DECOMPOSITION AND STABILIZATION OF RING-C-14-LABELED CATECHOL IN SOIL

Decomposition percentages for ring-14C-labeled catechol and coumaryl alcohol and anisic acid for comparison over a 12 wk incubation period at 1000 ppm in Greenfield sandy loam (pH 7.0) were 20, 50 and 75, respectively. When linked into model humic acid type polymers C losses were 10% for a catechol only polymer and 5-7% for polymers containing 17 additional phenolic units. In Chino loam (pH 5.6) losses of catechol C were about 28% at concentrations ranging from 1-10,000 ppm. In San Jacinto [USA], loam (pH 8.0) losses were 6% for the 1 ppm addition and 14% for concentrations of 10-10,000 ppm. When the soil was initially sterilized and reinoculated from 14 (1 ppm) to 50 (1,000 ppm) % of the C was evolved as CO2 from the acid soil and about 10% was lost from all concentrations in the alkaline soil. After 1 wk only a trace to 12% of the added catechol could be recovered by soil extraction. Under sterile conditions 6 and 90%, respectively, could be extracted from the alkaline and acid soils. After 5 wk a small amount of catechol was still present in the sterile acid and neutral soils and in addition 8 other phenolic compounds could be separated by TLC. About 50% of the catechol present in model humic acid reaction mixtures was recovered in polymer form when phenolase was used as a catalyst. Over 90% was recovered when peroxidase was used. The apparent high stability of catechol in soil probably is caused by a rapid polymerization into phenolic polymers or into existing soil phenolic polymers brought about by the action of existing phenolase enzymes in the soil, by phenolases associated with living organisms and by autoxidation.