流域地表水体污染过程的时空差异及其影响机制分析:以温榆河中上游地区为例

Analysis of Seasonal Variations of Surface Water Quality in the Middle and Upper Reaches of Wenyu River

以温榆河流域中上游地区作为研究区,通过2009年6～8月的地表水质监测,分析了水质的季节变化特征和空间差异.结果表明,温榆河上游与中游山前平原区的地表水体污染表现出明显不同的时空差异:①在温榆河上游山区,总氮、硝酸盐、氨氮及总有机碳在6～8月总体表现为先上升后下降的趋势,溶解氧及化学需氧量呈先下降后上升趋势;②在温榆河中游山前平原区,总氮、总磷、磷酸盐、化学需氧量从6～8月总体上呈先下降后上升趋势,溶解氧浓度呈下降趋势;③温榆河从上游山区至中游山前平原区,地表水质自净化能力在降低,营养盐污染趋势在加强;④温榆河流域上游山区和中游山前平原区水体污染过程和形成机制存在差异.山区水体在污染过程上具有短历时特性,雨季洪峰地表径流将大量陆地非点源污染物携带进入水体,加剧了地表水体污染;山前平原区因存在不同类型的污染源,水体污染过程特征不明显,雨季洪峰径流在一定程度上对地表水体污染起到了稀释作用.本研究结果可以为水生态功能分区提供科学依据.

The middle and upper reaches of Wenyu River was chosen as a case study area, and the temp-spatial difference of surface water quality was systematically studied by water sampling from June to August of 2009. It was found that distinct seasonal variations was exhibited on surface water quality in the study area. In the mountain regions, TP, TN, NO3- -N, NH4 -N and TOC concentration in the water increase from June to July, and then decline remarkably, whereas the DO and COD concentration in the water display an opposite pattern. However, in the piedmont plains of Wenyu River middle reaches, TN, TP, PO^--P and COD concentration decrease sharply from June to July and then increase substantially in August, while DO concentration shows a decline tendency from June to August. Furthermore, from the upper stream mountains to middle reaches of Wenyu river, self-purification capacity of surface water is reduced with its nutrient pollution aggravates, and the water pollution process and its formation mechanism are different. Altogether, the process of water pollution in the mountainous areas has a pulse pollution process in the rainy season, and the surface run-off in the rainy season may aggravate the pollution process by bring a large volume of non-point source pollutants into surface water from the land. Because of various types of pollution sources in the piedmont regions, the water pollution processes are unstable and peak surface run- offs in the rainy season may dilute the surface water pollutions. The results provide a scientific basis for ecological function regionalization.