三峡库区水库水质Streeter Phelps模型修正及COD变化规律的新探讨

水体复氧规律的研究对于预测和评价水中溶解氧含量, 确定有机污染水体的自净过程具有重要意义。天然水体中溶解氧的多少是评价水环境质量优劣的一项非常重要的指标, 是水质预测的一个重要任务。Streeter Phelps模型是目前进行河流水质研究常用的物理模型，具有良好的理论和实用价值，然而在某些特定水域，该模型的应用受到限制，主要原因是复氧系数的取定多在水流速度较大情况下得到的，而未考虑水面波动对复氧系数的影响，另外，在实际研究过程中发现三峡库区COD变化的规律出现异常：在离排污口相当远的水域，COD随时间变化趋势并不是指数衰减，而是在某个常值附近微小摆动，以往很多修正过的Streeter Phelps模型都无法解释这个现象。经研究表明：考虑波动效应后，对复氧系数进行修正能得到较好的模型计算结果；同时，COD变化规律不仅可以弄清楚，而且可以为进一步研究排污规律和泥沙运动提供科学依据。

APPROACH TO THE MODIFICATION OF STREETER PHELPS MODEL AND THE CHANGING LAW OF COD IN THREE GORGES RESERVOIR

The changing law of re aeration is of great importance for predicting and evaluating the oxygen content in water and the self purification process of organic pollutants. The content of oxygen in natural water is a key index to assess the standard of water. As an often used physical model with good theoretical and practical values, Streeter Phelps model has been widely used to study water quality. However, in some special water areas the utilitization of Streeter Phelps model has some limitation as confirming re aeration coefficient often comes from tests in rivers with fast water flow speed with no consideration of wave effects. Furthermore, in practical research in Three Gorges Reservoir, the changing rule of COD appears abnormally. In some water areas far from pollution source, the value of COD changes with time, but does not follow the exponential attenuation rule. This phenomenon can not be explained by former modified Streeter Phelps model. However, by modifying the re aeration coefficient, a good calculation result has been obtained. Similarly, the changing rule of COD can be monitored clearly, which may also provide scientific evidence to further understand the rules of pollution ejection and sediment motion.