To investigate the variations in water quality of the Phase I of the Eastern Route of the South-to-North Water Diversion Project before and after water diversion, based on monitoring data of 18 water quality indicators from 30 monitoring sections along the route, this study systematically analyzed the spatiotemporal distribution characteristics and influencing factors of water quality indicators before and after water diversion using significance analysis, correlation analysis, non-metric multidimensional scaling (NMDS), and positive matrix factorization (PMF) and other methods. The results indicated a significant improvement in water quality after the diversion, with concentrations of chemical oxygen demand (COD_Mn), ammonium nitrogen (NH⁴⁺-N), and total phosphorus (TP) decreasing by 24.7%, 87.9%, and 39.6%, respectively , and the comprehensive water quality index (WQI) improved by 1.3%. The hydrochemical types remained as Ca²⁺-Mg²⁺-Cl⁻-SO₄²⁻ and Ca²⁺-Mg²⁺-HCO₃⁻ without change after diversion. Spatial analysis showed ‘excellent’ WQI levels in both Jiangsu and Shandong sections, whereas the inter-provincial boundary section exhibited relatively high total nitrogen (TN) and total phosphorus (TP) concentrations. Correlation analysis revealed that the significant positive correlations between COD_Mn and nitrate nitrogen (NO₃⁻-N) and total dissolved phosphorus (TDP) shifted from a significant positive correlation to no correlation after the diversion, reflecting the difference in water sources before and after the diversion. Furthermore, PMF analysis indicated that the increase in nutrients concentrations in the inter-provincial boundary section was related to agricultural runoff input, and the rise in phosphorus content in some sections was associated with disturbance of regulation and storage lakes.

Phase I of the Eastern Route of the South-to-North Water Diversion Project, positive matrix factorization (PMF), water quality indicators

为探讨南水北调东线一期工程调水前后水体的水质变化情况, 基于沿线30个监测断面的18项水质指标监测数据, 采用显著性分析、相关性分析、非度量多维尺度分析(NMDS)和正矩阵分解(PMF)模型等方法, 系统地分析调水前后水质指标的时空分布特征及其影响因素。结果表明, 调水后水质显著改善, 其中化学需氧量(COD_Mn)、氨氮(NH⁴⁺-N)和总磷(TP)的浓度分别下降24.7%, 87.9%和39.6%, 综合水质指数(WQI)值提升1.3%。调水前水化学类型为Ca²⁺-Mg²⁺-Cl⁻-SO₄²⁻型和Ca²⁺-Mg²⁺-HCO₃⁻型, 调水后未发生转变。空间分析结果显示, 江苏段和山东段的WQI均处于优秀水平, 而两省交界段的总氮(TN)和总磷(TP)浓度相对较高。相关性分析结果表明, 调水后COD_Mn、硝酸盐氮(NO₃⁻-N)和总溶解性磷(TDP)等水质指标之间的相关性由显著正相关转变为不相关, 反映调水前后水体来源存在差异。PMF分析结果表明, 两省交界段营养盐浓度的升高与农业径流输入有关, 部分断面的磷含量升高与调蓄湖泊扰动相关。