Polybrominated Diphenyl Ethers in Air across China: Levels, Compositions, and Gas-Particle Partitioning

Air samples were concurrently collected using high volume air samplers for 24 h every week from September 2008 to August 2009 at 15 sites (11 urban, 1 suburban, and 3 background/rural) across China. Twelve polybrominated diphenyl ether (PBDE) congeners (BDE-17, -28, -47, -66, -85, -99, -100, -138, -153, -154, -183, and -209) were measured. Total PBDE concentrations (Sigma 12PBDEs) in air (gas + particle phases) were in the range of 11.0-838 pg m(-3) with a mean of 232 +/- 72 (mean +/- SE) pg m(-3). The site with the highest concentration was Guangzhou (838 +/- 126 pg m-3), followed by Beijing (781 +/- 107 pg m(-3)). Significant positive correlations were found between PBDEs levels and urban population (R = 0.69, P < 0.05) and gross industrial output values (R = 0.87, P < 0.001) as well. BDE-209 was the dominating congener with the contribution of 64 +/- 23% to Sigma 12PBDEs, followed by BDE-47(8 +/- 8%) and -99(6 +/- 5%) at all urban and suburban sites. At background/rural sites, however, BDE-47 was the dominating congener, followed by BDE-99, together accounting for 52 +/- 21% of Sigma 12PBDEs, while BDE-209 was only 11 +/- 2%. It was found that PBDEs at the 15 sites showed a primary distribution and fractionation pattern. This study produced more than 700 pairs of air samples in gaseous and particulate phases with a wide temperature range of similar to 60 degrees C, providing a good opportunity to investigate gas-particle partitioning for individual PBDE congeners. The results of gas-particle partitioning analysis for PBDEs using both subcooled-liquid-vapor pressure (P-L)-based and octanol-air partition coefficient (K-OA)-based models indicated that PBDEs in air at all sampling sites had not reached equilibrium because the slope values (m(O)) in the K-OA-based equation and the opposite slope values (m(p)) in the P-L-based equation at all 15 sampling sites were less than 1. It also found that both m(o) and -m(p) were significantly and positively correlated with the annual average temperatures of sampling sites and also significantly and negatively correlated with the mole masses of PBDE congeners, indicating a general trend that the higher the temperature at the sampling site and the lower the mole mass of the PBDE congeners are, the closer to the equilibrium the congeners approach and vice versa. To our knowledge, this is the first study to report the correlations of the slope values for both the K-OA-based and P-L-based equations with temperatures at sampling sites and mole masses for individual PBDE congeners.