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1.
HongQiang Yan KeFu Yu Qi Shi YeHui Tan HuiLing Zhang MeiXia Zhao Shu Li TianRan Chen LingYing Huang PinXian Wang 《科学通报(英文版)》2011,56(7):676-684
Field measurements of air-sea CO2 exchange in three coral reef areas of the South China Sea (i.e. the Yongshu Reef atoll of the Nansha Islands, southern South China Sea (SCS); Yongxing Island of Xisha Islands, north-central SCS; and Luhuitou Fringing Reef in Sanya of Hainan Island, northern SCS) during the summers of 2008 and 2009 revealed that both air and surface seawater partial pressures of CO2 (pCO2) showed regular diurnal cycles. Minimum values occurred in the evening and maximum values in the morning. Air pCO2 in each of the three study areas showed small diurnal variations, while large diurnal variations were ob-served in seawater pCO2. The diurnal variation amplitude of seawater pCO2 was ~70 μmol mol–1 at the Yongshu Reef lagoon, 420–619 μmol mol–1 on the Yongxing Island reef flat, and 264–579 μmol mol–1 on the reef flat of the Luhuitou Fringing Reef, and 324–492 μmol mol–1 in an adjacent area just outside of this fringing reef. With respect to spatial relations, there were large differences in air-sea CO2 flux across the South China Sea (e.g. ~0.4 mmol CO2 m–2 d–1 at Yongshu Reef, ~4.7 mmol CO2 m–2 d–1 at Yongxing Island, and ~9.8 mmol CO2 m–2 d–1 at Luhuitou Fringing Reef). However, these positive values suggest that coral reef ecosystems of the SCS may be a net source of CO2 to the atmosphere. Additional analyses indicated that diurnal variations of surface seawater pCO2 in the shallow water reef flat are controlled mainly by biological metabolic processes, while those of deeper water lagoons and outer reef areas are regulated by both biological metabolism and hydrodynamic factors. Unlike the open ocean, inorganic metabolism plays a significant role in influencing seawater pCO2 variations in coral reef ecosystems. 相似文献
2.
Comparative study of the net exchange of CO<Subscript>2</Subscript> in 3 types of vegetation ecosystems on the Qinghai-Tibetan Plateau 总被引:8,自引:0,他引:8
ZHAO Liang LI Yingnian ZHAO Xinquan XU Shixiao TANG Yanhong YU Guirui GU Song DU Mingyuan WANG Qinxue 《科学通报(英文版)》2005,50(16):1767-1774
Using the eddy covariance method, from 1 July 2003 to 30 June 2004, we conducted the observation and analysis of ecosystem CO2 flux in 3 types of alpine meadow vegetation (Kobresia humilis, Potentilla fruticosa shrub and Kobresia tibetica swamp meadows) on the Qinghai-Tibetan Plateau. The results show that the Kobresia humilis meadow, the shrub meadow and the swamp meadow's highest CO2 uptake rates are 16.78, 10.42 and 16.57 μmol·m^-2·-s^-1 respectively, while their highest CO2 release rates are 8.22, 7.73 and 18.67μmol·m^-2·-s^-1 respectively. The Kobresia humilis meadow and shrub meadow's annual atmospheric uptakes are 282 g CO2/m^2 and 53 g CO2/m^2, respectively, while swamp meadow's annual atmospheric release is 478 g CO2/m^2. This proves that the Kobresia humilis meadow and the shrub meadow on the Qinghai-Tibetan Plateau have relatively low potential for CO2 uptake and release compared to C4 grasslands, a number of lowland grasslands, and forests. Moreover, swamp meadow has relatively high release potential. This, in turn, reveals clear differences in carbon source/sink between different types of vegetation in the Qinghai-Tibetan Plateau alpine meadow ecosystem. These differences are mainly brought by differences in the vegetations' photosynthetic capacity and soil respiration. 相似文献
3.
Guo-qiang Liu Xi Wang Ya-jie Gao Lei Wen Guang-yin Liu Jian-jie Zheng Peng Cen Ying Li 《矿物冶金与材料学报》2012,19(5):457-460
Spinel compounds LiNi0.5Mn1.3Ti0.2O4 (LNMTO) and Li4Ti5O12 (LTO) were synthesized by different methods. The particle sizes of LNMTO and LTO are 0.5–2 and 0.5–0.8 μm, respectively.
The LNMTO/LTO cell exhibits better electrochemical properties at both a low current rate of 0.2C and a high current rate of
1C. When the specific capacity was determined based on the mass of the LNMTO cathode, the LNMTO/LTO cell delivered 137 mA·h·g−1 at 0.2C and 118.2 mA·h·g−1 at 1C, and the corresponding capacity retentions after 30 cycles are 88.5% and 92.4%, respectively. 相似文献
4.
The transient absorption spectrum technique was employed to investigate the cross-reaction mechanism of C6H5F-HNO2 aqueous solution irradiated at 355 nm. The characteristic and the kinetic parameters of transient species were also detected. Hydroxyl radical derived from the photolysis of HNO2 was added to monofluorobenzene with a second-order rate constant of (5.83±0.17)×10^9 L·mol^-1·s^-1 to form an adduct, C6H5F…OH, which was able to react with HNO2 as the main reaction pathway with a rate constant of (8.3±0.1)×10^7 L·mol^-1·s^-1. The C6F6…OH adduct can also be decayed by elimination of H2O to yield monofluorophenyl radical C6H4F-. By GC-MS technique, the final products were identified to be monofluorophenol, nitro-monofluorobenzene, nitro-monofluorophenol and para-fluorobiphenyl. 相似文献
5.
ZHANG Tiebang CHEN Yungui FU Hao TENG Baohua TANG Yongbai TU Mingjing 《科学通报(英文版)》2005,50(16):1811-1814
The giant magnetocaloric effect Gd5Si2Ge2 alloy was prepared with 99wt% low purity commercial Gd. Powder XRD and magnetic measurements showed that the Gd5Si2Ge2 alloy annealed at 1200℃ for 1h had a significant magnetic- crystallographic first order phase transition at about 270 K. The maximal magnetic entropy change is 17.55 J· kg^-1· K^-1 under a magnetic field change of 0-5 T. The distinct increase of magnetic entropy change belongs to the first-order phase transition from the orthorhombic Gd5Si4-type to the monoclinic Gd5Si2Ge2-type after high temperature heat-treatment. 相似文献
6.
QU Xiaosheng LI Jie WANG Zhiyong WANG Cunxin 《武汉大学学报:自然科学英文版》2007,12(3):511-514
A coordination complex was synthesized from NiCl2 and dipeptide glycylglycine(GG). It was characterized by element analysis, NMR and TG methods, and then was determined to be Ni(C4HsN2O3)2Cl2. Using an isoperibolic reaction calorimeter, the standard molar enthalpy of formation of Ni(GG)2Cl2(solid) has been determined to be -(1 674.66±2.02) kJ · mol^-1 at 298.15 K. 相似文献
7.
Kinetic studies of the decomposition reaction of dinuclear Fe(Ⅱ) adducts [Fe2(N-Et-HPTB){O2P(OPh)2}](Cl- O4)2 (1) and [Fe2(N-Et-HPTB) {O2P(Ph)2}] (ClO4)2 (2) with O2 have been carried out at low temperature using UV-vis spectra. The decomposition reaction of Fe(Ⅱ)/O2 adducts was first-order in the experimental conditions, and the activation parameters were obtained. ?H¹ = 85.62 kJ·mol-1, ?S¹ = 19.43 J·mol-1·K-1 for compound (1) and ?H¹ = 97.97 kJ·mol-1, ?S¹ = 55.68 J·mol-1·K-1 for compound (2). These results are similar to those of dioxygen adducts of other metals complexes and natural enzymes such as methane mono- oxygenase (MMOH). 相似文献
8.
The concentration of atmospheric CO2 in Beijing increased rapidly at a mean growth rate of 3.7% · a−1 from 1993 to 1995. After displaying a peak of (409.7±25.9) μmol · mol−1 in 1995, it decreased slowly. Both the almost stable anthropogenic CO2 source and increasing biotic CO2 sink contribute to the drop of CO2 concentration from 1995 to 2000. The seasonal variation of CO2 concentration exhibits a clear cycle with a maximum in winter, averaging (426.8±20.6) μmol · mol−1, and a minimum in summer, averaging (369.1±6.1) μmol·mol−1. The seasonal variation of CO2 concentration is mainly controlled by phenology. The mean diurnal variation of atmospheric CO2 concentration for a year in Beijing is highly clear: daily maximum CO2 concentration usually occurs at night, but daily minimum CO2 concentration does in the daytime, with a mean diurnal difference more than 34.7 μmol·mol−1. It has been revealed that the interannual variations of atmospheric CO2 concentration in winter and autumn regulated the interannual trend of atmospheric CO2, whereas the interannual variation of CO2 concentration in summer affected the general tendency of atmospheric CO2 in a less degree. 相似文献
9.
Electrochemical behavior of a carbon paste electrode (CPE) modified with nickel(II)-5, 11, 17, 23-tetra-tert-butyl-25, 27-bis(diethylcarbamoylmethoxy)
calix[4]arene (Ni (II)-L) complex and its electrocatalytic activity towards the oxidation of hydrogen peroxide were investigated
by cyclic voltammetric technique in a 5.0×10−2 mol/L NaClO4+1.0×10−3 mol/L NaOH solution. It was found that Ni(II)-L acts as an effective catalyst for the oxidation of hydrogen peroxide. The
modified electrode exhibited a linear response over a hydrogen peroxide concentrations in the range of 2.0×10−5−1.0×10−4 mol/L with a detection limit as low as 1.0×10−6 mol/L. The relative standard deviation was 3.5% for 5 successive determinations of H2O2 at 1.0×10−5 mol/L. The modified electrode was used successfully in rainwater analysis.
Foundation item: Supported by the Natural Science Foundation of Hubei Province (98J040).
Biography: Li Chun ya(1972-), Ph. D. candidate, research direction: electroanalysis and electrosynthesis. 相似文献
10.
Terrestrial carbon cycling is one of the hotspots in global change issues. In this paper, we presented the rationale for determination
of net exchange of CO2 between terrestrial and the atmosphere (NEE) and the methods for measuring several relevant components. Three key processes
for determination of NEE were addressed, including the separation of shoot autotrophic respiration from total CO2 emissions of the ecosystem, the partition of root respiration from soil CO2 efflux, and the quantification of rhizodeposition C from NPP. With an understanding of the processes involved in the CO2 exchange between terrestrial and the atmosphere, we estimated NEE of rice ecosystem in Nanjing based on field measurements
of CO2 emissions and several relevant biotic components as well as abiotic factors. The field measurements of CO2 emissions were made over the rice-growing seasons in 2001 and 2002 with the static opaque chamber method. Calculations indicated
that the seasonal pattern of NEE is comparable for two seasons. Either net carbon emission or fractional carbon fixation occurred
during 3 weeks after rice transplanting and thereafter net carbon fixation appeared with an increasing trend as rice growing.
Higher net carbon fixation occurred in the rice developmental period from elongating to heading. A decline trend in the fixation
was documented after rice heading. The mean daily NEE was -6.06 gC·m−2 in 2001 season and -7.95 gC·m−2 in 2002 season, respectively. These values were comparable to the results obtained by Campbell et al. who made field measurements
with the Bowen ratio-energy balance technique in irrigated rice, Texas USA. Moreover, the mean daily NEE in this study was
also comparable to the values obtained from a Japanese rice paddy with the eddy covariance method under the similar water
regime, either drainage course or waterlogged. It is concluded that NEE determined by the static opaque chamber method is
comparable and in agreement with those measured by Bowen ratioenergy balance and eddy covariance methods. 相似文献
11.
LIU Zhenhong WANG Yanqiu WANG Li & HE Guozhong State Key Laboratory of Molecular Reaction Dynamics Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian China 《科学通报(英文版)》2004,49(24):2585-2589
With the development of ultrafast laser technique,the femtosecond laser electric field is comparable to themolecular field experienced by valence electrons. In thiscase, the classical quantum mechanical theory, based onperturbation theory, becomes inapplicable. Theoreticalunderstanding of the interaction of molecules with intenselaser radiation is quite difficult. The Coulomb explosionhas been extensively studied[1—10] and explained by somesemiclassical models, such as the above threshold ion… 相似文献
12.
Conclusions The initial slope of A/ light curve became steep under high CO2 (700 μmol · mol-1) compared with that under low CO2 (350 μmol · mol-1) for the C3 species growing in very high CO2(>2 200 μmol · mol-1) for a long period. The light compensation points remained unchanged, but the light saturation points were found increased.
The ϕm,app and Amax of the C3 species increased respectively by 79 % and 80 %, while those of C4 species decreased by 10% and 14%, respectively. The shape of A/light curve of C4 species did not change. Such results indicated that C3 species increased the capacity of photosynthesis, while C4 did not change, otherwise it decreased a little.
This work only compared the changes of capacity in photosynthesis of some species under different CO2 levels in Biosphere 2. We need further investigation on the effects of high CO2 on the same species outside Biosphere 2, in order to fully undertand the effects and mechanism of response of plants to the
elevated CO2. 相似文献
13.
QIAN Shahua LIN Han LI Xueqin XIAO Mei DENG Hongbing XIANG Luojing School of Resource Environmental Science Wuhan University Wuhan Hubei China 《武汉大学学报:自然科学英文版》2007,12(2):349-352
A new absorbent of nanometer-size TiO2 colloid for Cu(Ⅱ) was studied in this work. The adsorption rate could reach above 99% when the pH values were at the range of 5-6. The adsorption balance time, adsorption capacities, and the eluent were investigated. A novel method of trace Cu(Ⅱ) preconcentration and separation with nanometer-size titanium dioxide colloid and determination by flame atomic absorption spectrometry (FAAS) was advanced. The detection limit (3σ) of the method was 1.15 μg· L~(-1) , and the relative standard deviation (R.S.D) was 1.53% (n=6). Environmental sample experiments were also conducted to test the feasibility of the method, and it came out that the recovery rates were between 95.9% and 97.8%. 相似文献
14.
Effect of CO<Subscript>2</Subscript> and H<Subscript>2</Subscript>O on gasification dissolution and deep reaction of coke 下载免费PDF全文
Zhi-yu Chang Ping Wang Jian-liang Zhang Ke-xin Jiao Yue-qiang Zhang Zheng-jian Liu 《矿物冶金与材料学报》2018,25(12):1402-1411
To more comprehensively analyze the effect of CO2 and H2O on the gasification dissolution reaction and deep reaction of coke, the reactions of coke with CO2 and H2O using high temperature gas-solid reaction apparatus over the range of 950-1250℃ were studied, and the thermodynamic and kinetic analyses were also performed. The results show that the average reaction rate of coke with H2O is about 1.3-6.5 times that with CO2 in the experimental temperature range. At the same temperature, the endothermic effect of coke with H2O is less than that with CO2. As the pressure increases, the gasification dissolution reaction of coke shifts to the high-temperature zone. The use of hydrogen-rich fuels is conducive to decreasing the energy consumed inside the blast furnace, and a corresponding high-pressure operation will help to suppress the gasification dissolution reaction of coke and reduce its deterioration. The interfacial chemical reaction is the main rate-limiting step over the experimental temperature range. The activation energies of the reaction of coke with CO2 and H2O are 169.23 kJ·mol-1 and 87.13 kJ·mol-1, respectively. Additionally, water vapor is more likely to diffuse into the coke interior at a lower temperature and thus aggravates the deterioration of coke in the middle upper part of blast furnace. 相似文献
15.
Sheng-nan Zhang Guang-yu Jiang Tie-jun Zhu Xin-bing Zhao Sheng-hui Yang 《矿物冶金与材料学报》2011,18(3):352-356
Nonstoichiometric ternary thermoelectric materials Ag0.84Sb1.15M0.01Te2.16 (M=Ce, Yb, Cu) were prepared by a direct melt-quench and hot press process. The carrier concentration of all the samples
increased after doping. Thermoelectric properties, namely electrical conductivity, Seebeck coefficient, and thermal conductivity,
were measured from 300 to 673 K. The phase transition occurring at about 418 K representing the phase transition from β-Ag2Te to α-Ag2Te influenced the electrical transport properties. The electrical conductivities of Ce and Yb doped samples increased after
doping from 1.9×104 to 2.5×104 and 2.3×104 S·m−1, respectively, at 673 K. Also, at room temperature, the Seebeck coefficient of the Ce doped sample relatively increased corresponding
to the high carrier concentration due to the changes in the band structure. However, all the thermal conductivities increased
after doping at low temperature. Because of the higher thermal conductivity, the dimensionless figure of merit ZT of these doped samples has not been improved. 相似文献
16.
A comparative study of the dissolution kinetics of galena ore in binary solutions of FeCl3/HCl and H2O2/HCl has been undertaken. The dissolution kinetics of the galena was found to depend on leachant concentration, reaction temperature,
stirring speed, solid-to-liquid ratio, and particle diameter. The dissolution rate of galena ore increases with the increase
of leachant concentration, reaction temperature, and stirring speed, while it decreases with the increase of solid-to-liquid
ratio and particle diameter. The activation energy (E
a) of 26.5 kJ/mol was obtained for galena ore dissolution in 0.3 M FeCl3/8.06 M HCl, and it suggests the surface diffusion model for the leaching reaction, while the E
a value of 40.6 kJ/mol was obtained for its dissolution in 8.06 M H2O2/8.06 M HCl, which suggests the surface chemical reaction model for the leaching reaction. Furthermore, the linear relationship
between rate constants and the reciprocal of particle radius supports the fact that dissolution is controlled by the surface
reaction in the two cases. Finally, the rate of reaction based on the reaction-controlled process has been described by a
semiempirical mathematical model. The Arrhenius and reaction constants of 11.023 s−1, 1.25×104 and 3.65×102 s−1, 8.02×106 were calculated for the 0.3 M FeCl3/8.06 M HCl and 8.06 M H2O2/8.06 M HCl binary solutions, respectively. 相似文献
17.
LI Gong GAO YunPeng SUN YiNan MA MingZhen LIU Jing LIU RiPing 《科学通报(英文版)》2007,52(4):440-443
The compression behavior of Ni77P23 amorphous alloy is investigated at room temperature in a diamond-anvil cell instrument using insitu high pressure energy dispersive X-ray diffraction with a syn- chrotron radiation source. The equation of state is determined by fitting the experimental data accord- ing to Birch-Murnaghan equation: -ΔV/V0=0.08606P-3.2×10-4P2 5.7×10-6P3. It is found that the structure of Ni77P23 amorphous alloy is stable under pressures up to 30.5 GPa. 相似文献
18.
ShuLian Wang YanFen Fang Yong Yang JunZi Liu AnPing Deng XiaoRong Zhao YingPing Huang 《科学通报(英文版)》2011,56(10):969-976
A TiO2@SiO2 hybrid support was prepared by the sol-precipitation method using n-octylamine as a template.The photocatalyst manganese phthalocyanine tetrasulfonic acid (MnPcS) was immobilized on the support to form MnPcS-TiO2@SiO2.X-ray diffraction (XRD) and UV-Visible diffuse reflectance spectra (UV-Vis DRS) were employed to characterize the catalyst.The photocatalytic degradation of rhodamine B (RhB) and the catalytic oxidation of o-phenylenediamine (OPDA) under visible light irradiation were used as probe reactions.The mineralization efficiency and the degradation mechanism were evaluated using chemical oxygen demand (COD Cr) assays and electron spin resonance (ESR),respectively.RhB was efficiently degraded by immobilized MnPcS-TiO2@SiO2 under visible light irradiation.Complete decolorization of RhB occurred after 240 min of irradiation and 64.02% COD Cr removal occurred after 24 h of irradiation.ESR results indicated that the oxidation process was dominated by the hydroxyl radical (·OH) and superoxide radical (O-·2) generated in the system. 相似文献
19.
Ta-doped In2O3 transparent conductive oxide films were deposited on glass substrates using radio-frequency (RF) sputtering at 300°C. The
influence of post-annealing on the structural, morphologic, electrical and optical properties of the films was investigated
using X-ray diffraction, field emission scanning electron microscopy, Hall measurements and optical transmission spectroscopy.
The obtained films were polycrystalline with a cubic structure and were preferentially oriented in the (222) crystallographic
direction. The lowest resistivity, 5.1×10−4 Ω cm, was obtained in the film annealed at 500°C, which is half of that of the un-annealed film (9.9×10−4 Ω cm). The average optical transmittance of the films was over 90%. The optical bandgap was found to decrease with increasing
annealing temperature. 相似文献
20.
Pei-hong Yuan Cai-mei Fan Guang-yue Ding Yun-fang Wang Xiao-chao Zhang 《矿物冶金与材料学报》2012,19(4):372-376
The powders of ilmenite structure NiTiO3 were prepared by a modified Pechini process using tetrabutyl titanate and nickel acetate as raw materials, and using citric
acid and ethanol as a chelating agent and a solvent respectively. The powder samples were characterized by thermogravimetric
and differential thermal analysis (TG-DTA) and X-ray diffraction (XRD). The photocatalytic activity of NiTiO3 under the irradiation of ultraviolet rays (UV) light was evaluated by degrading humic acid (HA) in water as a probe reaction.
The possible photodegradation mechanism was studied by the examination of active species ·OH, ·O2−, and holes (h+) through adding scavengers. The TG-DTA and XRD results indicated that the good crystal structure of ilmenite phase NiTiO3 could be obtained when the Ni-Ti citrate complex was calcined at 600°C. The photocatalytic activity experiments indicated
that NiTiO3 had favourable photocatalytic activity under the irradiation of UV light, and the photocatalytic degradation rate of HA reached
95.3% after a 2.5 h reaction with the photocatalyst calcined at 600°C and a photocatalyst dosage of 0.4 g/L. The possible
photocatalytic mechanism was deduced that holes (h+) and ·OH radicals are the major reactive active species in the photocatalytic reaction, and dissolved oxygen plays a weak
role in the degradation of HA. 相似文献