巻号一覧
35 巻 (2001)
- 6 号 p. 385-
- 5 号 p. 277-
- 4 号 p. 215-
- 3 号 p. 145-
- 2 号 p. 77-
- 1 号 p. 1-
35 巻, 4 号
選択された号の論文の7件中1～7を表示しています
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Iwao Kawabe, Akimasa Masuda2001 年 35 巻 4 号 p. 215-224
発行日: 2001/08/20
公開日: 2008/04/08
ジャーナル フリーGeochmeical studies reporting lanthanide tetrad effects in natural samples often cite the original examples of tetrad effect depicted by log Kd(org/aq) for Ln(III) in the two solvent-extraction systems (Peppard et al., 1969) and its theoretical interpretation (Jørgensen, 1970; Nugent, 1970). An improved equation for the refined spin-pairing energy theory (RSPET), which has been developed in pursuing tetrad effects in geochemical studies, makes it possible to examine more thoroughly the original examples of tetrad effect by using the digitized log Kd(org/aq) data. The log Kd(org/aq) values are found to be successfully described by the RSPET equation. Our analyses show that the ratios of relative differences in Racah parameters for Ln3+ ions in aqueous and organic phases, ΔE3/ΔE1, are 0.29 ± 0.07 and 0.25 ± 0.06 for the two extraction systems. They are comparable with the spectroscopic observations of nephelauxetic effect in Nd(III) compounds (ΔE3/ΔE1 = 0.23 ± 0.02). The tetrad effects in log Kd(org/aq) are experimental evidence for the thermochemical consequence of the nephelauxetic effect in Ln(III) complexes. Although Ln3+ ions in condensed phases are atomic-like, it is rather surprising that log Kd(org/aq) can easily be reproduced by the simple RSPET equation derived from the Slater-Condon-Racah theory for free Ln3+ ions in vacuum. The effect of coordination change of Ln3+ ion across the Ln3+(aq) series is not obvious in the series variations of log Kd(org/aq), suggesting that the coordination changes in the two Ln(III) complex series in the extraction systems are significantly canceled out in ΔGr°. The two sets of log Kd(org/aq) are analogous to the Masuda-Coryell plot in REE geochemistry with respect to their coordinates. This gives an insight into the fact that the Masuda-Coryell plot also depicts tetrad effects in the REE patterns for geochemical samples.抄録全体を表示PDF形式でダウンロード (146K) -
Masaki Kozono, Shinya Nomoto, Hajime Mita, Akira Shimoyama2001 年 35 巻 4 号 p. 225-236
発行日: 2001/08/20
公開日: 2008/04/08
ジャーナル フリーMaleimides were detected in organic solvent extracts and chromic acid oxidation products of Miocene to Pliocene sediments of the Shinjo basin and were very likely degradation products of porphyrins and/or chlorophylls. These maleimides included a series of 2-methylmaleimides with 3-n-alkyl substituents up to C5, benzomaleimide (phthalimide) and its methyl homologs, and tetrahydrobenzomaleimide. The total concentrations of free (the organic solvent extractable) and bound (the oxidatively extractable) maleimides ranged from 0.10 to 21 and from 1.5 to 75 nmol g-1, respectively. The most abundant compound was 2-methyl-3-ethylmaleimide both in free and bound forms in most of the sediments. The concentrations of free and bound maleimides showed different depth profiles from those of the reported extractable organic compounds (EOC) and the total organic carbon (TOC). Their ratios to TOC decreased with increasing depth of the sediments in the oil-generating zone of the sedimentary sequence and were characteristically low in the high EOC/TOC region. The molar compositions of free maleimides did not show marked dependence on the sediment depth, whereas those of the bound forms did. The depth profile of the molar ratio of bound 2, 3-dimethyl- to 2-methyl-3-ethylmaleimide showed a clearly increasing trend with depth, which agreed well with those of other widely-accepted maturity parameters.抄録全体を表示PDF形式でダウンロード (322K) -
S. J. Kao, S. Lin, C. H. Wang, I. T. Lin, K. K. Liu2001 年 35 巻 4 号 p. 237-244
発行日: 2001/08/20
公開日: 2008/04/08
ジャーナル フリーSurficial sediment samples were collected from two transects on the shelf of the East China Sea: one across the shelf and the other along the coast, both starting near the Changjiang river mouth. They were analyzed for contents of total nitrogen (TN%) and total organic carbon (TOC%) and for their isotopic compositions (δ15N and δ13CTOC). The TOC% and TN% values varied concomitantly in the ranges of 0.2 to 1.5% and 0.02 to 0.19%, respectively. The δ13CTOC value ranged from −25.1 to −19.6‰. The lower δ13CTOC values (<−21.5‰) all occurred in the inner shelf corresponding to higher TOC% (>0.5%). Away from the coastal zone, TOC% dropped sharply with corresponding increase in the δ13CTOC value. The δ15N value, varying from 3.6 to 4.9‰, displayed a more complicated distribution pattern. Distinctively lower δ15N values (<4.1‰) occurred near the Changjiang river mouth and near the shelf edge. Isotopically light riverine nitrogenous materials and preferential uptake of isotopically light nitrogen in the rich supply of nutrients in the Changjiang plume may have contributed to the observed low values near the river mouth, while nitrogen fixers in the Kuroshio waters may have contributed to those near the shelf break.抄録全体を表示PDF形式でダウンロード (276K) -
George W. A. Nyakairu, Christian Koeberl, Hans Kurzweil2001 年 35 巻 4 号 p. 245-256
発行日: 2001/08/20
公開日: 2008/04/08
ジャーナル フリーKaolin from the Buwambo deposit, located about 27 km north of Kampala (Uganda), has been analyzed for its mineralogical and chemical composition. The kaolin is derived from granite of the basement, which is exposed due to deeply weathered Buganda-Toro cover rocks. Kaolinite is the dominant mineral, with quartz and muscovite/illite as accessory minerals. Chemical data show that the kaolin is composed mainly of SiO2 and Al2O3, with the other oxides being present in trace amounts. The depletion in Ti, Fe, Mn, Mg, Ca, Na, and K not only shows the extent of the kaolinization, but also gives Buwambo kaolin its almost white color. The kaolinization and weathering processes have enriched Ni and depleted other trace element contents in the Buwambo kaolin. The chondrite-normalized rare earth element (REE) patterns show enrichment in the light REEs, with a negative Ce anomaly. The REE pattern and the content of the other trace elements, show evidence of alteration and weathering processes related to kaolinization. The mineralogical and chemical compositions indicate that the kaolin is suitable for industrial use.抄録全体を表示PDF形式でダウンロード (689K) -
Jun Murase, Atsuko Sugimoto2001 年 35 巻 4 号 p. 257-263
発行日: 2001/08/20
公開日: 2008/04/08
ジャーナル フリーThe spatial variation of methane contents and its stable carbon isotopic composition of sediments from a mesotrophic lake (Lake Biwa) were determined. Methane concentrations in the sediments (0–10 cm), ranging from 0.04 to 2.41 μmol ml-1, were weakly correlated with the amounts of organic carbon in the surface sediments (0–2 cm), but were poorly correlated with the nitrogen isotopic composition of the bulk sediments used as an indicator of the origin of the organic matter (autochthonous vs. allochthonous). The carbon isotopic composition of methane ranged from −61 to −80‰ and exhibited positive correlation with methane concentration and the carbon isotopic composition of total carbonate (ΣCO2). The apparent fractionation factor (αcCH4-CO2) between methane and ΣCO2 was in the range between 1.07 and 1.085, which were rather high compared to previously reported values in freshwater sediments. The results suggested that major parts of methane were produced via CO2-H2 in the Lake Biwa sediments.抄録全体を表示PDF形式でダウンロード (302K) -
Tsuyoshi Watanabe, Masao Minagawa, Tadamichi Oba, Amos Winter2001 年 35 巻 4 号 p. 265-269
発行日: 2001/08/20
公開日: 2008/04/08
ジャーナル フリーTrace elements (e.g., Sr, Mg, and U) in coral skeletons are widely used as a potential robust paleothermometers. However, there is little consensus among workers on the chemical pretreatment of skeletal samples, which contain small amounts of organic material and inorganic detritus enriched in many metals compared to the skeleton. We tested the analytical effects of chemical treatment on coral aragonite by comparing several chemical treatments for Mg/Ca and Sr/Ca ratios as well as oxygen and carbon isotopic ratios. Our results suggested that the Sr/Ca ratio and stable isotopic ratios are resistant to chemical treatments. However, organic matter or crystal surfaces in corals could absorb more than 40% of magnesium although 60% of magnesium in coral aragonite substitutes for calcium. Our results suggest that it is expedient to remove impurities by the method outlined here, especially before determining Mg/Ca ratios in corals for paleoenvironmental reconstruction.抄録全体を表示PDF形式でダウンロード (224K) -
Masahiro Sakata2001 年 35 巻 4 号 p. 271-275
発行日: 2001/08/20
公開日: 2008/04/08
ジャーナル フリーA simple and rapid method was developed for the δ15N determination of ammonium and nitrate in water samples. This method is based on an on-line isotope analysis using an elemental analyzer coupled to a mass spectrometer. The ammonium and nitrate in sample solutions are separated as ammonium into diluted H2SO4 from each other by sequential distillation techniques. Then, the ammonium in the distillate is precipitated directly as an insoluble salt of (C6H5)4BNH4, which is subsequently combusted in an elemental analyzer for δ15N determination. This precipitation step allows us to eliminate the evaporation step used for sample preparation in the previous on-line methods, which contributes to simple and rapid determination. The δ15N values of precipitates did not depend on the fraction (F) of NH4+ precipitated in the investigated range of F = 0.64–0.96, showing insignificant isotope fractionation during precipitation. Analyses of the solutions prepared from Reference Materials, (NH4)2SO4 and KNO3 distributed by the National Institute of Standards and Technology (NIST) and also the rain samples showed that this method can produce good quality isotope measurements.抄録全体を表示PDF形式でダウンロード (56K)
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