Registration Dossier

Data platform availability banner - registered substances factsheets

Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Environmental fate & pathways

Phototransformation in soil

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

Endpoint:
phototransformation in soil
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline draft (Phototransformation of Chemicals on Soil Surfaces)
Version / remarks:
(OECD January 2002)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
yes
Analytical monitoring:
yes
Analytical method:
other: TLC
Details on sampling:
Duplicate samples were taken after ca. 0, 16, 24, 40 and 163 h of irradiation. The dark controls were sampled after ca. 0, 16, 24, 40 and 208 h of incubation.

Details on soil:
The photodegradation of 14C-cyanamide was investigated on a ca. 10 mm layer of non-sterile, biologically active Derbyshire silt loam soil. Soil characterisation data are presented in the table below in "Any other information on materials and methods inclu. tables".

Light source:
Xenon lamp
Light spectrum: wavelength in nm:
> 300 - < 800
Details on light source:
Vessels were placed into a custom-designed test apparatus and exposed to simulated sunlight (24 hours of irradiation) from a xenon-arc source for a period up to about 9 days. Irradiation was adjusted to 55000 µW/cm2 (300-800 nm).
Details on test conditions:
- Round quartz glass test vessels (diameter of 6 cm) were filled with a soil layer of ca. ~10 mm thickness
- Soils were treated with 0.5 mL solution containing 2.65 mg 14C radiolabelled and non-labelled cyanamide dissolved in water corresponding to a nominal application rate of 9.4 kg ai/ha using a glass syringe
- Vessels were placed into a custom-designed test apparatus and exposed to simulated sunlight (24 hours of irradiation) from a xenon-arc source for a period up to about 9 days. Irradiation was adjusted to 55000 µW/cm2 (300-800 nm)
- Soil water content and temperature were maintained at 75 ± 10% of the water holding capacity at 0.1 bar and at approximately 20°C, respectively
- Dark control samples were included in vessels not exposed to light
- A series of traps was connected to each test vessel, i.e. three NaOH, one ethylene glycol and one H2SO4 to trap CO2 and possible organic volatiles. Sterile, hydrated, CO2-free air was continuously passed through the photolysis and dark control vessels in order to purge and trap volatiles
- Microbial biomass of the test soil was determined at test start and test end.
Duration:
9 d
% Moisture:
75
Temp.:
20 °C
Initial conc. measured:
9.4 other: kg ai/ha
Reference substance:
no
Dark controls:
yes
Computational methods:
The rate of degradation of cyanamide in irradiated and non-irradiated samples was calculated by linear regression using first order degradation kinetics.
Preliminary study:
No preliminary study
Test performance:
No unusual observations during the test performance
% Degr.:
99.9
Sampling time:
9 d
Test condition:
In the irradiated samples
Key result
% Degr.:
99.9
Sampling time:
16 d
Test condition:
In the non-irradiated samples
Key result
DT50:
2.4 h
Test condition:
In the irradiated samples
DT50:
2 h
Test condition:
In the dark control samples
Transformation products:
yes
No.:
#1
No.:
#1
No.:
#2
No.:
#3
No.:
#3
No.:
#4
No.:
#4
Details on results:
MASS BALANCE:
Recovery of radioactivity ranged from 92 % to 105 % for the irradiated samples and from 99 % to 106 % for dark control samples.

BOUND AND EXTRACTABLE RESIDUES:
The amount of extractable residues decreased rapidly from 91 % (immediately after application) to ca. 1 % of applied radioactivity 163 and 207 h after application in the irradiated and dark control samples, respectively. Unextractable residues accounted for ca. 4 % of applied radioactivity which accounted for almost all radioactivity in both irradiated and dark control samples at the end of the incubation period.

VOLATILISATION:
The total radioactivity in the H2SO4 and ethylene glycol traps accounted for < 0.01 % of applied radioactivity. Residues were observed only in the NaOH trapping solutions and were identified to be 14CO2 by precipitation as BaCO3.

TRANSFORMATION OF PARENT COMPOUND:
The amount of cyanamide decreased from 66.8% of the applied concentration on day 0 to ca. 0.1 % at the end of the inclubation period in both irradiated and dark control samples (Table MIIA 7.1 3). For the most part, cyanamide mineralised to CO2 in both irradiated and dark control samples as CO2 accounted for almost all radioactivity found at the end of the study period.
Four degradation products were identified: dicyandiamide, urea, Guanidine and guanylurea. The two latter substances could not be separated by TLC but reached on average max. 3.41 % AR during the study at day 0. The degradation products dicyandiamide and urea occurred on average at less than 10 % AR. After 9 days all degradation products were found at less than 0.4 % AR for the irradiated samples and 0.26 % AR for the non-irradiated samples.

The photolytic DT50 of cyanamide obtained from irradiated samples was calculated as 2.4 h with the SFO model (DT90 = 7.9 h) and 0.3 h with the FOMC model (DT90 = 2.2 h). The DT50 of cyanamide obtained from the non-irradiated samples was 2.0 h with the SFO model (DT90 = 6.6 h) and 0.01 h with the FOMC model (DT90 = 0.3 h). The even slightly shorter DT50 of the non-irrigated samples shows that cyanamide was not subject to photodegradation under the study conditions.
Results with reference substance:
No reference substance

Distribution of radioactivity in extracted soil samples treated with14C‑cyanamide (results expressed in % of applied radioactivity):






































































































Time after application [h]



Soil extractable



Un-extractable



14CO2


(NaOH)



Volatiles (H2SO4)



Volatiles (ethylene glycol)



Total



0



90.7



1.27



-



-



-



92.0



Irradiated samples



15.8



10.2



3.89



77.9



<0.01



<0.01



92.0



23.6



4.54



2.92



90.9



<0.01



<0.01



98.4



39.5



3.46



3.75



94.5



<0.01



<0.01



102



163



1.06



3.86



101



<0.01



<0.01



105



Dark Control



15.8



4.41



2.61



91.3



<0.01



<0.01



98.3



23.6



3.55



4.30



93.9



<0.01



<0.01



102



39.5



3.45



3.48



97.6



<0.01



<0.01



105



208



0.70



4.25



101



<0.01



<0.01



106



 


Distribution of residues in soil extracts (results expressed in % of applied radioactivity):




























































































Time after application [d]



Cyanamide



Dicyandiamide



Urea



Guanylurea, Guanidine



Total *



0



66.8



6.67



7.97



3.41



90.7



Irradiated samples



15.8



0.65



3.07



5.04



0.40



10.2



23.6



0.29



2.45



0.62



0.36



4.54



39.5



0.28



2.02



0.24



0.27



3.46



163



0.07



0.33



0.10



0.19



1.06



Dark Control



15.8



0.25



2.45



0.28



0.83



4.41



23.6



0.31



2.12



0.23



0.27



3.55



39.5



0.16



2.22



0.21



0.22



3.15



208



0.08



0.10



0.07



0.19



0.70



 

Validity criteria fulfilled:
yes
Conclusions:
With DT50 values (single first order) of 2.4 and 2.0 h, respectively the degradation of the cyanamide was fast both in irradiated and in the dark samples, indicating that the rate of degradation due to photolysis is negligible compared to the rate of degradation caused by biodegradation. Cyanamide almost completely mineralised to CO2 over the study period. Bound residues were < 5 % at the end of the study period. No major metabolites of cyanamide were encountered in the higher Tier soil photolysis study.
Executive summary:

In a higher tier soil photolysis study using a ca. 10 mm soil layer, the phototransformation of 14C-cyanamide was studied on a Derbyshire silt loam soil. Samples were inclubated for 9 days at ca. 75 % of field capacity and at approximately 20°C. Irradiation was adjusted to 55000 µW/cm2 (300-800 nm).


With DT50 values (single first order) of 2.4 and 2.0 h, respectively the degradation of the cyanamide was fast both in irradiated and in the dark samples, indicating that the rate of degradation due to photolysis is negligible compared to the rate of degradation caused by biodegradation. Cyanamide almost completely mineralised to CO2 over the study period. Bound residues were < 5 % at the end of the study period. No major metabolites of cyanamide were encountered in the higher Tier soil photolysis study.

Endpoint:
phototransformation in soil
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2000-06-29 until 2000-12-04
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
equivalent or similar to guideline
Guideline:
EPA Guideline Subdivision N 161-3 (Photodegradation Studies on Soil)
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: SETAC (Europe): Procedures for assessing the environmental fate and ecotoxicity of pesticides, Part 2 - Soil Photolysis (1995)
Deviations:
no
GLP compliance:
yes
Radiolabelling:
yes
Analytical monitoring:
yes
Analytical method:
other: TLC... (see attached file)
Details on sampling:
Irradiated and dark control samples were taken in duplicate immediately after application and after 1, 3, 6, 12 and 16 days of irradiation/incubation.
Details on soil:
The photo-degradation of [14C]-cyanamide on non-sterile, viable clay loam soil from Long Melford, U.K., was investigated. The soil characteristics are summarised in a table in the field "Any other information on materials and methods including tables"
Light source:
Xenon lamp
Light spectrum: wavelength in nm:
> 300 - < 400
Duration:
16 d
Temp.:
20 °C
Initial conc. measured:
7.5 other: mg ai/treatment area (25 cm²)
Reference substance:
no
Dark controls:
yes
Computational methods:
The rate of degradation of cyanamide in irradiated and non-irradiated samples was calculated by linear regression using first order degradation kinetics.
Preliminary study:
No preliminary study
Test performance:
No unusual observations during the test performance
% Degr.:
91.1
Sampling time:
6 d
Test condition:
In the irradiated samples
Key result
% Degr.:
100
Sampling time:
12 d
Test condition:
In the irradiated samples
Key result
% Degr.:
93.8
Sampling time:
16 d
Test condition:
In the non-irradiated samples
Key result
DT50:
1.45 d
Test condition:
In the irradiated samples
Key result
DT50:
4.22 d
Test condition:
In the dark control samples
Transformation products:
yes
No.:
#1
No.:
#2
No.:
#2
Details on results:
Material balance: Recovery of radioactivity ranged from 90.5 % to 103 % for irradiated samples and from 93.5 % to 103 % for dark control samples. The mean mass balance was 95.5 % and 98.8 % in the irradiated and non-irradiated samples, respectively.

Extractable residues: Extractable residues decreased from 102.7 % of the applied radioactivity at day 0 to 47.5 % and 17.8 % at day 16 in the irradiated and dark control samples, respectively.

Unextractable residue: Unextractable residues reached 9.9 % and 13.1 % of applied radioactivity at day 12 and day 16 in the irradiated and dark control samples, respectively.

Volatile degradation products: Volatile residues increased to 33.2 % and 62.6 % of applied radioactivity at day 16 in the irradiated and non-irradiated samples, respectively. Residues were observed only in the NaOH trapping solutions and were identified to be [14CO2] by precipitation as BaCO3.

Degradation of cyanamide: Residues of [14C]-cyanamide decreased rapidly from 100.5 % at day 0 to 9.4 % at day 6 in the irradiated samples and was not longer detectable thereafter

Principal degradation products: Three degradation products of cyanamide occurred in the irradiated samples. The major extractable degradation product was identified as urea, which accounted for 48.4 % of applied radioactivity on day 6 and decreased to 33.2 % of applied radioactivity after 16 days of irradiation. A further metabolite was identified as dicyandiamide, which remained fairly constant during the irradiation period (6.9 % on day 1 to 10.3 % on day 16). One unknown metabolite (M4) was detected in the irradiated samples, but did not exceed 4.0 % of applied radioactivity. In the non-irradiated samples the same metabolite pattern could be observed as in the irradiated samples. Urea amounted to 18.4 % of applied radioactivity on day 12. The urea concentration decreased to 1.1 % of applied radioactivity on day 16. Dicyandiamide and the unknown metabolite (M4) amounted to 8.7 % and 3.4 % of applied radioactivity on day 12 and day 6, respectively, and decreased to 6.5 % and 2.6 % of applied radioactivity on day 16. On day 16, a further unknown metabolite was detected amounting to 1.0 % of applied radioactivity.

DT50 and DT90 values: The degradation of [14C]-cyanamide was best described by first order degradation kinetics. The photolytical half-life of cyanamide was calculated to be 1.45 days. In the dark control samples the DT50 values was calculated to be 4.22 days. The DT90 values were calculated to be 4.85 days and 14.03 days in the irradiated and nonirradiated samples, respectively.
Results with reference substance:
No reference substance

Distribution of radioactivity in irradiated and non-irradiated samples treated with [14C]-cyanamide:






















































































































Sampling point


(days)



Soil extractables


[%]



Non-extractables


[%]



CO2


[%]



Organic vola-


tiles [%]



Total


[%]



 



Irradiated



0



102.7



0.3



-



-



103.0



1



91.0



4.9



2.4



< 0.1



98.3



3



81.5



7.7



7.2



< 0.1



96.4



6



71.1



8.7



12.7



< 0.1



92.5



12



57.5



9.9



24.6



< 0.1



92.0



16



47.5



9.8



33.2



< 0.1



90.5



 



Non-irradiated



0



102.7



0.3



-



-



103.0



1



86.5



5.5



6.7



< 0.1



98.7



3



77.0



7.7



14.3



< 0.1



99.0



6



62.0



9.7



24.3



< 0.1



96.0



12



48.7



9.8



44.2



< 0.1



102.7



16



17.8



13.1



62.6



< 0.1



93.5



 


Pattern of degradation products of [14C]-cyanamide in irradiated and non-irradiated soil samples:






















































































































Sampling point


(days)



Cyanamide


[%]



Dicyandiamide


[%]



Urea


[%]



M4


(unknown)


[%]



M5


(unknown)


[%]



 



Irradiated



0



100.5



-



 



2.3



-



1



53.0



6.9



29.6



1.6



-



3



24.8



9.9



44.7



2.2



-



6



9.4



9.6



48.4



3.8



-



12



-



10.1



43.8



3.7



-



16



-



10.3



33.2



4.0



-



 



Non-irradiated



0



100.5



-



-



2.3



-



1



72.7



2.9



9.1



1.8



-



3



57.3



5.0



12.1



2.7



-



6



34.2



6.6



17.9



3.4



-



12



18.8



8.7



18.4



2.8



-



16



6.7



6.5



1.1



2.6



1.0



 


DT50and DT90values of cyanamide in irradiated and non-irradiated soil samples:






























 



DT50



DT90



Correlation coefficient



Kinetic



[days]



Irradiated



1.45



4.85



0.9904



first-order



Non-irradiated



4.22



14.03



0.9899



first-order



 

Validity criteria fulfilled:
yes
Conclusions:
The results indicate that cyanamide is rapidly degraded on the soil surface with a photolytical half-life of 1.45 days. A relatively fast degradation with a DT50 value of 4.22 days could also be observed in the dark control samples. Whilst in the non-irradiated samples cyanamide is mainly degraded to CO2, indicating a complete mineralisation, the photolytical degradation leads to the degradation products urea and dicyandiamide.
Executive summary:

The photo-degradation of [14C]-cyanamide on non-sterile, viable clay loam soil was investigated. The radiolabeled test solution was applied dropwise on the surface of the soil thin layers (~ 2 mm thickness) at a nominal rate of 7.5 mg as/treatment area (25 cm²) corresponding to a field application rate of 30 kg as/ha. The temperature of the soil thin layers was maintained at 20.0 °C with a continuous flow of circulated, temperature-controlled water. These samples were continuously irradiated by xenon arc lamp for up to 16 days with simulated sunlight. The light intensity in the range 300 - 400 nm was comparable to the light intensity of natural daylight in the summer. Humidified air was drawn through the chamber and the outlet air was passed through the following series of gas traps: 2 x 2 N NaOH and ethylene glycol. The other half of thin layers (dark controls) were incubated in the same way, but maintained in darkness. Irradiated and dark control samples were taken in duplicate immediately after application and after 1, 3, 6, 12 and 16 days of irradiation/incubation. After the soil samples were extracted, radioactivity in the extracts was quantified by LSC. Thereafter, the four extracts per sampling interval were combined and analysed by TLC. Transformation products were identified by co-chromatography with authentic standards by TLC using different solvent systems. Extracted soil samples were combusted to determine levels of unextractable residues. The rate of degradation of cyanamide in irradiated and non-irradiated samples was calculated by linear regression using first order degradation kinetics (TD50, TD90). Results indicated that cyanamide is rapidly degraded on the soil surface with a photolytical half-life of 1.45 days. A relatively fast degradation with a DT50 value of 4.22 days could also be observed in the dark control samples. Whilst in the non-irradiated samples cyanamide is mainly degraded to CO2, indicating a complete mineralisation, the photolytical degradation leads to the degradation products urea and dicyandiamide. The occurrence of these metabolites can be explained by the special design of the photolysis study. The synthetic design of the study provokes that the soil on the plates dries out in spite of the humidified air stream. It can be assumed that the microbial activity decreases significantly under these dry soil conditions. As a result, the degradation process slows down and intermediate products like urea and dicyandiamide are not further degraded and accumulate.

Description of key information

Two studies examined the phototransformation of cyanamide in soil. In the newer higher tier soil photolysis study which was conducted under more realistic conditions, no major metabolites of cyanamide were encountered and cyanamide was almost completely mineralised to CO2 in both irradiated and dark control samples. The degradation of cyanamide was fast both in irradiated and in the dark samples with DT50 values of 2.4 and 2.0 h, respectively, indicating that the rate of degradation due to photolysis is negligible compared to the rate of degradation caused by biodegradation.

Key value for chemical safety assessment

Half-life in soil:
2.4 h

Additional information

Two studies examined the phototransformation of cyanamide in soil. An older study (Burri, 2000, Doc. No. 724-002) showed that in addition to the biotic degradation cyanamide is also photolytically degraded on the soil surface with a photolytic half-life of 1.45 days. Two major degradation products occurred in this photolysis study and were identified as urea and dicyandiamide. However, although these metabolites exceeded the trigger value of 10 % of applied radioactivity they are considered to be not relevant under realistic outdoor conditions. The occurrence of these metabolites is restricted to artificial laboratory testing conditions e.g. the soil on the plates dries out in spite of the humidified air stream and in consequence, the microbial activity decreases significantly. As a result the degradation process slows down and intermediate products like urea and dicyandiamide accumulate. This was confirmed by the fact that in the non-irradiated samples the same metabolite pattern was observed, but in lower concentrations. Whilst in the non-irradiated samples cyanamide is mainly degraded to CO2, indicating a complete mineralisation, the photolytical degradation leads to an accumulation of the degradation products urea and dicyandiamide.


 


This assessment was further confirmed by results from a newer higher tier soil photolysis study (key study: Limacher, 2009, Doc.No. 724-003) conducted under more realistic conditions, where no major metabolites of cyanamide were encountered and cyanamide was almost completely mineralised to CO2 in both irradiated and dark control samples. In this study (using a soil layer of ca. 10 mm) degradation of cyanamide was fast both in irradiated and in the dark samples (single first order DT50 values of 2.4 and 2.0 h, respectively), indicating that the rate of degradation due to photolysis is negligible compared to the rate of degradation caused by biodegradation.