N-cyclopropyl-1,3,5-triazine-2,4,6-triamine

Phototransformation in soil

Administrative data

Endpoint:

phototransformation in soil

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1999/07/28 to 2000/11/14

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2000

Report date:

2000

Materials and methods

Test guideline

Test guideline 1

Guideline:

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

Version / remarks:

Oct 1982

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: Richtlinien fur die amtliche Prufung von Pflanzenschutzmitteln Teil IV, 4 - 1: "Verbleib von Pflanzenschutzmitteln im Boden: Abbau, Umwandlung und Metabolismus": Biologische Bundesanstalt fur Land- und Forstwirtschaft, Bundesrepublik Deutschland

Version / remarks:

December 1986

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: EC, Working document 1607/VI/97 rev. 1; Amending Council Directive 91/414 Setac procedures for Assessing the Environmental Fate and Ecotoxicity of Pesticides

Version / remarks:

March 1995

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

N-cyclopropyl-1,3,5-triazine-2,4,6-triamine

EC Number:

266-257-8

EC Name:

N-cyclopropyl-1,3,5-triazine-2,4,6-triamine

Cas Number:

66215-27-8

Molecular formula:

C6H10N6

IUPAC Name:

N2-cyclopropyl-1,3,5-triazine-2,4,6-triamine

Test material form:

solid: particulate/powder

Radiolabelling:

yes

Remarks:

[U-14C]triazine labelled cyromazine

Study design

Analytical monitoring:

yes

Analytical method:

high-performance liquid chromatography

Details on sampling:

Duplicate samples were taken and analysed after about 17, 24, 41, 65, 137, and 240 hours of irradiation. Dark control samples were taken at the same time intervals of incubation in the dark.
Additionally, two unexposed samples were analysed at the start of the incubation (day 0).

Details on soil:

The soil was an irradiated Gartenacker loam/silt loam at either 75% FC or almost dry, the soil characteristics are detailed in Table 1.

Light source:

Xenon lamp

Light spectrum: wavelength in nm:

>= 290

Relative light intensity:

75

Details on light source:

Light form a xenon arc lamp filtered to remove light from wavelengths <290 nm was used to continuously irradiate the soils for periods of up to 240 hours, equivalent to 30 days natural summer sunlight at latitude 30-50°N. The mean light intensity of the lamp was approximately 75 W/m2.

Details on test conditions:

The photolytic degradation of [U-14C]triazine labelled cyromazine was evaluated on a soil surface at 20°C under an artificial light source (Heraeus Suntest equipment). Test samples were prepared by coating glass slides with a soil slurry and allowing the moisture to evaporate until either the soil was at 75% FC or almost dry. The thickness of the final soil layers was approximately 2 mm. 14C-cyromazine was applied to the soil surface at a rate of 3.2 µg/cm2 corresponding to a field rate of 320 g ai/ha.

Duration of test at given test condition

Duration of test at given test condition 1

Duration:

240 h

% Moisture:

75

Temp.:

20 °C

Initial conc. measured:

320 g/ha d.w.

Duration of test at given test condition 2

Duration:

240 h

% Moisture:

0

Temp.:

20 °C

Initial conc. measured:

320 g/ha d.w.

Reference substance:

no

Dark controls:

yes

Results and discussion

% Degradation

% Degradation 1

% Degr.:

12.1

Sampling time:

240 h

Test condition:

Non-irradiated, Moist Soil (Dark Control)

Remarks on result:

other: Based on 97.1% parent at time 0 and 85% at 240 h

% Degradation 2

Key result

% Degr.:

35

Sampling time:

240 h

Test condition:

Irradiated, Dry Soil

Remarks on result:

other: Based on 97.1% parent at time 0 and 62.1 % at 240 h

% Degradation 3

Key result

% Degr.:

96.1

Sampling time:

240 h

Test condition:

Irradiated, Moist Soil

Remarks on result:

other: Based on 97. 1% parent at time 0 and 1.0 at 240 h

Dissipation half-life of parent compound

Key result

DT50:

3.5 d

Test condition:

Moist irradiated soil

Remarks on result:

other: Days of natural summer sunlight

Transformation products:

yes

Identity of transformation products

No.:

#1

Reference

Reference substance name:

Unnamed

IUPAC name:

1,3,5-triazine-2,4,6-triamine

Inventory number:

InventoryMultipleMappingImpl [inventoryEntryValue=EC 203-615-4]

CAS number:

108-78-1

Identity:

1,3,5-Triazine-2,4,6-triamine

Molecular formula:

C3H6N6

Molecular weight:

126.12

SMILES notation:

Nc1nc(N)nc(N)n1

InChl:

InChI=1/C3H6N6/c4-1-7-2(5)9-3(6)8-1/h(H6,4,5,6,7,8,9)

Details on results:

The total recovery of radioactivity from samples of both the irradiated (moist and dry) and non- irradiated treatments was between 94 and 99% of total applied. Volatile radioactivity was <0.1% of applied radiochemical for all treatments, showing that no volatile components are produced from photolysis of cyromazine. The total recovery of radioactivity and the distribution is shown in Table1.
In moist irradiated soil, cyromazine degraded rapidly with 1% remaining at the end of the irradiation period (240 hours). The half-life of cyromazine was calculated to be 3.5 days by simple first order kinetics (DT90 12 days). Only one major degradate was observed, melamine, which increased throughout the irradiation period to 53% of applied radioactivity. Several minor metabolites were isolated but none accounted individually for more than 7% of the applied radioactivity. Non-extractable radioactivity in the soil increased with increasing time of irradiation to a maximum of 32.9% of the applied radiochemical by the end of the study.
In dry irradiated soil the level of cyromazine fell rapidly from 97% to 74% of applied radiochemical during the first 24 hours. Thereafter, degradation was slow with 62% of the parent remaining after the full 240-hour irradiation. The rapid initial loss was attributed to residual moisture in the soil catalysing the breakdown of cyromazine as in the moist soil. However, after 24 hours, the water had fully evaporated and the second phase of much slower degradation was a reflection of the rate of loss under true dry soil conditions. Melamine was again the only major product formed, which reached 15% of applied by the end of the study (240 hours of irradiation).
In moist non-irradiated soil degradation of cyromazine was very slow, 85% of the applied parent was recovered at the end of the incubation period (240 hours in the dark). No significant metabolites were formed under non-irradiated, moist conditions.

Any other information on results incl. tables

Table 2: Distribution and recovery of ¹⁴C-cyromazine and its degradates in irradiated and non- irradiated Gartenacker soil in % of applied radioactivity

Irradiation or incubation time (hours)	Extractables (%)	Cyromazine (%)	Melamine (%)	Unknowns **     (%)	CO2 (%)	Non- extractable (%)	Total (%)
Irradiated, Moist Soil
0	98.4	97.1	1.3	*	<0.05	0.6	99.0
17.3	81.9	60.6	17.3	3.1	<0.05	16.0	97.9
24.0	77.8	55.1	17.9	4.8	<0.05	17.3	95.1
41.3	75.5	35.3	30.9	9.3	<0.05	19.5	95.0
65.3	72.3	18.0	42.7	11.5	<0.05	22.0	94.3
137.3	65.3	5.5	49.2	13.1	<0.05	29.1	94.3
240.0	61.5	1.0	54.0	6.9	0.1	32.9	94.4

Continuation of Table 2.

Irradiated, Dry Soil
Irradiation or incubation time (hours)	Extractables (%)	Cyromazine (%)	Melamine (%)	Unknowns **     (%)	CO2 (%)	Non- extractable (%)	Total (%)
0	98.4	97.1	1.3	*	<0.05	0.6	99.0
17.3	87.2	77.6	8.6	1.0	<0.05	10.0	97.2
24.0	84.3	74.3	8.9	1.2	<0.05	9.9	94.2
41.3	82.6	69.3	11.0	3.1	<0.05	11.4	94.1
65.3	82.9	68.3	11.3	3.2	<0.05	11.2	94.2
137.3	80.3	65.4	12.1	3.2	<0.05	14.0	94.3
240.0	81.6	62.1	14.7	5.7	<0.05	14.2	95.8
Non-irradiated, Moist Soil (Dark Control)
0	98.4	97.1	1.3	*	<0.05	0.6	99.0
17.3	91.7	90.8	0.9	*	<0.05	4.3	95.9
24.0	89.4	88.4	1.0	*	<0.05	4.7	94.1
41.3	88.5	87.7	0.8	*	<0.05	5.5	94.0
65.3	88.0	87.3	0.7	*	<0.05	6.1	94.1
137.3	87.0	85.7	1.4	*	<0.05	7.4	94.4
240.0	86.3	85.0	1.3	*	<0.05	8.7	95.1

* Value below limit of detection

** Three unknowns separately quantified (M3, M4 and M5) maximum at any time was 6.9% of applied radiochemical

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified

Conclusions:

The results demonstrate that although cyromazine is stable to direct photolysis, its rapid loss on moist soils must be attributed to the effects of indirect photolysis by photosensitisers like e.g. humic substances. The major products of photolysis on moist soil are melamine and non-extractable soil residues.

Executive summary:

The photolytic degradation of [U-¹⁴C]triazine labelled cyromazine was evaluated on a soil surface at 20°C under an artificial light source. The soil used in this sutdy was an irradiated Gartenacker loam/silt loam. Test samples were prepared by coating glass slides with a soil slurry and allowing the moisture to evaporate until either the soil was at 75% FC or almost dry. The thickness of the final soil layers was approximately 2 mm. ¹⁴C-cyromazine was applied to the soil surface at a rate of 3.2 µg/cm² corresponding to a field rate of 320 g ai/ha. Light form a xenon arc lamp filtered to remove light from wavelengths <290 nm was used to continuously irradiate the soils for periods of up to 240 hours, equivalent to 30 days natural summer sunlight at latitude 30-50°N.

The total recovery of radioactivity from samples of both the irradiated (moist and dry) and non- irradiated treatments was between 94 and 99% of total applied. In moist irradiated soil, cyromazine degraded rapidly with 1% remaining at the end of the irradiation period (240 hours). The half-life of cyromazine was calculated to be 3.5 days by simple first order kinetics (DT₉₀ 12 days). Only one major degradate was observed, melamine, which increased throughout the irradiation period to 53% of applied radioactivity. In dry irradiated soil the level of cyromazine fell rapidly from 97% to 74% of applied radiochemical during the first 24 hours. Thereafter, degradation was slow with 62% of the parent remaining after the full 240-hour irradiation. The rapid initial loss was attributed to residual moisture in the soil catalysing the breakdown of cyromazine as in the moist soil.  Melamine was again the only major product formed, which reached 15% of applied by the end of the study (240 hours of irradiation). In moist non-irradiated soil degradation of cyromazine was very slow, 85% of the applied parent was recovered at the end of the incubation period (240 hours in the dark). No significant metabolites were formed under non-irradiated, moist conditions.

The results demonstrate that although cyromazine is stable to direct photolysis, its rapid loss on moist soils must be attributed to the  effects of indirect photolysis by photosensitisers like e.g. humic substances. The major products of photolysis on moist soil are melamine and non-extractable soil residues.