Influence of cation type, ionic strength, and pH on solubilization and mobilization of residual hydrocarbon by a biosurfactant

This study investigated the effect of cation type, ionic strength, and pH on the performance of an anionic monorhamnolipid biosurfactant for solubilization and removal of residual hexadecane from sand. Three common soil cations, Na⁺, Mg²⁺, and Ca²⁺, were used in these experiments and hexadecane was chosen to represent a nonaqueous phase liquid (NAPL) less dense than water. Results showed that hexadecane solubility in rhamnolipid solution was significantly increased by the addition of Na⁺ and Mg²⁺. Addition of up to 0.2 mM Ca²⁺ also increased hexadecane solubility. For Ca²⁺ concentrations greater than 0.2 mM there was little effect on hexadecane solubility due to competing effects of calcium-induced rhamnolipid precipitation and enhanced hexadecane solubilization. Efficiency of NAPL solubilization can be expressed in terms of molar solubilization ratios (MSR). The results showed that MSR values for hexadecane in rhamnolipid solutions increased 7.5-fold in the presence of 500 mM Na⁺, and 25-fold in the presence of 1 mM Mg²⁺. The presence of cations also reduced the interfacial tension between rhamnolipid solutions and hexadecane. For example, an increase in Na⁺ from 0 to 800 mM caused a decrease in interfacial tension from 2.2 to 0.89 dyn cm⁻¹. Similarly, decreasing pH caused a reduction in interfacial tension. The lowest interfacial tension value observed in this study was 0.02 dyn cm⁻¹ at pH 6 in the presence of 320 mM Na⁺. These conditions were also found to be optimal for removal of hexadecane residual from sand columns, with 58% of residual removed within three pore volumes. The removal of residual NAPL from the packed columns was primarily by mobilization, even though solubilization was significantly increased in the presence of Na⁺.     

高温烟气除尘系统改进野风阀使用的建议

分析了野风阀的降温原理及其影响因素,并对其使用提出改进建议。     

Carbon dioxide and methane emission from subsurface peatlands and its controlling factors北大核心CSCD

Peatland is an efficient carbon dioxide (CO2) sink on the continent and plays an important role in global carbon cycle. Climate change and human activities, two of the notable global environmental issues, have accelerated the degradation of peatlands during recent years. Global warming will increase the rate of aerobic decomposition in the surface of peatlands. Carbon stored in the subsurface of peatlands will be metabolized if the climatic conditions become favorable for decomposition. This study reviewed the carbon circle of subsurface peatland in natural environment and in environments disturbed by human activity or climate change. Furthermore, the major factors (environmental and human factors) that affect the carbon cycle were also discussed. According to a previous study, subsurface peatland will rapidly participate in the carbon cycle when the peatland is degraded. Water level, vegetation, and temperature were the main natural factors affecting the carbon cycle, whereas drainage, farming, and grazing were the main anthropogenic factors. Further studies should focus on different soil layer carbon dynamics, inorganic carbon content, and conservation and restoration of peatlands. The study methods should be a combination of macro with micro scale and focus on developing deep peat research techniques. Most of the previous studies focused on greenhouse gas emission and their response factors in short-term experiments. Thus, the mechanism and process of subsurface carbon are not clear and needs further study. © 2018 Science Press. All rights reserved.     

多氯酚QSAR数值模型比较研究

应用多元线性回归分析和新近发展起来的人工神经网络方法进行了一类重要环境污染物多氯酚的定量构效关系研究，并用所建立的模型进行毒性预报，计算值与实验值的比较表明，前的相关系数约为０．９２，后的相关系数约为０．９９．后的百分误差地明显小于前，后的预报能力略好于前，中还讨论了后优于前的的原因。     

Cultivar-dependent rhizobacteria community and cadmium accumulation in rice: Effects on cadmium availability in soils and iron-plaque formation

The association between the rhizospheric microbial community and Cd accumulation in rice is poorly understood. A field trial was conducted to investigate the different rhizobacterial communities of two rice cultivars with high Cd accumulation (HA) and low Cd accumulation (LA) at four growth stages. Results showed that the Cd content in the roots of the HA cultivar was 1.23 - 27.53 higher than that of the LA cultivar (0.08 - 10.5 µg/plant) at four stages. The LA cultivar had a significantly lower Cd availability in rhizosphere and a higher quantity of iron plaque (IP) on the root surface than the HA cultivar at four stages. This resulted in the reduction of Cd concentration in IPs and Cd translocation from IP-to-root. Microbial analysis indicated that the LA cultivar formed a distinct rhizobacterial community from the HA cultivar and had less α-diversity. The rhizosphere of the LA cultivar was enriched in specific bacterial taxa (e.g., Massilia and Bacillus) involved in Cd immobilization by phosphate precipitation and IP formation by iron oxidization. However, the rhizosphere in the HA cultivar assembled abundant sulfur-oxidizing bacteria (e.g., Sulfuricurvum) and iron reduction bacteria (Geobacter). They promoted Cd mobilization and reduced IP formation via the metal redox process. This study reveals a potential approach in which specific rhizobacteria decrease or increase Cd accumulation in rice on contaminated soil and provides a new perspective for secure rice production.     

油松排放萜烯类化合物浓度的日变化及排放速率的研究

 采用封闭式采样和气相色谱法分析监测了北京主要树种油松排放的萜烯类化合物，其中包括α和β蒎烯、蒈烯、松油烯、柠檬烯和罗勒烯，以及少量异戊二烯。松油烯、B蒎烯、柠檬烯和蒈烯的排放量之和占油松排放碳氢总量的94％以上。萜烯和异戌二烯排放速率随日照和温度的升高而增加。萜烯等浓度的日变化表明在正午和午夜油松有两个排放高峰。在日均气温为18℃时油松的碳氢化合物平均总排放速率约为8.7μh/h.g。     

FRP约束钢筋混凝土柱中钢筋屈曲行为研究

通过FRP约束钢筋混凝土柱的单向和往复轴压试验,研究了外包FRP的断裂应变、刚度、以及加载方式对钢筋屈曲性能的影响。采用了两种不同的纤维材料:CFRP和PET FRP,二者具有不同的断裂应变(CFRP1.5%;PET FRP5%)。在试验分析的基础上,发展了考虑FRP侧向约束作用的弹性地基梁模型,该模型能够较好地分析FRP约束钢筋混凝土柱中钢筋屈曲行为。基于弹性地基梁模型和试验数据,提出了考虑FRP侧向约束作用的钢筋屈曲经验模型。并将该模型通过二次开发的方法写入OpenSees数值分析平台,对FRP约束RC柱的往复轴压行为进行数值分析,分析结果与试验结果吻合较好。研究成果可为精确分析FRP约束钢筋混凝土结构的抗震性能提供有力的工具。     

定量构效关系(QSAR)在环境化学中的进展与方法

定量构效关系(QSAR)是化学品安全评价中有用的工具之一。本文叙述它的应用背景、基本原理、学科历史进展、概念模型、数学模型和算法,着重介绍作者开发的实用量子化学计算程序包,用以产生分子结构参数,所建立的化学物质毒性数据库可用来获取大量生物活性数据,还可用模式识别程序包构筑构效定量关系。本文对其研究前景也作了叙述。     

LPG低温储存装置管道泄露风险分析

介绍了液化气的危险特性,结合实际对洛阳石化液化气低温储存装置存在的管道泄漏风险进行了原因分析,提出了相应的措施,保证了装置安全运行.     

罐底含油泥热解动力学参数计算方法的优选

在化学反应设计中反应动力学是较重要的因素。为得到更合理的污泥热解动力学参数计算方法,利用热重分析仪,在氮气气氛下对罐底含油污泥的热解特性进行研究。根据热重实验数据,分别采用Coats-Redfern法、Kissinger法、FWO法和Popescu法计算污泥热解动力学参数,并获取罐底泥热解制油的主要阶段(第2阶段)的反应活化能E、频率因子A并分析各种方法反应机理。通过对比不同计算方法得到动力学参数及拟合曲线与实验曲线的相关性,确定了最佳罐底含油污泥热解动力学参数计算方法。研究表明,Popescu法得到罐底泥的热解过程符合Jander方程,活化能E为101.43 kJ/mol,与FWO法得到的91.20 kJ/mol相近,且预测曲线与实验曲线有较好的相关性(0.9816),说明Popescu法计算罐底泥热解动力学参数更合适。