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Environmental fate & pathways

Phototransformation in air

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Administrative data

Endpoint:
phototransformation in air
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: well documented study

Data source

Reference
Reference Type:
publication
Title:
Atmospheric loss processes of dimethyl and diethyl carbonate.
Author:
Katrib Y, Deiber G, Mirabel P, Le Calvé S, George C, Mellouki A, Le Bras G
Year:
2002
Bibliographic source:
J Atmos Chem 43: 151-174 (2002)

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Absolute rate coefficient data are reported for the OH radical reaction with diethyl carbonate in the temperature range 263-372K. OH radicals were produced by pulsed laser photolysis of H2O2 at 248 nm. The concentration of OH radicals was monitored at various reaction times ranging from 10 µs to 10 ms by pulsed laser induced fluorescence. A Nd:YAG pumped frequency doubled dye laser was used to probe the OH radical at 282 nm, the subsequent fluorescence was detected by a photomultiplier. The output pulse from the photomultiplier was integrated for a preset period by a gated charge integrator. Typically, the fluorescence signal resulting from 100 probe laser shots was measured for 10 to 15 different delay times and averaged to generate OH concentration-time profiles over at least three lifetimes. For the kinetic measurements, carbonate/H2O2 mixtures in helium diluent were flowed slowly through the cell, so that each photolysis/probe sequence interrogated a fresh gas mixture and reaction products did not build up in the cell. All experiments were carried out under pseudo-first-order conditions with [carbonate]>> [OH], the initial concentration of OH being lower than 2 × 10E11 molecule/cm³. The concentrations of the carbonates were calculated from their mass flow rates, temperature and pressure in the reaction cell.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): diethyl carbonate
- Substance type: ester
- Physical state: liquid
- Analytical purity: >99% (obtained from BDH), further purified by repeated freeze-pump-thaw cycles and fractional distillation
- Impurities (identity and concentrations): not reported

Study design

Light source:
other: laser
Light spectrum: wavelength in nm:
248
Reference substance:
no

Results and discussion

% Degradation
% Degr.:
50
Sampling time:
3.5 d
Test condition:
25°C; 1 x 10E6 OH/cm³

Applicant's summary and conclusion

Validity criteria fulfilled:
not applicable
Conclusions:
Half-lives in the range between 2.3 and 7 d can be calculated for the photodegradation of diethyl carbonate by reaction with OH radicals in dependance of the OH concentration.
Executive summary:

The OH reaction rate coefficient of diethyl carbonate was determined using laser photolysis - laser induced fluorescence. Based on the kinetic data a rate coefficient k (OH)=2.31 x 10E-12 cm³/molecule x s was obtained. Taking into account the reaction rate coefficient and OH radical concentrations of 5 x 10E5 OH/cm³ (24 h day) and 1.5 x 10E6 OH/cm³ (12 h day) resulted in half-lives of 7 and 2.3 d, respectively. The calculation of the tropospheric half-life using a OH radical concentration of 1 x 10E6 OH/cm³ as cited in this publication yielded a value of 3.5 d.