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Diss Factsheets

Environmental fate & pathways

Phototransformation in air

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Administrative data

phototransformation in air
Type of information:
experimental study
Adequacy of study:
supporting study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Relaible source

Data source

Reference Type:
Rate Constants for the Addition of OH to Aromatics (Benzene, p-Chloroaniline, and o-, m-, and p-Dichlorobenzene) and the Unimolecular Decay of the Adduct. Klnetics into a Quasi-Equillbrlum. 1
Wahner A and C Zetzsch
Bibliographic source:
J. Phys. Chem. 87(24): 4945-4951

Materials and methods

Test guideline
according to guideline
other: resonance fluorescence technique
not specified
GLP compliance:
not specified

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Test material form:
other: liquid
Details on test material:
- Purity: 98.7 % (plus 1.3 % isomers) analyzed by GC

Study design

Light source:
Light spectrum: wavelength in nm:
Details on light source:
The resonance fluorescence technique, originally developed by Stuhl and Niki (J. Chem. Phys., 57. 3671 (1972) is used to monitor OH radicals generated by pulsed vacuum-UV photolysis of H2O. The reaction chamber is made of black anodized aluminum. The flash lamp (FL), the microwave lamp (M\VL), and the photomultiplier tube (PM) are attached to the reaction chamber at light angles. Woods horns opposite to each of these components serve to reduce stray light. A capacito (C) (Condenser Products EC 503-25M, 0.05 µF) is discharged at 2-J flash energy in a slow flow of N2 at atmospheric pressure. A CaF2 window (W) cutting off the photolyzing light beam at λ < 125 nm is used to suppress formation of OH (A2Σ+) by the flash light. In the microwave Iamp
(MWL) the emission of OH (A2Σ+ ↔ X2II) is excited by a microwave discharge in a slowly flowing mixture of Ar (1 mbar) and H20 (0.5 mbar). The light is focused into the reaction chamber by means of a quartz-coated concave aluminum mirror (MI) and two quartz lenses (L). The resonance fluorescence emission from OH in the center of the reaction chamber is imaged onto the cathode of the photomultiplier tuhe (PM) (EMI 9789QB) by two planoconvex quartz lenses (L) through an interference filter (IF) (Omega Optical Inc. λmax = 309.5 nm, fwhm = 4 nm, Tmax = 55 %). The arrangement of light baffles minimizes the scattered light and Iimits the light paths (dashed lines) to a detection zone in the center of the reaction cell 1.7 cm in diameter, well separated from the vessel walls.
The signal from the photomultiplier is handled by photon counting using a fast preamplitier / discriminator combination (Ortec Models 9301, 454, 436). Decays of OH are accumulated in a multichannel scaler (Tracor TN 1710). The multichannel scaler is triggered by the light of the flash lamp by means of a photodiode, D. In most experiments the resonance fluorescence decays resulting from 100 consecutive flashes (every 5 s) are accumulated.
The decay curves of the resonance fluorescence signal are evaluated by using a built-in LSI 11/2 microprocessor with FLEXTRAN routines. This kind of on-Iine data processing enables us to handle large sets of data reproducibly in reasonable time. It can manage automatic background subtraction and evaluation of decay rates. Nonexponential decays are fitted to the sum of two exponential decays by the method of least squares. Reactant and water vapor concentrations are calculated from vapor pressure equations and inert gas flows (see below). The decays of OH are plotted in semilogarithmic diagrams showing the fitted functions and Iisting the experimental conditions using a printer plotter (Diablo 1620).
Details on test conditions:
Reactants are introduced to the reaction chamber by using slow flow conditions to avoid accumulation of reaction products and possibly competing consecutive reactions. Reactant and water vapor concentrations are controlled by passing slow flows of inert gas through saturators at atrnospheric pressure and diluting these saturated inert gas flows by further inert gas. The inert gas flows are detennined by calibrated rotameters.
Its temperature can be adjusted from -40 to 100 °C with a precision of ±0.1 °C by using a thermostat or a cryostat. A glass capillary (2-mm i.d.) separates the gas space above the reactant from the diIuting gas line in order to suppress diffusion of the reactant into the main gas flow. The concentration of the reactant
in the main gas flow due to diffusive transport is found to be more than 5 orders of magnitude lower than the vapor pressure of the reactant. When saturating at elevated temperatures condensation of the reactant is avoided by diluting the saturated inert gas flow in the thermostated region of the saturator.

Results and discussion

% Degradation
% Degr.:
Sampling time:
16 d
Degradation rate constant
Reaction with:
OH radicals
Rate constant:
0 cm³ molecule-1 s-1

Any other information on results incl. tables

The rate constant of 1,3-dichlorobenzene was reported as 0.000000000069 cm³/(molecule*sec) at 23 °C.

Applicant's summary and conclusion

Validity criteria fulfilled:
not specified
The photolysis of 1,3-dichlorobenzene were reported as a rate constant of approx. 0.000000000069 cm³/(molecule*sec) at 23 °C and a degradation of 50 % after 16 days.
Executive summary:

The measurement of indirect photolysis of 1,3 -dichlorobenzene showed a rate constant of approx. 0.000000000069 cm³/(molecule*sec) at 23 °C and a degradation of 50 % after 16 days.