Bioassay of baltimore harbor sediments     

Chu-Fa Tsai  Justine Welch  Kwei-Yang Chang  John Shaeffer  L. Eugene Cronin 《Estuaries and Coasts》1979,2(3):141-153

Baltimore Harbor, a tributary area of the northern Chesapeake Bay, has recelved and is receiving large quantities of chemical pollutants. As part of a cooperative study to explore possible corrective treatment for existing pollution burdens, gross bioassay analyses were performed for sediments from nine representative stations, employing two species of fish, mummichogs (Fundulus heteroclitus) and spot (Leiostomus xanthurus), and one mollusc, the soft-shell clam (Mya arenaria). Acclimated organisms were exposed in static systems to a series of concentrations of suspended sediment from each station, to fuller's earth in suspension, and in control tanks for 48 hours. Parallel analysis of the sediment was performed for the metals, Pb, Cr, Zn, Ca, As, for PCB's and for hexane extracts. The sediments were all substantially polluted with low correlations among components. Twenty-four hour TLm and 48-hour TLm increased proportionately with sediment concentration but display species specificity. The relationships observed permit use of mummichog data to index gross toxicity of sediments throughout the harbor. Further comparison of mummichog 24-hour TLm value with benthie species diversity determined in a previous study permitted zoning of the entire harbor into highly toxic, moderately toxic, low toxic and slightly toxic zones. Gross toxicity of sediments determined by bioassay can therefore be used as an index of the suitability of the sediments for benthic macroinvertebrate communities.  相似文献   

Book reviews     

W. Frank Bohlen  R. Eugene Turner  D. Jay Grimes 《Estuaries and Coasts》1983,6(4):436-438

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The mixed value of environmental regulations: do acroporid corals deserve endangered species status?     

Shinn EA 《Marine pollution bulletin》2004,49(7-8):531-533

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Posteruption glacier development within the crater of Mount St. Helens, Washington, USA     

Steve P. Schilling  Paul E. Carrara  Ren A. Thompson  Eugene Y. Iwatsubo 《Quaternary Research》2004,61(3):325-329

The cataclysmic eruption of Mount St. Helens on May 18, 1980, resulted in a large, north-facing amphitheater, with a steep headwall rising 700 m above the crater floor. In this deeply shaded niche a glacier, here named the Amphitheater glacier, has formed. Tongues of ice-containing crevasses extend from the main ice mass around both the east and the west sides of the lava dome that occupies the center of the crater floor. Aerial photographs taken in September 1996 reveal a small glacier in the southwest portion of the amphitheater containing several crevasses and a bergschrund-like feature at its head. The extent of the glacier at this time is probably about 0.1 km². By September 2001, the debris-laden glacier had grown to about 1 km² in area, with a maximum thickness of about 200 m, and contained an estimated 120,000,000 m³ of ice and rock debris. Approximately one-third of the volume of the glacier is thought to be rock debris derived mainly from rock avalanches from the surrounding amphitheater walls. The newly formed Amphitheater glacier is not only the largest glacier on Mount St. Helens but its aerial extent exceeds that of all other remaining glaciers combined.  相似文献   

Heterogeneous reduction of uranyl by micas: Crystal chemical and solution controls     

Eugene S. Ilton  Anca Haiduc  Steve M. Heald  David R. Veblen 《Geochimica et cosmochimica acta》2004,68(11):2417-2435

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Evidence from kimberlitic zircon for a decreasing mantle Th/U since the Archean     

Robert Eugene Zartman  Stephen H. Richardson 《Chemical Geology》2005,220(3-4):263-283

A decoupling in MORB of measured Th/U (κ = 2.5) from that calculated by Pb isotopes (κ = 3.8) for the depleted asthenosphere is well established, and has been referred to as the second Pb paradox (Kramers, J.D., and Tolstikhin, I.N., 1997. Two terrestrial lead isotope paradoxes, forward transport modelling, core formation and the history of the continental crust. Chem. Geol., 139, 75–110.) or the kappa conundrum (Elliott, T., Zindler, A., and Bourdon, B., 1999. Exploring the kappa conundrum: the role of recycling in the lead isotope evolution of the mantle. Earth Planet. Sci. Lett., 169, 129–145.). More controversial has been the cause and timing of this phenomenon, although a higher return flux of U⁶⁺ relative to Th⁴⁺ and(or) the recycling of crustal Pb into the mantle have become the preferred explanations of most workers. Such a combined mechanism effectively operating over the past 2.5 Ga was modelled in plumbotectonics (Zartman, R.E., and Haines, S., 1988. The plumbotectonics model for Pb isotopic systematics among major terrestrial reservoirs—a case for bi–directional transport. Geochim. Cosmochim. Acta, 52, 1327–1339. 709.33.), and found to be quantitatively feasible.A large TIMS, SIMS and LA-ICPMS database of Th and U concentrations for kimberlite-hosted zircon, particularly from Cr-poor megacrystic suites, now exists (Kinny et al., 1989, Berryman et al., 1999, Griffin et al., 2000 and Spetsius et al., 2002; Appendix A and Appendix B, this work). Six suites comprising 10 or more zircon grains with ages between 90 and 2550 Ma reveal consistent patterns when plotted on Th/U vs. U diagrams. We interpret these patterns as resulting from fractional crystallization of a melt with kimberlite affinity presumably derived from the asthenosphere, permitting the extrapolation to an initial Th/U at the time zircon crystallization began. A two-fold decrease is seen in this ratio over the past 2.5 Ga, suggesting that during this time a similar change has occurred in the parent silicate melt. Estimates of Th and U distribution coefficients between zircon and coexisting melt permit calculation of Th/U in the melt, which, for these highly incompatible elements, presumably is the same as for its mantle source rock. Kimberlitic zircon may thus indeed give evidence of a reduction in κ, tentatively calculated as from 4 to 2, since the Archean for the depleted asthenosphere.  相似文献   

Neotectonic Crustal Uplift on the Continents and its Possible Mechanisms. The Case of Southern Africa     

Eugene V. Artyushkov  Albrecht W. Hofmann 《Surveys in Geophysics》1998,19(5):369-415

According to a large volume of data an intensive crustal uplift began in the Oligocene over most of the continental areas after a long period of relative tectonic stability. This Neotectonic uplift formed most of the present positive topographic features on the continents, and its strong acceleration took place during the last several million years. In many regions the uplift was associated with magmatism. The main methods of studying the Neotectonic uplift are considered together with the data on the uplift of Southern Africa. In this area the uplift took place in the Early Miocene (up to 300 m) and in the Late Pliocene and Pleistocene (up to 900 m). It occurred without stretching or shortening of the crust. Rapid erosion of the lower part of mantle lithosphere by a plume material is proposed as a mechanism of the uplift. This material ascended from below and rapidly spread along the base of the lithosphere. Its spreading for 1000 km during a few million years is possible only under a low viscosity of normal asthenosphere (1019 Pa s) and a much lower viscosity of a plume material (2 × 1016 Pa s). As in Southern Africa, in most of the regions the Neotectonic uplift was associated with insignificant shortening or stretching of the crust. This indicates that in some regions a plume material ascended from below and rapidly spread along the base of the lithosphere and eroded the mantle lithosphere in vast areas beneath the continents. In regions with a hot asthenosphere a strong weakening of the mantle lithosphere which allows its erosion can be associated with a high temperature of the plume material. In regions where the asthenosphere is at moderate temperature weakening of the mantle lithosphere can result from infiltration of volatiles from the plume material.  相似文献   

A simple, but useful, application of image analysis     

Eugene F. Stoermer 《Journal of Paleolimnology》1996,15(1):111-113

Available image analysis tools are useful aids to some common tasks necessary for diatom identification. In particular, availability of this technology allows easier and more certain enumeration of closely spaced and difficult to resolve striae. Dimensional information may also be easily and accurately measured and recorded.  相似文献   

Application of a quasi-nonhydrostatic parameterization for numerically modeling neutral flow over an isolated hill     

Jerome D. Fast  Eugene S. Takle 《Boundary-Layer Meteorology》1988,44(3):285-304

A parameterization of the nonhydrostatic pressure was modified and adapted to a nonlinear numerical model of the neutral atmospheric boundary layer. A hydrostatic model and the quasinonhydrostatic version were used to simulate neutral flow over a symmetrical hill of uniform roughness. Mean-flow quantities and some turbulence characteristics of the flow from both models are presented. These results were compared with observations, analytic theory, and other numerical models.The quasi-nonhydrostatic method produced qualitative features commonly observed in such flows that the hydrostatic model could not simulate. For instance, the observed velocity reduction at the hill base and the speedup at the summit both were simulated by the quasi-nonhydrostatic model. However, computation of vertical velocities from the incompressible continuity equation is inadequate above regions of recirculation and presents a limitation to the method.Journal Paper No. J-12741 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2779.  相似文献   

OVER AGAIN ON WHAT IS HYDROGEOLOGY?     

Eugene V. Pinneker 《Ground water》1989,27(6):882-882

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