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Biodegradation in soil

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Endpoint:
biodegradation in soil
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
22 Jun 1998 - 25 May 1999
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: EU Council Directive 91/414/EEC as amended by Commission Directive 95/36/EC of July 1995, Section 7.1.1.1
GLP compliance:
yes
Test type:
laboratory
Radiolabelling:
yes
Oxygen conditions:
aerobic
Soil classification:
USDA (US Department of Agriculture)
Soil no.:
#1
Soil type:
loam
% Clay:
23.15
% Silt:
40.76
% Sand:
36.09
% Org. C:
2
pH:
7.8
CEC:
12.2 meq/100 g soil d.w.
Details on soil characteristics:
SOIL COLLECTION AND STORAGE
- Geographic location: The soil was collected fresh from Shelley field at Boarded Barns Farm, Ongar, Essex, UK, Ordinance Survey TL 557047, on 27 Feb 1998
- Storage conditions and length: at +4 °C until 28 Apr 1998, after sieving at 20 °C until 09 Jun 1998.
- Soil preparation (e.g., 2 mm sieved; air dried etc.): sieved to 2 mm
Soil No.:
#1
Duration:
266 d
Soil No.:
#1
Initial conc.:
63.865 other: µg/100 g soil dry weight
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
radiochem. meas.
Soil No.:
#1
Temp.:
20 ± 2 °C
Humidity:
45%
Microbial biomass:
244 µg C/g
Details on experimental conditions:
2. EXPERIMENTAL DESIGN
- Soil preincubation conditions (duration, temperature if applicable): Soil was sieved to 2 mm and distilled water (13.38 g/100 g soil dry weight) was added to obtain a moisture content of 45% maximum water holding capacity.
- Soil condition: fresh
- Soil (g/replicate): 100 g oven dried equivalent/replicate
- No. of replication treatments: 2
- Test apparatus (Type/material/volume): Erlenmeyer flasks, 7.5 cm diameter
- Identity and concentration of co-solvent: 3 mL acetonitrile were added to the radioactive test material prior to dispensing

Test material application
- Volume of test solution used/treatment: 120 µL
- Application method: Test material was applied on surface
- Is the co-solvent evaporated: yes

Experimental conditions (in addition to defined fields)
- Moisture maintenance method: Small amounts of distilled water were added to the soil surface once a month during the study and moistened CO2 free air was used for aeration.
- Continuous darkness: Yes

3. OXYGEN CONDITIONS
- Methods used to create the aerobic conditions: aeration at 23.5 mL/min

5. SAMPLING DETAILS
- Sampling intervals: 7, 14, 28, 60 (2 months), 91 (3 months), 120 (4 months), 177 (6 months) and 266 days (9 months) after treatment.
- Sampling method for soil samples: Soil samples from the sample flasks was transferred to plastic bottles for extraction with acetonitrile
- Method of collection of CO2 and volatile organic compounds: The associated volatile traps were taken at the same time, their volume recorded and an aliquot taken for LSC
- Sample storage before analysis: All soil samples were extracted on the day of sampling and concentrated within 5 days and chromatographically profiled within 28 days.
Soil No.:
#1
% Recovery:
100.49
Remarks on result:
other: Overall mean; range of 94 - 104% for individual samples
Soil No.:
#1
% Degr.:
84.5
Parameter:
test mat. analysis
Sampling time:
266 d
Soil No.:
#1
DT50:
41.2 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: r2 = -0.99681; calculated using the KIM modelling program, based on the mean of HPLC and TLC data
Soil No.:
#1
DT50:
33.24 d
Type:
other: square root first order decay
Remarks on result:
other: r2 = 0.9835; calculated using the Timme-Frehse program, based on the mean of HPLC and TLC data
Soil No.:
#1
DT50:
101.6 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: r2 = 0.9132; calculated using Excel, based on the mean of HPLC and TLC data
Soil No.:
#1
DT50:
87.5 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other: r2 = -0.99681; calculated using the KIM modelling
Soil No.:
#1
DT50:
70.6 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other: r2 = 0.9835; calculated using the Timme-Frehse program, based on the mean of HPLC and TLC data
Soil No.:
#1
DT50:
215.7 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other: r2 = 0.9132; calculated using Excel, based on the mean of HPLC and TLC data
Transformation products:
yes
No.:
#1
No.:
#2
No.:
#3
No.:
#4
Details on transformation products:
- Description of biotransformation pathway: Ethiprole is concurrently oxidised to RPA 097973 and hydrolysed to RAP 112916. The former metabolite is hydrolysed and the latter oxidised to RPA 112917. A minor amount is reduced to RPA 107566.
Evaporation of parent compound:
no
Volatile metabolites:
no
Residues:
yes
Details on results:
TEST CONDITIONS
- Aerobicity, moisture, temperature and other experimental conditions maintained throughout the study: Yes

MAJOR TRANSFORMATION PRODUCTS
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: 2.25% RPA 112916 and 11.09% RPA 097973 after 7 days, 1.69% RPA 112917 after 60 days
- Range of maximum concentrations in % of the applied amount at end of study period: 24.7% RPA 112916, 37.4% RPA097973 and 11& RPA 112917

MINOR TRANSFORMATION PRODUCTS
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: 2.12% RPA 107566 after 7 days
- Range of maximum concentrations in % of the applied amount at end of study period: 0.12% RPA 107566

TOTAL UNIDENTIFIED RADIOACTIVITY (RANGE) OF APPLIED AMOUNT: < 3.5%

EXTRACTABLE RESIDUES
- % of applied amount at day 0: mean 100.18%
- % of applied amount at end of study period: mean 91.06%

NON-EXTRACTABLE RESIDUES
- % of applied amount at day 0: 0.58%
- % of applied amount at end of study period: 10.87%

VOLATILIZATION
- % of the applied radioactivity present as volatile organics at end of study: 0.10%
Endpoint:
biodegradation in soil
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
03 Mar 1998 - 17 Sep 1999
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: US EPA Guidelines, Subdivision N, Section 162-1
GLP compliance:
yes
Radiolabelling:
yes
Oxygen conditions:
aerobic
Soil classification:
USDA (US Department of Agriculture)
Soil no.:
#1
Soil type:
sandy loam
% Clay:
6
% Silt:
33
% Sand:
61
% Org. C:
0.006
pH:
7.8
CEC:
6.2 meq/100 g soil d.w.
Bulk density (g/cm³):
1.38
Soil no.:
#2
Soil type:
silt loam
% Clay:
17
% Silt:
56
% Sand:
27
% Org. C:
0.026
pH:
6.1
CEC:
17.9 meq/100 g soil d.w.
Bulk density (g/cm³):
1.04
Details on soil characteristics:
SOIL COLLECTION AND STORAGE
- Geographic location: Soil #1 sandy loam: Madera CA, USA; soil #2 silt loam: Columbia MO, USA
- Collection date: Soil #1 sandy loam: 6 Jan 1998; soil #2 silt loam: 3 Feb 1998
- Soil preparation: The soil samples were 2 mm sieved.

PROPERTIES OF THE SOILS (in addition to defined fields)
- Moisture at 1/3 bar (%): Soil #1: 9.8, soil #2: 26.4
Soil No.:
#1
Duration:
365 d
Soil No.:
#2
Duration:
365 d
Soil No.:
#1
Initial conc.:
0.6 mg/kg soil d.w.
Based on:
act. ingr.
Soil No.:
#2
Initial conc.:
0.6 mg/kg soil d.w.
Based on:
act. ingr.
Parameter followed for biodegradation estimation:
radiochem. meas.
test mat. analysis
Soil No.:
#1
Temp.:
25 ± 1 °C
Microbial biomass:
Initial 61.5, final 34.2 µg C/g soil
Soil No.:
#2
Temp.:
25 ± 1 °C
Microbial biomass:
Initial 255.8 and 208.3 µg C/g soil
Details on experimental conditions:
1. EXPERIMENTAL DESIGN
- Soil condition: fresh, at 75 ± 5% of 1/3 bar water holding capacity
- Soil (g/replicate): 54 g of sandy loam (#1) and 63 g of silt loam (#2), equivalent to approx. 50 g of dry soil
- No. of replication treatments: 2
- No. of untreated controls: 4
- Test apparatus: 125 mL straight-sided glass containers
- Details of traps for CO2 and organic volatile: 15 mL ethylene glycol served as organic volatile trap, 15 mL of 2-ethoxyethanol:mono-ethanolamine (2:1 v/v) served as Co2 trap.

Test material application
- Volume of test solution used/treatment: Each container received 108 µL of the ethiprole dose solution.
- Application method: on top of the soil

Experimental conditions (in addition to defined fields)
- Moisture maintenance method: The weight of the soil was periodically checked and water was added when needed.
- Continuous darkness: Yes

2. OXYGEN CONDITIONS
- Methods used to create the aerobic conditions: aeration
- Evidence that aerobic conditions were maintained during the experiment: The aerobicity of the samples was monitored at all sampling times by measuring the redox potential of the soil which ranged between 214 and 452 mV for both soils.

3. SAMPLING DETAILS
- Sampling intervals: 0, 7, 14 days, 1, 2, 3, 6, 9, 12 months
- Sampling method for soil samples: Air flow to the sample containers was discontinued prior to removal of the soil samples from the environmental chamber. Soil samples were transferred to 250 mL Nalgene bottles for extraction.
- Method of collection of CO2 and volatile organic compounds: The volume of trapping solutions for each sample pair was recorded and aliquots were taken for liquid scintillation analysis. The trapping solutions were replaced in traps for all the remaining samples after each sampling interval.
- Sample storage before analysis: All samples were extracted and analysed within two weeks of sampling.
Soil No.:
#1
Remarks on result:
other: Range: 93 - 99%
Soil No.:
#2
Remarks on result:
other: Range: 93 - 101%
Soil No.:
#1
% Degr.:
> 50
Parameter:
test mat. analysis
Sampling time:
30 d
Soil No.:
#1
% Degr.:
98.4
Parameter:
test mat. analysis
Sampling time:
180 d
Soil No.:
#2
% Degr.:
> 50
Parameter:
test mat. analysis
Sampling time:
60 d
Soil No.:
#2
% Degr.:
98.3
Parameter:
test mat. analysis
Sampling time:
365 d
Soil No.:
#1
DT50:
30 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: DT90 = 100 d
Soil No.:
#2
DT50:
71 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: DT90 = 235 d
Soil No.:
#1
DT50:
99.9 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Soil No.:
#2
DT50:
236.4 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Transformation products:
yes
No.:
#1
No.:
#2
No.:
#3
No.:
#4
No.:
#5
Details on transformation products:
Formation and decline of each transformation product during test:
- RPA097973 (sulfone) was found to be the most significant metabolite in both soils. This metabolite gradually increased from about 3% and 5% at day 7 to a maximum of 43% and 60% and then gradually decreased to 35 - 42% after 12 months.
- RPA112917 (sulfone amide) was the second significant metabolite. It increased from 3 - 7% at day 90 to 27 - 33% at day 365.
- RPA112916 (amide) was detected after 30 days. In silt loam soil it accounted for 5% at day 30 and gradually increased to 19% at day 365. In sandy loam soil, RPA112916 was less significant, only accounted for 3 - 6% between day 30 and day 270. It was not detected in sandy loam soil at day 365.
- RPA107566 (sulfide) reached a maximum of about 10% at day 30 in sandy loam soil. It was not detected in sandy loam soil on day 90 and beyond. It was only detected in trace amounts in silt loam soil at day 30.
- RPA104615 (sulfonic acid) was detected in both soils after 6 months of incubation. It increased from about 2% at day 180 to 4 - 7% at day 365.

Description of biotransformation pathway:
- Ethiprole undergoes oxidation to RPA 097973 (sulfone) which is converted to RPA 104615 (sulfonic acid) or whose cyano group is hydrolysed yielding RPA 112917 (sulfone amide). Alternatively, the cyano group in ethiprole can be hydrolysed to RPA 112916 (amide) and the amide can subsequently be oxidised to RPA 112917 (sulfone amide).
Evaporation of parent compound:
no
Volatile metabolites:
no
Residues:
yes
Details on results:
TEST CONDITIONS
- Aerobicity, moisture, temperature and other experimental conditions maintained throughout the study: Yes

TRANSFORMATION PRODUCTS
RPA097973 (sulfone) was the major metabolite and accounted for up to 60% (0.36 ppm) of the applied dose in the sandy loam soil but did not accumulate in the soils. RPA112917 (sulfone amide) gradually increased to a maximum of about 30% (0.18 ppm) of applied dose at day 365. RPA112916 (amide) was more predominant in silt loam soil (maximum 19% or 0.11 ppm) at day 365. RPA107566 (sulfide) was more predominant in sandy loam (maximum 10% or 0.06 ppm) at day 30. The presence of RPA107566, however, was not detected in either soil beyond 30 days. RPA 104615 (sulfonic acid) accounted for 2 - 7% (0.01 - 0.04 ppm) of the dose. In both soils, the unknown metabolites accounted for a total of less than 9% (0.043 ppm) of the applied dose.

TOTAL UNIDENTIFIED RADIOACTIVITY (RANGE) OF APPLIED AMOUNT: less than 2 to 6% in both soils

EXTRACTABLE RESIDUES
- % of applied amount at day 0: 99% - 100%
- % of applied amount at end of study period: 93%

NON-EXTRACTABLE RESIDUES
- % of applied amount at all sampling intervals: < 10% (silt loam), < 8% sandy loam

VOLATILIZATION
- % of the applied radioactivity present as volatile organics at end of study: ≤ 0.02% in the sandy loam soil; no volatility was detected in the silt loam soil.

Degradation rate constant K sandy loam (soil #1): - 0.0098/day, r2 = 0.947

Degradation rate constant K silt loam (soil #2): - 0.023/day, r2 = 0.979

Proposed metabolic pathway of ethiprole: Initially, it appears that ethiprole undergoes oxidation to RPA097973 (sulfone). RPA097973 is then further converted to RPA 104615 (sulfonic acid). The cyano group contained in ethiprole or RPA097973 can be hydrolyzed to RPA112916 (amide) or RPA112917, respectively. RPA112917 can also arise from oxidation of RPA 112916. Reduction of the sulfiny] group in ethiprole affording RPA 107566 (sulfide) plays only a minor role in the degradation of the parent molecule. Since only trace amounts of volatiles were detected, the phenyl ring opening and further degradation to CO2 does not play a significant degradative role under the conditions of this study.

Endpoint:
biodegradation in soil: simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
18 Aug 1998 - 20 Jul 1999
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: EU Council Directive 91/414/EEC as amended by Commission Directive 95/36/EC of July 1995, Section 7.1.1.2
GLP compliance:
yes
Test type:
laboratory
Radiolabelling:
yes
Oxygen conditions:
aerobic
Soil classification:
USDA (US Department of Agriculture)
Soil no.:
#1
Soil type:
clay loam
% Clay:
31.84
% Silt:
44.62
% Sand:
23.55
% Org. C:
3.9
pH:
7.6
CEC:
47 meq/100 g soil d.w.
Soil no.:
#2
Soil type:
sandy loam
% Clay:
10.69
% Silt:
31.13
% Sand:
58.18
% Org. C:
3.1
pH:
6.2
CEC:
7.1 meq/100 g soil d.w.
Soil no.:
#3
Soil type:
loam
% Clay:
25.2
% Silt:
42.32
% Sand:
32.47
% Org. C:
2.5
pH:
7.2
CEC:
8.7 meq/100 g soil d.w.
Soil no.:
#4
Soil type:
loam
% Clay:
25.12
% Silt:
41.5
% Sand:
33.38
% Org. C:
1.9
pH:
7
CEC:
7.8 meq/100 g soil d.w.
Soil no.:
#5
Soil type:
sand
% Clay:
6.04
% Silt:
3.71
% Sand:
90.24
% Org. C:
1.6
pH:
5.8
CEC:
3.1 meq/100 g soil d.w.
Details on soil characteristics:
SOIL COLLECTION AND STORAGE
- Geographic location: #1 Flint Hall, Royston, Herts, UK; #2 Aldham's Farm, Manningtree, Essex, UK; #3 and #4 Boarded Barns Farm, Ongar, Essex, UK; #5 Roos Hall, Beccles, Suffolk, UK
- Collection procedures: according to ISO/DIS-10381-6 Part 6: Guidance on the collection, handling and storage of soil for the assessment of aerobic microbial processes in the laboratory
- Soil preparation: The soils were 2 mm sieved before use
Soil No.:
#1
Duration:
180 d
Soil No.:
#2
Duration:
180 d
Soil No.:
#3
Duration:
180 d
Soil No.:
#4
Duration:
180 d
Soil No.:
#5
Duration:
180 d
Soil No.:
#1
Initial conc.:
0.641 g/ha d.w.
Based on:
test mat.
Soil No.:
#2
Initial conc.:
0.641 g/ha d.w.
Based on:
test mat.
Soil No.:
#3
Initial conc.:
0.641 g/ha d.w.
Based on:
test mat.
Soil No.:
#4
Initial conc.:
0.641 g/ha d.w.
Based on:
test mat.
Soil No.:
#5
Initial conc.:
0.677 g/ha d.w.
Based on:
test mat.
Parameter followed for biodegradation estimation:
radiochem. meas.
test mat. analysis
Soil No.:
#1
Temp.:
20 °C
Humidity:
42.4%
Microbial biomass:
initial: 1120 µg C/g soil, final: 1056 µg C/g soil
Soil No.:
#2
Temp.:
20 °C
Humidity:
28.5%
Microbial biomass:
initial: 318 µg C/g soil, final: 413 µg C/g soil
Soil No.:
#3
Temp.:
10 °C
Humidity:
29.6%
Microbial biomass:
initial: 204 µg C/g soil, final: 211 µg C/g soil
Soil No.:
#4
Temp.:
20°C
Humidity:
26.8%
Microbial biomass:
initial: 222 µg C/g soil, final: 411 µg C/g soil
Soil No.:
#5
Temp.:
20 °C
Humidity:
17.6%
Microbial biomass:
initial: 133 µg C/g soil, final: 210 µg C/g soil
Details on experimental conditions:
1. EXPERIMENTAL DESIGN
- Soil condition: 45% of the maximum water holding capacity
- Soil (g/replicate): 100 g dry equivalent
- No. of flasks per soil sample: A total of 25 flasks were prepared for each soil type. Of these 3 flasks were designated for biomass determination at the end of the study and were not treated and four were left as untreated spares which could be treated at a later date should this prove necessary.
- Test apparatus (Type/material/volume): 250 mL straight-sided Erlenmeyer glass flasks (7.5 cm diameter)
- Details of traps for CO2 and organic volatile: The moistened carbon dioxide free air was passed at a constant rate, before passing through a trap of ethylene glycol and two traps containing 2 M aqueous potassium hydroxide to trap any liberated volatile material.

Test material application
- Volume of test solution used/treatment: 250 µL of an acetonitrile solution of [14C]-ethiprole
- Application method: The test material was applied on the soil surface.
- Is the co-solvent evaporated: yes

Experimental conditions (in addition to defined fields)
- Moisture maintenance method: aeration with moist air (23.5 mL/min), addition of small amounts of distilled water onto the soil surface
- Continuous darkness: Yes

2. OXYGEN CONDITIONS (delete elements as appropriate)
- Methods used to create the aerobic conditions: aeration with moist air

3. SAMPLING DETAILS
- Sampling intervals: For time zero sampling, two flasks of each soil type were treated and processed immediately after treatment. Duplicate sample flasks of each soil type were removed from the system at 7, 14, 30,61,90, 120 and 180 days after treatment. The associated volatile traps were taken at the same time.
- Sampling method for soil samples: Soil samples were directly transferred to plastic bottles for extraction.
- Method of collection of CO2 and volatile organic compounds: Sub-samples of 20mL were transferred to storage vials and from these aliquots
were taken for radioassay by LSC.
- Sample storage before analysis: There was no storage of unprocessed samples.
Soil No.:
#1
% Recovery:
100.35
Soil No.:
#2
% Recovery:
101.8
Soil No.:
#3
% Recovery:
99.9
Soil No.:
#4
% Recovery:
100.27
Soil No.:
#5
% Recovery:
99.19
% Degr.:
> 89 - < 100
Parameter:
other: Radiochem meas. and Test mat. analysis
Sampling time:
180 d
Soil No.:
#1
DT50:
10.53 d
Type:
other: KIM Power Rate
Remarks on result:
other: r2 = 0.99944; DT90 = 42.76
Soil No.:
#2
DT50:
20.13 d
Type:
other: KIM Power Rate
Remarks on result:
other: r2 = 0.99962; DT90 = 170.74
Soil No.:
#3
DT50:
17.82 d
Type:
other: KIM Power Rate
Remarks on result:
other: r2 = 0.99908; DT90 = 156.47
Soil No.:
#4
DT50:
18.8 d
Type:
other: KIM Power Rate
Remarks on result:
other: r2 = 0.99796; DT90 = 298.52
Soil No.:
#5
DT50:
50.84 d
Type:
other: KIM Power Rate
Remarks on result:
other: r2 = 0.99221; DT90 = 217.32
Soil No.:
#1
DT50:
22.4 d
Type:
other: KIM Power Rate
Temp.:
12 °C
Soil No.:
#2
DT50:
42.7 d
Type:
other: KIM Power Rate
Temp.:
12 °C
Soil No.:
#3
DT50:
14.7 d
Type:
other: KIM Power Rate
Temp.:
12 °C
Soil No.:
#4
DT50:
39.9 d
Type:
other: KIM Power Rate
Temp.:
12 °C
Soil No.:
#5
DT50:
107.9 d
Type:
other: KIM Power Rate
Temp.:
12 °C
Transformation products:
yes
No.:
#1
No.:
#2
No.:
#3
No.:
#4
No.:
#5
Details on transformation products:
- Formation and decline of each transformation product during test:
- Soil 98/04 (silty clay loam soil, incubated at 20°C): The degradation of parent ethiprole was particularly rapid in this soil and at 180 days it was no longer detectable. After seven days three metabolites had appeared: RPA 112196, RPA 097973 and RPA 107566. Of these RPA 097973 was present in the highest concentrations, accounting for 26 % of applied radioactivity (A.R.) at seven days and reaching a maximum of 55 % A.R. at 30 days before declining to 30 % at 180 days. Neither of the other two compounds reached a level of 10 % A.R. at any time during the study, RPA 107566 attaining a maximum of 8 % A.R. at 14 days but being undetected beyond 61 days whilst RPA 112916 reached a maximum of 8 % at 61 days and accounted for 5 % at 180 days. A fourth metabolite (RPA 112917) was first detected at 30 days (4 % A.R.) and rose steadily to account for 18 % at 180 days. The fifth metabolite detected (RPA 104615) appeared at 61 days and also increased steadily in concentration until it represented 22% A.R. at 180 days.
- The same compounds that were detected in the extracts of the silty clay loam soil were also found in the extracts of the other soils with the exception that RPA 104615 was not detected in any of the extracts from soil 98/26 (clay loam soil incubated at 20°C).
- Other soils incubated at 20 °C: In the extracts from the other soils incubated at 20 °C the levels of parent material (ethiprole) dropped steadily with 11% to 13% A.R. remaining at 180 days. RPA 097973 was the principal metabolite (32% to 39% A.R. at 180 days) followed by either RPA 112916 (two soils, 15% A.R.) or RPA 106415 (one soil, 15% A.R.) with smaller amounts of RPA 112917 (9% to 14% A.R.). RPA 104615 did not reach 10% A.R. in two of the soils (reaching a maximum of 6% A.R. in one and not being detected in the other). RPA 107566 did not reach a mean value of 10% A.R. in any soil at any time although it did go over 10% A.R. in an individual sample (10.35%) giving a mean of 9.97% A.R. at its maximum (soil 98/26, clay loam). RPA 112916 did not reach 10% A.R, in soil 98/28 (sandy soil) the same result as was seen with the silty clay loam soil, although it reached 15% or 16% A.R. in the other two soils.
- Soil sample 98/24 incubated at 10 °C: The degradation and metabolic pattern in the extracts of the soil incubated at 10 °C was fairly similar to that seen in the extracts from the soils incubated at 20 °C. Ethiprole levels had decreased to 11% A.R. at 180 days at which time RPA 097973 was the most abundant metabolite (55% AR.). There were low levels of RPA 106415, RPA 112916 and RPA 112917 (2% to 7% A.R. at 180 days) which had not reached 10% A.R. at any time. RPA 107566 accounted for only 4% of A.R. at 180 days but had reached a maximum of 13% at 14 days.
Evaporation of parent compound:
no
Volatile metabolites:
no
Residues:
yes
Details on results:
TEST CONDITIONS
- Aerobicity, moisture, temperature and other experimental conditions maintained throughout the study: Yes

MAJOR TRANSFORMATION PRODUCTS
RPA 097973 (oxidation product) was the most abundant metabolite in all soils. It reached 55% of the applied amount on the 30th day of incubation and 30% on the 180th day in the soil 98/04 (silty clay loam). In the other soils incubated at 20 °C, RPA 097973 reached 32 to 39% at 180 days. In the soil 98/24 incubated at 10 °C RPA 097973 attained 55%.

MINOR TRANSFORMATION PRODUCTS
Details are given for soil 98/04, but the degradation and metabolic pattern in the extracts of the other soils were similar.
- RPA 112916 reached a maximum of 8% at 61 days and accounted for 5% at 180 days.
- RPA 107566 reached a maximum of 8% at 14 days and was not detectable beyond 61 days.
- RPA 112917 attained 4% at 30 days and rose steadily to 18% at 180 days.
- RPA 104615 appeared at 61 days and increased steadily to 22% at 180 days (not detected in the extracts from soil 98/26).

EXTRACTABLE RESIDUES
- % of applied amount at day 0: 92 - 97
- % of applied amount at end of study period: 75 - 84

NON-EXTRACTABLE RESIDUES
- % of applied amount at end of study period: 17 - 23

VOLATILIZATION
- % of the applied radioactivity present as volatile organics at end of study: < 0.1

Table 1: DT50 values (in days) for Ethiprole, calculated based on additional kinetic models

Kinetic Model

Soil #1

(20 °C)

Soil #2

(20 °C)

Soil #3

(10 °C)

Soil #4

(20 °C)

Soil #5

(20 °C)

1stOrder

19.39

56.76

56.88

63.59

62.92

Fit criterion

0.8719

0.8250

0.7832

0.8137

0.9512

Timme-Frehse (Best Fit)

19.39

14.71

14.41

18.63

43.96

Fit criterion

0.8719

0.9783

0.9773

0.9936

0.9617

Table 2: DT90 values (in days) for Ethiprole,calculated based on additional kinetic models

Kinetic Model

Soil #1

(20 °C)

Soil #2

(20 °C)

Soil #3

(10 °C)

Soil #4

(20 °C)

Soil #5

(20 °C)

1stOrder

64.40

188.44

188.18

211.12

208.89

Fit criterion

0.8719

0.8250

0.7832

0.8137

0.9512

Timme-Frehse (Best Fit)

64.40

162.30

159.00

not calculated

not calculated

Fit criterion

0.8719

0.9783

0.9773

0.9936

0.9617

Description of key information

DT50 = 10.5 to 71 days (22.4 - 236.4 days, recalculated to 12 °C), 98 - 100% degradation after 180 to 365 days

Key value for chemical safety assessment

Additional information

Three reports are available for the degradation of the substance in the soil compartment. In an extensive study following GLP and EU Council Directive 91/414/EEC as amended by Commission Directive 95/36/EC, the fate of the substance was investigated over a period of 180 days. The degradation rate of the substance was determined in four soil types at 20 °C (clay loam, sandy loam, loam and sand) and in one soil type at 10 °C (loam). The half-life of the substance ranged from 10.5 days (clay loam) to 50.8 days (sand) at 20 °C (22.4 days to 107.9 days, recalculated to 12 °C) and was 17.8 days in loam at 10 °C (14.7 days, recalculated to 12 °C). The substance attained 89 – 100% degradation at test termination.

Another study according to GLP and US EPA Guidelines, investigated the degradation of the substance in two soils namely sandy loam and silt loam at 25 °C over a period of 365 days. The half-life was 30 days in sandy loam and 71 days in silt loam respectively (99.9 days and 236.4 days respectively, recalculated to 12 °C). The study was conducted according to US guidelines, which use drier soils, thus, the biodegradation is slowed down. The numbers for degradation were > 50% after 30 days and 98% after 180 days in sandy loam and > 50% after 60 days and 98% after 365 days in silt loam.

The results of a third study following GLP and EU Council Directive 91/414/EEC as amended by Commission Directive 95/36/EC are in the same range. The half-life of the substance was 41 days at 20 °C (87.5 days, recalculated to 12 °C) and it reached 85% degradation within 266 days in loam.