表面活性剂是天然水体中常见污染物。泥沙吸附表面活性剂后,泥沙表面性质发生变化,从而影响泥沙起动规律。以长江武汉段细颗粒泥沙为研究对象,通过循环水槽装置模拟泥沙起动过程的试验,从定性和定量两方面研究了离子型表面活性剂对泥沙起动的影响机理。结果表明:①泥沙的起动过程可细分为7个阶段,当流速为15.0~20.0 cm/s时,水明显浑浊,泥沙起动;②由于表面活性剂的存在,泥沙悬浮相对减少,平衡含沙量明显降低,只达到初始含沙量的50%左右;③随着阴离子表面活性剂浓度升高,泥沙临界起动流速从19.37 cm/s增加到23.05 cm/s,而完全起动流速略微减小,从37.06 cm/s降至36.15 cm/s;④随着阳离子表面活性剂浓度升高,泥沙临界起动流速从19.37 cm/s增加到23.32 cm/s,完全起动流速从37.06 cm/s降至32.12 cm/s。电子显微镜观测结果表明,表面活性剂促进了泥沙絮凝,从而显著影响了泥沙的起动规律,且阳离子表面活性剂对泥沙的影响较阴离子表面活性剂大。研究结果不仅具有现实意义,而且为进一步完善泥沙运动体系提供了理论依据。
Abstract
Surfactant is a common pollutant in natural waters. The adsorption of surfactant on sediment changes the surface properties of sediment, thus affecting the rules of sediment's incipient motion. With the fine grain sediment in Wuhan segment of the Yangtze River as research object, the effects of ionic surfactants on sediment's incipient motion were examined both in qualitative and quantitative terms by simulating the starting process of sediments in circulating flumes. Results suggest that the starting process of sediment can be subdivided into seven stages. When flow velocity was 15.0~20.0 cm/s, the water body was obviously turbid and sediments started. The presence of surfactant reduced the suspension of sediments and cut the equilibrium sediment concentration significantly to around 50% of the initial sediment content. A rising concentration of anionic surfactant helped augment the critical starting velocity of sediment from 19.37 cm/s to 23.05 cm/s, while curb the full starting velocity slightly from 37.06 cm/s to 36.15 cm/s. Increment in the concentration of cationic surfactant boosted the critical starting velocity of sediment from 19.37 cm/s to 23.32 cm/s, while lowered the full starting velocity from 37.06 cm/s to 32.12 cm/s. The presence of ionic surfactants promotes the flocculation of sediments, thus evidently affects the incipient motion of sediment. Cationic surfactant has a greater effect than anionic surfactant.
关键词
细颗粒泥沙 /
离子型表面活性剂 /
泥沙起动 /
临界起动流速 /
完全起动流速 /
平衡含沙量
Key words
fine grain sediment /
ionic surfactant /
sediment's incipient motion /
critical starting velocity /
full starting velocity /
equilibrium sediment concentration
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