Registration Dossier

Environmental fate & pathways

Phototransformation in air

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

Endpoint:
phototransformation in air
Type of information:
experimental 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 available
Principles of method if other than guideline:
The atmospheric reactivity of vinyl acetate to three main tropospheric oxidants (OH, NO3 and O3) has been experimentally determined and published.
GLP compliance:
no
Estimation method (if used):
PHOTOCHEMICAL REACTION WITH OH RADICALS
- Typical tropospheric concentration of radicals were used to determine tropospheric lifetimes (tau) of VAM: [OH] = 2x10^6 molecules/cm3; [NO3] = 2.5x10^8 molecules/cm; [O3] = 7.4 x 10^11 molecules/cm.
- Degradation rate constant: The rate constant of the OH-induced oxidation was determined by the relative rate technique using propene as a reference compound.
- Temperature for which rate constant was calculated: 293 ± 3 K

Light source:
Xenon lamp
Light spectrum: wavelength in nm:
60
Details on light source:
Experiments performed in an evacuable environmental chamber consisting of a pyrex reactor surrounded by 40 fluorescent tubes (Philips TL05 and TL03) and 16 xeon arc lamps.
Details on test conditions:
Experimental setup:
Contained within the reactor were two multiple reflection optical systems interfaced with a Fourier transform IR spectrometer and a UV-Vis grating spectrometer. The FTIR spectrometer contained a glowbar as the mid-infrared source and was recorded with a resolution of 0.5 cm^-1 and a path length of 156 m.

For the rate determination of NO3 oxidation of VAM, the nitrate radical was monitored using the UV-Vis spectrometer. The detector in this setup was a CCD camera which covers a spectral range of ca. 60 nm and a maximum resolution of 0.15 nm.

OH and NO3 radical generation:
The hydroxyl radicals were generated by photolysis of methyl/isopropyl nitrites (previously prepared via addition of a dilute solution of sulphuric acid to a mix of sodium nitrate and the applicable alcohol. The nitrate radicals were generated from thermal decomposition of dinitrogen pentoxide.

Rate constant determination:
The rate constant of the OH-induced oxidation was determined by using a relative rate technique using propene as a reference substance. The rate constant for the ozonolysis was determined using an absolute rate technique. Both VAM and ozone were both monitored using FTIR spectrometry. The NO3 oxidation rate constant was determined by both relative and absolute rate techniques during the experiment.

Experimental procedure:
All of the experiments were conducted at atmospheric pressure and 293 +/- 3 K. Initial concentrations of reactants (i.e. VAM, propene and O3 (or N2O5 or alkyl nitrite)) were in the PPM range. For the OH oxidation, NO was added to the mixture to assist in minimising nitrate radical and ozone formation. For the ozonolysis experiments, CO was added as an OH scavenger (ca. 2000 ppm). As the CO concentration was high, more than 90% of the OH radicals are scavenged. During the experiments, compounds were monitored for IR every 5 minutes (totalling around 100 co-added interferograms). These were calibrated by flushing known amounts of these compounds.
Duration:
8 h
Temp.:
293 K
Reference substance:
yes
Remarks:
Propene
Preliminary study:
No preliminary test performed
Test performance:
Tropospheric lifetimes of VAM towards OH and NO3 radicals and ozone were estimated. From the mechanistic study the main products of OH, NO3 and O3 oxidation of VAM were detected.
Reaction with:
OH radicals
Rate constant:
0 cm³ molecule-1 s-1
Remarks on result:
other: Relative rate
Reaction with:
other: NO3
Rate constant:
0 cm³ molecule-1 s-1
Remarks on result:
other: Relative rate
Reaction with:
other: NO3
Rate constant:
0 cm³ molecule-1 s-1
Remarks on result:
other: Absolute rate
Reaction with:
ozone
Rate constant:
0 cm³ molecule-1 s-1
Remarks on result:
other: Absolute rate
Transformation products:
yes
Remarks:
Details provided in 'any other information on results incl. tables'.
Results with reference substance:
The rate constant for propene with OH has been taken as being equal to 2.9 x 10^-11 cm3 molecule-1 s-1

Yields of oxidation products of VAM by OH and NO3 radicals and by O3:

Reaction

Product

Yield (%)

VAM + OH

Formic acetic anhydride

75 ± 7

Formaldehyde

96 ± 12

Acetic acid

20 ± 3

Formic acid

Secondary

Carbon budget

90 ± 18

VAM + NO3

Formic acetic anhydride

44 ± 6

Formaldehyde

46 ± 8

Organic nitrates

Not quantified

Carbon budget

44 ± 6

VAM + O3

Formic acetic anhydride

97 ± 8

Formaldehyde

20 ± 6

Formic acid

Not quantified

Carbon budget

78 ± 7

Detailed reaction mechanisms can be located in the publication itself. Tropospheric lifetimes of VAM were estimated as 6 hours, 6 days and 5 days for TauOH, TauNO3 and TauO3, respectively. This demonstrates that the reaction with OH radicals is likely to be the main tropospheric loss process for VAM.

Validity criteria fulfilled:
not applicable
Conclusions:
The tropospheric life times of VAM towards OH/NO3 radicals and ozone were estimated using typical concentrations of three oxidants alongside degradation rate constants and yields. This demonstrates that the reaction with OH radicals is likely to be the main tropospheric loss process for VAM.
Endpoint:
phototransformation in air
Type of information:
calculation (if not (Q)SAR)
Remarks:
Migrated phrase: estimated by calculation
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non-GLP, available in peer-reviewed literature, acceptable with restrictions
Principles of method if other than guideline:
Experimentally determined rate constant. Calculation to estimate atmospheric half-life
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
No data reported
Estimation method (if used):
No information on estimation method reported
Light source:
not specified
Details on light source:
No data reported
Details on test conditions:
No data reported
Preliminary study:
No data
Test performance:
no data
DT50:
14.6 h
Results with reference substance:
no data
Validity criteria fulfilled:
not applicable
Remarks:
estimation
Conclusions:
The atmospheric half-life of 14.6hrs has been estimated for vinyl acetate
Executive summary:

The atmospheric half-life of 14.6 hrs has been estimated for vinyl acetate. This value is used in the EU RAR.

Description of key information

The atmospheric half-life of 14.6 h has been estimated for vinyl acetate and the rate constant as 2.3x10^-11 cm2 molecule^-1S^-1. 

Key value for chemical safety assessment

Half-life in air:
14.6 h
Degradation rate constant with OH radicals:
0 cm³ molecule-1 s-1

Additional information

The study by Atkinson et al. (1987) is considered reliable and this value is used in the EU RAR. The study by Picquet et a. (2010) demonstrated that the reaction with OH radicals is likely to be the main tropospheric loss process for VAM.