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Environmental fate & pathways

Adsorption / desorption

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adsorption / desorption, other
Type of information:
calculation (if not (Q)SAR)
Estimated by calculation
Adequacy of study:
supporting study
Study period:
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
420 000 L/kg
Remarks on result:
other: Calculated value
A Koc value of 420000 was obtained for Octadecan-1-ol using a validated calculation method.
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
supporting study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was well documented and meets generally accepted scientific principles, but was not conducted in compliance with GLP.
equivalent or similar to guideline
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Principles of method if other than guideline:
The radiolabelled test substance was added to a system of natural river water and activated sludge solids (sterilised with mercuric chloride). The concentration of test substance in each phase was determined by LSC following an equilibration period.
GLP compliance:
Type of method:
batch equilibrium method
sewage sludge
Details on sampling:
- Sampling interval: 1,5,16, 30 and 72hrs.
Details on matrix:
- River water: Collected from the River Gowy, Ellesmere Port, UK on two successive daye and mixed and sterilised (0.01% (m/v) mercuric chloride). It contained 12 mg/L suspended solids (SS).

- Activated sludge: Chester, U.K. (United Utilities, Sealand Road) sewage treatment works, a plant that receives mainly (>90%) domestic derived wastewater. Stirred at 150 rpm and aerated for 5 days and then MLSS and mixed liquor volatile suspended solids (MLVSS) were determined according to Standard Methods (APHA, 1995) to be 2940 mg/L and 2210 mg/L, respectively. The total organic carbon was 880 mg/L. The mixture was sterilised and deactivated (mercuric chloride).
Details on test conditions:
- Suspended solids concentration: 30 mg SS/L.

- Type, size and further details on reaction vessel: Four 20 ml of synthetic STP effluent from each 100 ml were pipetted into sperate 300 ml bottles for dilution with 180ml river water and agitated for the specified time period.

- Number of reaction vessels/concentration: Four replicates for each of the sampling times. 100 ± 2 ¿g/L radiolabelled alcohol

- Method of preparation of test solution: 4L activated sludge in 10L aspirators were spiked with stock solution of radiolabelled alcohols and stirred for 24 hours. Spiked activated slude dispensed into five 500ml bottles and gently shaken and allowed to settle for 100 minutes. 100ml subsamples taken to create five synthetic STP effluent bottles having 30 mg SS/L.
471 350
log Koc
Recovery of test material:
Sorption onto the glass fiber filter resulted in 1, 9, 11, 25, and 21 % for the C12, C14, C15, C16 and C18 alcohols, respectively. These values were used to correct the sorption coefficient calculations for alcohols. The total recovery of radioactivity from the filtrate
and filters was 100, 75, 81, 85, and 89 % for C12, C14, C15, C16 and C18, respectively. The remainder of the radioactivity was assumed to be lost to adsorption of alcohols onto glass surfaces during the experiments.
Transformation products:
not measured

Table 1: Alcohol adsorption coefficients (72 hr results)

Carbon number 





























C15 was found to be an unexplained outlier.

The results for five substances are considered alongside each other since the results of the whole study are useful for comparison purposes.

QSAR equation developed:

Log Koc = 0.11 + 0.77 log Kow


                 R2 = 0.994

An adsorption coefficient of 471350 L/Kg was determined in a reliable study conducted according to generally accepted scientific principles.

Description of key information

Adsorption / desorption: Koc 4.71E+05 (batch equilibrium test with sewage sludge substrate).

Key value for chemical safety assessment

Koc at 20 °C:
471 000

Additional information

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 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.

An estimated Koc value of 420000 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.

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.

Koc values for octadecan-1-ol in the range 2010 - 840000 were obtained using the well-established QSAR calculation method for 'predominantly hydrophobic' substances; the method for 'Alcohol' substances and the method for 'non-hydrophobic' substances, developed by Sabljić and Güsten (1995) for the European Commission, and recommended in EU Guidance. The upper limit of this range, predicted with the predominantly hydrophobics equation, is closes to the value measured by the batch equilibrium method.

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.


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: 5.67]