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1.
Water quality assessment by pollution-index method in the coastal waters of Hebei Province in western Bohai Sea, China 总被引：8，自引：0，他引：8
Sources of pollution discharges and water quality samples at 27 stations in 2006 in the coastal waters of Hebei Province, western Bohai Sea, have been analyzed in this study. Pollutant loads from industrial sewages have shown stronger impact on the water environment than those from the general sewages. Analysis indicates that pollution of COD is mainly resulted from land-based point pollutant sources. For phosphate concentration, non-point source pollution from coastal ocean (fishing and harbor areas) plays an important role. To assess the water quality conditions, Organic Pollution Index and Eutrophication Index have been used to quantify the level of water pollution and eutrophication conditions. Results show that pollution was much heavier in the dry season than flood season in 2006. Based on COD and phosphate concentrations, results show that waters near Shahe River, Douhe River, Yanghe River, and Luanhe River were heavily polluted. Water quality in the Qinhuangdao area was better than those in the Tangshan and Cangzhou areas. 相似文献
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2003年淮河流域致洪暴雨过程的环流背景及其前兆信号 总被引：7，自引：2，他引：5
分析研究了2003年夏季淮河流域致洪暴雨过程的时空分布特征及其前期和同期欧亚地区环流背景的逐日变化特征,重点分析了致洪暴雨过程发生前后乌山地区阻塞高压强度指数(UBHII)逐日变化特征及其对淮河流域致洪暴雨过程的影响．结果表明：2003年淮河流域持续性强暴雨过程均发生在鸟山阻塞高压强高峰后的减弱期,即在淮河流域发生持续性强暴雨过程之前乌山阻塞高压就发生了突变;同时发现西太平洋副热带高压加强并登陆后的,其北界的位置变化对淮河流域致洪暴雨过程的发生和持续也有十分重要的作用．因此,乌拉尔山阻塞高压异常加强后的突然减弱和西太平洋副热带高压的加强并西进登陆,是淮河流域地区发生持续性暴雨过程的两个重要前兆． 相似文献
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Recent developments in numerical algorithms have enabled the construction of three‐dimensional models for the prediction of flows in open channels. These advances encompass improvements in both numerical solutions and the process representation required for an accurate system definition. However, to date, there is still little agreement on how to assess systematically and report the credibility of these simulations. This paper addresses this problem by adopting a Grid Convergence Index approach. The results indicate, for two simple hypothetical cases, a zero‐degree confluence and a meander bend, that the numerical code can be verified to an acceptable numerical standard. However, it is shown that this does not mean that verification is complete, as the literature implies, as whilst the discretization resolution may be sufficient to verify one of the model variables it does not imply that every variable has converged. Furthermore, the scheme may still be insufficient to capture all the processes of interest that are operating within the chosen environment. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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指标选取是人工神经元网络方法应用中最基础，最重要的五环，是判别工作成败的关键。但目前尚没有比较成熟的指标选取或指标显著性评价方法。因此，指标问题入往成了方法效果进一步提高的“瓶颈”问题。该问题在潜在震源区划分应用中也同样存在。 相似文献
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Salt-loaded effluents were introduced into the river Wipper during the mining period for almost a century. Beginning with the year 1990, the waste water load was strongly reduced due to the termination of the potash industry. Prior to 1990, monthly means of the chloride concentrations at times exceeded 6,000 mg l−1 in the strongly polluted sections. Maximum concentrations reached twice these values. Up to 1998, mean annual chloride concentrations decreased to values below 2,000 mg l−1. This led to more balanced fluctuations in salinity which had been pronounced before, depending on discharge and short-term changes in production. Similarly, the physiologically adverse ion conditions improved due to decrasing potassium and increasing calcium proportions.
In 1963/64, 1986 and 1998, samples of epilithic, epiphytic and epipsammic diatoms were taken at locations of different salinities along the river and examined for the effects of the salinization on the structure of the diatom assemblages. These structures changed in dependence on salinity. Increasing salt concentrations coincided with decreasing oligohalophilic and increasing mesohalophilic and polyhalophilic species numbers. Above a chloride concentration of about 3,000 mg l−1, the proportion of the latter exceed that of the former (halobion index > 50). Corresponding to different conditions of salinization along the river, characteristic diatom assemblages occur differring from each other and which are specific for the river section. Spring and autumn aspects of the diatom assemblages show also salt-dependent differences. The assemblages found in 1998 after decrease of salinization have changed markedly in comparison to those from 1963/64 and 1986. Halobiontic species predominating formerly occurred only occasionally or not at all. They were replaced by oligohalobic-indifferent forms.
An ecological assessment of the changes was performed based on the halobion index calculated from all the samples. For the strongly salinized section of the river Wipper, a shift from -mesohalobic/polyhalobic conditions in 1963/64 and 1986 to -oligohalobic/β-mesohalobic conditions in 1998 was found. However, constant -oligohalobic conditions are still not given. With regard to the transition from -oligohalobic (limnetic) to β-mesohalobic (brackish) conditions, a maximum chloride concentration of 600 mg l−1 was found. To guarantee -oligohalobic conditions, a maximum chloride concentration of 400 mg l−1 should not be exceeded. 相似文献
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Horst ZiemannClaus-Jürgen Schulz 《Limnologica》2011,41(2):90-95
Salinisation of running waters is a severe problem in many parts of the world. Monitoring and management of such waters require ecological methods which consider the hydrochemical effects of salinisation on the aquatic communities in order to set targets to protect habitats and biodiversity. Several bioassays have been developed for this purpose and are surveyed here. They are based on the salt sensitivity of the following groups of organisms: diatoms, ciliates and macroinvertebrates. In this paper experiences gained so far are also considered as well as practical applications originating from this research. 相似文献
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Spatiotemporal characteristics of drought based on the Standardized Precipitation Index (SPI) in the Liao River basin (LRB) are investigated in this study. High autocorrelation in SPI seems to lend itself to drought prediction. Drought is becoming more frequent, widespread, and severe in the LRB during the past several decades. Major factors affecting drought in this basin are analysed by investigating relationship between SPI and several circulations including western Pacific Subtropical High (WPSH), East Asian Summer Monsoon (EASM) and El Niño‐Southern Oscillation (ENSO) indices. Different correlation patterns between WPSH indices and SPI are obtained. Several significant positive correlations between the area, intensity of WPSH and SPI are observed in the west and the centre of the study area, while negative correlations are observed in the east. Reverse patterns are observed in the correlation between the ridge of westward longitude of WPSH and SPI. Corresponding lag‐correlation is dominated by positive correlations between the area, intensity of WPSH and SPI, and by negative correlation between the ridge of westward longitude of WPSH and SPI. EASM is mainly negative related with drought in the east of the LRB. Significant positive correlation between ENSO and SPI is mainly located in the east while negative correlation is located in west of the basin. Lag‐correlation (with lags of 1 to 12 months) between them is also investigated and results show that significant negative correlation is located in a broad area extending from the west to the centre of the basin, while less positive correlation is observed with the increase of lags. The possibility of employing general circulation models (GCMs) for drought prediction is discussed based on the above analyses. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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地形变强震前兆指标探讨 总被引：5，自引：2，他引：5
在多年形变前兆研究基础上，对形变应变前兆的复杂性进行了讨论，并对典型的形变应变短临前兆实例进行了总结，找出其共性。以描述其共性特征为目标，给出了异常指标K的计算模型，似可用该指标结合资料背景和实践经验进行综合分析，对某些6级以上强震作出中短或短临阶段的预报。 相似文献
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详细表述了森下指数的原理和如何选取工作参数。通过云南省几次中强震前森下指数图像动态过程的研究,结果表明,森下指数对复杂的地震空间分布图象具有较高识别判断能力,是一种是短期地震前兆指标的有效判定方式。 相似文献
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Research on the differential uplifting in the Palongzangbu region is crucial to understanding the tectonic deformation mechanism and establishing the model of the faulted blocks in the region of the east structural knot. In this paper, based on the ASTER-30m DEM, we calculate the hypsometry index (HI) of 19 watersheds in the Palongzangbu region, and study the differential uplifting in this region combining with seismic data, the ground deposition and erosion process. The result shows that the spatial distribution of the HI value can reflect the differential uplifting in the study area. Differential uplifting exists within different zones, and there are 2 relative strong uplifting centers. One center is near the east structural knot, and the other lies between the Lhari fault and Nujiang fault at their converging segment. Also, the watershed evolution, seismic activity, and ground deposition and erosion process are closely related to each other, and they constitute a chain of evidence which reveals the whole process from the tectonic movement underground to the landform evolution on the surface. 相似文献
11.
山西省地电监测能力综合评价 总被引：1，自引：0，他引：1
以影响地电观测资料可信度的因素及在一定有效监控能力范围之内的映震能力作为地电监测能力的综合评价指标,对山西省的４个地电台站逐一进行了分析研究,得出了山西地电阻率对３００ｋｍ以内５．０级以上中强地震有一定监测能力的结论。 相似文献
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In this paper, progressive methods for assessing drought severity from diverse points of view were conceived. To select a fundamental drought index, the performances of the Effective Drought Index (EDI) and 1-, 3-, 6-, 9-, 12-, and 24-month Standardized Precipitation Indices (SPIs) were compared for drought monitoring data accumulated over 200-year period from 1807 to 2006 for Seoul, Korea. The results confirmed that the EDI was more efficient than the SPIs in assessing both short and long-term droughts.We then proposed the following methods for modifying and supplementing the EDI: (1) CEDI, a corrected EDI that considers the rapid runoff of water resources after heavy rainfall; (2) AEDI, an accumulated EDI that considers the drought severity and duration of individual drought events; and (3) YAEDI, a year-accumulated negative EDI representing annual drought severity. In addition to these indices, to more accurately measure and diagnose droughts, we proposed the utilization of (4) the Available Water Resources Index (AWRI), an existing index that expresses the actual amount of available water.Using the improved methods above, we assessed and summarized important droughts that have occurred in Seoul over the 200 years from 1807 to 2006. 相似文献
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Abstract It is known that the El Niño Southern Oscillation (ENSO) phenomenon induces marked climate variability across many parts of the world. However, in seeking useful relationships between ENSO and climate, several indices are available. In addition to the choice of index, previous studies assessing ENSO effects have employed a range of different methods to classify periods as El Niño, La Niña or Neutral. It is therefore clear that significant subjectivity exists in the adoption of ENSO classification schemes. In this study, several ENSO classification methods are applied to a range of ENSO indices. Each method-index combination is investigated to determine which provides the strongest relationship with rainfall and runoff in the Williams River catchment, New South Wales, Australia. The results demonstrate substantial differences between the methods and indices. The Multivariate ENSO Index (or MEI) is found to provide the best classification irrespective of method. The potential for forecasting ENSO-related effects on rainfall, runoff and river abstractions is then investigated. A “rise rule” to account for dynamic ENSO trends is also assessed. Strong relationships were found to exist with runoff (rainfall) up to nine (eight) months in advance of the Summer/autumn period. Implications for improved forecasting of potential river abstractions are apparent. 相似文献
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Constantin Mares Mary-Jeanne Adler Ileana Mares Silvia Chelcea Emilia Branescu 《水文科学杂志》2013,58(6):1010-1025
ABSTRACTThe aim of this study is to analyse the seasonal characteristics of four Palmer indices calculated on the basis of data from 27 meteorological stations in Romania, and the impact of these indices on river discharges in the period 1931–1998. Our research also tests the influence of large-scale atmospheric circulation on these indices and on discharge. For each season, developments in the empirical orthogonal functions (EOF) and multivariate EOF (MEOF) are achieved. The MEOF representation highlights the overall characteristics of the four Palmer indices. It maximizes specific information for each season compared with individual information of each Palmer index. We then identify geographical areas with homogeneous distribution, taking into account both the discharge distribution and the rotated EOF components of each Palmer index. Finally, we analysed the impact of large-scale atmospheric circulation on hydro-climatic events in Romania by means of the Greenland-Balkan Oscillation Index (GBOI), which is shown to have a greater influence on southeastern Europe than the North Atlantic Oscillation Index (NAOI). 相似文献
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云南省县（市）区应急备震能力评估方法研究及应用 总被引：1，自引：1，他引：0
震前做好应急备震工作是有效应对地震灾害风险、减轻灾害损失的重要手段。本文基于云南地区震害背景和区域特征,采用层次分析法构建了围绕1个目标层、4个准则层和23个指标层的应急备震能力评估指标体系的层次模型,对云南省129个县（市）区的应急综合备震能力进行了评估和分级。结果表明:从全省单项指标分析结果看,地震应急组织机构健全度和地震应急资源基础保障能力2项指标差距小,空间分布均匀,综合指数较高的区域集中在滇中的昆明和滇西的大理地区;地震应急灾情获取与评估能力2项指标综合指数较高的县分布于滇东和滇西地区的昆明、玉溪、大理、楚雄等地;昆明、大理地震紧急救援能力相对较高。从应急备震综合能力分析结果看,云南省17个县较高,8个县相对较弱,综合能力较强区域主要分布在滇中、滇西等地的昆明、玉溪、普洱等地,滇西北的怒江和滇东南的文山等地综合能力较低。 相似文献
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本文从地震灾害、建筑物、人口、经济、抗震救灾等多方面出发，将自然属性与社会属性进行有效结合，对地震危险性、建筑物抗震性能等影响因素进行详细分析，构建城镇地震灾害风险评价指标体系，以张家口地区16个县区为例，采用专家-层次分析法，建立精细化地震灾害风险评估模型。研究结果表明，城镇建筑物抗震性能普遍较差，怀来县地震灾害风险最大，桥东区、蔚县、涿鹿县、桥西区次之，沽源县、康保县地震灾害风险最小，并对各县区地震灾害风险主要影响因素进行讨论，发现地震风险指数与地形结构、建筑物抗震性能具有相关性，评估结果可为城镇制定防震减灾规划提供依据。 相似文献