M. Krysell et al., APPARENT REMOVAL OF THE TRANSIENT TRACER CARBON-TETRACHLORIDE FROM ANOXIC SEAWATER, Geophysical research letters, 21(23), 1994, pp. 2511-2514
Two chlorofluorocarbons (CFC-11 and carbon tetrachloride, CCl4) widely
used as tracers for dating water masses, were measured in the Gotland
Basin of the Baltic Sea. At the time of the survey, the bottom water
of the basin had remained stagnant for 15 years and anoxic for about t
he same period of time, and the concentrations of both CFC-11 and CCl4
decrease dramatically with depth below the mixed layer. Furthermore,
the ratio of CFC-11 to CCl4 increases with depth under the mixed layer
along with a steep decrease in oxygen concentration. This is contrary
to what would be expected from the atmospheric histories. The most pl
ausible explanation for this is that there is a mechanism whereby the
CCl4 is removed from the water mass under anoxic and suboxic condition
s.