Near-infrared imaging of 222 nearby Hδ-strong galaxies from the Sloan Digital Sky Survey     

Michael L. Balogh  Chris Miller  Robert Nichol  Ann Zabludoff  Tomo Goto 《Monthly notices of the Royal Astronomical Society》2005,360(2):587-609

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Controls on regional variability in marine pore-water diagenesis below the seafloor in Upper Jurassic–Lower Cretaceous prodeltaic sandstone and shales,Scotian Basin,Eastern Canada     

Ann C. Okwese  Georgia Pe-Piper  David J.W. Piper 《Marine and Petroleum Geology》2012,29(1):175-191

Diagenesis in the uppermost Jurassic to Lower Cretaceous deltaic sandstones and shales of the Scotian Basin is an important control on reservoir quality. Ferruginous zone (sub-oxic) marine pore-water diagenesis controls the initial formation of Fe²⁺-silicates that are the precursors of grain-rimming chlorite that preserves porosity. This study assesses the regional controls on the type of marine pore-water diagenesis by studying the sedimentology, mineralogy, and geochemistry of the retrogradational units and underlying progradational units in parasequences from conventional cores in two wells in different parts of the basin. Coated grains preserve a record of whether marine pore-water diagenesis below the seafloor was dominantly in the ferruginous or sulphidic geochemical zone. Four types of coated grain were distinguished, each with a different mineral paragenesis. Mineralogical and chemical evidence of ferruginous zone diagenesis includes the presence of diagenetic chlorite and siderite, and the correlation of P with Fe or Ti. Pyrite and Fe-calcite are found where the sulphidic zone is more significant than the ferruginous zone. Ferruginous zone diagenesis was common in low-sedimentation rate retrogradational sediments with low organic carbon, and in delta-front turbidites and river-mouth sandstones. Estuarine, tidal flat and prodeltaic facies that are directly supplied by riverine sediments have a lower Fe:Ti ratio than do fully marine shoreface and open shelf facies as a result of input of detrital ilmenite and its alteration products. The relative contribution of colloidal iron (hydr)-oxides appears greater in distal low-sedimentation rate environments. Where large changes in sedimentation rate occurred at ravinement surfaces, the underlying progradational rocks have evidence of ferruginous zone diagenesis, whatever their facies. Rapid upward migration of the pore-water profile resulting from the change in sedimentation rate reduced the time available for mineral products to form in the deeper pore-water zones. This study has shown that the availability of Fe and organic carbon varying in a complex manner in marine deltaic sediments, but that the resulting diagenesis by marine pore-water can be predicted from facies and paleogeographic setting.  相似文献   

Chitin complex for the remediation of mine impacted water: Geochemistry of metal removal and comparison with other common substrates     

Mary Ann Robinson-Lora  Rachel A. Brennan 《Applied Geochemistry》2010

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Climatic change: communication changes over this journal’s first ‘century’     

Ann Henderson-Sellers 《Climatic change》2010,100(1):215-227

Over the century of ‘Climatic Change’ volumes and the 33 years that they span the climate has changed. Here I consider the challenge of interdisciplinary communication to which the first 99 volumes of this journal are dedicated. Have we succeeded and have climatic change researchers shared findings with a broader audience? If this journal has been successful, should the editorial board and publishers now consider new modes of communicating research to a still wider public, say by hiring a communication cartoonist or with an interactive blog?  相似文献   

Monitored Natural Attenuation of Contaminants in the Subsurface: Applications   总被引：3，自引：0，他引：3  

Ann Azadpour-Keeley  Jack W. Keeley  Hugh H. Russell  Guy W. Sewell 《Ground Water Monitoring & Remediation》2001,21(3):136-143

In recent years there has been increasing interest in the application of passive technologies to reduce or remove contaminants from the subsurface environment including soil and ground water. In most cases, the impetus for this interest lies in a perceived savings compared with more traditional remedial alternatives. In a few cases, the infrastructure at contaminated sites, such as buildings, paved areas, and utilities, makes the use of conventional remedial measures difficult and expensive.
To demonstrate that natural processes are effective in reaching established goals, it is necessary to determine that transformation processes are taking place at a rate that is protective of human health and the environment and that these processes will continue for an acceptable period of time. The basic conditions that must be present to confirm natural attenuation processes arc taking place are discussed along with the behavior of contaminated plumes, monitoring requirements, data analysis, rates of degradation, and mathematical modeling.  相似文献   

Acid-base status of soils in groundwater discharge zones — relation to surface water acidification     

Ann Catrine Norrstr  m 《Journal of Hydrology》1995,170(1-4):87-100

Critical load calculations have suggested that groundwater at depth of 2 m in Sweden is very sensitive to acid load. As environmental isotope studies have shown that most of the runoff in streams has passed through the soil, there is a risk in the near future of accelerated acidification of surface waters.

To assess the importance of the last soil horizon of contact before discharge, the upper 0–0.2m of soils in seven discharge zones were analysed for pools of base cations, acidity and base saturation. The sites were about 3–4 m² in size and selected from two catchments exposed to different levels of acid deposition.

The soils in the seven sites had high concentrations of exchangeable base cations and consequently high base saturation. The high correlation (r² = 0.74) between base saturation in the soils of the discharge zones and mean pH of the runoff waters suggested that the discharge zone is important for surface water acidification. The high pool of exchangeable base cations will buffer initially against the acid load. As the cation exchange capacity (meq dm⁻³) and base saturation were lower in the sites from the catchment receiving lower deposition, these streams may be more vulnerable to acidification in the near future. The high concentration of base cations in non-exchangeable fractions may also buffer against acidification as it is likely that some of these pools will become exchangeable with time.  相似文献   

The diurnal and semidiurnal barometric oscillations global distribution and annual variation     

B. Haurwitz  Ann D. Cowley 《Pure and Applied Geophysics》1973,102(1):193-222

Summary The global distributions of the annual and seasonal means of the diurnal (S ₁) and semidiurnal (S ₂) surface pressure oscillations are investigated by spherical harmonic analysis. The main waves are,S ₁ ¹ (with wave number 1) forS ₁ andS ₂ ² forS ₂.S ₁ ¹ is much less predominant among the waves ofS ₁ thanS ₂ ² among those ofS ₂. As in the case of the lunar semidiurnal barometric tideL ₂ the pressure maxima occur earlier in the Southern than in the Northern Hemisphere. In the case ofS ₂ the standing waveS ₂ ⁰ and the waveS ₂ ³ are also of interest besidesS ₂ ². Although the present analysis extends only from 60°N to 60°S, whileS ₂ ⁰ is largest at polar latitudes, its results show thatS ₂ ⁰ should be smaller at high southerly than at high northerly latitudes, as has been observed. Thus this observed asymmetrical distribution ofS ₂ ⁰ may be due to causes outside the polar regions rather than to their geographical differences. The best approximation to the observed distribution ofS ₂ ⁰ is obtained by including a mode representing an oscillation independent of longitude and latitude indicating a small semidiurnal variation of the mean global surface presure, which is an unlikely result on physical grounds.The seasonal variation ofS ₁ ¹ expressed in percent of the annual mean is smaller than that ofS ₂ ², and both are less than the unexplained seasonal variation ofL ₂ ².The main wavesS ₁ ¹ andS ₂ ² are expressed not only by associated Legendre functions, but also by Hough functions.National Center for Atmospheric Research, Boulder, Colorado, U.S.A., sponsored by the National Science Foundation.  相似文献   

Studying Regions by Studying Firms*   总被引：1，自引：0，他引：1  

Ann Markusen 《The Professional geographer》1994,46(4):477-490

This paper presents a method for inferring regional economic structure and prospects from key informant interviews. It describes assumptions which must be made and steps to be taken in moving from individuals to establishment, firm, and industry aggregations. A technique is offered for mapping core relationships among firms and other regional and external actors, and for aggregating firm-centered maps into industrial and regional maps. The mapping technique can be expanded to incorporate historicity and dynamic change.  相似文献   

Upscaling Permeability Measurements Within Complex Heterolithic Tidal Sandstones   总被引：2，自引：0，他引：2  

Matthew D. Jackson  Ann H. Muggeridge  Shuji Yoshida  Howard D. Johnson 《Mathematical Geology》2003,35(5):499-520

We investigate numerically the effect of sample volume on the effective single-phase permeability of heterolithic tidal sandstones, using three-dimensional models reconstructed directly from large rock specimens measuring 45 × 30 × 15 cm. We find that both individual and averaged effective permeability values vary as a function of sample volume, which indicates that permeability data obtained from core-plugs will not be representative at the scale of a reservoir model grid-block regardless of the number of measurements taken. However, the error introduced by averaged data may be minimized using the appropriate averaging scheme for a given facies type and flow direction.  相似文献   

Effects of seawater carbonate ion concentration and temperature on shell U, Mg, and Sr in cultured planktonic foraminifera     

Ann D. Russell  Bärbel Hönisch  Howard J. Spero 《Geochimica et cosmochimica acta》2004,68(21):4347-4361

We investigate the sensitivity of U/Ca, Mg/Ca, and Sr/Ca to changes in seawater [CO₃²⁻] and temperature in calcite produced by the two planktonic foraminifera species, Orbulina universa and Globigerina bulloides, in laboratory culture experiments. Our results demonstrate that at constant temperature, U/Ca in O. universa decreases by 25 ± 7% per 100 μmol [CO₃²⁻] kg⁻¹, as seawater [CO₃²⁻] increases from 110 to 470 μmol kg⁻¹. Results from G. bulloides suggest a similar relationship, but U/Ca is consistently offset by ∼+40% at the same environmental [CO₃²⁻]. In O. universa, U/Ca is insensitive to temperature between 15°C and 25°C. Applying the O. universa relationship to three U/Ca records from a related species, Globigerinoides sacculifer, we estimate that Caribbean and tropical Atlantic [CO₃²⁻] was 110 ± 70 μmol kg⁻¹ and 80 ± 40 μmol kg⁻¹ higher, respectively, during the last glacial period relative to the Holocene. This result is consistent with estimates of the glacial-interglacial change in surface water [CO₃²⁻] based on both modeling and on boron isotope pH estimates. In settings where the addition of U by diagenetic processes is not a factor, down-core records of foraminiferal U/Ca have potential to provide information about changes in the ocean’s carbonate concentration.Below ambient pH (pH < 8.2), Mg/Ca decreased by 7 ± 5% (O. universa) to 16 ± 6% (G. bulloides) per 0.1 unit increase in pH. Above ambient pH, the change in Mg/Ca was not significant for either species. This result suggests that Mg/Ca-based paleotemperature estimates for the Quaternary, during which surface-ocean pH has been at or above modern levels, have not been biased by variations in surface-water pH. Sr/Ca increased linearly by 1.6 ± 0.4% per 0.1 unit increase in pH. Shell Mg/Ca increased exponentially with temperature in O. universa, where Mg/Ca = 0.85 exp (0.096*T), whereas the change in Sr/Ca with temperature was within the reproducibility of replicate measurements.  相似文献