湖泊富营养化综合评价的坡度加权评分法

Slope weighted scoring method for eutrophication comprehensive evaluation of lake

通过对地表水富营养化评价标准的分析,发现对于同一评价指标10个区间的坡度不同,表明同一评价指标的权重分配应随其测定值的大小而动态改变.基于该思想,在插值评分法的基础上提出了一个新的湖泊富营养化综合评价方法———坡度加权评分法.对评价标准中各评价指标和营养状态分值的界值数据分别进行标准化处理,以消除量纲的影响;利用处理后的界值数据可以计算得到各评价指标在不同分级区间的坡度.应用该方法评价湖泊营养状态时,首先根据各评价指标测定值在评价标准中所处的区间,通过线性插值方法计算各评价指标的营养状态分值,并记录各指标测定值所处区间的坡度;再根据各指标对应的区间坡度计算各指标的权重,然后根据各指标的权重和营养状态分值,加权平均得到综合营养状态分值.该方法利用评价标准中各评价指标的区间坡度信息,实现了各评价指标权重的动态分配,符合富营养化综合评价问题的非线性特征.该方法对巢湖富营养化的综合评价结果与插值评分法有显著差异,与综合营养状态指数法有极显著差异.

There are different widths among 10 intervals of each assessment indicator through analysis on Control Standard for Eutrophication Surface Water, which indicate weight of each indicator should be changed with its monitored value. Based on above thoughts, a novel method, named Slope Weighted Scoring Method, is proposed for eutrophication comprehensive evaluation of lakes on the basis of Interpolation Scoring Method. All boundary data listed in assessment standard are normalized to eliminate influence of dimension. Slopes of 10 intervals of each indicator are calculated with normalized boundary data. First step of using this method is calculating corresponding trophic state score of each indicator with interpolation method according to its monitored value and assessment standard. The slope of each indicator is recorded simultaneously. Second step is allocating weight for each indicator with all recorded slopes. Finally, comprehensive trophic state score is obtained with weighted mean method according to scores and weights of all indicators. The proposed method makes the most of slopes of all indicators＂ intervals in assessment standard to allocate the weight of each indicator dynamically. The character of weights dynamic allocation answers to the nonlinear mapping essence of eutrophication comprehensive evaluation. Applying this method, Interpolation Method and Comprehensive Trophic Level Index Method to evaluate eutrophication of Chaohu Lake, the results showed that there was significant difference between this method and Interpolation Scoring Method, and the most significant difference between this method and Comprehensive Trophic Level Index Method.