Lead coprecipitation with iron oxyhydroxide nano-particles   总被引：1，自引：0，他引：1  

Peng Lu  Noel T. Nuhfer  Qin Li  Hiromi Konishi  Erika Elswick  Chen Zhu 《Geochimica et cosmochimica acta》2011,75(16):4547-4561

Pb²⁺ and Fe³⁺ coprecipitation was studied with sorption edge measurements, desorption experiments, sorbent aging, High Resolution Transmission and Analytical Electron Microscopy (HR TEM-AEM), and geochemical modeling. Companion adsorption experiments were also conducted for comparison. The macroscopic chemical and near atomic scale HRTEM data supplemented our molecule scale analysis with EXAFS (Kelly et al., 2008). Coprecipitation of Pb²⁺ with ferric oxyhydroxides occurred at ∼pH 4 and is more efficient than adsorption in removing Pb²⁺ from aqueous solutions at similar sorbate/sorbent ratios and pH. X-ray Diffraction (XRD) shows peaks of lepidocrocite and two additional broad peaks similar to fine particles of 2-line ferrihydrite (2LFh). HRTEM of the Pb-Fe coprecipitates shows a mixture of 2-6 nm diameter spheres and 8-20 by 200-300 nm needles, both uniformly distributed with Pb²⁺. Geochemical modeling shows that surface complexation models fit the experimental data of low Pb:Fe ratios when a high site density is used. Desorption experiments show that more Pb²⁺ was released from loaded sorbents collected from adsorption experiments than from Pb to Fe coprecipitates at dilute EDTA concentrations. Desorbed Pb²⁺ versus dissolved Fe³⁺ data show a linear relationship for coprecipitation (CPT) desorption experiments but a parabolic relationship for adsorption (ADS) experiments.Based on these results, we hypothesize that Pb²⁺ was first adsorbed onto the nanometer-sized, metastable, iron oxyhydroxide polymers of 2LFh with domain size of 2-3 nm. As these nano-particles assembled into larger particles, some Pb²⁺ was trapped in the iron oxyhydroxide structure and re-arranged to form solid solutions. Therefore, the CPT contact method produced more efficient removal of Pb²⁺ than the adsorption contact method, and Pb²⁺ bound in CPT solids represent a more stable sequestration of Pb²⁺ in the environment than Pb²⁺ adsorbed on iron oxyhydroxide surfaces.  相似文献   

Role of end-use technologies in long-term GHG reduction scenarios developed with the BET model     

Hiromi Yamamoto  Masahiro Sugiyama  Junichi Tsutsui 《Climatic change》2014,123(3-4):583-596

In this study, we develop a new integrated assessment model called the BET model (Basic Energy systems, Economy, Environment, and End-use Technology Model). It is a multi-regional, global model based on Ramsey’s optimal growth theory and includes not only traditional end-use technologies but also advanced end-use technologies such as heat-pump water heaters and electric vehicles. Using the BET model, we conduct simulations and obtain the following results. (1) Advanced end-use technologies have an important role in containing carbon prices as well as GDP losses when GHG (greenhouse gas) constraints are stringent. (2) Electrification based on energy services progresses rapidly in scenarios with stringent GHG constraints. This is because electricity can be supplied by various methods of non-fossil power generation, and advanced end-use technologies can drastically improve energy-to-service efficiencies. The BET’s results indicate the importance of analyses that systematically combine environmental constraints, end-use technologies, supply energy technologies, and economic development.  相似文献   

Toxicity of 17alpha-ethynylestradiol and norethindrone,constituents of an oral contraceptive pill to the swimming and reproduction of cladoceran Daphnia magna,with special reference to their synergetic effect     

Goto T  Hiromi J 《Marine pollution bulletin》2003,47(1-6):139-142

Toxicity of 17alpha-ethynylestradiol (EE2) and norethindrone (NOR), constituents of low dosage oral contraceptives, was assessed for the freshwater cladoceran Daphnia magna. Acute toxicity tests showed that 5 ppm of EE2, the highest concentration in this study, never inhibited swimming, whereas NOR inhibited swimming at >3 ppm: 48 h EC(50) for NOR was 6.41 ppm. Chronic toxicity tests were carried out for 25 days by measuring the number of offspring, moltings and sex ratios of neonates at 20, 100 and 500 ppb. EE2>100 ppb significantly decreased the number of offspring to 75% of the control; however, no effect was observed in molting and sex ratios at <500 ppb. NOR did not affect reproduction and sex ratios at <500 ppb. Mixture of EE2 (5.88 ppb) and NOR (94.12 ppb) also significantly decreased the number of offspring to 57% of the control. This result indicates the importance of examining synergetic effects of chemicals in the context of natural environments which face exposure to myriad chemicals.  相似文献   

Detection of free polyamine in coastal seawater using ion exchange chromatography     

Nishibori  Naoyoshi; Nishii  Akinori; Takayama  Haruyoshi 《ICES Journal of Marine Science》2001,58(6):1201-1207

  相似文献   

Has the 1998 regime shift also occurred in the oceanographic conditions and lower trophic ecosystem of the Oyashio region?     

Hiromi Kasai  Tsuneo Ono 《Journal of Oceanography》2007,63(4):661-669

To examine whether the regime shift in 1998 that has been variously reported to have occurred in the oceanographic conditions of the central and eastern North Pacific also occurred in the Oyashio region, western North Pacific, we compared data over the period 1990–2003. Oceanographic conditions were compared before 1997 with those after 1998, using the A-line dataset (1990–2003) obtained by the oceanographic surveys of the Hokkaido National Fisheries Research Institute, Fisheries Research Agency (HNFRI/FRA). Seasonal changes of the monthly-mean SST (as temperature in the surface layer) show a significant increase in spring after 1998. After 1998, the mean concentration of chlorophyll a at the surface was higher in spring than that before 1997. This was more remarkable in the main current of the Oyashio. These changes suggest that the spring phytoplankton bloom in the Oyashio region after 1998 was larger in magnitude and initiated earlier. Consumption of nutrients during the spring bloom and standing stock of netplankton also shows a distinct difference between the time period before 1997 and after 1998. These results support the occurrence of the regime shift around 1998 in the Oyashio region. The changes of hydrographical conditions accompanying with the 1998 regime shift are discussed. The hydrographic mechanism of enhancement of primary productivity during the spring phytoplankton bloom was not fully clarified, though. Results in this study may support the usefulness of the A-line dataset for analysis of long-term variability in the western subarctic Pacific.  相似文献   

Depolymerized pyribole structures derived from talc by heating     

Hiromi Konishi  Junji Akai 《Physics and Chemistry of Minerals》1991,17(7):569-582

Talc specimens heated to 700–1450° C were examined with an analytical high-resolution transmission electron microscope. Neither the amphibole-like structure nor the MPP structure (M = mica, P = pyroxene-layer), proposed by Avgustinik and Vigdergauz (1948) and Sueno et al. (1980), was found. On the contrary, a disordered pyribole structure was observed. This pyribole showed a structure disordered in terms of chain widths, with single and double chains predominant. A local MPP structure with 4–6 repeated units of (21) sequence was generally observed in a disordered region. The electron diffraction data were consistent with maximum symmetry A2/m for the proto-MPP structure. A HRTEM study of the fine structures associated with the depolymerization of talc was the basis of a structural model proposed for the depolymerization of biopyriboles. In this model, a pair of (010) faults with a displacement of 1/2 (a+c) took an important role. The acceptor and donor regions model was also discussed.  相似文献   

Positional isomer composition of monounsaturated fatty acids from a lacustrine sediment     

Hiromi Matsuda  Tadashiro Koyama 《Geochimica et cosmochimica acta》1977,41(2):341-345

From the surface sediment of a eutrophic lake (Japan), the double bond position in the monounsaturated fatty acids (C₁₅-C₂₆) has been determined by combined gas chromatography-mass spectrometry of the methoxylated derivatives. The relative abundance of 11-octadecenoic acid, suggested to be of bacterial origin, is higher in the chloroform-methanol extract than the extract by saponification.  相似文献   

Low-temperature heat capacities,entropies and enthalpies of Mg<Subscript>2</Subscript>SiO<Subscript>4</Subscript> polymorphs,and α−β−γ and post-spinel phase relations at high pressure     

M. Akaogi  H. Takayama  H. Kojitani  H. Kawaji  T. Atake 《Physics and Chemistry of Minerals》2007,34(3):169-183

The low-temperature isobaric heat capacities (C _p) of β- and γ-Mg₂SiO₄ were measured at the range of 1.8–304.7 K with a thermal relaxation method using the Physical Property Measurement System. The obtained standard entropies (S°₂₉₈) of β- and γ-Mg₂SiO₄ are 86.4 ± 0.4 and 82.7 ± 0.5 J/mol K, respectively. Enthalpies of transitions among α-, β- and γ-Mg₂SiO₄ were measured by high-temperature drop-solution calorimetry with gas-bubbling technique. The enthalpies of the α−β and β−γ transitions at 298 K (ΔH°₂₉₈) in Mg₂SiO₄ are 27.2 ± 3.6 and 12.9 ± 3.3 kJ/mol, respectively. Calculated α−β and β−γ transition boundaries were generally consistent with those determined by high-pressure experiments within the errors. Combining the measured ΔH°₂₉₈ and ΔS°₂₉₈ with selected data of in situ X-ray diffraction experiments at high pressure, the ΔH°₂₉₈ and ΔS°₂₉₈ of the α−β and β−γ transitions were optimized. Calculation using the optimized data tightly constrained the α−β and β−γ transition boundaries in the P, T space. The slope of α−β transition boundary is 3.1 MPa/K at 13.4 GPa and 1,400 K, and that of β−γ boundary 5.2 MPa/K at 18.7 GPa and 1,600 K. The post-spinel transition boundary of γ-Mg₂SiO₄ to MgSiO₃ perovskite plus MgO was also calculated, using the optimized data on γ-Mg₂SiO₄ and available enthalpy and entropy data on MgSiO₃ perovskite and MgO. The calculated post-spinel boundary with a Clapeyron slope of −2.6 ± 0.2 MPa/K is located at pressure consistent with the 660 km discontinuity, considering the error of the thermodynamic data.  相似文献   

Occurrence of Free-Gas Associated with Methane-Hydrate-Bearing Formations in the MITI Nankai Trough Wells, Offshore Tokai, Japan     

Tokujiro Takayama    Masatoshi Nishi  Hiroaki Yamamoto  Yoshinori Sanada    Shigemi Matsuda  Takashi Uchida 《Resource Geology》2004,54(1):89-98

Abstract. The MITI Nankai Trough wells were drilled for exploration of methane-hydrate-bearing sediments in association with seismic inferred bottom simulating reflectors (BSRs). In this project, log data showed low velocity compressional-wave (P-wave) layers below methane-hydrate-bearing formations. Dipole shear sonic acoustic tools (DSI) could not acquire accurate compres-sional velocity in this zone, thus it was not possible to accurately correlate between logging, VSP and surface seismic profiles.
Small amount of gas was presumed to cause the problem in obtaining the low velocity P-wave data. VSP interval velocity data was used to assess the DSI inferred low-velocity layer, which showed lower values than the velocity of the drilling muds. Synthetic seismogram was created by VSP-compensated velocity to compare against corridor stack of VSP. As a result, the depths above and below the methane-hydrate-bearing interval were correlated with synthetic seismograms and reflectivity events on the VSP profiles. By using this correlation technique, distribution of methane-hydrate-bearing formations and free-gas-bearing formations can be determined.  相似文献   

Carbon Mineralization Associated with Soil Aggregates as Affected by Short-term Tillage     

GUO Linlin  NISHIMURA Taku  IMOTO Hiromi  SUN Zhigang 《资源与生态学报(英文版)》2016,7(2):101-106

Tillage practice has received much attention due to its effects on greenhouse gas emissions from agricultural fields. The understanding of carbon mineralization associated with soil aggregates helps to explore the influence mechanisms of tillage practice on soil carbon dynamics. Total carbon and carbon mineralization rates associated with various sizes of soil aggregates under no-tillage and tillage treatments were studied with a volcanic ash soil. Total carbon content in microaggregates (<0.25 mm) was higher than that in macroaggregates (>0.25 mm) for both the no-tillage and tillage treatments, since microaggregates of the volcanic ash soil include more fine silts and clay particles absorbing more organic agents. The carbon mineralization rate and total carbon were highly correlated (R² = 0.6552, P = 0.002) for both treatments, suggesting that soil aggregate size is an important factor to influence the carbon mineralization rate. The no-tillage system showed the advantage of improving soil structure for volcanic ash soil. A larger proportion of microaggregates with relatively high carbon mineralization might contribute to the greater carbon loss from tilled soils. Unlike aggregate size, short-term tillage showed no significant effects on carbon mineralization rates associated with aggregates in a specific size class.  相似文献