Samples of road dust were collected from selected representative roads in Beijing in September 2004 and May 2013, and then re-suspended on filters using a NK-ZXF sampler to prepare road dust PM10 and PM2.5 samples. The concentrations of the chemical components in the road dust PM10 and PM2.5 were analyzed, and source profiles of the road dust in Beijing in 2004 and 2013 were established. The characteristics and interannual variation of the chemical components in the road dust in Beijing were analyzed and discussed. The results showed that the chemical components in the road dust PM10 and PM2.5 in Beijing were Ca, Si, organic carbon (OC), Al, Fe, K, Mg, SO42-, and elemental carbon (EC). The total content of these chemical components in the PM10 in 2004, PM2.5 in 2004, and PM2.5 in 2013 were 46.7303%, 56.9198%, and 38.7478%, respectively, and the total content of these chemical components accounted for 95.9%, 94.3% and 94.7% of the total content of all components tested, respectively. In 2004, the contents of Si and Al in the road dust of ring road were significantly lower than those of other road types, and the influence of soil dust on the ring road was the smallest. The content of Ca, a characteristic element of construction dust, was the highest in main road, and was the lowest in the expressway entrance to Beijing. The content of EC in the road dust from the expressway entrance to Beijing was significantly higher than that in other road types. However, in 2013, the total content of all components tested and the contents of Si, Al, and Ca in the road dust PM2.5 of secondary main roads were significantly lower than those for other road types. Due to the implementation of dust, motor vehicles, and combustion source control measures in Beijing and the relocation of the Shougang corporation, only the content of SO42- in the road dust PM2.5 in Beijing increased slightly by 2.0% in 2013 compared with in 2004; the contents of the other components decreased significantly. The contents of Ca, Si, OC, Al, Fe, K, EC, and NO3- decreased by 45.1%, 31.5%, 17.5%, 20.3%, 55.6%, 33.3%, 30.0%, and 50.3%, respectively. The results showed that the ratio of[NO3-]/[SO42-] did not accurately reflect the changes in the relative contributions of fixed sources and moving sources. The[OC]/[EC] ratios of PM10 in 2004, PM2.5 in 2004, and PM2.5 in 2013 were 9.77±3.88, 9.36±3.25, and 14.41±10.41, respectively. Secondary organic carbon (SOC) pollution was present in road dust in Beijing, and the SOC was an important component in the road dust PM10 and PM2.5. The source profiles of different urban road dust samples and the source profiles of road dust of different sizes in the same city were not very similar, so the corresponding source profiles should be established and updated in a timely manner.
Keywords: PM10 and PM2.5; characteristics of chemical components; interannual variation; road dust; source profiles.