Benzamide, N-[[4-[(cyclopropylamino)carbonyl]phenyl]sulfonyl]-2-methoxy-

Phototransformation in soil

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in soil

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 Sep 2004 - 24 Mar 2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Qualifier:

according to guideline

Guideline:

other: Commission Directive 95/36/EC amending Council Directive 91/414/EEC, 1995-07-14

Qualifier:

according to guideline

Guideline:

other: SETAC, Procedures for Assessing the Environmental Fate and Ecotoxicity of Pesticides, March 1995

Qualifier:

according to guideline

Guideline:

other: Canada PMRA DACO Number 8.2.3.3.1

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Analytical monitoring:

yes

Analytical method:

high-performance liquid chromatography

Details on soil:

COLLECTION AND STORAGE
- Geographic location: Latitude N 35° 29.303' and Longitude: W 078° 02.421'
City: Pikeville
County: Wayne
State: North Carolina
Country: USA

PROPERTIES
- Soil classification system and year: USDA (Fine-loamy, siliceous, sub active, thermic Aquic Paleudults)
- Soil texture. Sandy loam
- % sand: 76
- % silt: 16
- % clay: 8
- pH: pH in water (1:1, Soil: Water): 6.0 , pH in IN KC1: 5.1, pH in saturated paste: 6.0
- Organic carbon (%): 0.7%
- CEC (meq/100 g): 3.9
- Initial moisture at 1/3 atm (%):
- Water holding capacity: 9.9 for 1/10 bar(g/100g), 6.7 for 1/3 bar(g/100g) and 2.6 for 15 bar (g/100g)
- Bulk density (g/cm3): 1.31
- Initial microbial biomass/microbial population (unit): 92 (methoxybenzoyl label) and 92 (sulfonylbenzamide label)

PREPARATION OF SOIL
- Condition of soil: Sieved
- Air dried / fresh: Air dried

Light source:

Xenon lamp

Light spectrum: wavelength in nm:

>= 290 - <= 750

Relative light intensity:

683

Details on light source:

- Emission wavelength spectrum: 290-750 nm
- Filters used and their purpose: <290 nm cut-off filter- Suprax
- Relative light intensity based on intensity of sunlight: 58% of the light intensity of the artificial light source falls in the range
of 300-800 nm, which is the absorption region of interest of natural sunlight in the environment.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test apparatus or thin layers: 4-cm diameter quartz glass vessels fitted with rubber septa
- Volume of test solution used/treatment: 21 µL (methoxybenzoyl) 33 µL (sulfonylbenzamide)
- Method of application: 25 or 50 µL syringe, applied evenly as drops onto soil surface
- Co-solvent evaporated: yes, solvent allowed to air dry 3-5 minutes in laboratory hood
- Details of traps for volatile, if any: A static closed system was used. At sampling, volatiles were purged through closed system with nitrogen gas into
volatile traps.. Volatiles were purged at each sampling interval (except day 0) through 2 M KOH, ethylene glycol, and 1 M sulfuric acid.
- Indication of test material adsorbing to the walls of test apparatus: No

REPLICATION
- No. of replicates (dark): Duplicate
- No. of replicates (irradiated): Duplicate

MAINTENANCE OF TEST CONDITIONS SPECIFIED UNDER "DURATION"
- Moisture maintenance method: Not necessary, negligible moisture loss (< 0.4%)

Duration:

9 d

% Moisture:

75

Temp.:

20 °C

Initial conc. measured:

1.07 other: mg a.i./kg soil for (methoxybenzoyl)

Duration:

9 d

% Moisture:

75

Temp.:

20 °C

Initial conc. measured:

1.08 other: mg a.i./kg soil for (sulfonylbenzamide)

Reference substance:

yes

Remarks:

three non-radiolabelled substances

Dark controls:

yes

Remarks:

14C-dark controls

DT50:

>= 20.8 - <= 39.6 d

Test condition:

Methoxybenzoyl Label

DT50:

19.1 d

Test condition:

Sulfonylbenzamide Label

Transformation products:

no

The first-order half-life values of AE 0001789 in the methoxybenzoyl dark and irradiated samples were 39.6 days and 20.8 experimental days, respectively. The phototransformation rate constant, obtained by subtraction (kirradiated- kdark), resulted in a photo transformation half-life (DT50) of 43.8 experimental days, and a DT90 of 145.5 experimental days. These are equivalent to a DT50 of 144 and a DT90 of 478 solar days in, Phoenix, Arizona. The first-order half-life value of AE 0001789 in the sulfonylbenzamide irradiated samples was 19.1 experimental days. The half-life value was not calculated for the dark samples due to minimal degradation. Therefore, the calculated photo transformation DT50 was the same as the irradiated samples, 19.1 experimental days, and the DT90 was 63.6 experimental days. These are equivalent to a DT50 of 62.7 and a DT90 of 209 solar days in, Phoenix, Arizona, respectively.

The degradation rates for AE 0001789 in the dark samples are significantly lower than those observed in the aerobic soil metabolism studies, which used,Pikeville, NC, soil. Such difference may be attributed to a) the comparably low microbial biomass (attributed to low soil moisture content) measured for the present batch of soil, and b) an unfavorable ratio of the application solvent (ACN, potentially harmful to soil microbes) needed for solubility reasons and the relatively small amount of soil used in a soil photolysis test system (33 and 21 µL ACN per 3 g soil). However, such reduced soil microbial viability does not impair the objective of testing abiotic surface photolytic degradation processes.

The kinetic results are summarized in the tables below:

Half-lives under laboratory conditions (DT50) in experimental days:

Methoxybenzoyl Label:

Test System	Half-life (days)	First order	R²	DT50 (days)	DT90 (days)
		Regression equation (Ct = Co * e-kt)
Dark	39.6	Ct=101.1*e (-0.0750t)	0.7565	39.6	131.6
Irradiated	20.8	Ct = 98.88 * e (-0.3332t)	0.9507	20.8	69.1
Phototransformation Rate		k = 0.01582		43.8	145.5

Sulfonylbenzamide Label:

Test System	Half-life (days)	First order	R²	DT50 (days)	DT90 (days)
		Regression equation (Ct = Co * e-kt)
Dark	NC*	Ct=95.96*e (-0.00039t)	0.0023	NC	NC
Irradiated	19.1	Ct = 93.81*e (-0.03620t)	0.8168	19.1	63.6
Phototransformation Rate		k = 0.03620		19.1	63.6

**NC = not calculated (no degradation)

Validity criteria fulfilled:

not applicable

Description of key information

 DT50 19.1 – 43.8 days (EPA 161-3) 

Key value for chemical safety assessment

Half-life in soil:

43.8 d

Additional information

In the available GLP study (M-254211-01-1), the photolytic route and rate of degradation of Cyprosulfamide was studied on one sandy loam soil under exposure to simulated sunlight and aerobic conditions in the laboratory for 9 days at 20 °C, 75% of 1/3 bar water holding capacity and at an initial concentration of 1.04 and 1.07 µg a.i./g of soil. The study was performed according to EPA 161-3. The photolytic degradation half-live (DT50) for Cyprosulfamide in soil was estimated to 19.1 – 43.8 days.