基于灰色聚类法和模糊综合法的水质评价

Application of Grey Clustering Method and Fuzzy Comprehensive Assessment Method to Assess Eutrophication Level of Water Quality

根据2008年9月从昆承湖布设的12个监测点采集的样本中水质指标(叶绿素a、总磷、总氮和高锰酸盐指数)的浓度值,采用了灰色聚类法及模糊综合评价法对样本水质进行富营养化评价。灰色聚类法先建立白化权函数并无量纲化灰类来消除各水质指标浓度值量级差异的影响,然后根据水质指标浓度阈值的大小赋以其权值,综合水质指标对各级富营养状态的隶属度进行富营养化评价,结果显示,全部监测点的水样均处于中度富营养化状态,偏向轻度富营养化状态(聚类系数相差0.15左右)。模糊综合评价法通过建立模糊矩阵和模糊权向量,采用"最大,最小"算法进行矩阵运算,突出了主要决定因子总氮对水质富营养化的影响,评价结果显示,全部监测点的水样均处于中度富营养化状态,偏向重度富营养化状态(隶属度相差0.15左右)。

According to consistency value of water quality indicators such as Chl-a,TP,TN and CODMn of the samples taken from 12 monitoring sites located in Kuncheng Lake in September,2008,grey clustering method and fuzzy comprehensive assessment method were used to assess its eutrophication level.The grey clustering assessment method established the whitening function and did non-dimensional treatment to avoid the influence of magnitude of concentration values firstly,and then evaluated weights based on threshold of the indicators for assessing the eutrophication level.Assessment result showed that water samples of 12 monitoring sites were at moderately eutrophication level,on the verge of mildly eutrophication level,with clustering coefficients lower by 0.15.However,the fuzzy comprehensive assessment method,building fuzzy matrix and fuzzy vector,used the matrix operation based on maximum ＆ minimum algorithm to give prominence to the impact of chief factor on eutrophication,and assessment result showed that water samples of 12 monitoring sites were at moderately eutrophication level,on the verge of severe eutrophication level,with membership degrees lower by about 0.15.