ABSTRACT

The sea-to-air flux of C₂H₅I (iodoethane) in the Indian Ocean and the Southern Ocean was estimated from the Henry’s law constant (K_H) and the measured partial pressures of C₂H₅I in surface seawater and air. The values of K_H, defined as the ratio of molar concentration (mol l^–1) to partial pressure (atm), for ten volatile organic compounds (VOCs) (CFCl₃ (CFC-11), C₅H₈ (isoprene), C₂H₂F₄ (HFC-134a), CHF₂Cl (HCFC-22), CH₃I, CH₂Br₂, C₂H₅I, CH₂Cl₂, CH₂ClI, and CHBr₃) were measured with an equilibrator and a purge-and-trap system in combination with gas chromatography-mass spectrometry. Ours is the first report of the K_H values for C₂H₅I and C₅H₈ as functions of temperature. The K_H values for the other VOCs were in good agreement with previously reported values. We calculated the sea-to-air flux of C₂H₅I using the newly determined K_H. Large sea-to-air fluxes (average, 0.04 nmol m^–2h^–1) were widespread in the Southern Ocean. We suggest that high biological productivity led to a high rate of C₂H₅I production in the subpolar water, and that the strong winds that frequently blow over the Southern Ocean resulted in the large sea-to-air flux.