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981.
Solute transport through structured, undisturbed soil has been studied in transient, unsaturated experiments using columns from grass and woodland sites on the Lancaster University campus. Three anionic tracers have been used, bromide (Br−) and two fluorinated organic acids (pentraflurobenzoic acid and 2,6-diflurobenzoic acid). The process of displacement of stored water from undisturbed columns was investigated using successive inputs of different tracers under similar antecedent conditions. The results indicated that initial breakthrough was rapid, with a relative concentration of 0.8 being reached between 0.4 and 0.5 pore volumes of discharge. It was found that there was an apparent continued discharge of ‘old’ water, stored in the column before any additions of tracer, even after the addition of a total of 4.9 and 5.4 pore volumes of water for the grass and woodland columns, respectively. The implications of the results of these tracer studies for modelling solute transport in structured soils are considered. 相似文献
982.
Hiroaki Sato Setsuya Nakada Toshitsugu Fujii Michihiko Nakamura Keiko Suzuki-Kamata 《Journal of Volcanology and Geothermal Research》1999,89(1-4)
Pargasite commonly occurs in the dacitic groundmass of the 1991–1995 eruption products of Unzen volcano. We described the occurrence and chemical compositions of amphibole in the dacite, and also carried out melting experiments to determine the low-pressure stability limit of amphibole in the dacite. The 1991–1995 ejecta of the Unzen volcano show petrographic evidence of magma mixing, such as reverse compositional zoning of plagioclase and amphibole phenocrysts, and we used a groundmass separate as a starting material for the experiments. Reversed experiments show that the maximum temperature for the crystallization of amphibole is 930°C at 196 MPa, 900°C at 98 MPa, and 820°C at 49 MPa. Compared with the experimental results on the Mount St. Helens dacite, present experiments on the Unzen dacitic groundmass show that amphibole is stable to pressures ca. 50 MPa lower at 850°C. Available Fe–Ti oxide thermometry indicates the crystallization temperature of the groundmass of the Unzen dacite to be 880±30°C, suggesting that the groundmass pargasite crystallized at >70 MPa, corresponding to a depth of more than 3 km in the conduit. The chlorine content of the groundmass pargasite is much lower than that of phenocrystic magnesiohornblende in the 1991–1995 dacite of Unzen volcano, indicating that vesiculation/degassing of magma took place before the crystallization of the groundmass pargasite. The present study shows that the magma was water oversaturated and that the degassing of magma along with magma mixing caused crystallization of the groundmass amphibole at depths of more than 3 km in the conduit. 相似文献
983.
The mean flow at and around the Hebrides and Shetland Shelf slope is measured with ARGOS tracked drifters. Forty-two drifters drogued at 50 m were deployed in three circles over the Hebrides slope at 56.15°N in two releases, one on 5th December, 1995 and the second on 5–9th May, 1996. The circles span a distance of some 20 km from water depths of 200 m to 1200 m. Drifters are initially advected poleward along-slope by the Hebrides slope current at between 0.05 and 0.70 m s–1 in a laterally constrained (25–50 km wide) jet-like flow. Drifters released in winter remained in the slope current for over 2000 km whilst summer drifters were lost from the slope current beyond the Wyville-Thomson Ridge, a major topographic feature at 60°N. Dispersion from the slope region into deeper waters occurs at bathymetric irregularities, particularly at the Anton Dohrn Seamount close to which the slope current is found to bifurcate, both in summer and winter, and at the Wyville-Thomson Ridge where drifters move into the Faeroe Shetland Channel. Dispersion onto the continental shelf occurs sporadically along the Hebrides slope. The initial dispersion around the Hebrides slope is remarkably sensitive to initial position, most of the drifters released in shallower water moving onto the shelf, whilst those in 1000 m or more are mostly carried away from the slope into deeper water near the Anton Dohrn Seamount. The dispersion coefficients estimated in directions parallel and normal to the local direction of the 500 m contour, approximately the position of the slope current core, are approximately 8.8 × 103 m2 s–1 and 0.36 × 103 m2 s–1, respectively, during winter, and 11.4 × 103 m2 s–1 and 0.36 x 103 m2 s–1, respectively, during summer. At the slope there is a minimum in across-slope mean velocity, Reynolds stress, and across-slope eddy correlations. The mean across-slope velocity associated with mass flux is about 4 × 10–3 m s–1 shelfward across the shelf break during winter and 2 × 10–3 m s–1 during summer. The drifters also sampled local patterns of circulation, and indicate that the source of water for the seasonal Fair Isle and East Shetland currents are the same, and drawn from Atlantic overflows at the Hebrides shelf. 相似文献
984.
德国哈茨山St.Andreasberg热液矿床方解石巨晶的碳氧同位素研究 总被引:2,自引:0,他引:2
在德国哈茨山St.Andreasberg热液Pb-Zn矿床的方解石脉中,发现了一个方解石巨晶。对该方解石三个不同方向上的C和O同位素分析发现,方解石晶体内部存在明显的C-O同位素环带。通过对方解石同位素环带的理论模拟,发现在方解石生长过程中,有三种流体参与了作用。它们分别为A:温度约为60℃的近地表流体,δ^13C=-18.5‰,δ^18O=0‰;B:温度约为140℃的深源流体,δ^13C=-7.0%O,δ^18O=+10.0%o;C:温度小于20℃。δ^18O≤%O ,δ^13C≥ 14.0%o的大气降水 作用过程有四个阶段:① 方解石在流体A中等温生长;② 流体B开始与流体A在封闭体系内均匀混合;③ 流体B缓慢注入的同时,发生了一次性流体C的快速不均匀混合;④ 流体B继续与A缓慢混合,混合体系开放。流体混合的发现,为认识St Andreasberg热液矿床的形成机制提供了颟的视野。 相似文献
985.
Circulation and Mixing of Water Masses of Tatar Strait and the Northwestern Boundary Region of the Japan Sea 总被引:2,自引:0,他引:2
The deep waters of the northern portions of the Japan Sea are examined. It is found that the flow regime south of the southern
Tatar Strait region is generally cyclonic in the upper ocean, with only weak flows present below depths of a few hundred meters.
The Japan Sea appears to be remarkably well-mixed below depths of a few hundred meters, both horizontally and vertically.
Based on chlorofluorocarbon measurements, it is concluded that the deep waters of the Japan Sea have been only weakly ventilated
in recent decades. Results from a simple box model suggest two possible scenarios for the ventilation of the Japan Sea since
the 1930s. In the first scenario, deep ventilation of the Japan Sea was relatively weak, but constant, from the 1930s to the
present, with a deep-water residence time of approximately 500 years. In the second scenario, ventilation was relatively vigorous
through the mid-1960s, with a deep-water residence time of approximately 100 years; after the mid-1960s, the ventilation of
the deep waters stopped. The model results are consistent with the idea that presently the ventilation of the deep water of
the Japan Sea is weak or nonexistent.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
986.
Distribution of Rb and Sr in the Luochuan loess- paleosol sequence of China during the last 800 ka 总被引:4,自引:0,他引:4
The concentrations of Rb and Sr, and magnetic susceptibility in loess and paleosol samples from the Luochum profile have been
measured. The loess units deposited in different geological periods display a very similar pattern of Rb and Sr distribution
while paleosol units exhibit a dramatic increase in the Rb/Sr ratio, ranging from 20% to 120% in increase amplitude. Owing
to different geochemical behavior of the two elements, Rb appears to be immobile while Sr appears to be mobile in the processes
of weathering and pedogenesis. So variations of the Rb/Sr ratio in the loess-paleosol sequences could reflect intensities
of weathering and pedogenesis, thus recording the relative wind strength of the East Asian summer monsoon circulation. This
could be supported by the high degree of cornlation between the Rb/Sr ratio and the magnetic susceptibility. A continuous
record of the Rb/Sr ratio in the Luochuan profile over the last 800 ka bears a striking resemblance to the δ18 O curve of the deep sea sediments and is in accordance with the SPECMAP chronology. Such similarity between the terrestrial
and the deep sea records suggests that variability in global ice volume is a primary dynamic factor controlling long-term
changes of the East Asian summer monsoon intensity.
Project supported by the National Natural Science Foundation of China (Grant No. 49725307). 相似文献
987.
化学絮凝法对钛白废水的处理 总被引:1,自引:1,他引:0
详述了硫酸铝钾-聚丙烯酰胺体系处理钛白废水的研究,较全面地分析了江西赣东化工厂钛白废水的物质组成和污染负荷,对该处理体系的工艺条件进行了系统研究,确定了最佳工艺条件。结果表明,该体系处理钛白废水,能有效降低废水中污染物质,值得作进一步研究。 相似文献
988.
989.
碳酸盐岩化学溶蚀效应 总被引:8,自引:0,他引:8
本文根据大量模拟试验成果和野外观察资料,重点讨论了碳酸溶蚀效应、硫酸溶蚀效应以及几种混合液包括碳酸或硫酸加NaCl,MgCl2及CaCl2等对碳酸盐岩的混合溶蚀作用,并根据硫酸水溶蚀叠加于碳酸水溶蚀作用的研究,首次提出了碳酸盐岩叠加溶蚀效应的概念,指出由于叠加溶蚀效应的存在,使硫酸溶蚀明显较碳酸溶蚀强烈。 相似文献
990.
本文从石英包裹体的气液相成分分析数据和均一温度测定结果出发,计算出矿床的成矿压力、成矿热液的物理比学参数及其化学成分特征参数。结合矿床地质特征对矿床的成矿温度、矿床成矿热液的性质和来源、热液的流动方向、热液化学成分与金矿化的关系、热液中金的迁移形式和沉淀机制等问题作了进一步地探讨。结果表明,安家岔金矿床具有改造型金矿床的成因特点。 相似文献