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841.
Bomina Kim Ayeon Choi Kun-Seop Lee Chang-Keun Kang Jung-Ho Hyun 《Estuaries and Coasts》2017,40(5):1346-1357
To evaluate the impact of invading seagrass on biogeochemical processes associated with sulfur cycles, we investigated the geochemical properties and sulfate reduction rates (SRRs) in sediments inhabited by invasive warm affinity Halophila nipponica and indigenous cold affinity Zostera marina. A more positive relationship between SRR and below-ground biomass (BGB) was observed at the H. nipponica bed (SRR = 0.6809 × BGB ? 4.3162, r 2 = 0.9878, p = 0.0006) than at the Z. marina bed (SRR = 0.3470 × BGB ? 4.0341, r 2 = 0.7082, p = 0.0357). These results suggested that SR was more stimulated by the dissolved organic carbon (DOC) exuded from the roots of H. nipponica than by the DOC released from the roots of Z. marina. Despite the enhanced SR in spring-summer, the relatively lower proportion (average, 20%) of acid-volatile sulfur (AVS) in total reduced sulfur and the strong correlation between total oxalate-extractable Fe (Fe(oxal)) and chromium-reducible sulfur (CRS = 0.2321 × total Fe(oxal) + 1.8180, r 2 = 0.3344, p = 0.0076) in the sediments suggested the rapid re-oxidation of sulfide and precipitation of sulfide with Fe. The turnover rate of the AVS at the H. nipponica bed (0.13 day?1) was 2.5 times lower than that at the Z. marina bed (0.33 day?1). Together with lower AVS turnover, the stronger correlation of SRR to BGB in the H. nipponica bed suggests that the extension of H. nipponica resulting from the warming of seawater might provoke more sulfide accumulation in coastal sediments. 相似文献
842.
On CO<Subscript>2</Subscript> fluid flow and heat transfer behavior in the subsurface,following leakage from a geologic storage reservoir 总被引:1,自引:0,他引:1
Karsten Pruess 《Environmental Geology》2008,54(8):1677-1686
Geologic storage of CO2 is expected to produce plumes of large areal extent, and some leakage may occur along fractures, fault zones, or improperly
plugged pre-existing wellbores. A review of physical and chemical processes accompanying leakage suggests a potential for
self-enhancement. The numerical simulations presented here confirm this expectation, but reveal self-limiting features as
well. It seems unlikely that CO2 leakage could trigger a high-energy run-away discharge, a so-called “pneumatic eruption,” but present understanding is insufficient
to rule out this possibility. The most promising avenue for increasing understanding of CO2 leakage behavior is the study of natural analogues. 相似文献
843.
We present the software program THERIA_G, which allows for numerical simulation of garnet growth in a given volume of rock
along any pressure–temperature–time (P–T–t) path. THERIA_G assumes thermodynamic equilibrium between the garnet rim and the rock matrix during growth and accounts for
component fractionation associated with garnet formation as well as for intracrystalline diffusion within garnet. In addition,
THERIA_G keeps track of changes in the equilibrium phase relations, which occur during garnet growth along the specified P–T–t trajectory. This is accomplished by the combination of two major modules: a Gibbs free energy minimization routine is used
to calculate equilibrium phase relations including the volume and composition of successive garnet growth increments as P and T and the effective bulk rock composition change. With the second module intragranular multi-component diffusion is modelled
for spherical garnet geometry. THERIA_G allows to simulate the formation of an entire garnet population, the nucleation and
growth history of which is specified via the garnet crystal size frequency distribution. Garnet growth simulations with THERIA_G
produce compositional profiles for the garnet porphyroblasts of each size class of a population and full information on equilibrium
phase assemblages for any point along the specified P–T–t trajectory. The results of garnet growth simulation can be used to infer the P–T–t path of metamorphism from the chemical zoning of garnet porphyroblasts. With a hypothetical example of garnet growth in a
pelitic rock we demonstrate that it is essential for the interpretation of the chemical zoning of garnet to account for the
combined effects of the thermodynamic conditions of garnet growth, the nucleation history and intracrystalline diffusion.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
F. GaidiesEmail: |
844.
The Samborombon Bay wetland is located on the west margin of the Rio de la Plata estuary, in the Province of Buenos Aires,
Argentina. This paper analyses the geological, geomorphologic, soil and vegetation characteristics of the southernmost sector
of this wetland and their influence on surface water and groundwater. The study area presents three hydrologic units: coastal
dunes, sand sheets and coastal plain. Coastal dunes and sand sheets are recharge zones of high permeability with well-drained,
non-saline soils, and a few surface water flows. Changes in the water table are related to rainfall. Groundwater in coastal
dunes is Ca–Mg–HCO3 to Na–HCO3, and of low salinity (590 mg/l). Groundwater in sand sheets is mainly Na–HCO3 with a salinity of about 1,020 mg/l. The coastal plain exhibits medium to low permeability sediments, with submerged saline
soils poorly drained. Groundwater is Na–Cl with a mean salinity of 16,502 mg/l. A surface hydrological network develops in
the coastal plain. Surface water levels near the shoreline are affected by tidal fluctuations; far from the shoreline water
accumulates because of poor drainage. Both sectors have Na–Cl water, but the former is more saline. Human intervention and
sea level rise may affect the wetland severely. 相似文献
845.
Quantitative modeling of groundwater in Satluj River basin of Rupnagar district of Punjab using remote sensing and geographic information system 总被引:2,自引:1,他引:2
Chander Kumar Singh Satyanarayan Shashtri Amit Singh Saumitra Mukherjee 《Environmental Earth Sciences》2011,62(4):871-881
Water is a fluctuating resource making it difficult to measure in time and in space. To demonstrate the efficiency of the
geographic information system (GIS) for groundwater studies, information on the parameters controlling groundwater such as
lithology, geomorphology and lineament analysis were analyzed. LISS-III and Landsat satellite image of the area was used to
infer information on the geologic lineaments and geomorphology. To delineate linear features enhancement and direction, filtering
was performed on single bands of Landsat images. Thematic maps for geology, slope, geomorphology and lineament were prepared
and integrated in GIS by assigning the weights and ranking to various parameters controlling the occurrence of groundwater
to generate the groundwater potential map for the study area. The results indicate that the floodplain of river and its adjoining
areas have very good groundwater potential, whereas the steeply sloping area in the northern part having high relief and slope
possesses poor groundwater potential. 相似文献
846.
847.
Low-mature gases and their resource potentiality 总被引:1,自引:0,他引:1
In the 80’s of last century, based on the advances in natural gas exploration practice, the concepts of bio-thermocatalytic transitional-zone gas and early thermogenetic gas were proposed, and the lower limit Ro values for the formation and accumulation of thermogenetic natural gases of industrial importance have been extended to 0.3%–0.4%. In accordance with the two-stage model established on the basis of carbon isotope fractionation involved in the formation of coal-type natural gases, the upper limit Ro ... 相似文献
848.
Kryštof Verner Jiří Žák Jaroslava Pertoldová Josef Šrámek Jiří Sedlák Jakub Trubač Patricie Týcová 《International Journal of Earth Sciences》2009,98(3):517-532
The Plechy pluton, southwestern Bohemian Massif, represents a late-Variscan, complexly zoned intrusive center emplaced near
the crustal-scale Pfahl shear zone; the pluton thus provides an opportunity to examine the interplay among successive emplacement
of large magma batches, magmatic fabric acquisition, and the late-Variscan stress field associated with strike-slip shearing.
The magmatic history of the pluton started with the emplacement of the porphyritic Plechy and Haidmühler granites. Based on
gravity and structural data, we interpret that the Plechy and Haidmühler granites were emplaced as a deeply rooted, ∼NE–SW
elongated body; its gross shape and internal fabric (steep ∼NE–SW magmatic foliation) may have been controlled by the late-Variscan
stress field. The steep magmatic foliation changes into flat-lying foliation (particularly recorded by AMS) presumably as
a result of divergent flow. Magnetic lineations correspond to a sub-horizontal ∼NE–SW finite stretch associated with the divergent
flow. Subsequently, the Třístoličník granite, characterized by steep margin-parallel magmatic foliation, was emplaced as a
crescent-shaped body in the central part of the pluton. The otherwise inward-younging intrusive sequence was completed by
the emplacement of the outermost and the most evolved garnet-bearing granite (the Marginal granite) along the southeastern
margin of the pluton.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
849.
The maximum entropy method (MEM) is used here to get an insight into the electron density [ρ(r)] of phengites 2M
1 and 3T, paying special attention to the M1-formally empty site and charge distribution. Room temperature single crystal X-ray diffraction
data have been used as experimental input for MEM. The results obtained by MEM have been compared with those from conventional
structure refinement which, in turn, has provided the prior-electron density to start the entropy maximization process. MEM
reveals a comparatively non-committal approach, able to produce information related to the M1-site fractional occupancy, and
yields results consistent with those from the difference Fourier synthesis, but free of the uncertainties due to the abrupt
truncation of the series. The charge distribution is investigated by means of the notion of ‘‘site basin’’, i.e., those site-centered
volumes delimited by a surface such as ∇ρ·n = 0. In particular, we observe: (1) the overall partitioning of the basin total charge between cation and anion sites, and
the interlayer site charge seems to depend on sample composition, and (2) the apical-oxygen plane total basin charge and hydroxyl
basin charge are presumably related to the polytype. The MEM-determined electron density does not allow full exploration of
the critical points for very complex structures as micas, insofar as conventional room temperature experimental diffraction
data are used. 相似文献
850.
Variation in DOC and trace metal concentration along the heavily urbanized basin in Kathmandu Valley,Nepal 总被引:1,自引:0,他引:1
Water samples were analyzed for DOC and trace metals from Bagmati River within Kathmandu valley, Nepal, to understand the
variation trends of DOC and trace metals and their relationship along the drainage network. The variability in organic matter
and wastewater input within the Bagmati drainage basin appeared to control DOC and most of the trace metal concentration.
The large input of organic matter and wastewater creates anoxic condition by consuming dissolved oxygen and releasing higher
concentrations of DOC, trace elements such as nickel, arsenic, barium, cadmium, and copper with downstream distance. Concentrations
of DOC and trace metals like barium and zinc showed strong relationships with human population density and suggest that human
activities have strong control on these parameters along the drainage network. The DOC and most of the trace metal concentration
increased with downstream distance and appeared to be directly associated with human activities. The variation trends of most
of the trace metals appeared to be the same; however, concentration varied widely. Inputs of organic matter and wastewater
due to human activities appeared directly to be associated for the variation of DOC and trace metals along the Bagmati drainage
network within Kathmandu valley. 相似文献