1990-2016年湘江干流水质变化特征及影响因素分析

基于1990-2016年湘江干流主要断面的水质监测数据，采用综合污染指数法、Spearman秩相关检验和主成分分析法对流域水环境质量演变特征进行综合评价，并结合社会经济指标识别流域主要污染源。综合污染指数结果表明湘江水环境变化趋势明显分为两个阶段，1990-1996年间为水质变好阶段，除个别值外污染指数均小于0.2，1997-2016年间水质呈恶化趋势，水质维持在Ⅲ~IV类之间；Spearman秩相关检验结果表明污染物浓度总体呈增加趋势，其中TP、COD_Mn、Cd、Pb和石油类显著上升；主成分分析结果表明流域污染物主要为NH₄⁺-N、TP和Cd，污染源为生活点源和农业面源，从上游到下游污染程度明显增大，其中湘潭断面水质污染最严重，综合得分为0.9006，道县断面相对较轻，综合得分为-0.7014，城镇化因素是影响流域水环境的主要驱动因素。研究结果可为流域水环境保护和水生态修复提供科学依据。

Analysis on the water quality change characteristics and influencing factors of the Xiangjiang River mainstream from 1990 to 2016

Based on the water quality monitoring data of the Xiangjiang River mainstream from 1990 through 2016, the comprehensive pollution index method, Spearman rank correlation test and principal component analysis were used to evaluate the evolution characteristics of water environment and the main pollution sources of the river basin had been identified in combination with social and economic indicators. Analyzing the comprehensive pollution index showed that there were two stages of water quality changes in the Xiangjiang River basin. Firstly, the water quality had been better from 1990 through 1996, when the comprehensive pollution index had been less than 0.2, except for some special cases. Secondly, the water quality had been worsened, maintaining in between Grade Ⅲ and IV, from 1997 through 2016. Spearman rank correlation test results showed that the overall concentration of pollutants had been increasing, with TP, COD_Mn, Cd Pb and petrolem rising significantly. The principal component analysis results showed that the main pollutants in the river basin were NH₄⁺-N, TP and Cd. The sources of pollution were life point source and agricultural non-point source. The pollution degree had increased significantly from the upstream to the downstream. Among them, the water pollution in the Xiangtan section had been most serious, with a comprehensive score of 0.9006. Whereas that in Daoxian County had been relatively light, with a comprehensive score of -0.7014. Urbanization had been the main driving factors affecting water environment of the watershed. This research results will be useful for river basin water environment protection and water ecological restoration.