2006—2016年三峡水库出入库水质变化及影响因素分析

使用2006—2016年宜昌断面及朱沱断面水质数据与影响因素数据,计算水质变化幅度,基于VAR模型的脉冲响应函数和方差分解,得到各影响因素对三峡水库出入库断面水质变化幅度的影响时长及贡献率大小.研究表明:长江从朱沱断面到宜昌断面水质变化幅度2006年为0. 07,到2016年下降到-0. 24,在年度上呈好转趋势.水质综合指数对工业污染源废水排放量的响应最大,持续时间最长;对农药施用折纯量和化肥施用折纯量的响应非常小,持续时间最短,但受其间接影响的持续时间非常长.主要驱动因素在研究时间内的贡献率由大到小依次为:工业污染源废水排放量贡献率为38. 10%、城镇生活污水排放量贡献率为33. 78%、船舶油污水贡献率为24. 17%、化肥施用折纯量贡献率为2. 61%、农药施用折纯量贡献率为1. 33%.不同污染物指数变化的影响因素不同,溶解氧的主要影响因素为船舶油污水产生量,高锰酸盐的主要影响因素为工业废水排放量,氨氮的主要影响因素为城镇生活污水排放量.

Analysis of Water Quality Changes and Influencing Factors of the Three Gorges Reservoir's Inflow and Outflow from 2006 to 2016

Based on the impulse response function and variance decomposition from VAR model,this paper uses the water quality data and influencing factors of the Yichang section and the Zhutuo section from 2006 to2016 to calculate the extent of change in water quality. Thereby,we obtain the influence time and the contribution rate of each influencing factor on the variation range of water quality in the inlet and outlet sections of the Three Gorges Reservoir. The results show that,the extent of change in water quality of the Yangtze River section from the Zhutuo to the Yichang is 0. 07 in 2006 while dropping to-0. 24 in 2016,revealing an improved trend in the study period. The water quality composite index has the largest response to industrial wastewater discharge and its impact lasts the longest. The responses to pesticide application and fertilizer application are very small and the duration of their influences are the shortest,but their indirect effects are durable. The contribution rate of major driving factors in the year is listed successively from large to small: the contribution rate of industrial wastewater discharge is 38. 10%,urban sewage discharge 33. 78%,ship oil sewage 24. 18%,fertilizer application 2. 61%,and pesticide application 1. 33%. Different pollutant indexes have different influencing factors. For example,the main influencing factor of DO is the amount of oil produced by ship oil,the main influencing factor of CODMn is industrial wastewater discharge,and the main influencing factor of NH3-N is urban domestic sewage discharge.