Ecological and geochemical evaluation of ecosystems of the Curonian Spit (Russia)

ABSTRACT

This paper presents the results of the quantitative content of metals (Cu, Zn, Pb, Mn, Sr, Ni, Ca, Fe, Br, Rb) in the leaves of the flora dominants of the main ecosystems of the Curonian Spit (foredune, palve area, large dune ridge). The heavy metal content in the upper layer of sandy soils, forest ecosystems (palve area) and large dune ridge was analysed. In the accumulative horizon of soils, the heavy metal content did not exceed the sanitary standards (MAC (maximum allowable concentration)/TAC (tentative allowable concentration)), and their concentration was significantly lower than the similar level in urbanised territories which allows for taking their contents into account as a baseline for the Kaliningrad region. From the ecological and physiological points of view, the content of heavy metals in the studied plants is not toxic, and is typical of the accumulation features in plants.     

基于大型真三轴试验的砂砾石料强度–剪胀特性研究

为了揭示中主应力系数和应力水平对苏洼龙水电站坝基覆盖层砂砾石料的强度与变形特性的影响规律,结合一种微摩阻加载技术,开展一系列大型真三轴试验。在广义应力框架内讨论该砂砾石料的应力、强度和剪胀问题。结果表明:首先,对于该砂砾石料,内摩擦角随中主应力系数增加而增大,随应力水平提高而减小。3个经典强度理论中,Lade-Duncan准则的预测结果与试验结果更为相符,但当b值较大时,预测结果仍偏低估计了实际的内摩擦角;其次,随着中主应力系数b值增加,应力路径的斜率变缓,同时所达到的峰值强度提高,但峰值强度对应的q/p(q,p分别为广义偏应力和平均主应力)应力比越小,表明在单位平均主应力水平下所能发挥的最大强度减小。总体而言,剪胀角随应力水平增加而减小,亦随b增加而减小。     

砂砾地层后注浆灌注桩承载性能试验研究

后压浆技术从一定程度上有效地消除了传统钻孔灌注桩在施工中的固有缺陷,改善了桩周土层的物理力学性质以及桩与土之间的边界条件,有效地降低了桩的沉降量,显著提高了单桩承载力。对砂土地层的100根注浆试桩的单桩注浆量进行数据统计,分析了桩端注浆量的变化规律;结合沈阳夏宫工程五根桩端注浆桩和两根未注浆桩的静载试验,对比分析了注浆桩与未注浆桩的单桩极限承载力以及桩顶沉降量。研究结果表明:在砂土地层条件下,注浆桩单桩竖向极限承载力比非注浆单桩竖向极限承载力能提高44.4%以上,而且在相同荷载作用下,后注浆抗压桩桩顶位移比未注浆桩的降低了近50%,有利于控制基础的沉降。     

不同竖向应力和剪切位移下砂砾石与砂双层土渗透试验

目前很多高土石坝直接坐落在覆盖层上,修建坝体后,会使坝基覆盖层产生较大的应力和剪切位移,对覆盖层的渗透稳定有极大的影响。因此有必要开展考虑应力和剪切位移影响的坝基覆盖层渗透特性试验研究。利用粗粒土大型高压水平渗透仪,考虑竖向应力和剪切位移的影响,对砂砾石和砂双层土进行渗透试验研究,探讨了砂砾石和砂双层土试样的渗透性和抗渗坡降随竖向应力和剪切位移的变化规律,将渗透破坏的发生和发展分为稳定、过渡和破坏三个阶段。试验结果表明:随着竖向应力的增大,砂砾石和砂双层土的渗透系数逐渐减小,而细颗粒的启动坡降和试样的破坏坡降则逐渐增大。随着剪切位移的增大,砂砾石和砂双层土的整体渗透系数先减小后增大,破坏坡降先增大,后迅速减小。无剪切位移以及剪切位移较小时,细颗粒的启动坡降和试样的破坏坡降之间的过渡阶段较长;而发生大的剪切位移后,启动坡降和破坏坡降之间的过渡阶段大大缩短,达到启动坡降后很快就会出现渗透破坏。     

洪积相场地高层建筑物的勘察与评价

结合具体工程实例,介绍了洪积相场地高层建筑物的勘察与评价方法,并通过对天然地基进行载荷试验,验证了在洪积扇地形条件下,只要采用合理的设计方案,高层住宅楼采用天然地基是可行的。     

Research review of the cement sand and gravel (CSG) dam

The cement sand and gravel (CSG) dam is a new style of dam that owes the advantages both of the concrete faced rock-fill dam (CRFD) and roller compacted concrete (RCC) gravity dam, because of which it has attracted much attention of experts home and abroad. At present, some researches on physic-mechanical property of CSG material and work behavior of CSG dam have been done. This paper introduces the development and characteristics of CSG dam systematically, and summarizes the progress of the study on basic tests, constitutive relation of CSG material and numerical analysis of CSG dam, in addition, indicates research and application aspect of the dam.     

泉州市区砂砾卵石层PHC管桩单桩竖向承载力探讨

通过分析泉州市区以砂砾卵石层为PHC管桩桩端持力层的15个工程项目共51根静载试验桩,并结合东涂街改造工程的3根试桩,验证和探讨泉州市区砂砾卵石层PHC管桩单桩竖向承载力取值问题。     

黄河中下游冲积平原深长桩承载能力试验研究

介绍了处于黄河中下游冲积平原的郑州黄河公铁两用桥深长桩基承载力测试的传统静载荷试桩法。分析了大量的实测数据及相应的Q-s曲线,并将实测结果与规范方法所得结果进行了比较。结果表明:实测桩的承载力小于相应规范值,前者约为后者的74%;实测桩侧摩阻力与相应规范值基本相当,而实测桩端阻力远小于相应规范值,前者约为后者的20%;桩侧阻力先于桩端阻力的发挥,桩的沉降量主要是桩身压缩量。     

陕西金堆城钼矿地质—地球化学找矿模式

金堆城钼矿矿区位于华北准地台西南缘与北秦岭加里东褶皱带两大构造单元交界位置。北秦岭加里东褶皱带实际为秦岭古海洋板块自南向北向华北陆块下俯冲的接触带,华北陆块边缘一侧。成矿母岩是燕山中晚期钾长花岗斑岩,面积0.06 km~2,其SiO_270%,K_2O6%,K_2O/Na_2O远大于2,为酸性铝过饱和富碱高钾类型。围岩主要为长城系熊耳群安山玢岩,其内节理、裂隙发育。矿区断裂极为发育,以北东向断裂为主,此外有北西向断裂和节理、裂隙。围岩蚀变强烈。矿体以花岗斑岩为核心,向围岩呈锯齿状尖灭,矿化形态以细脉状为主。岩体及围岩以Mo、Zn、Cu组分高为特征,其中Mo-Zn为正相关,Mo-Cu为负相关。地球化学异常以Mo、Cu、Zn组合为主,其中Mo异常规模大、强度高,浓度分带清晰,内带面积大(涵盖了整个矿体,且内强外弱),Cu次之(浓集区围绕岩体分布于外接触带),Zn较弱。     

Foundation of a bridge over the Danube river in Bratislava (Czechoslovakia) in faulted granitoids

A new bridge has been constructed over the Danube in Bratislava, supported by 8 piers. With regard to expected good foundation conditions a statically indeterminate construction was designed. The allowable settlement of individual piers ranged between 10 and 15 mm. In foundation pits, situated in the river bed and on the north bank, crush breccia and gouges were found. This made the expected settlement problematic. For that reason pressuremeter tests in foundation ground under pier P3 in the river bed were performed. The pressurementer modulus of jointed granodiorite, crush-breccia, and tectonic clay were calculated. The settlement of the pier, calculated on the basis of these results, was consistent with the permissible value.     

Brief note on the influence of shape and percentage of gravel on the shear strength of sand and gravel mixtures

The paper records the influence of the shape and the percentage of gravel on the shear strength/frictional angle of sand and gravel mixtures using direct shear tests. The shear strength is mainly derived from the frictional forces developed due to sliding and interlock; they depend on the maximum particle size and shape, the uniformity coefficient, density and the effective normal stress. As the size of material in a mixture is variable, the shear strength also depends upon the ratio of the specimen diameter to the maximum particle size. In this study, two different shapes of limestone were used, angular and rounded, and the maximum gravel size was 6.3 mm in diameter. Air-dried samples were used in the tests. It is concluded that the shape and percentage of gravel have an important influence on the shear strength properties. Electronic Publication     

Sorption of phenols onto sandy aquifer material: the effect of dissolved organic matter (DOM)

The influence of dissolved organic matter (DOM) on the sorption of four phenols, 2,4,6-trichlorophenol (2,4,6-TCP), pentachlorophenol (PCP), 2,4-dinitrophenol (2,4-DNP) and 2-methyl-4,6-dinitrophenol (2-M-4,6-DNP), onto sandy aquifer material at different pH values was investigated using flow through column experiments. The pH-dependent sorption of the chlorinated phenols 2,4,6-TCP and PCP was not significantly affected by DOM (measured as dissolved organic carbon, DOC), whereas in the case of nitrophenols a significant lower retardation was found, depending on the DOC concentration and pH value of the aqueous solution. Sorption decreases with increasing DOC concentration, which indicates a binding of these compounds by DOM. The degree of sorption reduction depends on the pH value and increases with increasing fraction of neutral species. The different behaviour of nitrophenols in comparison to the chlorophenols is assumed to be a result of specific charge-transfer interactions. A combined sorption and complex formation model was used to describe the effect of pH and DOC concentration on the sorption of nitrophenols onto aquifer material and to estimate binding coefficients of neutral nitrophenols on DOM.     

A five-year study on the heavy-metal pollution of Guanabara Bay sediments (Rio de Janeiro, Brazil) and evaluation of the metal bioavailability by means of geochemical speciation

Surface sediments of the Guanabara Bay (Rio de Janeiro, Brazil) were analyzed by a sequential extraction procedure for Cd, Cr, Cu, Pb, Zn, Mn and Fe, determining their distribution among five geochemical phases and in the nitric acid extractable phase. Bioavailable phases and non-bioavailable phases have been determined in six transects in the bay to define the significant level of pollution due to sediment metal contamination. A multiple correlation showed limited responsibility of Mn and Fe oxides and humic acids in the adsorption process, which allowed discrimination among the different processes and suggested the strong influence of the hydrogen sulfide present in the highly reduced bay bottom environment. The authors suggest the need to avoid disturbing bottom sediment by dredging or by artificial bottom aeration which could result in a rapid worsening of the environment due to the accelerated formation of more soluble oxygenated metal compounds making the toxic metals much more available to the benthic fauna and to the bay biota in general.     

Recent damaging events on alluvial fans along a stretch of the Tyrrhenian coast of Calabria (southern Italy)

Debris flow and flood phenomena constitute the main natural hazards on alluvial fans. These processes, often occurring during intense rainfall events, may put many communities living on fan surfaces at high risk. This article focuses on an area along the Tyrrhenian coast of Calabria (southern Italy) where a set of mountain front alluvial fans has developed on the narrow coastal plain. This area has been heavily exploited, and tourism constitutes an important source of income. Rainfall events occurring in 2009, 2010 and 2011, albeit not significantly intense, induced debris flows endangering the population and damaging private property and infrastructures. The analysis highlighted that in the study area the risk due to debris flow and the vulnerability of the area have increased as a consequence of both the reactivation of construction processes in the alluvial fan feeder basin and the intense development of human activities in the same areas. The construction of protection facilities and the loss of the historical accounts of past catastrophic events have encouraged this development. Given the characteristics of the study area, the choice and design of the most appropriate measures need particular attention.     

Geotechnical map of Holocene alluvial soil deposits in the metropolitan area of Granada (Spain): a GIS approach

The results of a geotechnical research on Holocene alluvial deposits in 14 municipalities of the Granada basin are presented, and a procedure to draw a geotechnical map of foundation conditions, using ArcGIS 9.3 (ESRI 2009) is described. Three different alluvial soil units were distinguished: (1) cohesive soils; (2) cohesive and fine granular soil; (3) coarse granular soil, based on their properties concerning grain size, bulk density, cohesion, internal friction angle, and N_SPT value. The actual building structures have predominantly shallow foundations. The definition of the minimum depth to actual foundation level was based on the analysis of thickness of disturbed soils, man-made fillings, depth to the water table and bearing capacity. The depth to actual foundation levels varies from 0.5 to 4 m in the study area. Concerning the ground, the geotechnical data compiled on foundation conditions show a high heterogeneity expressed by the spatial distribution of the basic properties in the three distinguished units of cohesive, cohesive and fine-granular, and coarse granular soils, respectively. The fine-grained alluvial soil units (cohesive) have a low bearing capacity varying between 40 and 100 kPa and are associated with a shallow water table appearing near the surface. In contrast, across the wide extension of the coarse-grained alluvial soil unit, a bearing capacity ranging from 60 to 300 kPa is determined; this unit is associated with a deep water table appearing at more than 40 m below the surface. The usefulness of the obtained geotechnical map of foundation conditions extends to the analysis of further alternatives of urban expansion and for the delimitation of future trends for of land-use-development processes in the metropolitan area of Granada, mainly at local and regional scales.     

Seasonal variation of phosphorus release from the sediments of Shallow Lake Balaton (Hungary)

Phosphorus release was low from intact sediment cores of the mesotrophic area of the lake throughout the year, and amounted to 0.3 mg P m⁻² day⁻¹ during autumn in short-term incubations. In the hypertrophic area maximum release (2.8 mg Pm⁻² day⁻¹) was measured during summer.

Phosphorus release showed a rapid increase from long-term incubated intact sediment cores with the increasing pH of the overlying water. At the ecologically real maximum pH the release may amount to 0.8 and 4.0 mg P m⁻² day⁻¹ in the mesotrophic and hypertrophic areas, respectively. A release of 2.0–3.9 mg P m⁻² day⁻¹ was estimated from sediment suspensions of the hypertrophic area within a pH range of 8–9. These values are similar to the external phosphorus loadings of the respective areas.

The most important phosphorus mobilizing factors are pH and the decomposition of the organic matter in the sediments. Redox conditions may play a significant indirect role in the regulation of the internal loading.

A positive feedback is hypothesized between the internal phosphorus loading and primary production both processes being affected by the external loading in different ways.     

复方芪麻胶囊结合辛伐他汀治疗气虚痰浊型颈动脉粥样硬化患者的临床效果分析

目的:探讨复方芪麻胶囊结合辛伐他汀治疗气虚痰浊型颈动脉粥样硬化患者的临床效果。方法:选取2017年3月-2018年10月本院收治的气虚痰浊型颈动脉粥样硬化患者62例。按照随机数字表法将其分为研究组和对照组,各31例。对照组予以辛伐他汀治疗,研究组予以复方芪麻胶囊结合辛伐他汀治疗。比较两组颈动脉内膜-中膜厚度(IMT)、颈动脉粥样硬化斑块面积、血脂代谢指标(TC、TG、HDL-C、LDL-C)、丙氨酸转氨酶(ALT)、血管内皮功能指标(LOX-1、ox-LDL、APN)、炎性因子水平(MMP-9、TNF-α、IL-6)。结果:干预后,研究组IMT、斑块面积均小于对照组(P<0.05);研究组TC、TG、LDL-C、ox-LDL、LOX-1、IL-6、TNF-α、MMP-9均低于对照组,HDL-C、APN高于对照组,差异均有统计学意义(P<0.05);研究组ALT均低于干预前及对照组,但对照组高于干预前,差异均有统计学意义(P<0.05)。结论:复方芪麻胶囊结合辛伐他汀治疗气虚痰浊型颈动脉粥样硬化患者,可抑制其炎症反应、降脂、保护血管内皮功能,且安全性较高,可进一步降低或延缓血管损伤程度。     

Quarrying of aggregates in and around gauhati: Impact on the environment

The Gauhati city is situated in the northeastern part of India. Since the late 1960's Gauhati has been undergoin massive development with construction of innumerable buildings, roads and pavements leading to a huge demand for construction materials. Consequently, aggregate quarries have muschroomed on hillslopes in and around Gauhati, Unplanned quarrying activities on hillslopes have brought about the problem of aesthetic degradation and slope failure. This paper highlight these problems and suggests corrective and preventive measures for preservation of the beauty of the natural landscape and stability of the hill slopes.     

Nitrate probability mapping in the northern aquifer alluvial system of the river Tagus (Portugal) using Disjunctive Kriging

The Water Framework Directive and its daughter directives recognize the urgent need to adopt specific measures against the contamination of water by individual pollutants or a group of pollutants that present a significant risk to the quality of water. Probability maps showing that the nitrate concentrations exceed a legal threshold value in any location of the aquifer are used to assess risk of groundwater quality degradation from intensive agricultural activity in aquifers. In this paper we use Disjunctive Kriging to map the probability that the Nitrates Directive limit (91/676/EEC) is exceeded for the Nitrate Vulnerable Zone of the River Tagus alluvium aquifer.The Tagus alluvial aquifer system belongs to one of the most productive hydrogeological unit of continental Portugal and it is used to irrigate crops. Several groundwater monitoring campaigns were carried out from 2004 to 2006 according to the summer crops cycle.The study reveals more areas on the west bank with higher probabilities of contamination by nitrates (nitrate concentration values above 50 mg/L) than on the east bank.The analysis of synthetic temporal probability map shows the areas where there is an increase of nitrates concentration during the summers.