Trends Analysis and Evaluation of Water Quality in the Main Stream of the Yangtze River in 2004-2016

Abstract

依据多年水质数据，采用STL (Seasonal-Trend Decomposition using LOESS)、季节性肯达尔检验、Hurst指数法和水质综合指数(WQI)等，分析了长江干流水质现状、变化趋势等。结果表明：沿程水质变化趋势不一，攀枝花、重庆、岳阳、九江等溶氧有轻微下降趋势，宜昌和南京则有轻微上升趋势。攀枝花、宜昌和岳阳等高锰酸盐指数有显著性下降趋势，而重庆、九江和南京等CODMn则有显著性上升趋势。南京氨氮有显著性上升趋势，其余各点显著下降。以上单项水质指标变幅均较小。长江干流水质在较好和非常好之间波动；南京水质有显著恶化趋势；而岳阳则有显著改善趋势，其余各点持平，持续性强度均较强。南京水质下降可能与其处于最下游，受经济发展和人类活动影响较大有关，应引起有关政府部门的高度重视。 Based on years of water quality data, the STL (Seasonal-Trend Decomposition using LOESS), sea-sonal Mann-Kendal test, Hurst index method and water quality index (WQI) were used to analyze the current status and trends of the Yangtze River mainstream water quality. The results showed that the water quality trends along the mainstream were different. The dissolved oxygen in Panzhi-hua, Chongqing, Yueyang and Jiujiang had a slight downward trend, while Yichang and Nanjing had a slight upward trend. The CODMn of Panzhihua, Yichang and Yueyang showed a significant down-ward trend, while CODMn in Chongqing, Jiujiang and Nanjing showed a significant upward trend. Nanjing ammonia had a significant upward trend and the remaining points had dropped signifi-cantly. The above single water quality indicators had smaller variations. The water quality of the main stream of the Yangtze River fluctuated between good and very good; the water quality in Nanjing showed a significant deterioration trend; while Yueyang had a significant improvement trend, the other points were flat and the persistence intensity was strong. As Nanjing is at the most downstream, the decline in water quality may be caused by economic development and human ac-tivities, and should be highly valued by relevant government departments.