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湖泊沉积研究的历史进展与展望 总被引：23，自引：10，他引：13
回顾了国际和国内湖泊沉积研究历史,论述了国际古湖泊学研究的两大方向以及主要研究内容,对中国20世纪50年代以来的湖泊沉积研究进行了综述.针对目前湖泊沉积研究领域的薄弱环节,提出加强湖泊沉积环境指标的基础理论研究,提高时间分辨率,关注人类活动对湖泊环境的影响,开展湖泊沉积界面过程与机理研究,以及进一步加强区域和全球对比等建议与展望. 相似文献
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Temporal trends and spatial characteristics of drought and rainfall in arid and semiarid regions of Iran 总被引：5，自引：0，他引：5
Drought, a normal recurrent event in arid and semiarid lands such as Iran, is typically of a temporary nature usually leaving little permanent aftermath. In the current study, the rainfall and drought severity time series were analyzed at 10 stations in the eastern half of Iran for the period 1966–2005. The drought severity was computed using the Standardized Precipitation Index (SPI) for a 12‐month timescale. The trend analyses of the data were also performed using the Kendall and Spearman tests. The results of this study showed that the rainfall and drought severity data had high variations to average values in the study period, and these variations increased with increasing aridity towards the south of the study area. The negative serial correlations found in the seasonal and annual rainfall time series were mostly insignificant. The trend tests detected a significant decreasing trend in the spring rainfall series of Birjand station at the rate of 8.56 mm per season per decade and a significant increasing trend in the summer rainfall series of Torbateheydarieh station at the rate of 0.14 mm per season per decade, whereas the rest of the trends were insignificant. Furthermore, the 12‐month values of the standardized precipitation index decreased at all the stations except Zabol during the past four decades. During the study period, all of the stations experienced at least one extreme drought which mainly occurred in the winter season. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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如何看待我国地震预报研究在防震减灾中的作用 总被引：1，自引：0，他引：1
自20世纪60年代开始,地震预报研究至今已40多年,但到目前为止,仍然未取得突破性进展;而另一方面随着社会经济的迅速发展和对人的生命价值的重视,社会和民众对准确预报地震的期望十分迫切,特别是5·12汶川大地震的发生,使得一些群众对地震预报工作产生怀疑和不理解。地震预报研究到底有无作用？本文从地震灾害的特点、地震预报的难点和我国地震预报探索几十年来所取得的成效作一阐述,并对如何提高地震预报实效提出几点讨论意见。 相似文献
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现代固体地球科学已经认识到,地幔对流不再是少数动力学家的假想,它是地幔热动力系统的主要构架.地幔对流和板块运动驱动机理关系的研究已经从简单的主动或被动驱动的讨论转向对统一热动力系统的探讨.包括地幔热柱在内的地幔对流的深入研究不仅成为研究地幔热动力系统演化的主线,也成为研究大陆形成和演化驱动机理的主线.与此同时,以地震层析成像为主体的地震、地球物理观测资料和以地幔岩石化学组份为主体的地球化学观测成为认识地幔对流的强有力的工具.然而,地球化学和地球物理观测之间存在明显的差异,一些依赖于地球化学数据构思的新的热动力学框架对地幔对流的研究构成了强烈的挑战. 相似文献
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Han-Keng Lee Yir-Yarn Yeh Wei-Ming Chen 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,21(1):1-13
This study conducts risk assessment for an array of health effects that may result from exposure to disinfection by-products (DBPs). An analysis of the relationship between exposure and health-related outcomes is conducted. The trihalomethanes (THMs) species have been verified as the principal DBPs in the drinking water disinfection process. The data used in this study was collected from the Taiwan Water Corporation (TWC) from 1998 to 2002. Statistical analysis, multistage of Benchmark model, Monte Carlo simulation (MCS) and sensitive analysis were used to estimate the cancer risk analysis and assessment. This study included the statistical data analysis, epidemiology investigation and cancer risk assessment of THMs species in drinking water in Taiwan. It is more significant to establish an assessment procedure for the decision making in policy of drinking water safety predominantly. 相似文献
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新安江模型在资料匮乏的长江中下游山区中小流域洪水预报应用 总被引：1，自引：0，他引：1
水文资料匮乏流域的洪水预报(PUBs)是水文科学与工程中一个尚未解决的重大挑战.中国湿润山区中小流域大多是水文资料匮乏的流域,在此地区进行洪水预报的重要手段之一就是水文模型参数的估计.对基于参数物理意义的估算方法(以下简称物理估算法)及两种区域化方法进行了研究,将其用于新安江模型参数的估算及移植.皖南山区的29个中小流域被选作水文资料丰富的测量流域,鄂西山区的3个中小流域被视为水文资料匮乏的目标流域,目的是研究目标流域与测量流域空间位置较远但物理条件相似时,区域化等方法是否可以有效估计模型参数.结果表明,即使目标流域与测量流域空间距离较远,区域化及物理估算法也能一定程度上减少参数估计导致的模型效率损失,且在研究区的最优参数估计方案为单流域物理相似法结合回归法及物理估算法.为长江中下游资料匮乏的山区中小流域提出了可行的新安江模型参数估计方案,为该地区的洪水预报提供指导. 相似文献
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Water security in north China and countermeasure to climate change and human activity 总被引：2，自引：0，他引：2
This paper addresses the emergent issues by the case study of Haihe River Basin in North China. The advantage of the water international study and the background for the cause of these problems from natural change and in particular human activity are analyzed. The key points are addressed as four aspects: (a) the study of the water cycle process impacted by climate change and high intensity human activity; (b) water utilization related to new economic partner change, such as saving water model; (c) study on eco-hydrology, and the interaction of water and ecology impacted by climate change and human activity; and (d) reasonable water allocation that includs water diversion from south to north and saving water issue in the local areas. Several suggestions are proposed both on the study on the water cycle, which is a very important base of water security in north China, and on the application study of water resources and eco-environmental rehabilitation. These key issues will benefit both the advantage of water science and the sustainable development in China. 相似文献
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Geomagnetism and Aeronomy - A study of glacial−interglacial periods shows that, once ice sheets reach a critical maximal mass, the glaciation period changes to an interglacial one; the latter... 相似文献
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岩溶塌陷是覆盖型岩溶区最突出的地质灾害问题,是广西重要的地质灾害之一,对经济建设和人民的生活构成严重危害。文章从塌陷的物质组成及成因上讨论了广西岩溶塌陷的类型,分析了其危害、影响因素及其形成机制。在此基础上,提出了岩溶塌陷防治的对策建议。 相似文献
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Aerial surveys were conducted in the north-central Gulf of Mexico from June 1988 to May 1989. Sightings of marine debris and specifically large floating plastics were recorded during these surveys. Five study areas off the Louisiana coast were monitored and seasonal distribution and densities were estimated. Each study area contained plastic throughout the year. The estimated densities of plastic were largest in the offshore areas (4 & 5) and smallest in the inshore areas (1 & 3). Seasonally, density of plastic was smallest in the summer and largest in the fall. The reasons for the differences in seasons and study areas are not apparent but the amount of plastic in each area and season could be affected by variations in currents, winds, discharge from rivers, and human activity. 相似文献
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Drew C. McAvoy Jacqueline A. Greff D. Ronald Webb Greg S. Allgood 《Ground Water Monitoring & Remediation》1998,18(4):131-138
A field study was conducted to examine the fate and potential effects of olestra, a non-caloric fat replacer, in septic tanks. The study compared the performance of parallel septic tanks, which were led domestic waste water with liquid and solid forms of olestra, against a control tank receiving waste water without olestra. Results showed that 36 g/d of olestra dosed to the tanks (a three-fold exaggeration of expected loadings) had no adverse effect on system operation (based on visual observations and sludge accumulation) or performance (based on removal of organic content and solids) over a six-month period. Removal efficiencies for total suspended solids (TSS), carbonaceous biochemical oxygen demand (CBOD), and chemical oxygen demand (COD) were not significantly different (p<0.05) in the olestra tanks when compared to the control tank. In addition, a relatively small amount of the total olestra added (3 to 6%) was recovered in the septic tank effluents over the course of the study. Accumulation of tank solids was not affected as measured sludge levels in the tank at the middle and end of the study showed no difference between the olestra dosed tanks and the control tank. 相似文献
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Aierken Tuersun Yusufujiang Rusuli Aizezitiyuemaier Maimaiti Miriayi Maitudi Kadiayi Alimu 《洁净——土壤、空气、水》2020,48(5-6)
The Bosten Lake watershed investigated in this study has seen significant land cover and climate change. The spatiotemporal relationship between evapotranspiration (ET) and environmental factors remain unclear. In this study, trend analysis and correlation methods are applied to analyze the spatiotemporal characteristics of ET and the relationship between ET and its driving factors using remotely sensed ET data and measured climate data between 2001 and 2018. During the study period, high values of ET primarily occurr in the wetlands of the plain area and the mid‐elevation mountain areas. The ET values show a significantly increasing trend in the different vegetation types due to climate change and other factors. The ET change trend in the study area is in the range of ?13.4 to ≈35.9 mm per year; the desert area exhibits a significant decrease and most of the mountain areas show a significantly increasing trend. ET is significantly correlated with land surface temperature, normalized difference vegetation index (NDVI), and solar radiation. The dominant factor affecting ET is NDVI, accounting for 15.2% of the study area. The results of this study highlight the need for appropriate land‐use strategies for managing water resources in arid land ecosystems. 相似文献
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Geomagnetism and Aeronomy - Based on observations in the Hα and extreme ultraviolet lines, as well as in the radio and X-ray wavelengths, we study the eruptive events of September 22 and 24,... 相似文献
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利用重、磁和天然地震资料对中南地区进行了综合地质地球物理研究.根据研究区的重、磁异常的分布特征,可将其分为4个重力异常区、3个航磁异常区.根据重力资料反演计算得到的研究区的地壳厚度在295～41 km之间,总的趋势为西厚东薄,地壳厚度与地形起伏基本上呈镜像关系.根据磁力资料计算得到的研究区居里界面在12～40 km之间变化.地震层析成像结果表明研究区内的速度分布总体上体现了纵横交错的断块特征.在纵向尺度上,江汉－洞庭盆地以及周缘造山带的上地壳结构变化不大,中地壳和下地壳则普遍受到现今构造活动的改造,以致岩石的结构发生了一定的变化.它们主要表现为低速区域的扩大,尤其是在地壳下部尤为突出,这与断陷盆地的拉张以及造山带岩石层的底侵和拆沉作用密切相关.通过对研究区地球物理场的分析计算,在研究区共提取主要断裂带34条.根据岩石层板块大地构造理论,依据岩石层结构、地壳结构和结晶基底等深部结构的不同,将研究区中板内不同构造单元——块体作为一级构造单元,块体之间的深大断裂带作为块体的边界——块体结合带,据此原则在研究区中划分出两个一级构造单元,五个二级构造单元. 相似文献
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Robert M. Burgess Anna V. Terletskaya Mark Povolotskii Tatiyana A. Bogoslavskaya Tatiyana V. Vorobyova Artem Lyashenko 《Marine pollution bulletin》2009,58(8):1103-1115
In this study of Ukrainian estuaries, sediments and tissues from the Dnieper and Boh estuaries and Danube Delta on the mainland, Sevastopol and Balaklava Bays on the Crimean Peninsula, and coastal Black Sea along the Crimean Peninsula were collected in 2006. Contaminant analyses included several metals, the hydrophobic organic chemicals (HOCs) polychlorinated biphenyls, several chlorinated pesticides, and polycyclic aromatic hydrocarbons. When compared to estuarine sediments globally, the Ukrainian sediments were found to be moderately contaminated. However, several metals, especially mercury, were often shown to be elevated in the tissues of the Ukrainian organisms in comparison to organisms from other estuarine locations. Sediment quality guidelines indicate some of the estuarine sediments could be sufficiently contaminated to cause adverse toxicological effects. This investigation represents the first extensive study of HOC and metal baseline concentrations and distributions in Ukrainian estuaries and seeks to characterize exposures to aquatic organisms living in these systems. 相似文献
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A. M. Kurchavov 《Journal of Volcanology and Seismology》2009,3(2):71-80
Correct diagnostics of rocks requires the 3D study of the structure of their basis, since a splinter-like basis structure may occur only in a single observed section of a specimen of a rock that has a more complex structure of the plane-parallel or linear type. Ignimbrites differ from lavas with a similar silica content primarily in the presence of fiamme, a smooth outline of the phenocrysts, and their constant cataclasis; they differ from pyroclastic lavas by having broken-down phenocrysts enclosed in an undisturbed groundmass with smooth and undulating outlines of the volcanic particles and by the presence of fiamme showing a regular pattern of evolving composition. The study of the morphological and material features of all components of ignimbrites in their relationships with the silica content of the melt and the attitude of the ignimbrite geologic bodies they compose corroborates the hypothesis that ignimbrites are generated by the complex evolution of a gas-saturated melt of the emulsified type rather than by baking (welding) of ash-fall particles. 相似文献