Deposition versus Photochemical Removal of PBDEs from Lake Superior Air

Abstract

Analysis of a sediment core collected from Siskiwit Lake, located on a remote island in Lake Superior, provides evidence that polybrominated diphenyl ethers (PBDEs) are removed effectively from the atmosphere via deposition processes during long-range transport. A mass balance model based on photochemical rate constants and data from atmospheric samples was created to understand the relative importance of various photochemical and deposition processes in removing PBDEs from the atmosphere. Photolysis rate constants were derived from UV absorption spectra of 25 PBDEs recorded in isooctane over the range of 280-350 nm at 298 K. Photolysis decays measured for BDE-3 and -7 in the gas phase were substantial compared to a well-defined chemical actinometer, indicating that their photolysis quantum yields are significant. Dibenzofuran production was observed when PBDE congeners containing ortho-bromines were photolyzed in helium. From estimates of removal rates of PBDEs from the lower troposphere, we find that wet and dry deposition accountfor >95% of the removal of BDE-209, while photolysis accounts for -90% of the removal of gas-phase congeners such as BDE-47. These results help explain the deposition patterns of PBDEs found in lake and river sediments and have important implications concerning the inclusion of photolysis as a fate process in multimedia models.

Sources and environmental behaviors of Dechlorane Plus and related compounds — A review

“…The authors suspected that these decomposition products were either formed during LRAT by photodegradation or by biodegradation once DP entered into the ocean (Möller et al, 2010). Although photodegradation of DP was observed in the simulation experiment by Sverko et al (2008), Raff and Hites (2007) indicated that atmospheric particle bound semivolatile organic compounds (SOCs) might not be photodegradated due to the shielding effect of carbonaceous aerosols on sorbed SOC molecules. However, thermal degradation of DP may occur during e-waste burning processes since the recommended operating temperature of DP is 285°C, and decomposition may occur at 350°C (OxyChem, 2007).…”

Distribution of polybrominated diphenyl ethers and decabromodiphenylethane in surface sediments from the Bering Sea, Chukchi Sea, and Canada Basin

“…In the Canada Basin, the concentration of BDE-183 was at the same level with that of BDE-153 while, on the contrary, no BDE-183 was detected in the Bering Sea or the Chukchi Sea. This may indicate a local source of PBDEs from North America (de Wit et al, 2010;Raff and Hites, 2007). Furthermore, the ability of the particlebound congeners to increase with a decrease in temperature together with the relatively low concentrations of PBDEs, suggest that atmospheric deposition was also a significant input pathway Raff and Hites, 2007;Rayne et al, 2003;Su et al, 2007).…”

“…This may indicate a local source of PBDEs from North America (de Wit et al, 2010;Raff and Hites, 2007). Furthermore, the ability of the particlebound congeners to increase with a decrease in temperature together with the relatively low concentrations of PBDEs, suggest that atmospheric deposition was also a significant input pathway Raff and Hites, 2007;Rayne et al, 2003;Su et al, 2007). However, normality tests show that the skewness was 0.410-1.455 for P PBDEs and 1.057-2.506 for BDE-209, which further indicated that the distribution of PBDEs was not only dominated by atmospheric deposition (Su et al, 2007) but also by some local source from the coastal area.…”

Summer atmospheric polybrominated diphenyl ethers in urban and rural areas of northern China

“…), which was different from BDE-209. This is likely because that these lighter congeners are more mobile in the atmosphere while BDE-209 could be removed from the atmosphere via particle deposition during transport (Raff and Hites, 2007). BDE-47 has similar or higher concentrations at rural sites than urban sites, which might be due to the contributions of both atmospheric transport and local sources.…”