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1.
典型岩溶流域土地整理的生态评价——以云南小江流域为例 总被引：2，自引：0，他引：2
以云南小江典型岩溶流域为例,在GIS支持下,通过选择评价因子和建立评价模型对岩溶区的土地整理进行了生态评价。结果表明: 流域生态评价分值较高的土地面积较少,而生态评价分值较低的土地面积较大。分值在80～ 100的土地整理主要任务是在保护生态环境质量和耕地数量的前提下,加快流域经济结构的调整,提高土地利用的经济效益;分值在70～ 80的土地整理主要任务是耕地数量保护和质量保护并重,提高土地的生产能力,提高经济效益,同时防止水土流失及化肥、农药施用对地下水造成的非点源污染; 分值在60～ 70的土地整理主要任务是着重于生态环境的保护和重建以及立体农业的综合开发; 分值在60以下的土地整理主要任务是土地石漠化的治理。 相似文献
2.
北半球冰川物质平衡变化的若干特征及其气候意义 总被引：6，自引：0，他引：6
根据北半球连续观测的４０多条冰川物质平衡资料，分析了目前冰川物质平衡状态及影响它们的地形因互。冰川物质平衡的变化在区域间存在着一定的联系：斯堪的纳维亚、落基山和天山地 区冰川物质平衡的变化在大多数时间内存在着对应联 系，而与阿尔卑斯山冰川物质平衡的变化具有不同程度的反向波动特征。 相似文献
3.
本文据东海五口探井的559个碎屑矿物样资料,用主要重矿物的含量及其组合特征编绘了含量变化图,试图进行分层比较。位于西湖凹陷的平湖一井和玉泉1井重矿组合特征可比性较好;龙井2井三潭组以下与上两井缺少可比特点;灵峰1井除东海群外,其余地层与上列3井相比,差异是大的。 相似文献
4.
Landslide risk: some issues that determine societal acceptance 总被引：2，自引：1，他引：1
This paper illustrates approaches to landslide risk acceptance in various parts of the world in the context of the willingness to accept that risk, the willingness to pay to reduce the risk, and the willingness to alter the environment in the process. These factors are interlinked using the ternary ??willingness diagram?? which is also used to demonstrate how such willingness may change over time and to compare a range of generic approaches to landslide remediation as well as different conceptual approaches to landslide risk management. The willingness construct is intended to provide a readily understood framework for infrastructure owners and operators, amongst others, to understand how their approach to risk management compares with those in other regions, countries and contexts. Issues relevant to the response of society and groups of individuals to landslide risk, its acceptance and management include cultural factors, regulation and planning, budgetary constraints, vehicular vulnerability, and the often limited size of the event footprint compared to the vulnerability shadow that is cast are also discussed. 相似文献
5.
In an effort to gain a better understanding of the relationship between climate, sand supply and aeolian sand deposition, an investigation was undertaken in the Algodones dunefield of south-eastern California to determine: (1) the source of the sand and (2) the mode of sand supply to the Algodones dunefield. Textural, geochemical and mineralogical analyses show that the dune sands were mainly derived from Colorado River sands during episodes when the Colorado River drained west to the Salton Basin instead of south to the Gulf of California. A model is presented which relates episodic aeolian deposition in the Algodones dunefield to the growth of the resulting lake under a persistent, intense north-westerly wind regime and to subsequent desiccation of the lake following diversion of the Colorado River to the Gulf of California. Late Holocene radiocarbon ages for relict lake shoreline deposits correlate with documented episodes of extreme flooding and increased winter storminess across the south-western United States. These conditions are likely to have been the cause of intensified north-westerly winds which coincided with high stands of Lake Cahuilla. Although diversion of the Colorado River to the Salton Basin occurred at least three times during the late Holocene, it is evident that the river did not change its course in response to the majority of the floods. It appears that the critical control on diversion of the river was the difference in gradient between courses leading to the Salton Basin and Gulf of California, which in turn was influenced by fluvial deposition and tectonic activity. Flooding was able to cause diversion of the Colorado River to the Salton Basin only when the difference in gradient between the two courses was relatively small. 相似文献
6.
Investigations were carried out at seven underground coal mines in India to characterise the responses of roof and pillars of underground workings to the vibrations induced by adjacent open-pit blasting. The roof rocks of the selected underground instrumented panels were having RMR between 36.7 to 57. Monitoring of strata behaviour was carried out before and after blasts. Arrangements were made to mount the transducers of seismographs in roof and pillars to monitor the vibration. Attempts were made to monitor the vibration simultaneously, for a blast, in the pillar and at the junction of the roof or away from the junction in the gallery. 102 sets of such vibration data were recorded in the underground mines. It was observed that the roof of underground roadways vibrated with higher peak particle velocity (PPV) compared to pillars. The amplification of vibration in the roof compared to pillars, away from the junction, was 1.02 to 2.58 times whereas at the junctions, it was 2.04 to 5.57 times. 相似文献
7.
Zuwei WANG Xin LIU Hui ZHANG 《中国地球化学学报》2006,25(B08):86-86
Four soluble inorganic salts were used to examine their influences upon cadmium forms in the alkaline soil and the contents of cadmium absorbed by plants. After KCl solution added in the soil, the contents of effective form of cadmium in the soil increased from 28% to 122%, carbonate form decreased from 2% to 47%, iron-manganese oxidation form increased from 20% to 150%. As to the organic combination form, when the KCl solution of lower concentration was added in the soils, the organic combination form contents of cadmium would decrease, while the KCl solution of higher concentration was added in the soils, the organic combination form contents of cadmium would increase. After CaCl2 solution was added in the soils, the contents of effective form of cadmium in the soils increased from 7% to 33%, the carbonate form contents of cadmium decreased from 10% to 60%, the contents of the iron-manganese oxidation form of cadmium increased from 5% to 90%, the organic combination form of cadmium increased from 5% to 73%. After KH2PO4 solution was added in the soils, the contents of effective form of cadmium in the soils decreased from 20% to 46%, the carbonate form contents of cadmium decreased from 14% to39%, the contents of the iron-manganese oxidation form of cadmium increased from14% to 95%, the organic combination form of cadmium increased from 5% to 65%. After K2CO3 solution was added in the soil, the effective form contents of cadmium decreased from 5% to 22%, the carbonate form contents of cadmium increased from 12% to 64%, the contents of organic combination form of cadmium in the soils were similar to those of the carbonate form, increasing by 3%-38%. The content variation of the iron-manganese oxidation form of cadmium was slight after K2CO3 solution was added in the soils. 相似文献
8.
基于GIS的地下水模拟可视化系统开发的初步探讨 总被引：7，自引：2，他引：7
系统开发的目的是克服GIS时空分析能力的不足，实现地下水模型与MAPGIS的耦合集成，在集成的基础上构建系统的可视化功能，在GIS平台上为地下水模拟的全过程提供一个统一高效的计算机环境。系统开发采用面向对象的软件开发方法，对各种地下水模型进行分解、抽象，建立基本的C＋＋类类型，每个模型都是基本类及其派生类对象的聚集类。系统实现的技术途径是以MAPGIS的二次开发函数作为“后台”支持，以VC＋＋作为编程工具，在充分利用MAPGIS的可视化功能的基础上，借助于OpenGL并应用科学可视化技术开发更能满足地下水模拟需要的可视化功能。 相似文献
9.
Francisco Núñez‐González Juan Pedro Martín‐Vide Maarten G. Kleinhans 《Sedimentology》2016,63(5):1209-1232
Fine particles may infiltrate through coarse alluvial beds and eventually saturate the subsurface pore space. It is essential to understand the conditions that lead to bed saturation, and to forecast the packing characteristics of saturated beds to assess the effect of excess fine sediment supply on a number of processes that occur in the stream–sediment boundary. To address this problem, in this study, a new method is introduced to predict the grain‐size distribution for the saturated condition, and the resulting porosity decrease, given the characteristics of the bed and the supplied sediments. The new method consists of the numerical aggregation of infilling fines in a finite bed volume, during which the bed properties change to affect further infilling. An existing semi‐empirical, particle packing model is implemented to identify these properties. It is shown that these types of models are adequate to describe regimes of natural sediment fabric quantitatively, and are thus useful tools in the analysis of sediment infiltration processes. Unlike previous developments to quantify saturated bed conditions, which assume that the supplied material is uniform and finer than the bed pore openings, the method developed herein considers poorly sorted fines, and can identify size fractions that are able to ingress into the bed due to being smaller than the particles that form the bed structure. Application of the new method to published experimental data showed that the final content of infiltrated fines is strongly sensitive to the initial bed packing density, highlighting the need to measure and understand open‐work gravel deposits. In addition, the new method was shown to be suitable for assessing the degree of bed saturation, when it was applied to a published data set of field samples. 相似文献
10.
早前寒武纪古地热状态的构造环境意义 总被引：2，自引：0，他引：2
区域变质作用是在造山运动中地热流和动力联合作用的体现。在早前寒武纪的造山带中,随着地壳的缩短,古地热流向构造边界聚敛,形成由高温到低温的区域变质相带序列,它既指示古地热流运移的方向,又是构造边界的指向。古地热流值的高低同构造环境的性质有关,如陆内裂陷带的区域变质仅达绿片岩相,而陆缘活动带的则可高达角闪岩相。古地热流从活动带的边界向中心运移,具有向心性,随着构造层的深埋,构成地热槽,它的片段则表现为地热斜。识别这些古地热状态,可为构造环境属性的鉴定提供有力的依据 相似文献
11.
Pile load tests are used to refine designs and for quality assurance. They can also be used to verify the reliability of piles and pile groups. Stochastic methods have previously been developed to verify the reliability of single piles. A general stochastic method to verify the reliability of pile groups is developed in this paper. The method can be used to assess the reliability of groups where pile tests have been conducted to the ultimate capacity, to below the ultimate capacity but exceeding specified capacity, and where pile tests fail to achieve the specified capacity. In the latter case, the method allows decisions to be made as to whether the reliability of the entire pile group is satisfactory or whether additional piles need to be installed. 相似文献
12.
Celestine O. Okogbue Tochukwu S. Ugwoke 《Geotechnical and Geological Engineering》2012,30(5):1249-1260
Shale samples from designated units of the Imo, Nsukka, Mamu, Enugu and Nkporo Formations of the Anambra Basin were subjected to X-ray diffraction and geotechnical index tests to determine the potential of the Formations to either create hydrocarbon migration pathways or to form seals for hydrocarbon entrapment. The X-ray diffraction results indicate that the shales are made up of silicate minerals with carbonates and sulphates. Results of the geotechnical index tests showed that the plasticity index (PI) for the Enugu shale ranges from 16 to 24 (average of 20) while the toughness index (TI) ranges from 0.4 to 0.8 (average of 0.7). The PI for the shales of Imo and Nsukka Formations ranges from 62 to 72 and 34–59 with averages of 67 and 46 respectively while their TIs range from 0.8 to 1.7 and 1.5–2.2 with averages of 1.3 and 1.9, respectively. These properties dispose the Enugu shale to easy amenability to loss of cohesion, deforming in a brittle manner, when subjected to shearing stress with the ability to create joints and faults that are pathways of hydrocarbon migration. Conversely, the properties of the shales of the Imo and Nsukka Formations give them the capacity to absorb high shearing stress without loss of cohesion thereby deforming in a ductile manner, which prevents the leakage of fluids in fluid migration. Hence, Enugu shale has the highest potential of creating hydrocarbon pathways while the shales of the Imo and Nsukka Formations are better seal rocks than others. 相似文献
13.
As a result of human activities, coastal waters can be exposed to multiple stressors that affect primary producers and their interactions with higher trophic levels. Mesocosm experiments were conducted during spring and summer 1996–1998 to investigate the responses of natural populations of primary producers to multiple stressors and the potential for these responses to be transmitted to higher trophic levels (i.e., copepods, bivalves, anemones, and fish). The effects of two stressors, elevated nutrient and trace element loadings, were examined individually and in combination. Nutrient additions had a positive effect on biomass, productivity, and abundance of primary producers (Breitburg et al. 1999; Riedel et al. 2003). Growth or abundance of consumers increased with nutrient additions, but the magnitude of the response was reduced relative to that of their prey. Responses to trace element additions varied seasonally and among taxa. The responses of zooplankton and bivalves to stressor additions were affected by the biomass and changes in species composition of phytoplankton assemblages. The presence of fish predators did not alter zooplankton responses to stressor additions. These results suggest that the extent to which nutrient and trace element effects are transmitted from primary producers to higher trophic levels depends on the capacity of consumers to respond to stressor-induced changes in abundance and species composition of prey, on the absolute abundance of prey, and on the ability of predators to feed on alternative prey. The magnitude of the effects of stressors on estuarine food webs may depend on seasonal variability in species composition of phytoplankton assemblages, whether sensitive species dominate, and whether these species are important prey for secondary consumers. Because spatial and temporal patterns in nutrient and trace element loadings to the estuary can affect species composition of primary producers, it is critically important to examine the magnitude, timing, and spatial relationships of loadings of multiple stressors to coastal waters in order to understand the impacts of these stressors on higher trophic levels. 相似文献
14.
We identify and discuss ways to use existing information on the thermal ecology of freshwater fishes to assess the potential impact of climate change on wild populations of these organisms. Two primary questions are identified: (i) how do aquatic habitats change in response to atmospheric climate change? (ii) how do fish respond to habitat change at both the individual and population levels? In lakes, climate warming will lead to higher surface water temperatures, longer ice-free periods, and longer periods of thermal stratification. In rivers, climate warming will lead to higher groundwater temperatures with corresponding increases in both summer and winter temperatures, from headwaters to mouth. We describe several methods for predicting the biological effects of these changes in habitat. We examine the use of bioenergetic models to predict the impact of climate change on the growth of individual fish. We examine the use of thermal habitat models to assess the impact of climate change on population abundance. We examine the use of life cycle models to assess the impact of climate change on the zoogeographic distribution of species. Finally, we identify new research required to further develop these methods. 相似文献
15.
盆地中沉积地层具有明显的旋回性,对应不同的测井曲线特征,可以用它来进行层序地层划分。为降低在一个视觉层次上划分地层的人为主观性,使得层序地层单元的划分更加科学,将一维的测井曲线运用小波变换技术拓展为二维时频域,将不同时间( 深度) 尺度的沉积旋回清晰地展现出来。以梅河盆地钻井为例,选取a 值在0. 25 ～ 0. 5 amax区间利用小波时频能量图识别三—五级层序地层学单元特征明显。在小波时频能量图中,层序顶底高能量向中部减弱,进而划分出三级层序界面; 层序内部能量从向大尺度转移--向小尺度转移--趋于稳定--向大尺度转移,反映了体系域从低水位--水进－高水位--水退的垂向变化过程; 其内部每个小的能量团又可以看作是一个准层序。由此建立应用小波变换划分层序地层单元的模型,为层序地层学的定量划分提供了一种新手段。 相似文献
16.
3D geological models are created to integrate a set of input measurements into a single geological model. There are many problems with this approach, as there is uncertainty in all stages of the modelling process, from initial data collection to the approach used in the modelling scheme itself to calculate the geological model. This study looks at the uncertainty inherent in geological models due to data density and introduces a novel method to upscale geological data that optimises the information in the initial dataset. This method also provides the ability for the dominant trend of a geological dataset to be determined at different scales. By using self-organizing maps (SOM's) to examine the different metrics used to quantify a geological model, we allow for a larger range of metrics to be used compared to traditional statistical methods, due to the SOM's ability to deal with incomplete datasets. The classification of the models into clusters based on the geological metrics using k-means clustering provides a useful insight into the models that are most similar and models that are statistical outliers. Our approach is guided and can be calculated on any input dataset of this type to determine the effect that data density will have on a resultant model. These models are all statistical derivations that represent simplifications and different scales of the initial dataset and can be used to interrogate the scale of observations. 相似文献
17.
Challenges of analyzing multi-hazard risk: a review 总被引：9，自引：6，他引：3
Melanie S. Kappes Margreth Keiler Kirsten von Elverfeldt Thomas Glade 《Natural Hazards》2012,64(2):1925-1958
Many areas of the world are prone to several natural hazards, and effective risk reduction is only possible if all relevant threats are considered and analyzed. However, in contrast to single-hazard analyses, the examination of multiple hazards poses a range of additional challenges due to the differing characteristics of processes. This refers to the assessment of the hazard level, as well as to the vulnerability toward distinct processes, and to the arising risk level. As comparability of the single-hazard results is strongly needed, an equivalent approach has to be chosen that allows to estimate the overall hazard and consequent risk level as well as to rank threats. In addition, the visualization of a range of natural hazards or risks is a challenging task since the high quantity of information has to be depicted in a way that allows for easy and clear interpretation. The aim of this contribution is to give an outline of the challenges each step of a multi-hazard (risk) analysis poses and to present current studies and approaches that face these difficulties. 相似文献
18.
This study employed genetic adaptive neural networks in the classification of high-resolution satellite images from which data related to surface conditions in mountainous areas of Taiwan were derived. Principal component analysis was then used to extract factors associated with the threat of natural disaster, and logistic regression was used to compute the probability of disaster occurrence. Through field surveys, interviews with district officials and a review of relevant literature, the probability of a sediment disaster was estimated as well as the vulnerability of the villages concerned and the degree to which these villages were prepared, to construct a risk evaluation model. A geographic information system was used to plot regional risk maps as a means to enhance the safety of residents in the study area. The risk assessment model can be used by authorities to make provisions for high-risk areas, to reduce the number of casualties and social costs of sediment disasters. 相似文献
19.
The Southwest Florida Water Management District has implemented a management approach for unimpounded rivers that limits withdrawals to a percentage of streamflow at the time of withdrawal. The natural flow regime of the contributing river is considered to be the baseline for assessing the effects of withdrawals. Development of the percent-of-flow approach has emphasized the interaction of freshwater inflow with the overlap of stationary and dynamic habitat components in tidal river zones of larger estuarine systems. Since the responses of key estuarine characteristics (e.g., isohaline locations, residence times) to freshwater inflow are frequently nonlinear, the approach is designed to prevent impacts to estuarine resources during sensitive low-inflow periods and to allow water supplies to become gradually more uvailable as inflow increases. A high sensitivity to variation at low inflow extends to many invertebrates and fishes that move upstream and downstream in synchrony with inflow. Total numbers of estuarine-resident and estuarine-dependent organisms have been found to decrease during low-inflow periods, including mysids, grass shrimp, and juveniles of the bay anchovy and sand seatrout. The interaction of freshwater inflow with seasonal processes, such as phytoplankton production and the recruitment of fishes to the tidal-river nursery, indicates that withdrawal percentages during the springtime should be most restrictive. Ongoing efforts are oriented toward refining percentage withdrawal limits among seasons and flow ranges to account for shifts in the responsiveness of estuarine processes to reductions in freshwater inflow. 相似文献
20.
Izhak Schnell 《GeoJournal》2014,79(5):619-633
The paper is founded on the argument of moral geography on the one hand and Kolberg’s social-psychological theory of moral judgment in order to expose the ways Israelis morally judge the barrier with the Palestinian authority. I conclude that half of the secular Israelis who prove to make moral judgments based on universal criteria withdraw to more authoritative modes of moral judgment concerning the barrier. Legitimization of the barrier is based on dehumanization of the Palestinians. This trend is especially strong among rightists in the Israeli political spectrum who are more likely to withdraw to authoritative forms of moral judgment than leftists. Both rightists and leftists in Israel judge the moral dilemma based on values of human rights and safety. Rightists tend to emphasize the violent behavior of the Palestinians as a justification to the barrier. The worldview that allows for the withdrawal to authoritative moral judgments that justify the barrier tend to victimize the Israelis and dehumanize the Palestinians. Such a world view serves as a mean to maintain positive self image while managing a contractible conflict. 相似文献