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101.
Methane Production, Emission and Possible Control Measures in the Rice Agriculture 总被引:19,自引:0,他引:19
Wang Mingxing Shangguan Xingjian Shen Renxing Wassmann Reiner Seiler Wolfgang 《大气科学进展》1993,10(3):307-314
In the rice field methane is produced in the soil layer with depths of 2-25 cm. The vertical profile of methane production rate in the paddy soil during the water covering period differs from that in the paddy soil in dry phase. Only a small part, about 30%. of the produced methane is emitted to the atmosphere through rice plant, air bubbles, and molecular diffusion. Therefore, the methane emission rate from the rice field depends not only on the methane production rate in the soil, but also on the transport efficiency of the rice plant, air bubble formation that in turn depends on the production rate, and molecular diffusion.Field measurements show that methane emission rates from a particular rice field have very large diurnal, seasonal and interannual variations, which are related to soil characteristics, water regime, farming procedure, local climate, and rice growing activities. The relationship between the methane emission rate and the above mentioned factors is very complicated. The emission rate 相似文献
102.
Zeh Armin; Gerdes Axel; Klemd Reiner; Barton Jackson M. Jr 《Journal of Petrology》2007,48(8):1605-1639
A combined set of UPb and LuHf in situ laser ablationICP-(MC)-MS zircon analyses were obtained from orthogneissesand granitoids in the Central Zone of the Limpopo Belt, whichcomprises the Beit Bridge and Mahalapye complexes. The resultsindicate that by combining the two isotope systems primary magmaticzircon domains can be distinguished from those formed duringlater metamorphic events, even if the distinct zircon domainsunderwent multiple Pb loss and the textureage relationships,as obtained by cathodoluminescence images and UPb analyses,are ambiguous. Furthermore, the applied technique allows distinctionof zircon grains formed in juvenile magmas from those generatedby melting of older continental crust or affected by substantialcrustal contamination. The combined UPb and LuHfdata reveal that the Sand River gneiss suite of the Beit BridgeComplex was emplaced at 3283 ± 8 Ma and formed from meltingof an older Archaean crust, which was derived from a depletedmantle source at around 3·65 Ga. The hafnium model age(TDMHf) is significantly older than those obtained from zirconsfrom numerous Neoarchaean granitoids of the Beit Bridge Complex,comprising the Singelele gneiss (2647 ± 12 Ma), the Bulaigranite (2612 ± 7 Ma), the Regina gneiss (2649 ±9 Ma) and two samples of the Zanzibar gneiss (2613 ±6 Ma). These granitoids show initial Hf(t) values between +0·5 and 7·1, which correspond to initialTDMHf between 3·46 and 3·01 Ga. These variableTDMHfinitial and Hf(t)initial values are interpreted to be theresult of different mixtures of reworked 3·65 Ga Palaeoarchaeancrust with juvenile magmas extracted from the depleted mantleduring the Neoarchaean at 2·65 Ga. This conclusion issupported by results obtained from the Mahalapye Complex, whichwas affected by migmatization and granite intrusions duringthe Palaeoproterozoic at 2·022·06 Ga. TheMokgware granite (2019 ± 9 Ma) contains zircon xenocrystswith PbPb ages of 2·522·65 Ga and2·93 Ga and hafnium model ages of 3·03·4Ga, indicating that this granite is derived from remelting ofArchaean crust. In contrast, uniform TDMHfinitial ages of 2·612·67Ga obtained from a diorite gneiss (2061 ± 6 Ma) of theMahalapye Complex indicate that its protolith may have beenformed from remelting of a Neoarchaean juvenile crust. VariableHf(t)initial values from 3·7 to +6·3 ofzircon cores (2711 ± 11 Ma) in an adjacent leucosomealso support a model of mixing of juvenile mantle derived matterwith older crust in the Neoarchaean. KEY WORDS: Archaean; Palaeoproterozoic; Limpopo Belt; zircon, UPb dating; LuHf isotopes; LA-ICP-MS 相似文献
103.
Feng Yang Wei Zhai Xiaoming Sun Reiner Klemd Yanyan Sun Yunshan Wu Renmin Hua Siqi Zheng 《Resource Geology》2019,69(1):107-122
The Yaoling tungsten deposit is a typical wolframite quartz vein‐type tungsten deposit in the South China metallogenic province. The wolframite‐bearing quartz veins mainly occur in Cambrian to Ordovician host rocks or in Mesozoic granitic rocks and are controlled by the west‐north‐west trending extensional faults. The ore mineralization mainly comprises wolframite and variable amounts of molybdenite, chalcopyrite, pyrite, fluorite, and tourmaline. Hydrothermal alteration is well developed at the Yaoling tungsten deposit, including greisenization, silicification, fluoritization, and tourmalinization. Three types of primary/pseudosecondary fluid inclusions have been identified in vein quartz, which is intimately intergrown with wolframite. These include two‐phase liquid‐rich aqueous inclusions (type I), two‐ or three‐phase CO2‐rich inclusions (type II), and type III daughter mineral‐bearing multiphase high‐salinity aqueous inclusions. Microthermometric measurements reveal consistent moderate homogenization temperatures (peak values from 200 to 280°C), and low to high salinities (1.3–39 wt % NaCl equiv.) for the type I, type II, and type III inclusions, where the CO2‐rich type II inclusions display trace amounts of CH4 and N2. The ore‐forming fluids are far more saline than those of other tungsten deposits reported in South China. The estimated maximum trapping pressure of the ore‐forming fluids is about 1230–1760 bar, corresponding to a lithostatic depth of 4.0–5.8 km. The δDH2O isotopic compositions of the inclusion fluid ranges from ?66.7 to ?47.8‰, with δ18OH2O values between 1.63 and 4.17‰, δ13C values of ?6.5–0.8‰, and δ34S values between ?1.98 and 1.92‰, with an average of ?0.07‰. The stable isotope data imply that the ore‐forming fluids of the Yaoling tungsten deposit were mainly derived from crustal magmatic fluids with some involvement of meteoric water. Fluid immiscibility and fluid–rock interaction are thought to have been the main mechanisms for tungsten precipitation at Yaoling. 相似文献
104.
A Geodetic View on Isostatic Models 总被引:1,自引:0,他引:1
105.
106.
107.
德国4站点极端降水频数和强度趋势变化分析 总被引:1,自引:0,他引:1
根据不莱梅、波茨坦、卡尔斯鲁厄和楚格峰1901—2007年逐日降水量分析了各站极端降水的频数和强度趋势变化。结果表明:山区(楚格峰)出现的极端降水数量呈上升趋势,且强度显著增强,在冬、夏2季亦如此。这与全球变暖背景下,山区的积雪融化导致对流活动增强以及大气环流影响水汽输送增强有关;在超过绝对阈值的极端降水方面,北方地区(不莱梅和波茨坦)发生频数保持稳定,无显著趋势变化,南方地区(卡尔斯鲁厄)有显著减少的趋势,且不莱梅的频数变化趋势与波茨坦相似,具有强正相关,而此2站与卡尔斯鲁厄的频数变化趋势呈反位相,有较强的负相关;除楚格峰外,极端降水强度变化无显著趋势。低海拔地区在冬季极端降水的频数和强度上,大部分有显著上升的趋势,而夏季,在2方面均出现不同程度的下降;极端降水频数和强度呈强正相关。 相似文献
108.
Geoid models from the new generation of satellite gravity missions, such as GRACE and GOCE, in combination with sea surface
from satellite altimetry allow to obtain absolute dynamic ocean topography with rather high spatial resolution and accuracy.
However, this implies combination of data with fundamentally different characteristics and different spatial resolutions.
Spectral consistency would imply the removal of the short-scale features of the altimetric sea surface height by filtering,
to provide altimetric data consistent with the resolution of the geoid field. The goal must be to lose as little as possible
from the high precision of the altimetric signal. Using a one-dimensional example we show how the spectrum is changing when
a function defined only on a limited domain (ocean in the real case) is extended or not as to cover the complete domain (the
whole sphere in the real case). The results depend on the spectral characteristics of the altimetric signal and of the applied
filter. Referring to the periodicity condition, as it is requested in the case of Fourier analysis, the action of the two
classical filters (Ideal Low Pass and Gauss filter) and of two alternative procedures (wavelets and Slepian) is studied. 相似文献
109.
Wen Su Ming Zhang Simon A. T. Redfern Jun Gao Reiner Klemd 《International Journal of Earth Sciences》2009,98(6):1299-1309
Chemically-zoned amphibole porphyroblast grains in an eclogite (sample ws24-7) from the western Tianshan (NW-China) have been
analyzed by electron microprobe (EMP), micro Fourier-transform infrared (micro-FTIR) and micro-Raman spectroscopy in the OH-stretching
region. The EMP data reveal zoned amphibole compositions clustering around two predominant compositions: a glaucophane end-member
(
B
Na2
C
M2+
3 M3+
2
T
Si8(OH)2) in the cores, whereas the mantle to rim of the samples has an intermediate amphibole composition (
A
0.5
B
Ca1.5Na0.5
C
M
2+
4.5 M
0.53+
T
Si7.5Al0.5(OH)2) (A = Na and/or K; M
2+ = Mg and Fe2+; M
3+ = Fe3+ and/or Al) between winchite (and ferro-winchite) and katophorite (and Mg-katophorite). Furthermore, we observed complicated
FTIR and Raman spectra with OH-stretching absorption bands varying systematically from core to rim. The FTIR/Raman spectra
of the core amphibole show three lower-frequency components (at 3,633, 3,649–3,651 and 3,660–3,663 cm−1) which can be attributed to a local O(3)-H dipole surrounded by
M(1) M(3)Mg3,
M(1) M(3)Mg2Fe2+ and
M(1) M(3) Fe2+
3, respectively, an empty A site and
T
Si8 environments. On the other hand, bands at higher frequencies (3,672–3,673, 3,691–3,697 and 3,708 cm−1) are observable in the rims of the amphiboles, and they indicate the presence of an occupied A site. The FTIR and Raman data from the OH-stretching region allow us to calculate the site occupancy of the A, M(1)–M(3), T sites with confidence when combined with EPM data. By contrast M(2)- and M(4) site occupancies are more difficult to evaluate. We use these samples to highlight on the opportunities and limitations
of FTIR OH-stretching spectroscopy applied to natural high pressure amphibole phases. The much more detailed cation site occupancy
of the zoned amphibole from the western Tianshan have been obtained by comparing data from micro-chemical and FTIR and/or
Raman in the OH-stretching data. We find the following characteristic substitutions Si(T-site) (Mg, Fe)[M(1)–M(3)-site] → Al(T-site) Al[M(1)–M(3)-site] (tschermakite), Ca(M4-site)□ (A-site) → Na(M4-site) Na + K(A-site) (richterite), and Ca(M4-site) (Mg, Fe) [M(1)–M(3)-site] → Na(M4-site) Al[M(1)–M(3)-site] (glaucophane) from the configurations observed during metamorphism. 相似文献
110.