Topics of water sciences and technology

In the preceding series of contributions to ESPR typical examples from actual fields of water chemistry were presented on various topics: integrated water quality management, diagnosis of water bodies, therapy of aquatic systems, and fitness for aquatic systems. These contributions clearly showed the need and importance of more intensive research. In the principle committee III 'Basic Research' of the Water Chemical Society, various expert groups work on scientific backgrounds in these fields. Some relevant topics are selected in this outlook, mainly on interactions of solids with water, the role of environmental colloids, the development of modern biochemical methods for diagnosis, the impact of chemical speciation on bioavailability and water technology, and the development of advanced methods in water treatment technology. Innovative approaches to understand the interactions between pollutants, water and solids are crucial for assessment of contaminants with biochemical and analytical methods, for the development of new efficient technologies and for application of treatment methods with little or no waste and by-product formation.     

Photodegradation of new amino acid derivatives suitable for chelating agents in pulp bleaching applications

The purpose of this study was to evaluate photodegradabilities of the following new low-nitrogen chelating agents: N-bis[(carboxymethoxy)ethyl]glycine (compound 1), N-bis[(1,2-dicarboxyethoxy)ethyl]glycine (compound 2) and N-bis[(1,2-dicarboxyethoxy)ethyl]aspartic acid (compound 3). At first photodegradation of these chelating agents as uncomplexed Na-compound 1–3 and Cu(II) complexes were tested, both in lake and distilled water, by exposing them to near-UV region radiation at the range of 315–400 nm. Uncomplexed Na-compounds 2 and 3 were selected to sunlight exposure experiments carried out in lake and distilled water. Compound 3 was also tested in sunlight as Cu and Ca complexes in both solutions. Photodegradation of Na₆-compound 3 in distilled water was studied by exposing it to radiation at the wavelength of 253.7 nm. Photodegradation products were analysed by means of GC-MS (gas chromatography with mass selective detector).

The results demonstrated that compound 1 was quite photostable even as Cu complex while compounds 2 and 3 were found to be photodegradable. Over 90% reduction of compound 3 was achieved during one week and 80% reduction of compound 2 in two weeks' time when they were added as Na salt to lake water and exposed to sunlight. Compound 3 as Cu complex degraded totally in the sunlight in less than one week. In the case of compound 3, the degradation rate decreased depending on the counter cation in the order Cu > Na  Ca. The study demonstrated that photodegradation of Na₆-compound 3 does not result in total mineralization of the compound. A photodegradation pathway for Na₆-compound 3 is proposed.     

Application of KCl denuder for measuring gas phase mercuric species (Hg2+ ) in atmosphere

KCl denuder technique was meployed in the measurement of Hg(II) species in atmosphere firstly. Intensive lab tests indicate that Hg⁰ can pass through KCl denuder freely, while Hg²⁺ can be trapped in it very efficiently. The efficiencies for adsorbing inorganic Hg²⁺ averaged between 95% to 100% with a gross mean of 98%, and those for absorption of organic Hg²⁺ were around 94%. Mass balance calculation shows that mercury trapped in denuder can be quantitatively extracted by 1 mol/L HCl (super grade) and analysed by the method of SnCl 2 reduction CVAFS determination, thus, demonstrated the feasibility of KCl denuder in measurement of Hg(II) in atmosphere. Preliminary application at two sites Gteborg, Sweden and one site in Ireland, found 0 04—0 15 ng/m³ of Hg(II) species, contributing to 2%—10% of the total mercury.     

Al(III) speciation distribution and transformation in high concentration PACl solutions

Introduction Since water pollution has become a worldwide problem, many countries suffered from lack of quantity of source water to high quality and safe water or both. Increased attention has been paid to the purification of water in recent years. The ef…     

The chemical stability of heavy metals in a natural water system

A comprehensive investigation of heavy metal pollutants in Xiangjiang river was accomplished to evaluate their chemical stability through three different ways: (1) Chemical speciation by direct measurements; (2) Chemical equilibrium model simulation; (3) Sediment extraction experiments. All the results demonstrated that the directly bioavailable fraction was in a very limited amount. The metal bound to organic ligands, adsorbed particles and precipitated species presented a buffer for solution species. The majority of metals occured in the residues as solid particulates. It was inferred that the heavy metal pollutants in this aquatic system exhibited a high chemical stability. The critical limits of discharging load and pH values were suggested.     

固态聚合氯化铝的27Al NMR研究

聚合氯化铝(PAC)是一种水处理混凝剂,可为液态(PAC-L),也可浓缩成固体(PAC-S)、PAC-L在水中稀释时铝的形态的变化已用~(27)Al核磁共振法(NMR)进行了研究。本工作试图用~(27)Al NMR法对PAC-S及其在水中溶解稀释物中铝的形态进行研究,以探讨固化对PAC及其在水中铝的形态的影响。     

Chromium in intertidal sediments of the Clyde,UK: potential for remobilisation and bioaccumulation

Detailed surveys of intertidal sediments have been performed along the north and south shores of the Inner Clyde estuary, UK. Surface sediment data reveal significant spatial variation in Cr content and an association with major sediment characteristics and location within the estuary. Depth variation for Cr and other heavy metals cannot be explained by variation in major geochemical controls such as grain size and organic matter and highlights the impact of historical contamination on sediment quality. These elevated levels at depth may still have environmental impact through redox-reactivity, in association with iron and manganese. Sequential extraction of sediments and pore water analysis of Cr(VI) and Cr(III) provide detailed information on release potential from the sediments. The implication of Cr mobility for biota in the estuary has been assessed by the analysis of a common marine bivalve, Mytilus edulis (Blue Mussel) and a burrowing polychaete, Nereis diversicolor (rag worm) from a number of survey sites. Bioconcentration factors for Mytilus indicate that the weakly held portion of sediment Cr is available for uptake and in the case of Nereis, bioaccumulation appears to be inhibited by sediment organic matter.     

氯元素对烟气中汞的形态和分布的影响

采用化学热力平衡分析方法研究了在煤燃烧在气化过程中产生的瀵气里痕量元素汞的形态及分布，在一个大气压下，400K－2000K温度范围里，研究了汞－煤系统和汞－煤－氯系统中汞在还原性气氛和氧化性气氛的烟气中的化学形态和分布，着重探讨了煤中的氯元素对汞在烟气中的形态和分布的影响，化学热力平衡分析结果表明，在煤燃烧和气化的最高温度区域里，单质汞是示是主要形式，少量的氯元素可以大大地增强汞元素的蒸发;在气化的还原性气氛烟气中，汞的主要形式是单质汞，在氧化性气氛的燃煤烟气中随着在烟气中温度的降低，单质汞将发生化学反应而生成氯化汞；烟气中氯元素的含量越大，氯化汞作为稳定相的温度范围越宽。     

东南极海硒的形态和分布

采用新的现场分离了东海极海１２个表层海水样及３２个剖面样中硒及各主要溶存形态的含量，发现总硒含量高于其它各大洋，这可能与特殊的极地生态环境对其形态的影响有关〉Ｓｅ（Ⅵ）拟可作为水团指示剂