Cycling of radium and barium in the Black Sea

We report the first data for the concentrations of Ba and Ra-226 in Fivers draining into the Black Sea. For Ba, concentrations are in the range 215-40 5 nM L-1 for Ra-226, concentrations are in the range 0.4-4 Bq m(-3) These a re dissolved concentrations and do not represent additional inputs due to d esorption from fluvial particles, We also report new data for the concentra tions of Ba and Ra-226 in Black Sea surface waters from 1991 to 1995. Earli er studies documented significant reductions in the concentrations of these elements in Black Sea surface waters for the periods 1957-1988 (Ra) and 19 75-1988 (Ba), During the period 1988-89 to 1995, Ba concentrations followed the earlier trend and decreased by an additional 35%. On the other Ra-226 concentrations reversed the trend and increased by about 60% from 1988 to 1 995. hand, The reason for the recent divergence in behavior of these two el ements is unknown., (C) 1999 Elsevier Science Ltd. All rights reserved.