Abstract
The desorption behavior of dioxin congeners (9 PCDDs, 11 PCDFs and 12 Co-PCBs) from contaminated soils into water has been evaluated by a batch equilibrium experiment. Four soils collected from Japanese incinerators were shaken in 0.01 mol/a CaC12 solution at a soil/solution ratio of 1 : 425 (14.1 g/6l) . Desorption parameters were determined using the concentrations of dioxin congeners in contaminated soils and the desorption supernatant after 14-day agitation. The desorption percentages of dioxin congeners ranged from 0.01 % for OCDF to 1.48 % for 2', 3, 4, 4', 5-PeCB. In the case where the dioxin congeners have the same numbers of chlorine atoms in their molecules, the desorption percentages of Co-PCBs were higher than those of PCDD/Fs. The organic-carbon-normalized desorption coefficients (log Kdesoc) ranged from 6.62 to 8.51. The linear regression analyses of log Kdesoc for PCDDs, PCDFs and non-ortho-substituted Co-PCBs indicate that the desorptive behavior of each dioxin family decreases linearly with the number of coordinated chlorine atoms (R2>0.963) . This tendency was also observed for ortho-substituted Co-PCB congeners, although there is a poor relationship (R2>0.742) in comparison with other dioxin families.
