Polyhaloalkene

Phototransformation in air

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in air

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

Qualifier:

no guideline followed

Principles of method if other than guideline:

Long path length FTIR-smog chamber techniques were used to determine k(Cl + CF3CF=CH2), k(OH + CF3CF=CH2), and k(O3 + CF3CF=CH2) in 700 Torr of N2, N2/O2, or air diluent at 296 K.

Specific details on test material used for the study:

Test material was obtained from commercial sources. No specific details on the test material were provided.

Light source:

other: Fluorescent blacklamps

Key result

DT50:

15 d

Remarks on result:

other: Recalculation representing the worst-case, see 'Any other information on results incl. tables'

DT50:

11 d

Remarks on result:

other: Original value in the publication

Key result

Reaction with:

OH radicals

Remarks on result:

other: Rate constant = 1.05E-12 cm3/molecule/s

Transformation products:

not specified

DATA TAKEN FROM PUBLICATION

CF3CF=CH2 did not undergo photolysis, therefore it is not expected to be removed effectively by either wet or dry deposition. As no sufficient Cl atoms are present in the atmosphere, the lifetime of CF3CF=CH2 will not be impacted. Loss mechanisms for CF3CF=CH2 are expected to be the reaction with OH and O3. The value of k(OH + CF3CF=CH2) measured can be used to provide an estimate of the lifetime of CF3CF=CH2 in the atmosphere. This lifetime can be calculated using a global weighted-average OH concentration of 1.0E+06 molecules/cm3, which leads to an estimated lifetime of CF3CF=CH2 of 11 days with respect to reaction with OH radicals.

RECALCULATION

Recalculation is based on the R.16 guidance. By relating kOH to the average OH-radical concentration in the atmosphere, the pseudo-first order rate constant in air is determined:
kdegair = kOH x OHCONCAIR x 24 x 3600 (Equation R.16-12)

In this case KOH = 1.05E-12 cm3/molecule/s

OHCONCair = 5E+05 molecule/cm3

kdeg air = 1.05E-12 cm3/molecule/s x 5E+05 molecule/cm3 x 24 x 3600 = 4.54E-02 per day

The resulting DT50 = LN(2)/kdeg air = 1.53E+01 days

 

Validity criteria fulfilled:

not specified

Conclusions:

Based on the parameters determined in this experiment the atmospheric half-life of the test material was determined to be 15 days. The test material was found to have a negligible global warming potential and no significant contribution to radiative forcing of climate change is expected.

Executive summary:

In this publication, the atmospheric behaviour of CF3CF=CH2 was studied using long path length FTIR-smog chamber techniques. It was observed that CF3CF=CH2 will not undergo photolysis and effective removal by either wet or dry deposition is not expected. Cl atoms in the atmosphere will not be present in sufficient quantities to impact the lifetime of the test material. Loss mechanisms for CF3CF=CH2 are expected to be the reaction with OH and O3. The value of k(OH + CF3CF=CH2) measured can be used to provide an estimate of the lifetime of CF3CF=CH2 in the atmosphere. This lifetime can be calculated using a global weighted-average OH concentration of 1.0E+06 molecules/cm3, which leads to an estimated lifetime of CF3CF=CH2 of 11 days with respect to reaction with OH radicals, as reported in the publication.

Taking a worst-case scenorio into acount and recalculating the degradation constant in air by using a global annual average OH-radical concentration of 5E-5 molecules/cm3 leads to an estimated lifetime of CF3CF=CH2 with respect to reaction with OH radicals of 15 days. It is concluded that CF3CF=CH2 has a negligible global warming potential and will not make any significant contribution to radiative forcing of climate change.

Description of key information

Based on the parameters reported in Nielsen et al. (2007), a DT50 of 15 days in air was determined.

Key value for chemical safety assessment

Half-life in air:

15 d

Degradation rate constant with OH radicals:

0 cm³ molecule-1 s-1

Additional information

In this publication, the atmospheric behaviour of CF3CF=CH2 was studied using long path length FTIR-smog chamber techniques. It was observed that CF3CF=CH2 will not undergo photolysis and effective removal by either wet or dry deposition is not expected. Cl atoms in the atmosphere will not be present in sufficient quantities to impact the lifetime of the test material. Loss mechanisms for CF3CF=CH2 are expected to be the reaction with OH and O3. The value of k(OH + CF3CF=CH2) measured can be used to provide an estimate of the lifetime of CF3CF=CH2 in the atmosphere. This lifetime can be calculated using a global weighted-average OH concentration of 1.0E+06 molecules/cm3, which leads to an estimated lifetime of CF3CF=CH2 of 11 days with respect to reaction with OH radicals, as reported in the publication.

Taking a worst-case scenorio into acount and recalculating the degradation constant in air by using a global annual average OH-radical concentration of 5E-5 molecules/cm3 leads to an estimated lifetime of CF3CF=CH2 with respect to reaction with OH radicals of 15 days. It is concluded that CF3CF=CH2 has a negligible global warming potential and will not make any significant contribution to radiative forcing of climate change.