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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Based on a weight of evidence approach, including information on measured values for the read-across substances heptanal and nonanal, and a QSAR for octanal, the Koc was determined to be 428.3 L/kg.

Key value for chemical safety assessment

Koc at 20 °C:

Additional information

The adsorption coefficient for octanal ( aldehyde C8) presented here was determined by a weight of evidence approach. A QSAR estimation of the adsorption coefficient of octanal has been made using KOCWIN v2.00. A study is available for the related read-across substance heptanal (aldehyde C7), and a value from public domain information is available for the related read-across nonanal (aldehyde C9).

Estimated adsorption coefficient (Koc) of octanal

The adsorption coefficient of octanal was estimated by QSAR using KOCWIN v2.00. Estimates were made using a measured log Kow of 3.5. The following equation was used:

Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 2.8611

 Fragment Correction(s):

1  Misc (C=O) Group (aliphatic attach).... : -0.2293

From this the log Koc was estimated to be 2.6318 (Koc= 428.3 L/kg).

Adsorption coefficient (Koc) of heptanal (aldehyde C7 heptylic)

In this study the adsorption coefficient (Koc) on soil and on sewage sludge of heptanal was determined by reverse phase high performance liquid chromotographic (HPLC) methods according to OECD guideline no. 121. Six reference substances were used along with two calibration mixtures. The test was condunceted at 35oC. The chromotograms obtained showed that heptanal had an average retention time of 2.95 minutes. From this the adsorption coefficient was calculated (log Koc) to be 1.9. This equated to a Koc of 79 L/kg

Adsorption coefiicient (Koc) of nonanal (aldehyde C9 nonylic)

An experimental value for the log Koc of nonanal is available from the database of the Research Institute for Fragrance Materials (RIFM). The stated log Koc is 2.84 (Koc=691.8 L/kg).

Adsorption coefficient of Octanal to be used for CSA

Based on this information the QSAR calculated value is considered to be a good estimate of the adsorption coefficient. The Koc estimated for octanal is close to the mean of the experimentally derived values for heptanal and nonanal. Heptanal is a shorter chain aldehyde than octanal with one less carbon atom, while nonanal is a longer chain aldehyde than octanal with one more carbon atom. A such, the adsorption coefficient of octanal would be expected to be close to the mean of the adsorption coefficients for heptanal and nonanal. As the estimated Koc for octanal of 428.3 L/kg is close to the mean of the Koc values for heptanal and nonanal, it is considered to be sufficient for risk assessment purposes. As such, the adsorption coefficient for use in the chemical safety assessment is 428.3 L/kg.

[LogKoc: 2.6318]