A universal six-element connection number model for water quality assessment based on set pair analysis

Water quality assessment indexes are classified into the optimal minimum indexes and maximum optimal indexes for comprehensive assessments of water quality and the set pair analysis (SPA) theory is used in water quality comprehensive assessments for constructing the six-element connection number between the evaluation samples and the evaluation indexes. Because the coefficient of difference degree (CDD) of variation is difficult to calculate in conventional models, quintile interpolation algorithm(QIA) is proposed to calculate the CDD, and the calculation models with corresponding difference degree of variation coefficients are proposed; then the algorithm for calculating the SPA connection number is given. Finally, a universal comprehensive water quality assessment model based on SPA is proposed. The new model is a generic scheme that can be used to assess the quality of water on the earth surface or underground. The experiment shows that the result calculated by the model is reasonable.