成渝双城经济圈流域污染源解析与水质贡献研究

Analysis of pollution sources and water quality contribution in the typical basin of Chengdu-Chongqing Economic Circle

成渝地区双城经济圈建设发展战略的深入推进给地处区域核心的小安溪流域水环境质量稳定性保障带来更大挑战。为充分认识流域水质对污染排放负荷变化的响应关系,以重庆市小安溪流域为研究对象,采用清单分析、现场观测、模型模拟等方法开展污染源解析,并以街镇为最小单位划分污染类型,同时利用DHI MIKE Hydro模型模拟不同污染源类型及情景评估其对关键断面水质贡献大小。结果表明,小安溪流域污染排放空间荷载情况是铜梁区>大足区>永川区>合川区,主要负荷贡献来源均为城镇生活污染,流域各街镇在化学需氧量(COD)和氨氮(NH_(3)-N)方面多为生活及养殖污染复合贡献型乡镇;总磷(TP)方面多为种植畜养及城镇生活污染复合贡献型。面源污染负荷输入给流域带来的COD、NH_(3)-N和TP的浓度增长值分别为6.35 mg/L、0.06 mg/L、0.16 mg/L;点源则是1.96 mg/L、0.11 mg/L、0.10 mg/L;极端排污情况下,COD、NH_(3)-N和TP分别比现状值高出64.50 mg/L、0.63 mg/L、0.47 mg/L。此外,得到流域COD、NH_(3)-N、TP 3项指标的整体输移折算系数,分别为0.95、0.23、0.44。研究成果为流域水环境精准化管控治理提供了科学依据。

With the in-depth implementation and acceleration of national regional development strategies such as the development of the Yangtze River Economic Belt and the construction of the Chengdu-Chongqing Economic Circle,the water environment pressure brought by the rapid economic growth in the western district of Chongqing is constantly challenging the stability of the water ecological environment quality in the basin.Aimed to understand the response relationship of water quality of the basin to the change of pollution discharge load,Xiaoanxi basin in Chongqing was took as the research object to carry out pollution source analysis,by using mathematical statistics,field observation,model simulation and other methods.The types of pollution were classified with street towns as the smallest unit.At the same time,DHI MIKE Hydro model was used to simulate the contribution of different pollution source types and scenarios to the water quality of key sections.Results revealed that the spatial load of pollution discharge in Xiaoanxi River Basin was Tongliang District>Dazu District>Yongchuan District>Hechuan District,and the main load contribution sources were from urban domestic pollution.Most of the towns in the basin were combined contribution towns of domestic and breeding pollution in terms of chemical oxygen demand(COD)and ammonia nitrogen(NH_(3)-N),while most of the towns in the basin were combined contribution towns of planting,livestock and urban domestic pollution in terms of total phosphorus(TP).The concentrations of COD,NH_(3)-N and TP from non-point sources were increased by 6.35 mg/L,0.06 mg/L and 0.16 mg/L,while those from point sources were increased by 1.96 mg/L,0.11 mg/L and 0.10 mg/L,respectively;In the case of extreme pollution discharge,COD,NH_(3)-N and TP are 64.50 mg/L,0.63 mg/L and 0.47 mg/L higher than the current value.The overall transport conversion coefficients of COD,NH_(3)-N and TP were 0.95,0.23 and 0.44,respectively.The research results could provide a scientific basis for the precise management and control of water environment in the basin.