Humic acid and free radical in environment of Kaschin-Beck disease areas

The humic acid contents in drinking water and soil in Kaschin-Beck disease areas were found more than that of non-disease areas in this research. Changes of free radical concentration in drinking water were agreed with that of humic acid contents in drinking water of Kaschin-Beck disease areas. A positive correlation of free radical concentration and humic acid content in drinking water has been shown (r=0.913) . The structure of I. R. spectra of humic acid under ultraviolet light has been changed. Thus it indicated that free radical was resulted from benzoqiunonyl groups of humic acid in environment.     

黄腐酸与镰刀菌代谢产物的ESR谱性质的研究

以ESR谱仪为主要工具,配合大骨节病病因研究,进行了有关地区饮水中有机物,主要是腐殖酸的黄腐酸级分和粮食真菌——镰刀菌代谢产物性质的相似性比较研究.结果发现,病区粮食中自由基浓度高于非病区,而尖孢镰刀菌(Fusarium Oxysporum)浸染使玉米粉的自由基浓度增加.在氧化、还原、加热和改变酸碱度等处理过程中,菌粮自由基的ESR谱表现出和黄腐酸同样的变化规律.菌粮水提液经GDX-102树脂吸附后,其ESR谱和pH值的关系表明,镰刀菌代谢产物中的自由基集中于带有酸性基团的分子上.水提液的紫外及荧光光谱和黄腐酸具有一定的相似性,因而推论镰刀苗代谢产物的自由基与黄腐酸一样,都是半醌自由基.最后就这类自由基和大骨节病的关系进行了讨论.     

·OH的形成机理及在水处理中的应用

以产生大量·OH为特点的高级氧化水处理技术已逐渐成为各国水处理技术研究的热点。在讨论·OH氧化能力的同时 ,重点讨论了Fenton法、纳米光催化氧化法、电化学催化降解法以及超声降解法·OH的形成机理 ,介绍了它们在水处理中的工业化应用及进展情况 ,展望了今后在该领域中多种氧化降解方法协同作用的发展方向     

羟基自由基杀灭压载水赤潮入侵生物试验研究

采用羟基自由基对斯式根管藻、日本星杆藻、裸甲藻和细菌进行杀灭实验，确定杀灭入侵赤潮生物的所需OH^-比值浓度为0.68mg／L。当OH^-比值浓度达到0．68mg／L时，致死多甲藻(Peri.Spp)等10种赤潮生物效率达到99.8％，致死膝沟孢子、多甲藻孢子效率达到100％。试验数据表明，强电离先进氧化OH^-是治理赤潮有效、可行的绿色新方法。     

Isomer distribution of nitrotriphenylenes in airborne particles, diesel exhaust particles, and the products of gas-phase radical-initiated nitration of triphenylene

The formation of mutagenic nitro-polycyclic aromatic hydrocarbons (NPAHs) 1- and 2-nitrotriphenylene (1- and 2-NTP) via gas-phase OH or NO₃ radical-initiated reactions of triphenylene was demonstrated for the first time using a flow reaction system. In contrast with the results of conventional electrophilic nitration, 2-NTP was formed in larger yield than 1-NTP, but this is consistent with the mechanism proposed for gas-phase radical-initiated nitration of PAH. In diesel exhaust particle (DEP) samples, both 1- and 2-NTP were identified and their concentrations determined, as well as 1-nitropyrene (1-NP), which is a representative combustion-derived NPAH: the mean concentrations of 1-NTP, 2-NTP, and 1-NP were 4.7, 1.9, and 32 pmol mg_DEP^–1, respectively. The mean 2-NTP/1-NTP, 1-NTP/1-NP, and 2-NTP/1-NP ratios in samples of airborne particles collected in a residential area in Osaka, Japan, were>1.55,<0.25, and 0.37, respectively; these values are much higher than those of the DEP samples. This finding indicates that there is another source for airborne NTPs, especially 2-NTP, apart from diesel exhaust. These results strongly suggest that airborne NTPs originate from atmospheric processes such as radical-initiated reactions of triphenylene, and this has a significant influence on the atmospheric occurrence of NTPs.     

Modelling the environmental degradation of water contaminants. Kinetics and mechanism of the riboflavin-sensitised-photooxidation of phenolic compounds

The aerobic visible-light-photosensitised irradiation of methanolic solutions of either of the phenolic-type contaminants model compounds (ArOH) p-phenylphenol (PP), p-nitrophenol (NP) and phenol (Ph), and for two additional phenolic derivatives, namely p-chlorophenol (ClP) and p-methoxyphenol (MeOP), used in some experiments, was carried out. Employing the natural pigment riboflavin (Rf) as a sensitiser, the degradation of both the ArOH and the very sensitiser was observed. A complex mechanism, common for all the ArOH studied, operates. It involves superoxide radical anion (O₂^√−) and singlet molecular oxygen (O₂(¹Δ_g)) reactions. Maintaining Rf in sensitising concentrations levels (≈0.02 mM), the mechanism is highly dependent on the concentration of the ArOH. Kinetic experiments of oxygen and substrate consumption, static fluorescence, laser flash photolysis and time-resolved phosophorescence detection of O₂(¹Δ_g) demonstrate that at ArOH concentrations in the order of 10 mM, no chemical transformation occurs due to the complete quenching of Rf singlet excited state. When ArOH is present in concentrations in the order of mM or lower, O₂^√− is generated from the corresponding Rf radical anion, which is produced by electron transfer reaction from the ArOH to triplet excited Rf. The determined reaction rate constants for this step show a fairly good correlation with the electron-donor capabilities for Ph, PP, NP, ClP and MeOP. In this context, the main oxidative species is O₂^√−, since O₂(¹Δ_g) is quenched in an exclusive physical fashion by the ArOH. The production of O₂^√− regenerates Rf impeding the total degradation of the sensitiser. This kinetic scheme could partially model the fate of ArOH in aquatic media containing natural photosensitisers, under environmental conditions.     

有机污染物的光催化降解过程中的分析技术进展

本文对有机物的光催化降解动力学研究 ,降解产物的鉴定、定量检测等过程中所使用的一些分析技术和手段 ,尤其是在有机物的光降解机理研究中羟自由基的检测技术和方法进行了综述     

Optimizing electron spin resonance detection of hydroxyl radical in water

The parameters affecting the electron spin resonance (ESR) detection of hydroxyl free radical in water are studied and optimized. The hydroxyl radical is generated by the Fenton reaction with iron (II) ammonium sulfate and hydrogen peroxide reacting in a phosphate buffer using N-tert-butyl-alpha-phenylnitron as the spin trap. The concentrations of Fe²⁺, H₂O₂, and phosphate buffer are the parameters studied. The Taguchi method and the orthogonal experiment design were used to evaluate the effects of these parameters on the ESR signal intensity. By the analysis of the signal-to-noise ratio and the analysis of variance, the order of importance of the various parameters on the hydroxyl radical formation is determined for optimal ESR detection of hydroxyl radical. The results will help the development of water purification technologies using hydroxyl free radical as a green oxidant.     

Comparative study of the oxidation of atrazine and acetone by H2O2/UV, Fe(III)/UV, Fe(iii)/H2O2/UV and Fe(II) or Fe(III)/H2O2

In this study, the rates of degradation of organic compounds by several AOPs (H₂O₂/UV, Fe(III)/UV, Fe(III)/H₂O₂/UV, Fe(II)/H₂O₂ and Fe(III)/H₂O₂) have been compared. Experiments were carried out at pH ≈ 3 (perchloric acid / sodium perchlorate solutions) and with UV reactors equipped with a low-pressure mercury vapour lamp (emission at 253.7 run). The data obtained with atrazine ([Atrazine]_o = 100 μg/L) showed that the rate of degradation of atrazine in very dilute aqueous solution is much more rapid with Fe(III)/UV than with H₂O₂/UV. Photo-Fenton process (Fe(III)/H₂O₂/UV) was found to be more efficient than H₂O₂/UV and Fe(II)/H₂O₂ for the mineralization of acetone ([Acetone]_o = 1 mM).