1,3,5-Triazin-2-amine, 4-methoxy-6-(trifluoromethyl)-

Biodegradation in soil

Administrative data

Endpoint:

biodegradation in soil: simulation testing

Type of information:

experimental study

Adequacy of study:

other information

Study period:

not specified

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

secondary literature

Data source

Reference

Reference 1

Reference Type:

other: Draft Renewal Assessment Report under Regulation (EC) 1107/2009

Title:

Draft Renewal Assessment Report under Regulation (EC) 1107/2009 - Tritosulfuron

Year:

2018

Bibliographic source:

Draft Renewal Assessment Report under Regulation (EC) 1107/2009

Reference 2

Reference Type:

study report

Title:

Unnamed

Year:

2003

Materials and methods

Test guideline

Test guideline 1

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OTS 796.3400 (Soil Biodegradation)

Version / remarks:

The study setup is in line with current guidance.

Test guideline 2

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPPTS 835.3300 (Soil Biodegradation)

Version / remarks:

The study setup is in line with current guidance.

Test guideline 3

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 304 A (Inherent Biodegradability in Soil)

Version / remarks:

The study setup is in line with current guidance.

GLP compliance:

yes

Test type:

laboratory

Test material

Test material information

Constituent 1

Reference substance name:

4-methoxy-6-(trifluoromethyl)-1,3,5-triazin-2-amine

EC Number:

610-962-9

Cas Number:

5311-05-7

Molecular formula:

C5H5F3N4O

IUPAC Name:

4-methoxy-6-(trifluoromethyl)-1,3,5-triazin-2-amine

Radiolabelling:

yes

Study design

Soil classification:

other: According to DIN 19682

Soil properties

Soil properties 1

Soil no.:

#1

Soil type:

loamy sand

% Clay:

8

% Silt:

18

% Sand:

74

% Org. C:

0.55

pH:

5.8

CEC:

6.1

Bulk density (g/cm³):

1 629

% Moisture content:

21.68

Soil properties 2

Soil no.:

#2

Soil type:

silty clay loam

% Clay:

14.9

% Silt:

39.6

% Sand:

45.5

% Org. C:

0.57

pH:

7.4

CEC:

10.9

Bulk density (g/cm³):

1 739

% Moisture content:

26.15

Soil properties 3

Soil no.:

#3

Soil type:

clay loam

% Clay:

41

% Silt:

36.3

% Sand:

22.8

% Org. C:

2

pH:

6.8

CEC:

18

Bulk density (g/cm³):

1 233

% Moisture content:

32.11

Duration of test (contact time)

Duration of test (contact time) 1

Soil No.:

#1

Duration:

>= 0 - <= 120 d

Duration of test (contact time) 2

Soil No.:

#2

Duration:

>= 0 - <= 120 d

Duration of test (contact time) 3

Soil No.:

#3

Duration:

>= 0 - <= 120 d

Initial test substance concentration

Initial test substance concentration 1

Soil No.:

#1

Initial conc.:

0.05 g/kg soil d.w.

Based on:

other: Representation of the actual use rate of AMTT (50 g/ha, being roughly equivalent to 50 µg/kg dry soil)

Initial test substance concentration 2

Soil No.:

#2

Initial conc.:

0.05 g/kg soil d.w.

Based on:

other: Representation of the actual use rate of AMTT (50 g/ha, being roughly equivalent to 50 µg/kg dry soil)

Initial test substance concentration 3

Soil No.:

#3

Initial conc.:

0.05 g/kg soil d.w.

Based on:

other: Representation of the actual use rate of AMTT (50 g/ha, being roughly equivalent to 50 µg/kg dry soil)

Parameter followed for biodegradation estimation:

CO2 evolution

radiochem. meas.

Experimental conditions

Experimental conditions 1

Soil No.:

#1

Temp.:

20 ± 2 °C

Humidity:

max. 40 %

Microbial biomass:

12.2

Experimental conditions 2

Soil No.:

#2

Temp.:

20 ± 2 °C

Humidity:

max. 40 %

Microbial biomass:

12.9

Experimental conditions 3

Soil No.:

#3

Temp.:

20 ± 2 °C

Humidity:

max. 40 %

Microbial biomass:

19.5

Details on experimental conditions:

The soils were freshly sampled at the field site, air-dried and screened trough a 2 mm-sieve. Determination of soil moisture was carried out by differential weighing after drying of 10 g aliquots of each soil in a microwave oven. Thereafter, 100 g of dry soil equivalents were weighed into each 300 mL-Erlenmeyer flask. The soil moisture in each test vessel was adjusted to about 40 % of the maximum water holding capacity of the soil.
Afterwards, the vessels were closed with a cotton wool stopper and pre-incubated at 20 ± 2 °C in the dark for 14 days.
Application and incubation of test system
The initial concentration of AMTT was chosen as 5 µg/100 g dry soil, as to represent the actual use rate of AMTT (50 g/ha, being roughly equivalent to 50 µg/kg dry soil) and 100 % degradation of the parent compound to AMTT. No molecular weight correction factor was used.
AMTT was added to each test vessel individually by pipetting the appropriate amount of an aqueous application solution in small drops onto the soil surface. The actual weight of each test vessel was recorded.
Afterwards the test vessels were closed with a trap attachment (containing soda lime and oil wetted quartzwool) which allowed for some gas exchange but which adsorbed all volatile metabolites (including CO2). Samples were incubated for 0 (1 hour), 1, 3, 7, 14, 30, 62, 90 and 120 days at a temperature of 20 °C and a soil moisture of about 40 % of the respective soils’ maximum water holding capacity.

Results and discussion

Material (mass) balance

Material (mass) balance 1

Soil No.:

#1

Sampling day(s):

0 d

% Total extractable:

94.41

% Non extractable:

1

% CO2:

0

% Recovery:

95.41

Material (mass) balance 2

Soil No.:

#1

Sampling day(s):

120 d

% Total extractable:

38.69

% Non extractable:

9.67

% CO2:

46.42

% Recovery:

94.78

Material (mass) balance 3

Soil No.:

#2

Sampling day(s):

0 d

% Total extractable:

93.87

% Non extractable:

1.42

% CO2:

0

% Recovery:

95.29

Material (mass) balance 4

Soil No.:

#2

Sampling day(s):

120 d

% Total extractable:

58.2

% Non extractable:

15.21

% CO2:

17.22

% Recovery:

90.63

Material (mass) balance 5

Soil No.:

#3

Sampling day(s):

0 d

% Total extractable:

91.56

% Non extractable:

1.8

% CO2:

0

% Recovery:

93.36

Material (mass) balance 6

Soil No.:

#3

Sampling day(s):

120 d

% Total extractable:

64.09

% Non extractable:

18.71

% CO2:

16.05

% Recovery:

98.85

% Degradation

% Degradation 1

Soil No.:

#1

% Degr.:

89.9

Parameter:

radiochem. meas.

% Degradation 2

Soil No.:

#2

% Degr.:

79.5

Parameter:

radiochem. meas.

% Degradation 3

Soil No.:

#3

% Degr.:

58.6

Parameter:

radiochem. meas.

Half-life / dissipation time of parent compound

Half-life / dissipation time of parent compound 1

Soil No.:

#1

DT50:

35.3 d

Temp.:

20 °C

Remarks on result:

other: The kinetic calculations was done with ModelMaker 4.0

Half-life / dissipation time of parent compound 2

Soil No.:

#2

DT50:

53.9 d

Temp.:

20 °C

Remarks on result:

other: The kinetic calculations was done with ModelMaker 4.0

Half-life / dissipation time of parent compound 3

Soil No.:

#3

DT50:

94.5 d

Temp.:

20 °C

Remarks on result:

other: The kinetic calculations was done with ModelMaker 4.0

Applicant's summary and conclusion

Conclusions:

DT50 values for aerobic degradation of AMTT in soil are:
- weakly loamy sand (Birkenheide) 35.3 days
- silty clayey sand (Mussbach) 53.9 days
- clayey loam (Lufa S6) 94.5 days

Executive summary:

The test item was degraded under the actual incubation conditions. At the end of the incubation period, 10.1 %, 20.5 % and 41.4 % of the applied radioactivity were assigned to unchanged AMTT for the soils Birkenheide, Mussbach and Lufa 6S, respectively. Different non-identified metabolite zones were determined, amounting to 28.6 % of the applied radioactivity after 120 days incubation in soil Birkenheide, 37.7 % in soil Mussbach and 22.7 % in soil Lufa 6S, respectively. For all three soils a decrease of the portion of non-identified radioactivity was observed between 90 and 120 days.