Direct supercritical fluid extraction from water

Abstract

This paper describes the development of apparatus suitable for direct supercritical fluid extraction of organics from water. Results are presented for the extraction of pentachlorophenol present in water at concentrations of the order of 0.1 ppm. The effect of changes in apparatus design and supercritical fluid flow rate on recovery are discussed.     

多晶硅切割液废液的回收与利用

结合工程实际,介绍了太阳能产业用多晶硅片切割过程中产生的割液废液的处理工艺及回收工艺,并分析了它的投资成本和经济效益。     

四川省米易县新农村建设可持续发展SD分析——用系统观透视

县域新农村建设必然受到当地自然—社会—经济中众多因素及其复杂关系的制约.为了从长期性与整体性角度考察四川省米易县社会、经济、生态环境与新农村建设之间的相互作用关系,建立了由米易县系统动力学模型为主干,生态足迹模型和SWOT模型为支撑的米易县新农村建设可持续发展分析模型,以透视米易县新农村建设的前景,探讨规划的理论依据.     

计算流体动力学在模拟气升式环流反应器中的研究进展

计算流体动力学(CFD)是对气升式环流反应器进行数值模拟的重要手段.为此,本文综述了CFD模拟概况及气升环流反应器中流体数值模拟研究进展,总结了目前CFD模拟气升环流反应器存在的问题,并提出了进一步的研究方向.     

钻井废液的固液分离工艺与设备

影响钻井废液固液分离的因素包括钻井废液的稀释比例、脱稳处理药剂的种类和加量、固液分离设备。文章介绍了钻井废液处理的基本流程,分析了钻井废液pH值对固液分离效果的影响,论述了卧式螺旋卸料沉降离心机的基本结构、设备参数和操作参数对固液分离效果的影响。     

Ethnobotany and ecological perspectives on the management and use of plant species for a traditional fishing trap, southern coast of São Paulo, Brazil

The cerco-fixo is an artisanal fishing trap widely used by traditional communities in the estuarine region of the southern coast of the state of São Paulo, Brazil. The primary goal of the study was to investigate, through ethnobotanical and ecological approaches, the use of plant species by traditional fishermen to build the cerco-fixo at Cardoso Island State Park and Cananéia Island. Ethnobotanical data were collected through interviews, direct observation, plant collection and identification, and document analysis. An ecological evaluation was also done comparing five 20 × 20 m plots in a managed area to five 20 × 20m plots in an unmanaged area, both within arboreal sandy soil vegetation called restinga arbórea, found within the Brazilian Atlantic Forest domain. This study involved 34 fishermen living at Cardoso and Cananéia Islands. The fishermen know more than 90 Atlantic Forest plant species that can be used to build the cerco-fixo. Tree species from the family Myrtaceae were the most quoted in the interviews. With respect to the ecological evaluation, the cluster analyses showed greater heterogeneity in terms of floristic composition (i.e. greater floristic dissimilarity) within the plots of the managed area. The analyses of diversity showed a slightly higher species richness and slightly lower values for Shannon, Simpson, Hurlbert’s PIE and Evenness indices in the managed area (59 species; H′ = 3.28; 1/D = 10.77; E = 0.80; Hurlbert’s PIE = 0.91) compared to the unmanaged area (54 species; H′ = 3.39; 1/D = 20.21; E = 0.85; Hurlbert’s PIE = 0.95). The Hutcheson’s t test showed no significant difference between both areas’ Shannon diversity indices (t: −1.04; p: 0.30). These results are attributed to the greater dominance of the palm species Euterpe edulis Mart. in the managed area (28.2% of the trees sampled at this area; n = 118), which equals twice the percentage of individuals of the same species found for the unmanaged area (14.6% of the sampled trees; n = 48). We discuss the impact of the fishermen’s harvesting practices in the managed area with an emphasis on three main points: (1) the harvesting practices are likely not contributing to a decrease in diversity in the managed area; (2) the greater heterogeneity in terms of floristic composition found for the managed area may reflect a mosaic pattern created by the opening of small tree-gaps distributed across this area over the course of more than 50 years; (3) the disturbance promoted by the fishermen’s harvesting practices can be compared to natural disturbances of low impact that create mosaic patterns in tropical forests. This study emphasizes the prominence of the human dimension in ecological processes and the importance of considering the perspectives of local people when discussing the conservation of the natural environments in which these people live.     

System dynamics modeling for municipal water demand estimation in an urban region under uncertain economic impacts

Accurate prediction of municipal water demand is critically important to water utilities in fast-growing urban regions for drinking water system planning, design, and water utility asset management. Achieving the desired prediction accuracy is challenging, however, because the forecasting model must simultaneously consider a variety of factors associated with climate changes, economic development, population growth and migration, and even consumer behavioral patterns. Traditional forecasting models such as multivariate regression and time series analysis, as well as advanced modeling techniques (e.g., expert systems and artificial neural networks), are often applied for either short- or long-term water demand projections, yet few can adequately manage the dynamics of a water supply system because of the limitations in modeling structures. Potential challenges also arise from a lack of long and continuous historical records of water demand and its dependent variables. The objectives of this study were to (1) thoroughly review water demand forecasting models over the past five decades, and (2) propose a new system dynamics model to reflect the intrinsic relationship between water demand and macroeconomic environment using out-of-sample estimation for long-term municipal water demand forecasts in a fast-growing urban region. This system dynamics model is based on a coupled modeling structure that takes into account the interactions among economic and social dimensions, offering a realistic platform for practical use. Practical implementation of this water demand forecasting tool was assessed by using a case study under the most recent alternate fluctuations of economic boom and downturn environments.     

Factors Affecting Stream Nutrient Loads: A Synthesis of Regional SPARROW Model Results for the Continental United States1

Preston, Stephen D., Richard B. Alexander, Gregory E. Schwarz, and Charles G. Crawford, 2011. Factors Affecting Stream Nutrient Loads: A Synthesis of Regional SPARROW Model Results for the Continental United States. Journal of the American Water Resources Association (JAWRA) 47(5):891‐915. DOI: 10.1111/j.1752‐1688.2011.00577.x Abstract: We compared the results of 12 recently calibrated regional SPARROW (SPAtially Referenced Regressions On Watershed attributes) models covering most of the continental United States to evaluate the consistency and regional differences in factors affecting stream nutrient loads. The models – 6 for total nitrogen and 6 for total phosphorus – all provide similar levels of prediction accuracy, but those for major river basins in the eastern half of the country were somewhat more accurate. The models simulate long‐term mean annual stream nutrient loads as a function of a wide range of known sources and climatic (precipitation, temperature), landscape (e.g., soils, geology), and aquatic factors affecting nutrient fate and transport. The results confirm the dominant effects of urban and agricultural sources on stream nutrient loads nationally and regionally, but reveal considerable spatial variability in the specific types of sources that control water quality. These include regional differences in the relative importance of different types of urban (municipal and industrial point vs. diffuse urban runoff) and agriculture (crop cultivation vs. animal waste) sources, as well as the effects of atmospheric deposition, mining, and background (e.g., soil phosphorus) sources on stream nutrients. Overall, we found that the SPARROW model results provide a consistent set of information for identifying the major sources and environmental factors affecting nutrient fate and transport in United States watersheds at regional and subregional scales.     

雨雪冰冻灾害后粤北森林各林型凋落物动态

为了考察中国亚热带不同森林类型对雨雪冰冻灾害的响应模式,以粤北天井山3种代表性的林型—针叶林、阔叶林和混交林为对象,于不同森林类型中比较受损森林与未受损森林在凋落物年产量、成分及月际动态方面的差异,从而在凋落物水平上反映不同森林类型在雨雪冰冻灾害后的早期恢复力。研究结果表明,灾后针叶林、阔叶林和混交林的年凋落量分别为0.52、3.21、1.37 t.hm-2,比未受损的同种森林类型年凋落量显著减少,减少程度分别为87.89%、53.46%、76.78%。由此可以看出阔叶林的植被恢复情况最好,说明在凋落物水平上,其灾后恢复的早期阶段恢复力最强。在凋落物成分方面,灾后各森林类型叶凋落物所占比例显著增加,枝凋落物所占比例则显著减少。受损针叶林和阔叶林的凋落物月动态与未受损森林基本一致,但其波动幅度较小;在混交林中,受损和未受损森林其凋落量的季节动态模式则表现出不一致性且为不规则型。根据研究结果,建议在亚热带地区优先考虑种植阔叶林以促进受损森林在类似雨雪冰冻灾害的极端天气后的恢复。     

Forecasting population trend from the scaling pattern of occupancy

Forecasting the temporal trend of a focal species, its range expansion or retraction, provides crucial information regarding population viability. To this end, we require the accumulation of temporal records which is evidently time consuming. Progress in spatial data capturing has enabled rapid and accurate assessment of species distribution across large scales. Therefore, it would be appealing to infer the temporal trends of populations from the spatial structure of their distributions. Based on a combination of models from the fields of range dynamics, occupancy scaling and spatial autocorrelation, here I present a model for forecasting the population trend solely from its spatial distribution. Numerical tests using cellular automata confirm a positive correlation, as inferred from the model, between the temporal change in species range sizes and the exponent of the power-law scaling pattern of occupancy. The model is thus recommended for rapid estimation of species range dynamics from a single snapshot of its current distribution. Further applications in biodiversity conservation could provide a swift risk assessment, especially, for endangered and invasive species.