Effect of preparation method on structure and adsorption capacity of aluminum pillared montmorillonite

Aluminum pillared montmorillonites (Alpill-MMTs) were prepared by two different methods, i.e. conventional intercalation and ultrasonic assisted intercalation, in order to study the effects of preparation methods on their structures and adsorption abilities. In the conventional intercalation, a base-hydrolyzed solution of [AlO₄Al₁₂(OH)₂₄(OH₂)₁₂]⁷⁺, Al₁₃⁷⁺, was firstly prepared and then mixed with a suspension of sodium montmorillonite (Na⁺-MMT) for 24 h with vigorous stirring, resulting in the cation exchange between Al₁₃⁷⁺ and Na⁺ balancing ions in the MMT interlayers. On the other hand, the high power ultrasonic was used in the second method for creating the Al₁₃⁷⁺ ions and then in situ intercalating into the MMT suspension, in which the reaction was performed for 20 min. Both Al₁₃⁷⁺ intercalated MMTs were calcined at 500 °C for 2 h in order to obtain the Alpill-MMTs. The ultrasonic could not only shortening the intercalation process, but also increasing the amount of intercalated Al₁₃⁷⁺ in the MMT. The ultrasonic synthesized Alpill-MMT (Alpill-MMT-ultra) consisted of mesoporous structure with multiple pore sizes ranging from 3 to 30 nm; therefore, it possessed higher specific surface area and pore volume than the conventionally synthesized Alpill-MMT (Alpill-MMT-str). Adsorption capacities of Alpill-MMTs were investigated using cationic adsorbate, i.e. Basic Yellow 1 (BY1). The highest adsorption capacities were respectively about 95 and 81 mg/g for the Alpill-MMT-ultra and Alpill-MMT-str, when using initial BY1 concentration of 2000 mg/L. The Alpill-MMT-ultra showed higher efficiency for BY1 removal than the Alpill-MMT-str even after thermal regeneration. The adsorption kinetics of both Alpill-MMTs for BY1 removals were found to follow a pseudo-second-order model, while their adsorption data corresponded to Langmuir isotherm. These results indicated the competency of Alpill-MMTs as the adsorbents for treatment of wastewater containing cationic dye.     

陕西黑河流域土地利用变化对非点源污染的影响研究

本文借助RS和GIS技术,借鉴和应用景观生态学的有关理论和研究方法,分析了黑河流域土地利用从1976年至2000年的动态变化,讨论了土地利用变化的驱动机制。在此基础上,以率定的模型参数为基础,应用SWAT模型分别对2000年和1976年两期土地利用下的黑河流域1991～2000年非点源污染负荷进行模拟,由此确定土地利用变化引起的流域非点源污染负荷的变化。从控制非点源污染的角度,分析了土地利用变化趋势的合理性。研究结果可为研究区土地资源的合理开发利用、生态环境的保护及区域的持续发展规划提供科学依据。     

沣河水质与流量之间的关系分析

为了打造生态沣河,本文基于秦渡镇断面2001-2009年的定期水质监测资料,以及秦渡镇水文站2001年到2009年的逐日流量数据,以及2009年到2011年大峪口断面、秦渡镇断面的多场洪水监测资料,研究分析了沣河水质与流量之间的关系.结果表明:(1)监测断面流量的大小和每场洪水平均流量的大小均对NH3-N、TN和COD的污染浓度有影响,且流域上下游不同断面的水质流量之间的关系也有差异;(2)根据2002年到2008年秦渡镇断面所监测的6场洪水资料,可知洪水对COD非点源污染的影响较大.而2006年NH3-N、TN的点源污染严重,此外几年NH3-N的点源污染较严重,TN变化不稳定.     

A general framework incorporating knowledge,risk perception and practices to eliminate pesticide residues in food: A Structural Equation Modelling analysis based on survey data of 986 Chinese farmers

Following a variety of incidents in China relating to food poisoning due to the presence of pesticide residues, it is crucial to correct for farmers’ unsafe and improper practices towards pesticide use. Although most studies have focused on the role of external stakeholders such as government extension agencies and pesticide retailers, the attention paid to farmers’ intrinsic motivations is limited. This paper applies Structural Equation Modelling to investigate psychological motivational concepts such as farmers’ knowledge and risk perception, their formation mechanisms and the underlying processes of these concepts that lead to farmers’ practices to eliminate pesticide residues, based on a representative survey conducted with 986 Chinese farmers from 20 counties selected from six provinces. We found both a direct and significant effect of farmers’ knowledge on pesticides residue on their safe pesticide practices and also an indirect effect, i.e. knowledge influences on risk perception which in turn enhances safe pesticide practices. It was also reported that government support strategies are more effective in promoting safe pesticide practices than government regulation.     

Landscape effects of environmental impact on bay-area wetlands under rapid urban expansion and development policy: A case study of Lianyungang,China

This paper presents a synthesis of rapid landscape change and regional environmental dynamics in the Lianyungang bay area from 2000 to 2006 based on remote sensing data. We quantified the annual rate of urban land-use change in the study area using classified Landsat TM (2006-05-20) and ETM⁺ (2000-09-16) images. The classified images were used to generate maps of urban expansion and salt wetlands degradation, and landscape metrics were calculated and analyzed spatiotemporally across class and landscape level for each year. Results indicate that the Lianyungang bay area has a widespread urban–rural interface with rapid land-use changes, urban expansion and wetland degradation. Rapid increases in urban built-up land, which were often associated with large-scale salt wetlands degradation, have been prominent since 2005 when the eastern coastal development policy was implemented.     

An efficient,clean synthesis of 3,3′-(arylmethylene)bis(2-hydroxynaphthalene-1,4-dione) derivatives

A clean, simple and efficient method for the synthesis of 3,3′-(arylmethylene)bis(2-hydroxynaphthalene-1,4-dione) derivatives has been developed which uses the reaction of 2-hydroxynaphthalene-1,4-dione and aromatic aldehydes in the presence of a catalytic amount of LiCl in aqueous media. To the best of our knowledge, this is the first report on such a synthesis of 3,3′-(arylmethylene)bis(2-hydroxynaphthalene-1,4-dione).     

Effect of chemical and biological factors on the densification of filamentous sludge

Densification may be an alternative method for controlling sludge bulking; however, little information is available on the method. Various methods including different oxygen concentrations, surface velocities of aeration, calcium concentrations and extended starvation period were employed for triggering densification of filamentous sludge in this study. It was found that high surface velocity of aeration could effectively improve the settleability of filamentous sludge in the short term, which resulted in filamentous granulation, but could not avoid filamentous bulking even after granulation. Increase of calcium concentration could also improve the settleability by forming pigtail filaments colony in the short term, but could not trigger granulation. Extension of starvation period seems effective neither for further densification nor for granulation. Additionally, increased ovality of meshes formed by filaments was frequently associated with a dense structure of filamentous sludge. It was suggested that pigtail type of filamentous colony that thus increased the resistance to elevated shear force may encourage the densification of sludge, and two kind of densification growth patterns, i.e., granular or cluster growth pattern of filamentous sludge, were identified.     

五里湖富营养化及治理对策研究

分析了五里湖水体、底泥的氮、磷含量的变化趋势,并根据富营养评价等级判定了五里湖的富营养化程度．根据测得的数据,五里湖TP含量为0．099mg／L,属于Ⅳ类;TN含量为5．01mg／L．属V类：叶绿素和透明度分别为0．014mg／L和40-60cm,分别属于Ⅳ类和V类;CODMn含量为5．47mg／L,属于重富营养化。最后,基于五里湖的特点提出了鱼类防治、传统植物防治、生态清淤、调水工程和生态浮床技术等治理措施。     

NUMERICAL SIMULATION OF GAS TURBULENCE ENHANCEMENT BY PARTICLE-WAKE EFFECT

A new turbulence enhancement model was incorporated into the second-order moment two-phase turbulence model and was used to simulate gas-particle flows in swirling chambers and channels with different wall roughness. The results show that compared with the turbulence modification model not accounting for the wake effect,this model,together with the conventional particle source term,gives simulation results in better agreement with the experimental data.