title: 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.
authors.affiliation: School of Public and Environmental Affairs, Indiana University, Bloomington, Indiana 47405, USA.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Raff
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Hites
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry / Q000528:radiation effects*; D004784:Environmental Monitoring; D005618:Fresh Water; D019015:Geologic Sediments / Q000032:analysis; D017665:Hydroxyl Radical / Q000737:chemistry; D010647:Phenyl Ethers / Q000032:analysis* / Q000737:chemistry / Q000528:radiation effects*; D010782:Photolysis; D011075:Polybrominated Biphenyls / Q000032:analysis* / Q000737:chemistry / Q000528:radiation effects*; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry / Q000528:radiation effects
chemical_list: D000393:Air Pollutants; D010647:Phenyl Ethers; D011075:Polybrominated Biphenyls; D014874:Water Pollutants, Chemical; D017665:Hydroxyl Radical