest loss until 1990 since prior to human civilisation. NOAA-AVHRR-based land cover map and the FAO forest statistics have been used for 1990 land cover. A simulated land cover map, based on climatic data, is used for computing the natural land cover before the human impacts. With the 1990 land cover map as base and using the projected population growth, predictions are then made for deforestation until 2025 and 2050 in both spatial and statistical forms.     

Development of polygon shift method for generating 3D view map of buildings

The authors have developed a new method termed “Polygon Shift Method” that enables the generation of a 3D view map of a city with tall buildings with a simplified procedure to shift a polygon and check the overlap between the original and shifted polygon. Boolean operations are applied with a newly defined “Fore or Aft” side and a “Depth Distance” that functionally express the visibility criteria or hidden point processing in the 3D view. Since the polygon shift method can be operated with a raster-based structure, the computer processing for generation of a 3D view map of buildings with shadow is simple and efficient.     

The ultra-low-frequency magnetic disturbances associated with earthquakes

The ultra-low-frequency (ULF) electromagnetic emission is recently recognized as one of the most promising candidates for short-term earthquake (EQ) prediction. This paper reviews previous convincing evidence on the presence of ULF emissions before three major EQs. Then, we present further statistical study on the ULF occurrence, our networks of ULF monitoring in different spatial scales in Japan and finally we present several signal processings to identify the seismogenic emissions by showing latest results for recent large EQs.