水体紊动作用下湖泊泥沙解吸释放磷的实验研究

Experimental investigation of effect of flow turbulence on phosphorus release from lake sediment

为了揭示水体紊动对湖泊泥沙解吸释放磷的影响,本文选取东洞庭湖湖底表层泥沙作为研究对象,通过近似均匀紊流模拟装置模拟不同强度的紊动水体,研究紊动作用下泥沙解吸释放磷的影响因素和基本规律,结果表明:泥沙起动之前,在垂向紊动扩散作用下,表层泥沙孔隙水与上覆水之间的溶解态磷交换,是溶解态磷迅速增大的主要原因;在较强紊动作用下,泥沙普遍起动,悬浮泥沙所吸附的磷解吸至水体中,溶解态磷含量显著增大,泥沙浓度越高,溶解态磷含量增长速率越大,达到平衡的时间越短;紊动扩散作用对泥沙解吸释放磷影响显著。

The bottom sediment collected from the East Dongting Lake is used to study the effect of flow turbu- lence on the phosphorus release from the lake sediment. As an experimental approach to study turbulence and sediment transport, the oscillating grid turbulence device is introduced to study sediment suspension and phos- phorus release in this paper. As shown by experimental results, the process of the phosphorus release appeares to occur in two distinct stages. When the turbulence intensity of flow is low and sediment particles keep still, the dissolved phosphorus in pore water of bottom sediment releases into overlying water under the action of tur- bulent diffusion near the bed. When the turbulence intensity of flow is high enough and sediment is lifted up into the water, the phosphorus adsorbed on sediment will be released to water through the desorption process. The dissolved phosphorus concentration will increase as the sediment concentration increases. Turbulent diffu- sion is an important factor that affects the phosphorus release from sediment.