2015~2020年岷、沱江流域成都段水环境质量评价及变化趋势分析

Evaluation and trend Analysis of Water Environment Quality of Minjiang and Tuojiang River Basins in Chengdu from 2015 to 2020

为明晰“十三五”以来岷、沱江流域成都段水环境质量状况及变化特征,根据2015~2020年岷、沱江流域成都段15个监测断面(省控及以上断面)水质监测数据,采用单因子评价、水质类别比例、综合污染指数和秩相关系数等方法,从整体水质、不同水系和断面及主要污染物等方面进行水环境质量评价和变化趋势分析。结果表明:2015~2020年岷、沱江流域成都段地表水环境质量明显改善,总体由重度污染改善为优;沱江、岷江水系水质变化呈不同特征,总体均明显改善。岷江水系水质改善幅度大于沱江水系,岷(外)江水系水质始终优于岷(内)江;氨氮和总磷年均浓度下降明显,高锰酸盐指数和化学需氧量年均浓度均低于Ⅲ类水质标准;大部分断面主要污染物浓度下降趋势显著,值得注意的是,三皇庙断面污染物浓度除氨氮外均呈上升趋势,岷江入境成都断面黎明村总磷浓度上升明显。生态流量的增加和平衡叠加有效的污染减排措施有力促进成都市地表水环境质量改善。

In order to clarify the status and changes of water quality in the Chengdu section of the Min and Tuojiang River Basin since the 13th Five-Year Plan period(2016-2020),based on the water quality monitoring data of 15 monitoring sections in Chengdu of the Minjiang and Tuojiang river basins from 2015 to 2020,using the single factor evaluation,proportion of water quality classes,comprehensive environmental pollution index and coefficient of rank correlation methods,the water quality was evaluated and the variation trend was analyzed in terms of overall water quality,the major pollutants,different water systems and sections.The results showed that the water environmental quality of Minjiang and Tuojiang river basins in Chengdu significantly improved from severe pollution to excellent in 2015 to 2020.The water quality of Tuojiang and Minjiang river systems showed different characteristics,and both were significantly improved.The water quality improvement of Minjiang river system was greater than that of Tuojiang river system,and the Minjiang(outer)river system was always better than that of the Minjiang(internal)river system.The annual average concentration of NH_(3-)-N and TP decreased significantly,the annual average concentration of COD_(Mn) and COD_(Cr) were lower than the class Ⅲ water quality standard.The concentration of main pollutants decreased significantly in most sections.It is worth noting that the concentration of pollutants in the Sanhuangmiao section showed a rising trend except for NH_(3)-N.TP concentration in the section of Liming village entering Chengdu from the Minjiang river increased significantly.The increase and balance of ecological flow and effective reduction measures strongly promote the improvement of surface water environmental quality of Minjiang and Tuojiang river basins in Chengdu in recent years.