1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole

Biodegradation in soil

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in soil: simulation testing

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

25 Jan 1990 to 02 Apr 1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: Richtlinie Teil IV, 4-1 BBA der Bundesrepublik Deutschland: Verbleib von Pflanzenschutzmitteln im Boden - Abbau, Umwandlung und Metabolismus

Version / remarks:

December, 1986

Qualifier:

according to guideline

Guideline:

other: Requirement of Denmark for Pesticide Registration. Ministry of the Environment, Denmark National Agency of Environmental Protection: Translation LK, March 1988. Statutory Order from the Ministry of the Environment No. 79, on Chemical Pesticides.

Version / remarks:

December 10, 1987

GLP compliance:

yes

Test type:

laboratory

Radiolabelling:

yes

Oxygen conditions:

aerobic

Soil classification:

USDA (US Department of Agriculture)

Year:

1992

Soil no.:

#1

Soil type:

silt loam

% Clay:

11.3

% Silt:

29.3

% Sand:

59.4

% Org. C:

1.8

pH:

5.4

CEC:

15.5 meq/100 g soil d.w.

Parameter followed for biodegradation estimation:

radiochem. meas.

Parent/product:

parent

Soil No.:

#1

% Degr.:

41.9

Parameter:

radiochem. meas.

Sampling time:

322 d

Remarks on result:

other: Experiment 1

Parent/product:

parent

Soil No.:

#1

% Degr.:

92.6

Parameter:

radiochem. meas.

Sampling time:

322 d

Remarks on result:

other: Experiment 2

Parent/product:

parent

Soil No.:

#1

% Degr.:

26.5

Parameter:

radiochem. meas.

Sampling time:

322 d

Remarks on result:

other: Experiment 3

Parent/product:

parent

Soil No.:

#1

% Degr.:

87.2

Parameter:

radiochem. meas.

Sampling time:

322 d

Remarks on result:

other: Experiment 4

Key result

Soil No.:

#1

DT50:

40.6 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: low application rate (0.1 mg/kg)

Remarks:

Value presented in the best fitted model and normalized (from the best fitted model) according to EU FOCUS (2000) kinetics guidance in Harvey's study (2014)

Key result

Soil No.:

#1

DT50:

67.4 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: high application rate (1.0 mg/kg)

Remarks:

Value presented in the best fitted model and normalized (from the best fitted model) according to EU FOCUS (2000) kinetics guidance in Harvey's study (2014)

Soil No.:

#1

DT50:

42 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: low application rate (0.1 mg/kg)

Remarks:

Value presented in original study

Soil No.:

#1

DT50:

72 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: high application rate (1.0 mg/kg)

Remarks:

Value presented in original study

Transformation products:

not specified

Evaporation of parent compound:

no

Volatile metabolites:

no

Residues:

yes

Remarks:

See 'Any other information on results incl tables'

The mean total recovery from different experiments and different time intervals was 104.3 ± 5.3%. The extracted radioactivity after application was high for all experimental conditions, ranging from 99.0% (Experiment 4) to 105.4% (Exp. 2) of the applied radioactivity and decreased continuously until the end of incubation to 45.0 (Exp. 4) to 90.6% (Exp. 3). Non-extracted radioactivity increased at the beginning of the study from 2.0 (Exp.1) - 6.4 (Exp.4)% to 8.7 (Exp.3) - 48.3 (Exp.4)% of applied radioactivity. Mineralization was slow and CO₂ was not found before day 14 after treatment. Maximum amount of CO₂ was 2.0%. DT50 - and DT90 -values were calculated with first-order kinetic model. DT50 values varied 42 - 430 days and DT90 -values 141 - 1430 days.

 

Table 1. Material balance given as in percent of the applied radioactivity after 322 days of incubation.

Experiment	1.	2.	3.	4.
Sum of extractables	80.0	3.	90.6	45.0
Non-extractables	17.7	5.3	8.7	48.3
^14CO2	0.4	2.0	0.1	1.8
Total	98.1	100.7	99.5	95.1

 

Table 2. Total amounts of substance (mg/kg) under various experimental conditions at various time intervals.

Time (days)	Concentration mg/kg
	EXP.1	EXP.2	EXP.3	EXP.4
0	1.056	0.101	1.070	1.049
7	1.063	0.094	1.098	1.050
14	1.109	0.086	1.086	0.979
28	1.014	0.066	1.052	0.859
55	0.964	0.040	0.890	0.587
70	0.896	0.026	0.855	0.434
105	0.802	0.014	0.903	0.362
168	0.662	0.012	0.794	0.223
210	0.626	0.012	0.653	0.177
322	0.611	0.008	0.789	0.121

 

 

Table 3. DT50 - and DT90 -values in the different experiments.

Experiment	DT50 days	DT90 days
1	316	1051*
2	42	141
3	430*	1430*
4	72	238

* values not experimentally confirmed, only mathematically extrapolated

 

It was noticed that low soil moisture and temperature decreased degradation rate of substance.

 

Conclusions:

The DT50 values were determined to be 42 and 72 days for the low and high application rates, respectively. In a separated study (Harvey 2014), the raw data from this study was reanalyzed. The best fitted model DT50 values for the low and high application rates were determined and further normalized to be 40.6 and 67.4 days respectively, according to FOCUS (2000) kinetics guidance.

Executive summary:

The aerobic degradation of ¹⁴C-substance in soil Les Evouettes was studied under various experimental conditions. The degradation of ¹⁴C-substance was adequately described by a first-order kinetic reaction (all experimental parts). A more rapid degradation of ¹⁴C- substance was observed at 1/10 of the maximum field rate and 60% FC and 20 °C (part 2), e.g. DT50: 42 days. At the maximum recommended field rate and 60% FC and 20 °C (part 4), the degradation of the test article was slower resulting in a DT50 of 72 days. These values were recalculated with first-order kinetic model in a separate study (Harvey 2014) and were determined to be 40.2 and 67.4 days, respectively. In a separated study (Harvey 2014), the raw data from this study was reanalyzed. The best fitted model DT50 values for the low and high application rates were determined and further normalized to be 40.6 and 67.4 days respectively, according to FOCUS (2000) kinetics guidance. A very marked effect on the degradation of ¹⁴C- substance had the lower water content of the soil, since at the maximum recommended field rate (1.064 mg /kg) and 30% FC and 20 °C (part 1) , the DT50 observed was 316 days. An even more marked effect on the degradation of ¹⁴C-substance was observed because of a lower temperature (10 °C), dose level of 1.064 mg/kg and 60% FC (part 3), yielding an estimated DT50 of 430 days. Because at the two experimental conditions in which the degradation of ¹⁴C-substance was faster, also the highest amounts of non-extractable radioactivity were observed, it may be concluded that the bound radioactivity is composed of radioactive fractions other than the parent substance. Hence, microbial degradation plays an important role in the dissipation of ¹⁴C-substance, although this dissipation is rather slow under the conditions employed. The role of the concentration of test article used was of paramount importance, as well as the water content of the soil and of the incubation temperature, variables that as expected, were to slow down the degradation of 14C-substance.

Reference 2

Endpoint:

biodegradation in soil: simulation testing

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

16 Jun 2000 to 14 Dec 2001

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.4100 (Aerobic Soil Metabolism)

Qualifier:

according to guideline

Guideline:

other: Guidelines for the official Examination of Pesticides Part IV, 4-1: “Disposition of Pesticides in Soil: Degradation, Transformation and Metabolism”: Biological Federal Agency for Land and Forestry, Federal Republic of Germany, December 1986

Qualifier:

according to guideline

Guideline:

other: Dutch Registration Guideline, G.1: Behaviour in soil; Ministry of Agriculture and Fisheries, Ministry of Public Health and Environmental Hygiene, Ministry of Social Affairs, January 1987

GLP compliance:

yes

Test type:

laboratory

Radiolabelling:

yes

Oxygen conditions:

aerobic/anaerobic

Year:

2001

Soil no.:

#1

Soil type:

silt loam

% Clay:

11.4

% Silt:

50.5

% Sand:

38.2

% Org. C:

2.4

pH:

7.2

CEC:

15.7 meq/100 g soil d.w.

Bulk density (g/cm³):

1

Parameter followed for biodegradation estimation:

radiochem. meas.

Parent/product:

parent

Soil No.:

#1

% Degr.:

77

Parameter:

radiochem. meas.

Sampling time:

59 d

Key result

Soil No.:

#1

DT50:

26.7 d

Type:

(pseudo-)first order (= half-life)

Temp.:

19.4 °C

Remarks on result:

other: Recalculated value based on EU FOCUS (2006) kinetics guidance in Harvey's study (2014)

Soil No.:

#1

DT50:

29.1 d

Type:

(pseudo-)first order (= half-life)

Temp.:

19.4 °C

Remarks on result:

other: Original value presented in study

Transformation products:

yes

Evaporation of parent compound:

no

Volatile metabolites:

no

Residues:

no

The temperature of the soil was 19.4 ± 0.4 °C. The microbial biomass was at the beginning of the study 67.7 mg microbial carbon per 100 g dry soil and after the 120 days of incubation the respective value was 55. The results are presented in Tables 1 - 3. The total recovery varied from 97.2 to 104.8% of the applied radioactivity (average of the duplicates). In the aerobic experiment the extractable radioactivity declined continuously from 99.5% at the beginning of the study to 55.6% at the end. The non-extrables increased from 0.1% to 47.3% at the study termination. Soil organic matter fractionation of non-extractable residues (sampling day 120) showed that 14.7%, 8.1% and 1.9% of the applied radioactivity were associated with the fulvic acids, humin and humic acid fraction. Volatiles in form of CO₂ slowly increased and reached maximum at day 120.

Table 1. Mass balance of Gartenacker soil during 120 days aerobic incubation (% of the applied radioactivity, mean of the two samples)

Time	Total Extractables	Non-extractables	CO2	Organic Volatiles	Total
0	99.5	0.1	n.p.	n.p.	99.7
3	97.7	2.1	< 0.1	< 0.1	99.8
7	96.0	3.8	< 0.1	< 0.1	99.8
14	93.0	6.8	0.1	< 0.1	99.8
28	86.1	13.9	0.4	< 0.1	100.4
59	68.1	29.4	1.0	< 0.1	98.5
90	58.9	36.7	1.7	< 0.1	97.2
120	55.6	47.3	2.0	< 0.1	104.8

In the aerobic conditions the amount of the active substance decreased from 99.5% at the day 0 to 9.8% at day 120. 1,2,4-triazole was found up to 43.2% of the applied radioactivity in the soil extracts besides the test substance. Additionally it was found two minor metabolites, M3 (max 3.5%) and M1 (max 5.0%). Analysis of the harsh extracts revealed mainly M14 (8.4% of the applied radioactivity) but M3 and M1 were found at amount of below 0.8%.

 

Table 2. Distribution of the substance and its metabolites in Gartenacker soil incubated under aerobic conditions at 20 ºC (2D-TLC analysis)

Incubation time (days)	% of the applied radioactivity
	Substance	M3	M13	M1	M4	origin
0	99.5	< L.D.	< L.D.	< L.D.	< L.D.	< L.D.
3	91.5	2.3	0.4	0.9	2.3	0.4
7	81.2	3.1	0.7	2.4	7.4	1.3
14	69.1	3.5	0.9	5.0	13.3	1.1
28	48.8	2.1	0.9	4.6	27.6	2.0
59	22.5	1.0	0.4	1.9	40.3	2.0

AEROBIC/ANAEROBIC CONDITIONS

In the aerobic/anaerobic conditions the radioactivity in the aqueous phase was nearly constant, 12.4%.The extractable radioactivity declined slightly from 71.9% at day 7 after waterlogging to 68.8% at study end.Non- extractables residues increased from 13.8% to 20.2%. The concentration of CO₂ after waterlogging remained constant at a level of 0.3%. The organic volatiles were below the limit of detection.

 

Table 3.Mass balance of Gartenacker soil incubated in aerobic conditions for 29 days followed by anaerobic incubatio n at 20 ºC (% of the applied radioactivity, mean of the two samples)

Time	Total Extractables	Non-extractables	CO2	Organic Volatiles	Total
0	99.5	0.1	n.p.	n.p.	99.7
36	71.9	13.8	0.3	< 0.1	98.4
43	75.7	11.7	0.3	< 0.1	98.4
57	73.8	14.9	0.3	< 0.1	101.3
90	68.3	18.9	0.3	<0.1	100.7
119	68.8	20.2	0.4	< 0.1	102.8

The degradation times (DT50) were stated to be 29.1 days for the test substance, 1.5 days for M3 and 2.4 days for M1. The respective DT90 values were 96.7, 5.1 and 7.9 days. After the anaerobic conditions were established all degradation processes were stopped.

Conclusions:

The substance was degraded under aerobic conditions with a half-life of 29.1 days. This half-life value was recalculated in a separate study (Harvey 2014) based on EU FOCUS (2006) kinetics guideline. The recalculated DT50 value was 26.7 days.

Executive summary:

In this study, the biodegradation of the substance in soil was investigated according to the OECD TG Draft Guideline for 'Aerobic and Anaerobic Transformation in Soil' and in compliance with GLP criteria. The substance was rapidly degraded under aerobic conditions with a halflife of 29.1 days. This half-life value was recalculated in a separate study (Harvey 2014) based on EU FOCUS (2006) kinetics guideline. The recalculated DT50 value was 26.7 days.The very transient metabolite M3 was formed by degradation and oxidation of the propyl side chain. Opening of the dioxolan-ring led to M1 which was rapidly further metabolised to M4. Endpoint of the metabolic pathway was the formation of bound residues (up to 47.3%). After anaerobic conditions were established no further degradation was observed

Reference 3

Endpoint:

biodegradation in soil: simulation testing

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1980

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

GLP compliance:

not specified

Test type:

laboratory

Radiolabelling:

yes

Oxygen conditions:

aerobic/anaerobic

Soil classification:

USDA (US Department of Agriculture)

Year:

1980

Soil no.:

#1

Soil type:

silt loam

% Clay:

4.8

% Silt:

61.7

% Sand:

33.5

% Org. C:

2.7

pH:

7.6

CEC:

17.8 meq/100 g soil d.w.

Bulk density (g/cm³):

1.5

Parameter followed for biodegradation estimation:

CO2 evolution

radiochem. meas.

Parent/product:

parent

Soil No.:

#1

% Degr.:

85.9

Parameter:

radiochem. meas.

Sampling time:

52 wk

Key result

Soil No.:

#1

DT50:

115 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Value normalized (from the best fitted model) according to EU FOCUS (2000) kinetics guidance in Harvey's study (2014)

Soil No.:

#1

DT50:

10 wk

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Value presented in original study

Soil No.:

#1

DT50:

78.3 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Value presented in the best fitted model in Harvey's study (2014)

Transformation products:

yes

No.:

#1

No.:

#2

Evaporation of parent compound:

no

Volatile metabolites:

no

Residues:

yes

Remarks:

See 'Any other information on results incl tables'

Aerobic conditions: The total recoveries ranged from 87.9 to 98.9% of the dose applied. Non- extractable radioactivity increased during the study to 62.0%. Mineralization was slow and during the one year study period only 3.1% ¹⁴CO₂ was formed. Two main metabolites were found, M4. The amount of M4 increased up to 23.6% of the dose applied after 52 weeks. M8 increased up to 12 weeks (22.2%) and decreased thereafter. The amount of unknown polar metabolites reached a maximum of 2.5% after 12 weeks and decreased then. Graphically determined DT50 of substance was 70 days.

 

Table 1. Recovery of radioactivity and distribution of metabolites at different sampling times in aerobic conditions (in % of the radioactivity applied).

Weeks	0	4	8	12	24	52
Substance	90.7	75.3	59.7	40.9	19.7	4.8
M4	n.d.	2.1	3.6	6.4	17.0	23.6
M8	n.d.	10.9	16.4	22.2	21.5	5.4
Unknown metabolites	0.4	0.2	0.7	2.5	0.3	n.d.
Non-extractable	0.2	5.3	12.0	15.5	34.6	62.0
Volatiles ^14CO2	-	0.1	0.3	0.4	1.0	3.1
Total recovery	91.3	93.9	92.7	87.9	94.1	98.9

n.d. = not detectable

 

Aerobic/anaerobic and sterile/aerobic conditions. The amount of non-extractables reached 9.1% of the applied dose after 12 weeks in the aerobic/anaerobic conditions and 1.6% in the sterile/aerobic conditions. Evolution of ¹⁴CO₂-volatiles was ≤ 0.1% in both conditions. The amount of M4 and M8 did not increase further in anaerobicconditions and therefore it can be concluded that both compounds are result of aerobic degradation.

 

Table 2. Recovery of radioactivity and distribution of metabolites at different sampling times in aerobic/anaerobic and sterile/aerobic conditions (in % of the radioactivity applied).

	Sterile				Anaerobic*
Weeks	0	4	8	12	8	12
Substance	88.5	86.3	83.3	88.5	70.3	68.3
M4	n.d.	n.d.	n.d.	n.d.	1.9	1.9
M8	n.d.	n.d.	n.d.	n.d.	8.4	10.1
Unknown metabolites	0.2	0.1	0.2	0.2	0.3	0.4
Non-extractable	0.3	1.2	3.0	1.6	8.3	9.1
Volatiles ^14CO2	-	< 0.1	< 0.1	0.1	0.1	0.1
Total recovery	89.0	87.6	86.5	90.4	89.3	89.9

*after 4 weeks aerobic incubation

Conclusions:

Half-life of the substance in the aerobic experiment was 10 weeks. In the anaerobic experiment no significant degradation was seen. In a separated study (Harvey 2014), the raw data from this study was reanalyzed. The best fitted model DT50 value was determined to be 78.3 days. The best fitted model DT50 value was further normalized to 115 days, according to FOCUS (2000) kinetics guidance.

Executive summary:

Half-life of the substance in the aerobic experiment was 10 weeks. In the anaerobic experiment, no significant degradation was seen. Two major metabolites were found, the M4 and the M8, upon aerobic degradation only. In a separate study (Harvey 2014), the raw data from this study was reanalyzed. The best-fitted model DT50 value was determined to be 78.3 days. The best-fitted model DT50 value was further normalized to 115 days, according to FOCUS (2000) kinetics guidance.

Reference 4

Endpoint:

biodegradation in soil: simulation testing

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1981

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

GLP compliance:

not specified

Test type:

not specified

Radiolabelling:

not specified

Year:

1980

Soil no.:

#1

Soil type:

loamy sand

% Clay:

3.3

% Silt:

22.1

% Sand:

74.6

% Org. C:

1

pH:

7.2

Soil no.:

#2

Soil type:

sandy loam

% Clay:

4.9

% Silt:

33.7

% Sand:

61.4

% Org. C:

0.8

Duration:

224 d

Initial conc.:

50 other: µg/50g soil

Based on:

test mat.

Temp.:

25°C

Remarks on result:

other: See in 'Any other information on results incl tables'

Parent/product:

parent

Remarks on result:

not measured/tested

Key result

Soil No.:

#1

DT50:

63.8 d

Type:

(pseudo-)first order (= half-life)

Temp.:

25 °C

Remarks on result:

other: Value normalized (from the best fitted model) according to EU FOCUS (2000) kinetics guidance in Harvey's study (2014)

Key result

Soil No.:

#2

DT50:

89.8 d

Type:

(pseudo-)first order (= half-life)

Temp.:

25 °C

Remarks on result:

other: Value normalized (from the best fitted model) according to EU FOCUS (2000) kinetics guidance in Harvey's study (2014)

Soil No.:

#1

DT50:

41 d

Type:

(pseudo-)first order (= half-life)

Temp.:

25 °C

Remarks on result:

other: Value presented in original study

Soil No.:

#2

DT50:

56 d

Type:

(pseudo-)first order (= half-life)

Temp.:

25 °C

Remarks on result:

other: Value presented in original study

Soil No.:

#1

DT50:

39.7 d

Type:

(pseudo-)first order (= half-life)

Temp.:

25 °C

Remarks on result:

other: Value presented in the best fitted model in Harvey's study (2014)

Soil No.:

#2

DT50:

55.9 d

Type:

(pseudo-)first order (= half-life)

Temp.:

25 °C

Remarks on result:

other: Value presented in the best fitted model in Harvey's study (2014)

Transformation products:

not specified

Evaporation of parent compound:

not specified

Volatile metabolites:

not specified

Residues:

not specified

The degradation times 41 and 56 days. Recoveries ranged from 100 to 115 %.

- Recovery after 224 days: 0.09 mg/kg soil in Soil #1

- Recovery after 224 days: 0.23 mg/kg soil in Soil #2

Table 2: Degradation of the substance

Residues of the test substance in two different soils (mg/kg). Days	Soil 1	Soil 2
0	1.05	1.15
14	0.85	0.98
28	0.66	0.77
56	0.41	0.58
112	0.10	0.35
224	0.09	0.23

Conclusions:

Half life of the substance as measured under the test conditions were 41 (Soil #1) and 56 (Soil#2) days. In a separated study (Harvey 2014), the raw data from this study was reanalyzed. The best fitted model DT50 values for soil#1 and soil#2 were determined to be 39.7 and 55.9 days, respectively. The best fitted model DT50 values were further normalized to 63.8 and 89.8 days, respectively, according to FOCUS (2000) kinetics guidance.

Executive summary:

In this study the soil biodegradation of the substance was investigated, without following a specific guidieeline and not in compliance with GLP criteria. Half life of the substance as measured under the test conditions were 41 (Soil #1) and 56 (Soil#2) days. In a separated study (Harvey 2014), the raw data from this study was reanalyzed. The best fitted model DT50 values for soil#1 and soil#2 were determined to be 39.7 and 55.9 days, respectively. The best fitted model DT50 values were further normalized to 63.8 and 89.8 days, respectively, according to FOCUS (2000) kinetics guidance.

Reference 5

Endpoint:

biodegradation in soil: simulation testing

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1982

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

GLP compliance:

not specified

Test type:

laboratory

Radiolabelling:

yes

Remarks:

14C-dioxolane and 14C-phenyl ring labelled

Oxygen conditions:

aerobic

Year:

1982

Soil no.:

#1

Soil type:

silt loam

% Clay:

5.3

% Silt:

59

% Sand:

35.6

% Org. C:

1

pH:

7.4

CEC:

7.5 meq/100 g soil d.w.

Bulk density (g/cm³):

1.5

Parameter followed for biodegradation estimation:

CO2 evolution

radiochem. meas.

Parent/product:

parent

Soil No.:

#1

% Degr.:

76

Parameter:

radiochem. meas.

Sampling time:

168 d

Remarks on result:

other: 14C-dioxolane radio labelled substance

Parent/product:

parent

Soil No.:

#1

% Degr.:

79.1

Parameter:

radiochem. meas.

Sampling time:

168 d

Remarks on result:

other: 14C-phenylring radio labelled substance

Key result

Soil No.:

#1

DT50:

56.6 d

Type:

(pseudo-)first order (= half-life)

Temp.:

25 °C

Remarks on result:

other: Value normalized (from the best fitted model) according to EU FOCUS (2000) kinetics guidance in Harvey's study (2014)

Soil No.:

#1

DT50:

43 d

Type:

(pseudo-)first order (= half-life)

Temp.:

25 °C

Remarks on result:

other: 14C-dioxolane-labelled test substance

Remarks:

Value presented in original study

Soil No.:

#1

DT50:

47 d

Type:

(pseudo-)first order (= half-life)

Temp.:

25 °C

Remarks on result:

other: 14C-phenyl-labelled test substance

Remarks:

Value presented in original study

Soil No.:

#1

DT50:

38.4 d

Type:

(pseudo-)first order (= half-life)

Temp.:

25 °C

Remarks on result:

other: Value presented in the best fitted model in Harvey's study (2014)

Transformation products:

yes

No.:

#1

Evaporation of parent compound:

no

Volatile metabolites:

no

Residues:

no

The total recoveries ranged from 82.3 to 100.0 % of the dose applied. The amount of non-extractable radioactivity increased in the course of time up to 26.3 and 29.6% for ¹⁴C-dioxolane- and ¹⁴C-phenylring substance, respectively. Main metabolite in both trials was ¹⁴CO₂ and evolution of it was 42.0 - 45.8% of the dose applied at the end of the study. The transient metabolite fractions UAD and UAP were identical with each other and consisted of about equal amounts of M7, and another compound probably hydroxylated at the 4- or 5-position of the dioxolane ring. Unknown polar metabolites appeared occasionally, but never exceeded 1.5% of the applied dose. The graphically determined DT50 -values for ¹⁴C-dioxolane- and ¹⁴C-phenylring substance were 43 and 47 days

 

Table 1. Recovery of ¹⁴C-dioxolane radio labelled substance and distribution of metabolites at different sampling times in aerobic soil (in percent of the radioactivity applied).

Incubation time (days)
	0	28	56	84	168
Substance	88.2	54.0	34.6	23.5	12.2
UAD	n.d.	13.8	13.4	6.0	1.2
Unknown metabolite	0.9	0.7	n.d.	1.0	0.6
Non-extractable	0.9	11.5	19.3	23.3	26.3
Volatiles ^14CO2	-	11.2	24.4	35.4	42.0
Total recovery	90.0	91.2	91.7	89.2	82.3

n.d. = not detectable (< 0.05 %)

 

Table 2. Recovery of ¹⁴C-phenylring radio labelled substance and distribution of metabolites at different sampling times in aerobic soil (in percent of the radioactivity applied).

Incubation time (days)
	0	28	56	84	168
Substance	96.3	54.8	38.7	28.6	17.2
UAP	1.2	16.9	12.2	7.1	n.d.
Unknown metabolites	0.9	n.d.	n.d.	n.d.	1.3
Non-extractable	1.6	12.0	21.0	27.3	29.6
Volatiles ^14CO2	-	5.9	20.2	29.3	45.8
Total recovery	100.0	89.6	92.1	92.3	93.9

n.d. = not detectable (< 0.05 %)

 

Conclusions:

Under the conditions used the substance degraded with 43 days for the 14C-dioxolane-substance and 47 days for the 14C-phenyl-substance. In a separated study (Harvey 2014), the raw data from this study was reanalyzed. The best fitted model DT50 values of the substance (not specified the labelled location) was determined to be 38.4 days. The best fitted model DT50 value was further normalized to 56.6 days, according to FOCUS (2000) kinetics guidance.

Executive summary:

In this study the soil biodegradation of the substance was investigated, without following a specific guideline and not in compliance with GLP criteria. The degradation in soil of the substance has been originally studied with ¹⁴C-triazole labelled material. To extend our knowledge on the degradation of this substance in soil, the present additional studies in an aerobic silty loam were carried out with ¹⁴C-dioxolane-and ¹⁴C-phenylring labelled substance. Under the conditions used, the substance degraded with the following half-lives. ¹⁴C-dioxolane-substance: 43 days and ¹⁴C-phenyl-substance: 47 days. In a separate study (Harvey 2014), the raw data from this study was reanalyzed. The best-fitted model DT50 values of the substance (not specified the labelled location) was determined to be 38.4 days. The best-fitted model DT50 value was further normalized to 56.6 days, according to FOCUS (2000) kinetics guidance. The main metabolite found in both experiments was ¹⁴CO₂. Its amounts increased steadily during the experiments reaching values of 42.0 and 45.8% of the applied radioactivity for ¹⁴C-dioxolane- and ¹⁴C-phenylring-substance, respectively, after 168 days of aerobic incubation. This indicates that both the dioxolane and the phenylring-moieties are mineralized at about the same rate by soil microorganisms.With both labels, the same transient metabolic fractions UAD and UAP were observed. They reached a maximum amount of 13.8 and 16.9% of the dose applied after 28 days with the ¹⁴C-dioxolane and the ¹⁴C-phenylring labelled material, respectively. Chromatographic and MS data showed that this transient metabolite fraction consisted of approx. equal amounts of 2 compounds with the same molecular weight. One was identified as M 7 and the other compound was probably hydoxylated at the 4- or 5-position of the dioxolane ring. In addition, unknown polar metabolites appeared occasionally, but they never exceeded 1.5% of the applied dose. The amounts of non-extractable radioactivity increased in both trials during the incubation period. They reached values of 26.3 and 29.6% of the dose applied for the ¹⁴C-dioxolane and ¹⁴C-phenylring experiments, respectively, at the end of the experiments.

Reference 6

Endpoint:

biodegradation in soil: simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

18 Jul 2006 to 23 May 2007

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)

Version / remarks:

24 April 2002

GLP compliance:

yes

Test type:

laboratory

Radiolabelling:

yes

Oxygen conditions:

aerobic

Soil classification:

USDA (US Department of Agriculture)

Year:

2006

Soil no.:

#1

Soil type:

sandy loam

% Clay:

9

% Silt:

19

% Sand:

72

% Org. C:

3.5

pH:

7.3

CEC:

6.4 meq/100 g soil d.w.

Soil no.:

#2

Soil type:

silt loam

% Clay:

24

% Silt:

60

% Sand:

16

% Org. C:

2.9

pH:

5.5

CEC:

14.5 meq/100 g soil d.w.

Soil no.:

#3

Soil type:

silty clay

% Clay:

44

% Silt:

49

% Sand:

7

% Org. C:

4.2

pH:

7.5

CEC:

12.8 meq/100 g soil d.w.

Details on soil characteristics:

SOIL COLLECTION AND PROPERTIES OF THE SOIL
The study was conducted using three soils
- Soil 1: Pappelacker soil, location Les Barges, Switzerland. The soil was sampled on 3 July 2006. The Pappelacker field site had received no pesticide or fertilizer treatment for at least 12 months.
- Soil 2: Krone (Kroneacker) soil, location Mohlin, Switzerland. The soil was sampled on the 11th July 2006. The Krone field site had received no pesticide or fertilizer treatment for at least 12 months.
- Soil 3: Champaign soil, location Champaign, Illinois, USA. The soil was sampled on the 19th July 2007. The Champaign field site had received only glyphosate herbicide treatment in the previous 2 years.
- The soils were sampled in the field to a total depth of approximately 15 cm (6 inches for Champaign soil) after removal of turf, where present. On arrival at the lab, the soils were stored at ca. 20°C until use. Before use in the study, the soils were sieved (2 mm mesh). An aliquot of each sieved soil was submitted for determination of its physico-chemical characteristics. The methods used for analysis and the results obtained are summarised in Table 1 in “Any other information on materials and methods incl. tables”.
- Prior to incubation under study conditions, the soils were adjusted as close as practically possible to the moisture content at pF2 by the addition of de-ionised water, whilst limiting reformation of large soil aggregates. The moisture content of the adjusted soils was checked. The adjusted soil samples were stored in plastic containers at 20°C ± 2°C in the dark for up to 6 days prior to dispensing into glass pots and up to a further 12 days prior to application of the test substance.
- Microbial biomass: in the soil was estimated from the respiratory response following addition of glucose, based on the method of Anderson and Domsch. Initial biomass determinations were made on samples of each soil after adjustment of the soil moisture content. Final biomass measurements were made on untreated soil samples maintained under soil aerobic study conditions after ca. 120 days incubation. Microbial biomass results are tabulated in Table 3 in “Any other information on materials and methods incl. tables”.
- The water holding capacity at pF2 for undisturbed cores of each soil was experimentally determined. The water holding capacity at pF2 (10 kPa or 0.1 bar) of the test soils was determined. The soil cores were weighed and placed on a sand bank before being saturated with water. After saturation, they were removed from the sand bank, weighed again and placed on a ceramic plate. The instrument was set under a pressure of 0.1 bar for at least three days. The pressure was released, the cores were weighed again and dried in a vacuum oven for 24 hours. Finally, the cores were weighed. The results are shown in Table 2 in “Any other information on materials and methods incl. tables”. The moisture content of the sieved soils was measured by drying weighed subsamples overnight in an oven (at ca. 102°C).

Soil No.:

#1

Duration:

120 d

Soil No.:

#2

Duration:

120 d

Soil No.:

#3

Duration:

120 d

Soil No.:

#1

Initial conc.:

150 g/ha d.w.

Based on:

act. ingr.

Soil No.:

#2

Initial conc.:

150 g/ha d.w.

Based on:

act. ingr.

Soil No.:

#3

Initial conc.:

150 g/ha d.w.

Based on:

act. ingr.

Parameter followed for biodegradation estimation:

CO2 evolution

radiochem. meas.

Soil No.:

#1

Temp.:

20 ± 2°C

Humidity:

Incubate Moisture content: 34.4 g/100g dry soil

Microbial biomass:

Initial Microbial Biomass Carbon: 84.82 mg/100g soil

Soil No.:

#2

Temp.:

20 ± 2°C

Humidity:

Incubate Moisture content: 32.5 g/100g dry soil

Microbial biomass:

Initial Microbial Biomass Carbon: 54.08 mg/100g soil

Soil No.:

#3

Temp.:

20 ± 2°C

Humidity:

Incubate Moisture content: 33.6 g/100g dry soil

Microbial biomass:

Initial Microbial Biomass Carbon: 46.16 mg/100g soil

Details on experimental conditions:

OUTLINE OF STUDY
- 14C-substance was applied to the soil in individual soil vessels, at the appropriate application rate, and incubated under aerobic conditions for up to 120 days in the dark. Each soil pot was remoistened to its original weight on a regular basis, by the drop-wise addition of de-ionised water. At each sampling time, duplicate samples (of each soil ) were analysed for extractable parent compound, degradation products and unextracted residues. Volatile radioactivity was continuously flushed from the incubation vessels and collected in 2M NaOH traps (air being pushed through using a peristaltic pump). A mass balance was determined for each sample.

RADIOCHEMICAL PURITY
- The radiochemical purity of the treatment solution (pre- and post-application) was determined using the instrument conditions described (mobile phase gradient 1).

PREPARATION OF SOIL VESSELS
- Bulk sub-samples of each soil were adjusted to the relevant moisture content. Aliquots of these moisture-adjusted soil samples (equivalent to 100 g dry soil) were dispensed into glass centrifuge bottles (volume of vessel approximately 330 mL). The soil vessels were supplied with moistened air and maintained in the dark at the experimental temperature. The soils were pre-incubated under study conditions for at least 7 days prior to treatment with the application solution.

PREPARATION OF STOCK AND TREATMENT SOLUTION
- The radiolabelled substance (in acetone) was diluted with acetonitrile to give the stock solution. This solution was quantified by LSC and the volume required for the preparation of the treatment solution determined. The treatment solution was prepared by adding an appropriate volume of the stock solution to a volumetric flask and made up to volume with acetonitrile.

APPLICATION OF 14C-SUBSTANCE
200 pF of 14C-substance in acetonitrile (equivalent to 20 µg substance) was applied to each soil pot. This was at a rate equivalent to a field application rate of 150 g ai/ha (assuming even incorporation into the top 5 cm of soil and a soil bulk density of 1.5 g/cm). The solution was applied in droplets (10 x 20 µL) using an Eppendorf EDOS electronic dispenser. The soil surface was then mixed thoroughly by gently tapping and rolling of the vessel. Triplicate 200 µL (10 x 20 µL) aliquots of the treatment solution were transferred to 10 mL volumetric flasks (which were diluted to volume with acetonitrile) and quantified by LSC. This was performed before, during and after the application to check the homogeneity of the treatment solution and to determine the exact application rate.

INCUBATION OF TREATED SOIL VESSELS
The soil vessels were supplied with moistened air and maintained at 20 ± 2°C in the dark. The recorded temperatures measured from the 24th August 2006 which was the start pre-application incubation, to the 3rd February 2007, the end of incubation. Throughout the incubation period, the soil moisture levels were maintained by reweighing the vessels at regular intervals and re-moistening back to their original weights with de-ionised water. The weights before and after re-moistening were recorded and used to determine the fluctuation in moisture content with time.

TRAPPING OF VOLATILE PRODUCTS
Volatile products produced were trapped using a flow through system. Air was pushed (using a peristaltic pump) through a water trap, then through the incubation vessels and any volatiles were collected in the outlet 2M NaOH traps. At each sampling interval, the traps associated with the soil vessels sampled were removed and quantified by LSC.

SAMPLING OF INCUBATED SAMPLES
Duplicate soil pots, for each soil type, were sampled immediately after treatment (zero time) and 3, 7, 14, 28, 62, 90 and 120 days after treatment (DAT). All vessels were transferred back to the laboratory and extracted immediately.

SAMPLE EXTRACTION AND ANALYSIS
- Sample extraction was carried out by the addition of various solvents (150 mL volumes). Following the 0 DAT extraction, method development work was conducted and the extraction regime was optimised. The solvents used and the order of extractions were altered to ensure continued efficient extraction. For each extraction, the slurries were shaken on a flatbed shaker for 60 minutes at ca. 300 rpm. The soil slurries were then centrifuged for 15 minutes at 2000 rpm and the supernatants were transferred to pre-weighed storage bottles. For the 0 DAT extractions, the following extracts were used in the order: acetonitrile/water (80:20, v/v), acetonitrile/water (50:50, v/v), acetonitrile and ethyl acetate. For the remaining extractions, the following extraction regime was followed: ethyl acetate, acetonitrile/water (80:20, v/v) and acetonitrile/water (50:50, v/v). Aliquots of each extract were removed gravimetrically and the radioactivity quantified by LSC. The extracts of individual samples were then combined and concentrated using Zymark TurboVap 11 sample concentrators. The concentrated extracts were quantitatively transferred to 10-25 mL volumetric flasks and aliquots were removed in triplicate to determine the procedural recoveries. Mean procedural recoveries of 93.0% (range 85.5% to 96.6%) were achieved for the treated samples. Aliquots of the concentrated soil extracts were analysed using HPLC (mobile phase gradients 1 and 2). Identification of the parent and degradates was confirmed by co-chromatography with reference standards if possible. In addition to the extraction scheme above, aliquots (~50 g) of the 120 DAT samples (that had already been through the extraction regime) were also subjected to neutral (acetonitrile/water (4:1, 80°C. 2 hours)) and acidic (acetonitrile/0.1M HC1 (9: 1 , 80°C, 2 hours)) harsh extractions. The extracts were quantified, concentrated and analysed as detailed above. Extracted soil debris was air-dried prior to combustion and homogenised using a
gyromill. Sub-samples of the ground soil were weighed into cellulose combustion cones and combusted using the Packard 387 automatic oxidizer.

STORAGE STABILITY OF THE RADIOACTIVE COMPONENTS
- In order to provide information on the stability of the concentrated extracts when stored at <8 °C, selected extracts (0 DAT) were analysed 113 days after the initial analysis and the results obtained were compared.

Soil No.:

#1

% Recovery:

97.3

Remarks on result:

other: % of applied radioactivity in total

Soil No.:

#2

% Recovery:

97.9

Remarks on result:

other: % of applied radioactivity in total

Soil No.:

#3

% Recovery:

98.4

Remarks on result:

other: % of applied radioactivity in total

Parent/product:

parent

Soil No.:

#1

% Degr.:

70.3

Parameter:

radiochem. meas.

Sampling time:

120 d

Parent/product:

parent

Soil No.:

#2

% Degr.:

48.5

Parameter:

radiochem. meas.

Sampling time:

120 d

Parent/product:

parent

Soil No.:

#3

% Degr.:

49.5

Parameter:

radiochem. meas.

Sampling time:

120 d

Key result

Soil No.:

#1

DT50:

71.1 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Value presented in original study, in the best fitted model, and normalized (from the best fitted model) according to EU FOCUS (2000) kinetics guidance in Harvey's study (2014)

Key result

Soil No.:

#2

DT50:

131 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Value presented in the best fitted model and normalised (from the best fitted model) according to EU FOCUS (2000) kinetics guidance in Harvey's study (2014)

Key result

Soil No.:

#3

DT50:

124 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Value normalized (from the best fitted model) according to EU FOCUS (2000) kinetics guidance in Harvey's study (2014)

Soil No.:

#2

DT50:

128 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Value presented in original study

Soil No.:

#3

DT50:

112.4 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Value presented in original study

Soil No.:

#3

DT50:

126 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Value presented in best fitted model in Harvey's study (2014)

Transformation products:

yes

Details on transformation products:

RADIOACTIVE RESIDUES IN SOIL EXTRACTS
- The rate of degradation of substance, and the pattern of metabolite formation and decline, was established using the data from HPLC mobile phase gradients 1 and 2. Degradation of substance was fastest in Pappelacker soil. After 120 days substance accounted for 29.7% of the applied radioactivity. Degradation was slightly slower in Champaign and Krone soils, with parent representing 50.5% of the applied radioactivity after 120 days in Champaign and 51.5% in Krone. The degradation of substance was qualitatively similar in all three soils. Only four extractable degradates were observed. Three were identified by HPLC cochromatography with certified reference standards and confirmatory mass spectrometry while a structure for the fourth was proposed based on mass spectrometry alone. Confirmatory collision induced dissociation (CID) mass spectrometry was carried out using certified analytical standards and Krone and Pappellacker 62 DAT soil extracts. These soil extracts both contained optimal amounts of the four degradates of interest. The identity of substance was confined in the soil samples by comparison of the product ion spectra of a certified substance standard with the product ion spectra of the soil samples. Analysis of the standard using HPLC gradient 2 gave a peak at 25.8 minutes in the total ion chromatogram (TIC). The mass spectrum of this peak shows a pseudomolecular precursor ion m/z 342 from which a product ion spectra was generated. Analysis of the 62 DAT Krone soil extract using HPLC conditions 2 gave a peak at 25.7 minutes in the total ion chromatogram. Comparison of the product mass spectra derived from the pseudomolecular precursor ion m/z 342 with that of the substance standard confirmed the presence of substance in this sample. Analysis of the 62 DAT Pappelacker soil extract using HPLC conditions 2 gave a peak at 25.7 minutes in the total ion chromatogram. Comparison of the product mass spectra derived from the pseudomolecular precursor ion m/z 342 with that of the substance standard confirmed the presence of substance in this sample. The identity of M1 was confirmed in the soil samples by comparison of the product ion spectra of a certified M1 standard with the product ion spectra of the soil samples. Analysis of the standard using HPLC gradient 2 gave a peak at 14.5 minutes in the total ion chromatogram (TIC). The mass spectrum of this peak shows a pseudomolecular precursor ion m/z 258 from which a product ion spectrum was generated. Analysis of the 62 DAT Krone soil extract using HPLC conditions 2 gave a peak at 14.5 minutes in the total ion chromatogram. Comparison of the product mass spectra derived from the pseudomolecular precursor ion m/z 258 with that of the M1 standard confirmed the presence of M1 in this sample. Analysis of the 62 DAT Pappelacker soil extract using HPLC conditions 2 gave a peak at 14.5 minutes in the total ion chromatogram. Comparison of the product mass spectra derived from the pseudomolecular precursor ion m/z 342 with that of the M1 standard confirmed the presence of M1 in this sample. he identity of M3 was confirmed in the soil samples by comparison of the product ion spectra of a certified M3 standard with the product ion spectra of the soil samples. Analysis of the standard using HPLC gradient 2 gave a peak at 16.0 minutes in the total ion chromatogram (TIC). The mass spectrum of this peak shows a pseudomolecular precursor ion m/z 344 from which a product ion spectrum was generated. Analysis of the 62 DAT Krone soil extract using HPLC conditions 2 gave a peak at 16.0 minutes in the total ion chromatogram. Comparison of the product mass spectra derived from the pseudomolecular precursor ion m/z 344 with that of the M3 standard confirmed the presence of M3 in this sample. Analysis of the 62 DAT Pappelacker soil extract using HPLC conditions 2 gave a peak at 15.9 minutes in the total ion chromatogram. Comparison of the product mass spectra derived from the pseudomolecular precursor ion m/z 344 with that of the M3 standard confirmed the presence of M3 in this sample. The identity of M4 was confirmed in the soil samples by comparison of the product ion spectra of a certified M4 standard with the product ion spectra of the soil samples or multiple reaction monitoring (MRM). Analysis of the standard using HPLC gradient 2 gave a peak at 2.1 minutes in the total ion chromatogram (TIC). The mass spectrum of this peak shows a pseudomolecular precursor ion m/z 70 from which product ion spectra were generated. Analysis of the 62 DAT Krone soil extract using F1PLC conditions 2 gave a peak at 2.05 minutes in the extracted product ion chromatogram. Comparison of the product mass spectra derived from the pseudomolecular precursor ion m/z 70 with that of the M4 standard confirmed the presence of M4 in this sample. Analysis of the 62 DAT Pappelacker soil extract was carried out by MRM using the transitions 70 m/z to 43 m/z and 72 m/z to 45 m/z. The resultant chromatograms show peaks at 2.1 minutes confirmed the presence of M4 in this sample. Two possible structures were proposed for the fourth degradate (Unknown 1) of interest. A full scan mass range of 200 Da to 350 Da was applied to the Krone soil 62 DAT extract and gave a peak at 15.3 minutes in the extracted ion total ion chromatogram. The mass spectrum of this peak shows a pseudomolecular ion 344 m/z from which a product ion spectrum was generated. This degradate had a similar mass (m/z = 344) and isotopic pattern as M3. The product ion spectrum was also similar to M3 except product ion m/z = 256 which was absent from the spectrum. In addition the lower mass fragment at m/z = 275 was more abundant. The degradation profile in each soil was qualitatively similar. In Pappelacker soil, M3, Unknown1, M1 and M4 reached maximum levels of 6.1% (after 62 days), 6.4% (after 62 days), 7.2% (after 90 days) and 21.6% (after 120 days) of applied radioactivity, respectively. In Krone soil, M3, Unknown1, M1 and M4 reached maximum levels of 7.2% (after 14 days), 5.2% (after 62 days), 5.3% (after 14 days) and 5.9% (after 14 days) of applied radioactivity, respectively. In Champaign soil, M3, Unknown1, M1 and M4 reached maximum levels of 8.7%, 7.6%, 3.9% and 2.7% (all after 120 days) of applied radioactivity, respectively. HPLC analysis of the harsh extracts revealed that the distribution of components from all three soils were qualitatively similar. Parent and M3, Unknown 1, M1 and M4 were all observed in the harsh extracts. Substance was generally the main component in the harsh extracts accounting for 3.8, 9.8 and 15.0% of applied radioactivity in Pappleaker, Krone and Champaign soils respectively. Correspondingly, the metabolites were observed in smaller quantities, M3 (1.1, 3.4, 5.0%), Unknown1 (1.0, 2.0, 3.1%), M1 (1.5, 2.2, 0.8%) and M4 (14.5, 5.1, 1.3%).

Evaporation of parent compound:

no

Volatile metabolites:

yes

Remarks:

See 'Any other information on results incl. tables'

Residues:

yes

Remarks:

See 'Details on transformation products'

Details on results:

MICROBIAL BIOMASS
- The microbial biomass for the soils analysed prior to treatment and after the incubation period is shown in Table 3 in 'Any other information on materials and methods incl. tables'. The results indicate that there was a general decline in the biomass, however this is common in studies of this duration, and there was still a viable microbial population at the end of the incubation period.

RADIOCHEMICAL PURITY
- The mean radiochemical purity of the treatment solution (pre- and postapplication) was > 99 %, which was
considered adequate for the purposes of this study. The data confirmed that the treatment solution was stable throughout the application period.

APPLICATION RATE
- The amount of 14C- substance applied to each soil pot was determined by LSC of the homogeneity checks of the treatment solution. The LSC data confirmed that the treatment solution remained homogenous throughout the application period (coefficient of variation of 4.6 %). The mean application rate was calculated to be 0.20 mg/kg.

MASS BALANCE
- The total radioactivity recovered was calculated by summation of the activity in the soil extracts, soil residue on combustion and that trapped as 14CO2 in the 2M sodium hydroxide traps. The mass balances are summarised in Table 1 in 'Any other information on results incl. tables'. Total mass balances (means of two replicates for each soil) from the samples analysed immediately after treatment (zero time) ranged between 98.2% and 99.4% of the applied dose. Total mass balances for the remaining sampling intervals were 2t 91% for all incubation soils. The average total radioactive recovery for all conditions was 97.9 %. The amount of extractable radioactivity was found to decrease with time for all soil types. It ranged from 98.7%, 98.8% and 97.4% on day zero to 63.1%, 69.9% and 73.3% by day 120 (for Pappelacker, Krone and Champaign soils, respectively). This decline in extractable radioactivity with time suggests that the remaining radioactivity was bound or incorporated into the soil matrix or volatilised. Harsh extraction of the unextracted residues from the 120 DAT samples released a further 21.8%, 22.4% and 25.2% of applied radioactivity for Pappelacker, Krone and Champaign soils, respectively.

DEGRADATION KINETICS OF SUBSTANCE
- The percentage of applied radioactivity present as parent substance was plotted against incubation time and fitted to single first order kinetics using ModelManager version 1.1. The half-life and DT90 values obtained are summarised in Table 2 in 'Any other information on results incl. tables'. The simple first order half-lives obtained from this analysis were 71, 112 and 128 for Pappelacker, Champaign and Krone soils, respectively.

VOLATILE DEGRADATION PRODUCTS

- Low levels of radioactivity were evolved as volatile products, which were trapped in sodium hydroxide as seen in Table 1 in 'Any other information on results incl. tables'. consistent with it being ¹⁴CO₂. Accumulated levels of carbon dioxide reached a maximum of 2.6% of the applied dose in Pappelacker soil, 2.2% in Krone soil and 0.1% in Champaign soil.

STORAGE STABILITY OF THE RADIOACTIVE COMPONENTS

- The chromatographic profiles of the selected concentrated extracts, which had been stored refrigerated (at < 8 °C) for a minimum of 113 days, were compared with those of the original analysis. HPLC analysis of the extracts showed essentially similar profiles, therefore confirming that, in these cases, no significant additional degradation was observed after 113 days storage. Supplementary data also showed that all of the metabolites observed were stable during storage for at least 84 days.

Conclusions:

Degradation was faster in Pappelacker, than in Champaign and Krone soils. The single first order half-life values were 71, 112 and 128 days, respectively. In a separated study (Harvey 2014), the raw data from this study was reanalyzed. The best fitted model DT50 values for Pappelacker, Champaign and Krone soils were determined to be 71.1, 126 and 131 days respectively. The best fitted model DT50 values were further normalized to 71.1, 124 and 131 days, respectively, according to FOCUS (2000) kinetics guidance. The same four degradation products were observed in each soil. The presence of M1, M3 and M4 were confirmed by mass spectrometry analysis. Two tentative structures were assigned to the other compound, Unknown 1, both indicating degradation of the side chain. Low levels of radiolabelled carbon dioxide were produced by all soils during the incubation, indicating mineralisation of substance. Unextractable residues in Pappelacker, Krone and Champaign soils generally increased throughout the incubation period.

Executive summary:

The route and rate of degradation of the substance was investigated in Pappelacker, Champaign and Krone soils according to the OECD TG 307 and in compliance with GLP criteria. Individual vessels, containing 100 g (dry weight equivalent) of soil, were treated with test substance at a nominal rate of 0.20 mg/kg (which is equivalent to a normal field application rate of 150 g ai/ha). The treated soils were maintained in the dark using a flowthrough apparatus, at a moisture content of approximately pF2 for up to 120 days. This system maintained the aerobicity of the soil and flushed volatile degradation products into the trapping system. Duplicate soil pots were taken, of each soil, for analysis at 0 (zero time). 3, 7, 14, 28, 62, 90 and 120 days after treatment (DAT). The production of volatile degradates was quantified at each time-point and the soil was extracted to remove the radioactive residues. Soil extracts were analysed chromatographically and the unextracted residues quantified by combustion of the extracted soil.

Degradation was faster in Pappelacker, than in Champaign and Krone soils. The single first order half-life values were 71, 112 and 128 days, respectively. In a separated study (Harvey 2014), the raw data from this study was reanalyzed. The best fitted model DT50 values for Pappelacker, Champaign and Krone soils were determined to be 71.1, 126 and 131 days respectively. The best fitted model DT50 values were further normalized to 71.1, 124 and 131 days, respectively, according to FOCUS (2000) kinetics guidance. The same four degradation products were observed in each soil. The presence of M1, M3 and M4 were confirmed by mass spectrometry analysis. Two tentative structures were assigned to the other compound, Unknown1, both indicating degradation of the side chain. In Pappelacker soil, M3, Unknown1, M1 and M4 reached maximum levels of 6.1% (after 62 days), 6.4% (after 62 days), 7.2% (after 90 days) and 21.6% (after 120 days) of applied radioactivity, respectively. In Krone soil, M3, Unknown1, M1 and M4 reached maximum levels of 7.2% (after 14 days), 5.2% (after 62 days), 5.3% (after 14 days) and 5.9% (after 14 days) of applied radioactivity, respectively. In Champaign soil, M3, Unknown1, M1 and M4 reached maximum levels of 8.7%, 7.6%, 3.9% and 2.7% (all after 120 days) of applied radioactivity, respectively. Low levels of radiolabelled carbon dioxide were produced by all soils during the incubation, indicating mineralisation of substance. Accumulated levels of carbon dioxide reached a maximum of 2.6% of the applied dose in Pappelacker soil, 2.2% in Krone soil and 0.1% in Champaign soil. Unextractable residues in Pappelacker, Krone and Champaign soils generally increased throughout the incubation period with maximum levels of 26.6 (after 120 days), 23.8 and 23.7% (both 90 days) of the applied radioactivity, respectively.

Reference 7

Endpoint:

biodegradation in soil: simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 Aug 2011 to 8 may 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)

Version / remarks:

April 2002

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.4100 (Aerobic Soil Metabolism)

Version / remarks:

October 2008

Deviations:

no

GLP compliance:

yes

Test type:

laboratory

Radiolabelling:

yes

Oxygen conditions:

aerobic

Soil classification:

USDA (US Department of Agriculture)

Year:

2013

Soil no.:

#1

Soil type:

loamy sand

% Clay:

4

% Silt:

18

% Sand:

78

% Org. C:

1.28

pH:

7.2

CEC:

6.9 meq/100 g soil d.w.

Details on soil characteristics:

Key soil physico-chemical properties of the soil are given in the chart below and additional details are provided in Table 1 in 'Any other information on materials and methods incl tables'. Soil was sieved using a 2 mm mesh sieve prior to analyses and acclimation. Soil was acclimated and incubated under darkness at pF 2.0 at 20 ± 2°C for fourteen days.

Soil No.:

#1

Duration:

181 d

Soil No.:

#1

Initial conc.:

0.2 mg/kg soil d.w.

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

radiochem. meas.

Soil No.:

#1

Temp.:

20 ± 2 °C

Humidity:

pF2 soil moisture

Microbial biomass:

not specified in report

Details on experimental conditions:

STUDY DESIGN
The experimental design is summarized in Table 2 in 'Any other information on materials and methods incl tables'.

RADIOCHEMICAL PURITY
- The radiochemical purity of [14C]-substance in the treatment solution was measured by TLC prior to and following each application. The radiochemical purity was >99% for both pre and post analysis of the dose solution. The radioactive peak matched the Rf value by TLC in two separate solvent systems. This demonstrated 14C-substance was stable in the dosing solution(s) throughout the entire application period.

PREPARATION OF TREATMENT SOLUTIONS
- Test solution was prepared by diluting the amount received from the Sponsor with 10 mL of acetonitrile. The activity was radioassayed by LSC, and the concentration was calculated to be 38,139 dpm/μL (0.31 μg/ μL of [14C-triazolyl]-substance) using the specific activity supplied by the Sponsor. No further dilutions were necessary.

APPLICATION OF 14C-SUBSTANCE
A specified volume of application solution (in acetonitrile) required to achieve the targeted treatment rate was applied to the soil via Hamilton syringe. A volume of 48 L of treatment solution was applied to the soil surface of each sample then thoroughly mixed to distribute the test compound throughout the test system.

SAMPLING
The definitive sampling regimes are summarized in Table 3 in 'Any other information on materials and methods incl. tables'.

SAMPLE EXTRACTION AND ANALYSIS
- Sample extraction and analysis are summarized in Table 4 in 'Any other information on materials and methods incl tables'. In brief, non-harsh extractions used for kinetic calculations included ethyl acetate (no time zero), acetonitrile: water (80/20, v/v), acetonitrile: water (50/50, v/v) and if needed acetonitrile. All extraction supernatants were pooled, concentrated and re-radioassayed prior to radio-chromatography. Procedural recoveries upon concentration of all extracts were 90% or better.

INVESTIGATION OF UNEXTRACTED RESIDUES
- For residue exceeding 10% of the AR, select samples were subjected to organic matter fractionation (OMF) to determine 14C-associated with fulvic acid, humic acid and humin fractions. Organic matter fractionation (OMF) procedures are described in Table 4 in 'Any other information on materials and methods incl tables'.

STORAGE STABILITY OF THE RADIOACTIVE COMPONENTS
- Extractions were performed on same day as sample harvest. Concentrated extractions were subjected to HPLC chromatographic methods within 32 days of extractions. Samples were stored in a freezer after extraction. The HPLC method was changed so samples were reanalyzed with the updated method. Extracts were shown to be stable upon re-analysis.

ISOLATION AND IDENTIFICATION OF MAJOR DEGRADATES
- In order to confirm the identity of the substance and other degradates, representative extracts were analyzed using LC/MS and HPLC methods, co-chromatographing each with the authentic substance, M4, M1, M2, M11 and M12 reference standards. The retention times of the radioactive component(s) were then compared to the authentic reference standards under HPLC conditions. Mineralization to 14CO2 was significant reaching a maximum of 34.2% AR by the end of soil incubations, which was confirmed by BaCl2 treatment.

Soil No.:

#1

% Recovery:

97.1

St. dev.:

2.61

Remarks on result:

other: Total Recovery of Radioactivity as % of Applied Rate

Parent/product:

parent

% Degr.:

96.7

Parameter:

radiochem. meas.

Sampling time:

181 d

Key result

Soil No.:

#1

DT50:

28 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Value presented in the best fitted model and normalized (from the best fitted model) according to EU FOCUS (2000) kinetics guidance in Harvey's study (2014)

Soil No.:

#1

DT50:

27.95 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Value presented in original study

Transformation products:

yes

No.:

#1

No.:

#2

No.:

#3

Details on transformation products:

PROPOSED METABOLIC PATHWAY
SUBSTANCE underwent oxidation of the alkyl group to form the carboxylic acids, M5 (two isomers). Further degradation occurred by the cleavage of the dioxolane ring to form M1. Further degradation of the metabolites resulted in the formation of triazole, 14CO2, and unextractable radioactivity.

RADIOACTIVE RESIDUES IN SOIL EXTRACTS
The substance degraded quickly over time and was present at less than 50% AR by Day 28. The substance degraded primarily by oxidation to M11 and M12 followed by cleavage of the dioxolane ring to form M1. M11 reached a mean maximum of 15.6% AR at 28 DAT followed by decline. M12, which first appeared at 28 DAT and reached a maximum average level of 15.4% AR at 28 DAT. M1 appeared at 7 DAT and reached an average maximum of 8.0% at 61 DAT and showed a steady decline over time. M4 increased steadily from 2.0% at 7 DAT to a maximum of 35.0% at 90 DAT and declined to 20.8% by 181 DAT. Confirmation of the identity of 14C labelled substance, M5 (two isomers)and M1 residues in the selected soil extracts, 1509 and 1511, were obtained by LC/MS/MS and comparison of retention times with reference standards. The extractable 14C-residue distribution of the substance and minor unknowns are given in Table 4 in “Any other information on results incl tables” (per HPLC) for the Pappelacker soil.

Evaporation of parent compound:

not measured

Remarks:

See 'Any other information on results incl tables'.

Volatile metabolites:

no

Remarks:

See 'Details on transformation products'.

Residues:

yes

Remarks:

See 'Details on transformation products'.

Details on results:

MICROBIAL BIOMASS
Microbial biomass results in Table 1 in 'Any other information on materials and methods incl tables' demonstrate the soils were viable during the entire incubation period.

TEST SUBSTANCE TREATMENT RATE AND RADIOCHEMICAL PURITY
- The test substance application for the soil system was dosed 31 August 2011. Triplicate aliquots of the dose solution were analyzed by LSC before each treatment. The variation (CV) in the homogeneity of the dosing solution was < 1.4%. In addition, for each dose event, an aliquot of the actual dose solution volume used to treat the samples was analyzed by LSC before and after application. The dose volume (48 µL dose volume) was diluted to 10 mL in acetonitrile; triplicate 100 µL aliquots of the dilution were counted by LSC. The total dpm of the dose volume analyzed before and after treatment were in good agreement, with a %CV of less than 1.0%, indicating that the dose solution remained homogeneous throughout the treatment process. Total dpm applied was based on an average LSC value from the dose volume analyzed before and after application per dosing event. The actual amount of radioactivity and substance applied to each test soil sample is presented in the Table 1 in 'Any other information on results incl tables'. The amount of the substance applied was 100.5% of the target equivalent to a field application rate of ~150 g ai/ha. The radiochemical purity of the 14C-substance (cis/trans) was measured by TLC prior to and following each application. The radiochemical purity was >99% for each pre and post analysis of the dose solution. The radioactive peak matched the Rf value by TLC in two separate solvent systems. This demonstrated 14C-substance in the dosing solution(s) was stable throughout the entire application procedure.

MASS BALANCE
- The total radioactivity recovered, or the mass balance (8 sampling intervals per soil), was calculated as the sum of radioactivity in the soil extracts, soil-bound or unextracted residue and any volatile radioactivity trapped in the aqueous 1N NaOH traps and ethylene glycol (EG) traps. The mass balances are summarized in Table 2 in 'Any other information on results incl tables'. The overall mass balance average was 97.1% of applied radioactivity (AR), while the individual mass balances in all soil samples ranged from 91.4 - 102.2% AR. Total extractable residue ranged from a replicate average of 96.3 to 101.0% AR at Day 0 then decreased over time. At study termination, the total extractable was an average 25.8% AR.Unextracted residues were present at Day 0 ranging from a replicate average of 1.18 - 1.21% AR and increased thereafter, reaching a mean maximum of 34.0% AR for the Pappelacker soil at 181 DAT. Organic matter fractionation (OMF) was conducted on representative unextracted residues > 10% AR for selected soils samples. Fractionation demonstrated 14C associated predominantly with the humin and fulvic acid fractions (Table 3 in 'Any other information on results incl tables'). Mineralization to 14CO2 was significant in the Pappelacker soil, reaching a maximum of 34.2% AR by the end of soil incubations, as confirmed by BaCl2 treatments. Non-CO2 volatiles were not detected in the soil.

DEGT50 OF SUBSTANCE IN SOIL
- The degradation rate (DegT50 and DegT90) of substance was determined using non-linear regression and a single first order kinetic model (SFO). As given in Table 5 in 'Any other information on results incl tables', the DegT50 was approximately 27.95 days in Pappelacker soil. SFO kinetics describes the degradation of substance very well with R2 values > 0.97.

Table 1. Radioactivity and substance amount applied.

Soil System	Dose date	Samples Applied	Total dpm/sample	Total µg/sample	% of Target
Pappelacker	31-August -11	Days 0-181	1,236,900	0.20	100.5

 

Table 2. Distributions and Recovery of Radioactivity as %of Applied Rate:Pappelacker

Sample	Total Extractable	% Bound	% 14CO2	%VOC	Total % Recovery
Day 0-1500	100.98	1.21	na	na	102.19
Day 0-1501	96.29	1.18	na	na	97.47
Average	98.64	1.20	na	na	99.83
Day 7-1502	94.07	3.34	0.05	nd	97.46
Day 7-1503	95.93	2.97	0.05	nd	98.95
Average	95.00	3.15	0.05	nd	98.20
Day 14-1504	94.15	4.45	0.11	nd	98.71
Day 14-1505	93.93	4.31	0.11	nd	98.35
Average	94.04	4.38	0.11	nd	98.53
Day 28-1506	87.98	7.55	0.81	nd	96.34
Day 28-1507	89.93	7.17	0.81	nd	97.91
Average	88.95	7.36	0.81	nd	97.13
Day 61-1508	71.33	20.05	5.44	nd	96.83
Day 61-1509	72.99	18.84	5.44	nd	97.27
Average	72.16	19.44	5.44	nd	97.05
Day 90-1510	59.19	26.48	12.13	nd	97.80
Day 90-1511	62.49	25.06	12.13	nd	99.68
Average	60.84	25.77	12.13	nd	98.74
Day 120-1512	39.14	33.65	19.52	nd	92.32
Day 120-1513	44.76	30.77	19.52	nd	95.05
Average	41.95	32.21	19.52	nd	93.68
Day 181-1514	24.15	33.08	34.17	nd	91.39
Day 181-1515	27.36	35.01	34.17	nd	96.53
Average	25.75	34.04	34.17	nd	93.96
			Overall Mean		97.1%
			±SD		2.61%

na = not assayed. nd = not detected.

All reported values are rounded. All calculations are based on unrounded values.

 

Table 3. Organic Matter Fractionation of Selected Samples

Organic Matter Fractionation (OMF) of Selected Samples*

Selected samples for OMF		Percent of Applied Radioactivity
Harvest Interval (DAT)	Replicate	PES (Pre-OMF)	OMF Humin	OMF Fulvic Acid	OMF Humic Acid	OMF Recovery
181	1514	33.08	43.4	41.0	10.3	94.7
181	1515	35.01	38.1	46.1	11.7	95.9

*Selected samples of Pappelacker soil bearing>10% AR of bound residues were subjected to organic matter fractionation (OMF).

 

Table 4. Summary of Characterization / Identification of Radioactive Residues in Soil Extracts as % Applied Rate:Pappelacker

Sample	Substance	M4	M1	M5 (trans)	M5 (cis)	Others
Day0-1500 Day0-1501 Average	100.98 96.29 98.64	NDND ND	NDND ND	NDND ND	NDND ND	ND ND ND
Day 7-1502	87.65	2.12	ND	4.30	ND	ND
Day 7-1503	88.40	1.84	3.43	2.25	ND	ND
Average	88.03	1.98	1.72	3.28	ND	ND
Day 14-1504	84.31	2.08	4.20	3.56	ND	ND
Day 14-1505	78.18	3.58	7.13	5.03	ND	ND
Average	81.25	2.83	5.66	4.30	ND	ND
Day 28-1506	38.41	12.40	6.55	15.55	15.06	ND
Day 28-1507	52.22	9.71	3.30	8.96	15.74	ND
Average	45.32	11.06	4.93	12.25	15.40	ND
Day 61-1508	19.41	23.80	10.03	8.36	9.73	ND
Day 61-1509	17.91	20.36	5.88	12.01	16.84	ND
Average	18.66	22.08	7.95	10.18	13.28	ND
Day 90-1510	14.50	35.01	3.10	3.48	2.07	1.04
Day 90-1511	17.00	33.90	4.01	2.47	5.11	ND
Average	15.75	34.45	3.55	2.98	3.59	0.52
Day 120-1512	1.26	32.57	1.69	ND	3.09	0.54
Day 120-1513	7.51	19.39	4.31	ND	9.20	4.36
Average	4.38	25.98	3.00	ND	6.14	2.45
Day 181-1514	1.01	20.40	2.73	ND	ND	ND
Day 181-1515	2.86	21.15	ND	ND	3.35	ND
Average	1.94	20.78	1.37	ND	1.68	ND

nd = not detected.

All reported values are rounded. All calculations are based on unrounded values.

 

Table 5. Summary of DegT50 and DegT90 Values

Soil	SFO
	Number of datapointsused (Sampling Interval Range [DAT])	DegT50[days]	DegT90[days]	K	χ2	R2	Prob > t
Pappelacker	16 (0-181)	28.0	93.0	0.5776	8.297	0.9780	9.295E-15

Note: SFO: single first order kinetics (non-linear method) calculated usingCAKE Version 1.3 (Release) running on R Version 2.12.2 (2011-02-25). DegT50: Calculated degradation half-life of the substance. K: rate constant. χ2: chi-square statistical value. R2: linear regression coefficient. Prob> t: statistical probability value related to a statistical t-test.

Conclusions:

In a biodegrdation in soil study, performed following OECD TG 307, the half-life of the test substance using single first order (SFO) kinetics was 27.95 days in Pappelacker soil. In a separated study (Harvey 2014), the raw data from this study was reanalyzed. The best fitted model DT50 value was determined and further normalized to be 28 days, according to FOCUS (2000) kinetics guidance. Three metabolites were identified, M1, M4 and M5

Executive summary:

In this degradation study, performed according to OECD 307 and in compliance with GLP criteria, [¹⁴C-triazole]-substance was applied at approximately 0.20 ppm (equivalent to the single maximum label rate of 150 g/ha) to one soil type (Pappelacker (Switzerland) Loamy Sand). Treated samples were incubated aerobically for up to 181 days (under darkness at pF2 soil moisture and 20 + 2 °C). Duplicate samples were taken for analyses at 0, 7, 14, 28, 61, 90, 120 and 181 days after treatment (DAT). At each sampling time, samples were extracted and analyzed for extractable substances, degradation products and unextracted residues. Any volatile radioactivity was continuously flushed from the vessels and volatile collection traps were radioassayed.

The individual mass balances in all soil samples ranged from 91.4 - 102.2% of applied radioactivity (AR) (hereafter, replicate averages stated unless stated otherwise). The amount of extractable radioactivity in Pappelacker soil samples decreased with time from 96.3 - 101.0% AR at 0 days after treatment (DAT) to 24.1 - 27.4% AR by 181 DAT. The substance was present at 96.3 - 101.0% AR at 0 DAT and declined to 1.0 - 2.9% AR at study termination. The predominant major soil degradate was identified as M4, which reached a mean maximum of 34.5% AR at 90 DAT. The M1 reached a mean maximum of 8.0% AR at 61 DAT, M5 (trans-isomer) reached a mean maximum of 12.3% AR at 28 DAT and M5 (cis-isomer) reached a mean maximum of 15.40% AR at 28 DAT.  Carbon dioxide was a major end product of metabolism, reaching a maximum 34.2% AR by the end of the soil incubations. Based on the findings, the calculated degradation half-life (DT50) value was 27.95 days and the DT90 was 98.85 days. In a separate study (Harvey 2014), the raw data from this study was reanalyzed. The best-fitted model DT50 value was determined and further normalized to 28 days, according to FOCUS (2000) kinetics guidance.

Description of key information

All available data was assessed. The results from aerobic studies following standard test conditions are used for further risk assessment. The other studies are anaerobic studies and are included as supporting information.

The geometric mean DT50 in soil = 68.3 days, OECD TG 307, BBA IV 4 and (or) EPA OPPTS 835.4100 guidelines, Edwards 2007; Miner 2013; Keller 1980 and 1982; Muller-Kallert 1992 and Adam 2001

Key value for chemical safety assessment

Half-life in soil:

68.3 d

at the temperature of:

20 °C

Additional information

Fourteen studies are available for this endpoint. Seven of them followed standard test conditions and were used for further risk assessment (Reliability 1 or 2). The test conditions and key effect values are summarised in the table below.

Table. DT50 values for the test substance in soil under aerobic standard(a) test conditions

Soil name	Soil texture	Incubation temp. (ºC)	Moisture (%) [target]^a	best fitted model DT50 (days)	Corrected DT50 ^b (days)	Kinetic	Reference
Les Barges	Silt loam	25	23 [70% FC]	78.3	115	SFO	Keller, 1980
Loamy sand	Loamy sand	25	No data	39.7	63.8	SFO	Keller, 1981
Sandy loam	Sandy loam	25	No data	55.9	89.8	FOMC	Keller, 1981
Les Barges	Silt loam	25	23 [75% FC]	38.4	56.6	FOMC	Keller, 1982
Les Evouettes	Silt loam	20	27 [60% FC]	67.4	67.4	SFO	Muller-Kalert, 1992
Les Evouettes	Silt loam	20	27 [60% FC]	40.6	40.6	SFO	Muller-Kalert, 1992
Gartenacker	Silt loam	20	27 [40% MWC]	26.7	26.7	FMOC	Adam, 2001
Pappleacker	Sandy loam	20	34.4 [pF2]	71.1	71.1	SFO	Edwards, 2007
Krone	Silt loam	20	32.5 [pF2]	131	131	DFOP	Edwards, 2007
Champaign	Silty clay	20	33.6 [pF2]	126	124	DFOP	Edwards, 2007
Pappleacker	Loamy sand	20	33.4 [pF2]	28.0	28.0	SFO	Miner, 2013
Geometric mean^c				55.7	68.3
Maximum				131	131

a. Soils were incubated at either 40% MWC (maximum water capacity, i.e. at zero suction, 0 kPa), or at 60, 70 or 75% of field capacity (FC) or at pF2. Where moisture content was not available (“no data”) no correction was carried out.

b. Half-lives were normalised to default values 20ºC using a Q10 value of 2.58 and to a moisture content of 10 kPa (pF2) according to the methods in FOCUS (2000).

c. DT50 for soils from the same location were averaged first before taking the overall geometric mean

Four studies without following standard test conditions or standard test conditions are included as supporting information. The test conditions and effect values are summarised in the table below.

USDA / Name / Origin	Conditions	OC [%] / pH (water)	T. [°C] / Moisture	DT50 [d] - in original report	Author / Year
Sandy loam / Les Evouettes,/ CH	Aerobic, low temperature, 336 days	1.2 / 4.8	13.5 / 75% FC	128	Baranowski & Galicia, 1992,
Clay loam,Bussen, SE	Aerobic, Sterile soil	1.51 /5.55	20 / 54% MWC	26.1	Stenstroem, 2007
NA / Les Evouettes / CH	Aerobic, 61-67 g air-dried soil in crystallising dishes, unlabelled test item. Frozen at -20°C until analysis after 3 months	Not reported	25 / 75% FC	65	Mani, 1989
NA / Collombey / CH	Aerobic, 61-67 g air-dried soil in crystallising dishes, unlabelled test item. Frozen at -20°C until analysis after 3 months	Not reported	25 / 75% FC	75	Mani, 1989

Field dissipation - additional information
A large number of soil dissipation studies were conducted with the test material. As the information on soil dissipation is outside the scope of REACH, the studies are not summarized as an endpoint study entry but are briefly discussed here. The test material was tested for different applications in bare grounds or soil with sown grass with a rate ranging between 140 and 500 g ai/ha. The DT50 values reported in the original reports were between 7 and 190 days. The DT50 values as recalculated using the SFO model were between 5 and 148 days. The geometric mean DT50 (n=6) for soil dissipation was calculated to be 34.4 days (Offizorz 1990a; Offizorz 1990b; Offizorz 1991a; Offizorz 1991b; Stenstroem 2007; Jacobsen & Manuli 1999; Resseler 2003).