Coherence of iodine and bromine in the atmosphere of Hawaii, northern Alaska, and Massachusetts

Previously reported analyses of rain, snow, aerosols, and gas from Hawaii, Alaska, and Massachusetts, and new analyses of Antarctic and Alaska snow and ice, are compared. Both I and Br appear to be associated with aerosols of smaller particle sizes and longer residence times than Cl-rich aerosols. In most suites of samples there is a clustering at I/Br ~ 0.1-0.2, and Br/Cl exceeds the sea water ratio (3.4 x 10-3) several-fold. Aerosols collected over open sea water in Hawaii, however, show Br/Cl several-fold lower than in sea water. The latter particles are identified as “sea salt” aerosols whereas the Br-rich aerosols are smaller in size and may be basically different in composition, e.g. ammonium sulfate as discussed by Junge (1963). It is suggested that Br is “distilled” from the sea spray droplets, possibly by photochemical oxidation to Br2, and then “condensed” onto the smaller particles, possibly by participating in the oxidation of SO2 to sulfate. Iodine may engage in similar reactions, and the resulting I and Br-rich particles exhibit a world-wide constancy in I/Br. Precipitation analyses show a similar constancy in I/Br.