| Polybrominated diphenyl ethers (PBDEs) are an important kind of Brominated Flame Retardants, two commercial products of which have been added into the POPs list by the Stockholm Convention. There have been numours monitoring projects studing fate and environmental behavior of PBDEs in Chinese air, most of which, however, focused on studies on a small spatial scale or a short temporal range, and it is still lacking for comprehensive information of PBDEs in Chinese air on a national scale and in a long temporal period of a whole year. In this study, air samples (with both gaseous and particulate phases) were concurrantly collected at15sampling sites across China continuously for24hours once a week for a whole year, and levels, compositions, and transformations of PBDEs in Chinese urban, suburban, and background/rural sites were analyzed, with a particular focus on investigation of gas-particle partitioning of PBDEs in Chinese air. The results of this study will provide scientific base to better perform the Stockholm Convention, and finally completely eliminate the contamination by these chemicals in China.A national monitoring program, Chinese POPs Soil and Air Monitoring Program, Phase2(China POPs SAMP-II) was carried out by the International Joint Research Center for Persistent Toxic Substances (IJRC-PTS). High-volume air samplers had been used to collect air samples from11urban sites (Beijing, Harbin, Shihezi, Dalian, Lanzhou, Xi’an, Lhasa, Chengdu, Nanchang, Kunming, and Guangzhou),1suburban site (Lingang, Shanghai), and3background/rural sites (Wudalianchi, Heilongjiang Province, Xuancheng, Anhui Province, and Waliguan, Qinghai Province) in this study. The air samples were collected from September2008to August2009.12PBDE congeners (BDE-17, BDE-28, BDE-47, BDE-66, BDE-85, BDE-99, BDE-100, BDE-138, BDE-153, BDE-154, BDE-183and BDE-209) were analyzed using GC-MS (NCI). The annual average air concentrations of∑12PBDEs at the15sites were in the range of11.0-838pg m-3with a mean of232+277pg m-3. Concentrations of PBDEs in Chinese atmosphere were in the order of urban (306±475pg m-3)> suburban (67±98 pg m-3)> rural/background (14±13pg m-3). There were significant positive correlations between PBDEs levels and urban population (R=0.69,P<0.05) and even greater and more significant correlation between PBDEs levels and gross industrial output value (R=0.87,P<001). Most PBDEs exists in the particulate phase at urban sites and in the gaseous phase at the background/rural sites., The seasonally of the PBDEs concentration in Chinese air was also studied. With majority of PBDEs at the urban sites being in particulate phase, the total PBDE concentritions in fall and winter were higher than those in spring and summer; in contrast, PBDEs in air at the background/rural sites mainly presenting in the gas phase, the total PBDE concentritions in spring and summer were higher than those in fall and winter. Profiles of PBDEs at urban and suburban sites were similar, in which BDE-209was the dominated congener and the annual average contribution to the total PBDEs (∑12PBDE) air concentration was64±23%, Followed by BDE-209were BDE-47(8±8%) and-99(6±5%). In the background/rural air, however, the dominated PBDE congeners were BDE-47and-99, with the annual average contributions to the total PBDEs as28±11%and25±10%, respectively. Potential sources of PBDEs in background/rural sites had been identified by air mass trajectory analysis, indicating that Russian Far East, inland areas of central China, and Yangtze River Delta were possibly the main source regions for PBDEs in air at Wudalianchi, Waliguan, and Xuancheng, respectively.A huge amount of datasets was obtained for PBDE concentrations of more than700gas-particle pairs with a large spatial scale (11urban sites,1suburban site, and3background/rural sites across China) and a wide temperature range (～60℃), previding the greatest opportunity to study the gas-particle partitioning of PBDEs. Two equations (PL0based equation and KOA based equation) were used to analyze gas-particle partitioning of PBDEs at15sampling sites. Significant linear correlations between log KP and log PL (or logKOA) were obtained in all sites (r2=0.07～0.69, P<0.0001, or P0.05), but the values of the slope m deviated from-1or+1, indicating that PBDEs in the air at the15sampling sites did not reach equilibrium between gas and particle phases It was found that the values of the slope mo in the KOA based equation and the absolute values of mp in the PL0based equation at the15sampling sites significantly correlated with the annual mean temperature of the15sites, suggesting that the lower the temperature at the sampling site is, the lower are the abosolute values of slopes, and the farther away from the equilibrium for the PBDEs with the gas and particle phases. It was also obvious from the monitoring data that the lower brominated congeners showed closer to the equilibrium than the high brominated ones between the gas-and particle-phases. Similar to the KOA based equation under equilibrium, a PL0based equation under equilibrium was derived, which was used to predict the values of Kp, with the results comparable to those obtained by the KOA based equation. Both the KOA based and PL0based equations can accurately predict the values of Kp only for lower brominated PBDE congeners at high temperatures, but failed to do so for higher brominated PBDE congeners at low temperatures.The definitions for equilibrium state and steady state were carefully reviewed, and a suggestion was made that steady state, not the equilibrium state, should be applied for studing the gas-particle patitioning for SVOCs, including PBDEs. Two new equations under the steady state theory, one PL0based and the other KOA based, were thus derived, which were used to predict the values of Kp. The results clearly indicated that the two new equations were able to predict more accuratelly the values of Kp for all selected PBDE congeners in any temperature ranges (from-21℃to38℃) in this study. |
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