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Description of key information

No measured data are available for the photolysis of DTO.

The SRC AOPWIN program was used to obtain values of the rate constant kOH for reaction of each constituent with hydroxyl radicals. The program outputs for the individual constituents have been used to calculate a weighted average value for each block based on the modelled composition of DTO. The methods used to determine the rate constants are described in PFA (2010b). The resulting values for the blocks are shown in Table 4.1.

Table 4.1: Constituent blocks rate constants and half-lives for reaction with hydroxyl radicals

 

Block

Constituents

AOPWIN rate constant [cm3.molec-1.s-1]

Rate constant for degradation in air (d-1)

Half-life in air (d)

1

Low boiling fatty acids

1.68E-11

0.726

0.955

2

C16 saturated - C18.3 unsaturated fatty acids

1.17E-10

5.05

0.137

3

C18 saturated - C24 saturated and unsaturated fatty acids

1.16E-10

5.01

0.138

4

Abietic acid

1.93E-10

8.34

0.083

5

Palustric acid

3.01E-10

13

0.053

6

Pimaric acid

1.3E-10

5.62

0.123

7

Sesquiterpene

2.62E-11

1.13

0.612

8

Abietol

-

-

-

9

Tetracosanol and dehydrated sterol

1.08E-10

4.67

0.149

10

Aldehydes

1.87E-10

8.08

0.086

11

Dimethoxystilbene

2.58E-10

11.1

0.062

12

Sitosterols and analoque

1.33E-10

5.75

0.121

13

Polymeric acids*

-

-

-

14

Polymeric neutrals*

-

-

-

*not assessed because they are high polymeric constituents


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