Roof Dust Accumulation Characteristics and the Influencing Factors in Typical Urban Areas of Beijing

Understanding the characteristics of roof dust and its environmental drivers is crucial for assessing urban particulate matter dynamics. In this study, 159 roof and ground dust samples were collected from multiple locations within a university campus in central Beijing between December 2020 and November 2021, serving as a representative urban environment to investigate the vertical and temporal dynamics of dust accumulation. Dust mass, PM₁₀, and PM₂.₅ concentrations were analyzed and correlated with meteorological parameters. The results revealed clear seasonal patterns, with dust mass peaking in February and March, and lowest in summer and autumn. PM₁₀ concentrations showed a strong linear correlation with total dust mass (r = 0.773), indicating that coarse particles may be closely associated with rooftop dust accumulation. Dust accumulation was significantly enhanced by winds from the southeast (SE) and south-southwest (SSW) sectors, while winds from the north-northwest (NNW) had a suppressive effect. A wind-speed threshold effect was observed: rooftop dust loads began to increase above 2.5 m/s, with the strongest accumulation associated with wind speeds exceeding 5 m/s. Additionally, precipitation frequency and relative humidity were inversely related to dust accumulation (r = -0.755 and -0.773), indicating effective natural removal processes. Roof dust accumulation generally decreased with increasing building height, although unexpectedly high dust loads were observed on mid-rise buildings, likely due to higher building density and restricted local air circulation. These findings demonstrate that roof dust accumulation is strongly modulated by seasonal meteorology, wind regimes, and urban morphology. The vertical distribution patterns identified here provide a basis for integrating roof sampling into urban air quality monitoring and for refining models of particulate dispersion in dense cityscapes.