汉江中下游干流水质状况时空分布特征及变化规律

Spatial and Temporal Distribution and Variation of Water Quality in the Middle and Downstream of Hanjiang River

汉江是南水北调中线工程的水源区,其中下游水质状况是国家和湖北省政府重点关注的饮用水安全问题.研究南水北调中线工程影响区汉江中下游干流的水质状况和特征,为进一步分析工程运行对汉江中下游水质的影响奠定基础.收集了汉江中下游干流11个水质监测站2011—2014年p H、ρ(DO)、ρ(CODMn)、ρ(BOD5)、ρ(NH3-N)、ρ(TP)、ρ(TN)等7项水质指标,应用水污染指数法和层次聚类分析法,综合辨识2011—2014年汉江中下游干流的水环境时空变化特征.结果表明:(1)2011—2014年汉江中下游干流水质整体上为GB 3838—2002《地表水环境质量标准》的Ⅳ类～劣Ⅴ类水体,超标指标为ρ(TN)、ρ(TP)、ρ(BOD5),其中ρ(TN)超标最严重.(2)为深入辨识TN负荷对研究区域水质的影响,通过情景分析发现控制ρ(TN)可有效改善汉江中下游干流水质状况.(3)汉江中下游干流水质状况层次聚类分析表明,在时间上将研究时段分为2类,基本对应于汉江中下游的汛期和非汛期;在空间上将水质监测断面(沈湾、泽口、新沟、宗关、转斗、皇庄、汉南村、石剅、白家湾、余家湖、罗汉闸)分为3类,其中第3类可细分为3个子类,各子类所对应的水质监测断面与其空间分布基本对应.(4)汉江中下游干流富营养化严重,其中ρ(TP)和ρ(TN)在非汛期分别呈显著降低和增加趋势,汛期无明显变化.研究显示,江汉中下游污染严重,营养盐尤其丰富且ρ(TN)为主要影响因素.

Hanjiang River is the major water resource of the middle route of the South-to-North Water Transfer Project (SNWT),and water quality of the Middle and Downstream of HR (MDHR) is a critical issue for drinking water safety concerned by the national and Hubei provincial governments.To study the water quality status and characteristics of MDHR in the affected area of SNWT,and to lay the foundation for further research on the impact of the project operation on the water quality in MDHR,this study collected 7 water quality parameters from 11 monitoring sections in MDHR during 2011-2014 to comprehensively identify the temporal and spatial characteristics of the water quality in the study area,and apply the water quality index method and hierarchical cluster analysis method.The selected water quality parameters were pH,ρ(DO),ρ(CODMn ),ρ(BOD5),ρ(NH3-N),ρ(TP)and ρ(TN).The results were as follows:Firstly,water quality in MDHR was generally poorer than that of Category Ⅳ-Ⅴduring 2011-2014 according to ‘the environmental quality standards for surface water’(GB 3838-2012).The water quality parameters that failed to meet the standards were TN,TP and BOD5,among which TN was the most important indicator.Secondly,in order to further understand the impact of TN on the water quality of the study area,scenario analyses were performed by summarizing different concentration of TN,TP and both of them.The results indicated that controlling ρ(TN) could effectively improve the water quality in MDHR.And thirdly,the study applied a cluster analysis on the water quality in MDHR and divided the time into two categories,basically corresponding to the flood season and non-flood season in the study area.The monitoring sections were spatially divided into three major categories,namely Shenwan,Zekou,Xingou,Zongguan,Zhuangdou,Huangzhuang,Hannancun,Shilou,Baijiawan,Yujiahu,Luohanzha,among which the third one was further subdivided into 3 sub-categories corresponding to the geographical positions of the sections.Furthermore,the nutrient state analysis showed that the water body in MDHR suffered serious eutrophication and nutrient indexes such as ρ(TP) and ρ(TN) were significantly decreased and increased in the non-flood seasons,respectively,while there were no significant changes in the flood seasons.The results showed that water pollution in MDHR is heavy with serious eutrophication,and ρ(TN) is supposed to the mainfactor.