Dry and wet particle deposition of polybrominated diphenyl ethers (PBDEs) in Guangzhou and Hong Kong, South China.

PBDEs were measured in wet and dry particle deposition samples collected at the urban sites of Guangzhou and Hong Kong from December 2003 to December 2004. The depositional fluxes of BDE-209 ranged from 273 to 6000 ng m(-2) day(-1) in Guangzhou and from 29.1 to 1100 ng m(-2) day(-1) in Hong Kong. The depositional fluxes for Sigma(9)PBDEs (defined as the sum of BDE-28, -47, -66, -100, -99, 154, -153, -138 and -183) ranged from 0.96 to 604 ng m(-2) day(-1) in Guangzhou and from <LOD to 10.6 ng m(-2) day(-1) in Hong Kong. BDE-209 was the most abundant PBDE congener, showing that deca-BDE accounts for most of the total PBDE emitted in the environment. Distinct seasonal patterns were observed in the PBDE depositional fluxes in Hong Kong, with higher depositional fluxes during the winter monsoon period and lower fluxes during the summer. The air mass back trajectory analysis showed that the high concentrations of PBDEs in deposition samples in Hong Kong originated from the inland of the Pearl River Delta (PRD) region. With the exception of the highest depositional flux of BDE-209 observed during the periods of haze, the seasonal variation in the BDE-209 depositional fluxes in Guangzhou was less strong, suggesting the importance of local sources. The average dry deposition velocities of BDE-47, -99, and -209 were 0.32 +/- 0.12 cm s(-1), 0.24 +/- 0.16 cm s(-1), and 0.28 +/- 0.01 cm s(-1), respectively. The particle washout ratios (W(p)) of PBDEs decreased with increasing rainfall frequency and reached a consistent level afterwards. The median washout ratios of BDE-47, -99 and -209 were 1.1 x 10(5), 3.1 x 10(5), and 5.1 x 10(5), respectively.