Catechol and chlorocatechols in soil: Degradation and extractability

Catechol and chlorocatechols occur as intermediary metabolites during the degradation of naturally-occurring and synthetic aromatic compounds. Their degradation in soil was assessed under laboratory conditions using 14C-tracing techniques. Degradation of all compounds to CO 2 was rapid during the first 2 weeks (5–10% week −1, but gradually decreased to below 1% week −1 after 3 months. After 6 months. 44% of 4,5-dichlorocatechol, 38% of 4-chloro- and tetrachlorocatechols, and 30% of catechol were degraded to CO 2. In comparison, chlorophenols were degraded at similar rates, and chloroanilines were degraded more slowly. A mixed extradant of citric acid-ascorbic acid-acetone (1:1:2) was found to be most effective in extracting the catcchols from variously-treated soil samples. Recovery of added 14C from freshly fortified soils ranged from 74% for catechol to 98%, for tetrachlorocatechol. After equilibration of 14C-chemical with soil for 5–20 days, the extractability decreased to 38% for catechol, but remained over 86% for tetrachlorocatechol. Sterilization of soil before 14C addition had little effect on 14C extractability. After incubation of treated soil for 5 months, only 20–35% of residual 14C could be extracted. More than half of the nonextractable 14C-residues from incubated soil could be further removed by Na-pyrophosphate extraction.