高黏度污泥螺带螺杆搅拌混合特性的数值模拟

污泥处理过程通常需要加入添加剂,而高黏度污泥流动性差,搅拌混合是一个难点。选用螺带螺杆搅拌器加添加剂搅拌高黏度污泥,用Solid Works软件几何建模后,将模型导入Gambit划分网格,结合Fluent软件选用多重参考系法(MRF)分别对双螺带螺杆搅拌器与单螺带螺杆搅拌器下的污泥与添加剂混合过程进行了模拟,对比了两种搅拌桨的混合时间、体积分数流场分布及混合效率,分析了不同加料区域的影响,并将搅拌功率模拟与试验结果进行了对比。结果表明:螺带螺杆搅拌器适用于高黏度污泥的搅拌且双螺带螺杆搅拌器混合时间更短,体积分数流场更快趋于稳定且混合效率更高;最佳加料区域为搅拌槽的中部。     

Decomposition of hexachlorobenzene over Al2O3 supported metal oxide catalysts

Decomposition of hexachlorobenzene(HCB)was investigated over several metal oxides(i.e.,MgO,CaO,BaO,La2O3,CeO2,MnO2, Fe2O3,and Co3O4)supported on Al2O3,which was achieved in closed system at a temperature of 300°C.Catalysts were prepared by incipient wetness impregnation with different metal oxides loading and impregnating solvents.The decomposition effciency of different catalysts for this reaction depends on the nature of the metal oxide used,and Al2O3 supported La2O3 was found to be the most active one.Pe...     

改进的一次二阶矩计算埋地管道失效概率方法及其应用

为探究不同影响因素对埋地管道运行安全的影响,基于改进的一次二阶矩计算方法,综合考虑埋地管道环向受力和纵向受力的特性,依据应力-强度理论和钢制管道结构设计规范建立了埋地管道失效结构功能函数;通过对ABAQUS软件中的UVARM模块进行二次开发,建立了腐蚀、温度和不均匀沉降耦合作用下的三维管道-地层整体模型,模拟不同管道参数下的管道状况.运用该方法对工程实例进行了计算,分析可靠指标和失效概率的分布情况.结果表明:埋地管道工作内压与管道失效概率呈正相关关系,管道壁厚和管径与失效概率呈负相关关系;在影响参数变化相同的条件下,管道中部失效概率变化最快,两端的失效概率变化较慢.该模型计算结果体现了管道不同部位失效概率的特点,在管道设计、维护和风险评估方面有一定的借鉴意义.     

Constructed wetlands may lower inorganic nutrient inputs but enhance DOC loadings into a drinking water reservoir in North Wales

Environmental Science and Pollution Research - The objective of this study was to monitor a newly constructed wetland (CW) in north Wales, UK, to assess whether it contributes to an improvement in...     

澜沧江梯级水电站库区水环境时空差异性研究

根据2008年1—12月澜沧江下游的漫湾水电站、大朝山水电站库区的水质监测资料,对水环境时空差异性进行了分析,结果表明:两库区水质特征变化趋势比较相似,季节性变化明显,两库区水体有机污染程度小,水体氮磷含量较高,属于中—富营养水平,总氮在秋季最高,冬季最低,总磷在夏秋季最高,春季最低。梯级水坝的形成对水体中总氮含量、有机污染的累积效应不明显。     

Acute toxicity of aromatic and non-aromatic fractions of naphthenic acids extracted from oil sands process-affected water to larval zebrafish

The toxicity of oil sands process-affected water (OSPW) has regularly been attributed to naphthenic acids, which exist in complex mixtures. If on remediation treatment (e.g., ozonation) or on entering the environment, the mixtures of these acids all behave in the same way, then they can be studied as a whole. If, however, some acids are resistant to change, whilst others are not, or are less resistant, it is important to establish which sub-classes of acids are the most toxic.     

Modeling Inorganic Aerosols and Their Response to Changes in Precursor Concentration in Mexico City

Abstract

Based on data from the 1997 Investigación sobre Materia Particulada y Deterioro Atmosférico-Aerosol and Visibility Evaluation Research (IMADA-EVER) campaign and the inorganic aerosol model ISORROPIA, the response of inorganic aerosols to changes in precursor concentrations was calculated. The aerosol behavior is dominated by the abundance of ammonia and thus, changes in ammonia concentration are expected to have a small effect on particle concentrations. Changes in sulfate and nitrate are expected to lead to proportional reductions in inorganic fine particulate matter (PM_2.5). Comparing the predictions of ISORROPIA with the observations, the lowest bias and error are achieved when the aerosols are assumed to be in the efflorescence branch. Including crustal species reduces the bias and error for nitrate but does not improve overall model performance. The estimated response of inorganic PM_2.5 to changes in precursor concentrations is affected by the inclusion of crustal species in some cases, although average responses are comparable with and without crustal species. Observed concentrations of particle chloride suggest that gas phase concentrations of hydrogen chloride may not be negligible, and future measurement campaigns should include observations to test this hypothesis. Our ability to model aerosol behavior in Mexico City and, thus, design control strategies, is constrained primarily by a lack of observations of gas phase precursors. Future campaigns should focus in particular on better understanding the temporal and spatial distribution of ammonia concentrations. In addition, gas phase observations of nitric acid are needed, and a measure of particle water content will allow stable versus metastable aerosol behavior to be distinguished.     

Mixed-Grass Prairie Canopy Structure and Spectral Reflectance Vary with Topographic Position

Managers of the nearly 0.5 million ha of public lands in North and South Dakota, USA rely heavily on manual measurements of canopy height in autumn to ensure conservation of grassland structure for wildlife and forage for livestock. However, more comprehensive assessment of vegetation structure could be achieved for mixed-grass prairie by integrating field survey, topographic position (summit, mid and toeslope) and spectral reflectance data. Thus, we examined the variation of mixed-grass prairie structural attributes (canopy leaf area, standing crop mass, canopy height, nitrogen, and water content) and spectral vegetation indices (VIs) with variation in topographic position at the Grand River National Grassland (GRNG), South Dakota. We conducted the study on a 36,000-ha herbaceous area within the GRNG, where randomly selected plots (1?km² in size) were geolocated and included summit, mid and toeslope positions. We tested for effects of topographic position on measured vegetation attributes and VIs calculated from Landsat TM and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data collected in July 2010. Leaf area, standing crop mass, canopy height, nitrogen, and water content were lower at summits than at toeslopes. The simple ratio of Landsat Band 7/Band 1 (SR71) was the VI most highly correlated with canopy standing crop and height at plot and landscape scales. Results suggest field and remote sensing-based grassland assessment techniques could more comprehensively target low structure areas at minimal expense by layering modeled imagery over a landscape stratified into topographic position groups.     

Adaptive capacity determinants in developed states: examples from the Nordic countries and Russia

Adaptive capacity in a community context has so far mainly been studied in developing countries as well as indigenous communities in the industrialised world. This article adds to that literature through reviewing studies undertaken in the Nordic countries and Russia, highlighting the ways in which general determinants of adaptive capacity play out in Northern, industrialised contexts. The paper illustrates that the determinants of adaptive capacity in industrialised states exhibit systematic differences from mixed subsistence-cash based communities such as those found in Arctic Canada. We discuss in particular the importance of economic resources in a market-based system, technological competition, and infrastructure, in determining adaptive capacity of natural resource-dependent communities in the Nordic countries and Russia. The paper also illustrates differences in adaptive capacity within the case study region, including between peripheral and central locations with regard to economic resources and diversification possibilities, and between Nordic and Russian cases with regard to infrastructure and technology access. The findings indicate that understanding of determinants of adaptive capacity in resource-dependent communities would benefit from both further contextualisation and broad comparison, across different types of political and administrative systems.