Tidally oscillating bisulfide fluxes and fluid flow rates observed with in situ chemical sensors at a warm spring in Monterey Bay,California     

Josh N. Plant  Kenneth S. Johnson  Steve E. Fitzwater  Carole M. Sakamoto  Luke J. Coletti  Hans W. Jannasch 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(12):1585-1595

An In Situ Ultraviolet Spectrophotometer (ISUS) was coupled to a benthic chamber to characterize the bisulfide flux emanating from a warm spring at the Extrovert Cliff locality within Monterey Bay, California. The chamber was periodically flushed with bottom seawater to reset chemical concentrations, which enabled deployments over multiple days. Data from several deployments, each lasting at least 10 days, were used to calculate flow rates, fluid concentrations, and fluxes over time. The bisulfide concentration of the fluid entering the chamber varied from 75 to 4500 μmol l^?1. Positive temperature anomalies up to 3.5° were associated with these elevated concentrations. Linear flow rates ranged from 2 to >17 m day^?1, while the bisulfide fluxes varied from 0.2 to 80 mol m^?2 day^?1. The bisulfide originated at depth and was not produced in the surface sediments via an anaerobic oxidation of methane coupled to sulfate reduction. Tides modulated the flow as well as the composition of the fluid entering the chamber. It appeared that a deep sourced fluid, which supplied the bisulfide, was mixed with a second, ambient seawater-like fluid before entering the flux chamber. At low tides, flow rates were at their highest and the contribution of the deep sourced fluid to the fluid entering the chamber was at a maximum.  相似文献   

Australian Rainforests: Islands of Green in a Land of Fire: By David M.J.S. Bowman.     

Steve Turton 《New Zealand geographer》2001,57(2):50-51

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Petrologic diversity in Mount St. Helens dacites during the last 4,000 years: implications for magma mixing     

James E. Gardner  Steve Carey  Malcolm J. Rutherford  Haraldur Sigurdsson 《Contributions to Mineralogy and Petrology》1995,119(2-3):224-238

Mount St. Helens has explosively erupted dacitic magma discontinuously over the last 40,000 years, and detailed stratigraphic data are available for the past 4,000 years. During this last time period the major-element composition of the dacites has ranged from mafic (62–64 wt% SiO₂) to felsic (65–67 wt% SiO₂), temperature has varied by about 150°C (770°–920°C), and crystallinity has ranged between 20% and 55%. Water content of these dacites has also fluctuated greatly. Although the source for the dacitic magmas is probably partial melting of lower crustal rocks, there is strong physical evidence, such as banded pumices, thermal heterogeneities in single pumices, phenocryst disequilibrium, contrasts between compositions of glass inclusions and host matrix glass, and amphibole reaction rims, that suggests that magma mixing has been prominent in the dacitic reservoir. Indeed, we suggest that the variations in major- and trace-element abundances in Mount St. Helens dacites indicate that magma mixing between felsic dacite and mafic magma has controlled the petrologic diversity of the dacitic magmas. Magma mixing has also controlled the composition of andesites erupted at Mount St. Helens, and thus it appears that the continuum of magmatic composition erupted at the volcano is controlled by mixing between felsic dacite, or possibly rhyodacite, and basalt. The flux of the felsic endmember to the reservior appears to have been relatively constant, whereas the flux of basalt may have increased in the past 4,000 years, as suggested by the apparently increased abundance of mafic dacite and andesite erupted in this period.  相似文献   

Long-Term Stability Of Geoidal Geopotential FromTopex/Poseidon Satellite Altimetry 1993–1999     

Burša  Milan  Kenyon  Steve  Kouba  Jan  Müller  Achim  Raděj  Karel  Vatrt  Viliam  Vojtíšková  Marie  Vítek  Vojtěch 《Earth, Moon, and Planets》1999,84(3):163-176

The TOPEX/POSEIDON (T/P) satellite altimeter data from January 1, 1993to October 24, 1999 (cycles 11–261) was used for investigating thelong-term variations in the geoidal geopotential W₀ and/orin the geopotential scale factor R₀ = GM/W₀ (GM is theadopted geocentric gravitational constant). The mean valuesdetermined for the whole period covered are: W₀ =(62 636 856.161 ± 0.002) m² s^-2, R₀ =(6 363 672.5448 ± 0.0002) m. The actual accuracy is limited bythe altimeter calibration error (2–3 cm) and it isestimated to be about ± 0.5 m² s^-2 (± 5 cm).The yearly variations of the above mean values are at the formalerror level. No long-term trend in W₀, representing the oceanvolume change, was found for the seven years period 1993–9 on thebasis of T/P altimeter (AVISO) data. No sea surface topography modelwas used in the solution. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

EPA Develops Ground Water Protection Approach     

Bob Barles  Steve Ainsworth 《Ground Water Monitoring & Remediation》1993,13(1):98-100

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Climate change and transportation in Northern Canada: an integrated impact assessment     

Steve Lonergan  Richard Difrancesco  Ming-Ko Woo 《Climatic change》1993,24(4):331-351

The physical and economic impacts of climate warming in the Mackenzie River Valley, Northwest Territories, Canada are estimated using a combination of stochastic modelling, econometric-modelling and input-output analysis. The attempt was to illustrate the utility of using analytical models for long-term impact assessment as well as to estimate the potential impacts from projected climate warming in the region. A scenario approach, based on three global circulation models, was used, with an emphasis on modelling climate variability, river ice conditions and economic impacts. The transportation system was used as a central focus linking the physical and socio-economic components. Despite the significant warming projected for the region, results show the economic impacts from changes in transportation to be relatively minor, with the greatest changes being in the tertiary, or service, sector.  相似文献   

LAND-USE CONTROL: AN IMPORTANT PIECE OF THE GROUND-WATER PROTECTION PUZZLE     

Harry E. LeGrand  Donald K. Keech  Steve Ragone  Jay H. Lehr  David M. Nielsen 《Ground water》1983,21(1):2-3

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GROUND-WATER MONITORING SYSTEM CONSIDERATIONS     

Steve J. Nacht 《Ground Water Monitoring & Remediation》1983,3(2):33-39

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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   

In memoriam: Henri Kampunzu (1952–2004)     

Sospeter Muhongo  Jean-Paul Liegeois  Steve McCourt  Sadrack Felix Toteu  Estella Atekwana  Patrick G. Eriksson  Marek Wendorff   《Journal of African Earth Sciences》2004,40(5):195

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