Single particle analysis of oceanic suspended matter during the SEEDS II iron fertilization experiment     

Yoko Iwamoto  Yasushi Narita  Atsushi Tsuda  Mitsuo Uematsu 《Marine Chemistry》2009,113(3-4):212-218

Suspended particles collected from surface seawater during the SEEDS II (Subarctic Iron Experiment for Ecosystem and Dynamics Study II) experiment were analyzed individually using an electron probe X-ray micro analyzer and characterized by size and elemental composition. Their numbers, relative abundances, and relative particle volume all showed clear differences between samples collected inside vs. outside the phytoplankton bloom that developed following the addition of iron. Throughout the study, Si-rich, Ca-rich and Organic particles were dominant and their number increased inside the fertilized patch; these particles accounted for 21%, 13% and 58% of the particles examined, respectively. Si-rich or Ca-rich particles commonly consisted of fragments of diatom frustules and coccolithophorids. There was consistently greater percentage of Ca-rich particles and lower percentage of Si-rich particles inside the patch than outside of it in number, but both types of these particles apparently occupied a larger volume inside the patch than outside of it. Organic particles, that showed having peaks in smaller diameter particles, increased apparently inside the patch with time after iron fertilization. The Organic particles had a more diverse mixture of both bio-related and crustal trace elements than the other types of particles. These results suggest that the increase in suspended particles following the iron enrichment was due to a combination of detrital material and live phytoplankton.  相似文献   

Rapid precipitation of amorphous silica in experimental systems with nontronite (NAu-1) and Shewanella oneidensis MR-1     

Yoko Furukawa  S.E. O’Reilly 《Geochimica et cosmochimica acta》2007,71(2):363-377

Nanometer-size (<50 nm) precipitates of amorphous silica globules were observed in laboratory systems containing nontronite NAu-1, Shewanella oneidensis strain MR-1, and lean aqueous media. Their formation was attributed to the release of polysilicic acids at the expense of dissolving NAu-1, and subsequent polymerization and stabilization mediated by biomolecules. Rapid (<24 h) silica globule formation was confirmed in the immediate vicinity of bacterial cells and extracellular polymeric substances in all experimental systems that contained bacteria, whether the bacteria were respiring dissolved O₂ or Fe(III) originating from NAu-1, and whether the bacteria were viable or heat-killed. Silica globules were not observed in bacteria- and biomolecule-free systems. Thermodynamic calculations using disilicic acid, rather than monomeric silica, as the primary aqueous silica species suggest that the systems may have been supersaturated with respect to amorphous silica even though they appeared to be undersaturated if all aqueous silica was assumed to be monomeric H₄SiO₄. The predominant aqueous silica species in the experimental systems was likely polysilicic acids because aqueous silica was continuously supplied from the concurrent dissolution of aluminosilicate. Further polymerization and globule formation may have been driven by the presence of polyamines, a group of biologically produced compounds that are known to drive amorphous silica precipitation in diatom frustules. Globules were likely to be positively charged in our systems due to chemisorption of organic polycations onto silica surfaces that would have been otherwise negatively charged. We propose the following steps for the formation of nanometer-size silica globules in our experimental systems: (i) continuous supply of polysilicic acids due to NAu-1 dissolution; (ii) polysilicic acid polymerization to form <50 nm silica globules and subsequent stabilization mediated by microbially produced polyamines; (iii) charge reversal due to chemisorption of organic polycations; and (iv) electrostatic attraction of positively charged silica globules to net negatively charged bacterial cells. Rapid, biogenic precipitation of silica may be common in soil and sediment systems that appear to be undersaturated with respect to amorphous Si.  相似文献   

Diamond xenolith and matrix organic matter in the Sutter's Mill meteorite measured by C‐XANES     

Yoko Kebukawa  Michael E. Zolensky  A. L. David Kilcoyne  Zia Rahman  Peter Jenniskens  George D. Cody 《Meteoritics & planetary science》2014,49(11):2095-2103

The Sutter's Mill (SM) meteorite fell in El Dorado County, California, on April 22, 2012. This meteorite is a regolith breccia composed of CM chondrite material and at least one xenolithic phase: oldhamite. The meteorite studied here, SM2 (subsample 5), was one of three meteorites collected before it rained extensively on the debris site, thus preserving the original asteroid regolith mineralogy. Two relatively large (10 μm sized) possible diamond grains were observed in SM2‐5 surrounded by fine‐grained matrix. In the present work, we analyzed a focused ion beam (FIB) milled thin section that transected a region containing these two potential diamond grains as well as the surrounding fine‐grained matrix employing carbon and nitrogen X‐ray absorption near‐edge structure (C‐XANES and N‐XANES) spectroscopy using a scanning transmission X‐ray microscope (STXM) (Beamline 5.3.2 at the Advanced Light Source, Lawrence Berkeley National Laboratory). The STXM analysis revealed that the matrix of SM2‐5 contains C‐rich grains, possibly organic nanoglobules. A single carbonate grain was also detected. The C‐XANES spectrum of the matrix is similar to that of insoluble organic matter (IOM) found in other CM chondrites. However, no significant nitrogen‐bearing functional groups were observed with N‐XANES. One of the possible diamond grains contains a Ca‐bearing inclusion that is not carbonate. C‐XANES features of the diamond‐edges suggest that the diamond might have formed by the CVD process, or in a high‐temperature and ‐pressure environment in the interior of a much larger parent body.  相似文献   

Mineralogy and petrography of C asteroid regolith: The Sutter's Mill CM meteorite     

Michael Zolensky  Takashi Mikouchi  Marc Fries  Robert Bodnar  Peter Jenniskens  Qing‐zhu Yin  Kenji Hagiya  Kazumasa Ohsumi  Mutsumi Komatsu  Matthew Colbert  Romy Hanna  Jessie Maisano  Richard Ketcham  Yoko Kebukawa  Tomoki Nakamura  Moe Matsuoka  Sho Sasaki  Akira Tsuchiyama  Matthieu Gounelle  Loan Le  James Martinez  Kent Ross  Zia Rahman 《Meteoritics & planetary science》2014,49(11):1997-2016

Based upon our characterization of three separate stones by electron and X‐ray beam analyses, computed X‐ray microtomography, Raman microspectrometry, and visible‐IR spectrometry, Sutter's Mill is a unique regolith breccia consisting mainly of various CM lithologies. Most samples resemble existing available CM2 chondrites, consisting of chondrules and calcium‐aluminum‐rich inclusion (CAI) set within phyllosilicate‐dominated matrix (mainly serpentine), pyrrhotite, pentlandite, tochilinite, and variable amounts of Ca‐Mg‐Fe carbonates. Some lithologies have witnessed sufficient thermal metamorphism to transform phyllosilicates into fine‐grained olivine, tochilinite into troilite, and destroy carbonates. One finely comminuted lithology contains xenolithic materials (enstatite, Fe‐Cr phosphides) suggesting impact of a reduced asteroid (E or M class) onto the main Sutter's Mill parent asteroid, which was probably a C class asteroid. One can use Sutter's Mill to help predict what will be found on the surfaces of C class asteroids such as Ceres and the target asteroids of the OSIRIS‐REx and Hayabusa 2 sample return missions (which will visit predominantly primitive asteroids). C class asteroid regolith may well contain a mixture of hydrated and thermally dehydrated indigenous materials as well as a significant admixture of exogenous material would be essential to the successful interpretation of mineralogical and bulk compositional data.  相似文献   

Estimation of property loss and business interruption loss caused by storm surge inundation due to climate change: a case of Typhoon Vera revisit     

Jiang  Xinyu  Mori  Nobuhito  Tatano  Hirokazu  Yang  Lijiao  Shibutani  Yoko 《Natural Hazards》2015,84(1):35-49

This paper estimates property loss and business interruption loss under scenarios of storm surge inundation to explore the economic impact of climate change on Ise Bay, Japan. Scenarios-based analyses are conducted with respect to Typhoon Vera, which caused the most severe storm surge in the recorded history of Japan in 1959. Four different hazard scenarios are chosen from a series of typhoon storm surge inundation simulations: Typhoon Vera’s landfall with respect to the condition of the past seawall; Typhoon Vera’s landfall with respect to the condition of the current seawall; intensifying Typhoon Vera, but retaining its original tracks; and intensifying Typhoon Vera, but choosing the worst tracks from various possible typhoon tracks. Our economic loss estimation takes advantage of fine geographical scale census and economic census data that enable us to understand the spatial distribution of property loss and business interruption loss as well as identify the most potentially affected areas and business sectors on a sub-city scale. By comparing the property loss and business interruption loss caused by different hazard scenarios, the effect of different seawalls is evaluated and the economic impact of future climate change is estimated. The results indicate that although the current seawall can considerably reduce the scale of losses, climate change can cause Ise Bay to experience more serious storm surge inundation. Moreover, the resulting economic losses would increase significantly owing to a combination of climate change and the worst track scenario. It is, therefore, necessary to consider more countermeasures to adapt to climate change in this area.

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Characterization of particle size and settling velocity of cohesive sediments affected by a neutral exopolymer     

Xiao-ling TAN  Guo-ping ZHANG  Hang YIN  Allen H.REED  Yoko FURUKAWA 《国际泥沙研究》2012,27(4):473-485

In natural waters,exopolymers or extracellular polymeric substances(EPS) exuded by microorganisms interact with clay particles,resulting in the flocculation of clays and hence alteration to the properties of suspended cohesive sediments.To investigate and further understand how neutral EPS affect cohesive sediment transport and the final sediment yield,an experimental study was conducted on laboratory-prepared clay and guar gum(used as an analog for neutral EPS) suspensions to characterize EPS-induced flocculation and the settling velocity of resultant floes.Four different clays consisting of kaolinite,illite,Ca-montmorillonite,and Na-montmorillonite were studied to examine the influence of different layer charges on clay flocculation induced by neutral EPS.Floc size was determined by a laser particle size analyzer,and settling velocity estimated by analyzing the time-series floc settling images captured by an optical microscope.Results indicate that neutral EPS promote clay-EPS flocculation for all four clays with the particle/floc size significantly increased from～0.1-60μm to as large as～600μm.Clays’ layer charge has a profound influence on the clay-EPS flocculation.With the same floc size,the settling velocity of clay-EPS flocs is typically smaller than that of pure clay flocs,which is attributed to the reduced density of flocs caused by the EPS. However,for flocs of the same composition(e.g.pure clay or hybrid clay-EPS mixture),the settling velocity increases with size.The fractal dimension of these clay-EPS flocs estimated from settling velocity ranges from 1.39 to 1.47,which are smaller than that of pure clay flocs,indicating that these flocs are less compacted than the pure clay flocs.  相似文献   

Touhuanping Fault, an active wrench fault within fold-and-thrust belt in northwestern Taiwan, documented by spatial analysis of fluvial terraces     

Yoko Ota  Yu-Nung Nina Lin  Yue-Gau Chen  Nobuhisa Matsuta  Takuya Watanuki  Ya-Wen Chen 《Tectonophysics》2009,474(3-4):559-570

This study aims at the recent activity and development of an active wrench fault, the Touhuanping Fault in northwestern Taiwan. Northwestern Taiwan has been proposed in a current situation between the mature to waning collision in terms of tectonic evolution. The main drainage in this area, the Chungkang River, flows close to the trace of the fault mentioned above. We examined various types of deformation of fluvial terraces along the Chungkang River as a key to understanding the nature and rate of the late Quaternary tectonics. The E–W trending Touhuanping Fault has long been mapped as a geological boundary fault, but its recent activity was suspected. Field survey revealed that its late Quaternary activity is recorded in the offset fluvial terraces. Our result shows dextral slip and vertical offset with upthrown side on the south, and activated at least twice since the emergence of terrace 4 (older terrace 3 with OSL date of ca. 80 ka). Total amount of offset recorded in the Touhuanping terrace sequence is 15 m for dextral and 10 m for vertical offset. Estimated recurrence time of earthquake rupture may be a few tens of thousand years. Uplift on the upthrown side of the Touhuanping Fault also resulted in the formation of drowned valleys which were graded to terrace 4. Other deformation features, such as back-tilting, westward warping, and a range-facing straight scarp, were also identified. A second-order anticline roughly parallel to the Touhuanping Fault is suggested to be the origin of the northward tilting on terrace 3; it could have resulted from a flower structure on the Touhuanping Fault at shallow depth. This may demonstrate that the buried segment of the Touhuanping Fault has also been active since 80 ka. In the northern study area, the westward warping at terrace 2 probably represents late Quaternary activity of another NE–SW trending Hsincheng Fault.  相似文献   

Aggregation of montmorillonite and organic matter in aqueous media containing artificial seawater     

Yoko Furukawa  Janet L Watkins  Jinwook Kim  Kenneth J Curry  Richard H Bennett 《Geochemical transactions》2009,10(1):2-11

Background  

The dispersion-aggregation behaviors of suspended colloids in rivers and estuaries are affected by the compositions of suspended materials (i.e., clay minerals vs. organic macromolecules) and salinity. Laboratory experiments were conducted to investigate the dispersion and aggregation mechanisms of suspended particles under simulated river and estuarine conditions. The average hydrodynamic diameters of suspended particles (representing degree of aggregation) and zeta potential (representing the electrokinetic properties of suspended colloids and aggregates) were determined for systems containing suspended montmorillonite, humic acid, and/or chitin at the circumneutral pH over a range of salinity (0 – 7.2 psu).  相似文献   

Seismic subsidence near the source region of the 1662 Kanbun Hyuganada Sea earthquake: Geochemical,stratigraphical, chronological,and paleontological evidences in Miyazaki Plain,southwest Japan     

Masakazu Niwa  Takanobu Kamataki  Hideki Kurosawa  Yoko Saito‐Kokubu  Masafumi Ikuta 《Island Arc》2020,29(1)

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Heating experiments of the Tagish Lake meteorite: Investigation of the effects of short‐term heating on chondritic organics     

Queenie H. S. Chan  Aiko Nakato  Yoko Kebukawa  Michael E. Zolensky  Tomoki Nakamura  Jessica A. Maisano  Matthew W. Colbert  James E. Martinez  A. L. David Kilcoyne  Hiroki Suga  Yoshio Takahashi  Yasuo Takeichi  Kazuhiko Mase  Ian P. Wright 《Meteoritics & planetary science》2019,54(1):104-125

We present in this study the effects of short‐term heating on organics in the Tagish Lake meteorite and how the difference in the heating conditions can modify the organic matter (OM) in a way that complicates the interpretation of a parent body's heating extent with common cosmothermometers. The kinetics of short‐term heating and its influence on the organic structure are not well understood, and any study of OM is further complicated by the complex alteration processes of the thermally metamorphosed carbonaceous chondrites—potential analogues of the target asteroid Ryugu of the Hayabusa2 mission—which had experienced posthydration, short‐duration local heating. In an attempt to understand the effects of short‐term heating on chondritic OM, we investigated the change in the OM contents of the experimentally heated Tagish Lake meteorite samples using Raman spectroscopy, scanning transmission X‐ray microscopy utilizing X‐ray absorption near edge structure spectroscopy, and ultraperformance liquid chromatography fluorescence detection and quadrupole time of flight hybrid mass spectrometry. Our experiment suggests that graphitization of OM did not take place despite the samples being heated to 900 °C for 96 h, as the OM maturity trend was influenced by the heating conditions, kinetics, and the nature of the OM precursor, such as the presence of abundant oxygenated moieties. Although both the intensity of the 1s?σ* exciton cannot be used to accurately interpret the peak metamorphic temperature of the experimentally heated Tagish Lake sample, the Raman graphite band widths of the heated products significantly differ from that of chondritic OM modified by long‐term internal heating.  相似文献