流态化多级速度梯度混凝反应对絮体的保护作用

多级速度梯度的建立理论上可为絮体的成长创造更理想的环境。目前对流化床混凝工艺的研究多是基于单级速度梯度开展的。以粒径为800 μm 和1 200 μm的树脂颗粒为固相,建立多级速度梯度流化床混凝装置,探讨絮体的成长与形态特征。研究结果表明：在单级速度梯度流化床混凝装置中,当以1 200 μm树脂颗粒为固相颗粒、混凝时间为50.3 s时,絮体发生破碎,混凝效率较混凝时间为41.8 s时降低3%;相同初始填充高度的多级速度梯度条件下,絮体尺寸随着混凝时间的延长而逐渐增加,由5.7 μm成长至70.0~75.0 μm,同时混凝效率也较单级速度梯度下提高了5%~10%。絮体之间的碰撞为絮体成长的主要模式。     

大气水汽变化及其反馈效应研究进展

大气水汽变化的反馈作用是影响平衡气候系统敏感性的最大反馈作用之一,能够放大其他温室气体增暖的效应,并可能导致极端天气气候事件的发生趋多趋强。因此,全面分析大气水汽的时空分布特征及其长期变化趋势,评估大气水汽反馈的区域气候效应,对于我们深入认识和理解全球变暖背景下区域气候响应的机理具有重要意义。综合国内外最新研究,已基本能够确定水汽反馈效应为一种使得全球增暖加快近一倍的强烈正反馈,并已能够估计其大致变化范围,但是此估计仍存在较大不确定性。随着卫星和探空技术的发展,目前已有的长期水汽资料日趋丰富,但资料之间也存在一些不确定性问题,同时单个资料本身也存在非均一性问题。最新的气候系统模式已能够大致模拟大气水汽的反馈效应,但近年的进展速度却并不令人乐观。我国的水汽观测和水汽反馈效应的研究也已取得长足进步,可以基本确定为水汽变化与地面温度存在正反馈关系,而与降水的关系虽然也较为密切,但因区域气候变化仍存在较大的不一致性。     

平面应变下结构性对黄土基坑稳定性的影响

鉴于以往很少考虑黄土结构性对基坑开挖的影响,针对目前普遍存在的基坑稳定性问题,开展室内平面应变条件下的真三轴试验,建立黄土结构性与强度之间关系,通过FISH语言将其引入到基坑开挖数值模拟中,分析结构性对基坑开挖的影响。研究表明,结构性参数与强度指标的变化规律与以往研究结果基本一致,表现为结构性参数与黏聚力呈双曲线关系,但参数略有不同,其受摩擦角的影响较小;结构性影响下基坑侧壁出现明显滑带,且此时连续墙的侧向位移大于不考虑其影响时的位移,坑底隆起量亦如此。研究结果对黄土基坑工程的设计和施工具有一定的指导意义。     

基于黏性土分散机制的分散性土化学改性研究

分散性土具有遇水易分散的特性,可导致堤坝等水利工程的冲蚀破坏。基于黏性土分散机制的研究,选用AlCl3• 6H2O、MgCl2•6H2O、CaCl2及CaO作为分散性土的化学改性材料,采用针孔试验和碎块试验对其改性效果进行判别和比较。试验表明,上述改性材料均可将分散性土改性为非分散性土,显著提高土体的抗冲蚀能力。结果说明：在分散性土中掺加高价态阳离子的可溶性盐,通过置换土粒表面钠离子或降低土体碱性,减小颗粒扩散层的厚度,可抑制土体的分散性,从而达到改性的目的;根据黏性土分散机制以及改性试验结果,提出了分散性土化学改性的原则,即改性材料中含有高价态的可溶性阳离子,或改性材料呈酸性,且环境友好,价格低廉,施工方便。     

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盐城候鸟栖息地岸线变化特征及其对候鸟栖息地影响

近年来,黄（渤）海候鸟栖息地侵蚀严重,岸线分布变化迅速,这对海岸带生态与经济带来了挑战。本文基于2013—2022年8期Sentinel-2及Landsat 8多源卫星遥感影像,利用人机交互方法解译提取候鸟栖息地岸线,通过ArcGIS平台数字岸线分析系统（Digital Shoreline Analysis System, DSAS）将岸线数字化,计算得到年际与年内岸线变迁时空分布,并探讨了蚀淤变化的成因及影响。结果表明：2014—2022年候鸟栖息地侵蚀特征由原先的侵蚀范围广但侵蚀速率小,转变为侵蚀范围集中且侵蚀速率大幅增加,侵蚀危害严重加剧。侵蚀集中在春季及夏季。研究区域岸线变迁受到多种因素的综合影响,包括泥沙来源、近岸海流、沿岸地物类型、人工建筑及风暴潮等。明确近年候鸟栖息地重点侵蚀岸段动态变化并分析其成因,对当地海岸带的生态经济保护及管理具有重要意义。     

工程物探在岩溶地区地质勘察中的应用——以费县电厂为例

结合费县电厂工程地质条件,运用高密度电阻率法和探地雷达勘察法,进行岩溶地区工程勘察,对2种方法的勘察结果进行比较分析,在此基础上进一步钻探验证。证实工程物探能迅速查明岩溶区的工程地质条件,勘察过程高效快速,达到地质勘察效果。最后针对岩溶区的拟建场地进行地基评价并提出地基处理方案。     

Evaluation of the presence of major anionic surfactants in marine sediments

The contamination of aquatic environments has become the focus of increasing regulation and public concern due to their potential and unknown negative effects on the ecosystems. The present work develops a monitoring and statistical study, based on the analysis of variance test (ANOVA) and the multivariable analysis, both for insoluble soap and LAS in order to compare the behavior of different anionic surfactants in this environmental compartment. First, a novel and successfully validated methodology to analyze insoluble soap in these samples is developed. The matrix effect and the comparison of different extraction techniques were also performed. The optimized analytical methodologies were applied to 48 representative samples collected from the Almeria Coast (Spain) and then a statistical analysis to correlate anionic surfactant concentration and several variables associated with marine sediment samples was also developed. The results obtained showed relevant conclusions related to the environmental behavior of anionic surfactants in marine sediments.     

Residues and sources recognition of polychlorinated biphenyls in surface sediments of Jiaojiang Estuary, East China Sea

Twenty-three surface sediment samples were collected from Jiaojiang Estuary, East China Sea in order to assess the distribution, possible sources, and potential risk of polychlorinated biphenyls (PCBs) in the environment. Total concentrations of PCBs ranged from 4.93 to 108.79 ng g(-1) dry weight for all sampling stations, with a substantial higher concentration in the inner part of the estuary than the outer part of the estuary. PCB patterns in sediments from sites 1-8 were extremely dominated by tetra-PCBs, which probably due to the discharge of local industrial plants but not the expected input from the nearby e-waste recycling areas. Principal component analysis revealed that the sources of PCBs for sites 9-23 were associated with Aroclor 1248 or Aroclor 1221. However, physical migration and bio-degradation may also play a role on PCB distribution. Hazard assessment of PCBs indicated possible toxic potential, particularly in areas close to point sources.