The development of IFN-SPA: A new risk assessment method of urban water quality and its application in Shanghai

This study proposes a new set-pair analysis (SPA) method by enhancing existing SPA methods using interval-based fuzzy numbers (IFN), referred to as the IFN-SPA method. The IFN-SPA method uses the relative distance to express the degree of importance between assessment samples and criteria, which overcomes the limitations of existing SPA methods. It also simplifies the judgement membership functions of the existing SPA methods. To demonstrate the advantages of the IFN-SPA method, both the existing and new methods were employed to assess the water quality in Shanghai, China. The results show that the water quality in Chongming District is better than that of the other districts. The IFN-SPA and existing methods were compared, and the risk levels reported by the IFN-SPA were 25% higher. The assessment results are consistent with the actual water quality, and the results of the IFN-SPA method are more reasonable than those of the existing methods. (C) 2020 Elsevier Ltd. All rights reserved.