基于投影寻踪技术的南四湖下级湖水质评价

Water Quality Evaluation of Nansihu Lower Lake Based on Projection Pursuit Technique

为评价南四湖下级湖水质等级,采用投影寻踪技术,通过对局部密度窗口半径和局部密度做适当处理,建立了南四湖下级湖水质投影寻踪模型,并用加速遗传算法求解模型。使用建立的模型计算出南四湖下级湖四个水质监测站的水质等级y,并分析了水质等级序列的变化趋势。结果表明,南四湖下级湖四个测站的水质在2010年9月发生了突变,突变前水质处于Ⅲ、Ⅳ类,突变后水质基本处于Ⅱ、Ⅲ类,水质改善明显。研究成果为水质评价提供了参考。

The purpose of this paper is to evaluate the water quality of Nansihu lower lake by using the projection pursuit technology.Water quality projection pursuit model of Nansihu lower lake is established by making appropriate improvement of the model parameters R（local density window radius）and Dz（local density）.The model is solved by accelerating genetic algorithm.The water quality grade y of the four water quality monitoring station in Nansihu lower lake is calculated.Then the trend of water quality grade sequence is analyzed.It is concluded that in September of 2010,the water quality appeared sudden change point that before the point the water quality of Nansihu lower lake is gradeⅢ orⅣand after the point the water quality is gradeⅡorⅢ.That means the water quality of Nansihu lower lake became better as a whole.The research provides reference for evaluation of water quality.