[Pollution and Carbon Emission Reduction and Synergistic Pathways in the Operation Phase of Sponge City Source...

China is currently at a crucial stage of systematically advancing the construction of sponge cities and completely implementing the "synergetic enhancement of pollution and carbon emission reduction." The pollution and carbon emission reduction benefits during the operational phase of sponge source control facilities, as well as the synergistic path must be crucially understood scientifically. Taking 30 sponge city construction projects in Wuxi, Jiangsu Province as examples, we analyzed the pollution and carbon emission reduction benefits, construction costs, and determined the synergistic relationship among them during the operational phase. Additionally, we proposed a synergistic path among the three by utilizing a constrained NSGA-Ⅱ multi-objective optimization algorithm. The results showed differences in the pollutant and carbon reduction capacity and the composition of carbon reduction capacity （carbon sequestration by vegetation, carbon storage by runoff, and carbon reduction by pollution reduction） of sponge source control facilities （infiltration rain gardens, drainage rain gardens, undercrofts, planted swales, and permeable pavement）. Therefore, the ratio of the underlying surface area of the sponge source control facilities influenced the pollutant and carbon emission reduction benefits and costs of the project； however, a marginal effect was observed, which was mainly reflected in the permeable pavement to the pollution reduction benefits of the project （R²=0.423 9）. The synergy between the pollution reduction benefit and carbon emission reduction benefit of sponge projects was weak, in which the pollution reduction benefit had a trend of increasing marginal cost for the pollution reduction benefit （R²=0.784 4）, whereas the carbon emission reduction benefit was linearly correlated with the construction cost （R²=0.544 7）. Furthermore, a multi-objective optimization algorithm was employed to propose a series of distinct combinations of sponge source control facilities, each optimized for a distinct set of objectives. The results elucidate the pollution and carbon emission reduction benefits and synergistic optimization path of sponge source facilities in the operation phase, which can provide scientific basis for achieving the goal of "pollution and carbon emission reduction, greening, and growth" and maximizing ecological value.