Measurements and Modeling of the Air-Sea Exchange of Mercury

Evasion of elemental mercury (Hg(0)) from the ocean to the atmosphere is considered to be one of the major sources of atmospheric mercury. Most of the ocean's surface waters are saturated with Hg(0) which is produced in situ by photochemical processes (both oxidation and reduction can be photochemically mediated), and biological reduction may also be important in some instances. Until recently, measurements have been limited but analytical developments now allow the continuous collection of atmospheric and surface water Hg(0) concentrations, allowing for a more accurate assessment of the exchange flux. Recent data from various cruises in the North Atlantic Ocean will be presented and compared with data from other oceans. Global mercury models have incorporated Hg(0) evasion and the new modeling approaches better account for the various processes involved that have not been included in previous work. Our recent advances in the modeling of the exchange of Hg(0) will be presented as well as a comparison of the results of various model approaches. The policy implications of the model output will be discussed.