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mfw553947967金虫 (著名写手)
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Among the natural contaminants of water are humic acids and fulvic acids, substances that have been studied rather thoroughly.Humic acids contain aromatic rings having iso- and heterocyclic structures, which allows them to be regarded as natural polyoxy acids. Humic acids, their acid salts of alkali metals, and all salts of alkaline-earth metals form colloid solutions. Fulvic acids are close to humic acids in structure, but side bonds predominate in their molecules. It is generally agreed that fulvic acids are high-molecular hydroxycarboxylic nitrogen-containing acids, readily soluble in mineral acids. Fulvic acids usually account for the bulk of natural organic impurities (up to 80–90%), and they also account for 85–95% of the color of water [4]. The molecular mass of fulvic acids and humic acids lies in the range 100– 50000; their molecules measure from 5×10–10to5×10–8m. Despite the wide scatter in their molecular mass,most natural organic compounds have a molecular mass not exceeding 3000–5000. This is confirmed, inparticular, by Fig. 1, which shows examples of molecular mass distribution for a model solution of peat extract (having a color index of 88.7°) and for mechanically cleaned water from the Moscow River. Man-made organic substances enter into natural water bodies together with wastewaters, the latter being usually subdivided into industrial, agricultural, and domestic wastewaters. The amount of organic compounds discharged together with wastewaters in Russia annually totals more than 3 million tons. Industrial wastewaters have a diversified chemical composition; the greatest amounts of effluents are produced at petroleum refineries, metallurgical plants, chemical plants, and pulp-and-paper mills. The most considerable fraction of surface-water contaminants consists of petroleum products, surfactants, phenols and their compounds, ketones and esters, organic acids, and sugars. The molecular mass of these impurities is fairly low (petroleum products, 155–260; surfactants, 200–800;phenol compounds, up to 500; and sugars, up to 250). Effluents from the food industry contain proteins, carbohydrates,and fats. The molecular mass of proteins varies over a wide range—from a few thousand to several tens of millions—and that of carbohydrates and fats, from 200 to 300. |
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mfw553947967: 金币+30, 翻译EPI+1, ★★★很有帮助 2013-04-26 21:10:35
爱与雨下: 翻译EPI-1 2013-04-26 21:43:48
爱与雨下: 金币-30 2013-04-26 21:43:56
爱与雨下: 翻译EPI-1 2013-04-26 21:43:48
爱与雨下: 金币-30 2013-04-26 21:43:56
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2楼2013-04-26 19:19:41