CHEMICAL AND BIOLOGICAL 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN EQUIVALENTS IN FLY-ASH FROM COMBUSTION OF BLEACHED KRAFT PULP-MILL SLUDGE

Fly ash was collected from five large-scale or pilot tests in which bu rning of bleached kraft pulp mill sludge was studied. The content of d ioxin-like compounds in this fly ash was estimated both chemically and biologically. Fly ash was analyzed chemically for 17 PCDD and PCDF co ngeners by high-resolution GC-MS, and the data were transformed to Nor dic TCDD equivalents. The biological analyses were based on the induct ion of several enzymes (aryl hydrocarbon hydroxylase [AHH], 7-ethoxyre sorufin 0-deethylase [EROD], aldehyde dehydrogenase-3 [ALDG3]) by the fly ash extracts in a mouse hepatoma cell line, Hepa-1. The inducing p otencies were expressed as biological TCDD equivalents. There was a go od correlation between the Nordic and the biological TCDD equivalents. Differences in the amounts of dioxin-like compounds among the combust ions were attributed mainly to the boiler types and not to fuel charac teristics or combustion parameters.