【作者】 汤红亮；

【导师】 王超； 李勇；

【作者基本信息】 河海大学 ， 环境工程， 2006， 硕士

【摘要】 随着工业的发展,大量污废水排入城市河流,导致城市中河流底泥的重金属污染不断加重。为了更深入地了解城市河流底泥中的重金属在水土界面上的吸附与解吸过程,选取了淮安市里运河的四个断面处的底泥进行实验研究。通过现场采样,分析样品中的重金属含量,用实验手段模拟底泥中的重金属在水土界面上的释放过程,并建立了简单的数学模型来模拟底泥重金属在水体中的释放过程。 本文主要研究结果: （1） 里运河底泥重金属污染严重:各测点镉的质量分数均超过淮安市土壤背景值中镉的质量分数,最大质量分数是背景值的15.73倍;砷和硫化物的质量分数呈沿程降低趋势,但引河路和造纸厂断面砷的平均质量分数超过了淮安市土壤环境中砷的质量分数,砷的最大质量分数为土壤三级标准中砷质量分数的2.45倍;硫化物在引河路断面污染突出,明显高于其他3个断面底泥的硫化物质量分数;重金属在垂向分布上表现为中部的黑泥层质量分数最高;在污染河段的同一断面,河岸的重金属污染程度一般比河中要高。 （2） 静置条件下,底泥中的重金属Cd在开始阶段向水体中的释放量先逐渐增大,达到峰值后又逐渐减小,最后趋于稳定;As和硫化物在开始阶段向水体中的释放量先逐渐增大,最后趋于稳定。底泥中重金属含量的增加、底泥粒径的减小、扰动强度的增大、温度的升高、水流速度的加大等等,均能使重金属释放速度增大。 （3） pH值和离子浓度对重金属的吸附解吸的影响较大;温度对吸附解吸也有影响,但影响程度较小。随着pH值的增大,吸附质中镉的质量浓度相应减少,溶液中镉的质量浓度增大;随着加入NaCl质量的增多,吸附质中镉的质量浓度相应减少,溶液中镉的质量浓度增大。 （4） 建立重金属在水土界面上的释放模型C=k₁Q/V（k₁+k₂）+（C₀-k₁Q/V（k₁+k₂））e^{-（k₁+k₂）t},并得到了里运河底泥重金属镉的释放系数和吸附系数分别为0.015和0.429,该模型较好的验证了重金属向水体中释放的实验数据,但是该模型还有一些局限。 淮安市里运河底泥污染严重,在外界条件的变化下,会使里运河的水质重金属指标超标,需要对里运河底泥进行彻底清淤。更多还原

【Abstract】 With the development of industry, the pollution of the sediments in the city river is very serious. In order to study the process that the heavy metals release and adsorb between the sediments and the water, the experiment is done with the sediments from the four sections across the Liyun river. Firstly, content of the heavy metals in the sample is analyzed. Secondly, the process that the heavy metals release and adsorb between the sediments and the water is simulated in the lab. In order to know the main factors on the heavy metals release from the sediments, isothermal adsorption test is made. At last, the model is built to simulate the process.The main results are drawn from this paper as follows:(l)The heavy metals of the sediment in the Liyun river is serious: the quality fraction of cadmium at each monitoring point is greater than its background value in soil of Huai’an suburb, and the maximum at monitoring points is 15.73 times of the background value;the quality fractions of arsenic and sulfide are decreasing along the river, but the average values of arsenic at the sections of Yinhe Road and the paper plant are beyond their background values in soil;the maximum quality fraction of arsenic is 2.45 times as high as that of soil of grade-III, and the quality fractions of heavy metals in the middle of black mud layers are the highest in vertical direction, and the pollution caused by heavy metals at the riverbank is more serious than that at the center of the river at the same profile of polluted sections.(2)Under a static state, the amount of the discharge from the heavy metal Cd of the sediment will increase gradually to the maximum first, and then it will decrease to a certain amount. The amount of the discharge from As and sulfide will gradually increase first, and finally become a certain amount. The causes which will increase the rate of the amount of the discharge from the heavy metals of the sediment include the increase of the amount of the heavy metals from the sediment, the decrease of the diameter of the particles from the sediment, the increase of the intension of the vibration, the increase of the temperature in the water, the increase of the speed of the stream, and so on.(3)The value of pH and the concentrations of the irons are the two main factors on the adsorption ability of the heavy metals. With the increase of the pH value or with the increase of the quality concentration of NaCl in the overlying water, the quality concentration of cadmium increase in the overlying water and decrease in the sediment.(4) The model is established which is used to simulate the process that the heavy metal releases in sediment-water interface. The release and the adsorb coefficient of the cadmium in the sediment of Liyun river is obtained, which is 0.015 and 0.049.The pollution of the sediments in the Liyun river is very serious. The content of the heavy metals in the river maybe increase when the environmental conditions of the river changed. So it is necessary for the river to be dredged.更多还原