湖库富营养化的改进型模糊综合评价方法研究

针对水体富营养化评价系统的非线性、模糊综合评价法过程中权重赋予的主观随意性和隶属函数的不准确性等特点,对传统模糊综合评价法进行了改进,并据此对我国24个代表性湖库的富营养化程度进行了评价.其中以SPSS16.0和Yaaph软件为载体,采用层次分析法和主成分分析法相结合来确定选取因子的权重.根据确定的评价标准作自然对数变换使之线性化,并结合由基础数据统计分布情况,生成各评价因子隶属于各营养等级的对数形式的降半梯形隶属函数,进而得到各湖库的确定度,最后依据最大确定度得到湖库富营养化级别.该法所得结果与湖库实际富营养化状况以及现有多种评价方法的结果的对比表明,该改进方法的评价结果真实、准确、计算简单,具有可行性.

An improved fuzzy comprehensive evaluation method of eutrophication for lakes and reservoirs

As to characteristics of the nonlinearity of water body eutrophication evaluation system, the randomness of weight assignment and inaccuracy of subordinate function during the process of fuzzy comprehensive evaluation, an improved fuzzy comprehensive evaluation method has been pointed out through improving the traditional fuzzy comprehensive evaluation method, and it has been applied to evaluate degrees of eutrophication of water body in 24representative lakes and reservoirs in China. During the process of improvement, the analytic hierarchy process was combined with principal component analysis by software SPSS16.0and Yaaph to determine index weights, and the determined evaluation criteria were logarithmically transformed to linear, and also each index membership function of logarithmic and lower semi-trapezoid form corresponding to every trophic levels was generated based on distribution characteristics of detected field data, then the membership degree of each lake or reservoir can be obtained and its eutrophication level can be determined by the principle of maximum membership degree. The result of the improved method has been compared with actual eutrophication status of lakes or reservoirs and evaluated results obtained by present evaluation methods, which shows that the calculating process of the improved method is simple, and its result is true and accurate, thus the method is feasible and practical.