深海氧同位素第3阶段晚期长江三角洲古环境初步研究   总被引：14，自引：9，他引：5  

杨达源  陈可锋  舒肖明 《第四纪研究》2004,24(5):525-530

深海氧同位素第3阶段(MIS3)晚期,世界气候比较温湿,世界海平面比现代海平面低约20～40m。但是在长江三角洲地区,出现了更新世以来的最大海侵。海侵沉积层在太湖渡村分布在海拔-2.5～-12.25m之间,属河口海湾沉积;在上海分布在海拔-32.3～-72.76m之间,属浅海沉积。对长江三角洲MIS3海侵沉积层进行构造运动校正之后,长江三角洲MIS3古海平面高程约为-10m左右,一般比世界海平面要高的多。文章认为MIS3晚期长江三角洲古海平面偏高可能与古太湖湾潮涌、长江古洪水有关,海侵沉积层顶面偏高可能还与水力均衡作用有关。  相似文献   

基于GIS的城市势力圈测度研究--以长江三角洲地区为例   总被引：10，自引：1，他引：9  

王桂圆  陈眉舞 《地理与地理信息科学》2004,20(3):69-73

该文以长江三角洲地区为例,运用多种模型,探讨基于GIS技术的城市势力圈的测度。结果表明,通过GIS技术可以实现城市势力圈分析、预测的可视化。通过GIS的各种分析工具,可以实现常规方法无法做到的功能扩展,对探讨城市发展演变规律、预测未来变动趋势能起到很好的辅助决策作用,有较强的应用价值。  相似文献   

珠三角流动人口社会融入与生活满意度期望     

罗利佳  周春山  吴沛钊 《世界地理研究》2020,29(3):608-620

近年来有关流动人口社会融入和生活满意度的研究成为我国学者广泛关注的研究主题，较高的社会融入水平已成为流动人口获得生活满意度的根本。基于珠三角流动人口问卷调研数据建立两个结构方程模型，探究社会融入各维度及其影响因素的路径效应，进一步分析社会融入如何影响流动人口实现“生活满意度期望”，即感受到本地生活满意度高于老家的路径机制。结果显示：珠三角地区社会融入可分为经济融入和非经济融入两部分，但经济融入的基础作用不凸显；个体、家庭与制度等因素对社会融入各维度存在较大影响差异；社会融入影响“生活满意度期望”可归纳为“经济融入-生活满意度期望”的直接影响路径和“非经济融入-生活满意度-生活满意度期望”的间接影响路径；提高流动人口市民化和社会融入水平，不仅要关注流动人口的经济收入问题，还应注重流动人口与本地人邻里关系建设，以形成良性的城市更新与和谐的社区环境。  相似文献   

Tracing clinothem geometry and sediment pathways in the prograding Holocene Po Delta system through integrated core stratigraphy     

Alessandro Amorosi  Luigi Bruno  Bruno Campo  Bianca Costagli  Enrico Dinelli  Wan Hong  Irene Sammartino  Stefano Claudio Vaiani 《Basin Research》2020,32(2):206-215

Though clinothem geometry represents a key control on fluid flow in reservoir modelling, tracing clinothem boundaries accurately is commonly limited by the lack of sufficiently precise outcrop or subsurface data. This study shows that in basin systems with strongly heterogeneous compositional signatures, the combination of bulk-sediment geochemistry and benthic foraminiferal distribution can help identify clinothem architecture and generate realistic models of 3D deltaic upbuilding and evolution. Middle-late Holocene deposits in the Po Delta area form an aggradational to progradational parasequence set that reveals the complex interaction of W–E Po Delta progradation, S-directed longshore currents (from Alpine rivers) and Apennines rivers supply. Unique catchment lithologies (ophiolite rocks and dolostones) were used to delineate basin-wide geochemical markers of sediment provenance (Cr and Mg) and to assess distinctive detrital signatures. The geochemical characterization of cored intervals across different components of the sediment routing system enabled a direct linkage between clinothem growth, transport pathways and provenance mixing to be established. On the other hand, abrupt microfaunal variations at clinothem boundaries were observed to reflect the palaeoenvironmental response to sharp changes in sediment flux and fluvial influence. This study documents the ability of an integrated geochemical and palaeoecological approach to delineate three distinct sources (Po, Alps and Apennines) that contributed to coastal progradation and to outline the otherwise lithologically cryptic geometries of clinothems that using conventional sedimentological methods it would be virtually impossible to restore.  相似文献   

Naturalizing the freezeup regimes of regulated rivers and exploring implications to spring ice-jam flooding     

Spyros Beltaos  Daniel L. Peters 《水文研究》2021,35(8):e14321

Naturalization of the flow hydrograph and ice regime is a key step in assessment of ecological and socioeconomic impacts of regulation across large portions of Europe, Asia and North America, where many rivers are dammed for hydropower generation. Building on previous naturalization of early-freshet flows that influence the nature of breakup and jamming events, novel methodology is developed to estimate natural freezeup flows and thence determine associated water levels, also known to influence subsequent breakup events. Using reservoir inflows, the new methodology is applied to the lower portion of the regulated Peace River, Canada, which forms the northern boundary of the Peace-Athabasca Delta (PAD), a Ramsar wetland of international importance that partially depends on spring ice-jam flooding for recharge of its high-elevation, or “perched” basins. The PAD provides habitat for numerous aquatic, terrestrial and avian species and is vital to the maintenance of indigenous culture and lifeways. Naturalized freezeup levels in the lower Peace River are shown to be nearly always lower than corresponding regulated values, with the difference averaging ~1.6 m. Consistent with known physics of river ice breakup processes, the present results suggest that ice-jam flood frequency would likely have been greater under natural conditions. Though potentially adverse from the ecological standpoint, reduction of spring ice-jam flooding can benefit riverside communities. Implications of the present results to and comparison with, other Canadian and international rivers are discussed.  相似文献   

Effects of Social Learning on Rural Farmers’ Adaptive Capacity: Empirical Insights from the Vietnamese Mekong Delta     

Thong Anh Tran  Helen James  Dang Kieu Nhan 《社会与自然资源》2020,33(9):1053-1072

Abstract

Environmental challenges in the Vietnamese Mekong Delta characterized by adverse impacts of climate change, upstream hydropower development and localized dyke expansion present imperatives for rural farmers to “learn to adapt.” However, little is known about how learning contributes to improving their capacity in adapting to these “wicked” problems. This study investigates potential effects of farmers’ learning on their adaptive capacity, utilizing nine focus group discussions, 33 interviews, and a structured survey of 300 farmers. The exploratory factor analysis produced two factors for social learning: (1) learning through social interactions and (2) self-reflection, and one factor for adaptive capacity. The regression results show that the social learning factors have significantly positive effects on adaptive capacity. Farmers with a higher level of social learning are likely to demonstrate higher adaptive capacity. The findings call for policy considerations to promote learning in a broader context of the delta to enhance local capacity.  相似文献   

长江三角洲近46a气温和降水的变化趋势   总被引：2，自引：0，他引：2  

潘敖大  王珂清  曾燕  谢志清  苗茜 《南京气象学院学报》2011,34(2):180-188

利用长江三角洲地区84个气象站观测数据,分析了长江三角洲1961—2006年气温和降水的时空变化趋势。结果表明,46a间长江三角洲地区年平均气温上升趋势显著,冬季平均气温的增温幅度最大,春、秋次之。增温显著区域与城市带分布区域吻合。极端最低气温有明显上升,而年极端低温事件日数的下降趋势显著。部分地区的极端最高气温呈上升趋势,在城市密集带尤为突出。年降水量没有明显的变化趋势,但降水的季节分配有所变化,冬、夏季降水量呈现显著上升趋势,秋季降水量明显下降,春季没有明显变化。  相似文献   

Dispersal of Mississippi and Atchafalaya sediment on the Texas-Louisiana shelf: Model estimates for the year 1993   总被引：1，自引：0，他引：1  

Kehui Xu  Courtney K. HarrisRobert D. Hetland  James M. Kaihatu 《Continental Shelf Research》2011,31(15):1558-1575

A three-dimensional coupled hydrodynamic-sediment transport model for the Texas-Louisiana continental shelf was developed using the Regional Ocean Modeling System (ROMS) and used to represent fluvial sediment transport and deposition for the year 1993. The model included water and sediment discharge from the Mississippi River and Atchafalaya Bay, seabed resuspension, and suspended transport by currents. Input wave properties were provided by the Simulating WAves Nearshore (SWAN) model so that ROMS could estimate wave-driven bed stresses, critical to shallow-water sediment suspension. The model used temporally variable but spatially uniform winds, spatially variable seabed grain size distributions, and six sediment tracers from rivers and seabed.At the end of the year 1993, much of the modeled fluvial sediment accumulation was localized with deposition focused near sediment sources. Mississippi sediment remained within 20-40 km of the Mississippi Delta. Most Atchafalaya sediment remained landward of the 10-m isobath in the inner-most shelf south of Atchafalaya Bay. Atchafalaya sediment displayed an elongated westward dispersal pattern toward the Chenier Plain, reflecting the importance of wave resuspension and perennially westward depth-averaged currents in the shallow waters (<10 m). Due to relatively high settling velocities assumed for sediment from the Mississippi River as well as the shallowness of the shelf south of Atchafalaya Bay, most sediment traveled only a short distance before initial deposition. Little fluvial sediment could be transported into the vicinity of the “Dead Zone” (low-oxygen area) within a seasonal-annual timeframe. Near the Mississippi Delta and Atchafalaya Bay, alongshore sediment-transport fluxes always exceeded cross-shore fluxes. Estimated cumulative sediment fluxes next to Atchafalaya Bay were episodic and “stepwise-like” compared to the relatively gradual transport around the Mississippi Delta. During a large storm in March 1993, strong winds helped vertically mix the water column over the entire shelf (up to 100-m isobath), and wave shear stress dominated total bed stress. During fair-weather conditions in May 1993, however, the freshwater plumes spread onto a stratified water column, and combined wave-current shear stress only exceeded the threshold for suspending sediment in the inner-most part of the shelf.  相似文献   

A Monte-Carlo game theoretic approach for Multi-Criteria Decision Making under uncertainty   总被引：2，自引：0，他引：2  

Kaveh Madani  Jay R. Lund 《Advances in water resources》2011,34(5):607-616

Game theory provides a useful framework for studying Multi-Criteria Decision Making problems. This paper suggests modeling Multi-Criteria Decision Making problems as strategic games and solving them using non-cooperative game theory concepts. The suggested method can be used to prescribe non-dominated solutions and also can be used as a method to predict the outcome of a decision making problem. Non-cooperative stability definitions for solving the games allow consideration of non-cooperative behaviors, often neglected by other methods which assume perfect cooperation among decision makers. To deal with the uncertainty in input variables a Monte-Carlo Game Theory (MCGT) approach is suggested which maps the stochastic problem into many deterministic strategic games. The games are solved using non-cooperative stability definitions and the results include possible effects of uncertainty in input variables on outcomes. The method can handle multi-criteria multi-decision-maker problems with uncertainty. The suggested method does not require criteria weighting, developing a compound decision objective, and accurate quantitative (cardinal) information as it simplifies the decision analysis by solving problems based on qualitative (ordinal) information, reducing the computational burden substantially. The MCGT method is applied to analyze California’s Sacramento-San Joaquin Delta problem. The suggested method provides insights, identifies non-dominated alternatives, and predicts likely decision outcomes.  相似文献   

珠江三角洲地区全新世以来的沉积速率与沉积环境分析   总被引：3，自引：0，他引：3  

韦惺  莫文渊  吴超羽 《沉积学报》2011,29(2):328-335

为了探讨全新世以来珠江三角洲沉积演变的时空变化特征,将全新世珠江三角洲划分为4个阶段、12个区域,并根据92个钻孔,分别统计计算了不同阶段和区域的沉积速率。研究表明:（1）珠江三角洲在全新世4个阶段中的平均沉积速率有较大变幅,其中在10.0~7.5 ka BP最小,仅为1.27 mm/a,在7.5~5.0 ka BP阶段最大,为2.34 mm/a。这主要受沉积基底地形、海平面上升所引起的沉积空间的差异性所导致;（2）距今2 500年以来虽然由于人类活动频繁使珠江来沙量增多,但由于河湾中河道的形成、束窄,沉积物被输运到外海的比例不断增加,使得该时期平均沉积速率并不是全新世各期中最大;（3）由于三角洲复杂边界对河流和海洋动力的改造和重塑,高海面期三角洲的沉积中心同时分布在中部不同区域。表明三角洲的进积模式不同于其它大型三角洲——三角洲的发育并非单一自河口向外海逐渐发展,而是不同区域的沉积体同时多向发育。  相似文献