Structure of an urban green space indirectly affects the distribution of airborne particulate matter: A study based on structural equation modelling

Urban green spaces can effectively regulate microclimate and improve air quality. However, the relationship between the structure of an urban green space, meteorological conditions, and the concentration distribution of different sized particles inside and outside of green spaces is unclear. In this study, a field survey was conducted on the structures of 188 green spaces in Beijing. The temperature and relative humidity were also monitored, and the concentrations of different sized particles were measured both inside and outside of the selected green spaces to comprehensively analyse the relationships between these variables and the structure of a green space. The results of structural equation modelling showed that the structure of a green space indirectly affected the concentration distribution of particulate matter (PM) through the effects of cooling and humidification, while the direct effect was not obvious. In addition, the impact mechanisms of the structure of a green space on the concentration distribution of particles differed between PM 1 , PM 1–5 , and PM 5–25 , primarily due to the influence of particle size and meteorological factors on the movement of PM. This study deepens the understanding of the influencing mechanisms of the structure of a green space on the concentration distribution of PM, thus providing an important reference for subsequent related field and numerical simulation research. • Field experiments were carried out to explore the mechanisms of PM concentration distribution. • Green space indirectly affects the PM distribution by affecting microclimate. • Structural equation modelling was used to analyse the relationship between variables. • PM concentration distribution mechanisms vary with particle size (PM 1 , PM 1–5 and PM 5–25 ).