太湖流域上游平原河网污染物综合衰减系数的测定

改善太湖水质需要削减上游河流进入太湖的污染物总量.为了探求太湖流域上游平原河网的自净能力,开展原位实验测定了枯水期高锰酸盐指数、氨氮(NH_4~+-N)、总氮(TN)和总磷(TP)的综合衰减系数,根据河道的水力特征对综合衰减系数进行了修正,并利用一维稳态水质模型对修正前后综合衰减系数的可靠性进行了验证.结果表明,高锰酸盐指数、NH_4~+-N、TN和TP的综合衰减系数分别为:0.0296~0.4106、0.0224~0.3564、0.0137~0.3046和0.0555~0.5725 d~(-1).可靠性验证表明高锰酸盐指数、NH_4~+-N、TN和TP综合衰减系数修正前的平均相对误差分别为8.39%、14.40%、11.43%和19.22%,修正后的平均相对误差分别为10.65%、14.34%、11.37%和19.24%.修正前后高锰酸盐指数、NH_4~+-N、TN和TP的平均相对误差均小于20%且变化不显著,表明综合衰减系数的测定结果能够为太湖流域上游平原河网的污染物总量控制管理提供科学参数;也表明枯水期的水力条件对综合衰减系数的影响较小.

Determination of comprehensive pollutants attenuation coefficients of the plain river networks in the upper reaches of Lake Taihu Basin

Reducing pollutant loads of inputs is the prerequisite for water quality improvement in Lake Taihu. To investigate the self-purification ability of the plain river networks in the upper reaches of Lake Taihu Basin, in-site experiments were conducted to determine the comprehensive attenuation coefficients of permanganate index, ammonia (NH₄⁺-N), total nitrogen (TN) and total phosphorus (TP) in dry season. The integrated attenuation coefficients were adjusted based on channel hydraulic characteristics. The integrated attenuation coefficients before and after adjustment were validated by one-dimensional steady-state water quality model. Results show that the respective integrated attenuation coefficients of permanganate index, NH₄⁺-N, TN and TP were 0.0296~0.4106, 0.0224~0.3564, 0.0137~0.3046and 0.0555~0.5725 d^-1. Model validation showed that the average relative error for the integrated attenuation coefficients of permanganate index, NH₄⁺-N, TN and TP were respectively 8.39%, 14.40%, 11.43% and 19.22% before adjustment and 10.65%, 14.34%, 11.37% and 19.24% after adjustment. The average relative errors of permanganate index, NH₄⁺-N, TN and TP were all below 20% and without significant changes before and after adjustment, suggesting our results could provide reliable information for the pollution control and management in the upstream plain river networks of Lake Taihu Basin. Results also suggeste that the channel hydraulic characteristics had a limited influence on the integrated attenuation coefficients of studied pollutants in dry season.