Temporal variations of urban re-suspended road dust characteristics and its vital contributions to airborne PM2.5/PM10 during a long period in Beijing

Re-suspended road dust RRD as RRD2.5 and RRD10 can even more easily enter the atmospheric environment, showing a kind of significant potential to influence atmospheric environment. A campaign of sampling RRD samples at 53 sites and aerosol samples at a representative urban site in Beijing in October 2014, January, April and July 2015 was accomplished, and combined with RRD in 2003, and 2016–2018 periods to investigate the seasonal variations of chemical components in RRD2.5 and RRD10, long-term evolutions of RRD characteristics in 2003–2018, and source composition changes of RRD. Meanwhile a technique based on Mg/Al indicator for effectively estimating contributions of RRD to PM was developed. It is found that pollution elements and water-soluble ions in RRD were largely enriched in RRD2.5. The pollution elements presented an obvious seasonal variation in RRD2.5, however showed various seasonal variations in RRD10. These pollution elements in RRD, due to being mainly impacted by both increasing traffic activities and atmospheric pollution control measures, almost display a single-peak change in 2003–2018. The water-soluble ions in RRD2.5 and RRD10 presented various seasonal variations, and displayed an evident increase in 2003–2015. The source composition of RRD in 2003–2015 posed a significant change that traffic activities, crustal soil, secondary pollution species and biomass combustion became significant contributors to RRD. The contributions of RRD2.5/RRD10 to mineral aerosols in PM2.5/PM10 presented a similar seasonal variation. The synergistic effects of meteorological factors and anthropogenic activities in different seasons were significant motive force influencing the contributions of RRD to the mineral aerosols. The pollution elements Cr and Ni in RRD2.5 were the significant contributors to PM2.5, however, Cr, Ni, Cu, Zn, and Pb in RRD10 were the important contributors to PM10. The research will provide a new significant scientific guide for further controlling atmospheric pollution and improving air quality.