Study of the allocation strategy of water pollutant emission permits under a bidirectional ecological compensation mechanism

Water pollutant emission permits (WPEPs) allocation is a competing limited consumption resource designed to address the issue of reconciling water pollution with economic development. In the wake of increasing conflicts, a pressing challenge is how to motivate stakeholders associated with the basin to establish a balance between economic development and environmental preservation. Based on the unidirectional flow of basin pollution, this study established a bidirectional ecological compensation (BEC) mechanism, which incorporated the key water pollution indicators (WPEPs allocation volume) into the BEC mechanism. By integrating the BEC mechanism with the WPEPs allocation model, a multi-objective optimization framework for balancing the fairness and economic efficiency of WPEPs allocation under the BEC synergy mechanism has been proposed. The Tuojiang river basin in China was selected for the study, and the allocation results and ecological compensation mecha-nisms under different allocation preferences were analyzed to verify the validity and practicality of the model. Results revealed that (1) BEC mechanisms can be considered to ensure equitable and efficient allocation of WPEPs in the basin. (2) Under the perspective of watershed cooperation, the bidirectional compensation mechanism proves to be an effective measure to promote economic development and environmental protection of the watershed. (3) Preferences of watershed managers for allocation and ecological compensation mechanisms can have an impact on the outcomes of allocation and ecological compensation mechanisms. This study provides reference for effective management and adoption of optimal allocation strategy of watershed WPEPs and syn-ergistic management of BEC mechanisms.