长江干流水功能区水质评价与纳污限排分析

基于2016年长江干流水功能区水质监测数据、主要污染物入河量调查估算和相关规划成果,从水资源分区、水功能区类型角度,系统分析了长江干流水功能区水质类别、达标情况与超标特征、沿程水质变化,以及主要污染物COD、氨氮入河量与纳污限排的分布特点,据此探讨了影响长江干流水功能区水质的主要因素。结果表明:2016年长江干流水功能区双指标达标率接近95%,而全指标达标率不足65%,超标水功能区主要分布于重庆、湖北、江苏和上海段,以保护区、保留区和饮用、工业用水区数量较多。长江干流以工业用水区、排污控制区单位长度污染物入河量最大、污染程度最高,纳污限排需综合考虑水体自然环境容量与社会经济发展需求进行控制。目前,COD、氨氮已不是影响长江干流水功能区水质的关键因子,取而代之的是总磷,分析表明总磷沿江呈逐渐升高趋势。分步推进长江干流水功能区总磷评估考核工作,倒逼总磷污染物减排已刻不容缓。

Water quality evaluation and pollutant carrying capacity and discharge limitation analysis on Yangtze River water function zone

Based on the water quality monitoring data of the Yangtze River in 2016, the water quality grades, standard-attainment situation, standard-exceeding characteristics and spatial water quality variation of the Yangtze River water function zone were first analyzed. Then, based on the related planning results of the Yangtze River water function zone, the current pollutant discharge, pollutant carrying capacity and discharge limitation of chemical oxygen demand and ammonia nitrogen were analyzed from the viewpoint of water resources zoning and water function area types. Finally, the main factors affecting the water quality of the Yangtze River water function area was discussed in this paper. The results showed that double indicators standard-attainment rate of the Yangtze River water function zone was close to 95%, while all indicators standard-attainment rate was less than 65%. The standard-exceeding water function zones mainly distributed in Chongqing, Hubei, Jiangsu and Shanghai reaches and were mainly the protection area, reserve area, drinking water zone and industrial water zone. In the main stream of the Yangtze River, the per unit length inflow pollutants was the largest in industrial water area and sewage discharge control area, where the pollution was the most serious. The pollutant carrying and discharge capacity limitation of the basin should comprehensively consider the natural environmental capacity of the water body and the demand of social and economic development. At present, total phosphorus is the key factor affecting the water quality of the Yangtze River water function zone, rather than chemical oxygen demand and ammonia nitrogen. It shows that total phosphorus is gradually increasing along the Yangtze River. It is imperative to promote the evaluation of total phosphorus in the Yangtze River water function zone, thereby forcing the reduction of total phosphorus pollutants.