活性污泥中温与高温絮凝特性

为了揭示中温与高温活性污泥的絮凝特性及其作用机制,本研究采用序批式反应器,分别在35℃及55℃条件下培养了中温与高温活性污泥,考查了2种活性污泥的相互作用能与胞外聚合物的特性。研究结果表明：高温污泥系统出水浊度为（145±22．9）NTU,是中温污泥系统的近50倍。中温污泥的相互作用能曲线存在明显的势垒（313．4×10^-20J）,而高温污泥不存在明显势垒;高温污泥的松散型胞外聚合物与紧致型胞外聚合物的含量分别为中温污泥的12倍及3．5倍,且胞外聚合物中蛋白质、多糖、腐殖酸和DNA的含量均高于中温污泥的含量。这表明,尽管高温污泥相互作用能势垒低,但其胞外聚合物,尤其是松散型胞外聚合物含量过高,是高温污泥絮凝性能低的内在机制,而胞外聚合物组成特征不是中温和高温污泥絮凝性能差异的主要原因。     

Application of Unknown Groundwater Pollution Source Release History Estimation Methodology to Distributed Sources Incorporating Surface-Groundwater Interactions

Sources of contamination of groundwater are often difficult to characterize. However, it is essential for effective remediation of polluted groundwater resources. This study demonstrates an application of the linked simulation-optimization based methodology to estimate the release history from spatially distributed sources of pollution at an illustrative abandoned mine-site. In linked simulation-optimization approaches a numerical groundwater flow and transport simulation model is linked to the optimization model. In this study, topographic and geologic characteristics of the abandoned mine-site were simulated using a three-dimensional (3D) numerical groundwater flow model. Transport of contaminant in the groundwater was simulated using a 3D transient advective-dispersive contaminant transport model. Adsorption or chemical reaction of the contaminant was not considered in the contaminant transport model. Adaptive simulated annealing (ASA) was employed for solving the optimization problem. An optimization algorithm generates the candidate solutions corresponding to various unknown groundwater source characteristics. The candidate solutions are used as input in the numerical groundwater transport simulation model to generate the concentration of pollutant in the study area. This information is used to calculate the objective function value, which is utilized by the optimization algorithm to improve the candidate solution. This process continues until an optimal solution is obtained. Optimal solutions obtained in this study show that the linked simulation-optimization based methodology is potentially applicable for the characterization of spatially distributed pollutant sources, typically present at abandoned mine-sites.     

Mixing regime shapes the community assembly process, microbial interaction and proliferation of cyanobacterial species Planktothrix in a stratified lake

Lake mixing influences aquatic chemical properties and microbial community composition,and thus, we hypothesized that it would alter microbial community assembly and interaction. To clarify this issue, we explored the community assembly processes and cooccurrence networks in four seasons at two depths(epilimnion and hypolimnion) in a mesotrophic and stratified lake(Chenghai Lake), which formed stratification in the summer and turnover in the winter. During the stratification period, the epilimni...     

On a combined theory of pay level satisfaction

For decades, research on pay level satisfaction has focused on two theories and one approach: the direct link theory, the discrepancy theory, and the no‐difference‐scores approach. However, there are still unsolved puzzles facing pay level satisfaction research. We develop a combined theory to consider the impact of the interaction of reported pay and pay discrepancy. With this newly developed theory, we expect that (a) both reported pay and pay discrepancy have main effects on pay level satisfaction; (b) reported pay and pay discrepancy also interact with each other, in that the effect of pay discrepancy on pay level satisfaction decreases as pay level increases; (c) equitable payment is more related to pay level dissatisfaction when pay level is low; and (d) overpayment in general is related to pay level satisfaction, not dissatisfaction. An empirical study (N = 481) using four types of comparison standards was conducted, and the results supported our predictions. The findings of our study have important implications for both academic research and management practice.     

Effect of metallic pollutants on the physiology of lichen, Pyxine subcinerea Stirton in Garhwal Himalayas

Chl. a, Chl. b, total Chl., Carotenoid, Protein and OD 435/OD 415 ratio were measured to estimate the possible damage caused by the metallic pollutants in the lichen, Pyxine subcinerea Stirton collected from four different sites of Srinagar Garhwal, Uttaranchal, India. Multiple correlation analysis revealed significant correlation (P < 0.001) among the Fe, Ni, Cu, Cr, Zn and Pb metals analysed. Cd did not correlate with any other metals except Fe (P < 0.05). Cu, Pb and Zn, are the main constituents of the vehicular emissions had significant positive correlation (P < 0.001) with protein content while, the OD 435/OD 415 ratio values decreased statistically (P < 0.001) with increase in amount of Cu, Pb and Zn.     

考虑流固耦合的桥墩地震反应方法

跨海桥梁地震反应中,作用于桥墩上的动水压力具有明显的流固耦合特征。依据张量理论,推导时变区域散度变换关系及微分形式的几何守恒律;基于任意拉格朗日-欧拉描述,从采用欧拉描述的流体运动Navier-Stokes方程出发,推导时变区域的流体运动控制方程;给出流固耦合问题中的结构计算模型、耦合面接触条件、耦合场计算方法以及流场网格运动控制方法。以某跨海大桥为例说明桥墩地震反应方法,重点突出地震动输入、流场初始条件模拟等问题。计算结果表明:流固耦合理论能够模拟桥梁墩台地震反应中的流场和结构特性;流场初始条件的正确模拟可保证计算稳定性,并减少运算量;横向地震动激励下,桥墩基底剪力较大,纵向地震动激励下,结构运动剧烈;流固耦合系统中的线弹性结构在地震反应中具有明显的非线性特征。     

考虑水-饱和土场地-结构耦合时的沉管隧道地震反应分析

用理想流体介质模拟水层、流体饱和多孔介质模拟饱和土地层,在理想流体介质与流体饱和多孔介质相连接边界的连续条件基础上,结合已有的对理想流体介质、流体饱和多孔介质进行动力反应分析的显式有限元方法,开考虑地层与结构的动力相互作用,建立了进行水与场地、结构耦合动力分析的方法。利用该方法对沉管隧道的地震响应进行了研究,重点分析了水深、地质条件等因素对沉管隧道地震反应的影响,并从中得出了一些可供相关人员进行沉管隧道抗震分析时参考的结论。     

地震荷载作用下埋地玻璃钢夹砂管的动力响应分析

玻璃钢夹砂管在土木水利工程领域得到了愈来愈广泛的应用,但现有的埋地管道地震响应分析模型大多不考虑管-土动力相互作用,且多针对均质材料管道,无法应用于具有明显层状复合材料结构特征的玻璃钢夹砂管。基于玻璃钢夹砂管的层状复合材料结构特征,建立了完整的埋地玻璃钢夹砂管地震响应分析模型,在数值分析模型中,考虑了管-土间复杂的动力相互作用,以及地震散射波从有限域向无限域的传播。算例分析表明,所建立的埋地玻璃钢夹砂管地震响应分析模型可合理地分析埋地玻璃钢夹砂管在地震荷载作用下的动力响应。     

Interaction of DNA with aromatic hydrocarbons fraction in atmospheric particulates of Xigu District of Lanzhou, China

Voluminously epidemiological studies show that the relationships exist between the air pollution and human health and cancer. Aromatic hydrocarbons(AHs)in air form a large class of organic pollutants,which are widely in environment and many of them are known to be carcinogenic and/or mutagenic and contribute to ambient air pollution.In the past decades,bioassays mainly have been used to evaluate the toxicity of chemical mixtures in atmospheric particulates or aqueous environment.However,it is well known that the covalent complexes formed by carcinogens with DNA may be exert negative results in bioassay.So the main aim of this paper is to develop an evaluation method of toxicity effects of chemical mixtures in atmospheric particulates from chemical standpoint.In this study,the in vitro interaction of the AHs with DNA was investigated by absorption,fluorescence and resonance light scattering (RLS)spectroscopic techniques.The results showed that the AHs in the atmospheric particulates could combine with calf thymus DNA(ctDNA)and herring sperm DNA(hsDNA)without being activated or metabolized by organism,respectively.Intercalation may be present in the mechanism of interaction.The binding constants of the AHs with ctDNA and hsDNA were 2.5×10~2 and 2.0×10~3, respectively,which indicated that the interaction of the AHs with hsDNA is stronger than that with ctDNA.In addition,the relationships of dose-effect between the total mole concentration of chemical components and the ability of binding ctDNA and hsDNA were confirmed.This research made it possible to study the toxicity effects of chemical mixtures in atmospheric particulates by chemical method.It is believed that the composition and contents of unknown AHs and the interaction of DNA with AHs in atmospheric particulates of Xigu District of Lanzhou City,China are first reported in the past twenty years.     

Stakeholder participation in sustainability assessment of non-wicked problems: The case of a future seaweed industry in Sweden

Acceptance by, and cooperation with relevant stakeholders in developing new sustainability initiatives when they are generally perceived as positive, is one of the keys for successful implementation of such new sustainability initiatives later on. It is remarkable, however, that ample literature exists about involving stakeholders in research projects focusing on problems with diverging views (controversy) around facts and values (wicked problems), but there is very little literature addressing whether and how to involve relevant stakeholders in case of initiatives where diverging norms and values do not play a (substantial) role, like in sustainability assessment for a future seaweed industry. This perspectives paper addresses that gap, and explores how to design such sustainability assessment, illustrated by how stakeholder interaction influenced the assessment and its results for a future seaweed industry in Sweden, followed by a discussion whether and how a similar approach may benefit sustainability assessment of other non-wicked sustainability initiatives.