| 摘 要： |
Anthropogenic activities significantly alter the natural hydrological and nutrient cycles, and are recognized as a major influencing factor for water quality deterioration in the river. However, the relative contribution of different human activities, such as fertilizer usage, reservoir construction, and land-use type change, to the water quality pattern of the Yangtze River remained poorly understood. This study investigated the spatiotemporal pattern of water quality in the mainstream of the Yangtze River from 1981 to 2019, identified the dominating influencing factors, and quantified their relative contribution to the water quality change based on the long-term observation data and vector auto-regression model. The result showed that (1) the water quality was relatively poorer in the middle and lower reaches with a wide distribution of farms and construction lands; (2) the water quality experienced a deterioration during 1981-2005 with intense human activities, while it gradually improved during 2006-2019 because of the implementation of environmental protection policy; and (3) the evolution of water quality concentration in the upper reach was primarily affected by natural factors [CODMn, 43.6%; NH3-N, 70.2%; total phosphorus (TP), 55.8%], while in the middle and lower reach, it was mainly driven by fertilizer usage (CODMn, 29.1%; NH3-N, 48.8%; TP, 56.8%) and reservoir construction (CODMn, 33.0%; NH3-N, 40.2%; TP, 42.6%). Our study revealed the spatiotemporal pattern of water quality in the mainstream of the Yangtze River and quantified the effect of anthropogenic activities on water quality patterns, thus helping in the formulation of effective strategies to protect water resources. |
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