太湖湖体总氮平衡及水质可控目标

On the total nitrogen balance and water quality controllable target in Taihu Lake

通过对2007～2010年环太湖水文巡测及降水调查,进行了湖体总氮平衡分析,在充分调查现有与规划的各类型污染源总量控制工程措施的基础上,量化出具有空间分布的流域总氮污染削减率,利用构建的太湖流域及湖体水环境数学模型模拟污染削减后的太湖湖体总氮浓度场,并提出水质可控目标。结果表明:太湖出入水量共127.8亿m3,其中通过降水进入太湖的水量为24.9亿m3,占入湖总水量的19.5%;全年总氮收支量达到4.47万t,其中通过干湿沉降进入太湖的总氮量为0.70万t,占入湖总通量的15.5%,可见干湿沉降进入太湖的污染物不容忽视,其变化趋势与太湖地区降水特征相关性较好。同时通过模型推算,定出2015年太湖湖体不同功能区总氮的可控目标,整个湖体平均值约为2.3 mg/L,为太湖总量控制提供科学依据。

The analysis of total nitrogen balance in Taihu Lake is conducted using 2007-2010 patrol hydrometric and precipitation data.An investigation is carried out on the existing and planned engineering measures for controlling the total amount of pollutants entering Taihu Lake from multiple sources.Based on both analysis and investigation,a spatial and temporal reduction plan for total nitrogen loading from the Taihu Lake basin is proposed.A mathematical model for simulating lake water environmental problems is developed.The distribution of total nitrogen concentration in the lake is obtained using the model after the implementation of the engineering measures,and a controllable target is thus proposed.The result shows that the total volume of inflow and outflow in Taihu Lake reaches a value of 127.8×108 m3 including 24.9×108 m3 of precipitation that accounts for 19.5% of the total inflow.The annual exchange of total nitrogen loads is 4.47×104 t including 0.07×104 t of wet and dry deposition that can account for 15.5% of the total nitrogen loads.Thus,the nitrogen contribution from wet and dry deposition is significant and non-neglectable.The variation of wet and dry deposition is correlated well with precipitation.Using the simulation result of various water functional areas in the Taihu Lake basin,an average nitrogen value of 2.3 mg/L is proposed as the water quality controllable target for 2015 in the basin.The study provides the technical support and the scientific basis to water pollution control in Taihu Lake.