水相中POPs光化学降解研究进展

综述了近年来12种持久性有机污染物(POPs)在水体中光化学降解行为,从水体中POPs的光解途径、光解机理和定量结构-性质关系(QSPR)三个方面探讨了POPs在水体中的光化学行为,展望了水体中POPs光化学行为的研究前景.     

双酮基光化学高级氧化/还原技术:分子机制解析及研究进展

由于实际水体成分的复杂性,以强活性自由基反应为主导机制的传统光化学高级氧化/还原技术普遍存在光子利用率低、底物选择性差等问题.近年来,基于低分子量双酮的新型光化学氧化/还原技术因具有良好的反应选择性和抗共存基质干扰能力而渐受关注.本文总结了双酮在水相中的光化学研究进展,重点评述了烯醇式双酮在光化学体系中对电子和能量转移的调控作用,初步揭示了紫外/双酮法转化污染物的特点以及其在水污染控制中的应用潜力.进而通过分析目前研究中存在的问题,对今后的研究方向和趋势进行了展望.     

抗生素不同解离形态在水环境中的光化学行为

表层水体中存在众多可解离的有机污染物,揭示其不同解离形态的环境光化学行为,对于污染物的环境持久性和风险评价具有重要意义.抗生素是在水环境中广泛存在的新型有机污染物,其中氟喹诺酮类(FQs)、磺胺类(SAs)、四环素类(TCs)等抗生素因分子结构中含有羧基、羟基和/或氨基等可电离基团,在水中以多种解离形态共存而备受关注.抗生素的多种解离形态不仅以不同的丰度共存于环境表层水体中,而且不同的解离形态表现出相异的环境光化学转化行为和风险.本文总结了水环境中可解离抗生素光化学行为研究的最新进展,介绍了pH值对直接和间接光解动力学的影响,着重评述了抗生素不同解离形态的光化学反应动力学、转化产物和路径,讨论了可解离抗生素光化学转化的环境半减期和风险,最后对抗生素不同解离形态的光化学行为研究进行了展望.     

天然水体中可溶性有机质的自由基光化学行为

可溶性有机质在天然水体中广泛分布,是全球碳循环的重要组成部分。大部分的可溶性有机质含有苯环、羧基、羟基和羰基等发色团,能够吸收特定波长的太阳光,产生水合电子、单线态氧、羟基自由基等活性自由基,从而影响天然水体污染物的光化学转化以及降解过程。本文综述了20世纪90年代以来可溶性有机质的自由基光化学行为以及其在水体污染物转化中的作用方面的研究进展,并探讨了今后研究中应该关注的问题。     

有机污染物水解速度常数与腐殖质浓度定量关系的建立及验证

水解是有机污染物转化降解的重要途径.天然水体中的腐殖质影响有机化合物的水解速度常数,使之与蒸馏水缓冲系统中的测定值有较大差别.本文推导并验证了腐殖质浓度与水解速度常数的定量关系,测定了腐殖质与有机化合物的缔合系数.     

水环境中铜的光化学研究进展

水环境中的铜主要以配合物形式存在,大多具有光化学活性.由于铜在光化学过程中的氧化还原循环可以导致其配体以及水体中有机污染物的降解,所以铜及其配合物在污染修复技术中的应用逐渐受到关注.本文综述了水环境中铜的光化学研究进展以及在多相和均相光催化体系中铜对污染修复的影响.     

微囊藻毒素在单波长紫外光照射下的光降解动态研究

研究了两种微囊藻毒素在两种紫外光照射下的光降解行为,研究结果表明:UV-C是降解微囊藻毒素较好的光源;光照强度是影响毒素降解重要的因素,其次是温度和酸度;在UV-C的照射下,水体腐殖质对光降解具有抑制作用;微囊藻毒素的光解反应符合准一级动力学模型.同时本工作还按实际环境水体中毒素的含量水平进行了模拟研究,发现紫外光UV-C对环境水体中低含量的微囊藻毒素具有很强的去除能力.为今后发展无毒、高效、经济实用的饮用水处理技术做了有益的探索.     

土壤腐殖质的分析化学研究进展

对土壤腐殖质的分析化学研究进展作了综述。具体包含如下几个方面的内容；土壤腐殖质的组成和结构的研究，土壤腐殖质的起源和形成的研究，土壤腐殖质与土壤中有机，无机物质的相互作用的研究以及有机物料的分解，转化及其对腐殖质影响的研究，同时，对土壤腐殖质的研究中有待进一步用分析化学方法解决的几个问题进行了探讨。     

“第十三届全国光化学学术讨论会”在西安成功召开

<正>第十三届全国光化学学术讨论会于2013年8月7日—10日在陕西省西安市陕西师范大学成功举办.本届会议由中国化学会光化学专业委员会主办,中科院化学研究所光化学重点实验室、中科院理化技术研究所光化学转换与功能材料重点实验室、陕西师范     

硝基酚类化合物在海水中的光化学氧化研究

酚类化合物尤其是硝基苯酚属于国家严格控制排放的有毒物质 .由于工业排污等原因 ,在近岸水体中能检测到许多酚类化合物 .我国胶州湾和杭州湾表层海水中酚的含量分别高达 3和 9mg/L[1] .酚的毒性会影响海水生物的生长和繁殖 ,危及人类健康 .由于硝基苯酚难于生化降解 ,因此研究其在水体中的光降解十分重要 [2～ 6 ] .文献中关于有机污染物的光化学研究大多侧重于废水处理 ,且降解方法也多采用 Ti O2 催化降解 [7,8] .对于硝基苯酚在天然水体中的光降解则知之甚少 .本文通过模拟海水条件下硝基苯酚的光化学反应及其影响因素 ,更加深入地了…     

Stability and Mobility of Metal-Humic Complexes Isolated from Different Soils

The contamination of potable water aquifers by heavy metals is one of the most severe environmental threats. For the transport of heavy metals from various types of contaminated sites into the ground water and also into surface water aquifers, humic substances (HS) are recognized to be of main importance. Dissolved in natural waters humic substances are readily complexed with a variety of metal ions. Therefore, humic substances are of cardinal importance for the migration and, consequently, the pollution of ground waters with heavy metals. Our paper presents the results of a comprehensive comparison of several isolated humic acids of soils of different origin (different geochemical milieu) and their metal complexes. Two polluted sites in Germany, which differ in their geochemical milieu (pH-value) were selected. The aim of our experiments was to describe the properties of terrestrial humic substances depending on their origin and genesis as well as the effects of the transport of humic substance-bound metals into the water-unsaturated soil zone. After determination of heavy metals in the soils by photon activation analysis the activated soil was used as an inherent tracer in batch experiments with the isolated humic acid. After adsorption of the loaded humic acid on an XAD-8 resin column, the partition of metals mobilized by humic acids could be quantified. There are correlations of the formation of metal-humic complexes with the soil pedogenes, with the pH-value as well as with the humic acid concentration.     

Interference of Humic Substances in the Spectrophotometric Determination of Bromate by Phenothiazines in Natural Waters

Abstract

The spectrophotometric method of bromate (BrO₃ ^?) determination by phenothiazines was applied to natural water samples and the interferences due to the presence of inorganic and humic substances were investigated. Common ions present in natural waters did not interfere and only the less abundant NO₂ ^? and Fe²⁺ exhibited strong interferences. Interferences of the two latter ions, if they existed, could be controlled and the method proved to be accurate and with a low detection limit. However, it was found that the presence of soluble humic substances resulted in positive interference, rendering the method unsuitable for bromate determination in natural waters and restricted its use in pure bromate solutions. This interference can be attributed to the electron acceptor groups invariably existing in the humic molecules. Since humic substances can remain in the water even after its ozonation, they will also contribute to a positive interference in bromate determination in potable waters.     

Use of disposable clean-up columns for selective removal of humic substances prior to measurements with a nitrate ion-selective electrode

Measurements of nitrate in natural waters with a nitrate ion-selective electrode are seriously affected by the presence of humic substances. These can be removed quantitatively by a clean-up procedure with cheap disposable adsorption columns packed with chemically-bonded alkylamino silica. The method is applied to natural water samples with high contents of humic substances. The nitrate concentrations found were in good agreement with determination by ion chromatography.     

AFM study on the adsorption and aggregation behavior of dissolved humic substances on mica

Humic substances (HS) are a category of naturally occurring, biogenic, heterogeneous organic materials found in or extracted from soils, sediments, and natu- ral waters that can generally be characterized as being yellow-to-black in color, of highly variable relative molecular masses, and refractory[1,2]. Derived from a variety of organic precursors (plant biopolymers such as lignin etc.), plant residues and animal debris via both transformation and synthesis processes[3] under the profound ge…     

The use of linear potentiometric titration curves in the determination of alkalinity and acid-base properties of diluted solutions of humic substances

A critical study of the use of Gran and modified Gran functions for the determination of alkalinity and acid-base properties of diluted solutions containing humic substances is presented. These solutions were composed of 340 muM HCO3(-)(3) in 0, 10, 20.5 and 41 mg/1. of sodium humate in order to simulate natural waters with different levels of dissolved organic carbon. The results showed that the alkalinity may be determined in good agreement with the expected value using both methodologies. The modified Gran functions give information about acid-base speciation in addition to the alkalinity. The application of the modified Gran functions for determination of humic acid pK(a)s and stoichiometry was studied under conditions simulating waters rich in natural organic matter in terms of humic acid concentrations.     

Spectroscopic approaches to the study of the interaction of aluminum with humic substances

Aluminum ion (Al³⁺) in the ‘free’ (aquo) state is becoming increasingly prevalent in environmental waters, especially fresh waters, as a consequence of acid rain and other environmental processes. As Al³⁺ ion is known to affect markedly a wide range of biological systems, and since the presence of Al³⁺ in humans has been linked to a number of human diseases, it is important to understand the speciation of Al³⁺ ion in natural waters. Since some of the most important complexation agents for Al³⁺ in both fresh and sea waters are members of the complex humic substances group, it is important to understand the manner in which Al³⁺ interacts with this class of molecules, especially since binding of Al³⁺ to these molecules can effectively increase the bioavailability of this toxic metal ion to biological systems. The objective of this review is to present the current state of our understanding of aqueous aluminum complexation with the most acidic members (and therefore the most likely candidates for serving as Al³⁺ complexing agents) of the humic substances group, the fulvic acids. Much of the current knowledge has been revealed by comprehensive fluorescence titration analyses. Some additional information has come from other experimental approaches, including infrared spectroscopy, nuclear magnetic resonance spectroscopy, and a variety of electrochemical approaches. In this review, we also report on the results of our recent fluorescence and IR spectroscopy survey of the interaction of metals from of all three Nieboer and Richardson categories of environmental metals (Class A, Class B and Intermediate Class) with the fulvic acid sub-group of the humic substances. This has proven helpful in understanding some of the unique spectral behaviors of the Al³⁺-fulvic acid complex vis-a-vis fulvic acid complexes with many other metal ions. The results of our fluorescence and IR experiments with the model compounds, such as salicylic and phthalic acids, have allowed confirmation of the important roles played by both salicylic acid-like sites and phthalic acid-like sites in the unique complexation of Al³⁺ to humic substances, and help to explain some of the observed spectroscopic changes associated with Al³⁺ ion complexation to humic material. From the current work, it seems clear that major sources of the deviation in spectral properties between Al³⁺ and many other metal ions (across all three Nieboer and Richardson categories) are the unusually high value of its charge density and relatively low propensity for involvement in covalent bonding interactions (i.e. a very high ionic index combined with a relatively low covalent index in the Nieboer and Richardson classification of environmental metals), as well as affinity for certain functional groups.     

Determination of nitrate in natural waters by voltammetry at a stationary mercury drop electrode

Nitrate can be determined by second-sweep cyclic voltammetry at a stationary mercury drop electrode utilizing the autocatalytic effect of the hydroxyl ions formed at the surface of the electrode during the reduction of nitrate in the presence of an excess of trivalent cations. The reduction current in the second sweep with the same drop is proportional to the nitrate concentration in the range 1–1500 μmol l^?1 in natural waters. The humic substances present in natural waters have a favourable effect on the determination of nitrate. The method is applied to the determination of nitrate in drinking and river waters.     

Study of Aqueous Chemical Forms of Silicon in Organic-rich Waters

The study of silicon species in organic-rich waters is a very significant problem. This type of waters is widely spread all over the world. It is characterized by a high content of humic substances, high color of water and low pH. In this regard, a certain determination of silicon concentration in this type of waters is impossible without a preliminary investigation of silicon species. The aim of this research is therefore an investigation of the ratio of silicon dissolved forms in organic-rich waters depending on the silicon concentration and the acidity of the water. The study of pH influence on silicic acids and a silicon–humic matter interaction was carried out using model solutions and natural bog waters (Tomsk region). It has been found that the degree of polymerization of silicic acids essentially depends on the acidity of a solution. Scanning of spectrophotometric measurements has shown that silicon does not form stable complexes with fulvic and humic acids in weak-acid media (рН 3-4). Studying the bog waters of Tomsk Region has shown that they (рН=3.66-3.80) contain only monomeric-dimeric and polymeric forms of silicic acids.     

NMR diffusion analysis of surfactant-humic substance interactions

Surfactants can be introduced into the environment through wastewater or by direct contamination. Understanding the fate and transport of surfactants in the environment is important in assessing their role as pollutants. Humic substances are complex heterogeneous mixtures of decomposition products of natural organic materials. They are environmentally important because they are known to solubilize and transport organic pollutants. Therefore humic substances are likely to affect the environmental fate of surfactants. Diffusion coefficients measured with pulsed-field gradient nuclear magnetic resonance spectroscopy are used in this study to examine the intermolecular interactions of the surfactants sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) in the presence of various humic substances. These results indicate that humic substances enhance the aggregation of SDS prior to micellization with a more pronounced effect observed for the more hydrophobic humic materials. The positively charged surfactant CTAB forms stable ion pairs with the humic substances.     

Photodegradation of Selected Organophosphorus Insecticides Under Sunlight in Different Natural Waters and Soils

In this work photodegradation of four organophosphorus insecticides (ethyl-parathion, methyl-parathion, fenitrothion, fenthion) in different natural waters and soils was studied under sunlight. The origin of the waters was from the region of Ioannina (underground, lake, and river water) and from Preveza (sea water) in Northern-West Greece. The soils used had different percentages of organic matter (0.9-3.5%) and their characterization were SCL, CL, and SL respectively. The photodegradation kinetics of these insecticides were followed by GC-FTD. The identification of the photodegradation by-products was made by using GC-MS. The half-lives of the organophosphorus insecticides vary from 0.4 to 35.4 days in natural waters and from 3.4 to 21.3 days in soils. The humic substances and the other components of these environmental matrices seem to influence the degradation kinetics. The use of GC-MS allowed the identification of some important photodegradation by-products such as: fenthion sulfone, fenthion sulfoxide, fenoxon, 4-methylthio-3,5-dimethyl phenol, O , O , O -triethyl phosphorothioate, paraoxon, 4-nitrophenol, aminoparathion.