Cyanamide

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1990-09 until 1990-11

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)

Deviations:

no

GLP compliance:

yes

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

20 - 25°C

Analytical monitoring:

yes

Details on sampling:

Samples were shaken at 20 - 25 °C and at each sampling point an aliquot of the supernatant was sampled and the tubes shaken again.
The following sampling points were chosen:
Hörstel (8.97 mg/L): 0.5, 2, 4, 9, 27 and 52 h
Hörstel (0.89 mg/L): 0.5, 1, 2, 6, 24 and 48 h
Jülich (8.97 mg/L): 0.8, 1.5, 2, 6, 30 and 96 h
Borstel Ap (8.97 mg/L): 0.8, 1.5, 2, 6, 24 and 48 h

Details on matrix:

The adsorption/desorption characteristics of cyanamide on three soils were investigated: acidic sand (Hörstel), loamy silt (Jülich), and slightly acidic silty sand (Borstel Ap) .

Details on test conditions:

The air dried soil samples were equilibrated by shaking with 0.01 M CaCl2 solution (1:2.5, w/w) for 6 hours. Afterwards the samples were sterilised because cyanamide is suspected to be liable to biotic breakdown during the test. The samples were centrifuged and the CaCl2 solution decanted. Fresh CaCl2 solution was added to yield a soil/aqueous phase ration of 1:5 (w/w). [14C]-cyanamide dissolved in methanol was added to the soil suspensions in the CaCl2 solution to give a nominal concentration of 8.97 mg cyanamide/L. For the soil ”Hörstel” an additional adsorption kinetic was performed with an initial concentration of 0.89 mg cyanamide/L. Samples were shaken at 20 - 25 °C and at each sampling point an aliquot of the supernatant was sampled and the tubes shaken again.

Sample No.:

#1

Duration:

52 h

Initial conc. measured:

8.97 other: mg Cyanamide/L in Hörstel (acidic soil)

pH:

5.3

Sample No.:

#2

Duration:

48 h

Initial conc. measured:

0.89 other: mg Cyanamide/L in Hörstel (acidic soil)

pH:

5.3

Sample No.:

#3

Duration:

96 h

Initial conc. measured:

8.97 other: mg Cyanamide/L in loamy silt (Jülich)

pH:

7.1

Sample No.:

#4

Duration:

48 h

Initial conc. measured:

8.97 other: mg Cyanamide/L in Borstel (slightly acidic silty sand)

pH:

5.8

Computational methods:

Linear distribution coefficients (Kd) were calculated from the mean ratios of test substance adsorbed to test substance in the aqueous phase. In addition, the distribution coefficients Kd were related to the content of organic carbon of the soil sample and expressed as Koc.

Key result

Type:

Koc

Value:

> 0 - < 6.8

Adsorption and desorption constants:

Adsorption coefficients Koc: For the soil Hörstel adsorption coefficients, normalised to organic carbon Koc, of approximately 6.81 mL/g and 4.35 mL/g were calculated for the high (8.97 mg/L) and low (0.89 mg/L) test concentrations, respectively. For the soil Jülich the Koc value was calculated to be 6.34 mL/g, whereas with the soil Borstel Ap no adsorption was detectable.

The adsorption was measured as disappearance of the test substance from the aqueous phase. It was calculated as difference between the concentration of the test substance in a control solution and the concentration in the respective test solution (concentrations as determined by LSC). This difference was small in relation to the relatively high original LSC value and it was in the same order of magnitude as the standard deviation of the LSC results. Therefore, the error of determination is relatively high and the calculated distribution coefficients are scattering around the zero value.

Recovery of test material:

Not indicated

Concentration of test substance at end of adsorption equilibration period:

The results indicate that at the end of the adsorption kinetics the cyanamide concentration in the samples was only slightly decreased (< 10 %) in comparison to the controls (CaCl2-solution with test substance, but without soil).

Concentration of test substance at end of desorption equilibration period:

In compliance with the guideline, the desorption part of the study was not performed, because significant adsorption (approximately 25 % or less) had not occurred.

Sample no.:

#1

Duration:

48 h

% Adsorption:

< 2

Sample no.:

#2

Duration:

48 h

% Adsorption:

< 2

Sample no.:

#3

Duration:

48 h

% Adsorption:

< 2

Sample no.:

#4

Duration:

48 h

% Adsorption:

< 2

Transformation products:

not measured

Details on results (Batch equilibrium method):

Adsorption coefficients Koc: In all samples the adsorption of cyanamide to soil was low. After 48 hour, the adsorption was less than 2 % for all soils and both concentrations. The highest adsorption was measured for the soil Hörstel (1.88 % after 52 hours). For the soil Hörstel adsorption coefficients, normalised to organic carbon Koc, of approximately 6.81 mL/g and 4.35 mL/g were calculated for the high (8.97 mg/L) and low (0.89 mg/L) test concentrations, respectively. For the soil Jülich the Koc value was calculated to be 6.34 mL/g, whereas with the soil Borstel Ap no adsorption was detectable.

The adsorption was measured as disappearance of the test substance from the aqueous phase. It was calculated as difference between the concentration of the test substance in a control solution and the concentration in the respective test solution (concentrations as determined by LSC). This difference was small in relation to the relatively high original LSC value and it was in the same order of magnitude as the standard deviation of the LSC results. Therefore, the error of determination is relatively high and the calculated distribution coefficients are scattering around the zero value.

Stability of cyanamide: At the end of the adsorption kinetic TLC analyses were performed in order to check if a degradation of the test substance had occurred. The results indicate that at the end of the adsorption kinetics the cyanamide concentration in the samples was only slightly decreased (< 10 %) in comparison to the controls (CaCl2-solution with test substance, but without soil).

Desorption:In compliance with the guideline, the desorption part of the study was not performed, because significant adsorption (approximately 25 % or less) had not occurred.

Statistics:

Not indicated

Adsorption of¹⁴C-hydrogen cyanamide in three soils:

	Soil Type	pH (H2O)	Organic Carbon (%)	Kd (mL/g)	Koc (mL/g)
Hörstel (8.97 mg/L)	acidic sand	5.3	1.35	0.092	6.81
Hörstel (0.89 mg/L)	acidic sand	5.3	1.35	0.059	4.35
Jülich	loamy silt	7.1	0.95	0.060	6.34
Borstel Ap	slightly acidic silty sand	5.8	1.35	0	0
arithmetic mean					4.38

 

Validity criteria fulfilled:

yes

Conclusions:

The derived Koc-values (0- 6.81 mL/g) indicate that cyanamide will not be adsorbed in soils and point towards a high mobility potential of cyanamide in soil.

Executive summary:

Test system: The adsorption/desorption characteristics of cyanamide on three soils were investigated: acidic sand (Hörstel), loamy silt (Jülich), and slightly acidic silty sand (Borstel Ap). The air dried soil samples were equilibrated by shaking with 0.01 M CaCl2 solution (1:2.5, w/w) for 6 hours. Afterwards the samples were sterilised because cyanamide is suspected to be liable to biotic breakdown during the test. The samples were centrifuged and the CaCl2 solution decanted. Fresh CaCl2 solution was added to yield a soil/aqueous phase ration of 1:5 (w/w). [14C]-cyanamide dissolved in methanol was added to the soil suspensions in the CaCl2 solution to give a nominal concentration of 8.97 mg cyanamide/L. For the soil ”Hörstel” an additional adsorption kinetic was performed with an initial concentration of 0.89 mg cyanamide/L. Samples were shaken at 20 - 25 °C and at each sampling point an aliquot of the supernatant was sampled and the tubes shaken again.

 

The following sampling points were chosen:

Hörstel (8.97 mg/L): 0.5, 2, 4, 9, 27 and 52 h

Hörstel (0.89 mg/L): 0.5, 1, 2, 6, 24 and 48 h

Jülich (8.97 mg/L): 0.8, 1.5, 2, 6, 30 and 96 h

Borstel Ap (8.97 mg/L): 0.8, 1.5, 2, 6, 24 and 48 h

 

 

Analytical method

At the end of the adsorption kinetics (after 48 - 96 hours) the supernatants were analysed by LSC and TLC using a linear analyser for the radioactive spots and UV detection for the nonlabelled reference substances.

Linear distribution coefficients (Kd) were calculated from the mean ratios of test substance adsorbed to test substance in the aqueous phase. In addition, the distribution coefficients Kd were related to the content of organic carbon of the soil sample and expressed as Koc.

 

Adsorption coefficients Koc

In all samples the adsorption of cyanamide to soil was low. After 48 hour, the adsorption was less than 2 % for all soils and both concentrations. The highest adsorption was measured for the soil Hörstel (1.88 % after 52 hours). For the soil Hörstel adsorption coefficients, normalised to organic carbon Koc, of approximately 6.81 mL/g and 4.35 mL/g were calculated for the high (8.97 mg/L) and low (0.89 mg/L) test concentrations, respectively. For the soil Jülich the Koc value was calculated to be 6.34 mL/g, whereas with the soil Borstel Ap no adsorption was detectable.

 

The adsorption was measured as disappearance of the test substance from the aqueous phase. It was calculated as difference between the concentration of the test substance in a control solution and the concentration in the respective test solution (concentrations as determined by LSC). This difference was small in relation to the relatively high original LSC value and it was in the same order of magnitude as the standard deviation of the LSC results. Therefore, the error of determination is relatively high and the calculated distribution coefficients are scattering around the zero value.

 

Stability of cyanamide: At the end of the adsorption kinetic TLC analyses were performed in order to check if a degradation of the test substance had occurred. The results indicate that at the end of the adsorption kinetics the cyanamide concentration in the samples was only slightly decreased (< 10 %) in comparison to the controls (CaCl2-solution with test substance, but without soil).

 

Desorption: In compliance with the guideline, the desorption part of the study was not performed, because significant adsorption (approximately 25 % or less) had not occurred.

 

Conclusion: The derived Koc-values (0- 6.81 mL/g) indicate that cyanamide will not be adsorbed in soils and point towards a high mobility potential of cyanamide in soil.

 

Description of key information

The derived Kd (0-0-0.09mL/g) and Koc-values (0-6.8 mL/g) for cyanamide indicate a low adsorption to soil.

Additional information

The adsorption/desorption characteristics of cyanamide was investigated in three different soils: acidic sand (Hörstel), loamy silt (Jülich), and slightly acidic silty sand (Borstel Ap). The samples were sterilised because cyanamide is suspected to be liable to biotic breakdown during the test. Nominal concentration of 8.97 mg cyanamide/L was applied. For the soil ”Hörstel” an additional adsorption kinetic was performed with an initial concentration of 0.89 mg cyanamide/L. Samples were shaken at 20 - 25 °C and at each sampling point (until 96 h) an aliquot of the supernatant was sampled and the tubes shaken again.

 

In all samples the adsorption of cyanamide to soil was low. After 48 hour, the adsorption was less than 2 % for all soils and both concentrations. The highest adsorption was measured for the soil Hörstel (1.88 % after 52 hours). For the soil Hörstel adsorption coefficients, normalised to organic carbon Koc, of approximately 6.81 mL/g and 4.35 mL/g were calculated for the high (8.97 mg/L) and low (0.89 mg/L) test concentrations, respectively. For the soil Jülich the Koc value was calculated to be 6.34 mL/g, whereas with the soil Borstel Ap no adsorption was detectable.

 

In compliance with the guideline, the desorption part of the study was not performed, because significant adsorption (approximately 25 % or less) had not occurred.

 

The derived Koc-values (0- 6.81 mL/g) and Kd (0 -0.09 mL/g) indicate that Cyanamide will not be adsorbed in soils and point towards a high mobility potential of cyanamide in soil.