Air purification and cooling effects of green spaces: Mechanism, quantification, and interaction

The intensifying coupling of urban heat island effect and urban pollution island effect, driven by anthropogenic heat and pollutant emissions, poses significant environmental challenges. As a nature-based solution, green spaces (GS) are widely recognized for their air purification and cooling effects, offering an effective strategy to mitigate urban heat and air pollution risks. While various methods have been developed to quantify these effects, most studies rely on a single approach, lacking comprehensive comparisons and systematic evaluations. This limitation hinders the scientific selection and optimized application of different methods in practice. Therefore, we systematically reviewed the key mechanisms underlying GS cooling and air purification effects, along with their quantification methods, applicability, and limitations. Moreover, existing reviews often focus on GS cooling and air purification effects in isolation, overlooking their intrinsic connections. Whether these effects are synergistic or involve trade-offs remains unclear, limiting a comprehensive understanding of GS ecological benefits. To address this research gap, we investigated that GS could enhance air purification through cooling and strengthen cooling through air purification. Additionally, we identified six indirect interaction pathways between these two effects, underscoring the need for integrated research. Future studies should adopt multiple approaches to analyze the direct effects of GS cooling and air purification from long-term as well as multi-scale perspectives. It should also validate their interactive mechanisms, identify key indirect pathways, and conduct objective and comprehensive evaluation of GS enhancing strategies. By deepening the understanding of the interactions between GS, temperature, and air pollutants, this review highlights the potential synergistic benefits of GS in urban cooling and air purification.