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Dowty RA Shaffer GP Hester MW Childers GW Campo FM Greene MC 《Marine environmental research》2001,52(3):195-211
Research was conducted to assess the impact of oiling on fresh-marsh plant communities and to test the efficacy of techniques that may be used to enhance the bioremediation of crude oil spills in these environments while minimizing secondary anthropogenic impacts. To emulate field conditions, a mesocosm facility was used that houses 120 mesocosm vessels, each of 200-1 capacity. A five-way factorial treatment arrangement was used that included two substrates (inorganic, organic), two nutrient regimes (fertilized, not fertilized), two aeration levels (substrate aeration, no aeration), three oiling concentrations (0-, 5-, 10-1 m(-2) of South Louisiana Sweet Crude oil), and four vascular plant species (Alternanthera philoxeroides, Panicum hemitomon, Phragmites australis, Sagittaria lancifolia, and an unplanted control). Under the 5- and 10-1 m(-2) oiling concentrations, S. lancifolia displayed a short-term response of increased productivity, whereas P. hemitomon had the highest biomass production and photosynthetic rates at the end of the 18-month experiment. Overall plant growth and productivity, as well as oil degradation, were significantly higher in the inorganic substrate, indicating that biodegradation of oil spills in organic substrates may require a longer time period. Time-released fertilizer also stimulated plant productivity and resulted in higher soil respiratory quotients, suggestive of greater microbial activity, particularly in aerated mesocosms. The amount of oil remaining after 18 months was lowest in aerated and fertilized mesocosms containing either P. hemitomon or S. lancifolia and a substrate of low organic matter content. 相似文献
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Henry D. Schreiber G.Bryan Balazs Andrew P. Shaffer P.Lynne Jamison 《Geochimica et cosmochimica acta》1982,46(10):1891-1901
The production of metallic iron in silicate melts by the chemical reactions, 2Ti3+(melt) + Fe2+(melt) → 2Ti4+(melt) + Fe0(crystal)2Cr2+(melt) + Fe2+(melt) → 2Cr3+(melt) + Fe0(crystal)2Eu2+(melt)+ Fe2+(melt) → 2Eu3+(melt) + Fe0(crystal) has been demonstrated under experimental conditions in a simplified basaltic liquid, Such reactions may occur in lunar basalts and other reduced systems, and, thus, may aid in the understanding of the reduced nature of lunar basalts. The reactions were studied in a glass-forming Na-Ca-Mg-Al-silicate composition at a melt temperature of 1250°C and an imposed oxygen fugacity at the C/CO buffer (1 atm total pressure). Microtitrations of individually-doped samples were used in the quantitative assessment of their redox ratios and for the calibration of visible and near-infrared spectral absorptions. These spectral absorptions were then applied to the evaluation of the mutual redox interactions in dual-doped samples. 相似文献
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GP. Horedt 《Celestial Mechanics and Dynamical Astronomy》1972,6(2):232-241
We consider a large massM and two small massesm
1 andm
2 (m
1 m
2;m
1,m
2M). The orbit ofm
1 is initially circular and the motion ofm
2 hyperbolic with respect toM. The orbital elements of the small masses are strongly modified after a close, single encounter betweenm
1 andm
2.An approximative method, similar to the theory of stellar encounters, is used to determine the probabilities of collisions, hyperbolas, direct and retrograde ellipses, as well as the mean values of the semimajor axes and their root mean square deviation after the encounter.The results are close to those which are obtained if the massm
2 is negligibly small, (Mm
1m
2;m
2 0), as should be also expected on general grounds. 相似文献
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Sediment resuspension during and after mechanical excavation of macrophytes may have a significant impact on resident fish populations. Unfortunately, little is known about the influence of this sediment on the respiratory performance and feeding abilities of fishes in New Zealand waterways. We examined the effects of suspended sediment (SS) concentrations previously observed after a large-scale macrophyte removal operation on oxygen consumption (MO2) and feeding rates of brown trout (Salmo trutta). MO2 at 0 mg L?1, 150 mg L?1, 300 mg L?1, 450 mg L?1 and 600 mg L?1 of SS was measured using semi-closed respirometry. Feeding rates at the same SS concentrations were also measured using laboratory tank experiments. Results suggest that SS concentrations up to 600 mg L?1 have no effect on MO2. Conversely, feeding rates were significantly reduced at 450 mg L?1 (22% reduction) and 600 mg L?1 (31% reduction), indicating that sediment concentrations above 450 mg L?1 may negatively affect brown trout populations. 相似文献
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Topographic data from the Shuttle Radar Topography Mission (SRTM) captures the permanent deformation of a prominent highstand
of Mono Lake, California USA. Deformation of the Dechambeau Ranch highstand shoreline was measured using the elevation of
the beach berm—shoreline bluff break-in-slope. Point source models and a boundary element dike model were used to approximate
the source of deformation underneath the northern end of the Mono Craters. The point source model could not adequately explain
the observed deformation. The dike model yielded the best results for a NW trending dike dipping 60° NE and inflated to widths
greater than 60 m. The results suggest that the geometry of the source is more complex than a simple vertical dike and that
the deformation is better explained with a dipping dike following a normal fault, or an elongated cryptodome. 相似文献
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Pattern and process of land loss in the Mississippi Delta: A Spatial and temporal analysis of wetland habitat change 总被引：2，自引：0，他引：2
John W. Day Louis D. Britsch Suzanne R. Hawes Gary P. Shaffer Denise J. Reed Donald Cahoon 《Estuaries and Coasts》2000,23(4):425-438
An earlier investigation (Turner 1997) concluded that most of the coastal wetland loss in Louisiana was caused by the effects of canal dredging, that loss was near zero in the absence of canals, and that land loss had decreased to near zero by the late 1990s. This analysis was based on a 15-min quadrangle (approximately 68,000 ha) scale that is too large to isolate processes responsible for small-scale wetland loss and too small to capture those responsible for large-scale loss. We conducted a further evaluation of the relationship between direct loss due to canal dredging and all other loss from 1933–1990 using a spatial scale of 4,100 ha that accurately captures local land-loss processes. Regressions of other wetland loss on canal area (i.e., direct loss) for the Birdfoot, Terrebonne, and Calcasieu basins were not significant. Positive relationships were found for the Breton (r2=0.675), Barataria (r2=0.47), and Mermentau (r2=0.35) basins, indicating that the extent of canals is significantly related to wetland loss in these basins. A significant negative relationship (r2=0.36) was found for the Atchafalaya coastal basin which had statistically lower loss rates than the other basins as a whole. The Atchafalaya area receives direct inflow of about one third of the Mississippi discharge. When the data were combined for all basins, 9.2% of the variation in other wetland loss was attributable to canals. All significant regressions intercepted the y-axis at positive loss values indicating that some loss occurred in the absence of canals. Wetland loss did not differ significantly from the coast inland or between marsh type. We agree with Turner that canals are an important agent in causing wetland loss in coastal Louisiana, but strongly disagree that they are responsible for the vast majority of this loss. We conclude that wetland loss in the Mississippi delta is an ongoing complex process involving several interacting factors and that efforts to create and restore Louisiana’s coastal wetlands must emphasize riverine inputs of freshwater and sediments. 相似文献
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GP. Horedt 《Earth, Moon, and Planets》1976,15(3-4):439-443
If the mass of the Earth was not considerably larger than at present, the pre-capture orbit of the Moon was in the range 0.9–1.1 A.U. Capture occurred within several 108 years after formation of the Moon. 相似文献