Pyrocatechol

Biodegradation in soil

Administrative data

Endpoint:

biodegradation in soil, other

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

The study is not performed according to an internationally recognized guideline, but is well described, giving interesting insights on the catechol biodegradation in soil.

Data source

Reference

Reference Type:

publication

Title:

Biodegradation, stabilization in humus, and incorporation into soil biomass od 2,4-D and chlorocatechol carbons

Author:

Stott D.E., Martin J.P., Focht D.D., Haider K.

Year:

1983

Bibliographic source:

Soil Sci. Soc. Am. J., 47, 66-70.

Materials and methods

Principles of method if other than guideline:

Biodegradation in soil

GLP compliance:

not specified

Test type:

laboratory

Test material

Test material information

Constituent 1

Reference substance name:

Pyrocatechol

EC Number:

204-427-5

EC Name:

Pyrocatechol

Cas Number:

120-80-9

Molecular formula:

C6H6O2

IUPAC Name:

pyrocatechol

Details on test material:

The ring 14C-labeled catechol was synthesized according to Martin et al. (1979). The purity was tested by gas chromatography after direct silylation with N-methyl-N-trimethylsilyl-trifluoracetamide.

Radiolabelling:

yes

Study design

Oxygen conditions:

aerobic

Soil classification:

not specified

Details on soil characteristics:

Four soils were used for the tests:
- Steinbeck loam (pH: 5)
- Fallbrook sandy loam (pH: 5.5)
- Greenfield sandy loam (pH: 7)
- Sorrento loam (pH: 7.4)
The four soils used in this study were air-dried, sieved prior to use.
No more information.

Duration of test (contact time)

Duration:

6 mo

Initial test substance concentration

Initial test substance concentration 1

Initial conc.:

25 ppm

Based on:

other: test mat. / Concentration used in both testing periods (6 months and 1 year)

Initial test substance concentration 2

Initial conc.:

500 ppm

Based on:

other: test mat. / Concentration used in the 1-year testing period only

Parameter followed for biodegradation estimation:

CO2 evolution

Experimental conditions

Temp.:

23 °C

Humidity:

other: 60% of the water capacity

Details on experimental conditions:

TEST PROCEDURE
- Soils were incubated in the presence of the organic substrates in a closed system. The moisture content was 60% of the water capacity, the temperature was 23°C. The flasks were aerated with a constant stream of humidified and CO2-free air. The amounts of total CO2 and 14C02 released were analysed.
- Concentrations of 25 and 500 ppm were tested for 1 year. Only the concentration of 25 ppm was tested for 6 months.
- Each treatment was duplicated.

PARAMETER FOLLOWED
- The biodegradation of ring labelled catechol, free or linked into model humic acid polymers, was followed over 6-month and 1-year incubation periods, and the distribution of the residual activity in biomass, new humus, and 6N HCl hydrolysable substrates was determined.
- The 14C-labelled catechol was incorporated into model humic acid polymers by reacting about 1 g of a phenolic mixture with 14 mg of peroxidase over a 5-d period.
- The 14C activity of the organic substrates, the 14CO2 evolved during incubation, the residual 14C remaining in the soil after incubation or extractions have been described.

Results and discussion

% Degradation

% Degr.:

> 24 - < 50

Parameter:

other: dissipation

Sampling time:

6 mo

Transformation products:

not specified

Evaporation of parent compound:

not specified

Volatile metabolites:

not specified

Residues:

not specified

Details on results:

- 96% of the 14C-labelled catechol in the reactive mixture was recovered in the polymers.
- 37 to 50% of the catechol was lost over 1 year indicating substantial stabilisation of the compound, probably by enzymatic polymerisation reactions. Catechol incorporated into model polymers was still more stable with 6 to 22% of the 14C evolved as CO2.
- After 1 year, about 3 to 8% of the residual 14C activity from catechol was present in the biomass. The amount of residual C in the biomass from the catechol incorporated into the model polymers varied from 0.2 to 2.1%.

- % 14C evolved as 14CO2 in 6 months (catechol at 25 ppm):
in Steinbeck loam: 24
in Fallbrook sandy loam: 50
in Greenfield sandy loam: 28
in Sorrento loam: 26

- % 14C evolved as 14CO2 in 1 year (catechol at 25 ppm):
in Steinbeck loam: 39
in Fallbrook sandy loam: 39
in Greenfield sandy loam: 40
in Sorrento loam: 43

- % 14C evolved as 14CO2 in 1 year (catechol at 500 ppm):
in Steinbeck loam: 50
in Fallbrook sandy loam: 40
in Greenfield sandy loam: 38
in Sorrento loam: 37