Chlorine atoms as a potential tropospheric oxidant in the marine boundary layer

In the troposphere, the hydroxyl radical (OH) has been assumed to be the major oxidant for organics and CO. However, a variety of evidence from both laboratory and field studies over the last decade strongly suggests that atomic chlorine may play a key role in marine areas. Potential reactions of sea salt particles, formed in marine areas by wave action, which could generate photolytic precursors to atomic chlorine are reviewed. The results of laboratory studies of NaCl reactions as well as the recent detection of Cl₂ in the marine troposphere indicate that oxidation of organics in marine areas by atomic chlorine may rival or even exceed that of OH under some conditions. Data from recent field studies which are suggestive of chlorine atom chemistry in air masses which have travelled over the Pacific Ocean are discussed. Finally, some future studies are suggested which would help to clarify and evaluate the importance of chlorine atoms in the chemistry of the marine boundary layer.