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Volume 46 (2012)
- Issue 6 Pages 477-
- Issue 5 Pages 371-
- Issue 4 Pages 267-
- Issue 3 Pages 169-
- Issue 2 Pages 77-
- Issue 1 Pages 1-
Volume 46, Issue 2
Displaying 1-8 of 8 articles from this issue
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HIDEKO TAKAYANAGI, RYUJI ASAMI, OSAMU ABE, HIROYUKI KITAGAWA, TOSHIHIR ...2012 Volume 46 Issue 2 Pages 77-87
Published: April 20, 2012
Released on J-STAGE: November 02, 2013
JOURNAL FREE ACCESSWe present carbon- and oxygen-isotope compositions in a shell (δ13CS and δ18OS, respectively) of a modern brachiopod Campagea japonica collected at a water depth of 606 m off Aguni-jima, Central Ryukyu Islands, southwestern Japan. The δ13CS and δ18OS profiles of the outermost portions of the secondary shell layer along the axis of shell growth do not display significant seasonal variations. The δ13CS values display a gradual decrease with growth, whereas the δ18OS values are nearly constant. The δ13CS and δ18OS values along a particular growth line and from the inner shell surface are rather constant. The δ13CS values near the posterior shell edge of the ontogenetic series and the δ18OS values near the anterior shell edge of the inner series fall within the ranges of δ13C and δ18O values of calcite in equilibrium with ambient seawater (equilibrium calcite) (δ13CEC and δ18OEC, respectively). Therefore, they are the best portions to use as proxies of δ13C values of dissolved inorganic carbon (δ13ODIC) and temperature and/or δ18O values of seawater (δ18OSW), respectively. The δ13CS values of the ontogenetic series near the anterior shell edge and the entire isochronous and inner series display the smallest decrease (less than ~0.2‰) compared with the δ13CEC values. The δ18OS values of the entire ontogenetic series and an interior part of the inner series are slightly greater (less than ~0.3‰) than the δ18OEC values. Thus, these portions can be used as paleoenvironmental proxies if appropriate corrections are made. A significant positive correlation is recognized between the δ13CS and δ18OS values for the ontogenetic-series samples, which can be ascribed to a kinetic isotope effect. A metabolic isotope effect is not evident for the δ18OS values in these samples. Our study provides useful information for the appropriate selection of brachiopod taxa and shell portions that reflect isotopic composition of ambient seawater for paleoenvironmental studies.View full abstractDownload PDF (2397K) -
TOMOHIRO TOKI, YUTO UEHARA, KAZUNARI KINJO, AKIRA IJIRI, URUMU TSUNOGA ...2012 Volume 46 Issue 2 Pages 89-106
Published: April 20, 2012
Released on J-STAGE: November 02, 2013
JOURNAL FREE ACCESSPore waters were taken from core sediments of Sites C0001, C0004, and C0008 on the landward slope of the Nankai Trough and Site C0002 in the forearc basin of the Nankai accretionary prism off Kumano during Integrated Ocean Drilling Program Expeditions 315 and 316. The carbon isotopic ratios of CH4 and total carbon dioxide (∑CO2) in dissolved gases were measured. The contribution of thermogenic CH4 was negligible at all sites, while carbon isotopic separation between CH4 and ∑CO2 indicated that CH4 formation was mainly by microbial hydrogenotrophic methanogenesis. Evaluation of the isotopic fraction of the initial substrate ∑CO2 pool showed larger fractionation at Site C0002 than at the other sites in the transect. In addition, the NH4+ concentration was higher at Site C0002 than at the other sites, indicating that organic matter degradation occurred more actively at Site C0002 than at the other sites. Therefore, CO2 and H2 as well as NH4+ were actively generated by the organic matter degradation at Site C0002, which could stimulate methanogenesis utilizing CO2 and H2 as substrates at Site C0002. The high sedimentation rate at Site C0002 in the forearc basin was due to the geomorphological setting of the site, within the outer ridge rimming the sediment-filled Kumano Basin, leading to organic matter burial without aerobic degradation on the surface of the seafloor, which preserve labile organic matter for utilization by methanogenesis. On the other hand, slope sediments were already exposed by organic matter degradation, which leaves scarce labile organic matter for supporting CH4 generation. Geomorphology was possibly an important factor controlling CH4 formation and accumulation, and the Kumano Basin sediments have greater potential as a CH4 hydrate reservoir than the landward slope sediments in the Nankai accretionary prism off Kumano.View full abstractDownload PDF (3719K) -
XUFEI SHI, WEIHONG DONG, MANZHOU LI, YAN ZHANG2012 Volume 46 Issue 2 Pages 107-115
Published: April 20, 2012
Released on J-STAGE: November 02, 2013
JOURNAL FREE ACCESSThe sustainability of groundwater resources in the Henan Plains, located in the eastern portion of central China, has been threatened by both increasing industrial and agricultural pumping and periods of drought occurring since the 1990s. Therefore, there is an urgent need to improve water resources management in the Henan Plains. However, the recharge and annual renewal rate are very difficult to be calculated when based only on traditional hydrogeological methods because of inadequate hydrometeorologic data. In this study, tritium concentrations in groundwater and reconstructed 3H concentration time series from 1953~2009 in precipitation were used to determine the annual groundwater renewal rate. The 3H concentrations mostly ranged from 2.91 to 40.30 TU in the shallow groundwater with a mean 3H concentration of 19.13 TU, which suggested that the shallow groundwater was recharged from modern precipitation after 1953 in the study area. Three exceptionally low 3H concentration(less than 1 TU) wells were sampled in Xinxiang, Puyang and Zhengyang which indicated that those wells contained deep old groundwater recharge before 1953 as a result of over-pumping. High renewal rates (more than 4%/a) of groundwater are located mainly in the recharge areas such as the Yellow River nearby and the pediments of Taihang Mountain, Songqi Mountain, Funiu Mountain, Dabie Mountain, where the groundwater extraction volume could be increased. Moderate renewal rates (2~4%/a) of groundwater are mainly in the runoff areas where the groundwater extraction volume can be kept at current levels. Low renewal rates (1~2%/a) of groundwater are located mainly in the discharge areas in the eastern regions of Nanle, Puyang, Shangqiu, Luyi where the groundwater extraction volume should be reduced. The lowest renewal rates of (less than 1%/a) groundwater are in Fanxian, Xinxiang, Yongcheng, Zhengyang and Xixian, where the groundwater extraction volume should be restricted.View full abstractDownload PDF (1273K) -
CARMINE APOLLARO, ELISSAVET DOTSIKA, LUIGI MARINI, DONATELLA BARCA, AN ...2012 Volume 46 Issue 2 Pages 117-129
Published: April 20, 2012
Released on J-STAGE: November 02, 2013
JOURNAL FREE ACCESSThe Terme Sibarite and nearby thermomineral water discharges have Ca-SO4 to Ca-SO4-HCO3 composition, near neutral pH value of 6.9 to 7.6, outlet temperatures of 16° to 25.5°C, variable redox potentials (-0.23 to 0.2 V) and total dissolved solids from 20 to 35 meq L-1. The total flow rate of the Terme Sibarite springs is about 130 L s-1. Solubility of chalcedony and the K-Mg geothermometer show a full equilibrium reservoir temperature of 33°C. The δ34S values of dissolved sulfate are constrained by mixing of thermomineral waters with cold waters, both interacting with Upper Triassic carbonate-evaporite rocks, as well as occurrence of bacterial sulfate reduction. In the light of the geological and hydrogeological framework of the study area, this chemical and isotopic evidence suggests that the thermal circuit develops entirely into the Upper Triassic sedimentary sequence, without any interaction with the Messinian evaporites which are possibly present below the Upper Triassic sedimentary sequence. The thermomineral waters are meteoric precipitations infiltrating in the Pollino Massif, at average altitudes of 950-1090 m a.s.l, as indicated by the δ18O values of water. These waters descend to maximum depths of 600 m below the Sibari Plain, where the geothermal reservoir is situated. Circulating into it, waters extract heat from reservoir rocks, attaining thermo-chemical equilibrium at the temperature suggested by chemical geothermometers. Then, the thermomineral waters locally rise relatively quickly to the surface, along subvertical faults and fractures, preserving part of their physical and chemical characteristics. The methodological approach utilized in this research may be applied to other fault-controlled, low-temperature geothermal systems in other zones of Italy and other nations.View full abstractDownload PDF (3232K) -
YUSUKE NAKAGAWA, SHOTARO TAKANO, M. LUTFI FIRDAUS, KAZUHIRO NORISUYE, ...2012 Volume 46 Issue 2 Pages 131-141
Published: April 20, 2012
Released on J-STAGE: November 02, 2013
JOURNAL FREE ACCESSNatural variations in the isotopic composition of molybdenum (Mo) are showing increasing potential as a tool in geochemistry. Although the ocean is an important reservoir of Mo, data on the isotopic composition of Mo in seawater are scarce. We have recently developed a new method for the precise determination of Mo isotope ratios on the basis of preconcentration using a chelating resin and measurement by multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), which allows us to measure every stable Mo isotope (Nakagawa et al., 2008). In this study, 172 seawater samples obtained from 9 stations in the Pacific, Atlantic, and Southern Oceans were analyzed, giving global coverage and the first full depth-profiles. The average isotope composition in δA/95Mo (relative to a Johnson Matthey Mo standard solution) was as follows: δ92/95Mo = -2.54 ± 0.16‰ (2SD), δ94/95Mo = -0.73 ± 0.19‰, δ96/95Mo = 0.85 ± 0.07‰, δ97/95Mo = 1.68 ± 0.08‰, δ98/95Mo = 2.48 ± 0.10‰, and δ100/95Mo = 4.07 ± 0.18‰. The δ values showed an excellent linear correlation with atomic mass of AMo (R2 = 0.999). Three-isotope plots for the Mo isotopes were fitted with straight lines whose slopes agreed with theoretical values for mass-dependent isotope fractionation. These results demonstrate that Mo isotopes are both uniformly distributed and follow a mass-dependent fractionation law in the modern oxic ocean. In addition, Mo isotopic analysis revealed that δ98/95Mo of the standard used in this study was 0.117 ± 0.009‰ lighter than the Mo standard that was used by Archer and Vance (2008). A common Mo standard is urgently required for the precise comparison of Mo isotopic compositions measured in different laboratories. On the other hand, our results strongly support the possibility of seawater as an international reference material for Mo isotopic composition.View full abstractDownload PDF (1469K) -
GUODONG ZHENG, KATSUHIKO SUZUKI, YOSHIKI MIYATA, HIROSHI SHIMIZU2012 Volume 46 Issue 2 Pages 143-149
Published: April 20, 2012
Released on J-STAGE: November 02, 2013
JOURNAL FREE ACCESS187Os/188Os ratios and osmium concentrations were analyzed in sedimentary reference materials JSd-3, JMS-1, and JMS-2, issued by the Geological Survey of Japan, using the isotope dilution method with negative thermal ionization mass spectrometry (ID-N-TIMS). The chemical procedures used in this study are based on Carius tube digestion combined with carbon tetrachloride extraction to separate Os. The obtained 187Os/188Os ratios of JSd-3, JMS-1, and JMS-2 were 0.941-1.149, 0.3894-0.465, and 0.747-0.848, respectively, and their Os abundances were 27.07-39.32 ppt, 80.8-106.6 ppt, and 281-317.2 ppt, respectively. Variations among the samples presumably reflect differences in sources and depositional environments. The Os isotopic ratios and abundances were variable within individual samples. The relative 95% confidence intervals of Os concentrations and isotopic ratios were respectively 13% and 6.2% for JSd-3, 15% and 9.8% for JMS-1, and 4.3% and 4.2% for JMS-2. These variations probably reflect the heterogeneity of the original rock of each reference material. Low concentration and high isotope ratio of JSd-3 probably results from the derivation of the original rocks from continental components with low Os abundance and elevated 187Os/188Os. Inputs of anthropogenic Os were inferred in JMS-1, a nearshore sediment from an urbanized locality, which had high Os contents and relatively low Os isotopic ratios. Greatly elevated Os concentrations and high 187Os/188Os in JMS-2, a pelagic clay, may reflect the scavenging of Os in seawater into Mn-Fe oxyhydroxides deposited on the seafloor.View full abstractDownload PDF (78K)
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JIN-LIANG FENG, YONG-CHONG LIN, SHAO-PENG GAO, JI-FENG ZHANG2012 Volume 46 Issue 2 Pages 151-161
Published: April 20, 2012
Released on J-STAGE: November 02, 2013
JOURNAL FREE ACCESSThe distributions of trace elements in ferromanganese concretions (FMCs) and the surrounding terra rossa (TR) matrix overlying dolomite have been examined to extend our understanding of their mobilization, redistribution and fractionation during karst weathering and pedogenesis. This study demonstrates that the characteristics of trace elements in TR have been severely overprinted by weathering and pedogenetic processes. The composition of trace elements in FMCs within TR soil profiles varies greatly with depth. The concentrations of Be, Ni, Cu, Zn, As and Bi in FMCs fluctuate and tend to increase with depth; other trace element concentrations fluctuate in the profile but show no clear trend. The toxic elements Cr, As, Cd, Tl and Pb, as well as Co, are significantly enriched in FMCs relative to the surrounding TR matrix: arsenic exhibits strong affinity with Fe, but Cr and Cd contents are not significantly correlated with either Mn or Fe. Correspondingly, Co, Tl and Pb are related to the Mn in FMCs rather than the Fe. In FMCs, trace element distribution and partitioning in the Mn-Fe phases are governed by the location-specific formational pedoenvironment, with the weathering front etching downwards. Experiments with simulated acid rain indicate that desorption of elements from FMCs is generally pH-dependent regardless of the variation of the released amounts and their desorbability. Moreover, it seems that toxic elements bonded to Mn-phase were easily desorbed from FMCs. As a result, the bioavailability, mobility and activity of some toxic elements in FMCs and TR are potentially increased in field areas experiencing severe soil erosion and acid rain.View full abstractDownload PDF (3490K) -
SOU N. MATSUNAGA, ONNO MULLER, SATORU CHATANI, MASAHIRO NAKAMURA, TATS ...2012 Volume 46 Issue 2 Pages 163-167
Published: April 20, 2012
Released on J-STAGE: November 02, 2013
JOURNAL FREE ACCESSIsoprene is a reactive volatile organic compound (VOC), the annual global biogenic emissions of which are the largest of the non-methane VOC. Since isoprene emissions are partly temperature-driven, understanding the relationship between isoprene emission and climate must be improved. Isoprene emission was measured in Quercus crispula, the second-most dominant isoprene-emitting tree species in Japan. Four mature Q. crispula trees were exposed to artificial warming of their roots and branches at approximately 5°C warmer than ambient temperatures. Four un-warmed control trees were also measured and compared for their emissions over the course of five months. Basal emission rates of isoprene (defined as a normalized emission rate under standard light and temperature conditions) was calculated and compared between warmed and control branches. The basal emission rates varied from 0.17 to 38.5 nmol m-2 s-1 (average; 10.4 nmol m-2 s-1) over the seasons. However, the basal emission rate did not significantly differ between warmed and control leaves.View full abstractDownload PDF (554K)
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