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991.
Natural springs have been reliable sources of domestic water and have allowed for the development of recreational facilities and resorts in the Central Appalachians. The structural history of this area is complex and it is unknown whether these natural springs receive significant recharge from modern precipitation or whether they discharge old water recharged over geological times scales. The main objective of this study was to use stable isotopes of water ( $\delta^{18} {\text{O}}_{{{\text{H}}_{2} {\text{O}}}}$ and $\delta^{2} {\text{H}}_{{{\text{H}}_{2} {\text{O}}}}$ ), dissolved inorganic carbon ( $\delta^{13} {\text{C}}_{\text{DIC}}$ ) and dissolved sulfate ( $\delta^{34} {\text{S}}_{{{\text{SO}}_{4} }}$ and $\delta^{18} {\text{O}}_{{{\text{SO}}_{4} }}$ ) to delineate sources of water, carbon and sulfur in several natural springs of the region. Our preliminary isotope data indicate that all springs are being recharged by modern precipitation. The oxygen isotope composition indicates that waters in thermal springs did not encounter the high temperatures required for O isotope exchange between the water and silicate/carbonate minerals, and/or the residence time of water in the aquifers was short due to high flow rates. The carbon isotopic composition of dissolved inorganic carbon and sulfur/oxygen isotopic composition of dissolved sulfate provide evidence of low-temperature water–rock interactions and various biogeochemical transformations these waters have undergone along their flow path. 相似文献
992.
Abenezer Mekonen Prabhakar Sharma Fritjof Fagerlund 《Environmental Earth Sciences》2014,71(8):3751-3760
In this study, a series of sand packed columns were used to investigate the mobility of multiwall carbon nanotubes (MWCNTs) in unsaturated porous media under unfavorable conditions for deposition. The flow through column experiments were designed to assess water content, flow rate, and grain size effect on the mobility of MWCNTs. It was found that variation in water content had no significant effect on retention of MWCNTs until it was lowered to 16 % effective saturation. Thick water films, high flow rate, and repulsive forces between MWCNTs and porous media made MWCNTs highly mobile. Different porous media grain sizes (D 50 = 150–300 μm) were used in this study. The mobility of MWCNTs slightly decreased in finer grain sands, which was deemed to be an effect of increase in surface area and the number of depositional sites, in combination with low-pore water velocity. However, physical straining was not observed in selected fine-grain sands and aspect ratio of MWCNTs had low impact on mobility. Variations in pore-water velocity were produced by both changes in water saturation and in flow rate. At high pore-water velocities, the MWCNTs were generally mobile. However, for the combination of low-pore water velocity with either low water saturation or small grain size, some retention of MWCNTs was observed. Hence, low velocity in combination with flow through smaller pores increased MWCNT deposition. 相似文献
993.
The numerical simulations of the model equation governing the nonlinear evolution of kinetic Alfvén wave (KAW) in solar wind plasmas are performed. The nonlinear dynamical equation of KAW satisfies the modified nonlinear Schrödinger MNLS equation when the ponderomotive nonlinearity is incorporated in the KAW dynamics. The effect of Landau damping is taken into account in the KAW dynamics. The coherent (in the absence of Landau damping) and damped (with Landau damping) localized structures of pump KAW as a consequence of ponderomotive nonlinearity have been studied in the solar wind at 1 AU. A weak whistler signal propagating in these localized structures is amplified which leads to the development of its own coherent and damped localized structures. Magnetic field (KAW) and electric field (whistler wave) power spectra and their spectral indices are calculated. Our results reveal the change in spectral index because of the damping effect which has good agreement with the observations. These damped structures and steeper spectra may be one of the reasons responsible for the plasma heating and particles acceleration in solar wind. 相似文献
994.
Monthly mesoscale eddy kinetic energy (EKE) per unit mass has been computed for four years, 1993-1996, from TOPEX altimeter data in the Indian Ocean. It ranges from 50 cm2/s2 to 2,700 cm2/s2 (about 4,000 cm2/s2 near the Somali region in a few months). In the Arabian Sea and the Bay of Bengal, regions of high energies associated with various current systems under the influence of monsoonal winds have been delineated. Monthly variation of EKE near the Somali region has been studied. In this region the maximum EKE per unit mass has been observed during August every year, with variations in magnitude from year to year. The mesoscale eddy kinetic energy computed from TOPEX altimeter-derived SSH during 1993-1996 is highest near the Somali region during the SW monsoon, due to formation of mesoscale eddies and also because of upwelling. In the Bay of Bengal, high eddy kinetic energy is seen toward the western side during nonmonsoonal months due to the western boundary current. In the South Indian Ocean, it is high at a few places in some of the months. A large part of the Indian Ocean exhibits low eddy kinetic energy (less than 300 cm2/s2) year-round. 相似文献
995.
Role of atmospheric ammonia in the formation of inorganic secondary particulate matter: A study at Kanpur,India 总被引:1,自引:0,他引:1
Mukesh Sharma Shyam Kishore S. N. Tripathi S. N. Behera 《Journal of Atmospheric Chemistry》2007,57(1):1-17
Levels of fine Particulate Matter (PMfine), SO2 and NOx are interlinked through atmospheric reactions to a large extent. NOx, NH3, SO2, temperature and humidity are the important atmospheric constituents/conditions governing formation of fine particulate sulfates
and nitrates. To understand the formation of inorganic secondary particles (nitrates and sulfates) in the atmosphere, a study
was undertaken in Kanpur, India. Specifically, the study was designed to measure the atmospheric levels of covering winter and summer seasons and day and night samplings to capture the diurnal variations. Results showed are found to be significantly high in winter season compared to the summer season. In winter, the molar ratio of to was found to be greater than 2:1. This higher molar ratio suggests that in addition to (NH4)2SO4, NH4NO3 will be formed because of excess quantity of present. In summer, the molar ratio was less than 2:1 indicating deficit of to produce NH4NO3. The nitrogen conversion ratio (NO2 to NO3) was found to be nearly 50% in the study area that suggested quick conversion of NO2 into nitric acid. As an overall conclusion, this study finds that NH3 plays a vital role in the formation of fine inorganic secondary particles particularly so in winter months and there is a
need to identify and assess sources of ammonia emissions in India. 相似文献
996.
This paper presents the model equations governing the nonlinear interaction between dispersive Alfvén wave (DAW) and magnetosonic
wave in the low-β plasmas (β≪m
e/m
i; known as inertial Alfvén waves (IAWs); here
\upbeta = 8pn0T /B02\upbeta = 8\pi n_{0}T /B_{0}^{2} is thermal to magnetic pressure, n
0 is unperturbed plasma number density, T(=T
e≈T
i) represents the plasma temperature, and m
e(m
i) is the mass of electron (ion)). This nonlinear dynamical system may be considered as the modified Zakharov system of equations
(MZSE). These model equations are solved numerically by using a pseudo-spectral method to study the nonlinear evolution of
density cavities driven by IAW. We observed the nonlinear evolution of IAW magnetic field structures having chaotic behavior
accompanied by density cavities associated with the magnetosonic wave. The relevance of these investigations to low-β plasmas
in solar corona and auroral ionospheric plasmas has been pointed out. For the auroral ionosphere, we observed the density
fluctuations of ∼ 0.07n
0, consistent with the FAST observation reported by Chaston et al. (Phys. Scr.
T84, 64, 2000). The heating of the solar corona observed by Yohkoh and SOHO may be produced by the coupling of IAW and magnetosonic wave via filamentation process as discussed here. 相似文献
997.
Helga de Wall Stefan Schöbel Manoj K. Pandit Kamal K. Sharma J. Just 《Journal of the Geological Society of India》2010,75(1):239-253
The Mirpur granite body represents a relatively small (10 km2) pluton intruded along the northern margin of the adjacent Mt. Abu batholith (∼125 km2) in NW India. It is a visibly undeformed alkali feldspar rich pink granite; in contrast, the Mt. Abu is a composite granitoid
body and variably deformed. Both are intruded by rhyolitic dykes and the terminal magmatic events in both the cases are mafic
dykes. The AMS (Anisotropy of Magnetic Susceptibility) data identify the Mt. Abu with SE-dipping foliations and subvertical
lineations as a single structural domain while the Mirpur granite body shows two domains characterized by predominantly E
— W trend of magnetic foliation in the eastern part (domain I) and N — S orientations in the western part (domain II). The
domain I shows magmatic fabrics, typical for the peraluminous granites of Malani Igneous Suite (MIS). Change in fabric orientation
in the domain II has resulted from cataclasis wherein the samples show destruction of the original E — W fabric and complete
transposition by N — S trends. The foliations in the Mt. Abu granites have been related to SE orientation of maximum horizontal
stress. The same maximum stress direction can be inferred from dyke orientation in the Mirpur granite, which is interpreted
as continuation of the tectonic imprint in this region during emplacement of both the granites. Age of the cataclastic overprint
with a predominant N — S orientation is not yet constrained but corresponds with the trend of the nearby Sindreth basin within
the Malani Igneous Suite. The Neoproterozoic tectonic scenario for the region has been interpreted in terms of an ongoing
crustal convergence and granitic magma emplacement against the back stop offered by the rigid Delhi Fold Belt. 相似文献
998.
Pasquale Crea Concetta De Stefano Frank J. Millero Silvio Sammartano Virender K. Sharma 《Aquatic Geochemistry》2010,16(3):447-466
Oxidized glutathione (GSSG), which has four carboxylic and two amino groups, interacts with metal ions and may affect the
bioavailability and geochemistry of metals in natural waters. In the present paper, six stepwise protonation constants
K\textHi K^{\text{H}}_{i} for GSSG were measured as a function of salinity, S = 5–35‰ at t = 25°C (and in NaCl/MgCl2 mixtures at different ionic strengths), in order to provide thermodynamic data for their acid base properties, which are
useful for studying the interaction with metals in these media. The protonation enthalpies (ΔH
i
/kJ mol−1) were also determined at t = 25°C. The results were interpreted using the SIT model and Pitzer equations. The seawater model with the interaction parameters
accounts for the differences between the values in NaCl and seawater. The results suggest that it is important to consider
all of the ionic interactions in natural waters in examining the proton dissociation of GSSG. 相似文献
999.
Landslide susceptibility zonation of the Chamoli region, Garhwal Himalayas, using logistic regression model 总被引:5,自引:2,他引:3
A remote sensing and Geographic Information System-based study has been carried out for landslide susceptibility zonation in the Chamoli region, part of Garhwal Himalayas. Logistic regression has been applied to correlate the presence of landslides with independent physical factors including slope, aspect, relative relief, land use/cover, lithology, lineament, and drainage density. Coefficients of the categories of each factor have been obtained and used to assess the landslide probability value to ultimately categorize the area into various landslide susceptibility zones; very low, low, moderate, high, and very high. The results show that 71.13% of observed landslides fall in 21.96% of predicted very high and high susceptibility zone, which in fact should be the case. Furthermore, lineament first buffer category (0–500 m) and the east and south aspects are the most influential in causing landslides in the region. 相似文献
1000.
Numerical model and flume experiments of single- and two-layered hillslope flow related to slope failure 总被引:1,自引:0,他引:1
A hillslope flow model is developed considering 3D saturated and unsaturated flow of water during rainfall events. A finite difference-based numerical model of hillslope flow processes is developed. Four different experiments are done to see the effects of a single- and double-layered soil in pore-water pressure dynamics and slope failure. Results from the numerical model are verified with experimental results. The numerical and experimental values of the pore-water pressure and moisture contents are in good agreement. The results show that the hillslope heterogeneity caused by multiple layers of soil has greater influence on hillslope pore-pressure dynamics and slope failure patterns. The depth of slope failure shows high dependency on layering characteristics of the soil slope and pattern of rainfall. The proposed model provides a perspective on failure mechanism of a single- or double-layered slope under rainfall infiltration. 相似文献