珠江三角洲河网与河口区CBOD及TN和TP通量的模拟

基于一维河网与三维河口耦合水质模型,以1998年6月(丰水期)、1999年1月(枯水期)为案例计算分析珠江三角洲河网与河口区的碳质生化需氧量(CBOD)、总氮(TN)和总磷(TP)通量。结果表明,河网和河口区的污染物通量呈现明显的季节变化。在丰水期,河网区污染物的外源输入主要由上游输入的污染物通量(上游通量)贡献;经八大口门输入河口区的污染物通量(入河口通量)是河口区污染物的主要来源。在枯水期,河网区污染物的外源输入主要由河网污染负荷贡献;入河口通量是河口区TN、TP的主要来源,而河口区的CBOD主要来自河口污染负荷。丰水期的污染物上游通量、入河口通量分别是枯水期的8.0~20.2、15.1~21.5倍,同时,丰水期输入南海的污染物通量(入海通量)是枯水期的6.4~9.1倍。污染物主要经东四口门输入河口区,就各口门而言,虎门、磨刀门和蕉门是最主要的输入口门。总体上,河网和河口区对于CBOD、TN、TP均表现出"汇"的作用。

Modeling of CBOD,TN and TP fluxes in the river network and estuary of Pearl River Delta

A one dimensional and three dimensional coupled water quality model has been developed to simulate the fluxes of carbonaceous biochemical oxygen demand (CBOD), total nitrogen (TN) and total phosphorus (TP) in the river network of to Pearl River Delta (RNPRD) and Pearl River Estuary (PRE). The situation in the period from June 1998 (wet season) to January 1999 (dry season) is taken as a case study. The results indicate that the pollutant fluxes in the RNPRD and PRE exhibit significant seasonal variations. During the wet season, the external loads of pollutants in the RNPRD are significantly contributed by pollutant inputs from the upstream boundaries (the upstream fluxes). Pollutant fluxes passing through the eight river outlets (the riverine fluxes) are the primary external sources of pollutants for the PRE. During the dry season, waste loads in the RNPRD are the largest inputs of pollutants to the RNPRD. The riverine fluxes are the largest external sources of pollutants for the PRE, except that CBOD are mainly contributed by waste loads in the PRE. The upstream fluxes and the riverine fluxes of pollutants in the wet season are 15.1-21.5 times and 8.0-20.2 times of those in the dry season, respectively. Also, the pollutant fluxes exported from the PRE to the South China Sea (the estuarine fluxes) in the wet season are 6.4-9.1 times of those in the dry season. The eastern four river outlets are the major receiving outlets for pollutants. Individually, the Humen, Modaomen and Jiaomen are major receiving outlets. Conclusively, both the RNPRD and the PRE act as sinks for CBOD, TN and TP.