The distribution coefficient of 60Co in sediments from the Solway Firth, UK

The behaviour of 60Co in sea water sediments typical of the Solway Firth has been investigated. The distribution coefficient, Kd, of 60Co2+ in sediments was determined using the batch sorption method and the Kd variation with aqueous phase composition, sediment type and pH has been studied. Adsorption of 60Co by sediments was found to be highest in de-ionised water and lower in NaCl solution (31 per mille salinity). Adsorption was lowest in natural sea water, where the Kd range was 2.270 to 2.750. Variation of Kd with sediment grain size was observed. It was shown that 60Co adsorption was strongly dependent on pH in de-ionised water, with less variation in NaCl solution. Variance of 60Co Kd values were lowest in sea water in the range pH 5-8 indicating a more conservative behaviour of 60Co than previously recognised. Hence 60Co dispersion will be predominantly govemed by tidal behaviour. (author)