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781.
为了充分利用茶叶的性能以及开发新型功能保健茶,研究了沏茶时绿茶对金属离子镉(Ⅱ)的捕集行为。笔者试验了不同酸度、温度、沏茶时间对茶叶捕集镉(Ⅱ)离子的影响,并通过改变镉(Ⅱ)标准溶液加入量考查了绿茶对镉(Ⅱ)离子的捕集容量及捕集率。结果表明,在适宜条件下(pH=7、温度控制90℃、沏茶时间为20min),绿茶对水溶液中微量镉(Ⅱ)的捕集率最大可迭80%以上。此结果对减小茶水中镉离子对人体的影响具有一定的现实意义。 相似文献
782.
783.
作者于2000年和2002年对青藏高原东部长江河流溶质载荷进行了较为系统的野外取样工作,并对主要离子地球化学特征进行了分析研究。数据分析表明,长江水系TZ 高于世界河流1250μEq的平均值,主要介于2000~3000μEq之间,其次为1000~2000μEq。总体上,高原东部长江水系TZ 可以与世界上其它造山带相比较。高原东部长江水系主要阴离子的相对丰度和分布表现出HCO3->Si Cl- SO42-,河水富含HCO3-;阳离子主要表现为Ca2 >Mg2 Na K ,表明河水富含Ca离子特征。河水中富含HCO3-和Ca2 ,说明高原东部长江水系流域盆地中碳酸盐岩(主要是灰岩)应是河流中主要离子的风化源岩。 相似文献
784.
Martin Rosner Lary Ball Bernhard Peucker-Ehrenbrink Jerzy Blusztajn Wolfgang Bach Jörg Erzinger 《Geostandards and Geoanalytical Research》2007,31(2):77-88
We report a new approach to conduct fast and accurate lithium isotope ratio measurements by MC-ICP mass spectrometry after wet chemical sample preparation. In contrast to most previously published methods our MC-ICP-MS set-up did not use a desolvating system to achieve appropriate ion beam intensities and, therefore, was less affected by matrix-induced shifts of the instrumental mass bias. As the total lithium background and build-up in the sample introduction system was low, previous sample residues could be washed out by an extended uptake of the new sample. Elimination of a nitric acid rinse step increased the sample throughput by a factor of two and allowed the instrumental mass bias drift to be tracked more precisely. δ7 Li values of powdered silicate rock reference materials and seawater obtained in this study revealed good accuracy and an overall analytical uncertainty of typically 0.5‰ (2s). On the basis of a comparison between our lithium isotope data and compiled literature data, we recommend preliminary average δ7 Li values for seawater (+30.8‰) and several silicate rock reference materials (BHVO-1: +5.0‰; JA-1: +5.6‰; JB-2: +4.8‰). The compilation of published δ7 Li values for seawater suggests that the observed large lithium isotope differences are due to inter-method and/or interlaboratory bias. Most recently published δ7 Li values for seawater show little variation and confirm a constant lithium isotope composition (at the sub ‰ level) of seawater in well mixed ocean basins. 相似文献
785.
Assigning Dates to Thin Gneissic Veins in High-Grade Metamorphic Terranes: A Cautionary Tale from Akilia, Southwest Greenland 总被引:10,自引:0,他引:10
A granodiorite from Akilia, southwest Greenland, previouslysuggested to date putative life-bearing rocks to 3·84Ga, is re-investigated using whole-rock major and trace-elementgeochemistry, and detailed cathodoluminescence image-guidedsecondary ion mass spectrometer analyses of zircon UThPband rare earth elements. Complex zircon internal structure revealsthree episodes of zircon growth and/or recrystallization datedto c. 3·84 Ga, 3·62 Ga and 2·71 Ga. Rareearth element abundances imply a significant role for garnetin zircon generation at 3·62 Ga and 2·71 Ga. The3·62 Ga event is interpreted as partial melting of ac. 3·84 Ga grey gneiss precursor at granulite facieswith residual garnet. Migration of this 3·62 Ga magma(or meltcrystal mush) away from the melt source placesa maximum age limit on any intrusive relationship. These earlyArchaean relationships have been complicated further by isotopicreworking in the 2·71 Ga event, which could have includeda further episode of partial melting. This study highlightsa general problem associated with dating thin gneissic veinsin polyphase metamorphic terranes, where field relationshipsmay be ambiguous and zircon inheritance can be expected. KEY WORDS: Archaean; geochronology; Greenland; secondary ion mass spectrometry; zircon 相似文献
786.
Shearing instability of ion flow in an inhomogeneous plasma background in the magnetopause boundary layer at the high-latitude magnetotail is studied in this paper. By considering tail-aligned currents, we find that the instability excitation strongly depends on the disturbed wavelength. A quasi-critical wave number for instability is obtained. For relatively long perturbations, the instability tends to be excited at the inner edge of the boundary layer. The stable surface waves at the magnetopause and the K-H instability at the inner edge of the boundary layer can exist at the same time. This may contribute to the continuous transfer of momentum toward the magnetosphere. 相似文献
787.
HSUWeibiao 《《地质学报》英文版》2004,78(5):1060-1074
Coupled with a petrographical study, I carried out an ion probe study of rare earth element microdistributions in mineral phases of silicate inclusions from the Colomera IIE iron meteorite. Most mineral grains have homogeneous REEs, but show considerable inter-grain variations by a factor of 2 to 100. The whole rock REE abundances for Colomera,estimated by combining REE data with modal abundances, are relatively LREE-enriched with REEs of~10’CI, which suggest that Colomera silicates were highly differentiated and might represent a low degree partial melt (-10%) of a chondritic source. REE geochemistry of Colomera silicate inclusions points to an origin that involves differentiation,dynamic mixing, remelting, reduction, recrystallization, and subsequent rapid cooling near the surface of a planetary body. 相似文献
788.
海底天然气水合物的储量主要取决于水合物的分布面积、水合物稳定带的厚度、沉积层的孔隙度及水合物的饱和度 (或充填率 )等 ,其中水合物在沉积物孔隙中的饱和度对其储量的估计具有重要意义。目前很难通过原地直接测量来获得这种饱和度数据 ,一般根据地球化学或地球物理方法取得。水合物饱和度预测技术主要有 :利用岩心孔隙水氯离子浓度、地球物理测井、地震波速度等间接手段。每一种技术都不是完善的 ,而海底含水合物的沉积物又是一个复杂的系统 ,在预测中应根据实际情况选择比较合适的方法 ,并尽量选择一种以上的方法或模型作多方法校正 相似文献
789.
Accurate and High-Precision Measurement of Lithium Isotopes in Two Reference Materials by MC-ICP-MS 总被引:5,自引:1,他引:5
Romain Millot Catherine Guerrot Nathalie Vigier 《Geostandards and Geoanalytical Research》2004,28(1):153-159
We report here a newly developed method for measurement of Li isotopes by use of multi-collector ICP-MS (Neptune) allowing rapid and high precision determination of Li isotope ratios at low levels of lithium (15–20 ng). The lithium reference sample solution IRMM-016 was analysed over a period of ten months with an external reproducibility of 0.24% (2s, n = 52). Chemical separation of Li from matrix was performed on the seawater sample IRMM BCR-403, for which a mean δ7 Li value of + 31.0 ± 0.1 % (2s/√n, n = 31) was obtained. This mean value is in good agreement with those previously published for other seawater samples. BCR-403 seawater being readily available, we propose that this seawater sample be used as a reference sample for Li isotope measurements. 相似文献
790.
Fabien Thomas Bénédicte Prélot Frédéric Villiéras Jean-Maurice Cases 《Comptes Rendus Geoscience》2002,334(9):633-648
In aqueous medium, solid surfaces are in general electrically charged. The induced electrical and chemical properties govern numerous phenomena, such as colloidal stability or transport of pollutants. Numerous industrial processes make use of these properties. The understanding of the underlying mechanisms at molecular level is of high importance in order to predict and master the behaviour of dispersed matter in the environment and in industrial processes. The present paper shows the evolution of theories and experimental methods, their recent developments and applications. To cite this article: F. Thomas et al., C. R. Geoscience 334 (2002) 633–648. 相似文献