带丁坝型半封闭矩形海湾中M_2分潮潮波和潮流特性分析

将黄渤海海域概化为矩形海湾,山东半岛概化为垂直于海岸的巨型丁坝,形成一个带丁坝型半封闭矩形海湾。利用DELFT3D-FLOW计算模块在上述海湾中进行了M2分潮数值模拟,对其无潮点和辐射状潮流场的特性进行了分析。研究发现:考虑科氏力影响和巨型丁坝反射作用,坝前形成了明显的无潮点,但在等水深条件下并未形成辐射状潮流场,而叠加上倾斜海底地形后其得以形成;无潮点和辐射状潮流场顶端位置受水深影响明显,随着平均水深的增大,无潮点将向湾口和湾中轴线方向偏移,而辐射状潮流场顶端则向湾口方向偏移。研究结果有助于加深对带丁坝型半封闭矩形海湾中驻潮波系统形成机制和动力特性的理解和认识。     

基于模糊物元模型的中国旅游生态安全评价及障碍因子诊断研究

基于DPSIR模型构建旅游生态安全评价指标体系,利用模糊物元模型对中国31个省(市、区)(不含港澳台)旅游生态安全进行动态评价,并运用空间自相关分析空间格局演化特征.同时借助障碍度模型,对旅游生态安全的障碍因子进行诊断.结果表明:①旅游生态安全呈现出波动增长的"W"型演化趋势.2013-2016年中国旅游生态安全在空间...     

岷江上游潜在性泥石流堰塞湖危害及判识

汶川地震造成泥石流形成条件的改变,其次生灾害堰塞湖的危害已开始显现。如何对震后潜在性泥石流堰塞湖进行判识,成为迫切需要解决的问题。选取岷江上游映秀至汶川段为研究区,通过分析震后泥石流形成条件的变化、典型泥石流堰塞湖的危害及松散物质储量,选取潜在性泥石流堰塞湖的判识指标,利用模糊物元可拓模型,建立潜在性泥石流堰塞湖的综合判识模式。通过判识,研究区形成泥石流堰塞湖可能性高的一级支沟有17条,主要集中分布在映秀镇至草坡乡段,此段将是今后受堰塞湖危害的高危地段。     

复膜沙袋阻沙体与芦苇高立式方格沙障防沙机理风洞模拟实验

模型按1:10比例尺设计,在u_∞=7.0 m·s^-1、u_∞=10.0 m·s^-1和u_∞=15.0 m·s^-1实验风速下,先在纯气流作用下测定流场结构,然后在风沙流作用下测定蚀积状况。实验结果表明:紧密型、疏透型和通风型3种不同结构的复膜沙袋阻沙体前近处分布有拐角阻滞绕流区、阻沙体顶下方抬升加速区、阻沙体后回流区、阻沙体后贴地层低速回流区等流场特征结构,紧密型、疏透型两种类型复膜沙袋阻沙体防风阻沙效果显著;2.5 m×2.5 m、5 m×5 m和10 m×10 m的高立式芦苇方格前沿流速逐渐增大,最大值出现于迎风第一格上空,而后逐渐阻滞减速,至15~20 m处趋于稳定,区内积沙均匀。复膜沙袋阻沙体与原状芦苇高立式方格沙障适宜于流动性沙漠地区各种设施的沙害防治工程。     

内蒙古流动沙地治理技术发展回顾

归纳总结了内蒙古防沙治沙技术发展历程,并按照时间顺序划分了群众经验总结阶段、试验与观测研究阶段、快速发展阶段和新发展阶段等4个阶段。重点介绍了8项典型沙障固沙技术和4项治沙造林配置模式等具体内容,展望了产业治沙技术模式、沙障新材料及其铺设装备以及沙障+乔灌草疏林型配置技术模式等流动沙地治理技术发展趋势。     

Long-term performance evaluation of zero-valent iron amended permeable reactive barriers for groundwater remediation – A mechanistic approach

Permeable reactive barriers (PRBs) are used for groundwater remediation at contaminated sites worldwide. This technology has been efficient at appropriate sites for treating organic and inorganic contaminants using zero-valent iron (ZVI) as a reductant and as a reactive material. Continued development of the technology over the years suggests that a robust understanding of PRB performance and the mechanisms involved is still lacking. Conflicting information in the scientific literature downplays the critical role of ZVI corrosion in the remediation of various organic and inorganic pollutants. Additionally, there is a lack of information on how different mechanisms act in tandem to affect ZVI-groundwater systems through time. In this review paper, we describe the underlying mechanisms of PRB performance and remove isolated misconceptions. We discuss the primary mechanisms of ZVI transformation and aging in PRBs and the role of iron corrosion products. We review numerous sites to reinforce our understanding of the interactions between groundwater contaminants and ZVI and the authigenic minerals that form within PRBs. Our findings show that ZVI corrosion products and mineral precipitates play critical roles in the long-term performance of PRBs by influencing the reactivity of ZVI. Pore occlusion by mineral precipitates occurs at the influent side of PRBs and is enhanced by dissolved oxygen and groundwater rich in dissolved solids and high alkalinity, which negatively impacts hydraulic conductivity, allowing contaminants to potentially bypass the treatment zone. Further development of site characterization tools and models is needed to support effective PRB designs for groundwater remediation.     

Are carbonate barrier islands mobile? Insights from a mid to late-Holocene system,Al Ruwais,northern Qatar

Barrier islands are important landforms in many coastal systems around the globe. Studies of modern barrier island systems are mostly limited to those of siliciclastic realms, where the islands are recognized as mobile features that form on transgressive coastlines and migrate landward as sea-level rises. Barrier islands of the ‘Great Pearl Bank’ along the United Arab Emirates coast are the best-known carbonate examples. These Holocene islands, however, are interpreted to be anchored by older deposits and immobile. The mid-Holocene to late-Holocene depositional system at Al Ruwais, northern Qatar, provides an example of a mobile carbonate barrier island system, perhaps more similar to siliciclastic equivalents. Sedimentological and petrographic analyses, as well as ¹⁴C-dating of shells and biogenic remains from vibracored sediments and surface deposits, show that after 7000 years ago a barrier system with a narrow back-barrier lagoon formed along what is now an exposed coastal zone, while, contemporaneously, a laterally-extensive coral reef was forming immediately offshore. After 1400 years ago the barrier system was forced to step ca 3 km seaward in response to a sea-level fall of less than 2 m, where it re-established itself directly on the mid-Holocene reef. Since that time, the barrier has retreated landward as much as 1000 m to its current position, exposing previously-deposited back-barrier lagoonal sediment at the open-coast shoreline. In modern neritic warm-water carbonate settings mobile barrier island systems are rare. Their construction and migration may be inhibited by reef formation, early cementation, and the relative inefficiency of sourcing beach sediments from open carbonate shelves. Carbonate barrier island systems likely formed more commonly during geological periods when ramps and unrimmed shelves predominated and in calcite seas, when meteoric cementation was minimized as a result of initial calcitic allochem mineralogy. As with their siliciclastic analogues, however, recognition of the influence of these transient landforms in the rock record is challenging.     

无机盐溶液作用下砂-膨润土竖向隔离屏障材料化学相容性试验研究

土-膨润土竖向隔离屏障广泛应用于城市工业污染场地。化学溶液作用下屏障材料的化学相容性,即渗透系数及其变化程度,是评价防污性能的关键因素。通过柔性壁渗透试验研究重金属铅-锌复合、六价铬作用下砂-膨润土竖向隔离屏障材料渗透系数的变化规律。由于无机盐溶液中铅、锌、钙对膨润土双电层的压缩,铅-锌复合、钙溶液作用下屏障材料试样渗透系数随金属浓度升高而增大。铅-锌复合作用下,金属浓度增至500mmol/L时试样渗透系数增幅达11倍,且无法满足防渗要求。相反,由于铬以阴离子络合形式存在,其对试样渗透系数影响相对小;与未污染状态测定结果相比,渗透系数增幅≤2倍。在膨润土孔隙比基础上,考虑无机盐溶液对膨润土膨胀特性的影响,建立无机盐溶液作用前后砂-膨润土竖向隔离屏障材料渗透系数统一预测方法。     

单一裂隙优势渗流对黏土层防渗性能的影响分析

垃圾填埋体不均匀沉降等容易引起压实黏土防渗层开裂,显著降低其防渗性能。将裂隙作为高渗透性的多孔介质材料,建立了含单一裂隙压实黏土层的饱和/非饱和渗流模型,数值研究了含裂隙黏土层中的优势渗流过程,对比分析了裂隙位置、深度、宽度和渗透系数对压实黏土层水分击穿时间和稳定渗漏量的影响。结果表明,含裂隙压实黏土层的渗流过程可分为3个阶段：初始阶段、击穿阶段和稳定阶段;底部裂隙对压实黏土层防渗性能的影响较小,而顶部裂隙和贯通裂隙的影响较大;水分击穿时间随裂隙深度增大而迅速缩短,为保证黏土层防渗性能,宜将裂隙深度控制在0.1倍土层厚度以内;水分击穿时间和稳定渗漏量随裂隙宽度、渗透系数的增大而分别缩短和增加,且当其达到一定值后逐渐趋于稳定;裂隙贯通后将显著降低压实黏土层的防渗性能,其稳定渗漏量随裂隙宽度和渗透系数的增大而呈线性增长。     

Permeable Reactive Barrier for Groundwater Pollution Remediation: An Review

As an in situ, simple and passive technology, Permeable Reactive Barrier (PRB) is becoming widely used in groundwater remediation. Based on its definition and development process, the development of PRB can be divided into two stages: The traditional zero-valent iron PRB before 2000 and the PRB composed of novel mixed media after 2000. With the rapid worsening of groundwater pollution, the increasing application of PRB and the rapid development of materials science, the development of PRB technology in future will be mainly focused on the investigation of mixed and novel media, the design of mixed PRBs, the combination of PRB technology with other remediation technology, and the long term monitoring and management of PRB projects.