ATMOSPHERIC TRANSPORT AND TRANSFORMATION OF POLYCHLORINATED DIBENZO-P-DIOXINS AND DIBENZOFURANS

In a study concerning atmospheric transport of polychlorinated dibenzo -p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), 14 air s amples were collected at two locations in Sweden. The highest concentr ations were measured during sampling events with air masses coming wit h westerly to southerly winds, indicating long-range transport of PCDD s and PCDFs. Further evidence for long-range transport was shown by th e correlation between high levels of PCDDs and PCDFs and SO2, NO2, NO3 -, NH3, and soot. The congener profiles were found to vary depending o n wind trajectories, implicating source influences from industrialized and urbanized areas in other parts of Europe. By comparison with know n source profiles, air samples with a background profile were identifi ed during sampling occasions with air masses coming from the north. He re, the congener profiles were dominated by higher chlorinated congene rs. This profile is attributed to transformation processes such as pho tolytic degradation or hydroxyl radical reactions in the gas phase alo ne or in combination with formation mechanisms.