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Adsorption / desorption

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Description of key information

The Soil Adsorption Coefficient (Koc) of 1157 L/kg was calculated using MCI method - model KOCWIN v2.00 (US EPA, 2013b).  The estimated Koc indicates moderate sorption to soil/sediment and slow migration to ground water. The substance falls within the applicability of the domain and therefore the predicted value can be considered as reliable taking into account the statistical information for the MCI (Molecular Connectivity Index, first-order) training and validation datasets.
The predicted value was used for PNEC derivation using EPM method and is considered as adequate for the chemical safety assessment (CSA) and no additional information is required.

Key value for chemical safety assessment

Koc at 20 °C:
1 157

Additional information

KOCWIN estimates Koc using the Molecular Connectivity Index (MCI) and a log Kow-based method. The MCI method is more robust and been in use longer. The estimated Koc value using MCI method (KOCWIN v2.00) is 1157 L/kg (LogKoc = 3.0635). Currently there is no universally accepted definition of model domain. Log Koc estimates are less accurate for compounds outside the MW range of the training set compounds and/or that have more instances of a given fragment than the maximum for all training set compounds. 

Applicability of the domain is molecular weight (MW): 32.04 - 665.02 g/Mol. MW of DBP is 278.35.

Experimental results of study by Sullivan at al., 1982 shows that the adsorption of DBP from Seawater DBP dissolved in seawater minimally adsorb onto and desorb from three clay minerals (montmorillonite, kaolite, calcium montmorillonite), calcite, a sediment sample and glass test tubes. Average corrected partition coefficient for the adsorption / desorption of DBP in sea water varied between 0.01 and 0.44 depending on the adsorbent used. Authors also reported a partition coefficient in seawater and sediment of 0.149 (i.e. Koc = 1.4).

[LogKoc: 3.0635]

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