Fluorescence regional integration and differential fluorescence spectroscopy for analysis of structural characteristics and proton binding properties of fulvic acid sub-fractions

Structural characteristics and proton binding properties of sub-fractions (FA3–FA13) of fulvic acid (FA), eluted stepwise by pyrophosphate buffer were examined by use of fluorescence titration combined with fluorescence regional integration (FRI) and differential fluorescence spectroscopy (DFS). Humic-like (H-L) and fulvic-like (F-L) materials, which accounted for more than 80% of fluorescence response, were dominant in five sub-fractions of FA. Based on FRI analysis, except the response of F-L materials in FA9 and FA13, maximum changes in percent fluorescence response were less than 10% as pH was increased from 2.5 to 11.5. Contents of carboxylic and phenolic groups were compared for fluorescence peaks of FA sub-fractions based on pH-dependent fluorescence derived from DFS. Static quenching was the dominant mechanism for binding of protons by FA sub-fractions. Dissociation constants (pKa) were calculated by use of results of DFS and the modified Stern-Volmer relationship. The pKa of H-L, F-L, tryptophan-like and tyrosine-like materials of FA sub-fractions exhibited ranges of 3.17–4.06, 3.12–3.97, 4.14–4.45 and 4.25–4.76, respectively, for acidic pHs. At basic pHs, values of pKa for corresponding materials were in ranges of 9.71–10.24, 9.62–10.99, 9.67–10.31 and 9.33–10.28, respectively. At acidic pH, protein-like (P-L) materials had greater affinities for protons than did either H-L or F-L materials. The di-carboxylic and phenolic groups were likely predominant sites of protonation for both H-L and F-L materials at both acidic and basic pHs. Amino acid groups were significant factors during proton binding to protein-like materials of FA sub-fractions at basic pH.     

两种含氨基β-环糊精衍生物对萘和蒽的光催化降解作用

为进一步探讨含氨基β-CD(β-环糊精)衍生物对PAHs(多环芳烃)的光催化降解机理,合成了两种含氨基β-CD衍生物——ACD(氨基-β-CD)和EDCD(乙二胺-β-CD),并研究了其对溶液中萘和蒽的包合作用及光催化降解作用.结果表明:β-CD、ACD、EDCD对萘和蒽的包合能力分别为76.3和251 L/mol、111和394 L/mol、191和427 L/mol,由于β-CD亲水外缘极性基团的引入,使得其疏水空腔内部的水分子具有更高的能量,易移出,易被PAHs分子取代,因此ACD和EDCD的包合能力有所增强;对萘和蒽光敏化作用的大小表现为ACD＞EDCD＞β-CD,在溶液中分别加入3 g/L的β-CD、ACD和EDCD后,萘和蒽的光解率分别提高了40.0%～50.9%和44.3%～104%.研究显示:由于光解过程中含氨基β-CD疏水空腔对三重态PAHs起到了包合保护作用,导致三重态PAHs与三重态氧分子碰撞及产生高活性单重态氧的几率增加,包合作用越大光催化降解能力越强;但是ACD和EDCD的氨基会对三重态氧分子进攻三重态PAHs产生阻碍作用,导致光催化降解效率降低.      

机场安全氛围与LMX对员工安全行为的影响研究

为研究机场组织领导—部属交换关系(Leader-Member Exchange,LMX)、部门安全氛围对员工安全行为的影响机制以及安全氛围在其中的调节效应,从领导与组织氛围的视角寻找影响人员安全行为的重要因素,改善机场人员安全行为。提出研究假设,构建跨层次理论模型,并在武汉天河国际机场、广州白云国际机场、成都双流国际机场三个综合性机场进行线上线下相结合的问卷调查,获取数据后,借助SPSS19.0软件进行描述性统计分析、量表信效度分析,同时借助HLM6.0软件进行多层线性模型回归分析,从而验证了研究假设,即LMX与安全氛围对员工安全参与行为和安全遵守行为都有正向的促进作用,而安全氛围在LMX对安全行为的影响中起到负向调节作用,并挖掘出机场组织中LMX与安全氛围对员工安全行为影响的替代效应。     

Experimental investigation of ash deposits on convection heating surfaces of a circulating fluidized bed municipal solid waste incinerator

Incineration of municipal solid waste(MSW) is a waste treatment method which can be sustainable in terms of waste volume reduction, as well as a source of renewable energy.During MSW combustion, increased formation of deposits on convection heating exchanger surfaces can pose severe operational problems, such as fouling, slagging and corrosion.These problems can cause lower heat transfer efficiency from the hot flue gas to the working fluid inside the tubes. A study was performed where experiments were carried out to examine the ash deposition characteristics in a full-scale MSW circulating fluidized bed(CFB) incinerator, using a newly designed deposit probe that was fitted with six thermocouples and four removable half rings. The influence of probe exposure time and probe surface temperature(500, 560, and 700℃) on ash deposit formation rate was investigated. The results indicate that the deposition mass and collection efficiency achieve a minimum at the probe surface temperature of 560℃. Ash particles are deposited on both the windward and leeward sides of the probe by impacting and thermophoretic/condensation behavior. The major inorganic elements present in the ash deposits are Ca,Al and Si. Compared to ash deposits formed on the leeward side of the probe,windward-side ash deposits contain relatively higher Ca and S concentrations, but lower levels of Al and Si. Among all cases at different surface temperatures, the differences in elemental composition of the ash deposits from the leeward side are insignificant.However, as the surface temperature increases, the concentrations of Al, Si, K and Na in the windward-side ash deposits increase, but the Ca concentration is reduced. Finally,governing mechanisms are proposed on the basis of the experimental data, such as deposit morphology, elemental composition and thermodynamic calculations.     

石油污染土壤微生物修复过程中植物毒性变化规律

植物幼苗生长发育和叶片的生化指标能综合反映土壤石油污染的程度及其生态毒性的强弱.为探究植物对石油污染土壤生态毒性的指示效果和污染土壤在生物修复过程中毒性的变化规律,本研究采用3株对石油烃具有良好降解效果的降解菌构建混合菌体系,开展石油污染土壤模拟微生物修复实验.文章考察了5种典型植物指示不同修复时期土壤生态毒性强弱的可行性与敏感性,并进一步从生态学角度揭示修复过程中石油污染土壤生态毒性的变化规律.结果表明,小麦和萝卜相对于莴苣、黑麦草和小青菜而言,更适宜作为石油污染土壤的指示生物.石油污染土壤的生态毒性随着微生物修复过程的进行呈先上升后下降的趋势,石油污染土壤生态毒性在修复的第8 d达到最大.不同的供试植物对石油污染的响应存在一定的差异.小麦和萝卜的生长发育指标能较为敏感地指示石油污染土壤在微生物修复过程中的生态毒性,可作为石油污染土壤微生物修复效果的指示生物.     

Historical record of effects of human activities on absolute and relative concentrations of Polycyclic aromatic hydrocarbons (PAHs) in Lake Chao, China

正Polycyclic aromatic hydrocarbons(PAHs)are attracting concern because of their potential toxicity,posing serious threats to health of humans and ecosystems(Kim et al.,2013;Zhao et al.,2016).Generally,similar to other contaminants'behaviors(Wu et al.,2001;Zhang et al.,2007,2008;Lu et al.,2009),PAHs result from natural organic matter and activities of humans,the latter's contribution usually outweighing the inputs from other sources(Fernández et al.,2000;Srogi,2007).     

石油污染土壤的原位生物修复技术和多种土壤改良剂应用研究

土壤中的石油污染是一类严重的环境危害.针对石油污染的土壤修复技术有物理法、化学法和生物法.其中原位生物修复法由于简易性和生态可持续等优点成为了具有前景的一个发展方向.土壤改良剂的选取和添加是原位生物修复法中重要的一个部分,对生物修复的改进起到了至关重要的作用.土壤改良剂的种类有无机改良剂、有机改良剂和吸附性改良剂.以N、P、K为主的无机改良剂主要为生物生长提供营养元素;有机改良剂则可提高石油污染物流动性,提供生物碳源;吸附改良剂则通过吸附污染物,减少毒性,提供生物生长依附.通过对不同种类改良剂的分析和讨论,可为生物修复发展提供进一步的理论基础.     

森林旅游资源开发潜力定量评价研究--以武汉市为例

森林旅游资源定量评价是为发展森林旅游提供更为可靠的依据。研究了森林旅游资源开发潜力的定量方法，对武汉市森林旅游资源开发潜力进行了定量评价，得出了武汉市森林旅游资源的质量等级，为森林旅游的开发提供了可靠的依据。     

基于CES生产函数的企业安全投资决策方法研究

在分析当前我国安全投资决策研究基础上,讨论安全投资的边际效益理论,并利用其确定安全投资总量的合理值。利用不变替代弹性(CES)生产函数建立安全投入产出效益函数,反映安全投资结构对安全产出的影响,通过模型求解得到企业安全资源分配的优化结构和投资额。按边际效益理论和安全投资效益模型将有限的资源科学地配置到安全生产过程中去,有利于节约资本,实现安全效益最大化。     

城市景观规划中的防洪策略--以2002年欧洲特大洪灾为例

近年来，由于全球变暖、不合理地改造自然、城市化进程加剧以及人们的思想松懈等原因，世界上城市洪灾发生较为频繁，给各国城市和人民带来重大损失。城市防洪已成为城市发展过程中备受关注的问题。为此，以2002年8月欧洲部分国家爆发的特大洪水为例，在分析其原因的基础上，提出了城市景观规划中的防洪策赂，希望它能对我国的城市防洪事业和城市景观规划工作起到借鉴作用。