Assessing Particulate Matter Deposition and Resuspension by Living Wall Systems in a Wind Tunnel Setup

This study examines the particulate matter (PM) capture capacity of living wall systems (LWSs), focusing on leaf traits that facilitate PM deposition. Six LWS designs, differing in structure and substrate, were tested under constant airflow conditions with and without additional PM. Results showed that planter-based LWSs reduced PM0.1 by 2% and PM2.5 by 4%, while a textile LWS reduced PM0.1 by 23% and PM2.5 by 5%, though geotextile textile increased PM by 11% for both fractions. A moss substrate LWS worsened air quality, raising PM0.1 by 2% and PM2.5 by 5%. Magnetic analysis of leaf-deposited PM (SIRM) revealed species-specific differences (p < 0.001), with SIRM values ranging from 5 ± 1 µA to 260 ± 1 µA and higher PM accumulation in plants with lower specific leaf areas. No differences were observed in SIRM between deposition and resuspension phases, indicating the PM source lacked sufficient magnetisable particles. The findings highlight the potential of LWSs in urban environments for air quality improvement but underscore the importance of selecting suitable LWS structures and plant species.