基于两步聚类的城市闸控河流水质时空变异特征研究

SPATIO-TEMPORAL VARIATION ANALYSIS OF WATER QUALITY IN SLUICE-CONTROLLED URBAN RIVER BASED ON TWO-STEP CLUSTER

为探究典型城市闸控河流水质时空分布规律性差异,提供城市闸控河流水生态保护与精准调控依据,将两步聚类法应用于秦淮河南京段水质时空变异特征研究中。结果表明:近年来秦淮河南京段以氮、磷污染为主,且水质情况可分为3类(类型1-较优水质、类型2-中等水质、类型3-较劣水质);在空间分布上,河流流向与水质变化趋势存在密切关系,除入江口处断面,从上游至下游类型3水体的多年平均占比从15%增加至38%,水质污染程度逐渐增加;在时间分布上,年际间的类型3水体占比从31%(2008年)逐年降至1%(2015年),水质持续改善,且年内水质在夏秋季节较好。为改善城市闸控河段水质,可在保证城内河道不发生内涝的前提下增加入江口处闸门开启频次,同时加强冬春季节引调水力度。

To explore the spatio-temporal regular variation of water quality in typical sluice-controlled rivers of cities along the Yangtze River, and to provide support for hydro-ecological conservancy and precise regulation, the two-step clustering method was applied to the research on the spatio-temporal variation of water quality in the Nanjing reach of Qinhuai River. The results showed that, in recent years, the Nanjing reach was mainly polluted by nitrogen and phosphorus, and the water quality could be grouped into three types(i.e., Type 1-Better water quality, Type 2-medium water quality, and Type 3-poor water quality). In space, the direction of the river was closely related to the variation trend of water quality. From upstream to downstream, the average annual proportion of Type 3 water body increased from 15% to 38%, along the six sections except the section at the mouth of the Qinhuai River, indicating the gradual increase of water pollution degree. In time, the proportion of Type 3 water body decreased from 31%(2008) to 1%(2015), showing that the water quality continued to improve. In addition, the water quality was better in summer and autumn. To improve the water quality in the sluice-controlled river, the opening frequency of sluice at the mouth of the Qinhuai River could be increased under the premise of ensuring no waterlogging in the urban river, and the intensity of water diversion in winter and spring should be strengthened.