PERSISTENCE OF PCDD FS IN A SLUDGE-AMENDED SOIL/

Data are presented on PCDD/F persistence in a sludge-amended soil samp led from a long-term field experiment started in 1968. Over 50% of the PCDD/Fs present in the soil in 1972 were still present in 1990. The c oncentrations of all congeners were observed to decrease gradually and in the same manner over this time, indicating that either physical lo ss of material from the experimental plot had occurred or all congener s had undergone a uniform reduction in extractability over time. Half- lives for the disappearance of PCDD/Fs from the sludge-amended plot po st-1972 were of the order of 20 years; however, the degradation/altera tion of PCDD/Fs in soil may take much longer since these half-lives ar e believed to be principally affected by physical removal.