武汉市东沙水系水质现状及污染成因分析

Analysis on Water Quality Status and Pollution Causes in Dongsha Water Network of Wuhan

摘要: 东沙水系位于武汉市中心城区，连接长江和东湖，是典型的城市复杂水系。为探究东沙水系水污染成因，于2019年4月至2020年1月对东沙水系34个采样点进行8次水质采样，并测定pH、溶解氧(DO)、总磷(TP)、总氮(TN)、氨氮(NH₃-N)以及重金属(Cu, Se, Pb)共8项水质指标。监测结果表明，东沙水系的水环境污染较为严重，尤其是罗家港、东湖港、楚河等城市河道。各项水质指标中，TN超标比例最高，其中沙湖、东湖的TN浓度高于V类水标准的比例分别为100%和80.6%。综合其余七项水质指标进行水环境单因子评价，NH₃-N、TP和DO的超标比例较高，劣V类水质的点位占比分别为24.4%、17.3%和10.5%。从季节分布上看，劣V类水占比呈现冬季(41.2%) > 秋季(32.4%) = 夏季(32.4%) > 春季(11.8%)的规律。结合东沙水系结构及其汇水区下垫面特点对水环境影响因素进行分析，东沙水系水环境主要受到生活污水、面源污染、内源污染以及水系连通性的影响。城市河渠主要受到生活污水、固体垃圾排放以及底泥内源释放的影响，局部河道受到建筑工地排污的影响，城市湖泊主要受到面源污染的影响。东沙水系的水环境治理应以源头控制为主，水系连通为辅，综合考虑水系结构和水质状况，制定合理的生态调水方案。

Abstract: Dongsha Water Network is located in the center of Wuhan, connecting the Yangtze River and the East Lake, which is a typical complex urban water network. In order to explore the causes of water pollution, 34 water samples were collected 8 times from April, 2019 to January, 2020, and 8 water quality parameters including pH, dissolved oxygen (DO), total phosphorus (TP), total nitrogen (TN), ammonia nitrogen (NH₃-N) and heavy metals (Cu, Se, Pb) were detected. The results showed that the water pollution was serious, especially in Luojiagang River, Donghugang River and Chuhe River. Among all the parameters, the proportion of TN exceeding the standard was the highest, and the proportions of TN concentration belonging to inferior V category in Shahu Lake and East Lake were 100% and 80.6%, respectively. The single factor evaluation of water environment based on the other seven parameters showed that high proportion of NH₃-N, TP and DO exceeded the standard, and the percentages of inferior V category were 24.4%, 17.3% and 10.5%, respectively. The proportion of inferior V category demonstrated the seasonal order of winter (41.2%) > autumn (32.4%) = summer (32.4%) > spring (11.8%). The influencing factors of water environment in Dongsha Water Network were analyzed based on the water network structure and the characteristics of underlying surface in the catchment area. The results showed that the water environment was mainly affected by domestic sewage, non-point source pollution, internal source pollution and water network connectivity. Urban rivers were mainly affected by domestic sewage, solid waste discharge and internal release of sediment, some parts were affected by sewage discharge from construction sites, and urban lakes were mainly affected by non-point source pollution. The water environmental control should mainly rely on source control, supplemented by water network connection, and a reasonable ecological water diversion scheme should be formulated considering the water network structure and water quality condition.