近二十年汉江中下干流主要污染物通量时空变化趋势分析

Analysis on the Spatio-Temporal Changes of Main Pollutant Fluxes in the Middle and Lower Reaches of Hanjiang River in the Past Two Decades

摘要: 为了探索丹江口水利枢纽大坝加高前后汉江中下游干流主要污染物通量变化趋势，基于2004~2023年汉江中下游干流重要控制断面主要污染物及径流量监测数据，分析各断面水质、径流量以及污染物通量逐年变化规律，采用Spearman相关性分析法评估污染物通量与径流量相关性特征。结果表明：2004~2023年汉江中下游干流沿程各断面主要污染物高锰酸盐指数、氨氮浓度年际变化均呈现总体下降趋势，而总磷浓度年际变化不明显，但各断面总磷浓度波动范围进一步减小，水体质量更加趋于稳定；与汉江下游干流断面相比，汉江中游干流断面年径流量和主要污染物年通量特征值变化趋势一致性更高；汉江中下游干流主要污染物指标中高锰酸盐指数和总磷通量与径流量呈极显著性相关，氨氮通量与径流量呈显著性相关，因汉江干流水体含沙量本底较低，而丹江口水利枢纽坝体的拦截更进一步降低下游河道泥沙含量，因此很大程度上削弱了输沙量对汉江中下游干流总磷输移的影响。研究成果可为汉江中下游可持续发展和水资源保护提供科学支撑。

Abstract: In order to explore the trend of pollutant flux changes in the middle and lower reaches of the Hanjiang River before and after the dam elevation of the Danjiangkou Water Control Hub, based on the monitoring data of pollutants and runoff in important control sections from 2004 to 2023, the annual changes in water quality, runoff, and pollutant flux of each section were analyzed, and Spearman correlation analysis method was used to evaluate the correlation characteristics between pollutant flux and runoff. The results from 2004 to 2023, the annual variation of permanganate index and ammonia nitrogen concentration of major pollutants along the middle and lower reaches of the Hanjiang River showed an overall downward trend, while the annual variation of total phosphorus concentration was not significant. However, the fluctuation range of total phosphorus concentration in each section further decreased, and the water mass tended to be more stable. Compared with the cross-section of the lower reaches of the Hanjiang River, the annual runoff and pollutant annual flux characteristic values of the cross-section of the middle reaches of the Hanjiang River had higher consistency. The main pollutant indicators in the middle and lower reaches, including the permanganate index and total phosphorus flux, were significantly correlated with runoff, while the ammonia nitrogen flux was significantly correlated with runoff. The reason is that the cement and sand content in the Hanjiang River main stream is low, and the interception effect of the Danjiangkou Water Control Hub dam further leads to year-round water discharge, which greatly weakens the impact of sediment transport on the total phosphorus transport in the middle and lower reaches of the Hanjiang River. The research results can provide scientific support for appropriate development and water resource protection in the middle and lower reaches of the Hanjiang River.