Dynamics of Turbulence in Low-Speed Oscillating Bottom-Boundary Layers of Stratified Basins

This paper focuses on the impact of an oscillating low-speed current on the structure and dynamics of the bottom-boundary layer (BBL) in a small stratified basin. A set of high-resolution current profile measurements in combination with temperature-microstructure measurements were collected during a complete cycle of the internal oscillation (`seiching') in the BBL of Lake Alpnach, Switzerland. It was found that even a relatively long seiching period of 24 hours significantly changed the form of the near-bottom current profiles as well as the dynamics of the turbulent dissipation rate compared to the steady-state law-of-the-wall. A logarithmic fit to the measured current profiles starting at a distance of 0.5 m above the sediment led to inconsistent estimates of both friction velocity and roughness length. Moreover, a phase lag between the current and the turbulent dissipation of 1.5 hours and a persistent maximum in the current profile at a height of 2.5 to 3 m above the sediment were observed. The experimental findings were compared to the results of a k- turbulence model and showed good agreement in general. Specifically, the inconsistent logarithmic fitting results and the observed phase lag were reproduced well by the model.     

Current status of applying microwave-associated catalysis for the degradation of organics in aqueous phase – A review

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城市生活垃圾填埋场甲烷气资源的产量估算及其利用

本文论述了填埋场甲烷气体的产生过程及影响因素,介绍了三种产气量估算方法及其主要特点、适用范围,并指出运用数学模型对产气量作出预测,为垃圾填埋场气体收集与处理系统的设计提供可靠的依据。同时,论述了甲烷气体的减排和综合利用措施。     

The impact of the European landfill directive on waste management in the United Kingdom

The European Union Landfill Directive calls on member states to reduce the amount of biodegradable municipal solid waste disposed of to landfill. In addition, national waste strategies will require the constituent parts of the United Kingdom to achieve increased household waste recycling and recovery rates. Both these measures will require the development of the infrastructure to support national high-intensity recycling and composting schemes and the construction of at least 35 new municipal waste to energy incinerators. Before plans can be developed for meeting the targets several areas relating to municipal solid waste need to be clarified. Depending on the definition of municipal solid waste, its composition and likely future growth rates the number of incinerators required could be up to 170.     

生活垃圾焚烧底渣中重金属和多环芳烃的浸出实验研究

随着生活垃圾焚烧处理方式的不断推广,焚烧底渣的产生量也不断增加。按照我国的固体废物分类方法,底渣属于一般固体废物,无需进一步处置而可直接进入环境。实验结果表明,底渣中的重金属和多环芳烃可以被浸出而迁移进入环境。重金属的浸出浓度受到水相pH值和底渣粒度的影响,初期的浸出浓度最大。在底渣浸出液中,可以检测到8种环数≤4的多环芳烃,其中菲的浸出浓度最大（超过10ng／mL）。实验结果显示,底渣中的多环芳烃对环境造成的二次污染比较严重。     

The velocity of DNAPL fingering in water-saturated porous media: laboratory experiments and a mobile–immobile–zone model

Dense nonaqueous phase liquids (DNAPLs) are immiscible with water and can give rise to highly fingered fluid distributions when infiltrating through water-saturated porous media. In this paper, a conceptual mobile–immobile–zone (MIZ) model is presented to describe the structure of a DNAPL finger in water-saturated porous media and the velocity of finger propagation. A finger is composed of a finger body and a tip. The finger body has a mobile core and an immobile sheath. All the DNAPL within the tip of a finger is mobile. Lab experiments utilizing image analyses of a DNAPL (PCE) penetrating into water-saturated homogeneous glass beads were carried out in a two-dimensional transparent chamber. The results show that the fingers elongated almost linearly with time. The fingers did not grow laterally after the tip of the finger had passed. The average finger diameters were between 3.9 and 5.4 mm for PCE propagation in water-saturated glass bead porous media with mean particle diameters from 0.32 to 1.36 mm. The estimated mobile core diameters were 51–60% of the average finger diameters.     

Use of thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) on identification of odorant emission focus by volatile organic compounds characterisation

Volatile organic compounds (VOCs) from several different municipal solid wastes’ treatment plants in Mallorca (Spain) have been analysed by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Ambient (immission) air was collected during February and March 2011 by active sampling onto sorbents Tenax™ TA and Carboxen™ 1000. The study presents the chemical characterisation of 93 volatile organic compounds (VOCs) from an overall set of 84 immission air samples. 70 VOCs were positively identified.The linear fit for all 93 external standard calibration, from 10 mg L⁻¹ to 150 mg L⁻¹ (n = 4), was within the range 0.974 < r² < 0.998. Limits of detection of the method (LOD) for all the standards were within the range 1.1-4,213 pg, as the absolute standard amount spiked into sorbent tubes in 1 μL standard mixture (dissolved in methanol).Overall results stated systematic correlation between waste’s nature and VOCs’ air composition. Organic wastes show main contribution of terpenes, waste water sludge residues’ of reduced sulphured compounds (RSCs) and municipal solid wastes show contribution of a wide sort of VOCs. The use of a chemometric approach for variable’s reduction to 12 principal components enables evaluation of similarities and dissimilarities between facilities. PCA clearly related samples to its corresponding facility on the basis of their VOCs composition and the ambient temperature.     

加强城市固体废物污染防治促进循环经济的发展

为加强城市固体废物污染防治，促进循环经济的发展，文章论述了国内外城市固体废物污染防治现状，天津市固体废弃污染防治对策，“十五”期间天津市固体废物污染防治的十大工程项目。     

Prenatal demonstration of a cervical myelocystocele

Myelocystocele is a rare spinal cord disorder and has not been described prenatally. We report a case in which prenatal ultrasound and magnetic resonance imaging (MRI) demonstrated a posterior cervical mass which was initially thought to be a meningocele or an atypical cystic hygroma. Surgery performed at 1 day of age showed this to be a myelocystocele. Therefore, the differential diagnosis of an extracranial cystic mass in the posterior cervical region should be expanded to include myelocystoceles.     

生活垃圾焚烧飞灰水洗盐产生量预测及其对资源可持续利用的影响分析

针对水泥窑协同处置飞灰水洗预处理过程中水洗盐产生量不清,资源化利用潜力不明晰的问题,采用情景分析方法预测水洗盐产生量,评估其资源利用潜力。首先采用改进的灰色马尔科夫模型和产废系数法预测2021-2030年京津冀地区飞灰产生量;然后选择水泥窑协同处置比、厨余垃圾分拣率和塑料垃圾分拣率3个参数,利用组合情景预测协同处置和生活垃圾分类对水洗盐产生的影响。结果显示,到2030年,水洗盐产生量为9.2×10⁴~16.5×10⁴ t;在实现“十四五”时期飞灰资源化和生活垃圾分类发展要求的情景下,水洗盐产生量为12.7×10⁴ t,比低发展水平情景提高28.7%。提高垃圾分拣率,推进高效、低耗能分盐技术发展,可以降低水洗盐处理压力并提高氯化钾自给率,支持水洗盐资源可持续利用。