为探究汉江中下游丰、枯水期水质时空变化特征,于2019年6月丰水期和2020年1月枯水期对汉江中下游(丹江口-武汉段)开展全面调查,布设了18个干流采样断面和2个支流采样断面进行采样和分析,并采用综合污染指数法和综合营养状态指数评价法对水质进行评价。研究结果表明:汉江中下游干流综合污染指数在丰、枯水期整体表现为无显著性差异,但从各断面比较来看,大多数断面丰水期污染程度大于枯水期,空间上丰、枯水期沿程各断面变化趋势相似,污染较大的断面分布在襄阳、汉川和武汉段;主要污染因子为总氮(TN)、总磷(TP)、氨氮(NH₃-N),其中TN浓度在丰、枯水期各断面均超过地表水Ⅱ类标准,且丰水期显著大于枯水期,TP浓度多数断面丰水期大于枯水期,超过Ⅱ类水标准限值断面的比例为27.8%,NH₃-N在枯水期均处于Ⅱ类水标准限值内,仅在丰水期个别断面出现超标现象。通过综合营养状态评价可知,汉江中下游综合营养状态指数处于中营养到轻度富营养状态,整体上呈沿程递增趋势,时间上表现为丰、枯水期无显著性差异,但枯水期综合营养状态指数波动更大。对污染成因进行分析,汉江中下游水质主要受点源、非点源污染和支流汇入,以及水利工程等的影响。研究成果可为汉江中下游水资源保护和可持续发展提供科学依据。

In the aim of exploring the characteristics of the spatio-temporal changes of water quality in middle-lower Hanjiang River in wet season and dry season, a comprehensive survey was carried out on the middle-lower Hanjiang River (Danjiangkou-Wuhan reach) during the wet season in June 2019 and the dry season in January 2020. Eighteen sampling sections in the main stream and two sampling sections in the tributaries were arranged. The water quality was evaluated by using the overall pollution index and the overall trophic level index. The results indicated that the overall pollution index of water in the mainstream of the middle-lower Hanjiang River had no significant difference between wet season and dry season; in sectional scale, yet, the pollution of most sampling sections in wet season was more severe than that in dry season. Spatially, the change trends along the river during wet season and dry season were similar. Sections in Xiangyang, Hanchuan, and Wuhan were subjected to severe pollution, mainly total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (NH₃-N), among which TN concentration exceeded the limit of class II standard (GB 3838-2002) in all sections in both wet season and dry season, apparently larger in wet season, and TP concentration of most sections in wet season was greater than that in dry season, with 27.8% sections exceeding the limit of class II standard, and NH₃-N concentration of all sections were below the limit of class II standard in dry season, while exceeding the limit only in a few sections in wet season. Moreover, the overall trophic level in middle-lower Hanjiang River presented an increasing trend along the river, ranging from moderate nutrition to mild eutrophication. Except for larger fluctuations in dry season, the overall trophic level index saw no significant difference between wet season and dry season. The water quality in the middle-lower Hanjiang River was mainly affected by point source pollution and non-point source pollution, the confluence of tributaries, and water conservancy projects. The research findings offer scientific basis for water resources protection and sustainable development in the middle-lower Hanjiang River.