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101.
A global two-dimensional chemistry model is developed to study long-term trends of CH4 since industrial revolution.The sources of CH4,CO and NOx are parameterized as functions of latitude and time.With two long-term emission scenarios,long-term trends of CH4 are simulated.The results have a good agreement with observation from ice cores.The modeled CH4 increased from 760 ppbv in 1840 to 1611.9 ppbv in 1991, while the modeled number concentration of tropospheric OH decreased from 7.17×105 cm-3 in 1840 to 5.79×105 cm-3 in 1991.The increase of atmospheric CH4 can be explained by the increase of emission of CH4 and build-up because of decrease of OH radicals that remove CH4 from the atmosphere.The model is also used to simulate the distribution of CH4.Comparisons between the model results and observations show that the model can simulate both latitudinal distribution and seasonal variation of CH4 well. 相似文献
102.
103.
Using single-crystal X-ray diffraction from a diamond anvil cell, the compressibility of a synthetic fluorapatite was determined up to about 7?GPa. The compression pattern was anisotropic, with greater change along a than c. Unit cell parameters varied linearly with β a =3.32(8)?10?3 and β c =2.40(5)?10?3 GPa?1, giving a ratio β a :β c =1.38:1. Data fitted with a third-order Birch-Murnaghan EOS yielded a bulk modulus of K 0=93(4)?GPa with K′=5.8(1.8). The evolution of the crystal structure of fluorapatite was analysed using data collected at room pressure, at 3.04 and 4.72?GPa. The bulk modulus of phosphate tetrahedron is about three times greater than the bulk modulus of calcium polyhedra. The values were 270(10), 100(4) and 86(3) GPa for P, Ca1 (nine-coordinated) and Ca2 (seven-coordinated) respectively. While the calcium polyhedra became more regular with pressure, the distortion of the phosphate tetrahedron remained unchanged. The size of the channel extending along the [001] direction represented the most compressible direction. The Ca2–Ca2 distance decreased from 3.982 to 3.897?Å on compression from 0.0001 to 4.72?GPa. The anisotropic compressional pattern may be understood in terms of the greater compressibility of the channel size over the polyhedral units. The reduction of the channel volume was measured by the evolution of the trigonal prism, having the Ca2–Ca2–Ca2 triangle as its base and the c lattice parameter as its height. This prism volume changed from 47.3?Å3 at room pressure to 44.78?Å3 at 4.72?GPa. Its relatively high bulk moduli, 86(3) GPa, indicated that the channel did not collapse with pressure and the apatite structure could remain stable at very high pressure. 相似文献
104.
Modeling of dioctahedral 2:1 phyllosilicates by means of transferable empirical potentials 总被引:1,自引:0,他引:1
C. I. Sainz-Diaz A. Hernández-Laguna M. T. Dove 《Physics and Chemistry of Minerals》2001,28(2):130-141
Dioctahedral 2:1 phyllosilicates with different interlayer charge have been studied theoretically by using transferable empirical
interatomic potentials. The crystal structures of pyrophyllite, muscovite, margarite, beidellite, montmorillonite, and different
smectites and illites have been simulated. The interatomic potentials were able to reproduce the experimental structure of
phyllosilicates with high, medium and low interlayer charge. The calculated structures are in agreement with experiment for
the main structural features of the crystal lattice. The effect of the cation substitution in the octahedral and tetrahedral
sheets on the structural features has been also studied. Good linear relationships have been found, and the calculated effects
are consistent with experimental results. Some unknown structural features of the crystal structures of clays are predicted
in this work.
Received: 8 March 2000 / Accepted: 19 September 2000 相似文献
105.
Ahmad Sarfaraz Hasnain Syed Iqbal. Glacier Research Group School of Environmental Sciences Jawaharlal Nehru University New Delhi- India 《中国地质大学学报(英文版)》2001,12(1)
I-DtjcrONAlpine environment enjoys a distinct set of physicochemical conditions asl compared to other aqueous systems. Thehydrochemical characteristics of meltwater draining from thisenvironment are different from the other aqueous ecosystemsdue to their mountainous nature and extreme cold climatic conditions. The high concentration of various chemical constitu.ents in meltwater shows the intensive chemical weathering inthe basin. The rapid physical weathering due tO grinding actionof the gl… 相似文献
106.
青藏高原北缘可可西里鲸鱼湖、雄鹰台、双泉子火山岩中含有辉石岩包体 ,其主要矿物组成为单斜辉石和斜方辉石。辉石的化学成分与国内外幔源包体 -橄榄岩和辉石岩中的类似 ,与麻粒岩中的明显不同 ;辉石温压计计算结果表明 ,辉石形成的温度为 110 1~ 140 0℃ ,压力为 30× 10 8~ 6 0× 10 8Pa,结合岩浆动力学计算结果 ,推测岩浆的来源深度大于 15 0km ,这与地球物理研究得出本区地下深处存在低速层的结果相吻合。 相似文献
107.
R. N. Colvile T. W. Choularton J. N. Cape B. J. Bandy K. N. Bower R. A. Burgess T. J. Davies G. J. Dollard M. W. Gallagher K. J. Hargreaves B. M. R. Jones S. A. Penkett R. L. Storeton-West 《Journal of Atmospheric Chemistry》1996,24(3):211-239
Four case studies are described, from a three-site field experiment in October/November 1991 using the Great Dun Fell flow-through reactor hill cap cloud in rural Northern England. Measurements of total odd-nitrogen nitrogen oxides (NO
y
) made on either side of the hill, before and after the air flowed through the cloud, showed that 10 to 50% of the NO
y
, called NO
z
, was neither NO nor NO2. This NO
z
failed to exhibit a diurnal variation and was often higher after passage through cloud than before. No evidence of conversion of NO
z
to NO3
- in cloud was found. A simple box model of gas-phase chemistry in air before it reached the cloud, including scavenging of NO3 and N2O5 by aerosol of surface area proportional to the NO2 mixing ratio, shows that NO3 and N2O5 may build up in the boundary layer by night only if stable stratification insulates the air from emissions of NO. This may explain the lack of evidence for N2O5 forming NO3
- in cloud under well-mixed conditions in 1991, in contrast with observations under stably stratified conditions during previous experiments when evidence of N2O5 was found. Inside the cloud, some variations in the calculated total atmospheric loading of HNO2 and the cloud liquid water content were related to each other. Also, indications of conversion of NO
x
to NO
z
were found. To explain these observations, scavenging of NO
x
and HNO2 by cloud droplets and/or aqueous-phase oxidation of NO2
- by nitrate radicals are considered. When cloud acidity was being produced by aqueous-phase oxidation of NO
x
or SO2, NO3
- which had entered the cloud as aerosol particles was liberated as HNO3 vapour. When no aqueous-phase production of acidity was occurring, the reverse, conversion of scavenged HNO3 to particulate NO3
-, was observed. 相似文献
108.
109.
Sediment diatom and chemical analyses of cores from three poorly buffered extra-glacial lakes on the northeastern margin of the Canadian Shield (Cumberland Peninsula, Baffin Island) record interactions between aquatic and terrestrial spheres that were influenced by late Quaternary climatic conditions. Although differences exist between each of the lakes, notably with regards to the intensity of pre-Holocene catchment erosion and the timing of the onset of organic sedimentation, an underlying pattern of lake ontogeny, common to all three lakes, is identified. Although intensified watershed erosion characterized the Late Wisconsinan and Neoglacial cold periods, the lakes nonetheless remained viable ecosystems at these times. Sudden catchment stabilization during the late-glacial to earliest Holocene is associated with incipient organic sedimentation. Lake-water pH increased at this time, likely in response both longer base cation residence times as lake flushing rates decreased, and enhanced alkalinity production from sediment biogeochemical reactions. Subsequently, as the catchments remained stable during the productive early Holocene (c.9–7 ka BP), then gradually received a renewed increase of minerogenic sedimentation, the breakdown of sources of lake alkalinity resulted in natural acidification. Burial of cation-rich mineral sediments and the loss of permanent sedimentary sinks for the products of microbial reduction likely impeded within-lake alkalinity production, and catchment-derived base cations appeared ineffective in curtailing pH declines. The general nature of the Holocene development of these lakes is similar to that observed elsewhere on crystalline terrains, following deglaciation. Our data therefore suggest that catchment glaciation is not a necessary precursor for models of lake development characterized by initial base cation enrichment and subsequent gradual acidification. 相似文献
110.
鲁南苏北榴辉岩的特征及其成因 总被引:2,自引:0,他引:2
鲁南苏北榴辉岩按产状分为两类:一类是呈条带状、透镜状或肠状鳌合赋存于胶南混杂岩系中,另一类是呈透镜状赋存于石榴石橄榄岩中,以前者分布最为广泛,后者仅见于日照及东海地区。胶南混杂岩系中的榴辉岩由橄榄拉斑玄武岩深成变质作用形成,石榴石橄榄岩中的榴辉岩为地幔来源,它们共同经历了早期2.8 GPa,800℃的高温高压平衡结晶及后期600—700℃,1.1—1.3 GPa的退变质作用改造。Sm-Nd等时年龄为222±6Ma,~(143)Nd/~(144)Nd初始比值为0.511 36±3,推测本区榴辉岩形成于早三叠世华南陆块与华北陆块的碰撞事件。 相似文献