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1.
《科学通报(英文版)》1999,44(15):1424-1424
The ice core dust particulate sampled from Mt. Xixabangma has been analyzed by means of X-ray photoelectron spectrometer (XPS) and scanning electron microscope with energy dispersion X-ray analysis (SEM/EDAX). The results show that the contents of SO42- and SOl32- in the surface layer of the dust are significantly higher than those in the subsurface layer (with the exception of organic sulfide). This difference indicates that the surface SOX has been captured and then chemically converted by the atmospheric dust particulate before its deposition with snow, which is obviously different from those inner layer sulfates and sulfites contained by dust itself. In addition, it has been determined by SEM/EDAX that the dust contains relatively high concentrations of transition metal elements such as Fe and Ti oxides which could function as photocatalysts to the conversion of SOX adhered on the surface of the dust, and consequently accelerate the deposition of SOx to snow. Our research also demonstrates that the ad-sorptive carrying and the catalytic performance of the dust to the atmospheric SOX are most important causes of the positive correlation between SO42- and dust concentration records in ice cores. 相似文献
2.
Traces of tephra and increased sulfate (SO
4
2−
) concentrations were identified in the 1992–1994 snow layers in 2 firn cores from South Pole. The deposition of the Pinatubo
SO
4
2−
aerosol was delayed due to the long transport to the high south latitudes and its initial existence at high altitudes in
the Antarctic atmosphere. Electron microscopic analyses show that the element composition of the tephra is identical to that
of volcanic ash found near the Pinatubo volcano in Philippines. Detailed stratigraphic snow sampling resolved the Pinatubo
signal from that of Cerro Hudson eruption during August 1991 in Chile. The South Pole sulfate flux from Pinatubo is calculated
to be (10.9±1.1) kg·km−2, while the Hudson sulfate flux is (3.2±1.1) kg·km−2. This information will be useful to estimating the magnitudes of the past volcanic eruptions recorded in Antarctic ice core. 相似文献
3.
Carbonaceous particles concentrations of OC and EC are determined using a two-step gas chroma- tography system in Muztagh Ata ice core covering the time period of 1955--2000. Over the period represented by the core, OC and EC concentrations appear to have changed significantly, varied in the range of 17.7--216.7 and 6.5--124.6, and averaged 61.8, 32.9 ng·g^-1, respectively. The average concentration of EC in Muztagh Ata ice core is much lower than that in an Alpine ice core record (100--300 ng·g^-1) during the same period, but it is a factor of 14 in Greenland ice core (2.3 ng·g^-1), this may induce a strong impact on the snow albedo in the last 46 years in our study area. Observations indicate two periods with obviously high deposition concentrations (1955--1965 and 1974--1989) and two periods with low concentrations (1966--1973 and 1990--1995), as well as a recent increasing trend. By comparing EC and SO4^2- concentration variations and deciphering OC/EC ratios recorded in the same ice core, we can judge roughly that the carbonaceous particles deposited in Muztagh Ata ice core were attributed to fossil fuel combustion sources. 相似文献
4.
Summer monsoon and dust signals recorded in the Dasuopu firn core, central Himalayas 总被引:2,自引:0,他引:2
Shichang Kang Dahe Qin Tandong Yao Cameron P. Wake Paul A. Mayewski 《科学通报(英文版)》1999,44(21):2010-2010
In September 1997, a 15-m firn core was recovered from an elevation of 7 000 m a. s.l. from the Dasuopu Glacier in the central Himalayas. The analysis of δ18O values and major ion (Ca2+ , Mg2+ , NH4+ , SO42- and NO3-) concentrations shows that average annual accumulation is 0.75 m (water equivalent) in the Dasuopu firn core. The seasonal variations of δ18O values and major ion concentrations in the core indicate that present summer monsoon and dust signals are recorded with high-resolution in the Dasuopu Glacier. δ18O in precipitation are controlled by amount effect in summer monsoon season, more negative δ18O is representative of summer monsoon signal in snow layers. Higher concentrations of Ca2+ , Mg2+ , SO42- and NO3-are dominated by spring dust storm imput derived from the arid and semi-arid desert regions in central Asia. Also EOF analysis verifies that high spring concentrations of major ions are consistent. Due to the possibly different sources, the secondary variations of NH4+ and NO3- are negatively relevant with that of Ca2+ and Mg2+ . 相似文献
5.
Crystal structure and negative thermal expansion of solid solution Lu<Subscript>2</Subscript>W<Subscript>3−<Emphasis Type="Italic">x</Emphasis></Subscript>Mo<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>12</Subscript> 下载免费PDF全文
Jie Peng Xin-zhi Liu Fu-li Guo Song-bai Han Yun-tao Liu Dong-feng Chen Zhong-bo Hu 《矿物冶金与材料学报》2010,17(6):786-790
A new series of solid solutions Lu2W3−x
Mo
x
O12 (0.5≤x≤2.5) were successfully synthesized by the solid-state method. Their crystal structure and negative thermal expansion properties
were studied using high-temperature X-ray powder diffraction and the Rietveld method. All samples of rare-earth tungstates
and molybdates are found to crystallize in the same orthorhombic structure with space group Pnca and show the negative thermal expansion phenomena related to transverse vibration of bridging oxygen atoms in the structure.
Thermal expansion coefficients (TEC) of Lu2W3−x
Mo
x
O12 are determined as −20.0×10−6 K−1 for x=0.5 and −16.1×10−6 K−1 for x=2.5 but -18.6×10−6 and −16.9×10−6 K−1 for unsubstituted Lu2W3O12 and Lu2Mo3O12 in the identical temperature range of 200 to 800°C. High-temperature X-ray diffraction (XRD) data and bond length analysis
suggest that the difference between W-O and Mo-O bond is responsible for the change of TECs after the element substitution
in this series of solid solutions. 相似文献
6.
LIU YongChun LIU JunFeng HE Hong YU YunBo XUE Li 《科学通报(英文版)》2007,52(15):2063-2071
Heterogeneous oxidation of carbonyl sulfide (OCS) on mineral oxides including SiO2, Fe2O3, CaO, MgO, ZnO and TiO2, which are the main components of atmospheric particles, were investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), ion chromatography (IC), temperature-programmed desorption (TPD), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) methods. The main products and intermediates of the heterogeneous oxidation of OCS on these oxides were identified with in situ DRIFTS and IC. The reaction mechanism and kinetics were also discussed. It is found that the reaction mechanism on these mineral oxides is the same as that on Al2O3 for the same final products and the intermediates at room temperature. Namely, OCS can be catalytically oxidized to produce surface SO4^2- species and gaseous CO2 through the surface hydrogen thiocarbonate (HSCO2-) and HSO; species. The activity series for heterogeneous oxidation of OCS follows: Al2O3 ≈ CaO 〉 MgO 〉 TiO2 ≈ ZnO 〉 Fe2O3 〉 SiO2. The specific area, basic hydroxyl and surface basicity of these oxides have effect on the reactivity. This study suggests that heterogeneous reactions of OCS on mineral dust may be an unneglectable sink of OCS. 相似文献
7.
GUO Zhigang LI Juyuan FENG Jialiang FANG Ming YANG Zuosheng 《科学通报(英文版)》2006,51(17):2133-2140
Asian dust storms originating from the arid regions of central and eastern Asia and from the Loess Plateau in China frequently occur in spring [1,2]. Driven by the East Asian monsoon, Asian dust can be transported to northern Pacific Ocean[2―8]. Asian du… 相似文献
8.
NIU Jianrong LIU Wei DAI Hongxing HE Hong Zl Xuehong LI Peiheng 《科学通报(英文版)》2006,51(14):1673-1681
The volatile organic compounds (VOCs) emitted from the sources of industries are a kind of main pol-lutants to the atmosphere. The Environmental Protec-tion Agency (EPA) of the United States lists more than 300 VOC pollutants. 70% of the toxic compounds t… 相似文献
9.
Preliminary evidence indicating Dome A (Antarctica) satisfying preconditions for drilling the oldest ice core 总被引:4,自引:0,他引:4
Ian ALLISON 《科学通报(英文版)》2008,53(1):102-106
Lowest temperature and snow accumulation rate are preconditions for retrieving the oldest ice core from the polar ice sheets. The 10-m depth firn temperature at Dome A, the summit of the Antarctic Ice Sheet, recorded by an automatic weather station (AWS) was -58.3℃ in 2005 and -58.2℃ in 2006, respectively. The 10-m firn temperature is an approximation of the annual mean air temperature (AMAT), and this is the lowest AMAT that has been recorded on the surface of the Earth. The stable isotopic ratios (δ^18O and δD) of surface snow at Dome A are also lower than at other ice sheet domes along the East Antarctic Ice Divide such as Dome C, Dome F, Dome B and Vostok. These facts indicate that Dome A is the "pole of cold" on the Earth. The total amount of snow accumulation rate in 2005 and 2006 was only 0.16 cm, equaling 0.016 m water equivalent per year, the lowest precipitation ever recorded from Antarctica. Preliminary evidences indicate that Dome A is a candidate site for recovering the oldest ice core. 相似文献
10.
WANG PengLing YAO TanDong TIAN LiDe WU GuangJian LI Zhen YANG Wei 《科学通报(英文版)》2008,53(3):418-425
A 16.8 m firn core of middle Himalayas was recovered on the col of Dasuopu glacier in August 2006, being 7000 m above sea level. A total of 317 samples were measured for stable oxygen isotope ratios (6180) and major ion concentrations (Na+, NH+, K+, Mg2+, Ca2+, Cl-, SO4^2-, and NO3^-. The firn core dating and seasonal partitioning were carried out based on the marked seasonal variations along the stable oxygen isotopes and crustal species (Ca2+, Mg2+) profiles. The multi-parameters and high-resolution glaciochemical data set of Dasuopu firn core recorded the detailed chemical characteristics of pre cipitation in high-elevation region, middle Himalayas, since 1991 A.D., which mainly originated from the crustal and anthropogenic sources, while the sea-salt contribution was minor. The seasonal variability of major ion concentrations was dominated by the seasonal alternation of the prevalent air mass, atmospheric circulation situation and precipitation regime. Linear regression analysis indicated that most of the variance in annual ionic fluxes can be explained by a linear dependence on snow accumulation rate. 相似文献
11.
MEI Fanmin J. Rajot S. Alfaro L. Gomes ZHANG Xiaoye WANG Tao 《科学通报(英文版)》2006,51(7):878-884
It is essential for validation and improvement of a dust production model to perform field observations on dust emissions. The dust production model (DPM model) consists of two physically explicit sub-models, namely saltation model [1, 2] (eq. (1)) and sandblasting model [3] (eqs. (2) and (3)). Fh is saltation flux, E is fraction of erodible surface, C is a dimensional constant, ρa is air density, g is gravitational acceleration, U* is the wind friction velocity, Ut*(Dp) is threshold frict… 相似文献
12.
Precipitation variability in central Himalayas and its relation to Northern Hemisphere temperature 总被引:3,自引:0,他引:3
DUAN Keqin & YAO Tandong . Cold Arid Regions Environmental Engineering ResearchInstitute Chinese Academy Sciences Lanzhou China . National Laboratory of Western China抯 Environmental Systems Lanzhou University Lanzhou China 《科学通报(英文版)》2003,48(14):1480-1482
Agriculture, industry and hydroelectric power in south Asia are heavily dependent on the performance of the summer (June to September) monsoon rainfall, which provides 75—90% of the annual rainwater over most parts of the area. A weak monsoon year generally corresponds to low crop yields. And strong monsoon usually produces abundant crops, although too much rainfall may produce devastating floods. However, modeling efforts to forecast the monsoon have met with only moderate success[1]. Prev… 相似文献
13.
The results of research on the effects of anions on the biosorption of microelement cations by the edible marine macroalga Enteromorpha prolifera in singleand multi-metal systems are discussed in this paper. It was shown that the maximum biosorption capacity (qmax) in a single-metal system of Co(II) ions decreased in the following sequence: Cl- (46.0 mg g-1) > SO42- (42.8 mg g-1) > NO3- (41.9 mg g-1). In multi-metal systems, in which the ratios of Cl-, NO3-, and SO42- were 0:0:4, 1:1:2, 3:0:1, and 4:0:0, there were clear differences among the biosorption capacities. In all the examined systems (other than the 0:0:4 system), inhibition of the binding of microelement cations by the macroalga was observed. In all the systems, the highest value of qmax was obtained for Cu(II) cations; the value ranged from 31.9 mg g-1 in 0:0:4 (SO42- only) to 18.2 mg g-1 in 4:0:0 (Cl-only). 相似文献
14.
Zhongqin Li Mingjun Zhang Dahe Qin Cunde Xiao Lide Tian Jiancheng Kang Jun Li 《科学通报(英文版)》1999,44(24):2270-2270
Snow and firn samples recovered from two snow pits (2.5 and 4.5m deep) and one 50-m firn core along the route of the 1996/1997 Chinese First Antarctic Inland Traverse Expedition in Princess Elizabeth Land, East Antarctica, have been measured for chemical composition and oxygen isotope ratio. In the two snow pits, the variations of NO3- are partly in phase with that of δ18O, while the variations of Cl~ and Na+ are in inverse phase with that of δ18O. The variations of CI- , Na+ , NO3- and δ18O show obvious seasonal variations and annual stratag-raphy. However, with the depth increasing, the seasonal variations of δ18O are gradually smoothed below 3 m (corresponding to about 10-year mass accumulation) in depth while the seasonal variations of Cl- , Na+ and NO3- are kept fairly well in the whole profile of the 50-m firn core (corresponding to about 250-year mass accumulation). The results provide a useful tool for dating the snow stratum in this region. On the contrary, no obvious seasonal variations of Ca2 + are found in the profiles. 相似文献
15.
A new TFEL material ZnSxO1−x: Ce3+ is prepared. The EL brightness of ZnSxO1−x: Ce3+ is at least one order higher than that of ZnS: Ce3+ at the same doping concentration of Ce3+. The EL emission wavelength of ZnSxO1−x: Ce3+ (X = 0.5) ranges from 400 to 600 nm. The emission of ZnSxO1−x: Ce3+ may be used as the blue part of white TFEL. 相似文献
16.
S31603不锈钢具有优异的耐腐蚀性能,广泛应用于化工、沿海设施等领域。在使用过程中,长期经历内部应力、苛刻环境的腐蚀作用。其中,水溶液中的离子对S31603不锈钢的耐腐蚀性能有着重要影响。通过分析锈蚀S31603不锈钢的微观形貌、元素组成及化学状态等,研究非金属离子对其表面锈蚀的影响。结果表明,NO3−、NO2−、SO42−对S31603不锈钢锈蚀起关键作用,Cl-起辅助作用,且锈蚀主要发生在S31603不锈钢与水溶液长期接触的界面。通过对锈蚀表面进行物质鉴定,发现锈蚀表面含有Fe2(SO4)3、FeSO4、CrO2等多种化合物。 相似文献
17.
In this study,TiO2@MgO core-shell film was obtained by using a simple chemical bath deposition method to coat a thin MgO film around TiO2 nanoparticles. The core-shell configuration was characterized by X-ray diffractometer (XRD),scanning elec-tron microscopy (SEM),energy dispersive X-ray spectroscopy (EDX),and high-resolution transmission electron microscopy (HRTEM). Lattice fringes were observed for the TiO2 particles,and the MgO shell showed an amorphous structure,revealing a clear distinction between the core and shell materials. Applying the core-shell film as photoanode to the dye-sensitized solar cells (DSSCs),it shows a superior performance compared to the pure TiO2 electrode. Under the illumination of simulated sunlight (75 mW-cm-2),the short circuit photocurrent (Jsc),the open circuit photovoltage (Voc),and the fill factor (fF) are 8.80 mA-cm-2,646 mV,and 0.69,respectively,and the conversion efficiency (η) in-creased by 21.8% (from 4.32% to 5.26%) when dipping for opti-mum condition. 相似文献
18.
Effect of adsorption mode on photodegradation of H-acid in TiO2 suspension was studied using DFT calculation,UV-Vis spec-troscopy,FTIR,and ionic chromatography.At pH 2.5,H-acid was adsorbed on TiO2 surfaces by one dissociated sulfonic group.The adsorbed sulfonic group was attacked by surface ·OH,resulting in the production of SO42-and the cleavage of the naphtha-lene ring.At pH 5.0,H-acid was adsorbed on TiO2 surfaces by two sulfonic groups.The two adsorbed sulfonic groups were sim-ultaneously attacked by surface ·OH,leading to a faster initial production of SO42-and initial degradation rate of H-acid than those under pH 2.5.Microscopic adsorption structures may be more important than adsorption amount in controlling the photo-degradation pathways of organic pollutants. 相似文献
19.
CAOWenxi YANGYuezhong XUXiaoqiang HUANGLiangmin ZHANGJianlin 《科学通报(英文版)》2003,48(21):2344-2351
Knowledge about the spectral absorption properties of marine particulate matters is of important signification for various goals of optical oceanography, among them the most concerns are the bio-optical algorithms for ocean color remote sensing[1], basic theory of light radiative transfer in water column[2], bio-optical models for estima-tion of primary productivity and simulation of the upper ocean ecological process[3,4]. The spectral absorption by marine particulate matter is combined influe… 相似文献
20.
For a given incidence angle at the snow surface, a greater snow density causes a greater change in the incidence angle at
the snow-ground interface; for a given snow density, however, a larger incidence angle at the snow surface results in a greater
change in the refractive angle in the snow layer, by comparing the difference of incidence angle at the snow-ground interface
and the air-snow interface with different snow density. Algorithm for estimating dry snow density used backscattering measurements
with polarimetric SAR at L-band frequency is developed based on simulation of the surface backscattering componentsσ
g
hh
andσ
g
vv
using the IEM model and regression analysis. The comparison of the estimated snow density from SAR L-band images with that
from field measurements during the SIR-C/X-SAR overpass shows root means square error of 0.050 g/cm3. It shows that this algorithm can be accurately used to estimate dry snow density distribution. 相似文献