FY 1995

Chlorofluorocarbon-11 removal in anoxic marine waters

Bullister, J.L., and B.-S. Lee

Geophys. Res. Lett., 22(14), 1893–1896, doi: 10.1029/95GL01517 (1995)

Measurements of the chlorofluorocarbons CCl₃F (F-11) and CCl₂F₂ (F-12) made in the subsurface anoxic zones of the Black Sea and Saanich Inlet, B.C., Canada show a pronounced depletion of dissolved F-11. These zones are strongly reducing and are characterized by the absence of dissolved nitrate (NO₃⁻) and the presence of hydrogen sulfide (H₂S). Models incorporating the atmospheric input histories of these CFCs and the observed distributions are used to estimate residence times for water in these zones and first order in-situ removal rates for F-11. In contrast, measurements in the mid-depth low-oxygen zone of the eastern Pacific (where NO₃⁻ is present and H₂S is below detection limits) do not show evidence of similar rapid F-11 removal.