Direct evidence for destruction of polychlorobiphenyls by OH radicals in the subtropical troposphere

TitleDirect evidence for destruction of polychlorobiphenyls by OH radicals in the subtropical troposphere
Publication TypeJournal Article
Year of Publication2003
AuthorsMandalakis, M, Berresheim H, Stephanou EG
JournalEnvironmental Science and Technology
Volume37
Issue3
Pages542 - 547
Abstract

Although laboratory studies have indicated that OH radicals readily oxidize polychorobiphenyls (PCBs) in the gas-phase, this mechanism has never been positively demonstrated under real atmospheric conditions. By applying elaborated sampling and analytical techniques we achieved for the first time simultaneously a field study of the diurnal atmospheric cycle of OH radical and PCBs in a remote site of eastern Mediterranean. In all cases, the concentration of ΣPCB (sum of 27 congeners) showed a characteristic depletion during daytime, while the concentration of OH radicals was at the maximum levels. By assuming that the depletion of PCBs was caused solely by the destruction from OH radicals, PCB-OH rate constants (KOH) of different PCB congeners were determined from field data by applying the relative rate method. Our field-determined KOH values were notably coherent with those previously measured in laboratory experiments. In all measurement periods, the KOH values consistently decreased in sequence for those compounds showing an increasing degree of chlorination on the biphenyl group. Bytaking into account KOH values and latitude-dependent concentration of OH radicals, it was estimated that, near to tropical and subtropical regions, the atmospheric lifetimes of PCBs 8 and 110 should be substantially low (10 and 20 days, respectively). A significant fraction of PCBs should be destroyed during their residence over tropical/subtropical regions, due to the intensive destruction by OH.

URLhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0346668318&partnerID=40&md5=9bc18dfd9c1799007531e54c0c45343c

User login