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Environmental fate & pathways

Adsorption / desorption

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Endpoint:
adsorption / desorption, other
Remarks:
adsorption
Type of information:
calculation (if not (Q)SAR)
Remarks:
Estimated by calculation
Adequacy of study:
supporting study
Study period:
2004-5
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Remarks:
The result was obtained by the valid application of a well-established predictive method.
Justification for type of information:
Please refer to the associated QMRF and QPRF for details of the model validation, input parameters and other remarks. QSAR validation for this endpoint is discussed further in the Alcohols Environmental Fate Category Report.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Method: other (calculation): various methods
GLP compliance:
not specified
Type of method:
other: Prediction
Media:
soil
Radiolabelling:
no
Type:
Koc
Value:
112 000 L/kg
Remarks on result:
other: Non-hydrophobics method
Type:
Koc
Value:
63 000 L/kg
Remarks on result:
other: Calculated value (PCKOCWIN based on log Kow method)
Type:
Koc
Value:
2 390 000 L/kg
Remarks on result:
other: Predominantly Hydrophobics method (valid up to log Kow = 7.5. The result is presented for comparison only)
Type:
Koc
Value:
3 330 L/kg
Remarks on result:
other: Alcohols method (valid up to log Kow = 5. The result is presented for comparison only)

TGD Non-hydrophobics method: Koc = 112000 l/kg

TGD Alcohols method: Koc = 3330 l/kg

SRC PCKOCWIN method: Koc = 43800 l/kg

Note: the TGD Alcohols method is valid up to log Kow = 5.  The result is  presented for comparison only.

Conclusions:
A Koc value of 11200 was obtained for icosanol using a reliable calculation method.
Endpoint:
adsorption / desorption, other
Remarks:
adsorption
Type of information:
calculation (if not (Q)SAR)
Remarks:
Estimated by calculation
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
Please refer to the Alcohols Environmental Fate Category Report for details of the model validation, input parameters and other remarks.
Principles of method if other than guideline:
Method: other (calculation): various methods
GLP compliance:
not specified
Type of method:
other: Prediction
Media:
soil
Radiolabelling:
no
Type:
Koc
Value:
1 310 000
Remarks on result:
other: Calculated value
Conclusions:
A Koc value of 1310000 was obtained for docosan-1-ol using a validated calculation method.

Description of key information

Adsorption / desorption: Koc 1.31E+06 for docosan-1-ol based on log Kow-based QSAR validated by reliable values in the range C6-18 including hexadecan-1-ol (batch equilibrium test with sewage sludge substrate and OECD 121) and octadecan-1-ol (batch equilibrium test with sewage sludge substrate)

Key value for chemical safety assessment

Koc at 20 °C:
1 310 000

Additional information

An estimated Kocvalue of 1310000 has been derived by linear regression from log Kow, based on reliable measured data within the C6 -24 aliphatic alcohols category. This is validated by available measured data from batch equilibrium and HPLC studies within the substance category.Further details are presented in the endpoint study record. The reliable estimated value of log Kow = 7.75 for docosan-1-ol was used as the key input to this prediction.

Van Compernolle et al. (2006) report the adsorption of several long chain aliphatic alcohols (C12, C14, C16, and C18) to wastewater treatment plant solids. In this study the sludge was sterilised with formalin to prevent biodegradation and so the results relate to adsorption in a sterile system. This is useful for the understanding of the underlying physicochemical adsorption phenomena, but it is important to recognise that the fate and behaviour of alcohols in an active biological sludge system can only be modelled successfully if the important role of rapid degradation is also taken into consideration. Alcohol sorption coefficients showed some time dependence, reaching a plateau by 72 h. The Koc value for octadecan-1-ol, the nearest chain length to the registration substance tested in this study, was 4.71E+05.

It is notable that significant technical difficulties were encountered during method development for the study of the analogous substance decan-1-ol (CAS 112-30-1) in natural standard soils, in that it was not possible to detect sufficient substance and establish equilibrium in non-sterilised soil samples, due to the rapid rate of biodegradation of the test substance by the soil microbiota.

A Koc study using HPLC (OECD 121) methodology was conducted for a range of linear aliphatic alcohols in accordance with ISO 17025 (Shell Global Solutions, 2013).The good performance of the OECD 121 method for alcohols in this category is demonstrated by the close results obtained for decan-1-ol by OECD 121 as part of the same study and by the batch equilibrium method (OECD 106), which were within a factor of 2 for the same substance.

Discussion of trends in the Category of C6-24 linear and essentially-linear aliphatic alcohols:

Substantial evidence exists within the alcohols Category, in the form of sewage sludge adsorption measurements, literature values, High Performance Liquid Chromatography (HPLC) estimates conducted in accordance with OECD Guideline 121, and a recent OECD Guideline 106 test in soils and a wastewater treatment plant sludge. Predictive methods based on log Kowand MCI have also been explored for members of this Category. The available measured data supports the following conclusions:

- The HPLC predictions correlate very well with the available measured Koc data, requiring no additional correction.

- Adsorption results in the OECD Guideline 106 study conducted with the structural analogue decan-1-ol indicate that the alcohol interacts only with the organic carbon in the soils. This confirms the expectation that setting a value of Koc is sufficient to understand adsorption to the relevant substrates (soil, sediment, sludges).

- There are no confounding factors anticipated for the alcohols in this Category (e.g. unusual interaction with the stationary phase).

- Different log Kow-based QSAR predictions of Koc vary widely depending on which equation is selected. The log Kow-based prediction derived directly from reliable measured values by HPLC and batch equilibrium tests shows a very strong correlation and low standard error.

- HPLC measured Koc values across the series show a predictable increase in Koc value as the carbon number increases. Regression analysis shows that the linear relationship between carbon number and log Koc value measured using this method is extremely well correlated with very low error.

Reference:

Sabljić A and Güsten H (1995) QSARs for soil sorption. in: overview of structure-activity relationships for environmental endpoints. Hermens JLM (ed), report prepared wtihin the framework of the project "QSAR for prediction of fate and effects of chemicals in the environment", an international project of the Environmental Technologies RTD programme (DG XII/D-1) of the European Commission under contract number EV5V-CT92-0211.

[LogKoc: 6.12]