The accumulation process of pollutants in deposited particles of different sizes on different roads in Beijing, China.

Road-Deposited Sediments (RDS) samples were collected from four different roads in Beijing, and the distribution of pollutants in RDS with various particle sizes was compared. In this study, the cumulative mass of RDS exhibited a positive correlation with the number of dry days, and the RDS load below 75 μm was also influenced by road traffic volume. As traffic volume escalated, there was a corresponding increase in the load of these smaller RDS. Most pollutants accumulated within RDS with sizes below 150 μm, rendering them the primary contributors to the pollution. In terms of the antecedent dry-weather days, fifteen days emerged as a potentially pivotal point, with both the rate of pollutant accumulation and the contribution of pollution sources to RDS having stabilized after this duration. The origins of pollutants in roads of different functional areas exhibited certain disparities. The pollutants on major roads with high traffic volume were attributed to frequent vehicular activities. The pollutants on residential roads stemmed from soil particles and fallen leaves in the roadside green belts as well as from human activities. And the pollutants on urban-rural crossroad might be attributed to the industrial contamination with factories located on one side.