Cutting of Phragmites australis as a lake restoration technique: Productivity calculation and nutrient removal in Wuliangsuhai Lake, northern China

Reed is one of the most frequent and dominant species in wetlands all over the world, with common reed (Phragmites australis (Cav.) Trin. ex Steud.) as the most widely distributed species. In many wetlands, P. australis plays a highly ambivalent role. On the one hand, in many wetlands it purifies wastewater, provides habitat for numerous species, and is a potentially valuable raw material, while on the other hand it is an invasive species which expands aggressively, prevents fishing, blocks ditches and waterways, and builds monospecies stands. This paper uses the eutrophic reed-swamp of Wuliangsuhai Lake in Inner Mongolia, northern China, as a case to present the multiple benefits of regular reed cutting. The reed area and aboveground biomass production are calculated based on field data. Combined with data about water and reed nutrient content, the impact of reed cutting on the lake nutrient budget (N and P) is investigated. Currently, at this lake around 100,000 tons of reed are harvested in winter annually, removing 16% and 8% of the total nitrogen and phosphorus influx, respectively. Harvesting all available winter reed could increase the nutrient removal rates to 48% and 24%, respectively. We also consider the effects of summer harvesting, in which reed biomass removal could overcompensate for the nutrient influx but could potentially reduce reed regrowth.     

南极长城站验潮站数据处理和潮汐特点初步分析

继在南极中山站建成我国南极首个永久性验潮站后,2012年1月在南极长城站又建成了我国南极第二个永久性验潮站。通过对长城站验潮站相关数据进行分析处理,得到了验潮基准系统的水准网平差结果和验潮仪零点标定结果,以及长城站附近海域海洋潮汐170个分潮的调和常数,并据此进行了潮汐预报,同时分析了长城站潮汐余水位的变化特征,探讨了利用附近的Antarctic Base Prat验潮站的余水位改正长城站潮汐预报的可行性,结果表明使用Antarctic Base Prat验潮站余水位改正长城站潮汐预报,可以显著提高长城站验潮站潮汐预报的精度,余水位改正后2014时段的潮汐预报中误差为±3.42 cm,明显好于改正前的预报中误差±10.43 cm。     

赵各庄矿地下水位时间序列数字滤波分析

为了更好地了解煤矿地下水位的变化趋势,结合工程实例,运用递归和非递归2种滤波技术进行分析,通过对比2种滤波技术的滤波效果,可以得到地下水位的变化规律和成因机理。结果表明:滤波系数的调校对滤波效果的影响至关重要。根据平滑度指标、均方根误差和信噪比对现有观测数据进行计算的结果可知,当b=0.5时递归滤波效果相对较好,当q=5时非递归滤波效果相对较好。滤波结果可以作为预测未来该地区地下水位变化趋势的依据,也可以为安全生产提供参考。     

沂蒙缺水山区地下水赋存规律及找水定井范例

沂蒙山区是山东省重点贫困缺水地区,缺水区域分布较广,区内地质条件复杂,找水难度极大。通过综合分析区内气象水文、岩性特征、地质构造及地形地貌等地质因素,初步查明了不同地段含水层的结构和富水性;并结合水文地质调查、物探、钻探等综合勘探方法和手段,实施了探采结合孔8口,成功率100%,满足了区内约3万余人的饮用及300余亩土地灌溉用水需求,取得了良好的经济和社会效益。为我国北方严重缺水山区找寻地下水起到了宝贵的指导和示范作用。     

Analysis of soil nail walls performance - Case study

This study surveys the performance of temporary soil nail walls with a maximum height of 29.3 m in the Yas project, located in Tehran. Some numerical models, with various modelling approaches, were developed using finite element software and the proper modelling approaches were specified and verified.The modelling results were analysed and compared with the in situ monitored data. The results demonstrate the model’s horizontal deformations are generally greater than the in situ monitored values. To decrease the differences between models and monitored results, the effect of variations of the soil parameters had been surveyed and the limits of needed variations were specified.     

Effect of Groundwater Fluctuations on Pore Pressures and Earth Pressures on Coastal Excavation Retaining Walls

Pore water and earth pressures acting on retaining structures are investigated using an efficient coastal double-layered excavation model to determine offshore excavation responses to groundwater fluctuations outside foundation pits. Total pore water pressure includes excess pore water pressure (due to groundwater fluctuations) and steady pore water pressure (due to steady seepage) determined using one-dimensional consolidation theory of double-layered soil and one-dimensional steady-state flow theory, respectively. Rankine's active and passive earth pressures are obtained from pore water pressure. This method is applicable to arbitrary groundwater fluctuation conditions. How physical parameters affect pore water pressure is numerically investigated using examples, demonstrating the method's practicality for calculating pore water and earth pressures.     

Effects of Column Diameter on Setting Behavior of Dredged Slurry in Sedimentation Experiments

This article investigates the influence of dimensions of a settling column on the settling mode and the settling rate. End conditions of the settling stage in the hindered settling were also analyzed. It was found that the settling mode in a column with a smaller diameter tends to be consolidation settling. The effect of a settling column wall decreases with increasing column diameter, and it can be ignored provided the column diameter is larger than 14.5 centimeters. For the difference in initial water content, the settling behavior of the slurry develops a different sensitivity to the diameter effect. The influence of column diameter reduces as the initial water content of the slurry becomes higher. It is suggested that the internal diameter of the column used in a sedimentation experiment should be 14.5 centimeters.     

Comparative Study of Hydrogen and Carbon Isotopic Composition of Gases Generated from the Pyrolysis of a Peat under Saltwater and Freshwater Conditions

To understand the influence of the diagenetic water medium on the isotopic compositions of thermogenic coalbed gas, both hydrous and anhydrous closed-system pyrolyses were performed at temperatures of 250°C to 650°C on an herbaceous marsh peat. Compared to the results of anhydrous pyrolysis, the hydrocarbon gases generated from hydrous pyrolyses have very different hydrogen isotopic compositions. However, the carbon isotopic compositions of the hydrocarbon gases became only slightly heavier in hydrous pyrolysis, compared to that from anhydrous pyrolysis. With the progress of thermal evolution from peat to a more advanced thermal maturity of vitrinite reflectance values (Ro) of 5.5% during the pyrolysis, the difference in the average δD value increased from 52‰ to 64‰ between the hydrous pyrolysis with saltwater and anhydrous pyrolysis and increased from 18‰ to 29‰ between the hydrous pyrolysis with freshwater and anhydrous pyrolysis, respectively. The difference in the average δ13C value was only 1‰–2‰ between the hydrous and anhydrous pyrolysis. The relationships between the δD values of the generated hydrocarbon gases and Ro values as well as among δD values of the hydrocarbon gas species are established. The close relationships among these parameters suggest that the water medium had a significant effect on the hydrogen isotopic composition and a minimal effect on the carbon isotopic composition of the hydrocarbon gases. The results of these pyrolyses may provide information for the understanding of the genesis of coalbed gas from herbaceous marsh material with the participation of different diagenetic water media.     

帕米尔高原东北缘活动构造对塔什库尔干盆地地热控制作用

帕米尔东北缘位于青藏高原西北部,是新构造运动最强烈的地区之一。受控于公格尔拉张断裂作用的塔什库尔干盆地,活动构造强烈,高的大地热流值和丰富的地下水,使其具备地热资源形成的地质构造和水文条件。基于塔什库尔干盆地北部的曲曼地区地质构造、湖相地层年代学调查研究,该地区发育晚更新世的NNE向f_1和f_2正断层以及第四纪沉积物之下存在隐伏的近EW向的断层f_3。这3条断层是塔什库尔干断裂在不同构造演化时期形成的次级断层。结合EH-4电磁成像和钻孔及抽水试验等资料表明NNE向f_1和f_2正断层是地热系统的导水通道,而近EW向f_3断层为导热通道。该地区地热模式是大地热流为热源-地下水深循环逐渐加热-构造控水和控热。     

基于数值模拟的再生水对地下水质影响实例

为了探讨在再生水地表回灌条件下,再生水对地下水中氨素和主要盐分浓度变化的影响,选取现实存在的清河再生水湿地公园为例,以氨氮、Cl-离子为主要研究对象,利用Hydrus-1D溶质运移模型和Modflow、MT3DMSD耦合地下水模型,模拟了再生水长期利用后的地下水氨氮和Cl-指标变化情况。研究结果显示,再生水到达包气带底部时,水中氮氨、Cl-离子含量高于研究区潜水地下水中的相应指标含量,氨氮超出地下水质量Ⅲ类标准。预测5~20年后,潜水中氨氮超标面积不断扩展,20年后将达14km2,氨氮超标垂向延伸至第一层弱透水层;Cl-离子在潜水中不超标,但在湿地公园周边浓度有所增加。湿地公园再生水的长期地表回灌将给当地地下水质量带来负面影响。