片沸石、钙基膨润土去除垃圾渗滤液中有害物质的实验研究

以位于北京昌平小汤山的阿苏卫垃圾卫生填埋场渗滤液为研究对象,在不同的环境条件下:酸度(pH=5~9),温度(4℃~30℃),利用片沸石、钙基膨润土去除垃圾渗滤液中有害物质的实验,以化学耗氧量(COD)、氨氮为评价指标,分别探讨片沸石、钙基膨润土的COD、氨氮去除效果与其用量、渗滤液pH、温度、振荡时间的关系。研究表明,在实验条件下,片沸石对COD的最大去除量约为31×10-3,对氨氮的最大去除量约为27×10-3;去除COD、氨氮的最佳条件分别为:片沸石用量20 g/L、pH为5、温度4℃、振荡时间100 min。在实验条件下,钙基膨润土对COD的最大去除量约为63×10-3,对氨氮的最大去除量约为14×10-3;去除COD、氨氮的最佳条件分别为:钙基膨润土用量30 g/L、pH为5、温度4℃、振荡时间100 min。根据实验结果,对片沸石、钙基膨润土去除COD、氨氮的机理主要是氢键、静电作用及离子交换作用。     

Laboratory study of combined wave overtopping and storm surge overflow of a levee

Combined wave overtopping and storm surge overflow of a levee with a trapezoidal cross section was studied in a two-dimensional laboratory wave/flow flume at a nominal prototype-to-model length scale of 25-to-1. The goal of this study was to develop design guidance in the aftermath of Hurricane Katrina. Time series of water depth at two locations on the levee crown and flow thickness at five locations on the landward-side slope were measured along with horizontal velocity near the landward edge of the crown. New equations are presented for average overtopping discharge, distribution of instantaneous discharge, and distribution of individual wave volumes. Equations are also given for mean flow thickness, RMS wave height, mean velocity, and velocity of the wave front down the landward-side slope.     

The Coso volcanic field reexamined: Implications for obsidian sourcing and hydration dating research

Obsidian from the Coso locality, Inyo County, California, has long been regarded by archaeologists as a single “source.” However, studies by the U.S. Geological Survey have provided evidence of geochemical variability among flows within the volcanic field. to determine whether these geochemical distinctions could be applied productively to archaeological research, nondestructive x-ray fluorescence analyses were conducted on samples recently collected from 15 obsidian-bearing loci. the results of this research show that geochemically distinct varieties of artifact-quality obsidian can be recognized within the Coso volcanic field, and subsequent nondestructive x-ray fluorescence analyses of artifacts from two nearby archaeological sites document that different geochemical varieties of obsidian were used prehistorically to manufacture tools. Implications of these results for studies of prehistoric exchange and obsidian hydration dating are discussed.     

Floodplain inundation: Processes and relationships with channel discharge

The factors affecting the relationship between channel discharge and volume of inundation are discussed. For many floodplains this relationship is not simple, but involves hysteretic effects which vary according to the hydrological characteristics of individual floods and the way in which these interact with the surface form of the floodplain reach. Some methods of deriving or estimating the extent of the hysteresis on floodplain reaches are suggested, although an acute lack of available data prevents detailed examination at present. Further investigations are required before floodplain conductivity relations can be used as an aid to flood routing procedures or in floodplain management problems. A major priority must be the acquisition of sequential inundation data.     

Froude number effects on flow over topography

Abstract

The response or a depth independent two layer flow to an underlying topographic irregularity is studied for flows in which the square of the internal Froude number exceeds the Rossby number. Irrespective of the magnitude of the Rossby number, rotation is important for such flows. The flow generally adjusts so that the thickness of the lower layer is nearly constant. However small anomalies from the constant thickness are found to extend to very large distances from the topography when the Rossby number exceeds unity.     

Morphodynamic evolution of a coastal lagoon entrance during swash overwash

New field observations of beach berm growth resulting in the sub-aerial closure of an intermittently closed and open lake or lagoon are presented. These perched estuarine systems frequently exhibit ephemeral entrances that respond to process forcing almost instantaneously on a geomorphic timescale, with closure by a supra-tidal berm of depositional origin. The observations were made following a mechanical opening of the entrance and show very rapid vertical growth of an initially low beach berm as a result of swash overtopping and sediment overwash. Very little simultaneous seaward progradation was observed. Sediment overwash volumes were obtained from survey data over a period of 12 days either side of spring tide and the observations also provide an accurate measure of swash sediment transport at the berm crest. A process-based parametric model is developed through robust parameterisations of wave run-up, wave run-up distributions and sediment transport and is applied to predict the total overwash transport into and infilling the estuary entrance. The model is tested against the field data and compares well with the observations. While the field data are site-specific, the proposed modelling framework represents a first step in modelling the complex growth and recovery of natural beach berms in broad-scale morphodynamic models.     

Tropical Pacific – mid-latitude teleconnections in medieval times

Terrestrial and marine late Holocene proxy records from the western and central US suggest that climate between approximately 500 and 1350 a.d. was marked by generally arid conditions with episodes of severe centennial-scale drought, elevated incidence of wild fire, cool sea surface temperatures (SSTs) along the California coast, and dune mobilization in the western plains. This Medieval Climate Anomaly (MCA) was followed by wetter conditions and warming coastal SSTs during the transition into the “Little Ice Age” (LIA). Proxy records from the tropical Pacific Ocean show contemporaneous changes indicating cool central and eastern tropical Pacific SSTs during the MCA, with warmer than modern temperatures in the western equatorial Pacific. This pattern of mid-latitude and tropical climate conditions is consistent with the hypothesis that the dry MCA in the western US resulted (at least in part) from tropically forced changes in winter NH circulation patterns like those associated with modern La Niña episodes. We examine this hypothesis, and present other analyses showing that the imprint of MCA climate change appears in proxy records from widely distributed regions around the planet, and in many cases is consistent with a cool medieval tropical Pacific. One example, explored with numerical model results, is the suggestion of increased westerlies and warmer winter temperatures over northern Europe during medieval times. An analog technique for the combined use of proxy records and model results, Proxy Surrogate Reconstruction (PSR), is introduced.     

Field observations of nearshore bar formation

The formation of an inner nearshore bar was observed during a high‐energy event at the sandy beach of Vejers, Denmark. The bar accreted in situ during surf zone conditions and the growth of the bar was associated with the development of a trough landward of the bar. Measurements of hydrodynamics and sediment fluxes were obtained from electromagnetic current meters and optical backscatter sensors. These process measurements showed that a divergence in sediment transport occurred at the location of the developing trough, and observed gradients in cross‐shore net sediment flux were consistent with the morphological development. The main cause for the flux gradients were cross‐shore gradients in offshore‐directed mean current (undertow) speed which depended upon local relative wave height and local bed slope. Copyright © 2007 John Wiley & Sons, Ltd.     

测船处瞬时潮位的GPS精密确定

利用GPS载波相位差分测量技术，借助时间偏差改正、姿态改正、高程转换、信号处理和吃水改正，获得了测船处精密在航潮位。该方法已在几个GPS在航潮位测量实验中得到了验证，并取得了理想的结果。     

乌鲁木齐附近地区小爆破识别判据的研究

采用新疆乌鲁木齐地区多个地震台的位移仪及速度仪记录，探讨了人工小爆破记录与天然地震记录的差异及其识别判据。结果发现，爆破记录与地震记录在震相、P波垂直向初动符号分布、振幅衰减、振幅比As^-/Ap^-等方面具有不同的特征，据此我们制定出了识别爆破的单项判据和综合判据。