傍河水源地勘探方法的探讨

傍河取水已经成为我国某些城市缓解水资源紧缺状态的一种手段。本文讨论了傍河取水的理论根据和勘探步骤,井提出了相应的评价方法。     

Tidal mixing and trapping in mangrove swamps

Lateral trapping in mangrove swamps is a dominant process controlling longitudinal mixing in mangrove-fringed tidal rivers. In the dry season, the effective value of the longitudinal diffusivity is increased by the trapping effect by typically two orders of magnitude, from its value in the absence of swamps. In the wet season, freshwater is trapped within the swamp and the adjoining boundary in the tidal river, for long periods following the passage of a short-lived flood. This may have important ecological implications. A fluid-mud layer appears to be created by strong tidal currents over colloidal mangrove mud.     

Rare earth elements in fine-grained sediments of major rivers from the high-standing island of Taiwan

Thirty-eight sediment samples from 15 primary rivers on Taiwan were retrieved to characterize the rare earth element (REE) signature of fluvial fine sediment sources. Compared to the three large rivers on the Chinese mainland, distinct differences were observed in the REE contents, upper continental crust normalized patterns and fractionation factors of the sediment samples. The average REE concentrations of the Taiwanese river sediments are higher than those of the Changjiang and Huanghe, but lower than the Zhujiang. Light rare earth elements (LREEs) are enriched relative to heavy rare earth elements (HREEs) with ratios from 7.48 to 13.03. We found that the variations in (La/Lu)_UCC–(Gd/Lu)_UCC and (La/Yb)_UCC–(Gd/Yb)_UCC are good proxies for tracing the source sediments of Taiwanese and Chinese rivers due to their distinguishable values. Our analyses indicate that the REE compositions of Taiwanese river sediments were primarily determined by the properties of the bedrock, and the intensity of chemical weathering in the drainage areas. The relatively high relief and heavy rainfall also have caused the REEs in the fluvial sediments from Taiwan to be transported to the estuaries down rivers from the mountains, and in turn delivered nearly coincidently to the adjacent seas by currents and waves. Our studies suggest that the REE patterns of the river sediments from Taiwan are distinguishable from those from the other sources of sediments transported into the adjacent seas, and therefore are useful proxies for tracing the provenances and dispersal patterns of sediments, as well as paleoenvironmental changes in the marginal seas.     

An analysis of the balance of operational water discharge using a combined water-intake system

Possibilities of increasing the available water resources of small-river basins using combined water-intake systems are considered. The modern system of water intake, whose balance is supplied at the expense of reduced river flow, remains the main water-intake system. During low-water periods, a compensation water-intake system is used for maintaining the minimum permissible stream flow. The sources of compensation water-intakes are analyzed.     

Influence of geomorphological variables on mountainous stream water chemistry (Sierras Pampeanas, Córdoba, Argentina)

The relationship between geomorphological features and water geochemistry was studied for a group of mountainous rivers (from ~ 900 to ~ 2200 m a.s.l.) with similar geology and climate, in the Sierras Pampeanas of Córdoba (Argentina, 31° 30′, 32° 00′S, and 64° 30′, 65° 10′W). A multivariate approach was used to identify three morphological domains that describe the set of sampled rivers, namely “size” dominance, slope dominance, and drainage density dominance. The links between physicochemical and geomorphological variables show that “size” dominance is mostly related to major ions, conductivity, and pH, which tend to increase downstream. Slope dominance is associated with the total concentration of heavy metal (i.e., high heavy metal concentrations are associated with relatively flat areas with slightly acid to circumneutral pH, which promotes desorption). The drainage density dominance results in an association between well-drained catchments and low Cl⁻ concentration (i.e., preserving the chemical signature of atmospheric precipitation).     

中国大陆地区对外贸易差异的演变、成因与收敛路径

根据采用因子分析法进行的综合评价结果表明,中国大陆地区对外贸易水平呈现明显的非均衡发展态势。以变异系数度量的对外贸易总量差异表明,1985~2006年间,地带间外贸总量差异呈逐步增大的态势,地带内部外贸总量差异呈趋于收敛的态势。以制成品进出口占全国比重度量的对外贸易结构表明,四大地带中,东部始终占据全国主导地位且占比逐年上升。在地区对外贸易差异的形成过程中,对外开放政策、外商直接投资、人力资本、经济性基础设施、国内投资和地理区位等因素起到了决定性作用。以对数单位模型进行的实证检验表明,加大道路交通建设、提高中央与地方的分权水平、扩大投资规模、改善人力资本状况、提升通讯水平和加强省际外贸合作,是促进地区对外贸易向均衡方向发展的有效路径。     

Quantifying the temporal dynamics of wood in large rivers: field trials of wood surveying,dating, tracking,and monitoring techniques

Wood plays an important role in stream ecology and geomorphology. Previous studies of wood in rivers have quantified spatial distributions but temporal dynamics remain poorly documented. The lack of such data is related to limitations of existing methods, especially when applied to large rivers. Five techniques are field‐tested to assess their utility for quantifying the temporal dynamics in rivers: repeated high‐resolution aerial surveys, the measurement of wood physical characteristics as proxies for ¹⁴C dating, passive and active radio frequency identification (RFID) tags, radio transmitters, and video. The spatial distribution of wood is surveyed using aerial imagery with a resolution finer than 0·10 m. The estimation of temporal trends by repeated aerial‐based surveys needs to consider vegetation growth and hiding. Wood residence times can be calculated using ¹⁴C analysis, but the assessment of wood physical characteristics including decay status and wood density offers a cheaper, if less accurate, alternative. Wood resistance to penetration is tested but results are not significant. Radio transmitters are reliable for multi‐year (～5 year) surveys and can be detected at 800 m. Passive RFID tags are limited by a read range of 0·30 m but are reliable for longer term (>5 year) studies. Active RFID tags combine a moderate read range (10–300 m) and low cost with in‐flood detection but require more testing. Video monitoring of wood passing on the surface of a river is successfully implemented. For a single flood on the Ain River (France), wood transport rates are an order of magnitude higher on the rising limb of the hydrograph than on the falling limb. Overall, the techniques improve the ability to gather the data needed to understand wood transfer processes and calibrate budgets of wood in rivers. Copyright © 2009 John Wiley & Sons, Ltd.     

关于多因复成矿床的一些问题

作者于1979年开始提出多因复成矿床概念的主旨,是为了阐明从时空四维并重的角度来认识与研究成矿的重要性。作者认为：多因复成矿床以“五多”为特点。其中多成矿大地构造演化阶段是产生其他“四多”(多成矿类型、多控矿因素、多成矿作用和多成矿物质来源)的关键而属于主导地位的“一多”。由于多因复成矿床概念体现了历史—动力综合大地构造学所强调的四维思维,即把时间与三维空间兼顾的思维方法,所以这类矿床的“五多”特点中,以多成矿大地构造演化阶段这“一多”为最主要。     

CENOZOIC TECTONIC EVOLUTION AND GEODYNAMICS OF KEKEXILI BASIN IN NORTHERN QINGHAI—XIZANG PLATEAU

CENOZOIC TECTONIC EVOLUTION AND GEODYNAMICS OF KEKEXILI BASIN IN NORTHERN QINGHAI—XIZANG PLATEAU