Deposition versus Photochemical Removal of PBDEs from Lake Superior Air

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• 作者：Jonathan D. Raff ; Ronald A. Hites
• 刊名：Environmental Science & Technology
• 出版年：2007
• 出版时间：October 1, 2007
• 年：2007
• 卷：41
• 期：19
• 页码：6725 - 6731
• 全文大小：157K
• 年卷期：v.41,no.19(October 1, 2007)
• ISSN：1520-5851

文摘

Analysis of a sediment core collected from Siskiwit Lake,located on a remote island in Lake Superior, providesevidence that polybrominated diphenyl ethers (PBDEs) areremoved effectively from the atmosphere via depositionprocesses during long-range transport. A mass balancemodel based on photochemical rate constants and data fromatmospheric samples was created to understand therelative importance of various photochemical and depositionprocesses in removing PBDEs from the atmosphere.Photolysis rate constants were derived from UV absorptionspectra of 25 PBDEs recorded in isooctane over therange of 280-350 nm at 298 K. Photolysis decays measuredfor BDE-3 and -7 in the gas phase were substantialcompared to a well-defined chemical actinometer, indicatingthat their photolysis quantum yields are significant.Dibenzofuran production was observed when PBDEcongeners containing ortho-bromines were photolyzed inhelium. From estimates of removal rates of PBDEs from thelower troposphere, we find that wet and dry depositionaccount for >95% of the removal of BDE-209, while photolysisaccounts for ~90% of the removal of gas-phase congenerssuch as BDE-47. These results help explain the depositionpatterns of PBDEs found in lake and river sediments andhave important implications concerning the inclusion ofphotolysis as a fate process in multimedia models.