近年来长江水功能区水质达标情况分析

Standard-reaching Rate of Water Quality in Water Function Regions in Changjiang River Basin in Recent Years

根据近5 a来长江流域水资源质量公报和水资源公报等方面的监测数据,初步分析了长江干流及主要支流水功能区一级区和二级区中饮用水源区水质达标情况,并对主要污染物质变化情况进行了讨论。分析结果表明:(1)水功能区一级区达标率明显提高,其中河流达标率始终高于湖库,湖库达标率年内变幅较大;(2)水功能区二级区达标情况虽然也提高了11.6%,但湖库饮用水源地达标率仍然处于下降状态;(3)从长江流域水资源二级区看,各河段水功能区一级区达标率都有所改善,改善最明显的是宜宾—宜昌江段,其次是岷沱江,除金沙江石鼓以下干流和嘉陵江等山区河流外,大部分江段枯季达标率相对较差,说明长江水质总体尚好的主要原因是巨大的水环境容量;(4)河流饮用水源区达标率比较高,但年内变幅也较大,改善比较大的是宜宾—宜昌干流和湖口以下干流,分别提高了50.6%和29.2%,乌江有所退步,达标率下降了21.6%,主要超标项目是总磷;(5)随着点源治理效果显现,总磷已经超过氨氮和化学需氧量(COD),成为长江几乎所有水体最主要的超标项目。总之,要进一步提高长江水质达标率,需要根据各水域主要污染源,精准控源,科学调控和持久发力。

According to the data of water resource quality bulletin and water resource bulletin of Changjiang River Basin in recent five years,the standard-reaching rate of water quality of first-class water function region and drinking water source area of second-class water function region in main streams and main tributaries of Changjiang River Basin was examined,and the change of main pollutants was also analyzed.Research findings are as follows:(1) in first-class water function region,the standard-reaching rate of water quality has improved apparently,of which the rate of river water quality is always higher than that of lake water quality.The standard-reaching rate of lake varies significantly during a year.(2) In second-class water function region,despite that the standard-reaching rate of water quality has raised by 11.6%,the rate of lake maintains a downward trend.(3) The standard-reaching rate of water quality has improved in main streams and tributaries of the Changjiang River,among which the Yibin-Yichang reach witnessed the most obvious improvement,followed by the Minjiang River and Tuojiang River.Except for the stream below Shigu of Jinsha River and mountainous rivers of the Jialing River,the standard-reaching rate of water quality in dry season is relatively poor in most river segments of the Changjiang River,indicating that the huge water environmental capacity of the Changjiang River contributes to the good water quality in recent years.The standard-reaching rate of river water quality in drinking water source area is relatively high,but varies sharply during a year.The rate of Yibin-Yichang reach and the main stream in the downstream of Hukou increases by 50.6% and 29.2%,respectively,while the rate of Wujiang River drops by 21.6%,with total phosphorus as the major standard-exceeding pollutant.(5) As the point-source pollution control works effectively,total phosphorus has replaced ammonia nitrogen and COD to be the most important standard-exceeding pollutant in almost all water bodies of the Changjiang River.In conclusion,further improving the water quality of Changjiang River requires precisely targeted,scientific and steady control of main pollutants in different water regions.