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Environmental fate & pathways

Phototransformation in soil

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phototransformation in soil
Type of information:
experimental study
Adequacy of study:
supporting study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Principles of method if other than guideline:
Method: other (measured)
GLP compliance:
Specific details on test material used for the study:
14C-Carboxyl-EDTA 97 % (2.54 mCi/mM)
14C-Acetate-2-EDTA 98 % (1.36 mCi/mM)
Light source:
other: sunlight or UV light (254 nm)
Details on test conditions:
To examine the effect of light on degradation, 14C-acetate-2-EDTA was freshly dissolved in deionized, glass-distilled water, neutralized and stored in an aluminium foil-wrapped flask at 2 °C. This substrate was added to Spinks soil, four of which were wrapped with aluminium foil and incubated in the dark, and the four remaining were incubated in the light. 14CO2 production was measured weekly for 7 weeks.
After four weeks one light- and one dark-incubated flask were extracted with water; and the extract analyzed by 14C-TLC and autoradiography.
In a related experiment portions of an aqueous solution of the Fe(III)-chelate of 14C-carboxyl-EDTA were exposed to 5 hours of sunlight or 5 hours of UV light (254 nm). The resulting photodegradation mixture as well as unexposed chelate were incubated in Spinks soil.
Key result
% Degr.:
Sampling time:
5 h

The sensitivity of Fe(III)-EDTA to sunlight and UV light was apparent since 60.9 and 15.1 %, respectively, of the carboxyl label was mineralized by these treatments. When the remaining EDTA and photolysis products were incubated with soil, initial rapid mineralization occurred, particularly when no organic matter was added. This suggests that certain components of the photolysis mixture are more readily biodegradable than EDTA.
In the case of the sunlight pretreatment, approx. 86.5 % of the carboxyl groups were volatilized by the combined photo- and biocatalysis.

Description of key information

Key value for chemical safety assessment

Additional information

As phototransformation in soil is not a standard information requirement according to Regulation (EC) No. 1907/2006 and there is no indication from the Chemical Safety Assessment according to Annex I on the need to investigate further the fate and behavior of the substance (Annex X requirement), no further testing is considered necessary. Available supporting data for subcategory 1 members indicate that some EDTA species, especially iron complexes, are to a certain degree photolysable.