长江三角洲21世纪食物保障问题及对策

近年来,长江三角洲粮油等主要食物的供需平衡比较困难,其它食物生产存在一些问题,保障食物供给已成为长江三角洲可持续发展的重要问题之一。文章分析了长江三角洲食物保障的现状、问题,并重新构建了长江三角洲的食物保障体系,对确保长江三角洲可持续发展的食物供给有重要的意义。     

黄河三角洲地区防潮工程建设标准分析

黄河河口三角洲海岸线较长,石油、盐卤业及养殖业开发等经济发展对防潮工程提出了新的要求,现防潮工程建设已不能适应当地经济发展。在研究防潮保护区各防护对象具体情况的基础上,按照国家《防洪标准》,并考虑当地经济的发展,综合确定了各岸段堤防的防潮标准及建筑物级别。     

黄河三角洲地区水资源利用研究

黄河河口三角洲地区具有丰富的土地后备资源 ,是我国土地资源开发潜力较大的地区之一 ,但黄河水资源的可供水量有限 ,尤其是近年来深受黄河断流影响之苦。研究黄河河口三角洲水资源利用具有重要的意义。通过对黄河河口三角洲的水土资源条件和开发利用现状的分析 ,研究了河口地区的来水量 ,在此基础上 ,对河口地区的水资源开发利用方案进行了研究。文中建议河口地区的黄河可供水量为 7.8× 1 0 8m3/ a,此量既可以满足河口地区社会经济发展的需水要求 ,又可以保证河口地区的生态环境和所需输沙入海水量。     

Stratigraphic signatures due to flood deposition near the Rhône River: Gulf of Lions,northwest Mediterranean Sea

Episodic flood delivery provides the bulk of the solid discharge for many small to moderate river systems, including the Rhône River in the northwestern Mediterranean. Several recent studies have demonstrated that the fate of this sediment depends on the coherence between river discharge and energetic ocean conditions. The deposition of flood sediment in the ocean can be confirmed by common signatures of episodic discharge events: presence of ⁷Be, physical stratification, and elevated clay content associated with low ²¹⁰Pb activities.     

The thin blue line: A review of shoreline dynamics across time scales and environments

A major thread of theoretical research on the response of shorelines to changing boundary conditions has adapted the moving-boundary approach from heat transfer and solidification/melting. On sufficiently short time scales, shorelines respond to changes in relative sea level in a simple, geometrically predictable way. On longer time scales, their behaviour becomes far more complex and interesting, because the surface over which the shoreline moves is itself continually modified by morphodynamics that depend sensitively on shoreline location. This makes the shoreline the archetype of moving-boundary problems in morphodynamics, and subject to potentially counterintuitive behaviours over time scales on which the sediment surface modifies itself as relative sea level changes. We review existing moving-boundary theories and propose two significant extensions to allow inclusion of first-order effects of waves and tides. First, we show how wave effects can be included via planform diffusion linked to river-mouth location, which results in shoreline smoothing during delta-lobe growth and localized transgression after channel abandonment. Tides produce a low-gradient region in which the sea and land overlap; we show how this can be treated in a moving-boundary framework by replacing the shoreline with a ‘mushy region' so that the handoff from land to water occurs over a zone rather than a line. We also propose that the moving-boundary approach can be readily generalized to other dynamic moving boundaries, such as those separating different regimes of river transport. The shoreline thus serves as a prototype for modelling dynamic facies boundaries along the whole source–sink system. © 2019 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

Delta size and plant patchiness as controls on channel network organization in experimental deltas

Understanding the feedbacks between water, sediment, and vegetation in deltas is an important part of understanding deltas as ecomorphodynamic systems. We conducted a set of laboratory experiments using alfalfa (Medicago sativa) as a proxy for delta vegetation to investigate: (1) the effects of plants on delta growth and channel network formation; and (2) the timescales controlling delta evolution in the presence of plants. Experiments were conducted with fluctuating discharge (i.e. flood and base flow periods) and variable seeding densities. We found that when deltas were small, channels had no memory across flood cycles, as floods could completely fill the incised channel network. When deltas were large, the larger channel volume could remain underfilled to keep channel memory. Plant patches also helped to increase the number of channels and make a more distributive network. Patchiness increased over time to continually aid in bifurcation, but as vegetation cover and patch sizes increased, patches began to merge. Larger patches blocked the flow to enhance topset deposition and channel filling, even for the case of large deltas with a high channel volume. We conclude that both plant patchiness and delta size affect the development of the channel network, and we hypothesize that their influences are manifested through two competing timescales. The first timescale, T_v, defines the time when the delta is large enough for channels to have memory (i.e. remain underfilled), and the second, T_p, defines the time when vegetation patches merge, amplifying deposition and blocking channels. When run time is between these two timescales, the delta can develop a persistent distributary network of channels aided by bifurcation around plant patches, but once T_p is reached, the channel network can again be destroyed by vegetation. © 2018 John Wiley & Sons, Ltd.     

基于计算机断层扫描技术重构三维生物扰动构造——以长江口现代沉积为例

生物扰动作用能够加速水层与底质的物质交换,对水层和底质的耦合作用有着重要的影响。受限于观测手段和观测方法,当前对于生物扰动构造的研究多停留在定性-半定量化的阶段。本文选取长江口现代沉积区的4个沉积物柱状样,利用计算机断层扫描技术对生物扰动构造进行三维重构,运用数字图像处理实现生物扰动强度的定量表征,对研究区域生物扰动构造发育的影响因素进行初步分析。结果表明：CT（computed tomography）值与沉积物粒级构成和含水率具有一定关系,能够较好地指示沉积物密度变化;该区出现挖掘构造、觅食虫孔构造、逃逸虫孔构造、生物遗迹构造等显性扰动构造类型,生物扰动强度介于0%-10%,扰动强度极大值出现在长江水下三角洲前三角洲和陆架过渡区,垂向上以及不同站位生物扰动构造差异显著;底质沉积物类型、上覆水团性质以及沉积速率是影响该区生物扰动构造发育的主要因素。     

济阳坳陷牛庄洼陷沙三段三角洲前缘浊积岩特征

根据地质、测井、地震资料的综合分析,对济阳坳陷牛庄洼陷沙河街组三段三角洲前缘的浊积岩特征进行了研究。结果表明,该区存在砂质浊积岩体和细粒浊积岩体两种浊流沉积物。其中砂质浊积岩体粒度较细、结构成熟度和成分成熟度较低,结构和构造均反映了砂体具有滑塌再沉积的特点,可用Bouma序列来描述,常发育CDE,BCD,ABCD型浊流组合。砂质浊积岩体可进一步划为有根式和无根式两类。有根式砂体常呈扇形,可分为内扇槽道、中扇辫状水道、水道间、水道前缘和外扇无水道五种微相;无根式砂体常呈片状、舌状,可分为中心微相和边缘微相两个相带。细粒浊积岩属于低密度流的产物,不能用Bouma序列来解释,主要发育递变纹层泥岩和不均匀的块状泥岩两种细粒浊积岩。根据两类沉积物的沉积特征,建立了该区三角洲一浊积岩体综合沉积模式。论述了三角洲前缘浊积岩的成因及石油地质意义。     

珠江三角洲与外围地区的整合模式研究

分析了珠江三角洲与外围地区整合基础、整合条件、整合动因,提出了整合模式。珠江三角洲与外围地区在自然地理上紧密相关,历史上相互影响深刻,在地域上相连且同处中国华南核心-边缘结构之下;资源、产业及商品互补性强,改革开放20年其可达性大大改善,经济联系强度迅猛增长,两者具备整合的基础和条件。两区域整合,需充分重视市场力与政府力;极化效应与扩散效应;区域政策、交通、城镇体系、产业等多层次动力机制的结合在区域整合中的作用。应以注重效率、重视可持续性和兼顾公平,以倾斜式整合发展为区域整合目标,实施区域整合的六大模式。