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Environmental fate & pathways

Phototransformation in water

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phototransformation in water
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study meets generally accepted scientific principles
Study type:
other: ozonolysis
Principles of method if other than guideline:
Kinetic studies on ozonolysis and the photoinduced ozonolysis of aqueous solutions
GLP compliance:
not specified
Analytical method:
other: flow-cell coupled with FT-IR spectrometer... (see attached file)
Details on sampling:
The decay of ozone in excess dicarboxylic acid solutions was followed using UV spectrophotometry. Decay of ozone concentration was registrated immediately after the interruption of O3/O2 flow through the reaction solution. The dicarboxylic acid concentration decay was monitored using a flow-cell coupled with FT-IR spectrometer at constant ozone concentration.
Light source:
other: 100 W Hg arc lamp
Transformation products:
not measured

The results of both methods (ozone decay versus carboxylic acid decay) agreed within +/- 5%.
The measured ozonolysis rate constant for adipic acid in 0.1 mol/l  aqueous solution is:
                  1.7 +/- 0.1 E-3 l/mol/sec
The photoassisted ozonolysis rate constant is:
                  2.8 +/- 0.2 E-3 l/mol/sec
(The rate constants had been corrected for the ozone-self-decomposition  reactions)
The results obtained indicate that ozonolysis and photoinduced photolysis are not significant removal pathways for adipic  acid.
The authors estimated the dicarboxylic acid aerosols "lifetime" in air, assuming an ozone mixing ratio of 100 ppbv, which is an upper limit for its summertime mid-latitude continental Northern Hemisphere values. 

For adipic acid ozonolysis a half-life of about 13,000 years is estimated.

Executive summary:

A liquid phase kinetic study on the ozonolysis and on the UV-induced ozonolysis of selected dicarboxylic acids, including adipic acid was performed.For adipic acid ozonolysis a half-life of about 13,000 years is estimated, indicating thatozonolysis and photoinduced ozonolysis are not significant removal pathways for adipic acid.

Description of key information

A liquid phase kinetic study on the ozonolysis and on the UV-induced ozonolysis of selected dicarboxylic acids, including adipic acid was performed, resulting in an ozone-dependent life time of about 13,000 years.

Key value for chemical safety assessment

Additional information

The ozonolysis of several dicarboxylic acids including adipic acid was measured in liquid phase to elucidate the fate of these acids in aerosols. In one series of experiments, ozone was produced in an ozone generator, in another series it was produced in the liquid phase by UV irradiation. Adipic acid concentrations ranged from 0.001 to 0.1 mol/l. Kinetics were determined by measuring ozone decay and carboxylic acid decay. The measured ozonolysis rate constant (k) for the adipic acid in 0.1 mol/l aqueous solutions was 1.7x10-3 L mol-1 s-1. The photoassisted ozonolysis rate constant was 2.8x10-3 L mol-1 s-1. The results indicate that ozonolysis and photoassisted ozonolysis are no significant removal pathways for adipic acid. The authors estimated the ozone-dependent life-time of adipic acid in air to be about 13,000 years, assuming an ozone mixing ratio of 100 ppbv, which is an upper limit for its summer time mid-latitude continental northern hemisphere values. For ozonolysis related conversion times are expected (Nepotchatykh, 2002).