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281.
Variations in dilute-acid (partial digest) metal concentrations in bottom sediments from 49 stations on the Mississippi, Alabama
and Florida continental margin are investigated with the aid of ordination and other multivariate statistical techniques.
Total iron, carbonate content, clay fraction and water depth correlate well with the overall leachable sediment metal values
for pooled station replicates over four sampling periods. Individual metal concentrations also are correlated with these and
other environmental parameters using stepwise multiple linear regression techniques. A weak positive association between Ba,
Cu, Cr, Ni, Pb, and V burdens in the demersal fishSyacium papillosum and the dilute-acid leachable sediment metal TOC and carbonate concentrations is demonstrated. 相似文献
282.
David F. Johnson 《Estuarine, Coastal and Shelf Science》1985,20(6):693-705
Vertical and horizontal distributions are described for megalopae of 11 brachyuran taxa common to the lower Chesapeake Bay and adjacent shelf. Three distribution patterns are apparent from horizontal distribution.
- 1. (1) More than 75% of the megalopae of estuarine adults, such as Hexapanopeus angustifrons, Neopanope sayi, Panopeus herbstii, Rhithropanopeus harrisii and Pinnotheres ostreum, are retained in estuarine waters.
- 2. (2) The megalopae of three estuarine taxa, Callinectes sapidus, Uca spp. and Pinnixa sp., are most abundant on the shelf.
- 3. (3) More than 90% of the megalopae of the shelf species, Portunus sp., Cancer irroratus and Libinia spp. remained in shelf waters.
283.
Chi Shing Wong Nathalie A. D. Waser Yukihiro Nojiri Wm. Keith Johnson Frank A. Whitney John S. C. Page Jiye Zeng 《Journal of Oceanography》2002,58(2):227-243
The seasonal and interannual changes in surface nutrients, dissolved inorganic carbon (DIC) and total alkalinity (TA) were
recorded in the North Pacific (30–54°N) from 1995 to 2001. This study focuses on the region north of the subarctic boundary
(∼40°N) where there was extensive monthly coverage of surface properties. The nutrient cycles showed large interannual variations
in the eastern and western subarctic gyres. In the Alaska Gyre the seasonal depletion of nitrate (ΔNO3) increased from 8–14 μmol kg−1 in 1995–1999 to 21.5 μmol kg−1 in 2000. In the western subarctic the shifts were similar in amplitude but more frequent. The large ΔNO3 levels were associated with high silicate depletions, indicating enhanced diatom production. The seasonal DIC:NO3 drawdown ratios were elevated in the eastern and central subarctic due to calcification. In the western subarctic and the
central Bering Sea calcification was significant only during 1997 and/or 1998, two El Ni?o years. Regional C/N stoichiometric
molar ratios of 5.7 to 7.0 (>40°N) were determined based on the years with negligible or no calcification. The annual new
production (NPa) based on ΔNO3 and these C/N ratios showed large interannual variations. NPa was usually higher in the western than in the eastern subarctic. However, values of 84 gC m−2yr−1 were found in the Alaska Gyre in 2000 which is similar to that in the most productive provinces of the northern North Pacific.
There were also large increases in NPa around the Alaska Peninsula in 1997 and 1998. Finally, the net removal of carbon by the biological pump was estimated as
0.72 Gt C yr−1 in the North Pacific (>30°N).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
284.
Petrogenesis of Variscan high-temperature Group A eclogites from the Moldanubian Zone of the Bohemian Massif,Czechoslovakia 总被引:1,自引:0,他引:1
Brian L. Beard L. Gordon Medaris Jr. Clark M. Johnson Hannes K. Brueckner Zdenek Mísař 《Contributions to Mineralogy and Petrology》1992,111(4):468-483
High-temperature (HT), Group A eclogites from three localities in the Moldanubian Zone of the Bohemian Massif are interpreted to have formed in the mantle and to have been transported into the crust by their enclosing garnet peridotites during Variscan orogenesis. Garnet and omphacite are compositionally zoned and contain homogeneous cores and retrograde rims. Cores of minerals yield minimum temperatures and pressures of 850 to 985°C and 16.0 to 22.5 kb, based on Fe–Mg exchange between garnet and clinopyroxene and the jadeite content of clinopyroxene. Sugh high temperatures indicate equilibration in, and derivation from, the upper mantle. Trace element compositions, including the REEs, high MgO contents, and high Mg numbers suggest that the rocks formed by high pressure accumulation of garnet and clinopyroxene and variable amounts of trapped melt. Sm-Nd ages determined on four garnet-clinopyroxene pairs from the three localities are 377±20, 342±9, 336±16, and 323±7 Ma.
Nd and initial 87Sr/86Sr are negatively correlated, varying from +6.7 to -0.1 and 0.7027 to 0.7057, respectively. Field, compositional, and isotopic data indicate that the eclogites were derived from heterogeneous mantle that included depleted and enriched compositions; this heterogeneity may have resulted from subduction processes that occurred prior to the late Variscan collision of Gondwana and Baltica. 相似文献
285.
Electrical geophysical methods, including electrical resistivity, time‐domain induced polarization, and complex resistivity, have become commonly used to image the near subsurface. Here, we outline their utility for time‐lapse imaging of hydrological, geochemical, and biogeochemical processes, focusing on new instrumentation, processing, and analysis techniques specific to monitoring. We review data collection procedures, parameters measured, and petrophysical relationships and then outline the state of the science with respect to inversion methodologies, including coupled inversion. We conclude by highlighting recent research focused on innovative applications of time‐lapse imaging in hydrology, biology, ecology, and geochemistry, among other areas of interest. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
286.
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289.
The combined observations of Saturn's moon Enceladus by the Cassini CAPS, INMS and UVIS instruments detected water vapor geysers in which were present molecular nitrogen (N2), carbon dioxide (CO2), methane (CH4), propane (C3H8), acetylene (C2H2), and several other species, together with all of the decomposition products of water. We propose that the presence of N2 in the plume indicates thermal decomposition of ammonia, and hence high temperatures in the interior of the moon (e.g., 500 to 800 K). Such an environment also appears to be suitable for the production of methane (CH4) from carbon monoxide (CO), or carbon dioxide (CO2). The presence of C2H2 and C3H8 strongly suggest that catalytic reactions took place within a very hot environment. The internal environment of Enceladus is inferred to be or have been favorable for aqueous, catalytic chemistry. This permits the synthesis of many complex organic compounds that could be detected in future Cassini observations. 相似文献
290.
The spatial distribution of N+ in Saturn's magnetosphere obtained from Cassini Plasma Spectrometer (CAPS) data can be used to determine the spatial distribution and relative importance of the nitrogen sources for Saturn's magnetosphere. We first summarize CAPS data from 15 orbits showing the spatial and energy distribution of the nitrogen component of the plasma. This analysis re-enforces our earlier discovery [Smith, H.T., Shappirio, M., Sittler, E.C., Reisenfeld, D., Johnson, R.E., Baragiola, R.A., Crary, F.J., McComas, D.J., Young, D.T., 2005. Geophys. Res. Lett. 32 (14). L14S03] that Enceladus is likely the dominant nitrogen source for Saturn's inner magnetosphere. We also find a sharp enhancement in the nitrogen ion to water ion ratio near the orbit of Enceladus which, we show, is consistent with the presence of a narrow Enceladus torus as described in [Johnson, R.E., Liu, M., Sittler Jr., E.C., 2005. Geophys. Res. Lett. 32. L24201]. The CAPS data and the model described below indicate that N+ ions are a significant fraction of the plasma in this narrow torus. We then simulated the combined Enceladus and Titan nitrogen sources using the CAPS data as a constraint. This simulation is an extension of the model we employed earlier to describe the neutral tori produced by the loss of nitrogen from Titan [Smith, H.T., Johnson, R.E., Shematovich, V.I., 2004. Geophys. Res. Lett. 31 (16). L16804]. We show that Enceladus is the principal nitrogen source in the inner magnetosphere but Titan might account for a fraction of the observed nitrogen ions at the largest distances discussed. We also show that the CAPS data is consistent with Enceladus being a molecular nitrogen source with a nitrogen to water ratio roughly consistent with INMS [Waite, J.H., and 13 colleagues, 2006. Science 311 (5766), 1419-1422], but out-gassing of other nitrogen-containing species, such as ammonia, cannot be ruled out. 相似文献