INFLUENCE OF SOIL INOCULUM AND REDOX POTENTIAL ON THE DEGRADATION OF SEVERAL PYRIDINE-DERIVATIVES

The potential of four different soils to degrade several pyridine derivatives under aerobic and anaerobic conditions was investigated. There was little difference observed in the metabolic potential of unpolluted surface and unpolluted subsurface soils used as inocula from the same area. Under aerobic conditions, pyridine and hydroxylated pyridines were more rapidly transformed than the methylated pyridine derivatives. Under anaerobic conditions, none of the methylated or hydroxylated pyridine derivatives was completely degraded in 3 months by the unpolluted soil inocula. In using surface and subsurface soils which had been exposed to these compounds for several decades, all pyridine derivatives tested were biotransformed within 2 weeks in the presence of oxygen. However, under anaerobic conditions longer exposure was required. In the presence of sulfate, 3- and 4-picoline and 2- and 4-hydroxypyridine disappeared completely within 3 months when exposed to subsurface soil. On the other hand, the dimethylated and trimethylated pyridine derivatives were only partially transformed during this exposure period. Some of the heterocyclic compounds behaved quite differently when exposed to soil in the presence of either nitrate or sulfate under anaerobic conditions, indicating that the available electron acceptor influences the rate at which certain compounds are transformed.