Response of antimony distribution in street dust to urban road traffic conditions.

Little is known about the relationship between traffic congestion and antimony (Sb) distribution in street dust, which is essential for Sb control and emission reduction in urban areas. Sb concentrations and mass load of the street dust collected in 19 cities of China were determined before investigating the mechanism of traffic influence on Sb distribution through diverse statistical means. The results showed that the Sb concentrations in each city were 1.10-4.76 times higher than the local background values. Sb concentrations in transportation areas were significantly higher than those in residential and industrial areas, and were significantly affected by road network density. The effect of congestion on Sb load of street dust was influenced by vehicle flowrate. Only when the vehicle flowrate was high, the traffic congestion would promote the increase of Sb load obviously. The improved accounting method showed that the Sb dissipation from brake wear in major Chinese cities were higher than that in Stockholm, Sweden, in 2005. The latent path analysis illustrated that a 1% increase in congestion index was correlated with a 0.886% increase in the Sb load. Compared with Switzerland, which has a typical industrialized Sb consumption pattern, China needs to recycle brake pads in addition to taking various measures to alleviate traffic congestion and reduce brake pad wear, despite the fact that the maximum health risk of Sb was far below the safety threshold. This study will provide valuable insights for urban traffic management and brake pad recycling.