Assessing the air quality performance of urban garden designs: an integrated ENVI-met modeling and field measurement study in Guelma, Algeria.

Urban air quality degradation, driven by intensified urbanization and traffic, presents a critical public health challenge in most cities worldwide, such as Guelma, Algeria, where concentrations of fine particulate matter (PM2.5, PM10) and carbon dioxide (CO2) often exceed health standards. This study evaluates the efficacy of conventional greening by suggesting that the air purification potential of public gardens may be limited by suboptimal initial design. It is an exploratory modeling framework to propose a shift from qualitative landscaping to quantitative, performance-driven biophilic design. By simulating six parameterized intervention scenarios, this research indicates that simplistic canopy densification may be an insufficient strategy under high pollutant loads. Based on a specific summer field campaign and a limited temporal scope, the results identify a proposed design configuration protocol, where significant pollutant mitigation is achieved by a specific arrangement: a 60% urban forest index composed of high-efficiency species (Platanus × acerifolia, Acer saccharinum, Quercus spp.), combined with a 10% shrub layer and 40% grass cover to form a multilayered filter. This vegetative system is integrated with complementary engineered systems: linear water features covering 15% of the surface for particle wash-down, soil engineered to an aerodynamic roughness length (z0) of 0.15 m across 65% of the site to enhance deposition, and pollutant-absorbing paving on 20% of the surface. This study suggests that enhancing the functional efficiency of urban gardens requires precise, multimechanism integration of biomass, water, and engineered surfaces, providing an exploratory framework for designing public spaces as potential infrastructure for sustainable air quality improvement.