Seasonal Residence Time Variations for 210po/210pb Aerosol Particles in Shenzhen, China

210Pb and 210Po were used as tracers to determine the seasonal variations of residence times of aerosols (RTAs) in Shenzhen, China. The RTA for 210Pb/210Po aerosol particles ranged from 11.5 to 47.8 days (mean value of 25.3 ± 8.2 days), and it was lower in summer and higher in winter, meteorological conditions were considered the main factors affecting the RTA. The RTA was strongly affected by precipitation and was long under thermal inversions. In addition, the RTA calculated from the 210Po/210Pb ratio was strongly affected by old aerosols transported over long distances and the intrusion of upper atmospheric aerosols.