Removal of uranium(VI) from contaminated sediments by surfactants

Uranium(VI) sorption onto a soil collected at the Melton Branch Watershed (Oak Ridge National Laboratory, TN) is strongly influenced by the pH of the soil solution and, to a lesser extent, by the presence of calcium, suggesting specific chemical interactions between U(VI) and the soil matrix. Batch experiments designed to evaluate factors controlling desorption indicate that two anionic surfactants, AOK and T77, at concentrations ranging from 60 to 200 mM, are most suitable for U(VI) removal from acidic soils such as the Oak Ridge sediment. These surfactants are very efficient solubilizing agents at low uranium concentrations: ca. 100% U(VI) removal for [U(VI)]o,sorbed = 10(-6) mol kg-1. At greater uranium concentrations (e.g., [U(VI)]o,sorbed = ca. 10(-5) mol kg-1), the desorption efficiency of the surfactant solutions increases with an increase in surfactant concentration and reaches a plateau of 75 to 80% of the U(VI) initially sorbed. The most probable mechanisms responsible for U(VI) desorption include cation exchange in the electric double layer surrounding the micelles and, to a lesser extent, dissolution of the soil matrix. Limitations associated with the surfactant treatment include loss of surfactants onto the soil (sorption) and greater affinity between U(VI) and the soil matrix at large soil to liquid ratios. Parallel experiments with H2SO4 and carbonate-bicarbonate (CB) solutions indicate that these more conventional methods suffer from strong matrix dissolution with the acid and reduced desorption efficiency with CB due to the buffering capacity of the acidic soil.     

Ethoxylated Soybean Polyols for Polyurethanes

Soybean polyols prepared by ring opening reactions of epoxidized soybean oil with hydrogen active compounds (water, alcohols, organic or inorganic acids, thiols, hydrogen etc.) have a low reactivity in the reaction with isocyanates because the hydroxyl groups are secondary. This paper presents a simple and convenient method to increase the reactivity of soybean polyols with secondary hydroxyl groups by ethoxylation reactions with the preservation of triglyceride ester bonds. The method uses mild reaction conditions: low alkoxylation temperature of 35–45 °C, low pressure of 0.1–0.2 MPa (15–30 p.s.i.) and a superacid as catalyst (HBF₄). The new soybean polyols have a higher reactivity toward isocyanates in polyurethane formation due to the high percentage of primary hydroxyl groups. The primary hydroxyl content was determined by the second order kinetics of polyol reaction with phenyl isocyanate.     

环境物探技术在岩溶勘察中的应用及其效果

将高密度电阻率法及工程地震映像法两种环境物探技术同时应用于实际的地质灾害(岩溶)勘察中,结果表明:对于岩溶这样的地质灾害,单一环境物探技术虽然能清楚反映其埋深、规模和发育情况,但各有缺陷。而多种环境物探技术的综合使用,相互补充,将能大大提高岩溶勘察的准确性,提高勘察效果和效率。     

地裂缝上框架结构的抗震性能分析

地裂缝是严重影响我国人类生活、生产建设的主要地质灾害之一,是一种独特的地质灾害,近年来已引起人们的关注,它广泛分布于全国许多地方。框架结构是一种广泛使用的结构形式。由于人类活动或地质构造运动形成地裂缝,进而造成房屋开裂或倾斜。该文针对位于抗震设防区的框架结构房屋,分别用底部剪力法和PKPM静力分析法,来定量研究在地裂缝影响下框架结构的抗震性能,为双重灾害影响下结构抗震鉴定加固提供依据。     

Interspecific and intraspecific identification of Dendrobium based on the psbAtrnH intergenic region sequences and the 5S rRNA gene spacer sequences北大核心CSCD

This research aimed to investigate the interspecific and intraspecific identification of Dendrobium by using the multi-locus method so as to provide a molecular basis for Dendrobium identification through the combination of chloroplast psbA-trnH intergenic region sequences and ribosome 5S rRNA gene spacer sequences. PCR direct sequencing was applied to detect the chloroplast psbA-trnH intergenic region sequences as well as the ribosome 5S rRNA gene spacer sequences of 12 Dendrobium species, while the psbA-trnH intergenic region sequences of Dendrobium denneanum dq-2 variety and dq- 5line were cloned and sequenced for single nucleotide polymorphism (SNP) analyzing. The sequences were analyzed by the software Sequencher4.14, Bioedit7.0, MEGA5.2 and Dansp5.0; the interspecific and intraspecific Kimara-2-Parameter(K2P) distances were also calculated. The phylogenetic tree (using Neighbor joining method) was constructed with Bulbophyllum odoratissimum and Bletilla striata as outgroup. The results showed an average length of chloroplast psbA-trnH gene sequences in Dendrobium as 742.3 bp, with 72 variable sites, including 33 information sites; the average length of the ribosome 5S rRNA gene spacer sequences in Dendrobium was 336.4 bp, with 213 variable sites including 139 information sites. Using psbAtrnH intergenic region sequences in combination with ribosome 5S rRNA gene spacer sequences can not only identify D. denneanum, D. hancockil, D. thysiflorum, D. devonianum, D. moniliforme, D. chrysotoxum, D. officinale, D. heterocarpum and D. nobile, but also differentiate D. officinale from different geographical populations, and distinguish the dq-2 variety and dq 5line with SNP in the multi locus of D. denneanum.     

环境影响评价在中国环境管理中的作用及局限性研究

论述环境影响评价在中国环境管理中的作用,并结合实际工作分析,指出其存在如环境影响分析预测不准确、环保措施实施效果欠佳、监测计划作用发挥不到位、自身局限性等问题.针对存在问题并提出五点建议,即实现环境主管部门全过程监管、加强政府各部门的积极配合、建设环境信息共享平台、全民提高自觉环境保护意识、环评工作者加强自身专业知识培养,以调动全民积极主动性,充分发挥环境影响评价的作用.     

遥感调查方法在河北省省级自然保护区生态环境变化评估方面的应用研究

河北省省级自然保护区以自然生态系统类型为主,人类活动较为频繁,将遥感评估方法应用于河北省省级自然保护区生态环境变化评估具有重要意义。本文通过分析高分辨率遥感卫星影像的特点,结合河北省省级自然保护区的实际情况,优先选取分辨率为2m的民用卫星,提出了遥感调查方法在自然保护区人类活动和开发建设活动中自动监测、生态系统格局变化、生态系统质量变化以及人类活动干扰程度四方面的评估应用。     

车载接地装置的冲击接地阻抗研究

为解决车载装置在不同路面的接地问题,我们研制了可迅速安装和撤收的便携式接地装置,并选取一种组合在不同岩土介质地面上进行了实验,测得各自的冲击接地阻抗。然后,采用时域有限差分法对实验装置进行了数值分析,得出了该接地装置冲击接地阻抗的时域特性。与实验结果进行对比的结果表明,两者具有较好的一致性。