~(110)Ag~m Sorption and Desorption on Daya Bay Surface Sediment

In order to comprehend the transportation and movement of radioactive ~(110)Ag~m in water area of Daya Bay,the sorption/desorption of radioactive ~(110)Ag~m on four surface sediment samples collected from Daya Bay are investigated by batch method in sea water at ambient temperature.The experimental conditions are as follows: the concentration of silver ions,ρ((Ag~+))=1.3 ng/mL;the radioactivity concentration of ~(110)Ag~m,c((~(110)Ag~m))=10.0 Bq/mL,pH=8.20 and salinity 32.0 for sea water;ratio of sediment to sea water,n=1.0 mg/mL.The observed percentage of sorption (R_(ad)) of ~(110)Ag~m reached 28.6% by about 40 seconds which is the most shortest time could be obtained in the present sorption experiment,which suggest the initial sorption step is much quickly.Within 1 hour of contact time,R_(ad) is 30.0% averagely for four sediment samples and varied slightly.From 1 hour to 5 days of contact time,R_(ad) increase slowly from 30.0% to 64.4%.From 5 days to the end of experiment(113 d),no remarkable change of R_(ad) is observed,suggesting that the sorption process approach a steady state(after) 5 d of contact time.The distribution ratio(D) at steady state is around 1.86×10~3 mL/g for sorption experiment,which is almost the same as that of 1.90×10~3 mL/g for desorprtion experiment under the same experimental conditions.The effects of ratio of sediment to sea water(n) on D are clearly observed in the present paper.The values of D decrease with increase of n in the range of 4~250 mg/mL,increased with increase of n in the range of 250~1 000 mg/mL,and var small when n is greater than 1 000 mg/mL.