INITIATION OF [CL-36]HEXACHLOROBENZENE DECHLORINATION IN 3 DIFFERENT SOILS UNDER ARTIFICIALLY INDUCED ANAEROBIC CONDITIONS

The potential for reductive dechlorination of hexachlorobenzene was in vestigated in samples of three different, naturally oxic soils held un der conditions of high oxygen deficiency. The soils were water-saturat ed and the influence on dechlorination of adding different electron do nors, a surfactant and an anaerobic microbial consortium was tested. T he influence of supplied electron donors seems to depend on the organi c matter content of the soils. Dechlorination in the organic-matter-ri ch soil from Maulach was not affected by amendment with organic electr on donors. A release of about 40% chloride within 140 days was observe d for this soil in all biotic-treated assays. By contrast, the organic -matter-poor soil of Eppingen showed no dechlorination in unamended as says. However, when it was supplemented with organic electron donors d echlorination of 2%-37% occurred within 140 days, depending on the typ e of electron donor. Complex substrate (wheat strawdust), from which c arbon is slowly liberated, gave the best results. These two soils had an indigenous dechlorinating anaerobic microflora? whereas the third s oil (Rastatt) required inoculation with an anaerobic consortium for de chlorination. The addition of electron donors alone did not cause dech lorination in this sandy soil. The addition of a surfactant (Tween 80) to increase the bioavailability of hexachlorobenzene did nor enhance dechlorination. This process was not inhibited by inherent alternative electron accepters in soil (NO3-, SO42-, Fe3+). The dechlorination di d not require methanogenic conditions.