Butane and pentane isomers were measured in situ in the remote marine atmosphere at the Bellows Beach, on the east side of the Island of Oahu, Hawaii during July and August 1998. Air masses arriving at Bellows Beach site originated mainly from the eastern North Pacific, and sometime polluted air masses of island origin arrived at the sampling site. The median mixing ratios were 11 pptv (i-butane), 18 pptv (n-butane), 1 pptv (i-pentane), and 3 pptv (n-pentane) in clean marine air, which were 3-12 times lower than those encountered in the polluted island air. The observed mixing ratios of the alkanes in marine air are within the range of those previously reported in the Atlantic and Pacific Ocean. The concentration ratios of pentane isomers suggest that the sources of the observed pentanes in marine air were not only derived from the ocean but also from the unidentified anthropogenic sources. Based on the comparison with values in the literature on sea-to-air fluxes, oceanic emissions of these alkanes were estimated to account for less than 30% of the observed mixing ratios. Continental emissions are not the important anthropogenic source due to the air mass trajectory analysis, suggesting that there are unidentified anthropogenic sources associated with ship activity and oceanic oil pollution.

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Si and Mg isotopic compositions of melilite in three coarse-grained CAIs were measured by SIMS. Isotopic compositions of these elements were fractionated (1.0 to 2.9 ‰/amu for Si and 4.6 to 9.6 ‰/amu for Mg) relative to terrestrial values. These fractionations are similar to those reported for bulk CAIs (Clayton et al., 1988) and suggest that coarse-grained CAIs were formed by evaporative loss of some Si and Mg from high-temperature condensates as proposed by Grossman et al. (2000). No significant zoning of isotopic fractionations was observed in these CAIs. This suggests that the evaporative loss of these elements from CAIs were slow compared with diffusive homogenization and also suggests that evaporative loss ceased early before crystallization of Mg-rich melilite.

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Adakites are generally associated with subduction zones (i.e., at convergent plate margins). This paper reports geochemical and isotopic data for early Cretaceous high-potassium adakitic intrusive rocks in the Yueshan-Hongzhen area of east China, which occur in an extensional tectonic regime within a continent. Based on petrology and geochemistry, these adakitic intrusive rocks are classified into two groups. One group (the Hongzhen adakitic granites) is characterized by high SiO₂ (69-75%) contents and K₂O/Na₂O (>1.0), low MgO (or Mg^#) values, Ni and V concentrations, low ε_Nd(t) (-17.01∼-18.13), and high (⁸⁷Sr/⁸⁶Sr)_i (0.7071∼0.7072). The other group (the Yueshan and Zongpu adakitic rocks) is characterized by relatively low SiO₂ (58-67%) contents and K₂O/Na₂O (<1.0), high MgO (Mg^#) values, Ni and V concentrations, as well as relatively high ε_Nd(t) (-6.63∼-9.62) and low (⁸⁷Sr/⁸⁶Sr)_i (0.7064∼0.7069). Both groups are associated with the contemporary Dongling metamorphic core complex, A-type granites, and some per-alkaline igneous rocks that are formed only in an extensional setting. The tectonic setting and chemical compositions suggest that: (1) the adakitic intrusive rocks in the Yueshan-Hongzhen area were formed in an extensional tectonic regime within a continental plate; (2) the Hongzhen adakitic granites were most likely derived directly from partial melting of mafic material with high potassium contents at the base of the continental crust at pressures of ∼1.2 GPa, leaving residual garnet ± hornblende ± plagioclase in the source; (3) the Yueshan and Zongpu adakitic rocks were most probably derived from dehydration melting of basaltic materials delaminated into underlying mantle at pressures >1.2 GPa, leaving residual garnet + pyroxene in their sources. Both groups of adakitic rocks have high La/Yb and Sr/Y, indicating that the crustal thickness in the Yueshan-Hongzhen area exceeded 40 km when the adakitic magmas were generated in the early Cretaceous. The present thickness of the crust in the Yueshan-Hongzhen area is only ∼31 km, and therefore the crust appears to have been thinned by at least ∼10 km since the early Cretaceous. The relatively high MgO, Ni, and V values of the Yueshan and Zongpu adakitic rocks suggest that adakitic magmas interacted with mantle rocks, possibly concurrently with delamination of the lower crust.

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Some practical aspects were investigated for an on-line chromium reduction technique for measurement of D/H variations of natural waters using a conventional isotope ratio mass spectrometer. They include the configuration of the reaction system, the precautions taken before mass spectrometric measurement, the reproducibility of δD measurement, memory effects and salt effects. Approximately 150 water samples of 2 μl can be run with Cr powder (60 mesh) weighing approximately 16 g mixed with quartz glass sand (10 mesh). The mixture functions to avoid choking of the Cr reactor due to volume increase as Cr oxidation proceeds. The Cr powder-quartz glass sand mixture is placed in the middle of a quartz glass reaction tube and heated to >800°C. The reproducibility is ca. ±0.5‰ if care is taken for the above precautions and memory effects. This system can be easily installed on a conventional IRMS at low cost.

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Bed sediments of the Yamuna River and its tributaries in the Himalaya (Yamuna River System, YRS) have been analyzed for major elements and trace metals (Sr, Ba, Ni, Cu, Co, Zn, Pb and Cr). These results have been used to characterize chemical weathering and transport in the Himalaya, to assess relative mobility of elements during weathering and to understand heavy metal association. Concentrations of major and trace elements of YRS sediments vary between 20 and 50%. In general, elemental variability reduces when data are analyzed individually for the major rivers, suggesting that tributaries draining diverse lithology contribute significant variations. Comparison of sediment chemistry with composition of source rocks and average Upper Continental Crust (UCC) suggests significant loss of Na, K, Ca and Mg from source rocks during weathering, the degree of loss being more for Ca and Na. Chemical index of alteration (CIA) for YRS sediments averages at 59, indicating that weathering in the basin is of moderate intensity. This inference is also supported by major ion chemistry of YRS waters and is attributed to steep gradient and enhanced physical erosion in the basin. Available results seem to indicate that Na and Sr are effectively more mobile than Ba, which is thought to be a combined effect of higher solubility of Na and Sr, and the affinity of Ba to be adsorbed onto solid phase. Heavy metals show significant positive correlation with Al and weak correlation with Fe, Mn and P. These observations suggest that metal concentrations are controlled mainly by clay mineral abundances, and that Fe-Mn oxides and organic matter may be playing less significant role. Heavy metal concentrations of YRS sediments are lower than those of suspended particulates of the Yamuna river, presumably due to higher clay mineral abundances in the latter. Strong association of metals with Al, and lower metal concentrations in bed sediments compared to suspended matter underscores the importance of sediment transport and mineral sorting in influencing the YRS sediment chemistry. Enrichment factor and geo-accumulation index calculated for heavy metals in YRS sediments suggest that they are mainly of natural origin and that anthropogenic activities exert little influence on their abundances.

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Taking account of the size distribution of planetesimals inferred from recent theoretical studies of planetesimal accumulation, we examine gravitational separation of noble gases inside large porous planetesimals in the solar nebula. The size distribution is characterized by the value of the minimum planetesimal size R₀ for a given power-law distribution, which also determines the maximum planetesimal size for a given total mass of planetesimals. Both enrichment and isotopic fractionation of noble gases strongly depend on the value of R₀, as it determines the number of large planetesimals inside which gravitational separation of noble gases is significant. We find the ranges of the values of R₀ that can produce the enrichment and the isotopic fractionation of Xe similar to the terrestrial values separately, but the two ranges are found not to overlap. We also find significant isotopic fractionation of Kr for the parameter value that can produce the terrestrial isotopic fractionation of Xe, in contrast to the observation. These results suggest that the isotopic fractionation of terrestrial Xe cannot be explained if we only consider the gravitational separation inside porous planetesimals with the size distribution.

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The non-hydrocarbon fraction of immature-low maturity crude oils from the western Qaidam Basin which were formed in the source beds deposited in highly saline and strongly reducing environments were analyzed by GC-MS to determine their compositions. Abundant fatty acids, alkanols, fatty acid glycerol monoesters, and stenols were identified. Geochemical analyses suggested that these compounds were largely originated from the oil source rocks. The linear compounds consist primarily of the short-chain homologues (C₁₀–C₂₀). The C₂₇–C₂₉ sterols detected were dominated by C₂₇ stenols. The molecular characteristics suggest that algae and bacteria were the major source organism. The presence of abundant fatty acid glycerol monoesters suggests that the biological lipids, particularly bacterial phospholipids were important contributors to the formation of the crude oils studied. The existence of abundant unsaturated linear compounds, stenols and high CPI values of linear non-hydrocarbon compounds is consistent with the low maturity of these crude oils.

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In order to assess the effect of “overuse” in natural parks, roadside soil and dusts were collected from Kamikochi, Chubu Sangaku National Park (Kamikochi) to Matsumoto City, Nagano Prefecture, Japan. Also, the concentrations of As, Sb, Hg and 5 other heavy metals (Ni, Cu, Zn, Cd, Pb) were measured. The higher concentrations of these 8 elements were observed at Kamikochi Bus Terminal, Kama Tunnel, Matsumoto Interchange and the east exit of Matsumoto Station. These 4 sites are strongly affected by the presence of automobiles, which is believed to be responsible for the higher concentrations. Moreover, the concentrations were increased in the summer, probably due to the corresponding traffic volume, related to the tourist season. Many significant positive correlations among the 8 element concentrations were found as well. The information above suggested that As, Sb and Hg distributions are closely related to automobiles, which play an important role in transportation of visitors, meaning the anthropogenic pollution.

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Through the use of acid digestion and a modified distillation procedure the Ru contents in various terrestrial minerals have been determined via the stable isotope dilution mass spectrometry (IDMS) method, with isotopic analysis carried out via inductively coupled plasma mass spectrometry (ICP-MS) and negative thermal ionization mass spectrometry (N-TIMS). The uncertainties in the concentrations ranged from 2.1% to 6.0% (2σ) for ppb and ppm samples concentrations, which is comparable and in some cases better than previous work using NiS fire assay and ICP-MS (Shirai et al., 2003). However, uncertainties for ppt samples were in around 20%, due to low count rates during analysis. Results from three different mineral species show the effectiveness of this chemical dissolution and separation procedure for samples of varying Ru concentrations, ranging from ppm down to ppt levels, and varying geological matrices, from sulphides to silicates. Ru abundances measured showed results consistent with the siderophile nature of Ru, and reinforces the similarity in melt chemistry between Ru and Os.

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