大通湖湖区水质时空分布特征及其影响因子解析

运用主成分分析和聚类分析对2019年7—11月大通湖湖区33个采样点的8个水质指标进行了数据分析,采用单因子指数法和综合水质标识法对水质进行了综合评价,分析了大通湖湖区水质的时空特征,识别了主要影响因子和污染源。以单因子指数法为评价方法,2019年7月大通湖水质为Ⅴ类,8月为劣Ⅴ类,9—11月大通湖湖区水质有所改善,为Ⅳ类。以综合水质标识法为评价方法,大通湖湖区水质由好到差排序为:9月>11月>10月>7月>8月。从月际变化上来看,大通湖湖区水质总体上呈下降趋势,主要超标因子为TN、TP、COD_Mn在10—11月存在超标现象。从采样点看,湖区水质受入湖河流的影响较大。汛期(7,8月)湖区主要影响因子是NH₄+-N、SS、COD_Mn、TP,主要源自农田径流、湖外水产养殖污染等面源污染和生活污水;非汛期(9—11月)湖区主要影响因子为NH₄+-N、NO₃--N、COD_Mn和TP,主要源自生活污水、内源污染等,受到多种污染源的共同作用。

ANALYSIS OF TEMPORAL AND SPATIAL CHARACTERISTICS OF WATER QUALITY AND THE IMPACT FACTORS IN DATONG LAKE AREA

To identify Datong Lake's pollution sources and the main influencing factors, the spatial-temporal characteristics about water quality indexes of 33 sample points in Datong Lake were analyzed, based on two analytical methods(the principal component analysis and cluster analysis), and water quality assessment was carried out by two methods(single factor index method and comprehensive water quality identification method), during July to November 2019. Using single factor index method, in July 2019, Datong lake water quality was identified as Ⅴ class, and inferior Ⅴ class in August 2019. From September to November, the water quality got improved, for Ⅳ class. Using the comprehensive water quality identification method, the monthly water quality of Datong lake was in the sequence of(from good to bad): September>November>October>July>August. On the whole, water quality in Datong Lake showed a trend of getting worse. The main factors exceeding the standard were TN and TP, and it's worthy of noting that COD_Mn exceeded the standard in October and November. The water quality was extremely affected by the river entering the lake. In the flood season(July and August), ammonia nitrogen, SS, COD_Mn and TP were the main factors in the lake area, which were mainly from non-point sources such as farmland runoff, livestock and poultry breeding pollution and domestic sewage; in the non-flood season(September to November), the main factors were ammonia nitrogen, nitrate, COD_Mn and TP, which were mainly from domestic sewage and internal pollution, etc., affected by the joint action of multiple pollution sources.