Direct evidence of the feedback between climate and weathering   总被引：1，自引：0，他引：1  

Sigurdur R. Gislason  Eric H. Oelkers  Eydis S. Eiriksdottir  Marin I. Kardjilov  Gudrun Gisladottir  Bergur Sigfusson  Arni Snorrason  Sverrir Elefsen  Jorunn Hardardottir  Peter Torssander  Niels Oskarsson 《Earth and Planetary Science Letters》2009,277(1-2):213-222

Long-term climate moderation is commonly attributed to chemical weathering; the higher the temperature and precipitation the faster the weathering rate. Weathering releases divalent cations to the ocean via riverine transport where they promote the drawdown of CO₂ from the atmosphere by the precipitation and subsequent burial of carbonate minerals. To test this widely-held hypothesis, we performed a field study determining the weathering rates of 8 nearly pristine north-eastern Iceland river catchments with varying glacial cover over 44 years. The mean annual temperature and annual precipitation of these catchments varied by 3.2 to 4.5 °C and 80 to 530%, respectively during the study period. Statistically significant linear positive correlations were found between mean annual temperature and chemical weathering in all 8 catchments and between mean annual temperature and both mechanical weathering and runoff in 7 of the 8 catchments. For each degree of temperature increase, the runoff, mechanical weathering flux, and chemical weathering fluxes in these catchments are found to increase from 6 to 16%, 8 to 30%, and 4 to 14% respectively, depending on the catchment. In contrast, annual precipitation is less related to the measured fluxes; statistically significant correlations between annual precipitation and runoff, mechanical weathering, and chemical weathering were found for 3 of the least glaciated catchments. Mechanical and chemical weathering increased with time in all catchments over the 44 year period. These correlations were statistically significant for only 2 of the 8 catchments due to scatter in corresponding annual runoff and average annual temperature versus time plots. Taken together, these results 1) demonstrate a significant feedback between climate and Earth surface weathering, and 2) suggest that weathering rates are currently increasing with time due to global warming.  相似文献   

Sonication of bacteria, phytoplankton and zooplankton: Application to treatment of ballast water   总被引：2，自引：0，他引：2  

Holm ER  Stamper DM  Brizzolara RA  Barnes L  Deamer N  Burkholder JM 《Marine pollution bulletin》2008,56(6):1201-1208

We investigated the effect of high power ultrasound, at a frequency of 19 kHz, on the survival of bacteria, phytoplankton and zooplankton, in order to obtain estimates of effective exposure times and energy densities that could be applied to design of ultrasonic treatment systems for ballast water. Efficacy of ultrasonic treatment varied with the size of the test organism. Zooplankton required only 3-9s of exposure time and 6-19 J/mL of ultrasonic energy to realize a 90% reduction in survival. In contrast, decimal reduction times for bacteria and phytoplankton ranged from 1 to 22 min, and decimal reduction energy densities from 31 to 1240 J/mL. Our results suggest that stand-alone ultrasonic treatment systems for ballast water, operating at 19-20 kHz, may be effective for planktonic organisms >100 microm in size, but smaller planktonic organisms such as phytoplankton and bacteria will require treatment by an additional or alternative system.  相似文献   

Fluid-Rock Interaction in the Granulites of Madagascar and Lithospheric-Scale Transfer of Fluids     

Eric Pili  Simon M.F. Sheppard  Jean-Marc Lardeaux 《Gondwana Research》1999,2(3):341

The nature of synmetamorphic fluids and their flow is examined in the granulitic lower crust of Madagascar, part of a Precambrian crustal-scale network of vertical ductile shear zones. Based on three independent data sets - field and satellite mapping, C-, O- and H-isotope geochemistry and gravimetry - this crust is divided into three zones: outside of shear zones, minor shear zones (<140 km long and 7 km wide), and major shear zones (>350 km long and 20–35 km wide). The major shear zones are rooted in and are controlled by the mantle. They tapped mantle-derived CO₂ with carbon fluxes of the same order of magnitude as oceanic ridge degassing. One major shear zone shows abundant phlogopite-diopside-apatite-calcite mineralizations (a well known paragenesis in mantle metasomatism) due to mantle-fluid infiltration and their interaction with the crust. Carbonatitic magmas possibly collected in the major shear zones at the base of the crust and may be the source for CO₂ upwellings as well as other metasomatic agents. Small-scale minor shear zones were controlled by crustal deformation processes and focused crustally-derived H₂O-rich fluids. Pervasive fluid circulation was restricted to the vicinity (< 100 m) of synmetamorphic plutons. Fluid absent conditions dominate everywhere else. Mantle-CO₂ flushing is not required for granulite genesis but is a consequence of the high associated heat flux. Fluid transfer at the mantle/crust interface is controlled by the tectonic setting and the associated geothermal gradient. The C- and O- isotope systematics of metamorphosed carbonates sampled on a regional scale within a known petrological and structural framework are shown to be of great help to identify the distribution of major fluid-rock interaction processes associated with plate tectonics.  相似文献   

Other Types of Contamination     

Evan K. Nyer  Eric P. Carman  Raymond M. Flynn 《Ground Water Monitoring & Remediation》1999,19(2):61-64

"Hazardous levels of methane in the subsurface occur at numerous locations across the United States."  相似文献   

Concave accretion discs and X-ray reprocessing     

Eric G. Blackman 《Monthly notices of the Royal Astronomical Society》1999,306(3):L25-L30

Spectra of Seyfert 1s are commonly modelled as emission from an X-ray-illuminated flat accretion disc orbiting a central black hole. This provides both reprocessed and direct components of the X-ray emission, as required by observations of individual objects, and possibly a fraction of the cosmological X-ray background. There is some observational motivation for us to at least consider the role that an effectively concave disc surface might play: (1) a reprocessed fraction ≳1/2 in some Seyferts and possibly in the X-ray background, and (2) the commonality of a sharp iron line peak for Seyferts at 6.4 keV despite a dependence of peak location on inclination angle for flat disc models. Here it is shown that a concave disc may not only provide a larger total fraction of reprocessed photons, but can also reprocess a much larger fraction of photons in its outer regions compared with a flat disc. This reduces the sensitivity of the 6.4-keV peak location to the inner disc inclination angle because the outer regions are less affected by Doppler and gravitational effects. If the X-ray source is isotropic, the reprocessed fraction is directly determined by the concavity. If the X-ray source is anisotropic, the location of iron line peak can still be determined by concavity but the total reflected fraction need not be as large as for the isotropic emitter case. The geometric calculations herein are applicable to general accretion disc systems illuminated from the centre.  相似文献   

Improved mappint of the Lake Agassiz Herman strandline by integrating geological and soil maps     

Eric C. Brevik 《Journal of Paleolimnology》1999,22(3):253-257

Several discontinuous, segmented strandlines that mark the former shores of Lake Agassiz can be found in eastern North Dakota. These strandlines are difficult to map and correlate because of their segmented nature. Better mapping would benefit researchers working on a number of problems involving Lake Agassiz including dating the strandlines, reconstructing the lake's history, and calculation of asthenosphere viscosity beneath the Lake Agassiz basin. Elongated soil delineations representing beach-indicative soils with a north-northwest trend and extending from currently mapped areas of the Herman strandline were identified on Grand Forks County soil maps. This information was combined with the geologic map of Grand Forks County in an attempt to better define the location of the Herman strandline in the southern part of the county. This approach worked well, and it is recommended that similar studies be attempted on other Lake Agassiz strandlines in North Dakota and the surrounding area.  相似文献   

Transatlantic latest Cretaceous mosasaurs (Reptilia,Lacertilia) from the Maastrichtian type area and New Jersey     

Mulder  Eric W.A. 《Geologie en Mijnbouw》1999,78(3-4):281-300

Cranial and postcranial elements of the mosasaurid reptiles Mosasaurus hoffmanni Mantell 1829 and Plioplatecarpus marshi Dollo 1882 from the Maastrichtian type area, and of Mosasaurus maximus Cope 1869 and Plioplatecarpus depressus (Cope 1869) from New Jersey are compared. Views held by previous authors are discussed. It is concluded that these European and North American taxa are conspecific.  相似文献   

Globalizing cities – introduction     

Eric Clark 《Geoforum》2000,31(4)

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DAMÉE-NAB: the base experiments     

Eric P. Chassignet  Hernan Arango  David Dietrich  Tal Ezer  Michael Ghil  Dale B. Haidvogel  C. -C. Ma  Avichal Mehra  Afonso M. Paiva  Ziv Sirkes 《Dynamics of Atmospheres and Oceans》2000,32(3-4)

The results of an intercomparison experiment performed with five numerical ocean models of different architecture are presented. While all models are able to simulate the large-scale characteristics of the North Atlantic circulation with a fair degree of realism, they also exhibit differences that can be attributed to the choices made in vertical coordinates, domain size, and boundary conditions.  相似文献   

Hydrodynamic model of cells for designing systems of urban groundwater drainage     

Eric D. Zimmermann  Gerardo A. Riccardi 《Hydrogeology Journal》2000,8(5):538-548

An improved mathematical hydrodynamic quasi-two-dimensional model of cells, CELSUB3, is presented for simulating drainage systems that consist of pumping well fields or subsurface drains. The CELSUB3 model is composed of an assemblage of algorithms that have been developed and tested previously and that simulate saturated flow in porous media, closed conduit flow, and flow through pumping stations. A new type of link between aquifer cells and drainage conduits is proposed. This link is verified in simple problems with well known analytical solutions. The correlation between results from analytical and mathematical solutions was considered satisfactory in all cases. To simulate more complex situations, the new proposed version, CELSUB3, was applied in a project designed to control the water-table level within a sewer system in Cha?ar Ladeado Town, Santa Fe Province, Argentina. Alternative drainage designs, which were evaluated under conditions of dynamic recharge caused by rainfall in a critical year (wettest year for the period of record) and a typical year, are briefly described. After analyzing ten alternative designs, the best technical–economic solution is a subsurface drainage system of closed conduits with pumping stations and evacuation channels. Electronic Publication  相似文献