2,3,5,6-tetrachloropyridine

Phototransformation in air

Administrative data

Endpoint:

phototransformation in air

Type of information:

calculation (if not (Q)SAR)

Remarks:

Migrated phrase: estimated by calculation

Adequacy of study:

supporting study

Study period:

16 January 1991 to 19 February 1992

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Estimate was performed following previously established guidelines and is well documented in a GLP compliant report.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1992

Report date:

1992

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: ECETOC Technical Report No. 3, 1981. An Assessment of Test Methods for Photodegradation of Chemicals in the Environment, p.61

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

2,3,5,6-tetrachloropyridine

EC Number:

219-283-9

EC Name:

2,3,5,6-tetrachloropyridine

Cas Number:

2402-79-1

Molecular formula:

C5HCl4N

IUPAC Name:

2,3,5,6-tetrachloropyridine

Details on test material:

Lot number WP900914-748 of purity 98.6%

Study design

Estimation method (if used):

An estimate of the photodegradation of the substance was performed following guidelines established in ECETOC Technical Report No. 3, 1981. The UV/visible absorbance spectrum of the substance was measured to determine the potential for direct photolysis. A Perkin-Elmer Lambda 7 UV/VIS Spectrophotometer was used to measure absorbance over wavelengths ranging from 200 to 900 nm.

The method described by Zepp and Cline (1977) was employed to calculate the direct photolysis of the substance in both water and air.

A computer model (Atmospheric Oxidation Program, v.1.32 Syracuse Research Corporation, 1981) was employed to evaluate the potential for photooxidation of the substance in the atmosphere. This model assumed attack only by hydroxyl radicals.

Results and discussion

Any other information on results incl. tables

From the calculated rate constants, photolysis half -lives for the substance were determined. The estimated photolysis half-life was a fuinction of both the ф solar and depth of the water column. Photolyis half lives for the substance in water ranged from 18 hours to 101 years (see table below):

 

Results of direct photolysis in water

Ф Solar	Depth of water column (cm)	Kphotolysis(s^-1)	Half-life
0.1	1 5 50 500	1.09 x 10E-5 2.17 x 10E-6 2.17 x 10E-7 2.17 x 10E-8	18 hours 3.7 days 37 days 370 days
0.01	1 5 50 500	1.09 x 10E-6 2.17 x 10E-7 2.17 x 10E-8 2.17 x 10E-9	7.4 days 37 days 370 days 10.1 years
0.001	1 5 50 500	1.09 x 10E-7 2.17 x 10E-8 2.17 x 10E-9 2.17 x 10E-10	74 days 370 days 10.1 years 101 years

 

 A computer model was used to estimate the potential for photooxidation of the substance in the atmosphere via attack by hydroxy radicals. The model calculated photooxidation rates based on the molecular structure of the substance and the ability of the substance to react with hydroxyl radicals. Model simulations with the substance resulted in a second-order photooxidation rate constant of 1.52 x 10 -14 cm3 / molecule-sec. Assuming an average atmospheric hydroxyl radical concentration of 5 x 10E5 ^.OH / cm3, a calculated half-life of 1050 days was determined for photooxidation of the substance in the atmosphere.

Applicant's summary and conclusion

Conclusions:

The expected half-life of the substance for direct photlysis in air is approximately one week. The half-life through direct photolysis of the substance in water is approximately 1 year.

Photooxidation of the substance in the atmosphere by attack of hydroxyl radicals results in an estimated half-life of 3 years.

Executive summary:

The expected half-life of the substance for direct photolysis in air is approximately one week. The half-life through direct photolysis of the substance in water is approximately 1 year. These results are derived via a calculation method described by Zepp and Cline.

Photooxidation of the substance in the atmosphere by attack of hydroxyl radicals results in an estimated half-life of 3 years using a computer model (Atmospheric Oxidation Program, v.1.32 Syracuse Research Corporation, 1981).