中文摘要：

郁江位于珠江流域西江水系中游,作为其最大支流,在当地城镇居民、工农业用水等方面起着重要作用,探讨其长时间序列水质演变趋势及影响因素是开展流域水污染防治与水资源高效管理的重要内容之一。因此整合西江中游郁江41年间（1973-2013年）水质关键参数,包括pH、溶解氧（DO）、高锰酸盐指数、氨氮（NH4＋-N）、亚硝酸盐氮（NO2--N）和硝酸盐氮（NO3--N）6个水质指标,综合运用模糊综合法和非参数Mann-Kendall检验法开展流域水质评价和趋势验证分析,并结合社会经济指标识别流域主要污染源。研究结果表明,郁江在过去41年间水质总体良好,维持在Ⅰ、Ⅱ类水质之间。其水环境趋势演变可分为两个阶段,1973-2000年间为水质变差阶段,主要污染物高锰酸盐指数和＂三氮＂浓度增加,DO浓度下降,污染源主要为工业污染;2001-2013年间水质呈好转趋势,高锰酸盐指数和NH4＋-N浓度下降,流域城镇化过程和农业发展成为影响水质的主要驱动因素。

英文摘要：

As the largest tributary and located at the middle reach of Xijiang River Systems in the Pearl River Basin,Yujiang River plays an important role in supplying industrial and agricultural water and inhabitant drinking water. So it is a quite important theme to explore its long time sequenced trends and influence factors of water quality to improve the management of water resource and prevent water pollution. Based on this,six key water quality parameters of Yujiang River（the Middle Xijiang River）for 41 years（1973-2013）,including p H,dissolved oxygen（DO）,potassium permanganate index,ammonia nitrogen（NH4＋-N）,nitrite nitrogen（NO2--N）and nitrate nitrogen（NO3--N）,were integrated in this study for water quality assessment and trend analysis using fuzzy comprehensive method and nonparametric Mann-Kendall test method,respectively,and also combined with social and economic indexes to identify the major pollution sources. Results indicated that water quality of Yujiang River was good in general,which maintained between Grade Ⅰ and Ⅱ. There were two stages of water quality changes in Yujiang River. Firstly,the water quality worsened from 1973 to 2000,as shown from the concentrations of major pollutants such as permanganate index and nitrogen increasing and DO decreasing with the development and pollution of industry. Secondly,the water quality tended to turn better from 2001 to 2013,during which the concentrations of permanganate index and NH4＋-N decreased,indicating that the urbanization process and agricultural development became the main driving factors to affect the water quality.