Desorption kinetics of hydrophobic organic contaminants from marine plastic pellets     

Satoshi Endo  Masaki Yuyama  Hideshige Takada 《Marine pollution bulletin》2013

This study investigated the desorption behavior of polychlorinated biphenyls (PCBs) from marine plastic pellets. Long-term desorption experiments were conducted using field-collected polyethylene (PE) pellets. The results indicate that the desorption kinetics highly depends on the PE-water partition coefficients of PCB congeners. After 128 d of the experiment, the smallest congener considered (CB 8) had desorbed nearly completely (98%), whereas major fractions (90–99%) of highly chlorinated congeners remained in the pellets. An intraparticle diffusion model mostly failed to reproduce the desorption kinetics, whereas an aqueous boundary layer (ABL) diffusion model well approximated the data. The desorption half-lives are estimated to 14 d to 210 years for CB 8 to CB 209 in an actively stirred solution (ABL thickness: 30 μm). Addition of methanol to water enhanced the desorption to a large extent. A need for further work to explore roles of organic matter in facilitating solute transfer is suggested.  相似文献   

Experimental constraints on permeable gas transport in crystalline silicic magmas     

Satoshi Okumura  Michihiko Nakamura  Tsukasa Nakano  Kentaro Uesugi  Akira Tsuchiyama 《Contributions to Mineralogy and Petrology》2012,164(3):493-504

The gas and fluid transport in magmas via permeable flow through interconnected bubble networks controls the rate of outgassing from magmas ascending in volcanic conduits and the fluid transport in the mushy boundary layer of magma reservoirs. Hence, clarifying its mechanism and rate is crucial to understanding the explosivity of volcanic eruptions and the evolution and dynamics of a magma reservoir. Recent experimental studies have determined the gas permeabilities in crystal-free rhyolite and basalt. However, no experimental study has investigated the effect of the crystal contents on the permeable gas transport in magmas. In this study, we performed decompression experiments for hydrous rhyolitic melts having crystallinities of 30 and 50 vol% to examine the effect of crystals on the bubble microstructure and gas permeability during magma vesiculation. Size-controlled (100-meshed) corundum crystals were used as an analog of the phenocrysts in silicic magmas. Microstructural analyses using X-ray CT showed that bubbles coalesce and their connectivity increases with a decrease in the final pressure after the decompression, that is, an increase in the vesicularity. As long as the vesicularities of melt part in the crystal-free basis (melt vesicularity) were similar, no clear effect of the crystallinity on the degree of bubble coalescence and connectivity was observed at melt vesicularities <68 vol%. The corundum showed a large contact angle with aqueous fluid as well as plagioclase and alkaline feldspar; this failed to induce the efficient heterogeneous nucleation and coalescence of bubbles on its surface. The gas permeabilities of all the run products were lower than the detection limits of the present analysis (the order of 10⁻¹⁶ m²) at melt vesicularities <68 vol%. These results show that silicic magmas containing 30 and 50 vol% phenocrysts with a large contact angle have low gas permeabilities until the vesicularity becomes large (at least >68 vol%). This result indicates that the permeable fluid transport through a deep volcanic conduit, which has been proposed on the basis of the observations of volcanic gases and natural products, is so slow that other processes, like shear deformation or magma convection, may be needed to explain the observations.  相似文献   

Predominant hosting lead(II) in ternary mixtures of heavy metal ions by a novel of diethylaminomethyl-calix[4]resorcinarene     

N. N. M. Yusof  Y. Kikuchi  T. Kobayashi 《International Journal of Environmental Science and Technology》2014,11(4):1063-1072

Heavy metal ions from single and ternary systems of Pb(II), Cu(II), and Ni(II) adsorbed by calix[4]resorcinarenes in water–chloroform extraction were studied. Comparison was made of calix[4]resorcinarenes, 2,8,14,20-tetraundecyl calix[4]resorcinarene-4,6,10,12,16,18,22,24-octol, and diethylaminomethyl-calix[4]resorcinarene, 5,11,17,23-tetra(diethylaminomethyl)-2,8,14,20- tetraundecylcalix[4]resorcinarene-4,6,10,12,16,18,22,24-octol, for predominant extraction of their ions from the ternary mixture of aqueous solution at different pH in a water layer. The hosting of Pb(II) by the diethylaminomethyl-calix[4]resorcinarene occurred efficiently at pH 6–7. The hosting of Pb(II), Cu(II), and Ni(II) ions for the ternary aqueous mixture was applied to the Langmuir isotherm. Adsorption was studied using nuclear magnetic resonance spectroscopy in a water–deuterium chloroform extraction system. Results showed that as the heavy metal ions were included into the host cavity, the observation of shifted peaks of water molecules from downfield to higher field was visible in the nuclear magnetic resonance spectra, meaning that water molecules were included with heavy metal ion into the host cavity. The spectra also showed that the diethylamino group expressed formation of the coordination complex between the diethylaminomethyl-calix[4]resorcinarene and Pb(II) for the purpose of predominant hosting of Pb(II).  相似文献   

Sea surface ichthyoplankton off southeastern New Zealand,summer 1977–78     

D. A. Robertson  Satoshi Mito 《新西兰海洋与淡水研究杂志》2013,47(3):415-424

Plankton samples from the Chatham Rise, Pukaki Rise, and Campbell Plateau provided information on the young stages of a number of poorly known New Zealand fish species, and on the presence of a large spawning area of barracouta, Thyrsites atun, over the Mernoo Bank, The Chatham Rise was more important as a spawning area than the areas further south.  相似文献   

Degassing, crystallization and eruption dynamics at Stromboli: trace element and lithium isotopic evidence from 2003 ashes     

Federica Schiavi  Katsura Kobayashi  Takuya Moriguti  Eizo Nakamura  Massimo Pompilio  Massimo Tiepolo  Riccardo Vannucci 《Contributions to Mineralogy and Petrology》2010,159(4):541-561

During its 1800-year-long persistent activity the Stromboli volcano has erupted a highly porphyritic (HP) volatile-poor scoriaceous magma and a low porphyritic (LP) volatile-rich pumiceous magma. The HP magma is erupted during normal Strombolian explosions and lava effusions, while the LP one is related to more energetic paroxysms. During the March–April 2003 explosive activity, Stromboli ejected two typologies of juvenile glassy ashes, namely highly vesicular LP shards and volatile-poor HP shards. Their textural and in situ chemical characteristics are used to unravel mutual relationships between HP and LP magmas, as well as magma dynamics within the shallow plumbing system. The mantle-normalized trace element patterns of both ash types show the typical arc-lava pattern; however, HP glasses possess incompatible element concentrations higher than LP glasses, along with Sr and Eu negative anomalies. HP shards are generally characterized by higher Li contents (to ~20 ppm) and lower δ⁷Li values (+1.2 to −3.8‰) with respect to LP shards (Li contents of 7–14 ppm and δ⁷Li ranging between +4.6 and +0.9‰). Fractional crystallization models based on major and trace element compositions, combined with a degassing model based on open-system Rayleigh distillation and on the assumption that ^melt/fluidD_Li > 1, show that abundant (~30%) plagioclase precipitation and variable degrees of degassing can lead the more primitive LP magma to evolve toward a differentiated (isotopically lighter) HP magma ponding in the upper conduit and undergoing slow continuous degassing-induced crystallization. This study also evidences that in March 2003 Stromboli volcano poured out a small early volume of LP magma that traveled slower within the conduit with respect to later and larger volumes of fast ascending LP magma erupted during the April 5 paroxysm. The different ascent rates and cooling rates of the two LP magma batches (i.e., pre- and post-paroxysm) resulted in small, but detectable, differences in their chemical signatures. Finally, this study highlights the high potential of in situ investigations of juvenile glassy ashes in petrologic and geochemical monitoring the volcanic activity and of Li isotopes as tracers of degassing processes within the shallow plumbing system.  相似文献