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Environmental fate & pathways

Phototransformation in water

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Administrative data

Endpoint:
phototransformation in water
Type of information:
other: EU Risk Assessment
Adequacy of study:
other information
Reliability:
other: EU Risk Assessment
Rationale for reliability incl. deficiencies:
other: No reliability is given as this is a summary entry for the EU RAR.

Data source

Referenceopen allclose all

Reference Type:
secondary source
Title:
Unnamed
Year:
2003
Reference Type:
publication
Title:
Products and quantum yields for photolysis of chloroaromatics in water.
Author:
Dulin D et al.
Year:
1986
Bibliographic source:
Environ. Sci. Technol., 20(1), 72-77.
Reference Type:
publication
Title:
Photochemical dechlorination of 1,2,4-trichlorobenzene.
Author:
Akermark B et al.
Year:
1976
Bibliographic source:
Acta Chem. Scand. B 30, 49-52.
Reference Type:
publication
Title:
Improvement of the photostability of selected substances in aqueous medium.
Author:
Mansour M et al.
Year:
1989
Bibliographic source:
Toxicol. Envir. Chem., 20-21, 139-147.
Reference Type:
publication
Title:
Screening test for degradation of chemicals in water - Degradation test by photoirradiation.
Author:
Kondo M et al.
Year:
1988
Bibliographic source:
Eisei Kagaku, 34, 41-47.
Reference Type:
publication
Title:
Environmental hazard profile of organic chemicals.
Author:
Freitag D et al.
Year:
1985
Bibliographic source:
Chemosphere, 14 (10), 1589-1616.
Reference Type:
publication
Title:
Photoreaktivität organischer Chemikalien in wässrigen Systemen in Gegenwart von Nitraten und Nitriten. [in German]
Author:
Kotzias D et al.
Year:
1982
Bibliographic source:
Naturwissenschaften, 69, 444-445.

Materials and methods

Principles of method if other than guideline:
EU Risk Assessment
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent

Results and discussion

Any other information on results incl. tables

EU Risk Assessment (2003):

Degradation by direct photolysis is not expected to be essential because the maximum absorption value is 286 nm (Bayer spectral data). The half-life for sunlight photolysis in pure surface water at 40° latitude in summer was 450 years (Dulin et al., 1986). The recovery of 1,2,4-TCB from isopropanol solution in Pyrex glass tubing (with a cut-off at 285 nm) irradiated with 300 and 310 nm fluorescent lamps for 30 minutes was 89.4% under anaerobic conditions where O2 was replaced with N2 and 8.1% under aerobic conditions. The products of photodegradation were 1,3- and 1,4-dichlorobenzene (Akermark et al., 1976).

 

In a laboratory study using artificial light (high pressure mercury vapour lamp at wavelengths > 290 nm), the photodegradation was studied at a concentration of 2-5 ppm. 1,2,4-TCB was dissolved in distilled water and filtered river water. The photolytic half-life was estimated to be 16.7 hours in distilled water and 12.2 hours in river water. The photolysis products in river water were 1,4-dichlorophenol and 4-chlorophenol (Mansour et al., 1989).

 

The photolysis was studied by exposing 5 ml 1,2,4-TCB at 4µg/ml at a distance of 30 cm from artificial light (Fluorochemical lamps 20W.2) at 25°C. After 144 hours, 0% was degraded (Kondo et al., 1988).

 

In a test where 1,2,4-TCB was adsorbed on silica gel and irradiated with light at wavelengths > 290 nm for 17 hours, 9.8% of the applied amount was degraded to CO2 (Freitag et al., 1985).

 

In addition to the direct photolysis, the photodegradation may also follow an indirect photolysis by sensitisation by secondary reactions with OH- and O2-radicals. The photolysis was studied in water solutions 600 ml at 4-20 mg/l irradiated for 3 hours. The photoreactivity in solutions in the presence of nitrite was observed to increase the photodegradation rate. The rate constant in pure water was 1.5*10-4s-1resulting in T½ to be 1.2 hours. In water added nitrite, the rate constant k was 3.1*10-4s-1and the resulting T½ 0.4 hours (Kotzias et al., 1982). The study was conducted under artificial conditions but indicates that photolysis may be affected by the contents in water. In the study, salts were used but other organic substances and organic matter may also affect the photodegradation rate.

Applicant's summary and conclusion