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Environmental fate & pathways

Phototransformation in air

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Reference
Endpoint:
phototransformation in air
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2003
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Qualifier:
no guideline followed
Principles of method if other than guideline:
No method available
GLP compliance:
not specified
Light source:
not specified

Photo-oxidation half-life in air, based on estimated rate constant for the vapour phase reaction with hydroxyl radicals in air, in the range 65 - 646 hr.

1,2-Dichloropropane does not have any chromophores that absorb wavelengths >290 nm, so direct photolysis will not be a significant fate process. Vapour phase photolysis under simulated sunlight did not occur after prolonged exposure (period not stated). Experimental determination of its rate of reaction with hydroxyl radicals gave a half-life of >23 days. A computer estimate of its half-life due to H-atom abstraction by hydroxyl radical yields a calculated half-life of 7.12 days.

Description of key information

Key value for chemical safety assessment

Half-life in air:
23 d

Additional information

Photo-oxidation half-life in air, based on estimated rate constant for the vapour phase reaction with hydroxyl radicals in air, in the range 65 - 646 hr.

1,2-Dichloropropane does not have any chromophore groups that absorb wavelengths >290 nm, so direct photolysis will not be a significant fate process. Vapour phase photolysis under simulated sunlight did not occur after prolonged exposure (period not stated). Experimental determination of its rate of reaction with hydroxyl radicals gave a half-life of >23 days. A computer estimate of its half-life due to H-atom abstraction by hydroxyl radical yields a calculated half-life of 7.12 days.

Based on a review of the available data for1,2-dichloropropaneand for its structural analogue,1,2-dichloroethane, Kurland (2004) evaluated the potential of1,2-dichloropropaneto contribute to global warming (GWP), to photochemical ozone creation (POCP), and to ozone depletion (ODP), including a review of the available data on hydroxyl radical reaction rate for1,2-dichloropropane.

Photodegradation will account for some removal of 1,2-dichloropropane from the atmosphere. This is based on a calculated hydroxyl radical reaction rate of 5.2 x10-13 cm3molecule-1s-1(Yujing and Mellouki, 2001), which was in excellent agreement with a measured value of 4.6±0.6 x 10-13cm3 molecule-1s-1 (Atkinson, R., 1987; Kwok and Atkinson, 1995). The lifetime (τ=1/(k[OH]) of 1,2-dichloropropane, was estimated by using a global tropospheric 24-hour average OH radical concentration of 1x106molecule cm-3 (Hein et al., 1997) and the measured bimolecular rate constant at room temperature. The tropospheric lifetime of 25 days is in good agreement with another reported value of 27 days (Tauzon et al., 1984) and is relatively short. Kurland (2004) concluded that the products of oxidation of 1,2-dichloropropane will not result in the introduction of chlorine into the stratosphere, and that potential contributions of 1,2-dichloropropane to Global Warning, POCP, or ODP, were negligible