Interactive regulation mechanisms of misting-shading configurations on summer urban thermal environment and air quality: A field experiment in Xi'an,China

Abstract

Summer urban air pollution and heat waves pose serious health risks. Although mist spraying is widely used to alleviate heat stress, its combined effects with different shading conditions on outdoor thermal-pollution environments remain unclear. This study aims to identify the optimal integrated misting-shading system by evaluating their ameliorating effects. Field experiments on a university campus in Xi'an involved five groups: “natural shading + no mist spraying” “natural shading + mist spraying”, “no shading + mist spraying”, “artificial shading + mist spraying” and “no shading + no mist spraying” (control). We continuously measured air temperature, relative humidity, particulate matter (PM) and O₃ concentrations. The Mann–Whitney U test compared regulatory effects, and particle size ratios (PMx/PMy, x < y) analyzed condensation and deposition for PM₁, PM_2.5 and PM₁₀. Results show that “natural shading + mist spraying” achieved the most significant synergistic regulation, reducing air temperature by 12.6% and O₃ by 10.8%, while increasing relative humidity by 26.2%. “Artificial shading + mist spraying” most effectively promoted PM_2.5 condensation and deposition. Overall, this study offers a practical assessment of misting-shading systems to simultaneously alleviate heat and pollution, advancing integrated mitigation strategies and providing empirical evidence for climate-adaptive urban design.