Registration Dossier

Environmental fate & pathways

Adsorption / desorption

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

Endpoint:
adsorption / desorption, other
Remarks:
other: leaching experiment
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1990
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
abstract
Principles of method if other than guideline:
A column laboratory experiment was conducted to evaluate the mobility of DCD and urea or ammonium fertilizer in different soils of Egypt and to determine the extent to which DCD separates from applied N-fertilizer under unsaturated soil conditions.
GLP compliance:
not specified
Type of method:
other: column experiment
Media:
soil
Validity criteria fulfilled:
not applicable
Conclusions:
The results indicate that Dicyandiamide is not strongly adsorbed to soil.
Executive summary:

 

A column laboratory experiment was conducted to evaluate the mobility of DCD and urea or ammonium fertilizer in different soils of Egypt and to determine the extent to which DCD separates from applied N-fertilizer under unsaturated soil conditions. Under such conditions, DCD is separated from NH4+but not from urea. DCD and urea moved with the soil solution at about the same rate. Thus, leaching may affect the efficiency of DCD as a nitrification inhibitor. DCD profiles were influenced by the nature of nitrogen fertilizer to which DCD was applied. When applied to soil surface in conjunction with NH4-N, DCD seems to have a higher mobility than with urea.

Endpoint:
adsorption / desorption, other
Remarks:
other: leaching experiment
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1990
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
abstract
Principles of method if other than guideline:
A laboratory experiment was conducted to investigate the relative mobility of dicyandiamide (DCD) and jointly applied ammoniacal salts or urea in three different soils of Lower Egypt, and to determine the extent to which DCD separates from N-fertilizer in unsaturated soil undergoing leaching.
GLP compliance:
not specified
Type of method:
other: not specified
Media:
soil
Test temperature:
No data
Validity criteria fulfilled:
not applicable
Conclusions:
The results indicate that Dicyandiamide is not strongly adsorbed to soil.
Executive summary:

A laboratory experiment was conducted to investigate the relative mobility of dicyandiamide (DCD) and jointly applied ammoniacal salts or urea in three different soils of Lower Egypt, and to determine the extent to which DCD separates from N-fertilizer in unsaturated soil undergoing leaching. Under conditions of water flow, DCD was readily separated from NH4+but parts from urea to a far lesser extent. The large difference in mobility between DCD and NH4+should severely limit the effectiveness of DCD as a nitrification inhibitor in the three soils considered when applied in conjunction with ammoniacal salts. In two out of three cases, the situation is similarly unfavorable in the case of joint DCD and urea application. However, the observation that DCD, in a low CEC sandy loam, moves within the soil solution, at a slightly lower rate than urea suggests that joint application with urea would keep at least part of the DCD in contact with the NH4+ions and, therefore, would preserve some of the effectiveness of DCD under leaching conditions in this soil.

Endpoint:
adsorption / desorption, other
Remarks:
other: Adsorption modelling
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Study period:
October 2009
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification
Qualifier:
according to guideline
Guideline:
other: REACH guidance on information requirements and chemical safety assessment, chapter R.6: QSARs and grouping of chemicals, May 2008.
Principles of method if other than guideline:
The EPISuite™ 4.0 QSAR/Property package, as distributed by US EPA, was used for calculation.
EPISuite™ gives two different estimates, based on different types of models. The first estimate is based on a so-called MCI model, a model that uses molecular connectivity indices, parameters that can be derived solely from the 2-D representation (graph) of a molecular structure. Such models usually perform adequately for relatively non-reactive chemicals without highly electronegative or electropositive substituents. The other estimate is based on a correlation of the soil-carbon/water partition coefficient with the octanol/water partition coefficient. Such a model, since it is, preferably, based on a measured property of similar character (viz. KOW), is to be preferred for polar molecules like the guanidines.
GLP compliance:
no
Type of method:
other: calculation
Media:
soil
Radiolabelling:
no
Test temperature:
Not applicable
Details on study design: HPLC method:
Not applicable
Analytical monitoring:
not required
Details on sampling:
Not applicable
Details on matrix:
Not applicable
Details on test conditions:
Not applicable
Computational methods:
See "Principles of method if other than guideline"
Type:
Koc
Value:
5.25 dimensionless
Type:
log Koc
Value:
0.72 dimensionless
Details on results (HPLC method):
Not applicable
Adsorption and desorption constants:
Not applicable
Recovery of test material:
Not applicable
Concentration of test substance at end of adsorption equilibration period:
Not applicable
Concentration of test substance at end of desorption equilibration period:
Not applicable
Transformation products:
not measured
Details on results (Batch equilibrium method):
Not applicable
Statistics:
Not applicable

Table 1: KOC values for cyanoguanidine, as predicted by EPISuite™

 

KOC(L/kg)

 

Connectivity

Indices model

KP for soil with

10% OM

KOW-based model

KP for soil with 10% OM

Cyanoguanidine

8.93

0.50

3.41 (from estimated log KOW(-1.34))

0.19

5.25 (from experimental log KOW(-1.0))

 

0.29

 

  The most likely KOC values for cyanoguanidine is 5.25 L/kg.

Figure 2: SPARC speciation vs. pH plot for cyanoguanidine > see attached background material

Note that it is the protonated (charged) species that exists predominantly at pH values below the pKa value; this would be true for the SPARC derived pKa values just as it would for the reported experimental pKa value for cyanoguanidine. It is therefore to be expected that under normal envi- ronmental conditions in soil as well as in water (and sediment), cyanoguanidine would be present in protonated form. This could well significantly alter its adsorption/desorption behaviour when com- pared to the predicted behaviour based on the assumption of organic matter partitioning.

Validity criteria fulfilled:
not applicable
Conclusions:
It can be concluded that cyanoguanidine does not adsorb strongly to soil (or sediment). The KOC value derived with EPISuite™, based on the KOW-model, can be considered reliable for both modelling and environmental fate assessments.
Executive summary:

Data submission for adsorption/desorption screening for cyanoguanidine was provided based on non-experimental methods. Cyanoguanidine is a highly water-soluble, high nitrogen-containing organic substance. The aqueous solubility of cyanoguanidine is 32 g/L. It is also very hydrophilic, judging by its log octanol-water partition coefficient of -1.0. As such, one would suspect that cyanoguanidine would not adsorb to organic matter in soil to any appreciable extent. This is confirmed by the estimated KOC value of 5.25, as presented by the EPISuite™ QSAR/Property package, as distributed by the US EPA. According to the results presented by EPISuite™ it can be concluded that cyanoguanidine does not adsorb strongly to soil (or sediment). The KOC value derived with EPISuite™, based on the KOW-model, can be considered reliable for both modelling and environmental fate assessments.

Endpoint:
adsorption / desorption: screening
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance has a low octanol water partition coefficient and the adsorption potential of this substance is related to this parameter
Endpoint:
adsorption / desorption, other
Remarks:
Leachate experiments
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1982 to 1987
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment
Qualifier:
no guideline followed
Principles of method if other than guideline:
Amberger & Vilsmeier (1988) examined leaching of dicyandiamide after mineral fertilizing and slurry manuring and decomposition of dicyandiamide in flooded soils (simulated ground water conditions; silty loam, pH 6.5). The experiments were conducted at 5-12 °C for 60 weeks with an initial DCD content of 20 mg DCD/L water (300 g wet soil + 600 ml water) at aerobic and anaerobic conditions.
After mineral feeding, only 0.6-0.9 % of dicyandiamide applied in 5 years was leached.
Biodegradation of dicyandiamide was followed by test material analyses (HPLC).
GLP compliance:
not specified
Type of method:
other: laboratory and field trails
Media:
soil
Radiolabelling:
no
Transformation products:
not specified

DCD leaching took place in the trials N1 and N2 with Alzon, as well as in liquid manure October + DCD and liquid manure March + DCD. For the first 5 years (1982/83 to 1986/87), the DCD- and DCD-flowers were discharged with the leachate. The quantities of DCD discharged with the leachate were determined (Table 3). 1984 and 1986 did no DCD leaching occur.

 

Alzon

Manure

Leachate

N1

N2

October

March

G DCD-N/ha

mm

1982/83

10

12

856

3

260

1983/84

0

0

0

0

95

1984/85

298

593

586

422

386

1985/86

0

0

0

0

148

1986/87

0

0

1317

9

348

 

Validity criteria fulfilled:
not applicable
Conclusions:
The experiment demonstrate that leachate highly depends on the weather conditions, as “heavy rainfall” in May 1985 is mentioned as reason for the leachate. The given information in the publication is very limited: no amount of rainfall is documented, fate of dicyandiamide is not assessed and the remaining amount in the soil was not determined.
Executive summary:

Amberger and Vilsmeier (1988) conducted a lysimeter experiment on leaching of dicyandiamide in soils. Leaching of dicyandiamide was monitored over 5 years (1982 to 1987). Dicyandiamide was applied to the lysimeter surface (Lysimeter: 2 m² surface, 1 m depth; soil: 16 – 19 % clay, 69 -75 % silt, 1.4 % C, 0.14 % total N, pH 6.5.) in four different variations:

1)    Dicyandiamide in combination with mineral fertilizer Alzon at time coded N1 (no further information reported)

2)    Dicyandiamide in combination with mineral fertilizer Alzon at time coded N2 (no further information reported)

3)    Dicyandiamide in combination with manure in October

4)    Dicyandiamide in combination with manure in March

The dicyandiamide content in the leachate was determined for the four variations over 5 years. Though the authors conclude an overall low leaching potential, a considerable leachate was reported for the variants N1 and N2 in the year 1984/1985. This is explained byheavy rainfalls in May 1985. The leachate for this time period relates to 1.6 to 2.2 % of the applied amount in the same year. For the combination with manure, leachate was observed in 1982/83, 1984/85 and 1986/87 ranging from 1.7 % to 8.8 % of the applied amount (see table 1 and 2 for comparison).

The experiment demonstrate that leachate highly depends on the weather conditions, as “heavy rainfall” in May 1985 is mentioned as reason for the leachate. The given information in the publication is very limited: no amount of rainfall is documented, fate of dicyandiamide is not assessed and the remaining amount in the soil was not determined.

Description of key information

A study does not need to be conducted according to Regulation (EC) No 1907/2006, Annex IX, column 2, 9.3.3., because the substance has a low octanol water partition coefficient and the adsorption potential of this substance is directly correlated to this parameter. The log octanol-water partition coefficient of -1.0 (experimentally determined according to OECD guideline 107) demonstrates that dicyandiamide is a very hydrophilic substance, therefore the adsorption potential of dicyandiamide is expected to be low.

As no experimental data are available the soil/sediment organic carbon-water partition coefficient (KOC) was estimated by means of QSAR. An estimation of the KOC was conducted with EPISuite™ based on the KOWmodel.

According to the results presented by EPISuite™ it can be concluded that dicyandiamide does not adsorb strongly to soil (or sediment) (Verhaar 2009):

KOC= 5.25

log KOC= 0.72

Considering the water solubility, the experimental Kowvalue, and the estimated Kocvalue, dicyandiamide is not expected to adsorb to organic matter in soil to any appreciable extent.

Key value for chemical safety assessment

Koc at 20 °C:
5.25

Additional information

Dicyandiamide is a highly water-soluble, high nitrogen-containing organic substance. The aqueous solubility of dicyandiamide is 32 g/L. It is also very hydrophilic, judging by its log octanol-water partition coefficient of -1.0.

As such, one would suspect that dicyandiamide would not adsorb to organic matter in soil to any appreciable extent. This is confirmed by the estimated KOC value (5.25), as presented by the EPISuite™ QSAR/Property package, as distributed by the US EPA.

This is in line with information reported in the scientific literature:

Amberger and Vilsmeier (1988) conducted a lysimeter experiment on leaching of dicyandiamide in soils. Leaching of dicyandiamide was monitored over 5 years (1982 to 1987). An overall leaching potential was discovered which highly depends on the weather conditions. Dicyandiamide was applied to the lysimeter surface (Lysimeter: 2 m² surface, 1 m depth; soil: 16 – 19 % clay, 69 -75 % silt, 1.4 % C, 0.14 % total N, pH 6.5.) in four different variations:

1)    Dicyandiamide in combination with mineral fertilizer Alzon at time coded N1 (no further information reported)

2)    Dicyandiamide in combination with mineral fertilizer Alzon at time coded N2 (no further information reported)

3)    Dicyandiamide in combination with manure in October

4)    Dicyandiamide in combination with manure in March

The dicyandiamide content in the leachate was determined for the four variations over 5 years. Though the authors conclude an overall low leaching potential, a considerable leachate was reported for the variants N1 and N2 in the year 1984/1985. This is explained by heavy rainfalls in May 1985. The leachate for this time period relates to 1.6 to 2.2 % of the applied amount in the same year. For the combination with manure, leachate was observed in 1982/83, 1984/85 and 1986/87 ranging from 1.7 % to 8.8 % of the applied amount.

The experiment demonstrates that leachate highly depends on the weather conditions, as “heavy rainfall” in May 1985 is mentioned as reason for the leachate. The given information in the publication is very limited: no amount of rainfall is documented, fate of dicyandiamide is not assessed and the remaining amount in the soil was not determined.

This is further supported by column laboratory experiments with soils of Lower Egypt (Abddel-Sabour et al., 1990 and 1994) which were conducted to evaluate the mobility of dicyandiamide. It could be demonstrated that DCD moves with the soil solution and may undergo leaching. Therefore, it can be concluded that dicyandiamide does not strongly adsorb to soil (or sediments).