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331.
John C. Callaway Evyan L. Borgnis R. Eugene Turner Charles S. Milan 《Estuaries and Coasts》2012,35(5):1163-1181
Tidal wetlands play an important role with respect to climate change because of both their sensitivity to sea-level rise and their ability to sequester carbon dioxide from the atmosphere. Policy-based interest in carbon sequestration has increased recently, and wetland restoration projects have potential for carbon credits through soil carbon sequestration. We measured sediment accretion, mineral and organic matter accumulation, and carbon sequestration rates using 137Cs and 210Pb downcore distributions at six natural tidal wetlands in the San Francisco Bay Estuary. The accretion rates were, in general, 0.2?C0.5?cm?year?1, indicating that local wetlands are keeping pace with recent rates of sea-level rise. Mineral accumulation rates were higher in salt marshes and at low-marsh stations within individual sites. The average carbon sequestration rate based on 210Pb dating was 79?g?C?m?2?year?1, with slightly higher rates based on 137Cs dating. There was little difference in the sequestration rates among sites or across stations within sites, indicating that a single carbon sequestration rate could be used for crediting tidal wetland restoration projects within the Estuary. 相似文献
332.
L’ubomír Smr?ok Alexander I. Kolesnikov Milan Rieder 《Physics and Chemistry of Minerals》2012,39(9):779-787
Inelastic neutron scattering (INS) was used to study the vibrational dynamics of the hydrogen atoms in natural trioctahedral phlogopite, K0.93Na0.03(Mg2.47Fe0.22Al0.16Fe0.04Tl0.06)[Si2.84Al1.16]O10OH1.71F0.28Cl0.01, within the 50–1,000?cm?1 energy range. The INS spectra collected using direct geometry spectrometer SEQUOIA (ORNL) were interpreted by means of the solid-state DFT calculations covering both normal mode analysis and molecular dynamics. To optimize the structure and to calculate the vibrational modes under harmonic approximation, both a hybrid PBE0 and the AM05 functional were used, while the molecular dynamics calculations (60?ps/1?fs) were performed only with the computationally less-demanding AM05 functional. The main contributions to the dominant band within ~750–550?cm?1 are symmetric and antisymmetric Mg–O–H bending modes, overlapping with the skeletal stretching and bending modes causing weaker secondary movements of H atoms of inner hydroxyl groups. Signatures of the Mg–O–H bending modes appear down to ~400?cm?1, where a region of octahedra deformation modes starts. These deformations cause just shallow movements of the hydrogen atoms and are mirrored by the modes with close vibrational energies. The region from ~330?cm?1 down to the low-energy end of the spectrum portrays induced vibrations of the H atoms caused by deformation of individual polyhedra, translational vibrations of the parts of the 2:1 layer relative one to another, and librational and translational vibrations of the layer. The main difference between the INS spectrum of dioctahedral Al-muscovite and trioctahedral Mg-phlogopite is that the Mg–O–H modes are all assigned to in-plane vibrations of the respective hydrogen atoms. 相似文献
333.
The recharge of a karst aquifer, in terms of its quantity and spatial distribution, depends on various natural factors such
as climate, topography, vegetation, soil, and geology. Selection of an adequate method for assessing recharge in karst is
often a matter of dispute. Multi-parameter methods using Geographical information systems tools have recently been successfully
developed and applied in karstic terrains of Spain and Lebanon. Specific local conditions such as highly karstified terrains
could additionally complicate such an assessment. The Montenegro karstified terrains in the southern part of the External
Dinarides are characterized by a very high precipitation rate, irregular seasonal distribution, and absence of surface waters
(extremely high infiltration capacity of karst). Considering such conditions, an attempt to apply existing knowledge and experiences
to the development of an appropriate multi-parameter method for assessing spatial distribution of autogenous recharge has
been made. The KARSTLOP method has been developed, applied, and calibrated at catchments of several large karst springs of
Montenegro. Obtained results in tested catchment areas confirm that with some further improvements the KARSTLOP method could
be a useful tool to support research of karstic aquifers in similar highly karstified terrains. 相似文献
334.
In this work, we attempt to quantify forces that result from the interaction between the induced Sq-variation currents in
the Earth’s lithosphere and the regional Earth’s magnetic field, in order to assess its influence on the tectonic stress field
and on seismic activity. The study area is the Sinai Peninsula, a seismically active region where both seismic and magnetic
data are available. We show that both short-term and long-term magnetic changes correlate with the seismic activity extending
to this area in other previous studies. We also analyze a set of large earthquakes and magnetic data from observatories around
the world to deduce a relationship between earthquake magnitude and maximum distance up to which precursory variations of
the magnetic field are observed. 相似文献