泥沙颗粒和孔隙水在底泥再悬浮污染物释放中的作用

Effects of particles and pore water in release of pollutants due to sediment resuspension

在环境水动力学中,河流底泥污染物释放是人们研究的主要问题之一。污染物进入到水体中后会有一部分聚集在水体底泥中,并在底泥的上层形成一条污染底泥层。底泥再悬浮时,污染物会通过再悬浮颗粒以及孔隙水重新释放到上覆水体中。此文中分别以氯化钠和磷代表典型非吸附性污染物和吸附性污染物,研究底泥污染物释放中底泥颗粒相和水相在不同的水力条件下所起到的作用。研究表明,在底泥静止状态和瞬间悬浮条件下,底泥污染物的释放主要来自于水相孔隙水,非吸附性污染物的释放主要集中在这两个状态下;而在连续悬浮条件下,再悬浮颗粒的解吸释放起着主要的作用,吸附性污染物的释放大部分发生在此阶段。另外,此文还研究了两种类型的泥沙即粘性细颗粒泥沙和非粘性粗颗粒泥沙在底泥连续悬浮时的释放量和释放时间的异同。研究表明,再悬浮粗颗粒泥沙的污染释放量要比再悬浮细颗粒小,但前者释放持续的时间要比后者长。

The bed sediment plays a significant role in environmental hydrodynamics. Most pollutants entering water system may be stored in sediment resulting in a sediment-containing contaminant layer. The release of pollutants due tosediment resuspension has been investigated. Experiments were conducted in order to characterize the relative roles of re-suspended particles and pore water under different hydrodynamic conditions. Conservative tracer （NaC1） and reactive tracer （Phosphorus） were respectively used as the contaminant in bed sediment in a laboratory flume. When the sediment was static, only molecular diffusion on sediment-water interface was considered. When the sediment resuspension occurred, all the conservative pollutants released were from pore water; else when reactive tracer was used solely, pore water played a dominant role at the early stage of pollutant releasing, then the adsorbed tracer was desorbed from re-suspended particles, which controlled successor pollution. The mixing between overlying water and pore water occurred in a short time while the adsorption and desorption of contaminant from re-suspended particles would last relatively long. The different effects of coarse-grained and fine-grained sediment on the pollutant releasing flux were also studied, flux from coarse-grained sediment is smaller than that from fine-grained sediment, but the duration of release from coarse-grained sediment last longer.