Methyl (R)-2-(4-(3-chloro-5-trifluoromethyl-2-pyridyloxy)phenoxy)propionate

Phototransformation in soil

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in soil

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

according to guideline

Guideline:

EPA Guideline Subdivision N 161-3 (Photodegradation Studies on Soil)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: SETAC-Europe Procedures for Assessing the Environmental Fate and Ecotoxicity of Pesticides, Part 1, Section 2. "Soil Photolysis."

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

14C-radiolabeled in the 3,4 positions of the pyridine ring (Lot # INV1532) or uniformly labeled in the phenyl ring (Lot # INV1585)
Specific activities: 28.1 mCi/mmol (pyridine label) and 18.3 mCi/mmoI (phenyl label)
Radiochemical purity: 97% (pyridine) and 98% (phenyl)

Radiolabelling:

yes

Analytical monitoring:

yes

Analytical method:

high-performance liquid chromatography

Details on soil:

PROPERTIES
- Source: Marcham, UK
- Soil texture: Sandy clay loam soil
- % sand: 70.0
- % silt: 14.0
- % clay: 16.0
- pH: 7.9
- Organic carbon (%): 2.2
- CEC (meq/100 g): 17.3
- Bulk density (g/cm3): 1.19

Light source:

Xenon lamp

Duration:

14.7 d

Temp.:

20 °C

Initial conc. measured:

3.4 other: µg/g

Duration:

14.7 d

Temp.:

20 °C

Initial conc. measured:

3.2 other: µg/g

Reference substance:

yes

Remarks:

Non-radiolabeled test substance

Dark controls:

yes

Remarks on result:

other:

Remarks:

degradation occurs approximately seven times faster in the dark controls (k = 2.96 days-1) compared to the irradiated samples (k = 0.42 days-1), indicating that the test substance was stable to soil photolysis.

Remarks on result:

other: The test substance was stable to soil photolysis

Transformation products:

no

Conclusions:

The test substance was stable to soil photolysis

Executive summary:

This study determined the rate and route of photo degradation of the test substance on one sandy clay loam air-dried soil. 14C-test substance, radiolabeled either uniformly in the phenyl ring or in the 3,4-positions of the pyridine ring was applied to soil at an average application rate of 113 g acid equivalent/ha. Soil hydrolysis of test substance to form DE-535-acid allowed for analysis of DE-535-acid photolysis as well.

Samples were continuously irradiated using a xenon arc lamp to simulate average summer sunlight intensity at 40° N latitude. In addition to time zero, irradiated samples and dark controls were collected at 0.9, 1.7, 4.9, 8.7, and 14.7 days after treatment (DAT). Due to continuous irradiation and lamp intensity, these sampling times were equivalent to 2.6, 4.9, 13.8, 24.5, and 41.3 days of summer sunlight at 40° N latitude.

Both the test substance and DE-535-acid were stable to photolysis.

The material balance for the irradiated samples ranged from 91.2% to 104.7% (average = 97.3 ± 4.3%). The material balance for the dark controls ranged from 90.5% to 106.7% (97.0 ± 4.3%).

Description of key information

Study Type	Study Details	Value	Guideline	Reliability
Phototransformation in soil	Applied on sandy clay loam air-dried soil	Stable to photolysis	EPA 161-3	1