摘要
太湖是我国的第三大淡水湖,属于大型浅水湖泊,现在面临着严重的富营养化问题。国际上对浅水湖泊富营养化研究与治理实践表明,浅水湖泊沉积物是湖泊营养物质来源的一个重要方面。因此,本论文根据2000年太湖水文、水质监测数据,在现有水量模型之上,利用WASP5模型中的氮、磷循环理论,建立二维水量、水质耦合模型,模拟2000年5月～8月太湖在盛行风作用下,太湖流场、水质(TN、TP)浓度场和底泥分布之间的相互关系以及流场、浓度场与蓝藻爆发的关系。
通过模拟,本论文主要取得以下成果:(1)建立的二维水量水质耦合模型对大型浅水湖泊太湖的流场、TN和TP浓度场的模拟效果较好,具有较高的模拟精度;(2)太湖环湖河流TN、TP的污染负荷量是外源污染负荷的主要来源,是TN,TP浓度场形成的根本原因,TP在很大范围成为了太湖的限制性营养元素;(3)太湖底泥对TN、TP的释放净通量是内源污染的主要来源,是TN、TP浓度场形成的重要原因,TN、TP的释放净通量与底泥厚度及分布直接相关,受风场和周围水体TN、TP浓度的影响;(4)太湖蓝藻爆发与水体中TN、TP的浓度和风场有密切关系,当其他条件合适,TN、TP浓度都比较高(TN大于2mg/L、TP大于0.2mg/L),总氮和总磷浓度的比值(TN/TP值)在10～20之间,且水体流动缓慢时容易导致蓝藻爆发。
Lake Taihu, which is the third largest lake in China , belonging to shallow lake, confront a serious problem of eutrophication. The worldwide reasearch and control practice of eutrophication showed that the sediments in the lake are an important source of nutrients. According to the monitoring data of hydrology and water quality in 2000 and the nitrogen circle and phosphorus circle theory in WASP5 model, a two-dimensional flow-pollutants coupled model was developed on the basis of RBFVM-2D model in this paper, simulating the current field, relationship between concentration field and sediments and the relationship between blue algae bloom and current field & concentration field under the influence of wind field from May to August in 2000.According to the simulation, results showed that the current field, concentration field of TN and TP calculated by the two-dimensional flow-pollutants coupled model fitted well with the measured values;the pollution loads of TN and TP discharged by the river around Lake Taihu were the main source of outer-source pollution load and the fundamentally cause of the concentration field of TN and TP, TP became the limited nutrient in most area in Lake Taihu;the net flux of TN and TP released by the sediments in Lake Taihu was the main source of the inner-source pollution and an important cause of the concentration field of TN and TP, the net flux of TN and TP had a direct relationship with the thickness and the distribution of the sediments, and was influenced by the wind field and the concentration of TN and TP in the water;blue algae bloom had a close relationship with wind field and the concentration of TN and TP, when the concentration of TN and TP was high(TN>2 mg/L ,TP>0.2 mg/L), the value of TN/TP was between 10~20 and the velocity of the water was slow, the blue algae bloom was likely to break out.
引文
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