三峡蓄水对小江CODCr、NH3-N及TP纳污能力的影响

摘要

三峡蓄水后的高水位条件下,长江支流小江回水区水域水文情势发生变化,流速减小,水域污染物浓度本底值发生变化,水环境参数与天然河道相比改变很大,纳污能力受到很大的影响.根据小江水功能区划及水功能区水质目标,分析计算蓄水前后CODCr、NH3-N及TP纳污能力总量的逐月值和年总量.结果表明:每月的CODCr、NH3-N、TP的纳污能力受流量、流速、水位和水质控制目标的影响,蓄水后每年CODCr纳污能力总量减少约20.59％,NH3 -N的纳污能力总量减少约22.22％,TP的纳污能力总量减少约23.08％.小江回水区水域纳污能力减小是蓄水后富营养化现象增多的重要因素之一.%After the impoundment of The Three Gorges Reservoir the hydrological condition has been greatly affected in the Xiaojiang backwater, also the water velocity has slowed down significantly. Moreover, water from the Yangtze River pouring into the backwater changed the water pollutant concentration of the background, causing water environment parameters to be greatly different from those in the natural river. Eventually water environmental capacity will be affected greatly. The Xiaojiang area was studied through based on the data from the Water Functional Division and water quality control target, the water total environmental capacity of chemical oxygen demand (CODCr), ammonia nitrogen (NH3-N), total phosphorus (TP) and their monthly values were computed. Monthly water environmental capacity was affected by water discharge, water velocity,water level and water quality target. After the impoundment of the Three Gorges Reservoir, the water environmental capacities of CODCr, NH3-N and TP have reduced approximately 20.59%, 22.22% and 23.08% respectively.The reduction of water environmental capacity is one of the important factors of water eutrophication in the Xiaojiang backwater.