水利工程对南四湖现代沉积速率的影响

利用放射性同位素(137Cs、210Pb)测年法计算山东省南四湖的沉积速率,采用高纯锗γ谱仪(美国EG&G ORTEC公司)对南四湖上级湖、下级湖的沉积岩柱(DS2和WS2)样品进行137Cs、210Pb放射性活度测试,分析水利工程建设对湖泊沉积影响的程度与后果. 结果表明:上级湖、下级湖137Cs总蓄积量之比为9.7,说明在二级坝水利工程影响下,流域内侵蚀泥沙及其所吸附的137Cs主要沉积于上级湖;137Cs在湖泊沉积物中的剖面分布与137Cs大气沉降时序的分布模式相背离,故137Cs蓄积峰不具备时标意义. 利用210Pb计年的CRS(恒定补给速率)模式分析2个沉积岩柱不同质量深度所对应的年代,结果显示,150多年来南四湖上级湖、下级湖的沉积速率不稳定,以1960年为界划分为两大时段:沉积岩柱底部所对应的年代至1960年,上级湖、下级湖沉积速率平均值分别为0.069、0.160 g/(cm2·a);1960—2010年,二者沉积速率平均值分别为0.218、0.072 g/(cm2·a). 可见,二级坝水利工程对南四湖沉积速率产生了重要影响,210Pb计年的CRS模式分析结果可靠.      

全尾砂絮凝沉降参数GA-SVM优化预测模型研究

为了得到经济、高效的絮凝沉降参数,建立GA_SVM预测模型进行优化选择。在优选过程中,以供砂浓度、絮凝剂单耗和絮凝剂添加浓度作为输入因子,以沉降速度作为综合输出因子,通过室内试验,建立训练、验证样本集;建立支持向量机（SVM）回归预测模型,用训练集对模型进行训练,进而以验证集预测值的均方误差作为适应度函数,通过遗传算法（GA）对SVM模型参数进行优化选择,应用优化得到的SVM模型对絮凝沉降参数进行预测、优化。以湖南某铅锌银矿为例,通过建立的GA_SVM模型对全尾砂絮凝沉降参数进行预测,优选出该矿最佳絮凝沉降参数为:供砂浓度20%-25%,絮凝剂单耗8g/t,添加浓度009%。经实验对比,该模型对絮凝沉降参数预测结果的相对误差能控制在5%左右,精确度较高,可以作为絮凝沉降参数优选的一种新思路     

Classification of residential areas according to physical vulnerability to natural hazards: a case study of Çanakkale,Turkey

The selection of new settlement areas and the construction of safe buildings, as well as rendering built‐up areas safe, are of great importance in mitigating the damage caused by natural disasters. Most cities in Turkey are unprepared for natural hazards. In this paper, Çanakkale, located in a first‐degree seismic zone and sprawled around the Sartçay Delta, is examined in terms of its physical vulnerability to natural hazards. Residential areas are analysed using GIS (geographic information system) and remote‐sensing technologies in relation to selected indicators. Residential areas of the city are divided into zones according to an evaluation of geological characteristics, the built‐up area's features, and urban infrastructure, and four risk zones are determined. The results of the analysis show that the areas of the city suitable for housing are very limited. In addition, the historical centre and the housing areas near Sartçay stream are shown to be most problematic in terms of natural disasters and sustainability.     

巴东文家滑坡岩土体物理力学性质分析评价

依据文家滑坡的地质勘查成果,对其滑体、滑带、滑床等岩土体物理力学性质,特别对C、φ值的取定进行了分析评价,力求为滑坡稳定性分析及后期防治工程设计提供科学合理的依据.     

二氧化钛颗粒的制备及其脱硫吸附性能

采用溶胶-凝胶法(Sol-gel)在不同烧结温度(340℃,440℃,540℃,640℃)下制备了4种多孔TiO₂颗粒,X射线衍射法(XRD)测得4种样品的晶相均为锐钛矿型.低温77K氮气吸附法计算4种样品的比表面积为79～124m²/g,平均孔径56.8～254.8 A.电子扫描电镜分析了样品的表面结构为多孔高孔隙率结构在固定床中对4种样品进行动态脱硫试验,试验结果表明烧结温度在540℃时制备的样品品质较好,每g TiO₂颗粒可吸附38.9mg的SO₂.以SG 540样品为例,研究了固定床中吸附温度,气相中SO2的浓度以及气体流速对其脱硫吸附性能的影响.与活性炭、沸石物理吸附剂比较,TiO₂颗粒具有较高的脱硫吸附能力.FTIR红外光谱分析法,结合加热脱附试验的结果,得知TiO₂颗粒吸附剂脱硫的机理主要是物理吸附.     

再生水补给型城市景观水体的水生生物群落特征—以圆明园为例

为了解圆明园水环境生态和生物多样性现状,掌握圆明园生态修复区长期恢复状况,于2017年对圆明园水系末端长春园开展水质、大型水生植物、蜻蜓目(Odonata)昆虫、鱼类(Piscium)和软甲动物(Malacostraca)的调查.结果表明:圆明园经过园区内水生生物群落的净化作用,水质基本达到地表Ⅲ类～Ⅳ类水体标准,属于...     

Effects of alfalfa coverage on runoff, erosion and hydraulic characteristics of overland flow on loess slope plots

An evaluation of the interactions between vegetation, overland and soil erosion can provide valuable insight for the conservation of soil and water. An experiment was conducted to study water infiltration, runoff generation process, rate of sediment erosion, and hydrodynamic characteristics of overland flow from a sloping hillside with different draw-off discharges from alfalfa and control plots with 20° slope. The effect of alfalfa on runoff and sediment transport reduction was quantitatively analyzed. Alfalfa was discussed for its ability to reduce the overland flow scouring force or change the runoff movement. Compared to the bare-soil plots, alfalfa plots generated a 1.77 times increase in infiltration rate. Furthermore, the down-slope water infiltration rate for the bare soil plots was higher than in the up-slope, while the opposite was found in the alfalfa plots. In addition, alfalfa had a significant effect on runoff and sediment yield. In comparison to the control, the runoff coefficient and sediment transportation rate decreased by 28.3% and 78.4% in the grass slope, respectively. The runoff generated from the alfalfa and bare-soil plots had similar trends with an initial increase and subsequent leveling to a steady-state rate. The transport of sediment reduced with time as a consequence of the depletion of loose surface materials. The maximum sediment concentration was recorded within the first few minutes of each event. The alfalfa plots had subcritical flow while the bare-soil plots had supercritical flow, which indicate that the capability of the alfalfa slope for resisting soil erosion and sediment movement was greater than for bare soil plots. Moreover, the flow resistance coefficient and roughness coefficient for the alfalfa plots were both higher than for the bare-soil plots, which indicate that overland flow in alfalfa plots had retarded and was blocked, and the flow energy along the runoff path had gradually dissipated. Finally, the ability to erode and transport sediment had decreased.     

浅析混凝沉降实验研究与实际工艺的差异

介绍混凝沉降实验与实际沉降工艺各自的特点和存在的问题,从相似理论的角度出发,指出了玻璃量筒沉降实验和实际沉降工艺存在着几何尺寸、初始条件、运动条件三方面的不相似,较好地解释了两者的沉降速度和沉降效果的差异;并提出今后的混凝沉降实验应该进一步符合相似理论,从而更加合理地模拟实际沉降工艺.     

植被根系及其土壤理化特征在高寒小嵩草草甸退化演替过程中的变化

以野外样地调查和室内分析法研究了不同退化演替阶段高寒小嵩草草甸的植被根系空间变化和土壤环境因子间的关系。结果表明,不同退化演替阶段高寒小嵩草草甸群落植被根系和蕴育植被根系的土壤量发生了明显的变化。特别是0~10 cm土层的植被根系在重度退化阶段显著高于其它退化演替阶段（P〈0.05）,而蕴育植被根系的＂载体＂量在重度退化阶段显著低于其它退化演替阶段（P〈0.05）,根土比（根和土的重量比）明显高于其它退化演替阶段（P〈0.05）;随着退化演替阶段的进行,高寒小嵩草草甸群落物种数、地上部分、植被根系锐减,群落结构和功能明显发生变化;不同退化演替阶段,植被根系（0~40 cm）的垂直分布、根土比与土壤容重、土壤含水量以及土壤中N、P含量存在一定的相关性;不同退化演替阶段高寒小嵩草草甸土壤理化特性的变化影响草地群落地上部分和植被根系;土壤的稳定性是草地生产稳定和恢复的重要因素,在评价与改良退化草地时,要充分了解土壤的退化程度。在高寒草甸地下根系取样方法难以统一,而且土壤表层根系和土壤很难难以分离,加之根系采样破坏性大、工作量大,根土比可能是指示高寒草甸退化程度相对可靠的量化指标。     

黄土丘陵区生物结皮对土壤物理属性的影响

生物结皮在干旱、半干旱地区广泛发育。迄今,有关生物结皮发育过程中土壤物理属性的响应仍不明确。论文采用野外调查与室内分析相结合的方法,定量研究不同生物量生物结皮对土壤物理属性的影响。结果表明:①生物结皮的发育能够细化土壤,当生物结皮由初期藻结皮演替至60%~80%苔藓结皮时(5等级),生物结皮层粗砂粒含量降低了86%;②随着生物结皮生物量的增加,生物结皮层土壤容重和硬度较初期分别降低了15%和68%,田间持水量和孔隙度分别增加了36%和14%;生物结皮层粘结力是下层土壤的6~7倍;③生物结皮的发育对土壤物理属性的影响与生物量有关,当苔藓生物量达2.91±0.12 g/dm²时,其土壤物理属性基本稳定。研究结果为揭示生物结皮抗侵蚀机理提供了科学参考。