ENHANCING THE MINERALIZATION OF [U-C-14]DIBENZO-P-DIOXIN IN 3 DIFFERENT SOILS BY ADDITION OF ORGANIC SUBSTRATE OR INOCULATION WITH WHITE-ROT FUNGI

The potential for aerobic mineralization of [U-C-14]dibenzo-p-dioxin ( DD) was investigated in samples of three different agricultural soils already contaminated with polychlorinated dibenzo-p-dioxins and dibenz ofurans (PCDD/F) by industrial activities. The influence of amendments , i.e. wheat straw and compost, and of soil treatment by inoculation w ith lignolytic fungi, grown on wheat straw substrate, was tested. All the soils tested contained an indigenous DD-mineralizing microflora. T he soil characterized by the highest organic matter content and the hi ghest content of soil microbial biomass displayed the best DD minerali zation of 36.6% within 70 days, compared with the two organic-matter-p oor soils with an endogenous DD mineralization of 19.5% and 23.3% resp ectively. Amendments with compost increased DD mineralization up to 28 % in both soils with low organic matter and microbial biomass content, but did not affect mineralization in the organic-matter-rich soil. Ad dition of wheat straw had no constant influence on DD mineralization i n the soils tested. The best DD mineralization resulted from inoculati on with lignolytic white-rot fungi (Phanerochaete chrysosporium, Pleur otus sp. Florida, Dichomitus squalens) and with an unidentified lignol ytic fungus, which was isolated originally from a long-term PCDD/F-con taminated soil. A mineralization of up to 50% within 70 days was reach ed by this treatment. The influence of inoculated fungi on mineralizat ion differed between the soils investigated.