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1.
The ten-year progress of Chinese polar geodesy from 1996 to 2006 is summarized. Research on plate motion, crustal movement,
orbit determination, and atmospheric monitoring, including the ionosphere and troposphere, were performed using GPS data of
the Great Wall Station, Zhongshan Station and Yellow River Station. GPS was also applied in the Amery Ice Shelf, Grove Mountains
and Dome A expeditions to study ice dynamics. During the 2004/2005 austral summer season, the absolute gravity and relative
gravity were measured at the Great Wall Station with precision within ± 3 × 10−8 ms−2 and ± 10 × 10−8 ms−2 respectively. The tide gauge, which was set up in Zhongshan Station to monitor sea level change in 2000, recorded the 2004
Indian Ocean tsunami. SAR interferometry was applied to build the DEM of ice sheet and monitor ice flow in the polar region.
__________
Translated from Advances in Earth Science, 2007, 22(8): 784–790 [译自: 地球科学进展] 相似文献
2.
Feras Youssef Gunay Erpul Pieter Bogman Wim M. Cornelis Donald Gabriels 《Environmental Geology》2008,55(4):741-750
The trap efficiency of a catcher in wind erosion measurements plays a significant role, and in many cases suspension trap
efficiencies at high wind velocities are still unknown. The sediment trap efficiency generally changes with particles size
and with wind speed. In this study, the efficiency of Vaseline Slide (VS) and Modified Wilson and Cooke (MWAC) catchers were
determined with different sand particle sizes (<50, <75, 50–75, 200–400, and 400–500 μm) at a fixed wind speed (13.3 ms−1) and with different soil textures at different wind velocities (10.3, 12.3, and 14.3 ms−1) in the wind tunnel of the International Center for Eremology (ICE), Ghent University, Belgium. The traps were placed at
different heights (4, 6.5, 13, 20, 120, and 192 cm for VS and 1.5, 3, 5, 8, 11, and 30 cm for MWAC) to catch saltating and
suspended sediments in a 12-m long, 1.2-m wide and 3.2-m high working section of the wind tunnel. In the sand particle experiments,
the efficiency of the VS catcher was 92% for particles smaller than 50 μm and decreased with increasing particles size, falling
to 2.2% for 400–500 μm particle size at 13.4 ms−1. However, the MWAC’s efficiency was 0% for particles smaller than 50 μm and increased with increasing particle size to 69.5%
at 400–500 μm. In the experiments with different soil textures, the efficiency of each catcher significantly changed with
soil and with wind speed. It also considerably varied with the catchers: for instance, for sand (S), the MWAC efficiency was
very high (67.4, 113.4, and 90.5% at 10.3, 12.3, and 14.4 ms−1, respectively) while the efficiency of VS was relatively very low (5.2, 4.4, and 1.9% at 10.3, 12.3, and 14.4 ms−1, respectively). Results indicated that the efficiency depends critically on the particle size, type of catcher, and wind
speed, and these could be helpful to increase the robustness of wind erosion measurements. 相似文献
3.
Parameterization of sensible heat and momentum fluxes as inferred from an analysis of tower observations archived during MONTBLEX-90
at Jodhpur is proposed, both in terms of standard exchange coefficientsC
H
andC
D
respectively and also according to free convection scaling. Both coefficients increase rapidly at low winds (the latter more
strongly) and with increasing instability. All the sensible heat flux data at Jodhpur (wind speed at 10 m Ū10 < 8 ms−1) also obey free convection scaling, with the flux proportional to the ‘4/3’ power of an appropriate temperature difference
such as that between 1 and 30 m. Furthermore, for Ū10 < 4 ms−1 the momentum flux displays a linear dependence on wind speed. 相似文献
4.
Kusuma G. Rao 《Journal of Earth System Science》1996,105(3):273-287
Using MONTBLEX-90 mean velocity data, roughness lengths and drag coefficients are estimated at Jodhpur and Kharagpur. At Jodhpur,
since the surface is not uniform the roughness length is estimated separately in three different subsectors within the range
of prevailing wind directions and averages to 1.23 cm in the sector between 200° and 230° which is relatively flat with no
obstacles on the ground. At Kharagpur, where the terrain is more nearly homogeneous, the average value (for all prevailing
wind directions) is 1.94 cm.
The drag coefficient CD at Jodhpur shows variation both with the roughness subsector and with wind speed, the average over all directions increasing
rapidly as themean wind speed Ū10 at 10m height drops according to the power lawC
D
= 0.05 Ū
10
t-1.09
in trie range 0.5 < Ū10 < 7 m s−1. At Kharagpur, the drag coefficient is smaller than at Jodhpur by nearly 50% for the same range of wind speeds (> 3 ms−1). 相似文献
5.
Patrice Brehmer Jean Guillard Pablo I. Caballero Pinzon Pascal Bach 《Estuaries and Coasts》2011,34(4):739-744
Fish school swimming speeds is essential for ecological and management studies. The multibeam sonar in horizontal beaming
provided dynamic echo traces of mobile fish schools. We used two school swimming speed indicators: the average of a series
of instantaneous speed values, and the exploratory speed. These swimming speeds were estimated for each fish school observed
on the basis of their Euclidian position within the sonar beams. The average ISS values per school ranged from 0.15 m s−1 to 4.46 m s−1, while the ESS values per school were lower, ranging from 0.04 m s−1 to 3.77 m s−1. Multibeam sonar technology makes it possible to measure fish school swimming speeds in their natural habitat at small spatio-temporal
scales. This methodology can therefore be used to analyse in situ their movements, and has a wide range of applications in
behavioural studies and management purposes. 相似文献
6.
Variations in long term wind speed during different decades in Arabian Sea and Bay of Bengal 总被引:1,自引:0,他引:1
A study has been carried out by comparing the extreme wind speeds estimated based on NCEP/NCAR reanalysis data for 100 years
return period using Fischer Tippet-1 (commonly known as Gumbel) and Weibull distributions for three locations (off Goa, Visakhapatnam
and Machilipatnam) in the north Indian Ocean. The wind dataset for Goa is compared with that from ERA-40 data. For higher
wind speeds (12–20m s−1), NCEP wind speed has higher percentage of occurrence than that of ERA-40. Analysis has shown slight upward trend in the
annual maximum wind for location off Machilipatnam with an increase of 1.2 cm s−1 per year and a decreasing trend of −1.3 cm s−1 per year in the case of Goa. The Weibull distribution with shape parameter 2 fits the annual maximum wind data better than
FT-1 distribution. 相似文献
7.
Pratima M. Kessarkar V. Purnachandra Rao R. Shynu Ishfaq Mir Ahmad Prakash Mehra G. S. Michael D. Sundar 《Journal of Earth System Science》2009,118(4):369-377
Systematic studies on the suspended particulate matter (SPM) measured on a seasonal cycle in the Mandovi Estuary, Goa indicate
that the average concentrations of SPM at the regular station are ∼20mg/l, 5mg/l, 19mg/l and 5mg/l for June–September, October–January,
February–April and May, respectively. SPM exhibits low-to-moderate correlation with rainfall indicating that SPM is also influenced
by other processes. Transect stations reveal that the SPM at sea-end stations of the estuary are at least two orders of magnitude
greater than those at the river-end during the monsoon. Estuarine turbidity maximum (ETM) of nearly similar magnitude occurs
at the same location in two periods, interrupted by a period with very low SPM concentrations. The ETM occurring in June–September
is associated with low salinities; its formation is attributed to the interactions between strong southwesterly winds (5.1–5.6ms−1) and wind-induced waves and tidal currents and, dominant easterly river flow at the mouth of the estuary. The ETM occurring
in February–April is associated with high salinity and is conspicuous. The strong NW and SW winds (3.2–3.7ms−1) and wind-driven waves and currents seem to have acted effectively at the mouth of the estuary in developing turbidity maximum.
The impact of sea breeze appears nearly same as that of trade winds and cannot be underestimated in sediment resuspension
and deposition 相似文献
8.
The present study describes variations in the vertical fluxes measured concurrently with sediment traps at both a shallow
water (4 m) and a deeper water (7.5 m) position in a coastal lagoon in April 1995. A tripod equipped with five sediment traps
(trap openings at 0.35 m, 0.75 m, 1.05 m, 1.40 m, and 1.80 m above the seabed) was placed at the shallow water position. This
tripod was deployed three times during the study period and deployment periods varied between 2 d and 5 d. The second sediment
trap, placed at the deep water position in the central part of the lagoon, measured vertical flux for intervals of 12 h at
1.4 m above the seabed. The horizontal distance between the sediment traps was 8 km. The average maximum vertical flux at
the shallow water position reached 27.9 g m−2 d−1 during a period of high, westerly wind speeds, and a maximum vertical flux of 16.9 g m−2 d−1 was reached at the deep water position during a period of high, easterly wind speeds. Both strong resuspension events were
closely related to increased wave shear stress derived from surface waves. Maximum wave-induced resuspension rate was 10 times
higher at the shallow water position and 3.8 times higher at the deep water position compared with the net sedimentation rate
in the lagoon. Small resuspension events occurred at the shallow water position during periods of increased current shear
stress, Estimations of conditions for transport of sediment between shallow water and deep water showed that particles must
be resuspended to a height between 3 m and 4 m and that current speeds must be higher than about 0.1 m s−1. An average sedimentation rate of 3.8 g m−2 d−1 was obtained at the shallow water position during a period without wave shear stress and low current shear stress. This rate
measured by sediment traps is similar to a net sedimentation rate in the lagoon of 4.4 g m−2 d−1, which was determined by radiocarbon dating of a sediment core (Kristensen et al. 1995). 相似文献
9.
Assessment of heavy-metal contamination of floodplain soils due to mining and mineral processing in the Harz Mountains, Germany 总被引:9,自引:2,他引:7
2 study area was assessed with respect to its heavy-metal load on the basis of the current guideline values. The heavy-metal
loads of the soils in the study area have ranges of <0.2–200 mg kg−1 for Cd, <10–30,000 mg kg−1 for Pb, 7–10,000 mg kg−1 for Cu and 50–55,000 mg kg−1 for Zn. Mobility of the heavy metals was determined by extraction at different pH values. The acid neutralisation capacity
(ANCx) at these pH values was also determined to estimate the probability that the pH can drop to pH=x. The ANC values in the study area ranged from 6 to 3000 mmol H+ kg−1, from −33 to 800 mmol H+ kg−1 and from −74 to 160 mmol H+ kg−1 for ANC3.5, ANC5.0 and ANC6.2, respectively. Together with pedological data, the extraction experiments permit differentiation between soil units that
have been placed in the same environmental hazard class on the basis of total heavy-metal loads.
Received: 10 August 1998 · Accepted: 14 August 1999 相似文献
10.
Unit-cell dimensions of a natural phlogopite from Pargas, Finland, have been determined in the temperature interval of 27–1050 °C
by X-ray powder diffraction technique. Expansion rates vary discontinuously with temperature with a break at 412 °C. Below
this temperature, the linear expansions (α) for a, b and c axis lengths are 3.74 × 10−5 K−1, 1.09 × 10−5 K−1, and 1.19 × 10−5 K−1, respectively, and above that they are 0.86 × 10−5 K−1, 0.80 × 10−5 K−1, and 1.93 × 10−5 K−1. The volume thermal expansion coefficients are 6.26 × 10−5 K−1 and 3.71 × 10−5 K−1 for low-temperature and high-temperature intervals, respectively. The observed kink in the rate of thermal expansions with
temperature could be due to the different mode of structural changes. Thermogravimetric analysis of the sample indicates the
oxidation of iron in the temperature range of 500–600 °C and dehydroxylation as well as decomposition of phlogopite in the
temperature range of 900–1200 °C.
Received: 8 September 1998 / Accepted: 28 February 2000 相似文献
11.
Jurassic Ferrar rocks in Victoria Land (Antarctica) occur predominantly as basaltic or andesitic flows and sills. Both show
characteristic petrographical and chemical variations, which can be related to in-situ differentiation processes. Such characteristics
have been investigated at one flow (“Colonnade flow”) and one sill (“Thumb Point sill”) in the Prince Albert Mountains (Central
Victoria Land) based on a statistical grain size analysis and the application of the crystal size distribution theory. A third
magma body (“HiTi-unit”), which in previous literature was described as a flow, does not show clear similarities to either
the flow or sill. Sill and flow are in-situ differentiated with accumulation of silicic residual melt in the latest cooled
parts. For the flow this part is located in the lower half and for the sill in the upper third of their thickness. Thumb Point
sill additionally shows an accumulation zone of olivine in the lower third. The position of the residual melt accumulation
zone is an indicator for an origin as flow or sill. The HiTi-unit, by contrast, exhibits, only moderate petrographical and
chemical variations. Growth and nucleation rates have been determined using, with some modifications, the CSD theory introduced
by Marsh (1988). Growth rates of plagioclase for the flow vary from 10−11 to 10−10 cm/s and are comparable with literature values for basaltic lava lakes on Hawaii. Nucleation rates vary from 10−4 to 10−3 cm−3s−1, which are generally smaller than for Hawaiian basalts. Growth and nucleation rates for the sill cover a large range from
10−13 to 10−11 cm/s and 10−9 to 10−3 cm−3s−1, respectively. Systematic variations of these parameters with vertical position were obtained for the sill with its extensive
differentiation history. Nucleation and growth rates are dependant on the mode of cooling. Nevertheless, small but significant
differences between the flow and sill exist. Growth and nucleation rates of HiTi-unit (10−12 to 10−11 cm/s and 10−6 to 10−5 cm−3s−1) are intermediate between the flow and sill and thus do not allow a distinction of emplacement mode.
Received: 6 December 1995 / Accepted: 3 May 1996 相似文献
12.
M. M. Saç E. Yumurtaci G. Yener B. Camgöz A. Uğur B. Özden 《Environmental Geology》2008,55(3):477-483
Gediz Basin is one of the regions where intense agricultural activities take place in Western Turkey. Erosion and soil degradation
have long been causing serious problems to cultivated fields in the basin. This work describes the application of two different
137Cs models for estimating soil erosion rates in cultivated sites of the region. Soil samples were collected from five distinct
cultivated regions subject to soil erosion. The variations of 137Cs concentrations with depth in soil profiles were investigated. Soil loss rates were calculated from 137Cs inventories of the samples using both proportional model (PM) and simplified mass balance model (SMBM). When PM was used,
erosion and deposition rates varied from −15 to −28 t ha−1 year−1 and from +5 to +41 t ha−1 year−1, respectively; they varied from −16 to −33 t ha−1 year−1 and from +5 to +55 t ha−1 year−1 with SMBM. A good agreement was observed between the results of two models up to 30 t ha−1 year−1 soil loss and gain in the study area. Ulukent, a small representative agricultural field, was selected to compare the present
data of 137Cs techniques with the results obtained by universal soil loss equation (USLE) applied in the area before. 相似文献
13.
Estimation of methane emission from whole waste landfill site using correlation between flux and ground temperature 总被引:1,自引:0,他引:1
Tomonori Ishigaki Masato Yamada Masanao Nagamori Yusaku Ono Yuzo Inoue 《Environmental Geology》2005,48(7):845-853
A methodology to estimate a methane emission in a waste landfill site was developed. The methane flux at a waste landfill
site in summer, autumn, and winter was within the following ranges: from −1.3×10−2 to 16, from −6.4×10−2 to 7.5, and from −1.6×10−3 to 1.5×10−2 g-CH4 m−2 h−1, respectively. In those seasons, the mean methane emission rate and coefficient of variation were 1.1 g-CH4 m−2 h−1 ±290%, 0.57 g-CH4 m−2 h−1 ±347%, and 5.4×10−2 g-CH4 m−2 h−1 ±370%, respectively. These results simultaneously showed that fluctuations of methane emission from the landfill surface
were both of spatial and temporal variability. In each season, an exponential relationship was observed between the methane
flux density and the ground temperature. Total methane emissions were estimated to be 5.7×10−2, 7.1×10−3, and 1.7×10−3 g-CH4 m−2 h−1 in the summer, autumn, and winter surveys, respectively, using a temperature surrogated-kriging method. The results of this
study would improve upon the labor-intensive closed-chamber method, and could be a more practical way to estimate methane
emissions from waste landfills. 相似文献
14.
An integrated geochemical analysis of the well-exposed Pine Creek, California tungsten skarn deposit has been undertaken to
evaluate changes in chemical gradients across various lithologies. Thermodynamic calculations using available experimental
and thermodynamic data allow limits to be assigned to the activities of important chemical components in the metasomatic environment.
Quantifiable changes in “non-volatile” component activites (CaO, MgO, Al2O3, Fe2O3, WO3) and in fugacities (O2, F2) have been traced across the system. The activities of Al2O3, Fe2O3 and WO3 generally increase from the marble (<102, <10−6, <10−5 respectively), through the outer skarn zone and into the massive garnet skarn (10−1.7±0.3, 10−3.4±0.4, 10−4.8±0.1) While CaO and MgO activities decrease for the same traverse from 10−5 and 10−2.1±1 respectively, to <10−5.7 and <10−3. Calculated oxygen fugacities are 10−23.5+1.0 at T=800 K (527° C), about one log unit below QFM, and more reducing than that required by Mt-Py-Po. The high variance of the
garnet-pyroxene-quartz assemblages adds sufficient uncertainty to the calculated activities for individual specimens that
only the large-scale trends survive the small-scale scatter. None of the chemical variables emerge as major independent or
controlling factors for the mineralogy or phase compositions. Changes in the activity of one component may be offset by compensatory
changes in another resulting in an environment that, while different from Pine Creek, could still host scheelite mineralization.
Mass balance calculations indicate that the exposed endoskarn cannot have supplied the necessary chemical components to convert
the country rock to skarn. 相似文献
15.
In situ x-ray data on molar volumes of periclase and tungsten have been collected over the temperature range from 300 K to melting.
We determine the temperature by combining the technique of spectroradiometry and electrical resistance wire heating. The thermal
expansion (α) of periclase between 300 and 3100 K is given by α=2.6025 10−5+1.3535 10−8 T+6.5687 10−3 T−1−1.8281 T−2.
For tungsten, we have (300 to 3600 K) α=7.862 10−6+6.392 10−9 T.
The data at 298 K for periclase is: molar volume 11.246 (0.031) cm3, α=3.15 (0.07) 10−5 K−1, and for tungsten: molar volume 9.55 cm3, α=9.77 (10.08) 10−6 K−1.
Received: July 18, 1996 / Revised, accepted: February 14, 1997 相似文献
16.
Huan-Xin Weng Ya-Chao Qin Xiang-Wei Sun Xun-Hong Chen Jing-Feng Chen 《Environmental Geology》2009,57(1):9-15
Laboratory culture experiments have been conducted to evaluate the effects of light intensity on the growth of Cryptomonas sp. (Cryptophyceae) and the discrepancy in absorption of iron and phosphorus under different light conditions. Results show
that there is an exponential correlation between algal growth rate and light intensity. The saturating and semi-saturating
light values for Cryptomonas sp. cells are 150 and 47 μmol photons m−2 s−1, respectively. More uptake of Fe, P, and other trace elements such as Zn, Mn, Co, and Mo is observed in the low light cultures,
although the algal growth rates are slow. The growth rate at 10 μmol photons m−2 s−1 is only 10% of that at 150 μmol photons m−2 s−1, whereas Fe and P uptake increases by 150 and 100%, respectively. These results suggest potential implications of differentiation
in absorption of iron and phosphorus at different light intensities for the occurrence of harmful algal blooms (HABs). The
mechanisms of light intensity regulating nutrient uptake as well as the occurrence of HABs are also discussed. 相似文献
17.
Mohsen Jalali 《Environmental Geology》2009,56(7):1479-1488
This study was conducted to evaluate factors regulating groundwater quality in an area with agriculture as main use. Thirty
groundwater samples have been collected from Razan area (Hamadan, Iran) for hydrochemical investigations to understand the
sources of dissolved ions and assess the chemical quality of the groundwater. The chemical compositions of the groundwater
are dominated by Na+, Ca2+, HCO3
−, Cl− and SO4
2−, which have been derived largely from natural chemical weathering of carbonate, gypsum and anthropogenic activities of fertilizer’s
source. The production of SO4
2− has multiple origins, mainly from dissolution of sulphate minerals, oxidation of sulphide minerals and anthropogenic sources.
The major anthropogenic components in the groundwater include Na+, Cl−, SO4
2− and NO3
−, with Cl− and NO3
− being the main contributors to groundwater pollution in Razan area. 相似文献
18.
Tahir Rafique Shahid Naseem Muhammad I. Bhanger Tanzil H. Usmani 《Environmental Geology》2008,56(2):317-326
Groundwater samples were collected from various localities of Mithi sub-district of the Thar Desert of Pakistan and analysed
for fluoride ion along with other chemical parameters. The area is mainly covered by sand dunes and kaolin/granite at variable
depths. Results showed that collected water samples were severely contaminated by the presence of fluoride ion and most of
the samples have higher concentration than prescribed WHO standards (1.5 mg/l) for drinking water. Fluoride ion concentrations
ranged between 0.09 and 11.63 mg/l with mean and median values of 3.64 and 3.44 mg/l, respectively, in this area whereas,
distribution pattern showed high concentrations in the vicinity of Islamkot and Mithi towns. The content of F− has also been correlated with other major ions found in the groundwater of the study area. The positive correlation of F− with Na+ and HCO3
− showed that the water with high Na+ and HCO3
− stabilizes F− ions in the groundwater of the Thar Desert. The pH versus F− plots signifies high fluoride concentration at higher pH values, implying that alkaline environment favours the replacement
of exchangeable OH− with F− in the groundwater of Mithi area. The saturation indices (SI) of fluorite (CaF2) and calcite (CaCO3) in the groundwater samples showed that most of the samples are oversaturated with respect to calcite whereas majority of
samples have been found under saturated with respect to fluorite. The log TDS and Na/Na+Ca ratio reflected supremacy of weathering
of rocks, which promotes the availability of fluoride ions in the groundwater. Piper diagram has been used to classify the
hydrofacies. In the cation triangle, all samples are Na-type, while the anion triangle reflects major dominance of Cl-type
with a minor influence of HCO3
− and SO4
−. 相似文献
19.
The structural behavior of synthetic gahnite (ZnAl2O4) has been investigated by X-ray powder diffraction at high pressure (0–43 GPa) and room temperature, on the ID9 beamline
at ESRF. The equation of state of gahnite has been derived using the models of Birch–Murnaghan, Vinet and Poirier–Tarantola,
and the results have been mutually compared (the elastic bulk modulus and its derivatives versus P determined by the third-order Birch–Murnaghan equation of state are K
0=201.7(±0.9) GPa, K
′
0=7.62(±0.09) and K
″
0=−0.1022 GPa−1 (implied value). The compressibilities of the tetrahedral and octahedral bond lengths [0.00188(8) and 0.00142(5) GPa−1 at P=0, respectively], and the␣polyhedral volume compressibilities of the four-␣and␣sixfold coordination sites [0.0057(2) and
0.0041(2) GPa−1 at P=0, respectively] are discussed.
Received: 15 January 2001 / Accepted: 23 April 2001 相似文献
20.
A. Pavese V. Diella V. Pischedda M. Merli R. Bocchio M. Mezouar 《Physics and Chemistry of Minerals》2001,28(4):242-248
The thermoelastic parameters of natural andradite and grossular have been investigated by high-pressure and -temperature
synchrotron X-ray powder diffraction, at ESRF, on the ID30 beamline. The P–V–T data have been fitted by Birch-Murnaghan-like EOSs, using both the approximated and the general form. We have obtained for
andradite K
0=158.0(±1.5) GPa, (dK/dT )0=−0.020(3) GPa K−1 and α0=31.6(2) 10−6 K−1, and for grossular K
0=168.2(±1.7) GPa, (dK/dT)0=−0.016(3) GPa K−1 and α0=27.8(2) 10−6 K−1. Comparisons between the present issues and thermoelastic properties of garnets earlier determined are carried out.
Received: 7 July 2000 / Accepted: 20 October 2000 相似文献